Time-Dependent Seismic Fragility of RC Moment Frames in Corrosive Environment Considering Concrete Quality

Corrosion of steel reinforcement in concrete is a common problem for reinforced concrete buildings in coastal regions. It can have significant impacts on the seismic performance of these buildings. Corrosion in reinforced concrete members can cause problems such as concrete cover removal, longitudinal cracks in concrete, and reduction of the cross-sectional area of steel reinforcements. Moreover, corrosion causes changes in the stress-strain curves of reinforcement steel, reducing its resistance. This study investigates the impact of corrosion on the seismic performance of a four-story concrete frame. In this context, moment-curvature curves for structural elements are first obtained, considering the impacts of corrosion on steel reinforcements and concrete. These curves are then used to model the plastic hinges under corrosion conditions in a nonlinear static (pushover) analysis of corroded RC frames. The pushover curves are then utilized to investigate the impacts of corrosion on the ductility and seismic capacity of the frame. The results show that corrosion significantly impacts the ductility of Reinforced Concrete (RC) frames and can increase the probability of collapse. Fragility curves obtained by incremental dynamic analysis show that the probability of exceeding damage states for structures with higher values of water-to-cement ratio in a corrosion scenario with columns exposed on two sides is significantly higher.