Numerical Study on Stress Concentration Factors at Splice Welds of Structural Steel Pipes

Structural steel tubular elements are widely used in offshore structures, such as for marine piles, risers, and jacket bracings. Transversal weld is a common form for the splice of the structural steel pipes. The stress concentration at the splice weld is a critical effect to be considered in the structural analysis and design of the steel tubular elements. Researchers have provided solutions to the stress concentration factors (SCFs) for the splice welds under axial loading. Using finite element software ANSYS, this paper investigated the stress concentration due to in-plane bending moment. Various geometric configurations, such as diameter and thickness, determined according to normal marine steel tubular piles were modeled in the numerical models, and typical V-shape welding forms were adopted. Particularly, different thickness transitions applied in practice were modeled. Hot-spot stresses were determined based on the two-point linear extrapolation recommended by DNV-RP-C203. The stress concentrations at both toe and root were investigated. In addition, approximate solutions to the SCFs were derived based on flat-plate assumption. The computational results showed that the flat-plate solutions agreed with numerical solution in a reasonable manner, and correction factors were accordingly developed for the approximate solutions. It was also found that pipe thickness and thickness transition demonstrated significant impacts on the SCFs, while pipe diameter seemed less important. The numerical study establishes a fundamental database for the SCFs at pipe splice given in-plane bending moment. The findings will significantly support the practical fatigue assessment of spliced marine structural steel pipes subjected to complex loading effects.