Parametric equations to predict stress distributions along the intersection of tubular X and DT-joints

Accurate information on stress distributions along the intersection is required for fatigue strength assessment of tubular joints. However, there is no parametric equation currently available in the open literature to predict this information for tubular X and DT-joints. Systematic thin shell finite element (FE) analyses have been conducted for 330 different tubular X and DT-joints, typical of those used in offshore structures, subjected to six different modes of loading. A novel two dimensional regression methodology was developed to curve-fit all of the FE results from this work. A set of parametric equations was derived to predict the stress distributions along both chord and brace toes in tubular X and DT-joints under each mode of loading. These equations were assessed by comparing the predictions with available experimental data. Validation results show that they can be used to predict stress concentration factor (SCF) distributions along the intersection but also provide an alternative method for calculation of hot spot SCF.