Over the next 20 years,China's urban rail transit(hereinafter referred to as'urban rail')will face large-scalerenovation of existing line facilities and equipment,with more than 1000 km of renovated lines ...Over the next 20 years,China's urban rail transit(hereinafter referred to as'urban rail')will face large-scalerenovation of existing line facilities and equipment,with more than 1000 km of renovated lines to be added eachyear.In 2024,the China Association of Metros issued the Guiding Opinions on the Renovation of Existing UrbanRail Transit Lines in China,providing guiding opinions on norms,standards,and implementation approaches forthe renovation of existing lines in the coming period.In the practical work of renovating existing urban rail lines,it is necessary to continuously explore and refine relevant theoretical methods in line with industry developmenttrends and urban development requirements.The following are the author's recent reflections on theoreticalinnovation in this field.展开更多
This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail conta...This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail contact parameters,an optimal design method for rail grinding target profile is proposed from wear profile measurement to grinding profile design according to the actual railway track and vehicle operating conditions.We utilized Isight to create a simulation test and developed an RBF proxy model that incorporated both mechanical and geometric aspects of wheel-rail contact.By integrating rail modeling,wheel-rail contact analysis,and multi-objective optimization,we established a rail grinding optimization model that was solved using the NSGA-II algorithm.After optimization,the study achieved a 31.863%reduction in average contact stress,a 70.5%reduction in matching wear work,and a 100.391%increase in the difference in rolling radius between the wheel and rail.展开更多
Rail profile optimization is a critical strategy for mitigating wear and extending service life.However,damage at the wheel-rail contact surface goes beyond simple rail wear,as it also involves fatigue phenomena.Focus...Rail profile optimization is a critical strategy for mitigating wear and extending service life.However,damage at the wheel-rail contact surface goes beyond simple rail wear,as it also involves fatigue phenomena.Focusing solely on wear and not addressing fatigue in profile optimization can lead to the propagation of rail cracks,the peeling of material off the rail,and even rail fractures.Therefore,we propose an optimization approach that balances rail wear and fatigue for heavy-haul railway rails to mitigate rail fatigue damage.Initially,we performed a field investigation to acquire essential data and understand the characteristics of track damage.Based on theory and measured data,a simulation model for wear and fatigue was then established.Subsequently,the control points of the rail profile according to cubic non-uniform rational B-spline(NURBS)theory were set as the research variables.The rail’s wear rate and fatigue crack propagation rate were adopted as the objective functions.A multi-objective,multi-variable,and multi-constraint nonlinear optimization model was then constructed,specifically using a Levenberg Marquardt-back propagation neural network as optimized by the particle swarm optimization algorithm(PSO-LM-BP neural network).Ultimately,optimal solutions from the model were identified using a chaos microvariation adaptive genetic algorithm,and the effectiveness of the optimization was validated using a dynamics model and a rail damage model.展开更多
Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail ...Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.展开更多
Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects,...Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects, and this study evaluates an advanced on-vehicle AE detection approach using bone-conduct sensors—a solution to improve upon previous AE methods of using on-rail sensor installations, which required extensive, costly on-rail sensor networks with limited effectiveness. In response to these challenges, the study specifically explored bone-conduct sensors mounted directly on the vehicle rather than rails by evaluating AE signals generated by the interaction between rails and the train’s wheels while in motion. In this research, a prototype detection system was developed and tested through initial trials at the Nevada Railroad Museum using a track with pre-damaged welding defects. Further testing was conducted at the Transportation Technology Center Inc. (rebranded as MxV Rail) in Colorado, where the system’s performance was evaluated across various defect types and train speeds. The results indicated that bone-conduct sensors were insufficient for detecting AE signals when mounted on moving vehicles. These findings highlight the limitations of contact-based methods in real-world applications and indicate the need for exploring improved, non-contact approaches.展开更多
Many railway turnouts are often installed near metro depots and stations,leading to significant environmental vibrations reaching nearby infrastructure.Vibration in turnout zones can originate from various sources,suc...Many railway turnouts are often installed near metro depots and stations,leading to significant environmental vibrations reaching nearby infrastructure.Vibration in turnout zones can originate from various sources,such as rail joints,wheel-load transitions,uneven stiffnesses,rail corrugation,and small-radius curves.These factors contribute to turnout zones having considerably higher vibration levels than plain track sections.Additionally,in urban rapid transit systems,higher train speeds exacerbate wheel–rail impact excitation,further intensifying such vibrations.Despite turnout zones accounting for a large share of environmental vibrations,there have been few systematic studies on their specific sources and mechanisms in the context of rapid transit systems.This knowledge gap has hindered the development and optimization of vibration mitigation strategies for turnout structures.Therefore,in this study,we investigate five representative sets of turnouts from a rapid transit system in a Chinese city,with train speeds ranging from 80 to 150 km/h.Field tests were conducted on real operating trains,with vibration accelerations measured at turnout rails and tunnel walls.This study systematically examines the effects of turnout structure,train carriage position,speed,and vibration mitigation measures on the vibration source characteristics.Time-frequency methods were employed to analyze the test data.Our findings reveal that when train speeds exceed 100 km/h,leading and trailing carriages passing through turnouts induce low-frequency vibrations below 80 Hz,thus generating vibrations in the human-sensitive frequency range.Moreover,train-induced vibrations in turnout zones are primarily concentrated in three frequency bands:0–20 Hz(associated with structural and stiffness irregularities in the turnouts),50–80 Hz(P2 resonance of the wheel–rail system),and 150–200 Hz(natural frequencies of the rails).展开更多
Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the...Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.展开更多
The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail ...The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail inspection methods,specifically involving real-time,precise detection,and assessment of rail defects.Current applications fail to address the evolving requirements,prompting the need for advancements.This paper provides a summary of various types of rail defects and outlines both traditional and innovative non-destructive inspection techniques,examining their fundamental features,benefits,drawbacks,and practical suitability for railway track inspection.It also explores potential enhancements to equipment and software.The comprehensive review draws upon pertinent international research and review papers.Furthermore,the paper introduces a fusion of inspection methods aimed at enhancing the overall reliability of defect detection.展开更多
During the grinding train operation process,the grinding force between the grinding wheel and the rail is critical in ensuring the grinding quality and efficiency.The coupling vibration among the frame,the grinding wh...During the grinding train operation process,the grinding force between the grinding wheel and the rail is critical in ensuring the grinding quality and efficiency.The coupling vibration among the frame,the grinding wheels,and the wheelsets will seriously affect the stability of the grinding force.In this paper,the coupled mechanical model of the grinding wheel/rail is established based on the contact mechanics theory,which is embedded as a submodel into the dynamic model of the multi-rigid buggy.The interaction among the frame,the grinding wheels and the wheelsets is analysed by setting the convex irregularity on the rail.The grinding effect is evaluated in combination with the subway’s long wave corrugation grinding conditions.The results show that when the grinding buggy passes the convex irregularity,the vibration excited by the wheelset system has a significant impact on the dynamic behavior of the grinding wheels.The vibration of the grinding wheel is mainly transmitted between the grinding wheel and the frame,less affecting the wheelset.For the long wave corrugation of the subway,the grinding effect of the grinding wheel has a certain correlation with the phase angle of the wheelset through the corrugation.The research results provide an important reference for the setting of the grinding pattern.展开更多
As metropolitan areas expand spatially,they encounter constraints imposed by the fixed daily time budget.Rail transit enhances transport efficiency,reduces costs,and facilitates the formation of a“transit economic fi...As metropolitan areas expand spatially,they encounter constraints imposed by the fixed daily time budget.Rail transit enhances transport efficiency,reduces costs,and facilitates the formation of a“transit economic field”centered on rail networks,thereby alleviating such temporal-spatial pressures.This paper adopts an integrated temporal-spatial analytical framework.Following a conceptual clarification of the transit economic field,it dissects the mechanisms through which rail transit improves mobility and examines how this field influences urban spatial patterns,temporal dynamics,and their interrelationships.It constructs a theoretical framework to explain the co-development of transit economic fields and cities,supplemented by empirical case studies.The key findings are as follows:Firstly,the transit economic field represents a high-density development model that expands both horizontally and vertically around rail networks.It mitigates temporal-spatial conflicts.Secondly,with rail networks as the core,the field integrates diverse spatial functions,facilitating the establishment of economic connections and stabilizing temporal-spatial relationships.Thirdly,the transit economic field contributes to the preservation of urban natural ecosystems and enhances urban livability.Overall,this research can provide insights for promoting rail transit-oriented development transitions in large cities and urban agglomerations.展开更多
To investigate the effect of rail pad viscoelasticity on vehicle-track-bridge coupled vibration,the fractional Voigt and Maxwell model in parallel(FVMP)was used to characterize the viscoelastic properties of the rail ...To investigate the effect of rail pad viscoelasticity on vehicle-track-bridge coupled vibration,the fractional Voigt and Maxwell model in parallel(FVMP)was used to characterize the viscoelastic properties of the rail pad based on dynamic performance test results.The FVMP model was then incorporated into the vehicle-track-bridge nonlinear coupled model,and its dynamic response was solved using a cross-iteration algorithm with a relaxation factor.Results indicate that the nonlinear coupled model achieves good convergence when the time step is less than 0.001 s,with the cross-iteration algorithm adjusting the wheel-rail force.In particular,the best convergence is achieved when the relaxation factor is within the range of 0.3-0.5.The FVMP model effectively characterizes the viscoelasticity of rail pads across a temperature range of±20℃and a frequency range of 1-1000 Hz.The viscoelasticity of rail pads significantly affects high-frequency vibrations in the coupled system,particularly around 50 Hz,corresponding to the wheel-rail coupled resonance range.Considering rail pad viscoelasticity is essential for accurately predicting track structure vibrations.展开更多
Aiming to address the challenge of directly measuring the real-time adhesion coefficient between wheels and rails,this paper proposes an online estimation algorithm for the adhesion coefficient based on parameter esti...Aiming to address the challenge of directly measuring the real-time adhesion coefficient between wheels and rails,this paper proposes an online estimation algorithm for the adhesion coefficient based on parameter estimation.Firstly,a force analysis of the single-wheel pair model of the train is conducted to derive the calculation relationship for the wheel-rail adhesion coefficient in train dynamics.Then,an estimator based on parameter estimation is designed,and its stability is verified.This estimator is combined with the wheelset force analysis to estimate the wheel-rail adhesion coefficient.Finally,the approach is validated through joint simulations on the MATLAB/Simulink and AMESim platforms,as well as a hardware-in-the-loop semi-physical simulation experimental platform that accounts for system delay and noise conditions.The results indicate that the proposed algorithm effectively tracks changes in the adhesion coefficient during train braking,including the decrease in adhesion when the train brakes and slides,and the overall increase as the train speed decreases.The effectiveness of the algorithm was verified by setting different test conditions.The results show that the estimation algorithm can accurately estimate the adhesion coefficient,and through error analysis,it is found that the error between the estimated value of the adhesion coefficient and the theoretical value of the adhesion coefficient is within 5%.The adhesion coefficient obtained through the online estimation method based on the parameter estimation proposed in this paper demonstrates strong followability in both simulation and practical applications.展开更多
On December 19,2015,construction equipment including cranes and excavators stood at attention at Thailand’s Chiang Rak Noi Station.Then Chinese State Councilor Wang Yong and Thai Deputy Prime Minister Prajin Juntong ...On December 19,2015,construction equipment including cranes and excavators stood at attention at Thailand’s Chiang Rak Noi Station.Then Chinese State Councilor Wang Yong and Thai Deputy Prime Minister Prajin Juntong lit the ceremonial cable,officially launching the China-Thailand Railway project.The 845-kilometer high-speed line will be Thailand’s first.It will stretch from Bangkok to Nong Khai on the Thai-Lao border and,once completed,will connect with the operational China-Laos Railway,enabling direct travel from Bangkok to Kunming,capital of southwest China’s Yunnan Province.Currently,most of Thailand’s rail infrastructure dates back more than a century.Most trains run at speeds below 50 km/h,using outdated carriages with safety risks.The China-Thailand Railway is expected to significantly improve this situation.展开更多
Predictive maintenance is essential for the implementation of an innovative and efficient structural health monitoring strategy.Models capable of accurately interpreting new data automatically collected by suitably pl...Predictive maintenance is essential for the implementation of an innovative and efficient structural health monitoring strategy.Models capable of accurately interpreting new data automatically collected by suitably placed sensors to assess the state of the infrastructure represent a fundamental step,particularly for the railway sector,whose safe and continuous operation plays a strategic role in the well-being and development of nations.In this scenario,the benefits of a digital twin of a bonded insu-lated rail joint(IRJ)with the predictive capabilities of advanced classification algorithms based on artificial intelligence have been explored.The digital model provides an accurate mechanical response of the infrastructure as a pair of wheels passes over the joint.As bolt preload conditions vary,four structural health classes were identified for the joint.Two parameters,i.e.gap value and vertical displacement,which are strongly correlated with bolt preload,are used in different combinations to train and test five predictive classifiers.Their classification effectiveness was assessed using several performance indica-tors.Finally,we compared the IRJ condition predictions of two trained classifiers with the available data,confirming their high accuracy.The approach presented provides an interesting solution for future predictive tools in SHM especially in the case of complex systems such as railways where the vehicle-infrastructure interaction is complex and always time varying.展开更多
On-line rail milling technologies have been applied in rail maintenance, and are proving to be efficient and environmental friendly. Based on the field data of on-line rail milling, a program for comparing rail transv...On-line rail milling technologies have been applied in rail maintenance, and are proving to be efficient and environmental friendly. Based on the field data of on-line rail milling, a program for comparing rail transverse profiles before and after milling was designed and the root mean square （RMS） amplitude of longitudinal profile was calculated. The application of on-line rail milling technology in removing rail surface defects, re-profiling railhead transverse profiles, smoothing longitudinal profiles and improving welding joint irregularity were analyzed. The results showed that the on-line rail milling technology can remove the surface defects at the rail crown and gauge comer perfectly, re-profile railhead transverse profile with a tolerance of - 1. 0-0.2 ram, improve longitudinal irregularity of rail surface, with the RMS amplitude of irregularity reduced more than 50% and the number of out-of- limited amplitude reduced by 42% - 82% in all wavelength ranges. The improvement of welding joint irregularity depends on the amount of metal removal determined by the milling equipment and the primal amplitude.展开更多
Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugatio...Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.展开更多
This study examined the influence of the built environment surrounding rail stations on rail transit ridership and its spatiotemporal variations,aiming to enhance rail transit operational efficiency and inform station...This study examined the influence of the built environment surrounding rail stations on rail transit ridership and its spatiotemporal variations,aiming to enhance rail transit operational efficiency and inform station planning and development.Data from 159 metro stations in Nanjing,collected over a 14-d period,were analyzed to identify changes in weekday and weekend ridership patterns.The analysis included explanatory variables grouped into three categories:urban spatial variables,socioeconomic vari-ables,and transit service variables.A geographically and temporally weighted regression(GTWR)model was developed,and its performance was compared with that of ordinary least squares(OLS)and geographically weighted regression(GWR)models.The results demonstrated that the GTWR model outperformed others in analyzing the relationship between rail transit ridership and the built environment.In addition,the coefficients of explanatory variables showed significant variation across spatiotemporal dimensions,revealing distinct patterns.Notably,the influence of commuter flows led to more pronounced temporal heterogeneity in the coefficients observed on weekdays.These findings offer valuable insights for optimizing urban public transportation systems and advancing integrated urban rail development.展开更多
文摘Over the next 20 years,China's urban rail transit(hereinafter referred to as'urban rail')will face large-scalerenovation of existing line facilities and equipment,with more than 1000 km of renovated lines to be added eachyear.In 2024,the China Association of Metros issued the Guiding Opinions on the Renovation of Existing UrbanRail Transit Lines in China,providing guiding opinions on norms,standards,and implementation approaches forthe renovation of existing lines in the coming period.In the practical work of renovating existing urban rail lines,it is necessary to continuously explore and refine relevant theoretical methods in line with industry developmenttrends and urban development requirements.The following are the author's recent reflections on theoreticalinnovation in this field.
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2019JBM050).
文摘This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail contact parameters,an optimal design method for rail grinding target profile is proposed from wear profile measurement to grinding profile design according to the actual railway track and vehicle operating conditions.We utilized Isight to create a simulation test and developed an RBF proxy model that incorporated both mechanical and geometric aspects of wheel-rail contact.By integrating rail modeling,wheel-rail contact analysis,and multi-objective optimization,we established a rail grinding optimization model that was solved using the NSGA-II algorithm.After optimization,the study achieved a 31.863%reduction in average contact stress,a 70.5%reduction in matching wear work,and a 100.391%increase in the difference in rolling radius between the wheel and rail.
基金supported by the National Natural Science Foundation of China(No.52388102)the Sichuan Science and Technology Program(No.2023ZDZX0008)China.The authors would like to thank the Guoneng Shuo-Huang Railway Development Company,China for providing vehicle parameters and line data for this project.The authors would also like to acknowledge the Xplorer Prize for sponsoring the project.
文摘Rail profile optimization is a critical strategy for mitigating wear and extending service life.However,damage at the wheel-rail contact surface goes beyond simple rail wear,as it also involves fatigue phenomena.Focusing solely on wear and not addressing fatigue in profile optimization can lead to the propagation of rail cracks,the peeling of material off the rail,and even rail fractures.Therefore,we propose an optimization approach that balances rail wear and fatigue for heavy-haul railway rails to mitigate rail fatigue damage.Initially,we performed a field investigation to acquire essential data and understand the characteristics of track damage.Based on theory and measured data,a simulation model for wear and fatigue was then established.Subsequently,the control points of the rail profile according to cubic non-uniform rational B-spline(NURBS)theory were set as the research variables.The rail’s wear rate and fatigue crack propagation rate were adopted as the objective functions.A multi-objective,multi-variable,and multi-constraint nonlinear optimization model was then constructed,specifically using a Levenberg Marquardt-back propagation neural network as optimized by the particle swarm optimization algorithm(PSO-LM-BP neural network).Ultimately,optimal solutions from the model were identified using a chaos microvariation adaptive genetic algorithm,and the effectiveness of the optimization was validated using a dynamics model and a rail damage model.
基金supported by Natural Science Foundation of China(52178441)the Scientific Research Projects of the China Academy of Railway Sciences Co.,Ltd.(Grant No.2022YJ043).
文摘Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.
文摘Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects, and this study evaluates an advanced on-vehicle AE detection approach using bone-conduct sensors—a solution to improve upon previous AE methods of using on-rail sensor installations, which required extensive, costly on-rail sensor networks with limited effectiveness. In response to these challenges, the study specifically explored bone-conduct sensors mounted directly on the vehicle rather than rails by evaluating AE signals generated by the interaction between rails and the train’s wheels while in motion. In this research, a prototype detection system was developed and tested through initial trials at the Nevada Railroad Museum using a track with pre-damaged welding defects. Further testing was conducted at the Transportation Technology Center Inc. (rebranded as MxV Rail) in Colorado, where the system’s performance was evaluated across various defect types and train speeds. The results indicated that bone-conduct sensors were insufficient for detecting AE signals when mounted on moving vehicles. These findings highlight the limitations of contact-based methods in real-world applications and indicate the need for exploring improved, non-contact approaches.
基金supported by the National Natural Science Foundation of China(Nos.U2568212,52388102,52478474,and 52472458)the Sichuan Science and Technology Program(Nos.2025NSFTD0013,2024NSFSC0003,and 2025YFHZ0035)the National Key R&D Program of China(Nos.2023YFB2604304,2023YFB2604302,and 2023YFB2604303).
文摘Many railway turnouts are often installed near metro depots and stations,leading to significant environmental vibrations reaching nearby infrastructure.Vibration in turnout zones can originate from various sources,such as rail joints,wheel-load transitions,uneven stiffnesses,rail corrugation,and small-radius curves.These factors contribute to turnout zones having considerably higher vibration levels than plain track sections.Additionally,in urban rapid transit systems,higher train speeds exacerbate wheel–rail impact excitation,further intensifying such vibrations.Despite turnout zones accounting for a large share of environmental vibrations,there have been few systematic studies on their specific sources and mechanisms in the context of rapid transit systems.This knowledge gap has hindered the development and optimization of vibration mitigation strategies for turnout structures.Therefore,in this study,we investigate five representative sets of turnouts from a rapid transit system in a Chinese city,with train speeds ranging from 80 to 150 km/h.Field tests were conducted on real operating trains,with vibration accelerations measured at turnout rails and tunnel walls.This study systematically examines the effects of turnout structure,train carriage position,speed,and vibration mitigation measures on the vibration source characteristics.Time-frequency methods were employed to analyze the test data.Our findings reveal that when train speeds exceed 100 km/h,leading and trailing carriages passing through turnouts induce low-frequency vibrations below 80 Hz,thus generating vibrations in the human-sensitive frequency range.Moreover,train-induced vibrations in turnout zones are primarily concentrated in three frequency bands:0–20 Hz(associated with structural and stiffness irregularities in the turnouts),50–80 Hz(P2 resonance of the wheel–rail system),and 150–200 Hz(natural frequencies of the rails).
基金National Key R&D Program of China(2022YFB2602900)R&D Fund Project of China Academy of Railway Sciences Corporation Limited(2021YJ084)+2 种基金Project of Science and Technology R&D Program of China Railway(2016G002-K)R&D Fund Project of China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.(2021)R&D Fund Project of China Railway Shanghai Group(2021141).
文摘Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.
文摘The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail inspection methods,specifically involving real-time,precise detection,and assessment of rail defects.Current applications fail to address the evolving requirements,prompting the need for advancements.This paper provides a summary of various types of rail defects and outlines both traditional and innovative non-destructive inspection techniques,examining their fundamental features,benefits,drawbacks,and practical suitability for railway track inspection.It also explores potential enhancements to equipment and software.The comprehensive review draws upon pertinent international research and review papers.Furthermore,the paper introduces a fusion of inspection methods aimed at enhancing the overall reliability of defect detection.
基金Supported by National Natural Science Foundation of China(Grant No.52475137)Sichuan Provincial Science and Technology Program(Grant No.2024YFHZ0280)Sichuan Provincial Nature and Science Foundation Innovation Research Group Project(Grant No.2023NSFSC1975).
文摘During the grinding train operation process,the grinding force between the grinding wheel and the rail is critical in ensuring the grinding quality and efficiency.The coupling vibration among the frame,the grinding wheels,and the wheelsets will seriously affect the stability of the grinding force.In this paper,the coupled mechanical model of the grinding wheel/rail is established based on the contact mechanics theory,which is embedded as a submodel into the dynamic model of the multi-rigid buggy.The interaction among the frame,the grinding wheels and the wheelsets is analysed by setting the convex irregularity on the rail.The grinding effect is evaluated in combination with the subway’s long wave corrugation grinding conditions.The results show that when the grinding buggy passes the convex irregularity,the vibration excited by the wheelset system has a significant impact on the dynamic behavior of the grinding wheels.The vibration of the grinding wheel is mainly transmitted between the grinding wheel and the frame,less affecting the wheelset.For the long wave corrugation of the subway,the grinding effect of the grinding wheel has a certain correlation with the phase angle of the wheelset through the corrugation.The research results provide an important reference for the setting of the grinding pattern.
基金Hubei Social Science Foundation Project“Research on the Relationship Between Rail Transit and Intensive and Sustainable Development of Large Cities”(2020052)。
文摘As metropolitan areas expand spatially,they encounter constraints imposed by the fixed daily time budget.Rail transit enhances transport efficiency,reduces costs,and facilitates the formation of a“transit economic field”centered on rail networks,thereby alleviating such temporal-spatial pressures.This paper adopts an integrated temporal-spatial analytical framework.Following a conceptual clarification of the transit economic field,it dissects the mechanisms through which rail transit improves mobility and examines how this field influences urban spatial patterns,temporal dynamics,and their interrelationships.It constructs a theoretical framework to explain the co-development of transit economic fields and cities,supplemented by empirical case studies.The key findings are as follows:Firstly,the transit economic field represents a high-density development model that expands both horizontally and vertically around rail networks.It mitigates temporal-spatial conflicts.Secondly,with rail networks as the core,the field integrates diverse spatial functions,facilitating the establishment of economic connections and stabilizing temporal-spatial relationships.Thirdly,the transit economic field contributes to the preservation of urban natural ecosystems and enhances urban livability.Overall,this research can provide insights for promoting rail transit-oriented development transitions in large cities and urban agglomerations.
基金Project(2023ZDZX0008)supported by the Sichuan Major Science and Technology Project,ChinaProject(52308468)supported by the National Natural Science Foundation of ChinaProject(2022JBQY009)supported by the Fundamental Research Funds for the Central Universities(Science and Technology Leading Talent Team Project),China。
文摘To investigate the effect of rail pad viscoelasticity on vehicle-track-bridge coupled vibration,the fractional Voigt and Maxwell model in parallel(FVMP)was used to characterize the viscoelastic properties of the rail pad based on dynamic performance test results.The FVMP model was then incorporated into the vehicle-track-bridge nonlinear coupled model,and its dynamic response was solved using a cross-iteration algorithm with a relaxation factor.Results indicate that the nonlinear coupled model achieves good convergence when the time step is less than 0.001 s,with the cross-iteration algorithm adjusting the wheel-rail force.In particular,the best convergence is achieved when the relaxation factor is within the range of 0.3-0.5.The FVMP model effectively characterizes the viscoelasticity of rail pads across a temperature range of±20℃and a frequency range of 1-1000 Hz.The viscoelasticity of rail pads significantly affects high-frequency vibrations in the coupled system,particularly around 50 Hz,corresponding to the wheel-rail coupled resonance range.Considering rail pad viscoelasticity is essential for accurately predicting track structure vibrations.
基金supported by the National Natural Science Foundation of China(grant/award number 52072266).
文摘Aiming to address the challenge of directly measuring the real-time adhesion coefficient between wheels and rails,this paper proposes an online estimation algorithm for the adhesion coefficient based on parameter estimation.Firstly,a force analysis of the single-wheel pair model of the train is conducted to derive the calculation relationship for the wheel-rail adhesion coefficient in train dynamics.Then,an estimator based on parameter estimation is designed,and its stability is verified.This estimator is combined with the wheelset force analysis to estimate the wheel-rail adhesion coefficient.Finally,the approach is validated through joint simulations on the MATLAB/Simulink and AMESim platforms,as well as a hardware-in-the-loop semi-physical simulation experimental platform that accounts for system delay and noise conditions.The results indicate that the proposed algorithm effectively tracks changes in the adhesion coefficient during train braking,including the decrease in adhesion when the train brakes and slides,and the overall increase as the train speed decreases.The effectiveness of the algorithm was verified by setting different test conditions.The results show that the estimation algorithm can accurately estimate the adhesion coefficient,and through error analysis,it is found that the error between the estimated value of the adhesion coefficient and the theoretical value of the adhesion coefficient is within 5%.The adhesion coefficient obtained through the online estimation method based on the parameter estimation proposed in this paper demonstrates strong followability in both simulation and practical applications.
文摘On December 19,2015,construction equipment including cranes and excavators stood at attention at Thailand’s Chiang Rak Noi Station.Then Chinese State Councilor Wang Yong and Thai Deputy Prime Minister Prajin Juntong lit the ceremonial cable,officially launching the China-Thailand Railway project.The 845-kilometer high-speed line will be Thailand’s first.It will stretch from Bangkok to Nong Khai on the Thai-Lao border and,once completed,will connect with the operational China-Laos Railway,enabling direct travel from Bangkok to Kunming,capital of southwest China’s Yunnan Province.Currently,most of Thailand’s rail infrastructure dates back more than a century.Most trains run at speeds below 50 km/h,using outdated carriages with safety risks.The China-Thailand Railway is expected to significantly improve this situation.
基金the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4-Call for tender No. 3138 of 16/12/2021 of Italian Ministry of University and Research funded by the European Union-Next Generation EU. Award Number: Project code CN00000023Concession Decree No. 1033 of 17/06/2022 adopted by the Italian Ministry of University and Research, CUP D93C22000400001, “Sustainable Mobility Center” (CNMS). Spoke 4-Rail Transportation
文摘Predictive maintenance is essential for the implementation of an innovative and efficient structural health monitoring strategy.Models capable of accurately interpreting new data automatically collected by suitably placed sensors to assess the state of the infrastructure represent a fundamental step,particularly for the railway sector,whose safe and continuous operation plays a strategic role in the well-being and development of nations.In this scenario,the benefits of a digital twin of a bonded insu-lated rail joint(IRJ)with the predictive capabilities of advanced classification algorithms based on artificial intelligence have been explored.The digital model provides an accurate mechanical response of the infrastructure as a pair of wheels passes over the joint.As bolt preload conditions vary,four structural health classes were identified for the joint.Two parameters,i.e.gap value and vertical displacement,which are strongly correlated with bolt preload,are used in different combinations to train and test five predictive classifiers.Their classification effectiveness was assessed using several performance indica-tors.Finally,we compared the IRJ condition predictions of two trained classifiers with the available data,confirming their high accuracy.The approach presented provides an interesting solution for future predictive tools in SHM especially in the case of complex systems such as railways where the vehicle-infrastructure interaction is complex and always time varying.
基金The National Natural Science Foundation of China(No.50908179)Specialized Research Fund for the Doctoral Program of Higher Education(No.200802471003)Program for Young Excellent Talents in Tongji University(No.2008KJ026)
文摘On-line rail milling technologies have been applied in rail maintenance, and are proving to be efficient and environmental friendly. Based on the field data of on-line rail milling, a program for comparing rail transverse profiles before and after milling was designed and the root mean square （RMS） amplitude of longitudinal profile was calculated. The application of on-line rail milling technology in removing rail surface defects, re-profiling railhead transverse profiles, smoothing longitudinal profiles and improving welding joint irregularity were analyzed. The results showed that the on-line rail milling technology can remove the surface defects at the rail crown and gauge comer perfectly, re-profile railhead transverse profile with a tolerance of - 1. 0-0.2 ram, improve longitudinal irregularity of rail surface, with the RMS amplitude of irregularity reduced more than 50% and the number of out-of- limited amplitude reduced by 42% - 82% in all wavelength ranges. The improvement of welding joint irregularity depends on the amount of metal removal determined by the milling equipment and the primal amplitude.
基金support extended by the Joint Funds of Beijing Municipal Natural Science Foundation and Fengtai Rail Transit Frontier Research(Grant No.L211006)the Fundamental Research Funds for the Central Universities(Science and technology leading talent team project,Grant No.2022JBXT010)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2023YJS052)the National Natural Science Foundation of China(Grant No.52308426)。
文摘Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.
基金The National Key Research and Development Program of China(No.2022YFC3800201).
文摘This study examined the influence of the built environment surrounding rail stations on rail transit ridership and its spatiotemporal variations,aiming to enhance rail transit operational efficiency and inform station planning and development.Data from 159 metro stations in Nanjing,collected over a 14-d period,were analyzed to identify changes in weekday and weekend ridership patterns.The analysis included explanatory variables grouped into three categories:urban spatial variables,socioeconomic vari-ables,and transit service variables.A geographically and temporally weighted regression(GTWR)model was developed,and its performance was compared with that of ordinary least squares(OLS)and geographically weighted regression(GWR)models.The results demonstrated that the GTWR model outperformed others in analyzing the relationship between rail transit ridership and the built environment.In addition,the coefficients of explanatory variables showed significant variation across spatiotemporal dimensions,revealing distinct patterns.Notably,the influence of commuter flows led to more pronounced temporal heterogeneity in the coefficients observed on weekdays.These findings offer valuable insights for optimizing urban public transportation systems and advancing integrated urban rail development.
