2008 Woodie Awards
Cause of MN bridge collapse determined
Katie Jones
Issue date: 1/21/08 Section: News
On August 1, 2007, a highway bridge in Minneapolis, Minnesota collapsed, killing 13 people and wounding 145. The National Transportation Safety Board (NTSB) announced on Tuesday that they had determined the collapse occurred because of undersized "gusset plates," thus placing blame on the bridge design.
Prior to its collapse, the bridge carried 140,000 vehicles per day, making it Minnesota's fifth most frequented bridge.
A gusset plate is a plate that holds joints together as an alternative to welding, or when welding is not possible. The joint members are held together by the plate, which is then screwed or riveted together.
The design drawings for the bridge were never found, so it is unclear how the undersized gusset plates made it into the final construction. Also, more weight was added to the bridge after the original design and construction materials were present on the bridge on the day of the collapse as part of a resurfacing project. Before the bridge is renovated, engineers will perform new calculations on the entire bridge. This time they will not use undersized gusset plates.
The highway bridge, which opened in 1967, was a steel deck truss bridge supported by concrete columns. In 1990 the bridge was classified as "structurally deficient," as are many aging bridges in the US. The NTSB does not believe that a lack of maintenance caused the collapse. A replacement bridge is currently being planned and is expected to open in December, 2008.
Lawmakers in Minnesota plan to spend up to $500,000 hiring lawyers to lead a legislative inquiry about the collapse. President Bush has already signed a bill for $195 million to help replace the bridge, on top of $178 million already given to the state for the project. The replacement bridge is expected to cost about $234 million.
Prior to its collapse, the bridge carried 140,000 vehicles per day, making it Minnesota's fifth most frequented bridge.
A gusset plate is a plate that holds joints together as an alternative to welding, or when welding is not possible. The joint members are held together by the plate, which is then screwed or riveted together.
The design drawings for the bridge were never found, so it is unclear how the undersized gusset plates made it into the final construction. Also, more weight was added to the bridge after the original design and construction materials were present on the bridge on the day of the collapse as part of a resurfacing project. Before the bridge is renovated, engineers will perform new calculations on the entire bridge. This time they will not use undersized gusset plates.
The highway bridge, which opened in 1967, was a steel deck truss bridge supported by concrete columns. In 1990 the bridge was classified as "structurally deficient," as are many aging bridges in the US. The NTSB does not believe that a lack of maintenance caused the collapse. A replacement bridge is currently being planned and is expected to open in December, 2008.
Lawmakers in Minnesota plan to spend up to $500,000 hiring lawyers to lead a legislative inquiry about the collapse. President Bush has already signed a bill for $195 million to help replace the bridge, on top of $178 million already given to the state for the project. The replacement bridge is expected to cost about $234 million.
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