Durability Study Of Reinforced Concrete Bridge Under Chloride Ion Environment

Professor P.K. Metha pointed out in the state-of-art study on the durability of concrete in the past fifty years that corrosion of steel bars was the primary factor of durability of structures. Meanwhile, substantial events world-widely have blamed the chloride ions for the corrosion of steel bars. Therefore,"Salt Attack"has emerged as a global issue. Especially in China, special attention should be paid to"Salt Attack"in reinforced concrete structures subjected to the chloride environment. Past few decades of the 20th century have seen a huge development in economy, which lead to a rapid boom in highway and bridge construction, the budgets of some key bridge projects reaches as high as billion Yuan. Due to their high cost and significance to the society, the issue of bridge durability could never be neglected.The objective of this thesis is the study on the durability of the reinforced concrete bridge structures under chloride ion environment. The scopes of the study are summarized as follows:(1) Introduction of the significance the study on the durability of the reinforced concrete bridge structures under chloride ion environment and the review on the current study.(2) Study on the effects of chloride-induced corrosion of steel bars from the mechanism of corrosion under general environment to that under chloride ion environment. Based on previous study, development stages and failure stages of the corrosion of steel bars under chloride ion environment are analyzed. In the case of marine environment, durability protection measures considering the material properties of steel and concrete are proposed.(3) Derivations of the formulas for evaluating the initial corrosion time of steel bars under coastal chloride ion environments, according to deteriorations mechanism of steel bars and concrete and Fick's diffusion theorem. Parameters that greatly influence the corrosion of steel bars are investigated. Appropriate steel bar deterioration models and concrete deterioration models are selected according to their characteristics. Previous studies on resistance force models and load models are summarized; and durability analysis method based on reliability theory is presented.(4) Visual inspection-based condition assessment on Guangxi Tieshangang Bridge are conducted by field test, time-dependent durability analyses on 30m main span and piers of 20m span.(5) Tentative study on system reliability of Rizhao Wanpingkou Bridge is conducted.The reliability analysis of series connection systems is transferred to the member level for the durability analysis of the Rizhao Wanpingkou Bridge. Moreover, sensitive analysis on some significant parameters that greatly influence the failure probabilities of structures are congducted.