Research on the Seismic Performance of Steel Frames with Self-Centering SMA Joints

Shape memory alloy （SMA） possesses the characteristics of shape memory effect and superelasticity. Applying SMA materials to steel structure joints can impart self-centering and energy dissipation capabilities to the structures. Most existing studies focus on the performance of SMA-based beam-column joints， with limited research on the seismic performance of steel frames incorporating these self-centering joints. To investigate the behavior of steel frames with self-centering SMA joints under seismic action， a numerical model was developed using the finite element software OpenSEES. The accuracy of the simplified model was validated against experimental data. Using initial lateral stiffness， bearing capacity， maximum inter-story drift ratio， and residual inter-story drift ratio as analysis indexes， both nonlinear static analysis and dynamic analysis were carried out. The results showed that， compared to the traditional steel frame， the steel frame equipped with self-centering SMA joints exhibited lower initial lateral stiffness and bearing capacity. Under different lateral loading patterns， the maximum inter-story drift ratio in both frame types occurred in the lower stories； however， the frame with SMA joints demonstrated a smaller relative inter-story drift ratio. Due to the incorporation of self-centering SMA joints， this frame experienced larger inter-story deformation. Nevertheless， it essentially returned to its initial state post-earthquake， with a significantly reduced residual inter-story drift ratio compared to the traditional frame. The application of these SMA joints mitigated the considerable dispersion of inter-story displacements， leading to a more uniform distribution of forces. Consequently， the frame with SMA joints displayed superior seismic performance and stronger post-earthquake recoverability compared to the traditional steel frame， thereby enhancing the structural reparability.