Influence of Column Retrofitting on Seismic Fragility and Cost–Benefit Analysis for an Existing Reinforced Concrete Building

Fragility analysis is a well-established tool for evaluating the probability of damage to buildings subjected to seismic ground motions. In this study, the applicability and suitability of reinforced concrete (RC) jacketing—one of the retrofitting techniques for enhancing seismic performance of existing RC buildings—have been investigated through seismic fragility and cost–benefit analysis (CBA). The primary objective of the study is to observe the variation in investment amount while carrying out gradual retrofitting of columns in existing seismic-deficient buildings. For this, the study investigates a 20-year-old existing building located in one of the most seismically active regions of India. To analyze the seismic performance upon retrofitting, the fragility curves are generated by subjecting the building to far-field ground motions analytically. An incremental dynamic analysis (IDA) is implemented to evaluate the building safety before and after retrofitting. Additionally, the cost required, depending on the number of columns to be retrofitted, is also estimated. After rigorous analysis, the quantification is made by comparing the median values of the fragility curves before and after retrofit. It has been observed that the retrofit of the building significantly reduces the damage probability, and unexpected losses (in terms of monetary value) can be minimized to a large extent with the intervention of retrofit strategies.