Running Speed Of Trains Research Articles

Advances and Challenges in the Hunting Instability Diagnosis of High-Speed Trains.

With the continuous increase in train running speeds and the rapid complexity of operation environments, running stability of the high-speed train is facing significant challenges. A series of abnormal vibration issues, caused by hunting instability, have emerged, including bogie instability alarm, carbody swaying, and carbody shaking, posing a significant threat to the safe and stable operation of high-speed trains. Therefore, the monitoring and diagnosis of hunting instability have become important research topics in rail transit. This review follows the development of fault diagnosis for bogie hunting instability and carbody hunting instability. It first summarizes the existing evaluation standards and innovative diagnostic methods. Due to the current limitation of hunting instability evaluation standards, which can only detect large-amplitude hunting, this paper addresses the gap in evaluation criteria for early-stage, small amplitude hunting instability diagnosis. A thorough overview of the progress made by researches in this field of research is given, emphasizing three primary facets: diagnostic signal sources, diagnostic features, and diagnostic targets. Furthermore, given that existing methods only classify faults into small and large amplitudes, which does not meet the practical need for quickly and accurately identifying fault types and severity during operation, this review introduces existing works on the detailed assessment and fault tracing of hunting instability, as well as the mechanisms underlying its occurrence, with the aim of achieving a comprehensive diagnosis of hunting instability. Finally, the limitations of current methods and the future development trends in hunting instability diagnostics are discussed and summarized. This paper provides readers with a framework for the research process of hunting instability diagnosis, offering valuable references and innovative perspectives for their future research efforts.

Analysis of temperature characteristics of high‐speed train wheelset system under complex operating conditions

AbstractWith the rapid advancements in high‐speed train technology, the importance of ensuring the safety of train operations has become paramount. Bearings, being a critical component of train bogies, have garnered significant attention for their role in maintaining safety standards. Monitoring the temperature of bearings to evaluate their motion state is a common practice in high‐speed trains, emphasizing the need for further research into temperature fluctuations. In this study, a dynamic model is developed for the bearing rotor system of high‐speed trains. By considering the contact points between raceways and rolling elements, the power loss in the bearing is obtained and a transient temperature‐field model of the system is established. The relationship between node temperature and factors such as ambient temperature, train running speed, and load is illustrated, with a detailed presentation of the influence of bearing fault type and size on node temperature. The analysis results reveal that the node temperature increases with higher values corresponding to those quantifiable factors and is most affected by rolling element fault. Additionally, it is observed that the temperature rises rapidly in the initial stage and gradually flattens out over time. The comparative analysis of temperature under different fault conditions shows that the node temperature is most affected by the rolling element fault. Experiments and actual line temperature data are used to verify the validity of the model. The comparison results show that the simulation aligns well with experimental and line data. The transient temperature‐field model of the bearing rotor system in high‐speed trains can effectively simulate and predict the temperature change process of each node of the system. The simulation results hold certain theoretical guiding significance for further research and practical applications in ensuring train operation safety.

A novel vortex control method for improving anti-overturning performance of a high-speed train with leeward airbag structures under crosswinds

The high-speed train's head and cross sections have been designed in an innovative way to meet the requirements of aerodynamic drag reduction and crosswind stability of the train. However, with the continuous increase in the running speed of high-speed trains and the continuous reduction of the total weight of the car body, it is critical to develop new strategies to ensure train safety in crosswind environment. In the current study, a novel vortex control method with airbag structure installation on the leeward side (LWS) of the train was proposed to disturb the leeward large vortices, with expectation to weaken the vortices adjacent the train body and increase the surface pressure on the leeward side. The leeward airbag structures (LASs) contribute to reducing the pressure difference between the windward and leeward sides of the train body. As a result, a reduction of the lateral force and overturning moment coefficients is obtained. An amazing observation is that an extra lift force is achieved by LASs, which leads to an anti-overturning moment, further improving the anti-overturning performance of the high-speed train. Compared with the original model, the LASs can decrease the lateral force coefficients by 7.1%, while the lift coefficient is increased by 12.8%, which together reduces the overturning moment coefficient by 13.1%. It indicates that the main influence factor for crosswind stability of the train tends to be changed after the installation of LASs. The aerodynamic performance of the tail car is more sensitive to the LASs as compared to that of the head and middle cars, i.e., the reduction of the overturning moment coefficient is about 44.6% for the tail car, whereas it is only 7.8% and 12.5% for the head and middle cars, respectively. Thus, the LASs proposed in the current work can significantly improve the anti-overturning performance of high-speed trains, which will provide a novel anti-overturning approach for higher-speed trains.

Effects of train speed on dynamic performance of shoe-rail interaction system

The increase of the running speed of electric train has a certain influence on the dynamic performance of coupling of conductor rail and collector shoe. In this paper, the mechanical characteristics of coupling vibration between shoe and rail for high-speed trains are studied by using a numerical simulation method, and the effects of train speed on the vibration law of shoe-rail interaction system are analyzed. The results show that both the maximum displacement of the rail and the maximum contact force between the shoe and the rail increase with the increase of the train speed. The bending moment of the rail, the maximum displacement of the shoe, the elastic and viscous forces of the shoe all decrease first and then increase. In particular, when the train speed increases from 275 to 300 km/h, the displacement, bending moment, contact force, and other mechanical quantities increase significantly, which indicate that it will lead to a sharp increase in vibration degree when the train speed exceeds 275 km/h. Therefore, in the case of actual operating parameters in this paper, it is recommended that the train speed does not exceed 275 km/h.

Stability Deterioration Analysis of Toppling Dangerous Rock Mass under the Combined Effect of Vibration and Freeze-Thaw Cycles

To investigate the degree of stability deterioration in toppling dangerous rock mass under different action times, firstly, the vibration load generated by train travel in a single action and its decay law were studied, and the theoretical relational equation of rock strength deterioration under the action of vibration loading was obtained by analyzing the increase in half axle expansion of micro fissures inside the rock. Secondly, the freezing stress of the microfissures was determined according to the rock freezing and swelling theory, and the theoretical relational equation of rock strength deterioration under the action of freeze-thaw cycles was obtained by integrating the rock confinement and moisture migration conditions of the fissures wall. The stability coefficient of the toppling dangerous rock mass exhibited a rapid and then slow decreasing trend with increasing number of actions, which was non-linearly negatively correlated with the train running speed and the initial porosity of the rock, and non-linearly positively correlated with the freezing temperature. Controlling the freezing temperature and initial porosity of rock can significantly reduce the degree of deterioration in the stability of dangerous rock mass.

Analysis of Key Influencing Factors of Track Dynamic Irregularity Induced by Earthquakes in the High-Speed Railway Track–Bridge System

Stiffness degradation of track–bridge systems under earthquake excitations can lead to track dynamic irregularity, impacting the safety of train operations post-earthquake. In this paper, the nonlinear time-history analysis of CRTS II track–bridge system model established by ANSYS finite element analysis software is carried out under the action of transverse random earthquake. The train–track–bridge system model considering the stiffness degradation caused by earthquake is established by MATLAB, and the earthquake-induced track dynamic irregularity sample library is constructed. The probability distribution mode of the power spectral density sample of the earthquake-induced track dynamic irregularity is explored and the calculation method based on the probability guarantee rate is proposed. The influence of structural damping ratio, train running speed and train type on the power spectral density curve of the earthquake-induced track dynamic irregularity is analyzed. The results show that the power spectrum samples of track dynamic irregularity conform to the hypothesis test of a normal distribution. The power spectral density of earthquake-induced dynamic irregularity primarily consists of medium and low-frequency components. When the structural damping ratio increases from 0.03 to 0.04, 0.04 to 0.05, 0.05 to 0.06, and 0.06 to 0.07, the variation gradients are 0.1701, 0.1240, 0.1034 and 0.0999, respectively, which indicates that the structural damping ratio has a significant effect on the power spectral density of earthquake-induced irregularity, and the impacts of train speed and train type on the power spectral density of near-fault earthquake-induced irregularity are minimal.

Analysis of the Deformation and Dynamics of High-Speed Railway Bridge Under the Coupling Effect of Shield Tunneling and Train Load

In order to study the dynamic response of high-speed railway bridge and its deformation law under the coupling effect of vibration load and shield tunneling, a coupling model of shield tunneling and train load is established based on the actual case of tunneling under an adjacent bridge. The deformation characteristics and dynamic response of the bridge are investigated by analyzing the deformation under different tunneling conditions and train running speeds. The results show that the maximum disturbance of the original stress field around the bridge is caused when the shield penetrates to the near side of the bridge structure, at which time, the damping effect of the ground and bridge system on the vibration load is weakened, thus intensifying the dynamic response of the bridge system, and the additional deformation caused by the vibration load is the largest; the presence of train loads during the shield excavation slightly attenuates the differential settlement of the bridge, but increases the cumulative settlement of the bridge, in addition, the additional deformation of the bridge will increase with the increase of the train running speed; the additional deformation caused by the train load within 2[Formula: see text]m of the shield crossing on both sides of the bridge is large, so the construction should be avoided as much as possible when the train is running in this construction section.

Study on Aerodynamic Drag Reduction by Plasma Jets for 600 km/h Vacuum Tube Train Sets

In order to break through the speed bottleneck, researchers envision using tubes to cover high-speed maglev trains and extract some of the air inside the tubes, creating a low-density environment on the ground, greatly reducing the aerodynamic drag of the trains, and in a relatively economical and feasible way, making high subsonic (600 km/h and above) and even supersonic ground transportation possible. The faster the running speed of high-speed trains, the greater the impact of aerodynamic drag on their energy consumption. Studying the aerodynamic characteristics of trains with a speed of 600 km/h can help optimize the aerodynamic shape of the train, reduce aerodynamic drag, and reduce energy consumption. This has positive implications for improving train energy efficiency, reducing energy consumption, and environmental impact. This paper adopts the numerical simulation method to study the drag reduction effect of the plasma arrangement and different excitation speeds on the train set in four positions when the incoming wind speed is 600 km/h, to analyze the mechanism of drag reduction, and then to analyze the combination of working conditions in order to investigate the drag reduction effect of plasma on the vacuum tube train set with an ambient pressure of 10,000 Pa. The findings demonstrate that the plasma induces the directional flow of the gas close to the wall to move the flow separation point backward and delay the separation of the flow, thereby reducing the front and rear differential pressure drag of the train set and lowering the aerodynamic drag coefficient of the entire train. The plasma arrangement is located at the rear of the flow separation point and in close proximity to the flow separation point. The pneumatic drag reduction effect peaks when the excitation speed reaches 0.2 times the train speed and the pneumatic drag reduction ratio is around 0.88%; the pneumatic drag reduction ratio of the rear car peaks when the excitation speed reaches 0.25 times the train speed and the pneumatic drag reduction ratio is 1.62%. The SDBD (Surface Dielectric Barrier Discharge) device is installed at the flow separation point around the nose tip of the rear car.

An Integrated Method for Reducing Arrival Interval by Optimizing Train Operation and Route Setting

The arrival interval at high-speed railway stations is one of the key factors that restrict the improvement of the train following intervals. In the process of practical railway operation, sudden conflicts occur sometimes. Especially when the conflict arises at the station, because the home signal cannot be opened in time, the emergency may affect the adjustment of the train operation under the scheduled timetable, resulting in a longer train following interval or even delay. With the development of artificial intelligence and the deep integration of big data, the architecture of train operation control and dispatch integration is gradually improving from the theoretical point. Based on this and inspired by the Green Wave policy, we propose an integrated operation method that reduces the arrival interval by avoiding unnecessary stops in front of the home signal and increasing the running speed of trains through the throat area. It is a two-step optimization method combining both intelligent optimization and mathematical–theoretical analysis algorithms. In the first step, the recommended approaching speed and position are obtained by analytical calculation. In the second step, the speed profile from the current position to the position corresponding to the recommended approaching speed is optimized by intelligent optimization algorithms. Finally, the integrated method is verified through the analysis of two distinct case studies. The first case study utilizes data from the Beijing–Shanghai high-speed railway line, while the second one is based on the field test. The numerical result shows that the proposed method could save the entry running time effectively, compared with the normal strategy given by the train driver. The method can mitigate controllable conflict events occurring at the station and provides theoretical support for practical operation.

Effect of Train Vibrations on the Dynamic Response of a Multi-Span Double-Curved Brick Arch Thin-Shell Factory of Changleyuan

The dynamic characteristics of a multi-span double-curved brick arch thin-shell factory of Changleyuan in Baoji City and the dynamic response to train vibration load were studied using field dynamic tests and finite-element numerical simulations, and a vibration evaluation of the thin-shell factory was carried out. The results showed that the first-order frequency of the thin-shell factory was 6.24 Hz in the horizontal direction (east–west) and 9.31 Hz in the vertical direction. Moreover, it was established that the horizontal vibration is the overall vibration of the factory, while the vertical vibration is the individual vibration of the double-curved brick arch. In addition, the self-oscillation frequency obtained from the numerical simulation results was greater compared with the field measurements, with a maximum error rate of 7.14%. Both in acceleration and velocity, the vertical vibration for each measurement point was larger than the horizontal vibration, and the farther away from the railroad, the smaller the vibration. The vibration of the velocity at the bottom of the arch was almost the same as that at the top of the arch, while the acceleration vibration at the bottom of the arch was significantly larger than that at the top of the arch, with an average amplitude of 40.64%. For every 20 km/h increase in train running speed, the average increase in vertical acceleration amplitude, vertical velocity amplitude, horizontal acceleration amplitude, and horizontal velocity amplitude for each measurement point of the thin-shell factory was 35.4%, 29.8%, 23.7%, and 12.5%, respectively. When v = 150 km/h, the maximum velocity amplitude for each measurement point of the thin-shell factory was 1.163 mm/s, which is less than the security specification limit of 2.5 mm/s, such that the security of the thin-shell factory meets the requirement, and the maximum horizontal velocity amplitude was 0.272 mm/s, which is close to the integrity specification limit of 0.27 mm/s, such that the integrity of the thin-shell factory just exceeds the requirement; so it is suggested that train running speeds should not exceed 150 km/h and that the thin-shell factory needs to strengthen the monitoring and protection of its integrity.

Field Investigation of the Dynamic Response of Culvert-Embankment-Culvert Transitions in a High-Speed Railway.

The stiffnesses of embankments and culverts differ in the transition sections of high-speed railways (HSRs) due to their different supporting conditions. The dynamic irregularity caused by the different stiffnesses makes this transition area the weakest part of high-speed railways. Graded crushed stone combined with 5% cement is typically used to fill the subgrade in these transition areas. Thus, three different particle size ratios of crushed stone were matched and tested regarding the construction parameters to explore the most suitable materials to fill the roadbed in a transition section. Then, field dynamic tests were carried out on the culvert-embankment-culvert transition area where trains run at speeds of 5-360 km/h. A time-domain analysis of the test data was performed to obtain the laws of variation that cause the dynamic characteristics to change with the railway line and roadbed layer and the changes induced by a train's running speed, operating direction, and axle weight. The results indicate that (i) it is feasible to fill transition section roadbeds with well-graded crushed stone combined with 5% cement with optimal water contents; (ii) extreme dynamic responses in some special sections are observed, suggesting the value of taking special measures at the transition section. For example, the sections 14.5 m and 30 m from the 679 culvert and the bed layer should be specially stabilized; (iii) the train's axle load and driving direction show a great effect on corresponding sections and layers but present a small effect on the sections and layers nearby; and (iv) 260 km/h is a critical speed.

A velocity-related running safety assessment index in seismic design for railway bridge

With the rapid expansion of the high-speed railway (HSR) network, high-speed train running safety (TRS) over bridges is increasingly highlighted in the world. Previously, spectral intensity (SI) was proposed and considered as a performance-based index for discussing TRS over HSR bridges in seismic design. However, the speed independence of the conventional SI index greatly limits its rationality and generalisation in the performance-based bridge design under earthquake. To this end, the velocity-related SI index is proposed for the first time and improves the limitations of the conventional index in this research. The discrepancy between the proposed SI and the conventional SI is explained theoretically, and the correlation between the proposed SI and train running speed is illustrated in detail. Additionally, a series of scale model experiments are conducted to validate the feasibility of the train-bridge coupled (TBC) system. The probability analysis of the proposed SI index is presented to help discuss the randomness and economy of HSR bridges. Furthermore, systematic parametric analyses are finished by taking the train running speed as the kernel parameter based on the TBC model. The simulation results show the conventional SI index unduly neglected the velocity-induced vibration of the train under an earthquake. Within the common train running speed range, the proposed SI indices have the same varying pattern with the derailment factors and are comprehensively larger than the conventional SI indices. The vibration induced by train speed seriously threatens TRS under earthquake, but it was ignored in the seismic design for the HSR bridge before.

Design of tandem wing layout of pneumatic cooperative lift train

Pneumatic lift train together is the concept of under the background of further accelerate the speed of high-speed train running speed, in order to under higher speed train the whole life cycle cost, the researchers put forward the concept of aerodynamic lift high-speed train together, break through the traditional high-speed train aerodynamic shape design concept, combined with high speed trains and aircraft their respective advantages, hope that through increasing train aerodynamic lift, It is hoped that by increasing the aerodynamic lift of the train, the overall energy saving and consumption reduction of the high-speed train can be achieved. In this paper, a high lift airfoil is optimized to improve the lift coefficient as much as possible while the drag coefficient is basically unchanged. The thickness and drag coefficient of the optimized airfoil are almost unchanged at the designed Angle of attack, and the lift coefficient is increased by 13%. A flat wing is designed based on the optimized airfoil, and the influence of wall effect and tandem wing layout on the lift drag coefficient of the wing is studied. A better aerodynamic lift cooperative train tandem wing layout is obtained, which can reduce the weight of a single train by 17%.

Development and engineering application of integrated safety monitoring systems for China's high-speed trains

Abstract With the improvement of the running speed of China's high-speed trains, the demands for running status monitoring and security assurance of High-speed Electric Multiple Units (EMU) have increased significantly. However, the current safety monitoring systems are independent, which is not conducive to the comprehensive monitoring and information sharing of the whole vehicle. The temperature monitoring of running gear is insensitive to early failures. How to develop a train operation safety monitoring system with strong engineering implementation and high integration is a key problem to be solved. For the monitoring of running stationarity, frame stability and running gear health of China's high-speed trains, an integrated safety monitoring system framework is designed, and the logic and algorithm for the diagnosis of stationarity, stability and health states of rotating parts are constructed. Monitoring software which fused the temperature, high and low frequency vibration data is developed, and the design and installation of the vibration temperature composite sensors are completed. The research results have realized the integration and comprehensive processing of multiple monitoring systems, completed the improvement from single component and vehicle-level safety monitoring to multi-system, train-level and interactive monitoring. In the process of real vehicle application, the developed monitoring system acquires the vehicle operation status data accurately and in real time. The constructed diagnosis algorithm and logic evaluates the vehicle operation status accurately and in a timely manner, and avoids the progression from fault to accident. The research results show that the integrated safety monitoring system can provide technical support for train operation safety.

Speed Limit of Linear Induction Motor Subway Trains Running through 65 m Radius Curves on Yard Line

Linear induction motor (LIM) subway yard line often have very-small-radius curves and small turnouts with “S”-shaped curves in the middle. The lateral stability of the train is low, and wheel-climb (slipway) derailments often occur at a speed of 10 km/h. To study the derailment safety and speed limit of a linear motor subway train running through yard line, a coupling dynamic model of the train-track system is established, fully considering the driving characteristics of the linear motor, characteristics of the linear motor train, and track structure. The safety of train derailment is judged by the over-limit time of the derailment coefficient. Under the premise of a safe operation, the variations in the derailment coefficient, out-of-limit time, wheel unloading rate, and wheel-axle lateral force with the train running speed are studied. When the train runs at speeds below 25 km/h, for both new and worn rails, the derailment coefficient and lateral force of the wheel axle at each speed exceed the safety limits, and are less affected by changes in the speed. The duration of the derailment coefficient is within the safety limit because the speed of crossing the curve is low, and thus the train will not overturn and derail. Rail wear reduces the train derailment safety through the yard line, while the wheel wear improves the train derailment safety through the yard line. Considering the actual state of the yard line (wheel-rail wear, irregularity, etc.), the speed of the linear motor subway train running through the yard line should be limited to below 15 km/h.

Study on Vibrational Properties of Vehicle and Track System Caused by Deformation of Tunnel Base

In this paper, the vehicle track tunnel coupling dynamic model is established by using finite element software, and the model is verified. Based on this, the vibration characteristics of the vehicle and track system caused by the settlement of the tunnel foundation are studied. The calculation results show that: (1) the short wave in the tunnel settlement wavelength has a great influence on the dynamic characteristics of vehicles and track structures, and the vibration characteristics of vehicle track system decrease with the increase of wavelength, so it is suggested to control the wavelength above 25 m. (2) The dynamic index of the vehicle and track increases significantly with the increase of amplitude, which affects the driving stability and track operation. Through calculation, it is recommended to control the amplitude below 20 mm. (3) The influence of tunnel base settlement on driving is related to speed. The greater the train speed is, the greater the influence on driving will be. So the train speed should be controlled. (4) Higher running speed will endanger the safety of train operation and the stability of the track structure, so the train running speed should be lower than 200 km/h. The above research provides some theoretical guidance for track maintenance and operation.

Structural health monitoring of railway bridges using innovative sensing technologies and machine learning algorithms: a concise review

Abstract Railway bridges are a vital element of railway infrastructures, and their safety can directly affect the regional economy and commuter transportation. However, railway bridges are often subjected to severe loading and working conditions, caused by rising traffic levels and heavier vehicles, and increases in train running speeds makes the bridges extremely susceptible to degradation and failure. One of the promising tools for evaluating the overall safety and reliability of railway bridges is the bridge structural health monitoring (SHM) system, which not only monitors the structural conditions of bridges and maintains the safety of train operations, but also helps to expand the lifespan of bridges by enhancing their durability and reliability. While a multitude of review papers on SHM and vibration-based structural damage detection methods have been published in the past two decades, there is a paucity of literature that provides a review or overview on the SHM of railway bridges. Some of the review papers have become obsolete and do not reflect the state-of-the-art research. Therefore, the main goal of this article is to summarize state-of-the-art SHM techniques and methods that have been widely used and popular in recent years. First, two state-of-the-art SHM sensing technologies (i.e. fiber optic sensing (FOS) technology and computer vision-based (CV) technology) are reviewed, including the working principles of various sensors and their practical applications for railway bridge monitoring. Second, two state-of-the-art machine learning algorithms (i.e. convolutional neural networks (CNN) and transfer learning (TL)) and their applications for railway bridge structural condition assessment are exemplified. Third, the principle of digital twin (DT) and its applications for railway bridge monitoring are presented. Finally, issues related to the future direction and challenges of the monitoring technologies and condition assessment methods of railway bridges are highlighted.

Evolutionary power spectrum density of earthquake-induced rail geometric irregularities

China’s high-speed railway (HSR) construction has gradually extended to earthquake-vulnerable areas in recent years. However, there is currently a lack of studies on the characteristics of earthquake-induced rail irregularities, making it impossible to ascertain the threshold of post-earthquake train running speed. Taking the multi-span HSR simply supported girder bridge of a CRTS II-type track system as the research focus, the distribution models for residual rail irregularity under random seismic actions have been analyzed in this study. The statistical distribution of the evolutionary power spectrum density (EPSD) of the residual rail irregularity set is also explored. Based on the obtained results, the EPSD of earthquake-induced rail geometric irregularity was calculated, and a time-domain sample for earthquake-induced rail geometric irregularity was developed. Finally, the equating method of earthquake-induced rail geometric irregularity under different span numbers was discussed, and a method for fitting earthquake-induced rail geometric irregularity was proposed.

Static and dynamic effects of train-track-bridge system subject to environment-induced deformation of long-span railway bridge

Laying ballastless tracks on a long-span railway bridge with a main span greater than 300 m is a challenge in engineering practice and has aroused significant concerns. Influenced by complicated environmental factors, long-span railway bridges in service deform with large amplitudes and complex shapes, which may result in damage to the track structure and threaten the running safety and ride comfort of trains. In this study, we investigate some typical statics and dynamics problems under the actual conditions of a long-span cable-stayed high-speed railway bridge with a main span of 400 m and laying ballastless track. The track-bridge finite element model and dynamic interaction model of the train-track-bridge system are first established. Furthermore, the influences of the complicated environment-induced bridge deformations are comprehensively investigated using the curvature method that reveals the deformation compatibility of the bridge-track system and indicates the dynamic interaction behavior of the train-track-bridge system subject to train running speeds and bridge deformations. Results indicate that excellent dynamic performance of the train-track-bridge system can be achieved by setting an elastic cushion of 0.1 N/mm3 under the track bed. Interface damage between track layers will not occur directly because of the complex deformations of the bridge decks. The bridge deformations induced by the environmental temperature and the concrete creep are qualified. The dynamic responses of the train-track-bridge system are also excellent under the excitations of bridge deformations. Dynamic simulations of the train-track-bridge system are proposed to evaluate long-span bridge deformations subject to complicated service situations in comparison with an oversimplified statics evaluation.

Optimization of urban rail transit station spacing for minimizing passenger travel time

Urban rail transit, regarded as the backbone of urban public transportation, can effectively solve the problems of urban traffic congestion and automobile exhaust pollution. However, due to improper planning, unreasonable station location often appears, which seriously affects the service access and mobility of rail transit. In order to improve the station spacing and passenger transport efficiency, a calculation model of station spacing for minimizing passenger travel time was established. In order to enhance the adaptability of the model in different cities, the grid road network and radial road network are considered when establishing the model. The results show that the station spacing is related to the passenger access/egress speed, the passenger travel distance, the maximum train running speed, the train stop time and the train acceleration. The influence of these parameters on the station spacing is obtained through the control variate method, and there are indeed obvious differences under different road network conditions. The research results can provide theoretical reference for station planning of new lines. Since the station spacing of the operated lines cannot be changed, this study can provide reference for skip-stop operation.