Analysis of concrete tub at-grade railroad crossing by field instrumentation

Concrete tub crossings are at-grade railroad crossings used primarily on low-speed and low-tonnage rail lines. Concerns have been raised about the stiffness differential present between the track structure and crossing that could cause a localized shear strain increase. Due to this concern, much of the industry has limited speed of trains through these crossings to 40 kph (25 mph). This investigation evaluates a concrete tub crossing that experiences higher speeds and higher tonnage than typical. Visual observations and field performance indicate satisfactory performance of the crossing with little maintenance. Strain gauges mounted on the rail web were used to measure shear strains of trains at differing speeds. Results show little difference in maximum shear strain for train speeds up to 97 kph (60 mph). Concrete tub crossing shear demands are below shear capacity and independent of train speed, suggesting crossings can safely handle heavy railway traffic at greater speeds.