B&N was retained by the Kentucky Transportation Cabinet (KYTC) to complete a fracture critical inspection and gusset plate load rating of the Glover Cary Bridge over the Ohio River in downtown Owensboro, Kentucky.
Fracture Critical Inspection
B&N inspected the 4,320-foot long bridge using climbing techniques that minimized traffic disruptions, enabling all lanes of traffic to remain open throughout the duration of the inspection. Inspectors used webbing, ropes, and harnesses to position themselves on the structure and an 80-foot manlift to access portions of the approach spans from below the structure.
B&N performed arm’s length inspection of:
- Fracture critical members of the trusses (non-redundant steel members in tension)
- Floorbeam connections
- Floorbeams located directly under expansion joints where deficiencies were previously noted or observed from the connections
- Both faces of each girder in the two-girder approach spans
- Pier caps and bearings
- Category E and E’ fatigue-prone details in truss members, girders, and floorbeams
- Areas where significant problems were found during previous inspections
In addition to the arm’s length inspections, B&N also performed NBI and element-level visual inspections on all components of the structure, including the condition of the steel protective coating.
Gusset Plate Load Rating
KYTC also requested that B&N perform a load rating of the primary gusset plates on the through truss and deck truss spans of the bridge. Geometric data, section properties, and dead loads were provided by KYTC and used to construct a Midas Civil model. This model was used to develop concurrent loading for each of the gusset plates. Partial original design drawings and rehabilitation drawings were also provided, but no shop drawings were available.
To develop the gusset plate dimensions without the shop drawings, B&N inspectors marked several dimensions on each of the gusset plates and took photos of the plates using a drone. The photos were scaled in MicroStation and used to develop the gusset plate dimensions. B&N developed custom spreadsheets that utilized the loading from the Midas Civil model and the geometric data from the drone photos to calculate rating factors for each of the gusset plates.
This innovative approach of using drones resulted in significant time and cost savings as compared to previously-used methods of data collection, which included using telescopic poles with mounted digital cameras.