(Minneapolis Bridge No. 9791 / MnDOT Bridge No. 90664)
Bridge Description and Location
The St. Anthony Parkway Bridge is located in northeast Minneapolis, Minnesota. It carries vehicular and non-vehicular traffic over 24 sets of railroad track in the Burlington Northern Santa Fe (BNSF)’s Northtown Yard. The land on which the bridge piers are located is owned by the BNSF. The bridge is maintained by both the City of Minneapolis and the BNSF. The bridge was built by the Northern Pacific Railroad in 1925 and is identified as Minneapolis Bridge No. 9791 and MnDOT Bridge No. 90664. St. Anthony Parkway is a two-lane road with two-way traffic and average daily traffic (ADT) of 5,800 vehicles of which 17 percent are trucks.
History of the Crossing
A grade-separated crossing over the BNSF Northtown Yard has existed at the bridge’s present location since 1911. The original bridge was built at the existing bridge’s location in 1911 to carry motorized and non-motorized traffic along 33rd Avenue over the yard, which at that time included twenty tracks of the Northern Pacific, three of the Great Northern, and one track of the Soo Line. The bridge was 566-foot long and consisted of four Howe truss spans with pile trestle approaches, an 18-foot roadway and a single six-foot walk.
The original bridge was completely replaced by the Northern Pacific with the current bridge (Bridge 90664) in 1925. The City of Minneapolis required the railroad to build a wider bridge for the crossing, and in exchange for the railroad’s cooperation, vacated a number of streets allowing the railroad more area for yard expansion. The bridge was constructed to carry motorized and non-motorized traffic.
Modifications and Maintenance
- Bridge 90664 was modified in the early 1970s. The original roadway width of 34’-0” was reduced to the current 27’-0”, and an inboard 5’-8” walk on the north side of the roadway was added.
- In 1995, lights were installed and a 4’-0” chain link fence was added to the north railing.
- In 1999, the bituminous wearing surface was removed and a new 3” low slump concrete overlay was added to address deck maintenance issues.
- Recent maintenance activity has included the removal of loose concrete from the lower chords, temporary stringer shoring at Pier 3, and bituminous patching at the approaches.
The St. Anthony Parkway Bridge is eligible for nomination to the National Register of Historic Places (NRHP) for its engineering significance. It is a rare Warren through truss type of structure carrying vehicular traffic as well as a contributing element of the Minneapolis’ Grand Rounds Scenic Byway System. The Programmatic Agreement Concerning Pre-1956 Historic Bridges, 2007; a signed agreement between the Federal Highway Administration (FHWA), the Advisory Council on Historic Preservation (ACHP), the Minnesota State Historic Preservation Office (SHPO), the Army Corps of Engineers, and the Minnesota Department of Transportation (MnDOT) indicates that the bridge is eligible for listing on the NRHP. The bridge and St. Anthony Parkway are on the “Grand Rounds Scenic Byway System” in Minneapolis. The Grand Rounds is a part of the “National Scenic Byways Program” an FHWA collaborative effort established under the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), and reauthorized in 1998 under the Transportation Equity Act for the 21st Century (TEA 21). Under the program, the U.S. Secretary of Transportation recognizes certain roads as National Scenic Byways or All-American Roads, based on their archaeological, cultural, historic, natural, recreational, and scenic qualities. The Grand Rounds has been recognized by the FHWA as a premier National Urban Scenic Byway and is part of the City, regional parks and open space system. The Grand Rounds as a historic district is recommended eligible for listing on the NRHP. The bridge passes over a segment of the BNSF Railroad that has also been determined eligible for listing on the NRHP. The St. Anthony Parkway Bridge is deemed a contributing element to the Grand Rounds Historic District and the BNSF Railroad corridor.
Geometrics and Bridge Configuration
The 525-foot bridge is a highway “Warren truss” bridge, with five through-truss spans supported on four concrete piers positioned in the rail yard, and concrete abutments at either end. The four eastern spans are approximately 102 feet long and the western most span is 115 feet long. The riveted steel trusses are 37 feet apart and are set at a 27º skew to the substructures.
The bridge’s superstructure consists of five, skewed, rigid-connected, six-panel, steel Warren through trusses. The truss webs are all identically detailed. Two channel sections with cover plates and lacing bars comprise the truss’s top chord, while two concrete-encased channel sections form the bottom chords. Vertical members consist of four angle sections with a web plate; diagonal members are two channel sections with lacing bars; and the overhead sway bracing members consist of four angle sections with lacing bars. The bridge’s portal bracing includes inclined end posts, and relies on paired channel sections, while the overhead sway bracing utilizes four angle sections with lacing bars. Riveted gusset plates connect the truss members at the panel points. The flooring system consists of a floor beam made up of four angles with a web plate riveted to resemble an I-beam (44” built-up, riveted I-section) and S15 x 37.5 stringers, all with riveted connections. The floor beams, stringers, and bottom chord members are concrete encased. The floor beams and stringers support a concrete deck with a clear roadway width of 27’-0” that carries one lane of traffic in each direction. The north curb (which presently functions as a sidewalk) is 5’-8” wide and the south curb is 2’-8” wide. Both curb areas are located on the inside of the truss. A 6’-0” walk is cantilevered on steel brackets off of the south truss. A metal picket railing is located along the fascia of the south walk and a chain link fence is located along the north sidewalk.