I35 Bridge Collapse

Minneapolis, Minnesota

The I35W freeway bridge that spans over the Mississippi River suddenly collapsed, killing 13 motorists during the evening rush hour. At the time of the collapse, four lanes of the eight-lane 1,900-foot-long bridge were closed to traffic with staged construction materials and equipmment in preparation to began paving the overlay concrete on the deck top surface that was removed.  Investigation by The National Transportation Safety Board (NTSB) began immediately and RRJ was retained by the deck resurfacing contractor's legal counsel to investigate the cause including whether the contractor's resurfacing operations played any role in the collapse. RRJ gathered physical evidence at the bridge site and off site including information shared by NTSB. RRJ conducted structural analysis computational modeling of the bridge structure to evaluate the original design, the design as subsequently modified, the as-constructed structure including the deformations reported in several steel gusset plates, and comparison of required highway design live loading to the traffic and construction loads present on the bridge at the time of collapse. RRJ and NTSB both determined the probable cause of the collapse to be a gross inadequacy in the original bridge design which had escaped discovery for over 40 years.