Estimation of Probabilities of Crack Detection and False Indication in Visual Inspection of Structures

Abstract

The structural expressions for the distributions of the probability of crack detection (POD) and the probability of false crack indication (POF) in the visual inspection method are presented, where the scatters in the distributions are caused by many factors related to the applied inspection method and the defect conditions in the structure. In order to estimate the POD and the POF from the results of the field inspections carried out for a structure by an inspection team under a specified condition, multiple visual inspection method combined with the successive precise inspections which are carried out for limited locations is developed. The crack classification method is introduced to improve the accuracy of the capability evaluation. The applicability of the method is numerically examined for a structural model which has crack-form defects. The advantage of the method is that the mean values of POD and POF as well as their distribution properties can be estimated without using any information other than the results of field inspections.