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Each year, there can be three to six millions of service train axles running over an open plain track. In fact, these trains could impose a variety of dynamic loading conditions depending on the wheel and rail maintenance levels. Inevitably, the risk of high-intensity dynamic loading conditions by wheel-rail interactions due to wheel or rail irregularity cannot be disregarded. Imperfection of rail tracks could lead directly to the exceedance of permissible stress of a track component and later amplify rapid track deterioration rates causing cracking in sleepers and failure of track substructure. Practical railway track irregularities can be typically classified into short wave length (high frequency) and long wave length (low frequency) defects, of which previous researchers had studied each in isolation. This paper is the first to study the influence on railway track inspection and maintenance priorities caused by the coupling of wave lengths between dipped rail joint and differential track settlements. To study the dynamic coupling effects, P1 and P2 forces are evaluated at the track irregularity together with rail/sleeper contact force, ballast pressure and bending moments of sleepers using dynamic multi-body simulation approach. It is found that some patterns of coupling irregularity could cause a significant reduction in dynamic impact factors whilst some are associated with an increase in the wheel/rail impact force. The insight has then been integrated to establish track performance indicators that are paramount for prioritising track inspection and maintenance. [ABSTRACT FROM AUTHOR]

The number of railway lines both operational and under construction is growing rapidly, leading to an increase in the number of buildings adversely affected by ground-borne vibration (e.g. shaking and indoor noise). Post-construction mitigation measures are expensive, thus driving the need for early stage prediction, during project planning/development phases. To achieve this, scoping models (i.e. desktop studies) are used to assess long stretches of track quickly, in absence of detailed design information. This paper presents a new, highly customisable scoping model, which can analyse the effect of detailed changes to train, track and soil on ground vibration levels. The methodology considers soil stiffness and the combination of both the dynamic and static forces generated due to train passage. It has low computational cost and can predict free-field vibration levels in accordance with the most common international standards. The model uses the direct stiffness method to compute the soil Green's function, and a novel two-and-a-half dimensional (2.5D) finite element strategy for train-track interaction. The soil Green's function is modulated using a neural network (NN) procedure to remove the need for the time consuming computation of track-soil coupling. This modulation factor combined with the new train-track approach results in a large reduction in computational time. The proposed model is validated by comparing track receptance, free-field mobility and soil vibration with both field experiments and a more comprehensive 2.5D combined finite element-boundary element (FEM-BEM) model. A sensitivity analysis is undertaken and it is shown that track type, soil properties and train speed have a dominant effect on ground vibration levels. Finally, the possibility of using average shear wave velocity introduced for seismic site response analysis to predict vibration levels is investigated and shown to be reasonable for certain smooth stratigraphy's. [ABSTRACT FROM AUTHOR]

An innovative stochastic dynamic model of a 3D train-track-bridge coupled system (TTBS) with refined wheel/rail interaction is established for a high-speed railway based on the random theory of probability density evolution method (PDEM). The multi-coupling effect of excitations can be simultaneously input into the new model, e.g. random track irregularity, random vehicle loads, stochastic system parameters, et al. Moreover, a new approach, named “Number theoretic method of multi-target probability functions” (NTM- mp ), is developed to obtain the discrete point sets of multidimensional random parameters in hypercube space, aims to solve the point design of system uncertainty. The stochastic harmonic function (SHF) is applied to generate representative random track irregularity samples. The results of TTBS got by PDEM are verified with several typical case studies for its efficiency and reliability, which are the deterministic results in the representative publication, the Monte Carlo method (MCM) results, and the field testing results on the high-speed railway. At last, a typical case study of TTBS on a high-speed railway is presented for numerical analysis. Discussions and significant conclusions on the random dynamic responses are presented. [ABSTRACT FROM AUTHOR]

Recently, track mileage with concrete crossties has been increasing throughout the world. In North America, for example, approximately 30 million crossties are currently in service on Class I freight railroads. It is essential to understand the concrete crosstie bearing capacity and flexure behavior for both design and safety purposes. The American Railway Engineering and Maintenance-of-Way Association (AREMA) Recommended Practices and Australian Standard’s (AS) current flexural design methodologies consider rail seat loads to be vertically transferred to the neutral axis. However, the International Union of Railways (UIC) assumes rail seat loads are distributed at a 45 degree angle to the neutral axis. This load distribution behavior is commonly seen in the design of concrete corbels and spread footings, but is not well documented in the design of concrete crossties, and different assumptions (i.e. in AREMA and UIC design methods) will result in different designs. Better understanding the load distribution in concrete crossties will help to improve the design of concrete crossties and optimize their performance. This study presents preliminary results from an on-going research project at the University of Illinois at Urbana-Champaign (UIUC) focused on concrete crosstie mechanical behavior. A parametric study using three-dimensional (3D) finite element modeling (FEM) was performed to investigate stress distribution below the rail seat and quantify the corresponding distribution angles in prestressed concrete crosstie under static wheel loading. Laboratory experiments were also performed and successfully validated the results obtained from the numerical simulations. The results from both numerical simulation and laboratory experiments indicate the stress distribution angle under rail seat is not constant which disagrees with the assumptions in UIC 713R. Moreover, the stress distribution angle under rail seat is found to be sensitive to crosstie support conditions, and its value follows a direct relationship with rail seat load magnitude. The findings from this study can help to optimize prestressed concrete crosstie bearing capacity design. [ABSTRACT FROM AUTHOR]

The recent development and use of new rail track models due to the evolution of the railway, especially with high speed and freight, has meant the introduction of slab track models with an associated variety of transition zones (between ballast and slab track) across railway networks worldwide. However, there are no studies about how the position of the supports could influence the track performance in general and track transitions in particular, how much bigger or smaller the gap must be between slab track and ballasted track. This study tries to find the optimal distance between the supports while maintaining good track performance which is assessed in terms of sleeper vertical displacements and stresses on ballast. Reducing these movements and stresses will increase track life and means less maintenance work. The aim of this paper is to study these effects and try to provide an optimal and low cost solution for existing and future track designs. [ABSTRACT FROM AUTHOR]

This paper investigates, for the first time, the behaviour and design of railway double track open timber floor plate girder deck steel bridges under combined buckling modes including web distortional buckling. A 3-D finite element model has been developed for the railway bridges, which accounted for the bridge geometries, initial geometric imperfections, material nonlinearities of the bridge components, bridge boundary conditions, interactions among bridge components and bridge bracing systems. Most of the aforementioned parameters are not incorporated in current design codes of railway bridges, which are credited to this study. The simply supported bridges investigated had a span of 30m, a width of 7.2m and a depth of 3.12m. The bridge components comprising main plate girders, stringers, cross girders, connections, bracing members, stiffeners, bearings, and field splices were designed following the design rules specified in the European Code for steel bridges. The live load acting on the bridge was Load Model 71, which represents the static effect of vertical loading due to normal rail traffic as specified in the European Code. The finite element model of the double track bridge was developed depending on additional finite element models, developed by the author, for small and full-scale plate girder steel bridge tests previously reported in the literature. Ultimate loads, load-mid-span deflection relationships, failure modes, stress contours of the double track bridge as well as of the small and full-scale tests were predicted from the finite element analysis and compared well against test results. Parametric studies were performed on the railway bridges highlighting the effects on the structural behaviour and ultimate loads carried by the bridges owing to the change in the bridge geometries, slenderness and steel strength. The paper presents a complete piece of work regarding the finite element analysis and design of railway steel bridges, which can be used for further parametric studies, finite element analyses and investigations of the bridges under different loading and boundary conditions. The parametric study has shown that the presence of web distortional buckling causes a considerable decrease in the ultimate load of the steel bridges. It is also shown that the use of high strength steel offers a considerable increase in the ultimate loads of less slender steel bridges. The study has also shown that the design rules, loading and recommendations specified in the European Code provide accurate and conservative estimations for the design of railway steel bridges, except for the bridges failing mainly by web distortional buckling [ABSTRACT FROM AUTHOR]

Railway operations are inherently complex and source of several problems. In particular, track geometry defects are one of the leading causes of train accidents in the United States. This paper presents a solution approach which entails the construction of an ensemble classifier to forecast the degradation of track geometry. Our classifier is constructed by solving the problem from three different perspectives: deterioration, regression and classification. We considered a different model from each perspective and our results show that using an ensemble method improves the predictive performance. [ABSTRACT FROM AUTHOR]

Due to the modularity of the traditional track and the discreteness of the ballast bed, the application of the repeated and random train load would inevitably result in the accumulation of residual deformation and the track damage. A new steel pre-installed modular railroad track assembly was designed to provide better stability and reduce deformation. It includes a plurality of spaced-apart cross-ties, two side ties, intermediate ties and a pair of rails road track rails. In order to figure out the mechanical performance of this new steel pre-installed modular railroad track assembly, the 3-D finite element model of the steel modular railroad track including with the track, ballast bed, sub-ballast and the sub-grade was built. In this model, the load distribution and the vertical deformation of ties with different cross sections were discussed, and the stresses of the steel modular railroad track and the ballast bed were analyzed. The results indicate that, compared with the traditional track, the single wheel load will transfer to more ties of the new steel modular railroad track and the integrality of the new steel modular railroad track is much better. The maximum deflection of the steel modular railroad track located at the point of load application (under the wheel load). It is much smaller than that of the traditional track. As a result, it can be concluded that the new steel modular railroad track is more likely to induce less deflection under the series wheel load and have better rail regularity. [ABSTRACT FROM AUTHOR]

Crossties are critical components of the railroad track to facilitate load distribution to track substructure. Recent instrumentation at Kingston, Rhode Island indicated that a crosstie could have translations as well as rotations under train load repetitions. However, previous laboratory experiments on crossties did not fully take the crosstie rotations into consideration. In this paper, actual movements of railroad crossties under moving train loads were first characterized by numerical modeling and field investigation, and then the effect of tie rotations on track ballast performance was evaluated by discrete element modeling (DEM). A vehicle dynamics model coupled with a three-dimensional finite element track model were utilized to simulate the crosstie movements. To obtain the crosstie movements under train passage, field measurements were conducted on an Amtrak high-speed passenger line and a freight railroad short line. The measuring units were mounted on top of crossties to record the accelerations in vertical, lateral, and longitudinal directions and the Euler angles in roll, pitch and yaw. The translations of crossties were obtained by the double integration of accelerations and the rotations were represented in terms of the Euler angles. Both modeling results and field measurements indicate that crossties have not only translations but also rotations under moving trains. In addition, angular velocity and angular acceleration measured in the field tests indicate that the rotations could cause extra moments up to 5000 N-m on top of the ballast layer. The extra moments may not cause significant track failure, but may accelerate the deterioration of track components. Further, a DEM program was used to evaluate the effect of the crosstie rotations on track ballast. The results of DEM show that the crosstie rotations would increase the acceleration of individual ballast particles and contact forces between ballast particles. [ABSTRACT FROM AUTHOR]

Sealed-space-filling self-compacting concrete (SSFSCC) is used in China Rail Track System (CRTS) III ballastless slab track of high-speed rail, which has been originally developed in China recently. In this track system, SSFSCC needs to be grouted into a flat, narrow, and sealed space (90 mm × 2500 mm × 5600 mm) which is enclosed by above prefabricated slab and bottom base plate. Good bonding between SSFSCC filling layer and above prefabricated slab has to be secured since these two layers are required to work as a composite plate. SSFSCC presents some special characteristics in comparison with normal SCC. This paper elaborated the property requirements of SSFSCC and the structural characteristics of SSFSCC layer of CRTS III ballastless slab track of high-speed rail. The compositions and mix proportioning of SSFSCC as well as construction technology were briefly introduced. The challenges of the application of this special SCC were also addressed. [ABSTRACT FROM AUTHOR]

Ground-borne vibrations and noise, originated at the train/tram wheel–rail interface and transmitted through the rails to the ground, may cause significant disturbance to people passing by or residing alongside the railways. This paper presents a case study on the evaluation of the effectiveness for mitigating ground-borne vibration and noise by floating slab track system (FST). The underpass located at a major road junction in front of Konya Metropolitan Municipality building serves to thousands of people every day. The Konya Light Rail makes a curb right on top of the underpass, which generates considerable amount of noise and vibration to the environment. In this study, the noise and vibration acceleration measurements were taken before and after the FST system installment in order to evaluate the effectiveness of the isolation work. The collected acceleration data were analyzed and the resulting vibration velocity levels were compared. It was found that the vibrations and the ground-borne noise due to the passage of the trams were reduced considerably. The FST system was found to be quite successful in absorbing the vibrations. A noise level reduction up to 26 dBA was measured after replacing the old rail system with FST. [ABSTRACT FROM AUTHOR]

A composite railroad track is a rigid track system that is developed using quick-hardening infilling materials, and has the advantages of a reduced maintenance cost compared to a conventional ballasted track. Quick-hardening infilling materials were developed in this study, which does not require the processes of cleaning the aggregates crushed due to the repeated load imposed by rolling stock, and thus the materials can strengthen existing ballasted tracks with an enhanced level of efficiency and speed. Theoretical reviews of pore size, permeability, pore channel length and tortuosity depending on the size of the aggregate in ballasted tracks were conducted first to predict the influence of filling parameters of infilling materials for composite railroad tracks. Based on the theoretical filling performance analysis of ballasted tracks, a thermosetting polymer was developed, which is a 3D cross linking agent that performs redox radical polymerization reaction at room temperature. The polymer was used as a primary filling material to fill the lower ballast layer, which could not be filled by conventional cement-based filling materials. A double-layered composite was formed by filling the upper ballast layer with the ceramic-based secondary filling material using the reaction between dead-burned magnesia and acid ammonium phosphate. The performance of infilling materials was validated through strength measurement and microscopic analysis. [ABSTRACT FROM AUTHOR]

Sleepers are the primary structural components that provide the necessary gauge width and the structural stability to the ballasted railway track. High performance prestressed concrete sleepers of high-speed railways have strict design and production requirements to provide a safe, serviceable and a reliable railway superstructure. The production dimensions of a contemporary prestressed high performance concrete sleeper are within low tolerance values on the scale of a millimeter that is uncommon for ordinary structural concrete elements. Railways are within climatic conditions that could become effective in the dimensional stability of their sleepers. Within regions of low humidity levels, in addition to the elastic shortening of the prestressed sleepers, the effects of concrete creep and shrinkage could lead to total contraction values in excess of the allowed tolerances for the shoulder width of the sleepers. Therefore the dimensional design of a high performance prestressed concrete sleeper must include the effects of time dependent dimensional changes. This paper presents the possibility of falling out of dimensional tolerance for prestressed high performance sleepers and ways to mitigate those possibilities for railways in arid climatic conditions or within climatic zones undergoing a climate change. [ABSTRACT FROM AUTHOR]

A new theory is presented for predicting squat morphology on high and low rails of curves, based on tangential contact stress directivity for running bogies and local loading history. Notably, squats on high and low rails are predicted as distinct, with generally no branching on the latter. Field data confirm predictions, and illustrate three other aspects of squat growth: repetitive and transient tangential contact stress redistribution at the leading RCF-crack may explain branching; white etching material is found unrelated to crack initiation on head-hardened rails, and high-frequency dynamic wheel–rail interaction is shown incapable of explaining basic features of squat growth. [ABSTRACT FROM AUTHOR]

Abstract: Pavement and railtrack design is of huge importance to society and yet the theoretical basis for most current design methods is still very simplistic and crude (Brown, 1996; Yu, 2006). This paper is part of a concerted effort at the Nottingham Centre for Geomechanics to develop improved theoretical foundations for pavement and railtrack design. It is mainly concerned with the development of rigorous lower-bound solutions for shakedown of cohesive-frictional materials under three-dimensional moving traffic loads. Compared with previous studies, two important aspects are taken into account. First, this paper considers a more general case of elliptical contact area between traffic and material surface, as most previous lower-bound studies considered the traffic load is applied through an infinite long roller. Secondly, by introducing a critical self-equilibrated residual stress field, this shakedown problem is reduced to a formulation in terms of a load parameter only. By using a simple optimisation procedure, the maximum load parameter leads to a lower-bound shakedown limit to this problem. Results for the special case of circular contact area are also presented in analytical form, which can then be readily applied for practical design. [Copyright &y& Elsevier]

Abstract: A railway wheelset is subject to normal wear due to large part to friction contact between the wheelset and the rail. Because the wear of wheelset will bring the hidden security troubles to the operation of the railway, it is very important to measure the wheelset''s geometrical parameters, especially the flange thickness. The optoelectronic method is proposed and can dynamically measure the flange thickness on line. Fast Fourier transform and wavelet analysis methods are used to denoise the sensor''s signals. It is found that the wavelet transform produces a much better way of denoising of the signals compared with the fast Fourier transform. Comparisons of the flange thickness measurement with the wheelset creeping and the optoelectronic system are presented. The root-mean-square errors of the flange thickness with the manual measurement with the wheelset creeping and the optoelectronic method measurement with the wavelet analysis are 0.22 and 0.18, respectively. The changing range of manual measurement is much larger than that of the optoelectronic method because of the difference between every operator''s measuring standard. Measurement results of the optoelectronic method show that the system has better repeatability and reliability compared to the manual measurement. [Copyright &y& Elsevier]

Abstract: In this paper, the dynamic performance of a certain kind of existing bridge under the action of high-speed railway traffic is addressed. Short-to-medium-span simply supported structures are susceptible to experiencing harmful transverse vibrations under resonant conditions, leading to excessive levels of vertical acceleration, the subsequent premature deconsolidation and degradation of the ballast layer, passenger discomfort and high maintenance costs of the corresponding lines. This dynamic problem, which can require the reduction of the design velocity or the temporary interruption of the railway service to undertake corrective actions, has been reported in Europe, China and Japan during the last decades (European Rail Research Institute (2000) , Duan (1995) , Ishibashi (2004) ). In particular, single-track simply supported short bridges appear to be quite critical structures in this regard. In what follows, the authors present an evaluation of the dynamic performance of three real bridges on the Spanish railway network, located in double-track branches but composed of structurally independent decks. The objective of the investigation is to compare their performance with that of hypothetical modified double-track versions of the original decks. An orthotropic plate finite element model, whose properties are updated from experimental tests performed on the bridges in the past, is used to predict the structural dynamic responses in the time domain. Finally, the predominant effect of the increase in the mass of the bridges over the increase in the eccentricity of the tracks, the reduction in the natural frequency experienced by the torsion mode, and the relevance of three-dimensional modal contributions is proven, leading to remarkable reductions of the maximum acceleration levels in the multiple-track modified structures. [Copyright &y& Elsevier]

Abstract: Railway organizations are facing continuous increase in train frequency, running speed and axle load with ever limited financial resources. This is why methods broadening knowledge of external loads and internal rail stresses are of higher importance to address rail design or maintenance process. The following paper explains how the development and application of such methods has been conducted by a european partnership (called NOVUM) between railway organizations (SNCF, DB AG, RATP) and rail producer (CORUS) sharing their specific own competences, experience and material resources. Research institutes and universities (BAM, GKSS, INRETS, INSA, LMS) have been in charge of building sound numerical simulations or experimental tests and tools. Theoretical aspects of the method are described in independent paper “A global approach for modelling fatigue and fracture of rails”. A first task group of the program is dedicated to the determination of external forces coming from wheel/rail and from rail/support interactions. The second and third task groups are about material properties and internal stresses inside rail section. Laboratory and track validations are undertaken in the fourth task group. Two characteristic cases are then chosen to check the developed models. [Copyright &y& Elsevier]

A moving rail vehicle may cause propagating waves to the surroundings potentially leading to detrimental effects for the track construction, nuisances for the surroundings and interference with delicate electronic equipment. A full computational model should be able to couple a correct simulation of the rigid body motion of the different train parts with accurate prediction of the solid wave propagation in the ground. This paper integrates the dynamics of the vehicle and the elastic soil into one monolithic system. Equations of motion for the train have been merged the system representing the FEM problem for the rest of the structure. Three models of modern high-speed locomotives were run over a solid finite element model of a rail structure. [Copyright &y& Elsevier]