Academic literature on the topic 'Track buckling'

Nowadays, timber sleepers are still used for ballasted railway tracks to carry passengers and transport goods. However, the process of natural decay causes the problem of timber sleeper degradation over time. A temporary “interspersed” approach is used to replace rotten timbers with concrete sleepers. This implementation has several inadequacies, as interspersed railway tracks have inconsistent stiffness and experience significant deterioration over the years. Increased heat due to the change in the global climate can induce a compression force in the continuous welded rail (CWR), leading to a change in track geometry called “track buckling”. A literature review shows that track buckling on plain tracks has been widely studied. However, the buckling of interspersed tracks has not been fully studied. This study presents 3D finite element modelling of interspersed railway tracks subjected to temperature change. The effect of the boundary conditions on the buckling shape is considered. The obtained results show that the interspersed approach may reduce the likelihood of track buckling. This study is the world’s first to investigate the buckling behaviour of interspersed railway tracks. The insight into interspersed railway tracks derived from this study will underpin the life cycle design, maintenance, and construction strategies related to the use of concrete sleepers as spot replacement sleepers in ageing railway track systems. The outcome of this study will help track engineers to improve the inspection of the lateral stiffness of interspersed tracks in areas prone to extreme temperature.

In rail transport, track gauge is one of the principal factors that condition the passage of trains. For technical and economic reasons, in some circumstances it is necessary to build and operate the so-called dual gauge track, in which a third rail is added to allow operation of trains in two separate gauges. Although the problem of lateral buckling of rail tracks under thermal loading has been well researched, the addition of the third rail increases the steel area subjected to thermal loads, and thus requires a more accurate analysis. The objective of this paper is to develop an analytical model to analyse the lateral buckling under thermal loads on dual gauge tracks. An in-depth analysis of the effects of the thermal track buckling response produced by each fundamental parameter is presented and discussed. It is found that the risk of buckling is more in dual gauge tracks when compared with the conventional tracks. Finally, this model establishes a mechanism that can be used to perform a more effective infrastructure management policy.

In the National Spanish railway network, two types of track gauge with continuous welded rails are currently in use: the “Iberian” wide gauge (1668 mm) and the standard gauge (1435 mm). In order to improve links and freight traffic between different lines and with the rest of Europe, a dual gauge track with three rails was developed. This solution modifies the classical track configuration, so it is necessary to develop new methodologies and studies to understand its behavior. Among other loads applied on a continuous welded rail track, a considerable rise in temperature induces compressive stresses in the three rails that can lead to lateral track buckling. Moreover, on dual gauge tracks, the addition of the third rail increases the axial compression, which may lead to track instability. For this reason, a three-dimensional continuous welded rail model is developed in this study to be used for dual gauge track buckling analysis on straight tracks subjected to temperature load. The continuous welded rail dual gauge track model consists of beam, solid and spring elements, in which a non-linear behaviour of the ballast is considered. The results obtained may be used to predict the buckling capacity of the continuous welded rail on dual gauge tracks with respect to different parameters such as lateral resistance, lateral imperfections, sleeper spacing or torsional stiffness.

The use of continuous welded rails (CWR) is increasingly common and is particularly important when it comes to high-speed ballasted tracks. As the longitudinal displacements are restricted in CWR tracks, a considerable rise in temperature induces compressive stresses in the rails that can lead to track buckling. Given the nonlinear behavior of the ballast, usually represented by a linear plastic model, the problem of snap-through buckling may occur, for which only a few nonlinear analysis methods can trace the full response of the track structure. However, these methods fail to yield convergent solutions for problems with thermal loads when implemented in their conventional algorithm. For this reason, a new methodology is presented allowing the calculation of the safe temperature. In addition, some analytical results are also derived for comparison with the numerical results, obtained using three-dimensional finite element beam models provided by ANSYS.

Euler type analysis usually used for compression members in structural engineering does not work for railroad track. Euler type analytical formulas for horizontal and vertical buckling endorsed in a recent literature is reviewed to demonstrate its weakness. Using definition of moment and curvature as well as principle of equilibrium, the author suggests formula for horizontal buckling load of railroad track and demonstrates validation in context with currently accepted values, published results, and past field tests. The buckling load from suggested formula agrees with the recent buckling load formula based on total energy theorem. A formula is suggested to study the effect of misalignment on critical temperature differential or critical load. A vertical buckling load formula is derived from horizontal buckling load formula. A buckling process is narrated through step by step computation. Formulas are suggested to compute the effect of track misalignment on critical buckling load and threshold radius of a vertical curve.

Stress contained in rails, mainly due to thermally-induced expansion and contraction, results in large longitudinal loads which lead to broken rails and track buckling. According to the beam bending theory of structural dynamics with a consideration of the influence of axial load, a CWR track model is developed in the present study to be used for extensive buckling analysis of CWR tracks. The model discusses CWR track vibration characteristics with a length of unsupported rail subjected to the longitudinal force due to fluctuation of temperature. From the result, it can be gotten that the critical point of the temperature which may cause the rail have the danger of unstable. This model would help to evaluated and measure the real temperature in rail by analyzing the dynamic response of CWR track.

The article is about the issue of maintaining a contactless track. Due to the forces occurring in the track, arising from both temperature changes and from rolling stock rolling on the track, it is necessary to monitor a displacement of rail tracks and stress in rails. The article presents a summary of the methods for monitoring the contactless track condition. The comparison of the methods was also presented, showing the pros and cons of each of them. Keywords: contactless track, contactless track buckling, track stress

In order to ensure the safety of running train against the track buckling in a sultry weather, a speed reduction scheme has been implemented in railway operating companies. However, this scheme is based on the limited knowledge on the buckling behavior of the CWR track. The rational speed reduction scheme based on the probabilistic method for the buckling of the CWR track is proposed to apply to Korea high and normal speed railway. Permissible level of the reduced speed according to the rule of restricted speed signal, accepted degree of the buckling probability, the practically managing degree of the variation of the rail temperature, and effects of the maintenance work on the track condition are reflected in the rational speed reduction scheme.

There is no industry accepted analytical model to compute the critical temperature differential for the buckling of an unloaded curved track in North American literature. In this paper, the critical temperature differential for the buckling of an unloaded curved track is formulated by incorporating a value of unity for the factor of safety in the previously developed formula, which was developed considering thermal loading only. The factor of safety was the ratio between the resistance of a tie in an unloaded track against lateral displacement in the ballast and the lateral thermal load on a tie. The derived formula of the critical temperature differential for the buckling of an unloaded curved track is simple opposed to a complicated formula endorsed in the current European literature from 1969. The new formula is also validated in this paper. The critical temperature differentials for buckling of sharp and super-sharp curves have significant implications for track design and maintenance.

The axial buckling threshold force of continuous welded rail (CWR) depends on lateral stability of railway track. The conventional CWR buckling models are based on track static parameters and behavior. In this paper, a dynamic finite element model for investigating the relationship between the rail nature frequencies and the critical buckling axial force of CWR track is presented. This model consists of rails, sleepers and foundation, and covers factors of interest such as track curvature, supporting distance between adjoining sleepers. With the new dynamic model, numerical computations and analyses are performed. The correlations among the critical axial force of rail, the lateral stability and the nature frequencies of CWR track are studied. The computational results of the new dynamic model show a great agreement with the field testing results.

Extreme heat and temperature fluctuation in Queensland result in buckling of railway tracks which jeopardize the safety of train operation and cost huge sums to repair. This thesis carried out an elaborate investigation on the issue of track buckling and provided several approaches to mitigate the risks of track buckling to enable safer trains and lower maintenance costs for railway operators in Australia.

The diploma thesis deals with the curve radius influence on lateral stability of continuous welded rail. It is presented the overview of present state of knowledge in the field of stability of continuous welded rail. In practical part is created the model of a track section. The influence of some parameters on loss of stability of CWR was studied. The results it are compare with the analytic analysis.

Conventional railway track is the structure consisting of the ballast or slab track, upon which sleepers, fasteners and two rails are laid, allowing the passage of trains equipped with a certain gauge. Due that trains cannot pass from a line with one track gauge to an-other (only possible where the difference between the two gauges is small), track gauge is a dominant parameter determining interoperability, used as a descriptor of a route or net-work. Where trains encounter a different gauge, a break-of-gauge occurs, which entails delays, costs, and inconveniences. However, special situations such as the Spanish rail network can occur, where new in-teroperability and connection facilities have resulted in the construction of certain lines with dual gauge track. A dual gauge track configuration consists of three rails, where the two adjacent outer rails provide each of the gauges (1435 mm / 1668 mm), while the single outer rail is common to trains of both gauges. This new track structure is an important modification of the classical rail track with two rails and one gauge. In addition, long stretches of dual gauge tracks have not been implement-ed yet, so it is necessary to develop new methodologies and studies to understand its be-haviour. Specifically, with the use of continuous welded rails, variations in rail temperature produce compression stresses that, under certain circumstances, can led to dangerous lateral track displacements and train derailment. With that motivation, this PhD Thesis is focused on an appropriate theoretical framework for conducting a study that evaluates the potential risk of buckling in dual gauge tracks. To accomplish this task, different methods and techniques in order to improve the knowledge of this phenomenon and track design. This approach will allow us to establish track condi-tions and maintenance works that ensures the stability of the dual gauge track under ther-mal and train loads. In addition, a risk based methodology allows us to revise and redefine conventional track design methods in order to increase track stability under thermal loads.
La superestructura de vía clásica está compuesta por una serie de capas portantes en las que se sitúan las traviesas o losas de hormigón y sobre las cuales se disponen 2 carriles que permiten la circulación de los vehículos, en base a su utilización con un único ancho de vía. Debido a que los vehículos ferroviarios no pueden circular desde una línea con un ancho de vía a otra con un ancho diferente (solo es posible si la diferencia de ancho es muy reducida) el ancho de vía se establece generalmente como un único valor común para toda una determinada red, pues de lo contrario se crean una serie de "fronteras" entre las líneas con diferente ancho de vía, lo que provoca importantes problemas en la explota-ción y gestión de la red. No obstante, existen situaciones especiales como la que se produce en España, donde las circunstancias y las nuevas necesidades de conexión e interoperabilidad han dado como resultado la construcción de tramos ferroviarios de doble ancho o ancho mixto. La carac-terística fundamental de este tipo de vías es la dotación de un tercer carril, de tal forma que se parte de una vía de ancho ibérico (1.668 mm) sobre la que se dispone en su interior un tercer carril para conseguir el ancho estándar (1.435 mm). Así pues, esta nueva configuración de vía supone una importante modificación respecto a la vía clásica de un ancho y 2 carriles. Además, el uso del tercer carril en tramos largos es totalmente novedosa, lo que obliga al estudio y análisis del comportamiento de esta nueva superestructura de vía. En especial, la vía debe resistir los esfuerzos longitudinales, pues el uso de la barra larga soldada genera esfuerzos térmicos en los carriles que pueden oca-sionar, bajo unas ciertas condiciones de vía, la desestabilización y, como resultado, impor-tantes deformaciones laterales con efectos muy perjudiciales. Por ello, la presente tesis tiene por objeto el estudio teórico del riesgo de pandeo en vías de doble ancho mediante el uso de diferentes métodos y técnicas que permitan una mejor comprensión de este fenómeno y el diseño seguro de este tipo de vías. El análisis permiti-rá establecer las condiciones que aseguran el correcto funcionamiento de la superestruc-tura de vía antes las diferentes solicitaciones que debe soportar. Además, el planteamiento de una metodología de evaluación del riesgo de pandeo en vías de doble ancho permitirá la revisión y reformulación de criterios de diseño, aplicables a vías existentes o de nueva construcción, según las oscilaciones térmicas a las que esté sometida.
La superestructura de via tradicional està composta per una sèrie de capes portants en què se situen les travesses o lloses de formigó i sobre les que es disposen 2 carrils que permeten la circulació dels vehicles, segon l'ús d'un únic ample de via. Pel fet que els vehicles ferroviaris no poden circular des d'una línia amb un ample de via a una altra amb un ample diferent de la primera (només és possible si la diferència d'amples és molt reduïda), l'ample de via s'estableix generalment com un únic valor comú per a tota una determinada xarxa, ja que en cas contrari es generen una sèrie de "fronteres" entre línies amb diferent ample de via, el que produeix importants problemes tant en l'explotació com en la gestió de la xarxa. No obstant això, existeixen situacions especials com la que es produeix a Espanya, on les circumstàncies i les noves necessitats de connexió i interoperabilitat han donat com a resultat la construcció de trams ferroviaris de doble ample o ample mixt. La característica fonamental d'aquest tipus de via d'ample mixt és la col·locació d'un tercer carril, de tal forma que partint d'una via d'ample ibèric (1.668 mm) es disposa a l'interior un tercer carril que permet aconseguir l'ample estàndard (1.435 mm). Així, aquesta nova configuració de via suposa una important modificació respecte de la via clàssica d'un sol ample i 2 carrils. A més a més, l'ús del tercer carril en trams llargs és totalment nova, el que obliga a estudiar i analitzar el comportament d'aquesta nova estructura. En especial, la via ha de resistir els esforços longitudinals, degut a que l'ús del carril continu soldat genera càrregues d'origen tèrmic en els carrils que poden ocasionar, baix unes certes condicions de via, la desestabilització i, com a resultat, importants deformacions laterals amb efectes molt perjudicials. Per açò, la present Tesi té com a objectiu l'estudi teòric del risc de pandeig en vies d'ample mixt (amb 3 carrils) a través de l'ús de diferents mètodes i tècniques tal que permeten un major coneixement d'aquest fenomen i el disseny segur d'aquest tipus de via. L'anàlisi permetrà establir les condiciones que asseguren el correcte funcionament de la superestructura de via enfront de les diferents càrregues que deu suportar. A més, el plantejament d'una metodologia d'avaluació del risc de pandeig en vies d'ample mixt permetrà la revisió i reformulació dels criteris de disseny, aplicables a vies existents o de nova construcció, d'acord amb les oscil·lacions tèrmiques a les quals estarà sotmesa.
Villalba Sanchis, I. (2017). STUDY, ANALYSIS AND DETERMINATION OF BUCKLING LOAD IN DUAL GAUGE TRACKS THROUGH ANALYTICAL AND NUMERICAL METHODS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/93343
TESIS

The Paparoa Metamorphic Core Complex developed in the Mid-Cretaceous due to continental extension conditioning the crust for the eventual breakup of the Gondwana Pacific Margin, which separated Australia and New Zealand. It has two detachment systems: the top-NE-displacing Ohika Detachment at the northern end of the complex and the top-SW-displacing Pike Detachment at the southern end of the complex. The structure is rather unusual for core complexes worldwide, which are commonly characterised by a single detachment system. Few suggestions for the kinematics of the core complex development have been made so far. In this study structural-, micrographic- and fission track analyses were applied to investigate the bivergent character and to constrain the kinematics of the core complex. The new results combined with reinterpretations of previous workers’ observations reveal a detailed sequence of the core complex exhumation and the subsequent development. Knowledge about the influence and the timing of the two respective detachments is critical for understanding the structural evolution of the core complex. The syntectonic Buckland Granite plays a key role in the determination of the importance of the two detachment systems. Structural evidence shows that the Pike Detachment is responsible for most of the exhumation, while the Ohika Detachment is a mere complexity. In contrast to earlier opinions the southwestern normal fault system predates the northeastern one. The Buckland Pluton records the ceasing pervasive influence of the Pike Detachment, while activity on the Ohika Detachment had effect on the surface about ~8 Ma later. Most fission track ages are not related to the core complex stage, but reflect the younger late Cretaceous history. They show post core complex burial and renewed exhumation in two phases, which are regionally linked to the development of the adjacent Paparoa Basin and the Paparoa Coal Measures to the southwest and to the inception of seafloor spreading in the Tasman Sea in a larger context.

碩士
國立成功大學
土木工程學系
105
In order to provide better service for passengers, Continuously Welded Rail (CWR) has been used in the railway industry. However, rails can’t stretch with the change of temperature, stress accumulation will cause buckling and tension crack. The study found that lateral resistance impact buckling temperature a lot. Therefore, setting up a model of predict buckling temperature and lateral resistance. Further, the best way to increase buckling temperature and lateral resistance is accumulating ballast. Moreover, heaping on shoulder is the most effective.

"In this thesis, practices/procedures adopted by different railways to manage track stability have been collated and a gap analysis has been undertaken to help improve track stability. The analysis revealed that track stability management differs markedly/noticeably between railway companies, and that there is a need for a unified tool to determine the requirements of different preventive maintenance programs"--Abstract.

The railway track buckling occurs all over the world due to inadequate rail stress adjustment, which is greatly influenced by the variation in weather induced rail temperature and the rigidity of the track structure. Climate change and the ever increase in extreme changes in temperatures have made buckling an ever more prevalent problem in the railway industry. The ultimate goal of any research in the area of track stability management is to comprehensively manage rail buckling and the subsequent procedures that follow after buckling. The first step to have a clear understanding of how the temperature change of the rail track is influenced by the environmental conditions. The second step is to have an accurate prediction of what the environmental conditions will be in the next day so that management procedure can be put into place.

This study aims to develop a model and software that is capable of predicting rail temperature 24 hours in advance that is as accurate for use in the rail buckling management. Two distinct and separate mathematical manipulations are performed to achieve this goal.

One method used weather forecasts from the Australian Bureau of Meteorology (BoM) and forecasts the weather for the location that the rail is situated. This involves using 3-dimensional cubic interpolation that is the weather parameters are interpolated in 2-dimensions geographically and then 1-dimensionally through time. An interactive software is written in MATLAB to convert the BoM raw data into a rail temperature forecast for this study. The result is a 15 -minute forecast for every 3.06 km. The second method used multivariate linear regression, to predict the rail temperatures 24 to 48 hours in advance.

To validate the rail temperature predications, 3 months field test spanning June, July and August 2010, is conducted on Queensland Rail's (QR) coal network, this involved erecting an automated weather station (AWS) and adhering temperature sensors on to a section of track. The guidelines of World Meteorological Organization's (WMO) were followed for implementation of the AWS on site (WMO 2008). The AWS model WXT520 , produced by Vaisala (Vaisala 2009) was used in this study which an off the shelf product that is similar to what some rail compaies are already using for continues monitoring of critical sites.

The temperature sensors (surface thermocouples) and an off the shelf product Salient system's rail -stress modules are used to measure rail surface temperatures on both rails of the track (Salient Systems Inc 2009). The sensors were attached to the surface of the rail track to directly measure temperature change of the rail profile throughout the diurnal cycle. Statistical correlations between the different measured points of the rail profile are evaluated in relation to the diurnal cycle to assess the accuracy of current rail temperature measuring practices.

Statistical evaluation of how well the BoM predictions compare with weather parameters at the field experimentation site are performed, so too is a statistical evaluation of the accuracy of the rail temperature model developed. The prediction model is compared with the existing empirical methods as found in the literature review and an assessment of track conditions. This is a flag ship study in Australia; the main purpose of this study is to prove in a test case scenario that a rail temperature forecast without use of weather instrumentation is possible and the accuracy of the prediction is as good if not better than the instrumentation calculation.

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná
Railways are infrastructures subject to open weather conditions and also to temperature changes during the day and over the season. Due to this change, internal stresses may appear, whether tensile or compressive depending on the stress-free temperature and the current measure. High compressive stress may lead the track to buckle, meanwhile tensile stress can cause brittle failure. Given the importance of the temperature on railways, many models have been developed to correlate weather conditions and rail temperatures, in order to avoid the occurrence of mechanical instabilities which cause major problems in the operation of railroads. The present work validates one model developed by CNU university by comparing it with nite element solutions and also with experimental data of a rail track in the city of Mirandela-Portugal. A python package was developed to solve the model and is available to download. The model shows a good correlation between measured and simulated rail temperatures. In addition, by utilizing weather information of other locations in Portugal, the maximum expected rail temperatures were determined. Furthermore, mechanical analyses were made to analyze the critical temperature to reach the buckling mode of instability without the e ect of rolling loads and also the important parameters that a ect this phenomenon. The simulations show that the quality of the ballast and the initial miss-alignment of the track are the most important. Keywords:
Caminhos de ferro s~ao estruturas expostas a uma grande variedade de condi c~oes clim aticas e, concretamente a varia c~oes de temperatura durante o dia e ao longo das esta c~oes durante o ano. Devido a estas varia c~oes tens~oes internas ocorrem, podendo ser esfor cos de compress~ao ou tra c~ao, dependendo da temperatura neutral do per l. A ocorr^encia de tens~oes de compress~ao elevadas pode causar encurvadura da via, enquanto que os esfor cos de tra c~ao podem ocasionar a fratura fr agil. Devido a import^ancia das temperaturas nas vias f erreas, muitos modelos t^em sido desenvolvidos para correlacionar condi c~oes clim aticas com a temperatura da via tendo em vista o seu uso como ferramenta de preven c~ao de acidentes na opera c~ao. O presente trabalho utiliza um destes modelos, desenvolvido pela universidade CNU e valida-o utilizando solu c~oes com o m etodo dos elementos nitos e, tamb em, com dados experimentais de uma via f errea localizada na cidade de Mirandela-Portugal. Foi ainda desenvolvido um software utilizando a linguagem Python para facilitar a solu c~ao do modelo, estando ainda dispon vel para download. O modelo demonstrou boa correla c~ao entre as temperaturas simuladas e medidas. Al em disso, utilizando informa c~oes meteorol ogicas de outras localidades em Portugal, as temperaturas m aximas esperada das vias foram determinadas. Posteriormente, an alises mec^anicas de encurvadura foram realizadas para determinar em quais temperaturas uma via ferra pode sofrer encurvadura e, tamb em, quais par^ametros que in uenciam este fen^omeno. As simula c~oes mostram que a qualidade do balastro e as imperfei c~oes iniciais da via s~ao os mais importantes.

ABSTRACT In late 1829 or early 1830, Henry Thomas De la Beche (1796–1855), in collaboration with William Buckland (1784–1856), published Duria antiquior [A more ancient Dorsetshire], the earliest known paleoecological illustration of ancient life. De la Beche’s interpretation was based largely on fossils then recently uncovered from Lower Jurassic (Lias) rocks near Lyme Regis on the south coast of England. Many of these were brought to scientific attention by local fossil collector and dealer Mary Anning (1799–1847). De la Beche published Duria antiquior as a lithograph, copies of which were sold as a fundraiser for Anning, who was then in straitened circumstances. Duria antiquior represented a new style of paleontological illustration that pioneered a new scientific genre addressing the history of nature and an innovative viewpoint where the observer glimpses lifeforms through the water. Other authors modified and adopted De la Beche’s visionary illustration, and the style became commonplace in popular geological publications in the later nineteenth century. Duria antiquior can be acknowledged as the pioneering graphic from which fossil organisms’ reconstructions and modern computer-generated paleoecosystem animations trace their origins.

Thermal track buckling is probably the major problem due to the advent of continuous welded rail track. In fact, when the rails temperature rises over a critical value, the track can buckle, suddenly or progressively, in the lateral plane. Both poor ballast conditions and large lateral alignment defects are the principal causes of such phenomenon. In a previous paper, a parametric finite element model for thermal track buckling simulation was presented and validated by comparison with analytical results of the literature. In this study, the finite element model has been further validated by comparison with analytical and numerical results obtained by three other authors. Moreover, to take into account the effect on the buckling temperatures of the vertical loads due to train passes, the tie-ballast lateral resistance has been modified along the track, taking into account the vertical reaction forces distribution induced by axle loads. A sensitivity analysis has been carried out both for tangent and curved track, considering two values of the alignment defect amplitude, and different values of the parameters that characterize actual railway vehicles. It is found that the conditions to trigger progressive buckling (△Tmax ≈ △Tmin) are attained with small values of the truck center distance, and in a more accentuated manner in the presence of high values of the lateral alignment defect. △Tmax and △Tmin increase with axle spacing, and this increase is more pronounced for low values of the truck center spacing. △Tmax and △Tmin also increase with curve radius, but decrease for increasing values of the misalignment defect amplitude. In explosive buckling conditions (△Tmax ≠ △Tmin), there is a limit value of the truck center distance above which the vertical load has no more effects, and the results of the static thermal buckling are found.

The lateral stability of the continuous welded rail (CWR) depends on a number of parameters which contribute to the progressive loss of the initial alignment of the track and its consequent predisposition to deform sideways, gradually or sharply, with serious risks for the safety both of passengers and operators. Different types of initial lateral defect, in terms of shape and size, are introduced by many authors in their own numerical and analytical model, but essentially all of them can be traced back — except for small “personalizations” — to the model proposed by Andrew Kish, who hypothesized the existence of a misalignment defect having the shape of a sine curve extended for half-wavelength, characterized by amplitude and wavelength values typical of the USA railroads. Moreover, all previous studies focused their attention on the introduction, in a geometrically perfect railway track, of a single defect confined in a zone of finite dimensions and having a rather simple geometry which qualitatively approximates the real defect, with the aim of simplifying the calculation of the buckling temperatures of the track associated with such geometry. In this paper, it was preliminarily analyzed the way the defect introduced in the track affects the critical temperature values. It started with a defect created artificially, applying to a geometrically perfect track and in the absence of thermal loads, a lateral displacement in the central transversal section of the track, and calculating, with the hypothesis of linear elastic behavior, the resulting deformed shape, which was assumed, after zeroing the corresponding stress field, as the input geometry for the subsequent buckling calculation. The deformed shape so obtained, being a Zimmermann deformed shape type, has no geometrical discontinuities near the defect and interprets in a natural way the defected geometry of the track, due to the dependence of its configuration on the flexural stiffness of the entire track in the lateral plane. Afterwards, modeling was carried out taking into account the real behavior of the track after the loss of its rectilinear configuration: the defect was created simulating the response of the track to a momentary lateral load — resulting, e.g., from train passages — which succeeded to cause a permanent displacement resulting from the elastic-plastic response of the track. The deformed shape of the track obtained in this way was used as the input geometry for the calculation of the buckling temperatures, once without resetting the stress field induced in the structure by the loading–unloading hysteresis cycle, and then considering the track free from internal stresses. The results show that both the numerical model that contemplate the defect introduced “plastically”, and that where the track is free from internal stresses, lead to more conservative results against the risk of thermal buckling in railway tracks made with CWR. A better approximation of the realistic representation of a generic defected railway track was pursued considering an indefinite number of defects distributed along the track, where each defect was characterized by different amplitude and wavelength values. The obtained results show that the presence of multiple defects further reduces the safety factor against the thermal track buckling phenomenon. The paper ends with the proposal of an evaluation criterion that takes into account the effects of multiple alignment defects on the critical buckling temperatures in continuous welded rail tracks.

Abstract After the introduction of continuous welded rail, thermal track buckling has been recognized to be one of the unsolved problem caused by this technological railroad improvement. In general, both weak ballast strength in the lateral direction and large alignment defects are the principal causes of such phenomenon. In the UIC 720 Leaflet, which is the reference standard for the realization and maintenance of continuous welded rail tracks, two safety criteria against thermal track buckling are described: one is based on the maximum (ΔTmax) and minimum (ΔTmin) buckling temperatures, the other only on the minimum buckling temperature. In the literature, it is found that a correlation exists between ΔTmax and the maximum (or peak, FP) lateral resistance value of the tie-ballast system, and, analogously, between ΔTmin and the minimum (or limit, FL) lateral resistance. For this reason, railway technicians had to paid special attention in the assessment of FP and FL. Because FP concerns lateral displacements equal to 5÷10 mm, and FL occurs for lateral displacements greater than 80÷100 mm, some researchers have proposed to measure FP with a quasi-non-destructive experimental technique, the Single Tie Push Test (STPT), and, successively, to evaluate FL as a function of FP by empirical formulas, in place of the experimental evaluation of the full lateral resistance curve of the tie-ballast system. Based on these considerations, a concerning issue arises whether it is sufficient, and above all safe, to use the simpler, less destructive, and less expensive STPT technique, which requires that only one tie is detached from the rails, or if it is necessary to perform lateral resistance tests on track panels composed by 4 to 6 ties, as in the case of the Discrete Cut Panel Pull Test (DCPPT). For this purpose, in this paper the experimental results obtained in situ in full scale conditions with the two testing techniques are reported, and the differences obtained by performing tests with one, two, and four ties are analyzed with the aim of ensuring a safe evaluation of the main input parameters required for buckling temperatures calculation. It is found that the limit lateral resistance depends neither on the chosen experimental technique, nor on the compaction level of the ballast bed, whereas the peak lateral resistance appears to be dramatically altered if it is evaluated by mean of the STPT, with serious risks of an unsafe evaluation of the buckling temperatures.

Track buckling due to excessive rail temperature is a major cause of derailments with serious consequences. To minimize the risk of derailments, slow orders are typically issued on sections of track in areas where an elevated rail temperature is expected and risk of track buckling is increased. While the slow orders are an important preventive safety measure, they are costly as they disrupt timetables and can affect time-sensitive shipments. Optimizing the slow order process would result in significant cost saving for the railroads. The Federal Railroad Administration’s (FRA’s) Office of Research and Development has sponsored the development of a model for predicting rail temperatures using real time weather forecast data and predefined track parameters and a web-based system for providing resulting information to operators. In cooperation with CSX Transportation (CSX), ENSCO Inc. conducted a model verification study by comparing actual rail temperatures measured by wayside sensors installed on railroad track near Folkston, GA, with the rail temperatures predicted by the model based on weather forecast data over the course of summer 2011. The paper outlines the procedure of the verification process together with correlation results, which are favorable. The paper also presents results of several case studies conducted on derailments attributed to track buckling. These investigations improve our understanding of conditions and temperature patterns leading to increased risk of rail buckles and validate further use of the Rail Temperature Prediction Model as track buckling prediction tool and as an aid to the railroads in making more informed decisions on slow order issuing process.

Abstract Over the past two years, Transportation Technology Center, Inc. (TTCI) has been investigating how tie and ballast parameters affect lateral track strength after surfacing. This investigation included both a literature review of previous work in the United States and single tie push tests (STPTs) performed under a variety of tie and ballast conditions at the Facility for Accelerated Service Testing (FAST) in Pueblo, CO. Knowing which parameters affect lateral tie strength and comparing the influence of the various parameters can help in lateral stability risk-assessments in continuously welded rail (CWR) track. The results of both the literature review and the STPT testing showed that the parameters of post-surfacing tonnage accumulation (for ballast density), tie type, ballast shoulder width, ballast crib height, tamping lift height, and ballast particle characteristics all have a significant influence on the lateral tie strength of clean ballast. The results both emphasize the importance of considering multiple parameters when assessing track buckling risk and verifies the good practice of having both full ballast shoulders and crib heights for resisting lateral and longitudinal movements. TTCI plans to incorporate these parameters into mathematical models that predict the lateral tie strength based on measurable tie and ballast condition parameters, holistic track buckling prediction models, and risk-based rail neutral temperature (RNT) management recommendations.

From the advent of high-speed (HS) railways and with increasing traffic-induced loads transmitted to the superstructure, maintenance costs due to track geometry degradation have become a crucial problem for researchers and railway administrations. Moreover, the operations of ballast renewal, track tamping, and track re-alignment, that are indispensable to guarantee a good track geometry, have dramatic effects on the tie-ballast lateral resistance, which in turn reduce the track flexural strength in the lateral plane and increase the proneness of railway tracks made of continuous welded rails (CWR) to experience either progressive lateral shift of the track panel or thermal track buckling phenomena. To restore proper values of the tie-ballast lateral resistance, railway technicians either impose a speed reduction or compact the ballast bed mechanically by mean of the dynamic track stabilizing machines. Recently, elastic elements in railway tracks are receiving more and more attention due to their ability to reduce track geometry degradation and to attenuate noise and vibrations. Under Tie Pads, or Under Sleeper Pads (USP), guarantee better homogenization of the track vertical stiffness and have received more attention due to their ability to reduce maintenance costs. Most published studies focused their attention to USPs’ attitude to improve track performances in terms of dynamic impact force mitigation and track quality improvement; however, with few exceptions, no available literature exists on lateral resistance of ballasted track with USP, and some question still remains whether or not the lateral resistance is improved by USP. In this study, the experimental results of about 40 lateral resistance tests carried out in situ are reported and discussed. The tests were performed with the Discrete Cut Panel Pull Test (DCPPT) technique on three type of concrete ties, with and without USP; each type of tie and the related track conditions (ballast thickness, subgrade thickness and composition, shoulder width, ballast wall, etc.) were representative of specific track conditions, namely traditional tracks, high-speed lines and gallery. The tests were carried out in loaded and unloaded track conditions, in compacted and just-laid track conditions. In compacted ballast conditions the peak lateral resistance due to USPs can increase up to 20% — depending on the material used — and this variation is almost constant in the bedding modulus range considered in this study, which was quite well representative of typical static bedding modulus values of actual USPs. Even higher advantages seem to be achievable with softer USPs in weak or just-tamped ballast conditions.

The railroad industry uses slow orders, sometimes referred to as speed restrictions, in areas where an elevated rail temperature is expected in order to minimize the risk and consequence of derailment caused by track buckling due to excessive rail temperature. Traditionally, rail temperature has been approximated by adding a constant offset, most often 30°F, to a peak ambient air temperature. When this approximated maximum rail temperature exceeds a given risk threshold, slow orders are usually issued for a predefined period of the day. This “one size fits all” approach, however, is not effective and suitable in all situations. On very warm days, the difference between rail temperature and ambient air temperature can exceed railroad-employed offsets and remain elevated for extended periods of time. A given temperature offset may be well suited for certain regions and track buckling risk-related rail temperature thresholds but less accurate for others. Almost 160,000 hours of rail temperature measurements collected in 2012 across the eastern United States by two Class I railroads and predicted ambient air temperatures based on the National Weather Service’s National Centers for Environmental Prediction (NCEP) data were analyzed using detection theory in order to establish optimal values of offsets between air and rail temperatures as well as times when slow orders should be in place based on geographical location and the track buckling risk rail temperature threshold. This paper presents the results of the analysis and describes an improved procedure to manage heat-related slow orders based on ambient air temperatures.

Abstract The paper introduces lateral buckling mitigation techniques (sleepers, distributed buoyancy sections, and residual curvature method or RCM) used in deep water fields and provides a total installed cost comparison of these solutions in relative terms. A hypothetical deep-water scenario is used to compare all techniques within the same site environment. Historic benchmarks have been used to make a relative comparison of these buckle mitigation methods on the engineering, procurement, fabrication, and installation fronts. In addition, risks associated with engineering, procurement/fab and installation have been listed to illustrate the risks versus rewards tradeoff. While sleepers and distributed buoyancy have been previously used in deep water, RCM doesn't have a significant track record yet. RCM is a proven and cost-effective buckle mitigation solution in shallow water. This paper compares its application in deep water to the prevailing buckle mitigation methods and confirms if it creates value (savings and reduces risks) for an offshore installation project. It is assumed that each mitigation method is appropriate for the hypothetical deep-water scenario.

Railroads around the world are trying to increase hauling capacity on an already over-burdened rail system. This results in increased rail maintenance, increased cost from slow orders and increased risk of track failures. However, monitoring rails for neutral temperature drift, rail buckling and rail breaks is becoming easier and more cost effective with improved sensor technology. One major improvement is the ability to monitor long stretches of rail by networking a series of sensors together. This results in complete track coverage for a reasonable cost. New sensor technology capable of transmitting data wirelessly over several miles of track is presented in this paper. The antenna configuration is a critical factor to achieve adequate signal strength within several inches of the ground. The research presented here shows that it is possible to use the rails themselves as waveguides to help guide wireless signals down the rails to the next sensor.

Track buckling due to excessive rail temperature may cause derailments with serious consequences. To minimize the risk of derailments, slow orders are typically issued on sections of track in areas where an elevated rail temperature is expected and risk of track buckling is increased. While slow orders are an important preventive safety measure, they are costly as they disrupt timetables and can affect time-sensitive shipments. Optimizing the slow order management process would result in significant cost saving for the railroads. The Federal Railroad Administration’s (FRA’s) Office of Research and Development has sponsored the development of a model for predicting rail temperatures using real time weather forecast data and predefined track parameters and a web-based system for providing resulting information to operators. In cooperation with CSX Transportation (CSX) and FRA, ENSCO Inc. conducted a comprehensive model verification study by comparing actual rail temperatures measured by wayside sensors installed at 23 measurement sites located across the CSX network with the rail temperatures predicted by the model based on weather forecast data over the course of spring and summer 2012. In addition to the correlation analysis, detection theory was used to evaluate the model’s ability to correctly identify instances when rail temperatures are elevated above a wide range of thresholds. Detection theory provides a good way of comparing the performance of the model to the performance of the current industry practice of estimating rail temperature based on constant offsets above predicted daily peak ambient air temperatures. As a next step in order to quantify the impact of implementation of the model on CSX operations, heat slow orders issued by CSX in 2012 on 10 selected subdivisions were compared to theoretical heat slow orders generated by the model. The paper outlines the analysis approach together with correlation, detection theory and slow order comparison results. The analysis results along with investigation of past heat related track buckle derailments indicate that the railroad would benefit from adopting the rail temperature prediction model along with flexible rail temperature thresholds. The implementation of the model will have a positive impact on safety by allowing for issuing of advance heat slow orders in more accurate, effective and targeted way.

A steel girder bridge over a highway was found damaged by a truck running underneath. The collision damage in the girder was mainly the deformation of the lower flange and the bent of the web plate, but the buckling of the transverse stiffener and the separation of the transverse stiffener from the web were also noted. The influence of the damage on the safety of the bridge had to be evaluated, and yet the load-carrying capacity of a girder damaged by collision has not been investigated very much. In the present study, based on the data obtained from this bridge, the load-carrying capacity of the deformed girder is studied. To be specific, the deformation of the main girder due to collision is reproduced by the finite element analysis and the damaged steel girder is loaded to evaluate the loadcarrying capacity. The result indicates that the collision damage of the girder deformation, even if quite large, would not necessarily threaten the safety of the bridge.