Measuring Concrete Crosstie Rail Seat Pressure Distribution With Matrix Based Tactile Surface Sensors

Abstract

A sustained increase in gross rail loads and cumulative freight tonnages, as well as increased interest in high and higher-speed passenger rail development in the United States, is placing an increasing demand on railway infrastructure. According to a railway industry survey conducted by the University of Illinois at Urbana-Champaign (UIUC), rail seat deterioration (RSD) was identified as one of the primary factors limiting concrete crosstie service life. Therefore, it can be seen that there is a need for infrastructure components with increased strength, durability, and ability to maintain the tighter geometric track tolerances under demanding loading conditions. Researchers have hypothesized that localized crushing of the concrete rail seat is one of five potential mechanisms that contribute to RSD. Therefore, to better understand this mechanism, UIUC is utilizing a matrix based tactile surface sensor (MBTSS) to quantify the forces acting at the interface between the bottom of the rail pad and the concrete tie rail seat. The MBTSS measures the forces and distribution of pressure as a load is applied to the rail seat. Preliminary laboratory testing has shown that higher modulus rail pads distribute forces poorer than lower modulus rail pads, leading to localized areas with high contact pressure and a higher probability of crushing. Testing has also shown that as the lateral/vertical (L/V) force ratio increases, the pressure on the field side of the rail seat also increases, possibly accelerating RSD. The objective of future field testing is to be able to validate the assumptions made from this preliminary laboratory data. Data collected and analyzed throughout this research project will provide valuable insight into developing future concrete crosstie and fastening system component designs that meet the operational and loading demands of high speed rail and joint passenger/freight corridors.