Considerations for Mechanistic Design of Concrete Sleepers and Elastic Fastening Systems in North America

A sustained increase in heavy axle loads and cumulative freight tonnages, as well as increased interest in high speed passenger rail development, has placed an increasing demand on railway infrastructure and its components. One of the most critical areas of the infrastructure in need of further research and analysis is the concrete sleeper and elastic fastening system used in heavy haul and shared infrastructure applications. A limited understanding of the complex loading conditions affecting the concrete sleeper and elastic fastening system components led to a design process based primarily on practical experience and previous techniques, which fails to include key variables that relate to actual field loading conditions. This process, which is typically driven by production and installation economics, has generated components that do not achieve their design life. While initially functional, they ultimately require more frequent maintenance or fail prematurely, causing track outages, reduced capacity, and added cost. To address this challenge, the University of Illinois at Urbana-Champaign (UIUC) is analyzing and comparing the existing heavy haul and shared infrastructure loading environment to current recommended design practices within the international railway community. This paper discusses the use of field experimental data, as well as complete sleeper and fastening system analytical modeling, and how they can be used to improve the current understanding of the loading demands on each component within the system. Results from these tests and modeling efforts, along with probabilistic considerations with respect to dynamic and impact loading, will contribute to a greater understanding of the loading regime present in the concrete sleeper and elastic fastening system in heavy haul and shared infrastructure applications. Ultimately, this improved understanding will provide a basis for a mechanistic design process, contributing to improved recommended practices for concrete sleeper and fastening system design and improving safety, reliability, and rail capacity.