Study of the post-derailment safety measures on low-speed derailment tests

Prevention of train from derailment is the most important issue for the railway system. Keeping derailed vehicle close to the track centreline is beneficial to minimise the severe consequences associated with derailments. In this paper, the post-derailment safety measures are studied based on low-speed derailment tests. Post-derailment devices can prevent deviation of the train from the rail by catching the rail, and they are mounted under the axle box. Considering the different structures of vehicles, both trailer and motor vehicles are equipped with the safety device and then separately used in low-speed derailment tests. In derailment tests, two kinds of track, namely the CRTS-I slab ballastless track and the CRTS-II bi-block sleeper ballastless track, are adopted to investigate the effect of the track types on the derailment. In addition, the derailment speed and the weight of the derailed vehicle are also taken into account in derailment tests. The test results indicate that the post-derailment movement of the vehicle includes running and bounce. Reducing the derailment speed and increasing the weight of the head of the train are helpful to reduce the possibility for derailments. For the CRTS-I slab ballastless track, the safety device can prevent trailer vehicles from deviating from the track centreline. The gearbox plays an important role in controlling the lateral displacement of motor vehicle after a derailment while the safety device contributes less to keep derailed motor vehicles on the track centreline. The lateral distance between the safety device and rails should be larger than 181.5?mm for protecting the fasteners system. And for the CRTS-II bi-block sleeper ballastless track, it helps to decrease the post-derailment distance due to the longitudinal impacts with sleepers. It can also restrict the lateral movement of derailed vehicle due to the high shoulders. The results suggest that, CRTS-II bi-block sleeper ballastless track should be widely used in derailment prone areas.     

Transverse Vibration of Train-Bridge and Train-Track Time Varying System and the Theory of Random Energy Analysis for Train Derailment

Summary In this paper, the fundamental problems in the calculation of transverse vibration of train-bridge and train-track time-varying system (hereinafter referred to as the system) are expounded. That is, (1) Proper solution to transverse vibration of the system cannot be obtained by establishing separate transverse vibration equation groups for the car and the bridge (or track); (2) The exciting source of transverse vibration of the system has not been made definite; (3) It is difficult to carry out the random analysis of vibration of the time varying system as the theory of the random vibration analysis for the time varying system has not been established. Our thinking and methods to solve these problems are introduced. On the above-mentioned basis, the theory of random energy analysis for train derailment is presented. The main contents of this theory are as follows: method of random energy analysis of transverse vibration of the system; geometric criterion of derailment; mechanism of derailment caused by the combined track irregularity and energy increment criterion for derailment evaluation; calculation of the entire derailing process; method of improvement of track parameters for preventing straight line speed-raise freight trains from derailment and of the calculation of the safety coefficient against derailment. This theory is used to calculate a case of freight train derailment, which corresponds to an actually occurred accident. A train in another derailment test is judged to be not derailed and its maximum vibration responses are calculated. The field test results are well responded.     

Effect of curved track support failure on vehicle derailment

In order to investigate the effect of curved track support failure on railway vehicle derailment, a coupled vehicle–track dynamic model is put forward. In the model, the vehicle and the structure under rails are, respectively, modelled as a multi-body system, and the rail is modelled with a Timoshenko beam rested on the discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The model also considers the effect of the discrete support by sleepers on the coupling dynamics of the vehicle and track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the calculation of the coupled vehicle and track dynamics, the normal forces of the wheels/rails are calculated using the Hertzian contact theory and their creep forces are determined with the nonlinear creep theory by Shen et al [Z.Y. Shen, J.K. Hedrick, and J.A. Elkins, A comparison of alternative creep-force models for rail vehicle dynamic analysis, Proceedings of the 8th IAVSD Symposium, Cambridge, MA, 1984, pp. 591–605]. The motion equations of the vehicle/track are solved by means of an explicit integration method. The failure of the components of the curved track is simulated by changing the track stiffness and damping along the track. The cases where zero to six supports of the curved rails fail are considered. The transient derailment coefficients are calculated. They are, respectively, the ratio of the wheel/rail lateral force to the vertical force and the wheel load reduction. The contact points of the wheels/rails are in detail analysed and used to evaluate the risk of the vehicle derailment. Also, the present work investigates the effect of friction coefficient, axle load and vehicle speed on the derailments under the condition of track failure. The numerical results obtained indicate that the failure of track supports has a great influence on the whole vehicle running safety.     

Three-dimensional derailment analysis of crashed freight trains

In this paper, the collision-induced derailment of freight trains was investigated. The collision between two identical freight trains occurring on a curved path rather than along a straight line was investigated. This is because from the point of view of safety against derailment this collision scenario is thought to be more critical than the scenarios defined in the European standard EN 15227. In this work, one of the trains is stationary and the other moving train collides at 36 km/h. Two kinds of container wagons were simulated. One is the two-axle freight wagon Kls 442. Another is the freight wagon Rmms 662 with two Y25 bogies. Simulation results demonstrate that in terms of safety against derailment the bogie wagon Rmms 662 was found to have better behaviour than the two-axle wagon Kls 442. In addition, this study points out that there are many contributory factors to the responses of freight wagons during a collision, such as curve radius, distance between bogie pivots and loading mass. The derailment phenomenon is less likely to occur, when freight trains collide on the curve with a larger radius. Besides that the characteristics of freight wagons with large axle loads, low centre of gravity of car body and appropriate static strength are favourable for the collided wagons in reducing the risk of derailment.     

Study on flange climb derailment criteria of a railway wheelset

The wheel flange climb derailment, which can be usually considered as a quasi-static process, is one of the main types of derailment, and often occurs on curved tracks due to large wheel lateral force and reduced vertical force. The general formula for the wheel critical derailment coefficient Q/P, the ratio of wheel lateral force to vertical force, is derived through analysing the forces exerted on the flange climb wheel. Based on the Coulomb's friction law and the creep force laws, the Friction Formula and Creep Formula for the evaluation of derailment are derived, respectively. The analysis shows that the derailment coefficients of Friction Formula and Creep Formula required for derailment are increased considerably for smaller and negative yaw angles, and tend to the value of Nadal's Formula at larger wheelset yaw angles. The Creep Formula is more reasonable for the assessment of derailment. The effect of some parameters on flange climb derailment, such as wheel/rail friction coefficient, yaw angle, flange contact angle, wheel vertical load and curve radius, are investigated. Finally, a simplified formula for wheel climb derailment based on the Creep Formula is proposed.     

Study on the derailment behaviour of a railway wheelset with solid axles in a railway turnout

ABSTRACT

Dynamic wheel–rail interaction in railway turnouts is more complicated than on ordinary track. In order to evaluate the derailment behaviour of railway wheelsets in railway turnouts, this paper presents a study of dynamic wheel–rail interaction during a wheel flange climbs on the turnout rails, by applying the elasticity positioning wheelset model. A numerical model is established based on a coupled finite element method and multi-body dynamics, and applied to study the derailment behaviour of a railway wheelset in both the facing and trailing directions in a railway turnout, as well as dynamic wheel–turnout rail interaction during the wheel flange climbing on the turnout rails. The influence of the wheel–rail attack angle and the friction coefficient on the dynamic derailment behaviour is investigated through the proposed model. The results show that the derailment safety for a wheelset passing the railway turnout in facing direction is significantly lower than that for the trailing direction and the ordinary track. The possibility of derailment for the wheelset passing the railway turnout in facing and trailing directions at positive wheel–rail attack angles will increase with an increase in the attack angles, and the possibility of derailment can be reduced by decreasing the friction coefficient.     

Study on flange climb derailment criteria of a railway wheelset

The wheel flange climb derailment, which can be usually considered as a quasi-static process, is one of the main types of derailment, and often occurs on curved tracks due to large wheel lateral force and reduced vertical force. The general formula for the wheel critical derailment coefficient Q/P, the ratio of wheel lateral force to vertical force, is derived through analysing the forces exerted on the flange climb wheel. Based on the Coulomb's friction law and the creep force laws, the Friction Formula and Creep Formula for the evaluation of derailment are derived, respectively. The analysis shows that the derailment coefficients of Friction Formula and Creep Formula required for derailment are increased considerably for smaller and negative yaw angles, and tend to the value of Nadal's Formula at larger wheelset yaw angles. The Creep Formula is more reasonable for the assessment of derailment. The effect of some parameters on flange climb derailment, such as wheel/rail friction coefficient, yaw angle, flange contact angle, wheel vertical load and curve radius, are investigated. Finally, a simplified formula for wheel climb derailment based on the Creep Formula is proposed.     

A numerical study of the derailment caused by collision of a rail vehicle using a virtual testing model

This study investigated the wheel-lift and roll-over derailment mechanisms caused by train collisions using a precise virtual testing model (VTM) of a Korean high-speed train. The VTM was a complex, nonlinear finite element model composed of the shell, beam, solid, spring, and surface contact elements for the car body, bogies, suspensions, and wheel–rail interfaces. The VTM was validated by checking the errors in the total energy and the dynamic responses of the spring elements. To achieve a quick, dynamic relaxation of the dead weight of the VTM before the collision analysis, the artificial damping method and the artificial force method were introduced and numerically evaluated. The surface-to-surface contact model from commercial software, Ls-Dyna, was applied to the VTM in order to simulate the derailment mechanisms caused by collision accidents. The numerical analyses of the VTM colliding with a large deformable obstacle or a rigid wall revealed for the first time that a mixed slip/roll-over-type derailment mechanism generally occurs. Furthermore, the simulation results were consistent with the results from a simplified theoretical derailment model of a wheel set.     

Influence of creep forces on the risk of derailment of railway vehicles

The derailment mechanism in a railway vehicle is a complex mechanical phenomenon which has been, and still is, the subject of intense research activity due to the serious consequences it can entail. Since Nadal deduced his well-known formula, many researchers have put forward alternative equations which all attempt to move closer to the data obtained experimentally. This paper provides a summary of the best known and draws up a new formulation based on the theoretical 3-D study of creep forces emerging from the contact patch of the wheel likely to derail. It also provides an in-depth analysis of the role played by spin creepage, including its effect on obtaining theoretical derailment limits, which are more realistic than those obtained using Nadal's formula. Finally, a new derailment criterion is proposed. This new criterion leads to less conservative values than Nadal's equation for zero yaw angles. When the yaw angle is high enough, the results obtained are coincident with those predicted by Nadal's equation.     

Dynamic response of the train–track–bridge system subjected to derailment impacts

Derailments on bridges, although not frequent, when occurs due to a complex dynamic interaction of the train–track–bridge structural system, are very severe. Furthermore, the forced vibration induced by the post-derailment impacts can toss out the derailed wagons from the bridge deck with severe consequences to the traffic underneath and the safety of the occupants of the wagons. This paper presents a study of the train–track–bridge interaction during a heavy freight train crossing a concrete box girder bridge from a normal operation to a derailed state. A numerical model that considers the bridge vibration, train–track interaction and the train post-derailment behaviour is formulated based on a coupled finite-element – multi-body dynamics (FE-MBD) theory. The model is applied to predict the post-derailment behaviour of a freight train composed of one locomotive and several wagons, as well as the dynamic response of a straight single-span simply supported bridge containing ballast track subjected to derailment impacts. For this purpose, a typical derailment scenario of a heavy freight train passing over a severe track geometry defect is introduced. The dynamic derailment behaviour of the heavy freight train and the dynamic responses of the rail bridge are illustrated through numerical examples. The results exhibit the potential for tossing out of the derailed trains from the unstable increase in the yaw angle signature and a lower rate of increase of the bridge deck bending moment compared to the increase in the static axle load of the derailed wheelset.     

Three-dimensional derailment analysis of a crashed city tram

City tram collisions are simulated using multi-body dynamics. The aim of this paper is to investigate the collision-induced derailment. Simulation results demonstrate that the corner obstacle collision scenario defined in EN 15227 is mainly focused on the energy absorption process. Due to the large impact angle (45°), it is unlikely for a city tram to comply with this scenario without derailment. In order to avoid derailment, the maximum impact angle between city tram and oblique obstacle should be reduced to 25°. Moreover, some influence factors are analysed, such as mass of loaded passengers, friction coefficient, impact angle, etc. Derailment phenomenon is shown to be significantly dependent on these parameters. Two measures are proposed to prevent the collided city tram from derailment. One is using secondary lateral dampers to absorb collision energy. Another is increasing the lateral stiffness of secondary springs as well as the lateral clearance, so that more collision energy can be stored in the suspension. With these measures, the safety against derailment can be improved.     

Indirect method for wheel–rail force measurement and derailment evaluation

Wheel set flange derailment criteria for railway vehicles are derived and the influence of wheel–rail contact parameters is studied. An indirect method for wheel–rail force measurement based on these derailment evaluation criteria is proposed. Laboratory tests for the calibration of strain–force devices on the bearing box are carried out to determine the relationship between the applied force and the measured strain. The simulation package, SIMPACK, is used to develop a passenger car model to generate wheel–rail forces and vibration signals. Different cases are considered in this model to provide an accurate validation of the identified wheel–rail forces. A feasibility test is conducted in the Beijing Loop test line using a passenger car equipped with a set of strain gauges on the wheel set. The comparison of the force time history applied to the instrumented wheel set and that obtained using the indirect method is presented.     

Safety of a railway wheelset – derailment simulation with increasing lateral force

The motivation for this research is to make a comparison between dynamic results of a free railway wheelset derailment and safety limits. For this purpose, a numerical simulation of a wheelset derailment submitted to increasing lateral force is used to compare with the safety limit, using different criteria. A simplified wheelset model is used to simulate derailments with different adhesion conditions. The contact force components, including the longitudinal and spin effects, are identified in a steady-state condition on the verge of a derailment. The contact force ratios are used in a three-dimensional (3D) analytical formula to calculate the safety limits. Simulation results obtained with two contact methods were compared with the published results and the safety limit was identified with the two criteria. Results confirm Nadal’s conservative aspect and show that safety 3D analytical formula presents slightly higher safety limits for lower friction coefficients and smaller limits for high friction, in comparison with the simulation results with Fastsim.     

Dynamics of railway wagons subjected to braking/traction torque

Braking or traction torque is regarded as an important source of wheelset skid and a potential source of derailment risk that adversely affects the safety levels of train operations; therefore, this research examines the effect of braking/traction torque to the longitudinal and lateral dynamics of wagons. This paper reports how train operations safety could be adversely affected due to various braking strategies. Sensitivity of wagon dynamics to braking severity is illustrated through numerical examples. The influence of wheel/rail interface friction coefficient and the effects of two types of track geometry defects on wheel unloading ratio and wagon pitch are also discussed in the paper.     

Dynamic simulation of train–truck collision at level crossings

Trains crashing onto heavy road vehicles stuck across rail tracks are more likely occurrences at level crossings due to ongoing increase in the registration of heavy vehicles and these long heavy vehicles getting caught in traffic after partly crossing the boom gate; these incidents lead to significant financial losses and societal costs. This paper presents an investigation of the dynamic responses of trains under frontal collision on road trucks obliquely stuck on rail tracks at level crossings. This study builds a nonlinear three-dimensional multi-body dynamic model of a passenger train colliding with an obliquely stuck road truck on a ballasted track. The model is first benchmarked against several train dynamics packages and its predictions of the dynamic response and derailment potential are shown rational. A geometry-based derailment assessment criterion is applied to evaluate the derailment behaviour of the frontal obliquely impacted trains under different conditions. Sensitivities of several key influencing parameters, such as the train impact speed, the truck mass, the friction at truck tyres, the train–truck impact angle, the contact friction at the collision zone, the wheel/rail friction and the train suspension are reported.     

基于统计原理的铁路隧道运营期灾害类型及防灾对策研究

统计分析了83例国内外铁路隧道运营期事故资料,研究了铁路隧道运营期间主要灾害类型、原因及防灾对策。研究结果表明:1)铁路隧道运营期间主要灾害类型有火灾、列车碰撞、脱轨及衬砌剥落;2)铁路隧道运营期防灾应以隧道火灾为重点,同时兼顾列车碰撞、脱轨和隧道衬砌混凝土剥落等灾害;3)隧道内旅客列车火灾的主要原因为列车车辆关键部位故障、人为因素、列车车辆缺陷致列车碰撞或脱轨;4)依据土建设施规模及隧道结构分布特点,长大铁路隧道(群)运营期防灾模式可选择定点停车疏散救援模式、全长或局部范围内随机停车疏散救援模式;5)铁路隧道防灾涉及基础设施、铁道车辆和运输调度,应建立铁路隧道运营期灾害防范体系及预警系统,防止事故发生。     

Train–track–bridge dynamic interaction: a state-of-the-art review

ABSTRACT

Train–track–bridge dynamic interaction is a fundamental concern in the field of railway engineering, which plays an extremely important role in the optimal design of railway bridges, especially in high-speed railways and heavy-haul railways. This paper systematically presents a state-of-the-art review of train–track–bridge dynamic interaction. The evolution process of train–bridge dynamic interaction model is described briefly, from the simplest moving constant force model to the sophisticated train–track–bridge dynamic interaction model (TTBDIM). The modelling methodology of the key elements in the TTBDIM is systematically reviewed, including the train, the track, the bridge, the wheel–rail contact, the track–bridge interaction, the system excitation and the solution algorithm. The significance of detailed track modelling in the whole system is highlighted. The experimental research and filed test focusing on modelling validation, safety assessment and long-term performance investigation of the train–track–bridge system are briefly presented. The practical applications of train–track–bridge dynamic interaction theory are comprehensively discussed in terms of the system dynamic performance evaluation, the system safety assessment and train-induced environmental vibration and noise prediction. The guidance is provided on further improvement of the train–track–bridge dynamic interaction model and the challenging research topics in the future.     

减振型双块式无砟轨道合理刚度匹配研究

为研究城际铁路减振型双块式无砟轨道的合理刚度匹配,基于轮轨系统耦合动力学理论,结合我国城际铁路的运营特点,建立了城际铁路车辆-减振型双块式无砟轨道耦合动力分析模型,分析了列车在时速200 km和160 km时的轮轨动力响应。结果表明:对列车最高运行速度为200 km/h的城际客运专线,建议钢轨允许垂向位移控制在2 mm以内,减振垫的垂向位移应控制在1 mm左右;支点反力、钢轨位移受扣件刚度的影响显著,减振垫刚度是决定底座板加速度及道床板位移的决定性因素。城际铁路“在大站停”列车时速200 km、“站站停”列车最高时速160 km时,扣件合理刚度可取为42~49 kN/mm,减振垫的合理刚度可取为0.036~0.044 N/mm3。     

恶劣环境下铁路行车安全研究综述

强风沙、地震、泥石流等恶劣环境严重威胁列车的安全运行，研究和防治铁路自然灾害、确保列车安全运行、保障运输安全畅通已成为铁路科研的重大任务。为了避免恶劣环境导致列车脱轨和倾覆事故发生，针对恶劣环境下铁路行车安全性问题，综述了不同环境下列车脱轨机理和动力学特性、环境测量系统、调度系统、预警系统、控制系统、试验验证、防灾措施等关键环节的研究进展。总结了铁路恶劣环境的分类及特点，分析了不同恶劣环境对列车安全运行关键环节的影响，归纳了不同恶劣环境、路况和车型条件下车辆动力学特性及安全性能指标。梳理了复杂恶劣环境下的铁路行车安全控制方法和措施（如实施限速或紧急停车、道岔及受电弓除冰雪装置、挡风墙或风屏障、铁路监测预警与行车指挥系统等），及在实施相应控制方法和措施的过程中所采取的研究方法（如理论分析、数值计算、风洞试验、在线实车试验等）。展望了恶劣环境下铁路列车安全运行研究的重点和发展趋势。      

Experimental and numerical investigation on the derailment of a railway wheelset with solid axle

This paper presents the results of an experimental and numerical investigation on the derailment of a railway wheelset with solid axle. Tests were carried out under quasi-steady-state conditions, on a full-scale roller rig, and allowed to point out the effect of different parameters like the wheelset's angle of attack and the ratio between the vertical loads acting on the flanging and non-flanging wheels. On the basis of the test results, some existing derailment criteria are analysed in this paper and two new criteria are proposed. A model of wheel–rail contact is proposed for the mathematical modelling of the flange climb process, and numerical vs. experimental comparisons are used to obtain model validation.