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A Bridge Builder’s View of the I-35W disaster
John Dodge, Editor-in-Chief -- Design News, August 2, 2007
Check in with our I-35W bridge collapse coverage page for the latest news, videos and photos covering the failure.
Jack Parker, president of 79-year-old bridge builder Reed & Reed, cautions against speculation behind the cause of Minneapolis' I-35W bridge collapse, but believes the factors leading to the tragedy will be uncovered. Reed & Reed, based in Woolwich, ME, has built "hundreds" of bridges. Of recent note was the huge Prospect/Verona Bridge, which spans the Penobscot River and opened to traffic in May.
“This is a forensic science. They will be able string together the events that happened and find the cause,” says Parker, who said no bridge Reed & Reed has built has ever collapsed.
Reed & Reed builds bridges that would be able to withstand 80,000-lb trucks bumper-to-bumper, a circumstance which rarely, if ever, happens. “That [only] affects the [roadway] deck of a bridge,” he said. In other words, even such an unrealistic load would typically not bring a bridge down.
He also doubted that resurfacing on the I-35 bridge in Minneapolis or a train passing under one section of the bridge had anything to do with the collapse. “I don’t see an obvious connection between the rehab and the collapse. It was so catastrophic.” He added that all states have DOTs that provide comprehensive inspection services that even include divers who check out concrete piers.
As a bridge builder, Parker poignantly feels the emotion of the Minneapolis tragedy and especially for a missing construction worker. “Construction in heavy traffic is a dangerous job.” The collapse was during rush hour and traffic was bumper-to-bumper on the bridge.
According to the 2005 Report Card for America's Infrastructure by the American Society of Civil Engineers, 27.1 percent of the nation's 590,750 bridges rated structurally deficient or functionally obsolete in 2003. However, the report estimates it will cost $9.4 billion a year for 20 years to eliminate all bridge deficiencies. The ASCE attributes the long-term underinvestment to a lack of a federal transportation program.
The report states that a structurally deficient bridge is closed or restricted to light vehicles because of its deteriorated structural components. While not necessarily unsafe, these bridges must have limits for speed and weight. A functionally obsolete bridge has older design features and, while it is not unsafe for all vehicles, it cannot safely accommodate current traffic volumes or all vehicle sizes and weights.
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