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CivilComp Proceedings
ISSN 17593433 CCP: 88
PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and M. Papadrakakis
Paper 158
Structural Analysis of Corroded Pipelines Containing Complex Defects R.D. Machado, J.E. Abdalla F. and H.Y. Shang
Mechanical Engineering, Pontificia Catholic University of Paraná (PUCPR), Curitiba, Brazil R.D. Machado, J.E. Abdalla F., H.Y. Shang, "Structural Analysis of Corroded Pipelines Containing Complex Defects", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", CivilComp Press, Stirlingshire, UK, Paper 158, 2008. doi:10.4203/ccp.88.158
Keywords: pipes, corrosion, structural integrity, complex defects, remaining strength, failure pressure, semiempirical methods.
Summary
This paper considers the prediction of the limit load and remaining strength of
pipelines under complex corrosion defects. Semiempirical methods for isolated
defects such as B31G [1], modified B31G [2], RSTRENG and the DNV RPF101
method [3] are reviewed. Numerical models employing the finite element method
both with shell elements and 3D solid elements are constructed, and numerical
results are compared to those obtained using semiempirical methods. Nonlinear
analyses are carried out to represent the constitutive behaviour of materials.
Pipes containing isolated defects with different geometric parameters are analyzed and the results are compared with experimental results provided by Choi et al. [4]. Results show that values provided by finite element models are more accurate than the results provided by the semiempirical methods. The weighted depth difference method (WDD) [5] for predicting the failure pressure of complex corrosion defects is also presented. This method considers an irregular profile of the corrosion defect instead of a smooth lower surface as the other methods do. The influence of multiple defects is treated and some examples illustrate the interference of two close defects. First pipes containing three longitudinally aligned rectangular defects are analyzed. It is seen that both numerical models; namely, shell elements model and threedimensional solid elements model provide results which are very close. The influence of the distance between the defects is also investigated in the sense that there must be a distance for which defects may be considered as isolated. It is found that such a distance must be twenty four times the value of the thickness of the pipe walls. An attempt to determine the effectiveness of the WDD method is made by comparing the results provided by the WDD method to results provided the threedimensional solid finite element analyses. No pattern has been found. The results are problemdependent. Finally, pipes with three circumferential defects with different angular distances between them in the same crosssection have been considered. It is found that the influence between defects is minimized when the angular distance is 70°. References
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