Research Papers: Materials and Fabrication

On the Effectiveness of Composites for Repair of Pipelines Under Various Combined Loading Conditions: A Computational Approach Using the Cohesive Zone Method

[+] Author and Article Information
Shahin Shadlou

Department of Mechanical Engineering,
Dalhousie University,
1360 Barrington Street,
P.O. Box 15,000,
Halifax, NS B3H 4R2, Canada

Farid Taheri

Department of Mechanical Engineering,
Dalhousie University,
1360 Barrington Street,
P.O. Box 15,000,
Halifax, NS B3H 4R2, Canada
e-mail: farid.taheri@dal.ca

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received July 23, 2014; final manuscript received October 20, 2016; published online January 11, 2017. Editor: Young W. Kwon.

J. Pressure Vessel Technol 139(2), 021405 (Jan 11, 2017) (7 pages) Paper No: PVT-14-1110; doi: 10.1115/1.4035081 History: Received July 23, 2014; Revised October 20, 2016

ASTM PCC-2 standard provides a series of equations for establishing the composite repair's thickness required for bringing the capacity of dented/damaged pipes, to their original design state. However, the accuracy of the equations' predictions for pipes subjected to various combined loadings has not been fully explored. Moreover, the influence of the state of a pipe/composite wrap (CW) interface (i.e., whether perfectly intact or not intact), in reference to the predictions of the ASTM equations, has not been studied either. In consideration of the above-mentioned issues, a comprehensive finite-element (FE) study is conducted, using the cohesive zone methodology (CZM) to simulate the response of pipes repaired with composite wraps, under single and various combined loading conditions. Moreover, the influence of perfect (or tied) and imperfect (unintact) pipe/CW interface on the load-bearing capacity of repaired pipes is systematically investigated. Finally, the effects of composite repairs' thickness and length on their efficacy are also investigated. The results show that, although the pipe/CW interface state does not have any noticeable effect when the pipe is subjected to a combined loading state of bending moment and internal pressure, it plays a crucial role when the pipe is under a combined internal pressure and uniaxial loading condition. Furthermore, the predicted values calculated according to the ASME standard are compared with the finite-element results, demonstrating that ASTM-based predictions do not provide accurate results when a repaired pipe is subjected to an axial loading condition.

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Fig. 1

A typical FE mesh used in the study

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Fig. 2

A bilinear traction–separation response

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Fig. 3

The FE results with perfect pipe/CW interface and comparison of the FE results with the ASME standard's predictions for pipes subjected to (a) no internal pressure, (b) 5 MPa, (c) 10 MPa, (d) 15 MPa, and (e) 20 MPa of internal pressure, respectively

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Fig. 4

Normalized axial force causing the failure of pipe/CW interface—pipes with internal pressure of 5 MPa are shown with P5 and pipes with no internal pressure are shown with P0

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Fig. 5

Transition of pipe radial expansion due to the internal pressure going from the wrapped (on right) to unwrapped regions (on the left)—deformation scale factor = 2

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Fig. 6

Comparison of the normalized axial failure load for pipes with fully intact and completely nonintact pipe/CW interface, subject to combined internal pressure and axial loads (CW thickness = 10 mm)

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Fig. 7

The ultimate bending moment causing the failure of pipe/CW interface as a function of the CW thickness. Pipe is also subjected to 5 MPa of internal pressure.

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Fig. 8

The ultimate bending moment capacity of pipes reinforced with various thicknesses of CW with intact and imperfect pipe/CW interfaces (pipes are simultaneously pressurized with 5 MPa of internal pressure)

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Fig. 9

Comparison of pipes' ultimate bending moment capacity with fully intact and imperfect (nonintact) pipe/CW interfaces reinforced with various composite lengths (pipes are simultaneously pressurized with 5 MPa of internal pressure)




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