The 'Bugs' Ate the Bridge
At an age of only 32 years, an interstate bridge in the Upper Midwest carrying approximately 40,000 vehicles per day made national headlines in September of 2013 when one of the support piers moved downward two feet, creating a dramatic “dip” in the bridge superstructure and startling drivers.
When investigators observed extensive corrosion on the failed steel H-piles providing foundational support, engineers from Pivot were retained to determine the corrosion mechanism and provide recommendations for repairs. This included design recommendations to isolate the new foundation system from corrosion by providing a novel inert sleeve system around drilled shafts. Pivot personnel determined that the unique soil conditions in the vicinity of the failed pier promoted microbiologically induced corrosion activity, which drastically accelerated the rate of corrosion and significantly reduced the cross-sectional area of the steel piles.
Pivot personnel also designed and installed a custom corrosion monitoring system at multiple piers along the bridge site, giving the owner the ability to document below-grade corrosion activity. The system is currently being used to collect insightful data on corrosion rates and assess the remaining service life of the structure providing peace of mind to the bridge owner and its 40,000 daily users.
Structural Repair Recommendations
Cumulative Corrosion Rate
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