During the 1950’s, Norway developed a network arch bridge, a structure with inclined hangers that cross each other. American engineers have known about the design, yet no one had constructed such a structure on a skew until last year.
Detroit’s Second Avenue Bridge is the first network tied-arch bridge constructed on a skew in the U.S. This unique design gives the Motor City a new bridge with an elegant look.
Officials at the Michigan Department of Transportation (MDOT) saw a need for the bridge during the Interstate-94 modernization project, which reconstructed the freeway from the Interstate-96/I-94 interchange to Conner Avenue. They wanted to improve the area by building a bridge to span the future widened corridor without a center pier.
“What makes it unique is that the cables cross, which makes the bridge stronger for the amount of steel used,” said Terry Stepanski, MDOT’s senior project manager.
The landscape’s vertical curve was a challenge. The four corners of the structure were at different elevations and complicated the accelerated bridge construction techniques.
The structure’s conventional lateral bracing was eliminated, as the two bridge’s arches are offset by roughly 30 feet. The team decided to “tie” the arch ends, getting rid of lateral spread. If the design incorporated lateral bracing between the arch ribs, the bridge would have a warped appearance.
Putting the bridge into place was another story. The plan was to use four clusters of self-propelled modular transporters (SPMT) units to place the bridge skeleton. The 5-million-pound structure was jacked up 8 feet and loaded on to four stacks of timber cribbing. Temporary falsework was removed, and the SPMTs were driven beneath the bridge.
It took several hours for the skeleton to be moved. MDOT closed the interstate. Using hydraulic jacks, the team transferred the structure from skid tracks on the abutment above to the SPMTs down on the freeway. Next, they drove the skeleton across I-94.
The team removed the SPMTs and slowly jacked the bridge down onto the permanent bearings and welded it.
After careful inspection, the team determined the structure was safe for the travelling public.
The team did a stellar job delivering this project to completion and making history, not only in the Motor City, but in the U.S. This bridge is a testament to the hard work, careful planning, and masterful design of the team. It opened in late 2022. RB
Project: Second Avenue Network Tied Arch Bridge
Location: Detroit, Michigan
Owners: Michigan Department of Transportation
Designer: HDR / Tetra Tech
Contractor: Z Contractors
Cost: $26 million
Length: 245 Feet
Completion Date: December 2022
