Mixed-Mode Stress-Intensity Factor Solutions for Offshore Structural Tubular Joints

Accurate calculations of the stress-intensity factors (K) are essential for assessment of the integrity of structural components containing crack-like defects. For the complex tubular joints used in the construction of offshore structures, accurate K solutions do not exist. Only limited results using empirically derived K values are available in the literature. This paper presents a methodology for the mixed-mode K solutions for a surface crack at the weld toe of tubular joints. Example solutions were developed for tubular X-joints under brace tension and in-plane bending using three-dimensional finite-element analyses. The complex finite-element mesh was generated using a special mesh generator. The K values were obtained from the displacement solutions of quarter-point crack-tip elements. The results demonstrate the validity of the solution scheme and contribute to the understanding of the crack-tip behavior of tubular joints.