Fatigue cracks in the web gusset round weld are regarded as important targets in bridge inspection. In order to avoid the risk of fracture certainly, it is necessary to understand the propagation behavior of the crack, critical crack size and detection methods. For these purposes, fatigue loading test using a large-size girder specimen with same gusset details as actual bridge was carried out to clarify the crack propagation by introducing beach marks. At the same time, several crack detection methods were applied during the fatigue test to find their detection ability with respect to the crack size. Based on those results, the control limit size for the crack inspection is proposed.
