Plastic limit loads for piping branch junctions under out-of-plane bending

This paper presents approximate closed-form plastic limit load solutions for branch junctions under out-of-plane bending and under combined pressure and out-of-plane bending, based on three-dimensional finite element limit analyses for an elastic-perfectly plastic material. When bending is applied to the branch pipe, the plastic limit loads for out-of-plane bending are shown to be lower than those for in-plane bending. However, for bending to the run pipe, the opposite trend is found. For combined pressure and out-of-plane bending, either the circular interaction or the parabolic interaction rule can be used, depending on the bending location and the branch geometry. Comparison with published experimental plastic limit load data shows that the predictions agree relatively well with the test data.