寒区环境下CRTSⅢ型无砟轨道板抗拉时变可靠度研究

Study on the time-varying tensile reliability of CRTSⅢballastless track plate in cold region

为探究CRTSⅢ型无砟轨道板在寒区环境下的时变可靠度,开展无砟轨道列车轮轨力现场测试及寒区温度场试验,基于试验数据建立列车和温度荷载概率分布模型,并基于随机抽样方法生成随机荷载变量样本,随后输入有限元模型计算寒区复杂荷载耦合作用下无砟轨道结构荷载效应,并引入极值理论对轨道板荷载效应尾部数据进行拟合,获取设计年限内荷载效应最大值概率分布模型,同时结合时变抗力分布建立轨道板抗拉极限状态功能函数,最后基于蒙特卡洛法分析不同结构抗力退化速率下的结构时变可靠度。结果表明:在寒区复杂荷载作用下,不同运营环境(无退化、低速退化、中等退化和严重退化)的轨道板抗拉可靠度均随运营时间增加而逐步下降。结构抗力无退化及低速退化情况下,轨道板抗拉可靠度变化趋势相近,均始终满足要求;中等退化情况下,在第19年时低于目标可靠度;而寒区运营环境即严重退化情况下,第11年时已低于目标可靠度。不同抗力退化情况对结构时变可靠度指标变化趋势有着巨大影响,在第60年时,抗力严重退化情况下的可靠度指标下降幅度达到无退化情况的12.8倍。为保证无砟轨道在寒区恶劣环境下的长期运营安全,在设计时应提高安全储备系数,对轨道结构进行周期性管养维护,以确保其良好的服役状态。

To scrutinize the time-varying reliability of CRTSⅢballastless track plates in cold regions,field examinations of wheel-rail forces exerted by ballast track trains and temperature field assessments in cold locales were conducted.Leveraging the acquired empirical data,probability distribution models for both train and temperature loads were formulated,subsequently generating stochastic load variable samples through a randomized sampling methodology.These samples were then incorporated into a finite element model to compute the load effects on the ballast track structure amidst the complex interplay of varied loads in cold environments,with special consideration given to extreme values.Theoretically,the tail data of the load effects on track slabs were fitted,deducing a probability distribution model for the maximum load effect over the structure's design lifespan.Concurrently,the tensile limit state function of track slabs was established by amalgamating it with the distribution of time-varying resistances.Finally,the time-varying reliability of the structure under different rates of structural resistance degradation was scrutinized via Monte Carlo simulations.Our findings reveal a gradual decline in tensile reliability of track slabs across diverse operational conditions(no degradation,low-speed degradation,medium degradation,and severe degradation)as operating time increases amidst the complex loading dynamics of cold regions.Notably,track slabs with no degradation of structural resistances and those experiencing low-speed degradation exhibit a congruent trend,consistently satisfying the stipulated reliability standards.Conversely,track slabs subject to medium degradation fall below the target reliability threshold in the 19th year,while those experiencing severe degradation fail to satisfy the target reliability as early as the 11th year of operation.Furthermore,the severity of degradation markedly impacts the trajectory of the structure's timevarying reliability index,with a pronounced decline observed in the reliability index of the severe resistance degradation scenario,reaching 12.8 times that of the non-degradation case by the 60th year.To ensure the enduring operational safety of ballastless tracks in the harsh environment of cold regions,it is imperative to enhance the safety margin during design phases and institute periodic maintenance protocols to maintain the structural integrity and optimal functioning of the track system.