Diagrid Structures: Systems, Connections, Details

DIAGRID STRUCTURES SYSTEMS CONNECTIONS DETAILS TERRI MEYER BOAKE

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WHAT IS A DIAGRID?

The word “diagrid” is a blending of the words “diagonal” and “grid” and refers to a structural system that is single thickness in nature and gains its structural integrity through the use of triangulation. Diagrid systems can be planar, crystalline or take on multiple curvatures. Diagrid structures often use crystalline forms or curvature to increase their stiffness. This differentiates a diagrid from any of the three dimensional triangulated systems such as space frames, space trusses or geodesic structures, although it will be shown that some of the developments of diagrid structures have been derived from the details of these 3‐D systems. The diagrid structural systems that will be explored in this book will focus on the use of diagrid systems in the support of buildings, predominantly examining the perimeter systems that have come to be associated with mid‐rise to tall buildings. These perimeter diagrids normally carry the lateral and gravity loads of the building and are used to support the edge conditions of the floors.

Diagrid type systems are also being used as roofs to create large column free clear spans. These types of (predominantly steel) systems have been derived from lamella structures. Where lamella structures may be made from a variety of materials, they predominantly use wood. The majority of lamella structures use a diamond grid and tend not to triangulate. The structural ideas behind the wood lamella contributed to the evolution of the steel lattice grid. Lattice grids are seeing increased use as a structural support system to enable the glazing of large courtyards and enclosed spaces. Lattice grids are designed to span relatively large distances without columns and they typically do not support floor loads. The steel detailing of the lattice grid system is significantly different from that of the perimeter structural diagrid for larger buildings. This type of structure was addressed in my previous book “Understanding Steel Design: An Architectural Design Manual” in the Chapter12: Steel and Glazing Systems.

The design and technical exploration of diagrid structures addressed in this book will build on the introductory material addressed in “Understanding Steel Design: An Architectural Design Manual” in Chapter 9: Advanced Framing Systems: Diagrids.

THE INTENTIONS OF THIS BOOK

Although diagrids have their formative roots in engineering, this book is designed to explore a wide range of questions surrounding their contemporary use in service to architecture. This is not a book with calculations and it is not intended to replace the very necessary collaborative discussions that must take place amongst the architect, engineer and steel fabricator. The text will reference issues of scale and not the absolute size of members. Scale is a very important factor when looking at the relationship between the relative size and exposure of the steel structures to the spaces that they create and define. This would apply to the ultimate impact of diagrid structures on interior spaces as well as urban environments. Diagrid buildings tend to be purposefully selected to function as unique or iconic projects, and the diagrid has been employed to make the building stand out rather than blend into the surrounding urban fabric.

FROM SHUKHOV TO FOSTER

The origins of the diagrid structural typology lay at the crossroads of engineering and architecture. Engineering first as the initial explorations by Shukhov were intended to provide a structural system that served a civic works function that was not necessarily “architecture” in the purest sense of the word. The initial details and member choices were fairly utilitarian and simple. It is very important that Norman Foster has referenced the work of Shukhov as an inspiration for his diagrid explorations. This affirms the use of Shukhov’s towers as a precedent for buildings such as Swiss Re (30 St. Mary Axe) and the Hearst Magazine Tower. It also allows us to examine the changes that were made to the method of detailing and construction as the hyperbolic paraboloid form transitioned from a “hollow” tower to one that needed to support floor loads and was clad. This is a tremendous change in the role of the structure and the implications on the design, detailing and construction processes undertaken by Foster and ARUP in Swiss Re were significant. The decisions taken in the design of Swiss Re and the Hearst Magazine Tower continue to inform all variations of the diagrid to this date.

DIAGRID STRUCTURES: SYSTEMS, CONNECTIONS, DETAILS

Terri Meyer Boake

TABLE OF CONTENTS

PREFACE

1.

A COLLABORATIVE PROCESS  FROM SHUKHOV TO FOSTER  THE INTENTIONS OF THIS BOOK  THE IMPORTANCE OF COLLABORATION  THE ROLE OF BIM  WHY CHOOSE A DIAGRID?  DIAGRID DECISIONS, STEP BY STEP

2.

EARLY EVOLUTION OF DIAGRID FRAMING SYSTEMS  BIRTH OF THE DIAGRID IN RUSSIAN CONSTRUCTIVISM  THE IMPACT OF THE MODERN MOVEMENT  GEODESIC DOMES AND SPACEFRAMES  THE EMERGENCE OF THE DIAGONALIZED CORE TYPOLOGY  THE APPEARANCE OF THE DIAGRID SUPPORTED OFFICE BUILDING  THE FORMATION OF THE CONTEMPORARY DIAGRID  A TIME OF STRUCTURAL CHOICE: Diagonalized Cores, Outriggers and Mega Columns

3.

THE DEVELOPMENT OF THE CONTEMPORARY DIAGRID  THE CONCEPT AND DEFINITION OF A DIAGRID  EXPLORING THE POSSIBILITIES OF DIAGRID SYSTEMS  STRUCTURAL BENEFITS  THE FIRST CONTEMPORARY DIAGRID BUILDINGS o PROJECT PROFILE: LONDON CITY HALL | FOSTER+PARTNERS, ARUP o PROJECT PROFILE: SWISS RE | FOSTER+PARTNERS, ARUP o PROJECT PROFILE: HEARST TOWER | FOSTER+PARTNERS, WSP CANTOR SEINUK

 TIMELINE SHOWING THE PROJECTS IN THIS BOOK

4.

TECHNICAL REQUIREMENTS  DESIGNING FOR PERFORMANCE  WIND TESTING  SEISMIC DESIGN  FIRE PROTECTION SYSTEMS o Occupant Safety o Spray Applied Systems o Concrete Filled Tubes o Intumescent Coatings

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MODULES AND MODULARITY ISSUES OF SCALE AND SHAPE GOVERNING STRUCTURAL PERFORMANCE CRITERIA MODULE SELECTION CRITERIA OPTIMIZING THE MODULE FOR STRUCTURAL PERFORMANCE OF TALL BUILDINGS BRACING OF THE DIAGONAL MEMBERS MODULES AND CORNER CONDITIONS IMPACT OF THE MODULE ON THE NODE IMPACT OF THE MODULE ON THE FAÇADE APPLICATIONS OF MODULES o Small Modules: 2 to 4 Storeys o Mid Size Modules: 6 to 8 Storeys o Large Modues: 10+ Storeys o Irregular Modules NODE AND MEMBER DESIGN WHAT IS A NODE? MATERIAL CHOICES THE BASIS FOR NODE DESIGN: SWISS RE AND HEARST THE IMPACT OF EXPOSURE ON DESIGN AND DETAILING o Concealed Systems o Architecturally Exposed Systems NODE ADAPTATIONS FOR CONCEALED SYSTEMS NODE ADAPTATIONS FOR ARCHITECTURALLY EXPOSED SYSTEMS CORE DESIGN MATERIAL TRENDS IN TALL BUILDING DESIGN THE IMPACT OF 9/11 ON CORE DESIGN THE PURPOSE OF A CORE IN A DIAGRID BUILDING STEEL FRAMED CORES o Centered Steel Cores o Offset Steel Cores o Steel Cores Outside of the Building o Steel Cores for Hybrid Diagrid Buildings REINFORCED CONCRETE CORES o Centered Concrete Cores o Concrete Cores for Narrow Plans o Concrete Cores for Highly Eccentric Loading o Concrete Cores for Supertall Buildings CONSTRUCTABILITY SAFETY ISSUES ARCHITECTURALLY EXPOSED VERSUS CONCEALED STEEL ECONOMY THROUGH PREFABRICATION AND REPETITION IMPACT OF NODE AND MODULE CHOICES ON ERECTION TRANSPORTATION ISSUES STAGING AREA AND SITE RELATED ISSUES MAINTAINING STABILITY DURING ERECTION

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FAÇADE DESIGN CLADDING AND FAÇADE TREATMENT TRIANGULAR GLAZING RECTILINEAR GLAZING INTERMEDIARY GLAZING SUPPORT, LATTICE GRIDS

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EXTERIOR DIAGRIDS WHEN AN EXTERIOR DIAGRID IS APPROPRIATE ISSUES WITH EXTERIOR STRUCTURAL DIAGRIDS DIAGRIDS AS DOUBLE FAÇADE SUPPORT SYSTEMS

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CONTEMPORARY PROJECTS

 TALL BUILDINGS o THE LEADENHALL BUILDING, LONDON, ENGLAND

ROGERS STIRK HARBOUR AND PARTNERS W/ ARUP o CAPITAL GATE, ABU DHABI, UAE RMJM ARCHITECTS o GUANGZHOU INTERNATIONAL FINANCE CENTER, GUANGZHOU, CHINA

WILKINSON EYRE ARCHITECTS W/ ARUP o ARCELORMITTAL ORBIT TOWER, LONDON, ENGLAND

ANISH KAPOOR, CECIL BALMOND W/ ARUP o DOHA TOWER, DOHA, QATAR ATELIERS JEAN NOUVEL

 UNCONSTRUCTED VISONARY PROJECTS o LOTTE SUPER TOWER, SEOUL, KOREA

SOM o CITIC TOWER, BEIJING, CHINA

TFP ARCHITECTS