Safety assessment of cracked tubular Y-joints using failure assessment diagram (FAD) method

Abstract

This report covers the Failure Assessment Diagram (FAD) analysis of cracked circular hollow section (CHS) Y-joints according to British Standard BS 7910 FAD level 3C assessment criteria.Firstly, 3D mesh models of the CHS Y-joins ware generated with a surface crack of specific

depth and length. Axial tension loading and in-plan bending moment were applied to the brace end of the models and the relationship between the load and the displacement was obtained in the form of load displacement curve. Secondly, Plastic collapse loading (Pc) was then obtained by using two-elastic criteria to locate the intersection on the load displacement curve, and J-integrals of elastic and elastic-plastic were calculated using VCCT technique by ABAQUS software. Finally, FAD curves of all analyzed cracked Y-joints were constructed. It was found that the new mesh generating approach is effective and yield relative accurate results, and some parts of the constructed FAD curves fell inside the standard Level 2A FAD curve for some cracked RHS joints, which means that the evaluation results using standard Level 2A FAD curve might be unsafe.