Track Structure Research Articles

Mechanical behaviors of ballastless track under temperature and vehicle loads in high geo-temperature tunnel

To explore the temperature field, temperature effect and mechanical behaviors of the track structure under combined load in high geo-temperature tunnel, the temperature field test platform is built to simulate the conditions under which the track bottom is heated in high geo-temperature tunnel, and the temperature distribution of the track bed slab in the transverse, longitudinal, and vertical directions is investigated. Then, the numerical model is built to examine the displacement and stress of the track structure under temperature load and combined load consisting of temperature and static vehicle load. The results show that when the temperature load on the track bottom is 30 ℃, the vertical temperature gradient inside the slab is negative, with a maximum of 20 ℃/m, and the maximum temperature differences in the vertical, transverse, and longitudinal directions are 5 ℃, 3.25 ℃ and 2 ℃, respectively. The temperature deformation of the track bed slab is manifested as sinking in the middle and warping at the edge, with the maximum tensile stress occurring in the upper-middle region and the maximum compressive stress in the lower-middle region. Under the combined load, the most unfavorable position of the vehicle load is where the front wheel is in the center of the slab, and for every 5 tons increase in axle load, the maximum tensile stress of the slab increases by about 4%, and the maximum compressive stress increases by about 2%. The findings provide reference for the optimization design of track in high geo-temperature tunnel.

Adaptive Vibration Monitoring of Railway Track Structures Using the UWFBG by the Identification of Train-Load Patterns

Due to the capability of multiplexing thousands of sensors on a single optical cable, ultra-weak fiber Bragg grating (UWFBG) vibration sensing technology has been utilized in monitoring the vibration response of large-scale infrastructures, particularly urban railway tracks, and the volume of the collected monitoring data can be huge with the great number of sensors. Even though the train-induced vibration responses of urban railway tracks constitute the most informative and crucial component, they comprised less than 7% of the total operational period. This is mainly attributed to the temporal sparsity of commuting trains. Consequently, the majority of the stored data consisted of low-informative environmental noise and interference excitation data, leading to an inefficient structural health monitoring (SHM) system. To address this issue, this paper introduced an adaptive monitoring strategy for railway track structures, which is capable of identifying train-load patterns by leveraging deep learning techniques. Inspired by image semantic segmentation, a U-net model with one-dimensional convolution layers (U-net-1D) was developed for the pointwise classification of vibration monitoring data. The proposed model was trained and validated using a dataset obtained from an actual urban railway track in China. Results indicated that the proposed method outperforms the traditional dual-threshold method, achieving an Intersection over Union (IoU) of 94.27% on the segmentation task of the test dataset.

Predicting ground vibrations from railway tunnels using an improved 2.5D FEM-PML model with soil spatial variability

PurposeThis study establishes a method for predicting ground vibrations caused by railway tunnels in unsaturated soils with spatial variability.Design/methodology/approachFirst, an improved 2.5D finite-element-method-perfect-matching-layer (FEM-PML) model is proposed. The Galerkin method is used to derive the finite element expression in the ub-pl-pg format for unsaturated soil. Unlike the ub-v-w format, which has nine degrees of freedom per node, the ub-pl-pg format has only five degrees of freedom per node; this significantly enhances the calculation efficiency. The stretching function of the PML is adopted to handle the unlimited boundary domain. Additionally, the 2.5D FEM-PML model couples the tunnel, vehicle and track structures. Next, the spatial variability of the soil parameters is simulated by random fields using the Monte Carlo method. By incorporating random fields of soil parameters into the 2.5D FEM-PML model, the effect of soil spatial variability on ground vibrations is demonstrated using a case study.FindingsThe spatial variability of the soil parameters primarily affected the vibration acceleration amplitude but had a minor effect on its spatial distribution and attenuation over time. In addition, ground vibration acceleration was more affected by the spatial variability of the soil bulk modulus of compressibility than by that of saturation.Originality/valueUsing the 2.5D FEM-PML model in the ub-pl-pg format of unsaturated soil enhances the computational efficiency. On this basis, with the random fields established by Monte Carlo simulation, the model can calculate the reliability of soil dynamics, which was rarely considered by previous models.

Investigating the effect of ballast contamination in vertical and shear interlocking stiffness: Experimental and numerical study

The maintenance of railway tracks faces a significant challenge due to ballast contamination. This issue arises from the inevitable ingress of fine particles into the track structure through various means, such as fine sands, coal infiltration, aggregate breakage, and substructure pumping. Climate change exacerbates these conditions, leading to increased external debris contamination and the accelerated degradation of ballast aggregates. This contamination has major consequences, impacting track quality in terms of drainage capacity and dynamic behavior. As a response to this, the study focuses on assessing ballast contamination from sand infiltration, specifically evaluating vertical and shear interlocking stiffness through a dedicated experimental setup for ballast behavior analysis. Using materials from an actual track, contamination levels from clean to 30 % were simulated, and an empirical formulation of contaminated ballast stiffness was derived based on laboratory tests. Moreover, numerical sensitivity analyses were conducted to explore the impacts of ballast contamination on the dynamic behavior of track components. The findings indicate a significant increase in dynamic track responses up to a 30 % contamination level, based on gravimetric measurements, leading to substantial increases in maximum absolute accelerations of sleeper and ballast layer as well as exerted forces on the ballast layer by about 28 %, 21 %, and 46 %, respectively.

Floor vibration predictions based on train-track-building coupling model

With the objective of rational urban space utilization, the development of elevated metro depots and over-track buildings is progressing rapidly, with a particular focus on addressing the vibrations caused by trains. Unlike traditional metro depots, trains in elevated depots run on concrete floors, which may lead to excessive floor vibrations. Therefore, it is essential to evaluate the impact of these vibrations during the design phase. In this paper, a vertical vibration prediction model for trains running on building floors is proposed by integrating the train, track structure, and building structure into a unified system. The train model is conceptualized as a multi-rigid body connected by springs and dampers. The track structure comprises rails, fasteners, and track slabs. The building floor is simplified as a rectangular plate composed of multiple orthogonal structural girders and columns in vertical contact with the floor. To verify the proposed method, field measurements were conducted in an elevated metro depot. The proposed model provided estimates of the vibration transmission with good agreement from track to building floor by comparing with the measured vibrations. The model presented in this paper can be utilized to predict the base vibrations of buildings and further predict the floor vibrations.

СРАВНЕНИЕ ТЯГОВЫХ ПРИВОДОВ С ОПОРНО-ОСЕВЫМ И ОПОРНО-РАМНЫМ ПОДВЕШИВАНИЕМ ДВИГАТЕЛЯ

The problem of finding criteria for choosing between axial support and frame support drives for locomotives in the conditions of import substitution is considered. The changes in the criteria for choosing a traction drive design depending on the changes in requirements for locomotives are analyzed. The types of drives are compared according to their technological simplicity, weight and size indicators, the effect on the coupling properties of the locomotive and the damage to the track structure, taking into account the production of new traction drive designs of an integrated type with collector-free traction electric motors having an increased rotation frequency. It was found that for locomotives with collector traction motors, it is advisable to use a frame support drive with an axial gearbox or a hollow driveshaft, and when using collector-free traction motors , the axial support traction drive of an integrated layout on freight locomotives with 1250 mm wheel diameter to improve coupling properties by 12...15%, it is advisable to replace it with the one proposed by the authors, which is an aggregate-type drive with an elastic link in the shaft lines, or with frame support drives with an axial gearbox, and with a wheel diameter of 1050 mm – frame support drives with a hollow shaft on the axis. An application for a patent has been submitted for the proposed solutions.

A method for predicting vibration characteristics of track structure based on rail acceleration and deep learning

ABSTRACT The dynamic test on track structure plays a crucial role in evaluating the operational state. Nonetheless, existing testing approaches involve numerous sensors, resulting in high costs and time consumption. This study proposes an economical, high-precision, and swift solution to predict vibration responses and displacement variations in track structures using rail acceleration. Taking the ordinary track structure and the damping track structure as examples, based on the high correlation between the vibration responses of the rail, track slab and tunnel wall, combined with the proposed Bayesian optimized temporal convolutional neural network model (BOA-TCN), and taking the rail acceleration envelope and vibration level as input, the vibration of tunnel wall and the displacement of rail and track slab are estimated. The results demonstrate that the BOA-TCN model effectively solves the limitation of traditional neural network in accurately capturing vibration characteristics in the frequency range of 1 ~ 100 Hz. The absolute error of the total vibration level prediction is significantly reduced, only 0.74 dB. The single point prediction accuracy of track structure displacement is increased by 80%, the absolute error is 50% of the traditional model, and R2 can be increased to more than 90%.

Event-driven piezoelectric energy harvesting for railway field applications

Piezoelectric energy harvesters (PEHs) hold promises for revolutionizing railway structural health monitoring (SHM). However, the challenges of designing high-robust PEHs for handling complex and ever-shifting vibrations in practical railway scenarios remain formidable. Unlike conventional methods that align the fundamental frequency of the PEH with the dominant frequency of the vibration source, this study employs an event-driven enhancement method. This study commences by employing a high-fidelity dynamic model of the PEH and an advanced vehicle-track coupled dynamic model to evaluate energy harvesting efficiency across various railway scenarios. The vehicle-induced track vibrations are predicted across various train speeds, track structures, and track irregularities, considering 12 distinct vehicle-track conditions and totaling 3600 simulation datasets, each representing a specific event. We employ the particle swarm optimization (PSO) algorithm to identify optimal PEH designs for different events. To streamline this process, instead of offering one optimal solution for each event, we employ the K-means algorithm to cluster similar events. Subsequently, we choose the centroid design for each cluster as the representative solution for events within that cluster. This approach allows us to use a limited number of representative PEHs to effectively address most events across different clusters. Finally, we thoroughly examine and evaluate the dynamic responses of these representative designs to demonstrate their robust performance. This study explores PEH design optimization from a fresh perspective, bridging the gap between theoretical design and practical implementation in rail transportation systems.

Modelling and numerical simulation of high-speed railway slab track structure

In terms of maintenance and structural behavior, slab track proves to be an advantage over conventional ballasted track due to increasing train speed, axle load, and traffic density. Since the vibration, noise, and risk of derailment, all accelerate as train speed increases, an in-depth investigation of track dynamics becomes essential for identifying the fundamental cause of the problem. In this paper modelling and numerical simulation of high-speed railway slab track structure has been studied using finite element method. Using the multi-body simulation approach and the finite element method a model of the 3D slab track system is developed. The slab track model has rail, rail pad, and concrete slab, HBL, and subgrade layers. In order to determine the fundamental frequency and the mode shapes associated with it, a modal analysis is carried out. Dynamic response, or acceleration against frequency curves derived via harmonic response analysis, is the result of the numerical simulation. The dynamic reaction of the structure of a high-speed slab track is studied, and the effect of elastic materials on reducing vibration is investigated. The results suggest that a layer of elastic material, like a slab of mat, inserted between a layer of concrete slab and a layer of HBL is capable of lowering the amount of vibration response of the track.

Review Kerusakan Keausan Roda Pada Kendaraan Kereta Api

Damage due to wheel wear on railway trains has a significant impact on railway safety and comfort. This review examines various aspects related to wheel wear damage on trains. The primary focus of this review encompasses three critical areas: railway track, wheel-rail interaction, and the trains themselves. The first section discusses the structure and modeling of railway tracks, while the second section explores various types of interactions between wheels and rails as well as related mathematical models. The third section reviews the types of railway vehicles, their mathematical models, and their stability on straight and curved tracks. Furthermore, this review also examines the influence of wheel wear on the dynamic response of the system. It is hoped that this review will provide valuable insights for practitioners and researchers in improving and enhancing the reliability and safety of railway systems.

Оценка интенсивности накопления остаточных деформаций основной площадки земляного полотна на участках обращения тяжеловесных и длинносоставных поездов

Objective: the article presents an assessment of the intensity of accumulation of residual deformations of the main platform of the roadbed in the areas of circulation of heavy and long-composite trains formed from wagons with an axial load of up to 25 tons. Methods: measurements of residual deformations of the main site of the roadbed were carried out by geodetic methods by laying a closed leveling course. To do this, each experimental site was equipped with soil stamps installed on the main site of the roadbed and reference points. The measurements were carried out from 30.05.2022 to 08.11.2023. Results: as a result, the dependences of the accumulation of residual deformations of the roadbed on the missed tonnage have been established for various railway track structures, operating conditions and engineering and geological conditions. Practical importance: measures are proposed to reduce the intensity of accumulation of residual deformations of the main site of the roadbed.

Robust Artificial Intelligence-Aided Multimodal Rail-Obstacle Detection Method by Rail Track Topology Reconstruction

Detecting obstacles in the rail track area is crucial for ensuring the safe operation of trains. However, this task presents numerous challenges, including the diverse nature of intrusions, and the complexity of the driving environment. This paper presents a multimodal fusion rail-obstacle detection approach by key points processing and rail track topology reconstruction. The core idea is to leverage the rich semantic information provided by images to design algorithms for reconstructing the topological structure of railway tracks. Additionally, it combines the effective geometric information provided by LiDAR to accurately locate the railway tracks in space and to filter out intrusions within the track area. Experimental results demonstrate that our method outperforms other approaches with a longer effective working distance and superior accuracy. Furthermore, our post-processing method exhibits robustness even under extreme weather conditions.

Experimental study on interface performance of CRTS Ⅱ slab ballastless track under temperature loading

Interlayer interface damage poses a prevalent challenge in China Railway Track System (CRTS) Ⅱ slab ballastless tracks, with temperature playing a pivotal role in its occurrence. This study aims to scrutinize the mechanism of interlayer interface damage of track structure under temperature loading, vertical full-scale composite specimens were constructed for push-out and normal-tension model tests, and digital image correlation (DIC) technology was adopted to obtain the interlayer strain field distribution during loading and to get the mechanical property degradation, damage evolution law and damage mechanism of cement asphalt (CA) mortar layer interface under different temperatures. Based on the experimental study and fracture mechanics, the temperature cohesion damage model of the track slab-CA mortar interlayer interface was established. The results show that the bonding surface between the track slab and CA mortar layer is particularly susceptible to damage, and the interface damage exhibits "cold brittleness" and " thermal ductility" at low and high temperatures, respectively. Cohesion zone models (CZM) were constructed for both the normal and tangential interfaces at temperatures of 0 °C, 15 °C, 30 °C, 45 °C, and 60 °C. Furthermore, by defining field variables in the ABAQUS software, a temperature variation function describing key parameters of interface damage fracture behavior was integrated into the CZM, using defined field variables. The simulation results exhibited excellent agreement with the experimental findings.

Impact of speed and axle load on the static and dynamic mechanical behavior of the ballast bed laying under sleeper pads

With the evolution of railway infrastructure towards accommodating higher speeds and heavier loads, the under sleeper pad (USP) has emerged as a critical component in mitigating the deterioration of the ballast bed and reducing maintenance requirements. This study aims to enhance the understanding of the suitability of the USP for railway lines and to investigate the static and dynamic mechanical behaviors of the ballast bed (with USP) under the train load. To achieve this, the study conducts on-site tests and employs the discrete element method-multi-flexible body dynamics (DEM-MFBD) coupling analysis to develop a three-dimensional high-fidelity model of the ballast bed (with USP). This comprehensive analysis assesses the impact of varying train speeds and axle loads on the mechanical properties of the ballast bed with the USP, integrating both macroscopic and microscopic perspectives. The results show that there is an 8.54% reduction in longitudinal resistance of the ballast bed (with USP) compared to the ballast bed (without USP), yet it still fulfils the requirements of heavy railway lines. The ballast bed (with USP) exhibits significant improvements in vibration-damping performance, with the wheel-rail vertical force showing a reduction of 8.71% relative to the ballast bed (without USP). This suggests a potential extension of the track structure's lifespan. An increase in train speed markedly influences the vibration levels of the ballast bed (with USP), leading to an increase in ballast bed acceleration by 119.39%. The increase in train axle load demonstrates a minor effect on the plastic deformation of the ballast bed, indicating the ballast bed (with USP)'s capability to accommodate heavier axle load trains.

Investigation of Processes in the Traction Capacitor Circuit of the Model of High-Speed Magnetolevitation Transport

Purpose. High-speed magnetolevitation transport (maglev), based on the principle of electrodynamic suspension, has features in the form of large sections of the windings of the track coils. Therefore, there is a need to study electrical processes in the circuits of these coils to improve the efficiency of the energy performance of this type of transport. The study of electrical processes in the circuits of a track power plant makes it possible to substantiate the prerequisites for the creation of a distributed energy storage and transmission system. The power plant consists of separate subsystems, including a primary energy storage unit, an energy distribution unit, and a traction module. The main purpose of this study is to determine the nature of transients in the energy distribution unit and to obtain the characteristics of the traction capacitor discharge process. Methodology. We modeled an electrical circuit that would meet the needs of the corresponding energy distribution unit of the track structure for the required operating conditions of the maglev motion system – control pulses with different combinatorics. In the course of the study, computer modeling of physical systems in the Scilab software environment was used. Findings. A review of existing studies has been carried out and the relevance of the study of the track power plant for high-speed magnetolevitation transport has been substantiated. The basic mathematical dependences of electrical circuits with capacitive and inductive elements are given. A structural representation of the inductive section of the maglev motion system with a traction module is created: traction coils and a capacitor, as well as a converter-pulse signal unit. An effective tool for analyzing transient processes has been created. Originality. For the first time, the structural and elemental realization of the power distribution unit for the road power plant of high-speed land transport is proposed. The time dependencies describing the processes in the proposed system during the implementation of the principles of pulse control of traction coils are obtained. Based on the analysis of the nature of transients in the traction capacitor circuit, the directions of further development of this power plant are proposed. Practical value. The results of the work create the basis for further research and development of experimental research models (test bench) of the maglev in order to obtain new ratios and characteristics that will confirm the effectiveness and efficiency of the new control principle of the proposed system.

Long-term freeze–thaw cycle behavior of high-speed railway embankment in frozen soil regions and its effects on train-track dynamic interaction system

The high-speed railway embankment built in cold regions has a long-term freeze–thaw cycle behavior, and the frost heave of soil will inevitably affect the smoothness of the track structure laid on the embankment, resulting in the deterioration of the train running performance and the dynamic behavior of the ballastless track system. This work is motivated by the research to investigate the long-term freeze–thaw behavior of the embankment in frozen soil regions and its effects on the train-track dynamic interaction system. Based on this motivation, the temperature-deformation field model of the embankment and the train-track dynamic interaction model (TTDIM) are established as an integrated model. The additional track irregularity triggered by the frost heave deformation of the embankment is regarded as the excitation source in the TTDIM to achieve the co-analysis of two sub-models. Through an illustrative example, the evolution characteristics of the freeze–thaw cycle behavior of embankment is fully revealed. Moreover, the effects of time-varying frost heave deformation of embankment on the performance of train-track interaction are quantified from the aspect of representative responses and safety evaluation indexes. This paper provides a valuable model and research thought reference for the analysis and assessment of the performance of train-track interaction under the long-term freeze–thaw cycles of the embankment in frozen soil regions.

Field Experiment as a Tool to Verify The Effectiveness of Prototype Track Structure Components Aimed at Reducing Railway Noise Nuisance

The almost unlimited possibilities of modern computational tools create the temptation to study phenomena related to the operation of engineering objects exclusively using complex numerical simulations. However, the fascination with multi-parametric complex computational models, whose solutions are obtained using iterative techniques, may result in qualitative discrepancies between reality and virtual simulations. The need to verify on real objects the conclusions obtained from numerical calculations is therefore indisputable. The enormous cost and uniqueness of large-scale test stands significantly limit the possibility of conducting tests under real conditions. The solution may be an experiment focused on testing features relevant to the given task, while minimising the dimensions of the objects under consideration. Such conditions led to the concept of conducting a series of field experiments to verify the effectiveness of prototype track components, which were developed using numerical simulations to reduce the noise caused by passing trains. The main aim of this study is to examine the acoustic efficiency of prototype porous concrete sound absorbing panels, in relation to the ballasted and ballastless track structures. Presented results of the proposed unconventional experiments carried out on an improvised test stand using the recorded acoustic signals confirm the effectiveness of the developed vibroacoustic isolators.

Research on dynamic characteristics of railway side-cracked slab for train-track coupled system

The Ballastless track have been extensively implemented in high-speed railways. However, during the long-term operational process, degradation, such as side crack or defect phenomena produced on the slab inevitably, poses a threat to the stability and the durability of the track structure. Consequently, it is imperative to propose a dynamic approach that can effectively predict the impact of side-cracked slab (SCS) on the vehicle-track coupled system. This paper utilizes co-simulation technology to investigate the dynamic behavior of the slab with and without side crack. Firstly, the dynamic substructure of the finite element model of the SCS is obtained by eigenvalue analysis. Secondly, the SCS model has been applied to the classical vehicle-track coupled dynamic system, and the coupled dynamic model of the train-side cracked slab (TSCS) is established, which considers the multi-rigid-body vehicle subsystem, the flexible rail subsystem, the flexible SCS and subgrade foundation subsystem, and the wheel-rail nonlinear contact model. Later, the accuracy and reliability of the proposed model are verified by the comparison with field tests. Finally, the differences in the vibration characteristics of the vehicle and track structure with and without a side crack are compared and analyzed, and its dynamic stress of the slab as variable train speeds is revealed. The results indicate that the existence of a side crack will reduce the natural frequency of the slab, with a maximum decrease of 22.31%. Although the SCS has a minor effect on the vehicle responses, the existence of a side crack has a significant impact on the slab, especially on the root mean square (RMS) of the vibration acceleration of the slab, with a maximum difference of 74.10% laterally and an increase of 55.16% vertically. Meanwhile, the train speed remarkably affects the crack tip dynamic stress of the SCS, with a maximum increase of 76.07% in the longitudinal direction, 50.34% in the lateral direction and 49.09% in the vertical direction. Higher train speeds will further exacerbate crack propagation under long-term train loading. This study may contribute to the dynamic modeling of TSCS systems and the maintenance of the slab ballastless track.

Design and Analysis of an H-Type Pickup for Multi-Segment Wireless Power Transfer Systems

To tackle the complex wireless power supply requirements in the Automated Material Handling System (AMHS) of semiconductor wafer factories, this paper presents a design method for a magnetic coupling mechanism based on a Multi-Segment Wireless Power Transfer (MSWPT) system for dynamic wireless power supply in segmented track configurations. Firstly, the track is approached using Inductive Power Transfer (IPT) technology combined with an LCC-S resonant structure transmitter (Tx). Following this, the feasibility of the H-type pickup is assessed through magnetic and electrical circuit analyses, which leads to the preliminary determination of the pickup dimensions by means of finite element magnetic and thermal simulations. Furthermore, an analysis of the mutual inductance drop is conducted under various track structure parameters during track crossing and curve negotiation operation conditions. Secondly, a dual-coil winding method is proposed to reduce the insulation stress on the PCB board. Additionally, a method for calculating the wire length and a design process for the overall parameters of the pickup are derived. Finally, two Txs and a 1.5 kW power receiver (Rx) were designed to verify the mutual inductance fall under the aforementioned conditions. During low-speed full-load operations, a constant-voltage output was achieved through the proposed dual-loop PI control strategy, thereby meeting the requirements for a constant-voltage output in industrial applications.

Metro Monolithic Track Bed Vibration Characterization

With the rapid development of cities, metro transportation has also developed rapidly to solve the congestion problems caused by urban development. However, with the continuous development of metro transportation, the vibration problems caused by it have become increasingly obvious. Based on the phonon crystal theory, this paper investigates the vibration characteristics of the metro track structure. It analyzes the influence of the track structure parameters on the band gap characteristics to regulate the metro vibration band gap range. To study the band gap characteristics of metro monolithic bed track structure, establish the double-layer Euler beam model and use the plane wave expansion method (PWE) to calculate its energy band structure; use the finite element method (FEM) to calculate to get its band structure, frequency response function, and time domain analysis. The calculation of PWE shows that there is a band gap in the range of 0–300[Formula: see text]Hz for the metro monolithic track bed, which is 0–194.5[Formula: see text]Hz; the calculation of FEM shows that the range of band gap is 0–193.7[Formula: see text]Hz. Fastening spacing, stiffness, and sub-slab support stiffness will have an impact on the band gap, so appropriate fastening and spacing need to be selected for effective vibration damping of the track structure. The results show that the band gap characteristics of the metro monolithic track bed can be calculated effectively and accurately by using the phononic crystal theory.