St. Anthony Parkway Bridge

Challenge

Built in 1925 and located in the City of Minneapolis, the historic St. Anthony Parkway Bridge was in dire need of replacement. The five-span truss bridge was not structurally redundant; if one element of the bridge’s truss spans were damaged or severed, the whole span could fail. Complicating matters, the non-redundant bridge spanned 21 BNSF Northtown Rail Yard tracks (through which 50 trains pass daily) – posing safety issues for trains and workers underneath the bridge as well as travelers across it.

Careful design and coordination was required as replacing the bridge would affect the three historic resources – the existing Warren Truss Bridge, Historic Grand Round Scenic Byway and Northtown Rail Corridor. Structures with historic designations often cannot simply be removed and replaced, requiring the project team to work with historical agencies to design a way to mitigate any loss of historical elements.

Solution

SEH and the City of Minneapolis partnered to design and replace the St. Anthony Parkway Bridge – blending historic and environmental preservation with cutting-edge technology and public outreach. SEH served as lead designer for the project, led planning and construction engineering, and coordinated all aspects of the new bridge and approach roadway with the City, BNSF Northtown Rail Yard, MnDOT, MnDOT Cultural Resources Unit and the Minnesota State Historic Preservation Office.

The new bridge replaces a historic 85-year-old, five-span Warren truss bridge and features a 305 foot steel truss span and two-125 foot steel girder spans that carry two 12 foot lanes, a sidewalk and a bicycle trail over the BNSF Northtown Railway Yard. Due to the high volume of rail traffic, the truss span was erected along the west approach and incrementally launched over 12 tracks. The truss is a unique design that features a redundant post-tensioned bottom chord.

SEH worked closely with the City, community, historians as well as artisan and agency partners to preserve portions of the old trusses and integrate them into the design of an interpretive plaza. The plaza contains information kiosks outlining the historic designations and sculptures constructed using pieces of the old bridge. Today, the bridge and overlook provide a stunning view of the Minneapolis skyline, the bustling railyard, sculptural elements from the old truss, and panels that illustrate the history and development of the surrounding area.

Awards

• 2017 Projects of the Year | Finance and Commerce
• 2019 Grand Conceptor Award | American Council of Engineering Companies, Minnesota Chapter (ACEC-MN)