Shape Finding Methods of Shells

Shell structures are usually extremely thin and therefore heavily rely on an almost pure membrane stress state. In order to guarantee this stress state the shape of the shell plays a dominant role in the initial design of the structure. The present paper compares the classical geometric shapes with free form shells and discusses several shape finding methods. The most prominent procedure is the deforming flexible membrane under a controlling load case like pressure or dead load. The method has been applied experimentally as well as analytically. Other methods start with a prescribed stress state and take the surface geometry as unknown. The procedure may be based on membrane equilibrium equations or force-density equivalents. Finally, optimization schemes are applied using e.g. the strain energy as an objective and bounding the stress state to certain limits. Several examples for this approach are given.