scholarly journals A Numerical Study of Railway Track Dynamics: The Case of a Transition Zone

2016 ◽  
Author(s):  
E. Arlaud ◽  
S. Costa D'Aguiar ◽  
E. Balmes ◽  
G. Faussurier
Keyword(s):  
Transition Zone ◽  
Numerical Study ◽  
Railway Track ◽  
Track Dynamics

Numerical study of transition zone between ballasted and ballastless railway track

2015 ◽  
Vol 3 ◽  
pp. 58-67 ◽  
Author(s):  
Mojtaba Shahraki ◽  
Chanaka Warnakulasooriya ◽  
Karl Josef Witt
Keyword(s):  
Transition Zone ◽  
Numerical Study ◽  
Railway Track

Engineered Semi-Flexible Composite Mixture Design and Its Implementation Method at Railroad Bridge Approach

2021 ◽  
pp. 036119812110049
Author(s):  
Shuai Yu ◽  
Shihui Shen ◽  
Hai Huang ◽  
Cheng Zhang
Keyword(s):  
Transition Zone ◽  
Structural Adjustment ◽  
Asphalt Mixture ◽  
Vertical Displacement ◽  
Smooth Transition ◽  
Railway Track ◽  
Dynamic Force ◽  
Entire Structure ◽  
Bridge Approach ◽  
Composite Mixture

Considerable variation in the vertical displacement can cause railway tracks’ transition problems at the bridge approach. The vertical displacement gaps can result in amplification of the dynamic force and frequency, and gradually degrade the serviceability of the railway track. Many strategies, focusing on either modifying the track component or making changes to the entire structure, were used to mitigate transition problems. In particular, asphalt concrete underlayment as a structural adjustment method provides additional support to the ballast and protects the subgrade. However, its effect of reducing dynamic impact at the bridge approach is limited because asphalt mixture has a limited range of modulus and cannot make enough adjustments to the entire structure. Therefore, this paper aims to develop an engineered semi-flexible composite mixture (SFCM) design to mitigate the transition problem. The experiment showed that SFCM is a viscoelastic material with a wider modulus range, and its modulus can adjust with its air voids and the concrete slurry content. Track analysis using a 2.5D sandwich model was conducted to simulate the effects of the structure and material on the responses of the railway track under the dynamic loads and determine the arrangement of the transition zone. A four-segment transition zone design was eventually proposed for a special case of bridge approach. This method can be used to develop transition zones for achieving a smooth transition at the bridge approaches.

IMPORTANCE OF NONLINEARITY OF TRACK SUPPORT SYSTEM IN MODELING OF RAILWAY TRACK DYNAMICS

2013 ◽  
Vol 13 (01) ◽  
pp. 1350008 ◽  
Author(s):  
J. SADEGHI ◽  
M. FESHARAKI
Keyword(s):  
Support System ◽  
Field Tests ◽  
Field Investigation ◽  
Dynamic Responses ◽  
Railway Track ◽  
Nonlinear Properties ◽  
Railway Tracks ◽  
Track Dynamics ◽  
Track System ◽  
Axle Loads

Attention is drawn to the fact that the recent increase in axle loads, speed and traffic volume in railway tracks, as well as concerns over passengers' riding comfort and safety have resulted in fresh challenges that are needed to be addressed. These challenges can only be successfully tackled with a more accurate modeling of the dynamic behavior of railway tracks. Although a significant amount of research involving mathematical modeling of railway track dynamics has been conducted in the last two decades, the nonlinearity of track support systems has not been given sufficient attention. This paper is concerned with the effect of nonlinearity of the support sub-layers on the dynamic responses of the railway track. To this end, a railway track model that considers the nonlinear properties of the track sub-layers is developed. Then, a field investigation into the dynamic responses of the railway track system under moving trains is conducted. The effect of the nonlinearity properties of the track support system on the track responses is investigated by comparing the results obtained by the numerical model, with or without consideration of track support nonlinearity, with those from the field tests. It is illustrated that consideration of the nonlinear properties of the track support system improves the accuracy of the calculated responses by a factor of three. It is also shown that the train axle loads and track accumulative loading have a significant effect on the nonlinearity of the track support system and, as a result, on the modeling of track responses.

Experimental and Numerical Study of Railway Ballast Compactness during Tamping Process

2013 ◽  
Vol 690-693 ◽  
pp. 2730-2733
Author(s):  
Tao Yong Zhou ◽  
Bin Hu ◽  
Bo Yan ◽  
Jun Feng Sun
Keyword(s):  
Discrete Element Method ◽  
Numerical Study ◽  
Discrete Element ◽  
Railway Track ◽  
Analysis Model ◽  
Railway Ballast ◽  
Element Analysis ◽  
Before And After ◽  
Filling Method ◽  
Element Method

Railway ballast tamping operations is employed in order to restore the geometry of railway track distorted by train traffics. The main goal is to compact the stone ballast under the sleepers supporting the railway squeezing and vibrations. The ballast compactness is the most direct index for evaluating the effect of tamping operation. This paper presents an experimental method used to detect the railway ballast compactness before and after tamping operation based on water-filling method, and creates a discrete element analysis model of railway ballast which analyzes the change of ballast compactness before and after tamping operation based on discrete element method. The simulation results are very similar with experimental results, which verify that the discrete element method is an effective method to evaluate the change of railway ballast compactness during tamping process.

A numerical study of the influence of lateral geometry irregularities on mechanical deterioration of freight tracks

2012 ◽  
Vol 226 (6) ◽  
pp. 575-586 ◽  
Author(s):  
Kalle Karttunen ◽  
Elena Kabo ◽  
Anders Ekberg
Keyword(s):  
Numerical Study ◽  
Contact Point ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Field Measurements ◽  
Rolling Contact ◽  
Railway Track ◽  
Operational Conditions ◽  
Track Geometry ◽  
Track Maintenance

Optimisation of railway track maintenance requires knowledge of how a deteriorated track geometry will affect subsequent loading and damage of the track. This is the scope of the current study where, in particular, the influence on track shift forces and rolling contact fatigue is investigated through numerical simulations. To this end, track geometries are obtained from field measurements. Lateral irregularities are extracted and scaled to represent different levels of geometry deterioration. Multibody simulations of dynamic train–track interaction featuring two freight wagon types are performed under different operational conditions. Track shift forces and rolling contact fatigue damage are further evaluated from simulation results. It is found that track shift forces tend to follow a normal distribution for moderate levels of lateral track geometry irregularities, and that an approximate linear relationship between standard deviations of lateral irregularities and track shift forces can be established. The relation between lateral track irregularity magnitude and rolling contact fatigue is more complex. Increasing levels of lateral irregularities will decrease the fraction of curve length affected by rolling contact fatigue for sharp curves, whereas for shallow curves it increases. As detailed in the article, this is caused by the lateral movement of the contact point as imposed by the track irregularities. Furthermore, the influence of wheel/rail friction and wear is investigated.

Out-of-Plane Responses of Overspeeding High-Speed Train on Curved Track

2018 ◽  
Vol 18 (11) ◽  
pp. 1850132 ◽  
Author(s):  
Jian Dai ◽  
Kok Keng Ang ◽  
Van Hai Luong ◽  
Minh Thi Tran ◽  
Dongqi Jiang
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Contact Forces ◽  
Railway Track ◽  
High Speed Train ◽  
Track Segment ◽  
Out Of Plane ◽  
Train Speed ◽  
Curved Track ◽  
Design Speed

This paper presents a numerical study on the out-of-plane responses of a high-speed train running on a curved railway track segment using the moving element method. The accuracy and efficiency of the proposed computation model presented herein are compared with available analytical results from the literature and a finite element solver based on a simplified moving load model. Thereafter, a half-railcar moving sprung-mass model and a double-rail track-foundation model are presented to investigate the behavior of a high-speed train traversing a curved track, particularly when the train speed is greater than the design speed of the curved track segment. The results show that the train speed and severity of track irregularity significantly affect the contact forces on the rails. This paper also presents a case of a railcar overturning when the train speed is greater than 2.5 times the design speed of a curved track segment.

Load impact on railway track due to unsupported sleepers

2005 ◽  
Vol 219 (2) ◽  
pp. 67-77 ◽  
Author(s):  
A Lundqvist ◽  
T Dahlberg
Keyword(s):  
Computer Model ◽  
Interaction Force ◽  
Railway Track ◽  
Train Track ◽  
Traffic Loading ◽  
Track Geometry ◽  
Deterioration Rate ◽  
Track Dynamics ◽  
Force Increase ◽  
Load Impact

Ballasted railway tracks will settle as a result of permanent deformations in the ballast and in the underlying material layers. The settlement is caused by the repeated traffic loading and the severity of the settlement depends on the quality and the behaviour of the ballast, the sub-ballast, and the subgrade. As the behaviour of the material is not exactly the same under all sleepers, and since the loading of the track is irregular, the amount of settlement will differ from one sleeper to another. A result of this is that the sleepers are not always fully supported, and some sleepers may even become completely unsupported (voided). A gap appears between the sleeper and the ballast bed. As soon as the track geometry starts to deteriorate, the variations of the train/track interaction force increase, and this speeds up the track deterioration rate. This paper presents a computer model by which the dynamic train/track interaction can be simulated. The influence of one or several voided sleepers on the train/track interaction force and on the track dynamics is investigated. Track settlement due to hanging sleeper(s) is discussed.

Attenuating Railway Track Vibration by Rail Absorber for Noise Reduction

2008 ◽  
Vol 39 (9) ◽  
pp. 14-23 ◽  
Author(s):  
T. X. Wu
Keyword(s):  
Noise Reduction ◽  
Decay Rate ◽  
Vibration Reduction ◽  
Railway Track ◽  
Low Loss ◽  
Active Mass ◽  
Track Dynamics ◽  
Damping Material ◽  
Piecewise Continuous ◽  
Selection Of

A promising means to increase the decay rate of vibration along the rail is using a rail absorber for noise reduction. Compound track models with the tuned rail absorber are used for investigation of the performance of the absorber on vibration reduction. Through analysis of the track dynamics with the rail absorber some guidelines are given on selection of the types and parameters for the rail absorber. It is found that a large active mass used in the absorber is beneficial to increase the decay rate of rail vibration. The effectiveness of the piecewise continuous absorber is moderate compared with the discrete absorber installed in the middle of sleeper span or at a sleeper. The most effective installation position for the discrete absorber is in the middle of sleeper span. Over high or over low loss factor of the damping material used in the absorber may degrade the vibration reduction performance.

Variation of Track Response to Wheel Forces with Bogie Axle Spacing: Apparent Track Stiffness and its Influence on Dynamic Impact Forces on Railway Tracks

2021 ◽  
pp. 036119812110624
Author(s):  
Erdem Balcı ◽  
Niyazi Özgür Bezgin ◽  
Mohamed Wehbi
Keyword(s):  
Analytical Study ◽  
Mechanical Characteristics ◽  
Numerical Study ◽  
Railway Track ◽  
Dynamic Impact ◽  
Transition Zones ◽  
Railway Tracks ◽  
Impact Forces ◽  
Track Stiffness ◽  
New Perspective

Track stiffness is an important parameter that affects railway track response. Axle spacing influences the response of the track to wheel forces and has an effect on track stiffness. Track response to train wheels within a bogie or between neighboring bogies vary in relation to their mutual interference, depending on the mechanical characteristics of the layers composing the track, axle spacing and bogie spacing. This interference affects the force-deflection characteristic of the railway track under a wheel. Dynamic impact forces caused by track and wheel roughness relate to track stiffness. Therefore, everything else being the same, two trains with different bogie spacing may generate different dynamic impact forces on the railway track. As a result, the accumulated damage to a railway track over time can relate not only to cumulative tonnage but also to the axle spacing of the trains operating on the railway track. Through superposition of the estimated track deflections by the beam-on-elastic-foundation theorem and looking at it from a new perspective, this paper discovers a set of relations between the variations of track stiffness with bogie axle spacing. The paper introduces a new concept of apparent track stiffness and hypothesizes that dynamic impact forces on the railway tracks relate to axle spacing. The paper then presents a numerical study and an analytical study that analyzes wheel and track interaction along stiffness transition zones for different values of axle spacing and shows that bogie axle spacing has an effect on dynamic impact forces on railway tracks.

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