Large-size shape memory alloy plates subjected to cyclic tension: Towards novel self-centring connections in steel frames

In this study, the hysteretic behaviour of shape memory alloy (SMA) plates under cyclic tension-release loadings was examined to promote their seismic applications, with an emphasis on large-size SMA plates with different geometries. Based on a series of SMA plate coupons extracted from base plates with different geometries, the thermal characteristics were investigated, and the phase transformation behaviour of the SMA plates was characterised. Subsequently, cyclic tension-release tests were conducted on the SMA plates in the laboratory, and the key mechanical performance indexes including the transformation strength, post-yield behaviour, self -centring capabilities, and energy dissipation abilities were carefully investigated. According to the results, SMA plates have a comparatively encouraging self-centring ability and moderate energy dissipation capabilities within a specified strain range. However, larger SMA plates show less satisfactory self-centring behaviour and are prone to brittle fracture at the edges. Based on the test programme, a numerical investigation was conducted to offer further insight into the potential applications of large-size SMA plates in the seismic field. A practical modelling procedure, namely the hybrid finite element (FE) modelling technique, was proposed and used to reproduce the degradation and cumulative residual deformation in the SMA plates. Moreover, nonlinear response history analyses (NL-RHAs) were performed on a prototype steel frame equipped with SMA plates in the connections to verify the feasibility of using large-size SMA plates in steel structures.

Automated summary

This study investigated the hysteretic behavior of large-size shape memory alloy (SMA) plates with different geometries under cyclic tension-release loadings to enhance their seismic applications. The thermal characteristics and phase transformation behavior of SMA plates were characterized using extracted coupons from base plates with various geometries. Cyclic tension-release tests were performed on the SMA plates in the laboratory to examine their mechanical performance indexes, including transformation strength, post-yield behavior, self-centring capabilities, and energy dissipation abilities. The results showed that SMA plates have promising self-centring ability and moderate energy dissipation capabilities within a specified strain range, although larger plates exhibited less satisfactory self-centring behavior and were prone to brittle fracture at the edges. Numerical investigations using hybrid finite element (FE) modelling technique and nonlinear response history analyses (NL-RHAs) on prototype steel frames with SMA plates were conducted to further explore the potential applications of large-size SMA plates in seismic fields.