Research Of Fatigue Life Evaluation For Railway Steel Bridges

Resent years, the large number of bridges in China are presenting their aging status, while methods used for fatigue inspection and evaluation are needed to be improved. It has deteriorated the safety of railway traffic to some extent. To deal with this case, the method of the evaluation of fatigue life, which is based on the collected data from the project relating to the evaluation of fatigue life of the 3rd span (steel truss beam) of the Mihe River Bridge located in Beijing-Guangzhou Railway, is introduced in this paper. The detailed contents are as follows.1. The methods and the steps of evaluating fatigue life of railway steel bridges are presented. The details of on-site experiment methods such as the choice of the sensors' location, the selection of impulse frequency, the stress wave filtration of data, and others, are introduced.2. The application of the Load Simulation Method (LSM) in the evaluation of the remaining fatigue life for railway steel bridges is introduced. The presentation involves the data needed by LSM in the calculation of the fatigue stress spectrum, the method of forming typical simulation train model based on the data, and the statistical information of all kinds of the trains.3. The method of evaluating fatigue life by history phase partition of railway operation of existed bridges are introduced. The phase coefficients and their identification are also discussed.4. The next emphasis of this paper is the reliability of the fatigue life of railway steel bridges. Firstly, the ultimate limit functions, which may be adopted for the evalution of fatigue life, are taken into account. The distribution of the related random variables in the function are discussed. Secondly, the safety indexes of the function are deduced according to the Second-Moment theory. Reasonable results are obtained according to the deduced equotions and the statistics of the Mihe River Bridge. Further more, the method used for the statistic of different phase coefficients and coefficients' identification is introduced. The calculation of safety index in view of the partial safety factors and the history phases partition are carried out.5. At the end of the thesis, the corrosion fatigue influence and the theory of thefatigue reliability of structural system based on collected information are discussed simply.