Shape memory alloy plates : cyclic tension-release performance, seismic applications in beam-to-column connections and a structural seismic demand perspective

Abstract

This study examined the hysteretic behaviour of commercial Shape Memory Alloy (SMA) plates to promote their seismic applications in beam-to-column energy dissipation connections, and the research focus was given to the cyclic tension-release behaviour. Based on a series of SMA plate specimens, the investigation was commenced by examining the thermal characteristics, and the phase transformation behaviour of the SMA plates was characterised. Subsequently, cyclic tension-release tests of the SMA plates were conducted in the laboratory at room temperatures, and multi-phase tests considering varied loading protocols were carried out. It was observed that the self-centring capability of the SMA plates was comparatively less encouraging than bars and wires examined in the literature, whereas training cycles enabled stabilisation of the behaviour of the specimens by producing a newly recentring strain range with increased post-yield behaviour and decreasing martensite transformation stress. However, the energy dissipation of the SMA plates was reduced after experiencing the training protocols. Following the test programme, detailed numerical models of novel beam-to-column energy dissipation connection equipped with SMA plates were developed, and the feasibility of exploiting the cyclic behaviour of SMA plates was confirmed. Nonlinear spectral analyses of single-degree-of-freedom (SDF) systems representing structures were analysed to examine the influence of the structural hysteretic parameters on the structural inelastic demands quantified by strength reduction factor, and the influence of hysteretic parameters of the SMA plates on the structural seismic demand was characterised.