Fabric Formworks / Research

FABRIC FORMWORKS : 

Fabric formwork is a building technology that involves the use of structural membranes as the main facing material for concrete moulds. Unlike traditional formwork, the material is highly flexible and can deflect under the pressure of fresh concrete. The resulting forms exhibit curvature as well as excellent surface finishes that are generally not associated with concrete structures. 

Fabric formwork was invented proper in the Industrial Revolution but was also used briefly in the engineering of the Roman times. Architect and engineer Vitruvius, created cofferdams using two retaining walls that are filled with clay in woven reed baskets. Vaulting with a plaster finish was also constructed by the use of reeds tied together to form the lower surface on which a sand mortar is applied. Fabric formwork was until this point,only for  utilitarian purposes and started to make more of an architectural influence with Miguel Fisac, a Spanish architect, in the 1950s. Fisac was well travelled and found this own unique style. 

Diagram of Evolution of Fabric Formworks

Historical Review in Detail :  History


Interest: 

The production of thin, doubly curved shell elements, which are difficult to produce and reinforce with conventional means. These shell elements can be used as façade panels, self-bearing roofing structures, or permanent formwork elements. In the latter case, large spans can be realized, with very appealing design and a perfect surface finish.When adding flexible and dense glass fibre textile reinforcement to a fine tuned mortar, a ductile cementitious composite with tensile capacity can be produced. Hence, the steel reinforcement can be omitted and the freedom of shape, inherent to fluid fresh concrete, can be fully exploited. Creating Shell elements, using Geotextiles for enforcement. 

FormFinding

Some Examples :


1) Fabric Formed Hyperbolic Paraboloids
Hyperboloids

2) Structures:
These could be simply artworks or a way to carry complex systems within a building. 
Fatty Shell

3) Larger infrastructure Projects:

Large Span Cable Net and Fabric Formworks Bridge

This project investigates the feasibility of using large cable-nets with a secondary system of geotextiles as formwork for concrete shells. This new concept builds upon existing architectural vocabulary, ideas and advantages found in fabric formwork technology, cable-nets and tensioned membrane roofs, to allow for large-scale, long-span structures.

Bridge

4) FDM : Force Density Method for Fabric Formworks:

Design and analysis of fabric formworks

Fabric formwork is characterized by the use of coated fabrics or geotextiles as the main material for a concrete mold. This method allows concrete`s inherent fluidity to create new forms of concrete architecture and aesthetics. The design considerations for these formworks are similar to those in the design and engineering of tensioned membrane structures, involving the interaction of prestress, non-linear material behavior and the support conditions. Additionally, fabric formwork has concrete pressures, contact analysis and fabric wrinkling as complicating factors. Through combinations of form finding and analysis, this research aims to develop new tools for the structurally informed design of fabric formed structural systems.

5) Lightweight Structures

Lightweight structures video

6) CAST:
The casting of a full-scale panel using concrete requires finding a fabric capable of supporting the weight of the wet concrete. For this purpose, a geotextile fabric made of woven polypropylene fibers was utilized by C.A.S.T. The flexible fabric material was pre-tensioned in the formwork and assorted interior supports were added. Depending upon the configuration of these interior support conditions, three dimensional funicular tension curves were produced in the fabric as it deformed under the weight of the wet concrete
Cast



7) Geotextiles & Fabric Formworks

Woven PP and PE are produced with high tensile strength and low elongations. They have high capability for filtration and distribution of load and manufactured from individually woven, ultraviolet (UV)-resistant Polypropylene fibers. Geotextiles are produced as non-coated or coated using a layer of PE.The main use of Geotextiles is the stabilization of soil but some builders, architects and researchers have adopted them to be used as formwork for concrete.

In 1960 Felix Candela used burlap (jute) to form his concrete shells. A decade later, Miguel Fisac used plastic sheets as fabric formwork and in 1980’s Bindhoff and Lamberton used Nylon fabrics. PE and PP woven fabrics became commercially available in mid 1980’s. Use of PE and PP woven fabrics as formwork for concrete was introduced in late 1980’s by Mark West and Richard Fearn more or less at the same time along with Kenzo Unno who used a plastic construction scaffolding netting as concrete formwork.

In order to study specific effects on concrete strength and quality obtained by using commercially available woven polyolefin fabrics or geotextiles, it was necessary to form concrete cylinders using a variety of fabrics and concrete mix designs. A fabric used as concrete formwork must be strong enough to carry the hydrostatic pressure and the hoop tension imposed by wet concrete. In addition, it should be adequately porous to allow discharge (bleeding) of the excess mix water from the fresh concrete while preventing the loss of solid elements (fines) particularly cement and flyash particles.

8) Zero Waste Formworks



Unno's 'zero-waste' formwork uses a reinforcement cage to support the fabric, so bracing and propping elements are not required. For insulated construction, the fabric, together with rigid polystyrene insulation boards, forms the shuttering. Furring strips – long, thin strips of wood or metal –are used as support, and remain in place after the concrete is formed to provide fixing points for cladding. After use, the fabric, a woven polypropylene geotextile, can be washed and used again.

Other Interesting Links:

Concretely

Retaining Wall Project