STRESS CONCENTRATION FACTORS OF TUBULAR KK-JOINTS UNDER BALANCED AXIAL LOADING

摘要

The stress concentration factors (SCF) of tubular KK-joints are numerically investigated under balanced axial loading in this study. More than 30 finite element (FE)models of the joint have been created for the parametric study. In the analysis,quadratic brick element is suitable for modelling tubular KK-joints as such element can provide reasonably accurate modelling of the weld which has remarkable effect on the hot spot stress (HSS). As the HSS is critical for determining the fatigue life of tubular joints, the method of modelling the joint is also very important in the design of offshore tubular structures. The concept of dividing the tubular joint into different zones of mesh will increase the efficiency during modelling. For the parametric study,the stress concentrations on the chord of the joint can be reduced remarkably by reducing the brace thickness, increasing the chord thickness and decreasing the intersecting angle between the brace and the chord. Accordingly, it is effective to increase the brace diameter and reduce the intersecting angle between the brace and the chord to reduce the stress concentrations on the brace of the joint. From the stress distribution analysis along the weld toe, it can be concluded that the maximum SCF occurs at fixed position on the chord and at a position between the crown and the saddle on the brace.