When the Franklin Avenue Bridge opened in 1923, it had the longest concrete arch span in the world at 400 feet. Also known as the Cappelen Memorial Bridge, the 1,050-foot-long stretch of County Road 5 over the Mississippi River in downtown Minneapolis has been on the National Register of Historic Places since 1978 and part of the Grand Rounds Historic District. In 1985, the city council designated it a landmark.
A bridge that old is going to undergo change. In 1940, streetcar track removal added two lanes of traffic to the two existing lanes. In 1954, the West River Road was built under one span. In 1970, the superstructure to the top of the arches -- spandrel columns, cap beams, deck, rail, and lights -- was replaced. The deck was raised 3 feet and widened by about 6 feet. Distance between spandrel columns spread from 14 feet to 29 feet. Slightly taller and much wider cap beams with square ends were installed. (Click here for more details.) In the process, stylistic details that illustrated the transition from classical revival to art deco/moderne design were lost.
In 2007, an inspection by Wiss, Janney, Elstner Associates Inc. revealed below-deck steel reinforcement was corroded by road salt and that the original piers had freeze-thaw damage. The engineering firm recommended a deck replacement, concrete surface repair, and removing as many of the 15 existing expansion joints as possible.
Over the 2015 and 2016 construction seasons, Hennepin County transformed the structure into a historically accurate bridge that serves bicyclists and pedestrians as well as drivers with a reconfigured deck that separates people from vehicles. Concrete substructures were repaired, the deck and underside painted, railings treated, and vegetation re-established at both ends. As the agency overseeing the Franklin Avenue Bridge Rehabilitation, the county earned an American Public Works Association 2017 Project of the Year Award in the Historical Restoration/Preservation ($25 million to $75 million) category.
A report by the project historian and Minnesota DOT's Cultural Resources Unit outlined the work required and impact of rehabilitation options on historical elements. After factoring in how each option would affect the driving public, the county chose accelerated bridge construction (ABC) using prefabricated bridge elements and systems (PBES) consisting of precast concrete spandrel cap beams, deck panels, and ornamental rail panels. The construction method reduced bridge closure time from two years to four months.
A detailed erection plan and ABC schedule was developed by Kraemer North America, the primary contractor, and reviewed by the county for compatibility with contract requirements. Numerous pre-ABC activities, including saw cutting the existing deck and moving existing utilities, were completed before the bridge was closed to traffic.
Construction of the new Minnesota Vikings stadium increased costs by contributing to a concrete shortage, so the county looked for ways to save money. The precast concrete segments were made near to the river so they could be floated downstream on a barge and hoisted by water-borne cranes into their final positions. Crews also salvaged remnant piers from 1889. According to the Minneapolis Star-Tribune, the final cost of the estimated $28 million project was $43 million.
The county retained HNTB Corp. to provide project team management and coordination; environmental documents; load rating; public and agency involvement; rehabilitation report and preliminary design; final design and construction plans; and construction support services.
