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Laboratory and numerical investigation on the longitudinal resistance of ballasted railway tracks with steel sleepers
... Alizadeh et al. [28] experimentally investigated ballasted railway tracks' longitudinal resistance and stiffness with standard and advanced Y-shaped steel sleepers. They examined the shares of various track components in providing longitudinal resistance by measuring the displacement of the track panel. ...
Where railway tracks pass through tunnels, the temperature conditions on the railway superstructure are different from those on the connecting track sections. Due to the temperature difference at the tunnel, dilatation movements occur even in cases of construction of continuously welded rail (CWR) tracks. The aim of this research is to determine the magnitude of the movements resulting from heat expansion and the normal force in the rail in the region of the tunnel gates, both in the tunnel and in the sections of track on the connecting earthworks. Ballasted and straight tracks with rail section of 54E1 are assumed in this paper.
... While sleeper type is primarily associated with influencing a track's lateral resistance, some studies have also examined its effects on longitudinal resistance. Alizadeh et al. [5,4] investigated the influence of sleeper type on track longitudinal resistance and stiffness, highlighting its role in mitigating risks such as rail breakage, misalignments, and buckling. Their research focused on the longitudinal behaviour of the track, emphasizing the contribution of the sleeper and ballast system in transmitting longitudinal loads experienced by the rails. ...
... These sleepers are crucial for preserving the precise gauge between rails and evenly dispersing weights to the underlying trackbed. Ballasted tracks [3], commonly used in heavy haul and high-speed railways, comprise a layer of ballast, sleepers, and rails. The ballast layer, consisting of fragmented stone, supports the sleepers and evenly disperses the vertical, transverse, and longitudinal forces caused by the weight of trains and thermal expansion. ...
Since the 19th century, the evolution of railway infrastructure has been vital to industrial and economic growth, with railway sleepers being crucial components for track stability and performance. This study investigates the interaction between double-channel and Y-shaped sleeper tracks on a non-ballasted steel girder railway bridge in Ankali, Maharashtra, India. Previous research work is validated by the use of a finite element model (FEM) in MIDAS Civil software against Structural Health Monitoring (SHM) data. The study examines three moving load scenarios and four lateral load cases (LLCs) based on Indian Railways Bridge Rules. Influence line analysis is performed to determine the maximum response of the bridge under varying loads, ensuring precise evaluation of structural behaviour. Dynamic effects are considered by applying a Coefficient of Dynamic Augment (CDA) to the live load that generates maximum stresses and deflection. The Results show that Y-shaped sleepers significantly enhance structural performance in vertical and lateral direction compared to conventional double-channel sleepers. The Y-shaped configuration increases track rigidity, reducing average values of bridge vertical deflection by 2.36% and stress in the main girders by 1.79%, while rail stress is decreased by 33.23%. In addition, alternating periodic stiffness offers lateral stability, reducing average lateral deflection by 12.43% and stress in the sleepers by 48.20%. All interaction variables comply with established standard provisions, indicating that Y-shaped sleeper tracks can improve the structural stability of bridges and tracks in new construction projects.
... Esveld [3], Yang et al. [4], Yang et al. [5], Antonio et al. [6], obtained the LRBB with in-situ tests and proposed the recommended value of LRBB. Zakeri et al. [7], Jing et al. [8], Alizadeh et al. [9] conducted a series of resistance tests to investigate the influence of test method, crib level of ballast and types of sleepers on LRBB. Xiao et al. [10], Liu et al. [11] conducted cyclic loading experiments to analyze the effect of loading rates and displacement amplitude on LRBB with a full-scale test model of ballasted track. ...
Considering the longitudinal track-bridge interaction (TBI) of ballasted track significantly influences the corresponding calculation results in dynamic analyses of railway bridges. However, there is still a need for realistic and test-based characteristic parameters (dynamic stiffness and damping values). This paper focuses on an experimental determination of the dynamic properties of the longitudinal track-structure interaction. Based on extensive experiments using a large-scale test facility, the ballasted track's dynamic stiffness and damping values are determined for practical applications. The test spectrum covers a wide frequency and amplitude range, whereby influences due to vertical load of the track (loaded/unloaded) and climatic conditions (summer/winter) are also examined. The tests show that the dynamic properties change significantly with the vertical load and climatic influence. Different damping mechanisms occur depending on the excitation frequency regarding the damping properties. Both friction-based and viscous damping mechanisms appear in the lower frequency range, while only viscous damping occurs in the upper frequency range. The resulting damping characteristics act frequency-dependent and also slightly amplitude-dependent. The stiffness characteristics of the longitudinal track-structure interaction show for each configuration (loaded/unloaded, summer/winter) a non-linear behaviour deviating from the normative specifications, which acts primarily displacement-dependent and almost frequency-independent. Concerning the frozen ballast bed, EN 1991-2 equates the state of the frozen ballast bed with a fixed (ballastless) track. The tests show that this assumption (‘frozen = ballastless’) does not correspond to reality, whereby the temperature level fundamentally influences the longitudinal stiffness in this respect. While at temperatures just below zero (-2°C), no significant differences to the non-frozen ballast bed are discernible; the dynamic properties change considerably at temperatures far below zero (−10 °C). Furthermore, the tests also allow observing the ballast bed liquefaction phenomenon, which occurs at resonance when the excitation frequency matches the natural frequency.
The unintended vibrations and sound emerging from train operation have an enormous impact on the surroundings, including the deterioration of the way, buildings, and structures. One proposed strategy to mitigate this issue is the installation of a rail pad inserted between the steel rail and concrete sleeper to provide flexibility to the track and cushion the shocks and vibrations generated by the train wheels’ movement. These materials have nonlinear, dissipative properties influenced by service conditions like temperature and toe load. This work aimed to investigate the static stiffness of different materials of the rail pad under the influence of temperature and toe load. The rail pads were categorized as soft, medium, or hard based on static stiffness. A 3D model of the rail pad, steel rail, and concrete sleeper was simulated and analyzed using ANSYS FEM software. The neo-Hookean model was used to model the rail pad, and the isotropic elasticity model was used for the steel rail and concrete sleeper. The static stiffness of the ethylene propylene diene monomer (EPDM) pad was 85.42 kN/mm, lower than that of thermoplastic elastomers (TPEs, 138.98 kN/mm) and ethylene vinyl acetate (EVA, 303.70 kN/mm) under reference conditions (20 °C), without including toe load effects. Increasing the temperature decreased the rail pad’s static stiffness, with the highest reduction of 53.49 %. However, increasing the toe load contributed up to a 23.53 % increase in the static stiffness of the rail pad.
In the present paper, testing methods currently adopted to measure the in service ballast resistance
are synthetically reviewed to identify the main sources of uncertainty influencing the test loads and to define an
experimental methodology allowing the optimal control of the testing parameters without the introduction of
spurious or parasitic actions on the track sample. An alternative testing system, which allows applying on a fullscale
sample of a railway track testing loads very close the real ones, is presented. Of the new system, both the
ways of use for measuring the transversal and axial ballast strength, the general procedure to carry out the
experimentation and its application to a real scenario are described, highlighting its main advantages in terms
both of modalities for applying the loads and of testing parameter control.
The Technical Specifications of D.12/H. of Hungarian StateRailways specifies that a continuously welded rail track can be constructed through a bridge without being inter-rupted if the expansion length of the bridge is not longer than 40 m. If the expansion length of a bridge is greater than 40 m, the continuously welded rail should normally be interrupted; a rail expansion joint has to be constructed. The goal of this research is to provide technical solutions of track structureson bridges so a continuously welded rail can be constructed through the bridge from an earthwork without interruption, so rail expansion joints can be omitted.
Certain analytical elastic solution for curvilinear track section under uniform thermal loading has been proposed. Track section is composed of circular arc, transition curves and straight lines. Next step is the analysis of two-dimensional model of the track structure (stress plane, without vertical direction). The rails and the sleepers are assumed as elastic bodies. The fasteners and ballast are modeled as elastic-plastic elements. Non-linear properties of these elements are determined by comparison of numerical data with experimental results. Cyclic uniform thermal field is applied as the load of the system. Pre-buckling analysis is the basic part of the considerations. Certain remarks on the track stability, based on the previous author analyses, are also presented. It is shown that track structure with Y-shaped steel sleepers gives the possibility to use of continuous welded rail (CWR) track practically in any radius of curvature.
There are, on average, 12.5 Federal Railroad Administration reportable derailments per year on U.S. mainlines and sidings caused by “defective or missing spikes or rail fasteners.” Because fastener failures are most commonly caused by a combination of vertical, lateral, and longitudinal loads, it is important to quantify all loads placed on the fasteners to reduce the number of failed fasteners and increase rail safety. Multiple researchers have developed analytical models that leverage longitudinal track resistance and stiffness to quantify the fastener demands. Therefore, to support the refinement of these analytical models that leverage longitudinal track resistance and stiffness, track panel pull tests (TPPTs) were executed in the laboratory to expand on the values within the available literature. These TPPTs quantified the effect of sleeper type (i.e., timber versus concrete), given that 88% of previous studies have focused on concrete. Further, these novel tests quantified the effect of the fastening system, crib ballast height, shoulder width, and ballast condition on the panel’s longitudinal resistance and stiffness. From these experiments and the resulting analysis of data, multiple conclusions were drawn. For example, concrete sleeper panels exhibit 20% higher resistance than timber sleeper panels, disturbing ballast reduced the longitudinal resistance by 13% and stiffness by approximately 80%, and the crib, shoulder, and bottom ballast provide approximately 65%, 5%, and 30% of the total longitudinal resistance, respectively.
Longitudinal track resistance is one of the most critical parameters required to accurately analyze longitudinal load propagation and refine rail neutral temperature (i.e., stress-free temperature) maintenance practices. However, longitudinal track resistance has not been consistently defined and has been quantified using multiple methods that should not be conflated. This paper documents common definitions of longitudinal track resistance and the two methods regularly used for its quantification: track panel pull test (TPPT) and single rail break (SRB). Further, this paper documents the differences in mechanics between these methods, summarizes and discusses the critical factors influencing the longitudinal track resistance values found in the literature, and adds novel TPPT longitudinal track resistance values for timber sleeper track to address the current scarcity of data found in the literature. In summary, TPPT values provide insight into the mechanics of load propagation and pre-buckle analysis while the SRB values aid in the maintenance and restoration of rail neutral temperature after a rail break or destress. Additionally, the TPPT longitudinal track resistance values reported in the literature were independent of panel length, were influenced most by the presence of a vertical load, and were reduced by 25% when the ballast was disturbed. Finally, novel TPPT results indicated the longitudinal resistance of timber sleeper track was 19% lower than concrete sleeper track and that unfastened sleepers still transferred longitudinal load when the cribs were full and ballast was compacted.
Dynamic track stabilizers have been widely used in the maintenance of ballast track, but limited studies have been carried out for the theoretical analysis of track stabilizing operations. In the present study, the structure of ballast track is innovatively established using bi-directional coupling modeling method which include discrete element method and multi-body dynamics method. The model is verified by field experimental data. Based on the tamping operation model, the mechanical properties of the ballast bed after tamping are obtained. Later simulation analysis of stabilizing operation is carried out to explore the change rule of sleeper displacement, particle contact, compaction, resistance and support stiffness of ballast bed. The results show that stabilizing operation can force the sleeper of the new railway line to move down quickly by 5.56 mm. The most significant improvement to the average coordination number between ballast was in the top layer of the crib area, which increased by 19.3%. The most significant area for improving the compactness of the ballast bed is the uppermost layer at the bottom of a sleeper, with an improvement rate of 6.4%. After stabilizing operation, the longitudinal and lateral resistances and supporting stiffness of the ballast track increased by 45.1%, 37.9% and 172.0%, respectively.
Before the operation of newly constructed railways, tamping and stabilizing machines should be used to improve the quality of ballast beds. With the expansion of the railway network and increase of speeds and axle loads, higher quality and efficiency for tamping and stabilizing operation are required. However, previous studies did not involve the effects and parameters of three-sleeper tamping and stabilizing operation under complex working conditions. In the paper, the effect of a three-sleeper tamping and stabilizing machine on the ballast bed state has been studied by performing field experiments. The effect of important factors, including tamping modes, stabilizing frequency, and track lifting amount, are discussed in detail. The results show that the tamping operation on newly constructed railways causes a reduction of the lateral resistance by 56.5 % and a reduction of lateral resistance work by 64.9 %. After the stabilizing operation, the lateral resistance and lateral resistance work are increased by 168.6 % and 209.8 %, respectively. The tamping and stabilizing operation can significantly increase the support stiffness of ballast beds, which meets the requirements of train operation. Meanwhile, 2X tamping mode is more beneficial to improve ballast resistance. Besides, it is reasonable for a stabilizing frequency of 25 Hz to be used for newly constructed railways. The track lifting amount also has a large effect on the ballast bed quality, and it is recommended to keep the lift amount in the range of 20 mm ∼ 30 mm to achieve a better tamping quality.
A ballasted railway track's longitudinal stiffness and resistance with wooden sleepers were experimentally and numerically investigated. The longitudinal resistance was measured by measuring the force and displacement in the rail's axial direction by increasing the number of sleepers from one to five. The track longitudinal stiffness (TLS) and resistance force (TLRF) of the five-sleeper panel in the experiments were obtained as 15.3 kN/mm and 37.2 kN, respectively. The increased ratio of longitudinal resistance force per sleeper with increasing sleepers' numbers was measured constant. Next, a 3D numerical model was built based on the finite element method, it was verified with test results. TLS and TLRF were reported as 36.75 kN and 15.42 kN/mm in the numerical model. TLS and TLS sensitivity analyses were executed with influential parameters such as ballast property and ballast geometry. The models revealed that vertical load (140 kN) had maximum impact on TLRF with the increasing percentage of 190 %. Finally, two equations were proposed to estimate the variation of TLS/sleeper and TLRF/sleeper with R² = 0.95 ∼ 0.97.
Track longitudinal resistance is defined as the resistance generated by sleeper-ballast and rail-sleeper interactions against the imposing forces, which cause longitudinal displacement. This component is one of the important indicators of the continuously welded rail (CWR) track's stability and lateral resistance against buckling. In this paper, the track longitudinal resistance (TLR) and track longitudinal stiffness (TLS) have been investigated to determine the contribution of the fastening system and sleeper in TLR and TLS through laboratory tests and a numerical model. A track panel with one to eight sleepers fastened with 100, 80 and 60 Nm prestressed torqe-force applied to fastening screws was loaded. The average contribution of the sleepers in TLR in the case with a rail-pad for 100 and 60 Nm torque-forces is approximately 30% and 75%, respectively, and the average contribution of the fastening system in the same state is approximately 70% and 25%, respectively.
The longitudinal resistance of ballasted tracks is due to the longitudinal interaction of rail-fastener and ballast-sleeper. Longitudinal resistance is under the effect of various factors as well as the applied vertical load of the running train over the track structure. In this paper, the effect of vertical load on the longitudinal resistance of the ballasted railway track is experimentally and numerically investigated. First, the longitudinal resistance of a 3-m test panel with five B70 concrete sleepers under 0, 100, 200, and 300 kN vertical load were investigated. Second, a three-dimensional model of the track was developed using Abaqus software. Finally, the results of experiments and modeling were compared and the numerical modeling is validated based on tests’ results. In each test, track longitudinal stiffness (TLS) and track longitudinal resistance force (TLRF) were calculated. According to laboratory results, TLS was increased by 3.36, 3.63, and 3.83 times with increasing the vertical load as 100, 200, and 300 kN, respectively. In the mentioned order the increment values for TLRF were increased 2.1, 2.74, 2.97 times. Likewise, the numerical results of TLRF for the above-mentioned load order illustrated increasing values as high as 2.1, 2.6, and 2.81 times, respectively.
Lateral track stability is a critical parameter in ballasted railway tracks considering track buckling. The sleeper type has a direct impact on lateral track stability. Due to the Y-shape sleeper tracks’ truss structure, the lateral resistance increased in comparison with the monoblock sleepers, which is an efficient alternative, particularly in sharp curves. In this study, the lateral resistance of Y-shaped steel sleepers is examined using the single tie push test (STPT) as an alternative for the improvement of lateral ballast resistance. Furthermore, the discrete element method (DEM) was used to estimate the contribution of ballast components to the lateral resistance of the single sleeper. In addition, the effect of shoulder ballast width on the lateral resistance was considered in DEM models. DEM simulations confirmed that the higher sufficient lateral resistance (about 14 kN) could be achieved with a shoulder width of 200 mm.
In this paper, a new test method and a measurement technique were proposed to evaluate the track longitudinal resistance (TLR). The three-stage track longitudinal behavior was assessed. The track longitudinal stiffness (TLS) and track longitudinal resistance force (TLRF) were defined based on the analyses of force-displacement curves in each test. Next, the effect of ballast geometry on these two parameters was scrutinized. The resisting mechanism was described. Finally, the share of ballast geometry components in providing the TLS was determined, and contribution percentages were verified by comparing the results with those of previous studies. Nine test conditions were considered. The ballast depth (BD) was set at 30 cm, 40 cm, and 50 cm. In each ballast depth, the TLR was evaluated with and without the crib and shoulder ballasts. The average values of TLS and TLRF were obtained as 22.94 kN/mm and 35.52 kN, and the total share of the base, crib, and shoulder ballast was calculated as 21%, 67%, and 12%, respectively. It was found that the crib ballast had the most impact on the TLS and enhanced the TLS and TLRF up to 4.11 and 3.25 times.
Track lateral resistance ensures the track stability under operation and during its service life in lateral and longitudinal directions. Numerous methods and techniques have been considered to enhance track lateral resistance. Since sleeper, as one of the railway track superstructure components, has a significant contribution in providing the lateral resistance, using different types of sleepers, like Y-shape one, would alter the track lateral resistance. The utilization of Y-shape steel sleepers in railway tracks needs further investigation to comprehend the structural behavior. Hence, in this paper, the lateral resistance of the Y-shape steel sleeper was experimentally investigated by performing the lateral track panel loading test (LTPT) and single tie push test (STPT). The longitudinal resistance force (LRF) in STPT depends on the loading direction. The LRF was specified as 16 kN in Y-top direction and 13 kN in Y-bottom direction for a single sleeper. The LRF in STPT was enhanced by 90% on average compared to the conventional concrete sleeper. The LRF in LTPT was also obtained as 18 kN, and its increasing percentage was measured as 12.5%.
A ballasted track structure is one of the most representative types of railway construction. Due to the influences of low-temperature rain and snow environments in alpine regions, an in-depth study of the resistance characteristics and evolution patterns of ballasted track beds is urgently needed. A full-scale ballasted track model was constructed in an insulated test chamber with a programmable temperature-controlled environment. The longitudinal and lateral resistances of the ballast bed were tested for different temperature and humidity conditions, and the performance evolution patterns were analyzed. After the failure of the internal ice layers, a resistance test was carried out for the ballast bed in a low-temperature freezing environment, and the influence of the ice destruction on the characteristics of the ballast bed resistance was analyzed. By simulating the low temperature rise environment, the variation patterns of the ballast bed resistance during the freeze–thaw process were tested and analyzed. The results showed the following. The ballast bed resistance in a dry and low-temperature environment was different from that at normal temperature, and the variation with temperature was greater than that at a normal temperature. The resistance of the ballast bed in a wet state decreased compared to that in a dry condition; as the humidity increased from 34% (dry) to 91% (wet), the longitudinal resistance decreased by 22% and the lateral resistance decreased by 17%. The freezing environment could increase the ballast bed resistance when the sleepers had small displacements. However, after the displacement exceeded a certain value (3.8 mm longitudinally and 2.9 mm laterally under the test conditions), the ballast bed resistance was reduced, with the average reduction rates of the longitudinal and lateral resistances reaching 4.55 kN/mm and 2.90 kN/mm, respectively. The rapid rise and fall of the ambient temperature had an enormous influence on the ballast bed resistance. When an ice-water mixture appeared inside the ballast bed at about 0 �C, the longitudinal and lateral resistances were reduced to 31.64% and 30.28%, respectively, of the resistances in a normal situation. The state dependence of the ballast bed resistance on the low-temperature rain and snow environment indicated that more attention is necessary for the complex service characteristics of the ballasted track under similar conditions.
Rail fastening system plays an important role in safety of railway tracks. Despite proven nonlinear mechanical behavior of this system, it has been simulated as a linear spring-dashpot element in the current practice. Discussing this limitation, a nonlinear spring-dashpot element for simulation of vertical behavior of railway fastening system was developed in this study. For this purpose, influences of fastening stiffness, frequency of load and magnitude of preload (as the main influencing parameters) on the mechanical behavior of fastening system were investigated through parametric analyses of fastening systems. To this end, a finite element model of fastening system was developed and validated in this study. Using the results obtained, nonlinear mathematical expressions for the stiffness and damping of fastening systems were derived. The results led to propose a new technique for mathematical simulation/modeling of railway fastening system. Comparison of the results obtained from railway track models with and without consideration of the new simulation technique indicates a considerable improvement (60% in average(in accuracy of theoretical results with the use of nonlinear models. Based on the results obtained, the conditions, in which linear simulation of fastening system provides reasonably accurate results, were derived and discussed.
Lack of lateral resistance is one of the emerging problems in continuously welded rails. Lateral resistance is a type of resistance in which the railway track mobilizes against the applied lateral forces. Thus, curved tracks, especially sharp curves (curves with small radiuses), are the most susceptible segments for the lack of lateral resistance. The reason is, on curved tracks, in addition to the lateral forces applied by the train, longitudinal forces are decomposed into two parts, with one part being tangential (tangent to the curve) and the other part being radial. This radial force causes some defects to the track such as track buckling, transversal shifting of the track, pulling out of fastening shoulders, etc. Therefore, according to the general track instructions, welding of rails is not possible on curved tracks with a radius less than 400 m. With the help of laboratory tests, the authors of this paper previously showed that using two stiffeners under the steel sleeper increased the lateral resistance of the track adequately (by 140%) compared to the track with normal steel sleepers. In this paper, the effect of using two plate stiffeners under the steel sleepers was examined by field investigation on a real track. Two test methods, including the Single Tie (sleeper) Push Test (STPT) and the Multiple Tie (sleeper) Push Test (MTPT), were used to investigate the lateral resistance of the track. The results obtained by the STPT and MTPT methods showed an increase in lateral resistance by 139.6% and 135.5%, respectively. The obtained results are in accordance with the results of the laboratory tests. Moreover, the results showed that using two stiffeners under steel sleepers increased the lateral resistance of the track adequately, thereby enabling rails to be welded on curved tracks.
In this study, the lateral resistance of different types of steel sleepers, placed on the ballast layer with a
variety of shoulder height and shoulder width, has been investigated. A number of single tie push tests
were conducted to examine the effect of bumped-rubber layers and web steel stiffeners on the ballast/
sleeper interaction. In the next step, DEM simulations of STPTs were developed by PFC3D to estimate
the contribution of shoulder ballast height to the lateral resistance of steel sleepers. According to the laboratory
results, the use of 3 web steel stiffeners caused about 70% increase in the lateral resistance in
comparison with the conventional steel sleeper. On the other hand, DEM simulation results indicate that
ballast bed had a higher proportion to the lateral resistance of steel sleepers than that of all the other
ballast components and using web steel stiffeners could increase by 9% the contribution of the bottom
surface of steel sleepers to ballast/sleeper interaction.
In service, railway tracks must withstand the transverse and longitudinal forces that are caused by running vehicles and thermal loads. The mechanical design that adopts any of the track models available in the technical literature requires that the strength of the track is fully characterised. In this paper, the results of an experimental research activity on the sleeper–ballast resistance along the lateral and the longitudinal directions are reported and discussed. In particular, the work is aimed at identifying the strength contributions offered by the base, the ballast between the sleepers, and the ballast shoulder to the global resistance of the track in the horizontal plane. These quantities were experimentally determined by means of an ad hoc system designed by the authors. Field tests were carried out on a series of track sections that were built to simulate scenarios in which the ballast was removed from the crib and/or the shoulder. The results of this study indicate that the strength percent contributions from the crib, the sleeper base, and the shoulder are, respectively, equal to about 50%, 25%, and 25% in the lateral direction, and 60%, 30%, and 10% in the longitudinal direction. Moreover, the comparison of the acquired data with literature results reveals that a detailed knowledge about the testing conditions and the activated ballast failure mechanisms is needed in order to correctly use the test data for the design purpose.
Track buckling in continuously welded rail is a significant problem in the railroad industry [1–3]. Buckling is caused by the buildup of compressive stress (longitudinal force), which is primarily caused by an increase in rail temperature while the rail is constrained and cannot expand longitudinally. The buckling is typically manifested in the wavy lateral displacement of the track over a distance of approximately 100 feet [3]. Because buckling can cause the derailment of a passing train, extensive efforts are spent on preventive maintenance of the track. If a region of rail is known to be in a high state of compressive stress, the rail can be de-stressed by cutting it, allowing it to expand, and then welding it back together. Currently, one of the major difficulties in preventing track buckling is lack of a means for detecting the highly stressed areas.
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.
The Hungarian State Railways (MÁV Rt.) plans to reconstruct the tracks with short rails and rail joints in its trunk line network by continuously welded rails, that is possible by applying, among other technical solutions, the Y-shape steel sleepers. The first track with Y-shape steel sleepers was constructed in Hungary in November 2003, in the Szabadbattyán - Tapolea railway line at the stop of Badacsony. As a consequence of the application of the Y-shape steel sleepers, a continuously welded rail track has been constructed in a curve with a radius of R=300 m, where previously there had to be rail gaps and rail joints with the concrete sleepers. On behalf of the Hungarian State Railways (MÁV Rt.), the Budapest University of Technology and Economics, Department of Highway and Railway Engineering carried out research series on the track with Y-shape steel sleepers under operation. The series of track measurements had the following aims: 1 to assess the technical parameters of the track with Y-shape steel sleepers, 2 to compare the technical parameters of the Y-shape steel sleepered track with those of a track with concrete sleepers, 3 to determine how these parameters change with time. The track measurements included three series: 1 determining the displacements of the sleepers and the rails under dynamic load of a locomotive, 2 measuring the lateral displacement of the track in a curve, perpendicular to its centre line due to the change of temperature between the variation summer and winter, 3 assessing the graph of the track examination coach. In this paper, the first two subjects will be discussed. The third theme of the research will be investigated in another paper. In Chapter 2, the Y-shape steel sleepers and the tracks constructed with them are described technically in general. The first track section constructed with Y-shape steel sleepers in Hungary is introduced in Chapter 3. Chapter 4 discusses the measurements and their results carried out on the track with Y-shape steel sleepers in Hungary. An evaluation of the results and of the track is given in Chapter 5.
Continuously welded rails are a common remedy to prevent rail defects, including railhead batter, rail cracking or breakage, and lateral displacement of track, among others. However, at curves with a radius of less than 400 m, rail welding is practically impossible due to the lack of track lateral resistance. Therefore, finding a new method to increase the track lateral resistance is necessary to facilitate rail welding, especially on tracks with steel sleepers. This study proposes a new method of increasing the lateral resistance of a ballasted track with steel sleepers by using web stiffeners. The effect of such stiffeners is investigated through a comparison with tracks having regular steel sleepers. The single tie (sleeper) push test is used in this research. The results of the experimental investigations show that the lateral resistance increases by 24, 140, and 203 percent, respectively, with the use of one, two, and three web stiffeners under the steel sleeper compared with a steel sleeper without stiffeners. Thus, the use of two stiffeners is concluded to provide enough lateral resistance in the case of older tracks. Therefore, the welding of rails at tight curves becomes conceivable.
In this paper, the influence of modeling the fastening with solid railpads on the vertical dynamics of railway tracks with monoblock sleepers is investigated. A 3D finite element (FE) model is presented with four different fastening representations: (1) commonly used spring-damper pair, (2) area covering spring-damper pairs, (3) solid railpad connected to the rail, and (4) solid railpad in frictional contact with the rail and fixed to the support by preloaded springs, which represent the clamps. The response of the four models to hammer excitation is simulated in the time domain, and the calculated response is transformed into the frequency domain to analyze how the models capture the seven main characteristics of tracks with monoblock sleepers. The numerical results show that the model with solid railpads and clamps reproduce the seven characteristics at a maximum frequency difference of 6%, while the conventional model with spring-damper pairs reaches only a 27%. In the improvement of the fit from multiple spring-damper railpad models to solid railpad models, the two key aspects identified are the Poisson׳s effect and the damping of the ballast. Additionally, the railpad type investigated showed a frequency-independent behavior, at least with acceptable error. In view of the close fit, the models with solid railpads can be used for track and fastening design and to derive track parameters to, for instance, study the deterioration of tracks.
This paper aims at studying the behavior of a railroad track concerning the action of longitudinal forces, targeting the determination of the track-ballast resistance, in a real scale standard track model. This research, was developed at the São Paulo State University, and consisted of a comparative study of track-ballast resistance for railroad tracks built with four different types of sleepers. The first set of sleepers was made of steel, the second one was made of wood, the third one of prestressed-concrete and the fourth one of two-block concrete. In order to carry out this research, four 1600 mm gauge models were built with two TR-68 rails, fastened to seven sleepers by means of elastic fasteners and base plates. The sleepers, all of the same type for each model, were embedded in 0.35 m thick ballast, which was supported by a layer of 30 cm thick compacted soil. The computerized data acquisition system allowed displacement and force values to be obtained in real time. By convention, the maximum longitudinal track-ballast resistance corresponds to a displacement of 15 mm. The prestressed-concrete sleeper setup showed the greatest longitudinal track-ballast resistance per sleeper. The second best performance was obtained by the two-block concrete sleeper setup, followed by the wooden and the steel sleeper setups. The force-displacement curves showed an exponential rise to a maximum shape. The displacement corresponding to the maximum track-ballast resistances were different for each kind of sleeper setup. Correlations between forces and displacements (N= f (d)) were obtained for each type of sleeper. The relative displacements between the rails and sleepers were negligible, showing that the adopted elastic fasteners can bear the forces originated from the displacements of the track setup embedded in the ballast. The measured and analyzed data provided unpublished important parameters for the project of modern and permanent railroads using welded long rails.
Three-dimensional elastoplastic finite-element (FE) simulations of ballast deformation in a track with focus on lateral resistance have been conducted. Ballast geometry, vertical and lateral loading, and friction between ballast and sleeper are being varied in a parametric study. Sleeper displacements are studied under different conditions in order to find out which lateral resistance the ballast will provide and how this resistance depends on the various parameters. In addition to extending the state of the art, the knowledge gained in the study will be essential in the design of a structural element to represent the ballast in a model of the full track that is to be used for analysing lateral track stability [1, 2].
ERRI DT202/DT363, in Improved knowledge of forces in tangential tracks including switches,Determination of lateral and longitudinal ballast resistance of a railway track by experimental tests
- E R Institute
Parametric analysis and safety concepts of CWR buckling
- G Samavedam
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