Seismic retrofitting of existing reinforced concrete (RC) buildings is often required because of deficiencies in their original design, changes in seismic provisions, or increased functional demands. This study evaluates the effectiveness of steel bracing for improving the seismic performance of a ten-story, plan-irregular, L-shaped RC building. Nonlinear static pushover analyses and nonlinear dynamic analyses were performed for both the unretrofitted and retrofitted models. The response was evaluated in terms of plastic-hinge development, structural performance level, displacement demand, and base-shear capacity. The dynamic analyses were conducted using the Tabas, Northridge, and Landers ground motions after applying the specified record-processing and orthogonal-component procedures. The results indicate that the addition of steel bracing improves the seismic behavior of the investigated structure by increasing its lateral resistance and reducing its displacement demand. Based on the reported pushover results, the maximum displacement decreased from 0.4176 m to 0.0677 m, corresponding to a reduction of 83.8%, while the maximum base shear increased from 472.669 kN to 593.901 kN, corresponding to an increase of 25.6%. In addition, the results show that more than 80% of the columns remained undamaged after strengthening. These findings suggest that steel bracing can be an effective retrofit strategy for the investigated L-shaped RC building. However, because the study is based on a single numerical case study, the findings should not be generalized to all plan-irregular reinforced-concrete buildings without further parametric and experimental investigations.
