A study on mechanical mechanism of train derailment and preventive measures for derailment

The research status of train derailment is summarized. Major problems existing in current derailment research are pointed out. By applying system dynamics stability concepts, the mechanical mechanism of train derailment is described. The theory of random energy analysis for train derailment is then further expounded and preventive measures for train derailment and a calculation method for an anti-derailment safety coefficient (of train - track time variant system) are introduced. Finally, some train derailment cases are analysed. Six train - track time variant system vibration cases are calculated, four of which derailed and two that did not. The conclusion compares the results of the theoretical analysis with that which actually occurred.     

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.     

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.     

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.     

Influence of long-wavelength track irregularities on the motion of a high-speed train

Vertical track irregularities over viaducts in high-speed rail systems could be possibly caused by concrete creep if pre-stressed concrete bridges are used. For bridge spans that are almost uniformly distributed, track irregularity exhibits a near-regular wave profile that excites car bodies as a high-speed train moves over the bridge system. A long-wavelength irregularity induces low-frequency excitation that may be close to the natural frequencies of the train suspension system, thereby causing significant vibration of the car body. This paper investigates the relationship between the levels of car vibration, bridge vibration, track irregularity, and the train speed. First, this study investigates the vibration levels of a high-speed train and bridge system using 3D finite-element (FE) transient dynamic analysis, before and after adjustment of vertical track irregularities by means of installing shimming plates under rail pads. The analysis models are validated by in situ measurements and on-board measurement. Parametric studies of car body vibration and bridge vibration under three different levels of track irregularity at five train speeds and over two bridge span lengths are conducted using the FE model. Finally, a discontinuous shimming pattern is proposed to avoid vehicle suspension resonance.     

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.     

Enhancing rail infra durability through freight bogie design

The extensive usage of railway infrastructure demands a high level of robustness, which can be achieved partly by considering (and managing) the track and rolling stock as one integral system with due attention to their interface. A growing number of infra managers consider, in this framework, the track-friendliness of vehicles that have access to their tracks as a key control parameter. The aim of this study is to provide further insight into potential contributions to track-friendliness, assessed in relation to track deterioration mechanisms and cost, understanding how potential benefits are best to be utilised. Six proposed freight bogie design measures are evaluated with respect to the improvement in curving behaviour, switch negotiation and related track degradation mechanisms. To this purpose a sensitivity analysis has been carried out by means of track–train simulations in the VAMPIRE® multi body simulation software. Additionally, the impact on track deterioration costs has been calculated for those track-friendly design modifications identified as most promising. Conclusions show that the standard Y25L freight bogie design displays rather a track-friendly behaviour. Tuning the primary yaw stiffness shows a high potential to further improve track-friendliness, significantly reducing track deterioration cost at narrow radius curves and switches (by, respectively, 30% and 60%). When calculating the overall deterioration cost for the travelled route, the calculation model should include a well-balanced representation of switches and narrow radius curves.     

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。     

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.     

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.     

Sloshing effects and running safety in railway freight vehicles

This paper deals with the study of running dynamic effects for a partially filled railway tank vehicle. A computational fluid dynamics model in 2D is established and used to define the motion of the sloshing fluid and the forces generated on the tank, for curving conditions typical of railway freight transport. From these results, an equivalent mechanical model is identified which is able to correctly reproduce the forces generated on the tank. Finally, a mathematical model is defined for the entire freight car, including the bogies with primary suspensions, the tank and a discrete number of equivalent models positioned at different places along the longitudinal axis of the tank. This model is used to simulate the dynamics of the tank for a variety of curve geometries, train speeds and fill levels. By these simulations, derailment and rollover risks are evaluated and the most critical conditions for running safety are defined. Results show that sloshing can increase significantly the risk of tank rollover whereas its influence on the risk of derailment is minor.     

High-frequency random vibration analysis of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads using a hybrid SEM–SM method

A hybrid Spectral Element Method (SEM)–Symplectic Method(SM) method for high-efficiency computation of the high-frequency random vibrations of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads is presented. First, the Williams-Landel-Ferry (WLF) formula and Fractional Derivative Zener (FDZ) model were, respectively, applied for prediction and representation of the frequency-dependent dynamic properties of Vossloh 300 rail pads frequently used in China's high-speed railway. Then, the proposed hybrid SEM–SM method was used to investigate the influence of the frequency-dependent dynamic performance of Vossloh 300 rail pads on the high-frequency random vibrations of high-speed vehicle–track systems at various train speeds or different levels of rail surface roughness. The experimental results indicate that the storage stiffness and loss factors of Vossloh 300 rail pad increase with the decrease in dynamic loads or the increase in preloads within 0.1–10,000?Hz at 20°C, and basically linearly increase with frequency in a logarithmic coordinate system. The results computed by the hybrid SEM–SM method demonstrate that the frequency-dependent viscous damping of Vossloh 300 rail pads, compared with its constant viscous damping and frequency-dependent stiffness, has a much more conspicuous influence on the medium-frequency (i.e. 20–63?Hz) random vibrations of car bodies and rail fasteners, and on the mid- (i.e. 20–63?Hz) and high-frequency (i.e. 630–1250?Hz) random vibrations of bogies, wheels and rails, especially with the increase in train speeds or the deterioration of rail surface roughness. The two sensitive frequency bands can also be validated by frequency response function (FRF) analysis of the proposed infinite rail–fastener model. The mid and high frequencies influenced by the frequency-dependent viscous damping of rail pads are exactly the dominant frequencies of ground vibration acceleration and wheel rolling noise caused by high-speed railways, respectively. Even though the existing time-domain (or frequency-domain) finite track models associated with the time-domain (or frequency-domain) fractional derivative viscoelastic (FDV) models of rail pads can also be used to reach the same conclusions, the hybrid SEM–SM method in which only one element is required to compute the high-order vibration modes of infinite rail is more appropriate for high-efficiency analysis of the high-frequency random vibrations of high-speed vehicle–track systems.     

A model for vehicle–track random interactions on effects of crosswinds and track irregularities

A stochastic mathematical model is developed to evaluate the dynamic behaviours and statistical responses of vehicle–track systems when random system excitations including crosswinds and track irregularities are imposed. In this model, the railway vehicle is regarded as a multi-rigid-body system, the track system is modelled by finite element theory. These two systems are spatially coupled by the nonlinear wheel–rail contact forces and unsteady aerodynamic forces. The high efficiency and accuracy of this stochastic model are validated by comparing to the robust Monte-Carlo method. Numerical studies show that crosswinds have a great influence on the dynamic performance of vehicle–track systems, especially on transverse vibrations. When the railway vehicle initially runs into the wind field, it will experience a severe vibration stage, and then stepping into a relatively steady state where the fluctuating winds and track irregularities will play deterministic roles in the deviations of system responses. Moreover, it is found that track irregularities should be properly considered in the safety assessment of the vehicle even in strong crosswinds.     

Integration of car-body flexibility into train–track coupling system dynamics analysis

The resonance vibration of flexible car-bodies greatly affects the dynamics performances of high-speed trains. In this paper, we report a three-dimensional train–track model to capture the flexible vibration features of high-speed train carriages based on the flexible multi-body dynamics approach. The flexible car-body is modelled using both the finite element method (FEM) and the multi-body dynamics (MBD) approach, in which the rigid motions are obtained by using the MBD theory and the structure deformation is calculated by the FEM and the modal superposition method. The proposed model is applied to investigate the influence of the flexible vibration of car-bodies on the dynamics performances of train–track systems. The dynamics performances of a high-speed train running on a slab track, including the car-body vibration behaviour, the ride comfort, and the running safety, calculated by the numerical models with rigid and flexible car-bodies are compared in detail. The results show that the car-body flexibility not only significantly affects the vibration behaviour and ride comfort of rail carriages, but also can has an important influence on the running safety of trains. The rigid car-body model underestimates the vibration level and ride comfort of rail vehicles, and ignoring carriage torsional flexibility in the curving safety evaluation of trains is conservative.     

Lateral Vibration of Railway Bridge-Vehicle System Caused by Track Irregularities

SUMMARY

The lateral vibration of the bridge-vehicle system caused by track irregularities is investigated in this paper by means of frequency spectral analysis method. A railway cable-stayed bridge is taken as the model to study, on which a theoretical analysis is made to compare with the practical results measured. The method proves to be feasible. Then it is applied to studying the interaction between a long-span railway cable-stayed bridge and a freight car as well as the effect of track irregularities on the dynamic characteristics of the bridge-vehicle system, thus leading to a couple of conclusions of considerable significance.     

Stochastic analysis of dynamic interaction between train and railway turnout

The performance of a railway turnout (switch and crossing) is influenced by a large number of input parameters of the complex train–turnout system. To reach a robust design that performs well for different traffic situations, random distributions (scatter) of these inputs need to be accounted for in the design process. Stochastic analysis methods are integrated with a simulation model of the dynamic interaction between train and turnout. For a given nominal layout of the turnout, using design of experiments methodology and a two-level fractional factorial screening design, four parameters (axle load, wheel–rail friction coefficient, and wheel and rail profiles) are identified to be the most significant. These parameters are further investigated using a three-level full factorial design and stochastic analysis. The random distributions of transverse wheel profile and set of transverse rail profiles along the switch panel are accounted for by the Karhunen–Loève expansion technique. The influence of the random distributions of the input parameters on the statistical outputs of wheel–rail contact forces, wear and rolling contact fatigue is assessed using Latin hypercube sampling to generate a number of stochastic load realizations.     

Coupling Model of Vertical and Lateral Vehicle/Track Interactions

A new dynamic model of vehicle/track interaction is presented. The model considers the vehicle and the track as a whole system and couples the vertical interaction with the lateral interaction. The vehicle subsystem is modeled as a multi-body system with 37 degrees of freedom, which runs on the track with a constant velocity. The track substructure is modeled as a discretely supported system of elastic beams representing the rails, sleepers and ballasts. The normal contact forces between wheels and rails are described by Hertzian nonlinear elastic contact theory and the tangential wheel/ rail forces are decided by the creep theory. Numerical results are compared with those of conventional dynamic models of railway vehicles. Applications of the coupling model to the investigation of safety limits against derailment due to the track twist and the combined alignment and cross-level irregularities are reported at the end of the paper.     

Lateral Vibration of Railway Bridge-Vehicle System Caused by Track Irregularities

The lateral vibration of the bridge-vehicle system caused by track irregularities is investigated in this paper by means of frequency spectral analysis method. A railway cable-stayed bridge is taken as the model to study, on which a theoretical analysis is made to compare with the practical results measured. The method proves to be feasible. Then it is applied to studying the interaction between a long-span railway cable-stayed bridge and a freight car as well as the effect of track irregularities on the dynamic characteristics of the bridge-vehicle system, thus leading to a couple of conclusions of considerable significance.     

Lateral Vibration of Railway Bridge-Vehicle System Caused by Track Irregularities

The lateral vibration of the bridge-vehicle system caused by track irregularities is investigated in this paper by means of frequency spectral analysis method. A railway cable-stayed bridge is taken as the model to study, on which a theoretical analysis is made to compare with the practical results measured. The method proves to be feasible. Then it is applied to studying the interaction between a long-span railway cable-stayed bridge and a freight car as well as the effect of track irregularities on the dynamic characteristics of the bridge-vehicle system, thus leading to a couple of conclusions of considerable significance.     

Dynamic simulations of the freight three-piece bogie motion in curve

A loaded freight vehicle with two three-piece bogies is modelled using the accessible mathematical software MATLAB. The results are compared with its corresponding ADAMS/Rail dynamic multibody simulation model, where similar derailment factors are encountered for the freight vehicle. Both models reveal that the possibility of derailment increases immediately after entering and at the end of the curve – signifying the beginning and the end of the curve as two major points for derailment. Although a three-piece bogie construction is rather simple, its mathematical model proves to be very complex and is nonlinear due to the reported frictional contact at the rail/wheel interface as well as the friction wedges. This research is stimulated by bogie derailments that have occurred in the Iranian railways as well as those in the rest of the world.