Philippe Block, Tom Van Mele Matthias Rippmann, Noelle Paulson
Beyond Bending Reimagining Compression Shells
Philippe Block, Tom Van Mele Matthias Rippmann, Noelle Paulson
Beyond Bending Reimagining Compression Shells
CONTENTS
6 Foreword La Biennale di Venezia 11 Reporting from the Front The War on Bending By Alejandro Aravena 12 In the Footsteps of Vitruvius By John Ochsendorf
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Beyond Bending
17 Beyond the Slab I 20 Building with Weak Material 33 Beyond the Slab II 42 Building with Less Material 55 Beyond the Dome 64 Exploring Form and Forces 79 Beyond Freeform 90 Extending Stereotomy 101
The Making of the Armadillo Vault
103 116
Form and Structure
127 138
Stereotomy and Fabrication
147 170
Construction and Assembly
Engineering the Extreme A Conversation with Ochsendorf DeJong & Block
Informing Geometry A Conversation with the Block Research Group
Balancing Craft and Machine A Conversation with the Escobedo Group
178 Afterword A New Research-Driven Architectural Practice By Gilles Retsin 184 186 187 188 190
Authors Contributors Exhibition and Object Credits Image Credits Bibliography
FOREWORD
La Biennale di Venezia For a world of beams and slabs built with steel-reinforced concrete, compression-only shell structures, which can be extremely thin constructions, offer the potential to drastically reduce material requirements. Building with fewer materials means in turn less environmental strain caused by the construction industry. Drawing from a revival of forgotten principles combined with the latest methods for reimagining the design, engineering, fabrication and construction of compression shells, this book advocates for the logic of such forms. Through in-depth background on the state-of-the-art research, advanced engineering, and highly-skilled masonry craft that resulted in the Armadillo Vault and other innovations exhibited at La Biennale di Venezia, the 15th International Architecture Exhibition in 2016, by the Block Research Group, ETH Zürich, Ochsendorf DeJong & Block, and the Escobedo Group, it demonstrates dramatic ways to move beyond bending. In August 2015, in his role as the newly appointed curator of La Biennale di Venezia, Alejandro Aravena wrote to Philippe Block and John Ochsendorf to invite them to contribute to his exhibition “Reporting from the Front”. Aravena specifically asked Block and Ochsendorf to submit a report from the front of their “War on Bending”. Ideas quickly coalesced to form the plan for an exhibition entitled Beyond Bending. Their goal was to show what can be achieved when reinforced concrete slabs, which normally work in bending, instead take on curved, compression-only forms. A team was formed to include the Block Research Group at ETH Zürich (led by Philippe Block and Tom Van Mele), the engineering consultancy of Ochsendorf DeJong & Block (comprised of John Ochsendorf, professor at MIT, Matthew DeJong, professor at the University of Cambridge, and Philippe Block) and the construction and masonry experts of the Escobedo Group (led by David and Matt Escobedo). Although the team members had been collaborating in various constellations for over 10 years, the invitation to exhibit at the Biennale represented their first opportunity on such a large scale and on the world’s premier stage for architectural innovation. Aravena’s initial invitation included the statement, “The battle for a better built environment is neither a tantrum nor a romantic crusade”. This sentiment also fittingly describes what the team accomplished in Venice. The objects that were displayed in the Beyond Bending exhibition – and whose precedents, principles, and potentials are described in greater depth on the pages that follow – represent efforts toward achieving a better built environment. With their focus on compression-only structures, they show methods for more ap6
propriate construction. They demonstrate more efficient use of materials and labour in various contexts from developing countries in Africa to prosperous, high-income countries like Switzerland. Rather than being romantic attempts at revival for revival’s sake, these structures draw upon historical examples and “lost” techniques that have been reinvigorated and adapted for current technological and fabricational possibilities. Thus, the exhibition carried the subtitle “Learning from the past to design a better future”. Beyond Bending filled an entire room in the Corderie dell’Arsenale, a former workshop for the production of naval ropes, the initial construction of which began as early as 1303. For this exhibition, four examples of vaulted floor systems displayed in two of the corners formed “Beyond the Slab I” and “Beyond the Slab II”; a canvas of 19 form and force diagrams covering one wall constituted “Beyond the Dome”; and the Armadillo Vault, the exhibition’s centrepiece under the rubric of “Beyond Freeform”, spanned an area of 75 square metres. Visitors could enter the exhibition from one of two large, arched doorways. To move through the room, they were forced to either walk around or under the Armadillo Vault, with each path providing different perspectives. The format of this book follows the structure of the exhibition and its headings. “Beyond Bending” describes the objects displayed in Venice. Each section begins with a short explanatory text taken from the original exhibition labels followed by photographs to provide visual context. Then, pages with a shaded background allow for more in-depth, theoretical analysis. These sections each present precedents, principles, and potentials. They indicate past or present references, describe the architectural, computational, and/or structural methods behind the objects, and propose future possibilities for development and innovation. The second section charts the “Making of the Armadillo Vault” through photographs, diagrams, texts, and conversations with the team leaders covering various aspects of the vault’s realisation. This variety of perspectives demonstrates how constraints informed the design, engineering, fabrication, and construction of this remarkable structural achievement.
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Top view and sections of the Beyond Bending exhibition in the Arsenale building of La Biennale di Venezia, showing its main components.
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Original proposal with hand-drawn sketches submitted to curator Alejandro Aravena in ÂSeptember 2015.
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Alejandro Aravena
Reporting from the Front The War on Bending When people look at modern buildings, they tend to describe them as boxes: rectilinear cubic volumes defined by vertical and horizontal lines and elements. It is true that we need flat horizontal surfaces to walk around and use rooms in a reasonably simple enough way, but we tend to assume that the lower side of such surfaces (slabs) and the associated structural components (beams) also have to be flat. For some reason, not only is a horizontal beam seen as something inevitable but it is even seen as structurally desirable. A rectilinear horizontal beam naturally tends to bend. In this bending there are two forces at play: compression in the upper part (particles pushing against each other) and tension in the lower part (particles trying to pull away from each other). The invention of reinforced concrete consists in the introduction of rebars to resist tension, a force that concrete alone cannot support. The problem is that the mass needed in that lower part of the beam is not there to perform any structural operation, but only to protect the steel from rusting; structurally speaking, it is dead weight. This was the starting point of these engineers’ research. They studied old structures like the King’s College Chapel and Guastavino vaults, and concluded that if bending could be avoided and the structure could work only in compression, then something like 70 % of the matter could be saved. This has huge consequences for the weight and amount of matter used in the overall system, with potentially dramatic savings in direct costs. But it also has consequences in the amount of energy saved because less matter is needed – there is less energy spent in the fabrication and less energy spent in the transportation. It even saves time since less material has to be put in place. Using state-of-the-art engineering, software, and robotic prefabrication technology, their research may open a path for a global shift in the building paradigm.
Text from the catalogue of the 15th International Architecture Exhibition - La Biennale di Venezia (May 28th – November 27th 2016). Used with permission.
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Beyond Bending Throughout history, master builders have discovered expressive forms through the constraints of economy, efficiency, and elegance. There is much to learn from the architectural and structural principles they developed. Novel structural design tools that extend traditional graphical methods to three dimensions allow designers to discover a vast range of possible forms in compression. By better understanding the flow of compressive forces in three dimensions, excess steel can be eliminated, natural resources can be conserved, and humble materials like earth and stone can be reimagined for the future. By combining methods from the past with new technologies and fabrication techniques, this exhibition advocated for the logic of compression-only forms. It offered possibilities to move beyond the slab, beyond the dome, beyond freeform, and ultimately beyond bending.
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Beyond the Slab I An arch in compression with a tension tie makes more efficient use of material than a beam in bending. To create masterpieces in unreinforced masonry, great builders of the past discovered stable geometry in compression. The vaults and floor systems here demonstrate that compression geometry can be used to build with minimal steel and with relatively weak material. These structures can be visually exciting with lower cost, lower weight, and lower environmental impact than conventional concrete slabs. Ceramic Tile Vault  Builders have constructed thin tile vaults throughout the Mediterranean region for over 600 years. These vaults require minimal support from below during construction, making them economical to build. In this model, the doubly curved masonry shell carries loads efficiently in compression, and the horizontal thrust is resisted by steel tension ties. Stiffening ribs provide the required depth to carry concentrated loads and to ensure that the thin tiles remain in compression. This historical form serves as an inspiration for new designs in compression. Earthen Vault The masonry materials of a well-designed compression shell do not require high strength because stresses are low. To design for resource constraints, local soil can be used to create stabilised, unfired earth bricks. The earthen shell can serve as a low-cost floor system with dramatically lower environmental impact, up to 90 % less embodied CO₂ than conventional steel and concrete structures. Local masons can be trained in the production and construction of these systems, providing new economic livelihood as well.
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BE YO N D T H E SL AB I
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BE YON D TH E S L A B I
The tile-vaulted floor consists of diaphragms or spandrel walls on the top to stiffen the Âshallow, doubly curved shell underneath. The masonry shell is composed of two layers of thin ceramic tiles bonded with cement mortar
in a herringbone pattern. Four arches on the edges, initially supported by temporary falsework during construction, convey the loads to the supports.
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The Block Research Group and ODB Engineering designed, engineered and managed the construction of the tile-vaulted prototype of a module for the Droneport project by the Norman Foster Foundation and EPFL / Redline, also shown at the 2016 Venice Architecture Biennale.
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Using three-dimensional graphic statics for designing a spatial structure in compression-only allows components made from a weak material – here mycelium, essentially mushroom roots – to be used as load-bearing elements. The installation, a project with Prof. Dirk Hebel of the Karlsruhe Institute of Technology and his team, was shown at the 2017 Seoul Biennale of Architecture and Urbanism.
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Beyond Freeform Like the spectacular Gothic vaults, the cut stone vault at the centre of the exhibition was stable because of its geometry. This piece is not a romantic attempt to revive the Gothic, but rather a direct critique of freeform architecture. Standing without steel reinforcement, the expressively flowing surface highlighted the misconception that complex geometry need go hand-in-hand with inefficient use of material. It demonstrated creative possibilities within very tight design constraints. The Armadillo Vault  The Armadillo Vault embodies the beauty of compression made possible through geometry. Its shape comes from the same structural and constructional principles as the stone cathedrals of the past, enhanced and extended by computation and digital fabrication. Comprised of 399 individually cut limestone voussoirs, unreinforced and without mortar, the vault spans 16 metres with a minimum thickness of only five centimetres. The tension ties equilibrate the form, and its funicular geometry allows it to stand in pure compression. This sophisticated form emerged from the computational, graphic statics-based design and optimisation methods developed by the team. The engineering of the discrete shell also used innovative computational approaches to assess stability. Each stone is informed by structural logic, by the need for precise fabrication and assembly, by the hard constraints of a historically protected setting, as well as by tight limitations on time, budget, and construction. To simplify the fabrication process and avoid the need to flip the stones during cutting, the voussoirs are planar and smooth on the exterior. Their interior sides are marked by a series of grooves resulting from initial rough cutting. Rather than mill these surfaces away, they remain as an expressive feature, aligned with purpose to serve as visual reminders of the force flow. After its initial fabrication and test assembly in Texas, the vault was disassembled and shipped to Venice, where it was reassembled on site in just two weeks. Like an intricate 3D puzzle, it can be deconstructed and built again at future locations. 79
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The Making of the Armadillo Vault The Armadillo Vault is the result of extreme constraints in time, budget, weight, size, and geometry. Many of these constraints were determined by its location inside the Corderie dell’Arsenale in Venice, a historically protected building. In this context, designing, engineering, and assembling a self-supporting structure without any cranes or other heavy equipment presented challenges but also motivated innovations. The team combined their deep knowledge of traditional techniques in masonry with cutting-edge methods in computational form finding and analysis to create a soaring stone vault – proportionally as thin as a third of an eggshell – that seemed to grow out of the Arsenale itself. Furthermore, as the images, analyses, and conversations in this section demonstrate, the Armadillo Vault is truly an international structure – a vault of Texas limestone blocks, quarried and cut near Austin and shipped across the Atlantic to Venice. Combining the best of computation and craft, machine and handwork, researchers, engineers, and skilled master masons on two continents orchestrated the complexities of its form finding, fabrication, test assembly, shipment, and final assembly in the course of a few months. Although the exhibition in Venice was temporary, the team hopes the Armadillo will soon find a permanent home to stand again as an embodiment of what can be achieved when we move beyond bending.
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Form and Structure The Armadillo Vault is essentially a giant, intricate, three-dimensional puzzle of 399 limestone blocks. Its shape, which allows it to stand in pure compression, unreinforced and without mortar or mechanical connections between the stones, is the result of a form finding and optimisation process applying Thrust Network Analysis. This geometry-based approach to the exploration of structural forms – using computational inverted hanging models – facilitated the integration of assembly and fabrication constraints as well as architectural and functional requirements from the early design stages to create a dramatic and structurally surprising centrepiece for the exhibition.
Roughly triangular in plan, the stone surface wrapped around the existing columns in the exhibition space. Wide steel supports distributed the vault’s weight evenly over the historic floor. A system of ties connecting the outer supports absorbed the horizontal thrust, leaving only vertical reaction forces.
Design Various designs for the vault were first sketched on paper, laying out different combinations of features in response to the distinct characteristics of the exhibition space in the Corderie dell’Arsenale. The spatial qualities and overall structural performance of selected alternatives were further investigated through three-dimensional equilibrium studies with RhinoVAULT, a form-finding tool based on Thrust Network Analysis, for the design of compression-only surface structures. The chosen design had a roughly triangular shape in plan, covering an area of approximately 75 square metres with only four supports: one in the middle of the structure and three along the boundary. Large edge arches spanning more than 15 metres in various directions allowed the exhibition space to flow freely underneath, while two of the old masonry columns of the historic building pierced through large, oval-shaped openings in the stone surface of the structure.
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FO R M AN D ST R U CT URE
Form Finding The dominant self-weight of the vault was taken as the design load to define the funicular geometry of the middle surface of the structure. As the weight itself is a function of the geometry of this surface and locally assigned non-uniform thicknesses, this was an iterative process during which the overall design of the vault was continuously refined. Each iteration consisted of three steps. First, a thrust network was generated using form and force diagrams to explicitly control the reciprocal relationship between the direction and layout of force paths in three-dimensional force networks and the magnitude of forces in equilibrium along those directions, respectively. From this, a smooth control mesh was generated that allowed for more sculptural modifications to the geometry. A key concern was to have high positive double curvature everywhere in the shell. Finally, since the previous step did not necessarily maintain (compression-only) equilibrium, the closest possible thrust network to this modified design was generated using a “best fit” algorithm. One of the openings in the surface was pulled towards the ground to increase local double curvature even further, while maintaining an overall shallow design that evenly distributed the weight over all four supports. Because of the stress limitations on the floor, it was crucial to reduce the weight of the stone shell as much as possible. By increasing curvature, the effective structural depth necessary to resist asymmetric live loads could be increased through geometry rather than by adding mass. Based on material tests, it was determined that the minimum required thickness of the blocks was five centimetres. With large safety factors applied, this was the limiting thickness at which spalling of the stone due to eccentric loads at the interfaces could start occurring. For aesthetic reasons and to increase stability, the thickness was gradually increased towards the supports to 8 centimetres at the linear supports and 12 centimetres at the springing points on the boundary and in the middle.
Top: The distribution of horizontal forces that “best fits” the designed shell geometry with a compression-only thrust network for the assigned stone thickness is represented by (and controlled with) a force diagram. This two-dimensional equilibrium corresponds to a specific distribution of the horizontal forces along the edges of the three-dimensional thrust network.
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Right: An overview of early design options sketched digitally with RhinoVAULT, the free software plugin based on Thrust Network Analysis for the exploration of compression- only geometry under vertical loading, developed by the Block Research Group.
FOR M AN D STR UCTUR E
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The shell’s funicular geometry was carefully sculpted using advanced TNA-based form-finding and optimisation tools available through the Block Research Group’s open source computational framework, compas.
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Large blocks of the mild Texas Cream limestone being quarried. Part of the reason for choosing this stone was its few natural flaws, meaning that less of the stone was wasted.
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Some of the cut voussoirs waiting for the test assembly.
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AUTHORS
The Block Research Group (BRG), part of the Institute of Technology in Architecture at ETH Zürich, focuses its research on equilibrium analysis, computational form finding, optimisation and construction of curved surface structures, specialising in unreinforced masonry vaults and concrete shells. As part of the Swiss National Centre of Competence in Research (NCCR) Digital Fabrication, the BRG develops innovative, structurally informed bespoke prefabrication strategies and novel construction paradigms employing digital and robotic fabrication. The BRG translates its research in unique demonstrators, such as the ETH Pavilion using recycled waste for Ideas City 2015 in NYC, the unreinforced, cut-stone Armadillo Vault and the soil-pressed tile-vaulted Droneport at the Venice Architecture Biennale 2016, and the NEST HiLo research unit with its extremely thin concrete shells in Dübendorf, Switzerland. Philippe Block is professor and co-director of the BRG, and is the director of the NCCR Digital Fabrication. He studied architecture and structural engineering at the Vrije Universiteit Brussel (VUB) in Belgium and at the Massachusetts Institute of Technology (MIT) in the USA, where he earned his PhD under the guidance of Prof. John Ochsendorf in 2009, developing Thrust Network Analysis (TNA), an innovative approach for assessing the safety of historic vaulted structures with complex geometries and designing compression-only shells. With the BRG and as partner of the consultancy Ochsendorf DeJong & Block (ODB Engineering), he provides structural assessment of historic monuments and design and engineering of novel compression shell structures. Tom Van Mele is senior researcher and co-director of the BRG, where he has led research and development since 2010. In 2008, he received his PhD from the Department of Architectural Engineering at the Vrije Universiteit Brussel (VUB). His current research projects include the analysis of collapse of masonry structures, the engineering of flexible formwork systems for concrete shells, and the development of graphical design and analysis methods. He is the developer of the BRG’s web-based interactive teaching and learning platform, eQUILIBRIUM, and its open-source computational research framework for architecture, structures and fabrication, compas. Matthias Rippmann has been a member of the BRG since 2010, where he obtained his doctorate in 2016. Currently, he is a postdoctoral researcher, leading the BRG’s digital fabrication research in the NCCR Digital Fabrication. He conducts research in the field of structurally informed design and digital fabrication. He is the developer of the form-finding software RhinoVAULT, which offers TNA-based exploration of funicular shells. He studied architecture at the 184
University of Stuttgart and the University of Melbourne. He worked in Stuttgart at Behnisch Architekten, LAVA, the Institute for Lightweight Structures and Conceptual Design and Werner Sobek Engineers. In 2010, he co-founded the architecture and consultancy firm Rippmann Oesterle Knauss GmbH (ROK). Noelle Paulson completed her Master of Arts and doctoral degrees in nineteenth-century European art history at Washington University in St. Louis, Missouri, USA. Since moving to Switzerland in 2009, she has worked as a freelance art historical writer, editor and consultant as well as an executive assistant in the field of architecture and urban design. Her essays on late nineteenth-century French painting have appeared in museum exhibition catalogues for the National Gallery of Canada, Ottawa, the Phillips Collection in Washington D.C., and Kunstmuseum Winterthur, among others. A recipient of numerous travel and research fellowships, she has presented public talks in the U.S., Canada, and the U. K. She joined the direction of the Block Research Group as Administrative Coordinator in 2015.
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CONTRIBUTORS
Alejandro Aravena, a Chilean architect and executive director of Elemental S.A., curated the 15th International Architecture Exhibition – La Biennale di Venezia in 2016. He is also the recipient of the 2016 Pritzker Architecture Prize. Matthew DeJong, a structural engineer specialising in earthquake engineering and the analysis of masonry structures, is senior lecturer (associate professor) in engineering at the University of Cambridge, and a partner at Ochsendorf DeJong & Block. A former Fulbright scholar, he received his PhD from Massachusetts Institute of Technology (MIT) in 2009. David Escobedo is founding owner of the Escobedo Group where he leads a six-division, vertically-integrated general contracting firm. His primary focus is innovating the building process through digital fabrication and computation for complex and challenging structures in steel, stone and millwork. Matt Escobedo is General Manager of the Escobedo Group where he oversees the construction process for all divisions. His primary focus is providing holistic, hands-on management in the field, as well as facilities operations internally. John Ochsendorf, a structural engineer specialising in the history, preservation, and design of masonry vaulting, is the Class of 1942 Professor in the Departments of Architecture and Civil and Environmental Engineering at the Massachusetts Institute of Technology (MIT) and a partner with Ochsendorf DeJong & Block. In 2017 he was appointed the 23rd director of the American Academy in Rome. Gilles Retsin, a London-based architect, is lecturer and programme director of the M.Arch Architectural Design course at the Bartlett School of Architecture, University College London. He holds a Masters in Architecture + Urbanism (Dist) from the Architectural Association School of Architecture Design Research Laboratory (AA.DRL).
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EXHIBITION AND OBJECT CREDITS
Exhibition Concept Philippe Block, John Ochsendorf
3D-printed floor: Block Research Group, ETH Zürich – Matthias Rippmann, Ursula Frick, Andrew Liew, Tom Van Mele, Philippe Block
Authors Block Research Group, ETH Zürich Ochsendorf DeJong & Block Escobedo Group
Beyond the Dome Block Research Group, ETH Zürich – Matthias Rippmann, Robin Oval, Tomás Méndez Echenagucia, Tom Van Mele, Philippe Block
Texts Philippe Block, John Ochsendorf, Tom Van Mele, Noelle Paulson
Beyond Freeform – Armadillo Vault
Design Block Research Group, ETH Zürich – Philippe Block, Edyta Augustynowicz, Matthias Rippmann Lighting Lichtkompetenz, Artemide Sponsors Kathy and David Escobedo ETH Zürich – Department of Architecture MIT – School of Architecture+Planning NCCR Digital Fabrication Artemide Swiss Arts Council – Pro Helvetia Universitat Politècnica de València Fundación José Soriano Ramos
Structural design & Architectural geometry: Block Research Group, ETH Zürich – Philippe Block, Tom Van Mele, Matthias Rippmann, Edyta Augustynowicz, Cristián Calvo Barentin, Tomás Méndez Echenagucia, Mariana Popescu, Andrew Liew, Anna Maragkoudaki, Ursula Frick Structural engineering: Ochsendorf DeJong & Block – Matthew DeJong, John Ochsendorf, Philippe Block, Anjali Mehrotra Fabrication & Construction: Escobedo Group – David Escobedo, Matthew Escobedo, Salvador Crisanto, John Curry, Francisco Tovar Yebra, Joyce I-Chin Chen, Adam Bath, Hector Betancourt, Luis Rivera, Antonio Rivera, Carlos Rivera, Carlos Zuniga Rivera, Samuel Rivera, Jairo Rivera, Humberto Rivera, Jesus Rosales, Dario Rivera
Objects Beyond the Slab I Salvador Gomis Aviñó, Salvador Tomás Márquez, Jonathan Dessi-Olive, Camilla Mileto, Fernando Vegas López-Manzanares, Javier Gómez Patrocinio, Benjamin Ibarra Sevilla, John Ochsendorf Beyond the Slab II Concrete floor: Block Research Group, ETH Zürich – Dave Pigram, Tomás Méndez Echenagucia, Andrew Liew, Nick Krouwel, Tom Van Mele, Philippe Block
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IMPRINT
Authors Philippe Block, Tom Van Mele Matthias Rippmann, Noelle Paulson Editor Sandra Hofmeister Project management Sandra Hofmeister, Eva Herrmann Copy editing Raymond Peat Julian Jain Design concept Naida Iljazovic Graphic design / Cover Katja Römer Drawings Block Research Group, ETH Zürich Ralph Donhauser Production / DTP Roswitha Siegler Reproduction ludwig:media, Zell am See Printing and binding Grafisches Centrum Cuno GmbH & Co. KG, Calbe
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