Field Testing of a Railroad

The feasibility of using railroad flatcars (RRFCs) as the superstructure for bridges on lowvolume roads has been investigated in two previous research projects at Iowa State University. The results of these projects verified that RRFCs are efficient and economical alternatives for low-volume road bridges. Two county engineers involved with the RRFC project cited cost as the main factor for choosing to install more RRFC bridges in their counties. The last RRFC bridges built in their counties cost approximately $27 per square foot and $35 per square foot, respectively. Both of these figures are well below the typical IDOT standard slab bridge, the cost of which the engineers approximated to be $70 per square foot. Also, county forces can be used to install RRFC bridges, which saves time as well as money. In order to gather more data on the behavior of RRFC bridges, and to refine the design methodology presented in the previous project, the strains and deflections of another RRFC bridge were measured as a tandem-axle truck crossed the bridge. From these results, the bridge was deemed satisfactory to carry Iowa legal loads. Also, live load distribution factors were determined for RRFC bridges composed of two RRFCs. Finally, these live load distribution factors were incorporated into a rating procedure for RRFC bridges.