Retrofitting substandard reinforced concrete (RC) buildings is essential to reduce collapse risk during high-intensity earthquakes. Among advanced retrofitting methods, shape memory alloy (SMA) bars have emerged as a replacement for steel reinforcement at critical structural components. Owing to their superelastic properties, SMA materials can recover from plastic deformations within specific strain limits, which helps reduce post-earthquake residual displacements. However, the high cost of SMA compared to conventional materials limits their widespread use. This study analytically investigates various SMA rebar configurations placed at the plastic hinge regions of first-story columns in a previously tested substandard RC frame. A lattice modeling technique implemented in OpenSees was employed to simulate the nonlinear behavior of concrete and reinforcement, modeled as truss elements, under pseudo-dynamic ground motion records. Four different SMA layouts using Ni-Ti and Cu-Al-Mn alloys were evaluated. Comparisons of peak and residual interstory drift ratios revealed that certain partial SMA configurations can reduce residual drifts by up to 65% with minimal material usage. The optimization results suggest that the effectiveness of SMA retrofitting depends not only on the quantity but also on the positioning of SMA rebars. The ideal configuration is the one that achieves the greatest reduction in both peak and residual displacements while using the least amount of SMA material.
