Collision Study of Rigid Ships with a Deformable Offshore Wind Turbine Jacket Structure...
Transcript of Collision Study of Rigid Ships with a Deformable Offshore Wind Turbine Jacket Structure...
Collision Study of Rigid Ships with a Deformable Offshore Wind Turbine Jacket Structure Andres Barrera
La Spezia, Italy
February 17, 2014
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CHARGEOL Project • Project for the foundations of renewable marine energy.
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Focus of study:
• Risk of Collision.
• Understanding seabed behavior.
• Scouring issues.
• Better understanding of load response of the
structures.
Objectives • General:
Develop Numerical Basis for the Simplified Calculation Tool.
• Specific:
Characterizing the sensitivity of the jacket to:
Gravity Loads/Tower
Ship Type
Velocity/Collision Angle/Impact height
Determine Resultant Force Distribution
Comparison to simplified calculation tool
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Offshore Wind Turbine Jacket • Latticed Steel Structure.
• Developed from Oil and Gas Industry.
• Used in renewable wind industry up to depths of 45 m.
• Lower production costs than monopile structures.
• Weakness in welded nodes.
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Ship Models
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Displacement: 132797 tons
Added Mass: 6639 tons Displacement: 5000 tons
Added Mass: 250 tons
SIMULATIONS CARRIED OUT
Crude Oil Carrier Simulations
6 simulations.
Sensitivity of the structure to variation in impact location (leg-brace joint), speed and angle.
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• Sensitivity to Gravity Loads
2 m/s and 6 m/s simulations performed.
• Determination of Critical Scenario (Leg-Brace Joint).
• Sensitivity to OWT Tower
Leg Collision 6 m/s with tower
• Study of Resultant Force Transmission
Leg Collision, single impact location 6 m/s
• Comparison with Simplified Calculation Tool
Leg Collision, single impact location 2 m/s
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Sensitivity to Gravity Loads
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2 m/s Without Gravity Loads
2 m/s With Gravity Loads
Gravity Loads Without Gravity
Resultant Force Transmission
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-2.00
0.00
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6.00
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0.000 1.000 2.000 3.000 4.000 5.000 6.000
Resu
ltan
t F
orc
e (
MN
)
Penetration (m)
565
558
530
536
566
532
562
564
558_2
Simplified Tool Comparison
• 2 m/s leg section single impact point
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0
2000
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8000
10000
12000
14000
16000
18000
0 0.5 1 1.5
Resu
ltan
t F
orc
e (
KN
)
Penetration (m)
Simplified
LS_DYNA
Conclusions I • High Energy (Tanker):
High energy collisions at brace joint are sensitive to variation in collision angle.
Leg impact is more detrimental to jacket in high energy scenarios.
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Conclusions II • OSV Simulations
Leg impact more detrimental to jacket.
High sensitivity to collision angle; initial rupture of leg at 2 m/s.
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Gravity loads did not affect shock response of structure at 2 and 6 m/s.
Coupling between the tower, platform and transition piece cannot be simplified.
Legs are more sensitive to local deformation than braces are to bending or buckling failure.
Up to penetration of 0,58 m, simplified tool in accordance with simulation, error for internal energy and crushing force below 20%.
Further Work
• Better definition of connectivity between the OWT tower, the platform, transition piece and jacket.
• Additional OSV simulations varying collision height and impact location.
• Additional comparisons to simplified tool with different velocities, impacting ship section geometries (leg and stem).
• Simulations that account for soil/structure interaction.
• Detailed study of buckling of braces for analytical tool.
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