Completed in 2010, the Main Street Bridge spans the Scioto River in Columbus, Ohio and is the first single inclined arch crossing in the United States. The original Main Street Bridge was a multiple span, art-deco open-spandrel concrete deck arch bridge that was constructed in 1937.(3) After it had substantially deteriorated, the bridge was closed in 2000 to traffic. Demolition began on August 25, 2006.(7)
- Type: Open-spandrel Concrete Deck Arch
- Total Length: 638 feet
- Main Span Length: 109 feet
- Width: 40 feet
Desiring an iconic bridge to replace the art-deco bridge, the city of Columbus, after much public debate and discussion, contracted with Dr. Spiro Pollalis, professor of design technology and management at the Harvard University Graduate School of Design to design a new crossing.(3) Also leading the design was DLZ Ohio, a Columbus-based architectural, engineering and environmental services company for project management. DLZ was in charge of designing the substructure and handling traffic management, railing design, geotechnical engineering and approach roadway design. DLZ selected HNTB as a partner for the lead structural design work. The design criteria was established by state and federal transportation officials, city leaders, the state historic preservation office, the Franklin County engineer, area residential and commercial developers that were near the bridge, the Greater Columbus Arts Council and the downtown association, among others.
The projected cost in 2002 was $19.5 million for an inclined steel arch, but that estimate, premature and unauthorized, had come from an engineering firm that had wanted its particular company chosen for the contract.(5) A new estimate from 2004 pegged the cost at $29.2 million. But by 2005, the projected cost had escalated to $42 million. Construction was set to begin in October 2005 with an expected completion date of June 2009.(3)
The original concept called for a very shallow 10:1 span-to-rise ratio for the main arch, would have created significant axial and bending forces. To accomodate for that, the design called for high-strength steel and concrete for the bridge, which would have been cost prohibitive. Instead, the design was revised to a 6.6:1 span-to-rise ratio, giving the arch a taller stance and shortening it from 480 feet to 400 feet. The design saved 60,000 pounds of steel while keeping the 10-degree incline.(4)
Another alteration was the 13 I-struts that were required to attach the arch to the bridge deck. The original design called for tapering geometries which changed depending on the strut, creating 13 distinct structs that needed to be designed and tested separately, adding to the cost. The compromise included uniform steel members that were cheaper but similar in appearance. The redesign saved 400,000 pounds of steel from the struts.(4) In addition, two V-piers were to be constructed, formed by the convergence of the main arch and the secondary arches on both sides. The design was not structurally feasible, and so a crescent pier was constructed, removing two smaller arches on either side and creating a larger pier to provide better support.
The bridge deck was composed of two separate decks: a 35 foot wide vehicular deck carrying three lanes of traffic, and an 18 foot wide pedestrian and bike deck that is elevated over the vehicular deck.(1) The redesign of the bridge altered the deck supports, but the actual construction was just changed slightly.(4)
Part of the financing was derived from $15 million from the State Infrastructure Bank and $8.3 million in city bonds for the bridge design.(6)
- Type: Single Inclined Arch
- Total Length: 700 feet
- Main Span Length: 400 feet
- Approach Span Length: 131.2 feet (x2)
- Width: 35 feet driving deck, 18 feet pedestrian/bike deck
When bids were let for construction, the lowest construction bid was $44.1 million.(5) Construction began shortly after.(1) By May 2009, there were $2 million in construction cost overruns, which did not include $3 millon for design costs and $4.5 million for inspection. The bridge, completed on July 30, 2010, was the first single inclined arch suspension bridge in North America and the fifth in the world to use an inclined arch superstructure.(1) The cost of the bridge was $60.1 million.(2)
- Original Main Street Bridge at HistoricBridges
- “Main Street Bridge.” Downtown News Network. N.p., 2011. Web. 13 Mar. 2012. Article.
- “Main Street bridge opened to traffic.” Columbus Dispatch 30 July 2010: n. pag. Web. 13 Mar. 2012. Article.
- “Main Street Bridge.” Franklin County. N.p., n.d. Web. 13 Mar. 2012. Article.
- “The Main Street Replacement Bridge.” Rogowski, DeMond and O’Rork. Web. 13 Mar. 2012. Article.
- “NBC 4 Digs Into Over-Budget Main Street Bridge.” NBC4I. N.p., 20 May 2009. Web. 13 Mar. 2012. Article.
- “Landmark Opening.” Columbus Dispatch 30 July 2010: n. pag. Web. 13 Mar. 2012. Article.
- “Washington Blvd. closing for bridge demolition.” Columbus Dispatch 24 Aug. 2006: n. pag. Web. 13 Mar. 2012.