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AbstractRailway track buckling poses a significant challenge in railway engineering, necessitating a rapid and reliable method for evaluating buckling risks to aid in its prediction and prevention. This study introduces an innovative surrogate model using a multilayer perceptron algorithm to streamline this evaluation process. The model offers an efficient alternative to time-consuming and computationally demanding three-dimensional track simulations while effectively incorporating the complexities of track dynamics data. The primary objective of this study is to reduce the evaluation process time while maintaining high accuracy of predictions. The methodology involves the generation of comprehensive track dynamics data derived from 3D track multibody dynamics model simulations and training the multilayer perceptron algorithm on this data. The dynamics model is a multibody system that includes a mixture of rigid bodies, flexible bodies, and nonlinear friction. Results indicate that the proposed surrogate model reduces the evaluation time by ∼98% while maintaining similar prediction accuracy, achieving 99.44% accuracy in replicating buckling scenarios identified by the 3D model. This demonstrates a significant improvement in computational efficiency without compromising prediction reliability. The study concludes that the developed model is a viable alternative tool for faster evaluation of buckling risks, laying the groundwork for advancing toward real-time evaluation of buckling risks. [ABSTRACT FROM AUTHOR]

This paper presents the development of a dynamics model for long track sections. It is based on an established short track model that utilises the Finite Element Method to describe rails and block models to describe sleepers, ballast and subballast. By implementing a parallel computing method, this innovation enables the construction of a true long track model: by segmenting the long track into shorter segments that are easier to compute. The model facilitates simulations to be run in parallel, thereby permitting simultaneous calculations of various numerical track variables. The model employs a Message Passing Interface framework to seamlessly link the track segments, handling the flow of data among the computing cores designated to each subdivided section. This strategic framework allows the long track model with the capability to simulate tracks of virtually any length, with the only constraints being the available computational resources and time. The claimed contribution about modelling capability is verified using two case studies on a 6km-long track involving different practical and conceptual train operational scenarios: emergency braking and constant braking force with constant train speed. These case studies show the flexibility and scalability of the method and its capability to handle complex track dynamic systems. [ABSTRACT FROM AUTHOR]

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

Most railway track dynamics models focus on vertical and lateral directions. Vehicle dynamics have strong implications for track longitudinal dynamics, but railway track longitudinal force models are rarely published. This paper developed a three-dimensional railway track model which considers four structure layers: rails, sleepers, ballast and subballast. The rails are modelled using the Finite Element Method and each node has six Degrees of Freedom (DoFs). Sleepers are modelled as rigid bodies and each also has six DoFs. Ballast and subballast are modelled as blocks and each has three translational DoFs. Frictional behaviour is considered in the longitudinal direction of the fastening models as well as in the longitudinal and lateral directions of the sleeper-ballast force connections. Validations of the model are presented in this paper. Simulations of longitudinal forces are also presented. The results show that the model has the capability of simulating track longitudinal forces and the rail creep phenomenon. [ABSTRACT FROM AUTHOR]

Increasing the axle load causes track deterioration and permanent settlement of the ballast layer. In the ballasted railway tracks, due to the inevitability of unequal settlements in the ballast layer, part of the rail due to high flexural rigidity will become suspended, which causes the formation of the track with unsupported and partially supported sleepers. This situation increases rail vertical displacement and reactions on adjacent sleepers. Several models have been presented to study the effect of unsupported sleepers on dynamic responses of train-track interaction. In this paper, by applying mathematical model, unsupported and partially supported sleepers have been modeled and equations of motions for train-track interaction were written by assuming nonlinear behavior of rail and wheel contact. Following by solving the equations via numerical integration in the time domain, the effect of axle load and pad stiffness on rail vertical displacement were investigated. Results of the analysis suggested that through increasing the axle load rail displacement increased by 13 % in the unsupported sleeper and from 5 to 10 % in the partially supported sleeper. Also, by increasing the pad stiffness rail displacement decreased from 2 to 13 % in the unsupported sleeper and from 1 to 6 % in the partially supported sleeper. [ABSTRACT FROM AUTHOR]

• A compact ball screw based design reduces the backlash in the motion transmission. • A coupled model is developed to predict the energy harvesting performance. • Lab tests are conducted to evaluate harvester and validate the model. • Filed tests prove the performance of the harvester under the real condition. To enable the smart technologies and safe operation of transit and rail transportation, such as hot box detector, track health monitoring and wireless communication on the railroad side, a cost-effective energy source is in need. This paper presents the design, modeling, in-lab experiment and field-test results of a compact ball-screw based electromagnetic energy harvester with a mechanical motion rectifier (MMR) mechanism for smart railway transportation. The MMR mechanism is realized by the embedded one-way clutches in the bevel gears, which converts the bi-directional track vibration into the unidirectional rotation of the generator. Compared to previous designs, the proposed harvester has reduced backlash and thus can harvest energy from a small input of the track deflection induced by the moving train. Two prototypes with different key design parameters were built and tested. A comprehensive model considering the train-rail-harvester interaction was developed to analyze the dynamic characteristics of the coupled system and predict the energy harvesting performance of the harvesters at different train speeds. Both in-lab and field tests were carried out to examine the energy harvesting performance of the harvesters and validate the model. Field test results illustrated that an average power of 1.12 W and 2.24 W were achieved for two prototypes respectively when a Type A rapid transit passed by with a 30 km/h vehicle speed. [ABSTRACT FROM AUTHOR]

Abstract The dynamic properties of a railway track are important for both the generation of rolling noise and the development of rail corrugation. A conventional track consists of long rails mounted periodically on transverse sleepers and supported in ballast. In order to improve the predictions of the noise and vibration of the track, a model of a discretely supported track is proposed based on the so-called 2.5 dimensional (2.5D) finite element approach, which is used to model an infinite free rail. This is coupled to a finite number of sleepers, by means of an array of springs representing each rail pad, using a receptance coupling method. The sleepers are represented by flexible beams, supported on an elastic foundation. Results are presented in terms of the point mobility and track decay rate and these are compared with the corresponding field measurements for two tracks, one with soft rail pads and one with stiff rail pads. Very good agreement is found between the predictions and the measurement results, especially for the track with soft rail pads. The flexible sleeper model is shown to give improved results compared with a rigid mass model, especially for the track with stiff rail pads. [ABSTRACT FROM AUTHOR]

This paper reviews, synthesises and benchmarks new understandings relating to railway vibrations. Firstly, the effect of vibrations on passenger comfort is evaluated, followed by its effect on track performance. Then ground-borne vibration is discussed along with its effect on the structural response of buildings near railway lines. There is discussion of the most suitable mathematical and numerical modelling strategies for railway vibration simulation, along with mitigation strategies. Regarding ground borne vibration, structural amplification is discussed and how vibration mitigation strategies can be implemented. There is also a focus on determining how ‘critical velocity’ and ‘track critical velocity’ are evaluated – with the aim of providing clear design guidelines related to Rayleigh wave velocity. To aid this, conventional site investigation data is reviewed and related to critical velocity calculations. The aim is to provide new thinking on how to predict critical velocity from readily available conventional site investigation data. [ABSTRACT FROM AUTHOR]

Abstract: Vibration assessments are required for new railroad lines to determine the effect of vibrations on local communities. Low accuracy assessments can significantly increase future project costs in the form of further detailed assessment or unexpected vibration abatement measures. This paper presents a new, high accuracy, initial assessment prediction tool for high speed lines. A key advantage of the new approach is that it is capable of including the effect of soil conditions in its calculation. This is novel because current scoping models ignore soil conditions, despite such characteristics being the most dominant factor in vibration propagation. The model also has zero run times thus allowing for the rapid assessment of vibration levels across rail networks. First, the development of the new tool is outlined. It is founded upon using a fully validated three dimensional finite element model to generate synthetic vibration records for a wide range of soil types. These records are analysed using a machine learning approach to map relationships between soil conditions, train speed and vibration levels. Its performance is tested through the prediction of two independent international vibration metrics on four European high speed lines and it is found to have high prediction accuracy. A key benefit from this increased prediction accuracy is that it potentially reduces the volume of detailed vibration analyses required for a new high speed train line. This avoids costly in-depth studies in the form of field experiments or large numerical models. Therefore the use of the new tool can result in cost savings. [Copyright &y& Elsevier]

Abstract: A railway switch (turnout) is a very important element of the railway infrastructure. Due to the discontinuity in the rail geometry high dynamic amplification of the wheel loads occurs in the crossing nose. These dynamic forces can severely damage the turnout structure. Especially the high-frequency impact loads (the so-called P 1 forces) are responsible for RCF damage on the crossing nose. In the present study the relationship between the elastic properties of the turnout supporting structure (such as the rail pads, under sleeper pads and ballast mats) and the occurrence of RCF damage on the crossing point has been investigated. The RCF damage can be reduced by decreasing the high-frequency dynamic forces in the crossing nose. The dynamic interaction between the railway vehicle and track structure has been analysed numerically using DARTS_NL software (TU Delft). The performance of the turnout has been assessed using numerical simulations in which a railway vehicle (the ICE locomotive) was running through the turnout at 140km/h. In this simulation only the vertical dynamic forces in the crossing point have been considered: lateral behaviour was disregarded. The results of the parameter analysis have demonstrated that by varying the elastic properties of the supporting track structure the forces on the crossing point can be significantly reduced. It was also shown that by varying substructure elasticity the dynamic forces on other track components such as sleepers and ballast can be reduced as well. [Copyright &y& Elsevier]

• A unified platform for slab track dynamics analysis is constructed. • The wheel-rail coupling matrices have been derived as the ties of vehicle-track interaction. • An improved infinite computation method is proposed in the finite element framework. • The effects of multiple track slab finite elements and support string types have been discussed. With the rapid development of high-speed and urban rail transit, ballastless slab tracks have been widely used in many areas. The work on construction, design, and mechanics of ballastless slab tracks is abundant and achievements have been made. However, a platform for numerical simulation and dynamic analysis of slab track systems subjected to a moving train still needs to be probed into. In the MATLAB®, effective and easily programable methods are presented to guide the construction of the vehicle-slab track interaction system and the realization of long length computation in this present study. Based on previous studies, the formulation of slab track dynamics in the framework of finite element theory is founded with simplicities, and then the wheel-rail coupling matrices totally derived from the nonlinear wheel-rail normal contact/tangential creep forces using the energy variation method are presented. Following the dynamics modeling construction, an improved method for long or infinite length computation is proposed. With an implementation of this method, the effect of the spatial variability of track properties on vehicle-track system dynamic performance can be evaluated conveniently. Using this numerical simulation platform, extensive studies have been conducted to model and analyze the influence of spatial variability of filling layer support stiffness, the track slab finite element type and support type of steel spring for floating-slab tracks, etc. [ABSTRACT FROM AUTHOR]

When constructing a new railway line, its long length means there are significant financial implications associated with determining the geodynamic ground properties. Therefore, this paper presents recommendations to optimize the efficiency and depth of such a geotechnical site investigation. Firstly, a numerical analysis is performed to investigate the effect of soil layering, soil stiffness and track bending stiffness on critical velocity. It is shown that each of these variables play an important role, however for most practical cases, only the top 8 m of soil is influential. Track dynamics are rarely affected by soil properties at depths below this, meaning this is the maximum required depth of soil investigation. Using this knowledge, a hybrid experimental-analytical methodology is presented, based on a geophysical Spectral Analysis of Surface Waves (SASW) experimental setup to compute the ground dispersion curve and an analytical model to compute the track dispersion curve. The experimental and analytical results are combined directly, to accurately compute the critical velocity. This approach is attractive because: 1) SASW tests are typically accurate to ≈8 m (when using a mobile exciter) thus matching the required depth needed for critical velocity computation, 2) soil property uncertainties are inherently accounted for, 3) the uncertainties associated with SASW inversion are avoided. The approach is attractive when constructing new railway lines and upgrading the speed of existing lines because it can potentially yield site investigation cost savings. In-situ field work is performed to show the practical application of the technique. • An estimation of the depth required for geotechnical survey when dealing with critical speed problems is presented. • A hybrid approach for the assessment of the critical speed of railway lines is proposed. • It was found that prediction uncertainties can be reduced combining experimental and analytical methods. • Surface geophysical methods are suitable for geotechnical investigation in the ambit of critical speed assessment. [ABSTRACT FROM AUTHOR]