Prediction of stress concentrations and degrees of bending in axially loaded tubular K-joints

An extensive database of stress concentrations and degree of bending in tubular K-joints under balanced axial loading, generated recently in a finite element parametric study, has been used to develop parametric equations. The study covers a comprehensive range of geometric joint parameters which are commonly found in offshore structures. This database of thin shell finite element results was used to develop parametric equations for estimating stress concentration factors and the degree of bending at key locations on both the chord and brace. Formulae for the stress distributions around the intersection of K-joints were also derived using the parametric equations at key locations as input parameters, thus allowing the stress distributions to be predicted from the geometric joint parameters. Fracture mechanics fatigue calculations were performed to demonstrate that the information provided from the proposed equations could be used to obtain safe estimates of fatigue lives of tubular K-joints.