Dynamic Behaviour Of Railway Track Research Articles

A semi-analytical model of a discretely supported railway track

The dynamic behaviour of railway track plays an important role in the generation of rolling noise as well as the development of rail corrugation. A semi-analytical model is presented that includes vertical, lateral and axial dynamics and takes account of the discrete supports provided by the sleepers. The rail is represented by a semi-analytical beam model that includes vertical and lateral bending, extension and torsion, with warping and shear-centre eccentricity. A receptance-coupling method is used to couple the rails, through damped springs that represent the rail pads, with a finite number of flexible sleepers that are in turn supported on an elastic foundation. The model also accounts for the coupling between the two rails through the sleepers. Results are presented in terms of the point mobilities in different directions, including the vertical-lateral cross mobility, as well as the track decay rates, and the results are validated by comparison with measurements. The inclusion of torsion and warping is shown to have a significant effect on the lateral rail mobility, leading to better agreement with the measured results. The response on one rail due to excitation on the other rail is also explored and the results agree well with the measurements. It is found that the coupling between the two rails has only a limited effect on the resultant track response.

Experimental investigation of the dynamic behavior of railway track with sleeper voids

The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids. The increased dynamic loading in the voided zone and the ballast contact conditions cause the accelerated growth of the settlements in the voided zones, which results in the appearance of local instabilities like ballast breakdown, white spots, subgrade defects, etc. The recent detection and quantification of the sleeper voids with track-side and onboard monitoring can help to avoid or delay the development of local instabilities. The present paper is devoted to the study of the dynamic behavior of railway track with sleeper voids in the ballast breakdown zone. The result of the experimental track-side measurements of rail acceleration and deflection is presented. The analysis shows the existence of the dynamic impact during wheel entry in the voided zone. However, the measured dynamic impact is subjected to the bias of the track-side measurement method. Both the mechanism of the impact and the measurement aspects are explained by using the one-beam model on viscoelastic foundation. The void features in the dynamic behavior are analyzed for the purpose of track-side and onboard monitoring. A practical method of the void parameter quantification is proposed.

EXPERIMENTAL INVESTIGATION ON DYNAMIC BEHAVIOUR OF HEAVY-HAUL RAILWAY TRACK INDUCED BY HEAVY AXLE LOAD

The damage to the track structure and the influence to the line deformation have greatly deteriorated with the increase of the axle load compared with that of the ordinary trains. However, there is a paucity of experimental research on the dynamic influence of the heavier haul freight trains on the railway tracks. The objective of this study is to investigate the dynamic behaviour of heavy-haul railway track induced by heavy axle load by field experimental tests. The wheel–rail dynamic force, the track structure dynamic deformation and the track vibration behaviour are measured and analysed when the train operates in the speed range from 10 to 75 km/h and the axle load of vehicles varies from 21 to 30 t. Comparisons between the results for the axle conditions of 25 and 30 t are made in this paper to reveal the axle load effects. It is demonstrated that part of the indicators reflecting the dynamic behaviour of the railway track increases approximately linearly with the train running speed and axle load, while others are influenced negligibly

Analytical modelling of rail track to account for nonlinear properties of structure

It is known that nonlinear and stochastic properties of structures should be taken into account in the analysis of their dynamic behaviour. This statement remains valid for railway infrastructure, where trains acting on rail track cause their strong dynamic variations. It becomes even more important when one deals with high frequencies and speeds of trains. The recent HSR networks need new technologies and materials in order to increase train speeds and, in the same time, to protect the environment against negative factors produced by operational lines. Therefore all important aspects of new railway constructions should be analysed, especially in terms of mechanical vibrations and noise attenuation. The elements of rail tracks, such as sleepers, under sleeper pads, rail dampers, fastening systems and others, have nonlinear properties. Their influence on dynamic behaviour of railway tracks is still insufficiently researched. For this purpose, various analytical models are proposed which can give a new insight into detailed dynamic characteristics of such structures.

Effect of unsupported sleepers on rail track dynamic behaviour

Railway track behaviour with unsupported prestressed sleepers has been investigated in the literature. However, some of the important factors – such as prestressing forces, variations of the sleeper cross-section along its length, losing or recovering contact between the sleeper and the ballast layer – have been omitted. These limitations have been addressed in this research. The effects of unsupported sleepers on the dynamic behaviour of railway track have been investigated, using an improved three-dimensional numerical model of track developed here. The validity of the model is evaluated by comparing the results obtained from the model with experimental results (obtained in this research and available in the literature). The influences of the size of the gap between the sleeper and the underlying ballast, the vehicle speed and the number of unsupported sleepers on the track dynamic behaviour were investigated. The effects of the various unsupported conditions of sleepers on the rail seat load, sleeper bending moment and sleeper–ballast contact force at various train speeds were illustrated. It was shown that consideration of sleeper prestress forces, detailed geometry of the sleepers and a more realistic assumption for the sleeper–ballast contact has considerably improved the accuracy of the results obtained from theoretical models.

A semi-analytical beam model for the vibration of railway tracks

The high frequency dynamic behaviour of railway tracks, in both vertical and lateral directions, strongly affects the generation of rolling noise as well as other phenomena such as rail corrugation. An improved semi-analytical model of a beam on an elastic foundation is introduced that accounts for the coupling of the vertical and lateral vibration. The model includes the effects of cross-section asymmetry, shear deformation, rotational inertia and restrained warping. Consideration is given to the fact that the loads at the rail head, as well as those exerted by the railpads at the rail foot, may not act through the centroid of the section. The response is evaluated for a harmonic load and the solution is obtained in the wavenumber domain. Results are presented as dispersion curves for free and supported rails and are validated with the aid of a Finite Element (FE) and a waveguide finite element (WFE) model. Closed form expressions are derived for the forced response, and validated against the WFE model. Track mobilities and decay rates are presented to assess the potential implications for rolling noise and the influence of the various sources of vertical-lateral coupling. Comparison is also made with measured data. Overall, the model presented performs very well, especially for the lateral vibration, although it does not contain the high frequency cross-section deformation modes. The most significant effects on the response are shown to be the inclusion of torsion and foundation eccentricity, which mainly affect the lateral response.

Effects of sleeper support modulus on dynamic behaviour of railway tracks caused by moving wagon

Up to now, the effects of sleeper support modulus on the dynamic behaviour of railway tracks have attracted little attention from researchers. So the current study is allocated to investigating the issue through numerical simulations and field tests. For vehicle/track finite element simulations, a wagon system with 10 degrees-of-freedom, including car-body, bogies and wheel-sets, is considered in conjunction with the ballasted track components. In ballasted track modelling, the rails are connected to sleepers with fastening systems and each sleeper is considered as a beam on the viscoelastic foundation. In the field tests program, the ballasted track response is measured under the moving wagon. Comparing the numerical and field test results, good agreement is observed. Finally using the validated numerical model, the effects of sleeper support modulus and sleeper Young's modulus are investigated on the dynamic behaviour of railway track and many practical equations are presented in this regard.

Effects of sleeper support modulus on dynamic behaviour of railway tracks caused by moving wagon

Effects of sleeper support modulus on dynamic behaviour of railway tracks caused by moving wagon

Modeling the dynamic behavior of railway track taking into account the occurrence of defects in the system wheel-rail

This paper investigates the influence of wheel defects on the development of rail defects up to a state where rail prompt replacement becomes necessary taking into account different models of the dynamic contact between a wheel and a rail. In particular, the quasistatic Hertz model, the linear elastic model and the elastoplastic Aleksandrov-Kadomtsev model. Based on the model of the wheel-rail contact the maximum stresses are determined which take place in the rail in the presence of wheel defects (e.g. flat spot, weld-on deposit, etc.). In this paper, the solution of the inverse problem is presented, i.e., investigation of the influence of the strength of a wheel impact upon rails on wheel defects as well as evaluation of the stresses emerging in rails. During the motion of a railway vehicle, the wheel pair position in relation to rails changes significantly, which causes various combinations of wheel-rail contact areas. Even provided the constant axial load, the normal stresses will substantially change due to the differences in the radii of curvature of contact surfaces of these areas, as well as movement velocities of railway vehicles.

Experimental and numerical investigation of the dynamic behavior of ballasted track containing ballast mixed with TDA

The phenomenon of track rigidity in desert areas due to sand dune movement and ballast contamination is one of the most important causes of ballasted railway track degradation and consequently increase in train-induced vibrations. In addition to looking at the existing methods for reducing the track rigidity such as using ballast mat and installing the under sleeper pad, this paper focuses on evaluating the dynamic behavior of railway track including ballast mixed with tire-derived aggregate in a field study. Based on prior laboratory tests done by the authors and latest researches, 10 volume percentages of tire-derived aggregate were adopted as maximum suitable amount to be mixed with ballast for decreasing the track rigidity and increasing its damping property maintaining the basic ballasted track capabilities. In this regard, in a test track located in central desert of Iran in Bafgh-Jandagh railway route, the ballast was mixed with 0, 5 and 10% of tire-derived aggregate by tamping machine in three different sections with 20 m lengths. Moreover, another test section in the same route with fully fouled ballast was considered as a critical bench mark. Many tests were carried out on the mentioned sections using impact test method. In the next stage, the operational modal analysis method was utilized to achieve the tested sections’ mode shapes, natural frequencies and damping ratios as well as geometrical attenuation from the recorded responses. By knowing the modal properties, numerical models of tracks were developed, and the effect of tire-derived aggregate as well as fouling on track stiffness was evaluated.

Modeling on energy harvesting from a railway system using piezoelectric transducers

Theoretical models of piezoelectric energy harvesting from railway systems using patch-type and stack-type piezoelectric transducers are studied. An infinite Euler–Bernoulli beam on a Winkler foundation subjected to moving multi-loads is adopted to describe the dynamic behavior of railway track. The voltage and electric power of piezoelectric transducers installed at the bottom of a steel rail are derived analytically. Comparisons with earlier works and experimental results are given, indicating that the present solutions are reliable. Additionally, a parametric study is conducted to discuss the effects of axle loads, running velocity and load resistors on the solutions. The numerical results show that patch-type and stack-type piezoelectric transducers can harvest the available energy from track vibration to supply power for a wireless sensor network node and can also serve as sensors to monitor basic train information, such as the running velocity, the location and the axle load. The present investigations provide a theoretical guide in the design of piezoelectric patch and stack energy harvesters used in railway systems, which can serve as power sources for distributed wireless sensor networks in remote areas. The research results also demonstrate the potential of piezoelectric patches and stack harvesters in designing self-powered wireless sensor networks used in railway systems to ensure train operation safety.

Dynamic behaviour of railway tracks on transitions zones

Transition zones between structures as bridges or box culverts frequently present higher degradation rates compared to the remaining railway. This paper presents a numerical model for the dynamic loads on the ballast caused by trains passing a transition. The model was validated with field data obtained from an extensive field survey conducted in two transition zones in the Netherlands. Results show that the forces on the ballast vary significantly both in time and space on a transition, especially with the appearance of voids under the sleepers. Implications of the results on the long-term behaviour of transition zones are presented.

Investigation on dynamic behavior of railway track in transition zone

Railway track transition zone is a zone where track stiffness changes abruptly. This change occurs where the slab track connects to a conventional ballasted track, at the abutments of open-deck bridges, at the beginnings and ends of tunnels, at road and railway level crossings, and at locations where rigid culverts are placed close to the bottom of sleepers. In this paper, ballasted and slab tracks are simulated by two-dimensional model with two-layer masses. The transition zone is divided into three segments, each having a length of 6 meters with different specification and stiffness. The model of track consists of a Timoshenko beam as a rail and slab, lumped mass as sleepers, and spring and damper as ballast, sub-grade, and rail pad. The results of the dynamic analysis are presented and compared in two circumstances — one considering the transition zone and the other its absence.

Dynamic Behaviour of Railway Track - Experimental Measurements

The objective of the paper is devoted to in situ dynamic measurements on the track structure under traffic and briefly to present some experimental approaches in order to appreciate the dynamic behaviour of the track structure. The vertical vibration of rails, sleepers and free ballast field at a distance of 1m from the track and the direct dynamic interaction force the rail / the sleeper were measured and analysed in the time and frequency domain. Received results can give many usefulindications concerning the assessing of the superstructure dynamic behaviour.

The effects on railway rolling noise of wave reflections in the rail and support stiffening due to the presence of multiple wheels

Theoretical models that describe the high frequency dynamic behaviour of railway track, are applied to study two effects of the presence of multiple wheels on the rail. These are the influence of wave reflections in the rail induced by the multiple wheel/rail interactions and the local stiffening of the support due to the preload induced by the vehicle weight. Results are given in terms of overall track vibration, sound power spectra and A-weighted levels, and a comparison is made between tracks with three different types of rail pad. The results show that the preloading and wave reflections have significant effects on the rail receptance and the wheel/rail interaction force, but that their influence on the overall track vibration and noise radiation are limited to about 1 dB(A) for two of the three pads considered. For the track with soft pads that is considered, the track noise would be over-predicted by about 3 dB(A) if these effects were not included.

The dynamic behaviour of rail fasteners at high frequencies

The stiffness and damping of rail fasteners, and in particular the elastomeric pads inserted between the rail and sleeper, are important parameters determining the dynamic behaviour of railway track. For noise predictions, the frequency range from about 100 Hz up to 5000 Hz is important. Laboratory measurements are described in which the vertical and lateral dynamic stiffnesses of rail fastener systems have been measured under preload in the range 100–1000 Hz. Extension of the method to higher frequencies is also possible but would require a modified test arrangement. Field measurements are also described, which allow the stiffness and damping to be derived indirectly. Comparisons are made between the two sets of data.

Track Dynamic Behaviour at High Frequencies. Part 1: Theoretical Models and Laboratory Measurements

SUMMARY Three alternative theoretical models of the dynamic behaviour of railway track in the frequency range 50–6000 Hz are described. Using these models various physical phenomena of importance to rolling noise generation are pointed out, and the advantages and short-comings of the three models are compared. Finally, laboratory measurements are described in which the vertical and lateral dynamic stiffnesses of rail fastener systems has been measured under preload in the range 100–1000 Hz.

Track Dynamic Behaviour at High Frequencies. Part 2: Experimental Results and Comparisons with Theory

SUMMARY Three theoretical models, simulating the dynamic behaviour of railway tracks at frequencies up to 5 kHz are presented in a companion paper [1]. In this paper, experimental results obtained on several European tracks are presented. The validity of the models is assessed by means of comparisons between experiments and simulations: generally a good agreement is found. Recommendations are given for further improvements.