Rail Support Research Articles

Parameter identification of overhead conductor rail support and its influence on the contact forces

Overhead conductor rail (OCR) serves as a crucial device employed in tunnels to power electric locomotives. The OCR is hung by supports mounted on the tunnel ceiling. Previously, the support was usually considered as a linear spring when modelling the OCR. The linear stiffness and mass adopted to the support model were imprecise, and damping was absent. It may be insufficient to reproduce the pantograph-OCR system (POCR) dynamic behaviour. This paper is devoted to improving the accuracy of POCR dynamic model and makes it more realistic. Field tests are conducted in order to identify the support parameters, including stiffness, damping and mass, for the first time. Then, a novel nonlinear stiffness-damping-mass support model is developed utilising the identified parameters and verified by comparing simulation results with measurement data. Finally, in pursuit of improving current collection quality, the effects of support damping and train speeds on contact forces are investigated. The results show that the support damping can mitigate the OCR’s vibration. The increase of support damping within a specific range, 0–200 Ns/m, has a positive effect on the current collection quality.

Non-uniform variation characteristics of temperature field and corresponding thermal effect of longitudinal continuous slab ballastless track structure

The longitudinal continuous slab ballastless track structure (LCSBTS) easily suffers from interface and joint damage when subjected to extremely high-temperature loads, significantly affecting the running smoothness and safety of high-speed trains. This paper establishes a numerical model of the LCSBTS using the heat transfer principle and real-time shadow technology to replicate the time-varying evolution and spatial distribution of the temperature field. The corresponding thermal effect is obtained based on the sequential thermal-mechanical coupling method. The results show that the temperature variation and the corresponding thermal effect exhibit strong temporal-spatial non-uniformity on the horizontal and vertical planes of the LCSBTS. Solar radiation and heat convection are the dominant factors for the temperature field of the LCSBTS in the daytime and night, respectively, resulting in a higher temperature and greater thermal deformation on the sunny side than on the shady one. The temperature and vertical thermal deformation along the longitudinal direction vary periodically with a specific wavelength between the two adjacent rail support concrete blocks. The thermal deformation increments under the studied non-uniform temperature loads cause an interface damage increment. Finally, the consideration of a non-uniform temperature load produces remarkably different thermal effects from those given by the design temperature load.

Field investigation on the effect of the tamping machine and dynamic track stabilizer on changing the rail support modulus

Field investigation on the effect of the tamping machine and dynamic track stabilizer on changing the rail support modulus

Nonlinear dynamics simulation of the helical gear transmission system for high-speed train

Considering the bending-torsional-axial-coupled vibration of the helical gear transmission system, a 10 degrees of freedom high-speed train gear transmission system model, including motor and load, is established based on the lumped parameter method. In addition, the potential energy method based on the slicing principle is used to accurately calculate the time-varying meshing stiffness of helical gears. Furthermore, the influence of geometric parameters of helical gears on the time-varying meshing stiffness is studied, and the impact of time-varying meshing stiffness on the system is further investigated. Meanwhile, by analyzing the dynamic phenomena of the system under different parameter excitations under different parameter excitations, the influence of internal and external excitation parameters such as gear speed, wheel rail creep force, support stiffness, and support damping on the stability of high-speed train gear transmission system is deeply studied.

Predicting Axial Stress State In Continuously Welded Rail Using Impulse-Generated Vibration Measurements

Continuously welded rails are connected without stress relief joints and, thus, thermally induced rail movement is constrained, which can result in the development of excessive axial stress and risk of rail failure. Nondestructive testing (NDT) methods that estimate in-place rail stress state or rail neutral temperature are desired. Some methods have been developed, but none satisfy the requirements for ideal monitoring in practice. We propose an NDT technique based on impulse-generated vibration, seeking high-frequency rail vibration resonances whose frequency maintains a consistent correlation with rail axial stress/strain across different temperatures, stress states, and rail support conditions. Rail temperature, axial strain, and vibration data were collected from an active Class 1 commercial rail line over a period of nearly two years. The frequencies of four consistent and clear resonance modes of the rail were monitored. One of the identified modes demonstrates a unique linear relation with axial strain across a range of temperatures and stress states at each of the two measurement locations. The developed linear relations were used to predict in-place strain and rail neutral temperature with acceptable accuracy across all the measurement data, although each test location exhibits a unique relation.

The Numerical Study for the Effect of Stiffness Matching on Wheel–Rail Curve Squeal Noise

This study delves into the phenomenon of high-frequency squeal noise occurring as trains traverse small-radius curved tracks and investigates the factors influencing wheel–rail curve squeal noise, particularly focusing on stiffness matching. To achieve this, we initially construct a finite element model of the wheel–rail friction system using finite element software ABAQUS 2022, validating its accuracy against Coulomb’s friction law. Subsequently, we employ complex eigenvalue analysis to extract the complex eigenvalues and vibration modes of the wheel–rail system, enabling us to study the positions and vibrational patterns associated with squeal noise by analyzing the amplitudes of unstable modes. Finally, we assess the impact of wheel–rail stiffness matching on curve squeal noise, using wheel–rail material stiffness and rail support stiffness as key variables. The outcomes of this study reveal the following insights: (1) Unstable modes closely align with the resonant frequency and mode shape of the wheel and rail. (2) Curve squeal noise primarily emanates from vibrations at the rim, railhead, and rail foot. (3) Wheel and rail stiffness significantly affect squeal noise, with a significant deviation in the elastic modulus between rail and wheel increasing the likelihood of squeal noise, while an optimal ratio of about 1.2 is observed. (4) Rail support stiffness plays a discernible role in controlling curve squeal noise. Theoretically, maintaining an appropriate support stiffness level can minimize the negative damping ratio of unstable modes, providing a viable avenue for curve squeal noise control.

Stiffness profile spectral composition & geometry deterioration of railway tracks

This work addresses the contribution of the wavelength composition of the spectrum of the rail support stiffness profile to the expected long-term settlement. To that aim, purely harmonic stiffness variations of different wavelength are studied. The frequency-domain model with a double periodicity level previously developed by the first and last authors is adopted to embed the stiffness profile in one of the periodicity layers. Additional resonance velocities at which the resonance frequency of the track system coincides with the support-passing frequency or its multiples are found. The susceptibility to degradation is assessed both by quantifying the mechanical energy dissipated in the substructure under a moving train axle within one wavelength of the support stiffness variation, and the work performed by the wheel-rail contact force. It is shown that shorter wavelengths and larger standard deviations of varying ballast/subgrade stiffness result in an increasing energy dissipation in the substructure, and increase the work performed by the wheel-rail contact force, therefore leading to a reduced lifetime of the track. The energetic quantities increase for lower mean values of the stiffness profile, confirming the proneness of tracks on soft soils to degradation. The influence of varying stiffness vanishes for wavelengths of approximately 16 times the sleeper span, which is equivalent to a track length of about 10 m. High railpad stiffness values result in increased energy dissipation but the influence is limited. In general, an increasing train velocity amplifies the rate of track degradation, with no stabilizing trend in the high-speed regime (300 km/h).

Dampak Lingkungan Ekologis akibat Proyek Pembangunan Jalur Rel Light Rapid Transit (LRT) Jabotabek di Jakarta

Almost all developments of transportation facilities and infrastructure have positive and negative impacts on the ecological environment, social, and economic, such as the construction of rail lines and Light Rapid Transit (LRT) stations. The construction of rail lines and Light Rapid Transit (LRT) stations, both surface and elevated, has had various effects on the ecological environment, social and economic both during pre-construction, construction, and post-construction. The purpose of this paper is to identify the ecological environmental impacts due to green open space used for the construction of LRT rail lines and stations, especially the Jabodebek LRT line phase 1 in the city of Jakarta. This research was conducted by collecting data on the planning and construction of the 26 KM-long phases 1 rail line and LRT station. for the construction of rail lines and LRT station buildings. The results of the study show that with the rail pattern (elevated rail) it is possible to minimize the green open space used for the construction of rails and LRT stations. This study also recommends landscape proposals with vertical gardens on rail support pillars and station buildings as a substitute for some of the used green open space.

Analysis of Track Bending Stiffness and Loading Distribution Effect in Rail Support by Application of Bending Reinforcement Methods

Railway track is a linearly inhomogeneous object that consists of geometrical and elastic discontinuities such as bridges, transition zones, rail joints and crossings. The zones are subjected to the development of local instabilities due to quicker deterioration than the other tracks. Until now, there have been no efficient approaches that could fully exclude the problem of accelerated differential settlements in the problem zones. Many structural countermeasures are directed at controlling the sleeper/ballast loading with the help of fastenings/under-sleeper pad elasticities, sleeper forms and additional bending stiffness reinforcements. However, the efficiency of the methods is difficult to compare. The current paper presents a systematic approach in which the loading distribution effect in the rail support by application of two bending reinforcement methods is compared: auxiliary rail and under-sleeper beam. The study considers only the static effects to reach a clear understanding the influence of the main factors. The track equivalent bending stiffness criterion is proposed for comparing reinforcement solutions. The analysis shows that the activation of the bending stiffness of the reinforcement beams depends on the relative ratio of the rail fastenings stiffness and track support stiffness under sleepers (or under the under-sleeper beam). The comparison demonstrates that conventional auxiliary rail reinforcement solutions are ineffective due to their weak bending because of the high elasticity of fastening clips and the main rail fastenings. The share of an auxiliary rail is maximally 20% in the track bending stiffness and cannot be significantly improved by additional rails. The under-sleeper beam-based reinforcement solutions show noticeably higher efficiency. The highest effect can be achieved by the activation of the horizontal shear interaction between the under-sleeper beam and the rail. The additional track bending stiffness of the under-sleeper-based solutions is about 3.5 times more of the rail one and could be potentially increased to 6–10 times.

Evaluation of Spring Stiffness of Resilience Pads for Booted Sleeper Track System Using a Pressure Sensor

To date, the spring stiffness of resilience pads was mostly evaluated based on conventional (site measurement and laboratory tests) methods. Most studies in the past analyzed the effects of the deterioration of resilience pads on track damage. To examine the deterioration of resilience pads, evaluations were conducted based on laboratory tests using site measurements and samples were collected from the site, or based on loading tests using special equipment. such as TSS. However, no methodology was proposed to prove the theoretical equations of Zimmermann which compute the reaction force at the rail support point. Hence, this study aimed to prove that the reaction force increased if spring stiffness at the rail support point increased; this was achieved by using a pressure sensor according to the theoretical equations of Zimmermann. Furthermore, we aimed to propose a method to evaluate the spring stiffness of resilience pads to predict the extent of deterioration of the pads based on the increase in the pressure measured by a pressure sensor.

A novel data-based approach for monitoring fatigue crack propagation in welded joints under varying ambient temperature using the electromechanical admittance

Fatigue crack growth is one of the most common damage mechanisms of structural components and can result in a sudden and unexpected abrupt fracture which can cause catastrophic failure. Thus, monitoring of crack propagation is an important topic of structural health monitoring. For that reason, this work aims at the detection of crack propagation by the application of a high-frequency vibration-based method, using the electromechanical admittance (EMA). It enables the local monitoring of the coupled dynamic behavior of the structure and the piezoelectric transducer which changes, for example, due to damage. It is the purpose of this study to develop a method from the recorded data reflecting fatigue crack growth in weld zones. As it is known that the data are affected by temperature, a temperature compensation strategy is considered. In this study, a presentation of the coupled EMA data has been found, which allows the isolation of the crack propagation effects. Within the scope of fatigue experiments, fatigue cracks were introduced into threaded bolts of rail support points, welded onto base plates. In practice, they are embedded in a layer of mortar and, therefore, have poor accessibility. Electromechanical impedance measurements were carried out at different states of fatigue crack growth. The fatigue crack growth was validated by strain gauge measurements executed during the fatigue experiment. The proposed feature was calculated from the recorded EMA data. The technique produces promising results detecting fatigue cracks and can also be transferred to similar types of welded joints or rods where fatigue crack growth occurs.

Rail Structure Interaction Analysis for Providing CWR on Un-Ballasted Multi-Span Open Web Steel Girder Bridge

Rail structure interaction (RSI) requires thorough study to understand the force transfer mechanism between the track and bridge components due to train vertical live loads, braking/traction loads and thermal loads accordingly. RSI analysis gives us an outline of the axial stress in rail, support reactions transferred to the bridge components and the relative displacement caused between the track and bridge. This paper investigates rail structure interaction analysis of unballasted multi-span steel through girder railway bridge carrying dedicated freight corridor (DFC) of 32.5t axle load. For this purpose, RSI analysis is performed as per the guidelines given in UIC774-3R [7] Code of Practice (International Union of Railways) for two different multi-span bridge with a span configuration of 7x63m and 6x48m respectively and the axial stress in rail, relative displacement between rail and bridge and support reactions transferred to the bridge components are calculated based on the span and stiffnesses of the bridges. From the analysis results, it shall be concluded whether to explore the possibility of providing a provision of continuous welded rail (CWR) on the bridge or to adopt switch expansion joints (SEJ) or other expansion devices accordingly.

Training in an immersive virtual work integrated learning factory: A case of manufacturing an assembly rail support bracket

Training in an immersive virtual work integrated learning factory: A case of manufacturing an assembly rail support bracket

Feasibility study on the solution of replacing track slab with lateral pushing rail in one maintenance window time

The slab ballastless track is the primary type of high-speed railway. When the track slab in the ballastless track is severely damaged, the typical way to replace it requires cutting the jointless rail above the damaged track slabs. This paper discusses a solution of pushing the rail in the lateral direction (i.e., without cutting the rail) to replace the track slab. To study the feasibility and reliability of this solution, a finite element model for simulating the construction process of rail pushing is established. The necessary spacing of the support slides and the capability of the pushing device are analyzed. The influence of parameters such as the rail release length and the construction temperature on the mechanical state of the rail after being pushed is discussed. In practice, the repair time is limited to one maintenance window (i.e., 4 h). The control of the stress is critical in repairing progress. The corresponding relationship between the deformation curvature of the rail and the stress is studied, and the number of unlocking fasteners is reduced by optimizing the spacing of the rail support slides, which can effectively reduce the fine-adjustment range of the rail after changing the slab. By calculation and design, a “16 + 8 + 16 m” optimization plan is proposed, which can meet the needs of replacing the track slab in the four-hour maintenance window time of high-speed railway. Finally, the feasibility of the finite element model is verified through the comparative analysis of the monitoring data of the lateral pushing of the rail and the simulation analysis results.

Research on track damage identification based on the response of vehicle-rail contact point

In this paper, spring element is used to simulate the vertical support of ballast and sleepers to the rail, which is called “elastic support”. Low-pass filtering technology was adopted to extract the response of the driving frequency component in acceleration signal of the contact point between vehicle and rail, and Hilbert transform was carried out on it to obtain instantaneous amplitude squared (IAS) information to judge the damage of rail and elastic supports through the peak values in the IAS identification diagram. Based on this principle, the crack damage of rail and stiffness damage of elastic support are studied, the applicability of IAS method for the rail and elastic support under different damage degrees and damage amounts is analyzed, and the influence of parameters such as vehicle speed, vehicle damping ratio, vehicle mass and frequency, track damping and rail irregularity on IAS damage location method is discussed. The results show that the IAS method can accurately identify the damage of elastic support and rail under different damage locations and different damage degrees. Under proper vehicle speed, the IAS method can accurately locate the damage; The influence of vehicle frequency on damage identification results is small. With the increase of vehicle damping ratio, the amplitude of IAS results decreases, while track damping has almost no effect on damage identification. Due to the existence of track irregularity, the damage signal collected by test vehicle may be covered by irregularity, and the interference of track irregularity can be reduced by increasing the mass of test vehicle.

Influence of Fastener Failure on Dynamic Performance of Subway Vehicle

The track fasteners may be damaged by fatigue and impact load during long-term subway operation, resulting in the failure of the connecting components between the rail and the track plate, and the spacing of rail support becomes larger, resulting in an increase in its dynamic deformation, affecting the subway vehicle’s running performance, and, in severe cases, endangering the vehicle’s running safety. A vehicle-subway track system model was created to study the running performance of subway vehicles when fasteners failed. A multi-rigid, body spring damping system is used to describe the vehicle system. The model for the track system is created using the finite element method (FEM), and the vehicle dynamic performances under various fastener failure scenarios are calculated, as well as the vehicle’s running comfort and safety in various scenarios. The findings show that fastener failure has little impact on the vehicle’s running comfort but it has a significant impact on the vehicle’s wheel unloading ratio.

Dynamic Impact of a Rail Vehicle on a Rail Infrastructure with Particular Focus on the Phenomenon of Threshold Effect

The paper undertakes analysis of the dynamic impact of a rail vehicle on various types of a railway infrastructure with particular focus on the phenomenon of threshold effect within the transition zones of an engineering facility. The problem of locally variable stiffness of the railway infrastructure, which in turn could lead to the accelerated infrastructure degradation, is identified. Using the analytical and numerical background, the computational model is presented, based on which, it could be possible to determine the impact of the various rail support on the dynamic response of the entire infrastructure. The dynamic load, caused by the passage of the multiaxle rail vehicle, is taken into account in the paper. The fourth-order differential equation is solved by using the finite differences method with application of the numerical MATLAB script. The created numerical algorithm and a number of calculations allowed the formulation of several solutions that could reduce the dynamic impact of the rail vehicle on the railway surface within the transition zones. In the paper, theoretical results are compared to the field measurements conducted on a real dynamically loaded rail. Field experiments have been carried out on the railway track in operation. The vertical displacement of a rail, dynamically loaded by various types of rail vehicles passing by (both passenger and freight trains) has been investigated. Researches have been carried out in the area of transition zones of engineering facilities. Test points have been selected in places where there is a sudden change in parameters of the track structure (e.g., a change from concrete sleepers to wooden sleepers). Based on conducted researches it has been possible to validate results obtained from the numerical calculations.

Ranking of transport network development projects in the Sverdlovsk railroad area based on fuzzy logic

Relevance. Due to the turbulence of economic processes in the period of sanctions pressure on the economy, decisions should be made, effective, first of all, from a national position. For this purpose, it is necessary to justify them using multi-criteria and all available information, which at the initial stages is fundamentally incomplete, insufficiently reliable and sometimes weakly formalized. In such cases, it is advisable to use special methods to assess the decisions made in conditions of uncertainty, in particular methods of fuzzy logic and mathematics. Purpose of the study. The study is aimed at assessing the order of priority of transport rail support on the investigated most important in the federal and regional scale main lines by including the most significant technological and economic criteria, reflecting the nationwide priority. Data and Methods. To compare different methods of priority construction of the main lines of railway lines, we used the procedure of fuzzy multi-criteria analysis of the projects. The assumed priorities of transport rail support are based on four trunk line projects: the Middle Urals Latitudinal Railway on the N-Tagil - Perm section; the Troitsko-Pechorsk - Ivdel section; the Perm - Chernushka section; the Ust - Aha - Uray - Khanty-Mansiysk - Salym section. Results. The paper proves the possibility of applying the approach based on fuzzy logic to the analysis of economic processes in the period of shocks to the economy, caused, in particular, by the introduction of sanctions from unfriendly countries. The estimated priority of transport rail support on the four projects of the most important trunk lines is assessed. Conclusions. With the help of fuzzy logic methods, it is possible to find compromise options that satisfy the various interests of those affecting the decisions, regardless of the structural organization of the backbone industries, one of which is undoubtedly the transport industry.

Rail Surface Defect Detection and Analysis Using Multi-Channel Eddy Current Method Based Algorithm for Defect Evaluation

The railroad rail support trains and contributes to their operation. Internal and surface defects occur on the rail due to various combinations of causes including fatigue loading and cyclic tension and compression among others from the deterioration of the rail along with the temperature differences of seasonal changes. Surface defects such as head check, shelling, and squats start out in the rail head and become internal defects due to poor maintenance, ultimately resulting in rail failure. In order to prevent rail failure, it is important that defects are identified through nondestructive evaluation (NDE) in advance and to carry out maintenance techniques including grinding. NDE methods include MFL, EMAT, and ECT, and among these, the ECT method is a representative method with excellent detection sensitivity that nondestructively inspects metal surfaces such as rails and pipes using an electromagnetic field. Also, since the defect signal is obtained as an electrical signal, the depth, length, and width of defects can be assessed using a defect evaluation algorithm. This study investigated the field applicability and future practical use of the 16 channel eddy current testing equipment and defect evaluation algorithm developed in this study. Therefore, the field applicability of the equipment and defect evaluation algorithm was investigated through the detection of artificial defects with varying size and depth. Afterwards, future practical use was evaluated by inspection of areas of rail that are in use and with naturally occurring surface defects and analysis of their size (length, width), depth, and phenomena.

Design and Development of an Indoor Testing Facility for Downwash and Spray Distribution Evaluations of Agricultural UAV

The usage of UAV as a pesticide application technology is becoming a common practice in South East Asia with a very significant proportion of agricultural areas have now being treated using such method. Up to date, about more than 169 of various designs and configurations of UAV have been produced to cater the demand, however it is in doubt whether all these available models were optimally integrated with the spray systems to give the required spraying qualities. Despite of each UAV configuration has their own unique aerodynamic effects, it is crucial to determine their downwash airflow patterns, the spray distributions and the effective application parameters that could give high spraying quality. This research outlines the development of an indoor testing facility and its standardised testing procedure for evaluating the spraying performances of any model UAVs that are used in agricultural applications. The testing facility was developed to imitate the UAV in the actual field spraying operation. With 23 m travel length, the developed testing facility was designed to carry the test UAV up to 100 kg, adjust the test UAV at three levels of spraying heights (1.5, 2.5, and 3.5 m), and moves the test UAV up to a maximum travelling speed of 10 m/s. The 6x6 m sampling platform structure for the pressure sensors and water sensitive papers was built underneath the rail support structure to measure and collect data for spraying distributions and downwash 3D profile spectrum. With the availability of this indoor UAV Testing Facility, it is expected that any efforts to increase the spraying efficiency using UAV could be tested repeatedly with same standard protocols, so that proper recommendations could be made on the flying requirements of the UAV in order to achieve an efficient agricultural chemical spraying operation.