Design Equation for Offshore Overlap Tubular K-Joints under In-Plane Bending

Abstract

Overlap tubular K-joints are generally regarded as having higher axial strength than similar simple gap K-joints due to their more direct load transfer between braces. Due to congestion at the nodes in steel jackets, overlap K-joints are used as key structural elements in many existing offshore platforms. However, relatively little experimental research has been done to quantify their strength and this has prevented engineers from taking full advantage of overlapping in the design of new structures as well as in the life extension assessment of existing platforms. This paper presents the results of a numerical study on gap and overlap K-joints under in-plane bending. The parametric study reveals new insight into how the behavior and strength varies across the practical range of geometrical parameters. Based on the finite element strength database, a capacity equation has been derived and presented herein using nonlinear regression analysis techniques.