Effects of geometrical parameters on the degree of bending in two-planar tubular DYT-joints of offshore jacket structures

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. This stress distribution can be characterized by the degree of bending (DoB). Although multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity usually has a considerable effect on the DoB values at the brace-to -chord intersection, few investigations have been reported on the DoB in multi-planar joints due to the complexity of the problem and high cost involved. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified based on available parametric equations, was used to study the effects of geometrical parameters on the DoB values in two-planar tubular DYT-joints. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.

Automated summary

The through-the-thickness stress distribution in a tubular member has a significant impact on the fatigue behavior of tubular joints in steel offshore structures, which can be characterized by the degree of bending (DoB). However, there have been few investigations on the DoB in multi-planar joints due to the complexity and high cost involved. This study utilizes data from stress analysis of finite element models to develop new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.