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In the present work, the influence of the ballast-deck interface on the dynamic response of single ballasted track, simply supported high speed railway bridges is investigated. The ballasted track railway bridge is modelled by a composite Euler-Bernoulli beam with two layers connected between them through longitudinal springs and dampers representing the nonlinear friction behavior occurring at their interface. A constant moving load model termed (HSLM-A) is utilized to simulate the moving trains. The governing nonlinear transverse vibration equation of the system has been derived by using the Hamilton’s principle. By applying the Galerkin method and using the Differential Quadrature Method (DQM) and the Integral Quadrature Method (IQM), the time history of the studied beam is numerically solved by the Runge-Kutta scheme. Considering two railway bridges having different lengths, the obtained results have shown that the dynamics of the system is governed essentially by a Duffing like oscillator, where the ballast superstructure contributes through both additional nonlinear stiffness and damping. The ballast-bridge interface was found to affect largely the dynamic response at resonance of short-span bridge than that of lengthier structures. In this last case the ballast influence can be reduced to just an additional mass.

Monoblock prestressed concrete sleepers are the most dominant type of sleepers in ballasted railway tracks. As such, it is important to provide optimized designs to the concrete sleepers and the associated fastening systems to ameliorate railway safety and to save both capital and maintenance funds. Therefore, a three-dimensional finite element railway model was created and verified. The response of both concrete sleepers and fastening components to coupling vertical and lateral loading was quantified. Such loading form typically occurs at horizontal railway sections causing damage to the railway track components. The influences of the sleeper spacing, elastic modulus of the rail pad, and friction coefficient at the contact surfaces of the rail and sleeper with the rail pad under varied lateral loadings were investigated. The interaction influence between parameters was thoroughly discussed. Among the studied parameters, the finite element model outcomes showed that the elastic modulus of the rail pad and the coefficient of friction are the most critical parameters with respect to the lateral load path and the local response of concrete sleeper and fastening system, especially at high lateral loadings. By using a relatively soft rail pad (elastic modulus = 100 MPa), the concrete material remained below the compressive and tensile fatigue limits even under high lateral loadings provided that the coefficient of friction remains limited to 0.3. By contrast, for a given lateral to vertical loading ratio, a continuous increase in the developed stresses of the concrete material and rail pad was detected as the elastic modulus changed from 100 MPa to 2000 MPa and the coefficient of friction increased from 0.3 to 0.9. The influence of sleeper spacing on the behaviour of railway tracks is only tangible on the distribution of the vertical wheel load. Lastly, the peak stress magnitudes of the ballast bed could be increased by 50% as the lateral to vertical loading ratio reached 0.6 compared to the case where the lateral load is absent. The experience gained from this article would help to formulate specific recommendations to improve the design of concrete sleepers, fastening systems, and ballast bed.

Recently, attempts have been made to replace wooden sleepers with concrete sleepers with expanded sleeper spacing, especially on conventional railway lines. By extending sleeper spacing in the replacement process, the number of sleepers required is lower. A reduction in the number of sleepers can reduce replacement costs. Behind this attempt to change materials and spacing is the generally held notion the lateral resistance of a ballast is unchanged after the change in the sleeper spacing, whether it is a wooden or a concrete sleeper. However, the changes in the interference degrees of adjacent sleepers and in the rail weight supported by each sleeper are expected to affect the lateral resistance of the ballast. They can change the lateral stability of ballasted tracks in a more complicated fashion than the simple effect of a reduced number of sleepers. However, the current standard design does not consider the combined effects of these changes on the lateral resistance of a ballast. Accordingly, the design of ballasted tracks with extended sleeper spacing cannot be optimized. Therefore, the aim of this study was to investigate the lateral resistance characteristics of a ballast as associated with changes in the sleeper spacing of conventional railway lines. First, single-sleeper pullout tests were conducted on models based on various sleeper spacing conditions to evaluate the lateral resistance of the ballast. The effect of the rail weight on the lateral resistance of the ballast was determined from the test results. An increased frictional resistance at the sleeper bottom was considered to contribute to an increase in the lateral resistance; thus, the friction angle between the ballast and sleeper bottom was used to evaluate the degree of increase. Subsequently, track panel pullout tests were conducted by simulating an expansion of the sleeper spacing. Based on the test results, the effect of the interference between adjacent sleepers on the lateral resistance per sleeper was investigated. The obtained results were quantitatively modeled as a function by using the sleeper width as a parameter (as normalized by the sleeper spacing). Finally, a new approach was proposed for estimating the lateral resistance of a ballast which considered the change in the sleeper spacing for conventional railway lines. The method considered the combined effects of change in the interference of adjacent sleepers and in the rail weight supported by each sleeper on the lateral resistance. Based on the results calculated by the proposed method, practical applications were examined by determining the extent to which the sleeper spacing could be increased without reducing the lateral resistance of the ballast when replacing wooden sleepers with concrete sleepers. It was demonstrated that the proposed method could improve the estimation accuracy of the lateral resistance of a ballast track with extended sleeper spacing.

Progressive updating strategies are commonly used for the calibration of numerical models such as those of a track-bridge system. These strategies involve, first, updating the track model based on dedicated dynamic tests, and second, the calibration of the bridge model based on ambient vibration tests considering the updated track parameters. This subsequent procedure is suggested as some track parameters are, in relation to the modal responses of the bridge, generally not sufficiently sensitive for a successful parameter estimation. This work describes the calibration of a specific finite element (FE) model of a track section over a bowstring-arch railway bridge. The model includes the rails, rail pads, sleepers, the ballast layer and the interfaces with the bridge and neighbouring track sections. A track receptance test allowed for the identification of natural frequencies and mode shapes of the track by applying two different techniques, an output-only and an input-output. Several modes of vibration related to the movement of the sleepers on the ballast were identified using the SSI-DATA method, at frequencies between 83.8 Hz and 142.2 Hz. The calibration of the track FE model was performed using an iterative methodology by means of a genetic algorithm, which proves efficiency and robustness in estimating several track numerical parameters, besides a significant upgrade in relation to the numerical model before calibration.

With increasing demands for higher axle loads and line speeds, designers are left with no choice but to significantly increase track bed design thickness to accommodate the new operating conditions...

Current structural models used for the flexural design of prestressed concrete sleepers assume that ballast bearing support is static and located within a fixed region. This assumption implies a linear relationship between wheel load and bending moment. However, field data gathered from instrumented sleepers shows that this trend is non-linear, and the difference in flexural behavior between model predictions and field-measured demand is significant. Using back-calculation techniques and the development of a sleeper support analysis tool, this paper investigates the load-dependency of sleeper support condition. It is hypothesized that a given support condition redistributes ballast reaction forces due to the mechanical interaction of ballast particles with the sleeper’s deflected shape. It was found that redistribution of support conditions can reduce the expected flexural bending moment up to 45% when compared with moments calculated using traditional design guidelines. This effect (non-linearity) is greater as wheel loads increase. Results from revenue service field experimentation provided insight into the interaction between sleeper and ballast and serve as a foundation for the development of more complex analytical models. This will facilitate revisions to the future flexural design procedures for concrete sleepers, to ensure they are optimized for their expected service loading conditions.

In this study dynamic responses of a 10 MW offshore wind turbine supported by a multi-body floating platform that consists of a wide cylindrical platform and a cylindrical ballast body suspended by six tendons are analyzed and predicted for different tendon breakage scenarios. A newly-developed and validated fully coupled numerical tool (F2A) based on AQWA and FAST is used to perform aero-hydro-servo-elastic analysis of the floating offshore wind turbine (FOWT). The results indicate that the dynamic behavior of the platform is heavily influenced by the state of tendons health. Roll and yaw motions of the platform under a tendon breakage are found to experience 6 times magnitude amplification of the typical responses, depending on the specific environmental conditions considered. Moreover, the peak tension in the tendon adjacent to the broken tendon experienced an increase of 165% in magnitude. The collective-pitch mode of the platform and wave excitation that are the main contributors to the surge and pitch fluctuations are slightly affected by tendon breakages. The influence of tendon breakages is found to be only significant on the local-pitch and coupled-pitch modes of the platform. In addition, multifractal spectra of the platform accelerations under different tendon failure scenarios show distinct fractal characteristics that can effectively identify and diagnose tendon failures, which is essential to the development of a structural health monitoring system of FOWTs.

The effective maintenance and health monitoring of ballasted railway tracks, which involves the determination of differential settlement, track support stress and stiffness, and the strain-hardening property of ballast, is essential. The vertical stress–strain behavior of the ballast layer is primarily responsible for the irrecoverable strains and settlements in tracks, leading to further track degradation. This article reports the development of a series of applicable yet simple uniaxial models and the selection of the most plausible one for capturing the behavior of vertical stresses and strains in ballasts utilizing a set of measured vibration data of the rail–sleeper–ballast system from a Bayesian perspective. From the literature, the dynamic behavior of ballast can be divided into linear and non-linear regions. Under small amplitude vibration, the stress–strain property is linear and elastic, while the behavior becomes non-linear and inelastic once the elasticity limit is exceeded. By integrating the linear phase to some well-known non-linear engineering material laws, a list of new ballast stress–strain model classes was developed. An enhanced Markov chain Monte Carlo–based Bayesian scheme was utilized to explicitly handle the uncertainties in the model updating process, while the Bayesian model class selection method was employed to select the most plausible ballast stress–strain model class under the prevailing system conditions. The proposed methodology was verified using three sets of measured acceleration data from impact hammer tests on an in situ sleeper with simulated ballast damage. The obtained results suggest that the linear-elastic model is sufficient for small amplitude vibrations, while the modified Voce model is the most plausible amongst the investigated model classes for high impact load. The results also demonstrate the importance of the non-linear ballast model in ballast damage identification and the potential applicability of the selected ballast model in field track monitoring.

The article considers the issue of changing the stressstrain state of reinforced concrete sleepers depending on the value of the axle loads and the requirements for the modes of its bench endurance tests. This issue is very relevant, since at present, in certain sections of the network (directions of the Eastern operational area), due to the high traffic density, the impact on the track increases and the axle load increases. Such a change entails the need to revise the requirements for the methods for determining and confirming the resource of all track elements, including the loading modes of reinforced concrete sleepers during its bench tests. To determine the influence of the axle load, measurements were made of the actual stress-strain state of reinforced concrete sleepers laid on the tangent section of the Test Loop of the JSC “VNIIZHT”. The loading was realized by a running train of 72 cars and a specially formed experimental coupler of a locomotive and three cars with an axle load of 23.5, 25 and 27 tf, respectively. Measurements made it possible to obtain the dependence of the change in stresses and deformations on the change in the axle load, as well as to reveal the rheological features of the interaction of reinforced concrete sleepers and the ballast layer. Obtained measurement results were used as basic stresses and strains for calculating loading modes in bench endurance tests. Purpose of the calculation is to achieve the maximum identity of the stress state when the sleepers are loaded on the bench with its stress state during real operation. In addition, experimental bench loading of a reinforced concrete sleeper was carried out, during which the modes obtained by the calculation were implemented and its stress-strain state was measured. Results of comparing the stress state of a reinforced concrete sleeper obtained during full-scale measurements on the way and during loading on the stand showed their identity, which confirmed the adequacy of the calculated loading modes. The final result of the work was the loading modes for bench tests of reinforced concrete sleepers, taking into account the influence of the axle load value.

There are many factors that affect the decline in the quality of the railways including the stability of the geometry, the resistance of the upper structure and the lowwer structure of the railways. This research was conducted to determine the effect of geometry instability on the resistance railways structure that is focused on the structure of the railways. In assessing the geometry deviation value of the path using the calculation of the standard deviation each measurement parameter which is then processed into a track quality indexs (TQI). Measurement parameter data is obtained from Galunggung measuring train for 2018 and EM-120 measuring train for 2019. Differences in the calculation of the value of railways quality (TQI) with different years are used as a benchmark for determining the location of a manual survey using a measurement tool and meter listring. The results of field geometry measurements are modeled with a program to help calculate structural strength. Model simulation by analyzing using Finite Element Method (FEM) for several conditions according to the geometry deviation category (TQI). The results of this study found that, concrete sleeper material properties, with concrete compressive (Fc ') 54 MPa and 1400 MPa prestressed wire strength (Fy), rail type is R.54 and ballast property according to PM.60 of 2012. The axial load is working at 16,241 kg, From the analysis of the geometric deviation value of category 3 (25

With the commencement of high-speed trains in railway infrastructure, stresses throughout the railway substructure have increased. To have high bearing stress capacity, for construction of railway ...

The dynamic performances of a polyurethane-reinforced ballast bed and an unreinforced ballast bed at an operation site were tested by using the impact excitation technique. The influences of the ballast beds with and without polyurethane reinforcement on the natural frequency were investigated, along with the vertical and longitudinal vibration transmission characteristics of the track structure. The results show the following. Compared to the ballast bed, the polyurethane ballast bed has an inhibitory effect on the rail vibration in the range of 200–400 Hz, but there is an increased rail vibration amplitude in the higher frequency range. The polyurethane-reinforced ballast bed significantly increases the amount and amplitude of the dominant vibration frequencies of the sleeper. As the frequency increases (> 90 Hz), the superstructure of the polyurethane track rapidly transfers from being flexible to rigid, and the track thus absorbs and dissipates the impact load, quickly damping the vibration in the range of 90–470 Hz. The calculation results of the displacement transmission ratio (DTR) proposed in this study also support this finding, suggesting the use of DTR to more intuitively evaluate the vibration damping effect of each component of the track. The polyurethane material reinforces the ballast bed rather than the damping vibration, thereby improving the stability of the track structure.

The frequently moving subway trains often cause large vibration of the rack buildings especially tall buildings and noise problem, which lead to the discomfort of the occupants. Therefore, it is highly necessary to adopt measures to decrease the vibrations. The finite element model of vehicle-rail-foundation was established by using ABAQUS program, and vibration mitigation ability by using ballast mats was investigated. The results showed that the ballast mat has ability to mitigate train-induced environmental vibrations. The acceleration level can be highly reduced within 30 m from the track centerline on the ground. Increasing the thickness of the ballast mat and increasing the static foundation modulus can enhance the vibration mitigation effect. The research results can provide references for the train-induced environmental vibration mitigation design.

To study the mechanical characteristics of ballasted bed under dynamic stability, a three-dimensional discrete element model of ballasted bed with 1000 mm × 700 mm × 550 mm is established based on the discrete element method. Meanwhile, a simulation test bench with the same size is built for simulation analysis and experimental research. The variation law and trend of settlement, lateral resistance, and compactness of ballasted bed under different excitation frequencies are analyzed comprehensively. The results show that when the excitation frequency is constant, the lateral resistance of sleeper, the settlement of sleeper, and the compactness of track bed under sleeper increase first and then tend to be stable. With the increase in horizontal excitation frequency, lateral resistance of ballast bed, sleeper settlement, and compactness first increase and then decrease after stable operation. The values of these parameters are maximized when the excitation frequency is 36 Hz which is the relative optimal horizontal excitation frequency of this model.

This paper, respectively, considers the nonlinear contact and Coulomb friction between rollers and rails, the characteristics of a hydraulic cylinder, and the contact characteristics between sleepers and ballast. The models of hydraulic cylinders are employed to realize the characteristics of hydraulic circuits and clamping forces. And the effects of the Coulomb friction between the track roller and the rail are simulated by calling the Boolean operation in the bond graph simulation software 20-sim. Based on the above analyses, this paper explores deeply which effect the pressures in the hydraulic cylinders and the hydraulic resistances of the flow passes at the inlets and outlets of the hydraulic cylinders will have on roller–rail contacts and working effects. As a result, the increase in pressure of the hydraulic cylinder will stabilize the roller–rail contact and improve the energy transmission efficiency. The increase in the hydraulic resistance value can enhance the working effect to some extent. With regard to the friction, there are four forms of frictional contact between the roller and the rail.

Damage to a railway track during high-speed movement of heavy freight trains in its various sections is modeled using the grid-characteristic method on structured grids. The separation of sleepers from the ballast (unsupported sleepers) is studied. As a result of the computer simulation, various wave patterns and patterns of dynamic distributions of the Cauchy stress tensor (pressure) components during train movement on the railway were obtained. The cracking process is described.

Nowadays, railway transport plays a very important role in the transport system in a period of positive growth of commerce, economy and industry. In accordance with other modes of transport, railway is the most stable mode for transporting, safety, capability carrying, social and economic benefits. Sleepers have major roles in the complex railway system and distributed the load from rails when train goes through to the ballast. This study discussed pre-stressed concrete sleepers in Sudan railways and compare them with other varies of sleepers taken in consideration the service life, handling, weight of sleeper, damage, suitability for fastening and vibration resistance. On the other side explained the manufacturing stages that sleepers undergoes and the quality control accompanying them. A numerical static analysis for a pre-stressed concrete mono-block railway sleeper is carried out using finite element package named "ANSYS 15". Using SOLID65 solid element, the compressive strength of concrete is facilitated using plasticity algorithm while the concrete cracking in tension zone is accommodated by the nonlinear material model. Since the section of concrete sleeper is fully pre-stressed by nature, the smeared crack analogy is impracticable. Discrete reinforcement modeling with truss elements, LINK8, is then more suitable to utilize. Perfect bonding is presumed herein between concrete and pre-stressing wires. Thus, the results of the analysis that evaluate the effect of cables in deformed shape, strains, stress of pre-stressed concrete sleepers are compared to the solid concrete sleepers. Therefore, the insight into static behaviors will not only result in a safer and more reliable design method for railway infrastructure, but it can also translate and apply to other civil concrete structures.

The ballasted track structure of a high-speed railway repeatedly bears the action of vehicle loads, and the vibration energy is gradually diluted and dissipated due to the ballasted bed. It is difficult to monitor the structural health of ballasted track. By embedding sensors into the ballast, a ballast sensor was obtained. It was positioned on the ballasted track to study the structural health monitoring (SHM) under an impact excitation and to verify the Discrete Element Method (DEM)–Multi-body Dynamics (MBD) co-simulation model. Therefore, the SHM of the ballasted track is realized. The results showed that distributed ballast sensors can realize the SHM status of the ballasted track. Under an impact excitation, the peak of the main vibration frequency of the ballast at the sleeper box, sleeper end and ballast shoulder occurred at a frequency of 153 Hz. At twice the frequency, a secondary peak appeared in the ballast vibration amplitude at the sleeper box, while the vibration amplitudes at the sleeper end and ballast shoulder were suppressed. In low-frequency regime, the vibration damping performance of the ballasted bed structure was better than that in high-frequency regime. When the ballasted track structure was excited by high-frequency vibrations, the surface layer of the ballast at the sleeper box tended to splash, which affected the structural health state. Under the moving wheel load, both sides of the ballasted bed form a “cyclone” shape.

The paper gives a systematic overview of literature sources who consider impacts critical damage of mechanical, corrosive and thermal nature which may occur on railway axles during operation and which may be the causes of their fracture. The results of the research of the mechanisms that cause cracks, crack propagation and final fracture of the railway vehicle axle, such as material fatigue and the appearance of localized notches caused by paint (coating) separation, damage from ballast impact and pitting corrosion are presented. The influence of high temperatures and overheating on the axles was analyzed and an excerpt from the research published in one research report was given. Some significant suggestions for optimizing the design of the axles are highlighted which would take into account the analysis of time-varying axle stresses, stress spectrum in operation, axle tolerance to damage and the existence of residual surface stresses. The reliefs of the fracture surfaces of the axle after the railway incidents and the derailment of the rail vehicle from the rails are presented and explained.

The present paper scrutinizes the influence of one of the most important factors – solar radiation – on the results of thermo-technical analysis of a roadbed that form the basis for elaborating anti-heaving measures for traffic arteries in cold regions. There is a description of live experiments involving quantitative assessment of the influence of solar radiation on the change in thermal behavior of a surface of a ballast prism. There were compared experimental data obtained during the calculation accomplished with the use of a complex method that implies application of special software package designed to determine effective radiation of the exposed surface. Based on the results of comparison performed, a conclusion was made that answers the question whether it is consistent to use the above-mentioned method of calculating the temperature correction for solar radiation in order to determine thermal behavior of a surface of the ballast prism in the context of thermo-technical analysis of a railway roadbed. The extent of influence of the main initial data – Albedo and cloudage parameter – on the value of temperature correction in different climatic zones was determined. There was detected the sensitivity of results of calculation of the depth of freezing and thawing of a roadbed to a possible error in setting the temperature correction that determines the upper limit of the thermos-technical problem. A special role of considering the temperature correction when performing thermo-technical analysis was showed.

The article describes the analysis of the impact of a three-axle bogie ELH-3R installed under a platform wagon type Samms on the railway track. The computer calculation of indicators of the track impact is described when the wagon moves along tangent and curved track sections with radii of 430 and 650 meters. While doing that, the cases of the movement of the platform wagon in an empty and fully loaded state were considered. The simulation was carried out at different motion speeds depending on the investigated track on sand or gravel ballast. Based on the calculation results, an assessment of the compliance of the indicators of the three-axle bogie impact on the track with the requirements of the corresponding standards was made.

The dynamic behaviour of slab and ballast tracks was investigated using measurements and calculations. Hammer impacts and train passages were analysed and measurements were made using geophones (velocity transducers) which had been time-integrated to displacements. The calculations were carried out in the frequency-wavenumber domain for multi-beam-on-continuous soil models. The characteristics of the different tracks and track elements were established in theory and by experiment. The frequency-dependent compliances (displacement transfer functions) showed clear rail-on-railpad resonances or highly damped track-soil resonances. Compared to the rail and sleeper, the track slab had much lower amplitudes. The slab track usually had the highest rail amplitudes due to soft railpads. Train passage yielded track displacements which were a superposition of the axle loads from the two neighbouring axles of a bogie and from the two bogies of two neighbouring carriages. This global behaviour was characteristic of the track slab of the slab track, whereas the rails of the slab and the ballast tracks behaved more locally with only one bogie of influence. The measurements agreed very well with the theory of continuous soil in the case of the six measured slab tracks and acceptably well for the six measured ballast tracks. The measurements allowed us to find appropriate model parameters and to check the models. For example, the Winkler model of the soil was found to be less appropriate because it reacted more locally.

The main factor that contributes to the deterioration of track components is traffic load. Explanations on how the speed, load and repetition of traffic influence the long-term settlement of ballast in a ballasted track are very scarce. Having in mind that tracks subjected to the same load show different settlement behaviors, explanations of track settlements in accordance with the speed, load and repetition are needed. This study is motivated to show how traffic affects the long-term settlement of ballast and how the traffic parameters (speed, load and repetition) contribute to the process. Using finite element modeling software, the three-dimensional track is modeled and analyzed for different values of speed, load and number of repetitions. Drucker Prager plastic model is applied for the ballast and sub-ballast materials of the track. To get the parameters for the Drucker Prager plastic model of granular materials, triaxial test simulation is performed using discrete element software. Hertz’s contact theory is used to model the contact between the wheel and rail. The long-term settlement behavior of ballast material is analyzed by applying 8000 cycles of moving axel load. According to the analyses, a change in the speed and the number of repetitions of train movement changes the permanent settlement of ballast more than the variation in load. Increase in the speed of train movement by 20 km/hr. will increase the stress transferred to the subgrade by up to about 1000 kPa. Speed of train movement is the most contributing parameter in the degradation of ballast material more than the load and number of repetitions. In a conventional ballasted track after about 6000 repetitions of train movement ballast material will start to decrease its performance. The comparison of the effects of the variation of individual traffic parameters speed, load and number of repetitions on the settlement of ballast which is not touched by former researches is well addressed by this study which is very helpful for designing a new railway track and monitoring existing railway tracks. Based on the analysis of the model with the parameters from Ethio-Djibouti standard gauge railway track, the possible maintenance period of ballast material is predicted.

Prestressed concrete sleepers play an essential role in the railway track’s performance and safety responses, having an important function of transferring and distributing loads from the track’s superstructure to the ballast bed. Cracks on the prestressed concrete sleepers are mainly caused by impact loadings from wheel and rail interactions. Thus, the excessive railway track maintenance cost. The effect and optimization of different prestressed sleeper shapes under static and impact loadings have not been previously well investigated. Therefore, this paper focused on the optimization of prestressed concrete sleepers (PCS) shape looking at sleeper safety and sleeper volume. ANSYS 16 was used to analyze the static and impact loading on sleepers. The concrete part of the sleeper was modeled using a three-dimensional solid element, SOLID65, and the pre-stressing wires by truss elements, LINK180, to withstand the initial strain attributed to pre-stressing forces. This paper revealed that irregular hexagon sleeper shape with different width at rail seat and center section having 251 mm and 175 mm center width and height respectively; 281 mm and 200 mm end and rail seat width and height respectively is safe. This paper; thus, point out to irregular hexagonal shape sleeper are more economical and safe, unlike the other modeled shapes.

Introduction. Since nowadays ballast-free track structures are most often used in combination with continuous welded track solutions for organizing a rail string, it should be emphasized that stresses arising in the rail string affect the stress-strain state of the entire construction of the track superstructure; therefore, it is necessary to monitor the current state of the continuous welded track. Nevertheless, kinks are formed and assembled rails and sleepers lose stability during the operational period of a continuous welded track, and methods are needed to determine the pre-failure conditions related to the temperature range of operation of a continuous track. Materials and methods. In this study, we propose a model of a flat structure made of a material having anisotropic properties, which makes it possible to take account of initiation and propagation of wave processes under the action of an external dynamic load. Results. The considered methods of simulating the propagation of elastic waves in a plate will make it possible to identify the points where direct and reflected waves of various orders converge; these waves can both increase and reduce the overall intensity of wave processes, leading to an increase or reduction in stresses and deformations in the characteristic points of a structure. Conclusions. The proposed solutions are most relevant for the structural elements of transport infrastructure facilities, since they are the ones that are exposed to alternating dynamic loads having varying intensity and time distribution of characteristic values.

In this paper, the effect of ballast properties including ballast depth, shoulder width, shoulder height, inter particle friction angle and ballast porosity on track buckling capacity are investigated numerically using discrete element method (DEM) analysis. First, a Single Tie Push Test (STPT) is simulated using DEM and the results are validated with field data. Then a sensitivity analyses is carried out. To investigate the effect of ballast properties on buckling capacity, the STPT responses according to the DEM analysis are introduced as a lateral track stiffness into a finite element model of continuously welded rail track, and a thermal buckling simulation is performed. The results show a significant effect of ballast porosity on buckling temperature.

The conventional ballast track needs to be improved and replaced due to the rapid degradation of the track. While operating the conventional line, the track structure needs to be rapidly improved and constructed in a narrow restricted tunnel space during railway blockade time. Therefore, the precast slab track of discrete panel supporting rapid construction was developed, and analysis and performance tests were conducted. In this study, vehicle track interaction analysis was performed to evaluate the behavior that may occur in the transition of the ballast track and the slab track in the field and to evaluate the safety of the structure during the train operation. In addition, to verify the performance of the prefabricated slab under the load of the train and its applicability to the actual operating line, a load test was performed on the assembly test body consisting of precast panels, rails, and panel-discretely supporting elastic rubber. The results of the test indicated that the rails and panels of the assembled test body satisfied the required performance test and secured structural safety.

With the train speed and axle load increasing, excessive stresses are produced and transmitted to the ballast layer, inducing rapid ballast degradation. To solve this issue, the under sleeper pads (USPs) have been widely applied between sleepers and ballast particles as the elastic layer. In this research, laboratory tests using half-sleeper track were carried out to study the ballast bed performance with or without the USPs under static and cyclic loading. Results show that applying the USPs reduces the track stiffness and can decrease the settlement. However, installing the USPs increases the ballast bed acceleration and the sleeper vertical acceleration. The contact areas of sleeper-ballast with USPs are over 5 times as those without USPs. The USPs assist reducing ballast degradation mainly by avoiding the ballast particle breakage at the sleeper-ballast interface and can increase the stress distribution at the longitudinal direction.

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.

This paper details a linear-elastic approach to modeling crosstie-ballast interfacial load distribution in a railroad timber crosstie trackbed using RISA 3D, a finite element modeling software. RISA results closely mirrored experimental findings with some slight deviation as discussed in the paper. The modeling methodology outlined here advances previous trackbed research at the University of Kentucky, U.S., and could be used in future trackbed finite element analyses for design or research in load path distribution and load magnitude predictability. This paper details the approach used to model a timber crosstie trackbed superstructure, including initial troubleshooting stages, and explains the derivation of program input variables. A sensitivity analysis performed on the main model determined the workable extent of linearity. The analysis also examined the effect of a poor/muddy trackbed support loading condition. The paper concludes with potential recommendations in relation to the work.

This paper presents an analysis of a new railroad track design based on substructure containing a double layer of geocells plus an additional geogrid layer for application on a new rail line being constructed. This new line is designed to accommodate both passenger and freight operations. The analysis looked at the applicability of the proposed design to the track substructure conditions on this new line with a primary emphasis on the bearing strength of poor subgrade locations on the new line. The analysis approach used Beam on Elastic Foundation theory to generate stresses on the top of the ballast layer and top of sleeper and then follow-up analysis to include use of test results to analyze the distribution of these stresses through the substructure and the determination of the subgrade bearing stresses. These bearing stresses were then compared with the strength of soils representative of those found on the proposed line segment. Based on the results of the analyses, the proposed substructure design (with 2 geocell layers and one geogrid layer) was found to significantly reduce stresses on the subgrade so that the proposed track was appropriate for use on even the poorest soil types identified on this line segment. This is because of the improved strength and stiffness characteristics of the geocell reinforced ballast layer.

Purpose . For prospective speed increase in the work is aimed to consider the complex conditions of the dynamic interaction of the railway track with rolling stock. The nature and level of this interaction depends both on the design of the unit of rolling stock, its state and speed, and on the design and condition of the track itself. Methodology . Evaluation of the possible rolling stock impact on the track was investigated by the analytical method. The track stress state was determined by calculation using dependencies between force factors and the characteristics of the stress-strain state of the track. When determining the static pressure of the wheel on the rail, the influence of rolling stock skews in the rail track according to the “herringbone” scheme is considered, in which the additional lateral effect of the wheel pairs of the bogies on the track structure is maximal. Findings . When conducting theoretical studies, the dependencies of the lift resistance coefficient by longitudinal forces were obtained taking into account various types of inertia forces on irregularities both on the wheel and on the rail thread. The values of the friction coefficient in the wheel-rail contact on the movement speed were also obtained. Originality . For the first time, the rules for calculating the railway track for strength and determining the dynamic loading of the rail carriage are combined. This improvement will make it possible to calculate the structural speed of the car based on the axial loads, inertia forces due to the wheel and rails` irregularities, and also take into account the longitudinal quasistatic forces arising in the train during braking modes. Practical value . Determination of the car lift resistance coefficient using the above methodology will allow a more thorough consideration and justification of the cause of wheelset derailment. The application of this calculation method will allow us to determine the strength of the railway track and the ballast layer, taking into account the uneven load of rail threads in the case of distortions of the freight rolling stock under the action of compressive quasistatic longitudinal forces.

This study presents the experimental analysis of an innovative floatover installation method with the rapid transfer technique, in which the topside loads can be transferred fast and safely. In the rapid transfer process, 30% loads were firstly transferred onto the jackets within only 1 min using the jacking system. Then both the ballast system and the jacking system were employed to gradually transfer the loads onto the jackets. After 70% topside loads were transferred, the jacking system quickly offloads the remaining 30% loads within 1 min. The continuous load transfer operation was simulated in model tests. The complex motions of the barge and the topside as well as the loads on the Deck Support Unite (DSU) and the Leg Mating Unite (LMU) were analyzed. The maximum and minimum motions of the barge and the topside were statistically analyzed as well as DSU and LMU loads. Results indicate the barge pitch motions largely synchronize with the topside pitch before the second jack-down operation. The barge moved forward a little distance after twice jack-down operations. Results indicate DSU loads varied significantly during the jack-down operations and the jacking system should be designed to provide lateral restraints equivalent to 20% of the topside weight.

This paper presents a multi-layer railway ballast track and substructure model, where a coupled discrete and continuous method is used for macro-meso dynamic behaviour analysis under moving wheel loads. In this coupled model, the discrete element method (DEM) is utilised to build the superstructure of the ballast track (i.e. rail, fastener, sleeper and ballast layer), which considers the complex ballast shape and particle size distribution from mesoscopic level. The finite difference method (FDM) is used to simulate the substructure (i.e. subgrade and foundation) with a consideration of computing cost. And then, the coupled model is achieved by satisfying displacement, velocity and contact force compatibility between the FLAC and the PFC. Finally, the dynamic analysis is carried out by applying the wheel-rail forces obtained from a vehicle-track dynamics model into the coupled model. The DEM parameters of ballast particles are calibrated based on the results of the ballast direct shear tests, and the dynamic behaviour of railway ballast track and subgrade system is validated with the field measurement. Through the numerical analysis, it is confirmed that the coupled DEM/FDM model can reliably reflect macro-meso dynamic behaviour and accurately reveal the contact characteristics between the ballast layer and subgrade.

A comprehensive assessment of the effectiveness of heavy-haul traffic is a prerequisite for its implementation in world railway sector. The assessment should include the study of the effect of increased axial loads on degradation of the elements of the track’s superstructure, deformation parameters of the ballast layer and the track’s substructure, and of measures intended to reinforce the railway infrastructure accordingly. It is necessary to consider rather accurately the force factors acting on the track and generated by different types of rolling stock with various axial loads. The distribution of force factors for a specific section of a railway track is a multifactorial process, the quantitative parameters of which depend on the structure of the train traffic flow, the type of rolling stock and its share in the total daily train traffic passing through this section, speed limits set for the section, track profile (straight line, curve), technical conditions of rolling stock and elements of the track superstructure.The objective of the work was to develop a technique for determining the integral law of distribution of vertical and lateral forces affecting the track and caused by wheels of different types of rolling stock, depending on the share of the operation of the respective types of rolling stock in the daily train traffic flow. Methods of mathematical statistics were used.In the process of experimental studies of the effects of various types of rolling stock, the statistical distributions of vertical and lateral forces have been determined. The histograms of vertical and lateral forces have been approximated by theoretical laws. Kolmogorov–Smirnov fit criterion has been used to confirm goodness of chosen approximation functions. A technique has been developed for mixed freight and passenger railway traffic that allows to consider the contribution of the share of each type of rolling stock in the force impact on the track when calculating the total impact. The technique is based on real, experimentally established distributions of vertical and lateral forces, traffic speed at the considered section of the track with regard to seasonality (winter, summer), and can be used for the sections where heavyhaul traffic is being implemented.

The number of regularities detected in the experiments described by the author confirms that, despite of the differences in operating conditions between the middle of the 20th century and the present days, the methods of research and assessment of obtained results are still relevant.Features of the superstructure and track operation at the initial stage of introduction of the welded rails and continuously welded rail strings on the railways of the USSR are examined. It is demonstrated that axial displacement forces are occurred during the train movement, which are one of the most dangerous processes taking place in the track during the rolling stock movement. Axial displacement forces are manifested in the axial displacement of rails on the sleepers or displacement of rails with sleepers on the ballast. Knowledge of axial forces resulted from displacement of one rail line or the entire track is required for competent planning of installation and operation of the jointed rail track and continuously welded rail track, especially in the conditions of the Urals and Siberia. Methods and experimental results are provided for determination of additional axial forces acting in the track at the spike fastening and the individual intermediate fastening in front of braking train at the experimental sections of the continuously welded rail track in severe climatic conditions of the West-Siberian railway, where the annual fluctuations of therail temperature amount to 110°C.The following conclusions are made based on the analysis of the experiment results and experience of operation of the continuously welded rail strings: • no additional axial forces in front of braking train were detected in the continuously welded rail strings of the thermalstressed type without any release of thermal stresses on the independent fixation; • experiment confirmed possibility of installation and normal operation of continuously welded rail track on the entire network of railways of the Ministry of Transportation of the USSR; • recent wide introduction of trains of 7,100 t, combined trains of 12,600 and 14,200 tons require special attention to parameters of interaction of track and trains.

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 s...

Alternative railway sleeper technologies for replacement of timber are made of materials possessing a wide range of bending and compressive moduli. This poses a great challenge to railway authorities and engineers in designing a railway track supported by different sleeper technologies. This study evaluates the static behaviour of a railway track supported by different alternative railway sleeper technologies, i.e. recycled plastics (1.0 GPa), synthetic composites (7.4 GPa), timber (13.0 GPa), and low profile prestressed concrete sleepers (38.0 GPa), using a ballast box test representing a single sleeper section of a track. The deflection profiles along the length of the sleepers under a full service load was captured using Digital Image Correlation technique combined with the strain measurements at the top-centre of the sleepers. Three-dimensional Finite Element simulation of the sleepers’ behaviour based on the Beam on Elastic Foundation theory was implemented and validated by the experimental results. The results show that sleepers with bending modulus of less than 13.0 GPa will have W-shape deflection profile and a high rail seat deflection while sleepers with a bending modulus of 38.0 GPa will show nearly flat behaviour. Local deformation at the rail seat region accounts for almost 6 % of the total deflection of sleepers on a low subgrade modulus and as high as 10 % for high subgrade modulus. The results of this study provide a better insight into the in-track behaviour of alternative sleeper technologies having distinctive material properties.

The paper presents the results of vibroacoustic tests of a plate girder railway bridge consisting of two parallel dilated structures and a common ballast trough. The requirements currently set for railway bridges relate to, among others, vibrations considered as one of the criteria for traffic safety and to noise emissions that may pose a threat to the environment. In this article, the results of tests conducted on vibrations of elements of the analyzed structure are presented, and the level of these vibrations in terms of meeting the requirements of the European standards is assessed. Vibrating criteria of structure performance were checked, and safety was assessed. The results of noise measurements in the vicinity of the analyzed bridge are also presented, and the environmental impact of this structure is determined. The test results show that the bridge meets the requirements for vibration acceleration and noise. An increased acoustic emission in the analyzed case does not pose a significant threat, but if this type of structure was on high supports in an urbanized area, it would be a nuisance to the environment.

The accurate prediction of the track deformation under train-induced repetitive loading is inevitable to assess the efficiency of a railway track. This paper presents an analytical technique to calculate the transient deformations in a railway track subjected to train-induced loading. The method considers the track substructure as multilayered media in which the behavior of an individual track layer is simulated using a mass-spring-dashpot model. Unlike existing approaches to model the track substructure as an equivalent single or double layer, the proposed analytical approach considers all the three layers of the ballasted track (i.e., ballast, capping or subballast and subgrade). The accuracy of the proposed technique is investigated by comparing the predicted values of track displacement with the published data available in the literature. The predicted results are found to be in good agreement with past studies. A parametric study on the substructure behavior revealed that the elastic modulus of track layers significantly influences the track response.

The electric strain gauges method application to the elastic compensators effectiveness assessment for the "press-die" system of C-frame (gap-frame) presses is shown. The electric Wheatstone bridge was adapted, where the one arm is used on the equal mechanical stress calibration beam, and the other arm on the section of the press frame, which experiences maximum tensile stresses. The bridge arms' active and ballast purpose changed during calibration and research. After receiving the calibration characteristic between the current on the ammeter and mechanical stresses, the stress level in the press frame was estimated using various elastic compensators aimed at reducing them. It is shown that the use of elastic compensators based on polyurethane elastomers can reduce parasitic loads in the press frame by 15-42% compared to tensile stresses arising in the frame without a compensator. It has been established that the highest compensators efficiency is observed in the range of their upsetting up to 20-30%.

Vehicle lateral stability is evaluated using the static overturning angle. The correct value of this parameter depends on the calculation method. The aim of this study was to compare the latest standard with previously published methodology, to propose two alternative methodologies (Models 1 and 2) and to analyze the influence of various levels of rear wheel ballast weights and overall tire widths on the stability of universal and subcompact tractors. The results showed a significant regression effect of the rear wheel ballast weight on static overturning angle. The influence of the rear wheel ballast weight was higher in the subcompact tractor than in the universal tractor due to a larger distance between the height of the center of gravity and the center of the rear axle. Comparing the latest standard with the previously published methodology, the highest difference values were 13.82% and 7.30%. Both models are based on the previously published methodology and differ from each other in rolling and slope lines. The methodology proposed in Model 2 differed from the standard similarly to the previously published methodology, therefore, it is irrelevant. Model 1 reached differences of only −1.81% and −1.63%, representing a minimal difference from the standard.

This paper is devoted to track-bridge interaction phenomena in railway bridges of short simply-supported (SS) spans composed by ballasted tracks. These structures may experience high vertical acceleration levels under operating conditions. In particular, the coupling effect exerted by the ballast track shared by structural parts that are theoretically independent, such as consecutive simply-supported spans or twin adjacent single-track decks, is investigated. Experimental evidence shows that in these cases there may be an important vibration transmission from the loaded to the unloaded track, and that the interlocked ballast granules couple some of the lowest modes of vibration to an important extent. To this end a detailed three-dimensional (3D) Finite Element (FE) model of an existing bridge is implemented where the ballast in weakly connected regions is simulated as transversely isotropic material, in order to represent in a simplified manner the degraded state due to the relative motion between the disconnected structural parts. First, the bridge numerical model is updated from the ambient vibration response of the structure previously measured by the authors. Second, a sensitivity analysis is performed on the properties of the degraded ballast and their effect on the first five modes of vibration of the bridge is discussed. Finally, the response of the bridge under operating conditions is computed numerically, compared with the response measured experimentally in the time and frequency domains and conclusions are extracted regarding the model adequacy. Spanish Ministry of Science and Innovation PID2019-109622RB FEDER Andalucía 2014–2020 Operational Program US-126491 Generalitat Valenciana, Spain and Universitat Jaume I, Spain AICO2019/175 Generalitat Valenciana, Spain and Universitat Jaume I, Spain UJI/A2008/06

Long bearers are used at switches and crossings (SC (2) rigid joints, which may give a bending stiffness close to that of a continuous beam. The type of joint has implications for crossing performance, and the existence of alternative designs suggests that a universal solution has not been identified. This paper presents results from a laboratory study carried out to evaluate the effect of joint type on performance. In testing, repeated loading representative of >1 million cycles of a 20 tonne (20,000 kg) axle load was applied to the railseats of bearers supported on a ballast bed. Settlements and resilient movements at locations along the bearers were measured and analysed. The results show that the type or absence of a joint significantly affects the settlement and resilient deflections along the bearer length.

Ballast layer dynamic behavior is critically important for railway track design and maintenance optimization. This paper presents findings on crosstie and ballast particle dynamic responses obtained from: (i) laboratory tests conducted at Zhejiang University innovative high-speed rail tester (ZJU-iHSRT) and (ii) discrete element method (DEM) simulations using algorithms with newly featured parallel computing capability developed at UIUC. Overall, more than 170,000 ballast particles and eight crossties were assembled in the DEM model. A proportional integral derivative (PID) controller was utilized to ensure realistic dynamic loads applied on crossties at three train speeds: (1) 108 km/h; (2) 252 km/h; (3) 300 km/h. Crosstie vibration velocities predicted using the DEM model matched closely with measurements from laboratory tests both in trends and in magnitudes. With Fourier transformation and Butterworth filter techniques implemented on ballast particle vibration velocities captured in the DEM model, inherent signal noise could be reduced, and as a result, the predicted ballast particle vibration trends matched closely with laboratory sensor measurements. However, individual ballast particle vibration magnitudes predicted by the DEM simulations revealed certain discrepancies with the measurements since velocity sensors used in the experiment only recorded vibration responses of an assembly of ballast particles. Further studies are necessary to reveal more detailed findings.

The modern high-speed railway usually consists of track structure, subgrade and soil layers. The existence of track structure and subgrade can both improve the critical speed of railway especially when the railway is built on soft soil layers. However, the role that the track structure played hasn’t been distinguished from subgrade. Therefore, further research is needed to investigate the difference of the critical speeds in ballasted and ballastless track. In this paper, two different types of track structures, ballasted and ballastless track, are built on the same subgrade-soil model using two-and-half-dimensional (2.5 D) finite element method to calculate the vibrations induced by the same high-speed trains. The rails, rail pads and ballast layer in ballasted track and rails, rail pads, slab, CA layer, concrete base in ballastless track are modelled as Euler–Bernoulli beams resting on the subgrade. The subgrade and soil layers are modelled by the 2.5D finite elements. The critical speeds in ballasted track and ballastless track are compared to reveal the consequence of track structure. It reveals that the critical speed in ballastless track is equal or greater than that in ballasted track. When the subgrade has enough stiffness, the critical speeds in both ballasted track and ballastless track can be the same. It can be concluded that the subgrade is more dominant than track structure in deciding the critical speed of railway.

A receptance test was performed in a ballasted track section with three sleepers after cyclic loading tests. This physical model is installed in the laboratory of Heriot-Watt University. The ballasted track is resting on a compacted substructure that is characterized by a frost protection layer (FPL), subgrade and geosynthetic-reinforced soils (GRS). A geogrid TX190L was placed between the ballast and FPL. The ballasted track is characterized by BS113A continuous rails, elastic pads and three G44 sleepers (spaced 0.65 m) embedded on the ballast layer. The receptance test is a helpful tool in the identification of the resonant frequencies that characterize the dynamic behavior of the track, and the results can be used in a calibration process of a numerical model. The response of the track was evaluated through the accelerometers placed on the head and web of the two rails and on the sleepers. The experimental tests were performed over the three sleepers, and the obtained results were compared taking into account the coherence function. Furthermore, the identification of the main resonant frequencies (full-track resonant frequency, anti-resonant frequency of the sleepers and rail resonant frequency) was also analyzed considering the accuracy of the obtained results in terms of coherence (only values higher than 0.9 were considered).

Many empirical equations have been formulated in an attempt to model the settlement of ballasted railway track at an individual sleeper. Some equations have been used with vehicle track interaction models (VTI) to predict the development of differential settlement along the track iteratively and hence maintenance requirements, over potentially millions of cycles of load. For settlement equations to be suitable in such simulations, they require as an input a VTI model output that varies along the track, such as the force on the sleeper or the current resilient deflection range. For computational economy, these VTI simulations are usually run in large steps with the settlement predicted forward over many cycles. There is, however, no one generally applicable settlement equation, and it remains unclear whether the loss of accuracy that ensues from stepping the VTI analyses is acceptable. A realistic settlement equation needs to incorporate both stress- and load history-dependent behaviour. This paper proposes a new settlement model that allows for stress history and has the potential to be applied at every cycle within an iterative VTI simulation. The ballast layer is modelled by combining a nonlinear visco-elastic element to simulate the resilient response with a plastic-hardening element for permanent settlement. This leads to the calculation of permanent settlement without recourse to an explicit empirical equation. The parameters used in the model are determined using data from cyclic laboratory tests on a single sleeper. The effect of different loading histories on the model is considered.