Plastic limit load of welded piping branch junctions under internal pressure

In this work, a simplified estimation formula for plastic limit load of defect-free welded piping branch junctions subjected to the internal pressure is established. The relationship takes into account the effect of the internal forces between the run and branch pipe around the intersecting line. The formula is built on the following process: First, an equation between the limit load and internal force of branch pipe surrounding the intersection is derived on the basis of the force equilibrium condition. Secondly, regarding this internal force as an external force acting on the intersection of run pipe, the approximate solutions of internal force around the intersection on run pipe, under the plastic limit load, are given. Finally, referring to the von-Mises yield criterion, the plastic limit load of two intersecting cylindrical shells is then obtained. The formula's suitability and feasibility applied in engineering practice is also validated with finite element analysis and experimental results in the paper.