The Limit Pressure for a Cracked Branch Junction and Comparison With a Cracked Plain Cylinder Available to Purchase

The limit load of structures that contain defects may be determined using standard limit load solutions for simple components or by employing Finite Element (FE) procedures for more complex structures. This work considers the case of a pressurised piping branch junction (D/T = 20, d/D = 0.5, t/T = 1) which contains two axial through-wall cracks, symmetrically extending from each crotch corner at the crown of the junction. The structure is idealised as a plain cylinder containing a single axial defect with three proposed definitions of an equivalent crack length. Such a cracked cylinder can be analysed using a standard limit load solution or by FE analysis. The three crack length definitions used are the distance between the two outer crack tips, the sum of the two crack lengths and the length of one of the cracks. Estimates of branch junction limit pressures have been obtained by FE analysis using ABAQUS for a range of crack lengths. These are compared with the theoretical solutions for an equivalent plain cylinder of the run pipe dimensions containing a single crack whose length has been defined in each of the above ways.