Study on hot spot stress of three-planar tubular Y-joints under combined axial loads

Abstract Offshore wind turbines (OWT) tripod substructures are widely used in China; their weakest components are three-planar circular hollow section (CHS) tubular Y-joints that can lead to their fatigue failure. In this study, finite element (FE) models are established to calculate the geometric stress distribution along the weld toe of these joints. The multi-planar interaction factor (MIF) is defined to quantify the multi-planar effect. According to the results of the FE models, the stress concentration factors (SCFs) and MIFs along the weld of three-planar tubular Y-joints under an axial load are obtained. After a geometric parameter investigation and numerous nonlinear regression analyses, a set of parametric equations for extreme values of the SCF and MIF is derived. The proposed equations satisfy the acceptance criteria of the UK Department of Energy.