桥上CRTSⅡ型底座板疲劳时变可靠性研究

Time-dependent Fatigue Reliability Analysis of CRTSⅡFoundation Plate on Bridge

主要研究桥上CRTSⅡ型底座板在列车荷载、温度荷载、桥梁变形共同作用下的疲劳时变可靠性。为探讨列车荷载、温度梯度、桥梁变形的作用效应,依据CRTSⅡ型底座板混凝土、钢筋的疲劳性能,建立列车荷载、温度荷载、桥梁变形共同作用下的CRTSⅡ型底座板混凝土弯压和钢筋弯拉时的疲劳时变极限状态函数,分析混凝土疲劳强度、温度梯度、混凝土疲劳弹性模量、桥梁变形曲率、模型不确定系数、列车荷载产生弯矩的统计特征,采用PHI2方法开展底座板疲劳时变可靠性分析,并与传统时点可靠度方法的分析结果做对比,探讨底座板疲劳时变可靠指标对列车荷载、温度梯度、桥梁变形曲率的敏感性。研究结果表明:在底座板服役期内,底座板轨下截面处的混凝土弯压和钢筋弯拉的疲劳时变可靠指标均满足规范要求;传统时点可靠度方法求得的可靠指标偏大,给CRTSⅡ型轨道结构营运带来安全隐患;桥梁变形曲率的变化对疲劳可靠指标的影响最大,列车荷载的影响相对较小,温度梯度对可靠指标几乎无影响;荷载参数的均值大于变异系数对可靠指标的影响。研究成果可辅助确定CRTSⅡ型底座板养护维修的时间和方式,为高速铁路结构的运维提供理论参考。

The time-dependent fatigue reliability of China Railway Track SystemⅡ(CRTSⅡ)foundation plate on bridge under the combined actions of train load,temperature and bridge deformation was analyzed.Firstly,the structural response of the foundation plate was discussed considering the effects of train load,temperature gradient and bridge deformation.Secondly,based on the fatigue performance of concrete bending and compression and steel bending,the time-dependent fatigue limit state function was established.To analyze the statistical characteristics of concrete fatigue strength,temperature gradient,bridge deformation curvature,fatigue modulus of elasticity of concrete,model uncertainty coefficient and bending moment generated by train load.The PHI2 method was used to carry out the time-dependent reliability analysis of the foundation plate,and the results were compared with those using the traditional point-in-time method.Finally,the sensitivity of the time-dependent fatigue reliability of the foundation plate to train load,temperature gradient and bridge deformation curvature was discussed.The results show that during the service life of CRTSⅡfoundation plate,the time-dependent fatigue reliability indices of the concrete bending compression and the steel bending tension meet the requirement of China’s standard.The relatively larger reliability index obtained by traditional point-in-time method than that obtained using PHI2 method,may bring potential hazards to the operation of the whole track system.The change of the mean value of bridge deformation curvature has the greatest influence on the fatigue reliability with relatively less influence of train load and little influence of temperature gradient The influence of the mean values of above-mentioned load parameters on reliability is greater than the coefficient of variance.The research results can help to determine the time for the maintenance of CRTSⅡfoundation plate and provide a theoretical reference for the operation and maintenance of high-speed railway structures.