Abstract
The direction of the principal stress on gusset welded joint connected to a main girder web of a steel girder bridge changes instantaneously so that the direction of the shear stress reverses when a vehicle passes right above there. It is well-known that the fatigue crack initiates and propagates in the direction perpendicular to principal stress one, but fatigue crack propagation behavior and fatigue strength have not been made clear yet when the direction of principal stress changes. In the present study, for making the propagation behavior and the fatigue strength clear in the stress field where the direction of the principal stress changes, fatigue tests on girder specimens and fatigue crack propagation analyses have been performed.
