Investigators in bridge collapse focus on chilling video
Early signs of problems emerged in 1990, officials at the Minnesota Department of Transportation reported Thursday. Annual inspections found the bridge to be "structurally deficient," but safe for the time being.
About 73,000 bridges in the U.S. are rated structurally deficient, according to the Federal Highway Administration. It means the bridges will need to be replaced eventually, but they currently are still considered safe.
An estimated 141,000 vehicles made the trip on the I-35W bridge each day in the Twin Cities. It was the most-traveled bridge in Minnesota and one of the busiest arteries in the Midwest. By comparison, Chicago's Dan Ryan Expressway handles about 180,000 vehicles each weekday.
At the time of the accident, an I-35W bridge inspection that was set for completion in September was to determine whether to overhaul the entire bridge, or tear it down, Minnesota Gov. Tim Pawlenty said.
The surfacing of the video, which was provided to the Minneapolis Police Department, "is the equivalent of recovering the cockpit flight recorder" from a downed plane, said Mark Rosenker, chairman of the National Transportation Safety Board, which is leading the investigation.
Authorities were also buoyed by the news that a Federal Highway Administration employee had produced an exact computer software model of the Interstate 35W bridge when he was a Ph.D. candidate at the University of Minnesota. The model will be used in a failure-analysis study to map out every edge and surface of the 1,900-foot-long bridge structure, with the goal of pinpointing what went wrong, officials said.
About 73,000 bridges in the U.S. are rated structurally deficient, according to the Federal Highway Administration. It means the bridges will need to be replaced eventually, but they currently are still considered safe.
An estimated 141,000 vehicles made the trip on the I-35W bridge each day in the Twin Cities. It was the most-traveled bridge in Minnesota and one of the busiest arteries in the Midwest. By comparison, Chicago's Dan Ryan Expressway handles about 180,000 vehicles each weekday.
At the time of the accident, an I-35W bridge inspection that was set for completion in September was to determine whether to overhaul the entire bridge, or tear it down, Minnesota Gov. Tim Pawlenty said.
The surfacing of the video, which was provided to the Minneapolis Police Department, "is the equivalent of recovering the cockpit flight recorder" from a downed plane, said Mark Rosenker, chairman of the National Transportation Safety Board, which is leading the investigation.
Authorities were also buoyed by the news that a Federal Highway Administration employee had produced an exact computer software model of the Interstate 35W bridge when he was a Ph.D. candidate at the University of Minnesota. The model will be used in a failure-analysis study to map out every edge and surface of the 1,900-foot-long bridge structure, with the goal of pinpointing what went wrong, officials said.
Labels: Federal Jurisdiction of Interstate waterways and Bridges, MINNEAPOLIS, Minnesota Bridge Collapse
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