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The railway industry has been slow to adopt limit states principles in the structural design of concrete sleepers for its tracks, despite the global take up of this form of design for almost every other type of structural element. Concrete sleeper design is still based on limiting stresses but is widely perceived by track engineers to lead to untapped reserves of strength in the sleepers. Limit design is a more rational philosophy, especially where it is based on the ultimate dynamic capacity of the concrete sleepers. The paper describes the development of equations and factors for a limit design methodology for concrete sleepers in flexure using a probabilistic evaluation of sleeper loading. The new method will also permit a cogent, defensible means of establishing the true capacity of the billions of concrete sleepers that are currently in-track around the world, leading to better utilisation of track infrastructure. The paper demonstrates how significant cost savings may be achieved by track owners. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Understanding track geometry deterioration decisively influences the planning and optimisation of track maintenance and renewal works and consequently the substantial related costs (savings) each year of every railway. To understand this deterioration it must be accurately modelled, paving the way towards its forecasting into the future. The main aim of the present study was to model railway track geometry deterioration using multivariate statistical analysis of the variables involved and to predict the future behaviour of the track geometry deterioration. For this purpose, a track section of about 180 km in length was selected as the base for the model and divided into analytical segments of as uniform characteristics as possible using a special segmentation algorithm. The lengths of the individual analytical segments were not identical, but were also kept as close to uniform as possible. For each analytical segment, the following general information was collected: track structure, traffic characteristics, track layout, environmental factors, track geometry measurements records and maintenance and renewal history data. Consequently, multivariate statistical analysis was performed on the main track geometry parameters: twist, level, alignment, gauge and cant. The coefficients of the independent variables involved in track geometry were found for each parameter in order to predict future behaviour for the purposes of efficient maintenance and renewal management [ABSTRACT FROM AUTHOR]

Metronet's extensive programme of ballasted track replacements on London Underground lines causes a large number of high-consequence, low-probability structural risks. (The name 'Metronet' has recently ceased being used.) The acceptable level of risk is discussed. Many of the risks involve small temporary adverse changes, and it is shown that these are not acceptable simply because they are small. Economical mitigations of risk, involving reasoning or modest modification of the conditions during the track replacement, are described for situations where calculation alone cannot demonstrate an acceptable level of risk. [ABSTRACT FROM AUTHOR]