Summary
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.
Over the past decade, shape memory alloy (SMA) in the form of wires and cables have been extensively studied for various structural engineering applications. There are numerous application areas where pure compression (or coupled with tension) is the primary load bearing scenario, which requires larger size SMA bars. However, the compression behavior of SMA bars is not well known, and little is reported in the literature. In that perspective, this paper presents an experimental study on large diameter superelastic Nickel-Titanium (NiTi) bars subjected to a cyclic compression load. A total of nine SMA bars having slenderness ratios ranging from 60 to 90 were tested. Hysteretic stress-strain responses are plotted and critical buckling load, energy dissipation and residual strain of SMA bars with different slenderness ratios are presented.
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