Concrete sleepers are one of the most important applications of a railway track system. Researchers have previously studied the impact load characteristics and ultimate load carrying capacity of a prestressed sleeper, but research on the fatigue life of prestressed concrete sleepers is limited. Fatigue damage of a prestressed concrete sleeper is mainly due to the accumulation of defects caused by the repeated load of wheel-rail interaction. Fatigue load, fatigue characteristics, and the existing design methods of prestressed concrete sleeper are summarized in this paper. The commonly used fatigue assessment methods of concrete structures are also evaluated. Based on the results of former research, this article presents a convenient fatigue life assessment method for a prestressed concrete sleeper and contrasts with the test results. The insight information gained can be used to evaluate the service performance and predict the fatigue life of the concrete sleeper, as well providing design flexibility and broadening the design principle. The outcome of this study may also improve the rail track maintenance and inspection criteria, in order to establish an appropriate track condition monitoring network in practice.

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.

Railway sleepers are safety-critical and essential components in a ballasted railway track system. Sleepers could principally be made of different materials, such as, timber, steel, concrete, composite and plastic. The deterioration process of sleepers depends largely on the materials of which they are made. The most popular material for manufacturing sleepers nowadays is concrete. In very recent years, a new type of railway sleeper has been developed using composite and plastic materials. These plastic sleepers have been trialled as bridge transoms and, to a limited extent, as switch and crossing bearers. A limited application of composite (a combination of cement, steel and plastics) to bridge transoms can also be seen. At present, there is no unified design method or standard for these new plastic and composite sleepers and bearers. The lack of design information can compromise public safety. This paper thus highlights the design aspects for plastic and composite sleepers in comparison with traditional materials. It reveals that limit states design concept is the most optimal approach for sleeper design and manufacture. The insight will help rail asset owners and managers establish predictive and condition-based track design and maintenance.

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