Free hanging membrane model for shell structures

The paper presents a form-finding methodology based on a concept of a free hanging membrane (FHM). The numerical model of the membrane assumes that the material is inextensible, resists tension, has a specified area, but no fixed shape. The development of the numerical model has been motivated by a form-finding process aimed at predicting natural forms of shell structures, a process originally based on physical experiments involving a creation of hanging models made of fabric or chains. As demonstrated by the experimental work of Swiss designer, Heinz Isler, the inverted shapes of hanging membrane models give, within the limitations of fabric properties, perfect shell structures, the shapes of which can be scaled up to a full-size construction. The physical modelling process, however, is expensive and time consuming. The numerical alternative proposed here has a number of advantages. The FHM’s mechanical properties are deduced and its application to form-finding of hanging fabric models (inverted shell structures) is presented. It is shown, in cases where such configurations can be analysed, that the achieved shapes are minimum energy configurations. A number of examples of form finding are presented which show that the method is accurate and efficient. Copyright q 2007 John Wiley & Sons, Ltd