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Bending tests and cross-sectional analyses of multilayered flexible pipe models

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Abstract

Simplified models of multilayered unbonded flexible pipes for offshore applications were manufactured and put to a series of bending tests where biaxial bending strains of tensile armor wires were directly measured. Focusing on the effects of constraint on the tensile armor wires by outer layers on the bending stiffness of the pipe and the bending stresses of tensile armor wires, four types of pipe models with different specifications of holding bandages, which hold the tensile armor layers from the outside, were prepared. Cross-sectional analyses based on four kinds of methods were also carried out and comparatively examined with the above bending test results, and the applicability of each method was evaluated. As a result, it was found that the normal and binormal bending stresses of the tensile armor wires in the slip region remarkably change depending on the specification of the holding bandages, suggesting that the degree of constraint on the tensile armor wires by the outer layers should be taken into consideration in the cross-sectional analyses.

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Abbreviations

A* :

Bending stiffness of a helical component (N m2)

α :

Helix lay angle of a tensile armor (°)

E s :

Young’s modulus of a helical component (N/m2)

EI:

Bending stiffness of a pipe (kN m2)

ϕ :

Helical position angle of a tensile armor (°)

GJ:

Torsional stiffness of a tensile armor (N m2)

I b :

Moment of inertia of area for binormal bending of a tensile armor (m4)

I n :

Moment of inertia of area for normal bending of a tensile armor (m4)

κ :

Curvature of a pipe (1/m)

M :

Bending moment applied to a pipe (kN m)

m s :

Bending moment applied to a helical component (N m)

v :

Poisson’s ratio of a helical component

R eq :

Equivalent section radius of a helical component (m)

σ normal :

Normal bending stress (MPa)

σ binormal :

Binormal bending stress (MPa)

σ biax :

Biaxial bending stress (MPa)

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Authors and Affiliations

  1. Ocean Engineering Department, National Maritime Research Institute, 6-38-1, Shinkawa, Mitaka, Tokyo, 181-0004, Japan

    Ichihiko Takahashi, Sotaro Masanobu, Shigeo Kanada & Katsuya Maeda

  2. Ocean and Energy Section, Smart Energy Department, Power and System Laboratories, R&D Group, Furukawa Electric Co., Ltd., 6, Yawata-kaigandori, Ichihara, Chiba, 290-8555, Japan

    Hiroki Manabe & Takeharu Yamaguchi

  3. Department of Civil and Environmental Engineering, Faculty of Engineering and Design, Hosei University, 2-33, Ichigayatamachi, Shinjuku, Tokyo, 162-0843, Japan

    Yoshihisa Tanaka

Authors
  1. Ichihiko Takahashi
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  2. Sotaro Masanobu
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  3. Shigeo Kanada
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  4. Katsuya Maeda
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  5. Hiroki Manabe
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  6. Takeharu Yamaguchi
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  7. Yoshihisa Tanaka
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Correspondence to Ichihiko Takahashi.

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Takahashi, I., Masanobu, S., Kanada, S. et al. Bending tests and cross-sectional analyses of multilayered flexible pipe models. J Mar Sci Technol 25, 397–410 (2020). https://doi.org/10.1007/s00773-019-00649-w

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  • DOI: https://doi.org/10.1007/s00773-019-00649-w

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