In the welded joint, a tensile residual stress introduced by the weldeing is reduced when the crack initiates and propagates. Therefore, if the residual stress near the weld joint can be measured, it will be the fatigue crack detection method. Recently, residual stress in steel members is able to be measured by X-ray diffraction method on site. Therefore, in this research, a residual stress measurement using X-ray diffraction method is proposed for the detection technique of fatigue crack. To confirm the proposed methods, specimens of out-of-plane gusset joint and the specimen of joining between orthtorpic steel deck and U-shaped rib were tested under cyclic loading with measureing the residual stress. In the results of fatigue tests, the chaninging of the residual stress near the weld joint by the initiation and propagation of fatigue crack was observed by the proposed technique in all cases.
