A proposed approach to mitigate the torsional amplifications of asymmetric base-isolated buildings during earthquakes

Abstract

In this paper, the rotational behavior of asymmetric base-isolated buildings is compared with the similar asymmetric fixed-base buildings. A vast range of lead rubber bearings with different periods is considered to evaluate the effect of the isolation degree on seismic responses of the structures. The simulation results confirm that the base isolators are able to reduce rotation of stories. However, this reduction is negligible in large eccentricities. The numerical simulations show that increasing period of isolators results in large displacement at bearings located on the flexible edge of the isolation system. This paper proposes practical solutions to reduce torsional responses of the base-isolated structures. In order to investigate the effectiveness of the proposed solutions, four structural models are defined. Considering three earthquake excitations, the simulation results of these models indicate that increase in stiffness of flexible edge of isolation system can reduce torsional responses of asymmetric 3-story base isolated structure. Furthermore, the simultaneous increase in stiffness of flexible edge of isolation system and superstructure lead to a suitable reduction of torsional responses in asymmetric 8-story base-isolated structure.