Evaluation of Fracture Behavior for Pressurized T-Pipe by Finite Element Analysis

T-pipe is one of the typical structural elements of LWR piping as well as T-joint. In the present situation, the evaluation of wall thinning for T-pipe is accomplished by assuring the sufficient strength around the opening area by using the design and construction code. This evaluation often assumes the replacement of a local wall thinning with a global wall thinning, which leads to excessively conservative prediction of burst pressures. In this study, three-dimensional finite element analysis was conducted to simulate the fracture behavior of a pressurized T-pipe test. The accuracy of the predicted burst pressures and appropriate modeling of the welded joint at the junction of the main and branch pipes were investigated. It was found that the burst pressure could be adequately predicted by applying a proper fracture criterion. Allocation of experimental tensile property of weld metal to the welded joint gave more accurate prediction; nevertheless, allocation of experimental tensile property of base metal to the welded joint enabled suitably conservative prediction.