Seismic-reduction Performance And Failure Control Of Isolation Structures Under Multi-type Long-period Ground Motions

As one of major means of reducing seismic hazard to structures,isolation technology was wildely used in multi-storey and high-rise structures in recent years.However.near-fault pulse-like ground motions and far-field long-period ground motions featured by velocity or acceleration pulse and rich low frequency components,especially harmonic-like characteristic of far-field long-period ground motions,may cause severe damage on long-period structures(high-rise or super high-rise buildings,long-span bridge and isolation structures),and resulted in serious property loss and personnel casualty.At present,the seismic-reduction performance of isolation structures under long-period ground motions were not researched enough,especially under far-field harmonic-like ground motions.Therefore,the response characteristics of isolated structures under long-period ground motions should be examined.This research focused on the seismic reduction performance,damage mechanism and failure control of the mid-story isolation,new-type combination isolation and FPS isolation structures under multi-type long-period ground motions.The following work were accomplished by follows:(I)Seventeen different-type records of long-period ground motions were selected.Then,based on the acceleration response spectrum,velocity response spectrum,displacement response spectrum and fourier energy spectrum,the difference of response spectrum characteristics between long-period ground motions and common ground motions were analyzed.The principle of damage aggravating for long period structure under long-period ground motion were described,and it provided the theoretical basis for the dynamic response-of isolated structures under long-period ground motions.(2)The seismic-reduction performance and failure control of mid-story isolation structure with large chassis under multi-type long-period ground motions were studied.First,a single tower mid-story isolation structure with large chassis,in which the isolation layer using by rubber isolation bearings(LRB,LNR)were used in this isolation,is established to analysis dynamic response under long-period ground motions.The damage mechanism of isolation bearing,upper and lower structure of isolation layer were revealed.Then,a combined isolation scheme of viscous dampers and rubber bearings was proposed to control the response of isolated structures.At the end,seismic reduction performance of mid-story isolation structure considering SSI effect were studied.The results show that seismic reduction performance of mid-story isolation structures under long-period earthquake become worse,and the bearing deformation is overrun under rare earthquake.The combined isolation can effectively control the deformation of the isolation bearing and the validity of the isolation system is ensured.In addition,the adverse effects of SSI should be taken into account in the design of mid-story isolation structures in soil site of category ? and ?.(3)The seismic-reduction performance of new-type combined isolation system were studied under multi-type long-period ground motions.Two different types of high-rise new-type combined isolation schemes were put forward:?new-type combined isolation 1:slide bearing(ESD)+ restoration device of lead rubber.The vertical load was supported by the slide bearing,and the lead rubber bearing were used to provided restoring forces and energy dissipation without vertical load.? new-type combined isolation ?:slide bearing(ESD)+ restoration device of lead rubber+ viscous dampers,viscous dampers were used to controlled the displacement of the isolation layer.The seismic-reduction performance of the two isolation systems under multi-type long-period ground motions were studied.Then,the damage mechanism of different isolation systems were analyzed.At the end,seismic-reduction performance considering the SSI effect were studied.The results show that new-type combined isolation ? can ensure the validity of the isolation system and provide good seismic-reduction performance under near-fault pulse-like ground motions.New-type combined isolation ? can effectively control structural response under far-field long-period ground motions.In addition,the adverse effects of SSI should be taken into account in the design of high-rise isolation structures in soft site of category ? and ?.(4)The seismic-reduction performance and failure control of high-rise friction pendulum isolation structures under multi-type long-period ground motions were studied.The seismic-reduction performance of the frame-core tube friction pendulum(FPS)isolated structure under multi-type long-period ground motions were investigated.Then dynamic responses of frame-core tube friction pendulum(FPS)isolated structure were analyzed.Further,damage mechanism of isolation layer and superstructure were revealed,and the failure control scheme of frame-core tube friction pendulum(FPS)isolated structure under long-period earthquake was presented.Finally,the seismic reduction performance of frame-core tube friction pendulum isolation structure considering SSI effect were studied.The results show that the seismic performance of friction pendulum(FPS)base isolation get worse,even the seismic respones of the structures are enlarged under far-field long-period ground motions.The combined isolation system can effectively control the amplification effect of the seismic response and the deformation of the bearing,and can reduce the damage of the isolation structure.In addition,the adverse effects of SSI effect should be taken into account in the design of FPS base isolation structures.(5)Shaking table tests of isolation structures with a large chassis under multi-type long-period earthquakes were carried out.The experiences of a seismic frame structure,base isolation structure and mid-story isolation structure model was performed by shaking table.The acceleration time history,velocity time history and displacement time history responses of different floors under multi-type ground motions were measured.The seismic isolation effected of different isolation structures under multi-type ground motions were investigated,and it was compared with the finite element results.