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Title: Bridge Load Testing and Monitoring for Super-Heavy Permit Loads

Author(s): Brett Commander and Jesse Sipple

Publication: Symposium Paper

Volume: 323


Appears on pages(s): 4.1-4.20

Keywords: delayed ettringite formation (DEF), load rate, load test, permit load, prestressed concrete (PS/C), structural monitoring, super-heavy transport, strain transducer, crack gage.

DOI: 10.14359/51702434

Date: 5/1/2018

Load testing and structural monitoring facilitated the passage of several super-heavy permit loads at the Burns Harbor access bridge near Portage, IN. Twenty super-heavy permit loads, with gross vehicle weights reaching 848 kips (3770 kN), were required to cross the bridge, which was the only feasible route out of the port. Preliminary load ratings were acceptable due to three factors; the specialized transport’s large footprint effectively distributed load, the bridge was designed for Michigan Truck Trains, and the bridge was assumed to be in good condition. The last condition came into question due to significant cracks throughout the prestressed concrete girders caused by delayed ettringite formation (DEF). While DEF cracks were a function of improper curing and not related to live-load effects, the Indiana Department of Transportation (INDOT) was concerned that repeated heavy loads would negatively influence cracks and the bridge’s overall long-term performance. Due to the cargo’s importance to the local community and lack of an alternate route, INDOT allowed use of the bridge after load tests proved that the transports would not cause damage or reduce the bridge’s service life. Structural monitoring performed during the entire transport period verified structural performance was not diminished during the numerous crossings.