EMBEDDED TRACK DESIGN AND PERFORMANCE

The industry is gravitating to concrete slabs for embedded track designs. Designs with concrete have proven economies in construction and long-term performance. Yet there are concerns, such as the following: structural codes state that the codes do not apply to slabs on grade that are intended as the principal structural support; agencies press for minimum slab thickness to minimize conflicts with existing utilities; configurations to meet criteria for stray current control and ground vibration control may affect track integrity; design factors for future utility trenching around embedded track are inherently uncertain, potentially governing a design, or, if ignored, jeopardizing long-term track performance; the effects of elastomers on the slab performance have little research; and embedded track is among the least maintenance friendly - improvements in design analysis will allow confidence in new low maintenance concepts. This paper provides embedded track analysis methodology and results that are the basis for engineering decisions on, and increased confidence in, long-term embedded track performance. The analysis method treats the rail and support slab as two continuous beams interacting through an intermediate pad, with the support slab on a continuous elastic foundation (soil). The method produces deflections, moments, and stresses independently for the rail and support slab, and pressures in the intermediate pad and supporting soil. This information allows long-term maintenance assessments (slab life, required soil load capacity, and pad criteria) of a design. The methodology is explained and the results for the practical range of embedded track configurations are presented.