USA Today reports that the collapse of the St. Anthony Bridge in Minneapolis resulted from a design flaw in the gusset plates, ending speculation that poor maintenance caused the deaths of thirteen people last August:
Federal investigators have concluded that steel plates on the interstate bridge that collapsed last summer in Minneapolis were inadequate to hold the structure together and appear to have been what allowed it to fail, killing 13 people, two officials familiar with the investigation said Monday.
The National Transportation Safety Board (NTSB) plans to call Tuesday for states to perform safety assessments on the so-called gusset plates in steel girder bridges any time they add weight to a bridge, the sources said. Design changes in 1977 and 1998 added additional pavement and concrete barriers that increased the weight of the Interstate 35W bridge in downtown Minneapolis.
...
In the wreckage of the I-35W bridge, investigators found 16 gusset plates that were fractured, said one of the officials. Eight of the plates were in the location on the south side of the bridge where the collapse began, according to that official.
The fractures prompted engineers to calculate whether the plates were adequate to hold the bridge together. What they found was that the half-inch thick plates should have been an inch thick — double the size.
Recent Comments