Evaluation of Two Strengthening Methods for Rural Short-Span Precast Concrete Bridges in South Carolina

South Carolina has thousands of decades-old precast concrete slab bridges that were designed carry loads smaller than those designated in current standards. This paper presents an experimental program that investigated two strengthening methods for these bridges. The first method used steel plates bolted to the bottom of the slabs, and the second method used externally applied post-tensioning. These strengthening methods primarily involved work conducted below the bridge and are suitable for situations wherein minimizing traffic disruptions is paramount. Both methods achieved strength increases of more than 40% relative to similar unstrengthened slabs. By increasing the load carrying capacity, these strengthening techniques can extend the functional life of precast concrete slab bridges.