Chord-side SCF distribution of central brace in internally ring-stiffened tubular KT-joints: A geometrically parametric study

•The SCF distribution in internally ring-stiffened tubular KT-joints was experimentally investigated.•118 FE models were generated for parametric SCF analysis of ring-stiffened KT-joints.•Geometrical effects on the SCF distribution along the central-brace weld toe were studied.•A set of fatigue design equations was established to determine the SCFs.•Significant difference exists between SCFs in stiffened and unstiffened KT-joints.

Although the tubular KT-joints are quite common in offshore structural design and despite the crucial role of stress concentration factors (SCFs) in evaluating the fatigue performance of tubular joints, the SCF distribution in internally ring-stiffened KT-joints has not been investigated so far and no design equation is currently available to determine the chord-side SCFs of central brace in this type of joint. In the present paper, results of experimental and numerical investigations of the chord-side SCF distribution of central brace in internally ring-stiffened tubular KT-joints are presented. In this research program, experimental study has been followed by a set of parametric stress analyses for 118 steel ring-stiffened KT-joints subjected to balanced axial loads. The analysis results are used to present the general remarks on the effect of geometrical parameters on the chord-side SCF distribution along the weld toe of central brace, and to establish a new set of SCF parametric equations, through non-linear regression analysis, for the fatigue design of internally ring-stiffened KT-joints.