Advanced Steel Construction

Vol. 5, No. 4, pp. 406-420 (2009)




S.T. Lie * and Z.M. Yang

School of Civil and Environmental Engineering, Nanyang Technological University

50 Nanyang Avenue, Singapore 639798, Singapore

*(Corresponding author: E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.)

Received: 19 March 2008; Revised: 15 July 2008; Accepted: 28 July 2008




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The failure assessment diagram (FAD) has been widely accepted for assessing the safety and integrity of cracked and damaged metallic structures. Recently, the usage of this method for offshore structures has been validated extensively and included in the Annex B of BS7910 [1]. However, the recommended equations are valid only for uni-planar circular hollow section (CHS) T, Y, K and KT tubular welded joints. In this paper, an actual assessment has been carried out on cracked (CHS) tubular K-joint containing a surface crack located at the crown location. The fatigue crack depths a and lengths 2c vary from 3.30 mm to 20.83 mm and 70.40 mm to 191.78 mm respectively. The value of β, ratio of brace to chord diameter, is 0.52, which is within the validity range specified in the codes of practice. The recommended correction factor FAR, is used to calculate the plastic collapse load Pc, and the usage of BS7910 [1] Level 2A FAD for cracked CHS tubular K-joint is demonstrated accordingly.



Crack; circular hollow section (CHS); failure assessment diagram (FAD); fracture toughness; K-joint; plastic collapse load; stress intensity factor


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