Impact effect on seismic response of friction pendulum base isolated liquid storage tanks

Liquid storage tanks are important industrial structures that must continue their performance under severe earthquakes. The induced damages caused in the past earthquakes shows their poorly behavior of these structures. One of the most effective methods to retrofit and reduce the induced forces is to use base isolation. Friction Pendulum System called FPS has better performance compared to other base isolation systems, due to its period does not depend on the weight of the structures above it. The aim of this paper is to investigate the effect of FPS under three different hazard level earthquakes (SLE, DBE and MCE). It is also, the impact effect due to contacting the slider with the side restrainers is investigated. For the required analysis, two different liquid storage tanks are considered and their responses are compared in Fixed, Isolated without considering impact and isolated with considering impact conditions. The obtained results show, increasing the hazard level of ground motions leads to decreasing the performance of FPS. It is also observed, compared to SLE and DBE earthquake ground motions the MCE has the maximum probability of impact. The results also show that, the impulsive mass displacement, overturning moment and base shear increases when the impact occurs, while the impact has no special effect on convective displacement.