The Effect of Geometrical Imperfection of the Brace Member on Stress Concentration Factors in Tubular T-Joints of Jacket-Type Platforms under Axial Loading

Abstract

Brace and chord members of a tubular joint always have a degree of geometrical imperfection due to the manufacturing, transportation and installation processes and also the action of various loads during the lifetime of the structure. However, during the analysis and design of tubular joints, geometrical imperfection is not usually taken into account. Considering the geometrical imperfection in the analysis of a tubular joint, can lead to a more realistic prediction of the fatigue life. In this paper, the effect of geometrical imperfection of the brace member and dimensionless geometrical parameters on the stress distribution in tubular T-joints under axial loading is studied. The stress concentration factors (SCF) is used to investigate the stress distribution. The research is focused on the SCF values at the saddle, crown 0˚ and crown 180˚ positions. After the numerical modeling of the considered tubular joints using FEM-based software package ANSYS, verification of the FE models by experimental data, and the extraction of SCFs, a set of parametric equations is presented to calculate the SCFs at the saddle, crown 0˚ and crown 180˚ positions. The results show that the in-plane geometrical imperfection of the brace member can change the SCFs at the crown 0˚ and crown 180˚ positions, but does not have a considerable effect on SCF values at the saddle position.

Keywords

• geometrical imperfection
• stress concentration factors
• jacket-type platform
• tubular t-joint
• saddle and crown positions