Evaluating nonlinear behavior of a reinforced concrete building with shear walls and concentric steel bracings

The susceptibility of existing buildings has become an important issue since they did not satisfy modern seismic design requirements or they have been designed and constructed in accordance with the earlier codes. A great number of reinforced concrete (RC) buildings are located in the unsafe seismic zones and they have high vulnerability to damage. Therefore, either local or global strengthening strategies are required for such structures. This study aimed to assess the seismic performance of a typical residential building and its retrofitting by means of different approaches. For this purpose, an existing 9 story reinforced concrete (RC) building having the same floor plan (5x5 bays) was used as a case study. The building had a typical beam-column RC frame with no shear walls. For seismic performance upgrading of the building, RC shear wall and concentric steel bracing systems were employed. As a concentric bracing system, X-bracing, inverted-V bracing, and diagonal bracing were utilized. Analytical modelings of the existing and retrofitted RC buildings were realized by means of ETABS 2013. The performances of all structures were evaluated using the nonlinear static and dynamic analyses. From these analyses, the pushover curves, inter-story drift ratio, story displacements, and time history plots were obtained for the existing and retrofitted buildings. It was observed that the existing building had a performance level of collapse prevention and its performance improved to life safety after retrofitting. Keywords: Reinforced concrete building; Nonlinear analysis; Retrofitting system; Shear wall; Steel bracing.