Geometrical effects on the degree of bending in tubular YT-joints of jacket foundations for offshore wind turbines subject to in-plane bending loads

• Effects of geometrical parameters on the degree of bending (DoB) for tubular YT-joints were investigated. • In-plane bending (IPB) moment loading was considered for parametric study. • Extensive stress analyses were carried out on 81 FE models to extract the DoB at crown, toe, and heel positions. • Developed FE models were validated against available numerical data and parametric equations. • Four parametric design equations were developed for the calculation of DoB subject to IPB loading. This paper presents a comprehensive finite element (FE) investigation into the degree of bending (DoB) in tubular YT-joints of offshore jacket structures subject to in-plane bending (IPB) loading. A total of 81 FE models, verified against published numerical results and existing parametric formulations, were analysed to quantify the influence of joint geometry on through-thickness stress distribution at the weld toe which is a key factor governing fatigue performance. The effects of key dimensionless geometric parameters were systematically examined, and DoB values were evaluated at four critical weld-toe locations: the heel, toe, inner crown, and outer crown. Based on the resulting FE database, nonlinear regression analyses were conducted to derive four new parametric equations for predicting DoB at these locations. The proposed equations offer an efficient and reliable means of incorporating through-thickness stress effects into fatigue assessment and design of offshore jacket structures, thereby improving the accuracy of fatigue life predictions.