Seismic Fragility Evaluation of Retrofitted Low-Rise RC Structures

Abstract

In this research, a seismic fragility evaluation is used to assess the seismic performance of low-rise RC structures retrofitted with self-centering post-tensioned pre-cast concrete (SC-PC) frame with enlarged beam-ends. The seismic performance of the retrofitted structures is verified by constructing fragility curves for the retrofitted and retrofitted structure. Thirty natural time-history earthquake records are generated based on a design response spectrum to construct the seismic fragility curves. Nonlinear time history (NLTH) analysis is used to obtain the median structural demand. Limit states are defined based on seismic guidelines to represent the median structural capacity. The relation between the demand and capacity is modeled as a lognormal cumulative density function in a closed-form equation. The results of the study show that the SC-PC frame is effective in seismic retrofitting and significantly improves the structure seismic fragility for all limit states. In addition, the results show that the most significant improvement is found for the collapse-prevention limit state where severe earthquakes are expected.