Fatigue strength of welded joint between angle-shape shear connector and bottom plate in steel-concrete composite slab was investigated by fatigue tests. Local stress around the welded joint was also investigated by FEA. In fatigue tests, fatigue cracks initiated and propagated at the welded toe. The fatigue cracks were caused by stress concentration at the welded joints due to the local bending deformation of bottom plate. This local bending deformation was observed when the bond between concrete and steel plate was lost, and analytically simulated by FEA carried out on slab members in practice. After these investigations, it was confirmed the stress level at the welded joint was small and much less than the fatigue limit even when the desiun truck loads were atinlied.
