Abstract: Earthquakes are one of the most severe natural hazards that cause significant damage to structures, especially those not designed as per modern seismic codes. Many existing reinforced concrete (RC) buildings are vulnerable due to inadequate design, poor detailing, and lack of ductility. Therefore, strengthening and retrofitting of such structures has become essential to improve their seismic performance and ensure safety. The present study focuses on the dynamic analysis of a multi-storey reinforced concrete structure and its strengthening using steel jacketing technique. A G+9 storey RC building is modeled and analyzed using SAP2000 software. Two models are considered, namely the bare frame structure and the retrofitted structure with steel jacketing applied at critical regions such as beam-column joints. The analysis is carried out using linear time history analysis and nonlinear pushover analysis to evaluate the seismic behavior of both structures. The performance is assessed based on various parameters such as storey displacement, storey drift, base shear, time period, frequency, and plastic hinge formation. Real earthquake ground motion data such as Imperial Valley, Northridge, and Loma Prieta earthquakes are used to obtain realistic results. The results show that the retrofitted structure performs significantly better than the bare frame structure. The displacement and drift are reduced by approximately 20% to 40%, while the stiffness and load-carrying capacity are increased. The time period decreases and frequency increases after retrofitting, indicating improved dynamic characteristics. The formation of plastic hinges is also better controlled, enhancing the ductility and safety of the structure. Thus, the study concludes that steel jacketing is an effective and economical retrofitting technique for improving the seismic performance of existing RC structures. It enhances strength, stiffness, and stability, making the structure safer under earthquake loading conditions.
Kawale et al. (Mon,) studied this question.