Parametricism

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position statement

With the growth of the world’s population, the building industry will have an ever increasing environmental impact through its dramatic use of resources. Because it can be moulded into any shape desired, concrete is currently the most widely used building material.

Its production relies heavily on the use of aggregates and freshwater, while the world's yearly cement production accounts for more than five percent of the global carbon dioxide emissions. The challenge presented by a natural resource depletion and the necessity of reducing greenhouse gas emissions is an opportunity for innovation, where lightweight construction is increasingly more important. Reducing the amount of material and waste associated with construction is key as the embodied carbon of a building is predicted to be the main energy consumption component by 2050. In this respect, structural geometry (e.g. doubly-curved shell forms) can play a significant role in reducing the amount of material required, thus also reducing a structure’s weight and its stresses.

By designing structures that intelligently include structural performance and architectural geometry, previous generations of designers and structural engineers, like Robert Maillart, Félix Candela or Pier Luigi Nervi, demonstrated the interconnectedness of efficiency, elegance and economy.

By harnessing the power of well-thought-out structural design, efficient structural forms, such as shells or vaults, can significantly reduce material volume by placing it only where needed, according to the natural flow of internal forces for all loading cases. Thanks to their ability to uniformly distribute the load across their section, doubly-curved, rib-stiffened shells, and compression-only forms - in particular - offer the possibility of increasing the load-bearing capabilities of a structure in a material efficient and economical way. These structures have expressive, intricate and non-repetitive geometries and can therefore be challenging to build using traditional methods. This moves the problem of labour, cost and waste from the structure to the mould (formwork) needed to build it.

Formworks are usually bespoke constructions of cut timber or milled foam that often cannot be reused and are disposed of after construction. These systems often include scaffolding to support a heavy mold and depending on the intricacy of the design are also very costly (50-75% of the structure’s cost). To harness the full potential of these structures, the formwork systems used for non-standard and non-repetitive concrete construction need to be rethought.

Digital fabrication has created opportunities for exploring new material systems and for realising complex or unique forms using precise processes. The KnitCandela pavilion built at the Museo Universitario Arte Contemporáneo in Mexico City, in collaboration with the Computational Design Group (ZHCODE) of Zaha Hadid Architects and Architecture Extrapolated (R-Ex) demonstrates the possibilities brought by using a fabric formwork system as an alternative to traditional construction.

As an incredibly economical and efficient system through and through, the flexible formwork approach demonstrated in KnitCandela targets all those areas where project timelines and budgets often get out of control without sacrificing elegance along the way. Most importantly, it confronts the considerable challenges the industry now faces, offering practical, easily realisable, and elegant solutions for a more sustainable way of building.

KEYWORDS

Structural geometry, parametric design, flexible formwork, material efficiency, 3D knitting, concrete construction

project

KnitCandela - A flexibly formed, thin concrete shell at MUAC, Mexico City

KnitCandela is a thin, sinuous concrete shell built on a ultra-lightweight knitted formwork that was carried from Switzerland to Mexico in a suitcase.

GENERAL INFORMATION

Built at the Museo Universitario Arte Contemporáneo (MUAC) in Mexico City as part of the first exhibition of Zaha Hadid Architects in Latin America (20.10.2018 - 03.03.2019), KnitCandela is an homage to the famous Spanish-Mexican shell builder Félix Candela (1910 - 1997). It reimagines his spectacular concrete shells through the introduction of novel computational design methods and the KnitCrete formwork technology.

The shell’s dynamic geometry is inspired by the fluid forms of the traditional and colourful dress of Jalisco, Mexico. The builders’ nickname for the project was 'Sarape', which is a scarf or poncho with a stripe pattern. The shape also pays homage to Candela’s famous restaurant at Xochimilco, a trope he repeated in several subsequent projects.

While Candela relied on combining hyperbolic paraboloid surfaces (or “hypars”) to produce reusable formworks and thus reduce construction waste, KnitCrete allows for the realisation of a much wider range of anticlastic geometries. With this cable-net and fabric formwork system, expressive, freeform concrete surfaces can now be constructed efficiently, without the need for complex moulds. KnitCandela’s thin, doubly-curved concrete shell with a surface area of almost 50 m2 and weighing more than 5 tonnes, was applied on a KnitCrete formwork of only 55 kg. The knitted fabric of the formwork system was brought to Mexico from Switzerland in a suitcase.

COLLABORATION

Designed and constructed by multiple teams in Europe and Mexico, the realisation of KnitCandela is the result of a collaborative effort that harnessed collective expertise in computational design, engineering and fabrication. The architectural design is the latest expression of the evolving search of the Computational Design Group of ZHA (ZHACODE) for designs that utilise structural and constructional features to enhance the spatial experience of the user. For the realisation of this expression, the Block Research Group (BRG) of ETH Zurich introduced the KnitCrete formwork technology and developed the structural design and construction system. Architecture Extrapolated (R-Ex) managed the execution of the project on site in Mexico City as part of its continued engagement in the digitisation of building trades in Mexico.

The realisation of the project within very tight time, space and budget constraints is thus a demonstration of the rapid evolution and adaptation of digital design and fabrication to the challenges faced by the building industry. This project further highlights a social aspect of combining digital fabrication and manual craft and construction: provision of meaningful and challenging tasks to builders, the digital enhancement of their manual skills and its positive impact on their career prospects, etc.

KNITCRETE

KnitCrete is a novel, material-saving, labour-reducing and cost-effective formwork system for the casting of doubly curved geometries in concrete. The KnitCrete technology is being developed at ETH Zurich by the Block Research Group in collaboration with the Chair for Physical Chemistry of Building Materials, as part of the Swiss National Centre of Competence in Research (NCCR) in Digital Fabrication.

KnitCrete formworks use a custom, 3D-knitted, technical textile as a lightweight, stay-in-place shuttering, coated with a special cement paste to create a rigid mould, and supported by additional falsework elements such as a tensioned cable-net or bending-active splines. Compared to conventional weaving, knitting minimises the need for cutting patterns to create spatial surfaces, allows for the directional variation of material properties, and simplifies the integration of channels and openings, for example, for the insertion of additional formwork elements, insulation, reinforcements, electrical components and technical systems for heating and cooling.

The hybrid and ultra-lightweight KnitCrete formworks are thus easily transportable, reduce the need for additional supporting structure and scaffolding, and simplify the logistics on the construction site.

KNITCANDELA

The 50 m2 of textile shuttering of the formwork for KnitCandela is made up of four long strips ranging from 15 m to 26 m in length. Each of the four pieces is a seamless, double-layered textile produced in one go. The two layers of the textile fulfill different tasks. The visible inside is an aesthetic surface that displays a colourful pattern and reveals traces of the supporting cable-net falsework system. The backside fulfils technical needs by including features for inserting, guiding and controlling the position of additional formwork elements.

The pockets created between the two layers as part of the spatial knitting process are inflated using standard modeling balloons. These inflated pockets become cavities in the cast concrete, forming a structurally efficient waffle shell without the need for a complex, wasteful formwork. On the technical side of the textile, the pockets have different knit densities to control the inflated shape and openings for the insertion of the balloons, such that differently sized cavities can be created with one standard balloon size.

The interplay between the soft, warm, colourful fabric on the inside of the shell and its hard, cold concrete exterior is visible from all viewing angles. The stripe pattern visualises the short rows typical of the knitting fabrication process and expresses the radial symmetry of the shape. The pattern along with the simultaneous visibility of the soft inside and the hard outside of the shell, enhances the spatial experience of the curvatures of the shape and the space it defines.

PROJECT CREDITS:

DESIGN

ZHCODE: Filippo Nassetti, David Reeves, Marko Margeta, Shajay Bhooshan, Patrik Schumacher

BRG: Mariana Popescu, Matthias Rippmann, Tom Van Mele, Philippe Block

KNITCRETE TECHNOLOGY

BRG: Mariana Popescu, Tom Van Mele, Philippe Block

Chair of Physical Chemistry of Building Materials, ETH Zurich: Lex Reiter, Robert Flatt

FABRICATION AND CONSTRUCTION

BRG: Mariana Popescu, Matthias Rippmann, Alessandro Dell’Endice, Cristian Calvo Barentin, Nora Ravanidou

R-Ex: Alicia Nahmad Vazquez, Horacio Bibiano Vargas, Jose Manuel Diaz Sanchez, Asunción Zúñiga, Agustín Lozano Álvarez, Migue Juárez Antonio, Filiberto Juárez Antonio, Daniel Piña, Daniel Celin, Carlos Axel Pérez Cano, José Luis Naranjo Olivares, Everardo Hernández, Ramiro Tena.

STRUCTURAL ENGINEERING

BRG: Andrew Liew, Tom Van Mele

CONCRETE DEVELOPMENT

Holcim Mexico: Jose Alfredo Rodriguez, Carlos Eduardo Juarez, Delia Peregrina Rizo

SITE CONSTRUCTION COORDINATION

R-Ex: Alicia Nahmad Vazquez

EXHIBITION CONTENT, COORDINATION, AND CURATION

Zaha Hadid Exhibitions & Archives: Jillian Nishi, Margaratia Valova, Daria Zolotareva, Paz Bodelon, Elena Castaldi, Manon Janssens, Woody Yao

ZHACODE: Leo Bieling, Federico Borello, Filippo Nassetti, Marko Margeta, Henry David Louth, Shajay Bhooshan

BRG: Mariana Popescu, Matthias Rippmann, Noelle Paulson, Philippe Block

Prof. Dr. Philippe Block

Philippe Block is Professor at the Institute of Technology in Architecture at ETH Zurich, where he co-directs the Block Research Group (BRG) together with Dr. Tom Van Mele. He is director of the Swiss National Centre of Competence in Research (NCCR) in Digital Fabrication, and founding partner of Ochsendorf DeJong & Block (ODB Engineering). Block studied architecture and structural engineering at the VUB, Belgium, and at MIT, USA, where he earned his PhD in 2009. Research at the BRG focuses on computational form finding, optimisation and construction of curved surface structures, specialising in unreinforced masonry vaults and concrete shells. Within the NCCR, BRG researchers develop innovative structurally informed bespoke prefabrication strategies and novel construction paradigms employing digital fabrication. With the BRG and ODB Engineering, Block applies his research into practice on the structural assessment of historic monuments in unreinforced masonry and the design and engineering of novel shell structures.

Dr. Mariana Popescu

Dr. Mariana Popescu is post-doctoral researcher at the Block Research Group (BRG) at the Institute of Technology in Architecture at ETH Zurich, involved in the NCCR Digital Fabrication. Popescu is an architect with a strong interest in innovative ways of approaching the fabrication process and use of materials. She studied architecture at the Delft University of Technology, before obtaining her PhD at the BRG in 2019. Her research focuses on the development of KnitCrete, a novel, material-saving, labour-reducing, cost-effective formwork system for casting of doubly-curved geometries in concrete using 3D knitting. She is the main author of the award-winning KnitCandela shell and has been included in the MIT Technology Review Innovator Under 35 list in 2019.

Shajay Bhooshan

Shajay is a PhD candidate at the Institute of Technology in Architecture, ETH Zurich, where he is a research assistant in the Block Research Group. He also heads the research activities of the Computation and Design (co|de) group at Zaha Hadid Architects, London and works as a studio master at the AA DRL Master’s program. Previously, he worked at Populous, London and completed his Master’s Degree at the AA School of Architecture, London in 2006. He has taught and presented work at various events and institutions including Tensinet Istanbul '13, ICFF Bath ‘12 , Designers Gallery AU ’11, Design computation symposium AU ‘10 , simAUD ‘10 , Siggraph ‘08, Yale University and University of Applied Arts , Vienna. His current interests & responsibilities include developing design research and maintaining computational platforms for the same at ZHA.

Dr. Tom Van Mele

Dr. Tom Van Mele is Senior Scientist and co-director at the Block Research Group (BRG) of the Institute of Technology in Architecture at ETH Zurich, where he leads the computational and technical developments, supervises the postdoc team, and advises and supports the PhD candidates on a day-to-day basis. Tom is the lead developer of COMPAS, the open-source computational framework for collaboration and research in architecture, structures and digital fabrication. He is project lead of the HiLo unit developed by the BRG for NEST, the modular research and innovation building of Empa.

ZHACODE+BRG | Knitcandela