Inner pounding control of the RNC isolator and its impact on seismic isolation efficiency under near-fault earthquakes
Inner pounding control of the RNC isolator and its impact on seismic isolation efficiency under near-fault earthquakes
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DOI：
10.1016/j.engstruct.2014.12.041
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发表时间：
2015-03
影响因子：
5.5
通讯作者：
M. Ismail
中科院分区：
文献类型：
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作者：
M. Ismail
最近提出的RNC隔震器具有固有的自停止机制，在此用于防止近断层地震，并在不使用更大的隔震器或更大的地震间隙的情况下容纳预期的较大隔震器位移。缓冲机制被设计成将RNC隔离的上层建筑的任何可能的地震冲击向下拉，以便仅在RNC隔离器的边界内发生。本研究探讨如何使用被动和主动反馈控制来减轻这种内部RNC隔振器撞击可能产生的不良影响。首先，通过增加附加滞回阻尼力来被动控制内隔振器的碰撞。然后，将主动反馈控制力积分到纯被动RNC隔振器上，形成混合隔震系统。主动控制力旨在通过在隔振器自停止机构启动之前降低隔震结构的速度来减轻隔振器的内部碰撞。结果表明，在放大峰值结构加速度方面，隔振器的内部碰撞可能会降低隔震效率，但这种劣化可以得到有效的改善。本文采用无源和混合策略来控制内部RNC隔振器的冲击，能够减少甚至消除冲击的严重程度。然而，主动控制力降低了结构-地面的解耦程度，导致隔震效率较低，而采用附加滞回阻尼力的被动碰撞控制被发现是一种更实用、更有效的解决方案。此外，研究还发现，滚动式RNC隔震器即使在相对较小的隔震周期内也能够提供有效的抗震保护，此外，考虑到小轴承的设计位移，该隔震器还能够进行优化，以提供有效的隔震，在强地面运动下绝对不会发生内部碰撞。
The recently proposed Roll-in-Cage (RNC) isolator, with an inherent self-stopping mechanism, is used herein for protection against near-fault earthquakes and to accommodate the expected large isolator displacement without using larger isolators nor bigger seismic gaps. The buffer mechanism is designed to draw any possible seismic pounding of a RNC-isolated superstructure downward to take place only within the RNC isolator’s bounds. The study investigates how to alleviate possibly arising unwanted effects due to such inner RNC isolator pounding by using passive and active feedback control. The inner isolator’s pounding is first controlled passively using more added hysteretic damping. Then, active feedback control forces are integrated to the purely passive RNC isolator to form a hybrid isolation system. The active control forces are intended to alleviate the isolator’s inner pounding through reducing the velocity of the isolated structure before the activation of the isolator’s self-stopping mechanism. The results show that the developed isolator’s inner pounding may deteriorate isolation efficiency, in terms of amplified peak structural accelerations, but such deterioration can be efficiently improved. The use of passive and hybrid strategies to control the inner RNC isolator’s pounding in this paper were found able to reduce, or even eliminate, pounding severity. However, active control forces decrease the degree of structure-ground decoupling causing less efficient isolation, contrary to the passive control of pounding using added hysteretic damping, which was found to be a more practical and more efficient solution. Moreover, it was found that the rolling-based RNC isolator is able to provide efficient anti-seismic protection even at relatively small isolation periods, besides its ability to be optimized to provide efficient seismic isolation with absolutely no inner pounding under strong ground motions, considering small bearing’s design displacements.