FABRIC FORMWORK -TO DESIGN A FUNICULAR STRUCTURE Abstract The concept of using fabric or membrane as formwork to cast concrete

The concept of using fabric or membrane as formwork to cast concrete, has a long history in the field of architecture and technology. The use of fabric formwork suggests the opportunity to develop complexity of form using a rational process. Minimal use of material that requires minimal bracing, whose shape is dictated by its response to the forces it is intended to resist, will lead to a more expressive construction.

Fabric formed concrete provides relatively simple means to achieve individual solutions, employing forms with echoes of efficiency found in nature that achieve high levels of desirability. The design work for the research will be in two parts technical investigation and design implementation. Through the former part of research we can understand both the potentials and limitation of fabric formwork techniques. The test and experiments are done physically in parallel to digital exploration to develop subsequent design structure.

Fabric formwork is a rapidly evolving technology that challenges the conventional approach to the production of concrete structures and elements. Through the exploration of this system construction of large-scale prototypes, beams, columns, walls and shells as well as the structural development and testing of form-active beams. Fabric formwork is an effective and expressive technology, one that can be applied in a wide variety of applications. It demonstrates the characteristics of a disruptive technology, one that challenges the existing paradigm, in this case the predominance of rigid formwork.

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Through this research we are gone find formwork for the form-finding process and fabrication of funicular structure using flexible fabric formwork and digital architecture.

Formwork; Compressive material; Material symbiosis; Digital fabrication; funicular structure.

The design and materialisation of curved surface architecture typically results in complex structures only feasible through an increased consumption of advanced building materials. The utilisation of flexible design processes based on comprehensive funicular form finding and construction-aware modelling in the early design stage allows us to build such structures more efficiently. The construction of shells demands sophisticated building processes due to their complex geometry. Particularly, the realisation of concrete funicular shells, which are typically doubly curved, has always posed great challenges for architects, engineers and builders. The rather complicated building process and resulting inefficient and costly construction is indeed regarded as one major reason for the decline in the use of expressive, thin concrete shells.

Funicular StructureFunicular shells are a class of doubly curved shells, the shape of which satisfies the desired state of stress in its body for the given loading and boundary conditions. The state of stress desired in an unreinforced concrete thin shell will be pure compression unaccompanied by shear and bending stresses. In funicular shells, the shape of the shell is such that under a particular loading condition, the shell is subjected to pure compression unaccompanied by bending and shear stresses. Under other conditions of loading, bending moments would develop and the shell will no longer behave purely as a funicular element.

The funicular shell is constructed as per the configuration obtained from the analysis. By using simple techniques like the use of a sagging fabric, funicular shells can be cast to satisfy simple loading and boundary conditions (Ramaswamy and Chetty, 1960).Funicular shells are not limited by plan, shape or size. It can be triangular, square, rectangular, circular or elliptic of required dimensions.

Figure 1-Funicular formsFigure 2-Digital –form finding –funicular structutre00
Figure 1-Funicular formsFigure 2-Digital –form finding –funicular structutre
The material symbiosis of both concrete and fabric are very similar. They both have infinite textural possibilities and the both can be molded into any shape. These similarities allow these two materials to be used together in a mutually beneficial way. The fabric form work does not constrain the concrete like the other conventional formwork like wood and steel formwork, which makes the construction of organic and curvilinear geometries easier.

Concrete is one of the most widely used materials in the world. Cement, the active ingredient, is a global commodity with annual production in 2011 of 3.6 billion tonnes.The characteristic of concrete which is perceived by people are boxy, rugged ,dirty and cold. The monolithic surface which is durable is actually the result of the negative impression poured into the molds /formwork made of plywood and steel. The predominant reality of inexpensive concrete construction along with the restrictive behaviour of irregular formwork has prevented the construction field from embracing the potential of concrete as a fluid material that can be cast into any shape.

Fabric The material is an opposite of concrete in many ways. It is flexible; it provides warmth and protection; and never being used as a support. The flexibility of fabric allows it to be effortlessly shaped and produce a naturally organic surface quality. The flexibility also makes it difficult to retain the form in a particular shape permanently. Fabric also has a tendency to degrade rapidly over time because it’s woven from small fibres that are vulnerable to degradation from environmental factors such as temperature, sunlight, rain and wind.
Figure 3-Wet concrete – ‘liquid stone’Figure 4-Fabric
Figure 3-Wet concrete – ‘liquid stone’Figure 4-Fabric

Why fabric formwork??
The production process of concrete –formwork is used to define the shape of the wet concrete as it is cast. The formwork is critical in determining the quality, finish and efficiency of the process. Traditionally formwork has been made using timber and plywood that can be easily shaped by carpenters, and hence the quality relies largely on the experience and skill of that individual.
The most significant factor on the range of possibilities of concrete is the formwork, used to support the wet concrete has be described as ‘liquid stone’, define its shape and determine the quality of finish. In practice the range of forms and geometries possible is controlled by decisions regarding the formwork. Conventional formwork is most often constructed using planar rectangular components in timber or plywood leading to flat rectangular forms. Complex curved geometries may provide more efficient structural forms and more interesting architectural components but are generally more expensive due to the additional efforts needed to manufacture the formwork.

The materials and their associated fabrication processes generally lead to simple, prismatic and orthogonal geometries. As Pier Luigi Nervi (1956) noted:
It may be noted that although reinforced concrete has been used for over a hundred years and with increasing interest during the last few decades, few of its properties and potentialities have been fully exploited thus far. Apart from the unconquerable inertia of our minds, which do not seem able to adopt freely new ideas, the main cause of this delay is a trivial technicality: the need to prepare wooden forms, -PL Nervi 1956.

The following are the list of materials used for formwork
All of the a above mentioned materials has its own advantages and disadvantage when compared Fabric formwork even though fabric seems to lack the robustness needed to support a heavy and abrasive material such as concrete but it is surprisingly effective. The flexibility of the fabric responds to the hydrostatic pressure of the concrete and deforms to the most efficient shape to carry the load, Furthermore the permeable nature of the fabric acts as a filter that allows the excess water in the concrete mix to escape during casting, reducing the hydrostatic pressure on the formwork and also the permeability of the fabric encourages the passage of trapped air, which together with the reduction in the water/cement ratio produces a more durable surface finish with fewer defects.

Figure 5-Timber formworkFigure 6-Plywood formworkFigure 7-Steel formwork

Figure 8-Aluminium formworkFigure 9-Plastic formworkFigure 10-Magnesium formwork
Figure 5-Timber formworkFigure 6-Plywood formworkFigure 7-Steel formwork

Figure 8-Aluminium formworkFigure 9-Plastic formworkFigure 10-Magnesium formwork

Advantage of Fabric formwork
The use of flexible permeable formworks has considerable benefits in comparison with conventional rigid systems.

Formwork is lighter and easier to fabricate than conventional rigid techniques.

The fabric deforms to the optimum geometry. The fabric can carry only
the wet concrete by generating axial tensile forces in response to the hydrostatic
Pressure of the wet concrete.

Complex forms can be produced. By careful shaping of the fabrics optimised
Structural forms can be developed that would otherwise be very expensive with conventional systems.

The permeability of the fabric improves the quality of the concrete. The
Excess water in the concrete can escape during casting, reducing the pressure on the formwork and the water-cement ratio, which increases the compressive strength. Trapped air is also able to escape, resulting in fewer surface defects and hence a better quality of surface finish.

Large variety of surface finishes possible. An almost limitless variety of
Finishes that can improve the visual quality of the finished object considerably
Can be produced.

Research Objectives

To increase the efficiency in the design and construction of double curved structure.

To testify the structural stability of fabric formwork.

To that fabric formwork is economically feasible for construction of funicular structure.

The development of methods to explicitly control the form-finding process through the use of geometrical constraints.

To optimize the form and shape of the structure using digital architecture tool.

To execute physical scale model of the prototype.

History of fabric formwork
Figure 11-Miguel Fisac- Casa La MoralejaFigure 12-Sandy Lawton- non-traditional ‘treehouse”
Figure 11-Miguel Fisac- Casa La MoralejaFigure 12-Sandy Lawton- non-traditional ‘treehouse”
Although fabric formwork was not widely used until after the industrial revolution, early examples have been found in roman ruins. The Roman architecture have used several methods of casting concrete using woven reeds as formwork. British and American patents from the late 19th century document the first modern use of fabric formwork in the most common application ,inexpensive fabric stretched over a temporary steel structure and then covered in concrete to form ribbed parabolic vaults with span of up to 15m. During the beginning of the 20th century the fabric formwork was used for more of engineering purpose like burlap mattresses for river and coastal revetments, which later shifted the application so as to explore the architectural and aesthetic possibilities of fabric formwork. This shift is evident in the works of Miguel Fisac, who used fabric to produce patterns and shapes that would not be possible with conventional formwork.

Another architect who worked with fabric formwork is in Japan Architect Knezo Unno-fabric formed wall system since mid pf 1990’s it was the earthquake that struck Kobe motivated Unno to create residential designs that are intended to provide safe housing using simple methods of construction with little construction waste possible. Sandy Lawton-company name “Arro design” has used fabric to construct walls, floors and columns for a nontraditional “treehouse”.

New explorations in fabric-formed architecture
Figure 13-Prototype of ultra-thin roofFigure 14-Fabric forms composition proof of concept- 6 axis robotic arms.

Figure 13-Prototype of ultra-thin roofFigure 14-Fabric forms composition proof of concept- 6 axis robotic arms.

The experiments of Block research team- Full scale construction prototype of the NEST Hilo shell roof structure in order to investigate the feasibility of spraying a textile reinforced thin concrete shell using a lightweight flexible formwork composed of a tensioned cable net as falsework and tailored fabric shuttering. The cable-net and fabric formwork system was designed to dramatically reduce the material waste that is typically involved in the construction of concrete shell.

fabric-formed robotic facades –the robotic positioning of fabric formwork by Joseph Sarafian and Ron Culver –proposed a method to derive a parametric form which employs the precision of 6 axis robots and the flexibility of fabric to rapidly create a fabric formwork. Complex geometries can be cost-effectively executed in a precise digital to physical workflow. Robots in architecture will transform not just the forms themselves but also the process of constructing buildings, potentially limiting the cost of erroneous human interpretation in the construction process. With a robotic fabrication, digital commands translate the design, avoiding traditional information loss.

History of funicular structure
The design of funicular form demands a structurally-informed design process connecting architectural intent and structural necessity. Antoni Gaudí is well known for being one of the first architects to exhaustively use structurally informed design approaches for his creations (Huerta, 2006). Gaudí intensively employed graphic statics, hanging models and plaster scale models for catenary structures such as the Church of Colònia Güell, near Barcelona, Spain (1915). Following the work of Frei Otto, among others, on physical, model-based form finding and analysis, first computational methods for the design and optimisation of funicular structures have been developed, including the Force Density Method (Linkwitz and Schek, 1971; Schek, 1974), Dynamic Relaxation (Barnes, 1975) and approaches based on finite element analysis (Bletzinger and Ramm,1993). At a time prior to the widespread use of computers in architecture, these method were only accessible to very few collaborative groups of architects and specialists. Today computational form-finding methods increasingly surpass physical approaches in the design of funicular form due to their fast and cheap utilisation.

The realisation of concrete funicular shells, which are typically doubly curved, has always posed great challenges for architects, engineers and builders. The rather complicated building process and resulting inefficient and costly construction is indeed regarded as one major reason for the decline in the use of expressive, thin concrete shells after their golden age from the 1920s to the early 1960s.

Figure 15-Exhibition hall in Truin ,Italy
Figure 15-Exhibition hall in Truin ,Italy
The Italian shell designer and builder Pier Luigi Nervi recognised early on the advantages of a combination of prefabricated elements and in situ concrete to simplify the falsework and eliminate the shuttering of the concrete formwork, resulting in higher productivity and closer quality control (Nervi, 1953). For example, his design for the Exhibition Hall in Turin, Italy (1949) was constructed using prefabricated ferro-cement panels, which simplified the construction process considerably.

Initial literature study – Introduction-the history of fabric form work and the funicular structure and their explorations, the definition of funicular structure and analysis and wide variety of methods, theories and approaches to the design and fabrication of freeform and shell architecture.. The advantage and dis advantages of conventional formwork. Studies that prove the structural strength of fabric formwork products.

Case study – Studying the material characteristics of concrete and other compressive material like rammed earth. Studying of different fabrics for formwork and comparing the limitations and effects (Woven fabric, natural and synthetic fabric.) Testing the strength of concrete when different fabrics are used for example – woven, different direction in woven pattern, natural fibers and synthetic used in production of fabric. Exploring the flexible fabric in the form finding of funicular structure.

Data collection – to compile the analysed information from literature study.

Design process – Identifying the problems from the collected literature review and explore the material and form finding process physically and digitally. Various stages of design exploration to find an optimum funicular structure. Fabrication of the funicular structure.

Final design- Prototype of the final design structure which is optimized with all the information from both physical and digital exploration.

To conclude the research by finding the optimum method to prototype a funicular structure from the exploration and analysis.
To summarise the contribution of this research paper by acknowledging the structure existing in the field and finding the limitations and strength of fabric formwork system through exploration to attain the funicular structure. And thus adding value by fabricating a structure which is derived from the form which was explored with fabric.

I would like to thank Ar.Chirag Rangholia sir for the guidance through the process of finalizing the topic and also helping me focus the research in the direction which has a future potential scope. I would also like to thank my friends for their resourcefully inputs time to time.

Article: fabric-formed robotic facades-The robotic positioning of fabric formwork by
Joseph Sarafian ,Perkins + Will and Ron Culver ,Culver Architects.- facade tectonics institute
History and overview of fabric formwork:using fabrics for concrete casting by Diederik Veenendaal* ,Mark West ,Philippe Block (2011)
Fabric formed concrete structures and architectural elements by R.F. PedreschiThe University of Edinburgh- Edinburgh Research Explorer ,(2013)
The potential of advanced textiles for fabric formwork by Julie Brennan, University of Ulster, Belfast, UK , Pete Walker and Martin Ansell University of Bath, Bath, UK and Remo Pedreschi University of Edinburgh, Edinburgh, UK (ICE publication 2012)
Funicular Shell Design -Geometric approaches to form finding and fabrication of
Discrete funicular structures – presented by Matthias Rippmann Dipl.-Ing. (2016) ETH Zurich
Structure, form and construction- Fabric formwork for concrete By Remo Pedreschi1, and University Of Edinburgh, Edinburgh, Scotland – Daniel S.H. Lee2 -The Royal Danish Academy Of Fine Arts, Copenhagen, Denmark (2014)
Fabric formed concrete: physical modelling for assess-ment of digital form finding methods
Will Hawkins, John Orr, Paul Shepherd, Tim Ibell Department of Architecture and Civil Engineering, University of Bath, United Kingdom (2016) Research gate
Book – Fabric formwork by Alan Chandler University of East London and Remo F Pedreschi The University of Edinburgh (published April 2015)
Fabric form- advanced tectonics:surface+structure+material assembly –A3 fall of 2011
Southern California institute of architecture –Issuu publish cations
Rigid fabric – Master of architecture thesis book – spring of 2014 University of California, Berkeleyby Andrew Rastetter – Issuu publish cations