Parametric study on SCF distribution along the weld toe of internally ring-stiffened two-planar tubular KK joints under axial loading

Abstract

The internal ring stiffeners have been commonly introduced in tubular joints to improve the ultimate strength and fatigue life of offshore structures. However, for internally ring-stiffened multi-planar tubular joints which are frequently used in practical application, few investigations about stress concentration factor (SCF) in the joints have been reported so far and no parametric equation of the SCF is currently available for fatigue design. In this paper, the effects of geometrical parameters on the SCF distribution along the weld toe of the internally ring-stiffened two-planar tubular KK joints under axial loading are investigated by performing a set of three-dimensional (3D) FE stress analyses. Firstly, based on the requirements of AWS D1.1-2010, an approximate model of the actual weld profile is proposed. Then, several 3D FE models of various tubular joints are established to verify the proposed model. Subsequently, the effects of multi-planarity and stiffeners on the SCF in two-planar tubular KK joints are investigated. Additionally, the influence of geometrical parameters on both the SCF and the SCF distribution of the joints under axial loading is studied. Finally, SCF parametric equations for fatigue design of the internally ring-stiffened two-planar tubular KK joints under axial loading are developed from nonlinear regression analysis.