An integrated model is proposed for the computation of ultimate plastic state for a branch pipe connection (nozzle) with an axial crack. A large quantity of loading factors (internal pressure, axial forces in the main and outlet pipes) and of geometrical dimensions (pipes radii and wall thickness, crack depth and length, the reinforcement height and thickness) are taken into account by splitting the basic problem into a number of auxiliary ones. The solutions of those problems and the procedure of their subsequent synthesis are described. The results obtained are compared with the theoretical results given in literature for a defect-free nonreinforced branch pipe. It has been noted that the presence of many variables does not allow clear quantitative nomograms and graphs to be presented. For this reason, the main result of the model is the developed computer program. The need for future co-operative work on establishing the design criteria for branch pipe is emphasised.