Cyclic tension-compression behavior of superelastic shape memory alloy bars with buckling-restrained devices

Shape memory alloys (SMAs) show great potential in seismic applications because of their appealing superelastic feature and good energy dissipation capacity. The tensile behavior of SMA wires and bars has been extensively studied over the past decades. However, little attention has been paid to their compressive properties under cyclic loading. Thus, this paper presents a systematic experimental study on the cyclic behavior of superelastic SMA bars with buckling-restrained devices (BRDs) when subjected to tension-compression cycles. The detailed design of BRD is described first. The material properties such as “yield-like” strength, peak strength, self-centering capability, and energy dissipation of typical interest in seismic applications are evaluated with varying strain amplitudes, strain rates, and loading protocols. Test results show that satisfactory and stable flag-shaped hysteretic loops without any strength degradation are obtained in multiple loading cycles under cyclic tension-compression loading. Moreover, the SMA bars exhibit remarkable self-centering capability that is nearly independent of strain rate and loading protocol.