Residual displacements of reinforced concrete walls detailed with conventional steel and shape memory alloy rebars

Abstract

Modern reinforced concrete design codes can generally achieve the primary performance level of no collapse in the event of a rare to very rare earthquake. However, recent seismic events have shown that permanent damage and deformations of buildings prevent the structure from being serviceable, imposing high costs associated with repairs or demolition. Shape memory alloys have the ability to recover large strains upon removal of stress. Thus, replacing conventional steel with superelastic alloy rebars in the boundary ends of reinforced concrete walls has the potential to reduce residual seismic displacements for these types of buildings. This research paper investigates the lateral residual displacement of reinforced concrete walls detailed with conventional steel and shape memory alloy bars as a function of the in-plane drift. Namely, the force-displacement hysteresis of a large dataset of experimental walls with conventional steel are used to study the residual displacement as a function of several key design parameters. A state-of-the-art finite element modelling program is then used to investigate the residual displacements of walls detailed with shape memory alloy bars, and a parametric study is undertaken to investigate the influence of residual displacements of these types of walls. Most of the walls reinforced with shape memory alloys achieved residual displacements less than the permissible limit at large drift levels. The axial load was found to help suppress the residual displacements of walls with increasing drift. The curvatures were found to be distributed over a limited height at the base that was equivalent to the length of the shape memory alloy bar used. Plastic hinge analysis expressions are adapted to estimate the operational displacement of reinforced concrete walls with shape memory alloys.