Limit load interaction of cracked branch junctions under combined pressure and bending

This paper describes the effect of cracks on the plastic limit loads of branch junctions under combined pressure and bending, based on three-dimensional finite element limit analyses. For combined pressure and bending to the run pipe, the circular interaction rule can be used to estimate plastic limit loads. For combined pressure and bending to the branch pipe, either a circular or parabolic interaction rule can be used depending on the branch type. For through-wall cracked branches, the interaction curves move toward the linear interaction rule with increasing crack length. For surface cracks, the interaction diagrams change smoothly between the limiting cases of the un-cracked and through-wall cracked branch.