fragility functions

The objective of this study is to evaluate the effects of earthquake damage on future seismic performance of reinforced concrete columns. Strength and stiffness modification factors are proposed to modify force-deformation behaviors of damaged columns. Permanent displacement is considered to determine the damage severity. A method is developed to calculate the collapse fragility function of damaged RC columns using permanent displacement. Comparing the fragility function of intact and damaged columns the strength modification factor is calculated for different amount of residual displacement. The stiffness modification factor is also estimated using the change of the fundamental period of a RC column after exciting by ground motions. Having the modified the force-deformation behaviors of damaged columns, the performance of the damaged structure can be evaluated using pushover analysis.