The U.S. military must often deploy to other countries where bridges may have insufficient strength for their heavy tactical vehicles. Strong and lightweight Fiber Reinforced Polymer (FRP) materials have been shown to be useful for strengthening reinforced concrete bridges. However, to be useful by the military, an upgrade method must be fast and easy to use, two characteristics that are not usually associated with FRP materials. An effort is currently underway at the U.S. Army Engineer Research and Development Center (ERDC) to develop alternative rapid application methodologies for FRP materials to strengthen reinforced concrete bridges. The most promising technique to emerge has been the use of mechanical fasteners (i.e. nails) to attach FRP plates to the bottom of the beams, in place of the conventional adhesive bonding techniques. This paper provides an overview of an extensive series of flexural tests conducted on beams retrofitted with FRP plates using the mechanical fastening technique. The tests showed that strength gains close to that expected from conventionally-bonded FRP can be obtained and the failure mode is actually much more ductile than with conventional FRP upgrades. Results of several analytical parametric studies are also presented and provide insight into the effect of variations in material and geometric properties of the upgraded beams.