Paper 12: Stresses in and Flexibility of Mitred Bends and Lobster-Back Bends

Information available for the calculation of stresses in and flexibility of mitred pipe bends (including lobster- back bends) under elastic conditions, for internal pressure loading, and in-plane and out-of-plane bending loading, is assessed. The results of Owen and Emmerson (4) for single mitre bends under internal pressure loading and their application to lobster-back bends are discussed. The stiffening effect of a ring of varying degrees of stiffness at the joint is considered in the light of some experimental results. The results of in-plane bending tests on two separate single mitre bends of different mitre angles are compared and a further comparison is made with published results on lobster-back bends. It is concluded that the results for single mitre bends under in-plane bending cannot be applied to lobster-back bends, which are more closely approximated by smooth-bend theory. Out-of-plane bending loading is briefly discussed.