Gauging of concrete crossties to investigate load path in laboratory and field testing

To meet the demands of increasing freight axle loads and cumulative gross tonnages, as well as high-speed passenger rail development in North America, the performance and service life of concrete railway crossties must be improved. As a part of a study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, laboratory experimentation was performed at the Advanced Transportation Research Engineering Laboratory by researchers from the University of Illinois at Urbana-Champaign. This paper focuses on the behavior of concrete cross-ties as well as characterizing and quantifying the loads transmitted from the wheel/rail interface through the fastening system to the tie in the vertical direction. Concrete embedment strain gauges were cast belowrail seat to create a "load cell" to measure the rail seat vertical load. Laboratory instrumentation efforts have been done to calibrate this vertical "load cell". To understand the rail seat load and load path in the field, experimentation was performed at the Transportation Technology Center (TTC) in Pueblo, both static loading which were applied by TTC's Track Loading Vehicle and dynamic loading due to real wheel-rail interaction were discussed. Concrete cross-tie bending behavior was also investigated through the use of strain gauges applied in the longitudinal axis of the crossties in both laboratory and field experiments. Results from these findings will be utilized to aid in the recommendations for the mechanistic design of various components within the fastening system..