Prestressed concrete railway crosstie support variability and its effect on flexural demand

The increased presence of instrumentation on railroad track components in revenue service operation has provided vast amounts of data with the potential for improving the current modeling of track systems. The continuous improvement of components and track design depends on fine-scale optimization of models, prevailing assumptions, and gaining additional understanding into the underlying mechanical processes that the track system undergoes during loading as trains pass over. For example, the current structural models used for concrete crosstie flexural analysis and design assume that the ballast bearing support is static and consistently located in a specific region under the crosstie. This assumption implies a linear behavior of the wheel-load bending moment relationship. However, field and laboratory data show that this relationship is actually non-linear and the difference between measured behavior and prevailing assumptions is significant. Previous work has shown that the interaction of the crosstie’s deflected shape with the supporting ballast layer has the potential to modify the support distribution of the crosstie as load increases. To better understand the observed phenomenon and its implications, a generalized structural analysis model was developed along with an analytical model with the objective of explaining support redistribution under loading based on mechanics principles. The results show that the proposed algorithm explain the observed field data well and establishes a foundation for further analysis of this previously unquantified effect. The model I developed can serve as an initial structural analysis tool for the development of a mechanistic-empirical prestressed concrete crosstie design procedure