Stability and strength of conical shells subject to axial load and external pressure

The stability of conical shells with relatively low slenderness is in many cases influenced by plasticity effects. The buckling design of these structural elements, subject to the interaction of axial forces and external pressure, is only partially covered by current codes and recommendations. An accurate estimate of the collapse load and of the load-shortening effects in the presence of significant geometric imperfections may be achieved only by means of refined finite element models. Recently it has been demonstrated that a plastic mechanism approach can be a valid alternative to obtain a good estimate of the real behaviour. The main aim of the paper is to present a plastic mechanism model that can be a simple tool for estimating the collapse load and predicting the load-shortening response even in the presence of not negligible geometric imperfections. The fundamental points of the formulation are summarised and the model is validated by simulating some buckling experiments on axially loaded conical shells. Collapse domains for interaction of axial compression and external pressure are presented and discussed.