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8/17/2019 Offshore wind turbine foundation design issues
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Dynamics and Fatigue of Offshore Wind
Turbine FoundationsA linear approach to a non-linearproblem
Laszlo Arany Department of Engineering Mathematics
May 6, 2016
1Dynamics and Control rou! "eminar
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# Dynamics# Random vibrations
# Fatigue
# Control# Vibration
suppression
Dynamics and Control rou! "eminar 2
May 6, 2016
What do $ %or& on'
YES NOT REALLY…
(ong term beha)iour of offshore %indturbines and su!!ort structures*
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Why %or& on offshore %ind turbines'
Dynamics and Control rou! "eminar +
6 May 2016
Source: EWEA report on offshore wind in Europe (2015)Source: Gijs van der Veen !dentificationof wind ener"# s#ste$s
irbus +-0 .largest!assenger !lane/
The economics The engineering
10 - load cycles
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Why %or& on offshore %ind turbines'
Dynamics and Control rou! "eminar
6 May 2016
n)ironment andsustainability
Source: Various studies co%%ected the Wor%d 'uc%ear Association
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Why %or& on su!!ort structures'
Dynamics and Control rou! "eminar
6 May 2016
Onshore OffshoreSource: nre% "ov
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"tructure of the !resentation
I. Excitations o o!shore "ind turbinesII. Current oundation designIII. #ong term issuesIV. Fatigue in the re$uency domain
V. Integrated designVI.An unsolved problem % ideas "elcome&
Dynamics and Control rou! "eminar 6
May 6, 2016
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# 'ind
# 'aves# Currents# ()# *)# +hip impact,
earth$ua e, etc
Dynamics and Control rou! "eminar 3
May 6, 2016
$* 4citations of offshore%ind turbines
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8/17/2019 Offshore wind turbine foundation design issues
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The aerodynamics is non8linear
Dynamics and Control rou! "eminar :
May 6, 2016
Source: E 'Windener"ie
Source: S$art*%ade G$&+
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Wa)es are non8linear
Dynamics and Control rou! "eminar 10
May 6, 2016
Source: ,#ushu-niversit# we& pa"e
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"oil is non8linear
Dynamics and Control rou! "eminar 11
May 6, 2016
Source: o. (201/)
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;o% does the load !rocess actually loo&'
12
6 May 2016
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$$* Current load analysis of offshore %ind turbines ime domain analysis(.Create time history o "ind and "aves
/.0se it as input or multibody so t"are 1aero-hydro-servo-elastic simulation "ith +oil-+tructureInteraction 1++I22
*.3btain time history o loads or all re$uiredload scenarios 1hundreds o scenarios24.Fatigue5 rain6o" counting 7 linear damageaccumulation % a terthought
Dynamics and Control rou! "eminar 1+
6 May 2016
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Design of foundations
Dynamics and Control rou! "eminar 1
May 6, 2016
M
;
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Current design of offshore %ind turbines
Dynamics and Control rou! "eminar 1
May 6, 2016
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Current design of offshore %ind turbines
Dynamics and Control rou! "eminar 16
May 6, 2016
# Diameter'
# Foundation de!th'# mount of steel'# $nstallation
!rocedure'# Fatigue life'# Cost of nergy'
Optimal?
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$$$* (ong term issues
Dynamics and Control rou! "eminar 13
6 May 2016
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ffect of load cycles on fre5uency and dam!ing
Dynamics and Control rou! "eminar 1-
6 May 2016
Different beha)iour for sand and clay
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=atural fre5uency change %ith time
Dynamics and Control rou! "eminar 1:
6 May 2016
"isted 8ac et in 9ornsea :#o"e1/;(/2<
eference7>alleha)e and Thilsted .2012/
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9ile head deflection and tilt .1/# #ong term tilt =has to be> predicted
1according to standards2
# Very e" studies available on ho" to do itAchmus et. al. 1/;;?2, #e@lanc 1/;(;2, Cox et. al. 1/;(42
# Virtually no measurement data are
available# ilt is not monitored on existing o!shore"ind turbines
Dynamics and Control rou! "eminar 20
6 May 2016
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9ile head deflection and tilt .2/# +trict re$uirements increase
oundation costs# aximum ;./B 1or ;.B 2
# Re$uirements are arbitrarynumbers originating romonshore "ind technology = or
the sa e operation o theturbine> and =visual concerns># Cox et. al. 1/;(42
Dynamics and Control rou! "eminar 21
6 May 2016
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$?* linear a!!roach to a non8linear !roblem(. Determine trans er unction bet"een "ind spectrum and
mudline moment spectrum./. Determine trans er unction bet"een "ave spectrum and
mudline moment spectrum.*. Calculate natural re$uency using simpli ed model.4. Apply Dynamic Ampli cation Factors to "ind and "ave loads.B. Combine bending moment spectra rom "ind and "aves.
. 0se bending moment spectrum to determine stress
spectrum.. 0se stress spectrum to estimate damage rate using
re$uency domain atigue damage estimation methods.
Dynamics and Control rou! "eminar 2+
6 May 2016
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# 'ind load model basedon $uasi-static e$uation
# urbulent "indcomponent replaced byGaimal spectrum oturbulence
# 'ave spectrum5 83H+'A) spectrum
# #inear 1Airy2 "aves areused
# orison s e$uation orthe "ave load
Dynamics and Control rou! "eminar 2
6 May 2016
182* Transfer functions .1/
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182* Transfer functions .2/
Dynamics and Control rou! "eminar 2
6 May 2016
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$?* linear a!!roach to a non8linear !roblem(. Determine trans er unction bet"een "ind spectrum and
mudline moment spectrum./. Determine trans er unction bet"een "ave spectrum and
mudline moment spectrum.*. Calculate natural re$uency using simpli ed model.4. Apply Dynamic Ampli cation Factors to "ind and "ave loads.B. Combine bending moment spectra rom "ind and "aves.
. 0se bending moment spectrum to determine stress
spectrum.. 0se stress spectrum to estimate damage rate using
re$uency domain atigue damage estimation methods.
Dynamics and Control rou! "eminar 26
6 May 2016
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+* =atural Fre5uency
Dynamics and Control rou! "eminar 23
6 May 2016
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+* =atural fre5uency
Dynamics and Control rou! "eminar 2-
6 May 2016
of the to%er
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* "ystem ain .D F/
Dynamics and Control rou! "eminar 2:
6 May 2016
Source: Su *hattachar#a presentation
# =atural fre5uency determined using linear s!rings as foundation stiffness# !!ro4imate em!irical formulae fitted to 9D solutions# Dynamic m!lification by using a!!ro4imate dam!ing as in Cam! et* al* .200 /
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86* Mudline @ending Moment "!ectrum .1/
Dynamics and Control rou! "eminar +0
6 May 2016
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86* Mudline @ending Moment "!ectrum .2/
Dynamics and Control rou! "eminar +1
6 May 2016
;o% does a theoretical s!ectrum measure u! to reality'
9"D
Fre5uency
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$?* linear a!!roach to a non8linear !roblem(. Determine trans er unction bet"een "ind spectrum and
mudline moment spectrum./. Determine trans er unction bet"een "ave spectrum and
mudline moment spectrum.*. Calculate natural re$uency using simpli ed model.4. Apply Dynamic Ampli cation Factors to "ind and "ave loads.B. Combine bending moment spectra rom "ind and "aves.
. 0se bending moment spectrum to determine stress
spectrum.. 0se stress spectrum to estimate damage rate using
re$uency domain atigue damage estimation methods.
Dynamics and Control rou! "eminar +2
6 May 2016
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Dynamics and Control rou! "eminar ++
6 May 2016
3* Fre5uency domain methods .1/
Power spectral densityof moment / stress:
Pro a ility density ofstress amplit!des:
"ama#e rate:
$ati#!e life:
!oint on the "8= cur)e and in)erse slo!e
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Dynamics and Control rou! "eminar +
6 May 2016
3* Fre5uency domain methods .2/
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Dynamics and Control rou! "eminar +
6 May 2016
3* "im!le, em!irical e4!ressions
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Dynamics and Control rou! "eminar +6
6 May 2016
3* ;o% do they measure u! to reality'
easonable accuracyconsidering the
general accuracy offatigue estimations.failure any%herebet%een 0*3 and 1* /
O)erestimation ty!ical
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?* $ntegrated design benefits .1/# urbine componentsJparameters5
# +ingle speed, double speed, variable speedK# Direct drive or gearboxK 9o" many stepsK# Lenerator typeK# @lade designK
# Can impact natural re$uency,oundation siMe, li etime and settlement
Dynamics and Control rou! "eminar +3
6 May 2016
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?* $ntegrated design benefits .2/# +erviceability re$uirements 1tilt and
de6ection25# o"er stri eK# Na" motor or ya" brea diOcultiesK# Cooling 6uid problemsK# @earing li etimeK
# Costs can be reduced
Dynamics and Control rou! "eminar +-
6 May 2016
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n unsol)ed !roblem A $deas %elcome .2/# 9o" to treat it statisticallyK
Dynamics and Control rou! "eminar 0
6 May 2016
Wind
Wa)es
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?$* n unsol)ed !roblem A $deas %elcome .+/# #ong term tilt and de6ection "ith
# di!erent "ind and sea states 1'eibull
distribution2,# di!erent load combinations 1one-"ay and
t"o-"ay2,
# three dimensional problem,# directionality o "ind and "aves.
Dynamics and Control rou! "eminar 1
6 May 2016
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Than& you
6 May 2016