Superelastic shape memory alloy flag-shaped hysteresis model with sliding response from residual deformation: Experimental and numerical study

Superelastic shape memory alloy exhibits flag-shaped hysteresis with self-centering capability. Nevertheless, shape memory alloy undergoes some residual deformation after large plastic strain, especially under repeated cyclic loading. In order to accurately simulate this behavior during nonlinear dynamic time-history analysis, a shape memory alloy flag-shaped hysteresis model with sliding response has been developed. This article shows the gradual development process of this new hysteresis model and provides analysis and verification results to support this claim. A MATLAB-based superelastic uniaxial shape memory alloy material hysteresis model has been developed and was incorporated into a finite element program specifically designed for the piston-based self-centering bracing. This piston-based self-centering bracing system uses superelastic shape memory alloy bars for its energy dissipation and self-centering capability. A proof-of-concept brace specimen was fabricated and tested where numerical and experimental results showed excellent matching. The finite element program was utilized to capture the varying nonlinear quasi-static response of the piston-based self-centering brace. Finally, the piston-based self-centering brace responses from this analysis were used to develop a novel shape memory alloy flag-shaped hysteresis model with sliding response, which was implemented in finite element analysis and design software, S-FRAME. Nonlinear dynamic time-history analysis proves the effectiveness of such bracing in steel frames in reducing interstory drift.