Modeling and optimal design of composite-reinforced wood railroad crosstie

Due to in-service damage resulting in splitting and excessive wearing, over 12 million wood railroad crossties (sleepers) are replaced annually on Class 1 railroads in the United States at an approximate cost of $500 million. Therefore, a need exists to develop innovative means for improving the performance and service-life of wood ties. In this paper, the development and prototype evaluation of a wood tie wrapped by or encased in glass fiber-reinforced plastic (GFRP) composite is discussed. Using glass fibers, epoxy resin, and a resorcinol formaldehyde primer, wood cores are reinforced with a relatively thin layer of composite by the filament winding process. The paper includes the conceptual design, modeling, optimization, and testing of prototype samples. A 3-D finite element model of a beam on elastic foundation is used to predict the response of the composite reinforced wood crosstie, and the same model is used to conduct parametric studies of important design variables of the composite reinforcement. The finite element model is combined with innovative optimization techniques to minimize the volume of composite while simultaneously minimizing the critical stresses and deflections in the wood core. Based on the optimization results, a final recommended design is proposed and prototype samples are manufactured and evaluated. To verify the predictions of the model, both wood and composite reinforced wood samples are tested under combined static and moisture loadings. The predicted linear response of the samples correlates well with experimental results. The combined modeling, optimization and evaluation study presented in this paper provides design guidelines for the development of prototype composite-reinforced wood crossties. The future commercial manufacturing and potential implementation of this new product are also discussed.