Limit loads for thin-walled piping branch junctions under combined pressure and in-plane bending

Closed-form yield loci are proposed for branch junctions under combined pressure and in-plane bending, via small-strain three-dimensional finite element (FE) limit load analyses using elastic-perfectly plastic materials. Two types of bending loading are considered: bending on the branch pipe and that on the run pipe. For bending on the run pipe, the effect of the bending direction is further considered. Comparison with extensive FE results shows that predicted limit loads using the proposed solutions are overall conservative and close to FE results. The proposed solutions are believed to be valid for the branch-to-run pipe ratios of radius and of thickness from 0.0 to 1.0, and the mean radius-to-thickness ratio of the run pipe from 5.0 to 20.0.