Experimental and Numerical SCF Studies of Multiplanar Tubular XX-Joint

Abstract

A typical large-scale steel multiplanar tubular XX-joint specimen was tested with its in-plane and out-of-plane braces subjected to a total of 12 different load cases including the basic axial loads and axial load combined with the in-plane-bending or out-of-plane-bending moment. The stress concentration factors (SCFs), strain concentration factors (SNCFs), and the SCF to SNCF ratio (S/N ratio) at the potential hot spot stress locations were investigated. An average S/N ratio of 1.14 was obtained experimentally. The specimen was simulated using the finite-element method, and good agreement between the numerical and experimental SCF results was obtained. The test SCFs were also compared with those derived using the American Petroleum Institute equations, Romeijn's XX-joint equations, and the uniplanar joint solutions with the Efthymiou's influence function. Results showed that the American 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 multiplanar effects on the SCF of such a joint.