World Expos. A history of structures. (Full text) by wrex

WORLD EXPOS

This book is a fascinating journey along the history of architectural structures over the last 150 years, taking the World Expos as an original unifying thread. Nevertheless, it does not solely focus on the exhibition buildings; on the contrary, these are continuously being related to buildings beyond the scope of the Expos, thus ultimately providing a general vision of the history of modern structures.

A HISTORY OF STRUCTURES Isaac LĂłpez CĂŠsar

A HISTORY OF STRUCTURES

WORLD EXPOS

This essay is destined to become an essential work of reference within the history of architectural structures. It is generously illustrated with more than nine hundred large-scale illustrations, many of which have not appeared in contemporary publications. It offers innumerable facts that will interest architects, engineers or art historians. Likewise, members of the general public far-removed from these fields will also be able to enjoy many of the passages which are accessible to those who do not have any specific knowledge of architecture or engineering.

ISBN 978-84-946257-3-2

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WORLD EXPOS

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WORLD EXPOS A HISTORY OF STRUCTURES Isaac López César

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WORLD EXPOS A History of Structures

This book has been published with the support of the Bureau International des Expositions (BIE), Paris

Editorial Project By Architect Publications S.L. Carrer Llobateres, 16-18, Talleres 7 Nave 10 08210 Barberà del Valles Barcelona Publisher Marti Berrio Prieto Author Isaac López César English Translation Rebecca S. Ramanathan

When time, inexorable, has devoured us, history will remain. For those who have yet to come.

To my son Jacobo.

Art Director and Layout Geny Castell Cover Design Geny Castell Cover Photo Bettinotti, Massimo

© 2017 Isaac López César © 2017 By Architect Publications S.L. By Architect Publications S.L. Carrer Llobateres, 16-18, Talleres 7 Nave 10 08210 Barberà del Valles Barcelona Info@by-architect.com www.by-architect.com © Of illustrations, their authors ISBN: 978-84-946257-3-2 D.L.: B-16526-2017 Print in EU

All rights reserved. No part of this publication may be reproduced by any means or procedure, including reproduction, electronic storage or the distribution of copies by hiring or public lending, without the prior written permission of the owners of the copyright.

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CONTENTS

Acknowledgements.

Foreword: Vicente González Loscertales.

Secretary General of the Bureau International des Expositions (BIE), Paris. 21

Preface: Javier Estévez Cimadevila. PhD Architect. Full Professor in Structures in the Higher Technical School of Architecture in A Coruña.

Introduction.

CHAPTER 1 The Crystal Palace and the development of iron structures.

1.1 Foundations of the Industrial Revolution.

1.2 The Industrial Revolution in architecture.

1.2.1 Scientific breakthroughs.

1.2.2 New materials and typologies.

1.3 The Crystal Palace.

1.3.1 The Crystal Palace and prefabrication. A synthesis of the Industrial Revolution.

1.3.2 The Crystal Palace and the birth of the portal frame.

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CHAPTER 2

2.2.3 An extraordinary achievement: the Rotunde Building in the

World Expos in the 19th century. Developments in large

Weltausstellung in Vienna 1873.

span decks.

148

2.2.4 An undervalued milestone: the main building in the Exposition Universelle, Internationale et Coloniale in Lyon 1894.

158

2.1 The search for large spans and typological innovation in rectangular decks.

CHAPTER 3

2.1.1 Alexis Barrault and the expansion joint: the Palais de 69

The World Expos and the race for the tallest building

2.1.1.1 Precedents and a descriptive introduction.

in the world.

2.1.1.2 The problems of horizontal stabilisation and thermal movements.

2.1.1.3 The controversy surrounding the span record.

l’Industrie in the Exposition Universelle of Paris in 1855.

2.1.2 Neutralising thrusts in the metal arch and the Galerie des Machines in the Exposition Universelle of Paris in 1867.

2.1.3 A new portal frame typology for large spans: the Galerie des Machines from the Exposition Universelle of Paris in 1878.

2.1.3.1 Historical Precedents.

2.1.3.2 The solution to the thermal problem?

2.1.4 Origin and evolution of the metal arch: the Galerie des Machines from the Exposition Universelle of Paris 1889.

163

3.1 The Eiffel Tower: its precedents.

165

3.1.1 High-rise constructions: projects never built.

165

3.1.2 High-rise construction: the actual achievements.

169

3.1.3 The experience of Gustave Eiffel and his collaborators.

175

3.2 The Eiffel Tower: Project and construction.

182

3.2.1 The Tower project.

182

3.2.2 The structural principle.

186

3.2.3 The structural skeleton and puddled iron.

187

3.2.4 The foundations and Triger’s system.

198

3.2.5 Workers assaulting the skies: the prefabrication, assembly and lifts.

202

2.1.4.1 Precedents of the metal arch.

101

2.1.4.2 Main characteristics of the structure.

111

2.1.4.3 Horizontal stabilisation, thrusts and thermal issues.

120

2.1.4.4 The controversy surrounding the span.

121

CHAPTER 4

2.1.4.5 The metal three-hinged arch after the Gallery erection in 1889.

122

The arrival of reinforced concrete.

3.3 The Eiffel Tower and its architectural consequences.

209

214

2.1.5 The american response: the Manufactures and Liberal Arts Building from the World’s Columbian Exposition in Chicago 1893.

126 134

2.1.5.1 Contributions. 2.2 The search for large spans and typological innovation in circular decks.

134

2.2.1 The first iron and glass dome in the world: the Halle au Blé of Paris.

134

214

4.2 Reinforced concrete: the first large architectural structures.

222

4.3 Reinforced concrete and the World Expos.

230

4.3.1 Reinforced concrete up until the Brussels Expo in 1958.

231

4.3.2 Reinforced concrete after Brussels 1958: late shell structures and 242

proposals with a sculptural character.

2.2.2 Fire in the first american iron dome: the Crystal Palace from the 136

New York Expo 1853.

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4.1 Reinforced concrete: first developments.

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CHAPTER 5 Tension decks: origin and peak.

252

6.2.3 Osaka 1970: the Expo as an exponent of design singularity.

413

6.2.4 Osaka 1970: the Expo as a pneumatic structural ensemble.

420

6.2.5 Osaka 1970. Unbuilt projects: the Expo as a catalyst for th

5.1 Tensile structures in the 19 century.

252

the imagination.

422

5.1.1 The technological context: intermittent contributions.

252

6.2.6 Osaka 1970: the Expo as a generator of building codes.

426

5.1.2 Expos in the 19 century: brilliant, intermittent contributions.

258

6.2.7 Pneumatic structures in Expos after Osaka 1970.

427

5.2 The enormous boom in tensile structures in the 20 century. th

264 264

5.2.1 The technological context. 5.2.2 World Expos in the 20th century: the triumphant entrance of

268

tensile structures. 5.2.2.1 The Travel and Transport Building in the World’s Fair in Chicago 1933: an isolated structural experiment.

269

5.2.2.2 The rebirth of structural brilliance in Expo ’58 in Brussels.

278

5.2.2.3 The New York State Pavilion in the 1964-1965 New York’s World’s Fair: the continuation of the “bicycle wheel”.

CHAPTER 7 Space frames: the Expos between utopia and reality.

436

7.1 Space structures: origin and development.

437

7.2 The brilliant contribution made by the World Expos.

456

7.2.1 Space frames and false tensegrities.

456

7.2.2 Space megastructures: between utopia and reality.

461

310

5.2.2.4 The Seattle Center Coliseum in the Century 21 Exposition in Seattle 1962: “limitless spans”.

314

CHAPTER 8 The return to wood.

5.2.2.5 The Federal Republic of Germany Pavilion in Expo ’67 in

513

Montreal. Frei Otto: utopia and formal innovation through “natural autoshapes”.

325

8.1 Wooden structures: origin and development.

513

5.2.2.6 The influence of the change in direction initiated by Frei Otto.

339

8.2 The contribution of the Expos at three key moments.

531

5.2.2.7 Other historically relevant structures in the World Expos.

354

5.2.2.8 “Tensile designed” structures: the contribution of the Expos.

362

5.2.2.9 Tensegrity structures: the contribution of the Expos.

368

Afterword.

559

Notes and bibliography.

563

Biographic reference.

575

CHAPTER 6 World Expos: the zenith of pneumatic structures.

378

6.1 The origin of pneumatic structures.

378

6.2 The World Expos: the zenith.

389

6.2.1 The Expos prior to Osaka ’70: sporadic contributions.

390

6.2.2 Osaka 1970: the Expo as a stage for great structural milestones.

393

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ACKNOWLEDGEMENT

First of all I would like to offer my thanks to the Bureau International des Expositions (BIE) for supporting this book, and in particular to the Secretary General Mr. Vicente González Loscertales and the Deputy Secretary General Mr. Dimitri Kerkentzes for the enthusiastic backing they have given me. I thank Professor Javier Estévez Cimadevila for his encouragement, advice and his critical reading of each one of the chapters, which has undoubtedly contributed to refining the content. I am also indebted to the following people who have either directly or indirectly made a contribution: Juan Pérez Valcárcel, José Antonio Vázquez Rodríguez, Emilio Martín Gutiérrez, Pablo García Carrillo, Manuel Fernández Corral and Arturo López de la Osa Manso. I would furthermore like to thank Rebecca S. Ramanathan, who has been in charge of translating the book to English, for her high level of commitment and earnest work. To the editor of By Architect Publications, Martí Berrio, and the publisher’s graphic designer, Geny Castell, I express my thanks for the excellent collaboration that we have developed over the course of this project. Finally, I wish to say thank you to my family for all their effort. To my parents, Paz and Antonio. To my wife Nieves, who has accompanied me on this intense voyage. To Araceli Gil César and Manuel Casanova Ceniza.

For everyone, my deepest thanks.

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FOREWORD

World Expos are transformative and innovative mega-events that have a defining role in knowledge-sharing, cultural diplomacy and the promotion of progress for all. Gathering hundreds of countries from across the globe, World Expos are visited by millions, offering organisers and participants the opportunity to showcase their prowess, their ideas and their vision for the future. What defines a World Expo, as set out in the 1928 Paris Convention relating to International Exhibitions, is its duty to educate the public, its transient nature lasting no longer than six months, and its purpose to foster exchange around a universal challenge of the time. In reality, however, each World Expo offers much more than this. As global meeting points and ephemeral manifestations of progress, World Expos serve to push innovation to its boundaries, spreading ideas and leaving remarkable intellectual and physical legacies. The innovative role of World Expos is well documented; in the late 19th and early 20th centuries, Expos were the event of choice to showcase new inventions in the era of industrialisation. From the 1950s onwards, Expos have become a key platform for sharing solutions to the many challenges facing humanity, whether it be urban living, transport, energy or food. Throughout the past 160 years, the constant feature of World Expos is innovation. This technological, scientific, intellectual and artistic innovation is showcased, promoted and developed in multiple domains, including architecture and structural engineering. The very nature of Expos creates unique opportunities for architects and engineers to design and create novel types of structure that shape modern and future architecture. Beyond the visual impact of Expo pavilions, their innovative structures have a lasting influence on the adoption of new architectural techniques, building designs and construction materials. This evolution in structural typologies, functionality and protagonism can all be traced through the history of World Expos, from the Crystal Palace at the Great Exhibition of 1851 to the futuristic and self-sustaining pavilions designed for Expo 2020 in Dubai. In this book, Isaac LĂłpez CĂŠsar draws a clear line between developments in architecture and World Expos, embarking us on a technical yet engaging illustrated journey through the modern history of structures. The author skilfully demonstrates that since 1851, the structures designed and constructed for Expos have not only been stunning buildings, but also drivers of innovation.

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In World Expos, architects, designers and engineers find ripe testing grounds for new methods, new materials, new shapes, and new applications. As major events visited by millions, reported by the world’s media and noticed by industry professionals, Expos are open laboratories for pushing the boundaries of architecture and construction. International and corporate participants compete for visibility and esteem in a non-confrontational setting, encouraging host countries and participants to take bold decisions and to give maximum creative independence to architects. In turn, the ephemeral nature of Expos – most pavilions are not designed to be permanent – removes constraints on durability and lifespan that would otherwise limit the experimental nature of the structures.

Isaac López César vividly demonstrates that World Expos have a fundamental role in the evolution and development of structural systems and architectural methods. While the focus of Expos has shifted to respond to the different challenges facing humanity, progress remains at the core of their mission, and innovation remains central to their essence and legacy. In the case of the structures we build for today and for the future, it is certain that bold advancements are spurred on by the unique platform created by Expos. Vicente G. Loscertales. Secretary General of the Bureau International des Expositions (BIE).

The result is a “perfect storm” for structural innovation, giving architects a blank canvas to test new technologies, use new materials and try alternative approaches. The findings laid out in this book demonstrate the transformative power of Expos, which stems not just from their physical and intellectual impact, but also from the opportunities they create. These opportunities encourage ambition and progress, calling on engineers, architects and designers to make use of the latest methods and technologies to build a better future for humankind, one that is more comfortable, more sustainable, and more enjoyable for all. In 1851, the Great Exhibition’s pioneering Crystal Palace revealed the possibilities of using iron as a structural support and of incorporating prefabrication as a construction method. The lessons learnt paved the way for the construction of structures on ever-greater scales, a trend that led to such marvels as the Rotunde at Expo 1873 in Vienna and the Eiffel Tower at Expo 1889 in Paris. The latter, which remained the tallest structure in the world until 1930, reflected the growing international frenzy for height and marked the pinnacle of “iron architecture”. The intertwined history of architecture and World Expos is just as evident in other construction trends of the 19th, 20th and early 21st centuries. The use of reinforced concrete, used as a technical element for the Grand Palais and Petit Palais at Expo 1900 in Paris, culminated in the Palais du Centenaire built for Expo 1935 Brussels, and the highly recognisable Philips Pavilion of Expo 1958 in the same city. The Expos of the post-war period served as a ripe testing ground for the development of modern tension-based structures, the space frame, as well as a return to wooden structures. World Expos are the perfect environment to experiment with these forms of architecture, with dozens of pavilions reflecting and embodying bold new methods and styles – “Man the Explorer” at Expo 1967 Montreal, Takara Beautilion at Expo 1970 Osaka, or Japan’s pavilion at Expo 1992 Seville to name but a few. Moving into the late 20th and early 21st centuries, a tangible link is evident between developments in architecture and World Expos’ increased focused on sustainability. Pavilions at Expo 2000 Hannover, Expo 2010 Shanghai and Expo 2015 Milan continue to push the boundaries in terms of sustainability, low-carbon emissions and recyclability.

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PREFACE Thanks to their transitory nature and the competitive spirit between the participating nations vying to display their eminence before the thousands of visitors that flock to these events, the World Expos have constituted occasions of huge significance in the technological development of structures. The spirit of these Expos was clearly evinced in the words of Frei Otto in the International Congress on Light Structures for Large Spans held in Seville in 1992: “Expos are a wonderful opportunity to experiment and pave the way for the future”. On the other hand, in spite of the numerous publications that exist in the area of structures, most of them focus on calculation, while the number of publications dealing with the conceptual, historical and design aspects of structural systems is much lower. It is for this reason that this book represents a resource of great value, inasmuch as it presents a thorough and widely documented analysis of the World Expos from a structural perspective, bringing together historical and technological points of view in its appraisal of the buildings erected. Through this new approach, these Expos can be understood as laboratories of structures where new shapes and materials are experimented with, novel structural typologies are addressed, or the spans between supports and building heights are taken to limits never before imagined. In addition, it is worth noting the author’s wise decision to avoid falling into the trap of turning the publication into a mere collection of buildings. On the contrary, his analysis has focussed on those buildings which have made an indisputable contribution to the history of structural systems, and he has put their historical contribution into context through references to both the buildings that preceded them as well as those that were erected afterwards, and which could thus be considered as consequences of the same. In conclusion, the present book is a tour de force thanks to its approach, the thoroughness of its analysis, and its invaluable documentary contribution. In short, it is a highly useful resource for anyone interested in an in-depth journey through the great architectural events marked by the World Expos held since the mid-19th century. Javier Estévez Cimadevila. PhD Architect. Full Professor in Structures in the Higher Technical School of Architecture in A Coruña.

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INTRODUCTION

In 1851, the date of the first World Expo, electricity was not yet used for lighting or as a power source, the internal combustion engine did not exist, neither the radio nor the telephone had been invented, and the first motorised aeroplane had yet to take off. In architecture, the use of industrial iron was just beginning, while steel was not yet used in building. Reinforced concrete had not been invented. Since this date, the Expos have borne witness to and been the venue of the advances that have transformed the world to that which we know today. The Expos have been, and continue to be, places in which nations have substituted fighting on the battlefields with competence in fields of technological and industrial development, education and culture; the true engines of worlds past, present and future. From an architectural perspective, the structural contributions of the Expos have had enormous relevance and historical significance, intrinsically and permanently linking the Expos to the history of architectural structures. The role of the Expos as exponents of cutting-edge structural development came about for various reasons. In the first place, the chronological interval in which the Expos develop constitutes a period of huge structural productiveness. From the first that was held in 1851 to the present day, the Expos have witnessed significant developments in the field of structures: the development of iron engineering in the 19th century, the invention of reinforced concrete, the appearance of glued laminated timber, the development and far-reaching spread of space frames, the birth of cable networks and textile membranes, the development of pneumatic structures, as well as the revolution in the field of applied computer science. Consequently, we can find buildings that are bona fide paradigms of the history of structural systems. On the other hand, competition between nations to display their technological power would lead to a race in which each Expo aimed to outdo the structural achievements of the previous one. This gave rise to novel constructions, which in turn led to advances in the spans reached, the appearance of new structural typologies, and experimentation with new materials or research into new shapes. Other aspects favoured greater creative freedom in the field of structures. The transient nature of these events meant that certain issues such as durability were avoided; together with the purely representative or symbolic conception of numerous buildings which lacked a particularly rigid programme, the fact that many of them were built through architecture competitions enabled earlier research to be put into practice and the pioneering application of patents, as well as the implementation of new ideas that were in need of complete development or prior technological experience. On the other hand, the universal nature of these events granted these novelties widespread dissemination, brought about both by the millions of people who visited the Expos, and by the publication of the buildings and proposals presented to the various competitions in specialised journals. 23

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Another aspect that is intrinsically linked to the Expos is the transitoriness of its architecture. While some of the edifications associated to these events were built to stay, it is true that most of them were provisional. For this reason, exhibition architecture has usually been referred to as “ephemeral architecture”. One must therefore reflect on the relative nature of this term. From the perspective of time, if we take the existence of a man as a point of reference, then little architecture is “ephemeral” since inert molecular structures tend to outlive us. On the other hand, if we take the last thousand years (an insignificant period of time in geological terms) as an example, then a considerable portion of architecture has been “ephemeral”. In short, “ephemeral” is normally used as a metaphor for our own existence, as if the fate of our architecture was other than to dissolve into the earth. It is therefore reasonable to value this type of architecture not for its longevity over time, but for the historical impact it has had. It is no wonder that several Expo buildings are to be found in classic handbooks of modern architecture, in spite of having physically disappeared. We could ask ourselves whether the historical-architectural relevance of the Eiffel Tower would have been less had it been taken down at the end of the Exposition Universelle of 1889, according to plan. These reflections are not futile, given that the world in which we currently live is perversely drifting towards a tendency to disparage anything that does not generate an immediate and direct economic benefit; this type of short-lived architecture is sometimes seen as an expense of little use, and its cultural component and huge influence beyond the events for which it was created is forgotten. The present book offers a journey through the history of the architectural structures of the past 150 years, with the Expos as the unifying thread. While the book focuses on the structural contributions of the Expos, it is not exclusively limited to them. On the contrary, buildings not erected specifically for the Expos are mentioned on numerous occasions, and examples of these have gradually defined the historical-cultural context and been included through both written references and graphic material. This book is not a collection of buildings, but rather a historical narrative that has chosen those edifications which have been relevant from a structural point of view because of their singularity, their impact on later buildings or because they constitute important examples of architectural trends based on structural state-of-the-art technology. As mentioned earlier, there is a constant interrelation between the exhibition buildings and others unconnected to the Expos with the aim of putting them into context and constructing a coherent historical account. The book therefore acquires a dimension that transcends the Expos and offers a general view of the modern history of structures. The chapters are principally organised according to structural types or materials, since the most relevant contributions have been made in these two areas. This organisation allows for correlations to be made between edifications of the same type or material while each of them is contextualised by establishing its precedents and consequences, hence the part they play in the technological and architectural context of the time. Thus, the book may be read either as a monograph, by taking each chapter independently, or the characteristics of a specific building, the history of a material or of a specific structural type may be consulted via the index. With the aim of achieving the highest level of documentary soundness in this book, the following have pre-eminently been used: sources contemporary to the buildings in question, documents written by the project authors or collaborators themselves, official Expo

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reports and documents by prestigious authors. The same criterion has been observed when including quotes or choosing graphic material. In this sense, the basic information search methodology has consisted in going over the documents that make up the basic bibliography, that is, the books and articles that cover the general history of architecture, or the general history of structural systems. Apart from being a source of information, the bibliographies of said documents have enabled a search for more specific references. From there, the search for a new document begins, proceeding iteratively from the general to the specific, thus weaving a web of information that has led to the closest source on the subject – the document written by the creator of the project. All this documentation is geographically widespread, a fact that has implied requesting more than three hundred documents from international libraries. The Internet has also been a source of information, albeit a cautious one, for primarily consulting electronic libraries and official institution websites. Another method of searching for information has been through journal databases. This method has been used for Expos and “modern” edifications due to the fact that the detailed technical information relating to old buildings is to be found in old engineering and building publications whose content has yet to be transferred to architectural databases. Said documents have been accessed through the first method described above. The way of accessing reliable information will undoubtedly become easier in the near future, thanks to the digitalisation of complete text documents that is being carried out in national libraries and other institutions, as well as by private companies. Be that as it may, I would finally like to thank the following libraries for their help in contributing documentation for this book: Bibliothèque Nationale de France; British Library; Biblioteca Nacional de España; National Gallery of Canada Library; Bibliothèque du Conservatoire National des Arts et Métiers (CNAM), France; National Library of Australia; Bibliothèque Université Laval, Québec; Harvard College Library; Library of the University of Michigan; Queen Elizabeth II Library, Memorial University of Newfoundland, Canada; Centro Superior de Investigaciones Científicas (CSIC), Spain; Chalmers Tekniska Högskola Biblioteket, Gothenburg, Sweden; Bibliothèque Universitaire de Sciences de Grenoble, France; Swiss Federal Institute of Technology, Zurich, Switzerland; Bibliothèque Municipale de Lyon, France; Bibliothèque Sainte-Geneviève, Paris; Universitätbibliothek Hamburg, Germany; Institutt for Kunsthistorie og Klassisk Arkeologi, Universitetet i Oslo, Norway; Owen Library, University of Pittsburgh U.S.A.; Institutt for Stalkonstruksjoner Norges Tekniske Hogskole Bibliotek; Università degli Studi di Firenze, Biblioteca Umanistica, Italy; Seattle Public Library, U.S.A.; Universidad Politécnica de Madrid; Engineering and Science Library Queen’s University Kingston, Ontario, Canada; Biblioteca Nacional Vittorio Emanuele III, Naples; Université Libre de Bruxelles; Bibliothèque Universitaire Lille, France; Universidad Politécnica de Cataluña; Robarts Library, University of Toronto, Canada; Institut National d’Histoire de l’Art, France; Ohio State University Library, U.S.A.; Humboldt-Universität zu Berlin. Isaac López César A Coruña, winter of 2017

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CHAPTER 1

THE CRYSTAL PALACE AND THE DEVELOPMENT OF IRON STRUCTURES 1.1 FOUNDATIONS OF THE INDUSTRIAL REVOLUTION The Industrial Revolution began in England in the mid-1800s and spread to other countries during the 1900s. The Industrial Revolution would imply an unprecedented technological breakthrough and a radical change in the production system, the economy and society. Changes in architecture were a result of scientific progress, with the large-scale use of iron and glass and the appearance of new typologies deriving from the needs of a new society. From 1750 onwards, England underwent a rapid population increase from 6.5 million inhabitants to 14 million in 1831. This population growth was due to neither immigration nor higher birth rates, but rather health factors, principally thanks to breakthroughs in the field of medicine, as well as improvements in hygiene and diet. This growing population demanded an increase in manufactured goods, thus motivating the development of the textile and iron and steel works industries. Thus, the production of iron in England rose from 20,000 tonnes in 1760 to 700,000 tonnes in 1830. This escalation can be explained by the needs of the industrial machines, the new iron ships and the development of the railway system, with its locomotives, rails and stations. Another determining factor in the increase of iron production would be the depletion of English forests, which would also trigger an increase in coal mining. Given its high calorific value, coal rendered the smelting of iron minerals easier in order to obtain iron. This could be treated in two different ways: forging or casting. In forging, iron was heated in a forge and beaten to eliminate the slag, while at the same time being shaped and given a fibrous, compact structure, thus obtaining wrought iron. Alternatively, casting or moulding consisted in smelting the iron and consequently pouring it into a mould, allowing it to cool slowly to get cast iron. During the first years of the 18th century, Abraham Darby replaced coal with coke, which has an even higher calorific value. This breakthrough would become widespread in the mid-1800s, thus acting as a catalyst for the iron and steel works industry. Meanwhile, the traditional process for manufacturing steel was well-known, a process in which wrought iron and coal were heated over the course of various days during which the iron absorbed enough carbon to transform into steel. However, in 1855 Henry Bessemer invented the converter bearing his name which was capable of transforming smelted iron mineral into iron or steel by regulating the quantity of carbon in the process called decar-

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THE CRYSTAL PALACE

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general equation to determine the neutral axis and carried out studies on torsion, arches and the thrusts generated by land. In 1826 Louis Marie Navier published another seminal work, “Résumé des leçons données à l’École des ponts et chaussées, sur l’application de la mécanique à l’établissement des constructions et des machines”. This work synthesized and completed the theories drawn up during the 17th century, and would have far-reaching repercussions.

bonisation. The Bessemer Converter paved the way for large-scale iron and steel manufacture (Fig 1.1). Undoubtedly, however, the main achievement of the period was the transformation of a continuous flow of steam moving through the steam engine. Invented by Watt and patented in 1769 by Watt himself, it enabled the leap from a traditional manufacturing process to a mechanised, industrial system and led to the arrival of new means of communication such as the railway and steamboat. The first locomotive was built by Robert Stephenson. The first passenger train would travel from Liverpool to Manchester in 1830.

Likewise, empirical studies on various buildings would be carried out in this atmosphere of growing interest in knowledge. In 1748, the Italian physicist Poleni published a study on the stability of the dome of St. Peter’s Basilica. On the other hand, the church of Sainte Geneviève in Paris would be studied. There would also be considerable progress made in the field of project instrumentation: The invention of the decimal metric system, set up in various European countries during the first two decades of the 19th century, and in other South American countries from 1830 onwards. This system offered accuracy to all project scales. Once it became widespread, it would foster scientific exchange.

Fig 1.1. Perspective and cross-section of the Bessemer Converter. Henry Bessemer, 1855. [Source: its authors]

Gaspard Monge invented descriptive geometry based on the generalisation of advances from the Renaissance. Descriptive geometry allows any three-dimensional object to be represented in two dimensions, thus offering technicians an unambiguous method of representation and promoting the exchange of architectural information.

1.2 THE INDUSTRIAL REVOLUTION IN ARCHITECTURE

The examples cited above are merely a sample of the scientific innovations that came about. Given the availability of this material and this climate of cultural revolution, it is therefore unsurprising that both architects and engineers aimed to move on from traditional materials and construction systems.

Being as it is a result of the social, cultural, economic and technological reality of any given period, architecture was not immune to the changes taking place in this revolutionary period. The principal factors in the Industrial Revolution that were to have an impact on the historical development of architecture would be the scientific advances on the one hand, and the large-scale application of new materials (such as iron and glass) and the arrival of new building typologies on the other. These new typologies were the result of industry’s emergent needs and the development of means of transport which called for bigger and bigger spaces. Thus, railway stations, factories, warehouses, bridges, storage tanks, etc. would be built.

1.2.2 New materials and typologies The new materials were mainly iron and glass; while their use goes back to ancient times, it was in this period when they became widely used in construction. Iron was traditionally used for secondary purposes such as the connection between ashlars, ties, etc. It had also been occasionally used as a complete structural solution for certain decks, such as that of the Théâtre Français by Victor Louis (1786) (Fig 1.2).

1.2.1 Scientific breakthroughs In this period, there were highly significant scientific and technological breakthroughs. Science continued along the path begun in the previous era of the Enlightenment: In 1676, Robert Hooke established a law that bears his name. At the end of the 17th century and beginning of the 18th century, Bernoulli, Leibniz and Mariotte studied the strain caused by flexure. Mariotte established the concept of the neutral axis, although he mistook its position. In 1713, Parent specified its correct position. In 1773 Charles A. Coulomb published “Essai sur une application des règles de maximis et minimis à quelques problèmes de statique relatifs à l’architecture”, which became a principal reference in the history of the resistance of materials. In this work, Coulomb established a

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EXPOSICIONES UNIVERSALES.indb 28-29

Fig 1.2. Théâtre Français. Victor Louis. 1786. Arched deck with iron structure. [Source: Ref (97) Blanc, Alan]

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With the development of the iron works industry in England that was largely due to the substitution of coke for coal, as mentioned above, the availability of wrought and cast iron increased exponentially, and with it, its use in architecture. We can see that there are three main fields of application in construction: bridges, large iron and glass decks and multi-storey buildings with metallic structures. Thus, erection of the first iron bridge over the River Severn near Coalbrookdale began in 1777. The architect was T.F. Pritchard. Completed in 1779, it was made up of two joined cast-iron semi-arches and had a span of 30.5 metres (Fig 1.3 and Fig 1.4).

Fig 1.5. Bridge over the River Wear. Tom Paine. 1786. [Source: Ref (94) Benévolo, Leonardo]

By the end of the 18th century, iron chain suspension bridges, which are lighter than those made up of arches, were beginning to be built in Europe. Erected in 1741, the first was a footbridge over the River Tees that reached a span of 21.34 metres. Also worthy of mention are the Conway Suspension Bridge of 1826 by Telford (Fig 1.6), and the Clifton Suspension Bridge over the River Avon in Bristol with a span of 214 metres, one of the most spectacular bridges of the century that was erected by Isambard Brunel in 1836 (Fig 1.7). In this sense, it should be made clear that the first documented iron chain suspension bridges were erected in the 14th century in China, although they were very primitive typologies (Fig 5.10).

Fig 1.3. Bridge over the River Severn in Coalbrookdale. T.F.Pritchard. 1779. [Source: Ref (94) Benévolo, Leonardo]

Fig 1.4. Bridge over the River Severn [Source: Ref (94) Benévolo, Leonardo]

Fig 1.6. Conway Suspension Bridge. Telford. 1826. [Source: Ref (94) Benévolo, Leonardo]

Fig 1.7. Clifton Suspension Bridge over the River Avon in Bristol. Isambard Brunel. 1836. [Source: Ref (94) Benévolo, Leonardo]

In 1786 Tom Paine built an iron bridge over the River Wear. In this case, it was made up of a diminished arch with a span of 71.9 metres (Fig 1.5). In 1796 Telford built another iron bridge over the Severn with a span of 39.6 metres. In 1801 Telford designed a bridge for London with a cast-iron arch that has a span of 182 metres, although it was never built.

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EXPOSICIONES UNIVERSALES.indb 30-31

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In 1849 Robert Stephenson erected the Britannia Bridge, a truly singular structure because of its use of a tubular girder (Fig 1.8 and Fig 1.9).

Meanwhile, the use of iron in building was becoming more widespread, particularly in English textile factories; the use of cast-iron beams and columns facilitated the greater spans needed by these industrial buildings, as well as being a nonflammable structural material which gave it a fundamental advantage after the fires recorded in these buildings in the last years of the 18th century. A good example is the Philips & Lee cotton mill (1801) in Manchester, designed by Baulton and Watt (Fig 1.10).

Fig 1.8. (Left) Britannia Bridge over the Menai Strait. Robert Stephenson. 1849. [Source: Ref (261) Peters, Tom F.] Fig 1.9. (Right) Britannia Bridge. [Source: Ref (261) Peters, Tom F.]

Fig 1.11. Halle au Blé. Paris. François J. Belanger and F.Brunet. 1811. [Source: Ref (305) Vierendeel, Arthur] Fig 1.13. Halle au Blé. Paris. Assembly drawing. Note the nuts and bolts tightening process. [Source: Ref (267) Picon, Antoine]

Fig 1.12. Halle au Blé. Paris. Engraving from the period. [Source: Ref (237) Marrey, Bernard]

The development of the iron works industry in France took place later, beginning its growth in the first years of the 19th century. Thus started the application of iron to bridge construction and even to buildings of certain significance. Examples of these are the new Dome of the Halle au Blé in Paris (1811) by François J. Belanger and F. Brunet, which is the first system of iron pieces forming a framework of meridians and parallels joined with bolts, a truly unusual joining method for that time, reaching a span of 39 metres (Fig 1.11 to Fig 1.13), the deck of the Marché de la Madeleine (1824) by Vignon, or the substitution of the wooden deck in Chartres Cathedral for an iron one (1837).

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EXPOSICIONES UNIVERSALES.indb 32-33

Fig 1.10. Philips & Lee cotton mill. Manchester. Baulton and Watt. 1801. Plan and sections. Structure made up of beams and iron columns stabilised horizontally via masonry walls. [Source: Munce, James F.]

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The glass industry would also make considerable progress. Until the first half of the 19th century, the glass for glazing was manufactured through glass-blowing, creating cylinders that were cut lengthwise and stretched. This was known as the cylinder process. In 1848 Henry Bessemer patented glass manufacture by extrusion, a process in which the glass was stretched by being passed between two cylinders, thus enabling the manufacture of glass sheet up to 2.5 metres wide. As a consequence, there was a surge in glass production as it became a larger-scale construction material, used in conjunction with iron in both decks and vertical enclosures. The slenderness of iron as a new structural material enabled the dematerialisation of walls and decks. When iron was paired with glass, the results were examples such as the aforementioned Marché de la Madeleine by Vignon; the Galérie d’Orléans of the Palais Royal (1829), a prototype for the nineteenth century shopping arcades and designed by Percier and Fontaine (Fig 1.14); the Jardin des Plantes in Paris (1833), which is a greenhouse erected by Rouhault (Fig 1.15 and Fig 1.16); the Great Conservatory at Chatsworth (1837) by Paxton (Fig 1.17 to Fig 1.19), which is a mixed structure with curved wooden parts and iron columns; Palm House at Kew Gardens (1846), erected by Richard Turner, with cast-iron columns and wrought iron H-shaped beams that were precursors of modern metal girders (Fig 1.20 to Fig 1.23), and the London Coal Exchange (1846-1849) by J.B. Bunning, which was a structure wholly built of cast iron and topped with a dome covered in glass sheets (Fig 1.24).

Fig 1.16. Jardin des Plantes in Paris. Rouhault. 1833. Section. [Source: Ref (226) Loyer, François]

Fig 1.17. (Left) The Great Conservatory at Chatsworth. Joseph Paxton. 1837. [Source: Ref (200) Hix, John] Fig 1.18. (Right) The Great Conservatory at Chatsworth. Photograph of construction work. [Source: Ref (200) Hix, John]

Fig 1.14. Galérie d’Orléans in the Palais Royal. Percier and Fontaine. 1829. [Source: Ref (226) Loyer, François]

Fig 1.15. Jardin des Plantes in Paris. Rouhault. 1833. [Source: Ref (226) Loyer, François]

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EXPOSICIONES UNIVERSALES.indb 34-35

Fig 1.19. The Great Conservatory at Chatsworth. Joseph Paxton. 1837. Construction section. Note the curved wooden structural parts, combined with iron columns. [Source: Ref (267) Picon, Antoine]

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Fig 1.22. (Left) The Greenhouse at Kew Gardens. Richard Turner. 1846. Section. [Source: Ref (200) Hix, John] Fig 1.20. The Greenhouse at Kew Gardens, also known as the Kew Palm House. Richard Turner. 1846. [Source: Ref (200) Hix, John]

Fig 1.23. (Right) The Greenhouse at Kew Gardens. Richard Turner. 1846. Plan. [Source: Ref (200) Hix, John]

Fig 1.24. London Coal Exchange. J.B. Bunning. 1846-1849. Period engraving. [Source: Ref (197) Hitchcock, Henry-Russell] Fig 1.21. The Greenhouse at Kew Gardens. Richard Turner. 1846. [Source: Ref (200) Hix, John]

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EXPOSICIONES UNIVERSALES.indb 36-37

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Examples of the new construction typology that was the railway station also appeared, for which large iron and glass decks were created. Among the first examples erected are Euston Station in 1835, a work by Robert Stephenson and P.H. Hatdwick which, according to R.J.M. Sutherland, was probably the first wrought iron truss with bolted joints [Ref (294) Sutherland, R.J.M] (Fig 1.25 and Fig 1.26), and the Tri Junct Railway Station in Derby, erected in 1839 by Robert Stephenson and Francis Thompson with a 17 metre-span deck (Fig 1.27). Fig 1.25. Euston Station. Robert Stephenson and P.H. Hatdwick. 1835-1839. [Source: Ref (267) Picon, Antoine]

Fig 1.27. Tri Junct Railway Station. Robert Stephenson and Francis Thompson. 1839-1841. [Source: Ref (197) Hitchcock, Henry-Russell]

Finally, we come to the Crystal Palace by Joseph Paxton for the Great Exhibition of 1851, a transition piece which, while building on many of the previous contributions, would highlight new problems and serve as experience for future structural developments.

Fig 1.26. Euston Station. Robert Stephenson and P.H. Hatdwick. 1835-1839. Details of the wrought iron trusses with bolted joints. [Source: Ref (229) Mainstone J. Rowland]

1.3 THE CRYSTAL PALACE There had been industrial expositions before 1851 in France, though exclusively national. Thus, the first was held in 1798, followed by those held in 1801, 1802, 1806, 1819, 1823, 1827, 1834, 1838, 1844 and 1849. England had also been the venue of, again exclusively national, exhibitions of industrial products in 1847, 1848 and 1849. It would be in this country where the first World Expo would be held in 1851, and thanks to the liberal English economy, imported products were welcome. In 1850, a competition was held for the building that would house the first World Expo and which would be erected in Hyde Park. 245 competitors entered, among which we can mention names such as Horeau and Turner with an iron and glass building, as well as H.A. Bunning, the creator of the aforementioned Coal Exchange in London (Fig 1.24). Nevertheless, the appointed committee would decide against green-lighting any of the projects presented and instead chose to design their own building proposal, consequently holding a competition to decide who would build it. It was at that point after the first competition ruling and before the construction was awarded, when the gardener and greenhouse builder, Joseph Paxton, presented his project to Prince Albert and Robert Stephenson, one of the committee members, and published it in the â&#x20AC;&#x153;Illustrated London Newsâ&#x20AC;?. These first building drawings made a good impression on the committee, which decided to abandon their own Project proposal and award Paxton with building the project. Paxton built on the experience gained on works such as the aforementioned Great Conservatory at Chatsworth (Fig 1.17 to Fig 1.19) to create a building on a monumental scale that was the Crystal Palace. The structure design and calculations were done by Charles

CHAPTER 1

EXPOSICIONES UNIVERSALES.indb 38-39

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Fox, a railway engineer, and Charles Heard Wild, under the guidance of William Cubitt and Matthew Digby Wyatt. Charles Heard Wild and Owen Jones represented the Royal Commissionâ&#x20AC;&#x2122;s Building Committee, the body in charge of supervising and controlling the building design and erection.

1.3.1 The Crystal Palace and prefabrication. A synthesis of the Industrial Revolution Fig 1.28. Crystal Palace. Joseph Paxton. 1850. First sketches of the section and elevation of the building. [Source: Ref (141) Dunlop, Beth]

The Crystal Palace was made up of a large, longitudinal, tiered space of exceptional dimensions: 563.25 metres long by 124.35 metres wide. In the central area, the space was cut across by a transept. Although the transept was a flat volume in its uppermost part according to the initial proposal, Paxton finished it off with a barrel vault, as better befitted the tastes of that period. There were five naves across the building, two side naves, two intermediate ones and a central nave. The intermediate naves laterally included two floors, the central nave having three, all of which were connected by walkways crossing the building.

Fig 1.30. Crystal Palace. Ground floor. [Source: Ref (141) Dunlop, Beth]

Fig 1.31. Crystal Palace. First floor. [Source: Ref (141) Dunlop, Beth]

Fig 1.29. The Crystal Palace in Hyde Park. Joseph Paxton. 1851. Illustration from the period. [Source: Ref (243) McKean, John]

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Fig 1.32. (Above) Crystal Palace. Elevation / longitudinal section. [Source: Ref (233) Mallet, Robert]

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EXPOSICIONES UNIVERSALES.indb 42-43

Fig 1.33. (Below) Crystal Palace. Elevation / cross-section. [Source: Ref (233) Mallet, Robert]

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Fig 1.34. (Opposite page, above) Crystal Palace. Transept. Reproduction of the original carried out by Dickinson. [Source: Ref (138) Dickinson] Fig 1.35. (Opposite page, below) Crystal Palace. Longitudinal central nave. Reproduction of the original by Dickinson. [Source: Ref (138) Dickinson]

One of the conditions with which the building had to comply was that it had to be removable. On the other hand, it was an impressively large building. Both issues justified the use of a structural module with a 7.315 x 7.315 metre base and 7.5 metres high, basically made up of four cast-iron columns and four girders. Thanks to this, the building could be reduced to a small number of different pieces. These modules could be added horizontally and vertically, therefore in a three-dimensional manner (Fig 1.37 and Fig 1.38). The building spans would thus be multiples of this module; the spans of the side and intermediate naves were of 7.315 and 14.63 m, and those of the central nave were 7.315 and 21.945 m. The building’s modular and three-dimensional structural organisation represents its most significant difference when compared with the iron and glass greenhouses and winter gardens from which it derived, since these earlier constructions were closed structures. In this way, it is one of the Crystal Palace’s greatest contributions to the history of structural systems.

Fig 1.36. Crystal Palace. Photograph of the outside elevation. [Source: Ref (243) McKean, John]

Fig 1.37. Crystal Palace. Axonometric diagram of a structural model. Added horizontally. [Source: Ref (80) Araujo, Ramón]

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EXPOSICIONES UNIVERSALES.indb 44-45

Fig 1.38. Crystal Palace. Axonometric diagram of a structural model. Added vertically. [Source: Ref (261) Peters, Tom F.]

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To resolve the spans mentioned above, X-shaped trusses of various materials were used: cast iron, wrought iron and wood (Fig 1.39 to Fig 1.41). Basically, the cast iron girders with chords of varying width were used for the 7.315 m spans, while the wrought iron ones were used for the larger spans. The wooden trusses, also with chords of varying width, were used in certain areas to offer horizontal stability. Most of the girders were one metre deep, except for some that were in the transept area upon which their arches were propped up.

Fig 1.39. Crystal Palace. Cast-iron truss. From top to bottom: elevation, plan and various cross-sections of the members. [Source: Ref (141) Dunlop, Beth]

Fig 1.41. Crystal Palace. Wooden truss. Elevation and plan. [Source: Ref (243) McKean, John]

The columns had a slightly octagonal outer cross-section and circular inner cross-section. They sprang from foundations with a base plate and stiffening brackets. The outer size of the column was constant throughout the whole building, while the inside of the column varied in thickness based on the load conditions. This issue was fundamental in the prefabrication system since the module size was not altered. Indeed, this was apparently the first time that such a resource had been used in a building structure (Fig 1.44). On the other hand, these hollow columns allowed for the drainage of rain water through them, while the beams that connect the column bases, which had a hollow, circular cross-section, were used as horizontal drainage pipes (Fig 1.45 to Fig 1.47). This rain water drainage system was not a complete novelty, since Paxton had already used it in the Great Conservatory at Chatsworth in 1837. Note how in that case, in Fig 1.19, the horizontal drainage network started at the base of the columns. The structure of the Crystal Palace was essentially the buildingâ&#x20AC;&#x2122;s drainage system.

Fig 1.42. Crystal Palace. Floor structure. From top to bottom and left to right: cross-section; longitudinal section; section, plan and elevation of the tie joint; transversal and longitudinal elevations of the iron king post; plans and elevations of the capitals. [Source: Ref (243) McKean, John]

Fig 1.40. Crystal Palace. Wrought iron truss. From top to bottom and left to right: elevations of the girder; elevation details; horizontal and vertical cross-section; chord splicing via riveting;

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EXPOSICIONES UNIVERSALES.indb 46-47

elevation, vertical and horizontal cross-section at a vertical member; details of the joint with horizontal bracing bars. [Source: Ref (243) McKean, John]

Fig 1.43. Crystal Palace. Deck structure. From top to bottom and left to right: cross-section (note the woodwork valley beam, which is a girder with a double king post and, at the same time, a cambered gutter. Underneath this piece and on top of the girders there is an iron U-section profile that leads the water to the inside of the columns; details of the gutter beam. [Source: Ref (243) McKean, John]

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The Crystal Palace is the first architectural synthesis of the Industrial Revolution for various reasons:

Fig 1.44. Crystal Palace. Column elevations and cross-sections. Note the increase in the cross-section of the same while the outside of the columns remains unchanging. [Source: Ref (141) Dunlop, Beth]

In the first place, it was the first large metal building structure erected since the beginning of the Industrial Revolution, the building with the biggest surface area in the world that inaugurated the era of architectural giants that was typical of the World Expos in the 19th century. While it was not the first prefabricated building, it certainly was the first to use largescale prefabrication and to adopt a three-dimensional additive module. Furthermore, it standardised components, a characteristic of the new mechanised, industrial production system. It used materials on a large scale: glass and iron in its two forms, cast and wrought. It synthesised the experience gained from previous constructions, namely glasshouses and winter gardens with a metallic structure; a good example is the Great Conservatory at Chatsworth which combines structure and drainage, as does the Crystal Palace. Furthermore, the influence of the Crystal Palace would cross European borders and be an inspiration for dozens of buildings erected in Europe and America during the second half of the 19th century. Among the numerous examples we could give, it is worth mentioning the building for the Industrial Expo in Munich erected in 1853, also known as the Munich Kristallpalast (Fig 1.71 and Fig 1.72), or the main building of the Philadelphia Centennial Exhibition of 1876 (Fig 1.48).

Fig 1.45. (Left) Crystal Palace. Column base with hollow connecting beams – horizontal drainage pipe. Elevation. [Source: Ref (311) Wyatt, M.D.]

The pioneering construction of a metal structure of the magnitude of the Crystal Palace would bring to light two main problems: on the one hand, how to endow a structure with enough stability to counter the horizontal forces caused by the wind, and on the other hand, how to control the structural movements caused by the thermal variations directly associated with iron, given its high coefficient of linear thermal expansion. These issues will be discussed in the following section.

Fig 1.46. (Right) Crystal Palace. Column base with hollow connecting beams – horizontal drainage pipe. Plan. [Source: Ref (311) Wyatt, M.D.]

Fig 1.47. Crystal Palace. Sealing the drainage pipe joints – base column connecting beams. [Source: Ref (201) Hobhouse, Christopher]

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EXPOSICIONES UNIVERSALES.indb 48-49

Fig 1.48. Building for the Philadelphia Centennial Exhibition. 1876. Illustration from the period. [Source: Ref (227) Luckhurst, Kenneth W.]

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Fig 1.49. Hungerford Market. Fowler. 1835. Note the quarter-circle rigid connections used in the joint between girders and columns, arranged both across and along. [Source: Ref (294) Sutherland, R.J.M.]

1.3.2 The Crystal Palace and the birth of the portal frame One of the design problems posed by metal structures is how to get adequate stability against horizontal forces such as wind. Prior to the erection of the Crystal Palace, there are diverse examples of iron structures which shed light on the horizontal stabilisation systems used. We can basically differentiate between: -Decks in which quarter-circle rigid connections are used in the joint between girders and columns, or in which columns are joined by arched beams with the aim of gaining greater stiffening on that plane. Fowler’s Hungerford Market (1835) is a paradigmatic example of the first case, being a wholly cast iron structure (Fig 1.49). The second system can be seen in the aforementioned case of Euston Station by Robert Stephenson (1835-1839) (Fig 1.25). -Buildings that are stable thanks to their shape, made up of curved parts. Good examples of this are Paxton’s Great Conservatory at Chatsworth (1837) (Fig 1.17 to Fig 1.19) or Turner’s Greenhouse in Kew Gardens (1844) (Fig 1.20 to Fig 1.23). -Multi-storey buildings made up of cast-iron columns and beams and stabilised horizontally via masonry perimeter walls. Examples of this typology are basically five- or six-storey buildings that were spinning mills. The precedent of this typology is the Milford Warehouse by William Strutt (1792-93), in which brick masonry vaults were used between wooden beams that were protected from fire by plaster and cast-iron columns (Fig 1.51). The first multi-storey building to use iron in both columns and beams was the Benyons & Marshall Flax Mill in Shrewsbury (1796-97), built by Charles Bage and also known as Ditherington Mill (Fig 1.52 to Fig 1.54). Another early example is the aforementioned Philip & Lee Cotton Mill in Manchester, by Baulton and Watt (1801) (Fig 1.10). -Buildings that combine several of the previous stabilisation systems, such as Kew Gardens (Figs 1.20 to 1.23) in which rigid connections and a vaulted shape were used. Furthermore, a new system of “post-tensioning” was applied in this case, via a series of pipes that crossed the arches and which contained stretched wires, thus contributing to the horizontal stability. The pipes can be seen in Fig 1.21 and Fig 1.50. There are no documented multi-storey buildings with iron columns and girders erected before 1851 in which the horizontal stability depends exclusively on portal frames without the need for masonry walls or other stabilisation systems.

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Fig 1.50. Patent for Richard Turner’s horizontal stabilisation system. 1846. The iron rod running through the inside of the pipe has a tension bolt, which was not included in the patent. This system was implemented in the Greenhouse at Kew Gardens. [Source: Ref (294) Sutherland, R.J.M.]

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Fig 1.51. Milford Warehouse. William Strutt. 1792-93. The structure is made up of cast-iron columns with wrought iron transversal connectors, wooden beams protected from fire with plaster and vaulted brick masonry floors. Horizontal stabilisation was achieved through the masonry perimeter walls. It has been preserved in practically the same state, with some modifications in the West wing. [Source: Ref (290) Skempton, A. W. / Johnson, H. R.]

Fig 1.52. Benyons & Marshall Flax Mill in Shrewsbury, also called Ditherington Mill. Charles Bage. 1796-97. First multi-storey building with a structure of metal beams and columns. Horizontal stabilisation was achieved via masonry perimeter walls. [Source: Ref (290) Skempton, A. W. / Johnson, H. R.]

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EXPOSICIONES UNIVERSALES.indb 52-53

Fig 1.53. (Left) Benyons & Marshall Flax Mill. Charles Bage. 1796-97. Photograph from the period. [Source: its creators] Fig 1.54. (Right) Benyons & Marshall Flax Mill. Current photograph. [Sourcae: its creators]

We can see in the previous examples that there were technical resources for achieving horizontal stability in permanent structures. However, in the case of the Crystal Palace, we find ourselves before a removable construction that is straight, diaphanous, with light enclosures made with iron and wood frames and cast-iron columns. The key to this issue is in the connection between the truss and the column. As can be seen in Fig 1.55, the joint is made up of a cast-iron piece that was inserted and bolted in the column. This piece was basically formed by four upper and four lower clamps between which the four trusses were connected. The trusses were subsequently wedged with keys (labelled T and S in the figure). The transversal keys in the building’s main frame were made of iron. The role of the trusses running longitudinally was solely to stabilise or brace the main frames. Only the trusses which corresponded to the six spans at each end of the building and the six at each side of the transept were wedged with iron keys, while the rest were wedged with oak keys; the aim of using oak keys was that as they deformed, they would create space to allow for the building’s thermal movement. Some of the longitudinal iron trusses were even substituted with wooden trusses in an attempt to reduce the thermal expansion of the whole (Fig 1.58). However, accounts from that period would suggest that this did not work correctly. Thus, Robert Mallet states: “We ourselves […] had an opportunity, during the early afternoon of one of the hottest days of the summer of 1851, of examining with some accuracy the effects of expansion by solar heat upon the frame of the building; and we can testify to this as a fact, that at the extreme western end, and at the fronts of the nave galleries, where they had been here the longest and the most heated, the columns were actually about two inches out of plumb in the first range in height only. Unaided by measurements, we could not perceive that any change in the plumbness of the coupled columns at the corners of the intersection of the nave and transept had taken place. Their rigidity, and probably other causes, appeared to have resisted the whole thrust, and visited it upon the extreme outer ends of the building. As we gazed up at these west-end galleries densely crowded with people, […] and thought of […] the brittle stilting of the cast iron fabric, we certainly felt that ‘ignorance was bliss’”. [Ref (233) Mallet, Robert] (Fig 1.56). Regarding the thermal movement along the length of the structure, Heppel, a member of the Royal Commission’s Building Committee, quotes Thomas Tredgold in Committee discussions on this issue. Tredgold is the author of the first book on structural design in cast iron and other metals, published in 1824, “Practical essay on the strength of cast iron and other metals, containing practical rules, tables and examples”. Thus M.D. Wyatt recorded in the minutes of the Commission. Heppel states:

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“Tredgold (almost the only good authority on the subject) [says] that in this climate, the variation in the length of cast-iron bars exposed to the sun -and it was fair to presume that the girders in this building would be so exposed- amounted to 1/1270th of their length. This in a length of 1,848 feet would amount to about 18 inches; but as this building was intersected by a transept at, or about, the centre of its length, the half of this, or 9 inches, would be the variation in length of each portion; and supposing all the girders to have been fixed at a mean temperature, […] each extremity would oscillate, or shift in position, 9 inches, or 4.5 inches, on each side of its mean, or original position”. [Ref (311) Wyatt, Matthew Digby]. (Fig 1.57).

Fig 1.55. Crystal Palace. Detail of the truss-column joint. Note the keys labelled T and S, both in the elevation and front cross-section. [Source: Ref (261) Peters, Tom F.]

Heppel’s reasoning implies that thanks to the wooden semi-circular arches, the barrel vault transept would have a low enough level of rigidity to act as a large expansion joint. This same reasoning is maintained by Tom F. Peters [Ref (261) Peters, Tom F.]. However, this is contradicted by Mallet’s observations “in situ”, who did not note any of the columns that bordered the transept being significantly out of plumb. In any case, it is obvious that th e building had a clear structural problem that derived from thermal movement (Fig 1.59 to Fig 1.65).

Fig 1.56. Simplified diagram of Robert Mallet’s observations on the longitudinal expansion of the Crystal Palace. The building is divided into two portions by the barrel vault transept. Each of these portions would only expand towards its free end (Mallet noted the columns at each end were about 2 inches out of plumb only at the height of the first floor). No variation in the plumbness of the coupled columns bordering the barrel vault transept was observed. [Source: López César, Isaac]

Fig 1.57. Simplified diagram of Heppel’s hypothesis regarding the expansion along the length of the Crystal Palace. Heppel maintained that each portion would expand by 4.5 inches at each side. This would imply a low enough level of rigidity in the barrel vault transept in order for it to act as a large expansion joint. [Source: López César, Isaac].

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1,848 feet (563.25m.)

2 inches (5 cm) At the height of the first floor

1,848 feet (563.25m.)

4.5 inches. (11.4 cm)

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Fig 1.60. (Left). Crystal Palace. Photograph of the barrel vault transept. [Source: Ref (243) McKean, John]

Fig 1.58. (Opposite page, above). Crystal Palace. Photograph of the inside. Note the three types of truss used: cast iron, wrought iron and wood. [Source: Ref (243) McKean, John] Fig 1.61. Crystal Palace. Drawing from the period. Note how a worker is wedging a truss at the front of the photograph. [Source: Ref (239) Mattie, Erik]

Fig 1.59. (Opposite page, below). Crystal Palace. Photograph of the outside. [Source: Ref (243) McKean, John]

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Fig 1.62. Crystal Palace. Transept vault. Longitudinal section and cross-section. [Source: Ref (243) McKean, John]

Fig 1.65. Crystal Palace. Raising the vault. Period drawing. [Source: Ref (141) Dunlop, Beth]

Regarding the width of the building, Matthew Digby Wyatt, a member of the Control Committee, stated: “The anticipated amount of expansion and contraction was provided for in the longitudinal direction of the building, by using wooden keys, for fastening the girders into the snugs, whilst transversely, where great rigidity was essential for resisting pressure against the extended surface, and no injurious effect of expansion or contraction was anticipated, iron keys, driven quite home, were invariably employed.” [Ref (311) Wyatt, Matthew Digby]. Regarding horizontal stiffness, it seems that it was the designers’ intention to stabilise the building through the use of portal frames. However, their attempt to resolve three fundamental issues through one joint, namely removability, stiffness and thermal movement, led to that joint failing on the two latter issues, and subsequently contributed to the aforementioned problems. Thus, M.D. Wyatt includes statements by Professor Airy in the Control Committee minutes: Fig 1.63. (Left) Crystal Palace. Transept vault. Connection of the wooden arch with the metal structure. [Source: Ref (311) Wyatt, M.D.] Fig 1.64. (Right) Crystal Palace. Transept vault. Cross-section of the wooden arch. [Source: Ref (311) Wyatt, M.D.]

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“In considering the general plan of the building in Hyde Park, the first thing which must strike anyone who examined it with reference to its strength was, that the world had never seen such an instance of a purely rectangular structure. He was aware of the extent to which this principle was carried, in the Lancashire mills, and in buildings of that class generally; but in all those places, where vertical columns supporting rectangular combinations of girders were carried up story after story, there was an ultimate resource of strength, in the tying of those girders into the walls, and in the connection of the side walls with the strong end walls. Those structures, therefore, depended for their strength and stability, on considerations entirely different from those which applied to the glass building in Hyde Park.” 59

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Finally, some diagonals would be added to the building on vertical planes, so that ultimately, the horizontal stability of the building would be down to a combination of a semi-rigid truss-column connection and diagonal bracing bars (Fig 1.60 and Fig 1.67 to Fig 1.70). Placing diagonals effectively made the columns withstand compression, in line with the characteristics of the material. In this way, the generalised use of the portal frame would be postponed until the end of the century because of the widespread use of wrought iron and steel, thanks to reductions in its price and its better mechanical properties. In the second half of the 19th century the use of cast iron as a structural material would begin to decline due to the success in the use of riveted wrought iron employed in paradigmatic constructions such as the aforementioned Britannia Bridge (Fig 1.8 and Fig 1.9), as well as due to the collapse of various cast iron structures: two spinning mills (Grays Mill in Manchester and Radcliffe’s Mill in Oldham) and the Dee Bridge in Chester. In spite of the fact that it was unclear whether or not the nature of the material was the main cause for said disasters, as the negative publicity and the fact that there were fatalities would probably have played their role.

Regarding the horizontal stability of the building, he goes on to say: “When girders acted as these did, resisting any tendency to the inclination of the columns, by the thrust of the upper edge, and the pull of the lower edge, or vice versâ, their action became that of, what was called in theoretical mechanics, a ‘couple’. […] It was a question for practical men, whether the strength of the hooks, or snugs (which were of cast iron) in which the trusses connected to the columns, was sufficient to resist such a strain; I confessed that I had doubts on the point; I did not think them sufficiently strong; and considering this as the main support of the building, […] did not […] think the strength was sufficient.” [Ref (311) Wyatt, Matthew Digby] To this tension, we should add the shear from the transmission of gravitational loads. In this respect, the trusses underwent prior load tests, the results of which have been preserved in a table in the form of applied load and the deflection obtained, with the breaking load also included (Fig 1.66), but it seems that these tests would have been carried out with isolated trusses, as there is no reference to breakage of the cast-iron snugs. There is no mention of any tests being carried out with the trusses mounted on the columns, nor with a complete frame standing up to horizontal forces. Thus, the difficulty in designing a cast-iron joint should be highlighted. One should bear in mind the fact that cast iron is a fragile material which, in addition, is basically capable of resisting compression but performs poorly with bending, tension and shear. These poor mechanical characteristics limit the structural uses of this material.

Fig 1.67. Crystal Palace. Frame type with diagonal bracing bars. [Source: Ref (243) McKean, John]

Fig 1.68. Crystal Palace. Detail of the joint between the column and the diagonal bracing bars. [Source: Ref (243) McKean, John]

Fig 1.66. Crystal Palace. Some of the results from the truss load tests. Reference is made to the 24-foot (7.315 m) cast-iron truss breaking when loaded with 30.5 tonnes. It seems that it was so fragmented that there were doubts as to the place where the fracture started. [Source: Ref (311) Wyatt, M.D.] Fig 1.69. Detail of the joint between bracing bars. [Source: Ref (243) McKean, John]

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the whole, that probably more accurately represented the structure of the building as it stood in 1851, than any other part of it now does. More than enough was destroyed to prove that Professor Airy was not so widely wrong after all”. [Ref (233) Mallet, Robert]

Fig 1.71. Munich Kristallpalast. 1853. Period photograph. Note the absence of triangulations in the vertical planes. [Source: Ref (181) Gössel, Peter]

Nevertheless, Professor Airy would consider the diagonals included to be insufficient in the Crystal Palace: “It would be observed, that since the design of the building had been originally formed, a number of diagonal stays and ties had been introduced into various parts; as far as I could ascertain, from the information I had received, the space between one of those diagonals and another, measured along the length of the building, amounted to 192 feet [58.5 m]. […] and it was quite conceivable, that when the wind blew violently, the parts intermediate between these diagonals might be blown down, leaving in a standing state the frames which were strengthened with diagonals.” [Ref (311) Wyatt, Matthew Digby]. When the building was taken down and later rebuilt, more diagonal bracing bars were added. Even so, the structure partially collapsed. This is how Robert Mallet described events in an article in 1862: “ […] and has been re-erected at Sydenham in a manner greatly to increase its stability, as regards the greater part of the structure at least; and from 1851 to the present day London has never been visited by one of those ‘first-class’ tornadoes that about twice in a century sweep over even our temperate regions. Yet, nevertheless, a very large wing of the Crystal Palace has been actually blown down in the interval – that proportion of CHAPTER 1

EXPOSICIONES UNIVERSALES.indb 62-63

The Munich Kristallpalast (Fig 1.71 and Fig 1.72) was built for the Industrial Exposition in Munich. It was a slightly rectangular building that measured 234 x 67 metres, therefore much smaller than the Crystal Palace. Unlike its predecessor, the Munich Kristallpalast had been designed to be permanent and be used after the exhibition. There is no cross bracing system in vertical planes, as it cannot be seen in the period photographs or drawings, nor in the structural details. It seems that the building turned out to be significantly more stable

Fig 1.70. Crystal Palace. Note the triangulations of the horizontal stabilisation. Copy of the original by Dickinson. [Source: Ref (138) Dickinson]

Fig 1.72. Munich Kristallpalast. 1853. Period photograph. [Source: Ref (181) Gössel, Peter]

than it should have been, probably due to the greater stiffness of the connectors that joined the trusses with the columns. This stability was demonstrated by its permanence, since the building stood until 1931, when it was destroyed by a fire. 63

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A closer historical connection can be found between the negative experience of the Crystal Palace in London in 1851, regarding its horizontal stability, and the No. 7 Slip at the English Royal Navy Dockyard at Chatham (1852-54) (Fig 1.73 to Fig 1.76), given that it was built by Godfrey T. Green, a collaborator of Fox and Henderson, contractors for the Crystal Palace. In this case, we have a building with a 25 metre-span truss. But this building’s greatest innovation is probably the fact that it was the first to use modern H-shaped iron columns [Ref (289) Skempton A. W.]. It had three overhead cranes, which meant that the horizontal stability was even more important. This was achieved thanks to X-shaped trusses arranged both along and across, while H-girders were also connected longitudinally to the columns via braced rigid connections which contributed to the structural stability and reduced the buckling length of the columns in this direction. There is no documented evidence of any problems concerning horizontal stability in this building which stills stands to this day, albeit with modifications. Fig 1.75. Nave of the No. 7 Slip at Chatham Dockyards. Note the X-shaped trusses for horizontal stabilisation. [Source: Ref (294) Sutherland, R.J.M.]

Fig 1.73. Nave of No. 7 Slip at Chatham Dockyards. Godfrey T. Greene, a collaborator of Fox and Henderson, contractors for the Crystal Palace. 1852-54. Original drawing by the designer. [Source: Ref (294) Sutherland, R.J.M.] Fig 1.76. Nave of the No. 7 Slip at Chatham Dockyards. Photograph of the launch of a submarine in 1966. Note the H-shaped columns and the longitudinal girders with braced rigid connections halfway up on the right. These contributed to the horizontal stability of the whole and reduced the buckling length of the columns. [Source: its designers]

Fig 1.74. Nave of the No. 7 Slip at Chatham Dockyards. The building had three overhead cranes. Original drawing by the designer. [Source: Ref (294) Sutherland, R.J.M.]

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Following the historical thread through the work of Godfrey T. Greene, we come to The Boat Store Sheerness, on the Isle of Sheppey, Kent, Great Britain (Godfrey T. Greene, L.G. Harris. 1858-1860). This is the first example of a multi-storey building with a metal structure in which the modern version of the portal frame is used, and is probably also the first multi-storey building to use H-sections in both girders and columns. The enclosures were made of corrugated sheet metal, meaning that the building’s horizontal stability was entirely dependent on the rigid joints (Fig 1.77 to Fig 1.79). A clear personalised, historical connection can be seen in the figure of the engineer Godfrey T. Greene, who collaborated on the erection of the Crystal Palace in London, and who was therefore aware of that building’s problems. He was also the designer of the No. 7 Slip 65

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at the English Royal Navy Dockyard at Chatham, and of the Boat Store Sheerness, the first multi-storey building built with the modern shape of the portal frame.

The above highlights the enormous historical-structural relevance that the Crystal Palace had, not only through its better-known aspects regarding prefabrication, but also because the experiences gained and the problems observed in this building would lay down the foundations for future structural developments, particularly for the development of multi-storey buildings stabilised with wrought iron portal frames, and later made with steel. These advances would reach their peak during the last twenty years of the 19th century with the evolution of the Chicago School’s first high-rise buildings. This fact makes the enormous significance of the Crystal Palace patently clear; built on the occasion of the first World Expo, it constitutes an example of trial and transition, the protohistory and testing grounds of metal structural design. The Crystal Palace undoubtedly represents one of the innumerable cases of experimental buildings that the Expos encouraged, and for which its creators were lacking full prior technological knowledge.

Fig 1.77. The Boat Store Sheerness. Godfrey T. Greene. 1858-1860. Godfrey T. Greene had collaborated with Fox and Henderson in the erection of various buildings after they had finished working as contractors for the Crystal Palace. [Source: Ref (289) Skempton, A.W.]

In the July 1896 issue of the journal “Engineering Record”, Daniel Burnham would make the following statement, included by Leonardo Benévolo in his “History of Modern Architecture”: “The principle of supporting an entire building on a metal structure that has been carefully balanced, stiffened and fireproofed, comes from the work of William Le Baron Jenney. There have been no antecedents in this respect, and he deserves all the merit for this feat of engineering which he was the first to ever accomplish”. [Ref (94) Benévolo, Leonardo].

Fig 1.78. The Boat Store Sheerness. Godfrey T. Greene. 1858-1860. Photograph of the second floor. [Source: Ref (289) Skempton, A.W.]

Fig 1.80. Fair Building. Detail of the connection. William Le Baron Jenney. 1889. [Source: Ref (94) Benévolo, Leonardo]

Fig 1.79. The Boat Store Sheerness. Godfrey T. Greene. 18581860. Detail of the column-girder connection. [Source: Ref (289) Skempton, A.W.]

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Without wishing to detract from Le Baron Jenney’s pioneering work, we should not underestimate the influence of earlier contributions. The Crystal Palace and other experiences gathered here undoubtedly paved the way for the development of the first high-rise buildings based on portal frames. It would be incorrect to attribute all the merit for developing the metal portal frame to William Le Baron Jenney, as would it be incorrect to claim that there were no antecedents in this respect.

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2.1 THE SEARCH FOR LARGE SPANS AND TYPOLOGICAL INNOVATION IN RECTANGULAR DECKS CHAPTER 2

WORLD EXPOS IN THE 19TH CENTURY. DEVELOPMENTS IN LARGE SPAN DECKS To a great extent, the history of the World Expos in the second half of the 19th century makes up the history of iron architecture. The desire of each country to outdo the previous Expo in a display of economic and technological power led to the creation of buildings that were real structural milestones for their time. Along these lines, France wanted to emulate England to become the standard in the industrial world, with Paris and London being the cities in which the most World Expos were held during the 19th century. In this way, iron was used in each building, the previous boundaries of knowledge were defied, and evident innovation occurred in structural typologies leading to greater spans and new technological images. At the same time, the progress made through these singular buildings would translate into applications in ordinary construction. This process would come to a head in the Exposition Universelle held in Paris in 1889, with buildings such as the Galerie des Machines by F. Dutert and V. Contamin and the Eiffel Tower, an authentic emblem of the city. The erection of the first large buildings in the World Fairs were causing a huge impact and creating an atmosphere of technological optimism that seemed to portend great achievements. Thus, in an article already published in the February 1856 issue of the French architecture and engineering journal “Nouvelles Annales de la Construction”, the following can be found: “The buildings created for the World Expos are the most impressive and characteristic manifestation of modern architecture. Their appearance in the history of art is an example that may be used as a starting point for a new era of modernity. The surface area of the Crystal Palace in London is four times bigger that St. Peter’s in Rome. The surface area of the Palais de l’Industrie in Paris is two and a half times bigger than this basilica. These buildings lead us to believe that modern construction will produce colossal designs in the 19th century that will go down in the annals of History”. [Ref (38) Nouvelles Annales] Between 1851 and 1889, numerous World Expos were held: New York 1853, Paris 1855, London 1862, Paris 1867, London 1871, Paris 1872, Lyon 1872, Vienna 1873, Philadelphia 1876, Paris 1878, Sydney 1879, Melbourne 1880, Amsterdam 1883, Antwerp 1884, New York 1885, London 1886, Barcelona 1888, Brussels 1888 and Copenhagen 1888. The historical analysis will focus on those buildings that are key pieces in the typological evolution of iron structures. To do this, we will distinguish decks with a basically rectangular layout on the one hand (made up of parallel arches or portal frames) and those with a circular layout on the other.

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In this section we will refer to those decks with a slightly rectangular layout with structural typologies consisting of trusses, portal frames or arches arranged in a basically parallel fashion.

2.1.1 Alexis Barrault and the expansion joint: The Palais de l’Industrie in the Exposition Universelle of Paris in 1855 The “Première Exposition Universelle des Produits de l’Industrie” was held in Paris in 1855, in response to the earlier Expo in London in 1851. From this date onwards until the end of the 19th century, and in spite of the aforementioned rivalry between England and France, the most important Expos would take place in France, mainly due to its economic prosperity. The main building for the Expo was the Palais de l’Industrie, a construction with a metal inner structure and an ashlar enclosure that intended to align with French tastes of that time. Created by the architect M.M. Viel and the engineers Alexis Barrault and G. Bridel, the building would be located between the Champs Élisées and the Seine.

2.1.1.1 Precedents and a descriptive introduction To bring the technological context of the time into focus, we should mention two precedents to this building which, in turn, held the world record for span. They are Lime Street Station in Liverpool, which was built by Turner in 1849 and which reached a span of 150 feet (45.72 metres) (Fig 2.1 to Fig 2.3), and New Street Station in Birmingham, designed by E.A. Cowper from the firm Fox, Henderson & Co., the builders on the Crystal Palace in London, and finished in 1854 with a span of 212 feet (64.62 metres) (Fig 2.4 to Fig 2.7). Originally, railways stations were built with decks made up of various short spans supported by intermediate iron columns; examples of this are Euston Station (Fig 1.25 and Fig 1.26) and Tri Junct Railway Station (Fig 1.27), both mentioned earlier. This was a disadvantage for the movement of merchandise, passengers and machinery. Lime Street Station and New Street Station are two of the first examples of a large station in which the deck has only one span. Lime Street Station made use of curved trusses supported at two points and made of bars and cables. These trusses lay on a cast-iron column at one end, and on a masonry

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wall at the other. They were hinged to the columns and supported on the wall with rollers, which eliminated any risk of horizontal thrust. Following traditional techniques in stations, horizontal stabilisation was achieved along the building with a masonry wall running longitudinally at one end and arched iron girders joining the columns at the other end. A curved truss was also used in New Street Station in Birmingham, although in this case with X-shaped bars. The truss was hinged on a masonry wall and was connected to a cast-iron column with rollers. Along the building, horizontal stabilisation was achieved in the same way as in the case above, with a masonry wall running longitudinally and arched girders that joined the columns. In terms of span, these two buildings were the immediate precedents. The Palais de lâ&#x20AC;&#x2122;Industrie in the Exposition Universelle of Paris in 1855 was made up of a main volume that was 252.2 metres long by 108.2 metres wide (Fig 2.8 to Fig 2.14). Six other, smaller blocks were added to this structure, housing the accesses, stairs and other secondary uses. The building enclosure was formed by ashlar walls, while the inner structure was made up of wrought and cast iron. The deck of this large space had a truly novel design for a metal structure. It had a central vault flanked by two side vaults (Fig 2.13). The central vault had a span of 48 metres, while that of the side vaults was 24 metres. These side vaults encircled the building and can also be seen in the longitudinal section of the same (Fig 2.14). The

Fig 2.4. New Street Station, Birmingham. E.A. Cowper. 1854. Cross-section. [Source: Ref (305) Vierendeel, A.]

Fig 2.5. (Left) New Street Station, Birmingham. E.A.Cowper. 1854. Longitudinal section. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.1 Lime Street Station, Liverpool. Turner. 1849. Cross-section. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.6. (Right) New Street Station, Birmingham. E.A.Cowper. 1854. Detail of the joint between chords, vertical members and diagonals. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.2. Lime Street Station, Liverpool. Turner. 1849. Longitudinal section. [Source: Ref (305) Vierendeel, A.] Fig 2.3 Lime Street Station, Liverpool. Turner. 1849. Structural details. Note the sliding support in the two upper details. [Source: Ref (305) Vierendeel, A.]

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Fig 2.7. New Street Station, Birmingham. E.A. Cowper. 1854. Sliding joint between the truss and the cast-iron column. [Source: Ref (305) Vierendeel, Arthur]

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central vault was 192 metres long and measured 35.96 metres at its highest point above ground level. There were two galleries with a ground and first floor between the central and the side vaults. These galleries had a span of 4 metres measured at the column axes. There was another gallery along the perimeter with two levels and a span of 2.1 metres measured at the column axes. All these galleries also encircled the building and could be seen in the longitudinal section (Fig 2.14). The three vaults were covered with glass sheets. The intermediate and perimeter galleries were covered with zinc sheets. The three vaults were made up of wrought iron X-shaped trussed arches 2 metres deep (Fig 2.15). The main vault had 26 arches. The distance between axes was 8 metres, except at the ends, where it was 4 metres. The vaults were finished with Pratt trusses joined to the arches through quarter-circle rigid connections (Fig 2.21). Likewise, there was a third structural order which measured 50 cm at the axes, followed the curve of the arches and made up the ironwork for the glass panes. Fig 2.10. Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. Inside view in a period painting. [Source: its creators]

Fig 2.8. Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. [Source: Ref (101) Bouin, Philippe / Chanut, Christian-Philippe] Fig 2.9. Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. [Source: Bibliothèque Nationale de France]

Fig 2.11. Palais de l’Industrie. Photograph taken during an exhibition in 1896. [Source: Ref (226) Loyer, François]

Fig 2.12. Palais de l’Industrie. Plan. [Source: Ref (305) Vierendeel, Arthur]

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Fig 2.13. (Above) Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. Cross-section. [Source: Ref (38) Nouvelles Annales]

Fig 2.14. (Left) Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. Longitudinal section. [Source: Ref (28) Algemeine Bauzeitung]

Fig 2.15. (Right) Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. Elevation of one of the truss modules in the side vaults. [Source: Ref (38) Nouvelles Annales]

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2.1.1.2 The problem of horizontal stabilisation and thermal movements The central arch and the two side ones sprang from four pairs of cast-iron columns which made up the intermediate and perimeter galleries (Fig 2.17). Rainwater was channelled through the inside of these columns (Fig 2.16), a drainage system that had already been applied by Paxton in the Great Conservatory at Chatsworth (1837) (Fig 1.19) and in the Crystal Palace (1851). These columns were connected two-by-two to a transverse structure at the column head, half-way up and at their base, thus forming the rigid elements that would provide the whole with lateral stability against the cross-winds, as well as favouring a correct transmission from the arch thrusts. The side arches were arranged to counteract those in the main vault. Transverse stability was reinforced through an intermediate floor in the side galleries, with girders stiffly connected to the columns with quarter-circle connections, while the interme-

Fig 2.16. Palais de l’Industrie. Cross-section of standard column type at its foundation base. Note the similarity with those in the Crystal Palace in London 1851. [Source: Ref (38) Nouvelles Annales]

Fig 2.17. Palais de l’Industrie. A. Barrault, G. Bridel, M. Viel. 1855. Structural axonometrics. Note the transverse connection between the pairs of columns at the head, half-way up and at the foot at ground level. You can see the intermediate floor of the side gallery built with girders and columns with rigid joints. Longitudinally, the columns are connected via trusses that in turn are joined by rigid connections. [Source: Ref (305) Vierendeel, Arthur]

diate floor itself contributed to absorbing the thrusts of the side arches (Fig 2.17 and Fig 2.18). In terms of the whole structure’s longitudinal stability, this was guaranteed through the use of similar side vaults to those used longitudinally, which sprang from pairs of columns rigidly connected and which also had an intermediate floor, as well as through the placement of longitudinal portal frames with quarter-circle connections (Fig 2.14 and Fig 2.17). We can therefore see that the building concept involved a self-supporting iron structure that had perfect horizontal stability, while the perimeter building walls would only be enclosing elements. In this way, the outer twin columns were also elements that would act as buttresses to the perimeter walls. These walls were 1 metre thick, 18 metres high and were

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Fig 2.18. Palais de l’Industrie. 1855. Connecting area between the central and the side vaults. [Source: Ref (305) Vierendeel, Arthur]

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bolted to the columns at various heights. There is documentary evidence of the efficiency of these buttresses which would become clear during construction; given the delays in assembling the metal structure, the walls were built without stabilisation, which led to several sections being out of plumb [Ref (92) Barrault, Alexis]. Note that the transverse walls were placed at considerable distance in some cases, so that the stiffness between walls would be deficient in some areas. Nevertheless, once the iron columns had been joined to the masonry walls, a synergy would be generated in the resistance of the horizontal forces.

The creator of the building himself, Alexis Barrault, alludes to other pathologies present in the building in his publication in 1857 “Le Palais de l´Industrie et ses annexes: description raisonnée du système de construction” [Ref (92) Barrault, Alexis], though he does not confirm anything in this respect.

Regarding issues derived from structural movements caused by thermal variations, there is no documentary evidence of any pathologies stemming from the differential expansion of the iron structures connected to and enclosed between the stone masonry perimeter walls.

“The skylight had no provision in any of the roofs for ventilation at the top; and the want of this was one of the most serious structural drawbacks to the Exhibition of 1855. […] The defects of ventilation were in vain attempted to be remedied by artificial or forced ventilation during the Exhibition period”. [Ref (233) Mallet, Robert]

We can estimate the ∆Tª that the structure underwent at around 30°C, since a significant greenhouse effect occurred in the building, according to Robert Mallet:

On the other hand, it is likely that there was direct solar radiation on several areas of the longitudinal structure during a large part of the day due to the deck glazing. Under these conditions, the theoretical variation in length of an iron bar 250 metres long (the length of the building) would be 9 cm. This would mean each of the end columns being 4.5 cm out of plumb at the height of the first floor of the gallery. This floor had a height above ground level of 7.74 metres, which would give us a very high local offset from a true vertical line, with a height (h) / offset ratio of h / 172.

Fig 2.19. Palais de l’Industrie. Assembling the central arches with sliding scaffolding. Note that the side arches were erected first, together with the intermediate floor and the longitudinal intermediate galleries, which all together would counteract the thrusts of the central vault arches and stabilise the structure transversely against the horizontal forces. [Source: its creators]

Nevertheless, as mentioned earlier, there is no documentary evidence of any column being significantly out of plumb, as was the case with the Crystal Palace in London. The fact that the metal structure had been connected to the building’s longitudinal stone walls, together with the stiffness offered by the floors on their plane and the building’s own rigidity, would probably have contributed to reducing the risk of columns being out of plumb by converting the displacement into strain on the structural elements. On the other hand, it is likely that the building assembly would not have been carried out at an extreme atmospheric temperature, which would reduce the extent of expansion and therefore strain. In any case, we can deduce that while the original idea for the building seems to have been a self-supporting iron structure with an ashlar masonry enclosure, in terms of thermal expansion it seems that the perimeter walls would be contributing to ensure the columns were not significantly out of plumb. What is more, if the vertical enclosure had been made of glass, as in the case of the Crystal Palace, the greenhouse effect and even direct radiation on the structure would have been intensified, thus accentuating the phenomenon. Conversely, there is evidence of water seepage in the decks due to the iron structure’s thermal movement. If you look at the longitudinal section (Fig 2.14), you will see that, unlike the perimeter galleries, the vaults along the building are not surrounded by masonry walls that could partly restrict movement. Furthermore, the whole vault is enclosed in glass, thus exposing the structure to direct solar radiation. Robert Mallet makes the following statement:

Fig 2.20. Palais de l’Industrie. Dismantling carried out in 1897. Note that the opposite process to assembly was followed: the arches from the central nave were first dismantled, then the arches from the side and intermediate naves, which all together counteracted the thrusts from the central nave. [Source: Bibliothèque Nationale de France]

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“Accordingly, in the Palais de l’Industrie of 1855, M. Barrault tells us that under the bright sun of Paris the expansion of this building was sufficient to break glass and produce leakage. […] Such, however, is the great vice of the pure iron and glass columnar structure, in great unbroken lengths. Such distortions are a source of danger never to be neglected, because their precise values and conditions, in such complex combinations of framing, can never be exactly determined”. [Ref (233) Mallet, Robert] Robert Mallet goes on to say: “To meet the evil there is but one method, that pointed out and recommended by M. Barrault, namely, to subdivide all right-lined continuations in iron, cutting them up into

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separate short lengths, without abutting faces, though still connected by such ingenious arrangements as shall preserve at those points, staunchness or the other conditions required of the structure”. [Ref (233) Mallet, Robert]

After the building had been erected and various pathologies detected, Barrault even advised against glass decks for large spans: “The three large building decks also have their drawbacks. While they are equipped with enough solidity, these decks are subject to movements and vibrations which in principle are irrelevant for safety issues, but which could damage the sealing elements. This occurs in particular with iron decks, where the effects of expansion are considerable. We believe that the most appropriate span for glass decks is between 15 and 20 metres, and in those buildings with inside support, we could take advantage of these to drain the water from the deck. If metal sheets, which are not as delicate as glass, are used for the overlay, then large spans would be more advantageous.” [Ref (92) Barrault, Alexis]

He therefore suggested joining the building’s joists with connections that allowed each one free movement. This was a proposal for improvement which, as can be seen in the planimetry, was not applied to the building (Fig 2.21).

After the erection of the Crystal Palace in London, we can see how the issue of thermal movements in metal structures arises again, together with its associated pathologies. Beyond the huge achievement of having attained a diaphanous space of such a size with a novel structural design in iron, one of the designer’s important contributions to the history of structural systems are precisely the reflections he made after the building was erected, as well as his observation of the aforementioned faults. The appearance of the concept of the expansion joint and its inclusion in a technical text are especially relevant.

2.1.1.3. The controversy surrounding the span record Sigfried Giedion makes the following statement in his classic book on the history of modern architecture “Space, Time and Architecture”: “The Palais de l’Industrie (from the Exposition Universelle of Paris in 1855) had a span of forty-eight metres. It was the widest deck attempted in that era. It represents a considerable step forward compared to that of the Crystal Palace in London, which was approximately twenty-two metres”. [Ref (176) Giedion, Sigfried] In his publication in 1857, “Le Palais de l´Industrie et ses annexes: description raisonnée du système de construction”, the designer of the building, Alexis Barrault, first describes the building and its erection and then goes on to mention the improvements that could have been implemented as possible solutions to the pathologies observed: “This is the way a 50 metre span should be built. Arches are established at distances of 10 to 12 metres, placing joists that take up the whole height of the arches every 5 metres. These joists would support two or three more levels of structure that would sustain the deck enclosure. These extra two or three levels could be very light. We would establish a system of two slightly separated arches every 100 metres along. The joists would be connected in such a way as to allow for expansion movement and the glass enclosure would be assembled in this area so as to allow for expansion without allowing water to seep.” [Ref (92) Barrault, Alexis] As you can see, this is the concept of the modern expansion joint definitively brought to life through fragmentation of the structure, which Barrault generously establishes at 100 metres. CHAPTER 2

EXPOSICIONES UNIVERSALES.indb 80-81

Fig 2.21. Palais de l’Industrie. 1855. Joint between joists and arches. Note the design of the rigid connection with absolutely no clearance that enables the horizontal displacement of the joists. [Source: Ref (305) Vierendeel, Arthur]

We have to take issue with professor Giedion on that point. According to the article published in the February issue in 1856, page 19, of the prestigious publication of French engineering “Nouvelles Annales de la Construction”: “Works on the Palais de l’Industrie commenced in February of 1853 and finished in May 1855, with the exception of a few minor details”. [Ref (38) Nouvelles Annales] On the other hand, there is an article titled “Description of the Iron Roof, in One Span, over the Joint Railway Station, New Street Birmingham” published in “Minutes of the Proceedings of the Institution of Civil Engineers”, page 251, the author of which is Joseph Phillips [Ref (264) Phillips, Joseph], in which the structure and process used in the construction of the New Street Station in Birmingham are described. This article is dated 30th January 1855, thus leading to the conclusion that the station had already been built at that date. According to these documents, therefore, the New Street Station in Birmingham (Fig 2.4 to Fig 2.7) with a span of 212 feet (64.62 m) was finished at least in January 1855, while the Palais de l’Industrie with a span of 48 metres would be completed in May 1855.

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Moreover, the following is claimed in the aforementioned article: “One of the principal points to which attention should be directed in the roof (of the New Street Station at Birmingham) is its great span of 212 feet (64.62 m), the largest hitherto attempted; the nearest to it being the roof of 150 feet (45.72 m) span, erected by Mr. Turner, of Dublin, at the Lime-street station, Liverpool.” [Ref (264) Phillips, Joseph] In short, these elements demonstrate that the Palais de l’Industrie from the Exposition Universelle of Paris held in 1855, with a span of 48 metres, was no record-holder in that respect, since New Street Station in Birmingham with its span of 64.62 metres, would have been finished some months earlier. Nevertheless, it is not its exact dating, nor breaking a world record in span which would determine the importance of the Palais de l’Industrie, but rather its novel metal structural system and the reflections made by its creator on the pathologies it developed. These reflections would be used in future building experiences. The Palais de l’Industrie would be the seed for the large machine galleries of the 19th century which would culminate with that of Paris in 1889. Additionally, the Palais de l’Industrie would be used in future exhibitions until its demolition in 1900 when it was replaced by the Grand Palais.

2.1.2 Neutralising thrusts in the metal arch and the Galerie des Machines in the Exposition Universelle of Paris in 1867 A new Exposition Universelle was held in Paris in 1867. To mark the occasion, a main building named the Palais de l’Exposition Universelle was erected in 1867. The building would be designed by the engineer Frédéric Le Play, with the collaboration of J.M. Krantz as project manager and the engineer Gustave Eiffel. To a large extent, its originality lay in the shape of the plan, an ellipsis with a major axis measuring 490 metres and a minor axis of 380 metres. It was made up of seven concentric naves, each of which housed a different exhibition theme (Fig 2.22 to Fig 2.25). Transverse corridors divided the ellipsis into sectors, so that each one was allocated to a different country exhibiting there.

Fig 2.23. Palais de l’Exposition Universelle of Paris in 1867. Frédéric Le Play. [Source: Ref (223) Lemoine, Bertrand]

Fig 2.22. Palais de l’Exposition Universelle of Paris in 1867 in a view from the period. Frédéric Le Play. [Source: Ref (267) Picon, Antoine]

The largest vault in the building, called the Galerie des Machines, had a high level of structural interest (Fig 2.25). It was a space with a span of 35 metres measured at the column axes. The structural idea was to use an arch to achieve this span and absorb the thrusts inherent to this typology while avoiding using any ties that were visible on the inside. Up until then, this detail had been resolved in different ways. The following are cited as examples: -The previously described Palais de l’Industrie of 1855 (Fig 2.13). As explained earlier, this building made use of counteracting side arches that had an intermediate level and pairs of cast-iron columns stiffly joined at the bases, half-way up and at the top, thus forming an ensemble of considerable lateral rigidity to counteract the thrusts of the central arches.

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Fig 2.25. Palais de l’Exposition Universelle of Paris, 1867. Cross-section. Note at the bottom the numbering of the different naves which made up the building. The Galerie des Machines was number 2. [Source: Ref (188) Hanninger, Anton]

- In the case of the Gare de l’Est in Paris (Fig 2.26), built in 1852 by François Duquesney, the thrusts were neutralised through the use of inner ties. In this case, a hybrid structural system was employed which combined a system of cables based on an evolved Polonceau system, with a pointed curved truss. It had a span of 29.7 metres. - Built in 1863 by the German engineer Johann Wilhelm Schwedler, the Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin (Fig 2.27 to Fig 2.29 and Fig 2.63 to Fig 2.66) was designed with twelve three-hinged, X-shaped arches and a span of 32.95 metres. In this case, the thrusts were contained through masonry buttresses. For the 1867 Galerie des Machines, a system made up of an arch rigidly joined to two columns was designed. The inside tie had disappeared.

Fig 2.24. Palais de l’Exposition Universelle of Paris, 1867. Plan. [Source: Ref (188) Hanninger, Anton]

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Fig 2.26. Gare de l’Est in Paris. François Duquesney. 1852. [Source: Ref (240) Meeks, Carroll L.V.]

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Fig 2.27. Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin. Johann Wilhelm Schwedler. 1863. [Source: Ref (181) Gössel, Peter]

Fig 2.28. (Below left) Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin. Structural diagram of the deck. Note the buttresses. [Source: Ref (305) Vierendeel, Arthur] Fig 2.29. (Below right) Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin. Masonry walls with buttresses. [Source: Ref (305) Vierendeel, Arthur]

The columns reached up over the arches and had a type of “tie” between them made up of two pieces (Fig 2.30 and Fig 2.31). In this way, no tie could be seen from the inside of the building. This structural element was placed at distances of 12.27, 15 and 15.333 metres measured at the axes, according to the area of the ellipsis. Unlike the 1855 Galerie des Machines in which the arches were made of wrought iron and the columns cast-iron, in this case tubular wrought iron columns and arches in the same material were used. Additionally, the columns were joined at the foundations to the structure of the neighbouring Galleries (1 and 3) through each of the metal tie beams (Fig 2.32 to Fig 2.34). The arches of different portal frames were connected with H-joists which were rigidly joined to the arches.

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Fig 2.30. Axonometrics of the Galerie des Machines. Paris 1867. Structural perspective. Note the box sections of the standard column type corresponding to the lower and upper areas with

inside reinforcement. Also note the zinc pipe inside the columns for draining rain water. [Source: Ref (305) Vierendeel, Arthur]

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Fig 2.31. (Opposite page) Galerie des Machines. Paris 1867. Elevation of the standard portal type. The upper group of details corresponds to cross-sections of the arch. Said arch was made up of two vertical sheets 80 cm deep, separated by 65 cm and linked at regular intervals. Note the upper left-hand detail that represents the join between arch and joists. The lower group of details corresponds to column cross-sections at various heights. The rain water was also channelled through the inside of the arch, a solution that was used relatively frequently in this period. [Source: Ref (188) Hanninger, Anton]

Regarding this typology, it should be pointed out that it was not an integral solution in which one tie absorbed the whole thrust and converted it into tension. Conversely, the outer pieces transformed the arch thrust into bending on the columns; consequently, part of this thrust would be channelled through the side galleries built with portal frames with rigid quarter-circle connections. Finally, a part of this thrust would be transmitted to the foundations. No foundation ties, which could absorb this thrust by joining the columns of the large nave, were used. Instead, several tie beams were used to link the foundations of the two large columns in the main nave with that of the neighbouring columns (Fig 2.32 to Fig 2.34).

Fig 2.32. Foundation base of the columns in the Galerie des Machines. Note the metal tie beams that join the foundation of these columns with those from the adjacent naves 1 and 3. [Source: Ref (51) Nouvelles Annales]

Fig 2.33. Nave number 3. Cross-section. Note the rigid wrought iron portal frames with quarter-circle connections, and the foundation tie beams that

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link the columns in the main nave to the adjacent galleries [Source: Ref (188) Hanninger, Anton]

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Regarding the other naves in the building, naves 4 and 5 had a span of 23 metres each and 6 and 7 had spans of 15 and 8.5 metres respectively. They were made with trusses, with naves 4, 5 and 6 having Polonceau trusses with double king posts (Fig 2.37 and Fig 2.38). This structural system had been invented in 1837 by Camille Polonceau (Fig 2.39), its use becoming popular both in France and England in the ‘40s and ‘50s of the 19th century. Thus, none of these naves was novel in terms of its structural typology, nor in the spans attained, since it was in 1852 when the engineer Eugène Flachat had already erected the Gare Montparnasse in Paris, using Polonceau trusses with a 40-metre span (Fig 2.40). Nevertheless, it is clear that the lightness of the new material fostered its technological image.

Fig 2.34. Nave number 1. Cross-section. Note the tie beams that join the foundations of the two large columns in the main nave with that of the columns in bordering naves 1 and 3. Note that both naves 1 and 3 have rigid wrought iron portal frames with quarter-circle connections which contribute to containing the thrusts from the main nave. [Source: Ref (188) Hanninger, Anton]

Fig 2.35. Palais de l’Exposition Universelle of Paris 1867 in a period engraving. Note nave 1 built with rigid portal frames with quarter-circle connections and nave 2, or the Galerie des Machines. [Source: Ref (272) Ragon, Michel]

Fig 2.37. Inside view of naves 4 and 5 in a period engraving, made with Polonceau trusses with a 23-metre span. [Source: Ref (239) Mattie, Erik]

Fig 2.36. Palais de l’Exposition Universelle of Paris 1867. Simplified approximation to the deformation of the structure. [Source: López César, Isaac]

Fig 2.38. Cross-section of naves 4 and 5 made with Polonceau trusses with spans of 23 metres. [Source: Ref (188) Hanninger, Anton]

By inputting a simplified plane model into a programme that uses the matrix method, we can get an approximation to the deformation of the structure (Fig 2.36). The behaviour described above can be seen: the outside pieces that were arranged as a kind of “tie” transform the arch thrusts into bending over the columns. Said bending forces the horizontal displacement of the side portal frames, which end up contributing to the containment of the arch thrusts. We can therefore say that, together with the adjacent galleries (1 and 3), the Galerie des Machines (2) makes up a structural whole.

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2.1.3 A new portal frame typology for large spans: The Galerie des Machines from the Exposition Universelle of Paris in 1878

Fig 2.41. (Above) Palais de l’Industrie in Paris 1878. Henri de Dion. Period engraving. [Source: Ref (86) Baculo, A. / Gallo, S. / Mangore, M.] Fig 2.42. (Below) Palais de l’Industrie. Paris 1878. Plan. [Source: Ref (86) Baculo, A. / Gallo, S. / Mangore, M.]

In short, the main contribution of the Galerie des Machines in the Exposition Universelle of Paris in 1867 to the history of structural construction systems is that is constitutes a typological innovation that represents progress and a new experience in the development of metal structures. This innovation is based on the use of the metal arch in which the inner tie is substituted by a kind of outside “tie”. This resource is not an integral solution in which a tie may absorb all the thrusts in the form of tension, but rather they are transformed into bending on the columns, thus channelling part of the thrust through the side galleries made with rigid portal frames, and the foundations. Therefore, the main nave and the two adjacent naves make up a structural whole.

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A new Expo was held in Paris in 1878. The Palais de l’Industrie was built to mark the occasion, including the Galerie des Machines, a work by the engineer Henri de Dion. This building is significant because of its role in the development of iron decks, and as the immediate precedent to the Galerie des Machines in the 1889 Paris Expo. The 1878 Palais de l’Industrie was made up of various naves with a cross-section clearly inspired by the World Expo building of 1867. Nevertheless, the elliptic plan was abandoned in this case for a building with longitudinal naves (Fig 2.41 to Fig 2.43). The building’s structural interest resides in the main nave, called the Galerie des Machines; with a length of 645 metres and a span of 35 metres measured from the inner face of the columns, it was as big as the Galerie from 1867 (Fig 2.44 and Fig 2.45).

Fig 2.39. (Above) Polonceau system. Camille Polonceau. 1837. [Source: Ref (237) Marrey, Bernard / Chemetov, Paul]

Fig 2.40. (Below) Gare Montparnasse. Eugène Flachat. 1852. Structure made with Polonceau trusses with 40-metre spans. [Source: Ref (240) Meeks, Carroll L.V.]

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Fig 2.43. (Above) Palais de l’Industrie. Paris 1878. Cross-section. Note the main nave called the Galerie des Machines. The other naves were made with Polonceau trusses which, as explained earlier, were nothing new for that time. [Source: Ref (86) Baculo, A. / Gallo, S. / Mangore, M.]

Fig 2.44. Galerie des Machines in the Palais de l’Industrie of Paris 1878. [Source: Ref (176) Giedion, Sigfried]

The engineer Henri de Dion had spent years studying the different typologies of metal portal frames for large spans. In this case, he opted for a portal frame made of two box columns assembled with riveted iron sheets and rigidly joined to the foundations. A truss sprang from the columns, gabled along the extrados and with a diminished ogival arch curve along the intrados. The portal frames were arranged with a distance of 15 metres between axes. 17 Pratt trusses lay on the portal frames. In contrast to earlier buildings, a glass enclosure was not used with the deck, but rather metal sheets.

2.1.3.1. Historical precedents A review of historical precedents will allow us to determine to what degree this structure was novel. In this sense, we should make particular reference to two buildings: -The Galerie des Machines from the Exposition Universelle in Paris 1867 (Fig 2.25) with a span of 35 metres of which de Dion was undoubtedly aware, is the precedent created in

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Fig 2.45. (Opposite page above) Galerie des Machines. Paris 1878. Elevation of the portal frame and structural details. The cross-section of the columns was 400 mm deep, with a variation in width between 800 mm at the base and 1,300 at the head. [Source: Ref (25) Nouvelles Annales]

Fig 2.46. (Opposite page below) Galerie des Machines of the Palais de l’Industrie in Paris 1878. Cross-sections of the various elements that make up the portal frame. Note the cross-sections along the tubular columns in particular (K-O and H); the cross-section along the chords (A-A); along the vertical members (d) and the diagonal members (a and b). [Source: Ref (305) Vierendeel, Arthur]

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the previous World Expo. What the Galerie des Machines of 1878 managed to achieve was to equal the span of its 1867 predecessor while eliminating the outside “ties”, thanks to the use of the trussed portal frame and the vertical prolongation of the same. The tubular columns of variable cross-section are similar in both buildings.

In any case, and independently of its influences, H. de Dion’s contribution through the Galerie des Machines of 1878 consists in the creation of a new portal frame typology for large spans, and demonstrating its correct functioning for a 35-metre span. After erection, various load tests were carried out on some of the portal frames, loading them with 20 tonnes in the peak without any problems of resistance, while a deflection of around 20 mm was registered; this would mean a low deflection/span proportion of 1/1750 that validates the system.

- St. Pancras Station in London (Fig 2.47) built in 1868 by William H. Barlow and Ordish. With a span of 73 metres, it was the record-holder for span at that time, and therefore a landmark structure. However, it does have a different structural typology, given that it is a trussed fixed arch. Fig 2.49. Galerie des Machines from the Palais de l’Industrie in Paris 1878. Photograph of the inside of the building during the exhibition. [Source: its creators]

Fig 2.47. St. Pancras Station in London. William H. Barlow and Ordish. Cross-section. [Source: Ref (267) Picon, Antoine]

2.1.3.2. The solution to the thermal problem? The Galerie des Machines of 1878 was 645 metres long. If we consider an illustrative temperature variation of 25°C (bearing in mind the fact that the deck was not glazed in this case), an iron bar 645 m long would suffer a theoretical expansion of 19.4 cm. This would mean an approximate displacement of 9.7 cm towards each side of the building. For a height of 16 metres (height of the vertex between the inclined plane of the deck and the façade) we would get a ratio of height (h) / offset from the true vertical line of h / 165 , which would be excessive.

Fig 2.48. Galerie des Machines from the Palais de l’Industrie in Paris 1878. Period engraving. [Source: Ref (239) Mattie, Erik]

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With the aim of avoiding this problem, de Dion implemented the following expansion system: every 60 metres, that is, every four deck spans, the joint apertures of the lattice joists with the corresponding portal frame were oval, with bolts placed in these apertures with sufficient clearance to avoid any friction (Fig 2.50 and Fig 2.51). The expansion movement of an iron bar 60 metres long for a temperature variation of 25°C is 18 mm in total, that is, 9 mm for each end. Therefore, 9 mm would be the distance that each pin would move in the oval aperture. We can see that the movement of the aperture is sufficient according to the

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joint dimensions, as is the clearance between the latticed joist and the portal frame, so in theory, the detail should have functioned correctly. Nevertheless, in his book “La construction architecturale en fonte, fer et acier” published in 1902, Arthur Vierendeel states that the thermal movements would have been transferred from joist to joist in spite of these theoretical predictions due to friction, and it was made clear that the columns at the ends of the building were out of plumb to such an extent that they even managed to “dislocate the masonry foundations of the ends.” [Ref (305) Vierendeel, Arthur]

2.1.4 Origin and evolution of the metal arch: The Galerie des Machines from the Exposition Universelle of Paris 1889

In any case, whether the detail had functioned correctly or not, the important thing is that the phenomenon of thermal movement in metal structures had been taken into consideration and the necessary structural details had been adopted to avoid the pathologies associated with this. Bear in mind that more than two decades had gone by since the first problems regarding thermal movement had appeared in large metal building structures, as was the case of the Crystal Palace in London in 1851 and the Palais de L’Industrie in Paris in 1855. In this sense, we see how the transmission of the experiences acquired by technicians from one building to another was complex, slow and not always effective.

To celebrate the centennial of the French Revolution in 1889, a new World Expo was held in Paris. This Expo would be the most important manifestation of the 19th century in terms of structural development, marking the zenith of iron architecture. This would be the conclusion of a group of Expos directly linked to the technological development of metal structures in Europe. We will have to wait until the second half of the 20th century to witness a new series of World Expos that could reach a similar technological level, in structural terms, to that first series of Expos.

In short, we can state that the main contributions of this building were: -The introduction of a new portal frame typology for large spans and the demonstration of its correct functioning for a span of 35 metres, as the load tests carried out prove. -After the pathologies caused by the thermal movements detected in the Crystal Palace in London and in the Palais de l’Industrie from the Expo in Paris held in 1855, a system enabling the free expansion movement of the joists by using oval apertures every 60 metres in the lattice joist-portal frame joints. While it appears that the detail must not have worked correctly due to friction, the principal step forward was the realization of the importance of thermal phenomena in large metal building structures and the implementation of systems to avoid the pathologies associated with these. In particular, the use of this expansion system has carried on up to the present day.

Fig 2.50. (Left) detail of the joint between the joist and portal frame. Note the oval apertures to allow for the joists’ thermal movement. [Source (25) Nouvelles Annales] Fig 2.51. (Right) Detail of the joist-portal frame joint. Note the oval apertures in the joint on the right. This detail would be used every 60 metres. [Source (25) Nouvelles Annales]

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Fig 2.52. General view of the Exposition Universelle in 1889. Note the Eifffel Tower as the monumental entrance and the Palais des Machines or Galerie des Machines at the back. [Source: its creators]

Two main constructions were erected for this Expo in the Champs de Mars: the building known as the Galerie des Machines, named at the time the “Palais des Machines”, and the 300-metre Tower designed by Gustave Eiffel. The Galerie des Machines in the Exposition Universelle of Paris in 1889 was designed by the architect Ferdinand Dutert and the engineer Victor Contamin (Fig 2.53 to Fig 2.55). It had a central nave covered by three-hinged iron arches with a span of 110.6 metres measured at the axes of the springer hinges. At that time, it was the building with the longest span in the world and one of the milestones in the development of metal structure technology.

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2.1.4.1. Precedents of the metal arch The first applications of the metal arch can be found in the erection of bridges. Thus, in 1777, T.F. Pritchard built the first iron bridge, near Coalbrookdale over the River Severn. It was made up of cast-iron fixed arches and had a span of 30.5 metres (Fig 1.3 and Fig 1.4). In 1796, Tom Paine built a cast-iron bridge over the River Wear in Sunderland, made up of a diminished fixed arch with the considerable span of 71.9 metres (Fig 1.5).

Fig 2.55. Galerie des Machines, Paris 1889. Photographed before the Expo was set up. [Source: Ref (141) Dunlop, Beth / Hector, Denis]

The structural achievements in bridge building would have a notable influence on the erection of large-span decks. In this way, the aforementioned Palais de lâ&#x20AC;&#x2122;Industrie that had been designed by M.M. Barrault and Bridel (Fig 2.8 to Fig 2.20) was built for the 1855 Exposition Universelle in Paris, its central vault having a span of 48 metres and two side vaults with spans of 24 metres, made with hingeless, wrought iron trussed arches.

Fig 2.53. Galerie des Machines from the Paris Expo in 1889. Ferdinand Dutert and Victor Contamin. Main faĂ§ade under construction. [Source: Ref (306) Watson, William]

Fig 2.54. Galerie des Machines from the Paris Expo in 1889. Ferdinand Dutert and Victor Contamin. Photograph of the side galleries. [Source: Ref (141) Dunlop, Beth / Hector, Denis]

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100

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However, the greatest building structure made with metal arches to predate the Galerie des Machines of 1889 was St. Pancras Station in London, which is still in use in the present day, albeit with modifications (Fig 2.47 and Fig 2.56 to Fig 2.59). Designed by William H. Barlow in 1868, the covered space with a span of 73 metres is impressive. It was the building with the biggest span in the world. The structure of St. Pancras Station was made up of iron X-shaped arches with a slightly pointed, gothic-inspired shape. In this case, hingeless arches were arranged with a distance of 9 metres between axes. They sprang from large masonry pilasters with rigid connections. The thrusts were absorbed by iron bars with a diameter of 75 mm which connected the arch springers under the station platforms. These hingeless arches are statically indeterminate, with a degree of external statical indeterminacy equal to three. The advantage of the fixed arch is that, in the event of not adapting exactly to the anti-funicular shape, the bending developed is lower than with twoor three-hinged arches. However, the hingeless arch is the most statically indeterminate, and therefore has the greatest strain derived from thermal variations and settlement. This strain can occasionally be greater than that generated by bending.

Fig 2.56. St. Pancras Station in London. William H. Barlow. 1868. Fixed arch with a span of 73 metres. [Source: Ref (267) Picon, Antoine] Fig 2.57. St. Pancras Station in London. Cross-section and longitudinal section. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.58. St. Pancras Station in London. Detail of the rigid joint of the arch apex. [Source: Ref (80) Araujo, Ramรณn]

Fig 2.59. St. Pancras Station in London. Photograph of the construction with continuous scaffolding under the arch. Note the arch assembly in small sections by riveting onsite. [Source: Ref (267) Picon, Antoine]

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EXPOSICIONES UNIVERSALES.indb 102-103

102

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The incorporation of hinges in the springers lowers the degree of external statical indeterminacy, while simultaneously avoiding the transmission of bending moments to the foundations. Thus, two-hinged arches came into being.

The three-hinged arch has various advantages. In the first place, it is statically determinate or isostatic, which facilitates the calculation since the reactions in the springers and the forces transmitted to the apex hinge can be easily obtained. In addition, no bending moments are transmitted to the foundations. Settlements in the supports or thermal expansion and contraction movements that the arch may suffer do not lead to large strain increases in its members, as these can re-align themselves by turning at the hinges. On the other hand, having a hinge in the apex makes the assembly of medium-span structures easier.

In this sense, there are two bridges designed by Gustave Eiffel that are worthy of mention, and which are both structural milestones. Firstly, the Ponte Maria Pia over the River Douro in Porto (Fig 3.26 and Fig 3.27); erected in 1875, it had a span of 160 metres measured at the hinges. Secondly, the Garabit Viaduct designed in 1878 was made up of a parabolic arch with a span of 166 metres (Fig 3.28 to Fig 3.30). Both are two-hinged arches with a variable depth as well as variable width; this aspect provides a greater moment arm in the supports with regards to withstanding the horizontal forces from wind. As a matter of interest, we should mention Gustave Eiffel’s Project for the 1878 Exposition Universelle of Paris (Fig 2.60). He proposed a bridge made up of a two-hinged arch with a span of 150 metres, over which a building was to be erected, a nod to the tradition of some Parisian bridges which had buildings on the top (Fig 2.61 and Fig 2.62). In the end, it was never built.

The German engineer Johann Wilhelm Schwedler is the creator of various constructions made with three-hinged arches. The first building structure designed with this typology is the aforementioned Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin, made in 1863 by Schwedler (Fig 2.27 to Fig 2.29 and Fig 2.63 to Fig 2.66). It was a structure made up of twelve pointed, X-shaped, three-hinged arches with a span of 32.95 metres. As explained earlier, in this case the arch thrusts were absorbed by masonry buttresses (Fig 2.28 to Fig 2.29).

Fig 2.60. Gustave Eiffel’s Project for a bridge with a building on top for the Exposition Universelle of Paris in 1878. [Source: Ref (223) Lemoine, Bertrand]

Fig 2.61. The Pont Marie over the River Seine in Paris. Painting from the 18th century. [Source: Ref (155) Fernández Troyano, Leonardo]

Fig 2.62. The Pont Notre-Dame over the River Seine in Paris. Painting from the 18th century. [Source: Ref (155) Fernández Troyano, Leonardo]

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Fig 2.63. Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin. Johann Wilhelm Schwedler. 1863. Note

the assembly of the three-hinged arches through rotation. [Source: Ref (181) Gössel, Peter / Leuthäuser, Gabriele]

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In terms of span, the previous example was followed by the former Berlin East Railway Station (Fig 2.67 to Fig 2.69). Built by Johann Wilhelm Schwedler in 1866, it had a span of 36.25 metres. Masonry buttresses were used to neutralise the arch thrusts in this case as well. There is a special similarity between this example and the arch curve in the Galerie des Machines of 1889.

Fig 2.64. (Above) Retortenhaus or Great Hall of the Imperial Continental Gas Association in Berlin. Cross-section. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.67. Former Berlin East railway station railway station. Johann Wilhelm Schwedler. 1866. [Source: Ref (305) Vierendeel, Arthur] Fig 2.66. Retortenhaus. Detail of the hinged joint at the base of the arch. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.65. Retortenhaus. Detail of the apex hinge of the arch. Note that the joint between both semi-arches is only riveted in the upper area, thus enabling the turning movement. [Source: Ref (305) Vierendeel, Arthur]

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Fig 2.68. Former Berlin East railway station. Hinged joint at the base of the arch. [Source: Ref (305) Vierendeel, Arthur]

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Fig 2.69. Former Berlin East railway station. Apex hinge in the arches. [Source: Ref (305) Vierendeel, Arthur]

The Berlin Alexanderplatz railway station was also made with three-hinged arches with a span of 37.1 metres. It was built in 1880 by Johann Eduard Jacobsthal (Fig 2.70). The 1887 Frankfurt am Main railway station is also the work of J.W. Schwedler; with five three-hinged arches, the central three have spans of 55.75 metres each (Fig 2.71 to Fig 2.73).

Fig 2.71. Frankfurt am Main railway station. J.W. Schwedler. 1887. [Source: its creators]

Fig 2.72. (Left) Frankfurt am Main railway station. J.W. Schwedler. 1887. [Source: its creators] Fig 2.73. (Right) Frankfurt am Main railway station. J.W. Schwedler. 1887. Hinge joint [Source: its creators]

Lastly, mention needs to be made of the Palmenhaus der Flora in Charlottenburg in Berlin (Fig 2.74 to Fig 2.76). It was a winter garden made with three-hinged arches with 23.75-metres spans measured at the hinge axes. This structure is not very well-known. It was published in 1873 in issue 68 of the journal â&#x20AC;&#x153;Deutsche Buzeitungâ&#x20AC;? [Ref (16) Deutsche Bauzeitung]. In spite of not having an especially significant span, it has striking similarities with the 1889 Galerie des Machines, both in terms of the curve of the three-hinged arch and in the use of a variable depth. Nevertheless, it is difficult to ascertain whether the creators of the Galerie des Machines had any knowledge of this work. In any case, the aforementioned examples serve to demonstrate the widespread use of the three-hinged arch in the construction of large span decks in 1889. Fig 2.70. Berlin Alexanderplatz railway station. Eduard Jacobsthal. 1880. [Source: Ref (240) Meeks, Carroll Louis]

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Fig 2.76. Palmenhaus der Flora in Charlottemburg, Berlin. Detail of the apex hinge. [Source: Ref (16) Deutsche Bauzeitung]

2.1.4.2. Main characteristics of the structure The 1889 Palais des Machines or Galerie des Machines was made up of a central nave with a span of 110.6 metres, measured at the hinge axes, flanked by two side naves with spans of 16.85 metres, measured from the hinge axis to the outer column axis. The building therefore had a width of 144.3 metres (Fig 2.77 to Fig 2.81). Fig 2.77. 1889 Palais des Machines or Galerie des Machines. Ferdinand Dutert and Victor Contamin. Plan. [Source: Ref (193) HĂŠnard, EugĂ¨ne]

The central nave was designed with twenty three-hinged iron arches, with two hinges in the springers and the third in the apex. These arches were arranged with a distance between axes of 21.5 metres, with the exception of the end arches which were slightly different and had a distance between axes of 25.3 metres. The distance between the axes of the central arches was 26.4 metres. Therefore, the total length of the building between the axes of the end arches was 421 metres. The height of the arch extrados was 46.67 metres.

Fig 2.74. Palmenhaus der Flora in Charlottenburg, Berlin. Elevation of the three-hinged arch. Fragment of structure plan. Fragment of longitudinal section. [Source: Ref (16) Deutsche Bauzeitung]

Fig 2.75. Palmenhaus der Flora in Charlottemburg, Berlin. Detail of the springer hinges. [Source: Ref (16) Deutsche Bauzeitung]

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Fig 2.81. Galerie des Machines, 1889. Cross-sectional perspective. The arch depth was variable, being 3.7 metres at the base and decreasing to 3.15 metres at the apex. Each arch was made up of 50 panels, alternating narrow and wide panels. These measurements were varied in order to guarantee that there were vertical members to which the trusses could be attached. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.80. Galerie des Machines, 1889. Side gallery. [Source: Ref (141) Dunlop, Beth / Hector] Fig 2.78. Galerie des Machines, 1889. Expo photograph. [Source: Ref (141) Dunlop, Beth / Hector]

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Fig 2.79. Galerie des Machines, 1889. Arch springer hinges and the joint with the floor of the side galleries. [Source: Ref (141) Dunlop, Beth / Hector]

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Fig 2.82. (Previous page) Galerie des Machines. Paris, 1889. Structural exploded view. Note the four levels of the central nave structure: the three-hinged arches have a distance between axes of 21.5 metres; the trusses of variable depth with a distance between axes of 10.72 metres; the H-beams with a distance between axes of 5.37 metres; the ironwork deck bars with a distance between axes of 1.78 metres. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.83. Galerie des Machines. 1889. Details of the arch springer hinges in the main nave. [Source: Ref (192) Hénard, Eugène] Fig 2.84. (Below) Galerie des Machines. 1889. Details of the apex hinge of the arches in the main nave. Note the arch cross-section on the left. [Source: Ref (193) Hénard, Eugène]

Wrought iron was employed in the construction of the Galerie des Machines, cast-iron being almost completely abandoned. In this sense, numerous bibliographic sources maintain that this structure would have been made with steel rather than iron. Initially, the creators of this building were thinking about using steel for this structure, but in the end iron was chosen. In an article co-written in 1889, Victor Contamin and Gustave Eiffel doubtfully broach the subject of steel. They state that it has begun to be used by the engineers in bridge construction, while they refer to several tests carried out on girders over the last 10 years, with highly varied results. They also air their misgivings about which techniques would be suitable for riveting steel without compromising the resistance of the structural elements [Ref (146) Eiffel, G. / Contamin, V.]. This leads us to believe that it was the material’s relative novelty and limited structural knowledge which was behind the decision not to use steel in the Galerie des Machines or the Eiffel Tower. Nevertheless, this decision was made later, for the idea that steel would be the material of choice was even sustained in specialised journals from that time. Such is the case of the journal “Engineering”, which states in issue 3 of May 1889, page 454: “After trials made at Chattelerault it was decided to employ steel as the material of the new roof; this is the first time that metal has been used for a work of this kind.” [Ref (63) Engineering] The architect Eugène Hénard, in charge of general supervision of the building assembly, wrote the following work “Exposition Universelle de 1889. Le Palais des Machines. Notice sur l’édifice et sur la marche des travaux”, published in 1891, with a table included on page 56 with the weights of the various materials used in the building works. The following was allocated for metal construction: “ - Wrought iron (including the rivets that weigh 13,585 Kg): 12,361,595 Kg - Cast iron (including the pipework elements that weigh 5,623 Kg): 269,869 Kg - Steel: 154,846 Kg - Lead: 18,506 Kg.” [Ref (193) Hénard, Eugéne]

We therefore get the following percentages: Wrought iron: 96.5%; cast iron: 2.1%; steel: 1.2%; lead: 0.1%

In spite of the fact that all that metal would not have been used in structural elements, the difference is so obvious that we can state that it would be a structure basically made out of wrought iron. The building had eighty foundation points, forty of which corresponded to the main arches. The boring carried out revealed various stratigraphic profiles. In most cases a superficial foundation was used, but foundation with piles was necessary at twelve foundation points of the main arches (Fig 2.85 to Fig 2.87).

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Fig 2.87. Galerie des Machines. Paris 1889. Stratigraphic profile and cross-section of the pile caps and piles. Wooden piles with iron pile shoes and iron clamps were used. [Source: Ref (193) Hénard, Eugène]

The driving was carried out with the help of a steam hammer weighing 1.2 tonnes (Fig 2.88). In this sense, it should be pointed out that this system of pile driving was not new, as it had been used in the construction of bridge foundations since 1839, when James Nasmyth invented the steam hammer which would enable pile driving to be mechanised [Ref (120) Cilento, A.].

Fig 2.85. Galerie des Machines. Paris 1889. Plan in which the foundation points for the threehinged arches are indicated. The striped area shows the twelve points at which foundation with piles was used. [Source: Ref (306) Watson, William]

Fig 2.86. Galerie des Machines. Paris 1889. Plan of the standard pile caps. [Source: Ref (193) Hénard, Eugène]

The use of the three-hinged arch would be particularly suitable in this building; as mentioned earlier, the existence in this typology of potential differential settlement, derived in this case from the combination of a superficial foundation system with another, deeper one, would not cause significant increases in strain in the arch members, thanks to the fact that the hinges would allow these members to re-align.

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Fig 2.88. Galerie des Machines. Paris 1889. Pile driving with a steam hammer. [Source: Ref (193) Hénard, Eugène]

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Regarding the thrusts generated by the arches, the initial idea was to link the arch springers with underground ties, as William H. Barlow had done in 1868 with St. Pancras Station in London. However, given that the ties might interfere with the foundations of the heavy machinery on display and their transmission, it was finally decided to make the foundations in such a way as to withstand the thrusts. The thrust was therefore balanced through friction with the foundation. In this way, the architect in charge of works, Hénard, points out:

2.1.4.3. Horizontal stabilisation, thrusts and thermal issues Horizontal stabilisation was achieved longitudinally via the rigid connection of the lattice joists to the arches. In addition, the arches were also rigidly joined through the girders supporting the floor of the side galleries and the longitudinal arches of these side galleries (Fig 2.79, Fig 2.82 and Fig 2.89). The three-hinged arch itself is transversely stable.

“The arch has been considered to be isolated from the point of view of its resistance and able to withstand the whole load of the building on its own”. “I would add that the side galleries form a series of natural buttresses that contribute more effectively to the building’s lateral stability.” [Ref (193) Hénard, Eugéne] Given the building’s notable span of 110.6 metres, the thermal movements on the plane of the arches were significant. In this sense, we have already mentioned the advantage of using the three-hinged arch insofar as it allows for thermal expansion and contraction movement without significantly increasing strain in the same. In the longitudinal direction they used a method consisting in joining the longitudinal trusses every three sections, that is, every 64.5 metres, to the arches by means of bolts placed in oval holes. By using this system they could first guarantee horizontal stability in the longitudinal direction, and secondly allow for thermal movements. This system had already been used by Henri de Dion in the Galerie des Machines of 1878 (Fig 2.50 and Fig 2.51), although in that case it had not worked optimally due to friction. In the case of the Galerie des Machines of 1889, there is no documentary evidence of any pathologies due to thermal problems, leading us to conclude that the detail functioned correctly.

2.1.4.4. The controversy surrounding the span There has also been controversy surrounding the specification of the exact span of the 1889 Galerie des Machines, and it seems common ground for different authors to ascribe differing spans to this construction. Such disparity of data would seem surprising given that this building is a milestone in the History of Architecture. In the same vein, several discrepancies in bibliographic sources chronologically close to the building’s construction have also been detected. Examples of this are as follows:

Fig 2.89. Galerie des Machines. Paris 1889. Elevation of the side nave seen from the main nave. Note the arches and trusses of the floor of the side galleries. Both elements are rigidly joined to the main three-hinged arches, thus offering longitudinal stability to the structure. [Source: Ref (306) Watson, William]

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-“La Construction Moderne” includes a section of the building assembly in which the distance between the axes of the arch springer hinges is specified at 110.6 metres. [Ref (19) La Construction Moderne] - “Engineering” presents a half-section of the Galerie des Machines in which the half span of the building is specified at 55.5 metres, which would give a span of 111 metres. [Ref (78) Anon] - “Nouvelles Annales de la Construction” includes a half-section of the building which specifies a length of 55.3 metres, making the span 110.6 metres. [Ref (21) Nouvelles Annales] -In the publication “Paris Universal Exposition 1889. Civil Engineering, Public Works and Architecture” the metallic structures of the Exposition are graphically reviewed in great de121

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tail. It includes a half-section of the building with a length of 55.3 metres, making the span measured at the axes of the springer hinges to be 110.6 metres. [Ref (306) Watson, William]

than the span of the Galerie des Machines in 1889, a building with which it was trying to compete. It thus became the next world record holder for span in construction. We will cover this building in the next point.

Modern publications, among which we can find some of the classic handbooks of modern architectonic historiography, ascribe the building with spans that range from 109 to 115 metres:

After construction of the Galerie des Machines, the three-hinged arch would be used quite frequently in railway stations, with various notable examples especially in the United States. We should also highlight how the Exposition building would mark a considerable jump in attainable spans with respect to the constructions with three-hinged arches built before 1889. Subsequently, between 1891 and 1893 the Reading Station in Philadelphia (Fig 2.91 and Fig 2.92) was built by the architect F.H Kimball and the engineering company Wilson Bros. and Co. Its span was of 78.95 metres, with a significant similarity in the line of its arch to the Galerie des Machines of 1889 in the arch curve. Another example is the Broad Street Station also in Philadelphia (Fig 2.93 and Fig 2.94). It was built in 1894 by Wilson Bros. and Co. and had a span of 91.65 metres.

-Carroll L.V. Meeks. “The Railroad Station: an Architectural History”. Here the Galerie des Machines is said to have a span of 362 feet (110.33 metres). [Ref (240) Meeks, Carroll] -Donald Hoffmann states that the span is 111 metres. [Ref (202) Hoffmann, Donald] -Nikolaus Pevsner states that the building span was 109 metres. [Ref (263) Pevsner, Nikolaus] -Sigfried Giedion specifies the span to be 115 metres. [Ref (176) Giedion, Sigfried] Faced with such diversity in data, we have consulted what we consider to be the primary, and therefore most reliable, source. It is the publication called “Exposition Universelle de 1889. Le Palais des Machines. Notice sur l’édifice et sur la marche des travaux”, published in 1891 and written by Eugène Hénard. On the front cover of this work it states: “Edition accompanied by 41 figures based on original documents”. [Ref (193) Hénard, Eugéne] The editor states in the prologue of this publication that: “The present work is the carefully revised reproduction of a series of notes taken down daily during the studies and construction of the Palais des Machines. The author, Mr. Eugène Hénard, was in charge of general supervision of the work on the orders of M. Dutert, the architect of the building. The author has summarised his observations made during construction and the documentation used by him during this period. The facts that appear in the following pages and the construction details presented here are guaranteed to be absolutely authentic.” [Ref (193) Hénard, Eugéne] Bearing this in mind, said publication includes an assembly plan in which the distance between the arch springer hinges is specified. The figured length is 110.6 metres, coinciding with most of the sources consulted that are contemporary to the building. Faced with the impossibility of physically measuring the span and based on the documentation consulted, we can therefore conclude that the span of the Galerie des Machines in the Universal Exposition of 1889, measured at the axes of the hinges, was 110.6 metres.

Fig 2.90. Manufactures and Liberal Arts Building. Chicago World’s Fair 1893. [Source: Ref (109) Burnham, Daniel H.]

2.1.4.5. The metal three-hinged arch after the Gallery erection in 1889 The closest repercussion after the 1889 Galerie des Machines was undoubtedly the construction of the Manufactures and Liberal Arts Building on the occasion of the Universal Exposition held in Chicago in 1893 (Fig. 2.90). Said building was made up of three-hinged arches with a span of 112.16 metres, measured at the axes of the hinges, slightly bigger

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Fig 2.91. Reading Station in Philadelphia. F.H. Kimball. 1891-1893. Span: 78.95 metres. [Source: its creators]

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Fig 2.95. Marché aux Bestiaux in Lyon. Tony Garnier. 1909. Span: 80 metres. [Source: Ref (176) Giedion, Sigfried] Fig 2.92. Reading Station in Philadelphia. F.H. Kimball. 1891-1893. [Source: its creators]

Another paradigmatic application of the three-hinged arch in construction with a clear influence of the 1889 Galerie des Machines is the Marché aux Bestiaux cattle market in Lyon (Fig 2.95). Designed by Tony Garnier in 1909, it had a span of 80 metres. In short, we can consider that the Galerie des Machines from the Exposition Universelle in Paris in 1889 contributed to the history of structural systems in the following ways:

Fig 2.93. Broad Street Station. Philadelphia. Wilson Bros. and Co. 1894. Span: 91.65 metres. [Source: Ref (240) Meeks, Carroll Louis]

It was a highly notable technological step forward in structural terms. In spite of the three-hinged arch being a well-known typology, it was the first time such a large span had been achieved. The building set a new world record in terms of span in a building structure, reaching a span of 110.6 metres measured at the springer hinges, beating St. Pancras Station in London by more than 37 metres. The latter was built by William H. Barlow in 1868 and had a span of 73 metres, itself the previous holder of the world record for span. On the other hand, the Galerie des Machines was a structure in which cast iron was abandoned completely, and the modern use of standardised sections was consolidated: plates, L-sections or T-sections. In short, the building ultimately represents one of the highlights of iron architecture, and nowadays is considered to be one of the basic references in the history of metal structural design. As a consequence of this, the construction of the 1889 Galerie des Machines contributed to the three-hinged arch being used far more extensively in both temporal and geographical terms, and had important consequences such as a considerable increase in spans. This point constitutes one of this building’s greatest contributions; after its construction, the spans of the three-hinged arches used in building, principally serving large railway stations, doubled in length by growing from 50 to 100 metres. After the negative experiences in previous buildings, the problems of horizontal stabilisation and those related to thermal movements were resolved efficiently.

Fig 2.94. Broad Street Station. Philadelphia. Wilson Bros. and Co. 1894. [Source: Library of Congress]

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The arches of the 1889 Galerie des Machines also have the merit of reaching a significant agreement between structural needs and stylistic elements. We should point out that the arch is far from the optimal structural shape, which would be anti-funicular with distributed

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loads, that is, a parabola. In this sense, we can state that not only did it create the largest diaphanous space, but that the aesthetic concessions meant that it was created with admirable daring. Ultimately, it is a structure that manages to make significant progress in terms of span attained by building on the previous experiences described throughout these chapters. However, the most significant point is the fact that it managed to resolve two of the problems associated with the design of metal structures: horizontal stability and thermal expansion and contraction movements.

Fig 2.97. Manufactures and Liberal Arts Building. Chicago 1893. [Source: Ref (89) Bancroft, Hubert Howe]

2.1.5 The american response: the Manufactures and Liberal Arts Building from the World’s Columbian Exposition in Chicago 1893 In 1893 the World’s Columbian Exposition was held in Chicago to mark the celebration of the 400th anniversary of the arrival of Christopher Columbus in America. The previous World Expo held in Paris in 1889 had been a structural paradigm with the erection of two large milestones: the Galerie des Machines by Dutert and Contamin and the Eiffel Tower by Gustave Eiffel, holding world records in building span and height, respectively. The competitive spirit that is characteristic of the World Expos is clearly present in the Chicago Exhibition, marked by the attempt to surpass the structural achievements of Paris 1889. This fact is evident in some of the building proposals prior to the Exhibition. Thus, for example, there was a proposal for a structure with a circular plan with a diameter of 915 metres (Fig 5.23) which would be a competitor of the 1889 Galerie des Machines, as well as various proposals for towers which would be over 300 metres high and thus surpass the Eiffel Tower (Fig 3.62 to Fig 3.64). In the end, the Manufactures and Liberal Arts Building was built as a rival to the Galerie des Machines of 1889 (Fig 2.97 to Fig 2.99). This building was interesting because it was the covered structure with the largest span in the world in 1893, designed with a structural typology that was analogous to that of the Galerie des Machines from the Exposition Universelle of Paris in 1889; the three-hinged arch.

Fig 2.98. Manufactures and Liberal Arts Building. Chicago 1893. Under construction. [Source: Ref (109) Burnham, Daniel H.]

Fig 2.96. Aerial view of the World’s Columbian Exposition in Chicago 1893 in a period engraving. In the centre is the Manufactures and Liberal Arts Building. [Source: Ref (89) Bancroft, Hubert Howe]

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Fig 2.99. Manufactures and Liberal Arts Building. Chicago 1893. Under construction. [Source: Ref (109) Burnham, Daniel H.]

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As with the Galerie des Machines, different sources assign varying spans to this building, and even argue which of the two buildings had achieved the greatest span. Thus is the case of Donald Hoffmann’s article “Clear Span Rivalry: The World’s Fairs of 1889-1893”, published in “The Journal of the Society of Architectural Historians” [Ref (202) Hoffmann, Donald], in which an erroneous span is attributed to the 1889 Galerie des Machines in Paris, although its conclusion turned out to be correct in the case of the Manufactures and Liberal Arts Building in Chicago 1893. Given that the building is no longer standing, the only way to ascertain its exact span would be by consulting the plans provided by reliable contemporary sources. These sources provide the same span of 368 feet (112.16 metres) measured at the axes of the springer hinges: -The “Final Official Report of the Director of Works of the World’s Columbian Exposition” made up of four volumes, published in 1893 and written by Daniel Hudson Burnham, who was the building projects supervisor for the Fair, is the most reliable source as it is an official report [Ref (110) Burham, Daniel]. In volume 2, page 40e there is a building plan with partial dimensions. The sum of these dimensions produces an average span of 184 feet, which gives a span measured at the hinge axes of 368 feet, that is, 112.16 metres.

Fig 2.100. Manufactures and Liberal Arts Building. Chicago 1893. Plan of gallery perimeter. Note the arch springers in the central nave. [Source: Ref (109) Burnham, Daniel H.]

-Plate 11 of the 1893 issue of the German building journal “Allgemeine Bauzeitung” shows a building cross-section measured between the axes of the springer hinges which confirms the previous figure: 368 feet (112.16 metres). [Ref (307) Werner, Emeric A.] Therefore, if we take into account that the span of the 1889 Galerie des Machines was 110.6 metres and that of the Manufactures and Liberal Arts Building was 112.16 metres, this gives a difference between spans of 1.56 metres in favour of the latter. The building had a total width of 149.3 metres and a length of 421 metres. It was made up of a large central nave and two smaller side naves. The height of the central nave was 64.82 metres measured at the arch extrados (compared with the 46.67 of the Galerie des Machines of 1889) (Fig 2.100 and Fig 2.101). As explained earlier, the three-hinged arches had two hinges in the springers and the other in the apex (Fig 2.103 to Fig 2.106). These arches were arranged at a distance between axes of 15.24 metres. There was a second structural level consisting of X-shaped trusses linked to the arches via rigid joints with various distances between axes. A third structural level was made up of X-shaped trusses with a distance between axes of 3.6 metres. The deck ironwork was the last level.

Fig 2.101. Ground floor. Manufactures and Liberal Arts Building. Chicago 1893. [Source: Ref (109) Burnham, Daniel H

The ends of the building were finished with vaults made up of semi-arches with springer hinges (Fig 2.108). In the 1889 Galerie des Machines, the building architect Dutert, was in favour of finishing the ends with vaults. However, the building Control Committee cast doubts on building these vaults. Thus the engineer Contamin explained: “Placing vaults at the longitudinal ends of the building would be a difficult task and an unknown quantity to be feared.” [Ref (117) Chasseloup, M. de / Labaut] In comparison with the 1889 Galerie des Machines, the structure of this building was made of steel. A contributing factor to this was probably the fact that the United States was the largest steel manufacturer of the time. Thus, this country produced 11.4 million tonnes of steel in 1900, while France only produced 0.6 million tonnes in 1889; English production reached 2 million tonnes in 1885, while in the same year Germany manufactured 1.3 million tonnes. As mentioned earlier, the resistance, strength and ductility of steel due to the combination of iron with a certain amount of carbon had been well-known since ancient

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Fig 2.102. Manufactures and Liberal Arts Building. Chicago 1893. Indoor photograph during a concert with a capacity for 125,000 people. [Source: Ref (309) Wilde, Otto / Ganzlin, Albert]

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times. It was also common knowledge that steel had to contain more carbon than wrought iron, and that an excessive amount would transform it into cast iron, thus losing its ductility to the point of rendering it fragile and therefore impeding the forging process. In spite of this knowledge and following the invention of the Bessemer converter in 1855 and the Martin Siemens system in 1857 which would enable the industrial manufacture of steel, its use did not become generalised immediately. Apart from a certain initial mistrust on the part of architects and engineers, this was due to the technical manufacturing difficulties at the beginning, its high cost, and the greater development of iron production plants. Nevertheless, the favourable structural benefits of this metal compared with iron, as well as the overcoming of the technical difficulties and lowering of production costs, would slowly foster a more generalised use of steel.

Fig 2.103. Manufactures and Liberal Arts Building. Chicago 1893. Cross-section. [Source: Ref (307) Werner, Emerik A.]

Fig 2.105. Manufactures and Liberal Arts Building. Chicago 1893. Arch springer hinge. [Source: Ref (275) Rydell, Robert W. / Gilbert, James]

Fig 2.106. Manufactures and Liberal Arts Building. Chicago 1893. Arch springer hinge in a period engraving. [Source: its creators]

Fig 2.104. Manufactures and Liberal Arts Building. Chicago 1893. Longitudinal section. [Source: Ref (307) Werner, Emerik A.]

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Fig 2.109. Manufactures and Liberal Arts Building. Chicago 1893. Assembly photograph. [Source: Ref (109) Burnham, Daniel H.]

Fig 2.107. Manufactures and Liberal Arts Building. Chicago 1893. Structure plan. [Source: Ref (307) Werner, Emerik A.]

Fig 2.110. Manufactures and Liberal Arts Building. Chicago 1893. Assembly photograph. [Source: Ref (275) Rydell, Robert W. / Gilbert, James]

Fig 2.108. Manufactures and Liberal Arts Building. Chicago 1893. Indoor photograph. Note the ends finished with vaults. [Source: Ref (207) Ives, Halsey]

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and parallels and, according to Pevsner, the first iron and glass dome to be built [Ref (263) Pevsner, Nikolaus]. It was a hemispherical dome with a span of 39 metres, and had a central oculus. It was an example of structural rationalism since there is a direct link between its design and structural behaviour.

2.1.5.1. Contributions The Manufactures and Liberal Arts Building was a direct consequence of the Galerie des Machines of 1889, although its arch curve was more rational from a structural point of view, given its approximation to a parabola. This more efficient arch shape would therefore develop less bending stresses, while it must be said that there was a certain loss of daring and originality in comparison with the arch shape of the Galerie des Machines of 1889. In terms of the design of structural details, we should point out that the arch springer hinge in the Manufactures and Liberal Arts Building is massive, and shows none of the lightness and careful design of that of the Galerie des Machines of 1889. On the other hand, the fact that it has vaults finishing off the ends marks an achievement that had been sacrificed by the creators of the 1889 Galerie because of the uncertainty surrounding their use. Nevertheless, these vaults formally link the building closer to the old greenhouse in Kew Gardens (1846) than the 1889 Galerie des Machines de 1889 with its radical shape, as its aesthetic has more in common with railway stations. Perhaps the greatest contribution of this Chicago building was achieving a new world record for building span in a new material, namely steel. The Manufactures and Liberal Arts of Chicago would be a pioneer in this respect.

2.2 THE SEARCH FOR LARGE SPANS AND TYPOLOGICAL INNOVATION IN CIRCULAR DECKS

Typological innovation and the progress made in spans in metal structures would also affect circular decks. Several of the buildings erected on the occasion of the World Expos in the 19th century were exclusively or partially made with circular decks. A selection has been made of those that represent interesting historical-structural contributions. These are: the Crystal Palace from the Exhibition of the Industry of all Nations held in New York in 1853; the main building of the Weltausstellung (World Exhibition) in Vienna in 1873 and the main building of the Exposition Universelle, Internationale et Coloniale in Lyon held in 1894. We shall also look at those buildings which are precedents or relevant transitional pieces for understanding these developments beyond the World Expos.

2.2.1 The first iron and glass dome in the world: The Halle au Blé of Paris When on the subject of circular decks designed with metal structures, the dome of the Parisian Halle au Blé, mentioned in the previous chapter for being a reference point in this new typology, has to be discussed (Fig 1.11 to Fig 1.13 and Fig 2.111). The new dome was designed in 1811 by François J. Belanger and F. Brunet, after the previous dome was destroyed in a fire; it is the first system of iron pieces bolted to form a structure of meridians CHAPTER 2

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Fig 2.111. Dome of the Halle au Blé. Paris. François J. Belanger and F. Brunet. 1811. Elevation of the scaffolding set up for assembly. [Source: Ref (100) Boudon, Françoise / Chastel, André]

In this sense, the hemispherical domes made up of bars acting as meridians and parallels mainly develop tension and compression stresses. This is possible thanks to the existence of parallels that are in tension or compression, thus preventing the meridians from bending. In comparison with arches, therefore, this type of dome can be separated from the anti-funicular line without causing serious bending in its members. The meridians will be compressed, the compression increasing the closer we are to the dome base. These meridians deform towards the inside of the dome to about 52° measured from the vertical axis that passes through the centre of the sphere, and deform outwards above 52°. The parallel rings are there to prevent this deformation; those below 52° at the top of the dome are acted upon by compression, while those above 52°, which are located at the base and haunches of the dome, are in tension. In the Halle au Blé dome, we can see that the meridians have a variable depth with chords which increase in height towards the base; this increase corresponds to the higher compression at the dome base. The parallels decrease in height and depth the higher we get, but the separation between them gradually decreases so that they can withstand the compression at the top of the dome. The geometry itself of this typology is responsible for the fact that the length of the parallel portions is shorter in the top areas, which in turn helps prevent these pieces from buckling.

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Fig 2.113. Crystal Palace from the Exhibition of the Industry of all Nations held in New York in 1853. George Carstensen and Charles Gildemeister. [Source: Ref (287) Silver, Nathan]

2.2.2 Fire in the first american iron dome: The Crystal Palace from the New York Expo 1853

The building for the Exhibition of the Industry of all Nations held in New York in 1853 was influenced by the Crystal Palace from the London Expo of 1851. Such was the amazement that Paxtonâ&#x20AC;&#x2122;s building caused that there was even a proposal to bring it to New York, or failing that, to commission Paxton with a similar building. Finally, a competition was held to design a singular building for this Expo. One of the truly novel projects from a structural perspective to be presented to the competition would be a building by James Bogardus (Fig 2.112), which consisted of a 91.5-metre high cast-iron tower that was 23 metres wide at the base. This tower supported the buildingâ&#x20AC;&#x2122;s 122-metre wide circular deck by means of chains. We can therefore consider it to be an early precedent of modern tension structures. This project was never built.

In the end, the winning project was a building named Crystal Palace designed by the architects George Carstensen and Charles Gildemeister and the engineers C.E Cetmold, Horatio Allen and Edmund Henry (Fig 2.113).

Fig 2.112. Circular deck hung from chains and cast-iron tower. James Bogardus. 1853. [Source: Ref (262) Pevsner, Nikolaus]

The building had a floor plan in the shape of a Greek cross. Each of the arms of the cross was 111.4 metres long and 45.55 metres wide. The arms of the cross were joined by four lower, triangular naves (7.3 metres), giving the building an octagonal floor plan (Fig 2.114 to Fig 2.117). Fig 2.114. Ground floor. [Source: Ref (233) Mallet, Robert]

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Fig 2.115. First floor. [Source: Ref (233) Mallet, Robert]

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Fig 2.116. Crystal Palace from the Exhibition of the Industry of all Nations held in New York in 1853. George Carstensen and Charles Gildemeister. Cross-section. [Source: Ref (113) Carstensen,G. / Gildemeister]

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Fig 2.117. Crystal Palace from the New York Expo in 1853. Inside view from a period engraving. [Source: Ref (233) Mallet, Robert]

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The inside was made up of two orthogonal naves, each of them 12.6 metres wide. These naves were designed with semi-circular cast-iron arches. There was an intermediate floor or gallery along the side of the two main naves. In this area the columns were placed according to a grid made up of 8.23 m2 squares, which allowed for a certain logic of prefabrication, derived from the London Crystal Palace. As with the first building, the cast-iron columns were hollow and had an octagonal cross-section (Fig 2.119). Both the intermediate floor or gallery and the deck were made with X-shaped trusses. These trusses were placed in the two main directions of the building. Short cast-iron beams measuring 8.02 metres were combined with longer wrought iron girders 12.4 metres long, (Fig 2.118, Fig 2.120 and Fig 2.121). This resource had already been employed in the London Crystal Palace due to the fact that the structural qualities of cast iron were poorer than those of wrought iron, as well as the lower cost of wrought iron.

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Fig 2.118. (Above) Crystal Palace from the New York Expo in 1853. Elevation of the standard wrought iron girder type used. [Source: Ref (113) Carstensen,G. / Gildemeister] Fig 2.120. (Below) Crystal Palace from the New York Expo in 1853. Elevation of the standard castiron beam type used with chords of varying width. [Source: Ref (113) Carstensen,G. / Gildemeister]

Fig 2.119. Crystal Palace from the New York Expo in 1853. Elevation and cross-sections of the columns. Note the similarity with the London Crystal Palace from 1851 in terms of cross-sections, splice pieces, assembly pieces for the trusses and channelling of the rainwater along the inside. [Source: Ref (113) Carstensen,G. / Gildemeister]

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In the intersection of both naves there was a dome with a diameter of 30.5 metres (Fig 2.122). This was the building’s main feature. According to Robert Mallet: “It was the largest, indeed almost the only dome (made of iron), then erected in the United States.” [Ref (233) Mallet, Robert] The dome was made up of lattice meridians. In spite of there being parallels in the original plans (Fig 2.122 and Fig 2.123), in the end they were not used, as confirmed by the design-

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Fig 2.121. Crystal Palace from the New York Expo in 1853. Elevation of a standard portal frame type. Note the similarity with that of the London Crystal Palace from 1851. [Source: Ref (113) Carstensen,G. / Gildemeister]

Fig 2.122. Crystal Palace from the New York Expo in 1853. Cross-section. [Source: Ref (113) Carstensen,G. / Gildemeister]

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ers themselves in the publication “Illustrated description of the New York Crystal Palace”, [Ref (113) Carstensen,G. / Gildemeister,C.]. In fact, there are no parallels to be seen in any of the located engravings that represent either the axonometrics, the indoor or outdoor perspectives of the building (Fig 2.113, Fig 2.117 and Fig 2.124). Therefore, the dome would work as a set of arches which could develop bending stresses as they were not joined by parallels. We could say that this was perhaps a less rational structural design than that of the Halle au Blé in Paris.

The building was a direct consequence of the Crystal Palace from the London Expo in 1851. In their book “Illustrated Description of the New York Crystal Palace”, the architects of the building George Carstensen and Charles Gildemeister state:

Fig 2.123. Crystal Palace from the New York Expo 1853. Structural details of the dome. (Below right) Elevation of a meridian at its base. (Above, right) Elevation of a meridian at the top. (Above left) Join between a meridian with an upper compression ring. (Below left) Elevation of two meridians, diagonal bars and cast-iron parallels in a V shape. According to the designers themselves, the latter were not used in the end. [Source: Ref (113) Carstensen,G. / Gildemeister]

“Everybody must be aware of the motives which prompted the erection of a Crystal Palace in New York for the purpose of an Exhibition of the Industry of all Nations. The astonishing success which attended the original enterprise undertaken in London in the year 1851; the eagerness with which this example was followed by various countries that signified their intention of immediately entering upon a similar undertaking, all rendered it necessary that so grand a nation as America should in its turn realize on her own soil this novel idea of our progressive era.” [Ref (113) Carstensen,G. / Gildemeister,C.] Likewise, they also admitted: “To Messrs. Fox & Henderson we are indebted for the system of columns and girders. For the main construction of the rest of the building, its excellences or defects, we alone are responsible.” [Ref (113) Carstensen,G. / Gildemeister,C.] In October of 1858 the New York Crystal Palace collapsed due to a fire (Fig 2.124 and Fig 2.125). The fire destroyed the structure in fifty minutes [Ref (287) Silver, Nathan]. The iron, an incombustible material that advantageously substituted wood, showed one of its greatest weaknesses to a country destined to achieve great things in metal constructions: a notable loss of resistance and rigidity at high temperatures. In short, it appears that the structural design of the dome of the Crystal Palace from the New York Expo was not particularly brilliant. On the other hand, the building showed a clear influence from the Crystal Palace of the London Expo, although with a formalisation that perhaps prevented it from having the innovative, stylistic originality of the earlier building. However, its structural contribution was to introduce this deck typology in the United States, while having the largest diameter and probably being the first in this country to be made entirely of iron, according to Robert Mallet. Thus, the erection of this representative building would help demonstrate the formal and technical possibilities of iron with its virtues and defects in the United States, and would therefore contribute to the spread of so-called iron architecture in America.

Fig 2.124. Crystal Palace from the 1852 New York Expo. Image of the 1858 fire. [Source: its creators]

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Fig 2.125. Crystal Palace from the 1852 New York Expo. Image after the fire in 1858. [Source: its creators]

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- New Street Station in Birmingham. Carried out by E.A. Cowper in 1854. Its span was 64.62 metres (Fig 2.4 to Fig 2.7).

2.2.3 An extraordinary achievement: The Rotunde Building in the Weltausstellung in Vienna 1873

- St. Pancras Station in London. Built by William H. Barlow in 1868. It had a span of 73 metres (Fig 2.47 and Fig 2.56 to Fig 2.59).

May 1st 1873 witnessed the inauguration of the Weltausstellung in Vienna. The most remarkable building was the so-called Rotunde (Fig 2.126 to Fig 2.129). This building was made up of a central rotunda from which two longitudinal structures led off, offering access to 32 transverse pavilions. The creators were the English industrial and naval engineer John Scott Russel, the architect Karl von Hasenauer and the builder Wilhelm Engerth.

Fig 2.127. The Rotunde. Vienna 1873. John Scott Russel, Karl von Hasenauer, Wilhelm Engerth. [Source: Ref (72) Vienna, art and architecture]

From a structural point of view, the buildingâ&#x20AC;&#x2122;s most interesting feature is the central rotunda. The deck was trunco-conical with two lanterns. The dimensions were truly exceptional for the time. The Rotunde diameter was 104.78 metres measured at the column axes, and reached a total height of above ground level of 85.3 metres. The total length of the building was 900 metres (Fig 2.130 and Fig 2.131). The Rotunde set a new world record for span in a building structure. While they were designed with a variety of structural typologies, the following buildings held the previous span records for metal structures in the second half of the 19th century: - Lime Street Station in Liverpool. Built by Turner in 1849. It had a span of 45.72 metres (Fig 2.1 to Fig 2.3). CHAPTER 2

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Fig 2.126. General view of the Weltausstellung in Vienna 1873. The Rotunde building is in the centre. [Source: Ref (72) Vienna, art and architecture]

Fig 2.128. (Next page). The Rotunde. Vienna 1873. Plan and elevations. [Source: Ref (252) Oppermann, E.A.]

It is therefore clear that the Viennese Rotunde was a remarkable achievement. Built five years after St. Pancras Station, its span was greater by more than 31 metres. In addition, it would not be until sixteen years later that the Galerie des Machines would be built in Paris in 1889 and set the next world record thanks to its span of 110.6 metres, merely 5.8 metres larger than the Rotunde. Why, then, did this building not garner greater fame in the history of architecture, and why was it not as famous as the 1889 Galerie des Machines of Paris in terms of structural systems? This is due to the fact that the whole metal structure was hidden under other materials such as wood, plaster or stone, thus creating a historicist aesthetic far removed from the industrial essence of iron. In contrast, the 1889 Galerie des Machines was a work that encapsulated the structural achievement and the artistic expression of the industrial spirit of the time. On the other hand, the Paris building had been a reference for innumerable railway stations erected both in Europe and the United States, thanks to its typological formalisation. The lack of stylistic innovation was responsible for the Rotunde not having as great an impact as the 1889 Galerie des Machines. In spite of this, we should not undervalue its structural contribution which was undoubtedly extraordinary. 149

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Fig 2.132. The Rotunde. Vienna 1873. Below: detail of the column-girder joint. Note the cross-section of the girder at its base. Note the tension ring with a box-section. Note the perimeter gallery with public access (labelled A in the figure) which facilitates the structural scale.

The structure of the Rotunde (Fig 2.130 and Fig 2.131) was supported by thirty columns (Fig 2.133 and Fig 2.136). A girder sprang from each column, following the direction of the generatrix of the deck cone; these girders were 48 metres long and had a variable depth of between 1.5 metres at the bottom and 0.61 metres at the top. The girders were connected at the bottom to a tension ring with a box-section, and at the top to a compression ring with a trapezoid-section (Fig 2.132). Four intermediate rings were connected to the girders (Fig 2.134 and Fig 2.135).

Fig 2.129. The Rotunde. Thanks to the survival of the building until 1937, there are aerial photographs like this one. The transverse pavilions had been taken down. [Source: its creators]

Fig 2.130. The Rotunde. Structural diagram of the deck. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.131. The Rotunde. Vienna 1873. Cross-section. [Source: Ref (305) Vierendeel, Arthur]

Above: detail of the joint between the girder and the compression ring. Note on the left the cross-section of the girder at the top, as well as the compression ring with an open trapezoid cross-section. [Source: Ref (305) Vierendeel, Arthur]

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Above the upper ring sprang thirty more columns that supported the first lantern, which was also trunco-conical (Fig 2.133). The latter had a diameter of 30.9 metres. Such a size was unheard of. Note that the dome of the Halle au BlĂŠ in Paris (Fig 1.11 to Fig 1.13 and Fig 2.111) built in 1811 by FranĂ§ois J. Belanger and F. Brunet had a span of 39 metres. The lantern was designed in the same way as that of the lower deck, with thirty girders arranged in the direction of the cone generatrix. These beams were joined by a lower tension ring and another compression one.

Fig 2.133. The Rotunde. Vienna 1873. Below: Standard cross-section type of the main building columns with a box-section measuring 3.05 x 1.24 metres. Above: standard cross-section type of the columns that supported the first lantern. [Source: Ref (305) Vierendeel, Arthur]

Fig 2.136. The Rotunde. Vienna. 1873. Photograph of the building under construction. Note the braced columns, the lower tension ring with a box-section, still open, and the main variable depth H-girders. [Source: its creators]

Fig 2.134. (Left) The Rotunde. Vienna 1873. Cross-sections of the intermediate deck rings. [Source: Ref (305) Vierendeel, Arthur] Fig 2.135. (Right) The Rotunde. Vienna 1873. Cross-sections of the intermediate deck rings. [Source: Ref (305) Vierendeel, Arthur]

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Fig 2.137. The Rotunde. Vienna. 1873. Photograph of the building under construction [Source: its authors]

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The whole structure was covered with different materials. The columns were covered in wood and plaster on the inside and with zinc sheets painted to imitate the stone on the outside, the beams were covered with coloured fabric and painted plaster cornices were installed (Fig 2.138 and Fig 2.139).

Unlike other exhibition buildings, the Rotunde was designed to be permanent and to house various exhibitions and commercial fairs. The building was destroyed by a fire in 1937 (Fig 2.140 and Fig 2.141).

Fig 2.140. (Left) The Rotunde. Vienna. Photograph of the fire in 1937. [Source: its creators] Fig 2.138. The Rotunde. Inside image of the building in a period engraving. [Source: Ref (228) Lützow, Carl Friedrich]

Fig 2.141. (Right) The Rotunde. Vienna. Photograph after the fire. [Source: its creators]

In short, the main contribution of the Rotunde from the Weltausstellung in Vienna held in 1873 resides in having introduced a new metal structural typology and having achieved an exceptional span. The result was a circular deck with the largest diameter in the world.

Fig 2.142. Comparison of the cross-section of the Rotunde from the Weltausstellung in Vienna 1873 with the domes of other buildings. from larger to smaller: Rotunde from the Weltausstellung in Vienna; Dome of the Great London Exhibition in 1862; Dome of St. Peter’s Basilica in Rome and the Dome of St. Paul’s Cathedral in London. [Source: Ref (310) Wyatt, Digby]

Fig 2.139. The Rotunde. Indoor photograph during a later exhibition. [Source: its creators]

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2.2.4 An undervalued milestone: the main building in The Exposition Universelle, Internationale et Coloniale in Lyon 1894

Fig 2.145. Main building of the Exposition of Lyon 1894. [Source: Archives Municipales de Lyon]

The Exposition Universelle, Internationale et Coloniale of Lyon was held in 1894. This new Expo was supposed to be a lead-in to the Expo held in Paris in 1900. To mark the occasion of the Expo, a main pavilion would be built that would be very interesting from a structural point of view.

Fig 2.143. Aerial view of the Exposition universelle, internationale et coloniale of Lyon 1894. [Source: Ref (82) Arnaud, B.]

It was a circular building with a metal structure measuring 232 metres in diameter (Fig 2.143 to Fig 2.150). In this case, the aim was to allocate each exhibition theme to a circular sector, with raw materials on the edges and displaying their progressive manufacture towards the centre, where the finished products would be on show.

Fig 2.144. Main building of the Exposition of Lyon 1894. [Source: Ref (82) Arnaud, B.]

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Fig 2.146. Main building of the Exposition of Lyon 1894. Cross-section of the structure and horizontal structural diagram. [Source: Ref (280) Sarrazin, Otto / Hofsfeld, Oskar]

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Fig 2.147. Main building in the Exposition of Lyon 1894. Cross-section. [Ref (158) Fournier, V.]

Figs 2.148 y 2.149. Main building of the Exposition of Lyon 1894. [Source: Archives Municipales de Lyon]

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The building was made up of a central nave surrounded by two perimeter indoor galleries and a cantilevered outdoor gallery. The central nave was designed with a dome made up of parabolic arches with spans of 110 metres and 55 metres high. These variable depth trussed arches had a depth of 1.8 metres at the top. The arches were hinged at the springers and finished with an upper compression ring. It is surprising how little of an impact this building made on the specialised publications of the time. Neither structural descriptions nor detail drawings are to be found in the French engineering publications contemporary to the building, nor in more recent publications. The graphic information presented here comes from several publications that cover the Expo in a general way, and which are to be found in the Archives Municipales of Lyon. Another source was an article published in issue 50 of the German building journal “Centralblatt der bauverwaltung” from December 16th 1893 [Ref (280) Sarrazin, Otto / Hofsfeld, Oskar]. This building’s lack of notoriety was probably due to the fact that this Expo, modest in comparison with others, was held in a less relevant city than London, Paris, New York or Vienna.

CHAPTER 3

THE WORLD EXPOS AND THE RACE FOR THE TALLEST BUILDING IN THE WORLD

In any case, the building from the Exposition in Lyon was a worthy achievement in building structure. Note that while it was built merely five years after the Galerie des Machines of Paris 1889, it managed to attain a similar span, although with another typology. Its span would also be similar to that of the Rotunde in Vienna in 1873, although in this case, the structural typologies were again different. The outside image of the building was devalued because of the use of a series of access portals that were historicist in character, as well as quite an inelegant shape. In contrast, the structure is quite naked on the inside. The light was dealt with successfully, as it highlighted the rotundity that connected well with the industrial spirit of the time. Due to an initial lack of documentary dissemination, this building has been marginalised historically. Nevertheless, thanks to its structural value and spatial quality, this marginalisation is undeserved.

From ancient times, mankind has entertained the fantasy of making a building higher than anyone else. Loaded with an obvious symbolism, this yearning for great heights has been reflected in ancient religious texts. Such is the case of the Old Testament, in which the epic tale of the unfinished tower erected in the city of Babel is told, that city to the south of Bagdad in which this desire was intertwined with man’s ambition to reach heaven. This story is also an example of the belief in mankind’s great abilities when everyone is working towards the same goal (Fig 3.1).

Fig 2.150. Main building of the Exposition of Lyon 1894. [Source: Jules Sylvestre. Bibliothèque Municipale of Lyon]

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Fig 3.1. One of the representations of the Tower of Babel. [Source: its authors]

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Religion has not been the only catalyst stoking the desire for great height; the symbolism derived from political, economic and technological power has been seducing the human race right up to the present day. Thus, 2001 witnessed the collapse of the Twin Towers in New York after the terrorist attack which not only meant the loss of hundreds of lives, but also the destruction of one of the symbols of Western power exemplified through great height. In this way, menhirs, pyramids, obelisks, columns or basilicas have marked the history of great civilizations, representing a variety of symbolic aspects achieved through tall constructions (Fig 3.2).

Fig 3.2. Representation of some of the tallest edifications in Ancient Times. 1884. Most of them are funerary, religious or commemorative constructions. The tallest building is the Washington Monument. [Source: its authors]

3.1 THE EIFFEL TOWER: ITS PRECEDENTS The historical precedents of the Eiffel Tower can be classified into three groups: - Projects that were never made. This includes those projects for towers which aimed to beat records for height but which were never built. In spite of this, they contributed to the interest generated in the subject of great height. Many of the projects came about precisely on the occasion of World Expos. -Real achievements. These are svelte constructions made with iron structures. They had a similar effect to those projects which never came to fruition, as well as encouraging competition to make the highest building. -The experience of Gustave Eiffel and his collaborators themselves, which crystallised in some of his works in particular, through which they were to gain enough experience and use the technological resources which would later enable the design and construction of the tower.

3.1.1 High-rise constructions: projects never built

After iron began to be applied as the main structural material in building, it would start to fan the desire to erect a construction higher than any other. In this way, the first project we have any evidence of is the tower that Richard Trevithick wanted to build in London in 1832, called the Reform Column (Fig 3.3 and Fig 3.4). Trevithick, builder of the first steam locomotive, proposed erecting a tower 1,000 feet high (304.8 metres). It was a cast-iron, perforated column with a 30-metre diameter at the base and a 3.6-metre diameter at the top. There would be a tube on the inside along which a lift would ascend, propelled by a compressed air mechanism. 1,500 cast-iron sheets would be used to build it. In the end, after Trevithick passed away, the tower was never built.

The World Expos have also played their part in this fabulous longing. As described in the previous chapters, the evolution of iron had led to important structural developments, thus creating an atmosphere of considerable technological optimism which would feed the fantasies of architects, engineers and politicians. Industrialised iron would present possibilities for high-rise construction that had previously been unimaginable. On the other hand, the desire to build a tower taller than any other building was nothing new. A large Exposition Universelle was held in Paris in 1889 to commemorate the centenary of the French Revolution. This Expo would undoubtedly be the most important display of structural technology of the 19th century, with the erection of the Galerie des Machines with the largest deck span ever built, and the Eiffel Tower which was the tallest building in the world for its time. The so-called iron architecture would reach its technological peak in this Expo.

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On the occasion of the World Expo in New York in 1853, James Bogardus proposed building a cast-iron tower that would be 91.5 metres high and with a 23-metre diameter at the base (Fig 2.112). This tower would support the buildingâ&#x20AC;&#x2122;s circular 122-metre deck with iron chains. It could also be considered an early precedent of modern tension decks. This project never saw the light either. In 1852, a year after the inauguration of the World Expo in London, Charles Burton put forward a proposal for an iron tower that would recycle the structural elements from Paxtonâ&#x20AC;&#x2122;s Crystal Palace (Fig 3.5 and Fig 3.6). It was made up of three slightly square-plan bodies, the sides of which decreased in height and evolved into three circular-plan structures. We can see the modular arrangement of the columns horizontally and the recycled enclosure elements from the Crystal Palace vertically. Chapter 1 includes a description of the issues with horizontal stabilisation suffered by the London building which had even led to the collapse of part of the same after its reconstruction in Sydenham. We can deduce that a project for a tower with these characteristics with the same components and criteria would be impracticable. Nevertheless, whether the author would have made provisions for modifications or a new system of horizontal stabilisation remains unknown. 165

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Fig 3.3. (Above left) Reform Column. Richard Trevithick. Project from 1832. Elevation. [Source: Ref (178) Glibota, Ante / Edelmann, Frédéric]

Fig 3.4. (Above right) Reform Column. Richard Trevithick. Project from 1832. Plan and cross-section. [Source: Ref (178) Glibota, Ante / Edelmann, Frédéric]

Fig 3.7. Tower proposed by Clarke, Reeves & Company. 1874. [Source: Ref (261) Peters, Tom F.]

Fig 3.5. Charles Burton’s Tower. 1852. Elevation. [Source: Ref (102) Brino, Giovanni]

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Fig 3.6. Charles Burton’s Tower. 1852. Plan. [Source: Ref (102) Brino, Giovanni]

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Fig 3.8. Tower proposed by Clarke, Reeves & Company. 1874. Plan. [Source: Ref (261) Peters, Tom F.]

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On the occasion of the 1876 Centennial International Exhibition held in Philadelphia, the company Clarke, Reeves & Company, having ample experience in bridge building, proposed the erection of a metal tower 1,000 feet high (Fig 3.7 and Fig 3.8). This tower was made up of a central cylinder with a 9-metre diameter. A series of post-tensioned cables would join the crown with a circular foundation with a diameter of 45 metres. Due to a lack of capital and the fear sparked by the complex construction of the Washington Monument, the proposal was rejected. In 1881 the French engineer Sébillot proposed the so-called Tour Soleil. It was an iron tower with a lighthouse at the top that would be visible from all over Paris. In parallel to the Eiffel Tower, in 1889 Sébillot and Bourdais put forward a proposal for a granite tower that was 1,000 feet high for the 1889 Exposition in Paris (Fig 3.9). There were doubts as to its feasibility, given the limited ability of the ashlar to withstand the stresses caused by the wind. Neither of the two was to be built. We can see that many of the projects were put forward as a consequence of the celebration of a World Expo. This should therefore emphasise the role of the World Expos as a catalyst for structural creativity and as a place to express the structural fantasies of architects and engineers.

3.1.2 High-rise construction: the actual achievements There are also precedents of svelte constructions exclusively supported by an iron skeleton that were made, furthermore without any help from masonry walls. We shall highlight several lighthouses along these lines. The architecture of lighthouses originated in the classical world. However, it was in the Middle Ages when they would begin to spread geographically. This expansion would be consolidated in the 18th century with the Industrial Revolution and the proliferation of commercial sea routes. We can highlight Minot’s Ledge Light, Boston, built by W.H. Swift between 1847 and 1850 (Fig 3.11). It was a structure made entirely of iron with cast-iron columns and lintels, as well as X-shaped horizontal stabilisation bars. There were no triangulations in the upper span, so the horizontal stabilisation depended on the stiffness of the connections. It was a sensitive issue, bearing in mind the fact that cast iron does not withstand any notable bending.

Fig 3.9. Granite tower 1,000 feet tall (304.8 m) designed by Sébillot and Bourdais for the Exposition Universelle of Paris, 1889. [Source: Ref (261) Peters, Tom F.]

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Other cast-iron towers worthy of mention are those made by the American James Bogardus. These towers were used for shooting practice or to house a bell to sound the fire alarm. In this way, Bogardus would build an iron tower in Thirty-Third Street in 1851 as part of a fire alarm system for the city of New York (Fig 3.12). Between 1852 and 1853, another tower was built in Spring Street, New York, for the same purpose (Fig 3.13 and Fig 3.14). Some of these towers were considerably svelte. Their horizontal stabilisation depended on the stiffness of the connections, there being no diagonal stabilisation bars. In this sense, we should once again point out that cast iron had poor mechanical properties: it was fragile and incapable of absorbing great bending moments. As we can see in Fig 3.14, the connections were bolted, following a clearly rough and unrefined design. In any case, we should bear in mind that these were very early creations.

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Fig 3.11. Minots Ledge Light, Boston. W.H. Swift. 1847-1850. [Source: Ref (214) Kahn, David M.]

Fig 3.10. Prototypes of iron lighthouses from the 19th century. [Source: Museo Faro Cabo Vilán, A Coruña]

Another example that did get built would be the monument that paid homage to the first president of the United States, George Washington, called the Washington Monument (Fig 3.15 and Fig 3.16). In this case, it was a construction that combined various stone masonry panels with a nucleus of metal stairs connected at various points to the masonry. It would be the tallest edification in the world until the Eiffel Tower was built. Designed by the architect Robert Mills, it was supposed to be 183 metres high. Building began in 1848. Upon reaching 46 metres, the building began to be considerably out of plumb, which necessitated reinforcing the foundations. There were several delays in construction due to economic problems, and the project underwent various modifications after Mills’ death. It was finally completed in 1884, 36 years after construction began and 169 metres high. Fig 3.12. Cast-iron tower for sounding the fire alarm in Thirty-third Street, New York. James Bogardus. 1851. [Source: Ref (214) Kahn, David M.]

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Fig 3.13. Cast-iron tower for sounding the fire alarm in Spring Street, New York. James Bogardus. 1852-1853. [Source: Ref (214) Kahn, David M.]

Fig 3.15. Washington Monument. Robert Mills. 1848. Initial project. [Source: its authors] Fig 3.14. Cast-iron tower for sounding the fire alarm in Spring Street, New York. James Bogardus. 1852-1853. Detail of the bolted connection. [Source: Ref (214) Kahn, David M.]

Another relevant example is the commendable Latting Tower or Latting Observatory, built for the Exhibition of the Industry of All Nations in New York in 1853 (Fig 3.17 and Fig 3.18). It was made out of iron and wood by Waring Latting and William Naugle, and had a height of 96 metres. It had three floors which were accessed by steam-powered lifts. It was the tallest building in the United States for three years, until the fire of 1856. We should not forget to mention the progress that was being made in the construction of multi-storey buildings in the Chicago School, although the buildings erected before 1889 generally combined metal portal frame structures with masonry elements such as pilasters and inside walls, which had a supporting function. Leonardo BenĂŠvolo stated the following to this effect:

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Fig 3.16. Washington Monument. Current photograph. [Source: its authors]

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Fig 3.18. Latting Tower during the fire of 1856. Note the dome of the New York Crystal Palace in the background, which would suffer the same fate two years later. [Source: its authors]

Fig 3.17. Latting Tower or Latting Observatory. Exhibition of the Industry of all Nations in New York 1853. Waring Latting and William Naugle. Mixed structure in iron and wood. [Source: its authors]

“Built in 1885, the Home Insurance Building (which was 55 metres high), was considered to be the first building in Chicago to be built with an entire metal skeleton, while a part of the enclosure walls did have a supporting function.” [Ref (94) Benévolo, Leonardo] On the other hand, while the buildings in the Chicago School form an important part in the historical development of the rigid portal frame, they bear little relation to the Eiffel Tower due to their structural morphology and the lack of svelteness in those made before 1889. The main difference lies in the fact that the Tower’s sole objective was to set a world record in height, while the Chicago School buildings had to have a purpose and optimise land use, and therefore the use of slightly parallelepiped shape was better suited.

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Fig 3.19. (Left) Home Insurance Building. William Le Baron Jenney. 1885. Considered to be the first skyscraper in the world. [Source: its creators] Fig 3.20. (Right) Home Insurance Building. William Le Baron Jenney. 1885. Photograph of construction. [Source: its creators]

3.1.3 The experience of Gustave Eiffel and his collaborators The challenge of erecting a 300-metre high tower was only within the reach of a team of engineers with solid experience in the construction of metal works of a highly technical complexity. In the previous thirty years, Eiffel had made a series of large iron bridges and viaducts in which he had applied methods which would later be used with the Tower in 1889. This experience acquired in the use of iron would mark a considerable difference in contrast with the construction of other large metal buildings, such as the colossal Crystal Palace in London, or the first Parisian machine galleries that developed the first pathologies described in earlier chapters. The first large bridge built by Eiffel was the Passerelle Eiffel in Bordeaux (Fig 3.21). The project began in 1858. It was a bridge with a span of 77 metres designed with a continuous truss. The greatest difficulty posed here was setting the foundations in the river bed itself. This was done via a system involving cast-iron pipes with a diameter of 3.6 metres which were riveted together. Pressurised air was blown into the pipes to prevent the water from

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rising up or seeping in, so that dry excavation could be carried out. The same system would be used at a very superficial groundwater level on the banks of the River Seine when the foundations for the Eiffel Tower were laid down; in this case the system consisted in iron boxes into which air was injected, thus enabling the excavation under the groundwater level.

Other works which anticipated issues related to the Eiffel Tower were the two viaducts designed by Nordling, and which were adjudicated to Eiffel to be built. They are the Rouzat Viaduct over the River Sioule (Fig 3.22) and the Neuvial Viaduct (Fig 3.23 to Fig 3.25), both built in 1867. The two bridges have similar characteristics, once again designed with continuous trusses, but in this case on truss columns. The most important characteristic

Fig 3.21. Passerelle Eiffel in Bordeaux. Gustave Eiffel. 1858. [Source: Ref (223) Lemoine, Bertrand]

Fig 3.23. Neuvial Viaduct. Gustave Eiffel. 1867. [Source: Ref (155) Fernรกndez Troyano, Leonardo]

Fig 3.22. Rouzat Viaduct over the River Sioule. Gustave Eiffel. 1867. [Source: Ref (223) Lemoine, Bertrand]

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Fig 3.24. Neuvial Viaduct. Gustave Eiffel. 1867. Detail of column springer. [Source: Ref (155) Fernรกndez Troyano, Leonardo]

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of both bridges are the curved vertical members at the column base which increase the moment arm in order to withstand the horizontal forces of the wind. Furthermore, they were geometrically arranged in the same way as with the Eiffel Tower. In 1875 Eiffel would begin construction of the Ponte Maria Pia over the River Douro in Porto (Fig 3.26 and Fig 3.27). This bridge was an unprecedented structural display. It was made up of a two-hinged arch with a span of 160 metres with variable depth and width. A

Fig 3.25. Neuvial Viaduct. Gustave Eiffel. 1867. Note the technological development and the precision needed for the successively cantilevered assembly. [Source: Ref (223) Lemoine, Bertrand]

Fig 3.27. Ponte Maria Pia over the River Douro in Porto. Gustave Eiffel. 1875. Assembly photograph. [Source: Ref (155) Fernández Troyano, Leonardo]

truss lay on the arch and extended on either side, supported by truss columns. Théophile Seyrig describes it in these words: “This specially-shaped arch was supported on a simple hinge at the base and its depth progressively increased until the apex, thus adopting the shape of a croissant. This shape is particularly suitable for resisting unsymmetrical forces as it allows great depths to be reached in those parts of the arch which should withstand a larger load”. [Ref (223) Lemoine, Bertrand] Bridge arches are subject to mobile loads, making it impossible to determine the anti-funicular shape. Therefore, they will always develop certain bending stresses. In this case, the central areas were given the greatest depth; based on the supporting conditions of the arch and the points of loading of the columns on the same, it was understood that this area was where the bending moment would reach its highest values. The width of the arch progressively increases the nearer it gets to the springer, thus contributing to the stabilisation of the structure against the horizontal wind forces.

Fig 3.26. Ponte Maria Pia over the River Douro in Porto. Gustave Eiffel. 1875. [Source: Ref (155) Fernández Troyano, Leonardo]

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Another bridge with similar characteristics to the previous example was the Garabit Viaduct, made with a parabolic, two-hinged arch with a span of 166 metres (Fig 3.28 to Fig 3.30). This bridge would be designed and developed by Eiffel, Koechlin and Boyer in 1878. In this case, the triangulation bars used in the columns were tubular girders made up of four trusses (tubular-shaped trusses), a detail that would again be used in the Eiffel Tower.

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Fig 3.28. Garabit Viaduct. Gustave Eiffel. 1878. [Source: Ref (155) Fernรกndez Troyano, Leonardo]

Fig 3.29. Garabit Viaduct. Gustave Eiffel. 1878. Detail of the hinged arch springer. Note the triangulation with tubular-shaped trusses. Similar devices would be used in the Eiffel Tower. [Source: Ref (155) Fernรกndez Troyano, Leonardo]

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Fig 3.30. Garabit Viaduct. Gustave Eiffel. 1878. Assembly stages. [Source: Ref (261) Peters, Tom F.]

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was a compromise between Koechlin’s initial sketch and Sauvestre’s profusely embellished diagram. After the competition, the sketch would be simplified even further with the elimination of some decorative elements, and the structure of the Tower would become the main element of its architectural expression (Fig 3.33).

In this sense, it should be pointed out that these works were historic paradigms of building precision and prefabrication. In particular, the Garabit Viaduct had about five hundred thousand rivets, of which only half were used on site. In the case of the Eiffel Tower, this had about two and a half million rivets, of which only a third were used on site. On the subject of building the Garabit Viaduct, the words of Eiffel himself take on a special significance: “This assembly required a high level of precision in prefabrication, installation and calculation; in effect it was essential for the joining holes of the two arch halves to coincide to be able to rivet them. We achieved this with an almost mathematical precision.” [Ref (223) Lemoine, Bertrand] In short, the high level of technological development achieved in the works of Eiffel and his collaborators is evident, both in the structural conception and the erection. These experiences were fundamental and essential for the conception of the Tower project and its construction. All the previous towers, those that were only proposals and those that were built, created a favourable atmosphere for the conception of a very high tower. However, we can deduce from these examples that the technological precedents lay in the experience of Eiffel himself and his collaborators: in these large works, in the bridge columns, in the level of prefabrication attained, in the precision with which these structures were executed and the construction systems used.

3.2 THE EIFFEL TOWER: PROJECT AND CONSTRUCTION 3.2.1 The Tower project There is general agreement that the idea of building a 300-metre high tower must have resulted from a conversation between two of the engineers on the team made up of Gustave Eiffel, Maurice Koechlin and Emile Nouguier. This is what Bertrand Lemoine states in the prologue of the re-edition of the book “La tour de trois cents mètres” of which Eiffel himself is the author: “In 1884 the two main engineers from Eiffel’s firm, Emile Nouguier and Maurice Koechlin, proposed building a tower that was conceived as a large metal post made up of four lattice columns that were bell-shaped towards the base and gathered together at the top, joined together between them by crossbeams placed at regular intervals. Iron was the only metal with which a project of this calibre could be carried out: reinforced concrete was yet to exist” [Ref (144) Lemoine, Bertrand / Eiffel, Gustave] In effect, Koechlin drew a sketch (Fig 3.31) and Sauvestre, the architect of the firm, embellished it (Fig 3.32). This idea would lead to the patent registered by Eiffel, Koechlin and Nouguier, dated 18 September 1884 and titled: “New device which facilitates the construction of metal columns and posts at a height of over 300 metres”.

Fig 3.31. Eiffel Tower. Initial sketch by Koechlin. Note the comparison with other monuments such as Notre-Dame Cathedral, the Statue of Liberty, the Arc de Triomphe and several columns. [Source: Ref (157) Fortier Ifa, Bruno].

On the occasion of the Exposition Universelle of Paris in 1889, a call for proposals was made in 1886 for the erection of a 300-metre tower; Eiffel would win with a proposal that

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Fig 3.32. The Eiffel Tower. Koechlinâ&#x20AC;&#x2122;s diagram embellished by Sauvestre. [Source: Ref (223) Lemoine, Bertrand]

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Fig 3.33. The Eiffel Tower, exactly how it was built. [Source: Ref (144) Eiffel, Gustave]

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According to Eiffel, therefore, it would be possible to eliminate the triangulation on the side of the tower up to the second floor thanks to the principle described above; for any horizontal plane of section M-N, the extensions of the sectioned columns will intersect at the point of application of the total wind force for the area above the plane of section (Fig 3.35). He goes on to say:

3.2.2 The structural principle One of the basic structural principles upon which the tower design was based is described by Eiffel himself in a speech given on March 30 1885 in the Société des Ingénieurs Civils de France:

“The application of this principle is one of the peculiarities of the system used for building the tower, at least for the lower half, and will determine its external profile. Therefore, if we eliminate the diagonal bars from the lower half of the tower, it will rest upon four large columns connected at the height of the first and second floors with horizontal trusses. Thus, in order to fulfil this principle we should modify the curve of the columns the higher up we go, although this is only possible for a wind hypothesis.” [Ref (147) Eiffel, Gustave]

“Let us imagine for one instant that each of the tower faces has a simple lattice to withstand the strong winds labelled P’, P’’, P’’’ and PIV in the diagram (Fig 3.34 and Fig 3.35). We know that in order to calculate the axial forces on the three segments sectioned by plane NM, we should first calculate the amount P resulting from all the external forces acting upon that part of the tower that is above the section plane, in order to later determine the forces in the three sectioned bars. If for each horizontal MN cross-section we make, the prolongations of the two outer lattice chords converge at point of application P, then the sectioned diagonal bar will not be in stress and may be eliminated.” [Ref (147) Eiffel, Gustave]

“If we examine various wind distribution hypotheses, we should direct the columns along an average line corresponding to the average of all the hypotheses in the interest of reducing to a minimum the bending moments in the columns as a result of following one hypothesis or another.” [Ref (147) Eiffel, Gustave] In effect, this principle would only be valid for a wind hypothesis. However, two wind hypotheses were entertained when carrying out calculations for the tower, one that was constant at any height and another with a value that increased with height. The shape of the tower would therefore have been the result of applying the previous principle to the average of the two hypotheses. In spite of this being the theoretical principle, the reality was not quite the same. We can see how the columns up to the first floor have a straight profile in order to simplify their construction. In any case, the stiffness of the connections joining the first-floor truss to the columns is evident, as well as the fact that this stiffness enables these structural elements to withstand any moments that may be generated. We can conclude from this that the Eiffel Tower was conceived, at least theoretically, by implementing the structural shape which the designer believed to be optimum and without any other aesthetic or functional factors. This derived from the fact that the only purpose of the tower was to set a world record in height and become a symbol of technological power. Fig 3.34. Some explanatory sketches on the Tower’s structural shape. [Source: Eiffel, Gustave]

3.2.3 The structural skeleton and puddled iron The structure of the tower was made with puddled iron. Originally developed in 1783 and 1784 by Peter Onions and Henry Cort at the same time, puddling was a refining process for iron in which the carbon and especially the sulphur content were reduced to very low levels, resulting in a very pure metal with better mechanical properties.

Fig 3.35. Explanatory diagram of the Tower’s structural principal described by Eiffel. [Source: López César, Isaac]

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In the discussion on the 1889 Galerie des Machines in Chapter 2, it was seen that Contamin and Eiffel had given up on using steel as a structural material in both the Galerie des Machines and the Tower. Some sources allude to the high price of steel as the reason behind this decision. Regardless of the influence this factor may have had, it is true that both Eiffel and Contamin broached the subject of steel with hesitation in the article they co-wrote in 1889 in the “Congrès International des Procédés de Construction”. In the article, they explain that although steel had begun to be used in some bridges, over the previous

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ten years several tests had been carried out with steel girders, with highly variable results. They also cast doubts on the most suitable techniques for riveting steel without modifying the resistance of the structural elements. [Ref (146) Eiffel, G. / Contamin, V.]

Fig 3.37. Eiffel Tower. Elevation of one of the panels or triangulated quadrangles that make up the basic structural unit of the tower. Note the hollow tubular vertical members on the left and right, as well as the tubular trusses that are X-shaped (elevation) and in a zigzag (plan). [Source: Ref (144) Eiffel, Gustave]

Fig 3.36. Diagram of the Eiffel Tower with the panel numbering. The table on the left presents the weights of these panels. [Source: Ref (144) Eiffel, Gustave]

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Regarding the body of the tower, two main parts can be distinguished (Fig 3.33): The lower part from the base to the second floor, which is made up of four large columns rigidly joined by horizontal girders at the height of the first (57.63 m above ground level) and second floors (115.73 m). Following the principle explained above, there are no structural elements triangulating the tower faces. The arch that appears to support the first floor has a purely formal function. The upper part rises from the second floor, where the four columns are connected by horizontal bars and triangulation. This makes up the section known as the intermediate floor (195.93 m) that was designed exclusively for changing from one lift to another and for the third floor (276.13 m). The French flag that crowned the tower reached a height of 312.27 metres in 1889. The basic structural unit of the tower is the triangulated quadrangle (Fig 3.37). Constant throughout the tower, the triangulation offers complete rigidity against the wind. The maximum horizontal oscillation of the top is 7 cm which, given a height of 300 metres, implies a horizontal displacement / height proportion of 1/4285. Depending on the codes or bibliography, the current limit on this proportion for multi-storey buildings varies, with the most 189

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common values being considerably higher: 1/600, 1/750 or 1/1000. We can therefore see that the whole had a very high rigidity against the wind. Each of these quadrangles is called a panel in the original plans, dividing the structure vertically into twenty-nine numbered panels (Fig 3.36). The concept of module is unsuitable here, as both the shape and size of the panels are variable, with sides approximately ranging from 6 to 11 metres.

Fig 3.38. Eiffel Tower. The eight types of basic connections used to join the tubular vertical members and the tubular-shaped trusses. [Source: Ref (144) Eiffel, Gustave]

The basic elements that make up the quadrangles are the hollow tubular vertical members of the columns on one side, and the tubular-shaped trusses on the other. The hollow tubular vertical members make up the towerâ&#x20AC;&#x2122;s primary structure. Their cross-section has a diameter of 90 centimetres at the base and decreases the higher up the tower you go. The number of vertical members also decreases up the tower. There are four per column from zero level to the first floor; sixteen, in total. This figure progressively decreases to four at the third floor. The tubular-shaped truss is made up of four L-section chords riveted to L-shaped diagonals arranged in an X shape in vertical elevation, and in a zigzag in horizontal elevation. There is considerable variation in their length from panel to panel, the longest being 22 metres. The joint between the tubular-shaped trusses and vertical members is carried out with eight types of basic connections and riveted together, some of them in a considerably complex fashion (Fig 3.38 and Fig 3.41 to Fig 3.44). The connection at the intersection between trusses aims to offer each one continuity; this is especially complex when four trusses cross.

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Fig 3.39. Eiffel Tower. Springer of one of the columns. Elevation. [Source: Ref (144) Eiffel, Gustave]

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Fig 3.40. Eiffel Tower. Springer of one of the columns. Axonometrics. Three-dimensional aggregation of the triangulated quadrangle. Note the different types of connections labelled with letters. Also note that there is horizontal triangulation between the vertical members in each panel. [Source: Ref (144) Eiffel, Gustave]

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Fig 3.41. Eiffel Tower. Connection between vertical members and tubular-shaped trusses. Photograph from the present day. [Source: Ref (238) Martin, Andre / Barthes, Roland]

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The basic arrangement of the panels was interrupted in places coinciding with the first, second and third floors. The triangulation was denser here as these were areas which attempted to make a rigid connection between the four tower columns (Fig 3.45 to Fig 3.47).

Fig 3.42. Eiffel Tower. Connection between vertical members and tubular-shaped trusses. View from the inside. Photograph from the present day. [Source: Ref (238) Martin, Andre / Barthes, Roland]

Fig 3.43. Eiffel Tower. Connection between the trusses and vertical members. Photograph from the present day. [Source: Ref (238) Martin, Andre / Barthes, Roland]

Fig 3.44. Eiffel Tower. Connection at the intersection of four tubular-shaped trusses. Photograph from the present day. [Source: Ref (238) Martin, Andre / Barthes, Roland]

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Fig 3.45. Eiffel Tower. Detail of the connection area with the first floor. Note the increase in density of triangulation in this area with the aim of creating a rigid connection between the four columns. Note the decorative arch. (Structure between panels 1 and 6). [Source: Ref (144) Eiffel, Gustave]

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Fig 3.46. Eiffel Tower. Detail of the connection area with the second floor. (Structure between panels 8 and 14). [Source: Ref (144) Eiffel, Gustave]

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Fig 3.47. Eiffel Tower. Detail of the connection area with the third floor. (Structure between panels 24 and 29). [Source: Ref (144) Eiffel, Gustave]

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3.2.4 The foundations and Trigerâ&#x20AC;&#x2122;s system The complex building of the foundations for the North and West columns, closest to the Seine, was fundamentally due to the fact that it required excavating five metres under the groundwater level. The system used for this was Trigerâ&#x20AC;&#x2122;s, which Eiffel had already tested with the foundations for bridge columns in river beds. Developed in 1839 by the French mining engineer Charles-Jean Triger, this system consisted in a metal tube through which pressurised air was blown, thus creating a work chamber in which the operators could carry out the dry excavation (Fig 3.48). Initially associated with mining excavation, the system was later applied to bridge construction. One of the first to use it for a bridge was John Wright on Rochester Bridge (1851). It was also used by Isambard Brunel on the Royal Albert Bridge in Saltash (1854). It would later be applied to large bridges such as the Brooklyn Bridge (John Roebling, 1870), the largest suspension bridge in the world at the time, and the Forth Bridge (John Fowler, Benjamin Baker, 1883). The risks inherent to the system would become clear over time: on the one hand, working in a high-pressure environment, on the other, the possibility of a failure in pressure that could cause the chamber to be flooded in seconds.

Fig 3.49. Pneumatic caisson in the excavation of the Eiffel Tower. Cross-sectioned perspective. By pressurising the lower chamber, this system enabled excavations below groundwater level. [Source: Ref (306) Watson, William]

In the case of the Eiffel Tower, pneumatic caissons were used (Fig 3.49 to Fig 3.51), consisting of a hermetic metal box with two levels. The upper level was ballasted with concrete to avoid the hydraulic pressure from raising the caisson. Pressurised air was injected into the lower level to avoid the groundwater level from rising and potential seepage, as well as allowing the operators to carry out dry excavation with the aid of electric spotlights. There were two vertical conducts through which earth was removed. Fig 3.48. Diagram of the Triger excavation system with compressed air. Charles-Jean Triger, 1839. A pump injected pressurised air, while another evacuated the waste water. [Source: Ref (261) Peters, Tom F.]

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Once the excavation was completed a concrete slab was placed down upon which four stone masonry footings were built for each column, one per vertical member, and connected by masonry walls. To connect the vertical members, two iron bars about eight metres long were embedded in each footing. The space between the four footings of each column was also excavated to keep installation equipment such as machinery for the lifts and water pumps (Fig 3.52). 199

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Fig 3.50. Eiffel Tower. The pneumatic caissons already set up. [Source: Ref (238) Martin, Andre / Barthes, Roland]

Fig 3.51. Eiffel Tower. Plan showing the arrangement of the pneumatic caissons for the excavation of the North footing. Note the machine for injecting compressed air in the top left angle. [Source: Ref (144) Eiffel, Gustave]

Fig 3.52. (Opposite page above) Eiffel Tower. Foundation of one of the columns in stone masonry. [Source: Ref (238) Martin, Andre / Barthes, Roland]

Fig 3.53. (Opposite page below) Eiffel Tower. Start of assembly of the structural skeleton. [Source: Ref (238) Martin, Andre / Barthes, Roland]

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3.2.5 Workers assaulting the skies: the prefabrication, assembly and lifts Construction of the Tower commenced on 28th January 1887 and ended on 31st March 1889. It took five months to lay down the foundations and twenty-one more to assemble the building. For the assembly of the first floor, pyramid-shaped wooden scaffolding was used; it was built up from the land to brace the columns which were not balanced until the first floor was erected (Fig 3.54). Four large load towers were then built at each face of the tower, upon which the four large girders that make up the first floor were placed. From the first floor upwards, steam-propelled climbing cranes were set up on each of the columns; they travelled up by sliding over the vertical members that made up the structure itself, and were responsible for hoisting up the pieces of the tower (Fig 3.57). There were between 150 and 300 men simultaneously working on the tower. They had to assemble the pieces which arrived by railway; another hundred workers had manufactured and pre-assembled these pieces in Eiffelâ&#x20AC;&#x2122;s own workshops in Levallois-Perret on the outskirts of Paris. Teams of four men were organised to carry out the onsite riveting: one worked the portable forge; another inserted the prefabricated rivet into the orifice and held it by the head; a third hit the rod to shape the opposite head, and finally the fourth finished it off with a sledgehammer (Fig 3.58). There were forty teams working on the first stage, placing 4,200 rivets a day. Another noteworthy issue from a technological point of view is the development of the lifts. It was an unprecedented technical challenge, since never before had lifts that could go up 276 metres been built. Archimedes had begun to develop the lift in the 3rd century B.C. Following up on the Greeksâ&#x20AC;&#x2122; idea, the Romans installed a lift in the Coliseum which took the gladiators up from the hypogeum to the arena. Lifts drawn by donkeys were used in the Middle Ages. However, it was in the 1853 Exhibition of the Industry of All Nations in New York when Elisha Otis presented the first lift with safety measures in the Crystal Palace. Once in the lift, Otis cut the rope it was hanging from, and yet it did not plunge into the depths. This feat marked the most important development since the invention of the lift, and enabled its use to become generalised. In this way, the Otis brothers installed the first public lift in a five-storey building on Broadway in 1857. The first hydraulic lift would be installed in New York in 1872, and in 1878 Siemens would build the first electric lift. Hydraulic lifts were used in the case of the Eiffel Tower, since the technology based on electricity had yet to reach a high level of development. Several types of lift were used. In this sense, the Otis lift is worthy of mention as it went up to the second floor (Fig 3.59 and Fig 3.60). It was made up of a two-floor cabin that slid over inclined rails. There was a piston at the column springers which turned the pulleys, thus tensing the cables in order to raise the cabins. The Edoux lift (Fig 3.61) that went up to the third floor was made up of two balanced cabins. The upper cabin was moved by a hydraulic piston, while the lower one acted as a counterweight. In short, it was an unprecedented achievement that would fire the technological development of the lift. The Tower functioned like a laboratory in which the creation of lifts that could go up 276 metres had been made a reality. This paved the way for high-rise construction.

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Fig 3.54. Assembly diagram of the Eiffel Tower. Note the pyramid-shaped scaffolding and the load towers, as well as the climbing cranes. [Source: Ref (144) Eiffel, Gustave]

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Fig 3.57. Eiffel Tower. Steam climbing crane riveted on the tower itself. [Source: Ref (238) Martin, Andre / Barthes, Roland]

Fig 3.55. Eiffel Tower. Detail of the levelling piston located in the column springers. Once the first floor had been reached, it was discovered that there was a difference in height of various centimetres between each of the four columns. This problem was solved in the column springers; a cavity had been left above the foundation so that pressurised water could be injected, thus making it act like a piston and correcting this error. Once the columns were in position, a metal clamp fitted around the piston would settle them definitively. A similar system was used to correct other structural imbalances derived from the different levels of exposure to solar radiation of various parts of the Tower. [Source: Ref (144) Eiffel, Gustave]

Fig 3.58. A typical riveting team of four men, placing the rivets on the tower. [Source: its designers]

Fig 3.56. Workers injecting pressurised water to level out the columns. [Source: Ref (261) Peters, Tom F.]

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Fig 3.60. Detail of the Otis lift at the level of the second floor. Note the piston fluid injection deposit. [Source: Ref (144) Eiffel, Gustave]

Fig 3.59. Eiffel Tower. Otis lift. Note the piston that turned the pulleys to tense the cables, in the lower right angle. [Source: Ref (144) Eiffel, Gustave]

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3.3 THE EIFFEL TOWER AND ITS ARCHITECTURAL CONSEQUENCES For 42 years, the Eiffel Tower was the tallest building on the planet, until the erection of two North American skyscrapers that were completed in 1930 and 1931 respectively: the 319-metre high Chrysler Building by the architect William Van Allen, and the Empire State Building, designed by William F. Band with a height of 381 metres. In terms of those buildings which were affected more directly, it should be noted that the Eiffel Tower continued to feed architectural fantasy after its erection. Thus, on the occasion of the following Expo, the Worldâ&#x20AC;&#x2122;s Columbian Exposition held in Chicago in 1893, various proposals for towers that would be higher than the Eiffel Tower were put forward, with heights of over 300 metres. They are peculiar proposals, some of them of dubious stability. Examples are the Columbian Memorial by C.M.H. Vail (Fig 3.62), the Johnstone Tower by Alfred Roewade (Fig 3.63) or the Proctor Steel Tower by Holabird and Roche (Fig 3.64), this last example clearly inspired by the Eiffel Tower.

Fig 3.61. Edoux lift. Note the two self-balancing cabins on the right. [Source: Ref (144) Eiffel, Gustave]

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Fig 3.62. Columbian Memorial Tower. C.M.H. Vail. 1893. [Source: Ref (275) Rydell, Robert W. / Gilbert, James]

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Tower being used is the telecommunications tower erected in Tokyo in 1958 by the Japa– Naito – (Fig 3.65 and Fig 3.66). The antenna on top of this tower gives it a height nese Tachu of 332.5 metres. It was originally designed to be higher than the 381 metres of the Empire State Building, which was the world’s tallest building at that time. In contrast with the Eiffel Tower, this was made of steel. The metallic structure is considerably lighter, weighing 4,000 tonnes as opposed to the Eiffel Tower’s 7,300 tonnes.

Fig 3.65. Telecommunications – Naito. – tower in Tokyo. Tachu 1958. [Source: its creators]

Fig 3.63. (Left) Johnstone Tower. Alfred Roewade. 1893. [Source: Ref (275) Rydell, Robert W. / Gilbert, James] Fig 3.64. (Right) Proctor Steel Tower. Holabird and Roche. 1893. [Source: Ref (275) Rydell, Robert W. / Gilbert, James]

In terms of buildings that were actually made, it should be noted that the structural typology used in the Eiffel Tower has not been reiterated beyond some shorter examples designed for tourist amusement facilities. The scarce proliferation of this typology is due to its lack of applicability for the construction of multi-storey buildings with an optimal land use; in this case, slightly parallelepiped-shape buildings are more suited. Thus, it should be noted that in the end, the Eiffel Tower is a gigantic bridge column which was erected exclusively to beat a world record, to be a symbol, in short, a modern menhir. As described above, this was the reason behind allowing the creator to implement the design he saw fit for this purpose, with no other conditions imposed. Meanwhile, in the case of the multi-storey buildings in Chicago, making good use of the land and having the function of office space or housing dictated the need for basically parallelepiped-shaped buildings designed with structural typologies based on the metal portal frame. This morphology implied more serious issues with horizontal stability; this led to a need to develop various resources related to rigidity, a need which grew in proportion to the height of the buildings. This is the reason why the limited examples of this typology are to be found in telecommunication towers or bearing high-power lines. An example of the typology established by the Eiffel

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Fig 3.66. Telecommunications – Naito. – tower in Tokyo. Tachu 1958. [Source: its creators]

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In spĂŹte of the fact that the Eiffel Tower has not had a notable typological continuity, it is evident that the desire to set a world record in height has lasted to the present day; given the evidence, it would be redundant to provide examples to this effect.

Fig 3.68. (Left) Adziogol Lighthouse. Chersson, Ukraine. Vladimir Shukhov. 1911. [Source: Shukhov Tower Foundation]

After erection of the Eiffel Tower, the most noteworthy towers in structural terms could be those built by the Russian avant-garde engineer Vladimir Shukhov. These are extremely lightweight towers made up of a perimeter gridshell in the shape of a hyperboloid. With the aim of beating the Eiffel Tower in height, in 1919 Shukhov designed a project for a tower of these characteristics with a height of 350 metres; had it been built, it would have become the highest building in the world (Fig 3.67). In spite of the previous proposal never seeing the light, Shukhov made about two hundred shorter towers with the same typology. Some examples are the Shukhov radio tower in Moscow (Fig 3.69), built in 1922 with a height of 160 metres, the Adziogol Lighthouse in Chersson, Ukraine (Fig 3.68) with a height of 70 metres and built in 1911, and the six towers built in 1929 that allowed the high-power lines to cross the River Oka (Fig 3.70), with heights of 128 metres and a truly majestic appearance.

Fig 3.69. (Right) Shukhov radio tower in Moscow. Vladimir Shukhov. 1922. [Source: its creators]

Fig 3.67. Project for a 350-metre tower. Vladimir Shukhov. 1919. [Source: its creators]

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Fig 3.70. High-power towers on the banks of the River Oka. Unused in the present day. Vladimir Shukhov. 1929. [Source: its creators]

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“I take a quantity of limestone, such as that used for making roads; but if I cannot procure a sufficient quantity of the above from the roads, I obtain the limestone itself, and I cause the puddle or powder, or the limestone, as the case may be, to be calcined. I then take clay, and mix it with the limestone and water to a state approaching impalpability. After this proceeding I put the above mixture into a slip pan for evaporation. […] Then, I calcine it and it is ready for use.” [Ref (94) Benévolo, L.] The industrial production of artificial cement would commence in 1844, the same year in which Fox and Barret would patent a slab system consisting in cast-iron joists embedded in lime concrete. The patent was titled:

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“Cast-iron joists spaced 45 centimetres and sunk into lime concrete.” [Ref (127) Collins, P.]

THE ARRIVAL OF REINFORCED CONCRETE As described in previous chapters, the Industrial Revolution had promoted the generalisation of the use of iron and steel as structural materials, which led to the extraordinary development of metal structures in the 19th century. Following these significant developments, the most relevant historical event in structural terms was undoubtedly the invention and development of the technique of reinforced concrete; this in turn would lead to the birth of new structural typologies and novel architectural creations.

4.1 REINFORCED CONCRETE: FIRST DEVELOPMENTS

The invention of reinforced concrete cannot be attributed to only one individual. On the contrary, it is a material that was invented and developed through the contributions of various people, some of which bore little or no relation with architecture or engineering. Up until 1900, the theoretical and practical studies on reinforced concrete carried more weight than architectural or engineering works; it was during this initial stage that the first patents related to this new material were registered. From 1900 onwards, there would be an increase in the number of patents associated with large companies which would be responsible for commercialising and promoting this new material. It was therefore at the beginning of the 20th century when the use of reinforced concrete as a structural material started to be more widespread; in constructions of various types such as bridges, factories, warehouses, commercial buildings or tanks. Thus, the development of the first large structures in reinforced concrete would begin at the turn of the century. Reinforced concrete is a material with ancient precedents. The Romans used concrete in their constructions, made of natural cement or pozzolans. It was what they called “opus caementitium”. Returning to more recent times, the engineer John Smeaton noticed that lime mixed with clay hardened upon coming into contact with water; he went on to build the Eddystone Lighthouse in 1774 using this new conglomerate or cement in its stone masonry (Fig 4.1). However, it would be the discovery of artificial cement by Joseph Aspdin in 1824 that would signify the launch pad towards the invention and development of modern concrete. Aspdin’s patent describes the following:

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Fig 4.1. Eddystone Lighthouse. John Smeaton. 1774. [Source: Ref (288) Simonnet, Cyrille]

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In 1848, Joseph-Louis Lambot would build the famous cement boat reinforced with metal bars (Fig 4.3), and after presenting it in the Exposition Universelle in Paris 1855, he would patent a material “to substitute wood” (Fig 4.2) which he named “Ferciment”. Lambot’s patent reads as follows:

Fig 4.3. Reinforced cement boat with metal bars. J.L. Lambot. 1848. Exhibited in the Exposition Universelle in Paris 1855. [Source: Ref (288) Simonnet, Cyrille]

“The objective of my invention is to replace wood in shipbuilding and in any element at risk of being damaged by damp, such as wooden floors, water tanks, flowerpots, etc. This new substitute material is made up of a metal mesh of wires that are connected or woven in some way. This mesh is shaped in a way that best adapts to the object we wish to make, and is then embedded in hydraulic cement”. [Ref (217) Kind-Barkauskas / Kauhsen / Polony / Brandt] A fundamental contribution would be made by William Wilkinson in 1854; he introduced the idea of placing metal rods inside the slabs “in the parts subject to tension forces”. [Ref (103) Brown, J.M.]

Fig 4.4. Joseph Monier’s patent for flower boxes and pipes. 1855. [Source: Ref (217) Kind-Barkauskas / Kauhsen / Polony / Brandt]

Fig 4.5. Joseph Monier’s patent for reinforced concrete decks. 1881. [Source: Ref (94) Benévolo, Leonardo]

Fig 4.6. (Left) First slab with metal joists and iron bars arranged orthogonally. William Ward. 1875. [Source: Ref (115) Casinello, F.] Fig 4.2. J.L. Lambot’s patent for “Ferciment” as a substitute material for wood. 1855. [Source: Ref (217) Kind-Barkauskas / Kauhsen / Polony / Brandt]

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Fig 4.7. (Right) Use of torsioned metal bars as reinforcement. Ernest L. Ransone. 1880. [Source: Ref (115) Casinello, F.]

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It was at the end of the 19th century, however, when the first constructions of a considerable size would begin being made. In this sense, Matthias Koenen would build the bridge for the 1890 Bremen Industrial Fair (Nord-West-Deutsche Gewerbe und Industrie-Ausstellung) in Germany following the Monier system. This work is notable for its svelte cross-section, surprising to find in such an early period (Fig 4.9). Fig 4.10. Hennebique’s patent for the “continuous beam on various supports”. 1897. [Source: Ref (288) Simonnet, Cyrille]

In 1892 Hennebique built the first beam with stirrups and patented his system of reinforced concrete. This system would be highly perfected and eventually have a standardised use (Fig 4.10 to Fig 4.12). Likewise, Hennebique erected a reinforced concrete bridge with a span of 32 metres in Switzerland in 1894, while in 1895 he built the first reinforced concrete silo in Roubaix. Incidentally, F. Le Coeur erected the first reinforced concrete dome in 1897.

Fig 4.8. First slab solely reinforced with round bars. François Hennebique. 1888. [Source: Ref (135) Delhumeau, Gwenaël / Gubler, Jaques]

According to Cyrille Simonnet and other authors: “This makes him the real inventor of the procedure, since he was aware of its specific mechanical action, in spite of the fact that in 1877, Hyatt would experiment with and measure the mechanical interaction between both materials, placing particular emphasis on the strong adherence of the iron to the concrete”. [Ref (288) Simonnet, Cyrille] Another notable figure was the French gardener Joseph Monier, who would patent a flower box construction system in 1867 in which wires were crossed orthogonally (Fig 4.4). In the years to come, Monier would bring out more patents for the construction of girders, decks, stairs and bridges, and in 1880 would establish the so-called “Monierbeton” system (Fig 4.5). In 1875 William Ward would make the first reinforced concrete slab with metal joists and a grid of iron bars (Fig 4.6). In order to improve the adherence between the metal and the concrete, Ernest L. Ransone would use torsioned bars with a square cross-section in 1880; these can be considered a precursor of modern corrugated bars (Fig 4.7). The French engineer François Hennebique would build the first concrete slab solely reinforced with round bars in Belgium in 1888 (Fig 4.8).

Fig 4.11. The Hennebique stirrup. 1892. [Source: Ref (288) Simonnet, Cyrille]

Fig 4.9. Bridge for the Industrial Fair in Bremen, Germany. Matthias Koenen. 1890. [Source: Ref (267) Picon, Antoine]

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Fig 4.12. Hennebique’s reinforced concrete system. [Source: Ref (181) Gössel, Peter / Leuthäuser, Gabriele]

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At the same time, Robert Maillart was experimenting with the three-hinged arch made of reinforced concrete, a structural typology which had been tested at length in metal construction. Along these lines, the Tanavasa Bridge over the Rhine was erected in Switzerland in 1905, and was made up of a three-hinged concrete arch with a span of 51 metres (Fig 4.13 and Fig 4.14). In 1910 Maillart would trial a new typology in the GiesshĂźbel Warehouse in Zurich: the beamless slab, that is, the solid concrete floor slab with reinforcing rods distributed over the whole area while supported on isolated columns with mushroom capitals, the aim of which was to avoid punching failure (Fig 4.15).

Fig 4.15. GiesshĂźbel Warehouse, Zurich. Robert Maillart. 1910. [Source: Ref (217) Kind-Barkauskas / Kauhsen / Polony / Brandt]

Fig 4.13. Use of the three-hinged arch in reinforced concrete in the Tavanasa Bridge over the Rhine. Robert Maillart. 1905. [Source: Ref (139) Doordan, Dennis P.]

Fig 4.16. (Below) Illustration showing a comparison of different systems of reinforced concrete organised according to the typology of the structural element. 1902. [Source: Ref (267) Picon, Antoine]

Fig 4.14. Tavanasa Bridge over the Rhine. Robert Maillart. 1905. Project drawing. [Source: its creators]

From 1900 onwards there would be an increase in the number of patents (Monier, Coignet, Hennebique, etc) linked to large companies. In terms of calculation, diverse systems were used (Hennebique, Rabat, Cottancin, etc.). In this respect, there would be a particularly significant event in 1906: the publication in France of the first official regulations governing reinforced concrete, which would allow this new material to be used with the safety of a regulatory document.

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Concrete was gradually acquiring its own architectural language. Thus, in 1912 Heinrich Zieger built the enamel Factory in Ligetfalu, Slovakia (Fig 4.19). It had two adjacent naves with spans of 30 and 18 metres and a length of 150 metres. Both naves were designed with arched portals made of reinforced concrete. The expression that characterises this new material was starting to reveal itself, in this case through the continuity between the structural elements of the deck and columns.

4.2 REINFORCED CONCRETE: THE FIRST LARGE ARCHITECTURAL STRUCTURES The beginning of the 20th century would also mark the standardisation of reinforced concrete as a structural material, and with it, the first large structures. In this way, Plüdemann and Küster would erect the new Market Hall in Breslau in 1908 (Fig 4.17) applying the reinforced concrete arch. In this case, parabolic arches were used. Such was the popularity of iron in designing certain architectural typologies, that the structure was originally painted to simulate riveted iron. Additionally, Auguste Perret built the Théâtre des Champs-Élysées between 1911 and 1913, a building of considerable structural complexity for its time (Fig 4.18).

Another example of the buildings that inaugurated the new architectural language created by reinforced concrete is the Jahrhunderthalle or Centennial Hall in Breslau, Germany (now Poland), built in 1913 by Max Berg (Fig 4.20 to Fig 4.22). It is a building designed with a 65-metre-diameter reinforced concrete dome, made up of meridians and parallels and an upper compression ring. It was the largest reinforced concrete dome built at that time. While the building plan seems to have baroque reminiscences, the space created is surprisingly modern, and expresses the new formal possibilities of the new material brilliantly. It is probably the most significant early example of a reinforced concrete construction.

Fig 4.17. Market Hall in Breslau. Plüdermann and Küster. 1908. [Source: Ref (217) Kind-Barkauskas / Kauhsen / Polony / Brandt]

Fig 4.19. Enamel factory in Ligetfalu, Slovakia. Heinrich Zieger. 1912. [Source: Ref (181) Gössel, Peter / Leuthäuser Gabriele]

Fig 4.20. Centennial Hall. Breslau. Max Berg. 1913. Cross-section. [Source: Ref (217) Kind-Barkauskas]

Fig 4.21 Centennial Hall. Max Berg. 1913. Plan. [Source: Ref (217) Kind-Barkauskas]

Fig 4.18. Théâtre des ChampsÉlysées. Auguste Perret. 1911-13. [Source: Ref (168) Gargiani, Roberto]

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and 1923 (Fig 4.25 to Fig 4.27). These were vaults with 86-metre spans made up of a shell with a parabolic cross-section folded into forty waves. The height of the wave cross-section decreases from 5.4 metres at the base to 3 metres at the apex. The resulting shape is characterised by the great inertia obtained with a thin shell. This was one of the first works in which mechanical vibration compaction, invented by Freyssinet, was used as a method of concrete compaction. The Orly Hangars undoubtedly represent the highest technology achieved by reinforced concrete at that time.

Fig 4.23. The Henri Esders Tailor Shop. Auguste Perret. 1919. [Source: Ref (168) Gargiani, Roberto]

Fig 4.22 Centennial Hall. Breslau. Max Berg. 1913. [Source: Ref (217) Kind-Barkauskas]

Another noteworthy building was the Henri Esders Tailor Shop (1919). Built by Auguste Perret in Paris, what stands out is the large, diaphanous central space supported by refined, svelte arches. Straight guide pieces, arches, slabs of variable cross-section, medium and large spans, and the monolithic connections between the structural elements; together, they showcased the multiple technical, formal and spatial possibilities of this new material (Fig 4.23). However, it was reinforced concrete shells that would mark the important forward leap in terms of span, being the most developed typology in this material. In this way, shell structures would demonstrate that concrete could compete with iron and steel when it came to building large spans. One of the earliest examples is the dome of Sankt Blasien church in Germany, which was built in 1911 with a modest span of 15.4 metres [Ref (283) Schöne, L] (Fig 4.24). The role of French engineer Eugène Freyssinet is worth of mention in this field. He made innumerable contributions to the advance of reinforced concrete, one of the most significant being the development of large span decks. Between 1915 and 1929, he built many decks for factories and hangars. He built the Orly Hangars for dirigibles between 1921

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Fig 4.24. Sankt Blasien Church, Germany. Early example of a reinforced concrete shell structure. 1911. [Source: Ref (283) Schöne, L.]

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Fig 4.25. Orly Hangars. Freyssinet. 1921-1923. [Source: Ref (217) Kind-Barkauskas]

Fig 4.28. Factory for the Schott Company. Franz Dischinger. 1924. [Source: Ref (61) Architectural Forum]

Fig 4.29. Planetarium for the Carl Zeiss Company. Franz Dischinger. 1925. Concreting the dome. [Source: Ref (267) Picon, Antoine]

Another key figure in the development of shell structures was Franz Dischinger. We can highlight early examples of his work such as the factory for the Schott Company in 1924, made up of semi-cylindrical shell vaults with 35-metre spans and a thickness of five centimetres (Fig 4.28). In the case of the planetarium for the Carl Zeiss Company (1925) (Fig 4.29 to Fig 4.31), Dischinger used a steel bar mesh over which he projected concrete via the spraying method. The result was a dome with a diameter of 25 metres and a thickness of 6 centimetres that lay on a tension ring measuring 80 x 40 centimetres, in turn supported by twenty columns. This is one of the oldest existing reinforced concrete shells, and it was one of the first hemispherical shells to be used as a prototype to solve the structural issue of planetariums.

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Fig 4.26. (Left) Orly Hangars. Freyssinet. 1921-1923. [Source: Ref (288) Simonnet, Cyrille] Fig 4.27. (Right) Orly Hangars. Freyssinet. 1921-1923. Construction photograph. [Source: Ref (267) Picon, Antoine]

Fig 4.30. Planetarium for the Carl Zeiss Company. Franz Dischinger. 1925. [Source: Ref (267) Picon, Antoine]

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Fig 4.33. Leipzig Market Hall. Franz Dischinger. 1929. Photograph of the inside. [Source: Ref (267) Picon, Antoine] Fig 4.31. Planetarium for the Carl Zeiss Company. Franz Dischinger. 1925. [Source: Ref (217) Kind-Barkauskas]

Another of the principal works in the development of this typology is the Leipzig Market Hall, erected in 1929 by the same Franz Dischinger (Fig 4.32 and Fig 4.33). In this case, it was designed with domes made up of cylindrical sections with a simple curve; each octagonal dome had a diameter of 65.8 metres, a height of 29.9 metres and was 10 centimetres thick. Nerves were inserted both between and inside the sections to increase the rigidity. The dome lay on inclined columns that were an extension of the main deck nerves. The thrusts were absorbed on two planes: the ceiling located at the base of the dome and the basement ceiling located at the inclined column springers. Dischinger made a comparison between the dome of St. Peterâ&#x20AC;&#x2122;s in Rome (10,000 t in weight), the deck of the Centennial Hall in Breslau (6,340 t) and his own domes (2,160 t), which covered a greater area or surface than either of the former buildings.

Fig 4.34. Boulingrin Central Market Hall in Reims. E. Maigrot. 1928-1930. [Source: Ref (170) Garrido Moreno]

Other notable constructions in the field of shell structures is the Boulingrin Central Market Hall in Reims, erected between 1928 and 1930 by E. Maigrot (Fig 4.34 to Fig 4.36). The design involved a shell with a parabolic cross-section 7 centimetres thick with external nerves that increased the rigidity. The thrusts were contained by small shells perpendicular to the main one. Fig 4.35. Boulingrin Central Market Hall, Reims. E. Maigrot. 1928-1930. [Source: Ref (262) Pevsner, N.]

Freyssinet would contribute to a new forward leap in technology through the invention of prestressed concrete in 1928.

Fig 4.32. Leipzig Market Hall. Franz Dischinger. 1929. [Source: Ref (267) Picon, Antoine]

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Fig 4.36. Boulingrin Central Market Hall, Reims. E. Maigrot. 1928-1930. Cross-section. [Source: Ref (170) Garrido Moreno]

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4.3.1 Reinforced concrete up until the Brussels Expo in 1958 4.3 REINFORCED CONCRETE AND THE WORLD EXPOS

The patents that already existed in 1900 began to be used additionally in some of the World Expo buildings. Concrete was generally employed as a technical resource in these buildings, without bringing to light an expression of its own which so far had been non-existent and generally hidden under historicist façades. In this sense, Hennebique’s company built reinforced concrete slabs in the Grand and Petit Palais for the Exposition Universelle of Paris 1900 (Fig 4.37 to Fig 4.39). The Palais de L’Électricité was built for this same Expo; built by Eugène Henard and Paulin, it was a reinforced concrete structure in spite of its eclectic façade (Fig 4.40 and Fig 4.41). The contribution of these structures lies not in any noteworthy novelty they might offer, but precisely in the fact that they represent initial applications of patents, although they may be isolated examples.

It is clear through the examples mentioned above that avant-garde reinforced concrete structures were being built on the fringes of the World Expos, some of which had large spans that could be successfully adapted to the context of the large exhibition buildings that characterised World Expos in the 19th century. On the other hand, these developments were not corresponded by the World Expos; their contribution to the history of reinforced concrete in terms of buildings or projects was modest. This fact contrasts with the huge contribution made by the World Expos to the development of metal structures. The World Expos of the 19th century had been marked by the idea of industrialisation as a guarantee of welfare and infinite progress. This would lead to the solitary, colossal exhibition building made of iron; that is, a temple to industry. It is worth noting that many of these buildings were christened with the name “palace”: “Palace of Industry”, “Palace of Machines”, etc. After the First World War (1914-1918), a two-fold crisis occurred; on the one hand, the economic crisis, while on the other, what we could call an ideological crisis based on the prolongation of the War and its terrible severity due to the development in armament boosted by industrialisation. Europe would bear witness to the bitterest face of technological development; this was the reason why the idea of industry as a guarantee of welfare would fall into decline. As a result of these events, the World Expos would abandon the previous giantism that had been associated with industrial optimism and would turn instead to the decorative arts, diversifying into several small pavilions. This phenomenon would take place at the exact moment in which the first large reinforced concrete structures were being erected on the periphery of the Expos. This is one of the two causes for the almost total absence of significant structures in reinforced concrete in the World Expos of that time. At a later point after the Second World War and from the 1958 Brussels Expo onwards, the structural vanguard would centre on other typologies. Thus cable networks, cable-stayed structures, modern space grids or pneumatic structures would capture the public’s attention. Concrete had already proved its ability to achieve large spans in building on the margins of the World Expos: its moment as a cutting-edge material capable of representing nations’ economic and technological power had come to an end. The other factor that to some extent also influenced the almost total absence of concrete structures with any historical significance in the Expos was the inherent monolithic nature of reinforced concrete which prevented its dismantling. It is certainly true that many buildings had remained for years after the end of the Expos, put to alternative uses. Nevertheless, the design criterion that was generally given priority was that of provisionality, and for that concrete was not the most suitable material.

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Fig 4.37. (Left) Grand Palais. Paris. Henri Deglane and Charles Louis Girault. Exposition Universelle of Paris 1900. [Source: its creators] Fig 4.38. (Right) Petit Palais. Exposition Universelle of Paris 1900. [Source: its creators]

Fig 4.39. Construction of a slab for the Petit Palais. Hennebique Reinforced Concrete. 1900. Note the Hennebique stirrup. [Source: Ref (288) Simonnet, Cyrille]

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Fig 4.40. Palais de l’Électricité. E. Henard and Paulin. Exposition Universelle of Paris 1900. [Source: Ref (239) Mattie, Erik]

Fig 4.41. Palais de l’Électricité. E. Henard and Paulin. 1900. The engraving reads: “Cross-section showing the reinforced concrete work of the monument, main arch, secondary arches, slabs, terraces, stairs, etc.” [Source: Ref (125) Cohen, Jean L.]

Fig 4.42. Palais des Letres, Sciences et Arts. Sortais and Cordier. Exposition Universelle of Paris 1900. Note the combination of iron and concrete structures. [Source: Ref (135) Delhumeau, Gwenaël]

Fig 4.43. Saint-Jean de Montmartre. Anatole de Baudot. 18941904. Detail of the reinforced cement vaults. [Source: Ref (6) Anatole de Baudot]

In the same Expo in Paris 1900, the Palais des Letres, Sciences et Arts was built by Sortais and Cordier (Fig 4.42). In this case, it was an early example in which a metal structure was combined with reinforced concrete. The main nave’s large span was achieved via a metal structure, while the deck of the side galleries, of shorter spans, was built with reinforced concrete slabs and columns. Anatole de Baudot would be one of the pioneers of reinforced cement, a technique he preferred over reinforced concrete which only used sand and not gravel. His most noteworthy work may be the church of Saint-Jean de Montmartre, begun in 1894 and completed in 1904 (Fig 4.43 to Fig 4.45). It was made of reinforced cement with masonry infill panels made of reinforced brick masonry. Inside, the cement is exposed. CHAPTER 4

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Fig 4.44. Saint-Jean de Montmartre. Anatole de Baudot. 1894-1904. [Source: Ref (226) Loyer, François]

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Fig 4.45. Saint-Jean de Montmartre. Anatole de Baudot. 1894-1904. Project detail. Note on the left the reinforced cement nerves, which in the project were to be covered with brickwork, and on the right the reinforced masonry panels. [Source: Ref (6) Anatole de Baudot]

In 1894 Baudot designed a project for a function room for the Paris Exposition Universelle 1900, which was the result of this search for typologies that were suited to large-span reinforced cement decks (Fig 4.46 to Fig 4.50). It would be a slightly circular building covered by a dome built with overlapping prismatic elements made of reinforced cement. Baudot wrote about this project in the publication “L’architecture et le ciment armé”: “It was quite simple and logical to adapt a spine model laid horizontally which would join the support points two-by-two, repeating the system both at the base of the large upper lantern and at its higher part; the central hollow would not need to be closed, for its very small size does not pose a problem. It can be easily appreciated that the cement elements are used methodically and logically with this arrangement; in addition, thanks to the reduction in weight and length of these elements, the assembly of the whole piece can be carried out easily and simply”. [Ref (6) Anatole de Baudot 1834-1915, Rassegna, Milan] The project was rejected in the end.

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Fig 4.46. Unbuilt project for a function room for the Exposition Universelle of Paris 1900. Anatole de Baudot. [Source: Ref (6) Anatole de Baudot]

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Fig 4.47. to Fig 4.50. Unbuilt project for a function room for the Exposition Universelle of Paris 1900. Anatole de Baudot. Plan diagrams of the dome structure. [Source: Ref (6) Anatole de Baudot]

On the occasion of the fiftieth anniversary of the First World Expo held in London in 1851, the “Glasgow International Exhibition” was organised in Glasgow in 1901. In this exhibition we can highlight the project for the “Concert Hall” that Charles Rennie Mackintosh submitted to competition, and which was never built (Fig 4.51). This project, of which there is a record in a drawing kept in the archives of the Hunterian Art Gallery, University of Glasgow, would have formed part of the 1901 International Exhibition, to be later used as urban facilities. It was a considerably modern project and one of its creator’s most singular. The planned building had a circular floor plan covered by a diminished dome with a diameter of 48.75 metres. The dome thrusts would be absorbed by a tension ring reinforced by twelve buttresses. The thinness of the dome suggests that a reinforced concrete or cement shell structure would have been used, a complete novelty for that time. It is true that it could also be a spatial structure made of one sole layer, in the style of those built by Johann Wilhelm Schwedler for gas tanks in Berlin, which had spans of between 50 and 65 metres (Fig 4.52). In any case, the truth is that the structural typology intended for this building is unknown.

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Fig 4.51. Concert Hall. Project for the Glasgow International Exhibition. Charles Rennie Mackintosh. [Source: Ref (13) Charles Rennie Mackintosh]

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Fig 4.52. Deck for a gas tank in Berlin. Johann Wilhelm Schwedler. 1875. It has a span of 54 metres. [Source: Ref (283) Schรถne, L.]

Fig 4.53. Image of the Eiffel Tower covered in concrete. Charles Rabut. 1918. [Source: Ref (288) Simonnet, Cyrille]

The technological optimism generated by this new material would also lead to truly ludicrous proposals. Thus, in 1918 Charles Rabut would propose raising the Eiffel Tower to 500 metres by covering it in concrete. Apparently, the metal structure would act as the reinforcing bars (Fig 4.53). The first major International and Universal Expo organised in Europe since World War One was held in Brussels in 1935. The Palais du Centenaire, also known as the Grand Palais (Fig 4.54 to Fig 4.57) is worthy of mention. This is undoubtedly the most significant structural contribution of the World Expos to the history of reinforced concrete. It was built by the architect Joseph van Neck in 1930 on the occasion of the centenary of the independence of Belgium, recovered for the 1935 Brussels International Exposition as the Palais des Expositions and later used for the 1958 Expo. Still standing to this day, this building is comprised of a large nave designed with twelve three-hinged, reinforced concrete arches with spans of 86 metres and a height of 31 metres. There is a second structural order consisting of reinforced concrete girders with a span of 12 metres connecting the arches. The tiered deck is supported by columns that lie on the girders or arches.

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Fig 4.54. Palais du Centenaire or Grand Palais. Brussels. Joseph van Neck. 1930. Current photograph. [Source: its creators]

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This building has the same span as that of Freyssinetâ&#x20AC;&#x2122;s Orly Hangars, erected seven years earlier; in this case, however, three-hinged arches were used while in the earlier building a shell structural typology was used, thus rendering it more advanced and specific to concrete. It was described in earlier chapters how the three-hinged arch had been thoroughly trialled in metal construction. In the case of the typology of reinforced concrete, the most brilliant creations had been the works of Robert Maillart in bridge construction. In this sense we can highlight the Tanavasa Bridge over the Rhine (1905) (Fig 4.13 and Fig 4.14), made up of a three-hinged arch with a span of 51 metres. In 1929, one year before the erection of the Palais du Centenaire, Maillart would complete what would become one of his masterpieces, the Salginatobel Bridge (Fig 4.58), with a three-hinged, reinforced concrete arch spanning 90 metres. We should therefore note that the 86-metre span Palais du Centenaire was not the largest three-hinged, reinforced concrete arch in the world, but it was the biggest used in building for that time.

Fig 4.55. Palais du Centenaire. Brussels. Joseph van Neck. 1930. Current photograph. Three-hinged arches made of reinforced concrete and spanning 86 metres. [Source: its creators]

Fig 4.56. Palais du Centenaire. Brussels. Joseph van Neck. 1930. Cross-section. [Source: its creators]

Fig 4.58. Salginatobel Bridge. Robert Maillart. 1929. Threehinged, reinforced concrete arch with a span of 90 metres. [Source: its creators]

Fig 4.57. Palais du Centenaire. Brussels. Joseph van Neck. 1930. Plan. [Source: Its creators]

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Among the more sculptural proposals, we can highlight the Civil Engineering Pavilion (Fig 4.61 to Fig 4.67), also in Expo ’58 in Brussels. It was based on a proposal by the sculptor Jacques Moeschal, with J. Van Doorselaere as the architect and A. Paduart as the engineer. It was made of reinforced concrete and basically consisted of a large cantilevered girder with a length of 78.8 metres, its tip 35 metres above the ground. There was a walkway suspended from the cantilever. At the opposite end, a small building was corbelled and covered with a shell 6 centimetres thick. The artistic expressiveness of the ensemble that derived from the apparent imbalance was achieved through the lightened, V-shaped cross-section cantilever. There were two inner, prestressed concrete ties to support the shell-covered building.

4.3.2 Reinforced concrete after Brussels 1958: late shell structures and proposals with a sculptural character The Expo held in Brussels in 1958 marked a structural renaissance in the Expos, which had languished during the inter-war period after having made enormous achievements in the 19th century. Nevertheless, the structural avant-garde in ’58 was mainly established in the structural typologies whose mechanical principle was based on tension. Thus, cable-stayed decks or cable networks would be the main protagonists of this exhibition. The presence of reinforced concrete shell structures in the World Expos is scarce; while those that were built were a novelty within the field of the Expos, their contributions were not significant in the context of the history of structural typologies, given that they were late constructions. One example is the United Nations Pavilion in Expo ’58 held in Brussels (Fig 4.59). The design was a dome that resulted from the cut with six inclined planes, and therefore supported at six points. The dome is completed with a thicker edge nerve. Another example in the same Expo is the IBM Pavilion, made up of a folded shell which offers an incredibly light appearance that is emphasised by a completely glazed enclosure (Fig 4.60).

Fig 4.61. Civil Engineering Pavilion in Expo ’58 in Brussels. J. Van Doorselaere and A. Paduart. [Source: Ref (239) Mattie, Erik]

Fig 4.59. United Nations Pavilion. Expo ‘58. Brussels. [Source: its creators]

Fig 4.60. IBM Pavilion. Expo ‘58. Brussels. [Source: its creators]

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Fig 4.62. Civil Engineering Pavilion in Expo ’58 in Brussels. J. Van Doorselaere and A. Paduart. [Source: Ref (112) Cánovas, Andrés]

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Fig 4.66. Civil Engineering Pavilion. Scaffolds and formwork. [Source: Ref (256) Paduart, A.]

Fig 4.63. Civil Engineering Pavilion in Expo â&#x20AC;&#x2122;58 in Brussels. J. Van Doorselaere and A.Paduart. Longitudinal section. [Source: Ref (256) Paduart, A.]

Fig 4.65. Civil Engineering Pavilion. Cross-section along the reinforced concrete shell. [Source: Ref (256) Paduart, A.]

Fig 4.64. Civil Engineering Pavilion. Reinforcing bars in the cantilever. [Source: Ref (256) Paduart, A.]

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Fig 4.67. Civil Engineering Pavilion. Placing the cantilever reinforcing bars. [Source: Ref (256) Paduart, A.]

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Another notably singular work that was built for Expo â&#x20AC;&#x2122;58 in Brussels was the Philips Pavilion designed by Le Corbusier, which would be one of the last works of his career. The Greek architect and engineer Iannis Xenakis collaborated on the project (Fig 4.68 to Fig 4.76).

Fig 4.69. Philips Pavilion. Project drawing. [Source: Ref (302) Treib, Marc]

Fig 4.68. Philips Pavilion in Expo â&#x20AC;&#x2122;58 in Brussels. Le Corbusier and Iannis Xenakis. [Source: Ref (302) Treib, Marc]

Fig 4.70. Philips Pavilion. Arrangement of the hyperbolic paraboloids. [Source: Ref (302) Treib, Marc]

It was a small, geometrically complex pavilion created around twelve hyperbolic paraboloids. The intersection edges between the different paraboloids were joined with cylindrical reinforced concrete nerves with a diameter of 40 centimetres. The shells were made from small, precast, concrete panels 5 centimetres thick that were placed with the help of provisional wooden scaffolding. Once sealed and painted, an external, tensioning cable net with a diameter of 7 millimetres was placed at 50-centimetre intervals, its ends anchored to the reinforced concrete nerves. Normally in steel reinforced masonry systems, the metal reinforcing rods are located inside the joints. The novelty here resided in the fact that this was a post-tensioning reinforced masonry structure, in which the metal rods were placed on the outside. It was demolished after the Expo.

Fig 4.71. Philips Pavilion. Simulation of the wind forces on a model. [Source: Ref (302) Treib, Marc]

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Fig 4.72. (Above, left) Concreting the nerves placed on the intersection edges of the hyperbolic paraboloids. [Source: Ref (302) Treib, Marc] Fig 4.73. (Above, right) External tensioning cable network. [Source: Ref (302) Treib, Marc] Fig 4.74. (Below, left) Philips Pavilion. Construction of the surfaces with small, precast, concrete panels. [Source: Ref (302) Treib, Marc] Fig 4.75. (Below, right) Philips Pavilion. [Source: Ref (302) Treib, Marc]

Fig 4.77. Unbuilt proposal for the World Expo in Rome 1942. Pier Luigi Nervi. [Source: Ref (169) Garn, Andrew]

Complex shapes with a certain sculptural character were also present in proposals that never saw the light. Thus, a World Expo was planned in Rome for 1942. Due to the outbreak of World War Two (1939-1945), the Expo was postponed and later suspended after the fall of Mussoliniâ&#x20AC;&#x2122;s government. Nevertheless, some of the buildings had been completed before the start of the war, generally reinterpretations of Roman Classicism of little architectural interest. One exception is the unbuilt proposal by Pier Luigi Nervi, the Italian architect and engineer renowned precisely for his structural innovations with reinforced concrete. In this case, his design was for a curved, reinforced concrete pavilion (Fig 4.77).

Fig 4.76. Philips Pavilion. The completed building. [Source: Ref (76) Aloi, Roberto]

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Along the same lines, Paul Rudolph designed the Portland Cement Association Pavilion, also called The Galaxon (Fig 4.78), for the 1964 Worldâ&#x20AC;&#x2122;s Fair in New York. In this case, it was a large concrete girder supported on two columns with cantilevers on either side. The public would be able to go up this girder either via the stairs located on the inside of one of the columns, or by ramps. This construction, which would be better considered a sculpture than a building given its lack of a specific function, was designed to be the central element in the Expo. In the end it was never built either.

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Fig 4.78. Unbuilt Project for the Portland Cement Association Pavilion in the 1964 Worldâ&#x20AC;&#x2122;s Fair held in New Yok. Paul Rudolph. [Source: Ref (239) Mattie, Erik]

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Fig 5.1. (Above, left) Saharan nomadic tent. The fabric is superimposed on a series of cables anchored to supports and to the ground. Note the triangulation in the two main directions. [Source: Ref (95) Berger, Horst]

CHAPTER 5

TENSION DECKS: ORIGIN AND PEAK

A significant number of buildings with structural typologies fundamentally based on tension were erected on the occasion of World Expos. Some of these works have become paradigms in the history of structural systems because of their value in terms of innovation. It is a noteworthy fact that some Expos have managed to gather together such important or so many tensile structures so as to create a historical link with certain typologies. This is the case, for example, of Expo ‘58 held in Brussels and its association with structures made with prestressed cable nets, or Expo Osaka 1970 and the Exposición Universal de Sevilla 1992 with the notable presence of prestressed cable nets with textile enclosures and prestressed textile membranes. Upon analysing the technological context within the chronological period covered by the World Expos, two stages can be differentiated: on the one hand, there were specific and intermittent experiences during the 19th century, some of which form the cornerstone of modern, tensioned typologies. On the other hand, the second half of the 20th century witnessed a great boom and development of modern tensile structures.

Fig 5.2. (Above, right) Ottoman tent from the 17th century on exhibit in the Royal Palace in Dresden, Germany. Floor plan: 20 x 8 m. Height: 6 m. [Source: its creators] Fig 5.3. (Centre left) Chinese sailboat. [Source: Ref (95) Berger, Horst] Fig 5.4. (Centre right) Phoenician sailboats. [Source: its creators] Fig 5.5. (Below, right) Fresco discovered in Pompeii which shows the “velum” or amphitheatre sunshade. [Source: its creators] Fig 5.6. (Below, left) Reconstruction of the Roman “velum” by Rainer Graefe. Vitruvius includes this element’s folding mechanism in his treaty. [Source: Ref (95) Berger, Horst]

The large spans made possible by this way of working were exploited by civilisations located in mountainous regions in the building of suspension bridges made with ropes fashioned out of plant fibres. Those built by Andean and Himalayan tribes are particularly noteworthy (Fig 5.7 and Fig 5.8).

5.1 TENSILE STRUCTURES IN THE 19TH CENTURY 5.1.1 The technological context: intermittent contributions Structures whose mechanical principle is based on tension have been built since ancient times. The structural airiness achieved through this modus operandi was fundamentally exploited for building provisional or mobile structures, or those that could be dismantled. Such is the case of the tents of nomadic groups, made with wooden masts, fibres, ropes and animal skins or fabrics (Fig 5.1 and Fig 5.2). Other examples derive from the state-of-the-art technology attained by Phoenician, Roman or Chinese sailboats (Fig 5.3 and Fig 5.4). There are also documented examples of textile decks designed to cast shade over Roman amphitheatres, found in various frescoes discovered in the city of Pompeii (Fig 5.5 and Fig 5.6).

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Fig 5.7. (Left) Bridge over the Río Pampas on the road from Cuzco to Jauja (Peru). Span: 41 metres. Disappeared at the end of the 19th century. [Source: Ref (155) Troyano, L.] Fig 5.8. (Right) Traditional construction of a Peruvian bridge with plant fibre ropes. These are always bridges in which the deck is not independent of the catenary, but rather adopts its shape. [Source: Ref (221) Kronenburg, Robert].

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Bridges with iron chains were known to have been built in China from the 14th century onwards, although they are not believed to have reached the modern solution of hanging a horizontal deck from vertical cables attached to a parabolic cable. All known oriental chain bridges are catenary bridges with little deflection; for this reason the deck was not separated from the cable (Fig 5.9 and Fig 5.10) [Ref (155) Troyano, Leonardo]

chains attached between them; these are anchored to an iron support embedded in the masonry walls at each corner of the building. There are lighter, secondary chains attached perpendicularly to the main chains, with plaited wires crossing the former. The result is a mesh that Schnirch suggested covering with either cast-iron tiles or with planks and iron or copper plates. In short, it is a hanging deck in which stability is dependent on the weight of the overlay material, since there are no cables with opposing curvature to stabilise the whole against the suction force of the wind. According to Schnirch, the main advantage of this deck would be its low weight compared to that of a conventional deck.

Fig 5.9. (Left) Chain bridge. Chuka Bridge over the River Wang in Bhutan. 15th century. [Source: Ref (155) Troyano, L.] Fig 5.10. (Right) Ching-Lung chain bridge over the Yangtze River. Span: 100 m. [Source: Ref (95) Berger, Horst]

In the Western World, the first documented proposals for suspension bridges are included in the book Machinae Novae by Fausto Veranzio, published in Venice in 1615. There are two proposals in this book: the Pons Canabeus (Fig 5.11), a suspension bridge made with hemp ropes and a wooden deck, and the Pons Ferreus (Fig 5.12), a cable-stayed bridge with iron chains. In our opinion, the latter is truly sophisticated, since the chains were arranged at an angle, thus making it a chain-stayed bridge rather than a suspension one. Nevertheless, the fact that the beams forming the deck were hinged does not seem to be the best solution, bearing in mind that these types of bridge transmit compression to the deck, therefore running the risk of creating an unstable situation.

Fig 5.11. (Below, left) Pons Canabeus by Fausto Veranzio, published in his book Machinae Novae, Venice, 1615. Suspension bridge with hemp fibre ropes. [Source: Ref (249) Nardi, Guido]

Fig 5.13. Proposal for a hanging deck for a theatre. Friedrich Schnirch. 1824. Note above on the left the configuration of the main chains; above in the centre is the anchoring piece for the chains embedded in the masonry wall; below on the left, the fastening for the enclosure panels. [Source: Ref (183) Graefe, Rainer]

Fig 5.14. Proposal for a hanging deck for a theatre. Friedrich Schnirch. 1824. Secondary chains on the left; main chains, above in the centre; below on the right, a general diagram of the deck structure. [Source: Ref (183) Graefe, Rainer]

Going back to periods that are contemporary to the World Expos, we can state that the immediate precedents to tensile building structures developed during the 19th century are the suspension bridges with iron chains that began to be built in Europe at the end of the 18th century, as well as those referred to in Chapter 1 (Fig 1.6 and Fig 1.7). The first significant, documented reference to a tensile building structure in the 19th century appears in the article published by the engineer Friedrich Schnirch in 1824 titled “On wrought iron decks” [Ref (183) Graefe, Rainer]. In this article, Schnirch, a man with experience in building chain suspension bridges, includes a deck project for a theatre (Fig 5.13 and Fig 5.14). It is a rectangular-plan deck made up of two wrought iron supports 48 metres apart with main

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Fig 5.12. (Above, right) Pons Ferreus by Fausto Veranzio, published in his book Machinae Novae, Venice, 1615. Cable-stayed bridge with iron chains and wooden deck. [Source: Ref (249) Nardi, Guido]

A mast factory (Fig 5.15) was built in the military port in Lorient, France in 1839, in which the principle of iron chain suspension bridges (parabolic chain, vertical hanging chains and horizontal deck) was applied directly. It had a span of 44 metres and a width of 20 metres, the dimensions needed to manoeuvre the masts. The parabolic cables were anchored to the masonry walls in the adjacent naves. This building was published in J.M. Sganzin’s “Cours de Construction”, a very well-known engineering manual in the United States.

Fig 5.15. Mast Factory in Lorient military port, France. 1839. [Source: Ref (300) Thorne, Robert]

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Another innovative work was the deck for the Panorama in the Champs Élysées in Paris erected by Hittorff in 1839 (Fig 5.16 to Fig 5.18). In this case, it was a conical deck with a wooden framework. This deck was hung from twelve cables from another twelve masonry walls arranged in a circular fashion. It was worth noting the refined nature of the bars that were supported by the walls. The ties extended vertically inside the walls to the foundations.

metres. In short, it was a prestressed cable structure in which each cable was subject to the mutual force of the opposing curvature. This building represents a clear precedent to some cable structures erected at a later date both for Expos and other contexts. Along similar lines, Lehaire and Mondésir would carry out various proposals for largespan tension decks in 1866 (Fig 5.22). The proposals for circular-plan decks with spans of 100 metres stand out. In this case, the cables supported a central ring with a glass lantern. There are supports over the outer walls and backstay cables. Another of the proposals aimed for a rectangular-plan deck with a span of 75 metres. The arrangement of cables with opposing curvature and outer backstay cables can be seen. In this case, it was a prestressed cable structure. The deck enclosure could be vaulted (left area of the cross-section) or staggered (right area of the same). Once again, the modernity of both structural solutions is surprising. Fig 5.16. Panorama in the Champs Élysées. Paris. Hittorff. 1839. Elevation. [Source: Ref (183) Graefe, Rainer]

Fig 5.17. Panorama in the Champs Élysées. Paris. Hittorff. 1839. Cross-section. [Source: Ref (183) Graefe, Rainer]

Fig 5.19. (Above, left) Building for the German Song Festival in Dresden. Eduard Müller and Ernst Giese. 1865. Cross-section. Note the novel structural system of cables with opposing curvature. [Source: Ref (183) Graefe, Rainer] Fig 5.20. (Above, right) Building for the German Song Festival in Dresden. Eduard Müller and Ernst Giese. 1865. Longitudinal elevation. [Source: Ref (183) Graefe, Rainer] Fig 5.21. Building for the German Song Festival in Dresden. Eduard Müller and Ernst Giese. 1865. Elevation. [Source: Ref (183) Graefe, Rainer]

Fig 5.18. Panorama in the Champs Élysées. Paris. Hittorff. 1839. Structural details. From left to right, inner iron reinforcements in the masonry walls; cross-section of the deck; bars details. [Source: Ref (183) Graefe, Rainer]

In 1865, the architects Eduard Müller and Ernst Giese erected a surprising building for the German Song Festival in Dresden (Fig 5.19 to Fig 5.21 and Fig 8.22). The design here was for a structure with an incredible level of technological development. Made with wooden trusses, the deck was hung from cables with opposing curvatures, offering rigidity against the wind pressure and suction forces. In addition, backstay cables were installed towards the outside to reduce the horizontal force at the support heads. The span was about 45

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Fig 5.22. Proposals by Lehaire and Mondésir for large-span decks in tension. 1866. On the left, a circular-plan deck with a span of 100 metres. On the right, a rectangular-plan deck with a span of 75 metres. [Source: Ref (183) Graefe, Rainer]

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These are just a selection of the structural contributions made in the 19th century within the field of tensile structures. They are basically intermittent experiences, but of great value for two reasons: firstly, they are examples of advanced typologies at very early dates, in which the development of metal structures was in its initial stages, as described in Chapter 1. Secondly, some of them became precedents of highly significant structures built in the 20th century.

“The net-shaped deck obtained in this way represents a significant saving in weight when compared with other, more habitual ways. The net elements depend on one sole stress, tension (in the hyperboloid) or compression (in the net that makes up the finishing dome). The elements making up the net, riveted or bolted at the intersection points, form a surface capable of resisting large loads.” [Ref (183) Graefe, Rainer]

5.1.2 Expos in the 19th century: brilliant, intermittent contributions Following the historical pattern in the 19th century, the contributions of the Expo structures from that century in the field of tension are also one-time and intermittent, but not without interest. In the first place, we should highlight the building proposed by James Bogardus on the occasion of the Exhibition of the Industry of All Nations held in New York in 1853; Bogardus proposed building the aforementioned circular deck with a diameter of 122 metres and hung from iron chains anchored to a cast-iron tower 91.5 metres high and with a diameter of 23 metres at the base (Fig 2.112). This deck would be covered with metal sheeting. In spite of never being made, the value of this proposal lies in the novelty this design presented at such an early stage. Likewise, we have the unbuilt proposal by Entwurf von Leroy S. Buffington for the World’s Columbian Exposition in Chicago 1893 (Fig 5.23). Here, the size of the building makes it impressive. It would be a circular building with a central tower to which a tension deck covered by metal sheeting would be anchored. A spiral ramp would allow access to the deck over this sheeting surface.

Fig 5.24. Vladimir Shukhov’s patent for decks. 1895. On the left, joints of the intersections of the sheets or angles that make up the deck structure. [Source: Ref (183) Graefe, Rainer]

Fig 5.23. Unbuilt proposal by Entwurf von Leroy S. Buffington for the World’s Columbian Exposition in Chicago 1893. [Source: its creators]

The greatest contribution to this field made by the Expos in the 19th century, however, would undoubtedly be that of the Russian engineer Vladimir Shukhov. In 1895, Shukhov patented a deck structure system based on tension stress (Fig 5.24). The patent depicts a hyperboloid, the surface of which has double curvature and is either built with plates or metal angles that are crossed and riveted at their intersections. This surface could be suspended between concentric circles. The whole was completed with a dome following a similar system. According to Shukhov himself:

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On the occasion of the All-Russia Exhibition held in Nizhny-Novgorod in 1896, Shukhov would put this new structural typology into practice for the first time by erecting four exhibition buildings. The Rotunda or Pavilion of Structural Techniques (Fig 5.25, Fig 5.27 and Fig 5.28) stands out. It was a building with a diameter of 68.3 m and a height of 15 m, made up of two metal rings, an inner one with a diameter of 25 m supported by 16 columns, and another perimetral one at a distance of 21.5 metres from the first. Between the two rings there was a network made up of 640 plates that were crossed over and riveted at their meeting points. The central area was designed with an inverted spherical cap made of riveted sheets 1.5 mm thick. The Oval Pavilion (Fig 5.29 and Fig 5.30) was built according to similar principles. In this case, the mesh was held up by two central truss supports with sheet metal capitals and a fish belly beam. The dimensions were surprisingly large, with a length of 98 metres and

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a width of 51 metres. In this case, the mesh had double curvature in the area of the two semi-circular ends, and simple curvature in the area of the two straight sides. Additionally, it can be seen how Shukhov varied the opening in the plate mesh, making it denser in the whole perimetral area. Two other rectangular pavilions were built following the same technique, both 35 metres wide and 50 metres long (Fig 5.25 and Fig 5.26). In this case, a central row of trussed columns was used.

Fig 5.25. The Rotunda or Pavilion of Structural Techniques and the Rectangular Pavilion, under construction. All-Russia Exhibition held in Nizhny-Novgorod. Vladimir Shukhov. 1896. [Source: its creators]

Fig 5.26. Rectangular pavilion in the All-Russia Exhibition held in NizhnyNovgorod. Vladimir Shukhov. 1896. [Source: Ref (267) Picon, Antoine]

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Fig 5.27. The Rotunda or Pavilion of Structural Techniques, under construction. The All-Russia Exhibition held in NizhnyNovgorod. Vladimir Shukhov. 1896. [Source: its creators]

Fig 5.28. The Rotunda or Pavilion of Structural Techniques. The All-Russia Exhibition held in NizhnyNovgorod. Vladimir Shukhov. 1896. [Source: Ref (267) Picon, Antoine]

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The Expo presented a surprisingly innovative ensemble of the technical and formal possibilities of this typology.

Fig 5.29. Oval Pavilion. The All-Russia Exhibition held in Nizhny-Novgorod. Vladimir Shukhov. 1896. [Source: its creators]

While it is true that these decks are not the first to use tension work as a basic structural design principle, as has been shown, their great contribution lies in the fact that they are the most similar to a continuous surface of double curvature subject to tension for that time; in this way, they are precedents to modern tensile structures made of cable nets. The All-Russia Exhibition of 1896 would signify an opportunity for Shukhov to build the first examples of this typology, and thus make this invaluable contribution to the history of structural systems. Fig 5.30. Oval Pavilion. The All-Russia Exhibition held in Nizhny-Novgorod. Vladimir Shukhov. 1896. [Source: Ref (184) Graefe, Rainer]

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However, the event that would mark the start of the huge boom in tension decks in the second half of the 20th century would be in 1953 with the erection of Dorton Arena in Raleigh (Fig 5.33 to Fig 5.36), by the architect Matthew Nowicki and the engineer Fred N. Severud. This building would signify another fundamental milestone in the history of tension decks, demonstrating the enormous possibilities of this typology for large-span buildings. The structure was made up of a cable net in which the cables with opposing curvature were crossed orthogonally, thus offering the deck stability against wind pressure and suction forces.

5.2 THE ENORMOUS BOOM IN TENSILE STRUCTURES IN THE 20TH CENTURY 5.2.1 The technological context

The cable net in Dorton Arena is framed; this frame consisted in two parabolic arches inclined 21° and crossed. Its vertical component is absorbed by the vertical members that make up the enclosure, and which in turn are counterbalanced by the terraces. The net was made up of cables with diameters varying from 13 to 32 mm, separated by 1.8 m, and was covered by a sheet enclosure. The dimensions are 92 x 97 m. The impact that Dorton Arena had was enormous, becoming the cornerstone for the dissemination of this deck typology and an inspiration for innumerable cable decks built in Europe, the U.S.A. and the Soviet Union.

In spite of the huge contribution made by Vladimir Shukhov’s works, they did not become widely known until the ‘70s, thus rendering them isolated instances. Nevertheless, the French engineer Bernard Lafaille would build the Pavilion for the Republic of France in 1937 ˇ zbor (Fig 5.31 and Fig 5.32). It was a circular-plan construcfor the Zagreb Fair, Zagrebacki tion with a 30-metre span tension deck made of steel sheets 2 millimetres thick that were welded to a steel perimetral compression ring supported by columns in the same material. This building was widely disseminated in engineering manuals of the time, and Bernard Laffaille’s works became considerably important in the development of tension decks.

Fig 5.31. Pavilion for the Republic of France for the Zagreb Fair. Bernard Lafaille. 1937. [Source: its creators]

Fig 5.32. Pavilion for the Republic of France for the Zagreb Fair. Bernard Lafaille. 1937. Photograph of the deck. [Source: its creators]

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Fig 5.33. Dorton Arena in Raleigh. Matthew Nowicki and Fred N. Severud. 1953. [Source: Ref (267) Picon, Antoine]

Fig 5.34. Dorton Arena in Raleigh. Matthew Nowicki and Fred N. Severud. 1953. [Source: Ref (151) Escrig , Félix / Sánchez, José]

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Fig 5.37. Terminal of Dulles Airport. Eero Saarinen. 1962. Cross-section. [Source: Ref (151) Escrig , Félix / Sánchez, José]

Another influential work was the deck of the terminal in Dulles Airport, erected in 1962 by Eero Saarinen (Fig 5.37 and Fig 5.38). The structure here comprised a suspended deck with cables arranged in a single direction and stabilised by gravity through concrete slabs with a dead load of around 200 Kg/m2. Its span is 60 metres.

Fig 5.35. Dorton Arena in Raleigh. Matthew Nowicki and Fred N. Severud. 1953. [Source: its creators]

Fig 5.38. Terminal of Dulles Airport. Eero Saarinen. 1962. [Source: Ref (257) Parkin, Neil]

Fig 5.36. Dorton Arena in Raleigh. Matthew Nowicki and Fred N. Severud. 1953. Photograph of the building under construction. [Source: Ref (230) Makowski, Z.S.]

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Impressed upon observing the plans of Dorton Arena in Raleigh, the German engineer Frei Otto began his studies on tensile structures, making many creations. His work would gain great relevance in the development of these typologies. Among numerous others, we can highlight the first application of a prestressed textile membrane including high and low inner vertices to cover an orchestra in the Interbau (International Building Exhibition) in Berlin held in 1957 (Fig 5.39). Apart from practical applications, in 1962 and 1966 Otto would publish the two volumes of his classic book: “Tensile Structures”, in German, translated to English in 1967 and 1969 respectively [Ref (255) Otto, Frei], in which he gathered a large part of what was known about tensile structures at that time: basic concepts, typologies, reduced models, built examples, as well as the analysis of cable structures, cable nets and membranes.

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The number of structurally interesting World Expo buildings would multiply during this brilliant period. By now, it was customary to have individual pavilions focussing on different countries, different regions of the host country and various private companies. The Expo that would inaugurate this new period of splendour was Expo ’58 in Brussels. Nevertheless, as far as tensile structures are concerned, we first need to consider a notable building erected for the World’s Fair in Chicago in the inter-war period, specifically in 1933. It was the Travel and Transport Building.

5.2.2 World Expos in the 20th century: the triumphant entrance of tensile structures

Fig 5.39. First application of prestressed textile membrane including high and low inner vertices. Interbau, Berlin. Frei Otto. 1957. The membrane has a high central vertex and four low vertices. [Source: Ref (255) Otto, Frei]

5.2.2.1 The Travel and Transport Building in the World’s Fair in Chicago 1933: an isolated structural experiment

The previous section merely presented some of the first paradigms in the historical development of tensile structures in the 20th century. However, the World Expos would be an occasion to experiment and develop new structures, giving rise to new typological milestones.

In spite of the fact that the United States and Europe had been plunged into the worst crisis ever since the development of capitalism, it was decided to hold a World Expo in Chicago in 1933. This Expo would be the first to undergo a substantial change in organisation with respect to previous editions: the individual exhibition would take centre stage, that is, large private companies interested in having their own pavilions because of the publicity and dissemination this would offer their products. While the Fair would not be remembered for its architectural brilliance, there were limited classical references and the designated architects were protagonists of the beginning of the Modern Movement in the United States.

We will now consider how the significant tensile structures built for the World Expos in the 20th century have often had precedents or consequences in other relevant contemporary structures beyond the Expos. They have been highly relevant, on other occasions, due to the significant development in span they attained with a given typology, or because they constituted a formal innovation within the same. In any case, this means that tensile structures in the World Expos have been woven into the fabric of history to become fundamental pieces in understanding and developing these typologies. As we have seen over the course of the previous chapters, the World Expos were exponents of great structural and technological development during the 19th century. In the first part of the 20th century after the First World War (1914-1918), they primarily centred on displaying decorative objets d’art while diversifying into small pavilions. There were two crises behind this: the economic crisis and the ideological crisis that had begun to question a technology capable of destroying the populace. The Second World War (1939-1945) would also interrupt the progress made by the Expos. While there are some interesting structures that make an exception during the inter-war period (the Palais du Centenaire in the 1935 Brussels Expo, for example (Fig 4.54 to Fig 4.57)), in general there was no place for large-span structural typologies in the pavilions developed in these periods. In addition, it is difficult to find small buildings housing structural innovations of any significance. With a few exceptions, technological display yields centre stage during this era to the recreation of historicist styles, classical and even regionalist reinterpretations, and to sporadic appearances of rationalist or neoplastic architecture. Once World War Two had ended, the Expos would recover their structural-technological splendour once again, evinced in the great progress made by diverse structural typologies and new materials in the exhibitions: the considerable development in tensile structures, the enormous protagonism of space frames, the considerable profusion of pneumatic structures (which emerged in part due to the technology of WW2) or the development of structural products derived from wood. This structural apogee would last until the end of the 20th century.

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Fig 5.40. The Travel and Transport Building. H. Burnham, J.A. Holabird, E.H. Bennet, L. Skidmore, N.A. Owings and L.S. Moisseiff. 1933. [Source: Ref (75) Allwood, John]

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In structural terms, the most interesting building would undoubtedly be the Travel and Transport Building (Fig 5.40 to Fig 5.42) by the architects H. Burnham, J.A. Holabird and E.H. Bennet and the engineers L. Skidmore, N.A. Owings and L.S. Moisseiff. The Travel and Transport Building was primarily made up of three volumes: the General Exhibition Space, the Steamship Exhibition Hall and the Railroad Hall.

Fig 5.41. The Travel and Transport Building. 1933. Note the three volumes comprising the building. [Source: Ref (1) Architectural Forum] Fig 5.43. Railroad Hall. 1933. [Source: Ref (181) GĂśssel, Peter / LeuthĂ¤user, Gabriele]

The first two volumes are not very significant in structural terms. The first was designed with a portal frame system of steel girders and columns, both with an H-section and trusses, and the second with three-hinged, steel, trussed arches with a span of 30.5 metres. None of these structural typologies was therefore new. The truly innovative element which would unequivocally characterise the building was the Railroad Hall (Fig 5.43 to Fig 5.45).

Fig 5.42. The Travel and Transport Building. 1933. Floor plans. Note the three volumes comprising the building: the General Exhibition Space, with a system of metal portal frames; the Steamship Exhibition Halls, with a system of three-hinged steel trussed arches spanning 30.5 metres, and the Railroad Hall.

Fig 5.44. Railroad Hall. 1933. [Source: Ref (98) Blaser, Werner]

Fig 5.45. Railroad Hall. 1933. [Source: Ref (1) Architectural Forum]

[Source: Ref (1) Architectural Forum]

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The Railroad Hall (Fig 5.46 and Fig 5.47) was made up of a volume with a slightly circular plan with a dome supported by suspension cables linked to perimetral columns and backstay cables. The diameter measured between column bases was 63.1 metres and the height from ground level to the extrados of the dome peak was 38.09 metres. The structure had twelve steel trussed columns linked in threes to definitively make four space truss columns (Fig 5.49). The three columns in each group were inter-linked with horizontal and diagonal bars. The column heads had the necessary plates to connect the suspension cables (“suspension cable” in Fig 5.46) and for the backstay cables (“backstay cable” in Fig 5.46). The dome structure was light and formed by steel H-section meridians with a depth of 406 mm, and steel H-section parallels linked to the meridians. The difference in height between the base of the dome itself and the extrados of the peak was 5.79 metres. Vertical suspension cables supported the meridians. The load estimate in the dome was a dead load of 15 lb/ft2 (73 Kg/m2) and a snow load of 25 lb/ft2 (123.25 Kg/m2).

Fig 5.46. The Railroad Hall. 1933. Structural schematic cross-section and schematic floor plans of the deck structure. [Source: Ref (12) Engineering News Record]

Fig 5. 47. The Railroad Hall. 1933. Plan of foundations of three of the columns. Note the X-shaped column bases over pile caps and the reinforced concrete anchor blocks for the backstay cable anchorage. [Source: Ref (12) Engineering News Record]

Fig 5.48. The Railroad Hall. 1933. Detail of the backstay cables anchored in reinforced concrete anchor blocks. [Source: Ref (12) Engineering News Record]

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Fig 5.49. The Railroad Hall. 1933. Details of the columns. Note primarily: the standard trussed column elevation; the X-shaped cross-section of the main vertical member of the column and the column base in the foundations, allowing rotation of the same towards the inside of the building but preventing it towards the outside. [Source: Ref (12) Engineering News Record]

Fig 5.50. (Opposite page, above, left) The Railroad Hall. 1933. Putting up the columns. [Source: Ref (67) Architectural Forum] Fig 5.51. (Opposite page, above, right) The Railroad Hall. 1933. Perimetral structure of completely assembled columns. Note the columns grouped in threes and joined with horizontal and diagonal bars. [Source: Ref (67) Architectural Forum]

The main characteristic of this structure is its flexibility. Thanks to the variability inherent to live loads, the cables cause the perimetral column heads to move horizontally around 8 inches (20.32 cm). These columns are linked at the base through a support that enables rotation towards the inside (Fig 5.49). The three columns in each group move at the same time; as a result of these effects, the dome peak would lower approximately 3 feet (91.4 cm) and, to that effect, four radial joints had been installed which crossed the parallels and divided the dome into four quarters (“expansion line” in Fig 5.46). When the dome lowered, these joints would open and the dome’s diameter would increase. Once the dome elevated again, the joints would close and the diameter would decrease.

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Fig 5.52. (Opposite page, center, left) Assembling the meridians by hanging them from the vertical suspension cables. [Source: Ref (67) Architectural Forum] Fig 5.53. (Opposite page, center, right) Start of assembly of the dome enclosure. [Source: Ref (67) Architectural Forum]

Fig 5.54. Structure and enclosure upon completion. [Source: Ref (67) Architectural Forum]

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during World War One (1914-1918) and later adopted for the construction of large markets and specifically for the large hangars needed for the new airships. While there are design variations with different levels of sophistication, they basically consisted in horizontal trusses supported by suspension cables attached to other trusses that were formed by cables and anchored to hinged columns at the foundations, with backstay cables in place. Examples of this typology are the hydroplane hangar built in Cherbourg Arsenal, France, with a span of 197 feet (60 metres) (Fig 5.56) and the hangar erected in Bizerte Arsenal, Tunisia, with a span of 233 feet (71 metres) (Fig 5.57).

Fig 5.55. The Railroad Hall. 1933. Outdoor photograph of the suspension cables. [Source: Ref (67) Architectural Forum]

The following appeared in the October 1931 issue of the publication The Architectural Forum:

Fig 5.56. Hangar for hydroplanes in Cherbourg Arsenal, France. [Source: Ref (43) Engineering News Record]

“The dome of the Travel and Transport Building represents a daring step forward in architecture. We believe that this is the first time the principle of bridge suspension has been used to build a dome.” [Ref (67) Architectural Forum] Likewise, the historian Carl Condit explains in his book American Building Art: The Twentieth Century, published in 1961: “The greatest and most sophisticated example of a suspended building in the United States is the deck of Dorton Arena in Raleigh (Fig 5.33 to Fig 5.36), North Carolina (1953), designed by the architect W.H. Dietrick and the engineers Severud, Elstad and Krueger. […] The first building erected following the principle of suspension was the Travel and Transport Building from the Century of Progress Exposition in Chicago (1933-34).” [Ref (129) Condit, Carl] In the issue of 8th January 1931 of Engineering News Record, the following was said about this building: “Its suspended dome deck is going to be the first application of such a design.” [Ref (12) Engineering News Record] We should clarify these statements. In strict reference to domes, we believe that these three declarations are correct. However, as far as suspended, circular-plan decks are concerned, we should not overlook earlier precedents such as the Panorama in the Champs Élysées by Hittorff (1839) (Fig 5.16 to Fig 5.18), which in spite of its considerable technological differences, was definitively a structure made up of cables supporting a rigid, circular-plan deck. Along the same lines, we have also referred to Lehaire and Mondésir’s proposal (unbuilt, in this case) for a circular deck (1866) (Fig 5.22) that was supported by suspension and backstay cables. On the other hand, the principle of suspension had already been trialled with rectangular-plan decks; a good example is the Mast Factory in the Military Port of Lorient, France (1839) (Fig 5.15) or the sophisticated deck of the building erected for the German Song Festival in Dresden (1865) (Fig 5.19 to Fig 5.21 and Fig 8.22). There are also other precedents closer in time, such as the large-span, cable-stayed decks for hangars erected in France and published in the October 1921 of the journal Engineering News-Record [Ref (43) Engineering News Record]. These were developments gestated

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Fig 5.57. Hangar in Bizerte Arsenal. Tunisia. [Source: Ref (43) Engineering News Record]

In short, and aside from its precedents, this is a building with a structural design that is definitely new and interesting, specifically regarding the movements of the structural elements. It has particular value thanks to the fact that it was built in such an early period, when the boom in tensile structures had yet to begin (it would be twenty years before Dorton Arena in Raleigh was built). Nevertheless, we believe it to be a sophistication that was somewhat aggravated by the objective it aimed to achieve, which undoubtedly could have been met in a simpler way. Fragmenting the dome into quarters and allowing for perimetral movements might have made more sense in larger structures in which the thermal stresses could really be significant. On the other hand, when dealing with building structures, it is necessary to coordinate the structural movements, considerably large in this case, with sealing the enclosure and the deck itself. In this case and based on the documentation consulted, however, there is no evidence of the existence of any pathologies in this sense, to which the building’s provisional nature probably contributed. In any case, the building appears to have been conceived as a structural experiment which took advantage of the occasion in order to trial new issues that would serve future building experiences, tying in with the concept of the World Expos as a testing ground for structures.

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The first solution would be applied in the case of Dorton Arena in Raleigh. Following the death of Lafaille in 1955, René Sarger continued developing and carrying out some of the works that Lafaille had not completed, elaborating on the design of cable net typologies; this gave rise to two of the first milestones in this typology, built precisely for Expo ’58 in Brussels, namely the French Pavilion and the Marie Thumas Restaurant Pavilion.

5.2.2.2 The rebirth of structural brilliance in Expo ’58 in Brussels.

As explained earlier, the French Pavilion (Fig 5.59 to Fig 5.62) was made by the architects René Sarger and Guillaume Gillet and the engineer Jean Prouvé, and fanned the desire to recover the tradition of the large exhibition building in the style of the large, French galeries des machines from the 19th century. In this sense, the deck was constructed with two cable nets covering a total floor surface of 12,000 square metres. The result is an enormous deck with a floor measuring 80 x 150 metres. The dimensions of Dorton Arena in Raleigh, built five years earlier, were 92 x 97 metres (Fig 5.33 to Fig 5.36).

As described above, the Expos after WW2 once again became points of reference for the technological advances made in the field of building structures. We can affirm that the Expo that would restart this new era of brilliance after the extraordinary structural achievements in the Expos of the 19th century was the Exposition Universelle et Internationale of Brussels in 1958. We should point put that this Expo was characterised by a display of the new formal possibilities of buildings whose decks were made with cables or other tension elements, thus rendering it a show brimming with surprising structural ideas and new architectural forms. It was really in Brussels ‘58 when the World Expo would once again take the centre stage of the structural innovation which had languished after the turn of the century, with a few isolated exceptions. Some of the buildings erected for Expo ’58 would become true paradigms of the history of tensile structural typologies. Thus, the French Pavilion, the Marie Thumas Restaurant Pavilion, the U.S. Pavilion and the Soviet Pavilion would be the most significant demonstrations of these extremes. Let us not forget that the aforementioned Philips Pavilion by Le Corbusier (Fig 4.68 to 4.76) would also be erected here; although it was a shell structure built from small, precast concrete pieces, these pieces were post-tensioned via steel outer cables. The French Pavilion was developed by the architect René Sarger. Sarger was a disciple of Bernard Lafaille, the engineer whose greatest works centred on the development of thin decks made of both steel and reinforced concrete. We have already referred to one of his creations: the Pavilion of the Republic of France for the Zagreb Fair (1937) (Fig 5.31 and Fig 5.32). However, one of Lafaille’s projects would become a direct precedent to both Dorton Arena in Raleigh (Matthew Nowicki and Fred N. Severud. 1953) (Fig 5.33 to Fig 5.36) and the French Pavilion in this Expo. It was a preliminary project presented in 1951 in the competition for the future Centre des Industries Mécaniques (Lafaille and Camelot) (Fig 5.58); the design was for two perimetral reinforced concrete arches between which a hyperbolic paraboloid was installed, spanning 200 metres. The first proposal presented the paraboloid built with a cable net crossed orthogonally with opposing curvature, offering the deck stability against pressure and suction wind forces. Later, a second proposal would be drawn up in which 4 mm sheets and cables were combined.

Fig 5.59. General view of Expo ’58 in Brussels. Note on the right the French Pavilion and the U.S. Pavilion on the left, with a circular floor plan. [Source: Ref (75) Allwood, John].

Fig 5.58. Elevation of the preliminary project for the Centre des Industries Mécaniques. Bernard Lafaille and Camelot. 1951. [Source: its creators]

Fig 5.60. The French Pavilion in Expo ’58 in Brussels. René Sarger, Guillaume Gillet and Jean Prove. Note the two deck hyperbolic paraboloids, made with a prestressed cable net. [Source: Ref (267) Picon, Antoine]

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The initial idea for the Pavilion seems to have been a radial structure sustained on a single point of support. This idea would have originated in a previous project by Sarger and Gillet themselves for a covered market in the city of Caen. In the end, the project that materialised was based on a main structure comprising an inverted tripod which would be in the shape of a Y when projected horizontally. This Y was initially only going to have one support coinciding with the point at which its three arms converged, so that its cantilever, sticking out of the North façade, would act as a counterweight for the others. In the end, two metal bipods were attached to the ends of the latter two arms, thus partially altering the original concept (Fig 5.63 to Fig 5.69).

Fig 5.61. The French Pavilion in Expo ’58 in Brussels. René Sarger, Guillaume Gillet and Jean Prove. [Source: its creators]

Fig 5.63. The French Pavilion in Expo ’58 in Brussels. René Sarger, Guillaume Gillet and Jean Prove. Plan at a level of 19.5 metres. [Source: Ref (76) Aloi, Roberto]

Fig 5.64. The French Pavilion. Diagram. Note the Y-shaped superstructure, with an arm extending out through the North façade and the other two starting from point O to B1 and to B2 respectively. The

Fig 5.62. The French Pavilion. Note the façade trusses supporting the edge beams that frame the cable net. [Source: Ref (302) Treib, Marc]

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two metal bipods were placed at these points B1 and B2. [Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

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Fig 5.65. The French Pavilion. Cross-sections. [Source: Ref (76) Aloi, Roberto]

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Fig 5.66. The French Pavilion. Joint between the arms of the Y-shaped superstructure. [Source: Ref (44) Le libre des Expositions]

Fig 5.67. The French Pavilion. Joint between the arms of the Y-shaped superstructure. [Source: Ref (230) Makowski, Z.S.]

Fig 5.68. The French Pavilion. Photograph of the building under construction. Note the base of the Y-shaped superstructure. The edge beams frame the hyperbolic paraboloids and the façade trusses support the edge beams. [Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

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Fig 5.69. One of the arms of the Y forming the superstructure of the building. Note the support bipod at the back. [Source: its creators]

The two diagonal girders had an approximate span of 100 metres, and the cantilever that pointed out of the façade, around 95 metres. The deck was made up of two hyperbolic paraboloids, each framed by four trussed edge beams of varying section that were arranged in a slightly horizontal fashion in order to bear the cable tension; these girders were linked between them with semi-rigid joints (Fig 5.73 and Fig 5.74). The lowest vertices of this frame were sustained by the main Y-shaped structure. The rest of the frame lay on a series of tubular trusses placed every three metres all around the façade perimeter; these had the additional function of resisting the horizontal wind load on the façade enclosure (Fig 5.62). The enclosure was made of corrugated polyester on the South, East and West façades, while the North façade which housed the main entrance was made of glass. The two hyperbolic paraboloids had a common generatrix located on the building’s vertical plane of symmetry. Each paraboloid was made up of two families of cables with opposing curvature. The distance between the cables that made up the mesh was 1.05 m. Under the effect of the dead load, the snow load and the wind pressure load, the concave cables were tautened while the convex ones were relaxed. On the contrary, faced with wind suction load, the convex cables were stretched while the concave ones relaxed. In order to ensure deck rigidity, both families were prestressed, thus guaranteeing that none of the cables would completely relax under any combination of forces, but would always maintain a degree of residual tension. As explained, the perimetral frame of each paraboloid was made up of four truss girders of varying section fixed with semi-rigid joints and forming a quadrilateral. In this sense, the two diagonal arms of the Y (in Fig 5.64, OB2 and OB1) carry out the function of triangulating the quadrilaterals, thus stiffening them.

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Fig 5.70. The French Pavilion. Construction of the cable net. [Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

Fig 5.71. The French Pavilion. Construction of the cable net and placement of the steel covering sheets.

Fig 5.74. The French Pavilion. Detail of the truss girders that frame the cable net. [Source: Ref (76) Aloi, Roberto]

[Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

The façade trusses (Fig 5.73) were made of tubular chords, with the inner chord connected to the inner chord of the perimetral deck truss and the outer chord connected to its perimetral deck truss counterpart. As Pierre Vallée, the civil engineer and director of the Société des Anciens Établissements Eiffel in charge of erecting the building, said: “Under certain load conditions, the façade trusses could be subject to a tension force that would range from zero at the high points to 8 tonnes at the lowest points of the hyperbolic paraboloids, although in reality, this tension is always compensated by the dead load of the perimetral trusses and the façade trusses themselves.” [Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

Fig 5.72. The French Pavilion. Placement of the covering sheets. [Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

This whole framed cable net supported a covering of steel sheets, thermal and waterproofing insulation. In short, the cable net combined with the covering materials was incredibly light, weighing around 8 Kg/m2.

Fig 5.73. The French Pavilion. [Source: Ref (230) Makowski, Z.S.]

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Fig 5.75. The French Pavilion under construction. Note one of the support bipods of the Y-shaped superstructure. [Source: Ref (278) Sarger, René / Prouvé, Jean / Gillet, Guillaume]

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Another step forward in this line of technical-formal innovation would be the Marie Thumas Restaurant Pavilion (Fig 5.77 and Fig 5.78), belonging to a commercial canning company. The architect for this building was once again René Sarger, together with Baucher, Filippone and Blondel. In this case, the deck and enclosure fused together to create a continuous surface covering 53 x 36.8 metres. It should be noted that in his publication Tensile Structures, Frei Otto pointed out the existence of the odd earlier example with similar designs insofar as their use of ridge and valley cables with opposing curvature, the first anchored to cable-stayed columns and the second in the foundations. Such is the case of the small, portable Hangar model built in 1956 by Stromeyer in collaboration with Frei Otto himself (Fig 5.76), which went on to be manufactured in series. Its floor plan measured 36 x 30 metres, with a height at the centre of 8.5 metres [Ref (255) Otto, Frei].

Fig 5.76. Hangar model. Stromeyer. 1956. [Source: Ref (255) Otto, Frei]

Fig 5.78. Marie Thumas Restaurant Pavilion in Expo ’58 in Brussels 1958. Under construction. [Source: Ref (302) Treib, Marc]

Perhaps the most outstanding particularity of this pavilion is the fact that the cables were connected via fish belly beams (Fig 5.79) forming the cone-shaped generatrices (straight generatrices). In this case, enclosure fabric was substituted by coloured plastic sheets with a thickness of 0.4 mm, some of which were opaque, others translucent and yet others transparent.

The Marie Thumas Pavilion was formed by eight tubular, internal, trussed columns with varying cross-section that were arranged diagonally; they converged two by two, thus supported at four points. As with Stromeyer Hangar, ridge and valley cables with opposing curvature were used, the first anchored to the cable-stayed columns and the second in the foundations (Fig 5.80 and Fig 5.81).

The initial idea for the pavilion was to build the structure solely with steel cables; however, given the absence of clear calculation references adapted to this typology or wind tunnel tests, in the end it was decided to simplify the design with the beams. In this way, as René Sarger himself states in the article published in the April issue of the journal Acier=Stahl=Steel: “The initial project presented by the architects Baucher, Blondel and Filippone expressed their desire to use a light structure. The project anticipated using double curvature surfaces for the deck and façades, made of steel cables and plastic sheets. The weight of the construction itself would be reduced to the extreme, and the number of support points limited to four. Fig 5.77. Marie Thumas Restaurant Pavilion in Expo ’58 in Brussels, 1958. René Sarger, Baucher, Filippone and Blondel. [Source: Ref (279) Sarger, René / Vandepitte, D.]

The wind load on all these surfaces was a primordial element in all the stability calculations. By immediately assimilating and using the theoretical studies carried out both by Frei Otto and ourselves on the prestressed double curvature surfaces, we came up with a structure project in which the stability had to be guaranteed by the prestressing of all its elements.” [Ref (279) Sarger, René / Vandepitte, D.] Sarger goes on to say: “Faced with a lack of practical calculations methods adapted to these shapes, the wind tunnel tests were necessary to study the behaviour of the structure. These tests were impossible to carry out, given the deadlines. On the other hand, Bureau Seco, the technical control office, would have certain reservations regarding the calculation hypo-

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and Fig 5.81. The generatrices were formed by the aforementioned fish belly beams hinged with the cables at their joints. The longitudinal façades were constituted by a succession of hyperbolic paraboloids in which the joists were hinged directly in the foundations and in the steel tubular rigid edges BrCr and CrDr.

Fig 5.79. Marie Thumas Restaurant Pavilion. Note the arrangement of fish belly beams. [Source: Ref (267) Picon, Antoine]

Fig 5.80. Marie Thumas Restaurant Pavilion. Structural diagram. [Source: Ref (279) Sarger, René / Vandepitte, D.]

Fig 5.81. Marie Thumas Restaurant Pavilion. Structural diagram. [Source: Ref (279) Sarger, René / Vandepitte, D.]

theses carried out in the absence of references to a known construction type or results of tests on models. The initial project was thus re-designed incorporating the reduction in the number of cables and the use of light, semi-rigid beams.” [Ref (279) Sarger, René / Vandepitte, D.] In short, the building was made with a succession of conoids, each of which was limited by a concave ridge cable and another convex valley cable, as well as rigid edges made of tubular steel profiles with a square cross-section, labelled BrCr and CrDr in figures Fig 5.80

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As explained above, the whole structure was supported by eight inclined columns that lay on four foundation points via hinged joints (Fig 5.82). These hinges were key in prestressing the structure (Fig 5.83), since prestressing the vertical cables at the ends of the building would move the column heads, thus turning them and tensing the concave ridge cables (cable 1 in Fig 5.83); the latter tended to raise, thus tensing the beams (3 in Fig 5.83) that were prone to raising the convex valley cables (2 in Fig 5.83). In short, the whole ensemble would be tensed except for the columns. As with the case of the French Pavilion, the prestressing value would be calculated so that none of the elements would be completely relaxed in the face of any combination of forces, such as in the case of the concave ridge cables faced with suction wind load.

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The building was stabilised longitudinally via the triangulation that resulted from the arrangement of columns and cables (Fig 5.84). Transverse stabilisation (Fig 5.85) was ensured thanks to the triangles formed by the vertical façade cables and the columns, joined to the combination of ridge and valley cables connected by the aforementioned beams. Fig 5.84. Marie Thumas Restaurant Pavilion. Structural diagram illustrating the longitudinal stabilisation. [Source: Ref (279) Sarger, René / Vandepitte, D.]

Fig 5.85. Marie Thumas Restaurant Pavilion. Structural diagram illustrating the transverse stabilisation. [Source: Ref (279) Sarger, René / Vandepitte, D.]

Fig 5.82. Marie Thumas Restaurant Pavilion. Note the hinged column springers. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

Fig 5.83. Marie Thumas Restaurant Pavilion. Structural diagram showing the prestressing. [Source: Ref (279) Sarger, René / Vandepitte, D.] Fig 5.86. Marie Thumas Restaurant Pavilion. Under construction. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

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It should be pointed out that Sarger’s main contribution to the history of structural systems was perfecting the technique of deck structures made of prestressed cable nets, forming double curvature surfaces that gave large spans with limited thickness. He was one of the architects who based the renewal of the architectural shape between the ‘50s and ‘70s on the resources provided by the new structural technologies. In this aspect, the French Pavilion and the Marie Thumas Restaurant Pavilion were his original works.

Sarger made some interesting comments regarding these two pavilions in the April 1959 issue of the journal Acier=Stahl=Steel:

“The principle of prestressing is the basis of the spectacular creation of the French Pavilion in Expo ’58 in Brussels. In the case of the French Pavilion, we applied the principle only to the deck. On the other hand, the structure of the Marie Thumas Restaurant Pavilion was completely prestressed. In short, none of the vertical members of the Marie Thumas Pavilion façade is compressed. This leads to a greater airiness in the structures, demonstrated more conclusively here than what we ourselves did with the French Pavilion. We recurred to prestressing (in which the piece ends up in tension), as opposed to prestressing (in which the piece ends up compressed, referring to concrete). The operation involves sufficiently tensing an element prior to its definitive use in such a way that, while always remaining in tension to a greater or lesser degree, it diminishes those stresses that are trying to compress it. For example, the concave ridge cables in the Marie Thumas Pavilion can only resist the forces directed at the base of the building. How could they resist forces directed upwards which would generate a compression stress that a cable cannot develop? The first option would be to use a rigid arch, but then we would no longer be using a cable. The second option is to stiffen the cable via prestressing (in which the piece’s final state of stress is tension), in such a way that the forces directed upwards never compress it, but rather relax it partially. Fig 5.87. Marie Thumas Restaurant Pavilion. [Source: Ref (239) Mattie, Erik]

The deck and façade beams are capable of resisting certain bending moments that could alternatively compress one of its chords, depending on the acting force. There is a risk of flutter which should be taken into account in the calculations. However, if these beams are sufficiently prestressed so that none of their chords is ever compressed, then the flutter will be eliminated and less material will have to be used. This principle of prestressing demands certain architectural shapes, so that tensioning an element does not generate compression in others except for the edges, as in the French Pavilion, or the support masts, as in the Marie Thumas Pavilion.”

René Sarger goes on to say:

Fig 5.88. Marie Thumas Restaurant Pavilion. [Source: Ref (239) Mattie, Erik]

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“We sincerely believe that the Marie Thumas Pavilion is a building prototype that marks a new era which aspires to solve the eternal dilemma facing architects and engineers: how to cover the largest amount of space with the minimum material and support points. Independently of their supports, prestressed metal cable nets do not go over a weight of 7 or 8 Kg per metre squared covered. To cover the same surface with reinforced concrete shells of thicknesses below 8 cm, the weight of the material itself is 200 Kg/m2. This clearly demonstrates the superiority of the metal when it is used logically, that is, when its best quality, its resistance to tension, is put to use.” [Ref (279) Sarger, René / Vandepitte, D.]

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Fig 5.90. Covered Stadium of Saint-Ouen. René Sarger, Anatole Kopp and Metrich. 1968. [Source: Ref (267) Picon, Antoine]

Basing himself on the techniques perfected in the previous pavilions, Sarger would go on to erect other buildings such as the Covered Stadium of Saint-Ouen (René Sarger, Anatole Kopp and Metrich) (Fig 5.90 and Fig 5.91), completed in 1968. In this case, it is a structural typology based on two reinforced concrete arches and a prestressed cable net crossed orthogonally in the shape of a hyperbolic paraboloid. In this sense, it is worth noting René Sarger’s intervention in the “International Association for Shell and Spatial Structures” congress (I.A.S.S.) held in Leningrad in 1966 titled “Symposium on the problems of interdependence of design and construction of large-span shells for industrial and civic buildings”. In this intervention, Sarger asks for the establishment of a normative text based on the results obtained in wind tunnel tests for buildings with light decks with reverse double curvature, of which the French Pavilion would be a pioneer: “The information I will offer here is about the aerodynamic tests on models, and the example will be the research carried out in the Laboratoire de la Deutsche Bauakademie in Berlin in 1961 on the project for a Covered Stadium entrusted to me by the local authority Saint-Ouen, in collaboration with the architects Kopp and Metrich. Back when we were developing the French Pavilion for Expo ’58 in Brussels, we had to carry out wind tunnel tests in the “Laboratoire Eiffel” in Paris, as there were no rules on the effects of wind on reverse double curvature surfaces. These effects are essential

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Fig 5.89. Marie Thumas Restaurant Pavilion. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

Fig 5.91. Covered Stadium of Saint-Ouen. René Sarger, Anatole Kopp and Metrich. 1968. [Source: Ref (267) Picon, Antoine]

in such constructions, as well as being multiple; not only are there pressure and suction wind loads that are specific to these shapes, but also flutter phenomena. The analysis via tests carried out systematically is the only way of establishing the solid bases of a valid theory for the construction of prestressed decks covering large areas.

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Each one of us in our own project synthesis has been faced with a similar problem applied to a particular case. For two years, I myself had the task of directing three new tests in the Deutsche Bauakademie. I propose that an International Committee of the I.A.S.S. be named with the following mission: 1. To gather the results of tests carried out by the members of the I.A.S.S. from all over the world.

Fig 5.93. American Pavilion in Expo ’58 in Brussels. Cross-section-elevation. 1: upper cables; 2: lower cables; 3: tubular columns with a 318 mm diameter; 5: compression ring; 6: tension ring. [Source: Ref (187) Hähl, Hans]

Following the historical thread of tensile typologies through Expo ’58 in Brussels, we shall visit the American Pavilion, also called the “bicycle wheel Pavilion” (Fig 5.92). It was a radial structure made up of two families of cables, a lower and an upper one connected to a perimetral compression ring and to another central tension ring. The creators were the architects Edward Durell Stone and Blaton Aubert and the engineer W. Cornelius. The total outside diameter of the building is 104 metres, and the inside from the base of the cable structure is 92 metres (Fig 5.93 and Fig 5.94).

Fig 5.94. American Pavilion. Plan diagram of the structure. 1: Enclosure; 2: Upper cables; 3: Lower cables and perimetral cantilever. [Source: Ref (187) Hähl, Hans]

We should point out that there are precedents of circular-plan structures designed with cables connected to a perimetral compression ring and another inner tension ring, although these precedents do have typological variations. Mention should be made, in the first place, of the aforementioned unbuilt proposal from 1866 by Lahaire and Mondésir (Fig 5.22); a circular deck with a diameter of 100 metres with radial parabolic cables supporting a central ring with a glass lantern. It was designed with counteracting cables, and while it is not clear from the documentation, there could be cables with opposing curvature which would stabilise the structure against suction wind load, although it could also be a case of the dead load of the central lantern and deck offering stabilisation. In any case, the nearest precedents to the American Pavilion in Expo ’58 in Brussels that we have identified are two buildings erected in 1957. One of them is a small-scale prototype made on Columbia

2. To move on to complementary tests. 3. To analyse all these results and publish them with a view to establishing regulations or codes in all countries. I believe this proposal to be coherent with the aims of our Association, and it may be of great help in our daily work. If my intervention in this direction would enable such a proposal to be put into effect, then the present report, while incomplete, would not be futile.” [Ref (277) Sarger, René]

We can thus see how the World Expos have given rise to the construction of structural prototypes that were not without uncertainty in terms of their behaviour and the most suitable models for optimising their design. It has also become clear how these prototypes that were created for the World Expos have often led to the construction of structures of a similar typology beyond the Expos; consequently, this has meant that the technologies developed have been applied, and even more significantly, progressively perfected. The last quote from René Sarger reveals how buildings with innovative structures erected for the World Expos can even become the seed for establishing regulatory texts that may be generalised to a specific typology. All these factors combine to reinforce the idea of the World Expos as places for creating and experimenting with new structural typologies, and underpin their significant contribution to the history of structural building systems.

Fig 5.92. American Pavilion in Expo ’58 in Brussels. Edward Durell Stone, Blaton Aubert, W. Cornelius. [Source: its creators]

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University Campus, United States (Fig 5.95 to Fig 5.97); the other is the Town Stadium in Montevideo, also called the Cilindro Municipal (Town Cylinder) of Montevideo (Fig 5.98 to Fig 5.100), whose deck collapsed in October 2010 after a fire (Fig 5.101). The Columbia prototype was made up of a sole cable net stabilised by gravity via the arrangement of precast, trapezoidal, reinforced concrete pieces 10 cm thick placed between the steel cables.

Fig 5.95. (Left) Deck prototype carried out at Columbia University Campus. 1957. Note the cable net and the arrangement of the precast, trapezoidal, reinforced concrete pieces. [Source: its creators] Fig 5.96. (Right) Deck prototype carried out at Columbia University Campus. 1957. [Source: its creators]

Fig 5.97. Deck prototype carried out at Columbia University Campus. 1957. [Source: its creators]

In the case of the Cilindro Municipal of Montevideo, made by Leonel Viera and Luis Mondino, a perimetral wall was topped by a concrete compression ring with a diameter of 95 metres. A sole net of 256 steel cables was anchored to this ring, with a steel, inner tension ring installed too. The most singular element in this deck is the prestressing system, carried out by placing ballast on the concrete pieces, later concreting the joints, and lastly eliminating the ballast. This procedure would give rise to a monolithic deck of prestressed concrete, with the cables embedded in the concrete. Nevertheless, one of the problems with circular decks sloped towards the inside is how to eliminate rain water. Fernando Casinello says the following about the Cilindro Municipal of Montevideo: “When Viera and Mondino built their prestressed hanging deck, they ignored the fundamental deck problem that is water drainage, crudely resolving it with inner radial gutters.” [Ref (114) Casinello, Fernando]

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Fig 5.98. Town stadium of Montevideo or Cilindro Municipal. Leonel Viera and Luis Mondino. 1957. [Source: its creators]

Fig 5.99. (Left) Cilindro Municipal of Montevideo. Leonel Viera and Luis Mondino. 1957. Central tension ring under construction [Source: its creators]

Fig 5.100. (Right) Cilindro Municipal of Montevideo. Central tension ring, completed [Source: its creators]

Fig 5.101. Cilindro Municipal of Montevideo, which collapsed after a fire in 2010. [Source: its creators]

In the case of the American Pavilion in Expo ’58 in Brussels, two families of steel cables were employed. The lower family was made up of 36 cables with a diameter of 54 mm, while the upper family of 72 cables had a diameter of 32 mm, anchored to a perimetral compression ring and another central tension ring (Fig 5.102 and Fig 5.103).

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Fig 5.104. The American Pavilion in Expo ’58 in Brussels. Cross-section detail of the compression ring. [Source: Ref (187) Hähl, Hans]

The perimetral ring was formed by a horizontal steel truss (Fig 5.104) with 36 modules and sustained by two concentric circles of 36 supports each, with diameters of 92 and 104 metres; The central ring (Fig 5.105) in turn consisted of two rings, an upper and a lower one connected by a framework of vertical members, intermediate rings and diagonal bars; it had a diameter of 20 metres and a height of 8.5 metres.

Fig 5.102. The American Pavilion in Expo ’58 in Brussels. Edward Durell Stone, Blaton Aubert and W. Cornelius. Central tension ring and upper and lower families of cables. [Source: Ref (230) Makowski, Z.S.] Fig 5.103. The American Pavilion in Expo ’58 in Brussels. Edward Durell Stone, Blaton Aubert and W. Cornelius. Completed deck. [Source: Ref (230) Makowski, Z.S.]

Fig 5.105. American Pavilion in Expo ’58 in Brussels. Tension ring. Elevation, plan and cross-section. [Source: Ref (187) Hähl, Hans]

Fig 5.106. American Pavilion in Expo ’58 in Brussels. Deck assembly sketch. I: placing the lower cables; II: placing the central ring and the upper cables; III: post-tensioning of the upper cables (final position). [Source: Ref (187) Hähl, Hans]

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The lower family of cables was prestressed by the weight of the central tension ring itself, which helped stabilise the deck via gravity. Additionally, the upper family of cables was prestressed by applying tension to the order of 22 tonnes, contributing equally to stabilising the deck against possible suction forces (Fig 5.106). It is clear that the shape of the deck, with its enclosure of translucent plastic sheets, enabled the rain water to drain towards the building perimeter, while the central tension ring, under which a pond was located, remained open. As with the French Pavilion, wind tunnel tests were carried out in the absence of similar structural typologies as a reference. In this sense, we should remember the spectacular collapse of the Tacoma Narrows Bridge, a suspension bridge in Seattle, on November 7th 1940, four months after its inauguration; it became a classic example of collapse due to flutter, and at that time it would encourage reflections to be made on phenomena of dynamic instability, as well as contribute to the generalisation of wind tunnel tests.

As with cases described earlier, the American Pavilion in Expo ’58 in Brussels would have architectural consequences in the shape of buildings constructed beyond the Expos. Thus, this pavilion is the immediate precedent to the Utica Memorial Auditorium in New York, erected in 1959 by the engineer Lev Zetlin and the architect Gehron Seltzer (Fig 5.108 and Fig 5.109). With a diameter of 73 metres, it has a similar typology, though more sophisticated. Thus, the central tension ring is lighter, the upper and lower cables are prestressed, and there are rigid vertical bars connecting both families of cables, enabling any potential snow loads to be transferred to the lower family and thereby increasing the stiffness of the upper family.

Fig 5.107. American Pavilion in Expo ’58 in Brussels. [Source: its creators]

Fig 5.108. Utica Memorial Auditorium, New York. Lev Zetlin and Gehron Seltzer. 1959. This building is an immediate consequence of the American Pavilion in Expo ’58 in Brussels. [Source: Ref (255) Otto, Frei]

Fig 5.109. Utica Memorial Auditorium, New York. Lev Zetlin and Gehron Seltzer. 1959. Explanatory structural diagram by Horst Berger. [Source: Ref (95) Berger, Horst]

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Another building that drew on these earlier experiences, in terms of employing a perimetral compression ring and another inner tension ring connected by a family of radial cables, is Madison Square Garden in New York (Fig 5.110 to Fig 5.112), developed in 1962 by Severud Associates. Radial cables were also used in this case; however, unlike the American Pavilion in Expo ’58 in Brussels, the upper family was eliminated. In that earlier case, this family contributed to the stabilisation while giving the deck a slope towards the outside for rain water drainage. On the contrary, a sole family of cables stabilised with gravity was installed in Madison Square Garden. This stabilisation was offered by the weight of various elements located directly above the deck, such as a mechanical area or a cooling tower. The whole had a considerable span of 137 metres. Nevertheless, not only prestressed structural typologies made with cable nets based on radial cables were built in Expo ’58 in Brussels. This desire to experiment with tensile structures also gave rise to cable-stayed typologies. Such is the case of the Soviet Pavilion developed by the architects A. Boretski and V. Abramov and the engineers S. Ratskevitch and K. Vassilieva (Fig 5.113 to Fig 5.118). What stands out in this pavilion is the careful structural

Fig 5.110. Madison Square Garden, New York. Severud Associates. 1962. Explanatory structural diagram by Horst Berger. [Source: Ref (95) Berger, Horst]

Fig 5.112. Madison Square Garden, New York. 1962. [Source: Ref (95) Berger, Horst]

Fig 5.113. The Soviet Pavilion in Expo ’58 in Brussels, 1958. A. Boretski and V. Abramov, architects; S. Ratskevitch and K. Vassilieva, engineers. [Source: its creators]

design that is clearest in the building’s cross-section (Fig 5.114), based on lateral elements made up of a column and trusses of varying cross-section; these trusses were hinged to the column and cable-stayed at their ends. In addition, a central curved truss was used upon which lay a longitudinal skylight. The central nave had a span of 48 metres.

Fig 5.111. Madison Square Garden, New York. Severud Associates. 1962. Photograph of the structure under construction. [Source: Ref (95) Berger, Horst]

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Fig 5.114. (Opposite page, above) The Soviet Pavilion. Cross-section. 1: truss; 2: skylight; 3: cable with diameter of 40 mm; 5: cable-stayed trusses; 6: aluminium sheets for the enclosure. [Source: Ref (241) Meurel, J. / Fourmentin, B.] Fig 5.115. (Opposite page, middle) The Soviet Pavilion. Longitudinal section of the structure. [Source: Ref (241) Meurel, J. / Fourmentin, B.] Fig 5.116. (Opposite page, below) The Soviet Pavilion. Structural plan. [Source: Ref (241) Meurel, J. / Fourmentin, B.] Fig 5.117. The Soviet Pavilion. Photograph of the building under construction. [Source: Ref (241) Meurel, J. / Fourmentin, B.]

Fig 5.118. The Soviet Pavilion. Indoor photograph. [Source: its creators]

In this case the structure was less avant-garde than the other typologies exhibited, to the extent that there are precedents with even greater spans; examples of these are the aforementioned Hangar in the Cherbourg Arsenal, France (Fig 5.56) and the Hangar in Bizerte Arsenal, Tunisia (Fig 5.57). Nevertheless, the building exemplifies the variety in the tensile typologies developed in this Expo which, as explained, signify a renaissance in structural splendour following the great achievements of the Expos in the 19th century.

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In this case, the deck also had the distinctive feature of having an oval floor plan, its major axis reaching a span of 320 feet (97.5 metres) and its minor axis a span of 240 feet (73.15 metres). Additionally, the building is open and without façades. The deck enclosure is made up of coloured plastic sheets. The central tension ring is closed with a plastic dome. Regarding the issue of rain water drainage, particularly delicate in the case of these kinds of deck which slope down towards the inside, we believe the solution offered was a little heavy-handed; various horizontal pipes connected the centre of the deck with downpipes located inside the concrete columns (Fig 5.125).

5.2.2.3 The New York State Pavilion in the 1964-1965 New York’s World’s Fair: the continuation of the “bicycle wheel” The same engineer who worked on the Utica Auditorium, Lev Zetlin, would participate with the architect Philip Johnson on the design of another variation on the prestressed, radial structure in the style of the “bicycle wheel”. It was the New York State Pavilion for the New York World’s Fair in 1964 (Fig 5.119 and Fig 5.120). In this case, two families of prestressed cables were once again used, an upper, supporting family and another lower, stabilising one, both anchored to a perimetral compression ring that lay on sixteen concrete columns 30 metres high, and to a central tension ring, both rings made of steel (Fig 5.121 to Fig 5.123). Unlike the Utica Auditorium, when observed from above, the upper family is concave and the lower one convex, both connected with vertical cables. Gravitational loads are supported by the upper family, while the lower family resists wind suction loads.

Fig 5.119. Aerial view of the 1964-1965 New York World’s Fair. The New York State Pavilion is in the foreground. Lev Zetlin and Philip Johnson. [Source: its creators]

Fig 5.121. New York State Pavilion. Lev Zetlin and Philip Johnson.1964. Floor plan. [Source: Ref (210) Johnson, Philip / Frampton /Kenneth]

Fig 5.122. New York State Pavilion. Cross-section. [Source: Ref (210) Johnson, Philip / Frampton /Kenneth]

Fig 5.120. New York State Pavilion. Lev Zetlin and Philip Johnson.1964. [Source: its creators]

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Fig 5.123. New York State Pavilion. Structural diagram. [Source: Ref (128) Comstock, Henry]

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Fig 5.124. New York State Pavilion. Indoor photograph. [Source: Ref (48) Architectural Review]

Fig 5.126. New York State Pavilion. Detail of the perimetral compression ring with the connection pieces for the two cable layers. [Source: its creators]

Fig 5.125. New York State Pavilion. Note one of the pipes from the horizontal rainwater drainage network connecting with the downpipe located inside on of the columns. This is perhaps one of the most difficult aspects to resolve in this type of deck, in terms of design. [Source: Ref (169) Garn, Andrew / Antonelli, Paola]

Fig 5.127. New York State Pavilion. Current photograph of building in a state of abandonment. Again, note one of the pipes in the horizontal network for rain water drainage. [Source: Ref (211) Johnson, Philip / Payne, Richard]

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If we focus on the developments in radial cable structures described above, we see that the American Pavilion in Expo ’58 in Brussels is the direct precedent to the Utica Auditorium of 1959, designed by Lev Zetlin. We also observe how this same engineer would later participate in the design of the deck of the New York State Pavilion for the 1964 New York World’s Fair. In short, in this case we have a curious phenomenon whereby one experience acquired in an Expo building is applied to another construction beyond the scope of the Expos, with this new experience in turn being applied to a new exhibition building. This question once again shows us the extent to which the structural experiences developed in World Expos play a fundamental role in the history of structural building systems; we can see the synergies created between the attempts at structural innovation made with the World Expo buildings and those others built on the sidelines of the Expos.

Fig 5.129. Seattle Center Coliseum. Paul Thiry and Peter H. Hostmark. 1962. Project model. [Source: its creators]

The Seattle Center Coliseum had a square floor plan measuring 109.73 on each side. The deck was made up of four hyperbolic paraboloids designed with prestressed cable nets overlaid with an enclosure of light sandwich panels formed by two aluminium sheets with a polystyrene core (Fig 5.130 and Fig 5.131). These four paraboloids are framed by prestressed concrete edge beams that skirt the building, and four steel trusses that divide the deck into four parts. The trusses lay on four reinforced concrete tripod columns. The edge beams lay on the same tripod columns and on V columns spaced at 18.3 metres. The cables were installed diagonally in each of the squares. In this way, we can distinguish two families in each hyperbolic paraboloid when observed from the upper part of the building:

5.2.2.4 The Seattle Center Coliseum in the Century 21 Exposition in Seattle 1962: “limitless spans” The main building of the Century 21 Exposition in Seattle was the so-called Seattle Center Coliseum or Century 21 Coliseum (Fig 5.128 and Fig 5.129). This building is another of the examples built for World Expos reaching a considerable level of structural interest; it delves deeper into aspects brought up by previous buildings with respect to prestressed cable nets, and continues this open line of development by introducing a new structural design.

Concave cables or supporting cables: these were connected to the trusses and the concrete edge beams. Each paraboloid was made up of 29 cables separated 2.43 metres. Their aim was to withstand the gravitational loads. Convex cables or stabilising cables: they were arranged perpendicularly to the previous ones connecting the trusses to each other or one edge beam to the other. Each paraboloid had 30 cables also separated by 2.43 metres. Their aim was to transmit wind suction loads.

Fig 5.128. Aerial view of the Century 21 Exposition in Seattle in 1962. Note the Space Needle Tower (184 m) and the Seattle Center Coliseum. [Source: its creators]

The Seattle Center Coliseum was planned by Paul Thiry, an architect from Seattle, and by the engineer Peter H. Hostmark. The building was to live on after the end of the Expo as a leisure centre.

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Fig 5.130. Seattle Center Coliseum. Paul Thiry and Peter H. Hostmark. 1962. Construction of the cable net. [Source: Ref (247) Murray, Morgan]

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Fig 5.132. Seattle Center Coliseum. Joint between the trusses, the four prestressed cable nets and placement of the enclosure sandwich panels. [Source: Ref (167) Gandy, Joseph]

The edge beams were made of prestressed concrete and had a hollow triangular cross-section with longitudinal and transverse inner diaphragms (Fig 5.133). Prestressing tendons are located at the outer and inner corners and inside the longitudinal diaphragms. The deck cables penetrate the beams and are anchored inside them. One of this structureâ&#x20AC;&#x2122;s distinguishing features is that the air conditioning units and ducts are located on the inside of these edge beams, taking in the air from the outside through openings in the lower part of the beams and expelling it inside through side openings (Fig 5.133 and Fig 5.134).

Fig 5.131. Seattle Center Coliseum. Paul Thiry and Peter H. Hostmark. 1962. Assembling the sandwich panels for the enclosure. [Source: Ref (247) Murray, Morgan]

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The main problem envisaged by the engineers before carrying out their calculations was the difficulty in determining the position of the deck cables and their stress in order to ensure that the secondary cables would not loosen because of the gravitational loads, but rather maintain a degree of residual tension. In this sense, there was the added complication of the influence of deformation of the trusses and edge beams which were under dead and live loads. Another fundamental role here was played by thermal forces. This gave rise to an initial structural design based on formulae that were known to work with hyperbolic paraboloids. This design would be modified and corrected when the aforementioned variables were input.

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Another important difficulty would arise when calculating wind loads (Fig 5.135). In his talk given at the “15th Fall Meeting - American Concrete Institute” held between September 27 and 29 of 1962 in Washington, the building engineer Peter H. Hostmark stated: “To determine the effects of wind loads on the structure proved to be a complex problem. Due to its peculiar shape, no empirical or previously established wind load formulae could be applied to obtain the effects of wind on the roof surfaces. In order to solve the problem, it was necessary to construct an exact scale model of the structure and test it in a wind tunnel test. Under the direction of Professor F.B. Farquharson of the University of Washington, the model was tested in the University’s wind tunnel for a simulated 80 miles per hour (128.7 Km/h) blowing at a 45º angle to the building. It is interesting to note that the wind creates suction or uplift over the entire roof with the exception of one small area on the windward side where a light pressure is registered. The suction amounted to as much as 47.6 p.s.f. (pounds per square foot) (232.4 Kg/m2) on the ridges above the steel trusses.” [Ref (203) Hostmark, Peter H.]

Fig 5.133. Seattle Center Coliseum. Plan and cross-section of the prestressed, concrete edge beams. [Source: Ref (203) Hostmark, Peter]

Fig 5.135. Seattle Center Coliseum. Isobars of wind pressure obtained after the reduced model wind tunnel test with a wind speed of 128.7 Km/h. The pressure is indicated by the + sign and suction by the - sign. Note that the only area with pressure is the windward corner, the rest of the deck being suctioned. The highest registered suction is 232.4 Kg/m2. [Source: Ref (203) Hostmark, Peter]

Peter H. Hostmark (Fig 5.136) goes on to say: Fig 5.134. Seattle Center Coliseum. Inside. Note the prestressed concrete edge beam with the air conditioning discharge openings. [Source: its creators]

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“It may be of interest to note the great variation in the cable tensions. The tensions in the main cables vary from 163,000 lbs. (73.94 t) under snow loads and 57,100 lbs. (25.90 t) under wind loads. The forces in the hold-down cables vary from 7,000 lbs. (3.17 t) under snow loads to 62,900 lbs. (28.53 t) under wind loads.” [Ref (203) Hostmark, Peter H.] 319

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Fig 5.136. Seattle Center Coliseum. Maximum and minimum forces in the main cables and hold down cables under snow and wind loads. [Source: Ref (203) Hostmark, Peter]

Fig 5.137. Seattle Center Coliseum. Diagrams of the forces in the edge beams. Diagram of horizontal moments. Diagrams of axial loads when the deck is subject to snow or wind loads. [Source: Ref (203) Hostmark, Peter]

Regarding the prestressing, it should be pointed out that the edge beams were prestressed before the cable loads were applied. In this sense we should highlight: Vertical prestressing tendons: located in the longitudinal diaphragms of the beams, their objective is to support gravitational loads (Fig 5.133 and Fig 5.138). Horizontal prestressing tendons: located at the outer and inner corners of the beams. Their function is to support the horizontal bending moments transmitted by the cable net (Fig 5.133 and Fig 5.138). Both the snow load and the wind load that act on the cable net subject the edge beams to horizontal bending moments and axial loads (Fig 5.137). After construction of the Coliseum had been completed, Paul Thiry would say: â&#x20AC;&#x153;The technological development of the cables and the availability of aluminium and polystyrene panels would enable structures of this kind to be larger in the future. In the original plans, the Coliseum measured 600 feet along its side (182.9 metres), but in the end this was decreased to 360 feet (109.73 metres). A larger size would not pose any structural difficulties; our building is not bigger purely because of the spatial constraints of the allocated plot.â&#x20AC;? [Ref (285) Sherer, M.L.]

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Fig 5.138. Seattle Center Coliseum. Arrangement of the prestressing horizontal and vertical tendons. [Source: Ref (203) Hostmark, Peter]

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Fig 5.139. Seattle Center Coliseum. Indoor photograph during the last stages of construction. [Source: Ref (167) Gandy, Joseph]

Fig 5.141. Seattle Center Coliseum. Image of the Century 21 Exposition with the building completely finished. [Source: Ref (247) Murray, Morgan]

Fig 5.140. Seattle Center Coliseum. Outdoor photograph in the last stages of construction. [Source: Ref (167) Gandy, Joseph]

We can glimpse a sign of recovery in these words, a recovery of the spirit of structural optimism that was characteristic of the World Expos in the 19th century and which had gone into decline in the Expos during the first half of the 20th century for reasons outlined earlier.

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Fig 5.142. Seattle Center Coliseum. The plastic innovation and the spatial grandeur that were a consequence of the architectural language derived from the new structural typologies of prestressed cable nets can be easily appreciated in this period photograph. [Source: its creators]

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range of built references, the invalidity of building codes for determining wind loads and the need for wind tunnel tests are some of the added novelties and difficulties in the design and calculation of these cutting-edge structures.

Between 1994 and 1995, the building underwent a reform. Dennis Forsyth, the reform project manager, makes a reference to the considerable scale of the vertical moments in the cable net, probably due to a progressive loss of stress: “The deck was moving more than two feet (60.96 cm) up and down because of the wind, thus guaranteeing leaks. The magnitude of the deck’s vertical movement due to the wind had gradually led to failure in the watertightness between the panels that depended on an elastomeric membrane located between them. Additionally, numerous panel fastenings had failed over time.” [Ref (9) Architectural Record]

Fig 5.143. (Below left) Seattle Center Coliseum. Reform carried out in 1994. Assembly of one of the deck trusses. [Source: Ref (9) Architectural Record]

There was a keen desire to maintain this emblematic building’s appearance; an initial proposal suggested covering the deck with an impermeable membrane, thus maintaining the whole structural system and its panels. In the end a new, stiffer deck was chosen. The engineers Skilling Ward and Magnusson Barkshire substituted the cable net for beams and joists, further replacing the old trusses and adding new columns (Fig 5.143 and Fig 5.144). Unfortunately, the whole structural system that was the original and raison d’ètre of the building would be modified, and therefore it would lose its structural and historical value.

Fig 5.144. (Below right) Seattle Center Coliseum. Reform carried out in 1994. Note how the entire cable net was substituted by a truss framework. [Source: Ref (9) Architectural Record]

-Another relevant point is the fact that this building represents one of the early examples of prestressed cable nets that have endured up until the present day, given that it was designed to be permanent. Thanks to this, it has been possible to witness the pathologies that these first typological experiences have developed over time; in this particular case, we have been able to observe the problems of watertightness derived from the magnitude of the structural movements, as the existence of vertical movements in the cable net of around 60 cm has documented. It is the only building with both a groundbreaking use of cable nets and a link to the World Expos to survive to this day, while it should be remembered that the structure has completely lost its value. The Dorton Arena in Raleigh was luckier and was declared a national monument in spite of some problems regarding excessive deformation. As Professor Félix Escrig declared: “The Dorton Arena in Raleigh had marginal problems that needed fixing; as the deck sheeting was stiffer than the cable net and thus had incompatible connections, it made noises. Another issue was the incredible flexibility that caused considerable deformations through resonance; this was solved by adding some extra inner cables.” [Ref (151) Escrig, Félix]

5.2.2.5 The Federal Republic of Germany Pavilion in Expo ’67 in Montreal. Frei Otto: utopia and formal innovation through “natural autoshapes”

In short, we can state that the Seattle Center Coliseum built on the occasion of the Century 21 Exposition in Seattle in 1962 would garner considerable interest in the history of structural building systems for the following reasons: -It was an opportunity to delve into aspects that earlier buildings had given rise to in terms of prestressed cable nets, and it continued to develop this new line by introducing new structural designs that implied new technical challenges, thus enriching the formal repertoire of this structural typology, and consequently the new architectural language that was created by prestressed cable nets. -In this sense, cable nets were not only combined with steel trusses, but also with prestressed concrete edge beams, thus endowing the ensemble with an elevated technological level for that time. Additionally, and as confirmed by the building architect himself, Paul Thiry, it was the first structure to use sandwich panels to enclose a prestressed cable mesh. -This building once again highlights the difficulties, also previously described in earlier constructions, associated with the uncertainty inherent in the design and calculation of these structural typologies in these early days of their development. The absence of a broad

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The Federal Republic of Germany Pavilion in Expo ’67 held in Montreal (Fig 5.145) is undoubtedly one of the most relevant works of both the history of structural systems and the history of architecture itself. It was a building with a structure made of a prestressed cable net. In this case, however, it has a free shape with several masts defining the high and low points, thus bringing to life a formal freedom that distances it from the other examples mentioned above that were almost always framed by rigid elements and generally geometrically defined by well-known shapes such as the hyperbolic paraboloid or the conoid. While Frei Otto had already built significant smaller structures with both prestressed nets and prestressed membranes, this was the first time that a “free form”, prestressed cable net was to be applied to such a large structure. Note that it covered a completely irregular plan of 8,000 m2. Surprisingly, only twelve prolific years stand between the first, simple tensile structure built by Otto in 1955 (Fig 5.147) and the construction of the magnificent German Pavilion in Montreal; during this time, Otto would explore different typologies of both cable nets and prestressed membranes. Before 1955, Otto had carried out a variety of projects and sketches of tensile structures, some of which represent structures with enormous spans

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Although he would continue to develop idealistic proposals over the span of his career, Frei Otto’s first tensile structure was the simple Music Pavilion in the Federal Garden Exhibition (Bundesgartenschau) held in Kassel in 1955 and built with Peter Stromeyer (Fig 5.147). It was a basic surface in the shape of a hyperbolic paraboloid. It had two high vertices linked to cable-stayed columns and two low vertices directly connected to the foundations. Edge cables pre-tensioned this membrane made of 1-mm-thick cotton fabric, giving it a span of 18 metres.

that are remarkably utopian. Such is the case of the “City in the Antarctic” in 1953 (Fig 5.146), in which a structure made up of a cable net connected to an arch covers an urban settlement with the aim of climate control.

Fig 5.147. Music Pavilion in the Bundesgartenschau in Kassel in 1955. The structure belongs to the four-point typology in which two high and two low vertices support a hyperbolic paraboloid surface. Frei Otto and Peter Stromeyer. [Source: Ref (177) Glaeser, Ludwig]

Another example of Otto’s first tensile structures is the aforementioned portable Hangar built together with Stromeyer (1956) (Fig 5.76), consisting of columns, ridge and valley cables with opposing curvature and a prestressed membrane. We have also referred to the first application of a prestressed textile membrane with high and low inner vertices for the Interbau in Berlin in 1957 (Fig 5.39 and Fig 5.148).

Fig 5.145. Aerial view of the Federal Republic of Germany Pavilion in Expo ’67 in Montreal. Frei Otto and Fritz Leonhard. [Source: Ref (299) Thomas Nelson & Sons]

Fig 5.146. Sketch for “City in the Antarctic”. Frei Otto. 1953. [Source: Ref (254) Otto, Frei]

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Fig 5.148. First application of a prestressed membrane with high and low inner vertices. Interbau in Berlin 1957. Reduced model in elastic fabric. Frei Otto. [Source: Ref (254) Otto, Frei]

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One of his best-known works is the Dance Pavilion for the Federal Garden Exhibition of Cologne that same year (Fig 5.149). In this case, the construction was made up of a prestressed membrane belonging to the wave structure typology, in which the surface is defined by alternate high and low points. Furthermore, this example was a star-shaped wave structure. The cotton membrane is stretched over six cable-stayed masts that define six high points, while cables connected to a central ring define six other low points. As a whole, it has a refined design and is located over an artificial pond.

Another of the immediate precedents to the German Pavilion for Expo ’67 in Montreal is, in our opinion, the second design for Ulm Medical Academy (Medizinische Akademie Ulm) (1965), also unbuilt (Fig 5.151 and Fig 5.152). Both this project and the German Pavilion included a “free form” design for an irregularly-shaped cable net with inner masts of varying height. The cable net had a different design in the connection areas with the masts, where skylights were to be placed. All these details anticipated the German Pavilion.

Fig 5.149. Dance Pavilion for the Federal Garden Exhibition in Cologne. Frei Otto. 1957. [Source: Ref (254) Otto, Frei]

From the sixties onwards, several projects were carried out that are the most immediate precedents to the Pavilion in Montreal. These works generally display a higher level of formal complexity and have the goal of increasing spans. A good example of this is the project commissioned for the Bremen Port Authority to cover part of the city harbour (Fig 5.150). In the project, twelve masts are cable-stayed by a series of cables to which a cable net is connected; this was a mesh with 40-cm openings. It would cover a rectangular surface measuring 380 x 1,500 metres. The planned covering material was rigid PVC or metal sheets. There were also plans to create ventilation openings in the upper areas to allow the elimination of smoke and steam. The appearance of waterproof shipping containers around this time meant that carrying out this fantastic project no longer made that much sense.

Fig 5.151. Second unbuilt project for Ulm Medical Academy. Frei Otto. 1965. [Source: Ref (254) Otto, Frei]

Fig 5.150. Deck project for Bremen Harbour. Mesh model. Frei Otto. 1961. [Source: Ref (177) Glaeser, Ludwig]

Fig 5.152. Second unbuilt project for Ulm Medical Academy. Mesh model. [Source: Ref (254) Otto, Frei]

In 1964, Otto did a sketch for the covering of a pedestrian street and a canal in a fictitious city (Fig 5.153). This proposal combines several elements in a cable net; the utopia of a deck covering large urban spaces which was a constant factor during Otto’s career as well as in some utopian movements from that time, the large spans that were attained through this type of project, and the formal freedom of “free form” cable nets.

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These specific earlier examples would be seeds for the German Pavilion in Expo ’67 in Montreal. This means that the construction of this building would mark the beginning of a new stage, not only in Frei Otto’s work, but also in the history of structures whose working principle was based on tension.

Fig 5.154. (Left) Typology supported at four points and defining a hyperbolic paraboloid. [Source: Ref (254) Otto, Frei]

Models made by Frei Otto with soapy surfaces of varying typologies classified by the support system.

Fig 5.155. (Right) Hunchback typology (supports with a mushroom-shaped head or heads with flexible sheets). [Source: Ref (254) Otto, Frei] Fig 5.156. (Left) Typlogy with arched support. [Source: Ref (254) Otto, Frei] Fig 5.157. (Right) Star wave typology. [Source: Ref (254) Otto, Frei]

However, not all soapy surfaces are suitable as direct models for a structural membrane. Depending on the edges chosen, there may be surface areas with reduced curvature that would invalidate the model. On the other hand, it would not be necessary to strictly adhere to the exact equitensional shape when creating a real structure; nevertheless, the soapy surface can be a basic shape to build on, as it is the shape that determines the distribution of tension. Therefore, the structural “free form” that has apparently been designed randomly will be rooted in the physical laws that dictate the structural behaviour of these typologies. Otto would not only use soapy surfaces in his form-finding, but would combine this technique with reduced models based on mesh fabric. Fig 5.153. Sketch for the canal and pedestrian street covering. Frei Otto. 1964. [Source: Ref (254) Otto, Frei]

Nevertheless, Frei Otto’s contribution lay in the fact that the apparent formal freedom inherent in these structures was not random, but derived from the formal materialisation of the principles of physics governing these typologies. The design for the large deck of the German Pavilion in Expo ’67 in Montreal was based on models made with liquids with a high surface tension or soapy liquids. By submerging an edge skeleton in a soapy liquid, an equitensional surface is created; that is, the tension between its molecules is equal at all points and in all directions. Furthermore, the soapy surface covers the smallest possible area defined by those edges, in other words, a minimum surface. Thanks to the autonomous, natural process of creating these surfaces, we can call them “natural autoshapes” (Fig 5.154 to Fig 5.157). According to Otto: “There will be problems in any prestressed structure under unequal tensions. These structures have a tendency to wrinkle and stretch at the points where there is greater tension, so that the membrane may tear or take on a shape that strongly diverts from the original pattern. Structures that are correctly designed should display uniform tension in all directions.” [Ref (254) Otto, Frei]

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In short, Ottos’ works clearly open up a new perspective in the development of tensile decks, offering a great variety and formal freedom based on the laws of physics concerning “natural autoshapes”, and distanced from the formal stiffness of the first cable nets based on known geometric shapes such as the hyperbolic paraboloid or the conoid, and generally framed with rigid structural elements. Examples of these previous formalisations are the French Pavilion from Expo ’58 in Brussels (Fig 5.59 to Fig 5.75) or the Marie Thumas Restaurant Pavilion in the same Expo (Fig 5.77 to Fig 5.89), as well as the Seattle Center Coliseum from the Century 21 Exposition in Seattle 1962 (Fig 5.128 to Fig 5.142). The cable net in the German Pavilion had a regular mesh width of 50 cm, with 12-mm-diameter cables made of steel wires. Its plan was completely irregular and sustained by eight steel, tubular masts of varying heights, the tallest measuring 37 metres. The ridge and edge cables had a diameter of 54 mm. The latter were anchored at 34 foundation points. The mesh was connected to the mast heads with crest cables and eye- or tear-shaped elements which channelled the forces along the lines and acted as skylights. These tears also had meshes with their own order. The whole net was prefabricated in Germany and later assembled in Canada. Once assembled, the enclosure material was installed; this consisted in polyester fabric in the translucent areas and PVC sheets in the transparent ones (Fig 5.160).

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Fig 5.158. The German Pavilion in Expo ’67 in Montreal. Free form peak typology. Note the freedom evinced in the sinuous shapes based on natural creation. The loads are transmitted to the supports by the eye-shaped lines that enclose another mesh with its own order. Frei Otto and Fritz Leonhard. [Source: Ref (177) Glaeser, Ludwig]

Fig 5.160. The German Pavilion in Expo ’67 in Montreal. The inside during the Expo. [Source: its creators]

Fig 5.159. The German Pavilion in Expo ’67 in Montreal. Frei Otto and Fritz Leonhard. [Source: its creators] Fig 5.161. The German Pavilion in Expo ’67 in Montreal. [Source: Ref (254) Otto, Frei]

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The complexity of the calculations involved in these structures was largely due to the fact that the mesh deformations affected the stresses of the same, thus requiring second order calculations. Aware of this extreme, Fritz Leonhard, the engineer in charge of the Pavilion’s structural calculations, would state: “We were dealing with a system of internally statically indeterminate exchange, in which the deformations would have a fundamental influence on the stresses in the structural members.” [Ref (254) Otto, Frei]

Given that a structure of these characteristics had never before been made to such a large scale, a trial would be carried out at the University of Stuttgart, involving a prototype with a floor plan of 460 m2 and a cable net with an eye-shaped element and a sole inner mast 17 metres high (Fig 5.164 and Fig 5.165).

Given the lack of computer resources, the stresses generated in the structural elements would have to be determined via monitoring in reduced models. In this sense, it is clear that the German Pavilion would be one of those buildings that would act as a catalyst for the early development of the experimental instrumentation that basically involved surface-generating machines that worked with high-surface liquids and reduced model measuring devices (Fig 5.166). Thus, Berthold Burkhardt, an engineer at the “Institute for Lightweight Structures” at the University of Stuttgart (where Frei Otto was director), would say:

Fig 5.162. (Left) Detail of an eye- or tear-shaped element. [Source: Ref (254) Otto, Frei]

“One of the first research apparatuses at the Institute was the machine that enabled the use of high-surface tension liquids to resolve the minimum distances between a large number of points. The soap bubbles could be measured with the help of an optical workbench. The largest optical workbench arrived at the Institute with the project for the German Pavilion for the Expo in Montreal. It could be used to measure the curvature and topography of double-curvature nets and membrane surfaces with a precision to tenths of a millimetre. A model of this Pavilion was also used for a wind tunnel test.” [Ref (254) Otto, Frei]

Fig 5.163. (Right) Detail of the cable net. [Source: Ref (254) Otto, Frei]

Fig 5.164. Prototype made at the University of Stuttgart. Peak typology. The loads are transmitted to the mast head along cables in the shape of an eye or tear and containing a different mesh on the inside. [Source: Ref (254) Otto, Frei]

Fig 5.165. Note the use of models made with high surface tension liquids in order to determine the equitensional surfaces. Prototype model for the German Pavilion carried out at the University of Stuttgart. [Source: Ref (177) Glaeser, Ludwig]

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Fig 5.166. The German Pavilion at Expo ’67 in Montreal. Reduced model for determining the stresses on the net cables. [Source: Ref (254) Otto, Frei]

In spite of having been designed to last a summer, it remained standing in Canada for ten years. While the pavilion’s global stability had been amply demonstrated during this time, a large amount of snow accumulated during the winter of 1976, leading to a localised collapse in the mesh.

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Fig 5.167. The German Pavilion at Expo ’67 in Montreal. Plan representation of the deck topography. [Source: Ref (254) Otto, Frei] Fig 5.168. Deck for the Olympic

This building’s most important contribution essentially resides in the fact that it is the largest example of a “free form” prestressed cable net built at that time, in which the laws of physics governing the structure are directly responsible for its complex formalisation. The apparent randomness is just an illusion, since the basis of its design lies in the theory of minimum surfaces created from high-surface tension liquids. Thanks to its widespread dissemination, this building marked a transition in the conception of these typologies, paving the way for the erection of innumerable decks made with prestressed, cable nets and “free form” prestressed membranes. Additionally, it would act as a catalyst for research on shape determination and the search for new numerical models that would enable the computer generation of minimum surfaces. Likewise, the conception of this building implied the development and perfecting of a whole series of measuring instruments for reduced models and soapy surfaces. In short, we can see how a building erected for a World Expo acted as a key element in the history of structural systems, disseminating new methods of structural conception, representing a new milestone in size, leading to experimentation with new instrumental equipment and, in short, paving the way for the development of new structural creations. In this sense, the gigantic structure created by Frei Otto, Günter Behnisch, Fritz Leonhard and Heinz Isler for the Munich Olympic Games in 1972 (Fig 5.168) would be the direct heir to the German Pavilion in Montreal. The Swiss engineer Heinz Isler was convinced that it was possible to triple the span of the Expo ’67 structure in Montreal. This belief would result in a huge structural ensemble with enormous spans and a floor plan covering 74,000 m2, nine times that of the Montreal building five years earlier. Once again, the structure was formed by a cable net with two differentiated areas: firstly, the stadium deck, whose main feature is its geometry based on fragments of hyperbolic paraboloids and floating masts; and secondly the decks of the remaining installations (entrances, swimming pools and athletics installations), characterized by a free formalisation with internal and external masts and tear-like elements that acted as skylights where they connected with the masts, all features that directly link the construction with the German Pavilion.

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Games in Munich 1972. Frei Otto, Günter Behnisch, Fritz Leonhard and Heinz Isler. At the top, the stadium deck; on the right, the athletics installations; below, the swimming pool. [Source: Ref (254) Otto, Frei]

As with the German Pavilion in Montreal, the project for the Olympic Stadium in Munich would also foster the development and perfecting of experimental equipment (Fig 5.169). In this respect, the engineer Berthold Burkhardt at the “Institute for Lightweight Structures” at the University of Stuttgart would state: “The measurement instruments and experimental equipment were being continuously developed and adjusted along several lines at the Institute during the project for the deck of the Olympic Stadium in Munich: a new, improved machine for creating soapy surfaces to measure surface tension, apparatuses for determining tensions in prestressed nets, and other instruments were developed in collaboration with the Otto-Graf-Institut.” [Ref (254) Otto, Frei] At the same time Fritz Leonhard would make use of the first computers that arrived at the University of Stuttgart to start work on numerical models that would facilitate the representation of these structures through computerised methods. In short, the German Pavilion erected for Expo ’67 in Montreal would embody a series of structural advances that would be perfected and feed back into the Deck for the Olympic Games in Munich in 1972. The erection of these two magnificent structures would lead to a proliferation in these typologies, both in the field of World Expos and beyond.

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5.2.2.6 The influence of the change in direction initiated by Frei Otto There are several examples we could choose to represent the consequences of the formal freedom attained by Frei Otto in structures made with prestressed cable nets and prestressed membranes. Some of them are direct heirs, such as the decks for the West and East entrances in Expo ’70 in Osaka, while others embody new formal or technological searches; in any case, they are all the result of the historical turning point signalled by Otto’s work, particularly his original creation that was the German Pavilion for Expo ’67 in Montreal.

Fig 5.169. Deck for the Olympic Games in Munich 1972. Frei Otto, Günter Behnisch, Fritz Leonhard and Heinz Isler. Reduced model with photogrammetric equipment. [Source: Ref (254) Otto, Frei]

Thus, many of the tensile structures that were built for later Expos could be considered to have derived from the change in direction initiated by Frei Otto’s experiences. Logically, these new structures would gradually implement novel designs and therefore enrich the plastic repertoire of these typologies. They are structures that would also benefit from the logical evolution in materials, shape conception systems, calculation methods and representation methods, all of which were propelled by the general advances in computers and technology. It is worth noting that it would be in the ‘70s when the foundations of the finite element method would be perfected; while still dependent on the power of the large computers principally associated with the aerospace industry, it enabled the calculation of complex surfaces that were not easily determined with the bar elements that characterised the matrix method. In the ‘80s, commercial programmes based on the finite element method would begin to proliferate, in accordance with the increased calculation power of computers. The search for shape and the determination of the stress in structural elements would evolve from the study of physical models based on soapy liquids and reduced mesh models, to numerical models implemented by computer. Likewise, there would be an evolution in the technology linked to new materials too, in particular the cotton used in the first structures, and polyester would be gradually replaced by multilayer materials such as polyester with PVC or fibreglass with Teflon. This whole technological evolution would facilitate the construction of innumerable structures with a high degree of formal complexity, the philosophical origin of which lay in the German Pavilion for Expo ’67 in Montreal. There are so many examples of structures displaying the change in direction initiated by Frei Otto, both in subsequent World Expos and in buildings beyond them. Many of these examples can be found in various World Expos: Expo ’70 in Osaka, Expo ‘75 in Okinawa or Expo ’92 in Seville, among others. However, it was in Expo ’70 in Osaka and Expo ’92 in Seville where the greatest proliferation of both prestressed cable nets and prestressed membranes would appear.

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The East and West entrance decks of Expo ’70 in Osaka are undoubtedly direct consequences of the previous building (Fig 5.170). Designed by Otaka Architectural Design Office, Ltd., they are made of freeform prestressed cable nets with four masts and an inner lower point, as well as peripheral masts and low points. The covered area was 2270 m2 large and the maximum height was 18.45 metres. There were new features compared with the German Pavilion by Frei Otto. Nevertheless, their historical value lies in the influence of the previous building that it embodies.

Fig 5.170. Deck of the East entrance to Expo ’70 in Osaka. Otaka Architectural Design Office. [Source: Ref (32) Osaka Official Report]

On the occasion of Expo ’70 in Osaka, Frei Otto would continue to experiment with new cable net shapes, presenting the project for the Indian Pavilion in this Expo in 1967 (Fig 5.171), which remained unbuilt. In this case, it had a tree-shaped central mast to which 339

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radial cables were anchored. These cables were fastened at ten peripheral anchor points. Secondary cables were installed between the main cables, forming nets with a mesh width of 50 cm. Another noteworthy example is the Daidarasaurus Station built for Expo ’70 in Osaka by the architect Taneo Oki and the engineer Shigeru Aoki (Fig 5.172 to Fig 5.176). It was made up of a series of columns and cable-stayed high points, between which a prestressed PVC and vinyl fibre membrane was stretched. The structure covered 3,800 m2 and the height of the masts was 22 metres. The cable-stayed high points were arranged asymmetrically with respect to the longitudinal axis.

Fig 5.173. Daidarasaurus Station. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. [Source: Ref (206) Ishii, Kazuo]

Fig 5.174. Daidarasaurus Station. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. Plan and longitudinal elevation. [Source: Ref (206) Ishii, Kazuo]

Fig 5.171. Unbuilt project for the Indian Pavilion for Expo ’70 in Osaka. Frei Otto. 1967. [Source: Ref (177) Glaeser, Ludwig]

Fig 5.172. Daidarasaurus Station. Expo ’70 in Osaka 1970. Taneo Oki and Shigeru Aoki [Source: Ref (206) Ishii, Kazuo]

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Fig 5.177. Telecommunications Pavilion. Expo ’70 in Osaka. Toyoguchi Design Associates. [Source: Ref (206) Ishii, Kazuo]

This structure’s most interesting technical characteristic is the resources used to provide greater resistance to the strong winds. As the wind pressure tends to focus tension in the membrane vertices, a thinner membrane was used in this area so that it would break when faced with strong winds; consequently, the open hole would redistribute the tensions caused by the wind [Ref (206) Ishii, Kazuo].

Fig 5.175. Daidarasaurus Station. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. Detail of cable-stayed vertex. [Source: Ref (206) Ishii, Kazuo]

Fig 5.178. (Below, left) Telecommunications Pavilion. Expo ’70 in Osaka. Toyoguchi Design Associates. [Source: Ref (59) Expo ‘70, a photographic interpreter] Fig 5.179. (Below, right) Telecommunication Pavilion. Expo ’70 in Osaka. Toyoguchi Design Associates [Source: Ref (31) Osaka Official photo album]

Fig 5.176. Daidarasaurus Station. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. [Source: Ref (206) Ishii, Kazuo]

One of the structures displaying the most innovative execution for that time was the Telecommunications Pavilion designed by Toyoguchi Design Associates for the same event, Expo ’70 in Osaka (Fig 5.177 to Fig 5.181). In this case, the textile structure was made of a PVC and vinyl fibre membrane and took the appearance of the deck a step further by taking on a volumetric shape. Logically, an inside structure was used to make the building accessible.

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Fig 5.180. Telecommunications Pavilion. Expo ’70 in Osaka. Toyoguchi Design Associates. Cross-section. [Source: Ref (59) Expo ‘70, a photographic interpreter]

Fig 5.182. Deck of the South entrance to Expo ’75 in Okinawa. Okinawa Ocean Expo Architect and Assoc. [Source: Ref (206) Ishii, Kazuo]

The deck of the South entrance of Expo ’75 in Okinawa (Fig 5.182 and Fig 5.183) was designed by Okinawa Ocean Expo Architect and Assoc. It was a prestressed polyester fibre and PVC membrane suspended from a sole point and reinforced with five inner cables as well as edge cables. In spite of being a modestly sized structure, its historical contribution resides in the fact that it was the first prestressed membrane built to be modelled by the finite elements method; in his publication “Membrane structures in Japan” (Fig 5.184 and Fig 5.185), Kazuo Ishii states:

Fig 5.181. Telecommunications Pavilion. Expo ’70 in Osaka. Toyoguchi Design Associates. Plan. [Source: Ref (59) Expo ‘70, a photographic interpreter]

“This was the first structure to be built that was based on the analysis to determine tension and deformation based on the finite elements method.” [Ref (206) Ishii, Kazuo] Fig 5.183. Deck of the South entrance to Expo ’75 in Okinawa. Okinawa Ocean Expo Architect and Assoc. Plan. [Source: Ref (206) Ishii, Kazuo]

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These are just some of the examples of how the World Expos have contributed to the formal research in these typologies, the first-time application of new calculation models and the use of new materials and technological resources.

Fig 5.184. Deck of the South entrance to Expo ’75 in Okinawa. Equitensional surface obtained by the finite elements method without taking the weight of the membrane or of the cables into consideration. [Source: Ref (206) Ishii, Kazuo]

The numerical model was complemented with soapy surface models (Fig 5.186) and a physical model for the wind tunnel test, as Okinawa is a place often hit by typhoons. Kazuo Ishii himself offers detailed explanations of the modelling process in his article “Membrane structure shape in consideration of the weights of membrane and cable. Structural design and analysis. Okinawa Expo 75 Structure” [Ref (206) Ishii, Kazuo].

Fig 5.185. Deck of the South entrance to Expo ’75 in Okinawa. The former surface disregarded the membrane weight but considered the cable weight. [Source: Ref (206) Ishii, Kazuo]

Fig 5.186. Deck of the South entrance to Expo ’75 in Okinawa. Soapy surface model. [Source: Ref (206) Ishii, Kazuo]

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After Otto’s experience in Expo ’67 in Montreal, the most interesting tensile structure to be built for a World Expo would be Canada Place built for Expo ’86 in Vancouver (Fig 5.187 to Fig 5.189). Designed by Horst Berger and David Geiger, it was a structure made up of a prestressed fibreglass and Teflon membrane with ridge and valley cables with opposing curvature that basically created a wave typology. Conceived to be a permanent structure, the deck is located over an existing building at the edge of the port, taking on the appearance of a sail boat. The span measured transversely at the building axis is 55 metres. The diagonal span between masts is a considerable 73 metres. A prominent feature of the deck is the fact that it covers a circular theatre hall.

Fig 5.187. Canada Place. Expo ’86 in Vancouver. Horst Berger and David Geiger. [Source: Ref (95) Berger, Horst]

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This building’s most interesting features are, on the one hand, the use of a double membrane with an air chamber to improve the thermal insulation and acoustic soundproofing, with the outer membrane creating the structure; on the other hand, the diagonal arrangement of the ridge and edge cables with respect to the building axis from a formal perspective. According to the creator of the building himself, Horst Berger, the Folk Life Pavilion (Fig 5.190 and Fig 5.191) which he also built in 1978 in Penn’s Landing, Philadelphia and later rebuilt and reinforced “to face the winter forces”, would be the precedent to the design Canada Place [Ref (95) Berger, Horst]. However, the influence of Frei Otto is once again clear, since he had already built wave-type structures with floor plans that were asymmetrical in relation to the longitudinal axis such as the Wave Hall for the International Horticultural Exhibition in Hamburg, 1963 (Fig 5.192).

Fig 5.188. Canada Place. Expo ‘86 in Vancouver. Horst Berger and David Geiger. Physical model in elastic fabric. [Source: Ref (95) Berger, Horst]

Fig 5.190. Folk Life Pavilion. Horst Berger. 1978. Model in elastic fabric [Source: Ref (95) Berger, Horst]

Fig 5.191. Folk Life Pavilion. Horst Berger. 1978 [Source: Ref (95) Berger, Horst]

Fig 5.189. Canada Place. Expo ’86 in Vancouver. Horst Berger and David Geiger. Detail of the outside cable-stayed masts. [Source: Ref (205) Ishii, Kazuo]

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Fig 5.192. Wave Hall for the International Horticultural Exhibition in Hamburg, 1963. Frei Otto. [Source: Ref (254) Otto, Frei]

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The experience acquired by Berger with Canada Place in Expo ‘86 in Vancouver, as well as the double membrane used in the building in that Expo, would once again be used by the same designer for the deck of the Denver International Airport (Fig 5.193 to Fig 5.195). Built in 1994, this building is a truly experimental construction located in a particularly unfavourable area for these typologies: the local weather is characterised by strong snowfalls and hailstorms and fierce winds. The separation between layers was 60 cm. The span between masts was 45 metres.

Fig 5.196. Puerta Oleada from Expo ’92 in Seville. Harald Mühlberger. [Source: Ref (17) Expo ‘92, architecture et design]

Fig 5.193. Denver International Airport. Horst Berger. 1994. [Source: Ref (95) Berger, Horst]

Fig 5.194. (Below, left) Denver International Airport. Horst Berger. 1994. Snow load test on reduced model. [Source: Ref (95) Berger, Horst] Fig 5.195. (Below, right) Denver International Airport. Inside after snowfall. [Source: Ref (95) Berger, Horst].

Expo ’92 in Seville was particularly characterised by a proliferation of prestressed membranes and prestressed cable nets. Among the multiple buildings designed with these structural systems, we shall highlight two by Harald Mühlberger that exemplify the innovative heights these typologies had reached. The deck of the East Gate, also called the Puerta Oleada or Puerta Barqueta (Fig 5.196 to Fig 5.200) is made up of a prestressed membrane in which two 55-metre-high, central, inclined masts fasten two central beams via cables; these beams had opposing curvature, spans of 60 and 70 m and a tubular cross-section with diameters of 640 and 810 mm. The mast heads were anchored by cables at different points at the foundations. The structure was further complemented with some cable-stayed peripheral supports and the edge cables between which the four prestressed meshes were installed. The meshes themselves and the peripheral cable-stayed supports give the central curved beams lateral stability. The ensemble covers an extraordinary floor plan of 75 x 130 metres, and transmits a sensation of great lightness.

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Fig 5.197. (Below, left) Puerta Oleada. [Source: Ref (152) Escrig, Félix / Sánchez, José] Fig 5.198. (Below, right) Puerta Oleada. [Source: Ref (17) Expo ‘92, architecture et design]

Fig 5.199. Puerta Oleada at Expo ’92 in Seville. Harald Mühlberger. Longitudinal elevation. [Source: Ref (17) Expo ‘92, architecture et design]

Fig 5.200. Puerta Oleada. Transverse elevation. [Source: Ref (17) Expo ‘92, architecture et design]

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The intention to make the curved central beams three-dimensional structures with struts and cables was an interesting technical contribution. Some publications on that subject [Ref (91) Barnes, M. / Renner, W. / Kiefer, M.] mention tensegrity arches, although we believe this is a false case of tensegrity since compressed connected bars are part of their design (Fig 5.201 to Fig 5.203). The structure with its “tensegrity arches” was studied for the various load conditions and a reduced model would be tested in a wind tunnel. Finally, at an advanced design stage and basically due to economic constraints, these arches were replaced by the aforementioned tubular-section arches.

The deck for the North Gate or Puerta Itálica, also at Expo ’92 in Seville (Fig 5.204 to Fig 5.207), was made up of seven cable-stayed masts, peripheral supports that were cable-stayed too and an inner tensioning cable. In this case, it was a prestressed cable net with a mesh measuring 4 x 2.6 metres. Apart from its novel design, and bearing in mind its goal of providing shade, one of the technical contributions was the use of a porous textile enclosure material intended for reducing wind resistance, and thereby the forces it would transmit to the deck. Its height was around 47 metres and its floor plan measured 85 x 70 metres.

Fig 5.201. Puerta Oleada. Sketches of the proposed “tensegrity arches” which were eventually rejected. [Source: Ref (91) Barnes M. / Renner W. / Kiefer M.] Fig 5.204. (Above, left) North Gate at Expo ’92 in Seville. Harald Mühlberger. Axonometrics. [Source: Ref (17) Expo ‘92, architecture et design]

Fig 5.202. Puerta Oleada. Elevation of the first proposal with “tensegrity arches”. [Source: Ref (91) Barnes M. / Renner W. / Kiefer M.]

Fig 5.203. Puerta Oleada. Plan of the first proposal with “tensegrity arches”. [Source: Ref (91) Barnes M. / Renner W. / Kiefer M.]

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Fig 5.205. (Above, right) North Gate at Expo ’92 in Seville. Lateral elevation. [Source: Ref (17) Expo ‘92, architecture et design]

Fig 5.206. North Gate or Puerta Itálica at Expo ’92 in Seville. [Source: Ref (17) Expo ‘92, architecture et design]

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Fig 5.208. The Automobile Pavilion. Kunio Mayekawa. Expo ’70 in Osaka. [Source: Ref (32) Osaka Official Report]

The Automobile Pavilion in Expo ’70 in Osaka was designed by the architect Kunio Mayekawa (Fig 5.208 to Fig 5.212). It was made up of two circular-plan volumes; inside of each circle a cylindrical tower rose eccentrically with its head cut diagonally. A cable net was anchored at the head of this cylindrical tower, while at the bottom there was a metal compression ring connected to the foundations by triangulated bars that immobilised it. The cables follow oblique trajectories in order to offer stiffness against net torsion. The textile deck material that hung from the cable net had no structural function. Pavilion 1 had a diameter of 40 metres and a height of 25.4 m. Pavilion 2 had a diameter of 45 metres and a height of 17 m. The initial anticipated cable tension had to be increased to counter the wind loads of around 70 Km/h and even typhoons. On the other hand, the cable tension also had to be adjusted to reduce the imbalance from the resultant horizontal force on the cylindrical tower head.

Fig 5.207. North Gate at Expo ’92 in Seville. Harald Mühlberger. [Source: Ref (17) Expo ‘92, architecture et design]

It should be highlighted that the development of these structures, with their complex support systems and fabric under great tension, had run parallel to developments in computers and the finite element programmes enabling the evaluation of stress and facilitating the search for the ultimate shape. The examples described above have also demonstrated how the structures built for the World Expos contributed to the research into the formal possibilities of these typologies and materials; in many cases, these aforementioned examples made invaluable contributions to the history of structural systems and architecture.

5.2.2.7 Other historically relevant structures in the World Expos There are other structures which we believe do not demonstrate the change in direction initiated by Frei Otto so clearly; they are generally structures developed with simpler shapes, such as the Automobile Pavilion built for Expo ’70 in Osaka (Fig 5.208), structures that are simply cable-stayed, such as the Australian Pavilion in that same Expo (Fig 5.214), or perhaps because they have older precedents such as the Entrance Gate to Expo ‘89 in Yokohama (Fig 5.218). Nevertheless, these are still highly relevant from a historical perspective as they exemplify the enormous formal variety of these typologies. Additionally, they have had widespread, detailed coverage, a fact that has undoubtedly contributed to the transmission of their technical and formal innovations to architects and engineers.

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Fig 5.209. The Automobile Pavilion. Kunio Mayekawa. Expo ’70 in Osaka. Elevation. [Source: Ref (206) Ishii, Kazuo]

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Fig 5.210. The Automobile Pavilion. Kunio Mayekawa. Expo ’70 in Osaka. Cross-section. [Source: Ref (206) Ishii, Kazuo]

Fig 5.212. The Automobile Pavilion. Kunio Mayekawa. Expo ’70 in Osaka. Indoor photograph of the central mast. [Source: Ref (31) Osaka official photo album]

There are some common elements in the Automobile Pavilion for Expo ’70 in Osaka and the brilliant Yoyogi National Gymnasium built by Kenzo Tange, Tsuboi and Kawaguchi for the Tokyo Olympic Games (Fig 5.213) held six years earlier in 1964; bearing in mind the differences, the latter building’s potential influence can be evinced. These common elements are the connection to a sole mast that is off-centre at floor level, the final deck shape, and the use of a steel cable net, although a steel sheet enclosure was used for the Yoyogi National Gymnasium, while a textile enclosure was used in the Automobile Pavilion. Finally, both decks display a plastic eloquence that is linked to these new tensile typologies and fully rooted in this period. Fig 5.211. The Automobile Pavilion. Kunio Mayekawa. Expo ’70 in Osaka. Completed cable net and installation of the textile deck. [Source: Ref (206) Ishii, Kazuo]

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Fig 5.213. Yoyogi National Gymnasium for the Tokyo Olympic Games in 1964. Kenzo Tange, Tsuboi and Kawaguchi. [Source: Ref (95) Berger, Horst]

Fig 5.215. The Australian Pavilion. James Maccormick. Expo ’70 in Osaka. Cross-section. [Source: Ref (32) Osaka Official Report]

Built for Expo ’70 in Osaka, the Australian Pavilion (Fig 5.214 to Fig 5.216) was designed by the Australian architect James Maccormick and consisted of a building made with cable-stayed trusses. In this case, the building has quite a sculptural air about it. The trusses were arranged radially with a diameter of 48 metres, and were cable-stayed from a cantilevered mast made of a 40-metre-high metal structure covered in ferrocement. The truss ensemble was horizontally stabilised via connections at four foundation points.

Fig 5.216. The Australian Pavilion. James Maccormick. Expo ’70 in Osaka. Photograph of the building under construction. [Source: Ref (39) La Expo di Osaka]

Fig 5.214. The Australian Pavilion. James Maccormick. Expo ’70 in Osaka. [Source: Ref (32) Osaka Official Report]

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Four entrance decks made of prestressed longitudinal trusses with bars and cables were built for Expo ’89 in Yokohama. While the four decks displayed similar characteristics with some variation, perhaps the most representative and largest are those called Sakuragicho and Takashimacho Gates, both exactly the same (Fig 5.217 to Fig 5.220). Designed by G.K. Sekkei Associates and N. Inoue, they had a floor plan of 47 x 33 metres with a free transverse span of 37 metres. The structural layout involved cables of opposing curvature that were connected with bars in this case. The lower cable acted against wind pressure loads, while the upper countered wind suction loads.

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Fig 5.217. Takashimacho Gate. G.K.Sekkei Associates and N. Inoue. Expo ’89 in Yokohama. [Source: Ref (206) Ishii, Kazuo]

Fig 5.218. Takashimacho Gate. G.K. Sekkei Associates and N. Inoue. Expo ’89 in Yokohama. [Source: Ref (206) Ishii, Kazuo]

Fig 5.219. Takashimacho Gate. G.K. Sekkei Associates and N. Inoue. Expo ’89 in Yokohama. Cross-section. [Source: Ref (206) Ishii, Kazuo]

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Fig 5.220. Takashimacho Gate. Plan of the deck structure. Note the two trusses at the ends with opposing curvature that stiffen the deck horizontally. [Source: Ref (206) Ishii, Kazuo]

The idea of using cable trusses with opposing curvature is not new at all, having early precedents such as the aforementioned building for the German Song Festival in Dresden erected in 1865 by Eduard Müller (Fig 5.19 to Fig 5.21), or the large-span deck proposals by Lehaire and Mondésir (1866) (Fig 5.22). A more modern example with a framed radial layout is the Utica Memorial Auditorium by Lev Zetlin, built in 1959 (Fig 5.108 to Fig 5.109). Logically, in the case we are discussing here, the same principle has been applied with considerable technological developments. The most interesting feature in this building may be the way the prestressed trusses were connected longitudinally with cables in the lower area and by the textile cover in the upper area. As all these longitudinal connections have zero rigidity against compression, it was necessary to recur to some type of resource that would enable the deck to be stabilised longitudinally. For this purpose, two curved end trusses were installed in such a way as to transpose the principle of the opposing curvature cables used in section to the plan (Fig 5.220). In short, there was no need for any longitudinal connection bars at all, thanks to which the building has an appearance of extreme buoyancy.

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The principle is an old one; after the collapse of St. Paul’s Cathedral in 1668, Christopher Wren was in charge of its reconstruction (Fig 5.221). He designed a type of masonry cone reinforced with chains at the base to support the heavy stone lantern, its own weight and part of the wooden framework that supported the outer dome of this material. This cone had a shape that was halfway between a cone with a straight generatrix suitable for the lantern’s point load, and a cone with a catenary generatrix that would adequately withstand the uniformly distributed load of its own weight and the forces of the wooden framework.

5.2.2.8 “Tensile designed” structures: the contribution of the expos We can define “tensile designed” structures as those that primarily work under compression but which have been designed by inversion of another which, supporting the same loads, works under tension. We know that a cable that is subject to a load distributed according to its horizontal projection will assume the shape of a parabola; if, on the other hand, it is subject to a load distributed according to its directrix such as that produced by its own weight, it will assume a catenary shape. If we then invert these shapes, we get arches that, when applied with the loads generated by their shapes, will work exclusively under compression without developing any bending. These inverted shapes are what we call anti-funicular lines of the applied loads.

In 1695, Robert Hooke made a series of diagrams. One of them was interpreted by Richard Waller in 1705 with the following words: “Such as a flexible cable hangs, but inverted, the rigid arch will remain stable.” [Ref (134) Cowan Henry J.] Additionally, David Gregory published an article titled “on the properties of the catenary” in “Philosophical Transactions of the Royal Society” in 1697, in which he stated: “… when an arch … is supported, it is because in its thickness some catenaria is included.” [Ref (134) Cowan Henry J.] However, it was possibly the Spanish architect Antoni Gaudí who exploited this principle most brilliantly. The images of funicular models to determine the arching of some of his works, based on strings and small weights, are well-known (Fig 5.222).

Fig 5.221. St. Paul’s Cathedral. Cross-section of the reconstruction by Christopher Wren. 1668. [Source: Ref (134) Cowan, Henry J.]

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Fig 5.222. Funicular model for the design study of the Colonia Güell. Antoni Gaudí. Period photograph. [Source: its creators]

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The building has the highly interesting conceptual characteristic of transferring the creation of a physical model to the assembly system. That is, the model took its final shape from an initial flat chain mesh; assembly started with a double mesh of straight wooden members arranged at zero level, subsequently raising its points (Fig 5.224). The double mesh offered less stiffness against bending in order to curve it by lifting the joints. As in the chain model, the cross nodes between members were hinged to allow the original squares to be distorted. Once the final position had been reached, the node stiffness would be increased. The final result is a structure with an extraordinary sense of formal freedom and lightness, making it one of the most brilliant works in the history of structural systems and architecture (Fig 5.225).

In any case, one can deviate from the anti-funicular line of the applied loads when using materials that can withstand bending, such as wrought iron, steel, wood or reinforced concrete, although we should not forget that they will be subject to bending in this case. Nevertheless, even with these materials, an approximation to the anti-funicular line will enable these pieces to basically withstand compression, considerably reduce bending forces, and therefore display a more svelte cross-section. It should also be pointed out that the tensile structure from which this design derives is what we have referred to as a “natural autoshape”; nevertheless, this is not the case when inverting this structure, as it will basically develop compression forces and thus run the risk of buckling. Recently, Frei Otto literally made this principle his own; he says: “I also began to experiment with the principle of inversion, in other words, by developing vaults in a state of suspension. It is quite simple to submerge a cloth in plaster, hang it and turn it over once hardened. It was my father who gave me the idea. At that time I had not heard of Gaudí. With chains and inversion experiments, the whole world of domes and vaults opened up before my eyes.” [Ref (254) Otto, Frei] Thus, the most noteworthy application of this principle by Otto would be the Multihalle for the Federal Garden Exhibition held in Mannheim in 1975. The original design model would be based on hanging chains (Fig 5.223). This model was studied photogrammetrically and complemented with computerised numerical methods, thus enabling an approximation to the stress supported by the structural members and facilitating an electronic drawing of the ensemble.

Fig 5.223. Multihalle for the Federal Garden Exhibition in Mannheim. Reduced model of inverted chains. Frei Otto 1975. [Source: Ref (254) Otto, Frei]

Fig 5.224. Multihalle for the Federal Garden Exhibition in Mannheim. Assembly of the structure by lifting the joints. Frei Otto 1975. [Source: Ref (254) Otto, Frei]

Fig 5.225. Multihalle for the Federal Garden Exhibition in Mannheim. Indoor photograph. Frei Otto 1975. [Source: Ref (254) Otto, Frei]

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Some contributions to tensile designed structures would be made through the World Expos, two of the most important specifically being a product of Frei Otto’s intervention; the unbuilt design for the German Pavilion in Expo ’92 in Seville, and the Japanese Pavilion for Expo 2000 in Hanover. The unbuilt design entered in the competition for the German Pavilion in Expo ’92 in Seville by Frei Otto and Ted Happold (Fig 5.226) is a direct heir of the Mannheim Multihalle. It was a deck made of a mesh whose shape was determined by the inversion of chain models. In this case, the idea was to make a deck with metal profiles and a glass enclosure, with textile elements offering shade. Large openings were projected in the higher parts of the enclosure to enhance the natural ventilation. It was truly a new formal exploration along a path that would lead to the Mannheim Multihalle, as explained above.

The Japanese Pavilion in Expo 2000 in Hannover was designed by the Japanese architect Shigeru Ban with Frei Otto acting as a consultant. The final structure would be the result of inverting an initial tensile chain model (Fig 5.227 and Fig 5.228). This pavilion’s most curious feature was the fact that it was built with cardboard tubes, thus making it the largest construction ever made of this material. The pavilion had a span of 35 metres, a length of 70 and a height of 16. The tube diameter was only 12 cm. Bearing in mind when this pavilion was built, while the use of the inverse design method is significant (giving rise to truly svelte sections), what is really relevant is the use of cardboard as a structural material on this scale. For this reason, this building will be covered in Chapter 8 on structures built with wood and materials derived from the same (Fig 8.65 to Fig 8.66 and Fig 8.71 to Fig 8.79).

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Fig 5.227. Japanese Pavilion in Expo 2000 in Hanover. Inverted chain model. Shigeru Ban and Frei Otto. [Source: Ref (254) Otto, Frei]

Fig 5.226. Unbuilt design for the German pavilion in Expo ’92 in Seville. Frei Otto and Ted Happold. [Source: Ref (254) Otto, Frei]

Fig 5.228. Japanese Pavilion in Expo 2000 in Hanover. [Source: Ref (254) Otto, Frei]

These last two buildings once again demonstrate that while the formal freedom inherent to Frei Otto’s structures may seem to be random, it is based on the formal embodiment of the physical principles governing the structural typology in question. Such is the case of tensile structures designed with soapy surface models and “tensile designed” structures, whose models are inverted so that it is the compression stresses which are fundamentally developed. In other words, it is the structure and its governing physical principles which determine these buildings’ complex form.

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5.2.2.9 Tensegrity Structures: The contribution of the Expos Based on the observation of the sculptures by Kenet Snelson (Fig 5.229), Richard Buckminster Fuller defined tensegrity or self-tensioning structures in 1951 as follows: “We are before a self-tensioning system when a set of discontinuous components working under compression are combined with a system in which continuous elements work under tension, defining a stable volume in space.” [Ref (267) Picon, Antoine]

Fig 5.231. Tensegrity dome model by Buckminster Fuller. 1953. [Source: Ref (179) Gómez Jáuregui]

Fuller called this structural typology “tensegrity”, a term that comes from combining “tensile” and “integrity”, that is, integrity under tension. Fuller would later patent several shapes in this new typology, some of which would attain a high level of geometric complexity. The aim of architectural application is sometimes evident, as in the case of the patent for the tensegrity dome in 1953 (Fig 5.231 to Fig 5.234).

Fig 5.232. Patent by Buckminster Fuller for various tensegrity structures. 1959. [Source: Ref (219) Klotz, Heinrich]

Fig 5.230. Richard Buckminster Fuller showing a polyhedral tensegrity structure. [Source: Ref (219) Klotz, Heinrich]

Fig 5.229. Sculpture X. Kenet Snelson. 1948. [Source: Ref (151) Escrig, Félix / Sánchez, José]

The sculptor Kenet Snelson himself and other researchers such as David Georges Emmerich, René Motro, S. Pellegrino and Ariel Hannor would delve into the possibilities offered by this typology. However, Fuller would even go to the extreme of associating this principle with the integrity of the Universe, as he states in his book “Synergetics: explorations in the geometry of thinking”, published in 1975:

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Patented by Buckminster Fuller in 1974 (Fig 5.235), the nearest to a tensegrity structure that an architectural application has come is the so-called aspension dome. In this case, it was not a pure tensegrity or self-tensioned structure as it is not self-stable in space, but instead requires anchoring at points outside itself or to a compression ring that would generate a reaction to stabilise it. Professor Félix Excrig has presented some diagrams on these aspects (Fig 5.236 and Fig 5.237) [Ref (151) Escrig, Félix / Sánchez, José]

Fig 5.233. Mast-type tensegrity structure model. Buckminster Fuller. [Source: Ref (267) Picon, Antoine]

Fig 5.235. Proposal for an aspension dome. Richard Buckminster Fuller. 1974. [Source: Ref (151) Escrig, Félix / Sánchez, José]

Fig 5.234. Patent by Buckminster Fuller for various polyhedral tensegrity structures. 1973. [Source: Ref (219) Klotz, Heinrich]

Fig 5.236. Flat aspension truss. Drawing by Félix Escrig. [Source: Ref (151) Escrig, Félix / Sánchez, José]

“All structures, properly understood, from the Solar System to the atom, are tensegrity structures. Universe is omnitensional integrity.” [Ref (105) Buckminster Fuller, Richard] The truth is that no pure tensegrity structures for decks capable of covering large spaces have been built to date, pure tensegrity structure taken to mean one that needs no anchoring to external elements, nor connecting to a compression ring to maintain its shape. The embodiment of the pure tensegrity principle has been limited to architectural prototypes of rather small sizes, as well as to the field of sculpture. Fig 5.237. Aspension space truss. Drawing by Félix Escrig. [Source: Ref (151) Escrig, Félix / Sánchez, José]

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Fig 5.240. Olympic Gymnastics Arena for the Olympic Games in Seoul 1988. David Geiger. Sketch illustrating the elevation or aspension of the deck structure. 1-The structure is hung from the compression ring and rests on the ground. 2-Elevation of the first ring. 3-Elevation of the second ring. 4-Elevation of the third ring. 5-Elevation of the central ring and installation of the textile deck. [Source: Ref (205) Ishii, Kazuo]

We have already truly covered old structures, even ones that pre-date Fuller’s patent for the aspension mesh, made of cables and bars with no contact between them, but which need the aforementioned compression ring; such is the case of the Utica Memorial Auditorium, New York by Lev Zetlin (1959) (Fig 5.108 and Fig 5.109). In spite of not being purely self-tensioning structures, it is true that they are inspired by the principle. Nevertheless, what happens with many of the significant examples of aspension meshes is that the cables connecting the bars at their lower end are arranged concentrically or slightly parallel to the building’s outline; we believe that this increases the sensation of airiness or “buoyancy” of the bars that characterise these typologies (Fig 5.238).

Fig 5.238. Sketch of an aspension dome by David Geiger. Many of the most significant examples built to date are based on similar sketches. Perimetral compression ring, upper radial cables and lower annular cables. [Source: Ref (205) Ishii, Kazuo]

The most relevant creations in terms of aspension domes have been basically limited to large sporting venues. Thus, the first two applications of this structural system were the Olympic Gymnastics Arena and the Olympic Fencing Gymnasium built by David Geiger for the Olympic Games held in Seoul in 1988 (Fig 5.239 to Fig 5.241). These two buildings had a circular floor plan with a perimetral compression ring made up of a metal truss; their diameters were 119 and 90 metres respectively.

Fig 5.239. Olympic Gymnastics Arena for the Olympic Games in Seoul 1988. David Geiger. [Source: Ref (205) Ishii, Kazuo]

Fig 5.241. Olympic Gymnastics Arena for the Olympic Games in Seoul 1988. David Geiger. Cross-section. [Source: Ref (205) Ishii, Kazuo]

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Other aspension domes have attained truly remarkable spans. Along these lines, the 210-metre-span Suncoast Dome (Fig 5.242 and Fig 5.243) built by Geiger in Florida in 1989 displays a similar design to the Olympic Gymnastics Arena in Seoul, although in this case the compression ring is made of concrete. The biggest deck in this typology built to date is the Georgia Dome in Atlanta erected by Matiz Levy in 1994 (Fig 5.244 and Fig 5.245). It set a new world record for span and was a structure with an elliptical floor plan measuring 240 x 193 metres with a concrete compression ring and vertical bars that were 24 metres long.

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Fig 5.242. Suncoast Dome, Florida. David Geiger. 1989. [Source: its creators]

Fig 5.244. Georgia Dome. Atlanta. Matiz Levy. 1994. [Source: Ref (205) Ishii, Kazuo]

Fig 5.243. Suncoast Dome, Florida. David Geiger. 1989. Sectioned axonometrics and structural cross-sections. [Source: its creators]

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Fig 5.245. Georgia Dome. Atlanta. Matiz Levy. 1994. Structural diagram. [Source: Ref (205) Ishii, Kazuo]

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In these examples, the structure reaches such a size that the annular “cables” that connect the bars at their lower end usually act as maintenance walkways and installations (Fig 5.243 and Fig 5.244). Regarding the Georgia Dome, even the masts have external maintenance stairs attached to them. All these examples are covered in textile material. As shown, there have been no significant architectural applications of pure tensegrity structures to date, in terms of covering spaces with significant spans. The same cannot be said about aspension meshes, which have primarily been applied to decks in large sporting venues developed during the ‘80s and ‘90s, with the Georgia Dome in Atlanta even setting a world record for span. In spite of these relevant applications outside the Expos and the enormous possibilities offered by this typology for the decks of large, diaphanous spaces, aspension domes have not been applied in the World Expos themselves. We can, however, find examples such as the aforementioned Sakuragicho and Takashimacho Gates in Expo ’89 in Yokohama 1989 (Fig 5.217 to Fig 5.220), which were designed with a spatial combination of flat trusses made of bars without any contact between them, connected by a continuous cable net and needing external elements to generate the horizontal reactions for stabilisation. As far as pure tensegrity structures are concerned, there have been examples of these in the World Expos; sculptural creations following these principles that can be found both within and beyond the Expos. Among the examples we could mention is the sculpture at the Gate of Nations at Expo ’58 in Brussels (Fig 5.246 and Fig 5.247). Designed by P. Guillissen, J. Koning and A. Paduart, it had a height of around fifty metres. At that time, it was the largest example of a creation governed by tensegrity. Another of the various examples to be found is one of the sculptures exhibited at Expo ‘70 in Osaka (Fig 5.248).

Fig 5.247. Sculpture at the Gate of Nations. Expo ’58 in Brussels. Assembly photograph. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

Fig 5.248. Tensegrity sculpture at Expo ’70 in Osaka. [Source: Ref (31) Osaka Official Photo Album]

Fig 5.246. Tensegrity sculpture. Gate of Nations. Expo ’58, Brussels. P. Guillissen, J. Koning and A. Paduart. [Source: its creators]

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In reference to the last point, we should also add that, at the end of the 20th century, the protagonism of the World Expos as places of reference for structural development has had to be shared with buildings outside the Expos themselves, particularly with enormous buildings designed as sporting venues that had often been built on the occasion of the Olympic Games.

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to the hot-air balloon, although it was not until 1897 when David Schwarz would build the first airship with an inner skeleton. This technology would continue to be developed by Ludwig DĂźrr in 1905 when he built the Zeppelin LZ-2, made with polygonal rings connected by longitudinal bars, a typology that would be perfected over the following years (Fig 6.3).

CHAPTER 6

WORLD EXPOS: THE ZENITH OF PNEUMATIC STRUCTURES Pneumatic structures belong to the group of structural typologies whose mechanical principle is based on tension, covered in the previous chapter. Nevertheless, given the specificity of pneumatic structures and the notable contribution of the World Expos to the history of this typology, they deserve their own chapter. Their specificity is primarily based on the fact that they are membrane structures that are prestressed via the differential pressure between an internal and external fluid, thus generally needing a permanent electricity supply in order to maintain their shape.

6.1 THE ORIGIN OF PNEUMATIC STRUCTURES From bubbles made of liquid to membranes with pressurised fluids inside them, there are many examples of pneumatic structures in nature that have inspired mankind (Fig 6.1). However, the beginnings of the history of artificial pneumatic structures are linked to that of aeronautics. Thus, the hot-air balloon could be considered as the first artificial precedent of pneumatic structures for construction. Invented in 1783 by Joseph Michel and Jacques Etienne Montgolfier, its main link to construction typologies resides in the fact that it is a membrane that keeps its structural shape thanks to a difference in pressure between external and internal air (Fig 6.2). Invented by Jean Baptiste Meunier, the airship is contemporary

Fig 6.3. The airship LZ-126 under construction. A typology comprising polygonal rings connected by longitudinal bars. 1924. [Source: Ref (267) Picon, Antoine]

Fig 6.1. The soap bubble as a natural pneumatic structure. [Source: Ref (195) Herzog, Thomas]

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Fig 6.2. Lift-off of the hot-air balloon invented by Joseph Michel and Jacques Etienne Montgolfier. 1783. [Source: Ref (195) Herzog, Thomas]

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The enormous engineering effort invested in developing these giant, flying, pneumatic structures would be mirrored in construction. In this way, the English engineer Frederick William Lanchester would patent a provisional pneumatic hospital in 1917 (Fig 6.4) that would constitute the first known application to construction of the technology developed for air transport; unfortunately, it was never built. While there was no immediate continuity to Lanchester’s works, the patent brings to light some of these structures’ main architectural characteristics: their provisionality, easy transportation and speedy assembly.

Fig 6.5. (Above, left) Pneumatic decks to protect radars installed in the U.S. after World War Two. [Source: Ref (195) Herzog, Thomas]

Fig 6.4. Fig 6.4. Frederick William Lanchester’s patent for a provisional pneumatic hospital. 1917. [Source: Ref (195) Herzog, Thomas]

Once World War Two had broken out, these characteristics would contribute to the design of various pneumatic elements such as pneumatic boats. Military applications would continue to be developed after the war; thus, at the beginning of the ‘50s and in the context of the Cold War, the United States would begin construction of several radar antennae to protect their borders. Often located in inhospitable areas, these antennae needed a protective cover that would not interfere with the signals (Fig 6.5 and Fig 6.6). Along these lines, the engineer and Director of Cornell Aeronautical Laboratory, Walter Bird, studied and built several pneumatic decks. Bird’s works would be highly relevant in the development of pneumatic decks thanks to his inclusion of wind tunnel tests; the conclusion he reached through these tests was that structures with a diameter of 15 metres would be stable in winds of up to 240 Km/h [Ref (267) Picon, Antoine]. He also tested various synthetic fabrics such as nylon coated in neoprene, vinyl or hypalon.

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Given the satisfactory results obtained with pneumatic structures for military antennae covers, they would continue being used in the ‘60s to cover large telecommunications antennae, reaching spans of around 60 metres. An example of this is the low-pressure pneumatic cover of the Space Telecommunication Station of Pleumeur-Bodou (Fig 6.7 to Fig 6.9).

Fig 6.6. (Above, right) Pneumatic decks to protect radars installed in the U.S. after World War Two. [Source: Ref (195) Herzog, Thomas]

Fig 6.7. Space Telecommunication Station of Pleumeur-Bodou. Assembly of the membrane in the ‘60s. [Source: Ref (267) Picon, Antoine]

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These typologies were applied to itinerant exhibition buildings thanks to their aforementioned characteristics of provisionality, easy transportation and speedy assembly and dismantling; these buildings were structures with large spans and novel designs. Thus, Birdair Structures built the Pentadome for the U.S. Army in 1958, an exhibition building made up of five dome-shaped, low-pressure, pneumatic structures. The central dome had a diameter of 49.5 m and a height of 28 m (Fig 6.10 and Fig 6.11).

Fig 6.8. Space Telecommunication Station of Pleumeur-Bodou. [Source: Ref (267) Picon, Antoine]

Fig 6.10. Pentadome. Exhibition domes of the U.S. Army. 1958. [Source: Ref (195) Herzog, Thomas]

Fig 6.9. Space Telecommunication Station of Pleumeur-Bodou. Radar antenna and pneumatic dome. [Source: Ref (267) Picon, Antoine]

These applications started to extend to the civil sphere in 1955, when Walter Bird set up the company Birdair Structures Incorporated. From then on, pneumatic structures would begin to spread all over the U.S., appearing as basically semi-spherical or semi-cylindrical constructions with different architectural functions, such as sports installations or hangars. Fig 6.11. Pentadome. Inside the largest dome. 1958. [Source: Ref (255) Otto, Frei]

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Another notable example was the transportable exhibition pavilion of the United States Atomic Energy Commission, built in 1960 by Victor Lundy, Fred Severud and Birdair Structures (Fig 6.12 and Fig 6.13). In this case, it was a pneumatic structure with a novel design, a maximum span of 38 metres and a length of 90 m. The building was designed to withstand winds of 150 Km/h. The air cushion had a maximum thickness of 1.20 metres and was compartmentalised into various chambers to avoid damage to any one of them causing the whole structure to collapse.

The air pressure equipment was concealed behind the stage and was connected to the deck via two fabric tubes. The wind would tear the membrane during the deflation process.

Fig 6.12. Transportable exhibition pavilion of the United States Atomic Energy Commission. Victor Lundy, Fred Severud and Birdair Structures. 1960. [Source: Ref (267) Picon, Antoine]

Fig 6.14. Metropolitan Boston Arts Center. Carl Koch, Margaret Ross and Birdair Structures. 1959. Air cushion with a diameter of 44 metres, the largest built at that time. [Source: Ref (195) Herzog, Thomas]

Fig 6.13. Transportable exhibition pavilion of the United States Atomic Energy Commission. Victor Lundy, Fred Severud and Birdair Structures. 1960. Plan and cross-section. [Source: Ref (195) Herzog, Thomas]

Another relevant example from that era is the Metropolitan Boston Arts Center in 1959 (Fig 6.14 to Fig 6.17). Made by Carl Koch, Margaret Ross and Birdair Structures, it had a low-pressure deck and double membrane that shaped an air cushion connected to a 44-metre-diameter, steel, perimetral, compression ring at eighteen points. At its central point, the structure had a thickness of around 6 metres. It was the largest air cushion to be built at that time, while it should be noted that it was initially designed to act as formwork for a reinforced concrete shell.

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Fig 6.15. Metropolitan Boston Arts Center. Carl Koch, Margaret Ross and Birdair Structures. 1959. Elevation of the membrane. [Source: Ref (267) Picon, Antoine]

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Fig 6.16. Metropolitan Boston Arts Center. 1959. [Source: Ref (255) Otto, Frei]

Richard Buckminster Fuller also made an interesting proposal; a hybrid prototype combining a high-pressure pneumatic structure and a space structure with a layer of bars (Fig 6.18).

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Fig 6.17. Metropolitan Boston Arts Center. 1959. [Source: Ref (255) Otto, Frei]

Fig 6.18. Geodesic pneumatic structure. Richard Buckminster Fuller. [Source: Ref (255) Otto, Frei]

On the other hand, it should be noted that in 1962 Frei Otto published the first German edition of his classic book “Tensile structures” [Ref (255) Otto, Frei], in which a long chapter was dedicated to defining the pneumatic structures on the cutting edge, the main constructions of that time and the calculation of membranes. The impact of this publication and of the “First International Congress of Pneumatic Structures”, held in Stuttgart in 1967, would mean they would act as catalysts for knowledge, dissemination and research in this area [Ref (195) Herzog, Thomas]. One should not forget that Expo ’70 in Osaka (see below) was held only three years after this congress, and would undoubtedly become one of the high points in the history of pneumatic structures in terms of structural design and size. Six years after Expo ’70 in Osaka, Thomas Herzog published his classic book “Pneumatische Konstruktionen” [Ref (195) Herzog, Thomas]. Written after the erection of many of the principal milestones in pneumatic structures, this book updated the state of the art and made interesting classifications of these typologies, documenting the main pneumatic structures built to date and paying special attention to the physical aspects, offering technical data and even simplified diagrams to calculate some membranes. Herzog established different points of view from which to classify pneumatic structures, although it is true that the most significant classification is based on the differential pressure between internal and external fluids, distinguishing high-pressure and low-pressure systems. Low-pressure systems (Fig 6.19) are those in which the difference between internal and external pressure is between 10 and 100 mm of water pressure (10 Kg/m2 and 100 Kg/m2). Within the low-pressure systems, we can distinguish between those with a single membrane (in which the pressurised space coincides with the living space) and those with a double membrane. In high-pressure systems (Fig 6.20), the differential pressure has values that vary between 2,000 and 70,000 mm of water pressure (2,000 Kg/m2 and 70,000 Kg/m2). High-pressure systems basically consist of tube-like structures that are characterised by a pronounced curvature in one of their planes and null or little curvature in the orthogonal plane. The typologies derived from high-pressure systems (with elements such as beams, columns, portals, arches, trusses or meshes) may be fully or partially subject to compression forces. For this reason, as the membrane can only withstand tension, it has to be prestressed beforehand with differential high pressure.

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In general, for a same internal pressure, the greater the radius of curvature, the greater the stress developed by the membrane (Fig 6.21). For this reason, high-pressure systems are developed with elements with a short radius of curvature, while large radii of curvature are possible with low-pressure systems.

low pressure system single membrane structures no additional support

additional point support

additional linear support

additional point & linear support

additional linear support

additional point & linear support

negative pressure

positive pressure

Fig 6.21. Relation between the tension per unit of fabric length (T), internal pressure (P) and the radius of curvature (r). Thomas Herzog. 1976. Note: when the radius is large (small curvature), low pressure provides enough stress in the membrane; when the radius is short (large curvature), higher pressure is needed to achieve the tension needed in the membrane. [Source: Ref (195) Herzog, Thomas]

double membrane structures no additional support

additional point support

6.2 THE WORLD EXPOS: THE ZENITH

negative pressure

The characteristics of provisionality and easy transportation inherent in these structures connected perfectly with the nature of the Expos. Nevertheless, despite the effective acceleration in the assembly and dismantling of exhibition structures, the construction of these typologies in World Expos has generally responded more to the display of technological development than to a true spirit of dismantlement, transportation and use of the structure in another location; with the few odd exceptions, this has not been the case.

positive pressure

high pressure systems single elements

noncontinuous

continuous

On the other hand, the World Expos have been one of the most suitable stages for structural experimentation and aspiring to utopia; in this way, not only have the latest theoretical and practical developments had an impact on those Expos of a notable structural character like Expo â&#x20AC;&#x2122;70 in Osaka, utopian proposals from designers such as Frei Otto have also been influential. Along these lines, we shall highlight the 1967 proposal of a pneumatic dome to cover an island (Fig 6.22).

Fig 6.19. Classification of low-pressure pneumatic systems according to Thomas Herzog. 1976. [Source: Ref (195) Herzog, Thomas]

straight

bent Fig 6.20. Classification of high-pressure pneumatic systems according to Thomas Herzog. 1976. [Source: Ref (195) Herzog, Thomas]

arched

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Fig 6.22. Frei Otto. Proposal for a pneumatic dome to cover an island. 1967. [Source: Ref (254) Otto, Frei]

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Six years later in 1964 was the New York World’s Fair, in which the same creators who had designed the novel Transportable Pavilion of the United States Atomic Energy Commission in 1960 (Fig 6.12 and Fig 6.13), Victor Lundy, Fred Severud and Birdair Structures, would build the Brass Rail Restaurant (Fig 6.25 to Fig 6.28). In this case, and in spite of being modest in size (an 18-metre diameter and a height of 23 m), it was a structure that stood out for its original globular-bunch design with an interior steel mast. It is an example of how consolidated designers use the field of the World Expos as testing grounds for new structural designs. Various examples that were identical to these restaurants were built in this Expo.

6.2.1 The Expos prior to Osaka ‘70: sporadic contributions Earlier, we described how the spread of pneumatic structures to civil use started in the U.S. in 1955. Following this chronological line, the Pan American World Airlines Pavilion (Fig 6.23 and Fig 6.24) would be built for the next significant World Expo, that of Brussels in 1958. It was made by the architect J. Delalieux and comprised a sphere with a diameter of 16 metres with a vinyl-coated nylon cover, representing a globe upon which the routes of the airline company appeared. Screenings were shown inside. Access was through an air lock that limited pressure losses. Built the same year as the domes of the U.S. Army Pentadome, its singularity did not lie in the originality of its design or its considerable size, but in the fact that it was the first pneumatic construction structure to be designed for public display in Europe [Ref (136) Dent, Roger N.] [Ref (255) Otto, Frei].

Fig 6.25. Brass Rail Restaurants. New York World’s Fair of 1964. Victor Lundy, Fred Severud and Birdair Structures. [Source: Ref (32) Osaka Official Report] Fig 6.23. Pan American World Airlines Pavilion. Expo ’58 in Brussels. J. Delalieux. [Source: Ref (255) Otto, Frei]

Fig 6.24. Pan American World Airlines Pavilion. Expo ’58 in Brussels. J. Delalieux. [Source: Ref (255) Otto, Frei]

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Fig 6.26. Brass Rail Restaurant. New York World’s Fair of 1964. Victor Lundy, Fred Severud and Birdair Structures. Cross-section. [Source: Ref (195) Herzog, Thomas]

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Nevertheless, it was Expo ’70 in Osaka where pneumatic structures would undoubtedly reach their peak in terms of structural creativity and size. As evidenced in the previous section, this Expo took place after the erection of remarkable examples of pneumatic structures, following the publication of Frei Otto’s book “Tensile Structures” (1962) eight years earlier and the “First International Congress on Pneumatic Structures” (1967) held three years before. Expo ’70 in Osaka presented a truly varied and innovative set of pneumatic structures, and became one of the greatest moments in the historical development of these typologies. We can consider Expo ’70 in Osaka as the location of the true “explosion of pneumatic structures” in its two metaphorical senses: the culmination of these typologies, and as we shall later observe, the end of the same in terms of their relevance within the field of World Expos, with the exception of a few scattered cases. With the aim of highlighting its enormous value in terms of its contribution to the history of pneumatic structures, Expo ’70 in Osaka will be covered in the following sections from various perspectives.

Fig 6.27. Brass Rail Restaurant. New York World’s Fair of 1964. [Source: Ref (169) Garn, Andrew / Antonelli, Paola]

6.2.2 Osaka 1970: the Expo as a stage for great structural milestones There are various aspects of Expo ’70 in Osaka that should be highlighted in terms of the historical development of those structures whose stability is based on pneumatic principles. In the first place, emphasis should be placed on the individual value of certain pavilions, both due to the structural-typological innovation they reflect and the large spans they achieved. Two pavilions stand out in this sense; the U.S. Pavilion and the Fuji Group Pavilion. The U.S. Pavilion was a creation at the hands of David Geiger and Horst Berger (Fig 6.29 and Fig 6.30). Its main historical contribution resides in the fact that it is the first example of a series of low-profile vaults built and patented by Geiger and Berger; furthermore, it had the largest span for a low-pressure pneumatic structure at that time. This typology would also be later used by other designers. It is undoubtedly one of the structures with the greatest repercussion in terms of significant effects in construction in the whole history of World Expos; its historical importance underpins the idea of the World Expos as testing grounds and a platform for the dissemination of new structural typologies. David Geiger himself stated the following in the 1970 article titled “U.S. Pavilion at EXPO 70 Features Air-Supported Cable Roof”: “The U.S. Pavilion is an air-supported structure with the largest span ever built, as well as being the lightest for its span; it is also the first deck ever made of any material with a super-elliptical floor plan.” [Ref (173) Geiger, David]

Fig 6.28. Brass Rail Restaurant. New York World’s Fair of 1964. [Source: Ref (195) Herzog, Thomas]

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Fig 6.31. The U.S. Pavilion in Expo ’70, Osaka. Pressurised membrane. Inside under construction. [Source: Ref (195) Herzog, Thomas]

The U.S. Pavilion was made up of a low-pressure pneumatic vault reinforced with cables covering a space with a super-elliptical shape of exponent 2.5 measuring 83.5 x 142 m (Fig 6.31 to Fig 6.33). The low-profile vault was only raised 6.5 m above the ground and was encircled by a reinforced concrete compression ring, while the exhibition space remained half-buried. The super-elliptical shape was chosen for aesthetic reasons [Ref (173) Geiger, David].

Fig 6.29. The U.S. Pavilion in Expo ’70, Osaka. David Geiger and Horst Berger. [Source: Ref (206) Ishii, Kazuo]

Fig 6.32. The U.S. Pavilion in Expo ’70, Osaka. Arrangement of the cables, di-

Fig 6.30. The U.S. Pavilion in Expo ’70, Osaka. David Geiger and Horst Berger. [Source: Ref (206) Ishii, Kazuo]

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mensions and mathematical formulation of the super ellipsis. [Source: Ref (206) Ishii, Kazuo]

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While it is true that this low-profile, cable-reinforced typology was ground-breaking, we should not forget that the largest cable-reinforced pneumatic vault to date was erected in 1967 (Fig 6.34); the silo built by the Schjekdahl Company in Northfield, Minnesota with a diameter of 60 metres [Ref (255) Otto, Frei].

Fig 6.33. The U.S. Pavilion in Expo ’70, Osaka. Cross-section. [Source: Ref (206) Ishii, Kazuo]

Fig 6.34. Silo with cable-reinforced pneumatic vault. Schjekdahl Company. 60-metre span. Northfield, Minnesota. Photograph taken in 1967. [Source: Ref (255) Otto, Frei]

Fig 6.36. (Above, left) The U.S. Pavilion in Expo ’70, Osaka. The local bubbles increase the curvature and thus decrease the membrane stress. [Source: its creators] Fig 6.37. (Above, right) The U.S. Pavilion in Expo ’70, Osaka. The local bubbles increase the curvature and thus decrease the membrane stress. [Source: its creators]

Advantages include the fact that this typology allows for very low levels of differential pressure and enables large spans with limited height: this implies lower wind loads; a smaller internal air volume to be climatized, and advantages in terms of construction and safety, since the membrane can be hung and later pressurised for inflation, while it would also remain in place without invading the inhabitable space in case of accidental deflation (Fig 6.38 to Fig 6.42).

Fig 6.38, Fig 6.39, Fig 6.40 y Fig 6.41. The U.S. Pavilion in Expo ’70 in Osaka. Various construction stages of the Pavilion and the beginning of the pressurisation process. [Sources: (from left to right and top to bottom) its creators; its creators; Ref (267) Picon, A.; Ref (267) Picon, A.]

Low-profile pneumatic membranes offer certain advantages and drawbacks, an example of the latter being its low curvature which implies significant stress on the membrane. These membranes need to be reinforced with cables for three main reasons: the cables increase the elastic modulus of the whole, thus limiting deformation; they increase the resistance, and they make local bubbles with a greater curvature, thus diminishing stress in the textile membrane (Fig 6.35 to Fig 6.37) [Ref (152) Escrig, Félix / Sánchez, José].

Fig 6.35. The U.S. Pavilion in Expo ’70, Osaka. Below: detail of the perimetral compression ring at its connection with the cables. Above, right: detail of the intersection between the reinforcing cables and connection with the membrane. The simplicity of the details is prominent. [Source: its creators]

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In this sense, it should be pointed out that one of the main factors that determined the origin of this low-profile typology and therefore the construction of this innovative building was the demand made by Japanese building codes to carry out structural calculations for a wind speed of 241 Km/h. David Geiger explains:

The above underscores the fundamental role played by Osaka ’70 as the origin of this new structural typology, primarily developed because of the strong winds at this location. The cables were not arranged radially to avoid a concentration of cables at one point. In the same way, a central tension ring was not used, as its weight could create a hollow where water could accumulate. According to Geiger himself:

“It is difficult to design a long-span roof at low cost to resist 150 mph winds (241 Km/h). […] This demanded a deck with an aerodynamic cross-section. The cables make possible a very shallow dome (only 7-metre rise over a 79.85 m span). Because the structure is low, Japanese codes allow a reduced wind design speed of 125 mph (201 Km/h).” [Ref. (173) Geiger, David]. It was precisely due to the intention of making the structure more aerodynamic that a perimetral edge ramp was built. The wind tunnel tests carried out during the design of this pavilion revealed another advantage of low-profile vaults: under laminar wind conditions, pressure would only be generated on the perimetral ramp with the whole membrane being subject to suction forces, thus avoiding the need to increase the internal pressure (Fig 6.42). Likewise, under these same conditions it was observed that fluttering was not developed until 200 mph (322 Km/h). Under turbulent wind conditions, the fluttering could be controlled by increasing the internal pressure that would ordinarily be 0.03 psi (21 Kg/m2) [Ref (173) Geiger, David].

“Originally it was planned to array the cables parallel to the major and minor axes of the super-ellipse. However, it was found that the diagonal grid selected led to the savings of 33 percent in cable weight.” [Ref (173) Geiger, David] (Fig 6.43) Fig 6.42. The U.S. Pavilion in Expo ’70 in Osaka. Diagrams showing the wind force distribution on the deck, blowing in the direction corresponding to the short axis of the super ellipsis. Note that the area corresponding to the membrane is always subject to suction forces. [Source: Ref (206) Ishii, Kazuo]

Fig 6.43. Preliminary model for the U.S. Pavilion in Expo ’70 in Osaka. Note the initial arrangement of the cables in parallel to the major and minor axes of the super ellipsis. [Source: Ref (68) Architectural Forum]

The material used for the membrane was fibreglass cloth. In the context of the space race, the “National Aeronautics and Space Administration” (NASA) promoted the development of this fabric when faced with the need for a material that was mechanically resistant, fireproof and flexible. Fibreglass cloth needs to be coated to reduce its porosity, thus enabling it to be pressurised and impermeable. In the case of the U.S. Pavilion, the fibreglass cloth was coated in vinyl which, nevertheless, offers little resistance to ultraviolet radiation. This would be one of the problems to be addressed if this type of structure were to have a permanent use. David Geiger went on to say in 1970: “The vinyl used for the membrane undergoes ultraviolet deterioration and has a life of 7 to 10 years. It is believed that the state of the art in plastics is advancing at such a rate that in 10 years the replacement fabric will be improved so much as to be essentially permanent.” [Ref (173) Geiger, David]. In this historical context of the Cold War, a year after the moon landing, the sight of the space suits and space capsules on display inside the pressurised pavilion must have evoked the utopia of human settlement on other worlds, thus linking the Expo to the competition between the U.S. and the Soviet Union to cross the final frontier.

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Fig 6.44. The U.S. Pavilion in Expo ’70 in Osaka. Space capsules and astronauts’ suits on display inside the pavilion. [Source: its creators]

Fig 6.46. Arctic City. Frei Otto, Kenzo Tange and Ove Arup. 1971. Pneumatic dome reinforced with cables. [Source: Ref (254) Otto, Frei]

Fig 6.45. The U.S. Pavilion in Expo ’70 in Osaka. Recreating the moon landing. [Source: Ref (206) Ishii, Kazuo]

These statements made by David Geiger on the technological evolution that would lead to a greater durability in membrane plastics, as well as his claim that the structural typology of low-profile, cable-reinforced pneumatic vaults could be used for spans longer than 1,600 metres [Ref (60) Villeco, Marguerite], would be reflected in a variety of utopian proposals. In this way, Frei Otto, Kenzo Tange and Ove Arup would put forward the proposal for the Arctic City in 1971 (Fig 6.46 and Fig 6.47). Designed for between 15,000 and 45,000 inhabitants, it was to be covered with a low-profile dome with a diameter of 2,000 metres made of a transparent, cable-reinforced membrane. The cables would have a diameter of 270 mm and would be arranged at a distance of 10 metres. Thomas Herzog refers to the publication “City in the Arctic” published by the University of Stuttgart in 1971 in which the creators of this proposal declared that the first project of this type would come to fruition in the first years of the ‘80s [Ref (195) Herzog, Thomas]. This highlights the huge technological optimism vested in the typology that originated in Expo ’70 in Osaka, as had occurred in the 19th century with the erection of the first buildings with iron structures on the occasion of the World Expos.

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Fig 6.47. Arctic City. Frei Otto, Kenzo Tange and Ove Arup. 1971. Interior under the pneumatic dome. [Source: Ref (254) Otto, Frei]

In fact, the truth is that the impact of the U.S. Pavilion in Osaka ’70 would not be comparable to the previous construction extremes; the building would nevertheless be iconic, as evidenced by its architectural consequences. The pavilion constitutes the original work, but we should not underestimate other technological factors that would not only lead to the appearance of notable architectural repercussions, but would also influence the design of examples of a permanent nature. The most significant of these factors are: the technical evolution of the membrane materials whose virtues Geiger extolled, particularly the arrival of fibreglass coated in PTFE (Teflon) with its greater capacity for mechanical resistance, greater fireproof qualities, and in particular its higher resistance to ultraviolet radiation than the membrane used in Osaka, thus having increased durability; in addition, its low friction coefficient favoured its quality of being “self-cleaning”; the use of snow melt systems via

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hot air; and the computerised control of the inside-outside differential pressure taking into account various variables (such as wind speed, atmospheric pressure or the number of doors open). Thus, a mere five years after the U.S. pavilion was built for Expo ’70 in Osaka, Geiger would erect the Pontiac Silverdome (Fig 6.48 to Fig 6.52); with a floor plan of 160 x 220 metres, it became the deck structure with the largest span built to date [Ref (205) Ishii, Kazuo]. The main structure is the same as that of the U.S. Pavilion, although there are some variations; it had an octagonal floor plan and a fibreglass membrane coated this time with PTFE (Teflon).

Fig 6.50. Pontiac Silverdome. David Geiger. 1975. Plan. [Source: Ref (205) Ishii, Kazuo]

Fig 6.48. Pontiac Silverdome. David Geiger. 1975. [Source: its creators]

Fig 6.51. Pontiac Silverdome. David Geiger. 1975. Cross-section. [Source: Ref (205) Ishii, Kazuo]

Fig 6.49. Pontiac Silverdome. David Geiger. 1975. Note the acoustic absorbent strips. [Source: Ref (205) Ishii, Kazuo]

The covered area was more than three times that of Osaka, and strips made out of an absorbent material were hung from the cable net in order to reduce reverberation (Fig 6.49). Additionally, all the pressurising equipment was installed in the perimetral concrete U-section compression ring. Another of the problems that are known to be associated with this typology is the potential collapse from snow loads. David Geiger stated the following in the article titled “Low-Profile Air Structures in the U.S.A”, published in the March 1975 issue of the journal “Building Research and Practice”: “Snow loads up to 12 lb/ft2 (58.5 Kg/m2) may be carried by increasing the internal pressure. Beyond this load snow must be melted. In the event of failure of the snow melt or pressurization system, the roof slowly deflates and hangs free in the deflated position.” [Ref (172) Geiger, David]. Thus, a hot air system for melting snow was installed in the compression ring of this building. CHAPTER 6

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Fig 6.52. Pontiac Silverdome. David Geiger. 1975. Axonometrics of the membrane in its inflated and deflated positions. [Source: Ref (308) White, Richard / Salmon, Charles]

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Another notable consequence of the U.S. Pavilion in Expo â&#x20AC;&#x2122;70 in Osaka is the low-profile pneumatic deck of the BC Place Stadium in Vancouver, built in 1983 by Geiger and Berger (Fig 6.53). With a floor plan of 190 x 232 metres and a height of 60 metres, it was the largest area to be covered by a pneumatic vault. As with the Pontiac Silverdome, the membrane was made of fibreglass coated in PTFE. In this case, another inner, porous material was hung from the outer structural membrane, thus creating convex shapes that improved the acoustic conditioning (Fig 6.54). This building was also fitted with a snow melt system (Fig 6.55).

Fig 6.53. BC Place Stadium in Vancouver. David Geiger and Horst Berger. 1983. [Source: its creators]

Fig 6.54. BC Place Stadium in Vancouver. David Geiger and Horst Berger. 1983. [Source: Ref (205) Ishii, Kazuo]

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Fig 6.55. BC Place Stadium in Vancouver. David Geiger and Horst Berger. 1983. Cross-section diagram of the air insufflation system. Note the process of melting snow whereby hot air is injected between the two deck membranes. [Source: Ref (205) Ishii, Kazuo]

During the mid-80s, David Geiger and Horst Berger would erect various other vaults with the same typology in the United States and Canada. However, the technological sophistication applied to the typology created by Geiger in Osaka would reach one of its peaks with the deck built in 1988 by Nikken Sekkei and Takenata Komuten called the Tokyo Dome (Fig 6.56 to Fig 6.62). In this case, it was a squareplan deck with rounded corners that could be inscribed in an 180 x 180 metre square.

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Fig 6.56. Tokyo Dome, also called “Big Egg”. Nikken Sekkei and Takenata Komuten. 1988. [Source: Ref (206) Ishii, Kazuo]

Fig 6.58, Fig 6.59, Fig 6.60 y Fig 6.61. Tokyo Dome. Nikken Sekkei and Takenata Komuten. 1988. Various stages in the process of pressurising the membrane. [Source: Ref (206) Ishii, Kazuo]

This too was made with a fibreglass membrane coated in PTFE and fitted with a snow melt system, while the most remarkable characteristic is its sophisticated computerised monitoring system connected to internal and external barometers, wind gauges, devices for measuring snowfall and shifts in the membrane, and systems controlling the number of open doors. This system automatically varied the internal pressure from 30 mm of water pressure (30 Kg/m2) up to 90 mm (90 Kg/m2), according to the previous parameters (Fig 6.62).

Fig 6.62. Tokyo Dome. Nikken Sekkei and Takenata Komuten. 1988. Membrane shift sensor. [Source: Ref (206) Ishii, Kazuo]

Fig 6.57. Tokio Dome. Nikken Sekkei and Takenata Komuten. 1988. [Source: Ref (206) Ishii, Kazuo]

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As we can see, while having obvious variations and progressively incorporating technological advances, all these decks were based on the same principles as the ground-breaking U.S. Pavilion in Expo ’70 in Osaka: low-pressure and low-profile vaults, reinforcing cables arranged diagonally to the main axes, and perimetral compression rings. In this way, the enormous impact that building had on various proposals for making large urban settlements in inhospitable areas is evident. Nowadays, these proposals are viewed from a utopian perspective; in 1970, however, the belief in technological development and an energetic optimism led to a worldview of great expectations in this sense. All the aforementioned issues underscore the enormous historical transcendence of that Pavilion in structural and architectural fields.

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When dealing with the pneumatic pavilions in Expo ’70 in Osaka that had acquired an individual value both in terms of structural innovation and size, reference has to be made to the Fuji Group Pavilion. Created by the engineer Mamoru Kawaguchi and the architect Yutaka Murata, it was the largest high-pressure pneumatic structure ever built [Ref (74) Kawaguchi, Mamoru], as well as displaying a brilliant design of organic inspiration (Fig 6.63 to Fig 6.71).

Fig 6.63. Fuji Group Pavilion. Expo ’70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. Aerial photograph. [Source: Ref (206) Ishii, Kazuo]

Fig 6.64. Fuji Group Pavilion. Expo ’70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. [Source: Ref (31) Osaka Official Photo Album]

Fig 6.65. Fuji Group Pavilion. Expo ’70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. Photograph of the inside. [Source: Ref (206) Ishii, Kazuo]

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The structure was made up of 16 tubes 72 m long and with a diameter of 4 m filled with pressurised air. The tubes arched and were inter-connected by 50-cm-wide strips placed every 4 metres. The plan of the tube bases formed a circumference with an outer diameter of 50 metres. Each tube was connected at its base to a metal ring anchored to circular pile caps. All the tubes were the same length, while the central ones were semi-circular and the others were progressively raised the closer their bases were.

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Fig 6.68. Fuji Group Pavilion. Expo ’70 in Osaka. Details. [Source: Ref (206) Ishii, Kazuo]

Fig 6.66. Fuji Group Pavilion. Expo ’70 in Osaka. Floor plan. [Source: Ref (206) Ishii, Kazuo]

Fig 6.67. Fuji Group Pavilion. Expo ’70 in Osaka. Cross-section. [Source: Ref (206) Ishii, Kazuo]

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Given that it was a high-pressure structure of an unheard-of size, it offered further technical contributions, those related to the development of new combinations of materials for high-pressure pneumatic membranes being especially remarkable. Various materials were trialled, including fire tests in life-size tubes. In the end, the membrane was made of PVA (polyvinyl acetate) with an ultimate strength of 200 Kg/cm, arranged in two layers bonded with neoprene adhesive. The outside was coated in hypalon (chlorosulphonated polyethylene), a material characterised by its resistance to ultraviolet radiation, extreme temperatures and chemical agents; finally, the inside was coated in PVC. The final membrane was 4 mm thick and weighed 5 Kg/m2. The differential pressure varied between 800 mm of water pressure (800 Kg/m2) under normal conditions and 2,500 mm (2,500 Kg/m2) with strong winds [Ref (74) Kawaguchi, Mamoru]. At the end of the Expo, the Pavilion was depressurised and destroyed [Ref (195) Herzog, Thomas].

While the building could have been reused in another location after the Expo, its destruction underpins the idea previously put forward: the building of these typologies for the World Expos responded to a desire to display technological development, rather than the true spirit of dismantling, transporting and taking advantage of the structure at another location. In this sense, it should be pointed out that some authors link the zenith of pneumatic structures in Expo Osaka to the areaâ&#x20AC;&#x2122;s high level of seismic activity, as well as to deficiencies in the terrain [Ref (312) Yun Chi, Jung / Oliveira Pauletti, M.]. While the low mass of these structures certainly enhances their behaviour in the face of seismic acceleration, it is also true that numerous buildings were erected in the same Expo that belonged to other structural typologies, some of them genuinely remarkable in terms of size, such as the space frame in the Festival Plaza by Kenzo Tange and Yoshikatsu Tsuboi.

6.2.3 Osaka 1970: the Expo as an exponent of design singularity Another aspect of Expo Osaka that deserves mention is the construction of certain smaller structures than those presented above, yet whose designs are so singular that documenting their precedents and consequences is truly complicated. Clear examples of these are the Floating Theatre in the Electric Power Pavilion and the Mush-Balloons or Inflatable Umbrellas. The Floating Theatre (Fig 6.72 to Fig 6.74) was made by Mamoru Kawaguchi and Yutaka Murata, the same creators of the Fuji Group Pavilion. The building had a circular floor plan with a diameter of 23 m. The whole deck lay on three high-pressure pneumatic arches. The space between the arches was a low-pressure double membrane that was negatively pressurised, the lower membrane rising and the upper one lowering. The lower membrane was cable-stayed on the inside via five steel cables.

Fig 6.69. Fuji Group Pavilion. Experimental, life-size pressurizing. [Source: Ref (206) Ishii, Kazuo] Fig 6.70. (Below, left) Fuji Group Pavilion. Assembling the structure in the Expo. [Source: Ref (267) Picon, Antoine]

Fig 6.71. (Below, right) Fuji Group Pavilion. Assembling the structure in the Expo. [Source: Ref (267) Picon, Antoine]

Fig 6.72. Floating Theatre. Expo â&#x20AC;&#x2122;70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. [Source: Ref (195) Herzog, Thomas]

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The pavilion therefore constituted a structural typological innovation based on the combination of positive high-pressure pneumatic elements with other, negative low-pressure ones. Mamoru Kawaguchi himself referred to the singularity of this pavilion as late as 1993:

Fig 6.73. Floating Theatre. Expo ’70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. Cross-section. [Source: Ref (74) Kawaguchi, Mamoru]

“Designed by the late Yutaka Murata and myself, the Floating Theatre in the Electric Power Pavilion in Expo ’70 was truly a unique example of a pneumatic structure. Apart from this theatre being a “boat” floating on a small artificial lake and made with pneumatic cells whose pressure was controlled, an outstanding feature was the fact that it was a hybrid combining an inflated air structure (high pressure) and air support structures (low pressure).” [Ref (74) Kawaguchi, Mamoru] The differential pressure in the arches varied between 1,500 and 3,000 mm of water pressure (1,500 and 3,000 Kg/m2), based on the magnitude of wind force. The negative differential pressure between the double membrane was normally maintained at -10 mm of water pressure (-10 Kg/m2), reaching -20 mm (-20 Kg/m2) under extreme wind conditions in order to avoid fluttering in the upper membrane. The lower pavilion structure was comprised of a circular steel plate floating on 48 pneumatic chambers. There was an automated pressure regulation system in these chambers that prevented the building from keeling over from variations in the position of the loads. As stated earlier, such was the originality of this building that it is not easy to pinpoint any building precedents or consequences without seeming forced. It is true that a tenuous relation can be established with some of the earlier sketches included by Frei Otto in the first volume of his publication “Tensile Structures” (1962) [Ref (255) Otto, Frei], in which prestressed membranes are placed on a combination of pneumatic arches (Fig 6.75 and Fig 6.76), as well as some creations such as the British design based on a membrane placed on pneumatic arches (Fig 6.77), published in issue 28 of the journal Bauwelt in 1956. Nevertheless, the main difference lies in the fact that in these earlier examples, the membrane placed between the arches was not pneumatically prestressed.

Fig 6.75 and Fig 6.76. Various structural proposals with pneumatic arches and prestressed membranes included in Volume 1 of Frei Otto’s publication Tensile Structures. 1962. [Source: Ref (255) Otto, Frei]

Fig 6.74. Floating Theatre. Expo ’70 in Osaka. Mamoru Kawaguchi and Yutaka Murata. Floor plan with the drawing of the three pneumatic arches. [Source: Ref (32) Osaka Official Report]

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Fig 6.77. Structural design based on pneumatic arches between which a membrane was placed. 1956. [Source: Ref (255) Otto, Frei]

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Six years after Expo ’70 in Osaka, Thomas Herzog would publish the German edition of his “Pneumatic Structures: A Handbook of Inflatable Architecture” [Ref (195) Herzog, Thomas]. This author includes a table with more than eighty explanatory sketches of the possible combinations of positively and negatively pressurised pneumatic membranes (Fig 6.78). It should be noted, however, that none of the innumerable buildings erected at that time, also included in his book, makes use of negative pressurisation.

Fig 6.79. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. [Source: Ref (31) Osaka Official Photo Album]

Fig 6.78. Some of the explanatory sketches published by Thomas Herzog which show the combinations of positively and negatively pressurised pneumatic membranes. 1976. [Source: Ref (195) Herzog, Thomas]

Another clear example of singularity in the pneumatic structural design that characterised Expo ’70 in Osaka are the Mush-Balloons or Pneumatic Umbrellas. Developed by the architect Taneo Oki and the engineer Shigeru Aoki, they were five pneumatic structures of varying size, the largest having a diameter of 30 metres and a height of 29 m. They consisted of a pneumatic mattress connected to a central mast. This mattress could be opened or unfolded with the cables connected to the support (Fig 6.79 to Fig 6.84).

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Fig 6.80. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Taneo Oki and Shigeru Aoki. Floor plan. [Source: Ref (206) Ishii, Kazuo]

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It was observed during the wind tunnel tests that the structure was easily bent by the wind, an issue that could not be fixed by increasing the internal pressure [Ref (206 Ishii, Kazuo]. A folding system via cables was thus used in strong wind conditions. In this way, the structure could withstand a wind speed of 54 Km/h when open and of 216 Km/h when folded. The internal pressure varied from 150 mm of water pressure (150 Kg/m2) when open, and between 100 and 150 mm (100 y 150 Kg/m2) while being folded. The whole folding process and the pressure variations were controlled by computer. It was definitively a highly singular structure, being a novel hybrid of a pneumatic structure and a foldable structure.

Fig 6.83. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Floor plan, elevation and cross-section of the 20-metre-diameter model. [Source: Ref (206) Ishii, Kazuo]

Fig 6.81. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Deformation of the model of the structure unfolded in a wind tunnel. [Source: Ref (206) Ishii, Kazuo]

Fig 6.82. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Photograph of the folded structures. [Source: Ref (32) Osaka Official Report]

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Fig 6.84. Mush-Balloons or Pneumatic Umbrellas. Expo ’70 in Osaka. Construction section. Note the complexity of the internal development in contrast with the simplicity of the external image. [Source: Ref (206) Ishii, Kazuo]

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6.2.4 Osaka 1970: the Expo as a pneumatic structural ensemble Another aspect worthy of mention is the value of Expo ’70 in Osaka as a pneumatic structural ensemble. To this effect, we draw your attention to the series of pavilions that were built in addition to those described above; while these smaller pavilions did not represent milestones themselves, they do reinforce the value of the Expo as a pneumatic structural whole. We shall highlight the Information Pavilion and the Ricoh Pavilion. Designed by Taiyo Kogyo Co., the Information Pavilion was made up of a spherical membrane with a diameter of 12 metres (Fig 6.85 and Fig 6.86). The objective of this element was clearly to act as a landmark or an information desk for visitors.

Fig 6.87. Pavilion of the Ricoh Company. Expo ’70 in Osaka. Nikken Sekkei, Ltd and Goodyear Aerospace Corporation. [Source: Ref (31) Osaka Official Photo Album]

The Pavilion belonging to the Ricoh Company was even more singular, given that its deck could rise, thus revealing the building. Designed by Nikken Sekkei, Ltd and manufactured by Goodyear Aerospace Corporation (Fig 6.87 to Fig 6.89), the deck was made up of a slightly spherical membrane with a diameter of 25 metres, pressurised with helium and placed on a cylinder. The membrane was illuminated on the inside and could rise up to 40 metres. A tube was permanently connected to the membrane base in order to maintain a constant pressure.

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Fig 6.85. (Left) Information Pavilion in Expo ’70 in Osaka. Taiyo Kogyo Co. [Source: Ref (31) Osaka Official Photo Album] Fig 6.86. (Right). Information Pavilion in Expo ’70 in Osaka. Taiyo Kogyo Co. Axonometrics. [Source: Ref (195) Herzog, Thomas]

Fig 6.88. (Left) The Ricoh Pavilion. Expo ’70 in Osaka. Nikken Sekkei, Ltd and Goodyear Aerospace Corporation. Deck while rising. [Source: Ref (32) Osaka Official Report] Fig 6.89. (Right) The Ricoh Pavilion. Expo ’70 in Osaka. Nikken Sekkei, Ltd and Goodyear Aerospace Corporation. Axonometrics. [Source: Ref (195) Herzog, Thomas]

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6.2.5 Osaka 1970. Unbuilt projects: the Expo as a catalyst for the imagination Another remarkable aspect of Expo Osaka concerns those pneumatic projects that were never built. Presented to different competitions and published at that time, these proposals contributed to firing the imagination of designers, while underscoring the preference for these typologies at the structural forefront. The proposals for the German Pavilion and the U.S. Pavilion stand out among the numerous projects whose designs were based on pneumatic structures. The project for the German Pavilion was a design by Wolfgang Rathke and Eike Wiehe. The great novelty of this proposal lay in the fact that it was made up of a group of small units or pneumatic cells (Fig 6.90 to Fig 6.93). Cylindrical in shape, these cells would have a diameter of 1.25 metres and a variable height of between 5 and 15 metres. They would be connected with polyester strips. The cylinders would be inserted in the meshes when deflated. Once inflated, they would press against each other to form a hexagonal cross-section.

Fig 6.91. Unbuilt project for the German Pavilion. Expo ’70 in Osaka. Wolfgang Rathke and Eike Wiehe. Cross-sections of the pavilion. [Source: Ref (195) Herzog, Thomas]

A model was built to a scale of 1:2 to undergo tests. According to Professor Polyoni of the Berlin Technische Universität who was responsible for carrying out the tests: “The structure described uses a new type of supporting system based on joining the vertical, air-filled, cylindrical pneumatic elements with several horizontal belts. This system is resistant to bending, and thanks to its low weight it is apt for covering large spaces with any type of floor plan.” [Ref (195) Herzog, Thomas]

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Fig 6.92. (Below, left) Unbuilt project for the German Pavilion. Expo ’70 in Osaka. Model to scale of the pneumatic cylinders. [Source: Ref (195) Herzog, Thomas]

Fig 6.93. (Below, right) Unbuilt project for the German Pavilion. Expo ’70 in Osaka. Model of the hexagonal belts or meshes that would restrain the cylinders. [Source: Ref (195) Herzog, Thomas]

Fig 6.90. Unbuilt project for the German Pavilion. Expo ’70 in Osaka. Wolfgang Rathke and Eike Wiehe. Photograph of the model. [Source: Ref (286) Sigel, Paul]

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Perhaps the most critical element in these pneumatic typologies with a large number of independent units is the complexity involved in providing a continuous supply of monitored air to every pneumatic element in order to maintain the air pressure in each one. One of the unbuilt projects for the U.S. Pavilion was designed by Davis, Brody Associates, Rudoph deHarak and Chermayeff & Geismar Associates (Fig 6.94 and Fig 6.95).

Fig 6.94. Unbuilt project for the U.S. Pavilion. Expo ’70 in Osaka. Davis, Brody Associates, Rudoph deHarak and Chermayeff & Geismar Associates. [Source: Ref (68) Architectural Forum]

Fig 6.95. Unbuilt proposal for the U.S. Pavilion. Expo ’70 in Osaka. Cross-section. [Source: Ref (68) Architectural Forum]

This proposal was a competition winner but was never made due to its high cost. It had a remarkable, original shape with four spherical, pneumatic caps connected to a reinforced concrete structure. Each of the caps was a projection room. Another proposal put forward by the same designers was for a projection room which, in this case, was made up of a sole sphere (Fig 6.96 and Fig 6.97) and which constituted a type of giant planetarium. In the end it was Geiger’s project that was given the green light; while it was perhaps more modest in its plastic expression, it lent itself better to a more widespread use as a deck for other large spaces, as shown by the numerous examples erected in its aftermath.

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Fig 6.96. (Left) Unbuilt proposal for the U.S. Pavilion. Model. Expo ’70 in Osaka. [Source: its creators] Fig 6.97. (Right) Unbuilt proposal for the U.S. Pavilion. Cross-section. Expo ’70 in Osaka. [Source: its creators]

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6.2.6 Osaka 1970: the Expo as a generator of building codes

6.2.7 Pneumatic structures in Expos after Osaka 1970

Another of the noteworthy facets of Expo ’70 in Osaka was its role as a generator of new regulatory texts. Despite the fact that the first pneumatic structures were built in Japan in the ‘60s, it is worth noting that at that time there were no building regulations governing these typologies in that country. In fact, it was on the occasion of Expo ’70 in Osaka when the Japanese authorities published the first official code for the design of temporary pneumatic structures [Ref (206) Ishii, Kazuo]. Titled “The Standard for Structural Design of Pneumatic Structures”, this code was put together by the “Building Center of Japan” in collaboration with the “Membrane Structures Association of Japan”. Not only was it used in Japan for the Expo, but was applied for many years afterwards. In this case, we can see how the World Expo acted as a generator of new, legally-binding construction codes, thus facilitating the dissemination of pneumatic structural typologies beyond the field of the Expos themselves.

While the World Expos after Expo ’70 in Osaka offered up some relevant examples of pneumatic structures, the truth is that to date, no other Expo has ever presented such a significant group of them. After Expo Osaka, the World Expos would only offer sporadic contributions to the history of pneumatic structures. Some worthy examples of these are: the Fuyo Group Pavilion in Expo Portopia held in Kobe in 1981, the Technocosmos Pavilions in Tksukuba Expo ‘85 and the German Pavilion in Expo Seville in 1992. On the occasion of the Expo held in Kobe in 1981, the Fuyo Group built one of the first pavilions to be made with a pneumatic dome reinforced with a mesh [Ref (74) Kawaguchi, Mamoru] (Fig 6.99).

Along these lines, we should note the significance of the Siberia Expo held in 1974; this new Expo held in Tokyo would have a significant impact on the later development of pneumatic structures in Japan. A low-pressure pneumatic dome covering an area of 5400 m2 was seriously damaged after a snowfall (Fig 6.98). Although there were fortunately no victims, the accident made the Japanese authorities question the safety of pneumatic structures; this in turn led to a decrease in the number of pneumatic structures built in Japan in the following years [Ref (206) Ishii, Kazuo].

Fig 6.98. Siberia Expo 1974, Tokyo. Pneumatic dome which collapsed after a snowfall. [Source: Ref (206) Ishii, Kazuo]

Thus, while permanent stadiums covered with pneumatic domes were beginning to be built in the ‘70s in the U.S., the same would not occur in Japan until the mid-80s, when the Ministry of Construction authorised the building of the first permanent pneumatic membranes to cover large spaces. These events evince a certainly paradoxical situation that illustrates the decisive impact of the World Expos on the historical development of pneumatic structures: after the explosive development of these typologies in Japan that came to a head in Osaka, it would be another Japanese Expo that would hinder their later progress there.

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Fig 6.99. Expo Portopia, Kobe 1981. Pneumatic dome reinforced with cables and mesh. Fuyo Group. [Source: its creators]

In pneumatic structures, the membrane has a double function: to keep the structure airtight, thus facilitating the process of pneumatic prestressing, and to offer the necessary mechanical properties in order to withstand the prestressing stresses and external forces. When the pneumatic structure covers large spans, the membrane fabric may not be strong enough, thus necessitating reinforcement with cables. Membranes reinforced with a mesh are yet another step forward; in this case, the membrane is aided by the mesh, therefore developing low stress, and it is the mesh which basically contributes the mechanical properties. The role of the membrane is thereby almost exclusively limited to keeping the whole structure airtight. The Portopia Pavilion was comprised of a pneumatic dome with a span of 36 m and reinforced with a mesh and cables connected to the latter at various points.

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There were four more mesh-reinforced domes on the inside that created exhibition spaces at atmospheric pressure. The space between the inner domes and the outer one was pressurised with a differential pressure of 30 mm of water pressure (30 Kg/m2) that could be increased to 70 mm (70 Kg/m2) under strong wind conditions. Mamoru Kawaguchi and Yutaka Murata would later continue their research along these lines, creating notable structures such as the two Pavilions for the World Orchid Conference held in Tokyo in 1987 (Fig 6.100). One of the pavilions was a dome with a diameter of 75 metres, while the other was in the shape of a “worm” and had a width of 40 metres and a length of 100 m. Both structures were reinforced with cables between which a mesh made of synthetic fibre cables was stretched (Fig 6.101).

These two pavilions were undoubtedly influenced by the Grupo Fuyo Pavilion in Expo Portopia, since it is Mamoru Kawaguchi himself who established the relationship between these two works in the minutes of the “Primer Encuentro Internacional Estructuras Ligeras para Grandes Luces”, held in Seville in 1992. Kawaguchi refers to the Pavilions in the World Orchid Conference in the following way: “A more recent example of the same system (after describing the pneumatic dome in the Portopia Expo in 1981 as “a typical example of this system”) can be found in the two pavilions for the Twelfth World Orchid Conference held in Tokyo in March 1987, designed by myself with the collaboration of Yutaka Murata.” [Ref (74) Kawaguchi, Mamoru]

Fig 6.100. Pavilions for the World Orchid Conference. Tokyo 1987. Mamoru Kawaguchi and Yutaka Murata. Aerial view. [Source: Ref (206) Ishii, Kazuo]

Another significant pneumatic example to follow Expo Osaka is the Technocosmos Pavilions for the Tksukuba Expo 1985 (Fig 6.102 to Fig 6.104; Fig 6.106 and Fig 6.107). They were three pavilions with similar characteristics created by the architects Kohyama Atelier and the engineer Kazuo Ishii. The largest of these had a clear span of 27 metres, a length of 40 metres and an outside height of 16.5 metres. The main contribution of these pavilions was the use of a new patent for a pneumatic structure called “Airsolid”, consisting in a lenticular double membrane connected by inner elements. According to Professor Felix Escrig: “As they have a great radius of curvature, these structures develop large surface stresses and the inflated space may have considerable depth. The two skins are normally connected so that these connectors are under tension, thus limiting the depth. […] The fact that there are two layers implies generating global bending when external loads are applied. One layer is therefore under compression forces that should not exceed the tension stresses from the prestressing, while the other will be under increased tension forces. The greater the inflation pressure, the greater the resistance to this bending. […] If the connections between the two layers are vertical, then they will only diminish the separation between them; as they lean, they can collaborate with the shear stress.” [Ref (152) Escrig, Félix / Sánchez, José]

Fig 6.101. Domed pavilion at the World Orchid Conference. Tokyo 1987. Mamoru Kawaguchi and Yutaka Murata. Detail of the membrane reinforced with a mesh of synthetic fibre cables. [Source: Ref (71) Kenchiku Bunka]

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Fig 6.102. Technocosmos Pavilions. Tksukuba Expo 1985. Kazuo Ishii and Kohyama Atelier. [Source: Ref (206) Ishii, Kazuo]

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The idea for this patent was raised in Japan by the Canadian engineer Pierre Jutras, who would develop technical aspects of the system together with Kazhuo Ishii. Ishii stated: “While continuing experiments, trial modellings, and improvements, it was suggested to us to apply the Airsolid system to the Techno-Cosmos Pavilion at Tksukuba Expo 85. At the time, I hadn’t full confidence in its technical aspects. […] The Airsolid system was a completely new type of pneumatic structure, and therefore at the time it was put forward, there were no techniques established for precise analysis. For this reason, we built an experimental deck in order to obtain various data.” (Fig 6.105) [Ref (206) Ishii, Kazuo]

Fig 6.103. Inside the larger Technocosmos Pavilion. Tksukuba Expo 1985. Clear span of 27 metres. Kazuo Ishii and Kohyama Atelier. [Source: Ref (206) Ishii, Kazuo] Fig 6.105. Experimental deck built prior to the Tskuba Expo 1985 with the “Airsolid” patent. [Source: Ref (206) Ishii, Kazuo]

During the investigations carried out to develop these pavilions, various models were studied numerically. A summary of these results can be consulted in [Ref (206) Ishii, Kazuo]. We shall limit ourselves to highlighting some of the conclusions: “The increase in pressure naturally results in an increase in structural rigidity. It would be wise to increase the pressure in proportion to the increase in wind speed.” [Ref (206) Ishii, Kazuo] In this sense, the internal pressure was planned to be varied between 160 Kg/m2 for wind speeds of 43 Km/h to 650 Kg/m2 for speeds of 187 Km/h. The actual maximum wind speed recorded during the Expo was 90 Km/h, with visible deformation detected with an internal pressure of 160 Kg/m2. When the pressure was increased to 200 Kg/m2, the deformations, vibrations and any other type of movement were no longer apparent.

Fig 6.104. Technocosmos Pavilions. Tksukuba Expo 1985. Kazuo Ishii and Kohyama Atelier. Inside the pneumatic structure with the connecting elements between the membranes. [Source: Ref (206) Ishii, Kazuo]

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“If the connections between the membranes are arranged perpendicularly to the same, then the deformations from wind force are relatively large. The rigidity is increased when the connections are inserted diagonally.” [Ref (206) Ishii, Kazuo]

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Fig 6.108. Deck for a tennis court made with the “Airsolid” patent. Kazuo Ishii. 1987. A consequence of the Technocosmos Pavilions in the Tksukuba Expo 1985. [Source: Ref (206) Ishii, Kazuo]

Fig 6.106. Cross-section and longitudinal elevation of the Technocosmos Pavilion with the largest span. Tksukuba Expo 1985. Kazuo Ishii and Kohyama Atelier. [Source: Ref (206) Ishii, Kazuo]

Fig 6.107. Cross-sections and construction details of the “Airsolid” system. Kazuo Ishii and Kohyama Atelier. [Source: Ref (206) Ishii, Kazuo]

Fig 6.109. German Pavilion. Expo Seville, 1992. Cable-stayed pneumatic deck. Georg Lippsmeier and IPL Ingenieurplanung Leichtbau. [Source: Ref (286) Sigel, Paul]

Another of the examples mentioned is the German Pavilion for Expo Seville in 1992 built by Georg Lippsmeier and IPL Ingenieurplanung Leichtbau (Fig 6.109 to Fig 6.114). It has a remarkable lenticular pneumatic deck principally made of a perimetral truss in the shape of an ellipsis, and another circular one, both connected with internal cables (Fig 6.113 and Fig 6.114). Two pneumatic membranes stretched between the two trusses. The whole ensemble was connected with cables to a central mast and to the foundations along the perimeter. The originality of the solution is noteworthy; by using this pneumatic structural element that appears to be floating in space, a nearby open area where various activities were held was shaded.

Developed and built on the occasion of a World Expo, these structures would have some consequences in construction. Two years later in 1987, for example, following the satisfactory results obtained in the Expo in Tsukuba, a new structure was built with the “Airsolid” patent to cover a tennis court (Fig 6.108). According to Kazuo Ishii, this structure was still in use ten years later after having withstood several typhoons [Ref (206) Ishii, Kazuo].

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Fig 6.110. German Pavilion. Expo Seville, 1992. Cross-section. [Source: Ref (205) Ishii, Kazuo]

Fig 6.113. German Pavilion. Expo Seville, 1992. Horizontal representation of the perimetral truss, the circular truss, the internal connecting cables between both and the cables connected to the mast. [Source: Ref (91) Barnes M. / Renner W. / Kiefer M]

Fig 6.114. Detail of the perimetral truss including the connections with the cables that fastened to the foundations and the mast. [Source: Ref (205) Ishii, Kazuo] Fig 6.111. German Pavilion. Expo Seville, 1992. Photograph of the building under construction. [Source: Ref (205) Ishii, Kazuo]

Fig 6.112. German Pavilion. Expo Seville, 1992. [Source: Ref (205) Ishii, Kazuo]

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In short, in light of the issued described above, we can conclude that the World Expos have had a relevant role in the historical development of pneumatic structures, with their peak in Expo Osaka in 1970. With a few isolated exceptions, pneumatic structures would later lose relevance in the Expos. This was a natural process linked to general historical events. Note that between 1945 and 1972, the Westâ&#x20AC;&#x2122;s oil consumption had multiplied, reaching heights never before seen. Together with cheap access to this raw material, the increase in consumption was especially evident in Japan and the U.S. The first oil crisis would take place in the middle of 1973, due to the OPECâ&#x20AC;&#x2122;s decision to stop exports to those countries that had supported Israel during the Yom Kippur War, leading to an increase in the price of oil and an acceleration of the world economic recession. In this sense, the power consumption that these pneumatic typologies required purely to maintain their shape and therefore their stability, rigidity and strength was not in line with world events. Later on at the end of the 20th century and the beginning of the 21st century, the progressively more evident depletion of fossil fuels and new architectural currents would turn towards sustainability and energy saving. In this way, pneumatic structures were relegated to an inferior position in the face of other structural solutions that were adequate for large spans and whose shapes were not dependent on a power supply.

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7.1 SPACE STRUCTURES: ORIGIN AND DEVELOPMENT Several examples of metal space structures had already materialised during the 19th century. Along these lines we can highlight the single layer domes made by the German engineer Johann Wilhem Schweller to cover various gas tanks in Berlin, good examples of which are the tank from 1875 with a span of 54 metres (Fig 4.52), or that from 1893 with a span of 65 metres (Fig 7.1).

CAPÍTULO 7

SPACE FRAMES: THE EXPOS BETWEEN UTOPIA AND REALITY The evidence that any structure is created in a three-dimensional space indicates that all built structures can be defined as spatial. In this way, a structure made of columns, girders and joists is a space structure. Nevertheless, when using the term space structure we are normally referring to those made of bars with axial rigidity with a principal characteristic: an absence of any structural hierarchy in terms of the transmission of loads (from the slab to the joists, and from these to the girders, then to the columns and finally to the foundations). External forces are therefore not transmitted from one structural-hierarchical order to another in these typologies, but rather the stresses generated by the external loads are distributed spatially between the various bars that make up the structure. Within what we call space structures, a typology called space frame in modern times stands out in particular. Its singularity with respect to previous typologies resides in the fact that it comprises a group of independent bars, generally short in length when compared to the total size of the structure, arranged in what is called a bar and joint system; alternatively, they are prefabricated in polyhedral modules making modular systems. The bars or members are connected between them with joints or nodes that are generally standardised and designed to allow bars to be connected in different directions within the space. The bars may be organised in a sole layer or in various through polyhedral groupings, and are basically subject to axial stresses (tension or compression). The spatial distribution of these fundamentally axial stresses between a large number of bars implies using ones with a considerably thinner section than with other typologies; the weight of the bars thus being lower, this typology is particularly suited for covering large areas. It should be noted that the most frequently used materials in this typology have been steel and aluminium, both with tubular profiles, while other materials such as wood and bamboo have figured to a considerably lesser extent.

Fig 7.1. Gas tank in Berlin. Johann Wilhem Schweller. 1893. [Source: Ref (181) Gössel, Peter / Leuthäuser, Gabriele]

Another of the most noteworthy examples in construction is the unique deck built by the Russian engineer Vladimir Shukhov in Vyksa, Russia in 1897 (Fig 7.2). Made of spherical caps, it represents one of the first metal space structures with one layer and double curvature. Each of the caps is a space structure in the sense that there is no structural hierarchy. Nevertheless, it is not a space frame in the modern sense of the term, since the bars are not independent but rather continuous pieces that cross in space and are riveted at the joints; nor does it have a standardised independent joint piece. In any case, it is a brilliant example and a precedent of modern space frames.

This chapter presents an examination of some of the main historical milestones of space frames, while bringing to light the magnificent contributions made by the World Expos in this field.

Fig 7.2. Deck in Vyksa. Russia. Vladimir Shukhov. 1897. [Source: its creators]

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In this sense, Alexander Graham Bell is considered to be the great forefather of the modern space frame. During the first years of the 20th century, and coinciding with the development by the Wright brothers of the first aeroplane in the world, the Flyer III (1905), Bell experimented with space frames made of tetrahedra and octahedra. While it would appear that the invention was linked to aeronautics, Graham Bell published an article in 1903 in National Geographic Magazine titled “The tetrahedral principle in kite structure”, in which he claimed:

Fig 7.4. Prototype of a space frame. Alexander Graham Bell. 1907. [Source: Ref (79) Appelbaum, Stanley]

“The use of the tetrahedral cell is not limited to the construction of structures for aeroplanes. It is applicable to any type of structure in which we wish to combine lightness and strength.” [Ref (185) Graham Bell, Alexander] He made innumerable tetrahedral space frame prototypes along these lines. Particularly notable examples date back to 1903 (Fig 7.3) and 1907 (Fig 7.4). In that same year, he would build various kites with space frames (Fig 7.5); additionally, he would build the first known application of a space frame in construction together with the engineer Casey Baldwin. It was the Outlook Tower in Beinn Bhreagh, United States, consisting of tetrahedral modules made of steel tubes with a height of around twenty metres (Fig 7.6 to Fig 7.8).

Fig 7.5. Kite made with a space frame. Alexander Graham Bell. 1907. [Source: Ref (230) Makowski, Z.S.]

Fig 7.3. Prototype of a space frame. Alexander Graham Bell. 1903. [Source: Ref (161) Frazier, Charles]

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Fig 7.6. Outlook Tower in Beinn Bhreagh. Alexander Graham Bell and Casey Baldwin. 1907. [Source: Ref (230) Makowski, Z.S.]

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The modular Space Deck System was developed along these lines in the ‘50s and commercialised in 1958 (Fig 7.10 and Fig 7.11). It was made up of pyramid-shaped modules that were easily stacked, with a square plan measuring 1.22 metres along the sides and with heights of 1.05 and 0.61 metres. As it was a modular system, it was ideal for speedy dismantling.

During the ‘30s and ‘40s, other researchers such as Richard Buckminster Fuller, Konrad Wachsmann and Robert Le Ricolais would elaborate on the principles and development of the space frame. In this sense, one of the determining factors in the development of this typology was the design of the joint. This was one of the aspects upon which the researchers focussed their efforts, eager to design a joint that was simple to assemble and to which bars could be attached in various spatial directions. The invention of the MERO System by the engineer Max Mengeringhausen in 1943 would signal the start of a huge profusion in the use of space frames in architecture (Fig 7.9). The MERO System was the first to be available commercially, and probably the most used to date in both its original version and the innumerable imitations that sidestepped its patent. It basically consists of a sphere with eighteen threaded holes that allow another eighteen bars to be connected to it.

Fig 7.7. (Left) Outlook Tower in Beinn Bhreagh. Alexander Graham Bell and Casey Baldwin. 1907. Erecting the structure. [Source: Ref (219) Klotz, Heinrich] Fig 7.8. (Right) Outlook Tower in Beinn Bhreagh. [Source: Ref (143) Eekhout, Mick]

Fig 7.9. Joint from the MERO System. Max Mengeringhausen. 1943. [Source: Ref (79) Appelbaum, Stanley]

During the ‘50s and ‘60s, there were many patents for space frame systems, and ultimately innumerable space frame systems have been developed over time. Some of the most outstanding examples will be explained below, as well as some of the most significant works.

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Fig 7.10. Sketch of the modular Space Deck System. [Source: Ref (118) Chilton, John]

Fig 7.11. Space Deck System. Stacked modules. [Source: Ref (118) Chilton, John]

Stéphane du Château also registered various patents, the earliest being for the Tridirectionelle S.D.C System in 1957 (Fig 7.12 and Fig 7.13). In this case, the bars were welded to the node. An interesting example of a construction following this system is Boulogne Swimming Pool from 1962; it was made with a double layer frame with a plan of 50 x 50

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metres and a height of 2.3 metres (Fig 7.14 and Fig 7.15). Its calculations were carried out by assimilation to a continuous shell, a common practice when dealing with space frame calculations at that time. Another early work by this author with the same system is Drancy Swimming Pool in 1968 (Fig 7.16 to Fig 7.18); in this case, however, it was made of a one-layer dome with a diameter of 47 metres. Fig 7.12. Tridirectionelle S.D.C. System. Stéphane du Château. 1957. [Source: Ref (118) Chilton, John]

Fig 7.13. Tridirectionelle S.D.C. System. Stéphane du Château. 1957. [Source: Ref (267) Picon, Antoine]

Fig 7.14. Boulogne Swimming Pool. Stéphane du Château. 1962. Detail of the joint made using the Tridirectionelle S.D.C. System. [Source: Ref (267) Picon, Antoine] Fig 7.16. (Above) Drancy Swimming Pool. Stéphane du Château. 1968. [Source: Ref (235) Margarit, J. / Buxadé, C.] Fig 7.17. (Center) Drancy Swimming Pool. Stéphane du Château. 1968. [Source: Ref (235) Margarit, J. / Buxadé, C.]

Fig 7.15. Boulogne Swimming Pool. Stéphane du Château. 1962. [Source: Ref (267) Picon, Antoine]

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Fig 7.18. Drancy Swimming Pool. Stéphane du Château. 1968. [Source: Ref (235) Margarit, J. / Buxadé, C.]

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In 1959, Konrad Wachsmann would patent the Wachsmann System (Fig 7.19 and Fig 7.20), which was designed for the U.S. Army for hangars that could be transported by air. The only equipment needed to assemble the node was a hammer, since assembly consisted in inserting various metal wedges.

The Triodetic System was developed in Canada in 1953 (Fig 7.21 and Fig 7.22). Commercialised from 1960 onwards, this system was based on an original cylindrical, grooved joint made of aluminium; bars with their ends flattened and grooved were then connected to the joints. The system was experimentally trialled on a removable hangar with a floor plan of 21 x 20 metres made for the Canadian Army.

Fig 7.19. Model of a hangar for the United States Air Force. Konrad Wachsmann. [Source: Ref (230) Makowski, Z.S.]

Fig 7.20. Joint for the Wachsmann System for large spans. Konrad Wachsmann. 1959. [Source: Ref (267) Picon, Antoine]

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Fig 7.21. Triodetic System. 1953. Commercialised in 1960. [Source: Ref (118) Chilton, John]

Fig 7.22. Triodetic System. [Source: Ref (118) Chilton, John]

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At the beginning of the ‘70s, British Steel Tubes and Pipes developed the Nodus system designed with the company’s profiling in mind (Fig 7.23 and Fig 7.24). Between 1970 and 1973, Z.S. Makowski built an example of a space frame which stood out thanks to its great span; the British Airways hangar at Heathrow Airport in London (Fig 7.25). The deck was made of a double-layer space frame with a span of 67 x 138 metres and a depth of 3.66 metres. A patented system was not used in this case, but instead steel tubular profiles were bolted together.

Fig 7.23. Experimental space frame using the Nodus System. Built by British Steel Tubes and Pipes. [Source: Ref (118) Chilton, John]

Fig 7.25. British Airways hangar in Heathrow, London. Z.S. Makowski. [Source: Ref (267) Picon, Antoine]

Another significant patented system was the Harley System (Fig 7.26), which was characterised by the low cost of its nodes. It had continuous profiles in the upper and lower layers, while the connection with the diagonals was carried out by flattening their ends.

Fig 7.26. Harley System. 1980. Connection of diagonals by flattening. [Source: Ref (118) Chilton, John]

Fig 7.24. Nodus System. British Steel Tubes and Pipes. Beginning of the ‘70s. [Source: Ref (143) Eekhout, Mick]

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In the mid-80’s, the CUBIC system was developed in which the diagonal bars were eliminated (Fig 7.27 and Fig 7.28). An interesting construction that applied this system was a hangar for Stansted Airport with a rhomboid floor plan with columns at the four rhombus vertices (Fig 7.29 and Fig 7.30). The spans corresponding to the four axes of the rhombus measured 98 x 170 metres. 447

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Fig 7.27. CUBIC system. The three standard types of module. [Source: Ref (118) Chilton, John] Fig 7.30. Hangar at Stansted Airport. [Source: Ref (118) Chilton, John]

Another element that acted as a catalyst for the development of space frames can be found in geometric research; in particular, the significant work carried out by Richard Buckminster Fuller on the geodesic division of the spherical surface. Along these lines, he would patent the geodesic dome (Fig 7.31) in 1954, as a polyhedron created by projecting the vertices of an icosahedron or a dodecahedron onto a sphere. The edges of the dodecahedron or icosahedron can equally be subdivided, thus creating new vertices that in turn are projected onto the sphere. The number of times the edges are subdivided is referred to as the frequency of the geodesic dome.

Fig 7.28. CUBIC system. [Source: Ref (118) Chilton, John]

One of the most significant examples is the regional car repair workshop, also called the “Baton Rouge Dome” of the Union Tank Car Co. in Baton Rouge, Louisiana. Built in 1958, it consists of a gigantic geodesic dome with a diameter of 130 metres that stands 40 metres high (Fig 7.32 to Fig 7.35). The dome was made of two layers of hexagons with a depth of 1.2 metres. The steel plates that were used as an enclosure and welded together were located in the inside layer, thus reinforcing the whole. According to Fuller himself, it was at that time the largest surface ever built without intermediate supports (13.273 m2) [Ref (106) Buckminster Fuller], (it is understood that Fuller’s claim referred to circular-plan structures). Nevertheless, it would soon be overtaken by tensile typologies; thus Madison Square Garden was built in 1962 with a radial cable net stabilised through gravity and a diameter of 137 metres (Fig 5.110 to Fig 5.112) [Ref (95) Berger, Horst]. Fuller’s patents would give rise to the construction of numerous domes in the following decades.

Fig 7.29. Hangar for Stansted Airport built following the CUBIC system. [Source: Ref (118) Chilton, John]

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Fig 7.31. Patent for the geodesic dome. Richard Buckminster Fuller. 1954. [Source: Ref (219) Klotz, Heinrich]

Fig 7.34. Baton Rouge Dome. [Source: Ref (230) Makowski, Z.S.]

Fig 7.32. The regional car repair workshop of the “Union Tank Car Co” in Baton Rouge, Louisiana. Richard Buckminster Fuller. 1958. [Source: Ref (106) Buckminster Fuller, Richard]

Fig 7.33. Baton Rouge Dome. [Source: Ref (267) Picon, Antoine]

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Fig 7.35. Baton Rouge Dome. Construction image. [Source: Ref (267) Picon, Antoine]

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Fuller also studied another of the fundamental factors that would enable these typologies to evolve: assembly techniques. These structures could basically be assembled following two methods; the first consisted in assembling the whole frame or parts of it at zero level and then raising it up with cranes. The second process involved carrying out the assembly at height through the addition of bars or modules; an example of this is the Hangar at Stansted Airport (Fig 7.30). When the structure was dome-shaped the frame could also be built by starting at the perimeter and adding cantilevered bars or modules, an example of this being the Baton Rouge Dome (Fig 7.32 and Fig 7.35). Nevertheless, supporting elements during assembly might be needed when dealing with domes of a certain size. In 1957 Fuller built the 50-metre-diameter Kaiser Dome in Honolulu (Fig 7.36 and Fig 7.37). A novel system was used in this building based on the suspension of the dome from a central mast. The system allowed the operators to progressively assemble the bars along the perimeter from the ground as the dome gradually grew. The structure took 24 hours to assemble [Ref (106) Buckminster Fuller]. The same system would be applied in other domes built by Fuller, such as that at Wood River.

This system would later be used to assemble various space frames, revealing its versatility in its application to different shapes; a significant example in this respect is the Singapore Indoor Stadium built by Kenzo Tange and Mamoru Kawaguchi in 1989, measuring 219 x 126 metres (Fig 7.40 to Fig 7.43).

Fig 7.36. (Left) Kaiser Dome in Honolulu. Richard Buckminster Fuller. 1957. Photograph of assembly. [Source: Ref (106) Buckminster Fuller, Richard]

Fig 7.38. World Memorial Hall. Kobe. Japan. Mamoru Kawaguchi. 1984. Erected using the Pantadome System. [Source: Ref (118) Chilton, John]

Fig 7.37. (Right) Kaiser Dome in Honolulu. [Source: Ref (106) Buckminster Fuller, Richard] Fig 7.39. World Memorial Hall. Kobe. Japan. [Source: Ref (118) Chilton, John]

Fig 7.40, Fig 7.41, Fig 7.42 and Fig 7.43. Singapore Indoor Stadium. Kenzo Tange and Mamoru Kawaguchi. 1989. Drawings of the different stages of assembly and the completed building. [Source: Ref (118) Chilton, John]

In this sense, however, the most important advance is embodied in the Pantadome System, invented by the engineer Mamoru Kawaguchi. It basically consists in eliminating some of the frame bars to transform it into a mechanism, thus enabling it to be erected by unfolding. Once it is in its final position, the eliminated bars can be added. The system was used by this engineer for the first time in the World Memorial Hall in Kobe, Japan in 1984 [Ref (118) Chilton, John], which measured 70 x 110 metres (Fig 7.38 and Fig 7.39).

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Another relevant example of a building erected with the Pantadome System is the Namihaya Dome in Osaka, built in 1996 by Showa Sekkei Co. and Mamoru Kawaguchi with a frame of 110 x 127 metres and a height of 42.65 metres (Fig 7.44 to Fig 7.46).

A further fundamental aspect in the development of these typologies concerns the arrival of computers in the structural field. The huge advances in computers from the â&#x20AC;&#x2DC;80s onwards, both in terms of the greater computational power achieved and the development of new applications, has been one of the contributing factors in making progressively more complex creations, sidestepping the difficulties that were once inherent to these typologies and replacing methods of assimilation to continuous elements such as shells or slabs with modelling with matrix methods. Likewise, it has facilitated the representation and even the automatic generation of complex geometries. The use of design and calculation software connected to manufacturing systems has also facilitated the design of structures with many different types of joints and bars. In this respect, the Palau Sant Jordi, built by Arata Isozaki and Mamoru Kawaguchi for the Olympic Games in Barcelona 1992 and erected via the Pantadome System, is a paradigmatic example of the previous extremes (Fig 7.47 and Fig 7.48). The complexity involved in an asymmetrical floor plan with curved sides measuring 106 x 128 metres, as well as a cross-section designed with different curvatures, led to the use of a space frame with more than 3,000 different types of bars and 1,500 joint types.

Fig 7.44. Namihaya Dome. Osaka. Showa Sekkei Co. and Mamoru Kawaguchi. 1996. [Source: Ref (118) Chilton, John]

Fig 7.47. Palau Sant Jordi. Arata Isozaki and Mamoru Kawaguchi. 1992. Structure plan. [Source: Ref (118) Chilton, John]

Fig 7.45. Namihaya Dome. Osaka. Showa Sekkei Co. and Mamoru Kawaguchi. 1996. Cross-section. [Source: Ref (118) Chilton, John]

Fig 7.48. Palau Sant Jordi. Arata Isozaki and Mamoru Kawaguchi. 1992. Cross-section. [Source: Ref (118) Chilton, John] Fig 7.46. Namihaya Dome. Osaka. Showa Sekkei Co. and Mamoru Kawaguchi. 1996. Diagram of erection with the Pantadome System. [Source: Ref (118) Chilton, John]

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7.2 THE BRILLIANT CONTRIBUTION MADE BY THE WORLD EXPOS

Bearing in mind that the Space Deck was the first British space frame system to hit the market, the construction of this structure was an opportunity to promote this modular system that would later enjoy wide dissemination. Along these lines, in an article published in 1973 in the “Bulletin of the International Association for Shells and Spatial Structures” (IASS), Zygmunt Makowski commented on the enormous propagation of the Space Deck System, which at that time had already been applied to more than a thousand works [Ref (231) Makowski, Zygmunt S.].

Innumerable buildings have been erected on the occasion of World Expos, embodying significant advances in the field of space structures. These advances have pertained to technical aspects, as well as urban proposals on the edge of utopia; in this regard the Expos have acted both as manifestations and catalysts of these currents, with the field of structure becoming an element of urban creation.

7.2.1 Space frames and false tensegrities As covered in previous chapters, Expo ’58 in Brussels signified an authentic renaissance of structural splendour. It should therefore be no surprise that the first space frames to appear in a World Expo were built in Brussels. Thus, we should highlight the deck of the entrance to the U.K. Pavilion, created by the architects Edward D. Mills and Felix J. Samuely, which was a very early application of the Space Deck System (Fig 7.10 and Fig 7.11) that had been developed a few years before and commercialised precisely in 1958, the year of the Expo (Fig 7.49 and Fig 7.50).

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Expo ‘58 in Brussels was distinguished by a special profusion of structures made of cables and therefore based on tension; in this respect, a phenomenon was witnessed in which certain original combinations of space frames with cables were being created, resulting in structural solutions inspired by tensegrity.

Fig 7.49. (Left) Entrance Deck for the U.K. Pavilion. Edward D. Mills and Felix J. Samuely. Expo ’58 in Brussels. Space Deck System. [Source: Ref (230) Makowski, Z.S.] Fig 7.50. (Right) Entrance deck for the U.K. Pavilion. Expo ’58 in Brussels. [Source: Ref (76) Aloi, Roberto]

Fig 7.51. Project for the Polish Pavilion in Expo ’58 in Brussels. Jerzy Soltan. Prototype built by the Polish Building Research Institute. Mesh BX58. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

A notable, unbuilt project stands out in this sense; created by Jerzy Soltan, the Polish Pavilion used a novel system called “Mesh BX58” in reference to its first application in this Expo (Fig 7.51 to Fig 7.56). It was documented to this effect as late as 1972 by Zygmunt S. Makowski in his classic publication “Steel Space Structures” [Ref (230) Makowski, Zygmunt S.]. The system was based on monolithic reinforced concrete units consisting of four bars connected by cables that formed tetrahedral elements. This system was to be applied to both the pavilion deck and the vertical enclosures; in the end, all that was built was a prototype. While the system seems to have been based on tensegrity, in reality this was untrue in that the compressed elements were in contact, connected to the upper nodes. Nevertheless, the system’s originality and the sensation of floating were evident.

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Fig 7.54. (Left) Project for the Polish Pavilion in Expo ’58 in Brussels. Sketch done by Jerzy Soltan in 1956. [Source: Ref (137) Devos, Rika]

Fig 7.55. (Right) Project for the Polish Pavilion in Expo ’58 in Brussels. Jerzy Soltan. Prototype. [Source: Ref (112) Cánovas, Andrés]

Fig 7.52. Project for the Polish Pavilion in Expo ’58 in Brussels. Jerzy Soltan. Plan and elevation of Mesh BX58. [Source: Ref (230) Makowski, Z.S.]

Fig 7.53. Diagram of the module for Mesh BX58. [Source: Ref (230) Makowski, Z.S.] Fig 7.56. Project for the Polish Pavilion in Expo ’58 in Brussels. Sketch by Jerzy Soltan in 1956. [Source: Ref (137) Devos, Rika]

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Another striking structural manifestation was the Bell Tower also in Expo Brussels (Fig 7.57); in this case it was a structure involving a set of tetrahedra stabilised with cables.

7.2.2 Space megastructures: between utopia and reality

We are once again before an example of false tensegrity in which there is contact between the compressed elements. Nevertheless, the originality of the solution is remarkable, especially its singularity in terms of the application of the space frame principle to a svelte construction.

It is clear that the ability of space frames to cover large spans sparked considerable technological enthusiasm. This optimism had a significant impact on certain architectural movements hovering on the edge of utopia, and occasionally allowed them to tackle specific approaches to urban generation, those principally based on space megastructures. It was precisely the World Expos that provided an opportunity to build some of these megastructures, and to greater or lesser extent to make an approximation to previous theoretical approaches; thus, the capacity of space frames for building giant structures was evidenced. The World Expos have therefore played two roles: a place where reality has come close to utopia and as a catalyst of the same. We shall start by highlighting the Atomium, built for Expo ’58 in Brussels (Fig 7.58 and Fig 7.59).

Fig 7.57. Bell Tower in Expo ’58 in Brussels. [Source: Ref (230) Makowski, Z.S.]

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Fig 7.58. Atomium. André Waterkeyn. Expo ’58 in Brussels. [Source: Ref (162) Friebe, Wolfgang]

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Designed by the engineer André Waterkeyn, the building had the shape of a frame with a geometry based on pyramid-shaped modules with a square base, representing an iron molecule magnified 165 billion times. The shape of the building itself connects with the theme of the Expo developed inside; promoting the pacific use of atomic energy, following the catastrophic consequences of its military use during World War Two.

The structure of these spheres was basically made of meridians connected by parallels, with other substructures in place to support the enclosure sheets (Fig 7.61 to Fig 7.63).

Fig 7.60. Atomium. Under construction. Expo ’58 in Brussels. [Source: its creators]

Still standing today, the building is 102 metres high and made up of nine spheres connected by tubes, only six of which offered public access: the ones at the base and the centre, the highest one and the three that were connected by the emergency stairways. A lift started from the lower sphere and rose to the upper one, fully occupying the central tube. The length of these tubes varied between 23 and 29 metres, and had a diameter of between 3 and 3.3 metres. They were formed by steel plates reinforced with inner rings. The spheres that were accessible to the public had two or three floors and another, lower floor for services and installations (Fig 7.64). CHAPTER 7

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Fig 7.59. Atomium. André Waterkeyn. Expo ’58 in Brussels. [Source: Ref (137) Devos, Rika / de Kooning, Mil] Fig 7.61. Atomium. Photograph of assembly. [Source: Ref (44) Le libre des expositions]

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Wind tunnel tests were carried out to determine the acting wind forces (Fig 7.65).

Fig 7.62. Atomium under construction. [Source: Ref (137) Devos, Rika / de Kooning, Mil]

From a historical point of view, the structural worth of the building resides in the fact that it is a true space megastructure, with the distinguishing feature of the joints and bars themselves being the habitable elements; that is, the space frame is inhabited (Fig 7.66 and Fig 7.67).

Fig 7.65. Atomium. Wind tunnel test of a reduced model. [Source: its creators] Fig 7.63. (Below, left) Atomium. Placing the enclosure panels. [Source: its creators] Fig 7.64. (Below, right) Atomium. Cross-section of the frame joints. [Source: its creators]

Fig 7.66. Atomium. Expo â&#x20AC;&#x2122;58 in Brussels. View from inside one of the spheres. [Source: its creators]

Fig 7.67. Atomium. Expo â&#x20AC;&#x2122;58 in Brussels. Inside of one of the tubes. [Source: Ref (239) Mattie, Erik]

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In spite of the difficulties in documenting any repercussions in construction that this building may have had, it can be related to idealistic proposals on an urban scale. In this sense, we should make mention of the 1964 proposal named “Underwater City” by Warren Chalk, a member of the British group Archigram, which was a subaquatic habitable space structure (Fig 7.68).

A more recent proposal is that by the Japanese group Shimizu Corporation called TRY 2004, which consists of a multilayer space frame developed over water; residential and commercial buildings and office buildings over a hundred storeys high could be inserted between its nodes (Fig 7.70 to Fig 7.72). The space frame itself would make up the structure and urban communications network, with the nodes with 50-metre diameters being the network transfer points. This urban space megastructure would take on the global shape of a pyramid.

Fig 7.68. “Underwater City”. Warren Chalk. Archigram. 1964. [Source: Ref (133) Cook, Peter / Chalk, Warren / Crompton, Dennis / Greene, David / Herron, Ron / Webb, Mike]

Fig 7.69. Atomium. Expo ’58 in Brussels. [Source: its creators]

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Fig 7.70. TRY 2004 proposal. Shimizu Corporation. Habitable space frame. [Source: Ref (118) Chilton, John]

Fig 7.71. TRY 2004 proposal. Shimizu Corporation. Habitable space frame sustaining residential buildings. [Source: Ref (118) Chilton, John]

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Fig 7.73. The U.S. Pavilion in Expo ’67 in Montreal. Richard Buckminster Fuller. [Source: Ref (299) Thomas Nelson & Sons]

Together, Expo ’70 in Osaka and Expo ’67 in Montreal especially represent the structural gigantism applied to the construction of space structures. Some of the examples go beyond the concept of structure as a deck element and take it to its ultimate consequence: an integral solution that resolves the whole building enclosure and, in some cases, even all the surfaces in their practical entirety. Relevant examples of this extreme in Expo ’67 in Montreal are: the U.S. Pavilion, the Netherlands Pavilion and the Man the Explorer and Man the Producer Pavilions.

Fig 7.74. The U.S. Pavilion in Expo ’67 in Montreal. Richard Buckminster Fuller. [Source: Ref (299) Thomas Nelson & Sons]

Fig 7.72. TRY 2004 proposal. Shimizu Corporation. [Source: Ref (118) Chilton, John]

The U.S. Pavilion was made by Richard Buckminster Fuller in collaboration with Shoji Sadao, and Simpson, Gumpertz and Heger Inc. It was a double-layer geodesic dome made with 24,000 steel bars, the weight of the structure itself being 40 Kg/m2 (Fig 7.73 to Fig 7.76). The outer layer was made of triangles and the inner one of hexagons, reaching a diameter of 76 metres and a height of 61 m. The sides of the triangles and hexagons were no longer than 3.05 and 1.83 metres respectively. The outer bars had a diameter of 88.9 mm, while the rest had a 73-mm diameter [Ref (235) Margarit, J. / Buxadé, C.] (Fig 7.77 to Fig 7.79). With the aim of creating a homogeneous appearance, variations were fundamentally applied to the thicknesses of the bars, rather than their diameters, to the point of some solid bars being used. To reduce the stresses caused by thermal variations, horizontal movement was permitted in the dome base.

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Fig 7.79. The U.S. Pavilion in Expo ’67 in Montreal. Development of a fragment of the dome. The arrows indicate the position of the equator. Above on the right: plan of the dome. [Source: Ref (106) Buckminster Fuller, Richard]

Fig 7.75. The U.S. Pavilion in Expo ’67 in Montreal. Richard Buckminster Fuller. Note the independence of the enclosure skin from the inside exhibition structures. [Source: Ref (122) Clasen, Wolfgang]

Fig 7.76. The U.S. Pavilion in Expo ’67 in Montreal. Richard Buckminster Fuller. [Source: Ref (122) Clasen, Wolfgang]

Fig 7.77. (Left) The U.S. Pavilion in Expo ’67 in Montreal. Richard Buckminster Fuller. Detail of the geodesic framework. [Source: Ref (29) General Report on the 1967 World Exhibition] Fig 7.78. (Right) The U.S. Pavilion in Expo ’67 in Montreal. [Source: Ref (235) Margarit, J. / Buxadé, C.]

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Fig 7.82. The U.S. Pavilion in Expo ’67 in Montreal. Details of the mechanism with aluminium sheets to control the solar radiation. [Source: Ref (215) Kalin. I.]

Fig 7.80. The U.S. Pavilion in Expo ’67 in Montreal. Detail of standard joint. [Source: Ref (267) Picon, Antoine]

The enclosure was comprised of curved, acrylic panels that had been gradually tinted from the base to the peak, while the upper panels had ventilation vents installed (Fig 7.81). This enclosure was fitted with an automated system made with aluminium sheets which acted as a diaphragm to partially or totally block out the solar radiation; the system was computer-controlled and functioned according to the position of the sun (Fig 7.82 and Fig 7.83).

Fig 7.81. The U.S. Pavilion in Expo ’67 in Montreal. Detail of the framework and the acrylic enclosure panels. [Source: Ref (299) Thomas Nelson & Sons]

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Fig 7.85. The U.S. Pavilion in Expo ’67 in Montreal. Note at the bottom one of the singular access areas in the frame. [Source: its creators]

Although the first computer that appeared in the ‘60s would enable matrix calculation to be generalised, it was impossible to locate a computer capable of analysing the whole dome with this method; it had to be calculated by assimilation to a spherical continuous shell, while only specific areas such as those corresponding to the monorail entrance and exit apertures were analysed with the matrix method [Ref (235) Margarit, J. / Buxadé, C.] (Fig 7.84 y Fig 7.85).

Fig 7.83. The U.S. Pavilion in Expo ’67 in Montreal. Note the control mechanisms for the solar radiation, closed or partially open based on the position of the sun. [Source: its creators] Fig 7.86, Fig 7.87 and Fig 7.88. The U.S. Pavilion in Expo ’67 in Montreal. Various stages of the dome assembly. [Sources: left: Ref (40) Domus; below, left: Ref (267) Picon, Antoine; below, right: Ref (215) Kalin. I.]

Fig 7.84. The U.S. Pavilion in Expo ’67 in Montreal. Singular area where the monorail entrance was located. [Source: its creators]

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The dome at Montreal did not have the longest span among those built by Fuller. The Baton Rouge Dome, for example, had a diameter of 130 metres (Fig 7.32 to Fig 7.35). Nor was the Montreal dome the first geodesic structure to be built by Fuller that was more than half a “sphere”, as he had designed a standard deck to offer protection to the U.S. Army’s border radars in 1954 in the context of the Cold War. Multiple domes were erected between 1954 and 1956 following this same design or variations on it, with base diameters of between 10 and 15 metres (Fig 7.89 and Fig 7.90).

Fig 7.89. Project for a geodesic dome to protect surveillance radars. Richard Buckminster Fuller. 1954. [Source: Ref (163) Fuller, Richard Buckminster]

Fig 7.91. (Left) Regular Grid. The thick lines mark the projection of the edges of the icosahedron on the spherical surface. The numbers show the dome frequency or number of segments into which each of the edges is divided. The Regular Grid was the first to be used by Fuller in the construction of geodesic domes. [Source: Ref (276) Sadao, Shoji] Fig 7.92. (Right) 31 Diametrical Circles Grid. A drawback was the considerable difference in length between the shorter and longer bars. [Source: Ref (276) Sadao, Shoji] Fig 7.93. (Left) Alternate Grid. With less bars than the Regular Grid. [Source: Ref (276) Sadao, Shoji] Fig 7.94. (Right) Triacon Grid. Invented in 1951 by the mathematician and one of Fuller’s collaborators, Duncan Stuart. It is the result of decreasing the number of different bars and the difference in length between the same to the minimum. [Source: Ref (276) Sadao, Shoji] Fig 7.95 and Fig 7.96. Truncatable or Parallel Grid. Invented by William Wainwright, one of Fuller’s collaborators. When an attempt was made to build more than a half-sphere, the plane of section did not always coincide with the grid joints; they therefore needed to use bars with special lengths that formed irregular triangles. With frequencies of 3, 4 or 5, this grid sidestepped the issue. [Source: Ref (276) Sadao, Shoji]

Fig 7.90. Example of one of the geodesic domes built between 1954 and 1956 to protect border radars. [Source: Ref (163) Fuller, Richard Buckminster]

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Nevertheless, the dome at Expo ‘58 is the biggest geodesic structure made of more that half a “sphere” and is an extraordinarily large approximation to a sphere. It is probably for this reason, as well as having been built for a World Expo, that this is the best-known and most representative geodesic dome, symbolising the most emblematic of Fuller’s work in the field of geodesics. In short, thanks to its representation, symbolism and enormous dissemination, it is his most transcendental. On the other hand, the geodesic domes built by Fuller before 1967 had a primarily utilitarian function, often giving cover to industrial spaces. Through the World Expo, the building has become a symbol, representing the opportunity to erect a virtually complete “sphere” that goes beyond utility to become an almost exhibitionistic display of the possibilities of Fuller’s works in this field.

Fig 7.97. Zeiss-Planetarium in Jena. Germany. Walter Bauersfeld. 1922. Photograph of the reinforcement forming a geodesic dome. [Source: Ref (217)Kind-Barkauskas]

Fig 7.98. Zeiss-Planetarium in Jena. Germany. The concreted dome. [Source: Ref (274) Rothman, Tony]

The text reads:

Fig 7.99. German patent no. 415.395 of the Carl Zeiss Company in Jena dated 1922 and called “Method for the construction of domes and similar domed surfaces made of reinforced concrete” [Source: Ref (274) Rothman, Tony]

Fuller is often attributed with the invention of the geodesic dome; in fact, he registered his patent in 1954 (Fig 7.31), as mentioned earlier. The enormous value inherent in both his theoretical work and its practical applications is undeniable, constituting one his greatest contributions to the history of structural systems. Among other investigations, we can highlight the studies he carried out on different geodesic grids based on the icosahedron, such as the Regular Grid, the 31 Diametrical Circles Grid, the Alternate Grid, the Triacon Grid or the Truncatable or Parallel Grid (Fig 7.91 to Fig 7.96) [Ref (276) Sadao, Shoji]. Nevertheless, to tell the truth, the geodesic dome was invented by Walter Bauersfeld, chief engineer at the optical company Carl Zeiss. Together with the building company Dyckerhoff and Widmann, Bauersfeld made what would be the first known structural geodesic dome in 1922, as reinforcement for the concrete dome of the Zeiss-Planetarium in Jena, Germany. It had a diameter of 16 metres (Fig 7.97 and Fig 7.98) and the construction system was registered by the Carl Zeiss Company on 9th November of the same year as the German patent no. 415.395 titled “Method for the construction of domes and similar domed surfaces made of reinforced concrete” (Fig 7.99). Thus, the patent was registered 32 years before Fuller’s patent for the geodesic dome. Nevertheless, Carl Zeiss’ patent did not register the geometry of the reinforcement, only a construction method based on reinforcement with spatially arranged iron bars over which concrete would be sprayed. It is not known whether there is another patent in which the geometrical shape of the reinforcement was registered; to this effect, the Carl Zeiss Company was questioned by Shelter Publications. Their response was as follows: “All patents and recordings were confiscated by the Russian or American troops during the occupation of Jena in 1945. Dr. Walter Bauersfeld was taken to West Germany by the American army in 1945 […]. We have not been able to locate any patents pertaining to the Planetarium or its Dome.” [Ref (274) Rothman, Tony]. In short, whether Richard Buckminster Fuller was aware of the geometric configuration of the reinforcement of the Zeiss-Planetarium in Jena and based himself on this idea, or whether he simply reinvented the geodesic dome, it remains an enigma.

“The present invention deals with a method for the construction of domes and similar domed surfaces made of reinforced concrete that are especially characterised by their economy. This novel method consists in spraying a space grid made of iron bars with a layer of concrete. The space grid is freestanding, and once covered in concrete, it will bear a part of the total weight of the concrete. It is located on the building deck. Through the use of a light formwork connected to the grid and by spraying the concrete, it becomes completely supporting. Only a small portion of the formwork needs to be made; it is subsequently fixed to each part of the domed surface. This partial formwork is placed against the grid in such a way that the bars are under no bending stresses during construction of the concrete deck. With the application of the spraying method, not only is the concrete stronger, but vibrations and loads in the grid and formwork during construction are prevented. There are no notable bending stresses in the grid during application; the quantity of iron needed to build large-scale structures is therefore limited. Additionally, this method avoids the need for any lower reinforcement, which would be more costly.

CLAIM: Method for the construction of domes and similar domed surfaces made with reinforced concrete and characterised by spraying a space grid consisting of iron bars with a layer of concrete. The space grid is freestanding, and once concreted, it can bear a part of the concrete’s total weight. It is located on the building deck. Through the use of mobile formwork, it becomes completely supporting”.

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The Zeiss-Planetarium in Jena is the earliest documented precedent of the U.S. Pavilion. In reality, however, its immediate precedents were the numerous studies and domes carried out by Fuller and his collaborators. Examples of these are the Ford Rotunda made in 1953 in Dearborn, Michigan, which had a diameter of 28.4 metres, Fuller’s first large geodesic dome, and was followed by the registration of his patent for the geodesic dome a year later (Fig 7.100 to Fig 7.101); the Kaiser Dome, Honolulu 1957 (Fig 7.36 and Fig 7.37); or the “Baton Rouge Dome” for the Union Tank Car Co., Baton Rouge, Louisiana 1958 (Fig 7.32 to Fig 7.35).

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Especially worthy of mention is the unbuilt project from 1951 for an automated cotton spinning mill (Fig 7.102 and Fig 7.103). Proposed by Fuller three years before his patent for the geodesic dome was registered, this project consisted of a large-scale, geodesic, spherical cap made of a single layer which formally resembles the U.S. Pavilion in Montreal to a considerable extent. Thus, we can see how the U.S. Pavilion seems to have signified the return to an initial idea that materialised after a period of great productiveness in terms of research and creations.

Fig 7.100. Ford Rotunda. Richard Buckminster Fuller. 1953. [Source: Ref (118) Chilton, John]

Fig 7.102. Automated spinning mill. Richard Buckminster Fuller. 1951. Unbuilt project. Cross-section. [Source: Ref (148) Emili, Anna Rita]

Fig 7.101. Ford Rotunda. Richard Buckminster Fuller. 1953. Stress studies. [Source: Ref (154) Fernández Galiano, Luis]

Fig 7.103. Automated spinning mill. Richard Buckminster Fuller. 1951. Unbuilt project. Model. [Source: Ref (106) Buckminster Fuller, Richard]

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Regarding utopian proposals, the main precedent would be Fuller’s 1960 proposal for a geodesic dome to cover part of the city of New York with the aim of establishing a level of environmental control (Fig 7.104 and Fig 7.105). Fuller explains his proposal as follows:

In this sense, the dome built by Fuller in Montreal seven years later with its climate control systems, can be considered as a partial successor to his earlier dream of building controlled atmospheres. An uninterrupted view of the outside world, the structural independence of the exhibition elements, the control of solar radiation by means of computerised aluminium diaphragms that moved depending on the position of the sun, the use of acrylic domes as an enclosure with varying degrees of impermeability to the solar radiation and light, or the fact that vents were installed in the upper enclosure domes to help control the temperature; all these aspects connected to a certain extent with Fuller’s utopian proposal for a Dome over Manhattan. The pavilion thereby became an iconic element that represented the possibilities of this typology which Fuller had so warmly praised, not only in the purely structural field, but also in the field of urban megastructures based on atmospheric control. To this effect, Fuller described the Montreal Pavilion in 1971 in the following way:

“We have calculated a dome with a diameter of two miles to cover part of Manhattan. From the inside there will be uninterrupted contact with the exterior world. The sun and moon will shine in the landscape, and the sky will be completely visible, but the unpleasant effects of climate, heat, dust, bugs, glare, etc. will be modulated by the skin to provide Garden of Eden interior.” [Ref (106) Buckminster Fuller, Richard]

“If industry was to take it on, there are things that we could do in geodesic domes that are spectacular. I haven’t let so much of it be visible except that anyone looking at the geodesic dome in Montreal saw (…) there were curtains that could articulate by photosynthesis and so forth, could let light in and out. It is possible, as our own human skin, all of our pores, all of the cells organize, so that some are photo-sensitive and some are sound-sensitive, and they’re heat-sensitive, and it would be perfectly possible to create a geodesic of a very high frequency where each of these pores could be circular tangencies of the same size. One could be a screen, others breathing air, others letting in light, and the whole thing could articulate just as sensitively as a human being’s skin. And I really think geodesic domes such as that will be developed.” [Ref (106) Buckminster Fuller, Richard]

Fig 7.104. Proposal by Richard Buckminster Fuller to cover part of Manhattan with a geodesic dome. 1960. [Source: Ref (106) Buckminster Fuller, Richard]

Fig 7.105. Proposal by Richard Buckminster Fuller to cover part of Manhattan with a geodesic dome. 1960. [Source: Buckminster Fuller, Richard]

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Fuller thus reveals an incredible high level of trust in technological development while avoiding taking into consideration society’s acceptance of these proposals; although they could very well be justified in inhospitable and aggressive terrains, plans to cover existing cities would be highly disputed. In these cases, factors such as air quality can be controlled by other means that depend precisely on new technological developments. On the other hand, Fuller maintained that the dome over Manhattan would lead to an enormous saving in energy since its surface was 1/85 the size of the enclosures of the buildings it would cover, thus reducing the cost of energy expenditure by 1/85 [Ref (106) Buckminster Fuller, Richard]. In principle, if the thermal resistance of the dome enclosure were the same as the resistance of the building enclosures, the thermal flow would effectively be 85 times lower. This, however, circumvents the fact that the total volume of air needing climatization would be enormous; in principle, this is a difficult issue to tackle without the help of mechanical elements with a high level of energy consumption. In fact, apart from the aforementioned energy-efficient resources used for climate control, the U.S. Pavilion in Montreal 1967 was further equipped with a powerful air conditioning system with 750 tonnes of refrigerating liquid [Ref (215) Kalin, I.]. On the other hand, Fuller’s tendency to apply geodesic domes to the development of controlled atmospheres and the possibility of building this pavilion in Expo ‘67 are better understood by bearing in mind the stellar peak of the space race at that time. Proof of this can be found in the innumerable elements on display in the Expo that dealt with the theme: the reproduction of an imminent manned lunar landing, space buggies, photographs and elements related to the Apollo Programme, recordings of conversations with astronauts in flight, etc. In this sense, projecting a controlled atmosphere within a large-span area fit perfectly with the establishments of human settlements on other planets, and therefore with the space race itself.

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There are many examples of geodesic domes erected after Expo ’67 in Montreal; this event would act as a definitive catalyst for disseminating these typologies, as well as being the trigger for the social recognition of the magnitude of Fuller’s work. While it has a smaller diameter, the German Pavilion built in 1970 for Expo Osaka is noteworthy (Fig 7.108 and Fig 7.109). There is probably a stronger connection with the Space Ship Earth built in 1982 in the Disney Epcot Theme Park by Peter Floyd, one of Fuller’s collaborators on the pavilion in Montreal (Fig 7.110). Its geometry was based on the icosahedron with a frequency of 16, and while its span is of 50.3 metres, considerably less than the Pavilion in Montreal, it is made up of a complete sphere supported by columns.

During some renovation work carried out in May 1976, the U.S. Pavilion from Expo ’67 in Montreal caught fire. The acrylic enclosure panels went up in flames but the structure survived and is still standing to this day (Fig 7.107).

Fig 7.106. The U.S. Pavilion in Expo ’67 in Montreal. Some of the astronautics material on display. [Source: its creators]

Fig 7.108. German Pavilion. Expo ’70 in Osaka. [Source: Ref (31) Osaka 1970 Official Photo Album]

Fig 7.107. The U.S. Pavilion in Expo ’67 in Montreal. The fire started on May 20th 1976. [Source: its creators] Fig 7.109. German Pavilion. Expo ’70 in Osaka. [Source: Ref (31) Osaka 1970 Official Photo Album]

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However, in terms of constructions related to the bioclimatic field advocated by Fuller in the Pavilion in Montreal and the Manhattan Project, the most significant and closely linked project to this approach is perhaps the Eden Project created by Nicholas Grimshaw in Cornwall, Great Britain in 2001. It is formed by eight intersecting geodesic domes with a pneumatic enclosure made of sheets of ethylene tetrafluoroethylene (ETFE) (Fig 7.111 to Fig 7.112). Various climatic conditions are reproduced on the inside. Despite the domes basically functioning as greenhouses, it is also true that the project connects with Fuller’s approach in various aspects: on the one hand, the use of a geodesic dome as a structural typology capable of large spans, and on the other hand, the creation of artificial atmospheres capable of reproducing specific climatic conditions within spaces enclosed by materials that are semi-transparent to both light and solar radiation, although this was once again achieved at a considerable cost in energy.

Fig 7.110. Space Ship Earth. Peter Floyd. 1982. [Source: its creators]

The aspect of Fuller’s Pavilion in Montreal concerning the whole skin of the building being made with a space frame crops up in another paradigmatic example, the Netherlands Pavilion, although the geometrical approach here is somewhat more conventional (Fig 7.113 to Fig 7.119). Made by the architects W. Wijkelenboom and A. Middelhoek, it is an example of a space megastructure materialised in this case through the extensive application of the Triodetic System (Fig 7.21 and Fig 7.22). Fig 7.111. (Below) Eden Project. Cornwall. Nicholas Grimshaw. 2001. [Source: its creators]

Fig 7.112. Eden Project. Cornwall. Nicholas Grimshaw. 2001. Cross-section. [Source: its creators]

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Fig 7.113. Netherlands Pavilion in Expo ’67 in Montreal. W. Wijkelenboom and A. Middelhoek. [Source: Ref (299) Thomas Nelson & Sons]

Its general dimensions were 81 x 25 metres and it was 23 metres high. It had an impressive number of components: around 17,500 aluminium joints, 52,000 aluminium tubes and 5,000 steel tubes used for the bars under the most stress. Made up of two, three, four or five layers depending on the part of the building, the space frame completely covered the construction, not only comprising the primary structures but also the main plastic element defining it. The floor slabs were hung from or supported by this external structure (Fig 7.115 to Fig 7.119). 487

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Fig 7.114. Netherlands Pavilion in Expo ’67 in Montreal. W. Wijkelenboom and A. Middelhoek. [Source: Ref (29) General Report 1967 World Exhibition]

The pavilion was designed to be totally dismantled and transported to Holland after the Expo, but this was not possible because of the high cost that would incur. At that time, this building represented the most extensive and largest application of the Triodetic System [Ref (215) Kalin, I.] which, curiously, is Canadian. The fact that the building’s structural consultancy firm, C.B.A. Engineering Limited, was located in Vancouver probably played a part in the large-scale implementation of this national system in a foreign pavilion.

Fig 7.117. Netherlands Pavilion in Expo ’67 in Montreal. [Source: Ref (215) Kalin. I.]

Fig 7.115. Netherlands Pavilion in Expo ’67 in Montreal. Cross-section. [Source: Ref (29) General Report 1967 World Exhibition]

Fig 7.116. Netherlands Pavilion in Expo ’67 in Montreal. Second floor. [Source: Ref (29) General Report 1967 World Exhibition]

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Fig 7.118. Netherlands Pavilion in Expo ’67 in Montreal. Diagram of the space frame made with the Triodetic System. [Source: Ref (29) General Report 1967 World Exhibition]

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Nevertheless, the most representative examples of the space frame concept applied integrally are undoubtedly the Man the Explorer and Man the Producer pavilions designed for Expo ’67 in Montreal by the architects Affleck, Desbarats, Dimakopoulos, Lebensold and Sise. In these cases we have structures formed by 400,000 bars made of two steel angles and 100,000 joints which not only comprise the enclosure for these pavilions, but also the floors and some of the indoor sloping surfaces, while the global geometry of the frame is based on two truncated tetrahedral volumes.

Fig 7.120. View of one of the three buildings making up the Man the Explorer Pavilion. Expo ’67 in Montreal. Affleck, Desbarats, Dimakopoulos, Lebensold and Sise. [Source: its creators]

Fig 7.119. Netherlands Pavilion in Expo ’67 in Montreal. The floor slabs are supported by or hung from the Triodetic frame. Standard cross-section. [Source: Ref (215) Kalin. I.]

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Fig 7.121. Man the Explorer Pavilion. Expo ’67 in Montreal. The Man the Explorer Pavilion was made up of three independent buildings connected by walkways. [Source: Ref (299) Thomas Nelson & Sons]

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Fig 7.122. The Man the Explorer Pavilion. Expo ’67 in Montreal. Plan. [Source: Ref (29) General Report 1967 World Exhibition]

Fig 7.125. The Man the Explorer Pavilion under construction. [Source: Ref (40) Domus]

The Man the Explorer Pavilion was made up of three independent buildings that were connected by walkways. It had three floors and a height of 30 metres (Fig 7.120 to Fig 7.123). The frame module in both pavilions was also based on the truncated tetrahedron. The addition of these modules enabled the creation of parallel surfaces (Fig 7.124) [Ref (118) Chilton, John]. The basic distance between nodes was 990 mm.

Fig 7.123. The Man the Explorer Pavilion. Expo ’67 in Montreal. Elevation-section. [Source: Ref (29) General Report 1967 World Exhibition]

Fig 7.124. Figures (a) and (b): origin and addition or the truncated tetrahedra. Figure (c): plan of the basic space frame used for the floor slabs in the Man the Explorer and Man the Producer Pavilions. [Source: Ref (118) Chilton, John]

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Fig 7.126. Characteristic joint in the frames for the Man the Explorer and Man the Producer Pavilions. Note the bars made up of two angle profiles. The joint is not covered by any existing patent. [Source: Ref (268) Plésums, Guntis]

The global geometry of the Man the Producer Pavilion was more complex, given that it was based on the addition and intersection of those truncated tetrahedra of varying sizes (Fig 7.127 to Fig 7.132). In this case, the building had a height of 45 metres and seven floors.

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Fig 7.127. The Man the Producer Pavilion. Expo ’67 in Montreal. Affleck, Desbarats, Dimakopoulos, Lebensold and Sise. [Source: its creators] Fig 7.130. The Man the Producer Pavilion. Expo ’67 in Montreal. Ground floor. [Source: Ref (215) Kalin. I.]

Fig 7.128. The Man the Producer Pavilion. Expo ’67 in Montreal. [Source: its creators]

Fig 7.131. The Man the Producer Pavilion. Expo ’67 in Montreal 1967. First floor. [Source: Ref (215) Kalin. I.]

Fig 7.129. The Man the Producer Pavilion. Expo ’67 in Montreal. [Source: its creators]

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Fig 7.132. The Man the Producer Pavilion. Expo ’67 in Montreal. Cross-section. [Source: Ref (215) Kalin. I.]

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The structural consultant for both pavilions, Jeffrey Lindsay, made the following significant statement: “In Expo ’67, it was decided to investigate the viability of using a space frame that could coherently integrate structure, floor slabs, walls, decks, balconies, etc. inherently predetermining the whole architecture. The preliminary studies were positive, but we were unaware of a suitable system. We then had to develop an original space structure. […] The details are simple and have a rudimentary appearance. Not all of the pieces are interchangeable, so standardisation was not as precise or extensive as we would have liked. […] The transition to reality resulted in a complex mass of steel, bolts and sheets with a relatively anti-economical outcome.” [Ref (215) Kalin I.]

Fig 7.133. The Man the Producer Pavilion under construction. Expo ’67 in Montreal. [Source: Ref (10) Architectural Record]

Fig 7.134. The Man the Producer Pavilion under construction. Note the elevated structural density, and in the lower area, the roughness in the design of the frame joints that complement the basic joint in certain areas. [Source: Ref (10) Architectural Record]

In spite of such pessimistic words, these constructions have an indisputable value that fundamentally resides in the fact that they are truly early manifestations of the possibilities of space frames when applied integrally in architectural proposals based on space megastructures. It is evident that Expo Osaka in 1970 was heavily influenced by the utopian proposals of the Hungarian architect Yona Friedman from the Japanese Metabolism and Archigram Groups. The technological optimism fired by the space frame typology with its capacity for large spans can be felt in what may be Yona Friedman’s most remarkable proposal: the “Spatial City” (Fig 7.135 to Fig 7.136). This proposal consisted of a space megastructure elevated on columns that could be built over existing cities, swampy areas, rivers, etc. The residential areas would be inserted into the frame and alternated with other, empty areas in a kind of flexible and changing architecture.

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Fig 7.137. The Festival Plaza. Expo Osaka in 1970. Kenzo Tange, Yoshikatsu Tsuboi and Mamoru Kawaguchi. [Source: Ref (296) Tange, Kenzo]

Fig 7.135. Spatial City. Yona Friedman. 1960. The space frame is a habitable place. [Source: its creators]

Fig 7.138. The Festival Plaza. Expo Osaka in 1970. Kenzo Tange, Yoshikatsu Tsuboi and Mamoru Kawaguchi. [Source: Ref (96) Bettinotti, Massimo]

Fig 7.136. “Spatial Paris”. Yona Friedman. 1960. Superposition of a residential space megastructure over Paris. [Source: its creators]

These proposals had a profound influence on the Japanese Metabolism Group and even the Archigram Group. Established in 1960 by Kenzo Tange, Kiyonori Kikutake and Kisho Kurokawa, the Metabolism Group aimed to present proposals, some of them on an urban scale, that were based on technological development and capsule addition systems, in line with a society under continuous vital and technological change. Metabolic proposals are rooted in the Japanese cultural and sociological reality of that time: a huge demographic explosion; limited space in the island cities; a population with a high level of geographical mobility, whereby about 10% change cities every year; as well as the characteristic modulation of traditional Japanese architecture. These extremes led to urban proposals that reflected this continuously mutating reality, in a biological analogy of changing cells [Ref (313) Martín Gutiérrez, Emilio]. Thanks to their position in the technological cutting edge of that time and their aggregative nature, space frames would be the ideal vehicle to make these proposals a reality. Some of the structural works that approximate the previous proposals are the Festival Plaza by the architect Kenzo Tange and the engineers Yoshikatsu Tsuboi and Mamoru Kawaguchi, and the Takara Beautilion by Kisho Kurokawa. The Festival Plaza from Expo Osaka in 1970 was formed by a double-layer space frame with an exceptionally large rectangular floor plan measuring 108 x 291.6 m and a height of 30.11 m up to the lower layer of the structure. The height of the frame was 7.63 measured from the bar axes (Fig 7.137 to Fig 7.140).

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Fig 7.141. The Festival Plaza. Expo Osaka in 1970. Elevation of a column and the connection with the deck frame. [Source: Ref (32) Osaka 1970 Official Report]

Every aspect of the frameâ&#x20AC;&#x2122;s size was extraordinary; it had the shape of a square-based pyramid with sides measuring 10.8 metres. Both layers were connected with diagonal members that were also 10.8 metres long. The bars corresponding to the upper and lower layers were steel tubes with a diameter of 500 mm, while the diagonal members were again steel tubes with a diameter of 350 mm. The walls of the bars varied in thickness between 7.9 and 30 mm, depending on the stresses that they had to withstand. The joints were made up of slightly spherical steel elements with an external diameter of 800 mm. The frame was solely supported by six columns consisting of a central bar with a diameter of 1.8 metres connected via diagonal members to four side bars with diameters of 600 mm. The columns were topped by a mesh that acted as a capital that was connected to the deck frame (Fig 7.141). 2,272 steel tubes and 639 joints were used in total. Square-plan pneumatic cushions made of transparent plastic were used for the deck. The hoisting technique that was used was novel; the deck structure was assembled on the ground and later hoisted with pneumatic jacks up the central column bars which were completed with the side bars as the deck was raised (Fig 7.142 and Fig 7.143).

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Fig 7.139. (Above) The Festival Plaza. Expo Osaka in 1970. Kenzo Tange, Yoshikatsu Tsuboi and Mamoru Kawaguchi. Plan and elevation of the space frame. [Source: Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru] Fig 7.140. (Below) The Festival Plaza. Cross-section. [Source: Ref (32) Osaka 1970 Official Report]

Fig 7.142. The Festival Plaza. Several stages of the hoisting technique used. Elevation of the deck with pneumatic jacks along the central column bars. As the deck was raised, the columns were completed with the side bars. [Source: Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru]

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Fig 7.143. The Festival Plaza during the hoisting process. [Source: Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru]

Exhaustive calculations were carried out on the structural ensemble at several stages of the hoisting process, as well as on specific elements such as the joints and the bar ends. A rough initial calculation was carried out by assimilation to a continuous shell, while the final calculation was done by matrix methods. A second order calculation was also carried out, applying the most significant displacements obtained in the previous calculations to certain areas of the frame [Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru]. The joints were analysed numerically by assimilation to a continuous shell, while these calculations were complemented by real-scale tests. Tolerances were predicted in the joints with respect to both longitudinal errors and the connection angles. In this sense, the joints had a hole to allow the bar to be bolted from the inside. The bolt holes had a diameter 6 mm larger than the bolts, thus enabling control over any variation in the angles. The longitudinal errors were solved by adding or eliminating shims (Fig 7.144 to Fig 7.146). Fig 7.145. Image of a standard joint for a column. The diameter of each joint was 80 cm. [Source: Ref (59) Expo 70, a photographic interpreter]

Fig 7.144. The Festival Plaza. Standard joint in the space frame. Note the lower hole for moving the bolts from the inside of the joints and the set of shims for correcting the longitudinal errors. [Source: Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru]

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Fig 7.146. A joint undergoing a tension test. [Source: Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru]

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From a historical point of view, the technical contribution was undeniable, given the impressive scale of the space frame, with unheard-of bar and joint sizes for that time. As mentioned above, the hoisting system was also novel. These aspects were promoted thanks to the high level of dissemination of the building, not only in its role as the central architectural piece in the Expo, but also through the presentations given by its creators in several congresses. This helped to promote the technical details of the design in terms of construction and calculation, as well as the various tests that had been carried out. Among the presentations given, we can highlight that by Yoshikatsu Tsuboi and Mamoru Kawaguchi in the “IASS Pacific Symposium-Part II on Tension Structures and Space Frames”, held between 17th and 23rd October 1971 in Tokyo and Kyoto [Ref (303) Tsuboi, Yoshikatsu / Kawaguchi, Mamoru].

The Takara Beautilion, made by Kisho Kurokawa for Expo ’70 in Osaka, represents another paradigmatic example of the Japanese Metabolist movement (Fig 7.148 to Fig 7.153). The technological exaltation can be appreciated in the creation of a multi-layer space megastructure based on hexahedral polyhedra that allowed for an addition system of residential capsules. Around 200 modules were used, measuring 3.3 metres along their sides and made with bars with diameters of 100 mm. These modules with rigid joints were bolted together in the centre of each of their sides. The stainless steel capsules were inserted into the frame, thus creating an original example of an inhabitable space frame.

Its theoretical contribution that was largely based on the structural design is also of great historical relevance. Note that, together with Fuller’s Pavilion and the Man the Explorer and Man the Producer Pavilions in Expo ’67 in Montreal, the Festival Plaza in Expo ’70 in Osaka is the largest example of structural gigantism created through the use of space frames for that time. Thus, we can pinpoint a clear influence of the utopian proposals from the Hungarian architect Yona Friedman and the Metabolist Group of which Tange was a member. This evident utopian influence is seen in Kenzo Tange’s space frame: on the one hand in the unprecedented scale striving for urban proportions, and let us not forget that the building was called Plaza for a reason; and on the other hand, in a mesh that could be partially accessed by the visitor between its two layers, and which ultimately could be inhabited (Fig 7.147). In the article titled “The basic concept of Expo 70” included in the Official Expo Report, Kenzo Tange stated: “The Festival Plaza includes a series of interesting suggestions for town planning of the future. In the first place, it demonstrates the possibility of covering large spaces such as squares with similar structures. In the second place, as it has habitable spaces within the structure, the Festival Plaza is an approximation to an aerial city. The spatial structure could be extended and inserted into the same architectural spaces for living and working.” [Ref (32) Osaka 1970 Official Report]

Fig 7.148. Takara Beautilion. Kisho Kurokawa. Expo ’70 in Osaka. Space megastructure rendered habitable through the insertion of capsules. [Source: Ref (169) Garn, Andrew]

Fig 7.147. The Festival Plaza. Expo Osaka in 1970. The space frame is inhabited. Exhibition area located between the frame layers. [Source: Ref (32) Osaka 1970 Official Report]

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Fig 7.149. Takara Beautilion. Kisho Kurokawa. Expo ’70 in Osaka. [Source: Ref (169) Garn, Andrew]

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Fig 7.150. Takara Beautilion. Kisho Kurokawa. Expo â&#x20AC;&#x2122;70 in Osaka. Cross-section. Habitable spatial structure. [Source: Ref (32) Osaka 1970 Official Report]

Fig 7.152. (Left) Takara Beautilion. View of a capsule. [Source: Ref (296) Tange, Kenzo] Fig 7.153. (Right) Takara Beautilion. Assembling one of the capsules. [Source: Ref (219) Klotz, Heinrich]

Fig 7.151. Takara Beautilion. Kisho Kurokawa. Expo â&#x20AC;&#x2122;70 in Osaka. Plan of the third level. [Source: Ref (59) Expo 70, a photographic interpreter]

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Certain architectural proposals that had been put forward earlier reveal the interaction between fantasy and reality that the World Expos gave rise to. In this case, we are referring to the proposal offered by Peter Cook back in 1966, named Archigram Network (Fig 7.154); this basically consisted of an urban grid that was made up of space megastructures to which prefabricated residential capsules were added.

Fig 7.154. Archigram Network. Urban proposal made up of space megastructures and the insertion of prefabricated capsules. Peter Cook. 1966. [Source: Ref (148) Emili, Anna Rita]

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Several spatial structures of considerable technical and formal originality were also erected in Expo ’70 in Osaka. The singularity of the modules in the Toshiba IHI Pavilion, created by Noriaki Kurokawa Architecture (Fig 7.155), are remarkable; the pavilion was built with four types of tetrahedral modules of varying shape and size. A total of 1,476 modules were used, while their originality mainly resided in the fact that they were made of steel sheets (Fig 7.156 and Fig 7.157). The deck of a theatre with a diameter of 40 metres was hung from this spectacular space frame that lay on six support points. The base of the theatre had a piston that enabled it to ascend and descend, as well as rotate (Fig 7.158 and Fig 7.159).

Fig 7.157. Toshiba IHI Pavilion. Note the different type of module made of sheets used in the frame. [Source: Ref (169) Garn, Andrew]

Fig 7.155. Toshiba IHI Pavilion. Noriaki Kurokawa Architecture. Expo ’70 in Osaka. Theatre and tower structure. [Source: Ref (31) Osaka 1970 Official Photo Album]

Fig 7.156. Toshiba IHI Pavilion. Noriaki Kurokawa Architecture. Expo ’70 in Osaka. [Source: Ref (169) Garn, Andrew]

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Fig 7.158. Toshiba IHI Pavilion. Cross-section. [Source: Ref (32) Osaka 1970 Official Report]

Fig 7.159. Toshiba IHI Pavilion. Plan at the level of the mobile platform. [Source: Ref (32) Osaka 1970 Official Report]

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Another interesting construction was the 55-metre-high tower made with the same tetrahedral modules and complemented with cables (Fig 7.155). In the same vein, we should also touch upon the various historical high-rise proposals with integral solutions based on space frames. An example of this is the Signal Tower (Fig 7.160) erected by the MERO group for the World Expo called IVA ’65 held in Munich; this was a prototype that was meant to showcase the possibilities of the space frame for the development of high-rise buildings. It was part of a series of proposals for residential towers with which the company intended to broaden the system’s field of application (Fig 7.161). It is clear that the Signal Tower by MERO follows the metabolist line in aspects such as technological exaltation or the encapsulation of the residential elements.

Fig 7.162. Tetrahedral Tower Project. Louis Kahn. 1957. [Source: Ref (219) Klotz, Heinrich]

Fig 7.160. (Left) Signal Tower. Prototype erected by MERO for IVA ’65 in Munich. [Source: Ref (235) Margarit, J. / Buxadé, C.] Fig 7.161. (Right) Prototypes for residential towers built by MERO. [Source: Ref (235) Margarit, J. / Buxadé, C.]

Nevertheless, it should be pointed out that back in 1957, and following the evolution of technology, Louis Kahn had presented his Tetrahedral Tower for the city of Philadelphia (Fig 7.162). It was an office tower 190 metres high based on the principle of the space frame. Interestingly, it should be noted that the bars of the structure were made of concrete. In this sense, and in relation to high-rise buildings, we should also mention the Expo Tower built by Kiyonori Kikutate on the occasion of Expo ’70 in Osaka (Fig 7.163 to Fig 7.166). Kikutate, another member of the Metabolism Group, proposed a main steel structure consisting of three columns stabilised by connection to a space frame. This structure brought together the stairs and lifts and the installations; cantilevered secondary space frames that sustained habitable polyhedral capsules were then connected to it. The primary function of the tower was to act as an observatory which visitors could go up, as well as a radio station. While the initial plan was to erect a tower between 350 and 400 metres high, in the end this would not be possible for economic reasons, and finally the height of the Expo Tower was 120 metres. Conceptually, the building represents a high-rise space megastructure which offers the possibility of adding new modules and capsules, in line with the metabolic developments (Fig 7.166).

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Fig 7.163. (Left) Expo Tower. Kiyonori Kikutate. Expo ’70 in Osaka. [Source: Ref (31) Osaka 1970 Official Photo Album] Fig 7.164. (Right) Expo Tower. Kiyonori Kikutate. Expo ’70 in Osaka. [Source: Ref (31) Osaka 1970 Official Photo Album]

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CHAPTER 8

THE RETURN TO WOOD

The World Expos have housed buildings with structures made of wood or its derivatives which have made significant contributions to the history of structural systems. The following chapter will outline the reciprocal influence that the Expos have had, as well as the evolution of wooden structures. Subsequently, this interaction will be shown to have fundamentally occurred in three key moments in the history of this material. Fig 7.165. Expo Tower. Kiyonori Kikutate. Expo â&#x20AC;&#x2122;70 in Osaka. [Source: its creators]

Fig 7.166. Expo Tower. Elevation of one of the prefabricated capsules. [Source: Ref (31) Osaka 1970 Official Photo Album]

8.1 WOODEN STRUCTURES: ORIGIN AND DEVELOPMENT

We should point out that there has not been any historical continuity in terms of built examples of space frames applied to high-rise buildings, with the exception of those constructions that solely resort to using triangulation as an element of horizontal stiffness without representing integral applications of the principle of space frames.

As a natural element that is easy to handle, wood was used as a construction material by the oldest civilizations, and was probably the first to be used by mankind to make structures. These first deck structures must have been quite rudimentary, presumably involving a few branches intertwined and covered with vegetal elements or skins. In some cases, the construction tradition of certain typologies has prevailed and their simplicity and precariousness can still be seen among some primitive societies (Fig 8.1).

All of the issues that have been dealt with above highlight the importance of the role of the World Expos, not only in the history of structural systems from a technological perspective, but also as a stage for bringing to life proposals derived from those utopian architectural currents that have been largely sustained by the most cutting-edge structural advances.

Fig 8.1. Structure for a primitive cabin. [Source: Ref (229) Mainstone, Rowland J.]

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On other occasions, however, their ingenuity has reached surprising lengths, as in the case of the tent used by the nomadic people of the steppes of Central Asia, called a yurt, which consists of a perimetral wooden structure that can be deployed (Fig 8.2 and Fig 8.3). Wood has also been used in the construction of highly simple primitive bridges, made with basic logs supported at two points or with intermediate supports (Fig 8.4).

Fig 8.4. Berber bridge made of logs with intermediate supports. Atlas mountains. Morocco. [Source: López César, Isaac]

Fig 8.2. Mongolians setting up a yurt. Note above on the left, the perimetral structure being deployed. It is an extraordinarily ingenious structure that is quickly set up and easily transported. [Source: its creators]

Fig 8.3. Photograph of a yurt. [Source: Library of Congress]

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The Greeks and the Romans used simple and trussed wooden beams and arches in both bridges and decks. Along these lines, Vitruvius presents a cross-section of the wooden deck of a Greek temple in Book IV of his “De Architectura”; an understanding of the mechanical workings of this structural typology can be clearly evinced in the deck design (Fig 8.5).

Fig 8.5. Cross-section of the wooden frame for the deck of a Greek temple presented by Vitruvius in Book IV of his “De architectura”. Note the layout of the lower tie member that counters the horizontal thrusts on the columns. [Source: Vitruvius]

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Basing themselves on descriptions by Julius Caesar, several authors have attempted to graphically represent the bridge that the Emperor commanded be built over the Rhine for his troops to cross, and which was destroyed eighteen days later to hinder persecution from his enemies. In the sketches drawn by Andrea Palladio, it is seen to be formed by transversal portal frames driven into the river bed and stabilised through triangulation on one of its sides. The beams would be placed over them (Fig 8.6).

Fig 8.7. Trajan’s Bridge over the Danube. Relief from Trajan’s Column. [Source: Ref (155) Fernández Troyano, L.] Fig 8.6. Julius Caesar’s bridge over the Rhine. Representation by Andrea Palladio in 1570 based on the Emperor’s description. [Source: Ref (155) Fernández Troyano, L.]

Another Roman bridge of huge significance is documented in the reliefs of Trajan’s Column and several coins from that period: the magnificent Trajan’s Bridge over the Danube (Fig 8.7), attributed to Apollodorus of Damascus. It had X-shaped trusses and arches made of concentric pieces connected to other radial ones, with masonry stone piers. The spans were around 35 metres and the total length over a kilometre. In the Renaissance era, Leonardo da Vinci also proposed various structural diagrams of triangulated girders to be used in bridges (Fig 8.8). In the 16th century, Andrea Palladio himself built various wooden bridges, including the Bridge over the River Cismone (Fig 8.9) with a span of 30 metres and made with a truss with metal joints. He also designed various truss girders and arches that are documented in his treatise “I quattro libri dell’architettura” (Venice, 1570), which profoundly influenced the construction of wooden bridges up until the 19th century (Fig 8.10).

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Fig 8.8. Drawings of triangulated girders by Leonardo da Vinci. 16th century. [Source: Ref (155) Fernández Troyano, L.]

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Given their independent evolution, Eastern civilizations developed different bridge typologies than those in the West, examples of which are the successively cantilevered wooden bridges erected in India, China, Japan or Nepal. Some of these managed to attain spans of up to 40 metres by overlapping progressively longer wooden pieces to the point at which the central span could be completed with a simple girder (Fig 8.11). Another noteworthy typology is that exemplified by the Bridge over the River Jhelum in Srinagar, India, made of various piers built by overlapping wooden pieces crossed orthogonally (Fig 8.12).

Fig 8.9. Bridge over the River Cismone. Andrea Palladio. 1570. Elevation and plan. [Source: Ref (229) Mainstone, Rowland J.]

Fig 8.11. Successively cantilevered bridge in Bhutan. [Source: Ref (155) Fernández Troyano, L.]

Fig 8.10. Various proposals by Andrea Palladio for triangulated girders and arches included in his work “I quattro libri dell’architettura”. Venice 1570. [Source: Ref (155) Fernández Troyano, L.]

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Fig 8.12. Bridge over the River Jhelum in Srinagar, India. [Source: Ref (155) Fernández Troyano, L.]

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In 1561, the French architect Philibert Delorme published his book “Nouvelles inventions pour bien bastir et à petit frais”, which included the invention of a new system mainly applied to arches consisting of wooden sheets fixed with pins and keys, also made of wood (Fig 8.14). Furthermore, several variations were proposed; in one, the pins and keys were alternated with wooden clamps. It is interesting to note that the lamination was vertical. Through this system, Delorme erected arches with spans of up to 15 metres, giving rise to the construction of a variety of structures (Fig 8.15 and Fig 8.16).

Both before and even some years after the Industrial Revolution, naval production consumed huge quantities of wood and often needed large scantlings. Huge, high-quality, wooden logs were needed to build the masts for big ships. In making the special pieces required by the ships in large fleets, considerable amounts of wood were therefore wasted. At the same time, both wood and stone were the main raw materials used in construction; on top of that, wood was the main source of fuel before coal. Faced with the imminent depletion of the forests, England resorted to restricting tree felling; subsequently, builders started to have difficulties in finding large scantlings [Ref (317) Somoza Veiga, L.]. From early times, the desire to achieve large spans in both bridges and decks without having to rely on the availability of large wood logs led to proposals for how to make large scantlings by joining small pieces. These proposals are precedents of modern glued laminated timber. In this sense, the first documented ideas are probably those of Leonardo da Vinci, seen in Fig 8.13. The second from the top is of particular interest; it suggests making an arched girder by overlapping two pieces in a sawtooth connection, thus avoiding any slippage between the two. Another treatise writer, Fausto Veranzio, includes a similar example to da Vinci’s in his treaty “Machinae Novae”, published in Venice in 1615, [Ref (315) Laner, Franco].

Fig 8.14. Base of the arches with the Delorme System. 1561. Vertical lamination with wooden pins or clamps. [Source: Ref (314) Laner, Franco]

Fig 8.13. Drawings by Leonardo da Vinci including various proposals for assembling wooden pieces together to get other larger ones. [Source: da Vinci, Leonardo]

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Fig 8.15. Application of the Delorme System to the dome of Ludwigskirche Church in Darmstadt. Georg Moller. 1822-1827. Span: 33 metres. Published in 1884 in the “Trattato generale di construzioni civili” by G.A. Breyman. [Source: Ref (314) Laner, Franco]

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Fig 8.16. Application of the Delorme System for the deck of a gymnasium in Carlsruhe. Published in 1884 in the “Trattato generale di construzioni civili” by G.A. Breyman. [Source: Ref (314) Laner, Franco]

It was not until 1757 when any evolution in Delorme’s system would be seen, namely in the Reichenau Bridge by Hans Ulrich Grubenmann, crossing the Rhine in Switzerland (Fig 8.17). A new system was used in this bridge spanning 67 metres; the wooden planks were joined by bolts to make pieces with both straight and curved directrixes, thanks to a curving process that was followed by bolting. Sawtooth connections collaborated in transmitting the tangential stresses between the planks. As we can see, lamination was carried out horizontally in contrast to the previous system. With this bolted horizontal lamination system, Grubenmann and other authors such as Theodore Burr would go on to build various bridges.

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Fig 8.18. Moscow Manege. Agustín de Betancourt. Frame made of bolted laminated pieces with sawtooth connections. 1817. Span: 32 metres. [Source: its creators]

Bolted lamination would also be applied to building structures. Thus, in 1817, a date that was approaching the era of the first World Expos, the Spanish engineer Agustín de Betancourt built a brilliant example of a deck with a frame made of laminated pieces, the Moscow Manege, which had a span of 32 metres (Fig 8.18 and Fig 8.19).

Fig 8.19. Moscow Manege. Agustín de Betancourt. 1817. Detail of the bolted lamination with sawtooth connections between planks. [Source: its creators]

However, it was in 1828 when Colonel Emy, a French military engineer and Director of Fortifications in Bayonne, would publish his “Description d’un nouveau système d’arcs”; this would mark the dissemination of what would become known as the Emy System. This publication included the construction of laminated arches by curving and bolting planks in a similar fashion to the laminated pieces used by Grubenmann in his bridges, although in this case the sawtooth assembly was dispensed with. We can find an example of this system being applied in the deck of the Ancien Haras d’Aire riding school, in which bolted arches were used (Fig 8.20). A further notable example is the deck of a building in Cincinnati, Ohio (1884) made with two-hinged arches with chords, to which the Emy system was applied (Fig 8.21).

Fig 8.17. Reichenau Bridge over the Rhine, Switzerland. Hans Ulrich Grubenmann. Span of 67 metres. 1757. Horizontal lamination by bolting and a sawtooth connection. [Source: Ref (155) Fernández Troyano, L.]

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Nevertheless, in spite of the aforementioned technological advances, the growth of iron engineering in the 19th century and the appearance of the first large, reinforced concrete structures at the beginning of the 20th century, would mean that these new materials would often substitute wood, generally because of their greater durability and particularly due to their non-flammable nature. A good example of this is the erection of innumerable metal bridges, some of which have been described in Chapter 1 (Fig 1.3 to Fig 1.9), from the end of the 18th century and throughout the 19th century. Now moving on to the field of building, another instance is the gradual substitution of wooden structural elements in English spinning mills following the fires that occurred at the end of the 18th century. This transition is exemplified by the Milford Warehouse by William Strutt (1792-93), wherein the structure was made of cast-iron columns and wooden beams protected from fire by plaster (Fig 1.51). A further example is the Benyons & Marshall Flax Mill by Charles Bage (1796-97), which was the first multi-storey building with a metal structure that included columns and beams (Fig 1.52 to Fig 1.54). The use of wood in the area of building structures was generally circumscribed to the construction of beam and joist floors, or deck frameworks with short or medium spans. In spite of this, there are still some examples to be found in which the lightness of wood is combined with the tensile resistance of the new structural material that was wrought iron; such is the previously mentioned case of the Panorama in the Champs-Élysées built by Hittorff in 1839 (Fig 5.16 to Fig 5.18), in which a wooden framework was hung from iron cables, or the building for the German Song Festival of Dresden (1865) (Fig 5.19 to Fig 5.21 and Fig 8.22) by the architects Eduard Müller and Erns Giese, described earlier. In this case, the deck was made with wooden trusses and hung from cables with opposing curvature, reaching a span of around 45 metres.

Fig 8.20. Ancien Haras d’Aire riding school. Emy system. 1828. [Source: Ref (314) Laner, Franco]

Fig 8.21. Building deck in Cincinnati, Ohio, 1884. Two-hinged arches with chords to which the Emy system was applied. [Source: Ref (314) Laner, Franco]

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Fig 8.22. Inside of the building for the German Song Festival of Dresden. Eduard Müller and Ernst Giese. 1865. [Source: Ref (183) Graefe, Rainer]

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With the exception of these cases that represent uncommon situations, large diaphanous spaces were generally created with iron, steel or concrete structures. Another significant event in the development of wooden structures would occur well into the 20th century: the invention of glued laminated timber by the Swiss Coronel Karl Friedrich Otto Hetzer. He expressed his idea of substituting any type of mechanical joint between the planks, such as bolts or clamps, with a chemical bond in his 1906 patent; it includes a curved structural member with three laminations adhered with natural casein glue (Fig 8.23). His patent from 1900, showing a joist with a varying cross-section, is equally relevant (Fig 8.24). This new glued laminated timber system would be known as the Hetzer system, or “System Hetzerinl-Formen”, and would mark a new stage in the development of wooden structures.

Fig 8.24. Otto Hetzer. Patent for a composite joist glued with casein. 1900. [Source: Hetzer, Otto]

During the First World War (1914-1918), there was a surge in the use of laminated boards in the aeronautical industry, which led to the perfecting of the adhesive compounds used. However, it was in the decade of the ‘40s and coinciding with the aeronautical and naval military developments in World War Two, when the first synthetic glues appeared. Among their advantages over natural glues was their greater resistance to atmospheric agents, as well as to fire. This, in combination with the restrictions imposed on the use of steel during the War, would lead to an increase in the application of glued laminated timber, also employed in the construction of hangars, warehouses and the aeronautical industry (Fig 8.25). Thanks to this switch to wood, 360,000 tonnes of structural steel are estimated to have been saved in 1942 [Ref (318) Jordahl Rhude, Andreas].

Fig 8.23. Otto Hetzer. Patent for laminated timber glued with casein. 1906. [Source: Hetzer, Otto]

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Fig 8.25. The de Havilland Mosquito. A fighter-bomber actively used by the British Royal Air Force (R.A.F.) during WW2. Its airframe was made of wooden laminated planks glued with synthetic adhesive. It was designed by the engineer Geoffrey de Havilland in 1938 with the aim of creating a lighter plane which would not need such a scarce resource as steel in its construction. At that time it was one of the fastest planes in the world, capable of travelling over 600 Km/h. [Source: (Ref (314) Laner, Franco]

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The impetus brought about by the war would continue throughout the second half of the 20th century, giving rise to several structures built with this new material; among the notable examples is the Exhibition Pavilion in Klagenfurt (Austria) by the architect O. Loider, built in 1966 with ten three-hinged arches with spans of 96 metres and a distance between axes of 6.8 metres (Fig 8.26 to Fig 8.28). The cross-section of each arch had a variable depth and was made of two I-section members bolted together at specific points.

Fig 8.29. (Above, left) Artificial Ice Rink in Bern, Switzerland. W. Schwaar and F. Zulauf. 1970. [Source: its creators] Fig 8.26. Exhibition Pavilion in Klagenfurt, Austria. O. Loider. 1966. Three-hinged arches with spans of 96 metres. [Source: its creators]

Fig 8.30. (Above, right) Artificial Ice Rink in Bern, Switzerland. Tightening the cable of one of the cable-stayed arches. [Source: its creators]

Fig 8.31. Artificial Ice Rink in Bern. Two-hinged cable-stayed arches. Span: 85 metres. [Source: its creators]

Fig 8.27. (Left) Exhibition Pavilion in Klagenfurt, Austria. O. Loider. 1966. [Source: its creators] Fig 8.28. (Right) Exhibition Pavilion in Klagenfurt, Austria. Arch with double I-section made of laminated timber glued with synthetic adhesive. [Source: its creators]

Another notable example from this period is the Artificial Ice Rink in Bern, Switzerland, built in 1970 by W. Schwaar and F. Zulauf (Fig 8.29 to Fig 8.32). It is a structure with twohinged laminated timber arches that were cable-stayed at the springers. The singularity of this example lies in the fact that the arches were laminated in such a way as to give the wood a box section. The span of the arches was 85 metres and they measured 48.5 x 120 cm, with a wall thickness of 12 to 15 cm.

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Fig 8.32. Artificial Ice Rink in Bern. Structural details. Note the box section of the glued laminated timber arches. [Source: its creators]

It was in the â&#x20AC;&#x2DC;80s, however, when the biggest surge in the use of glued laminated timber for large spans would take place, mainly due to the technological development in production plants, but also given the huge structural advantages of the material itself, based on the combination of various physical characteristics: a low density and a high resistance to compression and tension parallel to the grain, and therefore to bending as well, thus offering a similar structural performance to steel in the face of these stresses; its greater durability in certain aggressive atmospheres such as those high in chlorides; the possibility of making larger pieces in a variety of shapes, an aspect which partly led to its structural and plastic possibilities being once again mined, and to the development of numerous varied structural designs.

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While there are innumerable relevant examples of structures made with industrial materials derived from wood during the last twenty years of the 20th century, we would like to mention the Oulu Sport Hall in Finland, created in 1985 by R. Harju and P. Heikkilä (Fig 8.33 and Fig 8.34), which had a dome with a span of 115 metres, and the Hamar Olympic Pavilion in Norway, built by Biong & Biong, Niels Torp Architects for the 1994 Winter Olympic Games (Fig 8.35 and Fig 8.36). The latter was designed with two-hinged, transverse, trussed arches with spans of between 48 and 97 metres, while the building was stabilised lengthwise by a 250-metre-span longitudinal arch that was connected to the transverse arches.

Fig 8.35. Fig 8.35. Hamar Olympic Pavilion, Norway. Biong & Biong, Niels Torp Architects. Erected for the 1994 Winter Olympic Games. [Source: its creators] Fig 8.36. Hamar Olympic Pavilion, Norway.1994. [Source: its creators]

Fig 8.33. Oulu Sport Hall, Finland. R. Harju and P. Hikkilä. 1985. Dome with a span of 115 metres. [Source: its creators]

8.2 THE CONTRIBUTION OF THE EXPOS AT THREE KEY MOMENTS Due to the rise of iron architecture as a means of displaying nations’ technological development, wood was not used in a significant way in the first World Expos; as explained previously, this was in spite of the fact that notable progress had been made in wood technology before 1851, the year that marked the first World Expo. Additionally, laminated wood had already facilitated the creation of some relevant constructions with various systems. In any case, and despite the technical innovations, wood had been eclipsed by iron, which had come to be considered the cutting-edge material, the hallmark itself of industrialisation. On the other hand, wood was unable to compete with the increasingly longer spans demanded by exhibition buildings. Note that the spans of the building structures made of wood during the 19th century were less than fifty metres, while the span of the Galerie des Machines from the Exposition Universelle in Paris in 1889, made of iron, was double the length. The German Railway Pavilion for the Exposition Universelle et Internationale in Brussels 1910 was a laminated timber structure made with natural glues and designed by the architect Peter Behrens and the engineer Hermann Kügler from Munich; it was groundbreaking in its typology and the first laminated timber building to be built for a World Expo (Fig 8.37 to Fig 8.39). It held a significant place in history as it meant the application of the Hetzer system with its 1900 and 1906 patents (Fig 8.23 and Fig 8.24), merely four years after the latter patent was published; it was thus one of the first structures known to use the Hetzer system. Its span of 43 metres was truly remarkable, bearing in mind it was one of the first applications of this new structural material. The fact that this building was awarded the Grand Prix for architecture underscores its avant-garde nature. The building was designed with arched portal frames with hinged supports; these portal frames were made of casein-glued laminated timber following Otto Hetzer’s 1906 patent. A metal tie was placed at a height of 8.3 metres to absorb the thrusts generated by this typology. 7.9-metre-joists with variable section were used according to the Hetzer patent from 1900. There was a third structural level made of the same material. In order to facilitate transport, each portal frame was divided into six parts that were connected rigidly on site.

Fig 8.34. Oulu Sport Hall, Finland. [Source: its creators]

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Fig 8.37. German Railway Pavilion in the Exposition Universelle et Internationale in Brussels 1910. Peter Behrens and Hermann Kügler. [Source: Ref (77) Anderson, Stanford]

Fig 8.39. German Railway Pavilion in the Exposition Universelle et Internationale in Brussels 1910. Elevation of the arched portal frame made of casein-glued laminated timber in accordance with Otto Hetzer’s 1906 patent. [Source: its creators]

Fig 8.38. German Railway Pavilion in the Exposition Universelle et Internationale in Brussels 1910. Peter Behrens and Hermann Kügler. Note the application of Otto Hetzer’s patents from 1900 on the joists and from 1906 on the arched portal frames. [Source: Ref (77) Anderson, Stanford]

Nevertheless, it should be made clear that Behrens and Kügler’s structure was an isolated case in the Expos of that time, and failed to hold the significant position in history that could have been expected of it. The First World War would break out only four years later, and in the interwar period there would be a change of direction in the Expos towards the decorative arts and small-scale pavilions. This fact did not help to disseminate the use of laminated wood in the Expos, given that it was a material with a high structural performance that suited large spans. In any case, the impact of this pavilion was enormous on the margins of the Expos. One can draw the conclusion that Europe was introduced to glued laminated timber thanks to the construction of this building in 1910. From that point onwards it developed tremendously, especially in Switzerland. A mere ten years after the Exposition Universelle et Internationale in Brussels, already more than two hundred buildings with glued laminated timber structures had been erected in Europe following the Hetzer system [Ref (318) Jordahl Rhude, Andreas], an example of which is the railway engine shed built in Weimar in 1912 by the Hetzer AG company (Fig 8.40) [Ref (319) Arriaga Martitegui, Francisco].

Fig 8.40. Railway engine shed built in Weimar in 1912 by the Hetzer AG company. It was one of the most immediate consequences of the German Railway Pavilion from the Exposition Universelle et Internationale in Brussels in 1910. [Source: (Ref 319) Arriaga Martitegui, Francisco]

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In contrast, the arrival in the ‘40s of laminated timber glued with synthetic adhesives, longer-lasting and more fire-resistant, had a significant impact on the next important World Expo to be held after the Second World War; in Expo ‘58 in Brussels, out of the forty-five pavilions erected with wooden structures, twenty-five pavilions had laminated timber structures that used a synthetic adhesive. A contributing factor to this was, to a large extent, the intensity of the campaigns organised in Belgium on the part of the “Bureau d’information sur le bois” in 1954, 1955 and 1956, with the aim of promoting timber construction in that country [Ref (137) Devos, Rika / de Kooning, Mil]. On the other hand, Expo ’58 in Brussels marked a rebirth of the structural splendour of the World Expos after World War Two, as described in Chapter 5. The main manifestation of this splendour was in the field of large structures whose mechanical principle was based on tension, although it is also evinced in the considerable number of medium-sized structures made of glued laminated timber with a synthetic adhesive base. One of the most singular examples was the Post Office Pavilion (Fig 8.41 and Fig 8.42), which had a dome with a triangular floor plan made with a mesh structure with glued laminated timber members organised into several structural orders. This structure transmitted the loads to three edge arches with spans of 30 metres. The scantlings varied from a depth of 5 cm up to 90 cm in the edge arches.

Fig 8.43. Information Pavilion in Place Brouckère. Expo ’58 in Brussels. René Sarger. [Source: Ref (137) Devos, Rika / de Kooning, Mil.]

Another highly singular example in Expo ’58 in Brussels was the Information Pavilion in Place Brouckère (Fig 8.43 to Fig 8.45), built by René Sarger, the creator of the magnificent French Pavilion in that same Expo (Fig 5.59 to Fig 5.75). In this case, the building was designed with a hyperbolic paraboloid made of three layers of 2-cm-thick planks, all three of which were solely connected by means of adhesive. The two lower points of the paraboloid lay directly on the foundations. The span between the higher points was 25 metres. The deck was glued on site by twenty operators in the space of thirteen hours under a tent that had been prepared to this effect (Fig 8.45). The scaffolding was removed three days after gluing had finished [Ref (137) Devos, Rika / de Kooning, Mil]. The fact that the planks were completely glued was innovative, and therefore constituted the most important contribution of this building. This technique would be imitated from 1959 onwards, especially in Great Britain where around one hundred and forty wooden hyperbolic paraboloids were erected between 1957 and 1975 [Ref (99) Both, Lionel Geoffrey]. After René Sarger’s Pavilion was built in Expo ’58 in Brussels, there was a clear preference for gluing in the construction of these structures, as opposed to using nails.

Fig 8.41. Post Office Pavilion in Expo ’58 in Brussels. [Source: Ref (114) Casinello, Fernando]

Fig 8.42. Post Office Pavilion in Expo ’58 in Brussels. [Source: Ref (114) Casinello, Fernando]

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Wooden hyperbolic paraboloids derive from their counterparts in reinforced concrete. It should be noted that while the Information Pavilion in Place Brouckère from Expo ’58 in Brussels was not the first hyperbolic paraboloid to be made of wood, it was certainly among the first. The first structure in Great Britain to be designed with hyperbolic paraboloids made of wooden planks was built a year earlier; the Royal Carpet Factory in Wilton (Fig 8.46) made by Hugh Tottenham [Ref (99) Both, Lionel Geoffrey]. It was made up of four hyperbolic paraboloids with sides measuring 17.4 metres each, and comprised of three layers of planks each 1.6 cm thick. In contrast with the Brussels Pavilion, these planks were nailed together, while only the 180-cm perimetral planks were glued to offer greater rigidity against the potential bending of the sheet where it met the edge girders made of glued laminated timber.

Fig 8.44. Information Pavilion in Place Brouckère. Expo ’58 in Brussels. René Sarger. Plan and two cross-sections of the hyperbolic paraboloid. [Source: Ref (137) Devos, Rika / de Kooning, Mil.] Fig 8.46. Royal Carpet Factory in Wilton. Hugh Tottenham. 1957. The first structure with hyperbolic paraboloids made of wooden planks to be built in Great Britain. [Source: Ref (99) Both, Lionel Geoffrey]

There were even earlier examples in the United States, such as the house built in Raleigh in 1954 by the Argentinian architect and professor at the Massachusetts Institute of Technology, Eduardo Catalano. Called Raleigh House or Catalano House (Fig 8.47), it was profusely published at the time, and was even praised by Frank Lloyd Wright. The paraboloid was made up of three layers of wood; in contrast to the Royal Carpet Factory and the Pavilion at Expo ’58 in Brussels, the layers were nailed together all over, while the edges of the sheet were finished off with steel profiles instead of pieces of glued laminated timber.

Fig 8.45. Information Pavilion in Place Brouckère. Expo ’58 in Brussels. René Sarger. Photograph of the gluing process under a tent. [Source: Ref (137) Devos, Rika / de Kooning, Mil.]

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Fig 8.47. Raleigh House or Catalano House. Eduardo Catalano. 1954. [Source: its creators]

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There were also more conventional typologies to be found among the timber structures present in Expo ’58 in Brussels, such as the Town Planning Pavilion, designed with glued laminated timber portal frames and varying cross-section (Fig 8.48). It reflects the typological and formal variety of the timber structures in this Expo.

possibilities of new typologies: space frames and decks based on tension, mainly cable networks, pre-stressed textile membranes and pneumatic structures, in short, typologies that would overshadow the development of timber at these events. The most noteworthy structural manifestations in timber and its derivatives would appear in the ‘90s; in this way, the Expos from this period would pick up the thread in general, historical, chronological terms as described above. In addition to the aforementioned remarkable properties of wood, both mechanical and aesthetic, the focus of the latest Expos would be on the idea of a more environmentally sustainable world. Thus, the purely industrial aspect of the World Expos in the 19th century gave way to a vision of environmental respect and restraint in energy consumption. Paradoxically, the application of this new industrial material, glued laminated timber made with progressively more environmentally-friendly adhesives, would appear to signify a return to the origins of humanity, given that wood is a raw material that harks back to the first structures ever built by mankind. The return to wood through glued laminated timber and other products derived from the same material implies a closer relationship between the industrial world and man and nature, and this through a material that chronologically originated before the Industrial Revolution. In short, the iron architecture linked to the Industrial Revolution prompted a deceleration in the development of wood; nevertheless, it was industrial materials derived from wood which would lead to a structural change of direction towards this raw material. Expo ’92 in Seville and Expo 2000 in Hannover housed numerous pavilions with wooden structures; the latter especially marked the return of the Expo as an exponent of the latest structural technology linked to a material, in the same way that the Expos in the 19th century showcased iron. In addition, Expo 2000 incorporated this new perspective of sustainability that encapsulated a new world view in which the environmental issues created by the excesses of industry were taken into consideration.

In spite of there being many wooden pavilions erected on the occasion of Expo ’58 in Brussels, their value resides not in having been great, individual, historical milestones in the development of wood, but rather in their value as a whole, which contributed to the dissemination among professionals and the general public of the structural and formal possibilities of wood and of laminated wood glued with synthetic adhesives. In the case of the latter, the exhibition buildings would especially show the possibility of creating different geometries, including elements with both straight and curved directrixes with variable cross-sections. On the other hand, they also showcased its application to diverse typologies, such as portal frame structures, arches, ribbed domes or shells such as hyperbolic paraboloids. After this Expo in which timber constructions were presented and promoted, it was not until the end of the 20th century that a pavilion considered groundbreaking within the historical development of wooden structures would appear. Nor would any Expo house a group of wooden structures worthy of mention, despite the fact that there were memorable applications in construction beyond the Expos in the second half of the 20th century, as explained in the previous section; some of these boasted considerable spans that could have adapted perfectly to the demands of the large exhibition pavilions that exemplified the World Expos. From Expo ’58 in Brussels onwards, the image of the structural vanguard centred on the

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Fig 8.48. Town Planning Pavilion. Expo ’58 in Brussels. [Source: Ref (137) Devos, Rika / de Kooning, Mil.]

Along these lines, several countries applied glued laminated timber to a variety of structural typologies in their pavilions in Expo ’92 in Seville. In any case, these pavilions are of unquestionable architectural interest, while their main value lies in the fact that they represent an upturn in the structural use of wood in Expos, thanks to their application in various structural typologies and designs. Nevertheless, these applications do not make any particularly notable contributions to the history of structural systems, given that they involve familiar typologies and small spans. Thus, the Belgian, Finnish or Chilean Pavilions presented portal frame typologies, the Swedish Pavilion displayed a tree-inspired typology and the Hungarian Pavilion had a threehinged arch. The Kuwait Pavilion designed by Santiago Calatrava (Fig 8.49 to Fig 8.51) stood out thanks to the singular way in which wood was applied to a mobile structure, as did the Japan Pavilion in particular (Fig 8.52 to Fig 8.54), where modernity came together with inspiration based on the tradition in oriental architecture of building by overlapping linear elements. The Kuwait Pavilion in Expo ’92 in Seville was made up of an upper, open space, while the exhibition area itself was half-buried. The upper area was protected by a moving deck consisting of sixteen laminated timber ribs that pivoted around two horizontal axes connected to leaning metal columns. Each of these ribs could be individually moved, crossing each other and offering varying shade to the pavilion’s upper square.

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Fig 8.49. Kuwait Pavilion. Santiago Calatrava. Expo â&#x20AC;&#x2122;92 in Seville. [Source: Ref (17) Expo 92 Seville]

Fig 8.50. Kuwait Pavilion. Cross-section in which the movement of the timber ribs can be seen. [Source: Ref (17) Expo 92 Seville]

Fig 8.51. (Opposite page) Kuwait Pavilion. [Source: Ref (17) Expo 92 Seville]

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Created by the architect, Tadao Ando (Fig 8.52 to Fig 8.54), the Japan Pavilion in Expo ’92 in Seville was principally supported by ten very singular columns with capitals made by orthogonally overlapping wooden members; this was inspired by the tradition of oriental architecture in which linear elements are overlapped. In relation to this aspect, reference should be made to the system in Chinese construction in which deck girders are overlapped (Fig 8.55 and Fig 8.56), as well as to the aforementioned successively cantilevered bridges, such as that in figure Fig 8.11 in Bhutan, or the River Jhelum Bridge in Srinagar, India (Fig 8.12), both of which have overlapping wooden linear elements. In spite of the fact that the examples described are not Japanese, it is true that Japan did develop a large part of its architectural practice using continental architecture as a base [Ref (149) Escrig Pallarés, Félix].

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Fig 8.52. Japan Pavilion in Expo ’92 in Seville. Tadao Ando. [Source: Ref (17) Expo 92 Seville]

Fig 8.55 and Fig 8.56. Overlapping of deck girders in Chinese buildings. [Source: Ref (149) Escrig Pallarés, Félix]

Fig 8.53. Japan Pavilion in Expo ’92 in Seville. Tadao Ando. Cross-section. [Source: Ref (17) Expo 92 Seville]

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Fig 8.54. Japan Pavilion in Expo ’92 in Seville. Capital made of the orthogonal overlapping of wooden members. [Source: Ref (17) Expo 92 Seville]

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Expo ’92 in Seville marked a trend towards the structural use of timber and its industrial derivatives; this tendency would reach its highest point in the World Expo held in Hannover in 2000. This Expo, called “Man, Nature, Technology”, would be the ideal ideological frame for the use of structural materials obtained with low energy consumption that were also recyclable and sustainable. In this way, this Expo presents several pavilions whose structure was made of timber, good examples of which are the Swiss Pavilion by Peter Zumthor that was designed with “walls” of stacked planks fastened with tensioners; the Hungarian Pavilion by G. Vadász with “walls” of leaning wood designed with an inner truss of sawn timber; the Hoffnung Pavilion by Buchalla & Partner with two-hinged arches, or the Finnish pavilion by SARC Architects Ltd. that was designed with rigid portal frames made of sawn timber. However, the building which undoubtedly represents this culmination and the return to wood at the end of the century is the Expo-Roof, made by the architect Thomas Herzog and the engineer Julius Natterer to cover the main entrance to the Expo (Fig 8.57 to Fig

Fig 8.57. (Above) Expo-Roof. Thomas Herzog and Julius Natterer. Expo 2000 in Hannover. [Source: Ref (196) Herzog, Verena]

Fig 8.59. Expo-Roof. Thomas Herzog and Julius Natterer. Expo 2000 in Hannover. Cross-section of one of the modules. [Source: Ref (196) Herzog, Verena]

8.64). This construction brilliantly manifests the structural possibilities of wood in all its variations: sawn timber, roundwood, glued laminated timber and micro-laminated timber boards, applied to a daring structural design that demonstrates a new dimension to structures made with timber shells.

Fig 8.58. (Below) Expo-Roof. Thomas Herzog and Julius Natterer. Note the modular aggregation. [Source: Ref (196) Herzog, Verena]

Fig 8.60. Expo-Roof. Photograph of the interior. [Source: Ref (196) Herzog, Verena]

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The building consisted of a large deck made of ten square-plan modules or “umbrellas” measuring 40 metres along the side and with a height of around 26 metres. Each of these modules was comprised of four glued laminated timber shells with double curvature, built with curved, glued laminated timber ribs that crossed. As these ribs were located on a sole surface, they are continuous in one direction, while in the other they are made of fragments fastened to the former. Each shell weighed 36 tonnes and the vertical distance between its lowest and highest points was 6 metres. These shells were supported by four cantilevers of variable section made of laminated timber and micro-laminated timber boards. With a truly remarkable length of over nineteen metres, the cantilevers followed the curve on the underside of the intersection edge of the shells. A large metal piece was installed at the point where the four shells intersected; the cantilevers were connected to this same piece that transmitted the loads to a tower. The metal piece had a base measuring 5.5 x 5.5 m and a height of 7 m.

Fig 8.62. (Left) Expo-Roof. Expo 2000 in Hannover. Connections of the nerves of a shell to the cantilever. [Source: Ref (248) Natterer, J.]

The tower is made up of four 200-year-old silver fir logs from the South of Germany, stiffened by micro-laminated timber boards sawn into triangular shapes and joined with metal pieces. The fir logs were cut longitudinally into two half-sections to accelerate the natural drying-out process. The two half-sections were subsequently bolted together, with timber wedges placed every 50 cm while leaving a gap between the two (Fig 8.63).

Fig 8.63. (Right) Expo-Roof. Expo 2000 in Hannover. Detail of the base of the fir logs. [Source: Ref (248) Natterer, J.]

The modules were connected between them at the ends of the cantilevers and at the shell corners. The deflection generated by dead load and snow and wind loads in an isolated module is 17 cm at the end of the cantilever and 50 cm at the shell corner. When the modules are connected, the deflection is 13 and 36 cm respectively [Ref (248) Natterer, J. / Burger, N. / Müller, A.]. The connection between the shells also prevents the appearance of the effects of torsion due to horizontal wind action on the tower. Reduced models were used to determine the snow loads, as well as in wind tunnel tests. The whole structure was covered by an impermeable membrane that was separated from the timber by 5 cm, thus enabling ventilation of the same. The modules were prefabricated and transported to the building site. In this sense, it was ensured that the connections on site were metal on metal. In short, the contribution made by this building, undoubtedly part of the history of structural systems, resides in bringing together a high level of structural audacity evinced in the remarkable dimensions it achieved, and a brilliant design with considerable complexity in the details, as well as a great variety in the use of timber and products derived from the same. It signified a brilliant display of the enormous possibilities of the new industrial materials made with this raw material, ingeniously synthesizing the return of wood at the end of the Century. The Japanese Pavilion can be found along this same conceptual line in Expo 2000 in Hannover; created by Shigeru Ban and Frei Otto (Fig 8.65 and Fig 8.66), it was made with a cardboard tube structure that was “tensile designed” and later inverted so that the main stress was compression, as described in Chapter 5 (Fig 5.227 and Fig 5.228).

Fig 8.61. Expo-Roof. Thomas Herzog and Julius Natterer. Expo 2000 in Hannover. Exploded view of one of the modules. [Source: Ref (196) Herzog, Verena]

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Fig 8.65. Japanese Pavilion in Expo 2000 in Hannover. Shigeru Ban and Frei Otto. [Source: Ref (88) Ban, Shigeru]

Fig 8.64. Expo-Roof. Thomas Herzog and Julius Natterer. Expo 2000 in Hannover. [Source: Ref (196) Herzog, Verena]

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Fig 8.66. Japanese Pavilion in Expo 2000 in Hannover. Shigeru Ban and Frei Otto. [Source: Ref (244) McQuaid, Matilda]

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On the other hand, Shigeru Ban and the engineer Gengo Matsui had been working on the development of cardboard-based structures since the mid-‘80s. While not wishing to delve too deeply into Ban’s works, on which there are innumerable bibliographical references, the 1998 Paper Dome is worthy of mention; being a vaulted deck, it is the nearest precedent to the Hannover structure, although the structural solutions applied in both are considerably different (Fig 8.67 to Fig 8.70).

Fig 8.67. Paper Dome. Shigeru Ban. 1998. Application of cardboard tubes in a vaulted structure. [Source: Ref (87) Ban, Shigeru]

Fig 8.70. Paper Dome. Shigeru Ban. 1998. Assembly works. [Source: Ref (244) McQuaid, M.]

Shigeru Ban’s studies on cardboard structures were accompanied by experimental campaigns; he carried out axial compression trials with loads of short and long duration, bending trials, and tests in which the influence of temperature and humidity changes on the mechanical properties of cardboard was examined. He additionally trialled different connection types between the tubes, some made of wood and others with metal elements. These experiments were complemented by others that were required by the German authorities for the construction of the Japanese Pavilion, including fire-resistance tests as well as mechanical ones. [Ref (244) McQuaid, M.]. The Japanese Pavilion had a span of 35 metres, a length of 70 and a height of 16. The structure was comprised of 440 recycled cardboard tubes with a diameter of 120 mm, a wall thickness of 22 mm and was more than 40 metres long. These tubes were arranged diagonally to the building axis. The side walls of the building were made with honeycomb cardboard panels, taking the shape of a triangular mesh reinforced with cables and metal connections. The building foundations were made with steel boxes that were scaffolding sheets filled with sand. The translucent enclosure material was a membrane with five layers of waterproof and fireproof paper. Fig 8.68. (Left) Paper Dome. Shigeru Ban. 1998. Connection of the cardboard tubes with glued laminated timber pieces. [Source: Ref (244) McQuaid, M.]

The fundamental concept of the building was based on using recyclable materials; however, there are certain elements that detract from this original idea to a certain extent. In the first place, the structure had to be reinforced with glued laminated timber arches in order to guarantee the stability of a meshed cardboard structure with connections that were hinged as they were made of fabric strips. In addition, a steel cable stabilising net had to be used, while the paper overlay membrane needed to be covered by another made of PVC (Fig 8.71 to Fig 8.73).

Fig 8.69. (Right) Paper Dome. Detail of the structural connection, deck timber sheet and polycarbonate panel. [Source: Ref (244) McQuaid, M.]

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Fig 8.72. Japanese Pavilion. Expo 2000 in Hannover. Reinforcing timber arches and stabilising cable net. [Source: Ref (33) Japanese Pavilion]

Fig 8.73. (Left) Japanese Pavilion. Expo 2000 in Hannover. Connection with fabric strips in between the cardboard tubes and between the tubes and the wooden structure. [Source: Ref (33) Japanese Pavilion] Fig 8.71. Japanese Pavilion. Expo 2000 in Hannover. Shigeru Ban. Structural composition: foundations, cardboard tube structure, timber structure with steel cable triangulation; paper and PVC enclosure membrane. [Source: Ref (88) Ban, Shigeru]

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Fig 8.74. (Right) Japanese Pavilion. Expo 2000 in Hannover. Details of the triangular mesh of the side walls with honeycomb cardboard sheets. [Source: Ref (33) Japanese Pavilion]

Nevertheless, these issues do not diminish the building’s remarkable contribution. In the words of Shigeru Ban himself: “Structural purity is important, but we had to develop a new type of structure using new methods and materials within a limited period of time.” [Ref (87) Ban, Shigeru] The building continues Frei Ottos’s legacy of the Multihalle for the Federal Garden Exhibition in Mannheim, held twenty-five years earlier (1975) (Fig 5.223 to Fig 5.225). Not surprisingly, Frei Otto acted as a consultant to Shigeru Ban on the Japanese Pavilion. Thus, the two buildings have certain points in common; they were both “tensile designed” through inverted models, and both used a system whereby the mesh was assembled on a plane. It should be noted, however, that assembly in Mannheim was effected by elevation of points, whereas in the Japanese Pavilion in Hannover it was carried out by elevation or lowering from an intermediate plane (Fig 8.75 to Fig 8.78).

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Fig 8.79. Japanese Pavilion. Expo 2000 in Hannover. Test in which a cardboard tube is bent to simulate the assembly process. The tube was subsequently fragmented and the fragments subjected to compression tests. [Source: Ref (244) McQuaid, M.]

The pavilion introduced the wide-scale structural use of cardboard, being the largest structure to be built in this material [Ref (254) Otto, Frei] and [Ref (244) McQuaid, M.]. As with iron structures in the 19th century, the pavilion synthesizes the desire to push the limits of knowledge on a material, clearly evinced in the final need to reinforce the structure with timber arches and triangulate it with steel cables.

Fig 8.75, Fig 8.76, Fig 8.77 and Fig 8.78. Japanese Pavilion in Expo 2000 in Hannover. Stages in the assembly process. [Source: Ref (88) Ban, Shigeru]

As mentioned earlier, the nearest precedent to the Hannover structure was the Paper Dome (Fig 8.67 to Fig 8.70) with its span of 27.2 metres, in terms of it being a vaulted deck made with cardboard tubes. In this sense, it should be noted that the Paper Dome had polygonal arches made of fragments of tubes with straight directrixes that were connected by wooden joints. In contrast, the assembly system applied in the Japanese Pavilion was novel, involving bending the cardboard tube during the assembly process. This is another of the Pavilionâ&#x20AC;&#x2122;s contributions, as it led to specific tests being performed in which the cardboard tube was subject to deformation corresponding to the maximum curvature that the piece would undergo during assembly; subsequently, the tube was cut into short fragments which were in turn tested under axial compression in order to detect any potential loss of strength (Fig 8.79). As a result of all this, the Japanese Pavilion in Hannover had an immediate architectural consequence in the dome erected by Shigeru Ban in 2000 in the Museum of Modern Art in New York, clearly inspired by the Japanese Pavilion and building on the experience acquired through it (Fig 8.80 to Fig 8.82). Its span of 26.5 metres is shorter that the Japanese Pavilion and the aim of the structure is not to enclose a space but rather to merely limit it; thus, the main load is the dead load. Nevertheless, its principal contribution is the fact that there are no wooden reinforcing arches; in their place, truss arches were used, formed by two cardboard chords bolted together and steel cable diagonals (Fig 8.81 and Fig 8.82). In this sense, the Japanese Pavilion would mark the jump from a hybrid structure with curved cardboard tubes and wood to a pure, curved, cardboard tube structure.

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Fig 8.80. Dome erected in the Museum of Modern Art in New York. Shigeru Ban. 2000. [Source: Ref (244) McQuaid, M.]

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Nevertheless, it should strictly be pointed out that after the Japanese Pavilion in Expo 2000 in Hannover and its succeeding structure in the Museum of Modern Art in New York that same year, Shigeru Ban would abandon the use of curved cardboard tubes, this in spite of the fact that no weakening in the tubes’ resistance to compression was detected after the curving tests were carried out for the erection of the Japanese Pavilion. Ban’s works in the first half of the 21st century reveal the use of straight tubes with wooden or metal joints in a variety of typologies such as domes or vaults, more in line with the Paper Dome from 1998 (Fig 8.67 to Fig 8.70). In short, we can conclude from the above that wood has played a leading role in the Expos as a structural material, a role that, while discontinuous, is relevant. This protagonism has primarily coincided with three key moments in the history of this material: The first of these is marked by Otto Hetzer’s patents for laminated timber glued with casein, dated 1900 and 1906 (Fig 8.23 and Fig 8.24). These patents had an immediate effect embodied in the German Railway Pavilion for the Exposition Universelle et Internationale in Brussels 1910 (Fig 8.37 to Fig 8.39); this is one of first known structures in which the Hetzer System was applied, and promoted the dissemination of glued laminated timber in Europe. The second key moment was marked by the arrival of glued laminated wood with synthetic adhesives in the ‘40s, which was longer-lasting and fire-resistant. This led to the erection of twenty-five pavilions made with glued laminated wood in the next relevant World Expo held in Brussels in 1958; this ensemble displaying a variety of typologies helped spread the structural and formal possibilities of glued laminated timber among technicians and the general public.

Fig 8.81. Dome erected in the Museum of Modern Art in New York. Shigeru Ban. 2000. [Source: Ref (244) McQuaid, M.]

Fig 8.82. Dome erected in the Museum of Modern Art in New York. Shigeru Ban. 2000. Detail of the stabilisation truss arches. [Source: Ref (244) McQuaid, M.]

The third key moment in the history of wood in the World Expos was heralded by the incredible technological development in products derived from wood at the end of the 20th century, as well as the new architectural currents based on criteria of sustainable energy. One of the most brilliant applications of the former was in the Expo-Roof in Expo Hannover 2000, which was an incredible demonstration of the huge structural possibilities of products derived from wood in all their variations (Fig 8.57 to Fig 8.64). The latter aspect was made manifest in the Japanese Pavilion in the same Expo, made with a cardboard tube structure (Fig 8.65 and Fig 8.66). At the end of the 20th century and following on from the excesses derived from industrialisation, the massive use of metallic materials and a period of great optimism in terms of energy sources, the situation appears to have adjusted itself with a return to origins, to the material of the first constructions: wood. Having passed through industry’s filter, it has gained protagonism as a structural material in the Expos, as well as in a considerable area of architecture in general. As a consequence, and based on the issues discussed above, we should conclude with the fundamental role of the World Expos as a testing ground for new materials and structural typologies, representing true sources of innovation; as the experiences garnered through the Expos overflow into buildings created beyond the scope of the same, they stand out as an intrinsic and unbreakable component in the history of structural building systems.

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AFTERWORD

This book has travelled along a historical overview in which the structural contributions made by World Expo buildings have been interlaced within the context of the general evolution of architectural structures. This has revealed the significant role played by the World Expos in this field; they are genuine test-beds in which new structural typologies and materials have been trialled, in many cases attaining greater spans and extending the limits of knowledge. The World Expos enabled the construction of buildings which progressively incorporated the technological advances that were fundamental to the history of structures, and consequently the history of architecture. Through the global analysis of the events presented in this book, several periods can be differentiated in terms of the development of structures connected to the Expos:

•The first period spans from the first World Expo held in London in 1851 to the beginning of the 20th century. It is characterised by the development of a considerable number of Expos with huge structural protagonism, linked to the peak of iron architecture and engineering. The Crystal Palace is the trigger for a technological surge, giving way to other structural creations beyond the scope of the Expos and resulting in this building being connected to the historical progression of the portal frame, and consequently to the first high-rise buildings from the Chicago School. Each Expo strived to outdo the previous one, in a process that aptly illustrates the nature of these events as areas of exhibition and rivalry among nations in terms of technological development. •The second period encompasses the interval between the beginning of the 20th century and Expo ’58 in Brussels. In the first part of the 20th century, after the First World War (1914-1918), the World Expos primarily turn towards the display of decorative objets d’art, diversifying into small pavilions and abandoning their industrial roots. Behind this was a twofold crisis; on the one hand, an economic crisis, and on the other, what we have called an ideological crisis based on the prolongation of the war and its terrible cruelty originating in the development of arms brought about by industrialisation. In this sense, doubts begin to be cast on the idea of technology and industry as guarantees of welfare and infinite progress. As a consequence, the Expos relinquish the construction of a sole, large building, of a “Palais de l’Industrie”. The Second World War (1939-1945) would also signal a digression in the development of the Expos. While it is true that some interesting constructions were built during the inter-war period,

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there was generally no place for large-span typologies in the pavilions erected at this time. Furthermore, it is hard to find small-scale buildings showcasing any structural innovations worthy of mention. With a few exceptions, technological exhibition yielded centre stage to the recreation of historicist styles, to classical and even regional reinterpretations, and to scattered appearances of rationalist or neoplastic architecture. •The third period covers the interval between Expo ’58 in Brussels and Expo ’92 in Seville. After World War Two, the Expos once again became reference points for the important technological advances developed in the field of structures. This aspect is seen clearly in the enormous level of progress made in the Expos in terms of diversity in structural typologies and new materials: the huge development in structures based on tension (cable nets, pre-stressed membranes), the great steps forward taken in space frames, pneumatic structures (which in part developed thanks to the technology of the Cold War), or the use of new structural products derived from wood. In the wake of the extraordinary structural achievements of the Expos in the 19th century, the World Expo that would inaugurate this new era of splendour was Expo ’58 in Brussels. 1958 truly was the year in which the World Expo would steal the limelight in structural innovation that had languished since the turn of the century, with a few isolated exceptions. From this point onwards, there have been several Expos of great structural significance, among which we can specifically highlight Brussels 1958, Montreal 1967, Osaka 1970 and Seville 1992. During the 19th century, the World Expos identified with iron architecture, iron being a cutting-edge material. In this new era, there were many structural, typological and material representations; while a specific typology may have been predominant, the Expos with structural protagonism could be related to a variety of them. An example of this is Brussels ‘58, which was primarily characterised by tensile structures that were cable-stayed or based on cable nets; nevertheless, glued laminated timber with synthetic adhesives played a leading role at the same time, as did some examples of space frames. Cable nets and space frames typified Expo ’67 in Montreal. On the other hand, Expo ’70 in Osaka gained importance thanks to the presence of pneumatic structures and space frames, although there was also room for cable nets and prestressed membranes. Expo ’92 in Seville stood out in particular thanks to the appearance of pre-stressed membranes and cable nets, with the additional presence of other typologies such as space frames and even some pneumatic structures. In short, it was already common to see individual pavilions devoted to different countries, various regions of the host country and innumerable private companies during this brilliant era. The number of structurally significant buildings in the World Expos greatly increased.

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•The last period defined here encompasses the final two decades of the 20th century, partially overlapping with the last fragment of the previous era, or qualifying it. In this last stage, we observe the growing demand for large, diaphanous spaces capable of housing large crowds of visitors. Thus, enormous sports or multi-purpose spaces, new airport terminals, transport transfer points, and new railway stations all competed for the structural cutting-edge protagonism that had formerly been so closely linked to the World Expos. The culmination of this period would be the World Expo Hannover 2000; christened “Man, Nature, Technology”, it would be the perfect ideological frame for the use of structural materials that were recyclable as well as procured with the minimum of energy consumption, particularly those derived from wood. After the era of optimism in terms of energy resources and the excesses of industrialisation, this environmental criteria opened up a new path which appears to be predominating not only in the World Expos held during the first decade of the 21st century, but also in a considerable part of architecture in general.

There has been no significant fundamental development in new architectural structural typologies in the first two decades of the 21st century. The buildings are essentially sustained by the same typologies, although they do showcase new designs and formalisations arising from the freedom granted by new computer resources. In many cases, the architecture has even achieved a certain level of plastic or sculptural innovation. This aspect of formal experimentation is not new; the architecture of the exhibition pavilion has been quite suitable for this purpose, given that it lacks a rigid functional programme and has often aimed at causing an impact among the public. What has happened is that the previous lack of existing calculation tools guided this innovation towards highly rational, structural shapes that were based on the logic of the physical laws governing our world. Nowadays, computer technology has provided us with practically limitless calculation, representation and manufacturing resources that facilitate the exploration of areas beyond this physical rationality. In short, the evolution of these periods has led to a mannerism in architecture in general terms that has been brought about by computers; this will undoubtedly mark an era that will be justly valued with historical perspective. While this phenomenon may prove to be positive from the perspective of plastic experimentation and innovation in space creation, we should be prudent and not forget that the machine is merely a means; the ultimate aim of architecture should unquestionably be mankind.

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Isaac López César (Ferrol, 1977) is a PhD Architect. University Specialist in the Design and Calculation of Building Structures. Professor of Physics and Structures at the Higher Technical School of Architecture in A Coruña since 2007. He has designed and calculated numerous structures in the spheres of both public and private construction. His research has centred on the field of deployable structures and the history of architectural structures. He is the author of several articles, as well as of a variety of patents related to mobile and deployable structures.

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