Behavior and modeling of superelastic shape memory alloy reinforced concrete beams

The re-centering phenomenon of superelastic Shape Memory Alloy (SMA) reinforced concrete is a unique characteristic that is appealing for structural applications, along with the ability to respond with stable hystereses and achieve similar strength and ductility to concrete reinforced with conventional deformed bars. The objective of this study was to investigate the structural performance of superelastic SMA reinforced concrete and to develop a preliminary constitutive model applicable to nonlinear finite element algorithms. Seven simply supported flexure-critical concrete beams, reinforced with either SMA bars in the critical region or conventional deformed reinforcement, were subjected to monotonic, cyclic, and reverse cyclic loading. The experiment results demonstrated the superior capacity of the SMA beams to recover inelastic displacements. The SMA beams sustained displacement ductility and strength capacity comparable to the conventional beams. Crack widths and crack spacing were larger in the SMA beams; however, upon removal of load, the crack openings were recovered. Energy dissipation was lower in the SMA beams, particularly when subjected to reverse cyclic loading. The constitutive model based on a trilinear backbone envelope response and linear unloading and reloading rules provided satisfactory simulations.

► Testing demonstrated consistency and reliability of larger size SMA rods in beams.
► SMA beams were superior at limiting residual displacements and crack widths.
► SMA beams experienced higher normalized yield and ultimate load capacities.
► Linear segmental hysteretic constitutive model for superelastic SMAs proposed.
► Constitutive model successfully simulated response of SMA reinforced beams and beam–column joint under cyclic loading.