Advanced Steel Construction

Vol. 8, No. 1, pp. 17-37 (2012)


ESTIMATION OF STRESS INTENSITY FACTORS IN TUBULAR K-JOINTS USING DIRECT AND INDIRECT METHODS

 

S.T. Lie 1,*, T. Li 2 and Y.B. Shao 3

School of Civil and Environmental Engineering, Nanyang Technological University,

50 Nanyang Avenue, Singapore 639798

Maritime Research Centre, Nanyang Technological University,

50 Nanyang Avenue, Singapore 639798

School of Civil Engineering, Yantai University, Yantai City 264005, P. R. China

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

Received: 9 February 2011; Revised: 15 June 2011; Accepted: 29 June 2011

 

DOI:10.18057/IJASC.2012.8.1.2

 

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ABSTRACT

The stress intensity factors at the deepest point and at the crack ends of a surface crack in a tubular K-joint are calculated by direct and indirect methods. In the direct method, the surface crack is modelled explicitly. An automatic mesh generator is developed to produce a well-graded mesh around the crack region. This is achieved by using five types of elements. Thereafter, the stress intensity factors of a surface crack located anywhere along the weld toe at the joint intersection are calculated using the J-integral method. The computed values had been verified by experimental test results. In the indirect method, the stress intensity factors are estimated by the T-butt solutions used in conjunction with the stress concentration factors (SCFs) and degree of bending (DOB) of the uncracked tubular K-joint. In this study, a total of 1024 models, covering a wide range of geometrical parameters and crack shapes, have been selected and analyzed. Both approaches are able to produce a safe estimation of stress intensity factors at the deepest point of the surface crack. However, the indirect method is found to be extremely conservative; it overestimates the stress intensity factor values by as much as 190.4% (β=0.5, γ=30, τ=0.5, a/T=0.1, c/a=5) at the deepest point, and 390.7% (β=0.4, γ=30, τ=0.5, a/T=0.5, c/a=8) at the crack ends of the surface crack respectively.

 

KEYWORDS

Direct method, Indirect method, J-integral method, Mesh generator, Stress intensity factor, Surface crack, Tubular K-joint


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KEYWORDS

Single layer latticed shell, Refined member calculation model, Member buckling, Plastic hinge, Second order effect, Dynamic damage cause