Analysis of the Lateral Load Path in Concrete Crosstie Fastening Systems

Abstract

Increasing axle loads of today’s North American heavy haul freight trains have presented numerous engineering challenges for the design and performance of concrete crossties and fastening systems. Several research studies have been conducted to understand the path of the vertical load from the wheel/rail interface through the fastening system and into the crosstie with successful results. However, problems arise due to the failure of fastening system components caused by high lateral and longitudinal loads in addition to vertical loads. Failed components are often seen in demanding track environments such as sharp curves or steep grades. It is hypothesized these component failures are caused by high lateral and longitudinal loads, respectively. Until now, attempts to measure lateral forces in the fastening system have been relatively unsuccessful. This study focuses on gaining a better understanding of the lateral load path in concrete crosstie fastening systems through the use of novel instrumentation techniques to quantify the magnitude of lateral forces induced from various types of rolling stock. A thorough understanding of the lateral load path, lateral load magnitudes, and their impact on failure modes will aid in the future mechanistic design of fastening systems. Ultimately, mechanistic design will lead to fastening system components that are able to withstand heavy axle freight train loads with longer service lives. Preliminary results show that the type of rolling stock and resulting wheel loads greatly affect the magnitude of lateral forces in the fastening system.