Angular distortion and misalignment are the typical initial imperfections of welded-joint in steel structure. Stress and strain concentration at the root and the toe of welded-joint become larger when the welded-joint has misalignment, as misalignment causes a moment with applied force. Therefore, fatigue strength of the welded-joint with misalignment is inferior to that without misalignment.
In this paper, fatigue strength of such joint was investigated using the specimen, which was scale-up model of a cross section of U-shape trough rib. Stress concentration factor of the root was analyzed by the finite-element method and was measured by static loading test. Cyclic loading test was carried out to clarify the effect of root shape on fatigue life and the relation between fatigue crack propagation rate and stress intensity factor range. Also, the effect of scale-up rate of the specimen was investigated.