A reduced stiffness approach for the buckling of open cylindrical tanks under wind loads

This paper reports on the implementation of a lower bound approach to the buckling analysis of cylindrical shells for tanks subjected to wind loads. The formulation is based on a reduced energy model of the shell adapted to a special purpose, semi-analytical, finite element program in which it is possible to separately compute the membrane and bending energy contributions. First, the energy components are investigated, in order to identify stabilizing and destabilizing contributions. Second, an eigenvalue analysis is carried out using a reduced value of the stiffness, in which membrane components are eliminated on the basis that they are assumed to be eroded as a result of mode coupling catalyzed by imperfections. The methodology is employed for thin-walled, above ground, tanks under wind pressures. It is shown that the resulting critical loads constitute lower bounds to those obtained using a nonlinear analysis of the shell, including imperfections, and also to those obtained from experiments.