Assessment Of Fatigue Life And Service Safety For Existing Concrete Bridges

In China, lots of reinforced concrete (RC) bridges were built in the past 60 years, and these RC bridges have been in-serves for several decades. These bridges are often required to carry increasing traffic loads. With considerable increases in traffic intensity and over wheel loads have caused obviously fatigue damage in RC bridges. Some reinforced concrete bridges were damaged seriously in China, leading to the whole bridge collapse sometimes because of overloading and oversize trucks. Therefore the assessment of fatigue life and service safety of existing reinforced concrete bridges is topic of considerable importance. The approach to evaluate the remaining fatigue life and service safety of existing reinforcement concrete bridges is required in order to make their safe use possible.Based on the literatures of many research results for fatigue failure mechanism in concrete structures, the assessment methods of existing reinforced concrete bridges based on S-N curve and fracture mechanics approach were proposed in the dissertation. Finally the assessment methods based on S-N curve and fracture mechanics approach were applied to a case study bridge.In this paper, the research works are investigated as follows:1. For the present problem of no traffic load spectrum in Chinese highway, the two methods which the load spectrum are derived from are listed and compared. Based on investigation 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 each representative type, wheel loads and the capacity of vehicle are investigated. Then in-situ monitoring data for the stress spectrum of typical rebar in the tension zone of concrete bridge are acquired.2. The two effective assessment methods of existing reinforced concrete bridges based on S-N curve and linear elastic fracture mechanics approach have proposed in the dissertation, and service safety of existing concrete bridges is proposed.3. The method based on S-N curve and linear elastic fracture mechanic for assessing fatigue life and fatigue safety evaluation is applied to an existing concrete bridge. 4. The stress amplitude and fatigue damage of different typical concrete bridges under the same load are analyzed. It is concluded that the fatigue damage of reinforcement increases with variation of spans.