摘要
无砟轨道板在实际的服役过程中受循环荷载作用,容易产生结构承载能力下降和疲劳失效破坏等问题,严重危害行车安全,因此,对服役状态下轨道板剩余承载能力的量化表征至关重要。该文基于混凝土塑性损伤理论,开展轨道板损伤实际状态试验与分析。结合轨道板温度场与轮轨力监测数据拟合荷载谱,设计了温度与动荷载耦合作用下轨道板的疲劳试验。对轨道板进行四点弯拉试验,分别获得了不同阶段下轨道板残余变形与跨中挠度,量化了疲劳荷载作用下轨道板的塑性损伤和抗弯承载能力的演变特征。多场耦合疲劳作用下无砟轨道板出现塑性损伤,导致其抗弯承载能力不断退化。经疲劳循环后轨道板残余变形增加了6.25%,抗弯承载能力下降了6.85%。服役状态下轨道板整体性能的劣化必然导致结构的受力与变形特征发生改变,在实际养护维修中应重点关注薄弱位置的实际状态并辅以补强措施。
[Objective]A ballastless track slab in service is repeatedly subjected to multiple cyclic loads,thereby becoming prone to issues such as decreased structural load-bearing capacity and fatigue failure under such conditions.These problems can seriously endanger the safety of train operations.Therefore,the remaining load-bearing capacity of track panels must be quantitatively characterized under service conditions.[Methods]Based on the theory of concrete plastic damage,experiments and analyses were conducted to assess the actual damage to track slabs.Using the temperature field of the track slab and the monitoring data of the wheel-rail force,a load spectrum was fitted to design a fatigue test under the coupling effect of temperature and dynamic load.A rigid cushion block with reasonable stiffness was arranged at the lower end of a prefabricated steel beam according to load requirements,which was used to ensure that the vertical load of the testing machine could be evenly distributed to the point of action of the track slab.Four-point bending and tensile tests were conducted on the track slab to obtain residual deformation and mid-span deflection at different stages.The evolution characteristics of plastic damage and bending bearing capacity under fatigue loads were quantified.[Results]The study found that multifield coupled fatigue effects cause plastic damage to the ballastless track slab,leading to continuous deterioration in its bending bearing capacity.After unloading,the mid-span of the track slab could not return to its original position,indicating some residual deformation.As the number of coupled load cycles increased,both the residual deformation and mid-span deflection of the track slab showed an upward trend.This indicates that internal damage within the track slab is gradually intensifying,leading to a decrease in overall bending resistance.After coupling with cyclic loads,the residual deformation of the track slab at mid-span increased from 0.048 mm to 0.051 mm,marking a 6.25%increase compared to the initial residual deformation.The mid-span deflection of the track plate increased from 1.645 mm to 1.766 mm,which is a 7.36%increase compared to the initial displacement.These changes indicate a 6.85%decrease in the overall bending bearing capacity of the track slab.[Conclusions]The residual plastic deformation of the track slab serves as a macroscopic characterization of internal damage.The gradual increase in plastic deformation with the number of load cycles indicates a deterioration in the actual load-bearing performance of the track slab.The increasing mid-span deflection further confirms the degradation of the actual bending bearing capacity.The overall performance deterioration of the track slab under service conditions would inevitably lead to changes in structural stress and deformation characteristics.In actual maintenance and repair,special attention should be paid to the actual state of weak positions in the ballastless track slab,and reasonable reinforcement measures should be adopted.
作者
吴文涛
何越磊
路宏遥
WU Wentao;HE Yuelei;LU Hongyao(College of Urban Rail Transportation,Shanghai University of Engineering Science,Shanghai 201620,China;Shanghai Key Laboratory of Structural Durability and System Safety of Rail Transit,Tongji University,Shanghai 201804,China)
出处
《实验技术与管理》
CAS
北大核心
2024年第9期41-46,共6页
Experimental Technology and Management
基金
上海市重点课程建设项目(s202310001)
国家自然科学基金资助项目(51978393)。
关键词
无砟轨道
多场耦合
疲劳损伤
四点弯拉
抗弯承载力
量化评价
ballastless track
multifield coupling
fatigue damage
four-point bending
flexural capacity
quantitative evaluation
