组合荷载下桥上纵连板式无砟轨道疲劳特性

Fatigue Characteristics of Longitudinally Connected Slab Ballastless Track on Bridge under Combined Load

基于列车—轨道—桥梁耦合动力学理论、无砟轨道与桥梁间纵向相互作用理论及无砟轨道温度场和温度效应理论,建立考虑服役期间无砟轨道钢筋与混凝土的相互作用、无砟轨道混凝土的开裂与闭合效应、无砟轨道荷载时变特性共同作用的桥上纵连板式无砟轨道疲劳寿命预测方法。以高速铁路32m多跨简支箱梁桥上无砟轨道为例,运用该方法研究组合荷载下桥上纵连板式无砟轨道的疲劳特性。结果表明:为了较准确地预测服役期间桥上纵连板式无砟轨道的疲劳特性,必须同时考虑列车荷载、温度荷载及温度梯度荷载的共同作用;桥上纵连板式无砟轨道的疲劳寿命由梁端处的轨道控制,梁端处轨道板底面混凝土和底座板顶面混凝土更易发生疲劳破坏;气候环境和无砟轨道裂缝间距对桥上纵连板式无砟轨道各部件的疲劳特性有很大影响,武汉地区无砟轨道的轨道板混凝土、底座板钢筋、底座板混凝土的疲劳寿命分别是哈尔滨地区的2.5,3.9和222.6倍,当裂缝间距由2倍扣件间距变为1倍时,无砟轨道钢筋的疲劳寿命增加10倍以上。

Based on the theory of train-track-bridge coupling dynamics,the theory of longitudinal interaction between ballastless track and bridge as well as the theory of temperature field and temperature effect on ballastless track,a fatigue life prediction method for the longitudinally connected slab ballastless track on bridge was established,which considered the interaction between steel bar and concrete in ballastless track,the crack and closure effect of ballastless track concrete as well as the combined effects of the time-varying characteristics of ballastless track load during service life.Taking the ballastless track on 32 m multi-span simply supported box girder bridge for high speed railway as an example,the fatigue characteristics of the longitudinally connected slab ballastless track on bridge under combined loads were studied with the proposed method.Results showed that,in order to accurately predict the fatigue characteristics of longitudinally connected slab ballastless track on bridge during service life,the combined action of train load,temperature load and temperature gradient load should be considered.The fatigue life of the longitudinally connected slab ballastless track on bridge was controlled by the track at the end of box girder.The bottom surface concrete of the track slab and the top surface concrete of the base plate at the end of box girder were more prone to fatigue failure.The crack spacing of ballastless track and climatic environment had great effect on the fatigue characteristics of each component of the longitudinally connected slab ballastless track on bridge.The fatigue life of track slab concrete,the steel bar of base plate and base plate concrete for the ballastless track in Wuhan area is respectively 2.5,3.9 and 222.6 times of those in Harbin area.When the crack spacing changes from 2 times to 1 time of fastenersgap,the fatigue life of steel bar in ballastless track will increase by more than 10 times.