I 35W Bridge Analysis

The I-35W Bridge in Minneapolis, Minnesota was built in 1967. The 8-lane bridge served 140,0000 vehicles per day. The bridge catastrophically failed during the evening rush hour on August 1, 2007. Thirteen people died and 145 were injured. 117 vehicles were damaged including a school bus. Compensation for victims who were on the bridge at the time of the collapse, as well as their family members totaled over $37 million.

Raths, Raths and Johnson, Inc. tasked ASI to provide analysis of the bridge and to identify the reason for the collapse. The bridge was modeled using original construction drawings. All structural details were modeled in 3D, which included steel truss, connections (gusset plate and bolts), concrete slabs, concrete piers and ramps. All applicable loads were taken into consideration such as gravity, traffic, and construction loads. The model also took into account the weakening of connections due to corrosion.

For this project, the results of these analyses helped identify the cause of failure of the bridge. The mode of failure in the ELS model created by ASI matched closely to the mode of failure observed in the actual failure reported by the National Transportation Safety Board (NTSB) and the Minnesota Department of Transportation (Mn/DOT).

Software Used: Extreme Loading for Structures (www.extremeloading.com/) is an advanced non-linear structural analysis software tool designed specifically for structural engineers. ELS allows structural engineers to study the 3D behavior of structures through both the continuum and discrete stages of loading. This includes static and dynamic loads such as those generated by a blast, seismic events, impact, progressive collapse, and the wind. Unlike many structural analysis software tools which are based on the Finite Element Method (FEM), ELS utilizes a non-linear solver based on the Applied Element Method (AEM). This allows ELS is to automatically analyze structural behavior during elastic and inelastic modes including the automatic yielding of reinforcement, detection, and generation of plastic hinges, buckling & post-buckling, crack propagation, membrane action & P-Delta effect, and separation of elements. The resulting debris and impacts with structural elements are also automatically analyzed and stress redistribution is inherently calculated.

Company: Applied Science International www.appliedscienceint.com/ or www.appliedscienceinteurope.com/