Optimization of a prestressed concrete railroad crosstie for heavy-haul applications

In response to rising energy costs, there is increased demand for efficient and sustainable transportation of people and goods. One source of such transportation is the railroad. To accommodate the increased demand, railroads are constructing new track and upgrading existing track. This update to the track system will increase its capacity and make it a more reliable means of transportation compared to other alternatives. In addition to increasing the track system capacity, railroads are considering an increase in the size of the typical freight rail car to allow larger tonnage. An increase in rail car loads will, in turn, require the design of track components to accommodate these loads. This design change is especially pertinent to crossties that support the rail and serve to transmit loads down to the substructure. Today, the use of concrete ties is on the rise in North America as they become an economical alternative, competitive with the historical wood ties used in industry, providing performance that surpasses its competition in terms of durability and capacity. Because of the increased loads heavy-haul railroads are considering applying to their tracks, current designs of prestressed concrete railroad ties for heavy-haul applications may be undersized. In an effort to maximize tie capacity while maintaining tie geometry, fastening systems, and installation equipment, a parametric study to optimize the existing designs was completed. The optimization focused on maximizing the capacity of an existing tie geometry through an investigation of prestressing quantity, configuration, stress levels, and other material properties. The results of the parametric optimization indicate that the capacity of an existing tie can be increased most efficiently by increasing the diameter of the prestressing and concrete strength. Findings of the study demonstrate that additional research is needed to evaluate the true capacity of concrete ties because of the impacts of deep beam effects and inadequate development length in the rail seat region.