Historic Bridges

Bridge 6679

History and significance

Bridge 6679 was built in 1949 to carry the vehicular traffic of State Highway 76 over the South Fork of the Root River near Houston in Houston County. It is a continuous/cantilevered, steel-beam design with three main spans, including a significant 100-foot center span and two approach spans. The main span includes a 65-foot suspended section pinned, at each end, to cantilever arms extending over the piers. The bridge railing features a Modernist reinforced-concrete rail design.

Bridge 6679 marked the emergence of a new type of bridge engineering in Minnesota, known as continuous/cantilevered steel-beam construction. The type's popularity partly resulted from the appearance on the market of new deep-section I-beams. When used in continuous construction, the new beams were feasible for clear spans exceeding 100 feet. In Bridge 6679 the state highway department used continuous/cantilevered design for a 100-foot main span, which was the longest steel-stringer span yet built in Minnesota. The bridge is significant as the best example of continuous/cantilevered steel-beam design in the state. It is also significant for the Modernist design of its concrete railings.

Rehabilitation activities

In 2012 MnDOT rehabilitated Bridge 6679. Work included replacement of curb, expansion joints, bearings, wingwalls, and the bridge deck. The deteriorated railings also did not meet current crash test requirements and needed to be replaced. The new railing was designed to accommodate new safety standards, while also adhering to preservation standards by replicating the Modernist style of the original rail.

Location

Sheldon Township (Houston County)
Latitude, Longitude: 43.73862175, -91.56425553

Bridge features