Shell form-finding: Physical and numerical design tools

This paper deals with the shape generation of structural shells within the field of Conceptual Design. Both physical models and computational simulations are presented and discussed. The design is based on the biological principle of homeostasis which states the following: When an external agent attacks the structure, the latter defends itself “intelligently” to recover its bearing capacity. Here, heat is the external agent used to cause the model material degradation. Thus the model adopts a more appropriate structural shape in order to continue to resist loads. The physical experiment is carried out by introducing a Polymethyl Methacrylate (PMMA) plate in an oven with defined boundary conditions and loads. The virtual simulation is performed using a finite element software. A thermal elasto-plastic material model is included to represent the PMMA behavior. A comparison between the shapes found with both approaches is presented. Notwithstanding the diversity of the methods and uncertainties in the material characterization the match is more than acceptable. The numerical simulation may constitute a low cost complement to shell form-finding using the Homeostatic Model Technique. Additionally, the obtained shape is employed as the geometry of a structural shell and both, experimental and finite element stress analyses are performed, yielding a quasi-membranal behavior.