Built in 1920, the Old Cedar Truss Bridge is a five-span, 865-foot Pratt-Camelback Truss crossing over Long Meadow Lake. The bridge was closed to vehicular traffic in 1993 and to pedestrian traffic in 2002 due to significant deterioration of the steel stringers, floor beams, and bottom lateral gusset plates. The trusses were supported on concrete piers that were in poor condition and tilting. The bridge was listed on the National Register of Historic Places in 2013.
SRF worked with the City of Bloomington, FHWA, MnDOT Cultural Resources Unit, and the Minnesota State Historical Preservation Office to rehabilitate the historic structure. Key goals included meeting the Secretary of Interior’s standards for rehabilitating historic structures as well as current pedestrian loading standards and extending the bridge’s useful life by 50 years while minimizing future maintenance costs. SRF also evaluated options to upgrade the bridge railing to meet current height and safety standards compatible with the historic bridge.
SRF developed a construction sequence process to remove and replace all of the deteriorated lower floor beams and stringers and to reconstruct the tilted piers. This included a complex shoring tower system to lift the trusses so all the lower gusset plates, floor beams and stringers could effectively be removed and replaced. This method also allowed for the piers to be reconstructed with new piling and concrete. 3D drawings were developed to assist in evaluating potential conflicts during construction.
