Short-Span Bridge Solutions

Large bridges get most of the headlines, but the nation’s huge network of small bridges (many with spans of less than 25 ft) may be more in need of replacement. Age, corrosion, increasing traffic volumes and excessive loads have taken a severe toll on the structural performance of many of these bridges. Others may no longer meet width and alignment requirements for safe operation. With funding from the Intermodal Surface Transportation Efficiency Act, an opportunity now exists to explore new construction techniques for these small bridges. One technique is the construction of buried culverts, which are simple to design and construct, as well as economically attractive to bridge owners. The advantages of culverts over conventional bridges include lower initial costs on most sites and resistance to bridge-deck icing and deterioration. In addition, culverts permit flexibility for widening and change in alignment, carry greater loads, and can be nearly maintenance-free. Regardless of the material from which the culvert is made (plastic, aluminum, metal or concrete), its performance depends to some extent on its interaction with the surrounding soil. Generally, if properly designed, the soil and culvert can act as a synergistic unit carrying greater load than a free-standing structure. Precast concrete arch boxes can be extremely effective. One such project employing precast boxes in Montgomery County, OH., was recently tested under extreme overload conditions and performed effectively.