Effects of Strengthening Options in Improving the Lateral Responses of RC Frame Building

During recent past, it was observed that a large number of existing RC frame buildings with irregularities have poor performance or even collapsed during a strong earthquake.Therefore, strengthening of these types of buildings is required because of its inherent irregularities and low resistance against lateral forces.In the present study, efforts were made to investigate and critically assess the effectiveness of some strengthening options in enhancing the seismic performance of typical four storey asymmetric RC frame building using nonlinear static analysis.The different strengthening options studied were infilled RC frames, design of soft storey RC beams and columns by 2.5 times higher design forces as per IS 1893(part 1), design of only soft storey columns by 2.5 times higher design forces, provision of bracing at open ground storey and provision of lateral buttresses in open ground storey.The effect of these strengthening options in improving the ductility as well as lateral strength of asymmetric RC frame building for enhancing seismic behaviour was also studied.The strengthening option suggested by IS: 1893, designing the beams and columns of soft-story for higher forces was found to increase the lateral strength of the RC building 2.29 times as compared to bare RC frame building but it observed ineffective in improving the lateral deformability/ductility of RC frame building.Yield and ultimate lateral strength of the RC frame building with diagonal braces in all bays was found to be the highest, which is 4.31 and 7.12 times higher than the bare RC frame building among all other strengthening option, indicating the most effective strengthening option.