State highway departments nationwide are scrambling to inspect all their steel-deck truss bridges in the wake of the I-35W bridge collapse in Minneapolis. “We will be re-inspecting all truss deck bridges rather than limiting our review to the 30 bridges originally identified as being similar in design to the one that tragically collapsed in Minneapolis,” said Allen Biehler, Pennsylvania's transportation secretary.
He said the Pennsylvania Dept. of Transportation (PennDOT) plans to re-inspect all 54 steel-deck truss bridges throughout the state by the end of November with an in-house team of more than 100 bridge inspectors, aided by contract experts from several civil engineering firms. Initial estimates put the cost of this effort at about $2 million, Biehler noted.
Similar re-inspection efforts are gearing up across the country, simply because so many highway bridges are in bad shape, according to the American Road and Transportation Builders Association (ARTBA).
Of the 594,709 bridges in the U.S., 26% are structurally deficient or functionally obsolete, according to data ARTBA gleaned from a 2006 Federal Highway Administration (FHWA) study.
“Structurally deficient means that significant load-carrying elements of the bridge are found to be in poor or worse condition due to deterioration and/or damage,” saidRuane, ARTBA president & CEO.
“Functionally obsolete bridges result from changes in traffic demand on the structure. For example, a bridge designed in the 1930s would have shoulder widths in conformance with the design standards of the 1930s,” he said. “However, design standards may have changed since that time, so the difference between the current required shoulder width and the 1930s standard represents a deficiency.”
Aside from the near-term need for bridge inspections, Ruane pointed out that better long-term strategic funding is necessary to prevent the national highway system from major deterioration. He pointed to a recently released forecast of Highway Trust Fund revenues showing a shortfall that could result in a $16-billion cut in federal highway investment to the states beginning in FY 2009. Compounding the problem, he said, are construction costs that have gone up over 30% in the past three years.
“America also needs a bold and visionary long-term plan — led by the federal government — that strategically focuses on meeting future national transportation needs, such as U.S. global competitiveness and efficient freight movement,” Ruane said.