T.Y. Lin International (TYLI) and SRF Consulting Group provided preliminary and final bridge design and engineering services, and is currently providing construction phase support services for the Lowry Avenue Bridge Replacement project. For the design, TYLI was responsible for the structure/main river crossing preliminary/type selection and final PS&E documents. The new tied arch bridge (with a main span length of 450 feet and a total length of 900 feet) will cross the Mississippi River upstream from downtown Minneapolis. The aging old bridge, a truss structure built in the fifties, posed a significant problem as one of the original piers was found to have tilted 11 inches off center and needed repair. Consequently, Hennepin County decided to replace this historic structure in order to provide a safe and functional connection to this area of Minneapolis.
Project Highlights:
- The winning bid of $52 million submitted in December 2009 was 25% below the estimate.
- Design of water-born piers.
- Architectural treatments for arch ribs, piers, and overlook.
For the preliminary design phase of the project, the team conducted several studies concurrent to the bridge type selection study, utilizing a Project Advisory Committee (PAC) and a Technical Advisory Committee (TAC) comprised of consultants, transportation officials, and community leaders. The proposed preliminary bridge plan—designed to Minnesota Department of Transportation (Mn/DOT) bridge standards—originated from seven alternatives including two cable-stayed, two arches, steel girder, steel box, and concrete box bridges.
The final selection of a basket-handle steel arch bridge was then designed to keep construction costs to a minimum. TYLI’s understanding of constructability practices enabled the team to successfully plan and design the project around several construction challenges, including clearing a major shipping channel in the Mississippi River and breaking up the project into phases to accommodate funding issues.
For Phase 1 Construction, currently underway, construction crews have completed the foundation and the pier elements. The side span box girder superstructure will be completed by the end of 2011, while the steel box segments of the arch are ready to be shipped to the site from the manufacturer’s facility.
Among the challenges of this project and yet, one the most positive experiences of the design team, was working with the Owner, elected officials, and community representatives to successfully find consensus and select the bridge type to replace the existing structure. The most technically challenging aspect of the project was the design and construction of aesthetically pleasing water-born piers as well as the development of redundant solutions for replaceable ties for this arch structure.