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.

The bucket is a metal entity, linked to a machine called DRAGLINE, used for loading the different sizes of granular materials in large quantities. Each bucket is provided with six teeth which in contact with materials to be discharged, in order to extract the mineral. These teeth are connected to the bucket via a semi-rigid connection. In operation, except for the wear phenomenon "normal", some teeth break after a few hours of operation at the fixed portion in the singularity region (radius of curvature equal to zero). We observed via elastic numerical simulation in quasi-static regime, performed using PATRAN and NASTRAN software, that hot spots are located at the singularity region. We also used this numerical calculation for analyzing the effect of the variation radius of curvature on the stress concentration factor by plotting the variation of this factor vs of said radius. To deepen, we repeated the same study but this time considering the material of the tooth as elastic perfectly plastic for seeking the limit load. For each value of the radius of curvature, was plotted the variation of the elasto-plastic external force according to the displacement of the front end of the tooth, knowing that the other end is fixed.

The welded tubular joints can be used in several industrial fields including, metallic bridges, telecommunication tripods, oil platforms and pipelines. These structures can be damaged by concentrated stresses located in the toe weld vicinity. Semi-parametric formulas, currently available in the literature, can be used to predict the value of the stress concentration factor without given the hot spot location. In this work, a Finite Elements modeling was carried out for a T-joint, in order to have the concentrated stress value around the weld toe. This work was investigated for a series of combined loads.