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Design Basis for OffshoreWind Structures

Copenhagen Offshore Wind 2005

Peter Petersen, Kristian Bendix Nielsen, Tove FeldOctober 2005

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Version Slide 231 October 2005

Overview

Introduction

Design waves

Ice loads

Wave slamming loads

Corrosion protection

Grout material / grouted connection

Conclusion

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Version Slide 331 October 2005

Introduction

Design basis Design briefs

Design documentation

- Drawings

- Calculations

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Version Slide 431 October 2005

Design waves

Determination of extreme designwaves:

- Definition of design wave- Basic wave data

- Statistical methods

Wave kinematics:- Shallow water

- Breaking waves (surging,

plunging, spilling)

Fatigue wave climate

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Version Slide 531 October 2005

Design waves

Determination of extreme design wave- Should be based on measured data rather than

observed data.

- Data quality and coverage should be assessed.

- Statistical methods, definitions and guidance notesare given in Design of Offshore Wind TurbineStructures, DNV-OS-J 101.

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Iceloads

Relevant for wind farms in e.g. the Baltic Sea

Data sources

-Thickness, dimension and distribution

-Type

- Mechanical properties (compressive and bending

strength)- Velocity and direction of drifting ice

Methods for calculation of load

Cone/ no cone

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Waveslammingloads

Horizontal members and other items in the splash zone

Dynamic response must be considered

Design requirements and guidance are given in DNVClassification Note 30.5 Environmental conditions andenvironmental loads.

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Corrosionprotection

Monopile design driven by fatigue

Corrosion reduces fatigue performance

Repair necessary $$$$$$

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Coating

Surface preparation

Coating application

Qualification requirements

- Prequalification of products

- Qualification of companies and personnel

- Qualification of work procedures

Inspection and testing

In-service inspection

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References

NORSOK Standard M-501, Surface preparation andprotective coating. 2004.

DIN 8566/2 (TSA)

ISO 2063 (TSA)

BS 2569 (TSA)

ISO 12944-5

ISO 12944-7

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Corrosionprotection

Atmospheric zone

- Ref. to ISO 12944-5, C5-M Systems S7.09 or S7.14

Splash zone

- Glass flake reinforced epoxy, DFT 1.5 mm

- Glass flake reinforced polyester, DFT 1.5 mm

-Thermally spayed aluminiumwith silicone sealer DFT

200 m

Submerged zone

- cathodic protection

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Material Qualification - Grout

High strength grout typically required.

- Density- Air content- Workability- Viscocity

- Stability (separation and bleeding)- Setting time- Compressive strength- Shrinkage/expansion

- Effect of admixtures

Properties must be well documented.

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Material Qualification - Grout

Approval by building authority

necessary in e.g. Germany Documentation

- Design documents

-Test reports

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Conclusion

Experience transfer:

Determination of design waves

Corrosion protection in general Coating

Wave slamming loads

Grout

Etc.

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