Pre-tensioned SMA cable tests and its application in a novel self-centering viscoelastic damper

The elastic modulus of superelastic NiTi shape memory alloy (SMA) is between normal structural steel and viscoelastic materials. To enhance the initial stiffness and self-centering capability of viscoelastic (VE) dampers, an innovative self-centering high-damping rubber damper (SC-HRD), which is parallel composed of an SMA-cable-controlled self-centering system and a traditional high-damping rubber damper, was proposed and investigated in this study. The influence of initial strain, loading amplitude, and strain rate on the behavior of SMA cables after training and pre-tensioning was also tested for the SC-HRD application. Configuration and working principles of the SC-HRD were subsequently illustrated, followed by numerical studies on the behavior of the novel damper. Parametric analyses were then carried out on several design parameters of the SC-HRD to optimize its mechanical performance. Results show that the initial stiffness and residual self-centering strength of the SMA cables, which are essential for the SC-HRD application, can be enhanced with the increasing initial strain and loading strain rate. Compared with traditional VE dampers, the SC-HRD has better initial stiffness and self-centering capacities. Initial strain and relative area ratio of the pre-tensioned SMA cables in the proposed SC-HRD are suggested to be designed as about 2% and 0.123%, respectively, to achieve appropriate initial stiffness, energy dissipation, and residual deformation of the proposed SC-HRD.