Study on the Predictive Evaluation Method for Loads Acting on Roof and Sidewall of Cylindrical Tank in Nonlinear Sloshing Based on Simplified Equations

Abstract

Abstract When a cylindrical tank installed on the ground, such as an oil tank or a liquid storage tank, receives strong seismic waves, including a long-period component, motion of free liquid surface inside a tank called sloshing may occur. If high-amplitude sloshing occurs and waves of free liquid surface collide with tank roof, it may lead to accidents such as damage to tank roof or outflow of internal liquid. There is also a possibility that tank sidewall may be damaged due to fluid force generated by high liquid surface level of sloshing. When sloshing wave height is small, liquid surface level and velocity can be calculated based on the linear velocity potential theory. When sloshing wave height increases, sloshing becomes nonlinear, and the difference between actual value and calculated value based on the linear velocity potential theory increases. Sloshing loads acting on roof and sidewall should be evaluated in consideration of nonlinear sloshing. In the previous study, simplified equations of nonlinear liquid surface shape and nonlinear liquid surface velocity distribution were proposed, as input parameters of evaluating sloshing loads. In this paper, a new method is proposed for nonlinear sloshing condition of cylindrical tanks, which can evaluate the vertical load acting on roof and the horizontal load acting on sidewall. In the proposed method, new pressure models modified from existing models are combined with simplified equations of nonlinear liquid surface shape and nonlinear liquid surface velocity distribution proposed in the previous study. A long calculation time as CFD analysis is not needed, because the proposed method is consisted of simplified equations.