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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.

More info

Concrete is one of the predominant building materials in construction. This applies to standard construction but especially to complex architectural shapes. Reinforced concrete lends itself well to such geometries. Furthermore, it is applicable to a wide variety of typologies, since, when given a formwork, concrete can take on almost any desired shape. This formal flexibility makes it an attractive building material. However, this flexibility comes at a cost. Concrete needs formwork upon which to be cast. To this extent, much of the design and manufacturing shifts to the design and fabrication of complex formwork. Additionally, nonstandard reinforcement strategies have to be developed.

This research focuses on those complex, bespoke geometries that need custom formwork with integrated solutions for the reinforcements.

There are two ways of manufacturing concrete structures: on site or as prefabricated elements. Currently, concrete prefabrication brings many advantages. It is an optimized process that speeds up the production and construction time while cutting costs compared to on-site fabrication. Two of the major challenges of prefabrication are transportation and on-site handling. Additionally, one of the major drawbacks of prefabrication is the fact that it is an optimised process for standard elements and serialisation, resulting in discretised, non-continuous elements. Many of these aspects are linked to the reusability of the formwork needed for casting.

Formwork is made out of several materials depending on the use, desired surface finish, durability and how often it should be reused. It has to support and sustain the structure until the concrete cures and accounts for a great part of the building cost. For bespoke geometries formwork can usually not be reused, as it is a one-off product and therefore becomes waste. This is a problem both in terms of cost and sustainability.

Finding an effective method for fabricating complex geometries at low cost while taking advantage of the optimised prefabrication process becomes a valid issue.

This research project aims at creating a prefabricated, spatial, textile formwork system, which will:

  • be easy to transport and handle

  • act as stay-in-place formwork

  • include reinforcements

  • be tensioned on site

  • have accurate placement of material

Publications

Popescu M., Rippmann M., Van Mele T. and Block P.Complex concrete casting: knitting stay-in-place fabric formwork,Proceedings of the International Association for Shell and Spatial Structures (IASS) Symposium 2016,Tokyo, Japan,2016.
ETH ZurichDARCHITA

 

ETH Zurich
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