Development of a New Multidirectional Deformation-Amplified SMA Damper: Device Design, Experimental Tests, and Structural Seismic Control Analysis

Conventional seismic dampers may exhibit reduced effectiveness under horizontal excitations acting from arbitrary directions and often provide limited control of residual deformation. To overcome this limitation, a new multidirectional deformation-amplified shape memory alloy (MDSMA) damper is developed to mitigate structural seismic responses and residual deformations. The device integrates radially arranged shape memory alloy (SMA) wires with a lever-spherical hinges displacement amplification mechanism, enabling multidirectional energy dissipation and self-centering behavior. A geometrically and mechanically coupled analytical model is established to describe the damper response, and horizontal quasi-static cyclic tests are conducted to evaluate its hysteretic behavior and to examine the effects of displacement amplification ratio, SMA prestrain, and loading direction. The results showed that prestrain and displacement amplification significantly influenced the damper performance: specimens without prestrain exhibited flag-shaped hysteresis, whereas introducing prestrain produced fuller loops and markedly enhanced energy dissipation at small displacement amplitudes. Increasing the amplification ratio activated SMA deformation earlier and increased restoring force via lever action, improving energy dissipation efficiency under limited deformation demands. The damper demonstrated stable hysteretic responses across different loading directions, and the proposed model captured these behaviors well. Finally, numerical case studies on a representative 3-story steel frame indicated that MDSMA dampers reduced roof peak displacement by about 15%–20% and roof residual displacement by more than 80%, with low sensitivity to the seismic loading direction. These findings suggest that the proposed MDSMA damper provides a promising self-centering solution for multidirectional seismic response control in building structures.