The National Transportation Safety Board got the cause of the Interstate 35W bridge collapse wrong, the lead attorney for victims of the disaster claimed Wednesday.
The collapse of the I35W bridge in August 2007 killed 13 people and investigators from the US National Transportation Safety Board (NTSB) found that gusset plates used to connect load bearing columns and trusses had inadequate load bearing capacity last year.
However according to attorney Chris Messerly, experts from engineering consultancy Thornton Tomasetti believe that the initiating event wasn’t the fracture of a key gusset plate in the bridge, but the failure of a horizontal beam.
Messerly said Thorton Tomasetti concluded that a chord buckled because of heat stress on the bridge that day, the weight of construction materials on it and frozen roller bearings that restricted the thermal movement of the bridge. The engineers said the chord failure then caused a gusset to fail, according to Messerly.