Buckling of steel tanks under earthquake loading: Code provisions vs FEM comparison

Abstract

A poor seismic design of liquid storage tanks may result in large economic losses or environmental impacts due to the spillage of their contents; therefore, an effective seismic design of these tanks is of vital importance. Moreover, many liquid storage tanks have suffered severe damage during recent earthquakes worldwide due to the buckling of their wall, which is one of the most common failures. In continuously supported tanks, anchors are an essential part of the seismic design; however, the effectiveness of incorporating them and the predictive ability of design codes on the behavior of these structures has not been extensively studied. This research evaluates the design recommendations (API-650 and NZSEE) through a comparison with nonlinear 3D finite element models. In particular, the compressive stress and the buckling capacity of the tank wall are evaluated. Three anchorage conditions are analyzed: (i) tank with a fully anchored base, (ii) tank with flexible anchors at the periphery of the base (bolted anchorage), and (iii) unanchored. Four tank geometries, two materialities (stainless steel and carbon steel), and different amounts of anchors for each geometry were analyzed. In total, 24 nonlinear 3D finite element models were developed and analyzed. The presented results provide a better understanding of the effectiveness of including anchors depending on the tank slenderness and the predictability capacity of design codes for these structures. Finally, some code guidelines for flat tanks are validated, and the need for additional detailed guidelines for slender tanks is highlighted.