Main Street Bridge
Main Street Bridge carries Main Street over the Scioto River in Columbus, Ohio. It is the first single inclined arch suspension bridge in North America and the fifth in the world to use an inclined arch superstructure.
The original Main Street Bridge was a multiple span, open-spandrel concrete deck arch bridge that was constructed in 1937. 3 The crossing was designed by Edward A. Ramsey and built by J.H. Prior. After it had substantially deteriorated, the Main Street Bridge was closed to traffic in 2000. Demolition of the original bridge began on August 25, 2006. 7
After the Main Street Bridge was closed to traffic, it was decided to replace the crossing rather than rehabilitate it due to cost considerations. The design criteria for the proposed new bridge 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. 3
After much public debate and discussion, the city of Columbus 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 The city also hired DLZ Ohio, a Columbus-based architectural, engineering and environmental services company, for project management. DLZ was in charge of designing the substructure and railing, conducting geotechnical engineering and designing the approach roadway. DLZ selected HNTB as a partner for the lead structural design work.
The original concept called for an inclined steel arch with a very shallow 10:1 span-to-rise ratio for the main arch, which would have created significant axial and bending forces. 4 To accommodate for those forces, the design called for the use of high strength steel and concrete for the bridge, although cost considerations led that option to be eliminated. The design was revised to a 6.6:1 span-to-rise ratio, shortening the arch from 480 feet to 400 feet. The design saved 60,000 pounds of steel while keeping a 10° incline.
The revised design also called for 13 I-struts to attach the arch to the bridge deck. 4 The original design called for tapering geometries that changed depending on the strut, creating 13 distinct structs that would need to be designed and tested separately, greatly adding to the cost. The redesign saved 400,000 pounds of steel.
The concept also featured two V-piers, formed by the convergence of the main arch and secondary arches, but it was found to not be structurally feasible. 4 A crescent pier was added and the two flanking arches were removed.
The initial project cost in 2002 was $19.5 million for an inclined steel arch, although the estimate was derived from an engineering firm that had wanted its particular company chosen for the contract. 5 A revised estimate was completed in 2004 that pegged the cost of an inclined steel arch at $29.2 million. The projected cost, however, had escalated to $42 million in 2005. Construction was set to begin in October 2005 with an expected completion date of June 2009. 3
Financing would be derived from $15 million from the state’s Infrastructure Bank and $8.3 million in city bonds for the bridge design. 6 When bids were let for construction in 2006, the lowest bid was $44.1 million. 5 Construction began shortly after. 1
By May 2009, the Main Street Bridge project had $2 million in construction cost overruns, which did not include $3 million in overruns for design costs and $4.5 million in inspection costs. 1
The new Main Street Bridge was completed on July 30, 2010 1 at a cost of $60.1 million. 2 It was the first single inclined arch suspension bridge in North America and the fifth in the world to use an inclined arch superstructure. 1