Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast trac...Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast track and simply-supported beam are combined with each other,was established.The laws of the track stress,the pier longitudinal stress and the beam-track relative displacement were analyzed.The results show that reducing the longitudinal resistance can effectively reduce the track stress and the pier stress of the continuous beam,and increase the beam-track relative displacement.Increasing the rigid pier stiffness of continuous beam can reduce the track braking stress,increase the pier longitudinal stress and reduce the beam-track relative displacement,Increasing the rigid pier stiffness of simply-supported beam can reduce the track braking stress,the rigid pier longitudinal stress and the beam-track relative displacement.展开更多
X-style arch bridge on high-speed railways(HSR)is one kind of complicated long-span structure,and the track-bridge interaction is essential to ensure the safety and smoothness of HSR.Taking an X-style steel-box arch b...X-style arch bridge on high-speed railways(HSR)is one kind of complicated long-span structure,and the track-bridge interaction is essential to ensure the safety and smoothness of HSR.Taking an X-style steel-box arch bridge with a main span of450 m on HSR under construction for example,a new integrative mechanic model of rail-stringer-cross beam-suspenderpier-foundation coupling system was established,adopting the nonlinear spring element simulating the longitudinal resistance between track and bridge.The transmission law of continuous welded rail(CWR)on the X-style arch bridge was researched,and comparative study was carried out to discuss the influence of several sensitive factors,such as the temperature load case,the longitudinal resistance model,the scheme of longitudinal restraint conditions,the introverted inclination of arch rib,the stiffness of pier and abutment and the location of the rail expansion device.Calculating results indicate that the longitudinal resistance has a significant impact upon the longitudinal forces of CWR on this kind of bridge,while the arch rib’s inclination has little effect.Besides,temperature variation of arch ribs and suspenders should be taken into account in the calculation.Selecting the restraint system without longitudinally-fixed bearing and setting the rail expansion devices on both ends are more reasonable.展开更多
A non-linear regression model is proposed to forecast the aggregated passenger volume of Beijing-Shanghai high-speed railway(HSR) line in China. Train services and temporal features of passenger volume are studied to ...A non-linear regression model is proposed to forecast the aggregated passenger volume of Beijing-Shanghai high-speed railway(HSR) line in China. Train services and temporal features of passenger volume are studied to have a prior knowledge about this high-speed railway line. Then, based on a theoretical curve that depicts the relationship among passenger demand, transportation capacity and passenger volume, a non-linear regression model is established with consideration of the effect of capacity constraint. Through experiments, it is found that the proposed model can perform better in both forecasting accuracy and stability compared with linear regression models and back-propagation neural networks. In addition to the forecasting ability, with a definite formation, the proposed model can be further used to forecast the effects of train planning policies.展开更多
Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parame...Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses(wheel-rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors(direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong 93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.展开更多
Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the...Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.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
Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stabil...Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stability and passenger safety.Since wheel/rail contact forces of high-speed train are very difficult to measure directly,a new estimation process for wheel/rail contact forces was introduced in this work.Based on the state space equation,dynamic programming methods and the Bellman principle of optimality,the main theoretical derivation of the inversion mathematical model was given.The new method overcomes the weakness of large fluctuations which exist in current inverse techniques.High-speed vehicle was chosen as the research object,accelerations of axle box as input conditions,10 degrees of freedom vertical vibration model and 17 degrees of freedom lateral vibration model were established,respectively.Under 250 km/h,the vertical and lateral wheel/rail forces were identified.From the time domain and frequency domain,the comparison of the results between inverse and SIMPACK models were given.The results show that the inverse mathematical model has high precision for inversing the wheel/rail contact forces of an operation high-speed vehicle.展开更多
In recent years,the safety and comfort of road vehicles driving on bridges under crosswinds have attracted more attention due to frequent occurrences of wind-induced disasters.This study focuses on a container truck a...In recent years,the safety and comfort of road vehicles driving on bridges under crosswinds have attracted more attention due to frequent occurrences of wind-induced disasters.This study focuses on a container truck and CRH2 high-speed train as research targets.Wind tunnel experiments are performed to investigate shielding effects of trains on aerodynamic characteristics of trucks.The results show that aerodynamic interference between trains and trucks varies with positions of trains(upstream,downstream)and trucks(upwind,downwind)and numbers of trains.To summarize,whether the train is upstream or downstream of tracks has basically no effect on aerodynamic forces,other than moments,of a truck driving on windward sides of bridges(upwind).In contrast,the presence of trains on the bridge deck has a significant impact on aerodynamic characteristics of a truck driving on leeward sides(downwind)at the same time.The best shielding effect on lateral forces of trucks occurs when the train is located downstream of tracks.Finally,the pressure measuring system shows that only lift forces on trains are affected by trucks,while other forces and moments are primarily affected by adjacent trains.展开更多
The track geometry is a critical factor that affects the running safety and riding comfort of trains moving on a high-speed railway bridge.This study addresses the mapping relationship between the track deformation an...The track geometry is a critical factor that affects the running safety and riding comfort of trains moving on a high-speed railway bridge.This study addresses the mapping relationship between the track deformation and lateral deformations of bridges.Equilibrium equations and natural boundary conditions of the track-bridge system are established based on the energy variational principle,and an analytical solution is derived for the track deformation accounting for lateral bridge deformations.A five-span simply-supported bridge with continuous welded rail has been selected as the case study.The mapping rail deformations are compared to the finite element results,and both results agree well with each other,validating the analytical method proposed in this paper.The influence factors on the mapping rail deformation are further evaluated.Results show that the mapping rail deformation is consistent with the girder displacement at the area that is away from the girder ends when the flexural stiffness ratio between the track and the bridge girder is low.The interlayer stiffness has a significant effect on the mapping rail deformation when the track flexural stiffness is of a high value.展开更多
基金Project(50678176) supported by the National Natural Science Foundation of China
文摘Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast track and simply-supported beam are combined with each other,was established.The laws of the track stress,the pier longitudinal stress and the beam-track relative displacement were analyzed.The results show that reducing the longitudinal resistance can effectively reduce the track stress and the pier stress of the continuous beam,and increase the beam-track relative displacement.Increasing the rigid pier stiffness of continuous beam can reduce the track braking stress,increase the pier longitudinal stress and reduce the beam-track relative displacement,Increasing the rigid pier stiffness of simply-supported beam can reduce the track braking stress,the rigid pier longitudinal stress and the beam-track relative displacement.
基金Projects(51378503,51178471) supported by the National Natural Science Foundation of China
文摘X-style arch bridge on high-speed railways(HSR)is one kind of complicated long-span structure,and the track-bridge interaction is essential to ensure the safety and smoothness of HSR.Taking an X-style steel-box arch bridge with a main span of450 m on HSR under construction for example,a new integrative mechanic model of rail-stringer-cross beam-suspenderpier-foundation coupling system was established,adopting the nonlinear spring element simulating the longitudinal resistance between track and bridge.The transmission law of continuous welded rail(CWR)on the X-style arch bridge was researched,and comparative study was carried out to discuss the influence of several sensitive factors,such as the temperature load case,the longitudinal resistance model,the scheme of longitudinal restraint conditions,the introverted inclination of arch rib,the stiffness of pier and abutment and the location of the rail expansion device.Calculating results indicate that the longitudinal resistance has a significant impact upon the longitudinal forces of CWR on this kind of bridge,while the arch rib’s inclination has little effect.Besides,temperature variation of arch ribs and suspenders should be taken into account in the calculation.Selecting the restraint system without longitudinally-fixed bearing and setting the rail expansion devices on both ends are more reasonable.
基金Project(2014YJS080) supported by the Fundamental Research Funds for the Central Universities of China
文摘A non-linear regression model is proposed to forecast the aggregated passenger volume of Beijing-Shanghai high-speed railway(HSR) line in China. Train services and temporal features of passenger volume are studied to have a prior knowledge about this high-speed railway line. Then, based on a theoretical curve that depicts the relationship among passenger demand, transportation capacity and passenger volume, a non-linear regression model is established with consideration of the effect of capacity constraint. Through experiments, it is found that the proposed model can perform better in both forecasting accuracy and stability compared with linear regression models and back-propagation neural networks. In addition to the forecasting ability, with a definite formation, the proposed model can be further used to forecast the effects of train planning policies.
基金Projects(51425804,51378439,51608459)supported by the National Natural Science Foundation of ChinaProjects(U1334203,U1234201)supported by the Key Project of the China’s High-Speed Railway United Fund+1 种基金Project(2016M590898)supported by China Postdoctoral Science FoundationProject(2014GZ0009)supported by Sichuan Provinial Science and Technology support Program,China
文摘Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses(wheel-rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors(direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong 93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.
基金Project(41030742) supported by the National Natural Science Foundation of ChinaProject(2009G010-c) supported by the Technological Research and Development Programs of the Ministry of Railways,China
文摘Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.
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Project(2009BAG12A04-A11)supported by the National Key Technology R&D Program in the"11-th Five-year Plan"of ChinaProjects(51275432,51005190)supported by the National Natural Science Foundation of ChinaProject(SWJTU09ZT23)supported by University Doctor Academics Particularly Science Research Fund,China
文摘Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stability and passenger safety.Since wheel/rail contact forces of high-speed train are very difficult to measure directly,a new estimation process for wheel/rail contact forces was introduced in this work.Based on the state space equation,dynamic programming methods and the Bellman principle of optimality,the main theoretical derivation of the inversion mathematical model was given.The new method overcomes the weakness of large fluctuations which exist in current inverse techniques.High-speed vehicle was chosen as the research object,accelerations of axle box as input conditions,10 degrees of freedom vertical vibration model and 17 degrees of freedom lateral vibration model were established,respectively.Under 250 km/h,the vertical and lateral wheel/rail forces were identified.From the time domain and frequency domain,the comparison of the results between inverse and SIMPACK models were given.The results show that the inverse mathematical model has high precision for inversing the wheel/rail contact forces of an operation high-speed vehicle.
基金Projects(52078504,51822803,51925808,U1934209)supported by the National Natural Science Foundation of ChinaProject(KF2021-05)supported by the State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures,China。
文摘In recent years,the safety and comfort of road vehicles driving on bridges under crosswinds have attracted more attention due to frequent occurrences of wind-induced disasters.This study focuses on a container truck and CRH2 high-speed train as research targets.Wind tunnel experiments are performed to investigate shielding effects of trains on aerodynamic characteristics of trucks.The results show that aerodynamic interference between trains and trucks varies with positions of trains(upstream,downstream)and trucks(upwind,downwind)and numbers of trains.To summarize,whether the train is upstream or downstream of tracks has basically no effect on aerodynamic forces,other than moments,of a truck driving on windward sides of bridges(upwind).In contrast,the presence of trains on the bridge deck has a significant impact on aerodynamic characteristics of a truck driving on leeward sides(downwind)at the same time.The best shielding effect on lateral forces of trucks occurs when the train is located downstream of tracks.Finally,the pressure measuring system shows that only lift forces on trains are affected by trucks,while other forces and moments are primarily affected by adjacent trains.
基金Project(2021RC2011)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProjects(U1934207,52178180)supported by the National Natural Science Foundation of ChinaProject(2021M703648)supported by the China Postdoctoral Science Foundation。
文摘The track geometry is a critical factor that affects the running safety and riding comfort of trains moving on a high-speed railway bridge.This study addresses the mapping relationship between the track deformation and lateral deformations of bridges.Equilibrium equations and natural boundary conditions of the track-bridge system are established based on the energy variational principle,and an analytical solution is derived for the track deformation accounting for lateral bridge deformations.A five-span simply-supported bridge with continuous welded rail has been selected as the case study.The mapping rail deformations are compared to the finite element results,and both results agree well with each other,validating the analytical method proposed in this paper.The influence factors on the mapping rail deformation are further evaluated.Results show that the mapping rail deformation is consistent with the girder displacement at the area that is away from the girder ends when the flexural stiffness ratio between the track and the bridge girder is low.The interlayer stiffness has a significant effect on the mapping rail deformation when the track flexural stiffness is of a high value.
