Minnesota I-35W Bridge Collapse
Problem - 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.
Analysis - 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.
Conclusion - 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).
Minnesota I-35W Bridge Collapse
Yanbu Gas Plant Construction Defect
Problem - During the construction process of a deethanizer vessel, several design mismatches between the anchor bolts and base plate holes were observed. To complete the installation process, the vendor widened and slotted nine holes in the base plate and removed three anchor bolts. In addition, several anchor bolts were damaged and several others were subjected to excessive heat during the torching/cutting of several bolts. This raised concern about its safety and structural integrity.
Analysis - ASI was tasked to provide a comparative model and analysis of the structure using our in-house structural analysis software, Extreme Loading® for Structures. The objective was to compare the as-designed case with the damaged as-built case with regard to wind and seismic loading.
Conclusion - ASI created a 3-D model and explicitly modeled all damaged portions and compared the behavior with the designed case. Based on the analysis, ASI was able to assure the client that the as-built structure met project level of safety requirements for design loading conditions.
Yanbu Gas Plant Construction Defect
St. Francis Hospital Implosion
Problem - Demolition workers tried to pull down a gutted 10-story hospital after weakening the structure. During the pull down process, the cables snapped. After several additional attempts, the management called for the services of ASI to perform two tasks; a vulnerability assessment of the existing condition of the structure and demolition analysis based on the new demolition plan.
Analysis - ASI applied a variety of wind loading scenarios to the structure to determine if in its weakened condition to ensure that it would not prematurely collapse. ASI also performed an analysis of the newly proposed implosion plan to assure local authorities, owners, and tenants of neighboring structures that the controlled collapse demolition would go as planned.
Conclusion - ASI determined that even under high wind loading conditions that there was a low potential of failure and that it was safe for demolition workers to enter the building to place explosives to implode the structure. When compared, video of the actual demolition and the predictive analysis of the implosion correlated closely.
St. Francis Hospital Implosion
Car Shade Collapse Due to High Wind
Problem - Under high wind conditions, a newly designed car shade structural failed catastrophically. The manufacturer of the car shade, who had installed the product at several other locations requested ASI expertise in the forensic investigation of the incident and subsequent design optimization car shade.
Analysis - ASI used created a three-dimensional model for the car-shed taking all construction details and material properties into consideration. ASI engineers performed nonlinear dynamic analysis of the structure under the effects of the wind loading.
Solution - Based on the 3D analysis, ASI showed the sequence of failure for the specified wind load case. ASI engineers provided recommendations to improve the design and prevent future failure.
Car Shade Collapse Due to High Wind