AASHTO Type III Bridge Girder with Half-Depth Precast Deck Panel

The girder you see was salvaged from an I‑75 overpass bridge in Sarasota County, Florida. The bridge used AASHTO Type III prestressed concrete girders with a deck composed of half‑depth precast deck panels topped by half‑depth cast‑in‑place concrete. Half‑depth precast deck panels have been used successfully in many states; however, Florida experienced significant problems with their performance and has since discontinued their use. As an early adopter, Florida once had nearly 200 bridges built with this method.

The poor in‑service performance of these bridges resulted from unintentional construction errors. Fiberboard bearings were used to support the precast panels, and the bearings were placed at the very edges of the panel with no overhang. This configuration left no space for cast‑in‑place concrete to flow underneath the panels, preventing the formation of a rigid support once the deck concrete was poured. The seriousness of this seemingly minor construction change became fully apparent nearly two decades later when seven punching‑shear failures occurred on major highways. Many repairs required full‑depth deck replacement and extended lane closures.

A research study evaluated eight different repair methods and found, notably, that asphalt patching can worsen—rather than mitigate—the deterioration problem.