EXPERIMENTAL STUDY OF STRESS CONCENTRATION FACTORS (SCFs) OF A COMPLETELY OVERLAPPED CHS K-JOINT

摘要

Fatigue failure of welded tubular joints used in offshore structures is mainly due to a stress concentration at the weld toe. For a completely overlapped K-joint, one brace called the lap brace is completely welded onto another brace called the through brace. Since the loads are transferred predominantly between the braces, the punching shear stresses on the chord wall can be reduced significantly. Because of easy fabrication and better static strength than a simple gap and partially overlapped K-joint, this type of joints has been gradually accepted in practice. However, the fatigue study of a completely overlapped K-joint has not been reported extensively in the literature. In this study, the stress concentration factors (SCFs) of a completely overlapped CHS K-joint are studied experimentally. A full-scale specimen was tested to investigate the strain and stress distributions along the joint intersections of the chord and the through brace as well as the through brace and the lap brace. The details include the test rig, loading conditions and data analysis. The load cases applied at the lap brace are axial (AX), in-plane bending (IPB), out-of-plane bending(OPB) and a combination of these loadings. For basic loadings, SCFs along weld toes and the corresponding locations of the peak SCF values of the specimen were obtained accordingly. Furthermore, stress distributions along the intersections of the specimen under combined loads were obtained and compared with the calculated results using the superposition method. It is found that the experimental study could produce the stress and SCF distributions of a completely overlapped K-joint reasonably well.