Quantification of Rail Displacements Under Light Rail Transit Field Loading Conditions


While timber crossties are widely used in North America, the popularity of concrete crossties has increased significantly in recent years. Concrete crossties require the use of premium elastic fastening systems to have a proper and stable system. The primary role of fastening system is to attach the rail to its support preserving track geometry. For this reason, past research has focused on its development and behavior. Even though a large amount of research has been conducted on heavy-haul freight railroad systems, little work has been conducted to focus on rail transit systems. Therefore, a field analysis of the behavior of fastening systems under rail transit system loading conditions has been executed, focusing on light rail transit loading conditions. To perform this study, revenue service field data were collected on a light rail transit system. The instrumentation used and how it was installed on site are described in this paper. The critical quantitative metric discussed in this study is the relative displacement of the rail with respect to the concrete crosstie. Analyzing vertical and horizontal displacements, as well as rotation, the performance of the fastening system can be evaluated. For this purpose, different sites on the same rail system were selected for study, comparing both curve and tangent track geometry. In addition to this, the movement of the rail under every axle of the light rail vehicle has been studied in detail. In summary, an analysis of how the rail performs in terms of displacement under light rail transit loading conditions has been completed. Based on field data, the analysis allows the reader to understand how the rail displaces under the given loads when it is installed in a ballasted concrete cross tie track and restrained by elastic fastening systems.