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Minnesota's Historic Bridges
Cedar Avenue Bridge
Description


Cedar Avenue Bridge

The Cedar Avenue Bridge is located less than one mile east of the city hall and downtown loop, and a few blocks north of the west bank campus of the University of Minnesota, in Minneapolis, Minnesota. It connects Cedar Avenue on the south, across the Mississippi, with Tenth Avenue Southeast on the north. When it was built it also linked with Johnson Street Southeast on the north. The original arrangement of streets in the vicinity of the Cedar Avenue Bridge was disrupted by the alignment of Interstate 35W, which was constructed in the 1960s-1970s. Parallel to, and a short distance from, the Cedar Avenue Bridge on the upstream is the Interstate 35W bridge, erected in 1967. A short distance downstream is the Northern Pacific Railroad bridge, which was erected in 1884-1885 and thoroughly remodeled in ca. 1917.

Aligned on a northeast-southwest axis, the Cedar Avenue Bridge is a reinforced concrete, open-spandrel, two-rib, continuous-arch bridge, with an overall structure length of 2,174.9 feet. In the original, continuous-arch unit, it has two main spans of 265.5 feet each that cross the river channels and five flanking spans of 93 feet each, two on the northeast end and three on the southwest end. The flanking spans are aligned so as to give the bridge an S-curve in plan, with the three southwest spans on a curve of 5 degrees 41 minutes. The two northeast spans are on a curve of 5 degrees 18 minutes. Thirteen minor, precast-concrete-beam, approach spans were added in 1971-76, replacing a series of I-beam approach spans. All the arch spans have two ribs 12 feet wide and 24 feet apart in the clear, with a thickness for the main spans of 3.5 feet at the crown and 7.5 feet at the haunches. A three-center radius of 154 feet and 48.5 feet is used for the intrados and a single radius of 167.5 feet for the extrados. Each rib of the main spans is reinforced with five steel ribs 31.5 inches deep at the crown, having chords composed of pairs of angles with smaller angles for the web members. In the 93-foot spans, each rib is reinforced with sixteen longitudinal bars at top and bottom, tied together with loop bars. Footings for the three river piers are 30 feet by 54 feet. At the east and center piers, they rest on the sandstone bedrock at 11.5 feet and 22.5 feet below low water, while the west pier footings are supported on 180 piles, 32 feet to 42 feet long, driven into a gravel formation. The main spans have a rise of 90.5 feet, with the crown about 110 feet above low water.

Transverse spandrel walls are practically the full width of the arch ribs and spaced 13.3 inches center to center in the main spans. Transverse spandrel walls are 12 feet in the flanking spans support floor beams that carry the deck and are cantilevered to support the sidewalks. With the 1971-1976 redecking of the bridge, the deck width is 68.1 feet, carrying a 55.5-foot roadway, with a sidewalk on one side and a bikeway on the other.

When built, the bridge had a simple, relatively unornamented surface taking its beauty from the elegant line, form and proportion of the engineering itself. A July 10, 1930, description in the Engineering News-Record stated that "Except for the rubbing of [the concrete] railing to a smooth finish no special treatment was given to the exposed concrete surfaces for the sake of appearance." Simple inset, vertical panels of mild Classical Revival/Art Deco style were the only stylistic additions to the piers and these were retained in the remodeling.


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