Failure assessment of cracked uni-planar square hollow section T-, Y- and K-joints using the new BS 7910:2013+A1:2015

Vipin Sukumara Pillai,Athanasios Kolios,Seng Tjhen Lie

doi:10.1007/s00419-018-1423-5

Vipin Sukumara Pillai, Athanasios Kolios + Show 1 more

Open Access

https://doi.org/10.1007/s00419-018-1423-5

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Abstract

This paper covers the validation of standard safety assessment procedure in the new BS 7910:2013+A1:2015 for cracked uni-planar square hollow section (SHS) T-, Y- and K-joints using the finite element analyses. The procedure is based on the failure assessment diagram (FAD) method. A completely new and robust finite element mesh generator is developed, and it is validated using the full-scale experimental test results. FAD curves are constructed using the elastic J-integral (J_{mathrm{e}}), the elastic-plastic J-integral (J_{mathrm{ep}}) and the plastic collapse load (P_{mathrm{c}}) values calculated using the 3D cracked models of the joints. The results reveal that the standard Option 1 FAD curve of the new BS code is not always safe in assessing the safety and integrity of cracked uni-planar SHS joints. Therefore, a penalty factor of 1.2 for plastic collapse load is recommended to move all the constructed Option 3 FAD curves above the standard Option 1 curve. The new Option 3 FAD curves are found to generate optimal solutions for cracked uni-planar SHS T-, Y- and K-joints.

Highlights

Several assessment methods based on fracture mechanics have been developed during the last 40 years
Option 3 failure assessment diagram (FAD) curves are constructed for cracked uni-planar square hollow section (SHS) T, Y- and K-joints to validate the standard Option 1 curve of BS 7910:2013+A1:2015 [2] and to recommend optimal solutions that can safely be used to assess cracked uni-planar SHS T, Y- and K-joints
In order to assist in safety assessment of cracked uni-planar square hollow section (SHS) welded joints, the current study develops an entirely new and robust finite element (FE) mesh generator

Summary

Introduction

Several assessment methods based on fracture mechanics have been developed during the last 40 years. The basis of the FAD approach was originally developed by Dowling and Townley [1] According to this approach, a structure can fail by either of two mechanisms, namely brittle fracture and plastic collapse. The final assessment procedure is quite straightforward, i.e. if the relative position of the point is inside the FAD curve, the structure is considered to be safe. Option 1 is intended for general applications and is independent of the structural geometry and the material stress–strain curve. It was developed from extensive experimental databases of laboratory specimens [4]. In Option 3 assessments, FAD curves are constructed based on the detailed information of stress–strain curves of the materials. Option 3 FAD curves are constructed for cracked uni-planar SHS T-, Y- and K-joints to validate the standard Option 1 curve of BS 7910:2013+A1:2015 [2] and to recommend optimal solutions that can safely be used to assess cracked uni-planar SHS T-, Y- and K-joints

New finite element mesh generator and validation

FADs of cracked uni-planar SHS joints

Conclusions