Performance analysis of gap-SMA isolation bearing and its negative stiffness improvement

Compared with traditional isolation bearings,shape memory alloy ( SMA) isolation bearings can improve the self-resetting and energy dissipation capacity of structures. However, early intervention of SMA may increase internal forces and acceleration responses of superstructure during moderate and small earthquakes. Here, to solve this problem, gap-SMA isolation bearing was formed by introducing gap into SMA isolation bearing to meet isolation requirements of different fortification targets. Firstly, the physical structural form of gap-SMA bearing was proposed, and cyclic tensile tests of SMA wire were conducted. Then, a simplified model of 2D0F frame structure was taken as an example to explore effects of gap length and SMA yield force on isolation effect. Finally,internal force and acceleration response of gap-SMA isolation bearing was reduced under large or great earthquake, the negative stiffness mechanism was further introduced to improve gap-SMA isolation system, and explore the feasibility of negative stiffness-gap type SMA bearing isolation. The calculation results showed that gap-SMA isolation bearing can effectively reduce internal forces and acceleration responses of superstructure during moderate and small earthquakes ; acceleration responses of superstructure are negatively related to gap length,and positively related to SMA yield force ; displacement responses of substructure are positively related to gap length and negatively related to SMA yield force ; after introducing negative stiffness,gap-SMA bearing can effectively control bearing displacement response under large or great earthquake,and significantly reduce internal forces and acceleration responses of superstructure. © 2023 Chinese Vibration Engineering Society. All rights reserved.