SR 56 Hurricane Bridge Rehabilitation

Originally built during the World War II era, this four-span cantilever deck truss bridge has served the area for more than 70 years. Like many bridges of this vintage, the Hurricane Bridge was reaching the end of its life-cycle and was in need of modernization to meet current design and safety standards. In 2009, the Tennessee Department of Transportation (TDOT) asked Modjeski and Masters (M&M) to conduct an evaluation of the bridge. The bridge was previously rated structurally deficient, resulting in a posted limit of 15 tons. Heavier vehicles were forced to take a 30-mile detour, which proved to be an enormous inconvenience for local industries.

M&M determined that a full rehabilitation was needed to upgrade the bridge to support current and significantly heavier AASHTO live load requirements. This included substantial strengthening of the truss members and rebuilding of the superstructure’s floor system members. Some innovations done to the structure during the rehabilitation include:

• A new deck made of lightweight concrete, which weighs 20 percent less than normal weight concrete. This lightweight concrete features a special mix design that significantly reduces the permeability and intrusion of water and deicing salts.
• Contractor used both conventional tarps and innovative Safespan™ under-bridge decking to prevent the release of lead (from the bridge's lead paint) into the atmosphere, the waterway and soil.
• Under-bridge decking system also helped to ensure worker safety and mobility during the construction process. 
• M&M conducted a comprehensive, 3-D finite element analysis study to determine permissible load combinations on the structure during construction. 

Throughout all of the major construction phases, alternating single-lane traffic was in effect. Once the superstructure strengthening and concrete deck replacement were completed, the bridge was fully opened to two-lane traffic.