基于联合概率法的重载铁路大跨钢桁梁桥剩余疲劳寿命评估

Residual life evaluation of a heavy-haul railway long-span steel truss bridge based on joint probability method

为准确评估在重载列车开行条件下大跨钢桁桥的疲劳损伤,提出基于联合概率法的重载铁路大跨钢桁梁桥剩余疲劳寿命评估方法。通过建立包含正交异性桥面的简支钢桁梁桥精细化分析模型,采用考虑车桥振动影响的重载列车移动简谐荷载,计算重载列车通过钢桁梁桥时的结构动力响应。基于雨流计数法和Miner线性疲劳累积准则,获得单次列车过桥时钢桁梁桥控制部位疲劳应力谱,研究列车类型、行车速度、车辆载重、编组车辆节数等对钢桁梁桥疲劳损伤的影响。根据等效列车历史运营谱和考虑年运量及典型疲劳列车发展趋势的未来运营谱,采用联合概率法计算了钢桁梁桥的剩余疲劳寿命。研究结果表明:钢桁梁桥的最不利疲劳控制部位为正交异性桥面板的横肋跨中下翼缘纵向角焊缝以及纵肋与桥面板焊接连接部位;运营列车类型对横肋、纵肋疲劳损伤的影响显著;钢桁梁桥纵肋、横肋疲劳损伤度随编组车辆节数增多而增大,随车速的变化具有不确定性;疲劳部位损伤度随车辆载重增加而增大,且当车辆载重超过某临界值后,将对钢桥疲劳产生重大影响;与定值分析法相比,采用考虑列车载重、车速正态分布的联合概率法计算疲劳损伤度更准确合理,估算包含正交异性桥面板的大跨简支钢桁梁桥的剩余疲劳寿命更可靠,可为开展重载铁路大跨钢桥疲劳分析提供参考。

In order to accurately evaluate the fatigue damage of long-span steel truss bridges under the influence of heavy-haul trains,a residual fatigue life evaluation method based on joint probability approach of a heavy-haul railway long-span steel truss bridge was proposed.A refined finite element analysis model of a simply-supported steel truss bridge with its orthotropic bridge deck was established.The dynamic responses of heavy-haul train passing through the steel truss bridge were calculated by adopting the harmonic heavy-haul train moving loads by considering the influence of vehicle-bridge vibration.Based on the rain-flow counting method and the Miner linear fatigue accumulation criterion,the fatigue stress spectrum of fatigue control parts when the train crosses the bridge once was obtained,and the influences of train types,driving speed,loads sustained,and the number of marshalling vehicles on the fatigue damage were studied.According to the equivalent historical traffic quantity and the prospective traffic quantity that can consider the development of the annual transportation and typical fatigue trains,the residual fatigue life of steel truss bridge was calculated with joint probability method.The results show that the most unfavorable fatigue parts of the steel truss bridge are the longitudinal fillet welds of the mid-span transverse ribs and the welding connection of the longitudinal ribs and the deck.Train types have a significant influence on the fatigue injury of transverse ribs and longitudinal ribs.The fatigue damage degree of longitudinal and transverse ribs increases with the increase of the number of marshalling vehicles,while it has uncertainty with the driving speed.The fatigue damage degree increases with the increase of the train loads.When the train loads exceed a critical value,it will have a significant influence on the fatigue damage of steel bridges.Compared with the fixed value analysis method,it is more accurate and reasonable to use the joint probability method considering the normal distributions of carrying loads and driving speed to calculate the fatigue damage degrees.It is also more reliable to estimate the residual fatigue life of long-span steel truss bridges with orthotropic bridge deck,which can provide reference for carrying out fatigue analyses of heavy-haul railway steel bridges.