The nature of loading conditions on railway tracks is mostly of regular loading patterns due to passage of wheels of rolling stock. Dynamic forces on a railway track caused by abnormal impacts due to wheel flats, rail dips, etc. are usually highly impulsive with short durations and high frequency contents. There have been a number of investigations on the wheel/rail impacts due to wheel and rail imperfections and track abnormalities. However, the effect of railway track environments including ballast and rail pads has yet been addressed. Intensive studies on the impact resistance of railway concrete sleepers have been conducted at the University of Wollongong, Australia. In order to understand more clearly the manner in which track components respond to those forces, and to clarify the processes whereby concrete sleepers in particular carry those actions, it is vital to ascertain the spectrum and amplitudes of forces applied to tracks. In addition, artificial impacts replicating the generic actual wheel/rail interaction must be identified, prior to investigating the shock responses of the railway concrete sleepers. This paper presents the experimental studies into the effects on dynamic loading conditions of track environments including the ballast support condition and rail pads. An assembled in-situ concrete sleeper has been constructed and subjected to artificial shock loading using a large capacity drop-weight hammer. The attempts to simulate the repeated impacts due to general wheel flats or engine burns are demonstrated so as to investigate of probabilistic impact failure of the concrete sleepers. The shock loadings under various track environments have been quantitatively monitored and recorded by National Instrument multi-channel PXI-SCXI using LabView8. These impacts could eventually lead to cracking and failure of the sleepers, and hence are important in the context of developing the new reliability-based design approach for the railway prestressed concrete sleepers.
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