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发展了一种基于车桥耦合系统随机振动分析的铁路钢桥疲劳可靠度评估方法,建立车桥耦合系统模型,选取车速和轨道不平顺作为基本随机变量进行随机振动分析,以此确定桥梁构件等效疲劳应力幅及其循环次数的概率模型。在此基础上,建立基于S-N曲线法的疲劳极限状态函数并进行疲劳可靠度分析。以一座铁路下承式钢桁梁桥为例进行了疲劳可靠度评估,并讨论了车速及轨道平顺性对构件疲劳可靠性的影响。结果表明:该文方法可有效用于铁路钢桥疲劳可靠度评估;受车速及轨道不平顺随机性的影响,列车引起的桥梁构件等效疲劳应力幅及其循环次数均具有一定的不确定性,应视为随机变量,二者可采用对数正态分布表示;车速和轨道不平顺可显著影响桥梁构件的疲劳可靠性,疲劳关键构件的可靠度指标随着轨道平顺性增强而提高。
A method of evaluating the fatigue reliability of railway steel bridges based on stochastic vibration analysis of vehicle-bridge coupling system is developed. The model of vehicle-bridge coupling system is established. The random vibration analysis of vehicle speed and track irregularities is taken as the basic random variable to determine the bridge components Probabilistic model of effective fatigue stress amplitude and cycle times. On this basis, the fatigue limit state function based on S-N curve method is established and the fatigue reliability analysis is carried out. Taking a railway steel truss girder bridge as an example, the fatigue reliability assessment is carried out. The influence of vehicle speed and track ride comfort on the component fatigue reliability is also discussed. The results show that the proposed method can effectively evaluate the fatigue reliability of railway steel bridges. Depending on the randomness of vehicle speed and track irregularities, the equivalent fatigue stress amplitude of bridge components caused by trains and the number of cycles have certain uncertainties , Which should be regarded as random variables. Both of them can be expressed by logarithmic normal distribution. The vehicle speed and track irregularity can significantly affect the fatigue reliability of bridge components. The reliability index of key components of fatigue increases with the increase of track smoothness.