Collapse assessment of high-rise reinforced concrete building under chloride induced pitting corrosion subjected to near-field and far-field ground motions

Abstract

Reinforced concrete structures are vulnerable to corrosion considering its influences on the performance of the structure during the possible earthquakes. Corrosion mostly occurs due to two main reasons: chloride and carbon dioxide penetration into the concrete that leads to the chemical reaction between them and concrete compositions. Chloride diffusion into the concrete brings about rebar pitting, while carbonation-induced corrosion causes uniform corrosion of rebars. In the present study, chloride-induced corrosion was investigated. In this regard, the Haselton 20story reinforced concrete model was chosen. At first, corrosion initiation time was determined by probabilistic Monte-Carlo Simulation methods for three water to cement ratios of 0.4, 0.45, and 0.5. Next, the effects of corrosion on the mechanical properties of the steel and the concrete were taken into account by using equations available in the literature. Seismic performance of corroded structure was evaluated by conducting Non-linear static and incremental dynamic analysis (IDA).FEMA p695 far-field and near-field ground motions were selected for dynamic analysis. The reduction of overstrength and ductility over 40 years after corrosion initiation was calculated. The results showed that ductility was more affected by corrosion rather than overstrength. The probabilities of the structure being at the four damage states of slight, moderate, extensive, and complete damage were estimated based on fragility curves obtained from IDA. It was observed that ten years after initiation of corrosion there is only a slight difference in the probability of damage states and after that considerable distinction was observed, especially in water to cement ratio of 0.5. Moreover, it was seen that exceeding selected damage states under non-pulse-like near field ground motions is more likely.