近年来，我国大量的铁路钢桥进入了老龄期，同时铁路钢桥的疲劳检测与评估方法还不成熟，对铁路安全运营产生了一定影响。本文针对这一现状，结合京广铁路洣河桥第三孔钢桁架梁的疲劳寿命评估项目中收集的资料,对铁路钢桥的疲劳寿命评估的分析方法进行了较为全面的介绍。具体研究内容包括以下几个方面：1．分析了进行铁路钢桥疲劳寿命评估的方法步骤。详细介绍了实测法在实测中测点的选择问题，测量频率的选择问题，测量后滤波的方法及注意事项。2．介绍了荷载模拟法在铁路钢桥疲劳剩余寿命评估中的应用。讨论了该法在进行疲劳应力谱计算中需要统计的资料以及分析资料建立典型列车模型的方法，提供了各型车辆的统计资料。3．介绍了通过划分阶段计算铁路钢桥疲劳剩余寿命的方法。介绍了在划分阶段中需要注意的各个修正系数以及这些修正系数的确定方法。4．另一个重点是讨论铁路钢桥疲劳寿命评估中的可靠度问题。首先分析了进行疲劳寿命评估时可以采用的几个极限状态方程，根据这些方程分析了相应的随机变量的概率分布。之后，根据二阶矩理论分析了极限状态方程的可靠度指标的计算方法，并结合洣河桥的统计数据给出了合理的计算结果。然后又分别分析了不同历史阶段中修正参数的概率统计以及最后的确定方法，以及在考虑分项安全系数以及结构历史阶段划分情况下的疲劳寿命评估可靠度计算。5．最后本文简要讨论了腐蚀疲劳在疲劳寿命评估分析中的影响以及将结构作为一个系统来分析疲劳寿命可靠度的方法。

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 the fatigue reliability of structural system based on collected information are discussed simply.