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1Challenge the future
Response-based analysis of FPSO systems for squall loadingsOMAE2012 Rio de JaneiroJuly 3rd 2012
OMAE2012-83633 - Joerik Minnebo - Amir Izadparast - Arun Duggal - René Huijsmans
2Challenge the future
Introduction
0 2000 4000 6000 8000 10000time[s]
(1‐minavg)w
indspeed[m/s]
originalsquallscaledsquall
3Challenge the future
Research goals
• Characterize the available squalls• Influence of the individual squall parameters• Compare the current design practice to a response based method
Presentation outline
4Challenge the future
Squall characterization
0 2000 4000 6000 8000 10000‐2
0
2
4
6
8
10
12
14
time[s]
windspeed[m/s]
OMAE2011-49855
• Rising slope• Peak wind speed• Decay (half‐life) time
OMAE2006-92328
5Challenge the future
Squall characterizationCorrelations and distributions
12 14 16 18 20 22
0.01
0.05
0.1
0.25
0.5
0.750.90.950.99
Peakwindspeedu0[m/s]
p(u0)
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
0.01
0.05
0.1
0.25
0.5
0.750.90.950.99
Risingslopesr(m/s2)
p(s r)
0 50 100 150
0.01
0.25
0.5
0.75
0.9
0.95
0.99
Decayhalflifetime[min]
p()
OMAE2011-49855
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
CurrentPracticeDesignValueSampleDistributionGPDfit58UnscaledSqualls
6Challenge the future
Spread Mooring Analysis
OMAE2011-49855
7Challenge the future
Spread Mooring AnalysisResponse Characteristics
10 12 14 16 18 20 220
1
peakwindspeedu0[m/s]
norm
alizedoffset
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.080
1
risingslopesr[m/s2]
norm
alizedoffset
0 50 100 1500
1
decayhaflifetime[min]
norm
alizedoffset
8Challenge the future
Spread Mooring AnalysisResponse Characteristics
20
202
uCukAC
y styw
st
st
dyny
y
yst
time[s]
Offset[m
]
ydyn
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.51
1.2
1.4
1.6
1.8
2
y dyn/yst
StepResponse
Tn=100sTn=130sTn=160sTn=190sTn=220sTn=250sTn=280sTn=310sTn=340sTn=370sTn=400s
u0
time[s]
windspeed
9Challenge the future
Spread Mooring AnalysisResponse Characteristics
050
100150
200
00.050.10.150.20.25
0.9
1
1.1
1.2
1.3
1.4
1.5
sr[m/s2]
[min]
y dyn/yst
=0.2=0.3=0.4=0.5
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.51
1.2
1.4
1.6
1.8
2
y dyn/yst
StepResponse
Tn=100sTn=130sTn=160sTn=190sTn=220sTn=250sTn=280sTn=310sTn=340sTn=370sTn=400s
10Challenge the future
Design Value Estimation
• Current Design Practice• Response Based Methods
“The 100 year event”
• Spread moored FPSO• 800m water depth• Tn = 290s• = 0.4
11Challenge the future
Design Value EstimationCurrent Design Practice
smu /3.27100 time[s]
(1‐minavg)w
indspeed[m/s]
u100originalsquallscaledsquall
12Challenge the future
Design Value EstimationCurrent Design Practice
29 30 31 32 33 34 35 36 370
5
10
15
20
offset[m]
numberofevents
my 8.35100
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20
5
10
15
20
25
30
35
40
risingslopesr[m/s2]
numberofevents
UnscaledsquallsScaledsqualls
13Challenge the future
Design Value EstimationResponse based on dynamic amplification
027.10 5 10 15 20 25 300
5
10
15
20
25
30
35
40
peakwindspeedu0[m/s]
offset[m
]
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
peakwindspeedu0[m/s]
offset[m
]
static=0.0402*u02
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
peakwindspeedu0[m/s]
offset[m
]
offset=0.0413*u02
static=0.0402*u02
20
20
20 0402.0
2uuCu
kAC
y styw
st
14Challenge the future
Design Value EstimationPeak wind speed relation and dynamic amplification
024.1, rsE
15Challenge the future
Design Value EstimationPeak wind speed relation and dynamic amplification
200 )( uCuyy ststdyn
0 5 10 15 20 25 300
10
20
30
40
50
peakwindspeedu0[m/s]
offset[m
]
static=0.0402*u02
offset=0.0413*u02
10‐410‐310‐210‐110010
15
20
25
30
35
40
ProbabilityofExceedancePE
Peakwindspeed[m/s]
1year
10year
100year
1000year
EstimatedProbabilityDistributionSampleDistributionExtremeValues
16Challenge the future
Design Value Estimation
• Case I Expected Values• Case II Maximum Observed Values• Case III 100 Year Return Values
Peak wind speed relation and dynamic amplification
17Challenge the future
Design Value Estimation
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
CurrentPracticeDesignValueCaseI:ExpectedValuesCaseII:Max.ObservedValuesCaseIII:100YearReturnValuesStaticValuesStepResponse
Peak wind speed relation and dynamic amplification
= 1.024 = 1.110 = 1.213ααα
18Challenge the future
Conclusions
• Characterized the squall events••••
Found the governing response characteristicsCompared the different DVE methodsCDP for spread moored is highly conservativeBest method is based on response knowledge
0 2000 4000 6000 8000 10000‐2
0
2
4
6
8
10
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14
time[s]
windspeed[m/s]
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
peakwindspeedu0[m/s]
offset[m
]
offset=0.0413*u02
static=0.0402*u02
10‐5
10‐4
10‐3
10‐2
10‐1
1000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValuesPWSrelation=1.027StepResponse=1.255DirectExtrapolationMonteCarloSimulations
19Challenge the future
Thank you for your attention!
20Challenge the future
14 Bachelor Programs38 Master Programs16,400 students
Master Program “Offshore Engineering”• Partly Civil Engineering• Partly Mechanical Engineering• Partly Maritime Engineering
21Challenge the future
22Challenge the future
Introduction
23Challenge the future
Design Value EstimationDirect Extrapolation
my 6.37100 10‐510‐410‐310‐210‐1100
0
10
20
30
40
50
60
70
8058unscaledsqualls
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
CurrentDesignPractice58unscaledsquallsEstimatedProbabilityDistribution95%confidenceintervals
24Challenge the future
Design Value EstimationMonte Carlo Simulations
my 0.30100 10‐510‐410‐310‐210‐1100
0
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
CurrentPracticeDesignValueSampleDistributionGPDfit58UnscaledSqualls
25Challenge the future
Design Value EstimationPeak wind speed relation and dynamic amplification
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPractice
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValues
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValuesPWSrelation=1.027
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValuesPWSrelation=1.027StepResponse=1.255
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValuesPWSrelation=1.027StepResponse=1.255DirectExtrapolation
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
70
80
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
SampleDistributionCurrentDesignPracticeStaticOffsetValuesPWSrelation=1.027StepResponse=1.255DirectExtrapolationMonteCarloSimulations
26Challenge the future
Turret Mooring
27Challenge the future
Turret Mooring
0
0
Xoffset[m]
Yoffset[m
]
0degrees
45degrees
90degrees
135degrees
180degrees
Response characteristicsu0
time[s]
windspeed
28Challenge the future
Turret MooringResponse characteristics
12 14 16 18 20 22 240
5
10
15
20
25
peakwindspeed[m/s]
Offset[m
]
0deg45deg90deg135deg180deg
29Challenge the future
Turret MooringResponse characteristics
30Challenge the future
‐60 ‐50 ‐40 ‐30 ‐20 ‐10 0 10 20 30‐10
0
10
20
30
40
Xoffset[m]
Yoffset[m
]
0deg18deg36deg54deg72deg90deg108deg126deg144deg162deg180deg
Turret MooringCurrent Design Practice
my 7.35100
31Challenge the future
Turret MooringDynamic Amplification limitations
α 2.60 α 2.67
32Challenge the future
Turret MooringDynamic Amplification limitations
12 14 16 18 20 22 240
5
10
15
20
25
30
peakwindspeed[m/s]
Offset[m
]
0deg45deg90deg135deg180degStaticMaxobservedDA100yearreturnDAMaxDA
33Challenge the future
Turret MooringDynamic Amplification limitations
10‐510‐410‐310‐210‐11000
10
20
30
40
50
60
ProbabilityofExceedancePE
Offset[m
]
100yearreturnvalues
CurrentPracticeDesignValueStaticResponseMaximumDAMaximumObservedDA100yearreturnDA
