Nondestructive Evaluation of Trunnion Pins on Jacksonville’s Main Street Bridge
BDI was engaged to evaluate the condition of the trunnion assemblies on the John T. Alsop Bridge (Main Street Bridge) in Jacksonville, Florida. The bridge’s 365-foot vertical lift span relies on four trunnion shaft systems to support the massive sheaves that transfer loads between the lift span and its counterweights, making these components essential to safe and reliable operation.
To assess their condition, BDI performed a comprehensive nondestructive evaluation (NDE) of the trunnion pins, transition fillet regions, keyed joints, and associated steel components. The team used Magnetic Particle Testing (MT) to identify surface and near-surface cracks, Straight Beam Ultrasonic Testing (UT) to detect internal flaws and determine whether surface cracks extended into the trunnion cross-section, and Dye Penetrant Testing (PT) to further characterize identified indications and estimate crack depth.
BDI’s engineers and field technicians conducted all field inspections, testing, data collection, and analysis. The team compiled the results into detailed reports, figures, and summary tables that documented crack locations, flaw characteristics, and the overall condition of the trunnion assemblies and related steel components.
By identifying potential defects and accurately characterizing existing deterioration, BDI provided the bridge owner and project team with the information needed to prioritize maintenance activities, develop targeted repairs, and extend the service life of this critical movable bridge.
