Etude numérique et expérimentale des jonctions tubulaires soudées "des plateformes offshore" soumises à des sollicitations complexes : analyse par contrôle non destructif

Abstract : In building offshore platforms, tubular members are used because of their good structural and mechanical properties. Tubular members are connected to one another by special welded joints, which represent structural discontinuities causing significant stress concentrations in the vicinity of the weld. For some joints, the stress concentration can produce a maximum stress at the intersection as high as thirty times the nominal stress acting in the members. Under repead loading, fatigue failures always initiate at the areas, which referred to as "hot-spot" where there are high-level stress concentrations, which called "hot spot stress (HSS)". For this reason, accurate computation of stress concentration is very important in tubular joints design. The first part of this study was devoted to the determination of the stress distributions in the cicinity of joint intersection and to the localization of the zones of stress concentration. With this intention, a modeling by finite elements of twelve types of welded joints commoly employed in offshore industry was established. The loading undergone in service leads to platform displacements in all directions, which takes change of wind direction into account, for this reason combined loading was investigated in addition to the three simple loading types (axial(AX), In Plane Bending(IPB) and Out of Plane Bending (OPB). This combined loading is composed of an axial loading (tension or compression) combined with a continuation of combined bending (rotational bending loading). In second part of this work, the fatigue behaviour of T-joint subjected to a rotational bending loading was investigated. Prior to fatigue testing, tow specimens were instrumented with strain gauges to allow for the measurment of hot spot stress in both the brace and the chord, and results obtained were compared with a detailed numerical study of T-joint to validate the numerical modelling results
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Mohamad Fathi Ghanameh. Etude numérique et expérimentale des jonctions tubulaires soudées "des plateformes offshore" soumises à des sollicitations complexes : analyse par contrôle non destructif. Autre. Université Paul Verlaine - Metz, 2007. Français. ⟨NNT : 2007METZ001S⟩. ⟨tel-01748958⟩

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