Influence of the Isolator Characteristics on the Response of the Isolated Buildings in the Near-Fault Earthquakes

Seismic base isolation are devices that used to limit the human and material damage caused by an earthquake. This devices diffuse the energy induced at the time of the earthquake before being transferred to the structure.The base isolated structures when subjected to the near-fault eathquakes which contain long-period velocity pulses that may coincide with the period of base isolated structures resulting in excessive deformation and rupture of isolators. Parameters of base isolation such as the yield strength and post yield stiffness ratio have significent effect on the displacement of isolation system. To study this effect, influence of these parameters on the dynamic response of the isolated structures in term of displacment, acceleration, base shear and absorbed energy has been studied. The results show that the increase in the bearing yield strength can reduce the bearing displacment signficantly without much alterning to the superstructure accelerations. Also the optimum yield strength and post yield stiffness ratio of the LRB is found to be in range of 0.8% - 1% of the total weight of the building and 0.08 – 0.12 of the ratio of plastic stiffness to elastic stiffness of base isolation respectively under near fault motions.