Experimental and numerical SCF studies of multiplanar tubular XX-joint

A typical large-scale steel multiplanar tubular XX-joint specimen was teste d with its in-plane and out-of-plane braces subjected to a total of 12 diff erent load cases including the basic axial loads and axial load combined wi th the in-plane-bending or out-of-plane-bending moment. The stress concentr ation factors (SCFs), strain concentration factors (SNCFs), and the SCF to SNCF ratio (S/N ratio) at the potential hot spot stress locations were inve stigated. An average S/N ratio of 1.14 was obtained experimentally. The spe cimen was simulated using the finite-element method, and good agreement bet ween the numerical and experimental SCF results was obtained. The test SCFs were also compared with those derived using the American Petroleum Institu te equations, Romeijn's XX-joint equations, and the uniplanar joint solutio ns with the Efthymiou's influence function. Results showed that the America n Petroleum Institute equations always underpredict the maximum SCFs while the other two methods always overpredict the SCFs. Further comparison study was conducted to have a better understanding of the influence of the multi planar effects on the SCF of such a joint.