Concrete Sleepers Research Articles

Numerical and experimental evaluations of the impact attenuation of a rail-fastening assembly

The stability of railway tracks relies on a complex arrangement of rail, rail pad, rail clip, sleeper, and ballast. Impact forces from wheel-rail irregularities can lead to concrete sleeper cracking. Traditional experimentation to assess impact attenuation of a rail-fastening assembly (BS EN 13146-3) is both costly and time-consuming. In this study, an experiment-finite element analysis coupling method was utilized. Dynamic properties of the rail pad were experimentally determined and incorporated them into finite element analysis (FEA) to simulate impact attenuation, which was then experimentally validated. Investigating the damping constant ( cP) and dynamic stiffness ( kP) of the rail pad revealed that while increasing cP doesn’t significantly alter sleeper strain, reducing kP decreases the initial peak strain. Therefore, the impact attenuation is primarily influenced by kP. This approach not only reduces evaluation costs and time but also aids in rail-fastening assembly design, analysis, maintenance, and development.

Fabrication and Characterisation of Kenaf Fibre Reinforced Polyamide Biocomposites for Railway Sleeper Applications

Railway passing traffic, speed, and load have significantly increased over the years, prompting industry stakeholders and researchers to seek an alternative sleeper material that can demonstrate its ability to potentially possess higher in-service bending resistance and be environmentally friendly and durable. To address these needs and due to environmental concerns, kenaf-reinforced polyamide has become of great importance. However, they could not be applied as railway track components because of the non-availability of their performance in this regard. In bridging this gap, this paper focused on fabricating and characterising six different formulations of treated kenaf fibre (TKF, 0–50% at 10% loading interval) reinforced polyamide biocomposites for railway sleeper applications. The result showed that the incorporation of TKF influenced the behaviour of the polyamide with respect to its water absorption, load-carrying capacity, and thermal stability. The result further demonstrated that the load-bearing capacity peaked at TKF 40 wt.%, surpassing conventional wooden and concrete sleepers. However, its water absorption (64-days saturation) behaviour increased significantly between 11%–21% as TKF rose from 10–50 wt.%, as expected due to TKF hydrophilic characteristics. On the other hand, TKF thermal stability was hampered beyond approximately 220°C for all TKF percentages. Kenaf fibre-reinforced polyamide biocomposites have demonstrated their potential for railway sleeper applications as their load-bearing capacity exceeded the minimum recommended AREMA specifications. Despite the milestone achieved, water absorption of kenaf fibre remained high. The development of sustainable and effective materials to meet the changing needs of contemporary railway infrastructure is greatly aided by the insights gained from this study.

Estimation of sleeper-ballast contact pressure based on fretting marks: field measurements and FEM modeling

The contact conditions between components of railway infrastructure are complex. This research focuses on the contact interactions between the ballast and steel sleepers. Unlike the prismatic design of concrete and wooden sleepers, steel sleepers are characterized by a unique U-shaped configuration, further contributing to the complexity of the contact conditions. To address this issue, this study focused on analyzing the lower surfaces of steel sleepers commonly used in railroads, which had contact marks resulting from the ballast and train load due to fretting. To simulate these contact marks, virtual ballast geometries were created and simplified to match the observed contact areas. Specifically, these contact areas represented 6% of the bottom area of the steel sleepers. We compared the efficiency of this approach using Finite Element Method simulations.

Swiss railway field laboratory: analysis of two years' data collection

Since May 2022, a 1 km long section of the regular train network of Switzerland between Lucerne and Olten has been equipped with a variety of sensors and microphones. The superstructure of this test track was renewed in December 2019 and consists of ballasted track with concrete sleepers, in part with and without stiff under sleeper pads, respectively. Since June 2022 the sensors and microphones have continuously recorded pass-by data for sound, vibration and track dynamics for every passing train. This long-term measurement installation allows studying different environmental influences on noise and vibration. The very large amount of data enables both statistical analysis and building statistical models. Furthermore, the railway field lab can be used determine the influence of different track components. In this paper, we report on our statistical analysis of the data gathered since June 2022 including statistical models of the influence of the environment and of different rolling stock on sound and vibration. Furthermore, we present the results of a novel high damping rail pad tested at the railway field lab. Based on these results, we present a proposal and discuss our thoughts on the best practice for measuring acoustic quantities.

Axial compression stress-strain relationship of lithium slag rubber concrete

Replacing cement with lithium slag and fine aggregate with rubber in concrete solves waste disposal, reduces material consumption, boosts sustainability, and enhances concrete performance. A set of prismatic concrete specimens with varying proportions were designed and experimentally tested in order to study the compressive stress-strain behavior of lithium slag rubber concrete (LSRC). The main factors affecting the specimens were lithium slag substitution ratio (SL=0%, 10%, 20%, 30%) and rubber substitution ratio (SR=0%, 5%, 10%, 15%). The results demonstrated that the LSRC exhibited good integrity during the damage. Furthermore, the incorporation of lithium slag (LS) was found to effectively compensate for the reduction in compressive strength due to the incorporation of rubber. When 10% of the fine aggregate was replaced with rubber and 20% of the cement was substituted with lithium slag, the axial compressive strength, elastic modulus, and peak strain of the tested specimens increased by 21.57%, 6.92%, and 17.26%, respectively. Compared with ordinary concrete, LSRC has good toughness, impact resistance and durability with minimal loss of strength, and has broad application prospects in engineering fields (such as airports, highways, housing expansion joints, concrete floors and railway concrete sleepers, etc.). Based on the experimental data, simplified modified equations to predict the compressive strength, elastic modulus, peak strain and axial stress-strain constitutive model of LSRC were proposed, so as to promote the development of LSRC.

IMPACT THE TREATMENT TYPES OF RECYCLED CONCRETE AGGREGATES ON CONCRETE STRENGTH

Problem statement. The National Strategy of waste management in Ukraine until 2030 provides the creation of conditions for market development of usage recycled construction and demolishing waste including the ways of characteristic determination to obtain the regulations for recycled construction and demolishing waste that will let re-use and disposal. One of ways the re-use of deconstructed concrete is the obtaining coarse and fine aggregates for subsequent manufacturing of building materials and products. The ordinary way of recycled aggregates obtaining includes crushing stages that do not allow recovering the purified, i. e. cement-free, aggregates. Therefore, it is necessary to search the effective methods of treatments for producing high quality recycled aggregates. The purpose of the article is compressive strength evaluation of concrete samples with usage of aggregates obtained from waste of railway reinforcement concrete sleepers. The comparison of concrete strength has been done for coarse aggregates which are cleaned with mechanical treatment or impregnation by sodium silicate solution. Conclusions. It is established that both the mechanical purification from old cement-sand mortar rests and impregnation enhance physical and mechanical properties concrete comparing to concrete with untreated aggregates. The mechanical treatment increases the compressive strength and reaches 98 % of compressive strength for concrete with natural aggregates. The impregnation of sodium silicate increases at 10 % concrete strength compare with strength of concrete with untreated aggregates. So, both treatment methods of recycled coarse aggregates can be used for concrete manufacturing with appropriate strength.

Selection of railway track superstructure design: Modern outlooks

The paper analyses the reasons for the current opinion that a higher mass of superstructure elements is necessary for railway track sections with higher traffi c density, speed and axial loads. With the help of known theories and the new one developed by the author that takes into account the time factor, it is proved that in terms of all the most signifi cant technical indicators the best solution within the realistic limits is to use lower-mass rails and reinforced concrete sleepers. The most essential argument in favour of the smaller mass of rails per unit length is the increased track stability produced by longitudinal compressive forces in rails. A reinforced concrete sleeper of a smaller mass has been proposed and tested that increases the resistance to shear in ballast across the track axis at least two times. For stable pressing of rails to sleepers by intermediate fasteners, elastic clips should be made of plate steel instead of bar steel. It is proposed to make a plate clip shaped as a ‘fish-bellied beam’. Specific examples of the proposed solutions for rails, reinforced concrete sleepers, and intermediate fastenings are given.

STUDY OF THE DESIGN OF RAILWAY TRACKS OF INDUSTRIAL ENTERPRISES WITHIN THE AREAS OF SMOOTH TRACK EXPANSION

The goal. Railway sidings of industrial enterprises are the shippers and receivers of goods, which determine their main nomenclature for transportation by mainline rail transport. The length of railway sidings of industrial enterprises varies widely, from a few hundred meters to hundreds of kilometers, including the length of the siding of PJSC ArcelorMittal Kryvyi Rih exceeding 700 km. The combination of factors such as the presence of technological transportation on the sidings, the development of the industrial enterprises' transportation system over time, and the master plan of the main production facilities leads to the need to apply railway transport design standards for severe and especially severe conditions. This is mainly expressed in reducing the radii of curved track sections to the minimum possible values. When using reinforced concrete sleepers of the Sh6 type, it is possible to arrange a track gauge of 1539 mm in curved sections. But currently, there is no approved design for smooth track widening sections on reinforced concrete sleepers in front of curves with radii of less than 300 meters. There is also a reasonable need to increase the track gauge to at least 1540 mm in curves of such radii. Together with the limited service life of wooden sleepers when they are laid in areas of smooth track widening compared to reinforced concrete sleepers, this necessitates the development of a track structure on reinforced concrete sleepers within the area of smooth track widening. Methods. Methods of scientific analysis and synthesis of the track development structure, methods of analytical geometry. Results. Based on the analysis of the design of intermediate fasteners of the KB50 type, the design of a section of smooth track widening using reinforced concrete sleepers of types Sh1-1 and Sh6 and rails R50 is proposed. The track widening from 1520 to 1545 mm is achieved by developing the order of laying sleepers of different types and turning the KB50 substrates. In this case, the length of the section of smooth track widening from 1520 mm to 1545 mm is 2800 mm, and the actual deviation is 8.9‰. Practical significance. The use of the considered structure within the areas of smooth track widening, provided that the results of trial operation and testing of the established procedure are positive, will reduce the operating costs associated with the current maintenance of industrial enterprises' tracks, the parameter of which correspond to severe and especially severe design conditions.

CONSTRUCTION OF THE RAILWAY TRACK OF UKRAINE AND PROSPECTS FOR THEIR IMPROVEMENT

The goal. The process of improving the design of the railway track requires a detailed study of the history of the development of its structural elements, methods of combination, interconnections and limits of mutual influence. Modern track designs are the result of many years of hard work by scientists and long operational tests. Some designs were inventions at the time, some were breakthrough technologies, some remained just ideas, and some have existed for more than a century. The study of the history of the development of railway track structures and modern existing structures in operation made it possible to identify a promising direction for improvement and further development, taking into account the existing problems on the mainline transport tracks and industrial enterprise tracks. Reinforced concrete sleepers and intermediate fasteners that allow for track gauge adjustment are the railroad track structure that should be improved in the coming years. Improving railroad track design is a continuous process in the development of rail transport. Recently, new track designs have been introduced on Ukrainian railways. As a rule, the problems of track facilities are first considered and technical tasks are formulated. Then, a public discussion is held in the scientific and practical environment and an appropriate development strategy is born. Such a strategy is reviewed and approved at scientific and technical meetings and specialized commissions. This article aims to identify promising areas for improving the track design and solving the problems of installing and operating a continuous track by analyzing existing designs and world experience of railways. Methods. Methods of scientific analysis and synthesis of track development design, methods of analytical geometry. Results. Based on the analysis of the history of the development of the railroad track structure and modern designs, a promising direction of improvement is proposed. A promising railroad track structure is defined as a reinforced concrete sleeper and fasteners capable of forming an adjustable track gauge of up to 1545 mm. At the same time, it is necessary that the new design has sufficient stability of the jointless track plates. Practical significance. The application of the proposed structure within small radius curves, provided that the results of trial operation and testing of the established procedure are positive, will reduce the operating costs associated with the current maintenance of the tracks, expand the scope of laying of the jointless track and use reinforced concrete sleepers in small radius curves at industrial enterprises.

Automatyczna diagnostyka elementów toru kolejowego z użyciem sieci neuronowych głębokiego uczenia

The article discusses a method for automatic diagnostics of a railway track. It consists in automatic evaluation of the technical condition of selected track elements, such as rails, wooden and concrete sleepers, fasteners and turnouts. It was carried out on the basis of analysis of video images of railroad track elements recorded by two line cameras placed on the diagnostic carriage. The selected FCN-8 deep learning neural network was used to assess the technical condition of the surveyed elements, and the effectiveness of the applied algorithm was determined on the basis of such measures as IoU, Precision, Recall. Conclusions on the application of the FCN-8 network in the automatic classification of features of selected railroad track elements are presented. The results obtained were compared with other methods used in vision diagnostics.

Effect of the Particle Size Distribution of the Ballast on the Lateral Resistance of Continuously Welded Rail Tracks

While the effect of ballast degradation on lateral resistance is noteworthy, limited research has delved into the specific aspect of ballast breakage in this context. This study is dedicated to assessing the influence of breakage on sleeper lateral resistance. For simplicity, it is assumed that ballast breakage has already occurred. Accordingly, nine granularity variations finer than No. 24 were chosen for simulation, with No. 24 as the assumed initial particle size distribution. Initially, a DEM model was validated for this purpose using experimental outcomes. Subsequently, employing this model, the lateral resistance of different particle size distributions was examined for a 3.5 mm displacement. The track was replaced by a reinforced concrete sleeper in the models, and no rails or rail fasteners were considered. The sleeper had a simplified model with clumps, the type of which was the so-called B70 and was applied in Western Europe. The sleeper was taken into consideration as a rigid body. The crushed stone ballast was considered as spherical grains with the addition that they were divided into fractions (sieves) in weight proportions (based on the particle distribution curve) and randomly generated in the 3D model. The complete 3D model was a 4.84 × 0.6 × 0.57 m trapezoidal prism with the sleeper at the longitudinal axis centered and at the top of the model. Compaction was performed with gravity and slope walls, with the latter being deleted before running the simulation. During the simulation, the sleeper was moved horizontally parallel to its longitudinal axis and laterally up to 3.5 mm in static load in the compacted ballast. The study successfully established a relationship between lateral resistance and ballast breakage. The current study’s findings indicate that lateral resistance decreases as ballast breakage increases. Moreover, it was observed that the rate of lateral resistance decrease becomes zero when the ballast breakage index reaches 0.6.

Aspects of Modeling Prestressed Concrete Sleepers Subjected to Positive Moment Test at Midspan

Aspects of Modeling Prestressed Concrete Sleepers Subjected to Positive Moment Test at Midspan

Effect of Graphene Quantum Dots (GQDs) on the mechanical, dynamic, and durability properties of concrete

Addressing ecological concerns stemming from concrete usage is paramount, prompting exploration into additives for mitigation. Graphene quantum dots (GQDs) have been recognized for their potential to improve the mechanical attributes of cement composites. Additionally, the electrochemical reduction of a saturated solution of carbon dioxide (CO2) and monoethanolamine (CO2-MEA) effectively removes CO2 from the atmosphere. This study delves into the influence of GQDs on the mechanical and durability aspects of concrete. It is noted that the control mix of concrete without GQDs was specifically designed for concrete railway sleepers. Varied proportions of GQDs, ranging from 0.3 % to 1.2 % at 0.3 % increments, were incorporated to assess their impact on fresh and hardened concrete properties. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength, and dynamic properties were evaluated. Durability assessments encompassing water absorption and chloride ion penetration were conducted. Microstructural analysis via Field Emission Scanning Electron Microscopy (FESEM) imaging and Energy-dispersive X-ray spectroscopy (EDS) elucidated the concrete's internal composition. Notably, an optimal GQDs percentage of 0.3 % was observed, signifying its efficacy in enhancing the performance of concrete. When 0.3 % of GQDs was added to concrete, compressive strength, split tensile strength, and flexural strength were enhanced by 10.8 %, 23 %, and 11 % respectively. The incorporation of GQDs resulted in a notable improvement in the fundamental frequencies and dynamic modulus of elasticity. Concurrently, a decrease in the damping ratio was observed for specimens containing GQDs. Additionally, the porosity and chloride penetration depth were lower by 6 % and 30 % for specimens with 0.3 % GQDs. The improvement in workability, mechanical, and dynamic properties of concrete, along with reducing CO2 from the atmosphere, makes GQDs an ideal eco-friendly material. This study is the first to open new pathways for the development of construction materials that are not only structurally superior but also environmentally responsible, marking a significant step forward in the field of civil engineering materials, especially in railway applications.

Finite Element Axisymmetric Models for Conical Wedge Anchorage Used in the Production of Prestressed Steel Reinforced Concretes

The anchor system plays a very important part of the prestressed structure, that contacts and transmits force to the cables when stretching to create residual stress. The operating conditions of the anchor system in general and the anchor core in particular are extremely harsh. In this paper, <I>ABAQUS</I> software was applied to model and numerically simulate the axisymmetric loading process of the anchor core in manufacturing prestressed concrete sleepers, to study the effects of tensile forces to the pressure resistance of the cylinder. To verify the analytical results, a Finite Element (<I>FE</I>)-model with the same material and geometrical properties was created. The difference is the assumption of plane stress in the analytical solution, can be solved using two - dimensional finite elements, which are most conveniently described in cylindrical (<i>r, θ, z</i>) coordinates. This articles also especially focused on calculating the change of stress on the edges of the anchor core teeth with different tensile forces. We also refered to experimental results to get data on traction force and working conditions to build a calculation model and select input parameters. Comparison of the stress generated on the teeth of the anchor core was performed with three different tensions of <i>171, 181</i> and <i>191 kN</i>. The maximum and concentrated stress at the top and root of the anchor core when tensioning the cable has been calculated.

Elastic discrete element analysis of natural vibration characteristics and settlement behavior of railway ballasted track

An elastic multi-body model of a ballasted track, consisting of an aggregate of ballast gravel and a single prestressed mono-block concrete sleeper, is constructed. Field-measured traffic load waveforms from an operational existing railway track are then applied to the left and right rail positions on the upper surface of the model using elastic discrete element method. The numerical results are subjected to frequency analysis to examine the relation between track settlement and natural vibration phenomena in ballasted tracks. The relative error between the measured and analyzed frequency values for the natural vibration modes of the ballasted track under 500 Hz is 2.23%, indicating that the current ballasted track model accurately reproduces the natural vibration characteristics of existing ballasted track structures. The analysis results reveal that the phenomenon of plastic deformation within the ballast layer occurs primarily in the upper part of the ballast layer, just below the sleeper. Additionally, for the bounce mode of the ballast layer in the frequency range of generally 100 Hz and below, it has been identified as the primary factor promoting significant vertical motion of the sleeper, along with the associated reverse U-shaped deformation of the sleeper, which accelerates the track structure degradation. Furthermore, when loosening occurs, the vibrational energy of this bounce mode increases, contributing directly to ballast degradation.

Sustainable Materials in Concrete Railway Sleepers: A Review of Current Developments and Future Prospects

Concretes have been the favoured material to make concrete railway sleepers due to better accessibility and weather compared to their timber counterparts. Railway sleepers are crucial infrastructure and 5% of concrete sleepers fail prematurely. Sleeper failure could result in catastrophic railway accidents. Hence, improvement is needed in the concrete sleeper mixes. Previous literature has identified two methods of improving concrete strength in concrete mixes with wastes, through replacement of concrete constituents or the use of alkali-activated materials. Use of wastes as partial concrete material replacements reduces the volume of concrete materials while alkali-activated material forms a concrete-like compound that eliminates the use of cement. These methods improve the strength performance and sustainability aspects of the concrete. While many studies have been conducted on these two types of sustainable concrete, their application in concrete railway sleepers has not been investigated. Thus, this paper looks to review the two different types of sustainable concretes through some previous literature that has been conducted on its application in concrete railway sleepers as well as those that have yet to be studied. Ultimately, identifying the best sustainable materials for concrete railway sleepers.

Analysis of the structural behavior of reinforced concrete components with acoustic emission analysis

The use of non-destructive testing methods can provide insights into processes within the interiors of structures. Acoustic emission testing is one of the non-destructive testing methods that allows the detection of material damage during its occurrence. When structures, such as concrete components, fail under load, elastic waves are generated, propagating within the component. These signals can be detected by acoustic emission sensors placed on the surface of the component, enabling the tracking of the material's condition and the location of failure. This paper summarizes recent applications of acoustic emission measurements on large-scale laboratory specimens made of reinforced concrete. The first example describes measurements during a tensile fatigue test on a large- scale reinforced concrete specimen to investigate the fatigue behaviour of an embedded concrete dowel. The second example involves measurements during a dynamic three-point bending test to examine the fatigue behaviour of a prestressed concrete railway sleeper. The third example describes a full-scale test conducted on a flat slab concrete test specimen with dimensions of 2.8 m × 2.8 m. The objective of these investigations is the development and optimization of new components to enhance punching shear resistance and provide an economical solution. To detect microcracking during loading acoustic emission measurement has been carried out using broadband sensors with a measurement frequency of up to 200 kHz which were especially developed for the detection of microcracks in concrete. For the three-dimensional location of the acoustic emission events, 16 of these acoustic emission sensors were attached to the surface of the specimens. Most of the events were in the centre of the sample in the punching area. These events form a circular structure with a diameter of approximately 1m. A visual inspection of the sample after the experiment shows that macroscopic cracks have formed in this area, which extend up to the surface of the sample.

Laboratory and Numerical Investigation of Pre-Tensioned Reinforced Concrete Railway Sleepers Combined with Plastic Fiber Reinforcement.

This research investigates the application of plastic fiber reinforcement in pre-tensioned reinforced concrete railway sleepers, conducting an in-depth examination in both experimental and computational aspects. Utilizing 3-point bending tests and the GOM ARAMIS system for Digital Image Correlation, this study meticulously evaluates the structural responses and crack development in conventional and plastic fiber-reinforced sleepers under varying bending moments. Complementing these tests, the investigation employs ABAQUS' advanced finite element modeling to enhance the analysis, ensuring precise calibration and validation of the numerical models. This dual approach comprehensively explains the mechanical behavior differences and stresses within the examined structures. The incorporation of plastic fibers not only demonstrates a significant improvement in mechanical strength and crack resistance but paves the way for advancements in railway sleeper technology. By shedding light on the enhanced durability and performance of reinforced concrete structures, this study makes a significant contribution to civil engineering materials science, highlighting the potential for innovative material applications in the construction industry.

Improving the mechanical performance of railway concrete sleepers using recycled materials: An experimental and numerical study

This paper explores the use of three waste materials available in vast quantities, including waste tires, glass bottles and bamboo furniture, in the manufacture of railway sleepers. Mechanical properties of recycled concrete have been studied to establish an optimal mix suitable for concrete railway sleeper manufacturing. Thus, 5%, 10%, 15% and 20% recycled rubber sands (RRS) by volume of fine aggregate are used instead of 30# and 60# mesh sizes of fine aggregate. Moreover, 20%, 40%, 60%, 80% and 100% of aggregate volume are replaced by recycled glass aggregate (RGA) particles. Furthermore, different percentages of recycled bamboo fibers (RBF) have been used as 1%, 2% and 3% by volume of concrete. According to the optimal concrete mixtures of RRS, RGA and RBF, twelve concrete railway sleepers are manufactured and tested for middle and rail seat bending strengths. Results show that ref. sleeper has almost 16% and 24% lower strengths than RGA sleeper in middle and rail seat, respectively, while ref. sleeper have higher strengths by 16% and 13%, and 18% and 7% than RRS sleeper (M60-R5) and RBF sleeper (B2) in middle and rail seat, respectively. The FEM results show that the ([Formula: see text]) of the RGA sleeper is the minimum ratio by 1.11 and 1.13 for rail seat and middle of sleeper, respectively, which is the best performance. In RBF sleeper FEM model, Bamboo fiber can only bear 5% and 8% of total stress in middle and rail seat, respectively, due to low mechanical properties of fibers.

Numerical simulation analysis of sleeper damage under dynamic load based on discrete element method

To analyze the damage development of concrete sleepers during railway operation, the discrete element method and the parallel bond degradation model are introduced into the damage analysis of concrete sleepers for the first time. The cracking resistance and dynamic characteristics of the sleeper model are verified by comparing the existing literature. The influence of load and the stiffness of the bottom support on the damage development of the sleeper is considered and the following conclusions are drawn: with the increase in the load amplitude, the damage of the sleeper will increase nonlinearly; under the conditions of the same time and the same load amplitude, the number of cracks of the sleeper will increase with the increase of load frequency, and increase exponentially with the number of loads. Different support stiffness at the bottom of the sleeper will change the dynamic characteristics of the sleeper under load, thus changing the damage development of the sleeper. For the sleeper with full support at the bottom, when the support stiffness at the bottom is low, the center of the sleeper is more likely to be damaged. When the support stiffness at the bottom of the sleeper is large, hanging the center of the sleeper about 1/3 of the length of the sleeper can reduce the damage to the center of the sleeper. The research results show that this method can be applied to the study of sleeper damage and provide a new idea for the structural damage of sleepers.