Flexural behavior of high-density polyethylene railroad crossties

Abstract

Hardwood timber has been the predominant material of choice for crossties since the establishment of the railroad industry in the US. Recently, several concerns, including higher speeds, heavier loads, durability and negative environmental effects associated with deforestation and wood-treating chemicals, have invoked the railroad industry's interest in alternative materials for crossties. Currently, several manufacturers offer alternative and sustainable solutions using different recycled plastic composite materials. Thousands of plastic crossties are currently in service in a wide variety of railroad applications. Several researchers have been studying and testing these new materials, specifically high-density polyethylene, however, their behavior when subjected to rail loading is not yet fully understood. Uncertainties in mechanical properties, failure modes and fracture render their performance and safety questionable. More research is required to properly characterize, describe and model the behavior of these materials as well as to assess the feasibility of implementing these materials in railway applications in terms of performance, safety, practicality and economy. Therefore, this study aimed to investigate the performance of plastic composite crossties through experimental testing and analytical modeling. A flexural testing program addressing two AREMA recommended tests for crossties; center and rail seat bending, was conducted. The behavior of the crosstie with the rail and fastening system installed was also investigated. An analytical finite element model, capable of simulating the flexural behavior of plastic crossties, was constructed using a material model that was calibrated using the experimental data. The plastic composite crossties demonstrated adequate performance throughout the experimental testing program. This paper also highlights the potential structural, social and economic benefits of implementing high-density polyethylene crossties in railroad applications.