The fatigue strength of transverse-fillet-welds in the attachment of diaphragms is a decisive factor in the design of box-section truss members. The fatigue strength of this joint is influenced by the profile of the fillet-welds at the scallop and the residual stress created by the corner weld. In order to study the fatigue strength at the ends of the scallops, a real size cruciform model was fabricated, where a pair of rib plates were welded on both sides of a base plate containing four longitudinal weld-beads. The size of the base plate was 45mm thick and 300mm wide. Fatigue tests were performed with an electro-hydraulic fatigue testing machine of a dynamic capacity of 4 MN. The tests were performed with stress rations at O, -1, -2 and -5.