Earthquake Response of Base-Isolated Liquid Storage Tanks for Different Isolator Models

The effect of different isolator parameters on earthquake response of base-isolated liquid storage tanks is investigated herein. Mechanical analog, with three lumped masses, is used to model ground supported base-isolated liquid storage tank, and analyzed for recorded earthquake ground accelerations. The nonlinear force-deformation behavior of the isolator is mathematically modeled in two different ways, represented by (a) equivalent linear elastic-viscous and (b) bi-linear hysteretic behaviors. The equations of motion for the base-isolated tank are derived and solved in the incremental form using New-mark's step-by-step method of integration. Two different configurations of liquid storage tank (i.e. broad and slender) are considered to show the effect of the equivalent linear and bi-linear modeling of the isolator on the important earthquake response quantities. Effect of nonlinear hysteretic modeling of the isolator on peak response of the base-isolated liquid storage tanks is also investigated. The effect on earthquake response of the base-isolated liquid storage tank is studied for different parameters of the isolator for a range of slenderness ratio of the tank. The parameters considered include the characteristic strength of the isolator, isolation time period, isolator yield displacement etc. Significant difference is observed in the earthquake response of the base-isolated liquid storage tanks owing to the equivalent linear and bi-linear modeling approaches of the isolator. However, for bi-linear and nonlinear hysteretic modeling of the isolator, difference between the peak earthquake response of base-isolated liquid storage tanks are insignificant. The earthquake response of base-isolated liquid storage tanks is significantly influenced by the variation in the isolator parameters and slenderness ratio of the tank