Running Safety Of High-speed Train Research Articles

Visual measurement of lateral relative displacement of wheel-rail of high-speed train under earthquake

When an earthquake causes the wheel-rail detachment of a high-speed train, the derailment evaluation criteria based on wheel-rail force faces failure. At this time, the lateral relative displacement of the wheel-rail (LRDWR) is more intuitive and continuous to assess the running safety of a high-speed train. In the past, many experimental studies have been conducted on measuring the LRDWR of trains. However, there is still a lack of effective measurement methods to solve the problem of LRDWR measurement in complex texture and high-speed dynamic scenes. Therefore, a lateral relative wheel-rail displacement measurement method based on machine vision and the improved Hourglass network (LRWRDVH) is proposed in this paper to determine the LRDWR by predicting the pixel coordinates of a few wheel-rail keypoints. The scaled-down bridge running test of the high-speed train is designed for validation, and then the LRDWR measurement of high-speed train under earthquake is carried out using the LRWRDVH method to evaluate the running safety of high-speed train. The test results show that the LRWRDVH method is effective and accurate and can be further used to study the running safety of high-speed trains under earthquakes.

Exceeding probability analysis for rail of high-speed railway under seismic excitations

PurposeThe smoothness of the high-speed railway (HSR) on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges, which may threaten the safety of running trains. Indeed, few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard. The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approachIn order to investigate the exceeding probability of the rail displacement under different seismic excitations, the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis (IDA) is proposed, and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined. Then a finite element model (FEM) of an assumed HSR track-bridge system is constructed, which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track. Under different seismic excitations, the seismic displacement response of the rail is calculated; the character of the rail displacement is analyzed; and the exceeding probability of the rail vertical displacement exceeding the allowable standard (2mm) is investigated.FindingsThe results show that: (1) The bridge-abutment joint position may form a step-like under seismic excitation, threatening the running safety of high-speed trains under seismic excitations, and the rail displacements at mid-span positions are bigger than that at other positions on the bridge. (2) The exceeding probability of rail displacement is up to about 44% when PGA = 0.01g, which is the level-five risk probability and can be described as 'very likely to happen'. (3) The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge, and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/valueThe work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.

An active suspension system for enhancing running safety of high-speed trains under strong crosswind

The running safety of trains subjected to strong crosswinds has become a major concern for the high-speed railways passing through complicated mountain areas. This paper reports an active secondary suspension system to improve the operation stability and running safety of high-speed trains under strong crosswind. The goal of the active suspension system is to regulate the lateral, yaw, and roll motion attitudes of high-speed train carbody, in which a controller is designed by combining with a disturbance observer and the sliding mode control method. To further verify the proposed active suspension strategy, a crosswind-vehicle-track coupled dynamics model is established, where the unsteady aerodynamic loads and random track irregularity excitations are considered. The results show that the proposed active suspension system has the efficient potential to regulate the carbody motion attitudes and enhance the anti-rolling performance of high-speed trains. In comparison to a quasi-static control strategy of active suspension, the use of the proposed active suspension system has led to a significant reduction in both wheel-load reduction ratios and derailment risks of high-speed trains.

Damage control analysis of components in high-speed railway bridge-track system based on combined seismic isolation design under earthquake

In order to ensure the running safety of high-speed trains, it is necessary to control the post-earthquake damage of the components in high-speed railway bridge-track system (HSRBTS). In this paper, the damage control indexes of each component in HSRBTS are determined, and the overall seismic performance objectives of HSRBTS are quantified based on the component damage control requirements. Based on the finite element analysis, the damage control of the components in HSRBTS is analyzed under the combined design of friction pendulum bearing and metal damping tenon. The analysis results show that the damage of track interlayer components can be controlled by the combined seismic isolation design, and the sensitivity of the damage response of components to ground motion characteristics can be reduced. The maximum damage overrun length (LDmax) proposed and adopted in this paper is used as the damage control index of track interlayer continuous components, which can quantify the damage degree of interlayer continuous components and realize the fine damage control of interlayer continuous components. By optimizing the parameters of the combined seismic isolation design, the damage control of CA mortar layer, fasteners and sliding layer can meet the quantified seismic performance objective proposed in this paper. The friction pendulum bearing and the metal damping tenon can play the seismic isolation performance together, which can avoid the concentrated damage of pier and bearing and realize the distribution and dissipation of seismic energy.

The coupled vibration of train and bridge as high-speed trains meet in crosswind

PurposeThis paper aims to study the influence of aerodynamics force of trains passing each other on the dynamic response of vehicle bridge coupling system based on numerical simulation and multi-body dynamics and put forward the speed threshold for safe running of train under different crosswind speeds.Design/methodology/approachThe computational fluid dynamics method is adopted to simulate the aerodynamic force in the whole process of train passing each other by using dynamic grid technology. The dynamic model of vehicle-bridge coupling system is established considering the effects of aerodynamic force of train passing each other under crosswind, the dynamic response of train intersection on the bridge under crosswind is computed and the running safety of the train is evaluated.FindingsThe aerodynamic force of trains' intersection has little effects on the derailment factor, lateral wheel-rail force and vertical acceleration of train, but it increases the offload factor of train and significantly increases the lateral acceleration of train. The crosswind has a significant effect on increasing the derailment factor, lateral wheel-rail force and offload factor of train. The offload factor of train is the key factor to control the threshold of train speed. The impact of the aerodynamic force of trains' intersection on running safety cannot be ignored. When the extreme values of crosswind wind speed are 15 m·s−1, 20 m·s−1 and 25 m·s−1, respectively, the corresponding speed thresholds for safe running of train are 350 km·h−1, 275 km·h−1 and 200 km·h−1, respectively.Originality/valueThe research can provide a more precise numerical method to study the running safety of high-speed trains under the aerodynamic effect of trains passing each other on bridge in crosswind.

Effects of Curved Wind Barrier on the Aerodynamic Characteristics of a Train–Bridge System and Its Static Wind Load

Wind barriers are important measures that guarantee the running safety of high-speed trains under crosswind conditions, however, they can change the aerodynamic coefficients of a train–bridge system and the distribution of the flow field around a train and bridge, and studies have often ignored the static wind load characteristics of wind barriers. In this paper, the effects of height and porosity on the curved and vertical fence-type wind barriers on the aerodynamic characteristics of a train–bridge system are investigated by using numerical simulation and wind tunnel test methods. The static wind loads of the two types of wind barriers are analyzed by comparing the drag coefficients and the surface wind pressure distributions. The results show that, compared with the vertical wind barrier, the curved wind barrier can reduce the drag force and moment of a train while reducing the impact of the aerodynamic forces on a bridge. The static wind load of the curved wind barrier is less than that of the vertical wind barrier, when a train is on the windward side of a bridge, the drag coefficient of the curved wind barrier is only about 35% of that of the vertical wind barrier.

An Adaptive Demodulation Band Segmentation Method to Optimize Spectral Boundary and Its Application for Wheelset-Bearing Fault Detection

Wheelset-bearing working states directly affect the stability of bogies, and existing defects may threaten the running safety of high-speed trains. Thus, the fault detection of wheelset-bearing is of great importance. In this paper, a novel wheelset-bearing fault detection method, named adaptive autocorrelated kurtogram (AAK), is proposed based on the developed autocorrelated kurtosis and the presented spectral segmentation method. Autocorrelated kurtosis is designed to reduce the unrelated components interference and increase the signal-to-noise ratio (SNR). The spectral segmentation method is proposed to obtain the fault zone as completely as possible. Based on the feature that rotation frequency is related to bearing fault frequency, the rotation frequency-based window size selection and extension strategy is proposed. With different frequency levels, the AAK is formed. The proposed method is validated by simulated and experimental data. The results show that this method can automatically and adaptively search for a reasonable demodulation bandwidth according to the fault information feature and resonance region position. The method can estimate the center frequency and bandwidth and avoid unrelated component interference. The AAK can provide accurate detection results and possesses excellent performance. Thus, it is suitable for wheelset-bearing fault detection.

Seismic optimization of high-speed railway bridges considering the running safety of trains in normal service

This article proposes a seismic optimization strategy to reduce the cost of piers of simply-supported bridges for high-speed railway (HSR) in China. The dimension and reinforcement ratio of piers are defined as variables. The running safety of high-speed trains during normal operation is considered by novelly setting the vibration amplitude of running trains to satisfy the corresponding constraint condition. Other constraint conditions include the structural fundamental frequency, buckling stability, and longitudinal stiffness, as well as the stress and crack width of piers during earthquakes. An improved genetic algorithm with a double-filter strategy is proposed to increase the efficiency of the optimization calculation. Six HSR simply-supported bridges with different pier heights are selected as examples to verify the effectiveness and applicability of the proposed optimization method. The result shows that for the example bridges, the cost of the optimised piers that are not higher than 30 m can be reduced by 33.38% to 50.65%. The optimised piers can ensure the integrity of the HSR bridges subjected to the considered earthquakes and can provide sufficient stiffness to ensure the running safety and stationarity of high-speed trains.

Effects of shear keys and track system on the behavior of simply-supported bridges for high-speed trains subjected to transverse earthquake excitations

China railway track system II (CRTS-II) slab ballastless track is usually constructed on high-speed railway (HSR) bridges to ensure the rail smoothness and the running safety of high-speed trains, but the use of the longitudinal continuous track system would significantly alter the dynamic characteristics of the bridges and therefore influence the bridge seismic responses. The pounding at shear keys has also been identified as one of the critical factors affecting the seismic behavior of bridges. To investigate the effects of shear keys and CRTS-II track system on the seismic behavior of HSR simply-supported bridges subjected to transverse earthquake excitations, detailed 3D finite element models are developed by using ABAQUS. The seismic responses calculated from the bridges with and without considering shear keys are firstly compared. The result shows that the shear keys can effectively limit the development of pier-girder relative displacement and thus decrease the potential of girder dislocation. However, large pounding forces would be generated between the shear keys and bearing pads and transferred to bridge piers, which will amplify the seismic responses of the bridge piers. The result of seismic analyses of multiple-span simply-supported bridges with and without considering the track system shows that the track system will significantly influence the distribution of seismic forces among the bridge spans. For a bridge with equal pier heights, considering the track system will reduce the seismic responses of side spans (close to subgrade) but will increase those of the middle spans. Whereas an opposite trend is found for bridges with high middle piers and short side piers.

Aerodynamic response of high-speed trains under crosswind in a bridge-tunnel section with or without a wind barrier

High-speed trains experience a sharp transition to a strong crosswind environment when running in a bridge–tunnel section due to the perennial prevailing crosswind in the canyon, and this sudden transition seriously affects train safety. In this study, a 3D computational fluid dynamics numerical model of the train–tunnel–bridge–wind barrier is established based on the delayed detached eddy simulation turbulence model and porous media theory. A dynamic analysis model of wind–train–bridge coupling is adopted. The effects of wind barrier with a height of 3 ​m and porosity of 30% on the aerodynamic coefficient, flow field structure and running safety of high-speed trains under crosswind in the bridge–tunnel section are studied. Results indicate that the sharp change effect of the aerodynamic coefficient is significantly weakened by more than 50% by the wind barrier. The aerodynamic fluctuation amplitudes in the bridge–tunnel section are 1.25–5.5 times higher than those in the bridge section. The difference in pressure distribution in the longitudinal direction is significantly reduced because of the obstruction and diversion of the wind barrier and the space limitation on the windward side. Accordingly, the change in amplitude of the aerodynamic coefficients in the bridge–tunnel section is reduced, and so is the safety of train operation. The bridge–tunnel section is the weak link of safety control. Using a wind barrier with the same parameters for the bridge and bridge–tunnel sections is unreasonable, that is, the parameters should be separately designed.

Running safety of high-speed train on deformed railway bridges with interlayer connection failure

In a railway bridge, the CRTS II slab ballastless track is subjected to interlayer connection failures, such as void under slab, mortar debonding, and fastener fracture. This study investigates the influences of interlayer connection failure on the safe operation of high-speed trains. First, a train-track-bridge coupled vibration model and a bridge-track deformation model are established to study the running safety of a train passing a deformed bridge with interlayer connection failure. For each type of the interlayer connection failure, the effects of the failure locations and ranges on the track irregularity are studied using the deformation model. Under additional bridge deformation, the effects of interlayer connection failure on the dynamic responses of the train are investigated by using the track irregularity as the excitation to the vibration model. Finally, parametric studies are conducted to determine the thresholds of additional bridge deformations considering interlayer connection failure. Results show that the interlayer connection failure significantly affects the running safety of high-speed train and must be considered in determining the safety thresholds of additional bridge deformation in the asset management of high-speed railway bridges.

DYNAMIC ANALYSIS OF A COUPLED HIGH-SPEED TRAIN AND BRIDGE SYSTEM SUBJECTED TO SEA WAVE HYDRODYNAMIC LOAD

In this study, the dynamic behavior of the 3D train-bridge system subjected to different hydrodynamic loads (TBW model) is established. By taking a continuous bridge with box girders as a case study, the dynamic responses of the bridge which is under train passing and subjected to several sea hydrodynamic loads are analyzed. Hydrodynamic forces are applied on piers according to Morison’s theory and car body is modeled by a 27-DoFs dynamic system. Model validation has been performed with other research by considering vessel collision load. In continuation, the dynamic responses of the bridge and the running safety indices of the train on the bridge under several conditions are analyzed. Consequently an assessment procedure is proposed for the running safety of high-speed trains on bridges subjected to wave loads. Results of TBW’s sensitive analyzes have shown the importance of sea-states conditions for train safe and comfortable running. These outputs indicates that in stormy conditions, the speed of the train crossing the bridges should be reduced and it is possible for the train to pass at low speeds in stormy conditions.

Dynamic reliability evaluation of vehicle–track coupled systems considering the randomness of suspension and wheel–rail parameters

The ride quality and running safety of high-speed trains are directly influenced by uncertainties of some key parameters, such as the damping and stiffness coefficients of suspension systems, wheel–rail coefficient of friction and wheel–rail profiles. Dynamic reliability problems of vehicle–track coupled systems under the influence of the above random parameters are studied in this article. An efficient numerical method is presented by combining a prediction-based iterative solution technique with subset simulation method. The solution efficiency of deterministic responses is improved by means of efficient prediction of wheel–rail forces, and the number of deterministic solutions required is reduced by expressing a small failure probability as a product of large conditional probabilities. The accuracy and the efficiency of the present method are verified by comparing with the direct Monte Carlo simulation. The failure probability distribution curves of the lateral ride index on straight track and the derailment coefficient during curve negotiation are obtained and the reliability sensitivity analyses are also carried out. The main conclusions are given as follows: the reliability of the system is higher when the randomness of the parameters with greater sensitivity is not considered; the increase of the damping of anti-yaw damper or the wheel–rail coefficient of friction will improve the ride quality on straight track, but will lower the running safety when negotiating a curved track.

Running safety of high-speed train on rigid frame bridge subjected to earthquakes

To research the running safety when high-speed train running over a high-pier rigid frame bridge subjected to earthquakes, a coupling vibration model is set up based on the traintrack-bridge dynamic interaction theory. In this model, the seismic action is solved by the relative motion method and the ballast track is simulated by the elastic point support model with three layers. As an example, a high-pier rigid frame bridge with spans of (88+168+88) m is modelled, and the dynamic responses of vehicle and bridge system under El Centro seismic wave are calculated. The analysis results show that the dynamic responses of the high-pier rigid frame bridge present weakly coupled in plane and out plane, moreover the running safety of the train is decreased along with the increase of seismic amplitude and train speed. In addition, the most threat direction to the running safety of the train on bridge is transverse, and the running safety threshold of ICE3 subjected to 7 degree, 8 degree and 9 degree frequent seismic is 275, 250 and 225 km/h.

Dynamic analysis of high-speed railway train-bridge system after barge collision

In this paper, a framework is proposed for dynamic analysis of train-bridge systems with a damaged pier after barge collision. In simulating the barge-pier collision, the concrete pier is considered to be nonlinear-inelastic, and the barge-bow is modeled as elastic-plastic. The changes of dynamic properties and deformation of the damaged pier, and the additional unevenness of the track induced by the change of deck profile, are analyzed. The dynamic analysis model for train-bridge coupling system with a damaged pier is established. Based on the framework, an illustrative case study is carried out with a 5x32 m simply-supported PC box-girder bridge and the ICE3 high-speed train, to investigate the dynamic response of the bridge with a damaged pier after barge collision and its influence on the running safety of high-speed train. The results show that after collision by the barge, the vibration properties of the pier and the deck profile of bridge are changed, forming an additional unevenness of the track, by which the dynamic responses of the bridge and the car-body accelerations of the train are increased, and the running safety of high-speed train is affected.

Two-dimensional analysis of the influence of windbreaks on airflow over a high-speed train under crosswind using lattice Boltzmann method

This research is concerned with identifying the effects of windbreak geometry on attenuating aerodynamic loads that can be strong enough to disturb the running safety of high-speed trains. The idea is to suggest the proper geometry for the windbreaks that can make them more efficient and increase their overall performance. Generally speaking, the desired windbreak is the one that can minimize the aerodynamic forces on the surface of trains. In order to reach such an aim, the flow of air around an Intercity-Express 3 high-speed train has been estimated through a two-dimensional modeling by using the lattice Boltzmann method. The flow of crosswind that hits the train is considered as turbulent. The geometry of the windbreaks including the height, the slot, and the edge angles has been investigated. It has been concluded that the windbreak performance, among other parameters, is highly dependent on its height and edge angle. This research expedites the trail for finding suitable choices of windbreak geometries that can in turn provide a reliable degree of running safety of the railway fleet.

A framework for carrying out train safety evaluation and vibration analysis of a trussed-arch bridge subjected to vessel collision

Safety is the prime concern for a high-speed railway bridge, especially when it is subjected to a collision. In this paper, an analysis framework for the dynamic responses of train-bridge systems under collision load is established. A multi-body dynamics model is employed to represent the moving vehicle, the modal decomposition method is adopted to describe the bridge structure, and the time history of a collision load is used as the external load on the train-bridge system. A (180+216+180) m continuous steel trussed-arch bridge is considered as an illustrative case study. With the vessel collision acting on the pier, the displacements and accelerations at the pier-top and the mid-span of the bridge are calculated when a CRH2 high-speed train running through the bridge, and the influence of bridge vibration on the running safety indices of the train, including derailment factors, offload factors and lateral wheel/rail forces, are analyzed. The results demonstrate that under the vessel collision load, the dynamic responses of the bridge are greatly enlarged, threatening the running safety of high-speed train on the bridge, which is affected by both the collision intensity and the train speed.

Probabilistic assessment of the train running safety on a short-span high-speed railway bridge

In this work the running safety of high-speed trains on a short-span bridge is assessed. A probabilistic approach that combines Monte Carlo simulation with the extreme value theory is used and the existence of track irregularities is taken into account along with the variability of parameters related to the bridge, the track and the train. As case study, a 12 m span filler beam bridge was selected as the train–bridge interaction effects are most significant for short spans. The running safety is assessed for the case of loss of contact between the wheel and the rail, taking into consideration only the vertical wheel–rail interaction and assuming that no lateral forces act on the train. This research enables the characterisation of the wheel unloading coefficient, the identification of the critical wheel and also the definition of the maximum allowable speed for trains to run safely on the bridge.

Numerical Study on the Running Safety of High-Speed Train under the Cross Wind

With the increasing speed, the crosswind effect is the more and more obvious. The three dimensional aerodynamic model of the high-speed train was set up to study the aerodynamic characteristics of the train under the cross wind. Based on the vehicle system dynamics, the couple model for dynamics of wind-train-rail systems was set up to study the train safety under the wind load. The derailment coefficient and reduction rate of wheel load were analyzed under the different train speed, different wind velocity. The results of this research can provide a theoretical basis for the high-speed train safety.

Dynamic response of a train–bridge system under collision loads and running safety evaluation of high-speed trains

Based on the authors’ previous work, an extended study of the train–bridge system under collision loads is presented. A continuous bridge with box girders is considered as a case study. The dynamic responses of the bridge and the running safety indices of the train on the bridge under three types of collision loads are analyzed. Large responses of the bridge induced by collision strongly threaten the running safety of trains. An assessment procedure is proposed for the running safety of high-speed trains on bridges subjected to collision loads, and related threshold curves for train speed versus collision intensity are defined.