Self-centering Capability of Seismically Isolated Structures After Earthquakes

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 a large deformation well under strong earthquakes. 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. In addition, it is difficult to repair and return to the original position after the earthquakes. For this reason, the provisions of the current design codes on the restoring capability of the isolation bearing were investigated. By combining the super-elastic 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 SMA–LRB exhibits excellent self-centering capability. Considerable residual deformation of LRBs may be observed even though the traditional LRBs can meet the code requirements. However, the residual deformation is not directly related to the maximum deformation of the isolation layer, which may be more prone to residual deformation under moderate earthquakes (such as design-based earthquakes). By contrast, the SMA–LRB isolation system exhibits excellent self-centering capability. © 2023 Editorial Department of Journal of Sichuan University. All rights reserved.