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Research Papers: Piper and Riser Technology

Improvements on the Numerical Analysis of the Coupled Extensional–Torsional Response of a Flexible Pipe

[+] Author and Article Information
Héctor E. M. Muñoz

Department of Civil Engineering,
Centro de Tecnologia,
COPPE/UFRJ,
Cidade Universitária,
Bloco I2000, Sala I116,
Ilha do Fundão,
Rio de Janeiro,
Brazil, CEP 21945-970
e-mail: hmerino147@gmail.com

José R. M. de Sousa

Department of Civil Engineering,
Centro de Tecnologia,
COPPE/UFRJ,
Cidade Universitária,
Prédio Anexo do CT, LACEO, 1° andar
Bloco I2000, Sala I116,
Ilha do Fundão,
Rio de Janeiro,
Brazil, CEP 2941-596

Carlos Magluta, Ney Roitman

Department of Civil Engineering,
Centro de Tecnologia,
COPPE/UFRJ,
Cidade Universitária,
Bloco I2000, Sala I116,
Ilha do Fundão,
Rio de Janeiro,
Brazil, CEP 21945-970

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received November 27, 2011; final manuscript received November 13, 2015; published online December 11, 2015. Assoc. Editor: Myung Hyun Kim.

J. Offshore Mech. Arct. Eng 138(1), 011701 (Dec 11, 2015) (13 pages) Paper No: OMAE-11-1106; doi: 10.1115/1.4032036 History: Received November 27, 2011; Revised November 13, 2015

In this paper, the coupled extensional–torsional behavior of a 4 in. flexible pipe is studied. The pipe is subjected to pure tension and two different boundary conditions are considered: ends free and prevented from axially rotating. The response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model. Some aspects of the obtained results are discussed, such as the effect of restraining the axial rotation at the extreme sections of the model; the effect of friction or adhesion between the layers of the pipe on the induced axial rotation (or torque) and elongation; and the reduction to simple plane behavior usually assumed by analytical models. The numerical results are compared to the ones measured in experimental tests. Reasonable agreement is observed between all results pointing out that the analyzed pipe is torque balanced and that friction mainly affects the axial twist induced by the applied tension. Moreover, the cross sections of the pipe remain straight with the imposed load, but different axial rotations are found in each layer.

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References

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Figures

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Fig. 1

Typical unbounded flexible pipe

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Fig. 2

Isometric view of the numerical model

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Fig. 3

Coordinate systems

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Fig. 4

Schematic representation of the normal stiffness of contact elements

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Fig. 5

View of the metallic frame

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Fig. 6

General view of the experimental apparatus

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Fig. 7

Load cells: (a) tension and (b) torsion

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Fig. 8

Detail of the displacement transducer 1

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Fig. 9

Inclinometers (a) 01 and (b) 02

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Fig. 10

Inductive sensors

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Fig. 11

Boundary conditions at an end of the flexible pipe (axial rotation free and imposed axial force)

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Fig. 12

Axial displacement distribution, in mm, along the flexible pipe: tensile load of 450 kN

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Fig. 13

Axial translations in each layer and cross section of the pipe: end free to rotate

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Fig. 14

Axial rotations in each layer and cross section of the pipe: end free to rotate

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Fig. 15

Axial rotations in each layer and cross section of the pipe: ends prevented from rotating

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Fig. 16

Axial deformation versus applied tension: end free to rotate

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Fig. 17

Axial deformation versus applied tension: ends prevented from rotating

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Fig. 18

Axial deformation versus axial rotation: end free to rotate

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Fig. 19

Axial deformation versus torque: ends prevented from rotating

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Fig. 20

Axial deformation versus radial displacement: end free to rotate

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Fig. 21

Axial deformation versus radial displacement: ends prevented from rotating

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