Abstract
Fixed point load fatigue tests (four points bending tests) and the moving load fatigue tests (wheel load driving tests) on I-section girder specimens with web-gusset welded joints have been performed in order to make clear fatigue crack initiation and propagation behavior from the weld toe of the joint and the fatigue strength under variation in principal stress direction. The test results suggested that the fatigue strength under moving loads is lower around 20 to 30% than the strength under the fixed point loads, and fatigue crack extending along the weld toe is long compared with that in fixed point loads, and the fatigue crack after leaving from the weld toe propagates in more inclined direction compared with the direction perpendicular to the principal stress direction.
