FEA OF OFFSHORE JACKET STRUCTURE SUBJECTED TO DEFORMABLE VESSEL COLLISIONS …m120.emship.eu/Documents/MasterThesis/2014/Jose Babu Maliakel.pdf · FEA OF OFFSHORE JACKET STRUCTURE

FEA OF OFFSHORE JACKET STRUCTURE SUBJECTED TO DEFORMABLE

VESSEL COLLISIONS

MASTER THESIS

Developed at ICAM, FRANCE

in the framework of the

“EMSHIP”

Erasmus Mundus Master Course

in “Integrated Advanced Ship Design”

FEA OF OFFSHORE JACKET STRUCTURE SUBJECTED TO DEFORMABLE VESSEL COLLISIONS 1


CONTENTS

1. Introduction

2. Accidental Collisions – Design Principles

3. Workflow

4. H-Brace Structure

• Geometric Model & FE Mesh

• FEA Results

• Conclusion

5. Jacket Model


6. OSV Bow


• FEA Results

• Conclusion

7. Bulk Carrier


• FEA Results

• Conclusion

8. Further Work


4 FEA OF OFFSHORE JACKET STRUCTURE SUBJECTED TO DEFORMABLE VESSEL COLLISIONS

1. INTRODUCTION



VALIDATION OF LS-DYNA MODEL

PARAMETRIC STUDY OF H-BRACE STRUCTURE

SET UP LS-DYNA COLLISION MODEL

RIGID SHIP COLLISON SIMULATIONS

DEFORMABLE SHIP COLLISION SIMULATIONS

OBLIQUE IMPACT SIMULATIONS

DATA SENT TO ANAST LABORATORY FOR SUPERELEMENT DEVELOPMENT

3. WORKFLOW


4. H-BRACE STRUCTURE

ICAM ERROR IN COMPARISON TO TEST RESULTS- %

UNIVERSITY OF ULSAN - ERROR IN COMPARISON TO TEST RESULTS- %

Local Denting Damage, dd .mm

Overall Denting Damage, d0 .mm

Local Denting Damage, dd .mm

Overall Denting Damage, d0 .mm

-10.324 -54.231 -10.1 -29.7

10.003 -53.243 19.3 13.5

7.267 -35.458 10.5 6.7

26.058 -64.579 44.1 3.6

13.047 -42.769 30.3 -2.4

7.867 -53.873 28.7 28.1

22.004 -49.501 32.9 18.6


EFFECT OF BOUNDARY CONDITIONS

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

0 0,02 0,04 0,06 0,08 0,1

Foce

[N

]

Displacement [m]

OWT A2 FORCE DISPLACEMENT CURVE

Poly. (AXIALY FLEXIBLE)

Poly. (FIXED BRACE)

0

50000

100000

150000

200000

250000

0 0,005 0,01 0,015 0,02 0,025 0,03

FOR

CE

[N]

TIME [s]

MEMBRANE FORCES - OWT-A2

Poly. (AXIALY FLEXIBLE)

Poly. (FIXED BRACE)


0

50000

100000

150000

200000

250000

0 0,01 0,02 0,03 0,04 0,05 0,06

FOR

CE

[N]

DISPLACEMENT [m]

FORCE V/S DISPLACEMENT FOR VARYING THICKNESS - OWT F2

Poly. (t=2.1)

Poly. (t=3.1)

Poly. (t=4.1)

Poly. (t=5.1)

Poly. (t=6.1)

Poly. (t=7.1)

Poly. (t=8.1)

EFFECT OF THICKNESS


0

10000

20000

30000

40000

50000

60000

70000

80000

0 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,09 0,1

FOR

CE

[N]

Displacement [m]

FORCE-DISPLACEMENT CURVE FOR VARYING DIAMETER, t=0.0031m

Poly. (DIAMETER=0.1143m)

Poly. (DIAMETER=0.0891m)

Poly. (DIAMETER = 0.0641m)

-10000

0

10000

20000

30000

40000

50000

60000

70000

80000

-0,01 0 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08

FOR

CE

[N]

GLOBAL DISPLACEMENT [m]

FORCE-GLOBAL DISPLACEMENT CURVE, t=3.1mm

Poly. (DIAMETER = 0.1143m) Poly. (DIAMETER = 0.0891m)

Poly. (DIAMETER = 0.0641m)

0

10000

20000

30000

40000

50000

60000

70000

80000

0 0,005 0,01 0,015 0,02 0,025 0,03 0,035 0,04

FOR

CE

[N]

LOCAL DISPLACEMENT [m]

FORCE-LOCAL DISPLACEMENT CURVE, t=3.1mm

Poly. (DIAMETER = 0.0641) Poly. (DIAMETER = 0.0891)

Poly. (DIAMETER = 0.1143)



MODEL UNITS

Yield Strength 260 Mpa

Density 7850 kg/m3

Young's Modulus 210000 Mpa

Poisson's Ratio 0.3

Strain Rate Parameter, C 40.4

Strain Rate Parameter, P 5

5. JACKET STRUCTURE


SHIP PARTICULARS

Length 78m

Depth 13.8m

Breadth 17.6

Double Bottom Height 1.4m

Displacement 3000 T

6. OSV BOW STRUCTURE

43.2m

32.2m


-2000000

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

-1,6 -1,4 -1,2 -1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6

FOR

CE

[N]

DISPLACEMENT [m]

SHIP JACKET

Poly. (Thickness=50mm)

Poly. (Thickness=40mm)

Poly. (D=60mm)

IMPACT LOCATION - 1


0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

0 0,05 0,1

FOR

CE

[N]

DISPLACEMENT [m]

THICKNESS=60 mm

Poly. (LOCAL)

Poly. (GLOBAL)

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

0 0,02 0,04 0,06 0,08 0,1

FOR

CE

[N]

DISPLACEMENT [m]

THICKNESS=50mm

Poly. (LOCAL)

Poly. (GLOBAL)

0

2000000

4000000

6000000

8000000

10000000

12000000

0 0,1 0,2 0,3

FOR

CE

[N]

DISPLACEMENT [m]

THICKNESS=40mm

Poly. (LOCAL)

Poly. (GLOBAL)


-1000000

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

0 0,2 0,4 0,6 0,8 1 1,2 1,4

ENR

GY

[J]

DISPLACEMENT [m]

THICKNESS = 40mm

SHIP JACKET

-2000000

0

2000000

4000000

6000000

8000000

10000000

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6

ENER

GY

[J]

DISPLACEMENT [m]

THICKNESS = 50mm

SHIP JACKET

-2000000

0

2000000

4000000

6000000

8000000

10000000

12000000

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6

ENER

GY

[J]

DISPLCAEMENT [m]

THICKNESS = 60mm

SHIP JACKET

40mm jacket leg, jacket dissipated 16%. Shared Energy Design. 77% Leg.

50mm jacket, the jacket dissipated 7%. Shared Energy Design. 58% Leg.

60mm jacket, the jacket dissipated 4%. Close to Strength Design. 50% Leg.

STRUCTURAL MEMBER ENERGY ABSORBED %

DECK PLATES 30

DECK STIFFENERS 24.13

CENTER GIRDER 20.32

HULL SHELL 14.89

SHELL LONGITUDINALS 12.93

FRAMES 1.8

WEB FRAMES 0.65


-2

0

2

4

6

8

10

12

14

16

18

0 0,05 0,1 0,15 0,2 0,25

R/R

C

wd/D

RESISTANCE TO LOCAL INDENTATION - COMPARISON TO NORSOK CODE

NORSOK CURVEb/D=2.75

NORSOK CURVE b/D=0

Poly.(THICKNESS=40mm)




-2000000

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

-1,5 -1 -0,5 0 0,5 1

FOR

CE

[N]

DISPLACEMENT [m]

SHIP JACKET

Poly.(Thickness=50mm)



COMPARISON BETWEEN 2 IMPACT LOCATIONS

DOTTED LINE = IMPACT LOCATION CLOSER TO LEG BOTTOM SOLID LINES = IMPACT LOCATION FURTHER AWAY FROM LEG BOTTOM



SHIP PARTICULARS

Length, OA 224.9m

Depth, MLD 20m

Breadth, MLD 32.25m

Double Bottom Height 1.7m

Draft, Scantling 14.15m

Scantling Displacement 88000 T

7. BULK CARRIER STRUCTURE

21.2m


-10000000

0

10000000

20000000

30000000

40000000

50000000

60000000

70000000

-1 -0,5 0 0,5 1 1,5 2 2,5

FOR

CE

[N]

DISPLACEMENT [m]

SHIP JACKET

THICKNESS = 60mm THICKNESS = 50mm THICKNESS = 40mm

IMPACT VELOCITY – 1 M/S


40mm leg, the jacket dissipated 90%. Close to ductile Design.

50mm leg, the jacket dissipated 87%. Close to ductile Design.

60mm jacket leg, the jacket dissipated 80% of the. Shared Energy Design.

-1E+10

0

1E+10

2E+10

3E+10

4E+10

5E+10

6E+10

-0,5 0 0,5 1 1,5 2 2,5

ENER

GY

[J]

DISPLACEMENT [m]

THICKNESS = 40mm

SHIP Poly. (JACKET)

-1E+10

0

1E+10

2E+10

3E+10

4E+10

5E+10

6E+10

-0,2 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8

ENER

GY

[J]

DISPLACEMENT [m]

THICKNESS = 50mm

SHIP JACKET

-1E+10

0

1E+10

2E+10

3E+10

4E+10

5E+10

6E+10

0 0,2 0,4 0,6 0,8 1 1,2

ENER

GY

[J]

DISPLACEMENT [m]

THICKNESS = 60mm

SHIP JACKET

STRUCTURAL MEMBER ENERGY ABSORBED %

HULL SHELL 44

HOPPER TANK LONGITUDINALS 30

WEB FRAMES 24

OTHER STRUCTURAL MEMBERS 2


0

10000000

20000000

30000000

40000000

50000000

60000000

70000000

-1 0 1 2 3 4 5 6 7

FOR

CE

[N]

DISPLACEMENT [m]

SHIP JACKET

Poly. (Thickness =60 mm) Poly. (Thickness =50mm) Poly. (Thcikness=40mm)

IMPACT VELOCITY 2 M/S



CONCLUSIONS

• H-BRACE Parametric Study:

• Important to consider the effect of surrounding member, increasing thickness leads to increasing strength, increase in diameter leads

to overall increase in strength with increasing susceptibility to local indentation.

• In the initial stage of impact, the total deformation of the brace is totally dependent on the local indentation of the brace.

• OSV Bow Collision:

• Majority of energy absorbed by the ship. Conservative to consider a rigid ship.

• Comparison with NORSOK code suggests it is conservative in nature.

• When impact location, is closer to the seabed, results suggest that the jacket strength is slightly reduced.

• Bulk Carrier Side Collision:

• Majority of energy absorbed by the jacket. Realistic to consider a rigid ship.

• When impact location, is closer to the seabed, results suggest that the jacket strength is slightly reduced.

• All the results & data will aid in the validation of the super-element based analytical tool


• We will publish a paper in the Journal of Marine Science and Technology - “ H. Le Sourne, A. Barrera, J.B.

Maliakel – Numerical crashworthiness analysis of an offshore wind turbine jacket impacted by a ship ”

• Post collision analysis with global loads would yield complete picture.

• An analysis which includes the soil stiffness would provide further more accurate insights into the overall jacket behavior.

• Windfarm support vessels constantly service the windfarm and a collision analysis of the same would also be advisable.

• Offshore windfarm installation vessels and installation barges may also pose a significant threat to the jacket structure, since it

functions in close proximity to jacket structures, a collision analysis could be relevant.

FURTHER WORK