Elephant Foot Buckling Analysis of Large Unanchored Oil Storage Tanks With Tapered Shells Subjected to Foundation Settlement

Abstract

This paper presents an numerical study on a large unanchored open-topped steel tank. The buckling behaviors of the tank are analyzed using the finite element computer package ANSYS by means of nonlinear stabilization algorithm. The effects of foundation harmonic settlement on the elephant foot buckling strength of large unanchored open-topped oil storage tanks with tapered shells under axial compression are explored by numerical modeling. Various items of actual geometrical structure which involve concrete ringwall foundation of tank, unanchored bottom with slope, shell tapering from the base to the top, wind girders and supports, top angles, stiffening rings and support plates are presented thoroughly in the non-symmetrical 3D finite element model. Geometric nonlinearity, nonlinear boundary conditions and elastic plastic material of Ramberg-Osgood model are involved simultaneously in simulate course. The obtained solutions are displayed graphically for selected values of system parameters: harmonic settlement amplitude, harmonic number, and critical buckling stress of axially compressed oil tank. The results will provide insights into the relationship between foundation harmonic settlement and buckling strength of the large cylinders.