Elastoplastic behaviour of T, Y, DT and DY-tubular joints under axial loading

Abstract

The offshore tubular structures are composed of beam elements which the intersecting areas present structural discontinuities. So, a high stress concentration appears in these areas, particularly, in the hot spots points. In this study, the finite element method (FEM) is applied on welded tubular T, Y, DT and DY-joints, in order to visualise the elastic stress distribution in the vicinity of the weld toe, and record the plastic limit load of each form. The aim of this work is to compare the elastic and elastoplastic behaviours, firstly, between T and Y tubular join, then, repeated this study for DT and DY joints. For elastic study, the evolution of von Mises equivalent stress along the weld toe was compared, knowing that the axial loads are applied in the free ends of the all braces. For nonlinear investigation, a comparison of tensile loads limits (collapse load) of these joints was realised, knowing that a tensile proportionally load is applied in the free ands of the braces. The mesh and the numerical calculation are performed using, respectively, Patran and Nastran software.