Sheer equilibrium Mark West
T he pliant nature of woven and sewn fabrics is a crucial determinant of the structural and physical approach that a fabric-formed con- crete method of construction requires. The structural capacity of any individual thread, any single stitch, is practi- cally negligible, and yet these light fabrics are very powerful indeed.This power is the result of a collective resistance; hundreds of thousands of individual threads and stitches each tally up their own small and individually insignificant contribution.This collective strength is the result of a fabric’s capacity to disperse an applied load throughout its web of constituent threads. When you push a fabric formwork filled with wet concrete you can feel the hydrostatic pressure pushing back. Every force applied to the fabric changes the shape of the mold as a new equilibrium of forces is reached; each force has a commensurate geometry that attends its action. The final shape of the formed concrete is a precise three-dimensional inscription of the materials’ physical struggle towards equilibrium. The thin woven skin is open enough to bleed water from the wet concrete through the tiny spaces between the warp and weft of the fabric. In this way the membrane container becomes a giant, fine-grained filter gathering a rich cement paste at its surface. Individual threads and needle holes from sewn seams can leave a perfect impression. This delicacy is matched by a surprising toughness, a sturdy robustness. The very pliability of a fabric formwork endows it with its own kind of stability that does not rely on rigidity. A two story-high column of wet concrete, weighing more than a ton, can be rocked back and forth in its fabric mold with no ill effects.The giant oscillations will slowly die out as the column stabilizes itself (via vertical pre-tensioning) back into its original vertical position. Motion and deflections are now understood as part of a new tool kit. Deflection is embraced as a most intelligent form-giver, calling into play the deepest fundamentals of natural structural law. Quantitative analysis of these structures is a new phase of our research which will be supervised by Dr Aftab Mufti. Our engineering collabora- tors at the University of Manitoba Faculty of Engineering will begin the structural analysis of some of our fabric-cast funicular shell and vault panels in the new year, using Finite Element Analysis and predicting both the deflections of the loaded, prestressed fabric formworks and the structural behaviour of the panels. Dr Jose Gonzales of the U of M Department of Clothing and Textiles will be analysing the mechanical and structural properties of various formwork textiles.
above: Araya Asgadom helping construct the installation at the Store- front for Art and Archi- tecture at 97 Kenmare Street in New York City in 1992. right: festival bollard.
Mark West works with the Centre for Architectural Struc- tures and Technology at the University of Manitoba.
L a nature souple du textile tissé et cousu est un facteur déterminant essentiel à l’approche structurelle et physique qu’exige une méthode de construction formée de tissus. La capacité structurelle de chaque fil, chaque maille, est pratiquement négligeable, mais toutefois, ces légers tissus sont très puissants. Cette puissance est le résultat
d’une résistance collective. Des centaines de milliers de fils et de mailles individuels ajoutent leur petite contribution, aussi insignifi - ante soit-elle. La force collective qui en résulte est due à la capacité du tissu à disperser la charge appliquée à travers la toile des fils qui le constitue. Cette fine peau tissée est suf - fisamment ouverte pour laisser
saigner le béton mouillé par l’entremise des fines espaces entre les chaînes et les trames du tissu. Vue de cette façon, la membrane qui contient le tout devient un filtre à grains fins géant qui con - tient l’accumulation de pâte de ciment riche à sa surface. Les fils individuels et les trous d’aiguilles des coutures peuvent laisser une impression parfaite.
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