Fatigue Life And Service Safety For Existing Steel Bridges

Fatigue failure problems of steel bridges are increasingly found with large construction of steel bridges and rapid development of economy in China. How to evaluate safety status of using steel bridges is a problem that is exigent to be solved. This paper is aimed at establishing fatigue life and safety reliability evaluation model based on engineering project. The problems in fatigue analysis and evaluation are solved from four aspects, including loading spectrum, stress range counting, theory of bridge evaluation and application of bridge evaluation.The results got from this thesis are shown as following:1. Mone-Carlo method is better than typical train loading spectrum method, by comparative analysis of two loading spectrum methods. Some significant factors affecting simulated result are found, and some valuable suggestions are listed.2. Basd S-N curve method, the comparative analysis of stress range counting methods is conducted, including the level crossing couting method, the mean crossing peak counting method, the stress range counting method and the rainflow counting method. Strong liner relationships are found among these counting methods.3. Based on typical theory of fracture mechanics, fatigue evaluation modal of steel bridges is established. Fatigue life evaluation applications are made for both railway steel bridges and highway steel bridge.4. Based on existing literature research results, a probabilistic reliability evaluation model of steel bridge is established. The best pseudo random number generator (PRNG) was found, and the compute program is written. The PRNG has longer cycle feature and can pass various inspections. The evaluation program can be applied in practical bridge assessment and follow-up research.5.The probabilistic reliability evaluation model of steel bridge is established based on bayers theory and existing researches. Two components are updated from a rivet highway steel bridge and a rivet railway steel bridge, respectively. Performance parameters have significant effect on update safety reliability.