Effect of Global Warming on Chloride Ion Erosion Risks for Offshore RC Bridges in China

Abstract

Chloride ion penetration, which leads to corrosion of steel reinforcement, is the leading cause of offshore reinforced concrete bridge deterioration. Global warming would accelerate the process of chloride ion penetration and then structural degradation. In China, durability design code for concrete structures has been issued in 2008, and some thresholds of design parameters have been specified to mitigate corrosion in concrete bridge. However, influence of global warming on structure durability was not considered in the issued code. This would overestimate the durability of concrete structures. In this paper, a reliability based method was adopted to evaluate the influence of climate change on the durability of offshore RC bridges considering the acceleration of chloride ion penetration caused by temperature rise. Two climate change scenarios according to IPCC report were considered to define the global warming. A baseline scenario, in which the mean average temperature equals to that of the year 2000, were defined. It is found that the amount of chloride ion on the surface of reinforcing steel bar in the global warming scenarios are 6%-15% higher than that of structure in the baseline scenario. Meanwhile, the probability of corrosion initiation and corrosion damage increased also. In 2100, structures in environmental categories III-C and III-F, designed according to Chinese codes, can no longer adapt the impact of climate change on structure. Comparison of reliability of improved and pre-improved structure was conducted to verify the effectiveness of the proposed improvement measures.