The support structure for an offshore wind turbine is subjected to combined hydrodynamic loads and aerodynamic loads. The tubular joints are the weakest component leading to fatigue failure of the whole structure. Based on the multi-pile foundation structure which is used widely in China, the typical threeplanar tubular Y-joints is selected to study stress concentration factor (SCF). Then, the load types subjected to axial loadings of three-planar tubular Y-joints are determined. The finite

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... ent models of three-planar tubular Y-joints are established and used to calculate hot spot stresses. The stress concentration factors along the weld of the three-planar tubular Y-joints under the axial forces are obtained. The effects of geometrical parameters on SCFs are studied.