Development of a new load-deflection method for characterization of North American heavy haul concrete sleepers

Over the past few decades, the use of concrete sleepers in North America has increased as a highperformance alternative to timber sleepers, especially in heavy-haul freight corridors. In order to accommodate heavier axle-loads and prevent center cracking, railroads and suppliers have consistently increased the center bending moment threshold that a sleeper must withstand, leading to stiffer elements that may be more prone to brittle cracking. In order to develop an alternate performance assessment method and ultimately improve the design practice for concrete sleepers, laboratory experiments were executed at the University of Illinois at Urbana-Champaign (UIUC). Using a loading frame, concrete sleepers were subjected to a four-point bending test, while recording the deflection at the center of the sleeper, using a protocol that was adapted from the Manual of Railway Engineering of the American Railway Engineering and Maintenance-of-Way Association (AREMA). Experimentation was performed on some of the most representative concrete sleeper designs that are currently installed in North American heavy-haul freight corridors. The resulting load versus deflection curves illustrate the variability of each of the sleeper’s response to load and characterize the stiffness of the sleepers. These results will be used as the basis to develop standardized laboratory tests aimed at optimizing future sleeper designs, to prevent failures due to excessive stiffness or brittleness.