Probabilistic assessment to predict the time to corrosion of steel in reinforced concrete tunnel box exposed to sea water

This study concerned the service life prediction, in terms of chloride-induced steel corrosion, of a concrete tunnel-box structure placed on seabed. To calculate the time to steel corrosion, the rate of chloride transport in the identical concrete mix to the structure was tested, and the chloride threshold level for corrosion was assumed by a literature review from 65 published data. Then, the Monte Carlo Simulation was used to calculate the probability of steel corrosion and its corresponding service life, assuming that the corrosion initiates at 10% of the probability of corrosion. As a result, the service life depended on the time dependency of chloride transport. The service life was equated to 31, 51, 85, and 147 years, at 0.1, 0.2, 0.3 and 0.4 of the age factors, respectively, while the time independent model indicated only 27 years of the service life. Finally, methods to raise the service life were discussed.