Nonlinear Static and Dynamic Analysis of Retrofit of Four-story RC Structures with Concentric Steel Bracing

Abstract

The study investigates the nonlinear seismic behaviors of 4-story retrofitted and non-retrofitted RC frames. The steel V-shaped bracings are used for retrofitting purposes. Nonlinear pushover and dynamic time history analyses were performed using seven earthquake records to assess the impact of retrofitting. The base shear, the fundamental time period (FTP) of the structure, capacity curves, failure patterns, maximum displacements, and maximum drifts are observed in both non-retrofitted RC frame and retrofitted RC frame structures. The steel V-shape bracings are designed to resist 50% of the total base shear of the structure. The steel bracings increase the base shear of the structures and decrease the fundamental time periods. Results show that the addition of steel V-bracing increased the base shear capacity from 1676kN to 2215kN and reduced the fundamental time period from 0.881s to 0.512s, indicating a significant improvement in lateral stiffness. Similarly, maximum displacements and inter-story drifts decreased by approximately 60%, demonstrating enhanced ductility and energy dissipation capacity. Adding the steel bracing in the existing structures improves the seismic base shear capacity and ductility of the structures. It also observed that to get the expected failure pattern, a minimum of 50% base shear is required to be resisted by the columns. The V bracings reduced the displacement and drift of the structures. The V-shaped steel bracings improve the seismic behaviors of the structures effectively.