The effect of multi-planarity on the SCFs in offshore tubular KT-joints subjected to in-plane and out-of-plane bending loads

• The SCFs in two- and three-planar tubular KT-joints under IPB and OPB loads were investigated.
• For the numerical study, a FE model was developed and verified against experimental data.
• The intensities of multi-planarity effect in considered load cases were compared.
• A large number of FE models were generated to study the geometrical effects on the SCFs.
• A new SCF parametric equation was developed for OPB-loaded three-planar KT-joints.

The majority of tubular joints commonly found in offshore practice are multi-planar. Investigating the effect of loaded out-of-plane braces on the values of the stress concentration factor (SCF) in offshore tubular joints has been the objective of numerous research works. However, due to the diversity of joint types and loading conditions, a number of quite important cases still exist that have not been studied thoroughly. Among them are multi-planar KT-joints subjected to bending loads. In the present research, results extracted from the stress analysis of finite element models, verified against available experimental data, were used to study the chord-side SCFs in two- and three-planar tubular KT-joints subjected to in-plane and out-of-plane bending loads. A geometrically parametric investigation was conducted and then followed by a set of nonlinear regression analyses to derive a SCF parametric equation for the fatigue analysis and design.