Of Existing Reinforced Concrete Bridges Based On Reliability, Durability Analysis

The durability of Reinforced Concrete (RC) Bridge is one of the world-wide concerned problems in the field of the structure engineering. To assess the durability and to predict the service life for the RC structure, not only can reveal the latent danger, and make decision to repair or dismantle, but also can be used for structure design directly. Improving the durability of the bridge will be one of the important sign for the development of bridge in the 21 century. Currently, the resistance degrading with time isn't considered in most reliability researches and structure designs, but the resistance degradation is a necessary result for degrading of structure performance. In this paper, the resistance degrading with time was considered, and based on the reliability theory, the analytical method of resistance degrading with time was established, and the failure probability model was also established on reliability performance function, the time-varying reliability index was deduced by establishing durability limit state equation. With using target reliability index, this method is easy to use, and harmonizes with the current reliability design standard.In this paper, many factors that affect the structure durability under the atmospheric environment were considered, such as the erosion of chloride ion, the freeze thawing and the carbonization of the concrete, and the corrosion of reinforcement The mechanism and reasons that affect the durability of the concrete bridge were analyzed. Of these factors, the carbonization of the concrete and the corrosion of reinforcement are the emphases to analyze and research.The loads, including the dead load and the live load, are the main effects on the bridge. In this paper, based on the investigating dates of home and abroad, the dead load model and the live load model were introduced separately. The dead load obeys normal distribution while the vehicle load obeys non-normal distribution, which can be separated normal traffic state and dense traffic state, and on these two states, the maximum distribution functions were established separately. Based on the resistance degradation model and the vehicle load model, the time-varying reliability index for bridge was calculated with using the corresponding program that was compiled by the method of JC, so the reliability and the durability of Reinforced Concrete Bridge were assessed. Service life prediction and optimum design for...