Structures for supporting tensile fabric
A tensile (tensioned) fabric structure is an architectural form made from fabric, placed under tension and taking on a shape according to its fixings and frame. This frame is therefore key in building fabric structures correctly, and may take the form of timber posts or tubular metal. But in all cases it needs to be able to deal with the loads that are imposed upon it. For this reason, even at the initial conversation stage of a project we will begin to consider these requirements. We also know that the supportive frame, as well as being appropriately discreet, needs to complement the fabric form. It's our job to make sure the structure works on these all levels.
In order to create this frame, we model it using 3D CAD to ensure that the structure works from all perspectives at the same time, considering the initial engineering, appearance, water run-off etc. and ultimately produce a supporting frame that is appropriate to the design and safe to build and install.
The drawing shown here of Roseworth School shows the kind of support frame, cables and foundation that are required to create this relatively simple shape. The masts providing the height and variation in the canopy, and thus the water run-off, while the cables tie the mast tops back to the foundations. The foundation has to resist both rotational pullout, downward pressure from the masts and inward sliding forces.
Another frame, in this case made of timber, at Rosendale Primary School is a classic hypar canopy fixed in place by cast-in sockets. Foundations again support these, but eye-level cables have been removed to avoid the potential danger of people walking into them. This does however mean that the column has to deal with far higher bending moment loads.
A completely different kind of frame, shown here at Travelex in Peterborough, demonstrates the kind of complex forms that are also required for interior structures. With close-up viewing possible the level of structure detailing must be to a very high standard, as well as obviously dealing with the engineering forces that such an interior fabric structure imposes.
The same applies in the case of exhibition structures. Although temporary, they need to be well designed, very often light-weight and ultimately easy to put together. The Pod for Lloyds TSB shows a complete departure from the classic freeform/free span canopy, instead using a web of support tubes to provide a frame that the stretch fabric can sit over. The frame in this case is made from a series of laser-cut parts, all bolted together, with inserted GRP tubes, and is combined with an aluminum extrusion that allows the panels into be inserted in quarter section.
As you can see, the variation in supportive frames is huge, but in all cases is extremely important. So don't be surprised if it's the first aspect we would like to discuss with you.