Field testing of concrete crossties and fastening systems for the understanding of mechanistic behavior

To adequately satisfy the demands placed on North America's railway infrastructure through ever increasing freight tonnages and development of its high speed rail program, the design and performance of concrete ties and elastic fastening systems must be improved. As a part of a study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, field experimentation was performed at the Transportation Technology Center (TTC) in Pueblo, CO by researchers from the University of Illinois at Urbana-Champaign (UIUC). This paper details the extensive instrumentation program which includes strain gages and linear potentiometers. Testing was conducted over seven adjacent concrete crossties in tangent and curve track utilizing TTC's Track Loading Vehicle (TLV) as well as passenger and freight train consists. Measurements taken consisted of the wheel-rail input loads, component stresses (e.g. insulator post compression), concrete tie strains, and displacements of the rail and concrete tie. The data was collected synchronously to provide a means to capture the load path, target areas of uncertainty, and provide comprehensive data for the validation of a multi-tie, 3-D finite element model being developed by UIUC. Varying train speeds, track curvature, and loading types provided a means to assess the loading variability that can be expected within the fastening system and lead to more purposeful and efficient instrumentation strategies. Furthermore, this data can be used to guide future research in further quantifying the field loading demands on system components, ultimately leading to the mechanistic design of the concrete crosstie and fastening system.