BASE-ISOLATED STRUCTURES WITH OPTIMIZED DISTRIBUTION OF LRB AND FPS ISOLATORS

Seismic base isolation is an earthquake resistant design method that is based on decreasing the seismic demand instead of increasing the seismic capacity. In this paper, the seismic response of base-isolated structures is numerically investigated. The effectiveness of an isolation system depends upon the dynamic characteristics of earthquake ground motion and the building superstructure. In order to evaluate the dynamic response of nonlinear base-isolated structures, different detailed 3D nonlinear analytical models with different characteristics are developed and analyzed under significant and strong motion earthquakes. Also in order to have the optimized behavior of system, different types of isolators including Lead-Rubber Bearing (LRB) and Friction-Pendulum (FPS) isolators were simulated between the superstructure and the foundation so as to provide lateral flexibility and energy dissipation capacity. Providing an optimized arrangement of different types of isolators in the structure is important since it affects the structural responses to earthquakes. The parametric study is concentrated on base shear, accelerations and displacements of isolated models. Also the comparison between hysteretic responses of models as a main criterion for energy dissipation of system has been investigated and evaluated. Results show that the model with FPS ratio of 25% has the best structural response against seismic loads.