Fatigue Performance Evaluation of Existing Concrete Girder Bridges

Abstract

Main steel bars and prestressed strands in critical parts of existing concrete girder bridges are at risk of fatigue and fracture under the combined action of heavy truck loads, increased traffic volume and the effects of environmental corrosion. Based on cumulative damage theory and fracture mechanics, this paper proposes a framework for evaluating the fatigue performance of existing concrete girder bridges. The evaluation framework contains four steps: investigation of the bridge archives; detection, monitoring and simulation; fatigue performance evaluation; and implementation of the maintenance and management recommendations. A combination of acoustic emission and weigh-in-motion (WIM) technologies was adopted to acquire vehicle information and evaluate girder performance, and a Monte Carlo method and function fitting were also applied to calculate a fatigue reliability index. The results of the evaluation indicate that the case-study bridge is extremely unlikely to fail as the result of fatigue during the design service life. In addition, the parameter analysis shows that the fatigue reliability of concrete bridges is sensitive to the combined effects of negative factors. The reliability index curve and the target value of the reliability index can be used to determine the recommended fatigue inspection intervals and the limits for the initial crack size in critical steel bars.