Abstract
Air inflated cushions are being used more and more as light roofs for large span structures, such as the Eden Project in Cornwall, UK (fig. 1). Most of the air inflated cushions are made of FTFE foil. Because air inflated cushions are form active structures they are subjected to geometric non-linear behaviour. This is usually dealt with by calculating these types of structures with form finding and finite element programmes with special membrane elements. For design purposes these calculations can be cumbersome, and do not necessarily provide the designer the required insight to make effective early design decisions. For this reason researchers have tried to derive simpler analysis methods without disregarding its geometric non-linear nature (Wagner [1]). The method presented in this paper is a further step in developing these.