Anna Maria Hardness Testing

Anna Maria Island (Manatee Ave.) Bridge connects the mainland city of Bradenton, FL to Anna Maria Island. This double-leaf bascule drawbridge, built in 1957, makes frequent openings due to the structure’s low clearance. While the bridge has been slated for replacement, due to its low clearance, narrow lanes, and older design, there is no established timeline for replacement, and it is critical that the bridge continues to operate safely and reliably until replacement. 

BDI was engaged by WSP to provide nondestructive evaluation (NDE) services on 12 in-place turn bolts on the pinion gear assemblies. Leeb rebound hardness testing was performed to determine whether the bolts met minimum specifications for an ASTM A449 bolt. Leeb testing works by measuring impact and rebound velocity of a spring-loaded impact ball. The ratio of these velocities is converted to the Leeb hardness scale, which can be used to estimate the tensile strength of the steel element. Testing was performed by BDI’s trained technicians in accordance with ASTM A956, using a Proceq Equotip tester.

Results were generally consistent between both bascules and indicated that four total of the tested bolts (two per side) did not meet the minimum tensile strength for ASTM A449, with approximately 30% lower tensile strength than the other bolts.