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 annua lly on Class 1 railroads in the United States at an approximate cost o f $500 million. Therefore, a need exists to develop innovative means f or improving the performance and service-life of wood ties. In this pa per, the development and prototype evaluation of a wood tie wrapped by or encased in glass fiber-reinforced plastic (GFRP) composite is disc ussed. Using glass fibers, epoxy resin, and a resorcinol formaldehyde primer, wood cores are reinforced with a relatively thin layer of comp osite by the filament winding process. The paper includes the conceptu al design, modeling, optimization, and testing of prototype samples. A 3-D finite element model of a beam on elastic foundation is used to p redict 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 volum e of composite while simultaneously minimizing the critical stresses a nd deflections in the wood core. Based on the optimization results, a final recommended design is proposed and prototype samples are manufac tured and evaluated. To verify the predictions of the model, both wood and composite reinforced wood samples are tested under combined stati c and moisture loadings. The predicted linear response of the samples correlates well with experimental results. The combined modeling, opti mization 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 implement ation of this new product are also discussed. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.