The Federal Highway Administration’s most recent Innovator edition profiles one of the largest projects to date combining precast concrete deck panels and ultra-high performance concrete connections: the Franklin Avenue Bridge in Minneapolis.
|PHOTOS: Hennepin County, HNTB Corp.
|Portland cement-based and steel fiber-rich ultra-high performance concrete is typically mixed on site. Transportation agencies have found the material especially effective in besting conventional concretes for precast bridge deck connections.
Steel fiber-reinforced UHPC has superior mechanical and durability properties compared to conventional concrete, FHWA notes, making it a good match for field construction with precast bridge components. Hennepin County (Minn.) approval of such specification allowed construction crews to remove and replace the entire 1,000 feet of the Franklin Avenue Bridge deck in 17 weeks. Listed on the National Register of Historic Places, the open-spandrel concrete arch structure opened in 1923 and last saw major work in the 1970s.
County engineers chose an accelerated bridge construction approach for the rehabilitation project to minimize disruption to users of the bridge, which connects two major pedestrian and bike corridors near the University of Minnesota. Prefabricating the deck panels offsite reduced closure time and the need for traffic detours. Crews completed below-deck concrete rehabilitation at the bridge site while the 350 deck panels were cast at an upriver location. The panels were floated by barge for placement upon bridge closure.