Applicability of the m_α-tangent method to estimate plastic limit loads of elbows and branch junctions

In this study, the limit loads calculated by the m_α-tangent method based on the linear finite element analysis are compared with the closed form solutions that are proposed by various authors. The objects of the analysis is to select the elbow and the branch pipe which are representative structure of piping system. The applicability of the m_α-tangent method are investigated by applying it to cases with various geometries. The internal pressure and the in-plane bending moment are considered and the m_α-tangent method is in good agreement with the existing solutions in case of elbows. However, the limit loads calculated by the m_α-tangent method for branch junctions do not agree well with the existing solutions and do not show any tendency. The reason is a biased result due to the stress concentration of the discontinuous parts.