High-speed railway aerodynamics is the key basic science for solving the bottleneck problem of high-speed railway development.This paper systematically summarizes the aerodynamic research relating to China’s high-spe...High-speed railway aerodynamics is the key basic science for solving the bottleneck problem of high-speed railway development.This paper systematically summarizes the aerodynamic research relating to China’s high-speed railway network.Seven key research advances are comprehensively discussed,including train aerodynamic drag-reduction technology,train aerodynamic noise-reduction technology,train ventilation technology,train crossing aerodynamics,train/tunnel aerodynamics,train/climate environment aerodynamics,and train/human body aerodynamics.Seven types of railway aerodynamic test platform built by Central South University are introduced.Five major systems for a high-speed railway network—the aerodynamics theoretical system,the aerodynamic shape(train,tunnel,and so on)design system,the aerodynamics evaluation system,the 3D protection system for operational safety of the high-speed railway network,and the high-speed railway aerodynamic test/computation/analysis platform system—are also introduced.Finally,eight future development directions for the field of railway aerodynamics are proposed.For over 30 years,railway aerodynamics has been an important supporting element in the development of China’s high-speed railway network,which has also promoted the development of high-speed railway aerodynamics throughout the world.展开更多
Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under earthquakes.Taking a high-speed railway simply-sup...Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under earthquakes.Taking a high-speed railway simply-supported girder bridge with eight spans crossing an active strike-slip fault as the research object,a refined coupling dynamic model of the high-speed train-CRTS III slab ballastless track-bridge system was established based on ABAQUS.The rationality of the established model was thoroughly discussed.The horizontal ground motions in a fault rupture zone were simulated and transient dynamic analyses of the high-speed train-track-bridge coupling system under 3-dimensional seismic excitations were subsequently performed.The safe running speed limits of a high-speed train under different earthquake levels(frequent occurrence,design and rare occurrence)were assessed based on wheel-rail dynamic(lateral wheel-rail force,derailment coefficient and wheel-load reduction rate)and rail deformation(rail dislocation,parallel turning angle and turning angle)indicators.Parameter optimization was then investigated in terms of the rail fastener stiffness and isolation layer friction coefficient.Results of the wheel-rail dynamic indicators demonstrate the safe running speed limits for the high-speed train to be approximately 200 km/h and 80 km/h under frequent and design earthquakes,while the train is unable to run safely under rare earthquakes.In addition,the rail deformations under frequent,design and rare earthquakes meet the safe running requirements of the high-speed train for the speeds of 250,100 and 50 km/h,respectively.The speed limits determined for the wheel-rail dynamic indicators are lower due to the complex coupling effect of the train-track-bridge system under track irregularity.The running safety of the train was improved by increasing the fastener stiffness and isolation layer friction coefficient.At the rail fastener lateral stiffness of 60 kN/mm and isolation layer friction coefficients of 0.9 and 0.8,r展开更多
In order to mitigate the risk of geological disasters induced by fault activation when roadways intersect reverse faults in coal mining,this paper uses a combination of mechanical models with PFC2D software.A mechanic...In order to mitigate the risk of geological disasters induced by fault activation when roadways intersect reverse faults in coal mining,this paper uses a combination of mechanical models with PFC2D software.A mechanical model is introduced to represent various fault angles,followed by a series of PFC2D loading and unloading tests to validate the model and investigate fault instability and crack propagation under different excavation rates and angles.The results show that(1)the theoretical fault model,impacted by roadway advancing,shows a linear reduction in horizontal stress at a rate of-2.01 MPa/m,while vertical stress increases linearly at 4.02 MPa/m.(2)Atfield excavation speeds of 2.4,4.8,7.2,and 9.6 m/day,the vertical loading rates for the model are 2.23,4.47,6.70,and 8.93 Pa/s,respectively.(3)Roadway advancement primarily causes tensile-compressive failures in front of the roadway,with a decrease in tensile cracks as the stress rate increases.(4)An increase in the fault angle leads to denser cracking on the fault plane,with negligible cracking near the fault itself.The dominant crack orientation is approximately 90°,aligned with the vertical stress.展开更多
When aerodynamic braking works,the braking wings can change the flow field around the train,which may impact on the comfort and safety.Based on a sliding mesh,the pressure wave and flow field around high-speed trains ...When aerodynamic braking works,the braking wings can change the flow field around the train,which may impact on the comfort and safety.Based on a sliding mesh,the pressure wave and flow field around high-speed trains with aerodynamic braking are analyzed.By comparing three typical intersection situations,the pressure wave of a high-speed train during braking (with or without aerodynamic braking) is studied.The analyses indicate that the pressure wave around the high-speed train body will change while using the aerodynamic braking,causing several pressure pulses on the surface of crossing high-speed trains.The distances between the pressure pulses are equal to the longitudinal distances of the brake wings,but the magnitudes of the fluctuations are less than those induced by the head of crossing trains.During the crossing,a train without aerodynamic braking will not impact the crossing train.展开更多
Objective: To conduct a cost analysis of pedestrian injuries at zebra crossings (marked lines only) in Stockholm city during 2008, and propose an intervention for reducing these incidents. Cost savings for the interve...Objective: To conduct a cost analysis of pedestrian injuries at zebra crossings (marked lines only) in Stockholm city during 2008, and propose an intervention for reducing these incidents. Cost savings for the intervention are calculated and presented. Method: A Cost of Illness (COI) method was used to calculate the cost for pedestrian injuries at zebra crossings. Cost of Illness included direct and indirect costs and excluded intangible costs due to lack of data. Data and statistics from STRADA, PAR and calculations from MSB were used to perform the COI. Results: During 2008, 73 pedestrians were injured at zebra crossings in Stockholm city, amounting an estimated social cost of 10.8 million Swedish Krona (SEK) (severe injuries 9.2 million SEK, minor injuries 1.6 million SEK). The costs for reducing pedestrian injuries and related social burden via the proposed intervention (zebra crossings constructed alongside asphalt speed bumps with adjacent lights on both sides of the crossing) were estimated to be 250,000 SEK at roads without intersections, and 1.6 million SEK at roads with an intersection. Conclusion: Pedestrian injuries place a large financial burden on society each year. It is recommended to add speed bumps and adjacent lights to zebra crossings where most pedestrian injuries occur. The intervention would reduce pedestrian injuries and also decrease the cost for the society due to these injuries. Cost savings for the intervention depend on the kind of injury avoided and what kind of road the intervention is built on.展开更多
文摘High-speed railway aerodynamics is the key basic science for solving the bottleneck problem of high-speed railway development.This paper systematically summarizes the aerodynamic research relating to China’s high-speed railway network.Seven key research advances are comprehensively discussed,including train aerodynamic drag-reduction technology,train aerodynamic noise-reduction technology,train ventilation technology,train crossing aerodynamics,train/tunnel aerodynamics,train/climate environment aerodynamics,and train/human body aerodynamics.Seven types of railway aerodynamic test platform built by Central South University are introduced.Five major systems for a high-speed railway network—the aerodynamics theoretical system,the aerodynamic shape(train,tunnel,and so on)design system,the aerodynamics evaluation system,the 3D protection system for operational safety of the high-speed railway network,and the high-speed railway aerodynamic test/computation/analysis platform system—are also introduced.Finally,eight future development directions for the field of railway aerodynamics are proposed.For over 30 years,railway aerodynamics has been an important supporting element in the development of China’s high-speed railway network,which has also promoted the development of high-speed railway aerodynamics throughout the world.
基金Project(51378050) supported by the National Natural Science Foundation of ChinaProject(B13002) supported by the “111” Project,China+2 种基金Project (8192035) supported by the Beijing Municipal Natural Science Foundation,ChinaProject(P2019G002) supported by the Science and Technology Research and Development Program of China RailwayProject(2019YJ193) supported by the State Key Laboratory for Track Technology of High-speed Railway,China。
文摘Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under earthquakes.Taking a high-speed railway simply-supported girder bridge with eight spans crossing an active strike-slip fault as the research object,a refined coupling dynamic model of the high-speed train-CRTS III slab ballastless track-bridge system was established based on ABAQUS.The rationality of the established model was thoroughly discussed.The horizontal ground motions in a fault rupture zone were simulated and transient dynamic analyses of the high-speed train-track-bridge coupling system under 3-dimensional seismic excitations were subsequently performed.The safe running speed limits of a high-speed train under different earthquake levels(frequent occurrence,design and rare occurrence)were assessed based on wheel-rail dynamic(lateral wheel-rail force,derailment coefficient and wheel-load reduction rate)and rail deformation(rail dislocation,parallel turning angle and turning angle)indicators.Parameter optimization was then investigated in terms of the rail fastener stiffness and isolation layer friction coefficient.Results of the wheel-rail dynamic indicators demonstrate the safe running speed limits for the high-speed train to be approximately 200 km/h and 80 km/h under frequent and design earthquakes,while the train is unable to run safely under rare earthquakes.In addition,the rail deformations under frequent,design and rare earthquakes meet the safe running requirements of the high-speed train for the speeds of 250,100 and 50 km/h,respectively.The speed limits determined for the wheel-rail dynamic indicators are lower due to the complex coupling effect of the train-track-bridge system under track irregularity.The running safety of the train was improved by increasing the fastener stiffness and isolation layer friction coefficient.At the rail fastener lateral stiffness of 60 kN/mm and isolation layer friction coefficients of 0.9 and 0.8,r
基金Australian Research Council,Grant/Award Number:DP210100437National Natural Science Foundation of China,Grant/Award Number:52274102Graduate Research and Innovation Projects of Jiangsu Province,Grant/Award Number:KYCX21_2335。
文摘In order to mitigate the risk of geological disasters induced by fault activation when roadways intersect reverse faults in coal mining,this paper uses a combination of mechanical models with PFC2D software.A mechanical model is introduced to represent various fault angles,followed by a series of PFC2D loading and unloading tests to validate the model and investigate fault instability and crack propagation under different excavation rates and angles.The results show that(1)the theoretical fault model,impacted by roadway advancing,shows a linear reduction in horizontal stress at a rate of-2.01 MPa/m,while vertical stress increases linearly at 4.02 MPa/m.(2)Atfield excavation speeds of 2.4,4.8,7.2,and 9.6 m/day,the vertical loading rates for the model are 2.23,4.47,6.70,and 8.93 Pa/s,respectively.(3)Roadway advancement primarily causes tensile-compressive failures in front of the roadway,with a decrease in tensile cracks as the stress rate increases.(4)An increase in the fault angle leads to denser cracking on the fault plane,with negligible cracking near the fault itself.The dominant crack orientation is approximately 90°,aligned with the vertical stress.
基金Project(No.2009BAG12A05-13) supported by the National Key Technology R&D Program of China
文摘When aerodynamic braking works,the braking wings can change the flow field around the train,which may impact on the comfort and safety.Based on a sliding mesh,the pressure wave and flow field around high-speed trains with aerodynamic braking are analyzed.By comparing three typical intersection situations,the pressure wave of a high-speed train during braking (with or without aerodynamic braking) is studied.The analyses indicate that the pressure wave around the high-speed train body will change while using the aerodynamic braking,causing several pressure pulses on the surface of crossing high-speed trains.The distances between the pressure pulses are equal to the longitudinal distances of the brake wings,but the magnitudes of the fluctuations are less than those induced by the head of crossing trains.During the crossing,a train without aerodynamic braking will not impact the crossing train.
文摘Objective: To conduct a cost analysis of pedestrian injuries at zebra crossings (marked lines only) in Stockholm city during 2008, and propose an intervention for reducing these incidents. Cost savings for the intervention are calculated and presented. Method: A Cost of Illness (COI) method was used to calculate the cost for pedestrian injuries at zebra crossings. Cost of Illness included direct and indirect costs and excluded intangible costs due to lack of data. Data and statistics from STRADA, PAR and calculations from MSB were used to perform the COI. Results: During 2008, 73 pedestrians were injured at zebra crossings in Stockholm city, amounting an estimated social cost of 10.8 million Swedish Krona (SEK) (severe injuries 9.2 million SEK, minor injuries 1.6 million SEK). The costs for reducing pedestrian injuries and related social burden via the proposed intervention (zebra crossings constructed alongside asphalt speed bumps with adjacent lights on both sides of the crossing) were estimated to be 250,000 SEK at roads without intersections, and 1.6 million SEK at roads with an intersection. Conclusion: Pedestrian injuries place a large financial burden on society each year. It is recommended to add speed bumps and adjacent lights to zebra crossings where most pedestrian injuries occur. The intervention would reduce pedestrian injuries and also decrease the cost for the society due to these injuries. Cost savings for the intervention depend on the kind of injury avoided and what kind of road the intervention is built on.
