隔震结构震后复位能力研究

隔震技术是在上部结构与下部支承结构或基础之间设置隔震层，通过延长结构周期并增加阻尼的方式，减少地震能量向上部结构传输从而保护上部结构，是高烈度地区减轻地震灾害最有效的方式之一。由于隔震层的刚度较小，隔震结构的变形绝大多数集中在隔震层。在强震或强风作用下，隔震装置虽然能够很好地满足大变形的需求，但是变形结束后，隔震装置在某些地震作用下很难自动复位到初始状态。隔震层明显的残余变形可能会导致主体结构正常使用功能的中断，并且难以保证隔震装置在多次余震或未来地震中继续发挥作用，从而对社会经济的发展带来严重的影响。如何提升隔震支座变形后的复位能力，是隔震结构设计的关键问题之一。本文首先介绍了传统隔震支座在地震与强风作用下复位能力不足的表现，总结了当前设计规范中对隔震支座复位能力的规定，阐述了提升隔震支座变形后复位能力的方法。基于此，以超弹性形状记忆合金（SMA）良好的变形自恢复能力为基础，结合铅芯橡胶隔震支座（LRB），提出了新型自复位隔震支座（SMA-LRB）。通过压剪往复加载试验，对比了传统LRB与SMA-LRB的力学行为。对基于不同规范限值的LRB以及SMA-LRB的单自由度体系进行非线性时程分析。结果表明，在满足规范设计的情况下，LRB隔震体系在震后仍可能出现较大的残余变形，而SMA-LRB隔震体系则表现出良好的震后复位能力。

Self-centering Capability of Seismically Isolated Structures After Earthquakes

Seismic base isolation system is one of the effective technologies that provides the flexibility and damping in the isolation layer and mitigate seismic damage in high seismicity regions. The isolation system is typically designed at the base of the structures or between the support structure and superstructure to protect the superstructure by reducing the transmission of earthquake energy to the superstructure. The deformation of the isolated structure is mostly concentrated in the isolation layer due to its low stiffness. Isolation bearings commonly meet the requirement of the large deformation well under strong earthquakes or winds. However, it is difficult for the bearings to recover to their initial state after such large deformation under some earthquakes. Significant residual deformations of base isolators may disrupt structural serviceability and reduce the capability of base isolators to withstand immediate aftershocks and future earthquakes, leading to severe socioeconomic losses. How to improve the self-centering capability of the isolation bearings is one of the key issues in the design of isolated structures. Firstly, this paper introduced several cases of the insufficient self-centering capability of the isolation bearings under strong earthquakes and winds. The provisions on the restoring capability of the isolation bearings in the current design codes were summarized. For this reason, by combining the superelastic behavior of the shape memory alloy (SMA) and lead rubber bearing (LRB), a novel self-centering isolation bearing (SMA-LRB) was proposed. The mechanical behaviors of traditional LRB and SMA-LRB were compared through compression-shear cyclic loading tests. Nonlinear time-history analyses of the single-degree-of-freedom isolated systems designed according to different code requirements and the SMA-LRB system were carried out. The results show that considerable residual deformation of LRBs may be observed even though the traditional LRBs can meet the code requirements. By contrast, the SMA-LRB isolation system exhibits excellent self-centering capability.