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Research Papers: Piper and Riser Technology

Simplified Finite Element Models to Study the Dry Collapse of Straight and Curved Flexible Pipes

[+] Author and Article Information
Alfredo Gay Neto

Department of Structural and
Geotechnical Engineering,
University of São Paulo,
São Paulo, SP 05508-010, Brazil
email: alfredo.gay@usp.br

Clóvis de Arruda Martins

Department of Mechanical Engineering,
University of São Paulo,
São Paulo, SP 05508-010, Brazil

Eduardo Ribeiro Malta

Department of Naval Architecture and
Ocean Engineering,
University of São Paulo,
São Paulo, SP 05508-010, Brazil

Rafael Loureiro Tanaka, Carlos Alberto Ferreira Godinho

Prysmian Cables and Systems,
Santo André, SP 09110-900, Brazil

1Corresponding author.

2Annulus is the region of the flexible pipe located between internal and external polymeric layers.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received January 5, 2015; final manuscript received November 13, 2015; published online January 21, 2016. Assoc. Editor: Myung Hyun Kim.

J. Offshore Mech. Arct. Eng 138(2), 021701 (Jan 21, 2016) (9 pages) Paper No: OMAE-15-1002; doi: 10.1115/1.4032156 History: Received January 05, 2015; Revised November 13, 2015

Dry collapse is one of the possible failure modes of flexible pipes. It refers to the situation in which no damage occurs in the flexible pipe external sheath. In this scenario, all layers of the pipe withstand the external pressure loading in a deep-water application. Such a situation is addressed in this work, which proposes some simplified modeling techniques to represent straight and curved flexible pipes subjected to external pressure, undergoing dry collapse during simulation procedure. The results of the proposed models are compared to other reference results, from a fully three-dimensional (3D) finite element model. Good agreement has been got, even with the proposed simplifications with a large reduction in computational cost when compared to full 3D model.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Geometry description example of the full model

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Fig. 2

Internal polymeric layer material curve. Adapted from Ref. [6].

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Fig. 3

External polymeric layer material curve. Adapted from Ref. [6].

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Fig. 4

Some contact regions of the pressure armor and external polymeric layer

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Fig. 5

Boundary conditions of the model: A and B pilot nodes

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Fig. 6

Geometry of model A. From inside to outside of the pipe: the carcass layer (as an equivalent ring), the internal polymeric layer, the pressure armor layer, and the external polymeric layer. (a) xz view and (b) xy view.

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Fig. 7

Center of curvature C of model A (exaggerated curvature with small r presenting overlapping of pressure armor profiles)

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Fig. 8

A mesh example of the dry collapse model with 71,163 nodes: (a) whole view and (b) detailed view

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Fig. 9

Expansion view of the mesh showing the flexible pipe curvature

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Fig. 10

Contact regions considered

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Fig. 11

External pressure loading

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Fig. 12

Displacement couplings to establish the desired kinematics of infinite pitches geometry

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Fig. 13

Different integration areas in which the external pressure acts in a curved flexible pipe, presenting a non-null resultant R

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Fig. 14

Boundary conditions “CC1”

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Fig. 15

Boundary conditions “CC2”

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Fig. 16

Boundary conditions “CC3”

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Fig. 17

Model B mesh example (1788 nodes and 720 elements)

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Fig. 18

API ovalization versus external pressure for the 2.5 in. flexible pipe.

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Fig. 19

API ovalization versus external pressure for the 4.0 in. flexible pipe.

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Fig. 20

API ovalization versus external pressure for the 2.5 in. flexible pipe. Comparison between models.

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Fig. 21

API ovalization versus external pressure for the 4.0 in. flexible pipe. Comparison between models.

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