Fatigue‐Reliability Updating through Inspections of Steel Bridges

A reliability‐based fatigue‐damage‐evaluation procedure developed in the companion paper is extended in this paper to incorporate information from nondestructive inspections (NDI). Since inspections are required at regular intervals, the results from these inspections can be used for fatigue maintenance of steel bridges. The sensitivity and capability of some of the inspection methods, including ultrasonic inspection, are investigated. Inspection information is beneficial; however, it adds uncertainty to the fatigue‐evaluation process. The detectability and the accuracy are the two additional sources of uncertainty in the NDI. The uncertainties in them are quantified. The detection events are classified into three cases, no crack detection, crack detection but without size measurement, and crack detection with the crack‐size measurement. Using the information from $k$ inspections, the distributions of the basic random variables and the corresponding reliability index are updated. Using the information on the updated reliability index, a decision can be made on what to do next, in terms of reducing the next scheduled inspection interval, or whether to repair, replace, or do nothing. The procedure is explained with the help of an example. It is concluded that the inspection results can be used to maintain the fatigue‐damage integrity of steel bridges. Fatigue damage‐control curves are also proposed for everyday use.