Fragility functions for code complying RC frames via best correlated IM-EDP pairs

This paper provides an investigation on the correlations between ground motion intensity measures (IMs) and engineering demand parameters (EDPs) through nonlinear dynamic analyses of MDOF systems under real earthquake recordings and then structural fragility curves are derived for the best correlated IM-EDP pairs. For this purpose, a parametric study on reinforced concrete (RC) buildings is carried out. Study buildings comprise 5-, 10-, 15- and 20-story, RC, code-complying, regular, moment-resisting frames designed for different strength reduction factors, e.g. R = 2, 4 and 6. The input ground motion dataset consists of 734 horizontal components of earthquake accelerograms. The best correlations between IMs and EDPs are computed by regression analysis. Sets of fragility curves in terms of maximum inter-story drift ratio, maximum plastic end rotation and maximum floor acceleration are derived based on log-normal distribution assumption. Fragility curves are presented not for a specific damage state such as slight, moderate etc. but for a range of damage thresholds on EDP.