Research On Seismic Behavior Of Re-centring Isolation System Under Near-fault Earthquake

Base isolation system can effectively reduce the seismic response of the upper structure by increasing the natural period of the building, can distinctly dissipate the seismic energy because of the certain damping attached to the base isolation bearing, which is widely applied to the engineering practice on account of the proven technique and promulgation of the related national code. The lead rubber bearing which is widely applied, is able to performance perfectly and plays a better vibration isolation effect against the frequently earthquake. whereas it could be destructed, even inactivated, has the limited energy-dissipation capacity, and can’t return to the initial position after seismic effect under the near-fault ground motion which contains larger velocity pulse and leads to the greater influence relative to the far-fault ground motion. However the research and development of the new materials which is shape memory alloy (referred to SMA) can provide the possibility to improve the performance of the lead rubber bearing.SMA are a class of novel intelligent alloy materials which possess the specific superelasticity effect (referred to PE) and the shape memory effect (referred to SME). Taking use of the self-recentring function provided by SMA stress-induced martensitic transformation can improve the deformation characteristics of LRB. This thesis focuses on the in-depth research and analysis for the seismic response of the self-recentring isolation system with shape memory alloys under the near-field ground motion. The main contents are included the following aspects:(1). Base on the proposed new self-recentring isolation bearing, a constitutive model was established and conducted the numerical simulation analysis utilizing the Simulink block library which provides a foundation for the research on the seismic response of the base isolation system under the effect of near-fault ground motion.(2). Considering the seismic reactions of the base isolation system respectively under the near-fault earthquake in both cases of seismic fortification intensity of 8,9 degrees, the inter-story displacement and absolute acceleration responses of the isolation layer and superstructure were studied. Also the vibration isolation effect of the new SMA self-recentring isolation bearing is examined. The results show that the SMA can effectively improve the deformation characteristics of isolation bearing.(3). The near-fault ground motion response of the self-recentring isolation system, LRB isolation system and non-isolated common building were performed respectively. The results show that both the SMA self-recentring isolation and the LRB isolation system can better reduce the seismic response of the superstructure, but in contrast to the greater inter-story displacement of the LRB which has lost its isolation ability, the inter-story displacement of the self-recentring isolation bearing is smaller which can effectively perform well to isolate the near-fault ground motion.(4). The seismic responses of SMA self-recentring isolation system under the near-fault ground motion with and without the velocity pulse effect were researched to verify the near-fault earthquake with velocity pulse effect has the significant influence on the structural response and the SMA self-recentring isolation bearing has good deformation characteristics. The results also indicate that the PGV values have greater impact on the structural response and the isolation rate decreases with the increasing PGV values.(5). The influences of the various parameters of SMA, such as quantity, yield displacement and prestrain on the seismic response of self-recentring isolation system were researched. And the results show that the SMA quantity and yield displacement have greater impact on the structure response with respect to the influence of the prostrain which is not obvious.