In the early 1980s, the City Of Quincy faced an interesting dilemma. Its existing Mississippi River Bridge, the Quincy Memorial Bridge, was structurally sound. And the two-lane through truss structure was eligible for listing on the National Register for Historic Places. However, it was inadequate for modern traffic demands. Replacing this bridge with one that featured the required width to handle increased traffic would be the most obvious solution, but that option was unavailable due to a lack of adequate funding. Another possibility was to close the outdated structure, but groups claimed that business in downtown Quincy would decline if the Quincy Memorial Bridge was shut down.
Modjeski and Masters had a creative solution: the historic bridge would continue to serve the City of Quincy, and a new structure would relieve traffic congestion, all at a cost the city could afford. Our strategy was to design and construct the first cable-stayed bridge of its kind in the U.S. – a hybrid, or composite, design. It was the first to combine cables, structural welded steel I-girders, and precast, post-tensioned concrete deck panels. An added challenge was the project’s deadline: Modjeski and Masters had only 18 months to complete the bridge’s final design. To meet the challenge, we established three bridge design teams: a team which specialized in the towers; a concrete deck team; and a composite deck team. An additional team, specializing in global structural analysis, met as needed. Characteristically, Modjeski and Masters exceeded the client’s expectations by developing two bridge designs. One was all concrete, and the other was a hybrid, or composite, type of bridge. The Illinois DOT accepted the hybrid bridge design.
The end result was a more evolved structure. The new Quincy Bayview Bridge was built in relatively small pieces to facilitate construction. And it achieved two milestones: not only is it the first hybrid cable-stayed bridge in the U.S., it is also the first to employ H-shaped towers with wall anchors, epoxy coating in the in the cable stays, and precast post-tensioned deck panels. Modjeski and Masters’ innovative cable-stayed bridge design solved both problems for the City of Quincy. The historic Memorial Bridge was maintained and used for eastbound traffic, while the new Quincy Bayview Bridge was utilized for westbound traffic.