Variability in corrosion damage models and its effect on seismic collapse fragility of aging reinforced concrete frames

Abstract

Corrosion of embedded reinforcement is an important form of degradation of reinforced concrete (RC) structures. The corrosion damage can degrade the mechanical behaviors of the corroded reinforcement, the surrounding concrete, and the interaction between them. These deterioration mechanisms can be simulated by different corrosion damage models. Different corrosion damage models could result in difference in the structural collapse capacity under earthquake excitations. However, the variability in these corrosion damage models and its effect on seismic collapse fragility of corroded RC structures are not well examined in the past studies. This study conducts an investigation of the variability in the available corrosion damage models. To do this, a total of 29 empirical models are collected to represent the corrosion-induced deterioration mechanisms. The results show that different corrosion damage models lead to significant variability. The changing range of the prediction by different corrosion damage models for the bond strength is even beyond three times wider than the minimum prediction value. As a further step, two typical RC frame structures are designed as the study cases. Then a suite of 19 corroded frame cases are modeled with their material parameters deteriorated according to the collected corrosion damage models. Their seismic collapse fragility curves are then generated and compared. It is found that, at a high corrosion rate of 0.2, the variability in the corrosion damage models can cause a significant difference in the collapse probability as high as 8.4% and 6.54% for the case frames designed with a low and high earthquake hazard levels, respectively. However, this effect due to the variability in the corrosion damage models is limited to the collapse probability when the structure is slightly or moderately corroded. Among the considered deterioration mechanism due to corrosion damage, the maximum difference of collapse probability are caused by the variability in the corrosion damage models for the yield strength and ultimate deformation of the corroded reinforcement, which are as high as 6.18% and 5.32%, respectively. While for the other deterioration mechanisms, the variability in their corresponding damage models leads to a limited effect on the collapse probability of structures.