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8~9-Approach to the Noninear soil model for OrcaFlex _Y.T.Kim.pptx
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Nonlinear soil model in OrcaFlex
Transcript of 8~9-Approach to the Noninear soil model for OrcaFlex _Y.T.Kim.pptx
• Dynamic Analysis – time simulation of
the motions of the model over a speci-
fied period of time, starting from the po-
sition derived by the static analysis.
• The simulation proceeds in a number of
stages each of a given duration.
• Before the main simulation stages,
there is a build-up stages
Dynamics
Dynamics
Build-up
•Wave & vessel motions are smoothly ramped up from zero to their full size.
•Make simulation gentle start and reduce the transients (generated by the change from the static to dynamic motion)
Main simulation stage-1, 2, …
•The start of the simulation time origin•The simulation time origin is at the end of the build-up stage
•Each wave train has its own time origin.•All of these time origins are defined rela-tive to the global time origin
3/33
Approach to the Nonlinear Soil ModelFor OrcaFlex (1)
Summarized by Y.T Kim
Offshore Engineering Lab. Seminar No. 8 & 9
Environment Data-Seabed
• Flat seabed • Profiled seabed • 3D seabed
Example of profiled seabed
Normal seabed stiffness the constant of proportionality of the spring force in the seabed outward normal direc-tion, equals the spring reac-tion force
Shear seabed stiff-nessused by the friction calcula-tion. A value of ‘~’ results in the normal seabed stiffness being used.
Environment Data-Seabed
Seabed Dampingthe constant of proportionality of the damping force, and is a percentage of critical dampingAlways “0” when using the implicit integration scheme
Environment Data-Seabed
Seabed stiffness with spring
𝐾=𝐹𝛥
K : soil stiffness per unit lengthF : force per unit lengthΔ : displacement
Linear soil stiffness Model static pipe/soil interaction, typically
used to represent the backbone curve
Static stiffness for pipe/soil interaction in clay with OCR=1, DNV RP F-105
Clay type KV,S
(kN/m/m)
Very soft 50~100
Soft 160~260
Firm 500~800
Stiff 1000~1600
Very stiff 2000~3000
Hard 2600~4200
Environment Data-Nonlinear Seabed
Shear Strength GradientUndraind shear strength increase with depth be-low the seafloor and can be written as a function in the form given below. SU = SU0 + SUGz
SU0 The undrained shear strength at soil surfaceSUG Undrained shear strength gradientz Depth below the surface
Typical geotechnical parameters for CLAY, DNV RP F-105
Environment Data-Nonlinear Seabed
Shear Strength GradientUndraind shear strength increase with depth be-low the seafloor and can be written as a function in the form given below. SU = SU0 + SUGz
SU0 The undrained shear strength at soil surfaceSUG Undrained shear strength gradientz Depth below the surface
*Non-linear seabed model parameters in GoM
*Fatigue generation mechanism in touchdown area of SCR in non-linear hys-teretic seabed. Kosar Rezazadeh, Hodjat Shiri, Yong Bai
*Above input data was referred from “Dynamic response of SCR using a seabed interaction under random loads”
Environment Data-referenceTypical geotechnical parameters for SAND, DNV
RP F-105
*Manipulated wave scatter diagram for a 30 year service life in Gulf of Mexico
*Fatigue generation mechanism in touchdown area of SCR in non-linear hysteretic seabed. Kosar Rezazadeh, Hodjat Shiri, Yong Bai
Linear vs. Nonlinear seabed model
Reference Data SCR_Dynamic_Far_Ex_100yr.sim & SCR_Dynamic_Far_Ex_100yr_Nonlinear.sim SCR1 (ES direction)
Linear vs. Nonlinear seabed model
0 500 1000 1500 2000 2500 3000 350005
10152025303540
Shear Force
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Shear
forc
e (
kN
)
0 500 1000 1500 2000 2500 3000 35000
1000
2000
3000
4000
5000
Effective Tension
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Eff
ect
ive T
ensi
on (
kN
)
Linear vs. Nonlinear seabed model
0 500 1000 1500 2000 2500 3000 35000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Seabed Normal Penetration/D
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Se
ab
ed
No
rma
l Pe
ne
tra
tio
n/D
2400 2500 2600 2700 2800 2900 30000
0.20.40.60.8
11.21.41.61.8
2
Seabed Normal Penetration/D
Far_SCR1_100yr_Linear
Far_SCR1_100yr_Nonlinear
Se
ab
ed
No
rma
l Pe
ne
tra
tio
n/D
2400 2500 2600 2700 2800 2900 30000
100
200
300
400
500
600
Bendmoment (kN.m)
Far_SCR1_100yr_Linear Far_SCR1_100yr_NonlinearB
en
dm
om
en
t (k
N.m
)
Linear vs. Nonlinear seabed model
0 500 1000 1500 2000 2500 3000 35001.00E-06
1.00E-05
1.00E-04
1.00E-03
Fatigue Damage
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Fati
gue D
am
age
2300 2350 2400 2450 2500 2550 2600 2650 2700
1.00E-05
1.00E-04
1.00E-03
Fatigue Damage
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Fati
gue D
am
age
Dynamic_Far_OP_100yr_LinearDynamic_Far_OP_100yr_Nonlin
ear
F.D Min 3.45E-04 3.10E-04
F.L Min 2900.09 3228.54
Linear vs. Nonlinear seabed model
0 0.05 0.1 0.15 0.2 0.25 0.30
0.5
1
1.5
2
2.5
3
3.5
Dynamic_Far_OP_100yr_Linear
Normal Penetration/D
Norm
al R
esi
stance
(kN
/m)
0 0.2 0.4 0.6 0.8 1 1.2
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Dynamic_Far_OP_100yr_Nonlinear
Normal Penetration/D
Norm
al R
esi
stance
(kN
/m)
Linear vs. Nonlinear seabed model
-0.3 0.2 0.7 1.2
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
Dynamic_Far_OP_100yr_Nonlinear
100~500 1000~1500 3000~3500 5000~5500 8000~8500 10000~10800
Normal Penetration/D
Norm
al R
esi
stance
(kN
/m)
Sensitivity of Suction value Suction Resistance Ratio 0.6 vs 0.2
0 500 1000 1500 2000 2500 3000 35000
10
20
30
40
Shear Force
Dynamic_Near_EX_100yr_SC0.6
Dynamic_Near_EX_100yr_SC0.2
Shear
forc
e (
kN
)
1700 1800 1900 2000 2100 2200 2300 2400 25000
10
20
30
40
Shear Force
Dynamic_Near_EX_100yr_SC0.6
Dynamic_Near_EX_100yr_SC0.2
Shear
forc
e (
kN
)
Sensitivity of Suction value Suction Resistance Ratio 0.6 vs 0.2
0 500 1000 1500 2000 2500 3000 35000
0.5
1
1.5
2
Seabed Normal Penetration/D
Dynamic_Near_EX_100yr_SC0.6
Dynamic_Near_EX_100yr_SC0.2
Se
ab
ed
No
rma
l Pe
ne
tra
tio
n/D
2200 2250 2300 2350 2400 2450 25000
0.5
1
1.5
2
Seabed Normal Penetration/D
Dynamic_Near_EX_100yr_SC0.6
Dynamic_Near_EX_100yr_SC0.2
Se
ab
ed
No
rma
l Pe
ne
tra
tio
n/D
Sensitivity of Suction value Suction Resistance Ratio 0.6 vs 0.2
0 500 1000 1500 2000 2500 3000 35001.00E-03
1.00E-02
1.00E-01
1.00E+00
Fatigue Damage
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Fati
gue D
am
age (
per
Year)
2100 2120 2140 2160 2180 2200 2220 2240 2260 2280 23001.00E-03
1.00E-02
1.00E-01
1.00E+00
Fatigue Damage
Far_SCR1_100yr_Linear Far_SCR1_100yr_Nonlinear
Fati
gue D
am
age (
per
year)
Sensitivity of Suction value Suction Resistance Ratio 0.6 vs 0.2
0 0.2 0.4 0.6 0.8 1 1.2
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Resistance vs. Penetration
Dynamic_Near_EX_100yr_SC0.6
Normal Penetration/D
Norm
al R
esi
stance
(kN
/m)
0 0.2 0.4 0.6 0.8 1 1.2-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Resistance vs. Penetration
Dynamic_Near_EX_100yr_SC0.2
Normal Penetration/D
Norm
al R
esi
stance
(kN
/m)
Future Plan
How to apply P-y model for OrcaFlex
The effect of Lateral movement for F.L of SCR in the TDZ
