Cecile9, StructuralEIT is trying to get you to explain yourself more clearly so that he can give you some good advice. If you explain what the structural set-up is, type of fasteners, loading situations etc, then it is easier to give you what your looking for.
What i think i understand is that you have a fastener which as a biaxial load and a shear flow in the area. If this is correct, then i would simply take the root of the sum of the axial loads squared. Cant see what your talking about by trying to add in the shear flow, as it is a function of the axial loads applied to the structure?