The welding of rail joints on sharp curves is not practicable due to the lack of sufficient lateral resistance of the railway track. Consequently, maintenance costs increase rapidly for many old railway tracks. Moreover, deterioration of the track components, plastic deformation and critical cracks in the rail head, failures in sleepers and fasteners, ballast bed damage and lateral movement of railway track occur in the rail joints. As the resistance of a sleeper to lateral displacement in a ballast bed mainly consists of the frictional forces between the ballast particles and the sleeper bottom, the present study investigated the changes in resistance of railway tracks to lateral displacement using the single sleeper push test on the frictional concrete sleeper (B70-F). The results were then compared with those for the standard sleeper, B70. An experiment was conducted on a track with and without frictional sleepers and its result showed that the lateral resistance of the railway track increased by 64% by using frictional sleepers. In addition, a field investigation was conducted on an actual track with and without B70-F sleepers in order to extend the results and the conclusion was that the resistance of the railway track to lateral displacement increased by approximately 68% when using B70-F sleepers.

Dynamic behavior of railway tracks when trains are running is influenced by several factors, i.e. rolling stock, the components of superstructure and their specifications. Usually, features like the sleeper spacing, rail pad stiffness, ballast damping and stiffness have an effect on the dynamic response of the track. The best method to study the dynamic behavior of the track is to model the track assembly and the train as a whole and carry out an analysis of dynamic interaction. Such analysis makes the identification of the track's dynamic behavior easer and helps to anticipate the deterioration of the track elements, and determines the effects of increase or decrease of mentioned parameters. This paper presents track-train dynamic interaction without considering irregularity of the rail face. A sensitivity analysis was carried out on the selected model. The analysis was undertaken with the view of varying one of the mentioned parameters and the results were presented to further identify the deterioration of the track elements.The results indicate that reducing sleeper spacing, rail pad stiffness, ballast stiffness, and increasing ballast damping reduces wheel-rail, rail-sleeper, and sleeper -ballast contact forces.

Despite the significant role of sleepers in railway track mechanical behavior, no thorough mechanistic approach has been presented for the development of the loading pattern they experience. The current theoretical methods in the analysis of the railway track system need further calibration and verification using field-measured data. In this paper, using specific load-cells between sleepers and the rail and beneath the sleepers, the vertical loading conditions of these main track elements are studied. The lateral resistance of the concrete sleepers in the ballasted tracks is investigated by using full scale sleeper pull-out tests. Moreover, track deflections under the sleeper as the main track analysis parameter are measured and the results are discussed, In this paper, with the results obtained from extensive field measurements, some suggestions are made leading to an improvement in the current understanding of the sleeper loading pattern and the track deflections.

The lateral stability of ballasted railway tracks is a function of the lateral resistance of the sleepers created by interaction with ballast materials. Thus, one of the approaches for increasing the lateral resistance of sleepers has been to increase bottom friction and use frictional sleepers. A review of the technical literature showed that numerous experimental studies have been performed on this type of sleeper; however, no numerical analysis has been conducted on its lateral resistance. Therefore, this paper developed a finite element numerical model for investigating frictional concrete sleepers. In this regard, a hardening elasto-plastic behavior model was developed for the ballast layer and ABAQUS software was used to numerically analyze the lateral resistance of this type of concrete sleeper. Using the developed model, some sensitivity analyses were performed on the parameters that affect the lateral resistance including the thickness and extent of the ballast shoulder, and the friction coefficient between the ballast layer and sleeper. The obtained results indicated that increasing the ballast shoulder from 25 to 40 cm resulted in about a 16-22% increase in lateral resistance, whereas increasing the friction coefficient from 0.1 to 0.8 led to about a 22-28% increase in the lateral resistance. On the other hand, on decreasing the ballast layer thickness from 30 to 20 cm, the lateral resistance increased by about 12-17%. In summary, it can be concluded that, compared with conventional concrete sleepers, frictional sleepers increased the lateral resistance by about 63-70%.

Employing a dynamic model of the railway wagon in three dimensions, this paper presents the results of dynamic wheel–rail forces under the presence of track irregularities. A mathematical model of the wagon system is developed using dynamic equations of the components, taking into account the vertical (bounce), pitch and roll motions of the system. The model examines the dynamics of the wagon system under arbitrary rail irregularities. The spectra of rail surface irregularities are fed into the vehicle model to extract the time histories of dynamic forces between the wheel and the rail. Using the irregularity spectra of left/right rails, vibration of the wheelsets is studied for the bounce–roll motions. The dynamic contact forces between wheels and rails are determined for three examples of the measured irregularities. Moreover, three V-shape defects are modelled as examples of the singular defects on rail surface. The results of dynamic simulations confirm the large amounts of impact forces due to the presence of rail irregularities, particularly for the cases with much unevenness between the left/right profiles.

Railway track transition zone is a zone where track stiffness changes abruptly. This change occurs where the slab track connects to a conventional ballasted track, at the abutments of open-deck bridges, at the beginnings and ends of tunnels, at road and railway level crossings, and at locations where rigid culverts are placed close to the bottom of sleepers. In this paper, ballasted and slab tracks are simulated by two-dimensional model with two-layer masses. The transition zone is divided into three segments, each having a length of 6 meters with different specification and stiffness. The model of track consists of a Timoshenko beam as a rail and slab, lumped mass as sleepers, and spring and damper as ballast, sub-grade, and rail pad. The results of the dynamic analysis are presented and compared in two circumstances -one considering the transition zone and the other its absence.

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