Influence of base plate bending stiffness on the seismic performance of liquid storage tanks

In the past, a number of investigations have been performed on the seismic behaviour of storage tanks. At the University of Auckland, a number of shake table experiments on tanks with different aspect ratios have been recently performed. The earthquake ground excitation was simulated based on a design spectrum from the New Zealand code NZS 1170.5, classification D for soft soils. The results show that the base plate stiffness of storage tanks may play a significant role in the magnitude of hoop stresses caused by the passage of the earthquake. To incorporate a low-damage seismic design philosophy, the tank is allowed to separate partially at the base. This temporary separation initiates rigid body like motion of the tank and thus reduce the wall local deformations. Consequently, the stress development along the wall can be reduced from that occurring with full base plate contact. This research focuses on the effect of the base plate thickness on the hoop stress development along the height of the tank wall for five radial directions.