Characterization of shape memory alloy energy dissipators for earthquake‐resilient structures

In this paper, a new shape memory alloy (SMA) damping device named confined superelastic dissipator (CSD) was examined. The proposed dissipator consists of a fused superelastic nickel-titanium (NiTi) SMA bar as the functional kernel component encased in grout-filled steel tube. The bar carries the axial load and dissipates energy through axial deformation while the steel tube and infill grout restrain the bar and precludes buckling in compression. First, theoretical derivations for the design of the buckling restraining system were discussed. Then, the hysteretic behavior of CSDs was investigated through cyclic quasistatic tests. A total of eight specimens were designed, fabricated, and tested. All specimens exhibited stable and flag-shaped hysteretic behavior with excellent self-centering characteristics. Response quantities of prime interest for earthquake engineering such as energy dissipation, equivalent viscous damping, and self-centering capability were evaluated. The effect of geometric parameters such as fuse diameter and bar length on these parameters as well as failure mechanisms of CSDs was studied. Based on the experimental results and visual observations of failed specimens, specific recommendations were made to improve the performance of the CSDs.