Seismic Performance Evaluation of the Base Isolation Systems

As Seismic isolation is one of the remedies for providing earthquake-resistant features for structural components, non-structural components, and contents of the building systems, its performance may become counter-productive under the effect of near-field ground motions, in which case an increased structural response might result due to resonance. For this reason, one of the greatest challenges of researchers is to understand the behavior of base isolation systems and base-isolated buildings under the conditions of different ground motions. The specific objective of this study is to evaluate the seismic response of multi-story base-isolated buildings with lead core rubber bearings (LCRBs) and buildings that are not isolated when subjected to different types of ground motions with different components. To this end, the vulnurablity of the base-isoated buildings and the isolation system against near-field pulse period ground motions as a result of resonance are being evaluated and shows that base-isolated builindgs and base isolation system are period dependent. Then, in this direction, the response of a high-rise and a low-rise building, which are isolated with Lead Core Rubber Bearing (LCRB) subjected to near-field pulse period ground motions are investigated. Since the fundamental natural period of a structure is not affected by fluid viscous dampers (FVD), FVD was implemented together with LCRB forming a kind of Fluid Viscous Damper-Base Isolation System (FVD-BIS).Therefore, several ground motions have been generated synthetically with a specific pulse period, and have been used in the analyses, which is set close to the fundamental period of the base-isolated high-rise building to facilitate resonance. However, some investigations have suggested that FVD can improve the performance of the base-isolated buildings, but the impact of FVD-BIS on the base- isolated high-rise and low-rise buildings at the time of resonance is not clear yet. The results of this study have been illustrated that the intensity of the resonance phenomenon can be sharply mitigated in the base-isolated high-rise building using FVD-BIS. Keywords: Lead core rubber bearing, Fluid viscous damper-base isolation system, Resonance phenomenon, Pulse-like ground motions, Probabilistic evaluation.