Modélisation numérique du comportement mécanique des jonctions tubulaires soudées des plateformes offshore.

Abstract

Tubular steel structures are widely used in the construction of offshore platforms; several types of junctions are used in this field. The tubular members are assembled by welding, thus forming complex brace/chord intersections which represent structural discontinuities leading to high stress concentration in the vicinity of the weld bead. These joints are subjected to repeated loading over time leading to fatigue damage, hence the need to predict stresses around welded intersections. It is with this in mind that a numerical modeling of the mechanical behavior was carried out using two software programs ANSYS, and COMSOLMULTIPHYSICS. A numerical modeling in 2D with thin Shell elements and 3D with 20 Nodes solid elements was carried out by applying three basic loadings axial loading AX, in-plane bending “IPB”, out-of-plane bending “OPB” and a combined loading COM, aiming to predict the concentrations of stresses around the weld bead area. The results obtained show that for the three types of loadings AX, OPB and COM; the maximum stresses are located at saddle point However, for IPB loading they are located in a position between the two crown and saddle points. A parametric study was also performed to analyze the effect of the dimensionless geometric parameters α, , , β, . The results of SCf are validated by the parametric equations.