The performance and consequence of FPSOs subjected to large impact loads such as collisions from supply vessels or merchant vessels are of great concern in the offshore industry, notably when they are located close to heavy traffic lanes. Due to the lack of operation experience for ship-shaped FPSOs, direct design procedures are needed to rationalize the structural design of FPSOs, which can mitigate the consequence of collision accident and avoid possible contaminated compartment flooding. In this paper, three collision scenarios between a FPSO and a bulbous supply vessel are analyzed through explicit nonlinear finite element analysis code LS-DYNA. Thereafter, a direct design procedure is proposed for ship-shaped FPSO side structure against accidental collision forces, which follows the principle of accidental limit state. The procedure comprises the determination of the impact forces, shell plating, and stiffener framing design, and the consideration of the acceptance criterion. The proposed method is especially useful in the preliminary design phase because the design procedure for plating and stiffener is based on analytical formulas derived from plastic method and appropriate collapse mechanism. The side structure decided by the proposed design procedure also complies with the strength design principle that has been adopted in NORSOK standard. The proposed approach is demonstrated by the design of the FPSO side structure against impact loads from a 7500 tons supply vessel and verified by means of integrated collision analysis. The procedure could also be served to estimate the damage due to accidental loads.

1.
Moan
,
T.
,
Amdahl
,
J.
,
Wang
,
X. Z.
and
Spencer
,
J.
, 2003, “
Risk Assessment of FPSOs With Emphasis on Collision
,”
Soc. Nav. Archit. Mar. Eng., Trans.
0081-1661,
110
, pp.
307
338
.
2.
OTO 052
, 1999, Effective Collision Risk Management for Offshore Installations.
3.
NORSOK Standard N-004
, 2004, Design of Steel Structures, Appendix A, Design Against Accidental Actions.
4.
Hong
,
L.
, and
Amdahl
,
J.
, 2007, “
Plastic Design of Laterally Patch Loaded Plates for Ships
,”
Mar. Struct.
0951-8339,
20
(
3
), pp.
124
142
.
5.
Hong
,
L.
,
Amdahl
,
J.
,
Alsos
,
H. S.
, and
Klæbo
,
F.
, 2007, “
Damage Assessment and Impact Resistant Design of FPSOs With Respect to Supply Vessel Collisions
,”
PRADS2007
, Houston, TX.
6.
Wang
,
G.
, and
Spong
,
R.
, 2003, “
Experience Based Data for FPSO’s Structural Design
,”
OTC 15068
, Houston, TX.
7.
Paik
,
J. K.
, and
Thayamballi
,
A. K.
, 2007,
Ship-Shaped Offshore Installations: Design, Building, and Operation
,
Cambridge University Press
,
Cambridge
.
8.
Pettersen
,
E.
, and
Soegaard
,
L. M.
, 2005, “
A Study of a Collision Incident Evaluated Against Ruling
,”
OTC2005
, Houston, TX, Paper No. 17156.
9.
Tavakoli
,
M. T.
,
Amdahl
,
J.
,
Alsos
,
H. S.
, and
Klæbo
,
F.
, 2007, “
Analysis of Supply Vessel Stern Impacts With an FPSO
,”
Proceedings of the Fourth ICCGS
, Hamburg, Germany.
10.
Kitamura
,
O.
, 2002, “
FEM Approach to the Simulation of Collision and Grounding Damage
,”
Mar. Struct.
0951-8339,
15
(
4–5
), pp.
403
428
.
11.
Alsos
,
H. S.
, and
Amdahl
,
J.
, 2007, “
On the Structural Resistance of Ship Grounding
,”
Mar. Struct.
0951-8339,
20
(
4
), pp.
218
237
.
12.
Yamada
,
Y.
,
Endo
,
H.
, and
Pedersen
,
P. T.
, 2005, “
Numerical Study of the Effect of Buffer Bow Structure in Ship-Ship Collision
,”
Proceedings of ISOPE2005
, Seoul.
13.
ISSC
, 2003, “
Committee V.3: Collision and Grounding
.”
15th ISSC
, San Diego, Vol.
2
, pp.
71
108
.
14.
ISSC
, 2006, “
Committee V.1: Collision and Grounding
,”
16th ISSC
, Southampton, Vol.
2
, pp.
1
62
.
15.
Cockcroft
,
M. G.
, and
Latham
,
D. J.
, 1968, “
Ductility and the Workability of Metals
,”
J. Inst. Met.
0020-2975,
96
, pp.
33
39
.
16.
Rice
,
J.
, and
Tracey
,
D.
, 1969, “
On the Ductile Enlargement of Voids in Triaxial Stress Fields
,”
J. Mech. Phys. Solids
0022-5096,
17
, pp.
201
217
.
17.
Törnqvist
,
R.
, 2003, “
Design of Crashworthy Ship Structures
,” Ph.D. thesis, DTU, Kgs. Lyngby, Denmark.
18.
Alsos
,
H. S.
, 2008, “
Ship Grounding: Analysis of Ductile Fracture, Bottom Damage and Hull Girder Response
,” Ph.D. thesis, Department of Marine Technology, Norwegian University of Science and Technology, Trondheim.
19.
Ehlers
,
S.
,
Broekhausen
,
J.
,
Alsos
,
H. S.
,
Biehl
,
F.
, and
Tabri
,
K.
, 2008, “
Simulating Collision Response of Ship Side Structures: A Failure Criteria Benchmark Study
,”
Int. Shipbuild. Prog.
0020-868X,
55
(
1–2
), pp.
127
144
.
20.
Simonsen
,
B. C.
, and
Törnqvist
,
R.
, 2004, “
Experimental and Numerical Modelling of Ductile Crack Propagation in Large-Scale Shell Structures
,”
Mar. Struct.
0951-8339,
17
, pp.
1
27
.
21.
Belytschko
,
T.
,
Liu
,
W. K.
, and
Moran
,
B.
, 2004,
Nonlinear Finite Elements for Continua and Structures
,
Wiley
,
New York
.
22.
Wang
,
G.
,
Arita
,
K.
, and
Liu
,
D.
, 2000, “
Behavior of a Double Hull in a Variety of Stranding or Collision Scenarios
,”
Mar. Structures
,
13
, pp.
147
187
. 0951-8339
23.
Daley
,
C. G.
,
Kendrick
,
A.
, and
Appolonov
,
E.
, 2001, “
Plating and Framing Design in the Unified Requirements for Polar Class Ships
,”
Proceedings of the 16th POAC
, Ottawa, Vol.
3
, pp.
779
791
.
24.
Hong
,
L.
, and
Amdahl
,
J.
, 2008, “
A Comparative Study on the Plastic Formulations of Ship Shell Plating Under Patch Loading
,”
OMAE2008
, Lisbon, Portugal, Jun. 15–20.
25.
Jones
,
N.
, 1972, “
Review of the Plastic Behavior of Beams and Plates
,”
Int. Shipbuild. Prog.
0020-868X,
19
, pp.
313
327
.
26.
Jones
,
N.
, 1989,
Structural Impact
,
Cambridge University Press
,
Cambridge
.
27.
Alsos
,
H. S.
, and
Amdahl
,
J.
, 2008, “
On the Resistance to Penetration of Stiffened Plates—Part I: Experiments
,”
Int. J. Impact Eng.
0734-743X,
36
(
6
), pp.
799
807
.
28.
DNV
, 2001, “
Rules for Classification of Ships
,”
Ships for Navigation in Ice
,
Det Norske Veritas
,
Norway
, Part 5, Chap. 1.
29.
Daley
,
C. G.
, 2002a, “
Derivation of Plastic Framing Requirements for Polar Ships
,”
Mar. Struct.
0951-8339,
15
, pp.
543
559
.
30.
Daley
,
C. G.
, 2002b, “
Application of Plastic Framing Requirements for Polar Ships
,”
Mar. Struct.
0951-8339,
15
, pp.
533
542
.
31.
Wang
,
G.
,
Basu
,
R.
,
Chavda
,
D.
, and
Liu
,
S.
, 2005, “
Rationalizing the Design of Ice Strengthened Side Structures
,”
Proceedings of Maritime Transportation and Exploitation of Ocean and Coast Resources
, Lisbon, Portugal.
32.
2007, ISO/CD 19906 Draft: Petroleum and Natural Gas Industries—Arctic Offshore Structures.
33.
Wang
,
G.
, 2002, “
A Direct Calculation Approach for Designing a Ship-Shaped FPSO’s Bow Against Wave Slamming Load
,”
Proceedings of the 12th ISOPE
, Kitakyushu, Japan, May 26–31.
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