The Main Street Bridge in Columbus, Ohio is a 700ft, three-span, inclined arch suspension bridge over the Scioto River. The bridge is the first in North America and the fifth in the world to use an inclined single-rib-tied arch superstructure. The final cost for the bridge was $60.1 million.HistoryThe original Main Street bridge was a multiple-span, art-deco open-spandrel concrete deck arch bridge, built in 1937. After years of degradation due to weather and traffic, the bridge was deemed unfit for use and closed in 2002.Wanting an iconic structure to replace the old bridge, the city of Columbus contracted Dr. Spiro Pollalis, professor of design technology and management at the Harvard University Graduate School of Design to design the bridge. His design, altered slightly for budget reasons, opened for traffic on July 30, 2010.When the former bridge closed, engineers estimated that a replacement would cost approximately $19.5 million. However, by 2004, estimates climbed $29.5 million. When planners received construction bids in 2006, the lowest was $44.1 million. Cost overruns, design changes and inspections added another $10 million to the structure's final cost.DesignArchThe original concept of the Main Street bridge was far more complex and costly than the final design. Initially, the bridge called for a very shallow 10:1 span-to-rise ratio for the main arch, creating significant axial and bending forces. To accommodate the excess forces, the design called for expensive, high-strength concrete and steel to support the bridge. Because of the high cost of materials and construction of such a span, the design of the arch was revised to a 6.6:1 span-to-rise ratio, making the main arch taller and decreasing its length from 480ft to 400ft. This design change was expected to allow for cheaper materials and save over 60000lb of steel while keeping the ten-degree incline that makes the bridge unique.
