EFFECT OF GEOMETRIC IMPERFECTIONS ON THE CAPACITY OF CONICAL STEEL TANKS UNDER HYDRODYNAMIC PRESSURE

摘要

Liquid tanks in the form of truncated steel cones are commonly used for liquid storage in North America and in other locations. The main cause of failure, for conical steel tanks in particular, which was identified in most of the failure cases, is the buckling of the tank's shell at locations of maximum compressive stress. Being constructed of steel, geometric imperfections in the conical tank walls will exist and their amplitude will be dependent on the quality controls applied by the builder. Such geometric imperfections play an important role in defining the buckling capacity of shell structures in general. Some studies found in the literature assessed the effect of geometric imperfections on the buckling capacity of steel tanks. However, most of these studies focused on hydrostatic pressure and not on hydrodynamic pressure that is induced on the tank walls when the tank base is subjected to either horizontal or vertical ground excitations. In this study, an expression for the critical imperfection wave length is obtained and the effect of the geometric imperfections' amplitude on the buckling capacity of conical steel tanks is assessed numerically under hydrodynamic pressure due to horizontal and vertical ground excitations. The study is conducted numerically through non-linear static pushover analysis using an in-house finite element model that accounts for the geometric and material nonlinear effects.