Intelligent Infrastructure Systems performed in-situ strain gage testing on a highway bridge to determine the actual stress/stain experienced during the crossing by an over dimensional, overweight, permit vehicle. The bridge, located in the Bronx, NY, carries Bruckner Boulevard bridge over an abandoned railroad.Â Intelligent Infrastructure Systems installed 21 vibrating wire strain gages on the bridge superstructure elements to capture the strain response to the permit load crossing.
After closing the bridge to traffic, the 380-kip permit vehicle, which was 185′ long, 14′ wide, nearly 14′ tall, crossed the Bruckner Blvd bridge around 11:00 PM on the evening of December 13, 2017. During the crossing, Intelligent Infrastructure Systems staff monitored the load induced strains and reported peak strain values and strain time histories for each strain gage immediately after the move.
During the heavy move, the measured peak strain was approximately 50% of the predicted peak strain, however given the short span length of the bridge, it was not possible for the full weight of the permit vehicle to be on the span at the one time due to the axle configuration and spacing. The bridge was loaded by three axles at a time and the maximum load on the span at any one time was approximately 62,000 lb. After reviewing the strain measurements, it was determined that individual girder strains were less than those predicted using AASHTO distribution factors, indicating a lower distribution factor for this loading configuration.