Parametric Study of SCFs in Unstiffened Gap Tubular KT-joints of Offshore Structures under OPB Moment Loading

In this paper, results extracted from a set of stress analyses performed on 46 FE models for unstiffened gap tubular KT-joints are presented and discussed. The main objective of the FE analyses, validated against experimental data, was to run a parametric investigation on the effects of geometrical characteristics of the joint on the values of the stress concentration factors (SCFs). The SCF is a key input parameter in the fatigue analysis and design of tubular joints commonly found in steel offshore structures such as jacket-type and jack-up platforms. Chord-side SCFs of central and outer braces were studied individually under four different types of out-of-plane bending (OPB) moment loads. After investigating the geometrical effects, a set of nonlinear parametric equations were developed for the computation of SCFs. Proposed equations, assessed according to the criteria recommended by the UK Department of Energy, can be reliably used for the fatigue calculations.