Seismic Response Reduction in Liquid Storage Tanks by Simple Smart Base Isolation Systems

In this paper, a nonlinear autonomous algorithm is proposed to control the variable dampers and to provide semi-active control of a liquid storage tank by taking advantage of similarity to friction models and avoiding demerits. Friction mechanism in sliding bearings shows rigid-perfectly plastic behavior with limited damping force. However, transition of vibrations of high frequencies and appearance of residual displacements after the excitation are the drawbacks of such systems. Considering a performance-based seismic design approach, the proposed damping mechanism is capable of controlling the system in a two-level seismic design criterion. The performance and applicability of both the proposed algorithm and a variable oil damper under this command were experimentally verified in previous research. The effect of passive and semi-active seismic control of a liquid storage tank on the response of the structure and sloshing liquid is analytically investigated. Three base isolation systems with passive viscous or sliding dampers are applied and compared with three hybrid semi-active base isolation systems. Pseudo-negative stiffness, skyhook and a proposed control strategy by author are utilized as the control systems. A lumped mass–spring model is employed to represent the dynamic behavior of the tank and the contained liquid. The structural response and sloshing are calculated and compared. It is shown that the smart base isolation system is effective in reduction in the base shear and displacement of the structure. The sloshing response observed through the displacement and kinetic energy of the convective mass is reduced by the hybrid control systems.