BS7159 Section 7.3.5 (Combined Stress: branch connections), is composed of three types of stresses, (1) branch circumeferential stress, (2) non-directional bending stress and (3) branch torsional stress...What is the proper allowable stress to be used for this type of stress?...Is it the longitudinal allowable stress (design strain x longitudinal modulus of elasticity, e x Elong) or (design strain x hoop modulus of elasticity, e x Ehoop)?....Many thanks in advance fellows...