Application of Superelasticity of SMAs in Bolted End-Plate Connection

Abstract

Superelastic shape memory alloys (SMAs) can experience large strains up to 8~10% and restore residual strains just by removing the stress. By employing this unique characteristic of SMAs, a new beam-to-column connection is presented in this paper. The proposed SMA connection consists of an extended end-plate, eight long shank Nitinol SMA bolts, beam flange ribs, beam web stiffeners and continuity steel plates for reinforcing column flanges. In order to predict the behavior of SMA connection, 3-D solid finite element models are set up in ANSYS. The numerical results indicate that the local buckling of beam is avoided and a plastic hinge forms at beam-to-column interface when the moment-carrying capacity of bolt cluster is below the elastic flexural capacity of connecting beam. The SMA connection shows stable moment-rotation hysteresis curves with re-centering capability, which demonstrates the connection’s self-healing deformations function. Far different from energy dissipated by steel yield in traditional connection, the SMA connection shows moderate energy dissipation capacity, and this amount of energy is mainly dissipated by the superelastic behavior of SMA bolts. Moreover, the connection model shows a large inelastic rotation capacity beyond 0.03 rad. The ductility of SMA connection is deeply influenced by the length of SMA bolts, and the 2.2 times length of normal bolt is suggested for SMA bolts.