Stiffening Ring Design for Prevention of Storm-Surge Buckling in Aboveground Storage Tanks

Abstract

This paper proposes the use of an additional stiffening ring to prevent buckling of aboveground storage tanks (ASTs) under storm-surge inundation and presents an approach to obtain an optimal design for the additional ring. This study addresses the lack of methods to prevent storm-surge buckling of ASTs even though it has been identified as a common mode of AST failure. For this purpose, finite-element simulations were performed to study the effect of the proposed stiffening ring on the buckling response of ASTs. The critical surge height, i.e., the lowest surge height that causes AST buckling, is evaluated for a wide range of tank geometries, material properties, ring section moduli, and positions of the additional ring. The critical surge heights obtained from these simulations are used to obtain a multiparameter regression equation that can predict the critical surge height. The regression equation is further used to derive the optimal section property and the position for the additional ring as a function of tank geometry and material properties. In order to demonstrate the effect of the additional stiffening ring, the change in the critical surge height due to the installation of the additional ring is evaluated for five case-study tanks. The results show that installation of the additional stiffening ring can significantly increase the critical surge height of tanks. Furthermore, considering uncertainties from level of fill in the tank and geometric imperfections, fragility analysis for one of the case study tanks underscores the reduction in fragility, i.e., conditional probability of buckling failure given surge level, due to the additional ring.