Impact of the excitation frequencies on wall stresses in a storage tank

Abstract

This research addresses the experimentally determined relationship between the excitation frequency and both hoop and axial wall stresses in an upright water storage tank. A low-density polyethylene tank, utilising six water height to tank radius ratios (aspect ratios), was tested using a shake table. The tank is unrestrained at the base, i.e., uplift can occur. Harmonic excitations with eight frequencies that cover the dominant frequencies of recorded strong earthquakes were applied. Additionally, Ricker wavelet excitations of two different dominant frequencies, within the earthquake range, were considered. The maximum wall stresses calculated from experimental data and those from a nonlinear elastic spring-mass model were compared. The results reveal that, under low dominant-frequency excitations, the sloshing behaviour governs the development of wall stresses. In contrast, under high-frequency excitations, uplift determines the wall stresses. Uplift and sloshing occur simultaneously, and the contribution of each of these factors to wall stresses depends upon the aspect ratio and both the frequency and acceleration of the excitation. The spring-mass model tends to overestimate both hoop and axial stresses when the aspect ratio is higher than two, regardless of the excitation frequency.