Superelastic Behavior of Ni-Ti SMA Bars under Shear and Bending: Experiments, Modeling, and Application in Beam-to-Column Connections

Shape memory alloy (SMA) is a class of smart materials that can recover large inelastic deformations either by heating (shape memory effect) or unloading (superelasticity). For structural applications, SMA components (such as bars and cables) are commonly designed to carry tensile forces only, rendering relatively low cost-efficiency. In this light, the present study thoroughly investigates the behavior and application of Ni-Ti SMA bars under shear and bending actions, which can enable more efficient uses of SMA. A comprehensive experimental program was first carried out to examine the cyclic behavior of SMA bars under pure shear and combined shear plus bending. The test results showed satisfactory performance of the SMA bars in terms of superelasticity, load capacity, and energy dissipation. With the increase of the bending effect, the SMA bars exhibited an increase in the recoverable deformation and decrease in the load capacity. Based on the experimental results, a numerical modeling method was developed for simulating the cyclic shear and bending behavior of SMA bars. The developed numerical model was subsequently used to further interpret the load-carrying mechanism of the tested SMA bars. Finally, the potential application of the SMA shear/bending bars was demonstrated via a novel beam-to-column connection equipped with SMA dowels. A full-scale cyclic test of the proposed connection showed a satisfactory self-centering performance up to a connection rotation of around 2.5%.