A New Approach to Acoustic Emission Testing of Difficult-to-reach Steel Bridge Details

The John F. KennedyMemorial Bridge, a large cantilever through truss opened in 1963, carries Interstate 65 across the Ohio River between Louisville, Kentucky and Jeffersonville, Indiana. According to a 2003 count, the bridge carries over 120,000 vehicles per day [1]. Inspections revealed a five-inch full-depth transverse crack in the horizontal web in a tension region of the top chord on the east truss, the site indicated in Figure 1a. A partial-depth saw cut and an irregularly-shaped hole of unclear origin are present along the web-flange weld, and a one-inch diameter stop hole is present at the end of the crack, as shown in Figure 1b. The crack is in a fracture-critical member, meaning that fracture of the member would likely cause failure of the bridge. Acoustic emission (AE) monitoring was employed in conjunction with other non-destructive evaluation techniques to help detect and characterize any indications that the crack might jump the stop hole or propagate into the vertical flange of the member.