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Such bridges are inspected at least once a year to check for fractures that could trigger a failure. But Maczko said he will be happy when the bridge is replaced, now scheduled for 2009. "The new codes have redundant systems in them, so that if one member fails another can hold it."
He said he wishes another fracture-critical bridge -- on I-35E over Cuyahoga Street -- would be replaced sooner than 2013 as currently planned.
State bridge engineer Dan Dorgan said that when the bridges now considered fracture critical were built in the 1960s, fatigue that could lead to such failure was not considered a problem in bridges. In the mid-1970s, engineers across the country started seeing problems in the design, he said.
Prof. Roberto Ballarini, head of the University of Minnesota Civil Engineering Department, said that bridges lacking structural redundancy are not necessarily bad, but require monitoring and maintenance. Adding redundant steel supports, for example, can affect other important bridge features, including how the structure expands and contracts, he said.
37 in state may need replacing
Minnesota has 37 bridges on federal and state highways labeled structurally deficient and possibly needing replacement. Throw in county road bridges and the number jumps to 460.
The data analyzed by the newspaper were contained in the Federal Highway Administration's National Bridge Inventory database as of February. The paper obtained a copy of the database from the National Institute of Computer Assisted Reporting in Columbia, Mo.
The U.S. Department of Transportation said Thursday that a label of "structurally deficient" means that certain elements of the bridge must be monitored and possibly repaired. "The fact that a bridge is 'deficient' does not imply that it is likely to collapse or that it is unsafe," the agency said in a prepared statement.
The debate over the backlog in bridge maintenance brought up finger-pointing in Washington over transportation spending. In his comments on the 35W collapse, Bush also used the occasion to rip Democrats in Congress for failing to finish work on the government's spending bills for the coming year, including an annual transportation appropriations bill.
He faulted the Democrats for exceeding his spending targets, prompting a sharp response from Senate leaders who accuse the White House of underfunding the nation's infrastructure needs.
"And when we try to invest what we believe is a better number, we just get veto threats," said Sen. Patty Murray, D-Wash., chairwoman of the transportation appropriations subcommittee.
Congressional Democrats and Republicans have been feuding since last month over an Office of Management and Budget report projecting a $4.3 billion shortfall in the federal Highway Trust Fund by the end of 2009.
Oberstar said that the Bush administration's unwillingness to commit to a "robust" transportation budget has led to the neglect of the nation's infrastructure, specifically bridges.
In 2003, the House Transportation Committee sent Bush a $375 billion transportation bill -- about $100 billion short of what the American Society of Civil Engineers recommended. Bush allocated $247 billion -- $90 billion less than the Transportation Department and the House committee passed.
Reporters Laurie Blake, Pat Doyle and Myron P. Medcalf contributed to this report.
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