近断层脉冲型地震动作用下高层建筑组合隔震的减震性能研究

Seismic absorption performance of composite isolation for high-rise buildings subjected to near-fault pulse ground motions

近断层地震动中的长周期、短持时、高能量的加速度脉冲将对长周期高层隔震结构的减震性能产生不利影响,尤其易使LRB(lead-rubber bearing)支座产生超限变形,导致在大的面压与位移共同作用下发生剪压破坏;此外,考虑土-结构相互作用(SSI效应)后隔震结构将产生动力耦合效应,可能进一步放大隔震结构地震响应。提出滑板支座、复位装置相结合的新型组合隔震系统,利用滑板支座承担大的竖向荷载、复位装置因不承担竖向荷载而获得更大的变形能力且起隔震层自复位作用。考察近断层脉冲型地震动作用下长周期高层隔震结构的地震响应规律,揭示隔震体系的损伤机理。基于集总参数SR(sway-rocking)模型,分析不同场地类别与不同地震动类型对隔震体系动力响应影响规律。结果表明:近断层罕遇地震下LRB隔震系统因变形超限而失效;新型组合隔震系统能保证近断层脉冲型地震下隔震的有效性,且具有较为良好的减震性能,但相比普通地震动减震效果变差;对于Ⅲ,Ⅳ类场地类别,考虑SSI效应使隔震体系的刚度弱化,致使层间位移角增大,且随着土质的变软增大的幅度也越明显。

The horizontal pulse motions of acceleration featured by long period,short duration and high energy in near-fault ground motions would exert the adverse impacts on the seismic performance of the long-period base-isolated high-rise structures,resulting in the excessive deformation of the LRB.The shear-compression failure of the isolation bearing would be caused under the cooperative action of large surface pressure and the excessive deformation.Furthermore,the soil-structure interaction(SSI)would result in the dynamic coupling effect,which may further amplify the seismic response of the isolated structure.To this end,a new-type composite isolation system that combined slide bearings and reset devices is presented,in which the slide plate bearings is used to resist large vertical load,and because of no bearing vertical load the reset devices get greater deformation capacity and act as a self-reset function of the shock isolation layer.Then,the impacts of near-fault pulse ground motions on the base-isolated high-rise structures are revealed,and the damage mechanism of the isolation system is examined.Further,based on the sway-rocking model,the effects of different site types and different ground motion types on the dynamic response of the isolation system are analyzed.The results show that the excessive deformation of the LRB system subjected to near-fault rarely ground motions are caused,resulting in the failure of the lead rubber system.The new-type composite isolation system can ensure the effectiveness of isolation subjected to near-fault pulse ground motions,and has good seismic absorption performance which is worse than that under ordinary ground motion.ForⅢandⅣsites,the interstory drift ratios increase obviously with the soil softening because of the SSI effect weakening the stiffness of the seismic isolation system.