Railway Turnout Research Articles

Effect of the vertical relative motion of stock/switch rails on wheel–rail contact mechanics in switch panel of railway turnout

In order to enable the vehicle to change among the tracks, the stock and switch rails are separated and provided with different rail resilience levels on the baseplate in the railway turnout switch panel. Therefore, there will be vertical relative motion between stock/switch rails under wheel loads, and the relative motion will change the combined profile of stock/switch rails and consequently affect the wheel–rail contact mechanics. A method is developed in this article to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact mechanics along the railway turnout switch panel. First, the possible rigid wheel–rail contact points, called primary and secondary stock/switch rail contact points, are calculated based on the trace line method; second, the actual contact points are determined by the presented equations; finally, the distribution of wheel–rail contact forces on the stock/switch rails is obtained based on the continuity of interface displacements and forces. A numerical example is presented in order to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact points, stresses, and forces, and the results are presented and discussed.

Ballast Degradation Modeling for Turnouts based on Track Recording Car Data

Turnouts play a central role in the railway infrastructure since they enable increased network capacity and allow for minimal impact of train delays. Their performance is of paramount importance for infrastructure managers, who face large maintenance cost in order to secure proper turnouts operability. Railway turnouts are complex mechanical systems, whose dynamic performance depends on the health state of the different components of the superstructure and substructure. A key component is the ballast as it provides the elastic support to the track and the sleepers and it largely contributes to the safety and reliability of the infrastructure. Ballast degradation can be a root cause of excessive failures in other components. A track recording car is typically used to collect geometry data that is used to assess the quality of the railway tracks; however this type of data has not been widely used for ballast quality evaluation in turnouts. One reason is that maintenance decision for turnouts are dominantly made based on visual inspections and/or manual measurement of track geometry, as turnouts are significantly more complex that traditional railway track. This study presents the application of fractal dimensioning of track longitudinal level for the monitoring of ballast degradation in railway turnouts. In other words, the irregularities of the track vertical profile related to the ballast degradation are quantified as a ballast quality index. The ballast quality index is the basis for developing ballast degradation models in different sections of the turnout based on a segmentation scheme. Using track geometry data of 88 turnouts in the Danish railway network for the period 2012-2017, this study develops and compares ballast degradation models based on regression analysis and stochastic processes (lognormal and Gamma processes). The models are estimated for different sections of the single turnout, for different turnouts at distinct geographical locations. The proposed method provides an efficient tool for the analysis of the effect of tamping on ballast degradation rate. Moreover, the effects on ballast degradation of track loading rate, train speeds and seasonal changes of weather conditions are quantified.

Dynamic Performance of Concrete Turnout Bearers and Sleepers in Railway Switches and Crossings

Abstract With constant changes of their geometry and alignment, wheel–rail forces, and track and operational parameters, railway infrastructures are exposed to nonlinear actions by nature. A detrimental type of loading condition that causes cracking in the railway concrete bearers in switches and crossings is the dynamic transient wheel force. The transient wheel forces are often due to the wheel–rail transfer over the dipped trajectory at a crossing nose. It is often found that most track deterioration incurs at the crossing panel. The turnout bearers crack and break. The ballast degradation then causes differential settlement and later aggravates the impact forces acting on partial and unsupported sleepers and bearers. In addition, localized ballast breakages underneath any rail seat increase the likelihood of center-bound cracks in railway sleepers and bearers because of the unbalanced support. This article investigates the dynamic performance of standard-gauge concrete bearers at crossing panel, taking into account the realistic, nonlinear tensionless nature of ballast support. A finite element model was established and calibrated with static and dynamic responses using past experimental results. In this article, nonlinear phenomena caused by topologic asymmetry on both sagging and hogging behaviors of crossing bearers are firstly highlighted. In addition, it is the first to demonstrate the effects of dynamic load impulses on the design consideration of turnout bearers in crossing panel. The outcome of this study will benefit the railway turnout design and maintenance criteria in order to improve train–turnout interaction and reduce unplanned maintenance costs.

In situ measurements of the crossing vibrations of a railway turnout

Vibration-based condition monitoring is a powerful tool for remotely assessing the quality of railway components. Due to its design, railway crossings suffer from faster degradation, because of the transition from stock rail onto the needle. Since this is also a repetitive load, a small amount of wear will increase the degradation. Measuring the dynamic response also contains information about the transition of the train wheel from the stock rail onto the needle.In this paper, a setup that measures the acceleration and the strain of a railway crossing during train passages is presented. The responses of these two measurement techniques are analyzed for two different types of trains. A linear correlation between the peak values of the strain and the nominal axle load is presented with a regression value of -1.8·10-5. From the accelerations, both the displacement and the transient wheel-rail contact can be analyzed.

Numerical investigation on effect of the relative motion of stock/switch rails on the load transfer distribution along the switch panel in high-speed railway turnout

ABSTRACTIn railway turnout, the stock rail and switch rail are separated to enable the vehicle changing among the tracks, and they are provided with different rail resilience level on the baseplate. Therefore, there will be vertical relative motion between stock/switch rails under the wheel loads, and the relative motion will affect consequentially the wheel–rail contact conditions. A method is developed to investigate the effect of the relative motion of stock/switch rails on the load transfer distribution along the switch panel in high-speed railway turnout. First, the rigid wheel–rail contact points of stock/switch rails are calculated based on the trace line method, and then the contact status is determined by the presented equations, finally, the distribution of wheel–rail contact forces of stock/switch rails is obtained based on the continuity of interface displacements and forces which using an approximate surface deformation method. Some parametric studies have been performed, such as the lateral displacement of wheel set, the vertical contact forces, the wheel profiles and the vertical stiffness of rail pad. The results of the parametric study are presented and discussed.

Diagnostics of railway turnout systems using tools of centralization blocking system

Turnout systems are one of the few most important components of the railway infrastructure. Recently there has been a revival of research aimed at prognostics and health management of railway turnout systems. The works of the researchers are devoted to evolution timely diagnosis of damage of mechanical components or failures electrical components of switch motor, and contaminated by turnout system. In this article, the approaches of the most common specialized systems of diagnosing and predicting the technical condition of railway turnout systems elements such as POSS, SIDIS W, and APK-DK. The work presented in this article are followed by available approaches and studies of centralization blocking system tools’ informativeness in the field of turnout systems failure diagnostic. The main point of view are methods of engine current analysis. The analysis of the motor current curves of the railway turnout obtained by the experimental method for different values of the ADC operating frequency is presented. Similar current curves are obtained by mathematical modeling of the normal operating mode of the elements of the railway turnout and under the condition of working with developing damage.

Bayesian Network-based probability analysis of train derailments caused by various extreme weather patterns on railway turnouts

Since multiple failure events associated with derailments could not be identified and derailment probability could not be reached quantitatively by event tree and fault tree analysis for safety assessment in railway systems, applications of Bayesian network (BN) were introduced over the last few years. The applications were often aimed at understanding safety and reliability of railway systems through various basic principles and unique inference algorithms focusing on particular railway infrastructures. One of the most critical engineering infrastructure, railway turnouts (RTs) have been investigated and analysed critically in order to develop a new BN-based model with unique algorithm. This unprecedented study reveals the causal relations between primary causes and the subsystem failures, resulting in derailment, as a result of extreme weather-related conditions. In addition, the model, which is designed for rare events, has been proposed to identify the probability and underlying root cause of derailment. Consequently, it is expected that various weather-related causes of derailment at RTs, one such undesirable event, which can result, albeit rarely, damaging rolling stock, railway infrastructure and disrupting service, and having the potential to cause casualties and even loss of life, are identified to allow for smooth railway operation by rail industry itself. The insight into this weather-derailment will help the industry to better manage railway operation under climate uncertainty.

Modeling of railway turnout geometry in the frog area with the vehicle wheel trajectory

In this study, three functions including the ‘V’, ‘U’, and ‘S’ shapes are considered for the analysis of alignment around the turnout in the frog area. The gap between the wing and nose rails is presented as an irregularity function that could be illustrated as a rectangular, single-slope, or double-slope trough model, and the dimension of the wheel of the vehicle is taken into account for the trajectory analysis. The wear and grinding of the nose rail are also demonstrated in detail. The vertical vibrations of the vehicle are simulated as passing through the functional model of the turnout. The results showed that the combination of an S-shaped alignment and a double-slope trough model could be suitable for the analysis of the turnout geometry in the frog area.

A Bayesian Probabilistic Approach for Acoustic Emission‐Based Rail Condition Assessment

AbstractThe investigation described in this article aims at developing a Bayesian‐based approach for probabilistic assessment of rail health condition using acoustic emission monitoring data. It comprises the following three phases: (i) formulation of a frequency‐domain structural health index (SHI), via a linear transformation method, tailored to damage‐sensitive frequency bandwidth; (ii) establishment of data‐driven reference models, using Bayesian regression about the real and imaginary parts of the SHI derived with monitoring data from the intact rail; and (iii) quantitative evaluation of discrimination between the new observations representative of current rail health condition and the baseline model predictions in terms of Bayes factor. If the deviation of the new observations from the predictions is within an acceptable tolerance, no damage is flagged, and the new data are further used to update and refine the reference models. If the observations deviate substantially from the model predictions in a probabilistic sense, damage is signaled, damage severity is quantified, and damage location determined. The proposed approach is examined by using field monitoring data acquired from an instrumented railway turnout, and the coincidence between the assessment results and the actual health conditions demonstrates its effectiveness in damage detection, localization, and quantification.

Composites for Timber-Replacement Bearers in Railway Switches and Crossings

Recent developments in composite materials have resulted in their pilot adoption in railway industry, such as ‘fibre-reinforced foamed urethane (FFU)’, ‘geopolymer concrete’, ‘recycled polymer’, and ‘CarbonLoc composite’. Railway track support systems are critical for safe and reliable operations of railway tracks. There are two types of support structures, which can be designed to be either a slab or a cluster of discrete bearers or sleepers. The choice of turnout support system depends on asset management strategy of the rail operators or maintainers. The aim of this paper is to present the criteria, fundamental and multi-disciplinary issues for the design and practical selection of composite materials in railway turnout systems. As a case study, a full-scale trial to investigate in-situ behaviours of a turnout grillage system using an alternative material, ‘fibre-reinforced foamed urethane (FFU)’ bearers, is presented. Influences of the composite bearers on track geometry (recorded by track inspection vehicle ‘AK Car’ and based on survey data), track settlement, track dynamics, and acoustic characteristics are highlighted in this paper. Comparative studies of composite materials for railway track applications are reviewed and presented in order to improve material design process. This state-of-the-art review paper will also focus on practicality and environmental risks of composite components in railway built environments. It embraces the requirement considerations of new materials for use as safety-critical track elements.

Low-complexity Behavioral Model for Predictive Maintenance of Railway Turnouts

Maintenance of railway infrastructures represents a major cost driver for any infrastructure manager since reliability and dependability must be guaranteed at all times. Implementation of predictive maintenance policies relies on the availability of condition monitoring systems able to assess the infrastructure health state. The core of any condition monitoring system is the a-priori knowledge about the process to be monitored, in the form of either mathematical models of different complexity or signal features characterizing the healthy/faulty behavior. This study investigates the identification of a low-complexity behavioral model of a railway turnout capable of capturing the dominant dynamics due to the ballast and railpad components. Measured rail accelerations, acquired through a receptance test carried out on the switch panel of a turnout of the Danish railway network, have been utilized together with the Eigensystem Realization Algorithm – a type of subspace identification – to identify a fourth order model of the infrastructure. The robustness and predictive capability of the low-complexity behavioral model to reproduce track responses under different types of train excitations have been successfully validated. It is anticipated that the identified model will be instrumental for the development of methods for diagnosis and prognosis of faults and degradation process in switches and crossings.

Derailment-based Fault Tree Analysis on Risk Management of Railway Turnout Systems

Railway turnouts are fundamental mechanical infrastructures, which allow a rolling stock to divert one direction to another. As those are of a large number of engineering subsystems, e.g. track, signalling, earthworks, these particular sub-systems are expected to induce high potential through various kind of failure mechanisms. This could be a cause of any catastrophic event. A derailment, one of undesirable events in railway operation, often results, albeit rare occurs, in damaging to rolling stock, railway infrastructure and disrupt service, and has the potential to cause casualties and even loss of lives. As a result, it is quite significant that a well-designed risk analysis is performed to create awareness of hazards and to identify what parts of the systems may be at risk. This study will focus on all types of environment based failures as a result of numerous contributing factors noted officially as accident reports. This risk analysis is designed to help industry to minimise the occurrence of accidents at railway turnouts. The methodology of the study relies on accurate assessment of derailment likelihood, and is based on statistical multiple factors-integrated accident rate analysis. The study is prepared in the way of establishing product risks and faults, and showing the impact of potential process by Boolean algebra.

LOD BIM Element specification for Railway Turnout Systems Risk Mitigation using the Information Delivery Manual

Railway turnouts are complex systems designed using complex geometries and grades which makes them difficult to be managed in terms of risk prevention. This feature poses a substantial peril to rail users as it is considered a cause of derailment. In addition, derailment deals to financial losses due to operational downtimes and monetary compensations in case of death or injure. These are fundamental drivers to consider mitigating risks arising from poor risk management during design. Prevention through design (PtD) is a process that introduces tacit knowledge from industry professionals during the design process. There is evidence that Building Information Modelling (BIM) can help to mitigate risk since the inception of the project. BIM is considered an Information System (IS) were tacit knowledge can be stored and retrieved from a digital database making easy to take promptly decisions as information is ready to be analysed. BIM at the model element level entails working with 3D elements and embedded data, therefore adding a layer of complexity to the management of information along the different stages of the project and across different disciplines. In order to overcome this problem, the industry has created a framework for model progression specification named Level of Development (LOD). The paper presents an IDM based framework for design risk mitigation through code validation using the LOD. This effort resulted on risk datasets which describe graphically and non-graphically a rail turnout as the model progresses. Thus, permitting its inclusion within risk information systems. The assignment of an LOD construct to a set of data, requires specialised management and process related expertise. Furthermore, the selection of a set of LOD constructs requires a purpose based analysis. Therefore, a framework for LOD constructs implementation within the IDM for code checking is required for the industry to progress in this particular field.

Review On Feasibility of Using Satellite Imaging for Risk Management of Derailment Related Turnout Component Failures

One of the emerging significant advances in engineering, satellite imaging (SI) is becoming very common in any kind of civil engineering projects e.g., bridge, canal, dam, earthworks, power plant, water works etc., to provide an accurate, economical and expeditious means of acquiring a rapid assessment. Satellite imaging services in general utilise combinations of high quality satellite imagery, image processing and interpretation to obtain specific required information, e.g. surface movement analysis. To extract, manipulate and provide such a precise knowledge, several systems, including geographic information systems (GIS) and global positioning system (GPS), are generally used for orthorectification. Although such systems are useful for mitigating risk from projects, their productiveness is arguable and operational risk after application is open to discussion. As the applicability of any novel application to the railway industry is often measured in terms of whether or not it has gained in-depth knowledge and to what degree, as a result of errors during its operation, this novel application generates risk in ongoing projects. This study reviews what can be achievable for risk management of railway turnouts thorough satellite imaging. The methodology is established on the basis of other published articles in this area and the results of applications to understand how applicable such imagining process is on railway turnouts, and how sub-systems in turnouts can be effectively traced/operated with less risk than at present. As a result of this review study, it is aimed that the railway sector better understands risk mitigation in particular applications.

Simulation of vertical dynamic vehicle–track interaction in a railway crossing using Green's functions

Vertical dynamic vehicle–track interaction in the through route of a railway crossing is simulated in the time domain based on a Green's function approach for the track in combination with an implementation of Kalker's variational method to solve the non-Hertzian, and potentially multiple, wheel–rail contact. The track is described by a linear, three-dimensional and non-periodic finite element model of a railway turnout accounting for the variations in rail cross-sections and sleeper lengths, and including baseplates and resilient elements. To reduce calculation time due to the complexity of the track model, involving a large number of elements and degrees-of-freedom, a complex-valued modal superposition with a truncated mode set is applied before the impulse response functions are calculated at various positions along the crossing panel. The variation in three-dimensional contact geometry of the crossing and wheel is described by linear surface elements. In each time step of the contact detection algorithm, the lateral position of the wheelset centre is prescribed but the contact positions on wheel and rail are not, allowing for an accurate prediction of the wheel transition between wing rail and crossing rail. The method is demonstrated by calculating the wheel–rail impact load and contact stress distribution for a nominal S1002 wheel profile passing over a nominal crossing geometry. A parameter study is performed to determine the influence of vehicle speed, rail pad stiffness, lateral wheelset position and wheel profile on the impact load generated at the crossing. It is shown that the magnitude of the impact load is more influenced the wheel–rail contact geometry than by the selection of rail pad stiffness.

철도 분기기 밀착검지기 Life expectancy의 유지보수 주기 결정에 관한 연구

철도 분기기는 철도에 가장 중요한 시스템 중 하나이며, 분기기가 이상이 발생하였을 경우에는 사고가 발생할 수 있다. 분기기의 상태를 검지하기 위해서 밀착검지기를 사용한다. 밀착검지기의 고장은 분기기의 고장으로 간주되어 열차운행에 커다란 장애가 될 수 있다. 분기기 밀착검지기의 고장 특성분석은 분기기의 운용에서 매우 중요하다. 밀착검지기의 운용특성 및 고장특성을 분석하기 위해서, 밀착검지기를 본선(A) 및 측선(B), 분기기 동작 횟수가 10회 미만(C) 및 80회 이상(D)로 분류하였다. 선정된 밀착검지기 140대를 기준으로 밀착검지기 고장특성을 분석하였다. 분기기의 고장은 제어부, 케이블 및 검지센서에 발생하였으며, 이 데이터를 운용 환경(A, B, C, D)에 따라 분류하였으며 각각의 고장밀도함수를 선정하고 모수를 추론하여 사전분포 값을 선정하였다. Bayesian추론을 이용하여 기기의 평균수명과 한계수명(Life expectancy)을 예측하여 밀착검지기 제어부에 대한 교체시점을 제시하였다. Railway turnout systems are one of the most important systems in a railway and abnormal turnout systems can cause serious accidents. To detect an abnormal state of a turnout, turnout clearance detectors are widely used. These devices consider a failure of a turnout clearance detectors to be a failure of the turnout system, that could hinder train operations. Analysis of turnout clearance detector failures is very important to ensure normal train operation. We categorized failures of detectors into four groups to identify failure characteristics of the 140 detectors, which are composed of main line detectors (A), side tracks (B), detectors that are in operation more than 80 times a day (C) and detectors that are in operation fewer than 10 times per day. Failures of detectors have mainly been caused in the control part, in the cables and sensors; failures are classified into four groups (A, B, C and D). We have tried to find failure density distributions for each type of failures, inferring the parameter distributions a priori. Finally, using the Bayesian inference we proposed a maintenance time for control parts through the mean time of the detector, life and the life expectancy.

ANALYSIS OF DYNAMIC EFFECTS ACTING ON RAILWAY CROSSINGS

The paper is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. Attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the paper is the assessment of influence of soft rail pads on spread of dynamic energy through the construction.

The application of nonlinear curvature sections in the turnout diverging track

The paper presents the analytical method of modelling the diverging track of railway turnout with nonlinear curvature sections. These sections were used for smoothing the graph of curvature in the extreme areas of turnout. The problem of the curvature distribution was identified with the use of differential equations. The resulting solutions are of universal nature for example the ability of assuming any values of curvature at the beginning and ending of the layout. The comparative analysis was performed for two cases with nonlinear curvature and corresponding cases where linear curvature was used. As a result, the analysis of selected cases showed a beneficial curvature distribution in a nonlinear variant, the extreme areas of circular arc are smoothed as well as the curvature at both ends of the layout is equal to zero.

Study of the dynamic vehicle-track interaction in a railway turnout

This paper analyzes the vertical dynamic response of a railway track subjected to traffic loads in a turnout, especially around the switch blades and the crossing nose. In order to study the influence of vehicle and track parameters on the vehicle-track dynamics, a numerical feedback interaction between a multi-body model of the vehicle and a 3D finite elements model of the track is carried out. For this purpose, two different models are developed. In the first one, the track is modeled by means of a FE model in the time domain through ANSYS software; while in the second one, the vehicle is simulated as a multi-body model by means of VAMPIRE PRO software. The influence of different parameters (e.g., speed, sprung masses, track stiffness and vehicle eigenfrequencies) on the generation of dynamic loads in a turnout, especially in the switch blades and the crossing nose, is studied. Finally, the vibrations induced by the passing of the vehicle are calculated for different scenarios.

고속철도 분기기 시스템 진단 시스템에 관한 연구(II)

철도에 사용되고 있는 분기기는 중요한 시스템 중 하나이다. 분기기 시스템의 건전성은 철도운용 안정성에 매우 중요하다. 분기기 시스템을 진단하기 위하여, LVDT와 accelerometer를 분기기에 설치하였다. LVDT는 분기기에서 변위가 발생하는 부분에 설치하여, 분기기의 이동과 차량의 주행에서 발생되는 변위를 측정하였다. Accelerometers는 충격과 진동이 발생하는 부분에 설치하여 충격량과 진동을 측정하였다. 측정된 데이터를 이용하여 변수화를 위한 데이터를 추출하였으며, 이 변수들은 진단에 사용하였다. 진단 알고리즘은 확률분포와 인공신경망을 사용하였다. 변수화된 값이 확률분포를 이용하여 판단할 수 있으면 확률분포를 사용하였으며, 형태를 보고 판단할 필요가 있으면 인공신경망을 활용하였다. 본 논문에서는 정상적인 상태에서 데이터를 측정하여, 정상상태의 조건을 위한 학습을 수행하였다. The railway turnout system is one of the most important systems that set train routes. Turnout system integrity should be guaranteed for robust train operation. To diagnose the turnout system status, LVDT and accelerometers are installed on a turnout system in a high speed line. The LVDT and accelerometers produce signals containing physical meaning of the turnout systems. The LVDT produces the displacement of the rail gauge and vibration when point moving or a train passes on turnout systems and the accelerometer produces impact forces induced by wheel sets. We performed data extraction from the measured signals and parameterized the extracted signals into meaningful quantities. The parameters are used for classifying whether the turnout status is normal. We proposed two methods for the classification, one uses probabilistic distribution and the other artificial neuron networks. The probabilistic distribution is used for the parameter being classified by the quantities and the artificial neuron networks for the form classification. Finally, we show how to learn the normal status of a turnout system.