Form-finding and structural analysis for the design of hybrid structures

In the design of membrane structures, the integration of bending-active elements (rods) allows for interesting new designs. In classical form finding the stress-state is prescribed and equilibrium will be satisfied in the formfound geometry. In contrast, the stress-state of bending-active elements depends on their deformation. The opposing behaviors of these two types of members lead to the term "hybrid structures". A simulation technique for these hybrid structures is presented in this paper. The necessary equations for incorporating elastic members in the form-finding and analysis of membrane structures are presented, and methods of applying the results of form-finding to the structural analysis are discussed. The necessity of incorporating elastic members from the beginning of the design process is demonstrated with small-scale examples. Finally the simulation of a 29 m umbrella that is part of an ongoing research project is used to demonstrate the possibilities and limits of accurate simulation of membrane structures with integrated bending-active elements.