Effects of initial form-finding models on shape, force paths, and buckling of anti-funicular shells with free edges

Abstract

This paper presents an analysis on the effect of the initial form-finding models properties on the shape of shells with free edges, and consequently on the structural behaviour concerning force paths and buckling. The stiffness distribution of these initial models determines the membrane forces that equilibrate the applied loadings and, in this way, the obtained shape. With physical models, this question corresponds to the choice of material: latex rubber membrane or orthotropic fabrics. Continuous models with isotropic materials lead to a higher distribution of forces and reduced curvatures, without concentration along the free edges; this is in contrast to what occurs in discrete models without in-plane shear stiffness. In shells with free edges, the effects on the structural behaviour are related to curvatures and even more dependent on the initial model properties. Solutions with higher curvatures have higher concentrations of forces in the free edges. The reduction of curvatures and forces along the free edges of shells with an approximately square plan is favourable; this is in contrast to shells with elongated rectangular or triangular plans. The presented results and discussion aim to contribute to the design of new thin-shell structures.