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Fabric framework opens up new possibilities in building design

September 1st, 2007 / By: / Feature

Maintaining straight lines and super-flat surfaces in construction has a price. One architect recounts his epiphany about materials while researching fabric formwork.

It was nearly 10 years ago that the chief engineer came for an inspection of the construction site I was supervising. “I have never seen such straight walls up north,” he said, standing above a 183m-long section of 6m-high concrete walls that we had just poured. I couldn’t help being proud of my crew and our work, especially since this was a remote isolated community [where?] with very few resources.

All materials for the multimillion-dollar project had to be transported hundreds of miles on dozens of flatbed semi-trailer trucks across frozen lakes during the winter. The convoy of materials and machinery was astounding, as each trailer could be loaded only to a fraction of its normal axle capacity to avoid breaking through the ice.

Throughout my career in construction I have waged a battle against every structural force imaginable in order to maintain a straight line and a flat surface at virtually any expense. It didn’t matter what the forces were. With enough plywood, rebar, concrete, and two-by-fours we could capture any curved tension or compression force within a rectilinear mass.

My career in construction has been put on hold as I work to complete my Master’s of architecture at the University of Manitoba, Canada. I have also abandoned my battle against structural forces, and I am happy to announce that I am now fighting for the other side. It took only a few hours working with director Mark West at the Centre for Architectural Structures and Technology (CAST) for me to realize that I had spent too much of my life and wasted too much of the earth’s resources suppressing a beautiful thing.

Imagine building an entire building out of two-by-fours and plywood. Imagine surrounding this building with two complete cages of steel bar. Now build another entire building out of more two-by-fours and plywood just 8 inches away from the first one. Then fill the small space between the two buildings with concrete and throw away all the material that is too damaged to re-use.

This is the all-too-familiar construction scenario that Mark presented back to me one day [when?], opening my eyes to my own ignorance. Why do we fight these forces? Why do we waste so much material working against them? How can we use these forces naturally? What would these forces look like if we set them free? These are some of the questions we are researching at CAST using a unique building material: fabric.

The structural principle is simple. If you hang a piece of fabric by any number of points, then the entire weight of the fabric will be distributed in pure tension from those points. Hang each point from a spring scale, and you will even know the exact force and direction for each point. The fabric will fold and ripple as needed to find its own gravitational equilibrium. No computers or calculations are necessary for this natural, real-time, structural form-finding adventure.

Now “set” the fabric by spraying it with plaster or Shot-Crete. The shape may change slightly depending on how thick it is applied at various points, but it will always find its own structural equilibrium while it supports the wet concrete. Once it is hard, turn it upside down and set it on the points from which it was held. Every tension force is converted to a perfect compression force. The support points will exert the exact reciprocal force back down to the earth.

CAST is a place where art and science work together and feed off each other. It is a place where we try to understand structural forces and master the tools needed to create an architecture that does not deny anything. We do not think up some “cool” shape and then try to make a structure for it. We also do not apply a decorative shape to a structure. The fabric formwork adjusts dynamically and creates its own structure and its own expressive sculptural beauty. Form can still be explored through the fabric as it hangs this way or that way as we pull and push it, but it is always form and structure at the same time.

The points from which we push and pull all have meaning. Perhaps there is a desk or a window in a wall. Just apply a block-out with similar weight and dimensions to the fabric in the desired location, and the structure will automatically compensate for it wherever you choose to add to it. Of course, the placement will affect the form. Every constraint yields a different result, and each will result in its own beautiful, unique form that must, by the nature of the fabric, always be structural. The forces which create the form are so complex that they would require advanced computer modeling to calculate. However, the principle is so basic that you don’t even need a computer to calculate them to know that they work.

One of the primary benefits of this building methodology is the massive reduction of materials. Structural wall panels can be sprayed and cast off a piece of fabric hanging from scaffolding. We use picnic tablecloth to make models. The fuzzy side of the tablecloth is sprayed with plaster first, and the two (cloth and plaster) become a mold. Then we can spray and cast repeatedly off the other release side, since it is smooth. At full scale, we currently use an uncoated, woven polypropylene geotextile by Propex commonly used in road construction, and NovaShield II, a coated polyethylene fabric by Intertape Polymer, since both can support the weight of the wet concrete. Both are inexpensive and tough enough to be reused many times over, unlike plywood. Mark is still seeking a fabric with a rough side for the concrete to adhere to and a smooth side for a mold release.

There is also a substantial savings in materials in the structural member itself. The double curvature created by the fabric form means that the thickness of the wall panel, for instance, could be 50mm of concrete instead of 203mm and still have the same structural depth. The mass of a beam may be reduced by about 40% simply by eliminating the concrete from areas without any forces. Columns can be formed using a large sock of fabric formed to bulge into any shape desired when they are filled.

In school, I often hear people say that architecture is in a state of crisis. We live in an increasingly multicultural society, yet homogeneity is on the rise. We dare not celebrate any one culture or religion for fear of offending the others. And in not celebrating any one, we seem to offend everyone. Everywhere people are looking for new meaning or a sense of purpose in architecture. I like to call the wild zany stuff being built today “Because I Can” style of architecture. In the apparent absence of any universal truth, we pull out the computer and attempt to blind everyone with senseless razzle-dazzle. Then we throw a mountain of material at it, squeeze a structure in somehow, somewhere, and apply bright colors or shiny metals because that makes it “cheery.”

I have discovered a fantastic new architecture while working at CAST. I have finally found a sense of purpose in architecture that transcends cultural or religious symbolism and stylistic trends. It does not require dozens of semi-trailers of materials. A straight line at any cost is definitely not something to be proud of. Nothing is denied or suppressed. The truth is, this approach in general terms isn’t anything new. It is actually very old and quite common. It can be found in times and places without excess means. It is architecture at its core when we choose not to suppress natural forces with infinite resources. Modern materials like fabric have given us new creative control, and the possibilities for this fabric-formed architecture are wide open. I consider myself extremely fortunate to be able to participate in the work at CAST.

Kyle Martens is a research assistant at the Centre for Architectural Structures and Technology, and a master’s candidate in the School of Architecture, University of Manitoba, Canada. He welcomes all inquires and would appreciate hearing from readers. Contact him at kyle_martens@yahoo.com or by phone at +1 204 261 9334.

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