Stress Concentration Factor Evaluation of Offshore Tubular KT Joints Based on Analytical and Numerical Solutions: Comparative Study

Abstract

Fatigue damage is treacherous and can lead to the failure of offshore structures. The purpose of this research is to evaluate and discuss the stress concentration factor (SCF) values for two geometries of offshore tubular KT joints using different calculation methods to be used in fatigue design. The work was done by using analytical calculations, formulations from the literature, and numerical solutions, finite-element method (FEM) analysis using commerically available software, supported by international standard recommendations. For the analytical formulations, geometrical parameters were used as defined in standard recommendations. For the numerical model, two different geometries of tubular KT joints are presented where different shell (S4R), solid (C3D8R), and solid with weld (C3D8R) element-type models were built in the software environment. After considering 23 different types of loading conditions, a comparison between the standard SCF and finite-element analysis (FEA) SCF values for the critical load case has been performed. The results have shown that the values of SCF from the standard are more conservative than SCF from FEA. However, FEA SCF values for the solid and solid with weld element types have shown little differences.