Original Article Journal of Intelligent Material Systems and Structures 1–27 Ó The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1045389X19844328 journals.sagepub.com/home/jim Superelastic shape memory alloy flag-shaped hysteresis model with sliding response from residual deformation: Experimental and numerical study ABMR Haque 1 , Anas Issa 2 and M Shahria Alam 2 Abstract Superelastic shape memory alloy exhibits flag-shaped hysteresis with self-centering capability. Nevertheless, shape mem- ory 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 super- elastic uniaxial shape memory alloy material hysteresis model has been developed and was incorporated into a finite ele- ment 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 match- ing. 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. Keywords Shape memory alloy, superelasticity, residual deformation, sliding, hysteresis, bracing 1. Introduction Recent earthquakes and enormous damages in Nepal (7.8 M w on 25 April 2015), New Zealand (6.3 M w on 22 February 2011), Japan (9.0 M w on 11 March 2011), Chile (8.8 M w on 27 February 2010), and Haiti (7.0 M w on 12 January 2010) have renewed interest in self- centering structural systems. A self-centering structural system, in theory, is able to come back to its original position after large nonlinear deformations. Therefore, after a major earthquake, it is expected that a self- centering structure or one equipped with such systems will be able to come back to its original position/shape. This behavior will be able to reduce permanent defor- mation and prevent possible post-earthquake collapse. However, not many self-centering systems are readily available in the market. So far researchers have devel- oped numerous technologies in this field, such as Spring-Based Piston Bracing (SPB) (Issa and Alam, 2019), piston-based self-centering (PBSC) (Haque and ALAM, 2017), Self-Centering Energy Dissipation Device (SCED) (Tremblay and Christopoulos, 2012), Memory Alloys for New Seismic Isolation Devices (MANSIDE) (Dolce et al., 2000), Reusable Hysteretic Damping Brace (RHDB) (Zhu and Zhang, 2007), or the post-tensioned beam-column joints. Researchers have also developed base isolation systems with good 1 Parsons Corporation, Vancouver, BC, Canada 2 School of Engineering, The University of British Columbia, Kelowna, BC, Canada Corresponding author: M Shahria Alam, School of Engineering, The University of British Columbia, 1137 Alumni Avenue, EME 4225, Kelowna, BC V1V 1V7, Canada. Email: shahria.alam@ubc.ca