Comparison on Stress Concentration Factors of Y/T Tubular Joints between Numerical and Parametric Formulation Results

The action of environmental loads such as wind and waves on offshore steel structures is locally emphasized by complex tubular connections, giving place to high stress concentration in correspondence of welds between pipe elements. This phenomenon, which heavily influences the fatigue life of the joint and, as a consequence, the operability of the whole platform, can be quantified by the Stress Concentration Factor. SCF can be determined either by experimental approach, numerical analysis and parametrical formulas developed mainly in the seventies-eighties by specialized authors like Kuang, Wordsworth, Smedley and Efthymiou. Even though these formulas, quoted as reference in the main world recognized rules, represented for a long time a useful tool for the designers of most projects, some discrepancies have been found to exist among them. A research has then been jointly promoted by University of Genoa and RINA Industry in order to compare the results of the parametric formulas with those coming from a finite element analysis performed on very refined numerical models made of brick elements. In this investigation attention has been focused on Y/T type joints; a wide range of configurations has been analysed by varying the most important parameters defining the geometry of the joint. Each configuration has been loaded by axial force and in/out of plane bending moment.