Performance evaluation of longer crossties in railroad track transition zone: Finite element analysis and laboratory experimentation

Abstract

Transition zones in railway tracks are characterized by abrupt changes in the track stiffness which induces differential track displacement and can result in settlement. Failure to promptly address these issues through maintenance activities can lead to accelerated track component degradation and a loss of passenger comfort. This study investigated the effectiveness of a conventional strategy involving the implementation of longer crossties to mitigate abrupt variation of track stiffness especially in the open track to bridge transition. The study initially explored various properties and layouts of elastomers (i.e., rubber pads) through finite element analysis (FEA) to determine the appropriate support condition as an alternative to ballast to ensure consistency across the tests. Different hardnesses and configurations of rubber pads were considered to replicate the behavior of the ballast, and a dual layer of 60 shore A rubber pads with 25 holes exhibited crosstie displacement of 0.16 in. (0.41 cm), aligning with the range of field data. Based on this selected support condition, three different crosstie lengths (i.e., 102 in. [259 cm], 132 in. [335 cm], and 168 in. [427 cm]) were evaluated through both FEA and laboratory experimentation. Modeling results showed a 4.2 % reduction in displacement under the rail seat for the 168 in. (427 cm) crosstie compared to the standard crosstie (i.e., 102 in. [259 cm]). Similarly, laboratory experimentation demonstrated an 8.2 % decrease in vertical rail displacement. These findings suggest that the implementation of longer crossties within the track transition zone may not be considered an ideal methodology for achieving a gradual increase in track stiffness.