Assessment Of Fatigue Life And Service Safety For Existing Concrete Girder Bridges

Since our founding, with the constant improvement of the national economy, as animportant part of infrastructure construction, highway traffic industry developing rapidly.The augment of axle weight and traffic volume lead to fatigue problems more seriously.Now many bridges are under the long-term effects of repeated loading, which makes thecurrent engineering need to estimate the residual life of the bridge structures, in order toserve the fatigue life assessment and maintenance decision of bridges.In view of the concrete bridge fatigue failure theory put forward the assessmentmethods of existing reinforced concrete bridges based on S-N curve and fracture mechanicsapproach were proposed in the dissertation. Finally the assessment methods based on S-Ncurve and fracture mechanics approach were applied in in-service concrete bridge.In this dissertation, the research works are investigated as follows:1. For the present problem of no traffic load spectrum in highway, the two methodswhich the load spectrum are derived from are analyzed and compared. Based oninvestigation of the statistic traffic data of three typical highway bridges in Shanxi province,the representative types of vehicle are classified. At the same time, the ratios of eachrepresentative type, wheel loads and the capacity of vehicle are investigated.2. Based on the measured data of main highways in shaanxi province, we come upwith fatigue car types for traffic situation of this line, and put forward the suitable forshaanxi highway bridges fatigue of the car type.3. Assessment methods for existing reinforced concrete bridges based on S-N curveand fracture mechanics analysis are proposed in the dissertation, and service safety ofexisting concrete bridges is proposed.4. By using the proposed standard fatigue car, analysis the different spans, crosssection form and structure, to analyze the fatigue stress amplitude and any differences oftypical reinforced concrete beam bridge.5. The method based on S-N curve and linear elastic fracture mechanic for assessingfatigue life and fatigue safety evaluation is applied to an existing concrete bridge. Resultsshow that the S-N curve of fatigue analysis method, if considering the influence of corrosion on concrete bridge, the fatigue life decreased to269years, using fracture mechanics bypushing for muscle fatigue life of about245years.