REDWIN – REDucing cost in offshore WINd by integrated structural and geotechnical design

EERA DEEPWIND January 2018

Skau, K.S., Senior engineer, NGI and PhD candidate, NTNUKaynia, A.M., Technical Expert and Professor II, NTNUPage, A.M., PhD Candidate, NTNULøvholt, F., Senior Specialist, NGINorén-Cosgriff, K., Head of Section CGM, NGISturm, H., Discipline leader Offshore renewables, NGIJostad, H.P., Technical director offshore energy NGI and Professor II, NTNUNygard, T.A., Senior researcher IFE and Professor, NMBUAndersen, H.S., Structural Engineer, Dr. Tech Olav OlsenEiksund, G., Professor, NTNUHavmøller, O., Senior researcher, Statoil ASAStrøm, P., Lead Geotechnical Engineering, Statoil ASAEichler, D., Senior Lead Structural Engineer, Vattenfall

REDWIN

4-year research projectSponsors: NFR, Statoil, Vattenfall, StatkraftPartners: NGI, NTNU, IFE, Dr. Tech. Olav Olsen16 mill NOKBottom fixed OWT1 year left

Load frequencies and eigen frequncy

0 0.2 0.4 0.6 0.8 1f (Hz)

0

4

8

12

Rat

ed p

ower

(MW

)

Blade load frequencies (1P and 3P)Wind spectrum (Kaimal)Wave spectrum (JONSWAP, Hs = 2.4 m)

Turbines: DTU 10 MWVestas V164 (8MW)Siemens SWT-6.0-154 (6MW)Siemens SWT-3.6-107 (3.6 MW)Vestas V90 and V91 (3MW)

Soft-soft Soft-stiff Stiff-stiff

Source: Arany, L., Bhattacharya, S., Macdonald, J. H. G. and Hogan, S. J. (2016)

The importance of the foundation

4 8 12kfoundation / ktower

0.6

0.8

1

f n /

f n,c

lam

ped

Clamped towerFlexible foundaitonInterpreted trend lineReal design

The importance of the foundation

0

0.04

0.08

0.12

Den

sity

0.9 0.95 1 1.05 1.1 1.15 1.2 1.25fn,measured / fn,design

0.97 0.98 0.99 1 1.01 1.02fn / fn,ref

0.96

1

1.04

1.08

Nor

mal

ized

fatig

ue d

amag

e

Source: Kallehave, D., Byrne, B. W., LeBlanc Thilsted, C. and Mikkelsen, K. K. (2015)

Adapted from: Schafhirt, S., Page, A., Eiksund, G. R. and Muskulus, M. (2016)

Integrated dynamic analyses

Aero dynamicsHydro dynamicsStruktural dynamicTurbine controller (pitch)Soil/foundation respons

Geotechnical involvment

Current practisep-y springs (API, PISA) for monopilesLinear elastic springs for shallow fundations

0 0.2 0.4 0.6 0.8 1γ / γ

f

0

0.4

0.8

1.2

τ / τ f

γ50

REDWIN model principlesApplication oriented models, such that the choice of model appear intuitive.

User interface understandable for practitioners.

General models, adaptable to different ground conditions.

The models have to work in time domain analyses.

F1

𝑉𝑉2 + 𝑀𝑀2

𝑢𝑢ℎ + 𝑢𝑢ℎ

AB

A

B

F2

𝑉𝑉2 + 𝑀𝑀2

𝑢𝑢ℎ + 𝑢𝑢ℎ

AB

A

BC

C

F1

F2

𝑉𝑉2 + 𝑀𝑀2

𝑢𝑢ℎ + 𝑢𝑢ℎ

AB

A

BC

D

D

C

F1

F2

𝑉𝑉2 + 𝑀𝑀2

𝑢𝑢ℎ + 𝑢𝑢ℎ

AB

A

BC

D

D

C

E

E

F1

F2

Monopiles

Foundation and substructre Model applicable Loading regime

Redwin model 1

Distributed 1D model to be applied to any DOF.

Redwin model 2

HM-loading

Redwin model 3

VHM-loading

Redwin model 3

VHM-loading

p, y

y

p

Soil –support model

M

H

uθ

uh

Foundation – structureinterface

V uv

Foundationmodel

Monopiles

Foundation and substructre Model applicable Loading regime

Redwin model 1

Distributed 1D model to be applied to any DOF.

Redwin model 2

HM-loading

Redwin model 3

VHM-loading

Redwin model 3

VHM-loading

p, y

y

p

Soil –support model

M

H

uθ

uh

Foundation – structureinterface

V uv

Foundationmodel

Gravity based foundations

Foundation and substructre Model applicable Loading regime

Redwin model 1

Distributed 1D model to be applied to any DOF.

Redwin model 2

HM-loading

Redwin model 3

VHM-loading

Redwin model 3

VHM-loading

p, y

y

p

Soil –support model

M

H

uθ

uh

Foundation – structureinterface

V uv

Foundationmodel

Bucket foundations

Foundation and substructre Model applicable Loading regime

Redwin model 1

Distributed 1D model to be applied to any DOF.

Redwin model 2

HM-loading

Redwin model 3

VHM-loading

Redwin model 3

VHM-loading

p, y

y

p

Soil –support model

M

H

uθ

uh

Foundation – structureinterface

V uv

Foundationmodel

Foundation and substructre Model applicable Loading regime

Redwin model 1

Distributed 1D model to be applied to any DOF.

Redwin model 2

HM-loading

Redwin model 3

VHM-loading

Redwin model 3

VHM-loading

p, y

y

p

Soil –support model

M

H

uθ

uh

Foundation – structureinterface

V uv

Foundationmodel

Model demonstration

Foundation damping

𝐷𝐷𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 =∑ 𝑉𝑉 � 𝐸𝐸ℎ

4𝜋𝜋∑ 𝑉𝑉 � 𝐸𝐸𝑝𝑝

Effect of foundation behaviour on fatigue

0.8

1

1.2

1.4

Nor

mal

ized

fatig

ue d

amag

e

Mode Ap-y elements

Model B Lumped linear elastic

Model C Lumped linear elasticwith viscous damper

Model DLumped nonlinearREDWIN model 1

Aasen, S., Page, A. M., Skau, K. S. and Nygaard, T. A. (2017)

Comparison of model and measured response

0.4 0.6 0.8 1 1.2 1.4f / fn,measured

1E-005

0.0001

0.001

0.01

0.1

1

Nor

mliz

ed P

SDRevised analyses with Redwin model 2

Design prediction range

Summary and conclusionsThe models and tools developed in REDWIN seems to contribute to more accurate descriptions of foundations in design They include damping, which is often neglected. The knowledge of soil and site can be better utilized in designImproved accuracy reduce costsCurrently working om cost reduction effects in more detail.

Thanks to:The Norwegian research council, Statoil, Vattenfall og Statkraft

..and co-authors and contributors !

And thanks for your attention !

@infoNGI

NORWEGIAN GEOTECHNICAL INSTITUTENGI.NO