Effect of track conditions on the flexural performance of concrete sleepers on heavy-haul freight railroads

Concrete sleepers have been widely used throughout the world as an alternative for timber sleepers. In North America, heavy-haul railroads have increased their use of concrete sleepers in recent years for a variety of factors. According to an international survey conducted by researchers at the University of Illinois at Urbana-Champaign (UIUC), railroad industry representatives consider center cracking to be one of the most common concrete sleeper failure mechanisms. Having a better understanding of sleepers’ flexural behaviour can potentially reduce the occurrences of center cracking by ensuring both designs and maintenance practices are adequate for the field conditions. To measure the bending moments experienced in North American heavy-haul freight service, field experiments were conducted at three Class I railroad sites in North America under different track conditions. Concrete surface strain gauges were installed on concrete sleepers at each location to record bending strains experienced by the sleepers under the passage of trains. These strains were converted into moments using calibration factors determined either by calculations based on the sleepers’ cross-sectional and material properties or by laboratory experimentation. This paper compares the measured moments from three test sites to analyse the effect of track conditions on the flexural performance of concrete sleepers.