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Seongkyu Chang - One of the best experts on this subject based on the ideXlab platform.

Michaël Steenbergen - One of the best experts on this subject based on the ideXlab platform.

  • railway track degradation the contribution of a spatially variant support stiffness local variation
    Journal of Sound and Vibration, 2019
    Co-Authors: Mehran Sadri, T Lu, Michaël Steenbergen
    Abstract:

    Abstract The effect of large-scale variation in the support stiffness on railway track degradation is studied using a frequency-domain approach. The model used can deal with parametric excitation due to both the discrete Sleeper Spacing and arbitrary large-scale spatial track non-uniformity. Adopted stiffness profiles are based on realistic datasets in the literature. The sensitivity to degradation is assessed by quantifying the energy dissipation in the substructure over the influence zone. Results show that the effect of spatial stiffness variation generally increases with the speed, for any subgrade condition; system resonance however leads to increased degradation at resonance speeds and increases with the mean value of the track stiffness. The speed is shown to have a larger influence in the presence of non-uniformity than it has for uniform track with a mean value of the same non-uniform track stiffness, independent of this mean value. In general, support stiffness non-uniformity and poor track conditions (in terms of a low overall stiffness) may have comparable effects; the combination of both is a worst-case scenario. Predictions are independent from the randomness for measured datasets and have therefore general validity. Further, an excellent correlation is found between the spatial variation of the dynamic track stiffness, the differential energy dissipation in the substructure, and the work performed by the moving contact load with respect to the track, independent of the train speed. This confirms existing empirical evidence of the dynamic track stiffness for non-uniform track as an indicator for degradation.

  • Dynamic Axle Loads as a Main Source of Railway Track Degradation
    2015
    Co-Authors: Michaël Steenbergen, Edward De Jong, A. Zoeteman
    Abstract:

    During train operation, geometrical irregularities develop in soil-supported ballasted railway tracks as a function of born tonnage. This form of degradation is combatted by periodic maintenance in the form of tamping by specially equipped trains in order to guarantee predefined levels of structural performance. The growth of irregular settlements depends on one hand on track properties (such as Sleeper Spacing, rail bending stiffness, subsoil geotechnical properties) and the intensity of longitudinal stiffness variations (variations in soil profile, switches and crossings, transitions etc.). The latter stiffness variations include both the static and the dynamic, frequency-dependent stiffness. On the other hand also the nature of the loading has an important influence. Running trains exert – depending on their velocity – quasistatic loads on the infrastructure due to the passing axles with a constant loading. Apart from this a dynamic loading component may occur with different frequencies as a result of non-perfect wheels, as a function of the speed. In general, the structural design of a railway line can be optimised with respect to its structural performance for the whole lifecycle. However, for existing lines this is difficult, and the only way to limit degradation and associated costs is to influence the condition of the rolling stock. The present study discusses theoretical backgrounds of track degradation in the form of differential settlements. It then shows results of an analysis of the loading conditions on Dutch railway lines, with both mixed passenger and freight transport and with dedicated freight traffic, based on actual measurements. Conclusions are drawn regarding deterioration and the effects of different loading types. Results show that especially on freight lines huge improvements are possible, with reductions in geometrical degradation up to 52% of actual values. The main driver of excessive degradation appears to be the low-frequency dynamic axle loading component.

  • Railway track degradation: The contribution of rolling stock
    Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit, 2015
    Co-Authors: Michaël Steenbergen, Edward De Jong
    Abstract:

    During train operation, geometrical irregularities develop in soil-supported ballasted railway tracks as a function of the carried tonnage. This form of degradation is combatted by periodic tamping using specially equipped trains, in order to guarantee predefined levels of structural performance. The growth of irregular settlements depends on both track properties (such as Sleeper Spacing, bending stiffness of the rail, and geotechnical properties of the subsoil) and the intensity of variations in the longitudinal stiffness (variations in soil profile, switches and crossings, transitions, etc.). These variations affect both the static and dynamic, frequency-dependent stiffness of the track under the moving wheels. In addition, the nature of the loading exerted by the rolling stock has an important influence. Trains running at a constant speed exert quasi-static loads on the infrastructure due to the constant axle loading. Also, a dynamic loading component may occur as a result of non-perfect wheels, with ...

Jabbar Ali Zakeri - One of the best experts on this subject based on the ideXlab platform.

  • Numerical-experimental study of contact-impact forces in the vicinity of a rail breakage
    Engineering Failure Analysis, 2020
    Co-Authors: Mosab Reza Tajalli, Jabbar Ali Zakeri
    Abstract:

    Abstract Broken rails or welds are among the rail discontinuities that generate significant impact forces in the wheel-rail contact surface. These forces lead to contact loss and thus an increase in the derailment probability. In this paper, experimental and analytical data are employed to study the impact force as the wheel crosses over a broken rail. In the experimental tests, the wheel-rail impact forces were measured using a Wheatstone bridge circuit. Prior to the field tests, the calibration factor of the Wheatstone bridge was determined by lab experiments. A three-dimensional finite element model (3D FEM) of the wheel and rail was developed and verified using the experimental test results. Using the numerical model, the effects of the distance between the breakage location and the adjacent Sleeper, temporary repair of broken rails, and Sleeper Spacing on the wheel-rail impact forces were studied. The developed numerical model provided acceptable estimations of wheel-rail impact loads, as the difference of estimated and measured impact load is limited to 17%. According to the results of the numerical model, if the rail breakage is positioned between the two adjacent Sleepers, impact forces are almost half of that of when the rail breakage occurs close to a Sleeper. Moreover, the wheel-rail contact is not lost for any crossing speed of the vehicle. Also, by increasing the Sleeper Spacing from 60 cm to 70 cm, the impact load increases by an average of 20%, while reducing the Sleeper Spacing from 60 cm to 50 cm can decrease the impact loads by an average of 13%.

  • An Experimental and Numerical Study on the Effect of Different Types of Sleepers on Track Lateral Resistance
    2015
    Co-Authors: Arash Bakhtiary, Jabbar Ali Zakeri, Hun Je Fang, Ahmad Kasraiee
    Abstract:

    Lateral resistance of railway track is one of the most important parameters in lateral stability. This parameter depends!on the conditions of different components of ballasted railway track (such as density of ballast layer, Sleeper Spacing, type of Sleeper, etc.). From this perspective, type of Sleeper has an important effect on lateral resistance. However in some conditions, in technical and economical investigations, using a special type of Sleeper is not avoidable. In this research, concrete, wooden, and steel Sleepers are studied using experimental and numerical analysis by finite element method. According to the experimental results, concrete Sleeper B- 70 with 2.06 tons has the most lateral resistance among three types of Sleepers. Steel and wooden Sleepers with the amounts of 1.32 and 1.10 tons are in the next ranking. On the other hand, numerical analysis (modeled according to field conditions) shows that the lateral resistance of concrete, steel, and wooden Sleepers is equal to 2.10, 1.36, and 1.15 tons, respectively.

  • Influence of unsupported and partially supported Sleepers on dynamic responses of train–track interaction
    Journal of Mechanical Science and Technology, 2015
    Co-Authors: Jabbar Ali Zakeri, Morvarid Fattahi, Mohammad Mehdi Ghanimoghadam
    Abstract:

    One of the major problems of railroad deterioration is uneven settlement which occurs due to various reasons, including existence of defects in substructures, using non-homogenous ballast, or being poorly drained. Sometimes, because of these problems, Sleepers remain freely as a part of vertical displacement and contact the ballast with load increase. Different models have been presented for checking the effect of hanging Sleepers on the dynamic interaction of rail and train. In this paper, a mathematical model was developed for railway track and differential rail displacement with supported and unsupported Sleepers was compared by modeling Sleepers such as partially supported ones. On this basis, the motion equations of the train-track system were solved considering the non-linearity of wheel/rail contact form and using numerical integration in the time domain. Longitudinal sections of the track model were coded in Matlab software and the effect of one, two, or three partially supported Sleepers and various Spacing of Sleepers on the Sleepers and rail displacement was studied and compared with that of the unsupported one. It was shown that, with increasing the Sleeper Spacing from 50 to 75 cm, rail displacement increased from 7 to 22% in the unsupported Sleeper and 5 to 8% in the partially supported Sleeper. Additionally, rail displacement increased from 13 to 74% by changing the number of the unsupported Sleeper from 1 to 9. Also, it increased from 6 to 24% in the partially supported Sleepers.

  • Sensitivity analysis of track parameters on train-track dynamic interaction
    Journal of Mechanical Science and Technology, 2008
    Co-Authors: Jabbar Ali Zakeri
    Abstract:

    Dynamic behavior of railway tracks when trains are running is influenced by several factors, i.e. rolling stock, the components of superstructure and their specifications. Usually, features like the Sleeper Spacing, rail pad stiffness, ballast damping and stiffness have an effect on the dynamic response of the track. The best method to study the dynamic behavior of the track is to model the track assembly and the train as a whole and carry out an analysis of dynamic interaction. Such analysis makes the identification of the track’s dynamic behavior easer and helps to anticipate the deterioration of the track elements, and determines the effects of increase or decrease of mentioned parameters. This paper presents track-train dynamic interaction without considering irregularity of the rail face. A sensitivity analysis was carried out on the selected model. The analysis was undertaken with the view of varying one of the mentioned parameters and the results were presented to further identify the deterioration of the track elements. The results indicate that reducing Sleeper Spacing, rail pad stiffness, ballast stiffness, and increasing ballast damping reduces wheel-rail, rail-Sleeper, and Sleeper - ballast contact forces.

Johan Oscarsson - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Train-Track Interaction: Linear and Non-Linear Track Models with Property Scatter
    2020
    Co-Authors: Johan Oscarsson
    Abstract:

    A numerical method was developed to investigate the vertical dynamic behaviour of a railway track subjected to the loading of a moving train. The numerical simulations are carried out in the time-domain with what is known as a moving mass model. This doctoral thesis emphasises especially the influence on the train-track dynamics of the ballast mass (giving rise to inertia forces when a train passes), the influence of the non-linear characteristics of the railpad and of the Sleeper support, and the part played by scatter in some track structure properties, such as varying railpad stiffness, varying ballast stiffness and varying Sleeper Spacing. Full-scale measurements in the field sometimes reveal a track resonance at low frequency (somewhere in the region of 20 to 150 Hz). This resonant behaviour cannot be modelled unless the ballast-subgrade inertia is included in the track model, which is done here. Both laboratory and full-scale field measurements have shown that the load deflection behaviour of the railpad and the Sleeper support are non-linear. In a realistic demonstration example, the influence of a state dependent railpad on railpad compression and rail wear was investigated. It was shown that, for a weakly state dependent railpad, the difference in results compared with those obtained for a linear model is negligible. Measurements have also shown that track parameter values are not constant along the track. In fact, very dissimilar properties have been observed even between neighbouring Sleepers. It is concluded that, if one wants to investigate the mean values and variations of selected track parameters, a method that does not restrict the variation and distribution of the stochastic variables is, while not necessary, certainly preferable.

  • Dynamic Train-Track-Ballast Interaction with Unevenly Distributed Track Properties
    Vehicle System Dynamics, 2016
    Co-Authors: Johan Oscarsson
    Abstract:

    ABSTRACTA numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been extended to account for stochastic properties in the track structure. Here, the rail pad stiffness, the ballast stiffness, the dynamic ballast-subgrade mass and the Sleeper Spacing are modelled as random variables. The numerical simulations have been carried out in the time-domain with a moving mass model. Full-scale measurements in the field and laboratory experiments have been carried out to get realistic data for the selected stochastic variables. Two conceptual different methods (a perturbation and a Monte Carlo method) were used to investigate the influence of the randomness of selected stochastic parameters in the track structure. The investigated quantities have been the maximum value of the rail-wheel contact force, the maximum magnitude of the vertical wheelset acceleration and the maximum value of the Sleeper displacement. Mean values and standard deviations of these quantitie...

  • Dynamic Train-Track Interaction: Variability Attributable to Scatter in the Track Properties
    Vehicle System Dynamics, 2002
    Co-Authors: Johan Oscarsson
    Abstract:

    A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and Sleeper Spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the v...

Javad Sadeghi - One of the best experts on this subject based on the ideXlab platform.

  • Experimental investigation on loading pattern of railway concrete slabs
    Construction and Building Materials, 2017
    Co-Authors: Javad Sadeghi, Hassan Liravi, M. Hassan Esmaeili
    Abstract:

    Abstract Although construction of ballast-less track is booming in recent years, there is a lack of sufficient researches into the design and construction of this system. This research addresses this limitation by investigating the amount of loads transferred from the rail to the support slabs as the main parameter in the design and construction of railway concrete slabs. A comprehensive experimental investigation was conducted in various light and heavy passenger transit lines. The effects of the main influencing parameters including Sleeper Spacing, rail bending modulus, track stiffness, train speed, and wheel load on the amount of rail seat loads were investigated. The results were analyzed, leading to derive a mathematical expression for the rail seat load and the loading pattern of concrete slabs. The reliability and accuracy of the loading patterns currently used in the analysis and design of concrete slabs were evaluated by comparisons of the experimental results obtained here with those of the current practice. The results obtained have made considerable improvements in the analysis and design of railway concrete slabs.

  • Investigation of the Influences of Track Superstructure Parameters on Ballasted Railway Track Design
    Civil engineering infrastructures journal, 2015
    Co-Authors: Javad Sadeghi, Araz Hasheminezhad, Mohammad Essmayil Kaboli
    Abstract:

    The main design criteria of ballasted railway tracks include rail deflections, rail bending stresses, rail wheel contact stresses, Sleeper bending moments and ballast Sleeper contact pressures. Numerous criteria have been defined for the design of ballasted railway tracks owing to the various mechanical properties of track components and their complex interaction. Therefore, railway track designing is a difficult and time-consuming process. These complications highlight the need to focus attention on the necessity of a thorough investigation into effect of the track and rolling stock parameters on the design criteria. In an attempt to overcome this problem, sensitivity analysis for the main railway track design criteria was conducted in this study. Consequently, the roles of track and rolling stock parameters (including track modulus, Sleeper Spacing, train speed and axle load) in the design of railway track were investigated for various track design criteria. The research findings provide new, practical suggestions for consideration in the analysis and design of ballasted railway tracks.

  • Influences of Track Structure, Geometry and Traffic Parameters on Railway Deterioration
    International Journal of Engineering Transactions B: Applications, 2007
    Co-Authors: Javad Sadeghi, Hossein Askarinejad
    Abstract:

    The roles of the several parameters that influences railway track deterioration most, are examined in this research with a view to make railway track maintenance more effective and cost efficient. The results presented are based on a comprehensive study of railway track degradation on super structure, sub-structure and geometrical aspects. The changes in TQI (Track Quality Index), the track settelement and the average growth of track's irregularity are considered to be the main track deterioration criteria from the aspects of track geometry,on the tracks sub-structure and super structure, respectively. In this research the sensitivity of the closely related parameters between, ballast conditions, subgrade compaction, rail-pad stiffness, rail types, Sleeper Spacing, initial track quality, tonnage, train speed, axle loads, and load cycles are studied. It is shown how one can control the rate of track deterioration by the verification and modification of the track structure, geometry and traffic parameters.