Cyclic behavior of superelastic SMA cable and its application in an innovative self-centering BRB

Abstract

This paper presents an innovative self-centering buckling-restrained brace (SC-BRB) composed of a shape memory alloy (SMA) cables based self-centering system and an all-steel BRB. This study commences with cyclic tests on individual SMA cable to understand the influence of annealing schemes and pre-tension procedures on their fundamental mechanical properties, such as strength, stiffness, self-centering capability, energy dissipation, as well as their degradation of the properties during cyclic loading. Based on the test results, the desired annealing scheme and training procedure for the SMA cables in the proposed SC-BRB were presented. The configuration and working principle of the proposed SMA-cables-based SC-BRB were subsequently described, followed by theoretical studies on hysteretic models of the proposed brace. Numerical simulations and parametric studies were carried out to investigate the mechanical performance of the proposed SC-BRB. The results show that the investigated SMA cable can reasonably scale up the satisfactory properties of the SMA wire. The initial elastic stiffness and the ‘residual’ self-centering force strength of the SMA cables, which are essential for the proposed SC-BRB application, can be greatly enhanced by inflicting certain pre-stress. The initial strain and area ratio of the pre-tensioned SMA cables are suggested to be designed as about 2.5% and in the range of 60%–71.4%, respectively, to achieve appropriate energy dissipation, residual deformation, and material cost of the proposed SC-BRB.