Numerical study of multiplanar tubular DX-joints subject to axial loads

In this paper, 20 multiplanar DX-joints (double X) with in-plane braces and out-of-plane braces subjected to various combination of axial loads were analysed. The multiplanar effect of loaded and unloaded out-of-plane braces and the load-interaction of multiplanar DX-joints were investigated. The influence of geometric parameters on the stress concentration factors of the joints was also studied. The results obtained from the analyses of multiplanar DX-joints are compared with those of the corresponding uniplanar X-joints. It is found that, when the out-of-plane braces are not loaded, the multiplanar effect is not significant when the brace diameter is much smaller than the chord diameter. When the out-of-plane braces are loaded, the hot spot stresses are found to be lower or higher than the values predicted based on uniplanar joints. The deviation can be as much as 87% or 94%, respectively, depending on the combination of the load conditions and geometrical parameters.