Numerical investigation of collapse of the Minnesota I-35W bridge

The I-35 Bridge over the Mississippi River in Minneapolis, Minnesota catastrophically failed during the evening rush hour on August 1, 2007, collapsing to the river and riverbanks beneath. In the years prior to the collapse, several reports cited problems with the bridge structure. This research analytically investigated the cause of the collapse using the Applied Element Method, which recently presented its capability to study the behavior of collapsing structures. The bridge was modeled using the original construction drawings, where all the structural details were taken into consideration (steel truss, gusset plates, concrete slabs, concrete piers, etc.). All the loads at the time of collapse were taken into consideration including traffic and construction loads. It was proven that AEM was capable of analyzing and investigating the cause of collapse of the I35-W bridge. The cause of collapse was found to be the failure of the gusset plates at connections L11 and U10, which well agreed with the field investigations of the collapsed bridge. The under-designed thickness of the plates, their corrosion, and the over loading due to traffic and construction loads at time of collapse were the reasons for the bridge collapse.