| Résumé | Rail steel is produced in fixed lengths of between 12 to 120 m. To build track, rails can be joined either mechanically with joint bars and bolts or by welding the sections together as continuously welded rail (CWR). The general industry view is that CWR is preferred for main track construction as it eliminates discontinuities in track support. However, with this type of track construction, the rail steel is fixed in place and not free to expand or contract with changes in temperature. This results in thermally induced stresses in the rail (compressive when hot, and tensile when cold), which can be extremely large and contribute to rail breaks during cold weather conditions, and rail buckles under hot weather conditions. Although North American railways have operated with CWR since the 1950s, there is insufficient information on how rail behaves under stress, how longitudinal stress changes over time, how stress impacts the interaction between track and trains during operations, what exact stress condition(s) would cause broken rail or track buckling, nor how effective are current stress management practices. A literature review of thirty-three technical documents revealed a recurring theme of the difficulty in quantifying the level of stress being experienced by rails in CWR construction. Three potentially game changing technologies for longitudinal rail stress measurement were identified, including frictional strain sensing, X-ray diffraction and fibre optic sensing. These are commercial technologies already used in industries including oil and gas, construction, geotechnical and mining. A way forward is also proposed to test and validate the technologies, and deploy those suitable for the rail operating environment. |
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