Dynamic Behavior Evaluation of FPS Isolated Liquid Storage Tanks Subjected to Pulse-like Excitations

On-grade liquid storage tanks are vulnerable to strong ground motions, as some recent major earthquakes have demonstrated. Seismic base isolation is one of the most efficient techniques to mitigate earthquake damage in these structures. Among the various base isolation devices, the Friction Pendulum System (FPS) provides several benefits: the independence of isolation period from superstructure mass/weight which can be varied in some structures such as liquid storage tanks, re-centering related to the spherical surface, and high energy dissipation based on velocity-dependent friction (Mokha et al., 1991; Zayas et al., 1990). Although the base isolation has been known as an efficient technique to protect civil structures, the performance of base-isolated structures under near-fault ground motions containing long-period pulses has been questioned in recent years. In this paper, a parametric study is carried out to investigate the seismic behavior of FPS isolated liquid storage tanks under near-fault ground motions represented by analytical pulse-like functions. For this purpose, the liquid storage tanks are modeled using equivalent mechanical models and then dynamic analyses of the models are done using pulse-like excitations. The effects of the tank type, isolator specifications and the input excitation characteristics on the various response parameters are investigated.