Simplified procedure for design of liquid-storage combined conical tanks

Steel vessels in the form of combined conical-cylindrical shells are commonly used for liquid storage in elevated water tanks. A number of such tanks collapsed in different places around the globe due to instability of the steel shells. An essential cause of those collapses is the lack of adequate design procedures for such structures. In this study, a simplified design approach is developed to ensure safety of hydrostatically loaded combined steel conical tanks against buckling. The study is conducted numerically using a non-linear finite element model that accounts for the effects of large deformations and geometric imperfections on the stability of combined conical tanks. The finite element results together with a non-linear regression analysis are used to develop magnification functions that relate the overall shell stresses to the membrane stresses which can be evaluated analytically. Numerical examples are presented to explain application of the suggested design approach.