Adequacy of the U10 & L11 Gusset Plate Designs for the Minnesota Bridge No. 9340 (I-35W over the Mississippi River) - Interim Report   [open pdf - 412KB]

"The I-35W Bridge over the Mississippi River in Minneapolis, MN had 14 spans and a total length of 1,907 feet. The primary structure of this bridge was a variable depth steel deck truss of 1,064 feet in length that carried I-35W over the river and gorge. On August 1, 2007 a failure in the river span of the deck truss caused a complete collapse of the entire truss structure and some of the approach spans resulting in the tragic loss of 13 public motorist lives. The National Transportation Safety Board (NTSB) is the primary agency investigating this failure to determine a probable cause. The Federal Highway Administration (FHWA) is assisting and collaborating with both the on-site and broader activities of the NTSB investigators. The FHWA team consists of personnel from the Turner-Fairbank Highway Research Center (TFHRC), the Office of Bridge Technology (HIBT), the Resource Center (RC) and several Division offices. One of the tasks performed by the FHWA team was a review and assessment of the original bridge design calculations by Sverdrup & Parcel. This report will focus on the findings of this assessment unique to the gusset plate design methodology used for the primary truss and more specifically the design of the gusset plates at locations U10 and L11. The initial on-site investigation of the collapsed structure identified the failure of the U10 gusset plates as occurring early in the event. The L11 gusset plates are detailed similarly to those at U10."

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National Transportation Safety Board: http://www.ntsb.gov/
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