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KnitNervi - An actively-bent, knitted formwork for ribbed concrete shells at MAXXI, Rome, 2022

Knitnervi is a pavilion-scale demonstrator of a flexible formwork system for constructing a ribbed concrete shell. It consists of a bending-active gridshell, as falsework and reinforcement, encapsulated by a CNC-knitted shuttering. It was constructed for the exhibition "Technoscape: The architecture of engineers" at the MAXXI National Museum of 21st Century Arts in Rome, Italy, 2022.

General Information

KnitNervi draws inspiration from the pioneering Palazzetto dello Sport by Pier Luigi Nervi to reimagine ribbed, thin-shell, reinforced-concrete construction. The project breaks away from the prefabrication and standardisation paradigms enabling expressive and efficient concrete shells by proposing a construction system without the need for complex, wasteful moulds.


The installation embodies a flexible formwork system for ribbed reinforced concrete shells. The highly articulated, doubly-curved geometry is form found to act in pure compression with a tension ring at its perimeter. A bending-active gridshell serves as the primary structure of the formwork and simultaneously as the integrated reinforcement of the final concrete shell. KnitCrete, a CNC-knitted flexible stay-in-place shuttering, encapsulates the expressive geometry.  


Part of the Technoscape exhibition at the MAXXI, KnitNervi offers a roadmap for interdisciplinary co-development in architecture, engineering and construction. The ambition is to nurture a conversation on sustainable and structurally-efficient architecture in the XXIst century.

Discover more here:

Short credits

ETH Zurich - Block Research Group (BRG) & TU Delft - Prof. Mariana Popescu

Full credits


  • ETHZ BRG: Lotte Scheder-Bieschin, Serban Bodea, Tom Van Mele, Philippe Block
  • TUDelft: Mariana Popescu, Nikoletta Christidi

Structural engineering

  • ETHZ BRG: Lotte Scheder-Bieschin, Philippe Block

Knitted formwork

  • TUDelft: Mariana Popescu, Nikoletta Christidi

Fabrication and construction

  • ETHZ BRG: Kerstin Spiekermann,  Lotte Scheder-Bieschin,  Serban Bodea, with support of Eva Schneuwly, Damaris Eschbach, Rolf Imseng, Stefan Liniger
  • TUDelft: Mariana Popescu,  Nikoletta Christidi

Project and site construction coordination

  • ETHZ BRG: Serban Bodea
  • TUDelft: Mariana Popescu

Exhibition content, coordination, and curation

  • ETHZ BRG: Lotte Scheder-Bieschin, Serban Bodea, Mariana Popescu, Kerstin Spiekermann, Noelle Paulson, Katharina Haake, Philippe Block

with support of Eva Schneuwly, Rolf Imseng


  • NCCR Digital Fabrication
  • ETH Zurich
  • Debrunner Acifer Bewehrungen
  • Doka Switzerland and Italy
  • Jakob Rope Systems
  • NOWN
  • Symme3D
  • Gisler Bewehrungen AG

Special thanks

  • Debrunner Acifer Bewehrungen: Pascal Pfister
  • Doka Switzerland: Mirko Bartelt
  • Doka Italia: Luca Chiappa
  • Jakob Rope Systems: Fabian Graber
  • ETH Zurich Facility Services: Oliver Zgraggen
  • ETH Zurich Robotic Fabrication Laboratory: Michael Lyrenmann, Tobias Hartmann
  • Berner Fachhochschule: Simon Von Gunten, Olivier Barth
  • Gisler Bewehrungen AG: David Gisler

Documentation and Video

  • Footage: Thom de Bie, Mariana Popescu, Lotte Scheder-Bieschin, Serban Bodea
  • Editing: Thom de Bie
  • Animations: Lotte Scheder-Bieschin, Michele Capelli

Fact sheet

  • Global dimensions shell: 9.0m x 9.0m x 3.3m
  • Covered area: 56.6 m2
  • Weight steel reinforcement: 533 kg
  • Weight shuttering: 30 kg
  • Weight of formwork system: 10.8 kg/m2
  • Total length steel splines: 0.7 km 
  • Type of yarn: Polyester (PES)
  • Knitting time: 80 hours
  • Number of supports: 29


MAXXI National Museum of 21st Century Arts, Rome, Italy - 41.928649060976156N, 12.467783161497518E


Funicular funnel shells

Funicular funnel shells

This research introduces a new typology of structurally efficient, funnel-shaped shells for light and open architectural applications. It uses a novel approach for the structural form finding of funicular shell shapes by defining free boundaries that are balanced by continuous tension rings.

Bending-active membrane structures

Bending-active membrane structures

This research develops a new hybrid form finding and numerical modeling approach for combined tension and bending elements, building upon and extending the existing form finding framework. Through case studies, the possibilities and advantages of integrating bending-active elements ("splines") in membrane structures will be investigated and demonstrated.

Stay-in-place knitted formworks for complex concrete structures

Stay-in-place knitted formworks for complex concrete structures

This research, part of the NCCR Digital Fabrication, focuses on developing a formwork system for complex, bespoke geometries needing custom formwork with integrated solutions for reinforcement. Creating a fabric stay-in-place formwork combines flexibility of moulding with structural properties. The formwork system is based on a prefabricated textile, transported with minimised volume, tensioned on site. It has accurate placement of material, incorporates reinforcement and acts as stay-in-place formwork. The prefabricated fabric formwork is created by combining knitting and weaving techniques for technical textiles made out of fibres such as alkali resistant glass fibre, carbon fibre, etc.


Scheder-Bieschin L., Spiekermann K., Popescu M., Bodea S., Van Mele T. and Block P.Design-to-fabrication workflow for bending-active gridshells as stay-in-place falsework and reinforcement for ribbed concrete shell structures,Design Modelling Symposium Berlin 2022 - Conference Proceedings,Springer Fachmedien2022.
Popescu M., Rippmann M., Liew A., Reiter L., Flatt R.J., Van Mele T. and Block P.Structural design, digital fabrication and construction of the cable-net and knitted formwork of the KnitCandela concrete shell,Structures,31: 1287-1299,2021 (June).


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