运营期公铁两用悬索桥温度效应研究

Investigation on Temperature-induced Effect on Rail-cum-Road Suspension Bridge during Service Life

针对公铁两用悬索桥运营期温度效应引起桥梁线形和轨道长波不平顺问题,根据桥梁健康监测系统实测环境、结构温度和主梁挠度,采用经验小波分解方法和FastICA盲源分离算法,将实测主梁挠度分解为温度长周期和短周期效应,建立不同周期温度效应与环境温度的线性关系。结果表明,温度长周期效应引起结构的整体升降温,是主梁线形变化的主要影响因素,每摄氏度环境温度变化主梁跨中挠度变化30 mm以上;温度短周期效应引起结构的非均匀温度场,对主梁线形的影响较小,每摄氏度环境温度变化主梁跨中挠度仅变化5 mm左右;夏季和冬季温度短周期效应对主梁跨中的影响较大,春季和秋季次之。基于夏季和冬季现场试验,采用全站仪对主梁线形进行短期监测,并利用铁路天窗点通过静力水准仪实测同一时刻主梁和轨道线路绝对高程,研究环境温度对桥梁、轨道线形及线路不平顺的影响。现场实测结果表明,轨道绝对高程相对于桥梁绝对高程具有良好的跟随性,可采用主梁线形代替轨道线形。温度作用对轨道线路不平顺有影响,环境温度短期升降温对千米级公铁两用悬索桥的运营性能有一定影响,这主要是由于桥梁线形变化带动桥上轨道线路。通过数值算例,模拟夏季和冬季极端环境条件对轨道长波不平顺弦测值的影响,冬季、夏季大幅降温、升温均对桥上轨道线路平顺性有较大影响,工务作业中需要重点关注冬季大幅降温对轨道运营性能的影响。

In response to the rail track alignment and rail track vertical irregularity of a kilometer-scale rail-cum road suspension bridge during service life caused by temperature effects,based on the measured environment,structural temperature,and main girder deflection of the bridge structural health monitoring(SHM)system,the empirical wavelet decomposition method and FastICA blind source separation algorithm were used to decompose the measured main girder deflection into short and long term temperature effects.A strong linear relationship was established between the ambient temperature and temperature-induced effects.It is concluded that the long-term temperature-induced effects cause an overall temperature variation of the structure,as the main factor on the girder deflection.The deflection of the mid span of the main girder varies by more than 30 mm per degree Celsius of ambient temperature change.The short-term temperature effect causes a non-uniform temperature field in the structure,with a relatively minor impact on the alignment of the main girder.The deflection of the mid span of the main girder only varies by 5 mm.The short-term temperature effects in summer and winter have a significant impact on the mid span of the main girder,followed by spring and autumn.The on-site test results indicate that the absolute elevation of the rail track has good followability relative to the girder.Moreover,based on numerical examples the impact of extreme environmental conditions in summer and winter was simulated on the chord offset values of the long wave irregularities of rail track.The results show that the ambient temperature dramatical variations have a significant impact on the rail track irregularity on the bridge.These findings provide an improved recommendation for maintaining rail track operation performance during service life.