Steel Bridge Research, Inspection, Training, and Engineering Center
28. Probability of Detection Study Frame
Donated by: Steel donated by Steel Dynamics Inc., Structural and Rail Division. Galvanization Donated by AZZ Glavanizing, Inc. Bolts were donated by Nucor Fastener Division
Year Built: 2014
Structure Type: Number of details is equivalent to a 350’ to 400’ Bridge
Height: 30 ft
Total Length: 84 ft
Longest Span: 42 ft
Number of Spans: 2
Width: 16 ft 4 in
The Probability of Detection (POD) Frame at S-BRITE is an innovative training and research tool designed to evaluate and improve the visual inspection capabilities of bridge inspectors. Built to mimic a two-span, three-girder highway bridge, the structure holds 183 full-size bridge specimens, some containing controlled fatigue cracks introduced through laboratory testing. These specimens simulate real-world bridge conditions with coatings, scratches, and environmental damage for a highly realistic inspection environment.
The POD Frame enables inspectors to test their ability to locate and size fatigue cracks in critical areas like out-of-plane distortion, weld toes, and rivet holes. Data collected during these inspections, including inspector accuracy, crack characteristics, and environmental conditions, provides valuable insights into inspection reliability and identifies areas for improvement.
Findings from the study show a wide range in performance, with inspectors detecting an average of 65% of cracks and highlighting variability in detection capabilities. To achieve a 50% detection rate, cracks needed to be at least 1 inch long, while a length of 4 ½ inches was needed for 90% of inspectors to reliably detect them. This research informs more effective training programs, enhances damage-tolerant bridge designs, and establishes benchmarks for evaluating new inspection technologies. The POD Frame underscores S-BRITE’s commitment to advancing bridge safety and inspection standards through hands-on learning and rigorous research.
