A comparative study of fatigue inspection methods

Bridges are inspected, regularly or otherwise, for fatigue cracks using a variety of different methods. However, for all of these methods, inspection does not necessarily imply detection due to a number of factors including the inspector’s experience and the physically inherent limitations of the method. Consequently, traditional inspection methods do not have a limitless capacity for crack detection. As fatigue is a phenomenon involving crack growth over time, application of a particular method will have a time-dependent probability of detecting a crack. In this paper, crack growth, as this may be observed in a typical bridge fatigue detail, is quantified using fracture mechanics and the performance of four different inspection methods over time is compared in terms of their probability of detection. Although the results presented here are pertinent to the particular type of bridge detail and loading conditions, fracture mechanics may also be applied to a wide variety of different details in order to compare detection capabilities at different time instances.