Forensic Investigation Modeling (FIM) Approach: I35 West Bridge Collapse Case Study

The investigation into the causes of collapse of the I-35W Bridge in Minnesota required a vast amount of design, retrofit and maintenance data to be sorted prior to beginning the complicated work of analyzing the condition and loading of the bridge at the time of collapse. A Forensic Information Model (FIM) was created to store all of this data, as well as the geometry, as a 3-D visual database enabling the engineers to pinpoint possible trouble areas in need of further investigation. SAP models were built to evaluate the linear behavior of the structure. Components were modeled in Abaqus to study the post buckling capacity at a member level. The results were combined into a LS-DYNA model to capture the bridge's initiation of failure. The collapse simulation matched well with existing video of the failure. This paper will describe the interaction between the models, how the FIM was instrumental in guiding the numerical modeling to its conclusion, and the subsequent creation of a 3-D animation that allowed the client to better visualize the collapse mechanics.