Analysis of a Three-Dimensional Tank-Liquid-Soil Interaction Problem

A three-dimensional analysis of the dynamic behavior of liquid-filled elastic cylindrical tanks based on flexible grounds, undergoing horizontal and vertical earthquake excitation is presented. The interaction of the ideal fluid with the elastic shell and with the flexible ground yields a problem of linear potential theory which must be solved together with the equations of motion of the shell and of the ground. With the unknown modal shapes of vibration developed in Fourier and in Fourier-Bessel series, the partial differential equations are transformed into coupled generalized equations of vibration by a weighted residual approach. The results show the strong influence of the flexible ground characterized by a remarkable shifting of natural frequencies, by the existence of additional natural frequencies, and by high damping ratios.