Seismic response of column supported tanks considering uplift effect and soil-structure interaction

In this paper, the seismic responses of column supported tanks under horizontal earthquake are obtained by finite element method. Two types of structures are discussed including the anchored tank with columns fixed on the ground and the resilient tank whose columns can uplift. The uplift effect is realized by the contact algorithm to allow the column move upwards in a vertical direction and the soil-structure interaction (SSI) is considered by equivalent soil springs. Different soil types and hard ground condition are adopted to study SSI effect on natural frequencies of tanks and seismic responses of the anchored tank, as well as coupling effect (both uplift and SSI effects) on seismic responses of the resilient tank. The structural displacement and acceleration, the stress of tank walls and columns, the base shear and the overturning moment, the uplift displacement of columns are discussed. The results of tanks in different conditions are compared with each other, which show that SSI has a significant impact on seismic responses of column supported tanks. As the stiffness of soil decreases, the tank has larger displacement, smaller natural frequency, and stress level of structural members especially when it is sited on softer soil type. Compared to the anchored tank, due to the combination of both uplift effect and foundation deformation, the resilient tank has smaller displacement to prevent its overall collapse and lower responses such as the base shear and the overturning moment. The resilient tank has better seismic performances regardless of soil conditions.