IMPORTANCE OF FOUNDATION DESIGN

• HIGH COST OF THE FOUNDATION ( NEARLY 25%-35% OF OVERALL COST )• NATURAL FREQUENCIES OF THESE STRUCTURES ARE VERY CLOSE TO THE

FORCING FREQUENCIES OF THE WIND, WAVE, ROTOR FREQUENCY AND BLADE SHADOW FREQUENCY.

FOUNDATION DIFFERENCES OIL & GAS PLATFORM VS WIND

TURBINESRELATIVELY STIFF RELATIVELY FLEXIBLESTRUCTURAL DYNAMICS NOT CRITICAL STRUCTURAL DYNAMICS VERY CRITICALWAVE LOAD DOMINANT WAVE AND WIND LOAD BOTH IMPORTANTSTRAIGHT FORWARD RELATION FORCE-RESPONSECOMPLEX, UNCORRELATED LOADING‘PROTOTYPE’ GENERALLY LARGE NUMBERS

DESIGN CRITERIA & CONSIDERATIONS

• LOADS: MAGNITUDE OF THE PERMANENT LOAD OF THE PLATFORM WIND / WAVE / CURRENT

RATIO VERTICAL / HORIZONTAL LOADS QUASI STATIC / CYCLIC

• WATER DEPTH• SEA FLOOR

SOIL TYPECURRENT -> SCOURING

• FABRICATION, TRANSPORTATION & INSTALLATION AVAILABLE CONSTRUCTION SITES / EQUIPMENT

GRAVITY FOUNDATIONS

• LOADING SITUATION VERY DIFFERENT FROM PILED FOUNDATION• SUBSTANTIAL VERTICAL LOADING REQUIRED ( STABILITY)• GENERALLY IMPRACTICAL SUPPORT STRUCTURE FOR WIND

TURBINES IN RELATIVELY SHALLOW WATER

PILED FOUNDATIONS• FLEXIBILITY / ADAPTABILITY :

SOIL CONDITIONSWATER DEPTHSCOURDIAMETER AND WALL THICKNESSTENSION & COMPRESSIONPENETRATION AND NUMBERTRACK RECORD / EXPERIENCEDIFFERENT INSTALLATION METHODS

CHOICE OF FOUNDATION TYPE• LOADS WIND / WAVE / CURRENT

HORIZONTAL AND VERTICALQUASI STATIC / CYCLIC

• WATER DEPTH• SOIL CONDITIONS• STORAGE REQUIREMENTS• TRANSPORTATION / INSTALLATION EQUIPMENT REQUIREMENTS• AVAILABLE CONSTRUCTION SITES / EQUIPMENT• ECONOMICS

THINK ABOUT ????????Depth of

water column

Mass needing Support

Turning and bending forces on structure

Location specific issues

Seabed geology and soils

Scour and sediment

movementEnvironmental impact

Construction

requirement

Installation requiremen

tCAPEX OPEX Materials

CURRENT & FUTURE PROTOTYPES

• CURRENT FOUNDATION TYPES INCLUDES FOUNDATIONS CURRENTLY AVAILABLE TO OFFSHORE WIND

DEVELOPERS• FUTURE PROTOTYPES

INCLUDES FLOATING AND DEEPWATER CONCEPTS

FOUNDATIONS USED ON UTILITY-SCALE OFFSHORE WIND PROJECTS TODAY:

•Mono pile

•Gravity foundation

•Tripod foundation

FLOATING CONCEPTS:

WHILE SEVERAL FLOATING OFFSHORE WIND CONCEPTS EXIST, TWO DESIGNS ARE THE BEST KNOWN:

• HYWIND• WINDFLOAT

HYWIND WINDFLOAT

ANALYSIS TO BE DONE :Prelimin

ary Sizing

Stability

Load Case

Structural

Design

DESIGN LOAD CASES:

• POWER PRODUCTION FAULT• PARKED FAULT• ADDITIONAL CASES• ULTIMATE STRENGTH LOAD CONVERGENCE• FATIGUE LOAD CONVERGENCE

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THANK YOU