Longitudinal Resistance Modeling for Frozen Ballast

On behalf of the Federal Railroad Administration (FRA), Transportation Technology Center, Inc. (TTCI) developed a “proof-of-concept” finite element (FE) longitudinal resistance model to simulate a rail break based on historical data. Longitudinal track resistance (fo) is an important parameter for rail break repairs to re-establish the rail neutral temperature (RNT). If an incorrect fo is used, the resulting RNT could be too high, which increases the risk of additional rail breaks. Conversely, if it is too low, this increases the risk of the track buckling. This project was undertaken to better define fo on frozen ballast due to the lack of sufficient data for this condition. Researchers developed an FE model to support much-needed field testing in the future. Research was conducted between Fall 2021 and Spring 2022. The FE model differs from the historical closed-form longitudinal resistance calculation in that it is mechanistically based; it directly simulates the longitudinal force-displacement response and can represent the longitudinal resistance at both the rail-to-tie and tie-to-ballast interfaces. To match historical datasets, the model required an assumed tri-linear force-displacement curve at the rail-to-tie and tie-to-ballast interface. This resulted in the model’s sensitivity to changes in the force-displacement curve. Before the FE model can be considered validated, it requires additional laboratory or field data that directly characterizes the rail-to-tie and tie-to-ballast force-displacement curves. However, if realistic force-displacement curves can be used, this model has the potential to provide fo values for a wider range of track conditions than has currently been tested in the field. These untested conditions can include, but are not limited to, frozen ballast.

• Record URL:
  • https://railroads.dot.gov/elibrary/longitudinal-resistance-modeling-frozen-ballast
• Record URL:
  • https://rosap.ntl.bts.gov/view/dot/64361
• Publication Date: 2022-7

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References;
• Pagination: 4p
• Serial:
  • Research Results
  • Issue Number: RR 22-22
  • Publisher: Federal Railroad Administration
• Publication flags:

  Open Access (libre)

Subject/Index Terms

• TRT Terms: Cracking; Finite element method; Freezing; Mathematical models; Mechanical resistance; Railroad rails; Repairing; Track ballast
• Subject Areas: Maintenance and Preservation; Railroads;

Filing Info

• Accession Number: 01860480
• Record Type: Publication
• Files: NTL, TRIS, ATRI, USDOT
• Created Date: Oct 5 2022 12:20PM