Experiment on hysteretic behavior of beam-to-column connection using martensite NiTi shape memory alloy threaded rods in steel frame

In order to investigate the mechanical properties and energy dissipation capacity of the beam-to-column connections using martensite NiTi shape memory alloy threaded rods (SMA connections), the monotonic tensile properties and shape memory effect of NiTi alloy bars were tested, and the quasi-static tests of the SMA connections and the retests of the above connections after heating repair were conducted. The experimental results show that the NiTi alloy has so large recoverable strain that it can satisfy the rehabilitation requirements of various damage states of the connection. The SMA connection exhibits stable hysteretic behavior and energy dissipation capacity. The post-strengthening effect of the connection attributed to the SMA rods, can make up for or eliminate the performance degradation of the connection caused by the damaged elements to some extent. The unique shape memory effect and superior fatigue property of NiTi alloy ensure the reusability of SMA threaded rods and the rehabilitation capability of the connections. The deterioration of the shape memory effect is induced by large strain of NiTi rods, which will result in residual deformation even after heating repair. Finally, through the behavior comparison with the angle connection and the connection using steel rods, it is found that SMA connections have better ductility and energy dissipation capacity.