Presentation of a simplified method for the crashworthiness of offshore wind turbine jackets

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Presentation

of a simplified method

for the crashworthiness

of offshore wind turbine jackets

T i m o t h é e P i r e ( U L g , F R I A fe l l o w s h i p )

H e r v é L e S o u r n e ( G e M / I C A M )

L o ï c B u l d g e n ( U L g )

P h i l i p p e R i g o ( U L g )

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Context

• More and larger wind farms

• Closer to traffic lanes

(passengers and commercials)

• Need of maintenance

Collision risk

analysis

Probability

Damage

[offshorenergytoday.com]

[northnorfolknews.co.uk]

[maritimejobs.org]

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Context

• Several wind turbine

supporting structurures :

• Monopile

• Tripod

• Jacket

• Floating

• Finite elements : accurate but time demanding

• Need for a faster method for pre-design stage :

Continuous Elements Method

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State of art

• Only local crushing taken into account

• Good results for low energy impact

s

• Model too rigid

in case of large energy impacts

• Other deformation modes have to be added

0 10 20 30 40 50 60 0 0,5 1 1,5 2 2,5 3 3,5 4

For

ce

[M

N

]

Displacement [m]

Resultant force

SE LS-DYNA 0 20 40 60 80 100 120 0 0,5 1 1,5 2 2,5 3 3,5 4

En

er

gy

[M

J]

Displacement [m]

Total energy

SE LS-DYNA

[BULDGEN L., LE SOURNE H., PIRE T., Extension of the Super-Elements Method to the Analysis of a Jacket Impacted by a ship, Marine

Structures, 2014, vol. 38, pp. 44 – 71]

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Global deformation

0 0,5 1 1,5 2 2,5 3 3,5 0 0,05 0,1 0,15 0,2 0,25 0,3 En ergy [MJ ] Displacement [m]

Total energy

SE LS-DYNA -2 0 2 4 6 8 10 12 14 16 0 0,05 0,1 0,15 0,2 0,25 0,3 Force [MN ] Displacement [m]

Resultant force

SE LS-DYNA

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Local crushing : model

[BULDGEN L., LE SOURNE H., PIRE T., Extension of the Super-Elements Method to the Analysis of a Jacket Impacted by a ship, Marine

Structures, 2014, vol. 38, pp. 44 – 71]

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Local crushing : developments

• Local crushing

• Rings

𝐸

_𝑏

= 2𝑚

₀

𝑉

𝐵

𝑅

₂

+

1 𝑅

₂

−

1 𝑅

₁

𝑉

𝐹

+

_𝐹

𝐸

χ

₁

𝑑𝑙 +

𝐷

𝐹

χ

₂

𝑑𝑙

• Generators

𝐸

_𝑚

θ, δ = 𝑛

₀

−ξ

₂

ξ

₁

ε

_𝑚

θ, δ, 𝑦 𝑑𝑦 = 𝑛

₀

δ

1 ξ

₁

+

1 ξ

₂

𝑤 θ, δ

𝜕𝑤

𝜕δ

• Total

𝑃

_𝑙

δ 𝑎 δ =

𝑖

𝐸

_𝑖

• Three-hinges mechanism

𝑃

_𝑔

δ =

𝐿

1 + 𝐿

2 𝐿

₁

𝐿

₂

1 + ξ

𝑡

𝑀

0 1 −

𝑁 δ

2 𝑁

₀

2 + 𝑁(δ) δ − δ

𝑡

cos γ

𝑡

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Punching : model

[HSIEH J.-R., Analytical formulations for ship-offshore wind turbine collisions, Master thesis, Nantes : ICAM (EMSHIP Erasmus Mundus Master

Course), 2015, 104 p.]

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Buckling : developments

• Hinges 1-3

𝐸

𝐻,1−3

= 2𝑚

0

0 π/2

_𝜕α

𝜕θ

𝑅𝑑θ θ

• Hinge 2

𝐸

_𝐻,2

= 4𝑚

₀

0 π/2

_𝜕α

𝜕θ

𝑑𝑠𝑑θ θ

• Membran

e

effect

𝐸

_𝑀

= 4𝑛

₀

0 𝐻

0 π/2

ε𝑑𝑠𝑑β𝑑𝑧

= 4𝑛

₀

θ

π𝑅

₀

𝐻

𝐿

2 _α

𝑑𝑧

• Total

𝑀 θ =

𝑖

𝐸

𝑖

1

3

2 β

R

L

_α

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Buckling : results

0,000E+00 5,000E+06 1,000E+07 1,500E+07 2,000E+07 2,500E+07

0,000E+00 5,000E-02 1,000E-01 1,500E-01 2,000E-01 2,500E-01 3,000E-01

Mo m en t [N m ] Theta [-] SE LS-DYNA 0,000E+00 5,000E+05 1,000E+06 1,500E+06 2,000E+06 2,500E+06 3,000E+06 3,500E+06 4,000E+06

0,000E+00 5,000E-02 1,000E-01 1,500E-01 2,000E-01 2,500E-01 3,000E-01

E [

J]

Theta [-]

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Complete model : scenario

• Colliding ship :

• Non-bulbous OSV

• 6000 tons (added mass included)

• 5m/s initial speed

• 75 MJ kinetic energy

• Impact point

• On a leg, between two nodes

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Complete model : results

0 10 20 30 40 50 0 0,5 1 1,5 2 2,5 3 3,5 4

For

ce

[M

N

]

Displacement [m]

Resultant force

SE LS-Dyna 0 20 40 60 80 0 0,5 1 1,5 2 2,5 3 3,5 4

En

er

gy

[M

J]

Displacement [m]

Total energy

SE LS-Dyna

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Complete model : comparison

• Better accuracy for large energy impact

0 10 20 30 40 50 60 0 0,5 1 1,5 2 2,5 3 3,5 4

For

ce

[M

N

]

Displacement [m]

Resultant force

StateofArt LS-Dyna SE 0 20 40 60 80 100 120 0 0,5 1 1,5 2 2,5 3 3,5 4

En

er

gy

[M

J]

Displacement [m]

Total energy

StateofArt LS-Dyna SE

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Conclusions

• Short computation time : ≈ 5 minutes (instead of ≈10h for FE)

• Good accuracy in results : difference of max. 10% in terms of energy

• Still needs more validation tests

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Acknowledgements

FRIA fellowship – Federal governement of Belgium

Financial support for the PhD research : Development of a

code based on the continuous elements method to analyse

the ship impact on the jacket of an offshore windturbine

MSC Software Corporation

Technical support to the use of the software

Patran and Nastran to create numerical models

and perform finite element analyses.

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