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Officials find bridge plates deficient in collapse probe
2008-01-15
More than a dozen steel support plates suspected in a 2007 fatal bridge collapse in Minnesota were deficient in size and a routine inspection would not have uncovered the problem, safety officials said on Tuesday. The National Transportation Safety Board (NTSB) will not reach a final conclusion until autumn on why the I-35W bridge in Minneapolis collapsed into the Mississippi River, killing 13, on August 1. But preliminary findings show 16 gusset plates -- large flat steel pieces that hold load-bearing columns in place -- were too thin to support the weight they held. "During the wreckage recovery, investigators discovered that gusset plates at eight different joint locations in the main center span were fractured, safety board Chairman Mark Rosenker said at a news conference. Safety board investigators discovered the original design process of the bridge led to a serious error in sizing some of the plates of the bridge's main skeletal structure. Investigators have not pinpointed why the apparent sizing issue occurred but suspect a calculation error, adding that a bridge inspections would not have uncovered it. About 1,000 feet of the bridge collapsed into the river during the evening rush. Vehicles plummeted into the water, killing 13 and injuring another 145. There was no deficiency in the quality of concrete or steel found in the Minneapolis bridge, the safety board said. The safety board said "there is no evidence" to suggest that the deficiencies found in Minneapolis are widespread "or even go beyond" that bridge. Investigators are not aware of any similar failures. Transportation Department officials, immediately following a safety board recommendation, advised states to go beyond usual practice and include gusset plates in their bridge strength calculations. There are 13,000 steel truss bridges in the United States. Days after the collapse, regulators instructed states to inspect all bridges of similar design to the Minneapolis span. (Reporting by Lisa Richwine in Washington and John Crawley in Detroit, editing by Philip Barbara)
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