Probability-based modeling of chloride-induced corrosion in concrete structures including parameters correlation

This paper presents a practical approach for probabilistic modeling of chloride-induced corrosion of steel reinforcement in concrete structures based on the First-Order Reliability Method (FORM). The method enables to take into account the uncertainties in the parameters that govern the physical-models of chloride ingress into concrete and corrosion of carbon steel including concrete diffusivity,-concrete cover depth, surface chloride concentration and threshold chloride level for onset of-corrosion. The governing parameters are modelled as random variables with different levels of correlation and the probability of corrosion is determined and compared to the predictions obtained by more rigorous approaches, such as Second-Order Reliability Method (SORM) and Monte Carlo simulation (MCS). The approach is applied to predict the level of corrosion in the top layer of reinforcing carbon steel of a highway bridge deck that was exposed to chlorides from deicing salts. The results illustrate the accuracy and efficiency of FORM when compared to SORM and MCS. The paper also shows that the impact of correlation between the chloride diffusivity and chloride threshold level on the corrosion-probability is negligible and can be ignored.