On the imperfection sensitivity and design of spherical domes under external pressure

Abstract

Deep spherical shells are often used as pressure vessels in ocean and aerospace engineering. When subjected to external pressure, these thin-walled shells are prone to buckling. The corresponding critical buckling pressure heavily depends on deviations from the ideal shell shape.In general, these deviations are defined as geometric imperfections, and although imperfections exhibit comparatively low amplitudes, they can significantly reduce the critical load. Considering the influence of geometric imperfections adequately into the design process of thin-walled shells poses major challenges for structural design.The most common procedure to take into account the influence of imperfections is based on the classical buckling pressure obtained by a linear analysis which are then corrected by a knockdown factor. The knockdown factor represents a statistical lower-bound with respect to data obtained experimentally for different types of thin-walled shells.This article presents a versatile and simple numerical design approach for deep spherical shells under external pressure. The new design procedure leads to significantly improved critical load estimations in comparison to lower-bounds obtained empirically. Different design example are given and validated with experimental results.