Seismic Rehabilitation of Liquid Storage Tanks using Friction Pendulum Base Isolation subjected to the Near-Fault Ground Motions

Document Type: Regular Paper

Authors

1 Islamic Azad University

2 Civil Engineering Department

Abstract

Cylindrical liquid storage tanks are considered as vital structures in industrial complex whose nonlinear dynamic behavior is of crucial importance. Some of these structures around the world have demonstrated poor seismic behavior over the last decades. There are several methods and techniques for rehabilitation and reducing damages in these structures which among them passive control devices, in particular seismic base isolators, are noticeable. Friction Pendulum System (FPS) is the most popular base isolation system. In this paper, the effectiveness of FPS is studied on reducing the seismic responses of base isolated liquid storage tanks as well as the impact effect of slider to the side restrainer. To this end, the whole mass of liquid storage tank is considered as three lumped masses known as convective mass, impulsive mass which is connected to tanks with corresponding spring, and rigid mass which is connected rigidly. By means of state space method the time history analysis is done using 60 earthquake records to obtain dynamic responses under the different hazard levels i.e. SLE, DBE and MCE ground motions. The results show that the normalized base shear force in squat tank decreased 59%, 62% and 33% respectively under SLE, DBE and MCE ground motions. The reduction of normalized base shear force in slender tank is 53%, 49% and 35% under the aforementioned hazard levels. Examining the effect of side restrainer’s stiffness on the maximum responses show that the impact effect must be considered particularly when the system is excited by MCE’s ground motions.

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