Seismic fragility analysis of shear-critical concrete columns considering corrosion induced deterioration effects

Shear-critical reinforced concrete structures such as older columns with insufficient transverse reinforcement details or short columns are found to be vulnerable to earthquake loading. Meanwhile, in the aggressive environment, RC structures tend to be more vulnerable to earthquake since corrosion of reinforcements will cause deterioration of the material properties. In the present study, a new framework is proposed for seismic fragility analysis of shear-critical structures with the consideration of corrosion effects. A new model for corroded concrete columns is proposed which can account for shear performance deterioration due to corrosion and the seismic flexure-shear interaction (FSI) behaviors. The modified Ibarra-Medina-Krawinkler deterioration model is adopted to simulate the shear response in order to capture shear strength and stiffness deterioration as well as pinching behavior of corroded shear-critical columns. The deteriorating material properties are determined based on corrosion modeling methods, and the corrosion level differences between transverse and longitudinal reinforcement are addressed. Furthermore, the proposed framework adopts time-variant structural capacities as obtained from the proposed numerical model in the fragility analysis. The developed framework is demonstrated with a shear-critical bridge column. The results clearly indicate the adverse effects of corrosion on seismic fragility of shear-critical columns, especially at severer damage states. Using flexure model and time-invariant capacity index will underestimate seismic fragility compared with the results obtained using the proposed method.