Strength of Multiplanar Tubular KK-Joints under Antisymmetrical Axial Loading

Abstract

A parametric study is presented of the ultimate strength of multiplanar KK-joints in circular hollow sections, which are commonly found in both onshore and offshore structures. The study was carried out using a well-calibrated and validated finite-element model, and the joints were subjected to antisymmetrical axial loading. In all, 40 joints were analyzed to investigate the effect of the various geometric parameters on static strength. Those joints that failed by chord bending can be divided into two groups: one with cracking occurring in the transverse gap region and the other with cracking occurring in the longitudinal gap region. This finding is in accord with experimental evidence from previous research. The finite-element data and the existing test and numerical data form a database on which multiple regression analysis was carried out. Two sets of strength equations were developed from the regression analysis: one provides correction functions that can be applied to an existing planar K-joint equation and the other relates the nondimensional strength directly to the geometric parameters. Both sets of equations were found to provide strength predictions to a very high degree of accuracy.