Benchmark for Evaluating Performance in Visual Inspection of Fatigue Cracking in Steel Bridges

Abstract

Visual inspection is the primary means of ensuring the safety and functionality of in-service bridges in the United States and owners spend considerable resources on such inspections. While the Federal Highway Administration (FHWA) and many state departments of transportation have guidelines related to inspector qualification, training, and certification, an inspector’s actual capability to identify defects in the field under these guidelines is unknown. This paper describes the results from 30 hands-on, visual inspections performed on bridge specimens with known fatigue cracks. Background information was collected on each inspector and correlated with inspection performance. Field temperature, duration, experience, and training were significantly correlated with detection rate. Probability of detection (POD) curves were fit to the inspection results and the 50% and 90% detection rate crack lengths were determined. This POD study was conducted to provide a benchmark measure of visual inspection capability for detecting fatigue cracks in steel bridge components under controlled conditions. It is believed to be the first study in which a statistically significant set of data focused on visual detection of fatigue cracks in steel bridge components has been collected.