Technology Digests / Thermal Effects on Track Gage of Engineered Polymer Composite Ties: Part 2

TD23-021

November 13, 2023
Authors
  • Yin Gao
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Key Findings

  • The model showed that the intraday track gage can widen as much as 0.27 inch due to daily temperature swings, based on typical thermal properties of EPC ties.
  • The intraday track gage widening, combined with the seasonal gage variation, may vary as much as 0.35 inch.
  • While the magnitude of gage widening in the modeling did not exceed the regulatory safety standards for any track class, thermal gage widening may immediately reduce allowable gage widening by 20–to 30 percent.
  • Appropriate levels of CTE and TC need to be developed and recommended in the AREMA Manual for Railway Engineering. According to the modeling, a CTE at 1×10-5 in./in./°F of a composite tie would generate minimal (less than 0.06 inch) thermal expansion in track gage regardless of the TC value.

Thermal Effects on Track Gage of Engineered Polymer Composite Ties: Part 2

Since the early 2000s, MxV Rail has been investigating the performance of engineered polymer composite (EPC) ties. Recent field investigations1,2 have found that temperature changes caused more gage variation with track that used EPC ties than with track that used wood ties. Specifically, the gage measurement on track built with EPC ties was 0.15–0.25 inch wider in the afternoon than it was in the cooler temperatures of the morning. Previous simulation efforts3 indicated that both the coefficient of thermal expansion (CTE) and the thermal conductivity (TC) properties of the EPC ties could be affecting these variations in the track gage. This Technology Digest presents a comprehensive simulation to understand how the CTE and TC of EPC ties affect track gage. INTRODUCTION EPC ties are generally composed of a post-consumer recycled plastic such as high-density polyethylene (HDPE), in addition to any additives,a fillers, or fiber and particle reinforcements that may be…