Influence Of Train Speed Research Articles

Numerical Investigation on Dynamic Performance of a Bridge‐Tunnel Transition Section with a Deep Buried Pile‐Plank Structure

To address the track irregularity at transition zones between subgrade and rigid structures (bridge, tunnel, etc.), some common transition approaches, such as trapezoid subgrade, were adopted in many engineering areas. However, in regard to a mountainous area, the common transition approaches may not be practicable anymore due to the limitation of the length between subgrade and rigid structures. In this paper, a new type of bridge‐tunnel transition section with a deeply buried pile‐plank structure (DBPPS) for short‐distance transition is introduced. A three‐dimensional finite element model that considers vehicle‐track‐subgrade coupling vibration is proposed to study the dynamic performances of a DBPPS transition section in the Shanghai–Kunming high‐speed railway. With this model that has been validated with measured responses from field tests, the dynamic responses and the smoothness in track stiffness along the transition zone are analyzed. In addition, the influences of train speed, axle load, and train direction on dynamic responses are investigated, and the influences of two optimization strategies, including varying‐length piles and constant‐length piles, on the stiffness smoothness of the DBPPS transition section are discussed. Results show that the vibration level of the DBPPS transition section is lower than that of the abutment and the tunnel, and the additional load caused by vertical track stiffness difference aggravates the vibration at the connections between the DBPPS transition section and the abutment (or tunnel). Furthermore, the smoothness in stiffness along the transition zone can be significantly improved by the improvement strategy with varying‐length piles.

Bayesian time–frequency analysis of the vehicle–bridge dynamic interaction effect on simple-supported resonant railway bridges

Abstract Monitoring the conditions or damages of bridges under train passages demands a high-accuracy modal-characteristic identification method that separates the apparent fluctuations caused by vehicle–bridge dynamic interaction (VBI) effects from other fluctuations. This study proposes a novel method based on a time-varying autoregressive model, which is solved using a hierarchical Bayesian estimation approach. The VBI effect is estimated from the displacement response of the railway bridges as temporal fluctuations of the natural frequency and modal damping ratio. The exogenous variable is the train load, expressed as an external force. Numerical experiments verified the higher accuracy of the proposed method than the existing method. The influences of train speed and rail irregularity on the VBI effects are clarified by the application of the proposed method to various VBI simulations. The proposed method was applied to the measured resonance responses of actual bridges and succeeded in empirically demonstrating the decreased natural frequency and the increased modal damping ratio under train passage. Additionally, using the proposed method, modal characteristics variation due to VBI effect calculated using VBI model simulation was verified by comparing with those estimated from the measured results.

Model Test Study on the Influence of Train Speed on the Dynamic Response of an X‐Section Pile‐Net Composite Foundation

Based on a large‐scale X‐section pile‐net composite foundation model, we experimentally studied the dynamic characteristics of the pile‐net composite foundation under a high‐speed railway train load; analyzed the distribution characteristics of the dynamic stress, dynamic displacement, speed, and acceleration of the foundation soil under different train speeds; and investigated the vibration response of the track subgrade foundation system, as well as the distribution characteristics and attenuation pattern of the dynamic stress inside the subgrade foundation under cyclic train loading. The following results are obtained. The peak vertical vibration speed and the peak acceleration attenuate by 90% and 62.5%, respectively, after passing through the embankment. The vibration velocity increases linearly with the train speed; the ratio of the peak dynamic soil stresses at the top of the piles and between the piles is approximately 3.4. The change in train speed does not have a large influence on the peak dynamic displacement or peak dynamic soil stress. The peak spectral vibration acceleration caused by the train loading is located within the range of medium‐to‐low‐frequency vibrations, and the characteristic frequency corresponds to the passing frequency of the bogies and carriages; as the train speed increases, the peak spectral vibration acceleration increases, and the high‐frequency components increase significantly.

Three-dimensional finite element modelling and dynamic response analysis of track-embankment-ground system subjected to high-speed train moving loads

A finite element approach is presented to examine ground vibration characteristics under various moving loads in a homogeneous half-space. Four loading modes including single load, double load, four-load, and twenty-load were simulated in a finite element analysis to observe their influence on ground vibrations. Four load moving speeds of 60, 80, 100, and 120 m/s were adopted to investigate the influence of train speed to the ground vibrations. The results demonstrated that the loading mode in a finite element analysis is reliable for train-induced vibration simulations. Additionally, a three-dimensional finite element model (3D FEM) was developed to investigate the dynamic responses of a track-ballast-embankment-ground system subjected to moving loads induced by high-speed trains. Results showed that vibration attenuations and breaks exist in the simulated wave fronts transiting through different medium materials. These tendencies are a result of the difference in the Rayleigh wave speeds of the medium materials relative to the speed of the moving train. The vibration waves induced by train loading were greatly influenced by the weakening effect of sloping surfaces on the ballast and embankment. Moreover, these tendencies were significant when the vibration waves are at medium and high frequency levels. The vibration waves reflected by the sloping surface were trapped and dissipated within the track-ballast-embankment-ground system. Thus, the vibration amplitude outside the embankment was significantly reduced.

A computational simulation study on the dynamic response of high-speed wheel–rail system in rolling contact

The dynamic wheel–rail responses during the rolling contact process for high-speed trains were investigated using the explicit finite element code LS-DYNA 971. The influence of train speed on the wheel–rail contact forces (including the vertical, longitudinal, and lateral forces), von Mises equivalent stress, equivalent plastic strain, vertical acceleration of the axle, and the lateral displacement of the initial contact point on the tread, were examined and discussed. Simulation results show that the lateral and longitudinal wheel–rail contact forces are very smaller than the corresponding vertical contact forces, and they seem to be insensitive to train speed. The peak value of dynamic vertical wheel–rail contact force is approximately 2.66 times larger than the average quasi-static value. The elliptical wheel–rail contact patches have multiple stress extreme points due to the plastic deformation of the wheel tread and top surface of the rail. The vertical acceleration value of the axle in the steady condition is around ±5 m/s2 for the perfected wheel–rail system with the running speed below 300 km/h.

Field study on high-speed train induced fluctuating pressure on a bridge noise barrier

The pressure variations induced by a CRH380A EMU on a 2.15 m high bridge noise barrier are investigated in a field measurement. The familiar fluctuating pressure time history curves and the peak-to-peak pressure (ΔP) distributions attributing to the train head on the barrier surfaces are presented. A comparison of the positive head pulse pressure is made between the measurement results and the data calculated by empirical equations in EN 14067-4. Furthermore, the influences of train speed, train running lines, locations of measurement points, train marshalling length and environmental wind speed on ΔP are analysed. The results indicate as the train speed increases, the corresponding time intervals of ΔP decrease gradually, whereas their slopes become increasingly steep. For a CRH380A EMU, the aerodynamic length of the train head is between 7.63 and 7.64 m, which differs from the physical length of a realistic train with 12.00 m. Along the noise barrier from bottom to top, the ΔP values on the inner surface decrease with the increase of height, while these values on the outer surface increase. Taking the wind direction into account, the ΔP values are a little higher when the high-speed trains run against the wind direction.

Influence of train speed and blockage ratio on the smoke characteristics in a subway tunnel

This paper focuses on the smoke characteristics in a subway tunnel when a subway train travels between two consecutive stations at different speeds and at different tunnel blockage ratios. The piston effect caused by the train movement significantly influences the airflow in the tunnel and at the stations. To simulate the blockage effect of a vehicle and to accurately describe the smoke flow characteristics, a 3-D full-scale computational model of a subway train, two stations and a tunnel was established. To study the influence of the blockage ratio on smoke flow in the tunnel, five different cross-sectional areas were modeled. The dynamic mesh technique was used to simulate train movement in the tunnel. The results show that the maximum temperature occurs at the same position for different blockage ratios when the train runs at the same speed. The maximum temperatures in cases 2–5 decrease by 21–55% relative to the maximum temperature in case 1 at 30 s and by 11–37% relative to the maximum temperature in case 1 at 270 s. For different train speeds, the maximum temperature occurs at different positions, and the maximum temperature of all the cases is 6 to 10 times higher than that of case 6 at 30 s. The influence of train speed on the smoke movement distance is much smaller than the influence of the blockage ratio.

Numerical simulation of floor vibrations of a metro depot under moving subway trains

With the development of subway lines in urban areas, building structures are sometimes subjected to train-induced vibrations, and there is a need to develop prediction models to evaluate the vibration serviceability. In this paper, a new type of subway-depot system is investigated, where subway trains run through the top story of a 3-story metro depot, while the first two stories were developed for offices and shops to avoid the waste of large city areas. Considering the increasing use of such a structural system and the possible serviceability problems, the floor vibrations of a metro depot under moving subway trains were numerically simulated, where the train-track system was treated as the vibration source and studied separately, and the influence of train speed and fastener configuration on the vibration response was discussed. The metro depot was modeled taking the stiffness of the partition walls into account, and vibration responses of the building at different locations were compared and validated through field tests. Besides, vibration level of the second floor was evaluated using an acceleration index that considers frequency weighting. Finally, parameter analysis was carried out so as to provide some references to the vibration control.

The effect of heavy haul train speed on insulated rail joint bar strains

This paper investigates the effectiveness of train speed restrictions on the performance of Insulated Rail Joint (IRJ) joint bars, for typical train speeds utilised on heavy haul rail networks (20–90 km/hr). The work presented in this paper was prompted by a series of premature IRJ failures on Iron Ore heavy haul lines, in the Pilbara region of Western Australia, via cracking of the IRJ joint bars. This failure mode is characterised by partial, or complete failure of one or both of the IRJs connecting joint bars through fatigue crack initiation and propagation through the joint bar steel section. Train speed restriction is an approach commonly implemented by railway operators, as a risk mitigating control when travelling past failure prone IRJ locations. Field testing of in-service IRJs has been conducted. Strain gauge, sleeper displacement and wheel load measurements were obtained and analysed, via regression analysis, to investigate the influence of train speed on joint bar strains. This analysis clearly indicates that there is not a strong relationship between train speed, and joint bar strains, over the observed speed range of 20–90 km/hr. This result suggests that speed restrictions provide little or no benefit in reducing IRJ joint bar strains. While this result is consistent with theory presented in the literature, it is in contrast with typical operator practices. The data presented in this paper also indicate that there is a significant variability in both the strains developed in IRJ joint bars, and vertical sleeper displacements, between the installation locations monitored. For the two sites, the variability in peak bending strains was of the order of 40–45%. The analysis presented in this paper indicates that this variability is not related to differences in train speed.

Further study on the wheel–rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

ABSTRACTA comprehensive dynamic finite-element simulation method was proposed to study the wheel–rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel–rail materials and thermal stress due to the wheel–rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel–rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel–rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.

Random dynamic analysis of a train-bridge coupled system involving random system parameters based on probability density evolution method

The development of high-speed railway has made it important to clarify the influence of random system parameters (i.e. vehicle load, elastic modulus, damping ratio, and mass density of bridge) on train-bridge dynamic interactions. The probability density evolution method (PDEM), a newly developed theory which is applicable to train-bridge systems, can capture instantaneous probability density functions of dynamic responses. In this study, PDEM is employed to implement random dynamic analysis of a 3D train-bridge system subjected to random system parameters. The number theory method (NTM) is employed to choose the representative point sets of random parameters, whose initial probability distribution is divided by Voronoi cells., MATLAB® software is prepared for calculation, the Newmark-β integration method and the bilateral difference method of TVD (total variation diminishing) are adopted for solution. A case study is presented in which the train travels on a three-span simply supported high-speed railway bridge. The calculation accuracy and computational efficiency of the PDEM has been verified and some conclusions are provided. Furthermore, the influence of train speed under various combinations of random parameters is beyond discuss.

Study of the train-induced vibration impact on a historic Bell Tower above two spatially overlapping metro lines

There is concern regarding the long-term vibration effects caused by metro trains on historic buildings. In this paper, the impact of metro train-induced vibrations on the Bell Tower in Xi’an above two spatially overlapping tunnels was studied.Metro Line 2 has been operational since 2011, and Line 6 is still under construction. To study and control the effect of micro vibrations on the Bell Tower, a metro train–track–tunnel–soil 3D dynamic FE model was developed. The vibration response generated by Line 2 was then predicted, and the influences of train speed on ground vibration were analysed. In addition, a detailed in situ measurement, which helped calibrate the numerical model and determine the dynamic behaviour of timber structures, was performed. Finally, the calibrated models and measured results were used to predict vibrations caused by road traffic and trains from two spatially overlapping metro lines. This was performed under different route schemes and train operation conditions.The results showed that installing steel spring floating slab tracks (FST) and decreasing train speeds had obvious effects on controlling the ground peak particle velocity (PPV). Simulated results from both the input impulse and output response generated by metro Line 2 matched well with actual measurements. If correct designs are employed, it is possible to resolve the vibration problem on historic buildings caused by metro trains.

Aerodynamic Effects of Unvented Hoods on the Initial Compression Wave Generated by a High-Speed Train Entering a Tunnel

The influence of unvented hood on the initial compression wave generated by a high-speed train entering a tunnel is investigated using computational fluid dynamics. Comparisons with experimental data are first carried out to verify the numerical model. The relationship between the pressure gradient peaks and main aspect factors is studied by parametric analysis. Influences of train speed, blockage ratio of train to tunnel, section area ratio of hood to tunnel, and hood length are investigated. Based on the numerical results, two empirical formulations are proposed to predict the influence of hood and tunnel geometries on the maximum pressure gradient during the CRH3 entering a tunnel with unvented hood.

Random vibration analysis of train-slab track-bridge coupling system under earthquakes

This study aimed to investigate the random vibration characteristic of train-slab track-bridge interaction system subjected to both track irregularities and earthquakes by use of pseudo-excitation method (PEM). Each vehicle subsystem was modeled by multibody dynamics. A three-dimensional rail-slab- girder-pier finite element model was created to simulate slab track and bridge subsystem. The equations of motion for the entire system were established based on the constraint condition of no jump between wheel and rail. The random load vectors of equations of motion were formulated by transforming track irregularities and seismic accelerations into a series of deterministic pseudo-excitations according to their respective power spectral density (PSD) functions by means of PEM. The time-dependent PSDs of random vibration responses of the system were obtained by step-by-step integration method, and the corresponding extreme values were estimated based on the first-passage failure criterion. As a case study, an ICE3 high-speed train passing a fifteen-span simply supported girder bridge simultaneously excited by track irregularities and earthquakes is presented. The evaluated extreme values and the PSD characteristic of the random vibration responses of bridge and train are analyzed, and the influences of train speed and track irregularities (without earthquakes) on the random vibration characteristic of bridge and train are discussed.

Random vibration analysis of train–bridge under track irregularities and traveling seismic waves using train–slab track–bridge interaction model

The frequent use of bridges in high-speed railway lines greatly increases the probability that trains are running on bridges when earthquakes occur. This paper investigates the random vibrations of a high-speed train traversing a slab track on a continuous girder bridge subjected to track irregularities and traveling seismic waves by the pseudo-excitation method (PEM). To derive the equations of motion of the train–slab track–bridge interaction system, the multibody dynamics and finite element method models are used for the train and the track and bridge, respectively. By assuming track irregularities to be fully coherent random excitations with time lags between different wheels and seismic accelerations to be uniformly modulated, non-stationary random excitations with time lags between different foundations, the random load vectors of the equations of motion are transformed into a series of deterministic pseudo-excitations based on PEM and the wheel–rail contact relationship. A computer code is developed to obtain the time-dependent random responses of the entire system. As a case study, the random vibration characteristics of an ICE-3 high-speed train traversing a seven-span continuous girder bridge simultaneously excited by track irregularities and traveling seismic waves are analyzed. The influence of train speed and seismic wave propagation velocity on the random vibration characteristics of the bridge and train are discussed.

Random Vibration Analysis of Train Moving over Slab Track on Bridge under Track Irregularities and Earthquakes by Pseudoexcitation Method

This paper investigates the random vibration and the dynamic reliability of operation stability of train moving over slab track on bridge under track irregularities and earthquakes by the pseudoexcitation method (PEM). Each vehicle is modeled by multibody dynamics. The track and bridge is simulated by a rail-slab-girder-pier interaction finite element model. The coupling equations of motion are established based on the wheel-rail interaction relationship. The random excitations of the track irregularities and seismic accelerations are transformed into a series of deterministic pseudoexcitations by PEM. The time-dependent power spectral densities (PSDs) of the random vibration of the system are obtained by step-by-step integration method, and the corresponding dynamic reliability is estimated based on the first-passage failure criterion. A case study is then presented in which a high-speed train moves over a slab track resting on a simply supported girder bridge. The PSD characteristics of the random vibration of the bridge and train are analyzed, the influence of the wheel-rail-bridge interaction models on the random vibration of the bridge and train is discussed, and furthermore the influence of train speed, earthquake intensity, and pier height on the dynamic reliability of train operation stability is studied.

Influence Analysis of Train Speed on Vibration Responses of Footbridge

Influence analysis of train speed on vibration responses of footbridge entrance to platform induced by wind pressure due to main line train have been researched in the paper. With some footbridge as the research background, different wind pressure produced by different train speed acting on the bridge surface simulated by CFD method has been adopted to the bridge, thus influence of train speed on vibration responses of footbridge induced by wind due to main line train are obtained. Simulating results show that the vibration responses of footbridge entrance to platform intense with the increase of train speed.

Train-induced vibration on elevated railway station

Results of in-situ vibration measurement carried out at Tianjin West Elevated Railway Station which has the trains running on the station structure were reported. The main excitation source is the train passing through the station. Vibration measurements were recorded in the vertical direction of the supporting track beam, the platform and the steel truss beam of the waiting hall, as well as in the vertical, longitudinal and transverse directions of the roof arch base of the station. Acceleration time responses were obtained. The maximum value, vibration level and one-third octave band RMS spectra of the measured accelerations were studied. The propagation of vibration in different structural floors was discussed. The influence of train speed, distance to the vibration source and the type of train on the structural vibration were analyzed. Results show that the vibration level increases with the train speed, while it attenuates with the distance to the track. Furthermore, the vibration responses of different structural floors were compared, and it is noted that the vertical vibration of the bottom slab of the platform is most severe and the transverse vibration of the roof arch base is the smallest. The results provide reference on the vibration characteristics and vibration energy distribution of this type of “Train on building frame” system used as an elevated railway station.

Parameters Analysis of Train Running Performance on High-Speed Bridge during Earthquake

A model of coupled vehicle-bridge system excited by earthquake and irregular track is established for studying train running performance on high-speed bridge during earthquake, by the methods of bridge structure dynamics and vehicle dynamics. The results indicate that under Qian’an earthquake waves vehicle dynamical responses hardly vary with the increasing-height pier, but vehicle dynamical responses increase evidently while the height of pier is 18m, which the natural vibration frequency is approaching to dominant frequency of earthquake waves. Dynamic responses are linearly increasing with earthquake wave strength. Dynamic response of vehicles including lateral car body accelerations and every safety evaluation index all increase with train speed, so the influences of train speed must be taken into account in evaluating running safety of vehicles on bridge during earthquakes, but lateral displacement of bridge is varying irregularly. Dynamic responses and lateral displacement of bridge reduce under the higher dominant frequency of earthquake wave. Derailment coefficient, later wheel-rail force and lateral vehicle acceleration become small with increasing damping ratio. Vertical vehicle acceleration and reduction rate of wheel load are hardly varying with damping ratio.

Acceptance criterion for rail roughness level spectrum based on assessment of rolling contact fatigue and rolling noise

▶ A reference short-pitch rail corrugation spectrum has been derived. ▶ Development of acceptance criterion regarding noise emission and RCF risk. ▶ Demonstration on employing the criterion to analyze altered operational conditions. ▶ Significantly improve means of planning preventive actions, e.g. grinding. The influences of train speed and rail roughness level on rolling noise and subsurface initiated rolling contact fatigue (RCF) impact are studied. In particular, the consequences of short-pitch rail corrugation on tangent track with wavelengths in the interval 3–8 cm are simulated using models of dynamic vehicle–track interaction. Based on the calculated results, a criterion in terms of a limit for maximum levels of rail roughness with respect to the current traffic conditions can be determined. Such a criterion may be useful for planning of rail grinding intervals if used together with a system for regular monitoring of rail roughness levels. It is concluded that the importance of controlling rail roughness increases with increasing train speed. Increasing axle loads on freight vehicles from 22.5 tonnes to 30 tonnes leads to a significant increase in RCF impact. In operational practice, this is usually compensated for by introducing more conformal wheel–rail profile combinations. Calculated vertical wheel–rail contact forces and rolling noise levels show good agreement with field measurements.