HAPPY BRIDGE BUILDING

The Tennessee Department of Transportation pushed the envelope when they designed and built the new bridge that carries Route 50 over Happy Hollow Creek in Hickman County. The bridge, at 1,175 ft, holds the record as the longest totally jointless integral abutment precast concrete bridge to be built in the United States. It features a composite concrete deck supported by 72-in. Bulb-T concrete girders. Designed as a simple span for dead loads of beam and slab, it is continuous for live loads and composite dead loads. What gives the bridge its unique character is the fact that it has no expansion bearings and no roadway expansion joints. As engineers designed the bridge, they calculated that it would tend to bow or bend laterally along the curved axis well beyond the normally accepted 2-in. maximum range. The bridge, a graceful 4 deg curving structure, is superelevated as it transitions into a spiral curve. The only accommodation to bridge movement from thermal expansion is at the end of the 25-ft approach pavements where an elastomeric concrete-silicon sealing joint protects the approach roadway pavement. To provide continuity in the bridge structure, a common diaphragm joins both ends of the girders in adjacent spans and the cast-in-place slab. The bridge's unique construction earned for its designers the 1999 Harry H. Edwards Award for Industry Advancement presented by the Precast/Prestressed Concrete Institute.