Experimental study of the effect of a flexible base on the seismic response of a liquid storage tank

Abstract

Previous studies have demonstrated that strong earthquakes can cause severe damage to storage tanks. In many countries tanks are built near the coast on soft soils. Because of the difference in stiffness between the tank (rigid) and the soil (flexible), the soft soil causes an elongation in the period of the impulsive mode of the soil-foundation-tank system and, therefore, this flexible base can have an important effect on the seismic response. Numerical studies by other researchers have shown the influence of a flexible base on the seismic response of storage tanks. However, experimental investigation on the effects of a flexible base using sand box on the key design parameter, i.e. stress developed in the tank shell, has not been reported. In this research shake table experiments were performed. Sand in a box is used to simulate the flexible base. Actual earthquake records scaled to the New Zealand design spectrum for Wellington City are used. The results showed that in comparison with the rigid base case (model placed directly on the shake table) the axial compressive stresses decreased. The experimental results are corroborated by a numerical model.