Continuous Welded Rail Research Articles

Field monitoring and prediction of the thermal response of an in-service curved continuous welded rail using distributed fiber optic strain measurements

Field monitoring and prediction of the thermal response of an in-service curved continuous welded rail using distributed fiber optic strain measurements

A data-driven approach to quantify track buckling strength through the development and application of a Track Strength Index (TSI)

Railroads are increasingly adopting advanced technologies to enhance safety and state of good repair of their track infrastructure, some of which employ artificial intelligence-based inspection methods. The objectivity of these inspection techniques, along with their detailed measuring capabilities, has created opportunities for railroads to improve both inspection and operational efficiency. This is achieved through more frequent and precise track data collections and technical data aggregations. This paper explores the potential of these track inspection methods to address one of the few drawbacks of continuous welded rail (CWR): track buckling. While track buckling mechanics and prevention have been the subject of numerous studies, the need for a practical and objective method to assess resistance to buckling remains. Numerous track health indices for geometry parameters and some for railway components have been developed and utilized in various applications. Yet, the opportunity exists to develop a metric that combines geometric parameters with the condition levels of railway components, particularly designed to quantify the resistance of track to buckling. Such a holistic view of the track and network-wide time series analyses of the proposed metric demonstrate whether the buckling resistance improves, remains in a steady state, or declines. In this study, a sensitivity analysis conducted using CWR-Risk software identified misalignment amplitude, track curvature, lateral resistance, torsional resistance, and longitudinal resistance as the main factors contributing to buckling resistance. Based on the sensitivity study and with a focus on the capacity side of the track buckling equation, a methodology was proposed for converting inspection data into 10-point scales that were combined through weighted averaging into a single Track Strength Index (TSI) to quantitatively assess the resistance to buckling at a track-system level. The influence of ballast condition on TSI output was evaluated using 15 ballast configuration scenarios, ensuring that the index accurately reflects ballast deficiencies in a proportionate manner. Lastly, the proposed metric was tested leveraging revenue service data collected from a Class I railroad mainline in the United States.

Quantifying the effect of fixed structures on rail stress management: A numerical investigation

From 2012 to 2021, FRA accident data indicate that there have been 132 derailments caused by track buckles. Out of the 132 total derailments, 59 (or 45 %) occurred within 152 m (500 ft.) of a fixed structure. Therefore, this paper presents, validates, and applies a 3D finite element-based model to study the effect of the fixed structure on the rail gap size given a rail break. Specifically, the model was used to quantify the effect of the: 1) temperature differential between the rail neutral temperature (RNT) and the actual rail temperature (dT), 2) distance of the cut to the fixed structure, and 3) fixed structure length and anchoring patterns (ETA and EOTA). Model results indicated that at low dTs (e.g., <13.9ºC (25ºF)) the effect of the fixed structure can be considered if the cut occurred at the edge of the fixed structure with EOTA anchoring pattern and the fixed structure length of at least 18.3 m (60 ft.). At a dT of 22.2ºC (40ºF), the fixed structure should be accounted for when there is an edge cut. At extreme dTs (e.g., > 44.4ºC (80°F)) the fixed structure should be considered if the cut occurs within 152.3 m (500 ft.). Therefore, it is recommended that railroads refrain from strictly following open track guidelines for CWR (continuous welded rail) management and rather, consider the influence of fixed structures in relevant situations.

Concept of Thermal Shrinkage-Resistant Railroad Rail for Use in Continuous Welded Rail Track

This paper presents the concept of a modified 60E1 rail dedicated to continuous welded rail (CWR) track. The presented solution is the subject of a patent application by the authors of the publication. The paper describes problems associated with the operation of CWR track and the phenomena of so-called “rail stressing”, i.e., stresses created in the rail due to thermal shrinkage that, in extreme cases, can lead to the buckling of the rail track. Simulation calculations of longitudinal track loads to represent the occurrence of thermal force as a result of the occurrence of high air temperatures were carried out for the constructed conventional model of the railroad track as well as the track with the proposed solutions. A discussion of the simulation results is presented, indicating the possibility for the wider application of both varieties of modified rail.

Effect of Subsequent Subgrade on Seismic Response of the High-Speed Railway Track–Bridge System

As an important part of the boundary conditions on both sides of the high-speed railway track–bridge system, the seismic response of the subgrade structure is different from that of the bridge structure. This difference has become increasingly significant with the widespread adoption of continuous welded rail technology in bridge construction. Therefore, investigating the seismic response of the bridge system, with a specific focus on the longitudinal constraint effects of the subsequent subgrade track structure, is of paramount importance. Utilizing finite element software, two distinct bridge models are developed: one incorporating the subsequent subgrade track structure and another excluding it. Through nonlinear time history analysis under varying seismic intensities, it is demonstrated that the longitudinal constraint of the subsequent subgrade track structure mitigates the longitudinal displacements and internal forces in critical components of the high-speed railway track–bridge system. Concurrently, acknowledging the heightened complexity and cost associated with post-earthquake repairs of the bridge structure compared to subgrade structure, this study uses a risk transfer connecting beam device. This device can redirect seismic damage from bridge structure to subgrade structure, thereby potentially reducing post-seismic repair expenses for the bridge.

Birefringence Technique for Evaluating Thermal Stresses in Railroad Rails

This paper discusses the development of an in situ noncontact electromagnetic acoustic transducer (EMAT) nondestructive evaluation technology to determine rail neutral temperature and estimate rail stress in continuous welded rail (CWR). Stresses develop in CWR due to a lack of expansion joints to accommodate thermal expansion and contraction of the rail when ambient temperatures vary over time. The novelty of the work presented is the usage of ultrasonic birefringence properties using EMATs to estimate thermally induced stresses in rails. EMATs produce polarized shear waves propagating through the rail web in the pulse-echo mode. Experimental tests were performed on machined 136RE and 141RE rail material with applied compressive and tensile stresses to explore the stress-birefringence behavior. Two additional sets of experimental tests were conducted on full-size rail sections with in situ surface conditions to study variations in the in situ birefringence and the acoustic stress constant in different rail materials including 115RE rail, 119RE rail, two different 136RE rails, and 141RE rail. The results show a highly linear relationship between the stresses applied and the measured acoustic birefringence.

Nondestructive Estimation of Neutral Temperature in Rails: A Comparative Study of Machine Learning Strategies

This paper presents the latest findings of a nondestructive evaluation technique currently under development at the University of Pittsburgh to determine the rail neutral temperature (RNT) in continuous welded rails. The technique is based on the extraction of relevant features from rail vibrations and the use of machine learning (ML) to associate these features to the longitudinal stress of the rail of interest. The features contain the spectral information of the vibrations and are pooled together by frequency domain decomposition for input to ML algorithms. Minimum redundancy–maximum relevance and neighboring component analysis are used to identify relevant features to reduce the size of the input vector. In addition, seven algorithms were considered to identify the most accurate model for neutral temperature with respect to the ground truth RNT measured with a strain-gage rosette. The data used in this study were collected from a 5° curved rail on concrete ties. The vibrations were triggered with a hammer and recorded with a few wireless and wired accelerometers attached on the railhead. The results showed that the Gaussian process regressor performs best, and as few as 20 frequencies can be used to predict the RNT with sufficient accuracy.

Mathematical models and algorithms for determining the modes of an intelligent stage control sensor

In article discusses models of unlimited track circuits with a receiver, adapting to different working conditions, applied double receiver with one power supply in the middle, which allows you to extend the length of the continuous rail circuit. For this, a goal is set, in which is the development of models of jointless track circuits with an adaptive receiver, in which the rail line must take into account the total stress distribution along the rail line and disturbing factors. The article presents the equivalent circuits of continuous welded rail circuits with an adaptive receiver, algorithmic expressions for determining currents and voltages at the ends of the rail circuit, the coefficients of rail lines with an adaptive receiver are developed, calculation algorithms are presented. In conclusion, a graph is given, according to which it is shown that a continuous rail circuit with an adaptive receiver can operate with an insulation resistance three times lower than the threshold value in any modes of the rail circuit, taking into account the fact that, minimum allowable insulation resistance for tone-on-tone continuous rail circuits is taken as Ri=0,7ohm*km. Derived for the theory and synthesis of solutions, and also proposed new approaches to ensure the operating modes of the rail circuit, taking into account the real and weather conditions of operation.

Analysis of the impact of rail head wear on railway superstructure stability

Continuous welded rail track (CWR) is a superstructure construction of the railway that withstands significant compressive forces from the longitudinal extension of the rails due to temperature changes, ensuring the safe railway operation. The applicable for the Bulgarian railway system methodology for determining the critical compressive force at which the CWR loses stability has been examined. Different types of rails with their respective design parameters, important for the force calculation, have been taken into consideration. The considered design parameters, as moment of inertia and sectional modulus of the rails, change during operation due to the rail head wear. The aim of the article is to examine specific examples of railway tracks on curves, analyzing the impact of the changed operational design parameters of the rail on the stability of the track. The operational and geometric parameters of the railway track have been considered.

Nondestructive determination of longitudinal rail stress from guided wave dispersion properties

The determination of the longitudinal stress in continuous welded rails is essential for the safe operation of high-speed railways. Guided wave inspections have many advantages, and can provide an effective tool for non-destructive measurements of the longitudinal stress in rails. This paper provides a new method for determining longitudinal rail stress using ultrasonic guided wave dispersion properties. First, the characteristic equations of guided waves propagating in a waveguide with existing longitudinal stress are constructed, generating the dispersion properties of the waveguide such as the wavenumber, phase velocity and group velocity. The sensitivity of the dispersion properties of propagative modes to the longitudinal rail stress is investigated, which is then used for selecting appropriate modes for guided wave inspections. On the basis of the perturbation method, the relationship between the change in longitudinal rail stress and the change in dispersion properties is developed, which can be used for determining the longitudinal rail stress from dispersion properties. Furthermore, a mode selection index considering both the stress sensitivity and mode shape characteristics is employed for selecting appropriate propagative modes for guide wave inspections. Finally, a numerical example for CHN60 rail is adopted to demonstrate the effectiveness of the proposed method. From the results, the proposed method can accurately determine the longitudinal stress in the rail by using the dispersion properties available.

Effect of Critical Factors Influencing Longitudinal Track Resistance Leveraging Field Experimentation

As extreme temperatures increase, there is an increased need to ensure that continuous welded rail (CWR) stresses are more accurately set and better maintained. Therefore, to improve the management of CWR rail stresses and to increase safety through the reduction of buckled track derailments this paper documents the results from a field experimentation program of controlled single rail breaks (SRBs). SRBs were conducted at multiple field site locations to quantify the longitudinal resistance on both timber and concrete sleeper track. Accurate longitudinal resistance values are critical, because if the wrong value is selected, the rail neutral temperature could easily be set to a low value, increasing the probability of a track buckle or rail pull-apart, further compounding the impact of extreme temperatures. The results presented quantify the effect of sleeper and fastener type as well as ballast consolidation, and compare them with relevant results from the literature. From this, it was found that well-maintained concrete sleeper track exhibited a longitudinal resistance greater than the currently recommended value. Further, well-maintained timber sleeper track with anchors on every other sleeper exhibited a longitudinal resistance 44% lower than concrete sleeper track and 30% lower than timber track with anchors installed on every sleeper. Additionally, disturbing the ballast reduced the longitudinal resistance by 15%. Finally, the results indicated that slip was primarily occurring at the rail–sleeper interface for unanchored timber sleepers and at the sleeper–ballast interface for anchored timber sleepers and concrete sleepers.

Track‐Bridge Interaction: Influence of Transition Zone on the Stability of Continuous Welded Rail

AbstractRealization of high‐speed rail track demands continuous welded rail (CWR) to be laid on bridges without providing special expansion joints. In India, the existing rail bridges must be evaluated for their suitability for upgradation to CWR. CWR Inherently develops axial stress on account of the surrounding temperature changes. CWR in track‐bridge transition zone is subjected to additional stress and displacements as a result of track‐bridge interaction (TBI). Longitudinal thermal loading is a major source of rail stress and substructure forces due to TBI. Also, TBI results in accumulation of large compressive stress in transition zone. Further, the tamping effect in the transition zone by passing vehicles due to sudden change in vertical stiffness weakens the transition zone ballast. CWR is a slender steel element prone to buckling under large compressive stress. A numerical model is developed for track bridge interaction phenomenon in SAP2000 considering the aspect of CWR track buckling. In this study, the developed model is utilized to perform nonlinear buckling analysis to assess the influence of change in ballast stiffness on CWR stability in transition zone. Also, the influence of missing ballast contact raising from ballast subsidence locally in the transition zone was investigated. A single span simply supported steel bridge is considered. Longitudinal thermal loading is considered in this study. CWR supported on the ballasted track is considered. Material Nonlinearity associated with ballast is considered. Maintenance of CWR track is found to play a key role in track stability as the loose ballast or missing of ballast underneath the rail sleeper is to introduce discontinuity in CWR track support and reduces the critical buckling temperatures of the track considerably. Overall, this study contributes to the understanding of track‐bridge interaction and the stability of CWR in the transition zone.

Vulnerability Analysis of Catenary-Bridge-Track System

Continuous welded rails on bridges are extensively employed in high-speed railways, where trains are predominantly electrically powered, and the open-air catenary represents the weakest link in the system. Despite the widespread use of continuous welded rail on bridges for high-speed railways, there exists a relative dearth of research on their vulnerability, particularly regarding seismic vulnerability studies that consider the catenary, track type, and bridge collectively. The vulnerability of fasteners and catenary on bridges under the longitudinal resistance of the line was investigated by constructing a 7−32 m high-speed railway double-line simply-supported box girder bridge. It reveals, for the first time, the influence of the longitudinal resistance of the line on the vulnerability of fasteners and catenary under seismic action. The study indicates that both the fasteners’ and catenary’s vulnerability increases with the intensity of ground shaking, with the catenary being more susceptible. The longitudinal resistance of the line has a greater impact on the fasteners’ vulnerability than the catenary. When the degree of damage is minimal, the order of damage to the fasteners is the ballasted track, small resistance fastener, and ballastless track when the probability of exceedance is 5%. The ballastless track can significantly increase the probability of no damage to the fasteners, and it is recommended that the ballastless track be used when designing high-speed railway bridges in earthquake-prone regions.

Additional Criteria of Change of Curvature and Temperature of Rails for Monitoring the Pre-Failure State of a Continuous Welded Rail in Plan

The article discusses proposals referring to a new way to control the state of a continuous welded rail.The main factors that have the greatest impact on the state of a continuous welded rail are displacement of rail and the state of a continuous welded rail in plan. This group of factors describes the temperature-stressed nature of operation of a continuous welded rail. Evaluated factors determining the properties which prevent displacement include the state of rail fastenings, the width of the shoulder of the ballast prism, the presence of hanging and unsupported sleepers, and fulness of the ballast cribs, space between the sleepers.The combination of these factors makes it possible to identify a complex coefficient with a high degree of reliability to assess the pre-failure state of a continuous welded rail associated with the risk of loss of stability of a continuous welded rail, the degree of danger of violation of train traffic safety.In order to assess the state of a continuous welded rail and the degree of its deterioration, the paper presents evaluation criteria. They allow getting a comprehensive picture of the state of any section of a continuous welded rail based on the results of its inspection by diagnostic tools and creating a list of recommendations to eliminate the identified violations.The paper highlights also the shortcomings of the existing methodology for assessing the state of a continuous welded rail in plan, which is based on the analysis of changes in the curvature of welded rails in plan in time. The retrospective analysis carried out by the author shows that there are cases of a sharp change in the state of a continuous welded rail in plan, which are currently not considered by the existing evaluation criteria. To increase detectability of such sections of a continuous welded rail, it is proposed to supplement the existing algorithm with additional evaluation criteria referring to changes in curvature of welded rails and in rail temperature, which allow timely identification of the places of a sharp change in the state in plan.Subsequent studies are suggested to establish the relationship between the rail temperature and the sites of a sharp change in the state of a continuous welded rail in plan.

Machine Learning for the Nondestructive Prediction of Neutral Temperature in Continuous Welded Rails

ABSTRACT This paper describes the application of machine learning (ML) in the framework of a data-driven nondestructive evaluation (NDE) method to estimate the rail neutral temperature (RNT) of continuous welded rails (CWR). The method consists of triggering vibration of the rail of interest and extracting the power spectral densities (PSDs) of the accelerations associated with the lowest modes of vibration. The PSDs then become the input of an ML algorithm trained to associate the PSD to longitudinal stress and then RNT. In the study presented in this article, the proposed NDE method was tested on a tangent track on wood cross-ties. Vibrations were induced with a hammer and detected with several wireless and wired accelerometers. The PSDs across the 0–700 Hz range were extracted from the time-series. These densities in both the lateral and vertical directions constituted part of the input of an artificial neural network trained and tested with experimental data. The predicted neutral temperatures showed very good agreement with the RNT estimated by an independent party and based on conventional strain-gage rosettes.

Research on non-destructive testing of stress in ferromagnetic components based on metal magnetic memory and the Barkhausen effect

In this paper, the relationship between the effective field of metal magnetic memory (MMM) emission and the structural stress of the ferromagnetic components is studied. The relationship between the voltage of the received magnetic Barkhausen noise (MBN) and the excitation source is also studied. Moreover, the characteristics of the emission spectrum of the MMM and MBN detection signals, and the influences of the lift-off distance on the stress detection accuracy of the two detection methods are studied. The advantages and disadvantages of the two magnetic non-destructive testing (NDT) techniques are analyzed separately, and their functions are combined to enhance the advantages and weaken the disadvantages. Modern signal analysis methods such as wavelet packet transform and signal feature extraction are introduced to process MMM signals, and a classifier for stress grading is established in combination with machine learning methods. On this basis, graded detection of the temperature stress of the continuous welded rail (CWR) was carried out. The detection accuracies of the 30–50 MPa, 50–70 MPa and 70–90 MPa stress grade ranges of CWR reach 71.43%, 82.76% and 75.00% respectively. The rapid grading detection of the temperature stress of the CWR and the rapid judgment of the structural stability of the CWR are realized based on the MBN-MMM detection technique.

Mechanical deformation properties of Continuous Welded Rail on kilometer-span suspension bridge for high-speed railway

The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail (CWR) brings great challenges to CWR designing. Taking a suspension bridge with laying CWR as a case, the mechanical properties of CWR on the bridge are analyzed to reveal the sensitive areas of the track, and the design method of CWR and track structures on the beam ends are proposed. The results show that the unidirectional Rail Expansion Joints(REJ) need to be installed on the beam end of the kilometer-span bridge to reduce rail longitudinal force. Due to the bridge characteristics, there is no CWR fixed area on the kilometer-span bridge, and rail longitudinal force on the main span caused by bending loads needs to be concerned. The deformation of track on the beam end is complex, which is the weak area on the kilometer bridge, the large relative displacement between the stock rail of REJ and the main beam can cause poor stability of ballast bed on beam end, small resistance fasteners need to be laid on the sides of stock rail on the main beam to increase the stability of ballast and fasteners on the beam end. To improve the driving safety and comfort of beam end, the Sleeper-Supporting Apparatus (SSA) should be specially designed to ensure the uniform transition of track on beam ends. Temperature and wind loads have a significant impact on track regularity on the kilometer span bridge, the dynamic response of trains and bridges under those loads needs to be attended to.

Fatigue Characteristics of Long-Span Bridge-Double Block Ballastless Track System

The key issues in designing ballastless track for high-speed railway bridges are to reduce maintenance and improve track smoothness by understanding fatigue damage characteristics. This paper is based on the principle of bridge-rail interaction and train-track-bridge coupling dynamics, the refined simulation model of bridge-CRTS I Bi-block ballastless track system is established by using the finite element method. The longitudinal force distribution law of CWR (Continuously Welded Rail) and the dynamic response characteristics of coupling systems are studied, based on the Miner rule and S-N curve. The fatigue characteristics of ballastless track system laying on long-span bridge under the dynamic train load and the effect of ballastless track system design parameters changes on fatigue characteristics are discussed. The results show that the extreme values of longitudinal force of CWR all appear in the middle of the bridge span or near the bridge bearing, and attention should be paid to the strength checking of CRW laying on long-span bridge. Under the dynamic train load, the fatigue life curve of rail on the bridge is relatively smooth and the minimum life of rail which is laying on continuous bridge decreases from 27.1 years to 17 years that which is laying on cable-stayed bridge. The life curve of track plate laying on continuous bridge is relatively smooth, and the life curve of track plate laying on cable-stayed bridge is related to the stiffness of elastic cushion, which decreases in a stepped manner, and there will be no fatigue failure on the track plate during service. The life curve of the baseplate is related to the type of bridge, the minimum life value of the baseplate appears near the bridge bearing, and there will be no fatigue failure on the baseplate during service. Increasing the stiffness of elastic cushion can effectively improve the fatigue life of track plate, and increasing the vertical stiffness of fasteners can enhance the connection between rail and track plate and improve the fatigue life of rail. The increase in train speed will increase the dynamic stress amplitude of track structure and reduce the fatigue life of the rail.

Effect of Random Lateral Ballast Resistance on Force-Deformation Characteristics of CWR with a Small-Radius Curve

To address the randomness of lateral ballast resistance in the field and its effect on the force-deformation behavior of Continuous Welded Rail (CWR) with small-radius curves, field tests were first conducted to investigate longitudinal and lateral ballast resistance on a 250 m-radius curve. It was found that the lateral ballast resistance follows a normal distribution based on the Shapiro-Wilk test. A finite element model of a small-radius curve CWR track was then established based on actual field conditions, and the force-deformation characteristics were analyzed under thermal loading. The results showed that it is of great significance to incorporate the randomness of the lateral ballast resistance as the deformation mode is closer to the actual field situation. In particular, attention should be given to areas where the lateral ballast resistance is weak. The research presented here has significant implications for railway maintenance practice.

Nondestructive rail neutral temperature estimation based on low-frequency vibrations and machine learning

This paper describes the latest advancements of a non-invasive inspection/monitoring technique to estimate the rail neutral temperature (RNT), which is the temperature at which the net longitudinal force in continuous welded rails is zero. The technique is based on the measurement of the lowest modes of vibration of the rail of interest, and the application of machine learning (ML) to predict the RNT from the spectral densities of the vibrations’ frequencies. In the study presented in this article, the proposed technique was tested twice in the field. Vibrations were induced with an instrumented hammer on a 5° curved rail on concrete ties, and detected with a few wireless and wired accelerometers. The time-series were post-processed to extract the power spectral densities across the 0–700 Hz range. These densities constituted the input vector of a ML algorithm trained with experimental data and then tested with different experimental data. The RNT predicted by the algorithm were compared and showed very good agreement with the temperature estimated by an independent party and based on conventional strain-gage rosettes.