Seismic Response of Soil-Supported Unanchored Liquid-Storage Tanks

Abstract

A systematic study is made of the effects of base uplifting on the seismic response of cylindrical liquid-storage tanks that are supported directly on flexible soil foundations. First, a detailed investigation is made of the effects of system parameters on the uplifting resistance and energy dissipation capacity of the partially uplifted base plate. It is shown that: (1) the hydrodynamic base pressures reduce the uplifting resistance as well as the energy dissipation capacity of the base plate; (2) the uplifting resistance increases with increase in the thicknesses of the base plate and the tank wall, and the stiffness of the foundation soil; and (3) the energy dissipation capacity increases with an increase in the base-plate thickness and the yield level of plate material, and reduces with increase in foundation stiffness and the thickness of the tank wall. Next, an efficient method is presented for the dynamic response analysis of flexibly supported unanchored tanks. It is shown that the flexibility of the foundation reduces the overturning base moment, and reduces significantly the axial compressive stresses in the tank wall, but these reductions are accompanied by increased values of plastic rotations and (in some cases) base uplifting and hoop compressive stresses.