Abstract
The main functions of the sleepers in ballasted tracks include transferring loads, securing rail gauge and maintaining railway track geometry. Sleepers can be manufactured using timber, concrete, steel or other engineered materials, but concrete is most commonly used around the world. There are a number of researches on the impact load characteristics and the ultimate load carrying capacity of prestressed concrete sleepers, but research on the fatigue life of prestressed concrete sleepers is very limited. A prestressed concrete sleeper's fatigue damage is mainly due to the repeated loads derived from dynamic wheel-rail interactions, especially when either wheel or rail irregularity is present. Fatigue failure is thus a time-dependent limited state where a concrete sleeper accumulates damage to a failure point over its service life. Concrete sleepers could usually suffer from the dynamic fatigue loading spectra throughout their whole lives, and simultaneously, both static and dynamic load-carrying capacities of concrete sleepers degrades over time. Therefore, a fatigue life assessment is an important and complicated research frontier. Field loading conditions, material time-dependent and dynamic properties, and the dynamic bending moments of prestressed concrete sleepers are quantitatively analysed in this study. This paper also presents an updated fatigue life assessment method for concrete sleepers, and provides a case study based on actual field loading conditions and the time-dependent behaviour of materials. The new insights obtained from this study will improve concrete sleeper maintenance and inspection criteria, and provide a new reference for a rational dynamic design principle of railway concrete sleepers and bearers.
Highlights
Railway sleepers are one of the most significant railway components that lie between the rail and the ballast [1].The functions of a sleeper include transferring and distributing the wheel-loads from the rail to the ballast bed, and maintaining the geometry of the railway track within a suitable range [2]
It should be noted that, Eqs. (13), (14) were gained from the stick environment. These results are conservative for prestressed concrete sleepers and the fatigue life calculated from this study is conservative
A method based on the damage accumulation concept to assess the fatigue life of a concrete sleeper is demonstrated
Summary
Railway sleepers are one of the most significant railway components that lie between the rail and the ballast [1].The functions of a sleeper include transferring and distributing the wheel-loads from the rail to the ballast bed, and maintaining the geometry of the railway track within a suitable range [2]. In some good quality lines the concrete sleepers are likely to be over designed, in some severe loading environment lines the concrete sleepers cracks develop rapidly due to the repeated impact loads They put forward that a Fatigue Limit State (FLS) should be included in the process of a concrete sleeper design. The FLS can still be divided into two different types according to the judgement criteria, the first one takes the cracking states as criteria (crack width or depth etc.), and the second one uses the fracture as criteria (reinforcement or prestressing steel fracture) From another view, the FLS includes the ULS and the SLS under fatigue loading. The focus is on the fatigue life of a concrete sleeper calculation and the particular assessment method is based on the field loading condition and the time-dependent behaviour of material
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