研究目的：以可靠度理论为基础的极限状态设计法是铁路工程结构设计规范发展的必然，而目标可靠指标是其重要组成部分，随着铁路事业的飞速发展，原有可靠指标校准值的基础条件部分发生了改变，这就需要结合新情况对铁路钢桥的承载能力目标可靠指标进行分析。
研究结论：本文得到了新形势下铁路钢桥抗力统计参数，校准了铁路钢桥承载能力极限状态的目标可靠指标，得到了抗力、恒载和活载的分项系数，通过验证，满足由容许应力法向极限状态设计法转轨中安全度继承性的要求; 通过对抗力和荷载参数的灵敏度分析，表明抗力和活载的统计参数对可靠指标影响权重大，而恒载的统计参数和恒载与活载标准值效应比影响权重较小。
Research purposes:Limit states design method based on reliability theory is the trend of development for the design code in railway engineering structures，and the target reliability index is an important part among it．With the rapidly development of railway industry，the basic conditions of the original calibrate value have partly changed，which requires analysis of target reliability index for steel railway bridges’ultimate limit states under the new situation．
Research conclusions:Under the new situation，resistance statistical parameters of steel railway bridge have been listed．The target reliability indexes of ultimate limit states are calibrated．At the meantime，the partial factors of dead load and live load and resistance are advised，which can meet needs of safety requirements of inheritance in transition from the allowable stress method to limit states design through verification． According to the sensitivity analysis of load and resistance parameters，the statistical parameters of resistance and live load have a large effect on the reliability index，while the parameters of dead load and the ratio of dead load and live load have little effect on it．
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