Hysteretic Behaviour of a Piston Based Self-centering (PBSC) Bracing System Made of Superelastic SMA Bars - A Feasibility Study

Buildings designed and constructed using current seismic design codes are expected to experience permanent deformation during high seismic events. Nonlinear material properties generate high hysteretic damping forces and reduce stiffness, which are often necessary to reduce seismic load effects on regular structures. Hence, traditional structural systems experience high residual deformation after an earthquake. In order to resolve this issue, smart structural systems have been proposed by many researchers. One such system is the proposed novel piston-based self-centering bracing (PBSC) system. This study investigates the feasibility of such a system and its cyclic behaviour in finite element environment and predicts its load-deformation hysteresis during seismic events. This newly developed bracing system utilizes superelastic shape memory alloy (SMA) bars inside a sleeve-piston assembly for its self-centering mechanism. During cyclic tension-compression loading, the bars are pulled from opposite directions in order to avoid compressive loading on the bars. The energy dissipation is achieved through nonlinear load deformation hysteresis. Furthermore, the PBSC bracing system is designed to be fully buckling restrained. Several solid element based brace models were built in ABAQUS software and a quasistatic cyclic axial loading was applied to determine their hysteretic response. From the analysis, the resultant load-deformation behaviour shows flag shaped hysteresis with negligible residual deformation.