panels is supported by a web of steel cables. Because the covering in this case was designed to be relatively rigid, deformation in the cable sys- tem had to be minimized by very powerful pre- tensioning, leading to high costs for the masts and other anchoring members.
Membrane structures
Unlike the preceding two types, the roof covering material forms both the structure and the enclosure. Suitable fabrics include:
• PVC-coated polyester fabric. This is cheaper ini- tially than the next type below, and easy to handle. But it has a life of only about 15 years, the fabric tends to sag with time, and the surface becomes sticky with age and requires frequent cleaning.
• Teflon-coated glass fibre fabric (also known as PTFE-coated glass fibre fabric). This is an expen- sive roof by any standards but it has a longer life than the type listed above and, being Teflon, it is to some degree self-cleaning. Use of this material is limited or banned by some authorities because of a tendency to produce toxic fumes in a fire. But as fire is not normally a hazard in stadium roof
situations the material ought to be acceptable in this context. Use of an expert designer is essen- tial, together with a fire engineering approach.
The Faro Stadium in Portugal (Figure 5.11) and Oita Stadium in Japan (Figure 5.14) provide elegant examples. Examples in the UK include the Mound Stand at Lord’s Cricket Ground, London of 1987 (see Figure 5.2) with a translucent PVC-coated woven polyester fabric with PVDF top coat; the Sussex Stand at Goodwood Racecourse of 1990; and the Don Valley Stadium at Sheffield in 1991. The Riyadh Stadium in Saudi Arabia is an example of a complete stadium roofed in fabric.