Technology Digests / Rotational Resistance Characterization of a Wood Tie for Track Buckle Analysis

TD24-015

January 24, 2025
Authors
  • Stephen Wilk
  • Sirius Roybal
  • Yin Gao
  • Duane Otter
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Key Findings

  • Based on laboratory testing, both the number of spikes and the spike hole condition had a significant influence on seated rotational resistance of wood ties while anchors had a lesser influence. The rotational resistance range measured during the laboratory testing could theoretically result in changes of track buckle strength by over 50°F, but it is currently unclear whether the 50°F increase could actually be obtained in wood tie track.
  • The amount of rotational slack that occurs before the rotating rail engages the tie plate (i.e., seating) causes the primary uncertainty in defining rotational resistance. This uncertainty has significant implications regarding track buckle strength because if the buckle occurs within the “slack” portion of the torsional-rotation curve, none of the tie plate resistance (parameters in previous bullet) will be engaged. It is also possible that some ties are in the “slack” portion while others are engaged due to uneven plate placement, tie skew, and rail rotation.

Rotational Resistance Characterization of a Wood Tie for Track Buckle Analysis

MxV Rail used laboratory testing to characterize the rotational resistance of different wood tie conditions. The rotational resistance is one of the four main static track buckle strength parameters (tie/ballast interaction, rotational resistance, longitudinal resistance, and track misalignments), but previous testing and knowledge of rotational resistance to resist track buckles is limited. While the laboratory testing simplifies the buckle rotational mechanism, the testing was able to isolate various wood tie parameters and their effect on rotational resistance. This work is part of an ongoing effort to provide inputs for track buckle models,1,2 and it was supported by the Association of American Railroads (AAR) under its Strategic Research Initiatives (SRI) Program. ROTATIONAL RESISTANCE In continuously welded rail (CWR) track, the rail can develop internal compressive forces when the rail temperature exceeds the rail neutral temperature (RNT). In these situations, the rail can be conceptualized as a column with the track structure…