A shell equilibrium modeling for stress distribution of offshore tubular joints

In this study, an optimal shell element modeling approach for tubular joints in ocean engineering was developed utilizing a structural stress analysis. Setting the weld seam thickness of the shell element model to the weld throat size ensured equivalent stiffness between the shell and solid element models. The accuracy of the proposed shell element model was verified by comparing the hot spot stress obtained from the axial loading tests of the three-plane Y-joints carry out by Dalian University of Technology (DUT). The influence of the ratio of chord outer diameter to wall thickness (γ) and the ratio of brace outer diameter to chord outer diameter (β) on stress concentration of K-joints was investigated to evaluate the fatigue performance. The results revealed that for K-joints where the chord is in tension, the β should be as close to 0.5 as possible and should minimize the γ to reduce the stress concentration. For the brace of K-joints under tension, as β and γ increases, the location of fatigue crack initiation transitions from the lower weld toe to the upper weld toe. The β should be avoided around 0.5 and the γ should be as small as possible to minimize the stress concentration.