Effect of pneumatic rubber fenders on the prevention of structural damage during collisions between a ship-shaped offshore installation and a shuttle tanker working side-by-side

Figures & data

Figure 1. A ship-shaped offshore installation and a shuttle tanker working side-by-side.

Figure 2. Pneumatic rubber fenders (red ellipses) for absorbing and dampening the impact energy during side-by-side collisions between a ship-shaped offshore installation and a shuttle tanker.

Table 1. Pneumatic rubber fender crushing test conditions.

Test No.	Loading speed (mm/s)	Max. deformation (mm)	Rest time (min)
1	0.05	250	10
2	1.00	250	10
3	100	250	10
4	200	250	10

Figure 3. Structure of a pneumatic rubber fender.

Figure 4. Full-scale pneumatic rubber fender used for the crushing test in this study.

Figure 5. Synthetic tyre cord fabrics forming the middle layer that reinforces the pneumatic rubber fender.

Figure 6. Stress–strain relationship of tyre cords as obtained through tensile testing.

Figure 7. Schematic of the crushing test set-up for the pneumatic rubber fender: (a) elevation view, and (b) plan view

Figure 8. Photograph of the pneumatic rubber fender crushing test equipment.

Figure 9. A 500-kN dynamic loading actuator.

Figure 10. Finite element model of the pneumatic rubber fender developed using four-noded finite elements.

Table 2. Pneumatic fender modelling data input into LS-DYNA.

Material	MAT_077_OGDEN_RUBBER (LS-DYNA)
Length	1000 mm
Diameter	500 mm
Mesh size	Approximate element size 40 mm

Table 3. Material properties of the rubber model.

Feature	Outer rubber layer	Inner rubber layer
Material type	Vulcanised rubber	Vulcanised rubber
Density	1.18	1.18
Poisson ratio	0.49999	0.49999
Tensile strength (MPa)	20.31	18.62
Shear modulus (MPa)	1.609	1.609

Table 4. Definitions of the contact conditions.

Slave part	Master part	Contact condition
Reaction wall	Pneumatic fender	Automatic surface to surface
Compression plate	Pneumatic fender	Automatic surface to surface
Pneumatic fender	–	Automatic single surface

Figure 11. LS-DYNA modelling of the internal pressure in the pneumatic rubber fender.

Figure 12. Finite element model of the entire test set-up.

Figure 13. Result of the convergence study to determine the optimum mesh size.

Figure 14. Crushing shapes in the (a) physical test and (b) proposed model.

Figure 15. Reaction force–penetration relationship measured in the physical tests.

Figure 16. Absorbed energy–penetration relationship measured in the physical tests.

Figure 17. Reaction force–penetration relationship simulated by the proposed model.

Figure 18. Absorbed energy–penetration relationship simulated by the proposed model.

Figure 19. Experimentally measured and numerically modelled absorbed energy–penetration relationships at a loading speed of 0.05 mm/s.

Figure 20. Experimentally measured and numerically modelled absorbed energy–penetration relationships at a loading speed of 1 mm/s.

Figure 21. Experimentally measured and numerically modelled absorbed energy–penetration relationships at a loading speed of 100 mm/s.

Figure 22. Experimentally measured and numerically modelled absorbed energy–penetration relationships at a loading speed of 200 mm/s.

Table 5. Experimentally measured and numerically modelled absorption energy capacities of the pneumatic fender.

Loading speed	Measured absorption energy capacity (kJ)	Modelled absorption energy capacity (kJ)	Difference (%)
0.05 mm/s	4.01915	3.70464	−7.83
1 mm/s	4.67146	4.17057	−10.73
100 mm/s	5.31513	5.41602	+1.89
200 mm/s	6.17058	6.56826	+6.44

Figure 23. Side-by-side collision between an FPSO unit hull and a shuttle tanker.

Figure 24. Procedure for determining the recommended size and number of pneumatic rubber fenders.

Table 6. Principal dimensions of the VLCC class FPSO and the Suezmax class shuttle tanker.

Parameter	FPSO	Shuttle tanker
Overall length (m)	305.0	270.2
Breadth (m)	60.0	48.0
Depth (m)	30.0	23.7
Draught (m)	21.6	16.0
Deadweight (ton)	334,500	157,500
Transverse frame spacing (m)	5.69	4.80

Table 7. Recommended number and size of pneumatic rubber fenders depending on the size of the tonnage (PIANC 2002).

Displacement (ton)	Recommended number of pneumatic fenders	Recommended fender size (m)
100,000	at least 4	3.3 × 6.5
150,000	at least 5	3.3 × 6.5
200,000	at least 5	3.3 × 6.5
330,000	at least 4	4.5 × 9.0
500,000	at least 4	4.5 × 9.0

Table 8. Examined case studies and the corresponding collision conditions.

Case study	Striking ship	Collision speed (kt)	Number of pneumatic rubber fenders installed
1	Shuttle tanker	2	0
2	Shuttle tanker	2	4
3	Shuttle tanker	2	5

Table 9. Mesh sizes for the structural crashworthiness analysis of a side-by-side collision.

Structure	Fine mesh size (mm)	Coarse mesh size (mm)
FPSO hull	220 × 220	880 × 880
Shuttle tanker hull	220 × 220	880 × 880
Pneumatic rubber fender	220 × 220	–

Table 10. The number of elements for the structural crashworthiness analysis of a side-by-side collision.

Structure		Fine mesh	Coarse mesh	Total
FPSO		858,603	300,786	1,159,389
Shuttle tanker		342,686	184,221	526,907
Pneumatic fenders	4	12,384	–	12,384
	5	15,480	–	15,480

Table 11. Material properties for modelling the hull structures of the FPSO and the shuttle tanker.

Material property (unit)		Mild steel	High-tensile steel
			AH32
Density, $\rho$ ($\mathrm{t}\mathrm{o}\mathrm{n}/{\mathrm{m}}^3$)		7.85	7.85
Young modulus, $E$ ($\mathrm{M}\mathrm{P}\mathrm{a}$)		205,800	205,800
Poisson ratio		0.3	0.3
Yield stress, ${\sigma }_Y$ ($\mathrm{M}\mathrm{P}\mathrm{a}$)		281.57	400.97
Cowper–Symonds coefficient	C	40.4	3200
	q	5	5

Figure 25. Finite element model of the FPSO hull equipped with five pneumatic rubber fenders and the shuttle tanker involved in a side-by-side collision.

Table 12. Dynamic properties of steel for the analysis of structural crashworthiness during a side-by-side collision.

Steel grade	Collison speed (kt)	Strain rate (1/s)	Yield stress (MPa)	Dynamic yield stress (MPa)	Static fracture strain	Dynamic fracture strain	Critical fracture strain
Mild steel	2	2.370	281.57	441.25	0.429	0.076	0.120
AH32	2	2.370	400.97	495.81	0.324	0.080	0.099

Figure 26. Structural damage on the FPSO hull with no pneumatic runner fenders at a 2-knot side-by-side collision between a Suezmax class shuttle tanker and an FPSO: (a) side view, (b) cross-sectional view.

Figure 27. Collision-induced buckling of horizontal girders on the struck FPSO hull with no pneumatic rubber fenders.

Figure 28. Change in absorbed energy components over time for the FPSO and shuttle tanker hulls with no pneumatic rubber fenders in a 2-knot side-by-side collision scenario.

Figure 29. Change in absorbed energy components over time for the FPSO hull (equipped with 4 fenders) and the shuttle tanker hull in a 2-knot side-by-side collision scenario.

Figure 30. Change in absorbed energy components over time for the FPSO hull (equipped with 5 fenders) and the shuttle tanker hull in a 2-knot side-by-side collision scenario.

PIANC. 2002. MarCom WG 33: Guidelines for the design of fender systems (2002-2004). Report of Working Group 33 of the Maritime Navigation Commission, The World Association for Waterborne Transport Infrastructure, Brussels. Belgium.

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