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Possible Causes of Bridge Collapse Investigated

Investigators with the National Transportation Safety Board have been re-creating the layout of the Interstate 35W Bridge in attempt to find possible causes for the collapse.
They have begun to inspect specifically the section of the bridge that fell first. By analyzing these gusset plates, investigators are hoping to find out what played the biggest role in the collapse.
Significant corrosion was found in three of the gusset plates found from this section of the bridge. According to one structural engineer, runoff of salt and other de-icing chemicals could have contributed to this corrosion.
The L-11 gusset plate was corroded somewhat more than the other plates. Of the more than 100 gusset plates total from the bridge, this one could have played a substantial role in the collapse on August 1.
Another possible contributing cause of the collapse, according to investigators, is the temperature changes. Even though the bridge had roller bearings, they may not have worked effectively. MnDOT records that state that inspectors found the bearings weren’t working correctly because of corrosion and buildup of debris.
Although major advances have been made in the investigation, authorities are saying that it could be a long time before the causes for the collapse are completely understood.