A 51-year-old steel truss bridge over the Mississippi River in St. Cloud, Minn., was shut down after inspectors found that its gusset plates...
CHICAGO — A 51-year-old steel truss bridge over the Mississippi River in St. Cloud, Minn., was shut down after inspectors found that its gusset plates were bending, a problem similar to the one believed to have critically weakened the Interstate 35W bridge that collapsed in Minneapolis in August.
Transportation officials said closing the bridge, which is similar in design to the collapsed bridge, was necessary until the structure can be repaired or replaced. The bridge carries Highway 23, one of St. Cloud’s biggest arteries, over the river.
The bent plates were discovered late Thursday after a visual inspection that was part of what Bob McFarlin, the acting transportation commissioner, called an “extensive, systematic and continuous review” of 25 truss bridges across the state.
The inspection found that several gusset plates — metal slabs used to reinforce bridge joints — had bent one-quarter of an inch out of shape.
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The bridge was scheduled for replacement in 2015, but state officials planned to accelerate that, McFarlin said.
Officials acknowledged that the I-35W bridge collapse, which happened Aug. 1, influenced their decision to halt the traffic flow in St. Cloud, northwest of Minneapolis.
The National Transportation Safety Board has not yet established the overall cause of the collapse in Minneapolis, which killed 13 people and injured 145 when cars plunged into the Mississippi River.
But earlier this week, the board said the bridge was stressed after workers put 99 tons of sand on the roadway directly over two of the bridge’s weakest points.
Stress at one of the two weakest points was 83 percent more than the bridge could have handled, according to an interim report released by the Federal Highway Administration.