Seismic Response Analysis of Cylindrical Tanks With Initial Irregularities on Side Walls

Abstract

The objective of this paper is to report the findings of the study on the effects of initial irregularities on the seismic response of cylindrical tanks. The initial irregularities induce circumferential hydrodynamic pressure components of high-order modes, which are neglected in current design assumptions. Seismic response formulas for cylindrical tanks with arbitrary initial irregularities have been derived from Lagrange’s kinematic equation taking into account natural frequencies, vibrational modes and the hydrodynamic pressure. The hydrodynamic pressure in an irregular tank is evaluated by using velocity potential function. Natural frequency analysis is done by means of the transfer matrix method taking into consideration the initial hoop stress. The effect of aspect ratio H/D (H: liquid height and D: tank diameter) and the shape of initial irregularities are further examined by numerical calculations.