Local joint flexibility of completely overlapped tubular joints under out-of-plane bending

Parametric equations are proposed to predict the local joint flexibility (LJF) of completely overlapped tubular joints under lap brace out-of-plane bending (OPB). MARC, a general finite element (FE) package, is adopted to simulate the joint behavior with 8-node thick shell element. The FE model is calibrated and verified with existing database of both completely overlapped tubular joints and T/Y-joints. Using the verified FE models, a comprehensive parametric study is subsequently conducted to explore how each selected non-dimensional parameter affects local joint flexibility coefficient (f_LJF) and mechanism is given based on a simplified mechanical model. According to the findings from parametric study, significant design recommendations are put forward to reduce the LJF of the joint. A set of parametric equations is proposed based on the regression database of 5184 FE models and have been assessed against the acceptance criteria of Fatigue Guidance Review Panel. Finally, the comparison of f_LJF calculated by the proposed equations and existing T/Y-joint equations indicates that it is excessively conservative to use T/Y-joint equations directly to predict LJF of completely overlapped tubular joints.