A Simplified Mechanical Analog for Characterization of the Axisymmetric Response of Combined Shells Under Internal Hydrodynamic Pressure

Abstract

Elevated liquid-storage tanks are commonly built with a combined vessel consisting of a truncated cone and a superimposed top cylindrical cap. As a result of the inclination of the walls of the conical segment, compressive meridional stresses are induced in the shell by the hydrostatic pressure of the contained fluid and the hydrodynamic pressure associated with vertical ground excitation. The current paper aims at identifying the dynamic characteristics of liquid-filled combined tanks subjected to vertical ground excitation. Numerical analysis is conducted based on a coupled finite-boundary element formulation that accounts for the fluid-structure interaction associated with this type of analysis. A mechanical analog is developed to simulate the seismic response of liquid-filled combined vessels to vertical base excitation. The mass of the contained fluid is idealized as rigid and flexible components connected by a linear spring that represents the flexibility of the vessel walls. The proposed analog provides a simplified tool to predict seismically-induced shell forces due to the vertical component of earthquake excitation. In addition, the analog can be used to evaluate the maximum overall forces acting on the supporting structure.