Study On The Safety Evaluation And Sevice Life Prediction Of Reinforced Concrete Bridges

Reinforced concrete bridges become structurally deficient for several reasons, includingcorrosion of steel, increases in allowable truck weights, deterioration due to age and exposureto deicing salts. All these result in an urgent need to strengthen many of these bridges with an effective and reliable method. For numerous deteriorated, underrated, and overloaded agingbridges in our country, it has important economic and research value to analyze the remaining bearing capacity of the bridge, follow-up service period performance, and to assess accurately the security and forecast remaining life of bridge. Combining with the research program " study on detection evaluation and reinforcemt techonolege of highway bridge", on the basis of the current domestic and foreign research results and the existing codes, synthesis security evaluation system of bridge was studied, the evaluation criteria in the evaluation system was established ,using AHP to evaluate bridge security and putting forward the remaining life prediction method of concrete bridge, the main achievements are as follows:First, evaluation level of the reinforced concrete bridge was divided. For the deterioration situation of the different bridge components and how to impact the integral safety of the bridge in the bridge structure research, the safety evaluation indexes of typical bridge components was proposed, and the using security was listed in the evaluation system, consequently, safety evaluation index system of reinforced concrete bridge was established.Secondly, on the basis of established evaluation system and referencing information and existing codes, evaluation criteria of all index was put forward, the security of concrete bridge was evaluated using of multi-level comprehensive evaluation method.Then, amending the resistance model and load model of existing reinforced concrete bridge deterioration according to detecting information, load-bearing capacity check-calculation index of existing concrete bridge was calculated. And according to set threshold value for the end-of-life, forecast of the bridge structure residual life was carried on.Finally, 6 old RC beams replaced from existing bridges are tested under three-point loading. The section strains, deflection, maximum crack width, maximum crack height of old and new RC beams under different levels of loads are analyzed. The results showed that reinforced concrete beam serviced 11 years and with a certain cumulative damnification is still basically in line with the plane section assumption. The old beam which appears a larger crack, deformation before destruction was still ductile. Based on flexural capacity of beam, the relationship between bearing capacity degradation of reinforced concrete beam and deterioration level of the concrete was given, providing a basis for security evaluation for the bridge.