Parametric FE modeling to predict hot spot stress concentrations of bird-beak SHS joints in offshore structures

Abstract

Bird-beak square hollow section (SHS) joint is a new type of welded tubular joints that could be used in offshore structures. This paper presents a parametric finite element modeling strategy to predict the hot spot stress concentration factors (SCFs) of both diamond and square bird-beak SHS joints. ANSYS parametric design language (APDL) was employed by introducing three typical non-dimensional parameters (i.e., β, 2γ, τ) of SHS joints as main controlling variables, and the novel configurations of crown and saddle areas were accurately simulated during the modeling process. Tetrahedral-shaped solid elements were used so that the refined FE meshes generated from the map meshing match the requirements of extrapolation region that have been specified in IIW and CIDECT fatigue design guides. All extrapolating works were automatically implemented by pre-coded programs. The accuracy of constructed FE models has been validated by comparing with existing experimental data. The SCF variations with non-dimensional parameters were obtained by conducting parametric analysis, and the SCF comparisons between two types of bird-beak joints have been conducted. The proposed modeling approaches are applicable to bird-beak joints of different shapes and to the joints under various load cases and boundary conditions.