Load Rating Assessment of Three Slab-Span Bridges over Shingle Creek

Status:  Complete
Report Date:  10/04/2022


The corridor along I-94/I-694 across Shingle Creek is a critical freight transportation route in Minnesota. Some trucks, however, are forced to take a 15-mile, more congested detour if they exceed the bridges’ legal weight limit. MnDOT can issue overweight permits based on several factors that ensure safe passage. Load ratings calculated according to federal and state guidance, however, prevent larger trucks from being permitted. New MnDOT research has the potential to ease this burden. An in-depth analysis of the Shingle Creek bridge load capacity found that existing load rating factors for the Shingle Creek bridges are overly conservative. After a thorough visual inspection, researchers performed numerous live loading tests with trucks, and evaluated various measures of how the bridge and bridge materials responded. Using this field data in conjunction with a complex computational model as well as a simpler numerical model, researchers generated more representative load distribution factors than were previously calculated. MnDOT now has more flexibility in permitting overweight trucks to cross the Shingle Creek bridges and tools to refine load ratings for other bridges.

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