Fender Design Trelleborg Doc

Fender Design Section 12

Trelleborg Marine Systems

www.trelleborg.com/marine Ref. M1100-S12-V1-3-EN

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Ship Tables Berthing Modes Coefficients Berth Layout Panel Design Materials Fender Testing 13/04/2011 2:55 PM

12–2

FENDER DESIGN Fenders must reliably protect ships, structures and themselves. They must work every day for many years in severe environments with little or no maintenance. As stated in the British Standard†, fender design should be entrusted to ‘appropriately qualified and experienced people’. Fender engineering requires an understanding of many areas: B B B B B B B B

Ship technology Civil construction methods Steel fabrications Material properties Installation techniques Health and safety Environmental factors Regulations and codes of practice

Using this guide This guide should assist with many of the frequently asked questions which arise during fender design. All methods described are based on the latest recommendations of PIANC* as well as other internationally recognised codes of practice. Methods are also adapted to working practices within Trelleborg and to suit Trelleborg products. Further design tools and utilities including generic specifications, energy calculation spreadsheets, fender performance curves and much more can be downloaded from the Trelleborg Marine Systems website (www.trelleborg.com/marine).

Codes and guidelines ROM 0.2-90

1990

Actions in the Design of Maritime and Harbor Works

† BS6349 :

1994

Code of Practice for Design of Fendering and Mooring Systems

Part 4 : 1994

Exceptions

EAU 1996

1996

Recommendations of the Committee for Waterfront Structures

These guidelines do not encompass unusual ships, extreme berthing conditions and other extreme cases for which specialist advice should be sought.

PIANC Bulletin 95

1997

Approach Channels – A Guide to Design Supplement to Bulletin No.95 (1997) PIANC

Japanese MoT 911

1998

Technical Note of the Port and Harbour Research Institute, Ministry of Transport, Japan No. 911, Sept 1998

* PIANC 2002

2002

Guidelines for the Design of Fender Systems : 2002 Marcom Report of WG33

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GLOSSARY Commonly used symbols Symbol B C CB CC CE CM CS D EN EA FL FS H K KC LOA LBP LS LL M M50 M75 MD P R RF V VB α δ θ μ ϕ

Definition Beam of vessel (excluding beltings and strakes) Positive clearance between hull of vessel and face of structure Block coefficient of vessel’s hull Berth configuration coefficient Eccentricity coefficient Added mass coefficient (virtual mass coefficient) Softness coefficient Draft of vessel Normal berthing energy to be absorbed by fender Abnormal berthing energy to be absorbed by fender Freeboard at laden draft Abnormal impact safety factor Height of compressible part of fender Radius of gyration of vessel Under keel clearance Overall length of vessel’s hull Length of vessel’s hull between perpendiculars Overall length of the smallest vessel using the berth Overall length of the largest vessel using the berth Displacement of the vessel Displacement of the vessel at 50% confidence limit Displacement of the vessel at 75% confidence limit Displacement of vessel Fender pitch or spacing Distance from point of contact to the centre of mass of the vessel Reaction force of fender Velocity of vessel (true vector) Approach velocity of the vessel perpendicular to the berthing line Berthing angle Deflection of the fender unit Hull contact angle with fender Coefficient of friction Velocity vector angle (between R and V)

Units m m – – – – – m kNm kNm m – m m m m m m m tonne tonne tonne tonne m m kN m/s m/s degree % or m degree – degree

Definitions Rubber fender

Units made from vulcanised rubber (often with encapsulated steel plates) that absorbs energy by elastically deforming in compression, bending or shear or a combination of these effects.

Pneumatic fender

Units comprising fabric reinforced rubber bags filled with air under pressure and that absorb energy from the work done in compressing the air above its normal initial pressure.

Foam fender

Units comprising a closed cell foam inner core with reinforced polymer outer skin that absorb energy by virtue of the work done in compressing the foam.

Steel Panel

A structural steel frame designed to distribute the forces generated during rubber fender compression.

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WHY FENDER? ‘There is a simple reason to use fenders: it is just too expensive not to do so’. These are the opening remarks of PIANC* and remain the primary reason why every modern port invests in protecting their structures with fenders. Well-designed fender systems will reduce construction costs and will contribute to making the berth more efficient by improving turn-around times. It follows that the longer a fender system lasts and the less maintenance it needs, the better the investment. It is rare for the very cheapest fenders to offer the lowest long term cost. Quite the opposite is true. A small initial saving will often demand much greater investment in repairs and upkeep over the years. A cheap fender system can cost many times that of a well-engineered, higher quality solution over the lifetime of the berth as the graphs below demonstrate.

10 reasons for quality fendering B B B B B B B B B B

Capital costs

Maintenance costs 700

180 160

120

500

400

80

300

Purchase price

100

60 40 20

Trelleborg

200

rg

o Trelleb

100

Other

Purchase price + Design approvals + Delivery delays + Installation time + Site support = Capital cost

er Oth

Other costs

600

140

0

Safety of staff, ships and structures Much lower lifecycle costs Rapid, trouble-free installation Quicker turnaround time, greater efficiency Reduced maintenance and repair Berths in more exposed locations Better ship stability when moored Lower structural loads Accommodate more ship types and sizes More satisfied customers

0

10

20 30 Service life (years)

40

50

Wear & tear + Replacements + Damage repairs + Removal & scrapping + Fatigue, corrosion = Maintenance cost

Capital cost + Maintenance cost = FULL LIFE COST

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DESIGN FLOWCHART Functional B type(s) of cargo B safe berthing and mooring

B better stability on berth B reduction of reaction force

Operational B berthing procedures B frequency of berthing B limits of mooring and operations (adverse weather) B range of vessel sizes, types B special features of vessels (flare, beltings, list, etc) B allowable hull pressures

B light, laden or partly laden ships B stand-off from face of structure (crane reach) B fender spacing B type and orientation of waterfront structure B special requirements B spares availability

Site conditions B wind speed B wave height B current speed

B topography B tidal range B swell and fetch

B temperature B corrosivity B channel depth

Design criteria B B B B B B

codes and standards design vessels for calculations normal/abnormal velocity maximum reaction force friction coefficient desired service life

B B B B B

safety factors (normal/abnormal) maintenance cost/frequency installation cost/practicality chemical pollution accident response

Design criteria

Calculation of berthing energy

Mooring layout CC berth configuration factor CS softness factor

CM virtual mass factor CE eccentricity factor

B location of mooring B strength and type B pre-tensioning of equipment and/or dolphins of mooring lines mooring lines

Calculation of fender energy absorption

Assume fender system and type

B selection of abnormal berthing safety factor

Computer simulation (first series) Selection of appropriate fenders Check results Determination of: B energy absorption B reaction force B deflection

B check vessel motions in six degrees of freedom B check vessel acceleration

B environmental factors B frictional loads B angular compression B chains etc B hull pressure

Check impact on structure and vessel B horizontal and vertical loading B chance of hitting the structure (bulbous bows etc) B face of structure to accommodate fender

B check deflection, energy and reaction force B check mooring line forces

Computer simulation (optimisation)

B implications of installing the fender B bevels/snagging from hull protrusions B restraint chains

Final selection of fender B determine main characteristics of fender B PIANC Type Approved B verification test methods

B B B B

check availability of fender track record and warranties future spares availability fatigue/durability tests

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12–6

THE DESIGN PROCESS Many factors contribute to the design of a fender:

Ships Ship design evolves constantly – shapes change and many vessel types are getting larger. Fenders must suit current ships and those expected to arrive in the foreseeable future.

Structures Fenders impose loads on the berthing structure. Many berths are being built in exposed locations, where fenders can play a crucial role in the overall cost of construction. Local practice, materials and conditions may influence the choice of fender.

Berthing Many factors will affect how vessels approach the berth, the corresponding kinetic energy and the load applied to the structure. Berthing modes may affect the choice of ship speed and the safety factor for abnormal conditions.

Installation and maintenance Fender installation should be considered early in the design process. Accessibility for maintenance, wear allowances and the protective coatings will all affect the full life cost of systems. The right fender choice can improve turnaround times and reduce downtime. The safety of personnel, structures and vessels must be considered at every stage – before, during and after commissioning.

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ENVIRONMENT Typical berthing locations Berthing structures are located in a variety of places from sheltered basins to unprotected, open waters. Local conditions will play a large part in deciding the berthing speeds and approach angles, in turn affecting the type and size of suitable fenders.

Non-tidal basins With minor changes in water level, these locations are usually sheltered from strong winds, waves and currents. Ship sizes may be restricted due to lock access.

Tidal basins Larger variations in water level (depends on location) but still generally sheltered from winds, waves and currents. May be used by larger vessels than non-tidal basins.

Coastal berths Maximum exposure to winds, waves and currents. Berths generally used by single classes of vessel such as oil, gas or bulk.

River berths Largest tidal range (depends on site), with greater exposure to winds, waves and currents. Approach mode may be restricted by dredged channels and by flood and ebb tides. Structures on river bends may complicate berthing manoeuvres.

Tides

Currents and winds

Tides vary by area and may have extremes of a few centimetres (Mediterranean, Baltic) or over 15 metres (parts of UK and Canada). Tides will influence the structure’s design and fender selection.

HRT

HRT HAT MHWS MHWN MLWN MLWS LAT LRT

MLWS

Highest Recorded Tide Highest Astronomical Tide Mean High Water Spring Mean High Water Neap Mean Low Water Neap Mean Low Water Spring Lowest Astronomical Tide Lowest Recorded Tide

HAT MHWS MHWN

MSL MLWN

LAT LRT

Current and wind forces can push vessels onto or off the berth, and may influence the berthing speed. Once berthed, and provided the vessel contacts several fenders, the forces are usually less critical. However special cases do exist, especially on very soft structures. As a general guide, deep draught vessels (such as tankers) will be more affected by current and high freeboard vessels (such as RoRo and container ships) will be more affected by strong winds.

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STRUCTURES The preferred jetty structure can influence the fender design and vice versa. The type of structure depends on local practice, the geology at the site, available materials and other factors. Selecting an appropriate fender at an early stage can have a major effect on the overall project cost. Below are some typical structures and fender design considerations.

Features Open pile jetties

B Simple and cost-effective B Good for deeper waters B Load-sensitive B Limited fixing area for fenders

Design considerations B Low reaction reduces pile sizes and concrete mass B Best to keep fixings above piles and low tide B Suits cantilever panel designs

B Vulnerable to bulbous bows

Dolphins

B Common for oil and gas terminals

B Few but large fenders

B Very load-sensitive

B Total reliability needed

B Flexible structures need careful design to match fender loads

B Low reactions preferred

B Structural repairs are costly

Monopiles

B Inexpensive structures B Loads are critical B Not suitable for all geologies B Suits remote locations B Quick to construct

B Large panels for low hull pressures need chains etc

B Fenders should be designed for fast installation B Restricted access means low maintenance fenders B Low reactions must be matched to structure B Parallel motion systems

Mass structures

B Most common in areas with small tides

B Keep anchors above low tide

B Fender reaction not critical

B Care needed selecting fender spacing and projection

B Avoid fixings spanning pre-cast and in situ sections or expansion joints

B Suits cast-in or retrofit anchors B Many options for fender types

Sheet piles

B Quick to construct B Mostly used in low corrosion regions B In situ concrete copes are common B Can suffer from ALWC (accelerated low water corrosion)

B Fixing fenders direct to piles difficult due to build tolerances B Keep anchors above low tide B Care needed selecting fender spacing and projection

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SHIP TYPES General cargo ship B B B B

Prefer small gaps between ship and quay to minimise outreach of cranes. Large change of draft between laden and empty conditions. May occupy berths for long periods. Coastal cargo vessels may berth without tug assistance.

B B B B

Need to be close to berth face to minimise shiploader outreach. Possible need to warp ships along berth for shiploader to change holds. Large change of draft between laden and empty conditions. Require low hull contact pressures unless belted.

B B B B B

Flared bows are prone to strike shore structures. Increasing ship beams needs increase crane outreach. Some vessels have single or multiple beltings. Bulbous bows may strike front piles of structures at large berthing angles. Require low hull contact pressures unless belted.

B B B B

Need to avoid fire hazards from sparks or friction. Large change of draft between laden and empty conditions. Require low hull contact pressures. Coastal tankers may berth without tug assistance.

B B B B B

Ships have own loading ramps – usually stern, slewed or side doors. High lateral and/or transverse berthing speeds. Manoeuvrability at low speeds may be poor. End berthing impacts often occur. Many different shapes, sizes and condition of beltings.

B B B B

Small draft change between laden and empty. White or light coloured hulls are easily marked. Flared bows are prone to strike shore structures. Require low hull contact pressures unless belted.

Ferry

B B B B B

Quick turn around needed. High berthing speeds, often with end berthing. Intensive use of berth. Berthing without tug assistance. Many different shapes, sizes and condition of beltings.

Gas carrier

B B B B B

Need to avoid fire hazards from sparks or friction. Shallow draft even at full load. Require low hull contact pressures. Single class of vessels using dedicated facilities. Manifolds not necessarily at midships position.

Bulk carrier

Container ship

Oil tanker

RoRo ship

Passenger (cruise) ship

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SHIP FEATURES Bow flares

Common on container vessels and cruise ships. Big flare angles may affect fender performance. Larger fender may be required to maintain clearance from the quay structure, cranes, etc.

Bulbous bows

Most modern ships have bulbous bows. Care is needed at large berthing angles or with widely spaced fenders to ensure the bulbous bow does not catch behind the fender or hit structural piles.

Beltings & strakes

Almost every class of ship could be fitted with beltings or strakes. They are most common on RoRo ships or ferries, but may even appear on container ships or gas carriers. Tugs and offshore supply boats have very large beltings.

Flying bridge

Cruise and RoRo ships often have flying bridges. In locks, or when tides are large, care is needed to avoid the bridge sitting on top of the fender during a falling tide.

Low freeboard

Barges, small tankers and general cargo ships can have a small freeboard. Fenders should extend down so that vessels cannot catch underneath at low tides and when fully laden.

Stern & side doors

RoRo ships, car carriers and some navy vessels have large doors for vehicle access. These are often recessed and can snag fenders – especially in locks or when warping along the berth.

High freeboard

Ships with high freeboard include ferries, cruise and container ships, as well as many lightly loaded vessels. Strong winds can cause sudden, large increases in berthing speeds.

Low hull pressure

Many modern ships, but especially tankers and gas carriers, require very low hull contact pressures, which are achieved using large fender panels or floating fenders.

Aluminium hulls

High speed catamarans and monohulls are often built from aluminium. They can only accept loads from fenders at special positions: usually reinforced beltings set very low or many metres above the waterline.

Special features

Many ships are modified during their lifetime with little regard to the effect these changes may have on berthing or fenders. Protrusions can snag fenders but risks are reduced by large bevels and chamfers on the frontal panels.

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BERTHING MODES Side berthing

α Typical values

ϕ

0° ≤ α ≤ 15° 100mm/s ≤ V ≤ 300mm/s

V

60° ≤ ϕ ≤ 90°

Dolphin berthing

α

Tug

Typical values 0° ≤ α ≤ 10°

ϕ

100mm/s ≤ V ≤ 200mm/s 30° ≤ ϕ ≤ 90°

V End berthing

α

Typical values

ϕ

0° ≤ α ≤ 10°

V

200mm/s ≤ V ≤ 500mm/s 0° ≤ ϕ ≤ 10°

Lock entrances

V

Typical values

ϕ

0° ≤ α ≤ 30°

α

300mm/s ≤ V ≤ 2000mm/s 0° ≤ ϕ ≤ 30°

Ship-to-ship berthing

ϕ

α

Typical values 0° ≤ α ≤ 15° 150mm/s ≤ V ≤ 500mm/s

V

60° ≤ ϕ ≤ 90°

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12–12

BERTHING ENERGY The kinetic energy of a berthing ship needs to be absorbed by a suitable fender system and this is most commonly carried out using well recognised deterministic methods as outlined in the following sections.

Normal Berthing Energy (EN) Most berthings will have energy less than or equal to the normal berthing energy (EN). The calculation should take into account worst combinations of vessel displacement, velocity, angle as well as the various coefficients. Allowance should also be made for how often the berth is used, any tidal restrictions, experience of the operators, berth type, wind and current exposure. The normal energy to be absorbed by the fender can be calculated as:

EN = 0.5 × M × VB2 × CM × CE × CC × CS Where, EN = Normal berthing energy to be absorbed by the fender (kNm) M = Mass of the vessel (displacement in tonne) at chosen confidence level.* VB = Approach velocity component perpendicular to the berthing line† (m/s). CM = Added mass coefficient CE = Eccentricity coefficient CC = Berth configuration coefficient CS = Softness coefficient * PIANC suggests 50% or 75% confidence limits (M50 or M75) are appropriate to most cases. † Berthing velocity (VB) is usually based on displacement at 50% confidence limit (M50).

Abnormal Berthing Energy (EA) Abnormal impacts arise when the normal energy is exceeded. Causes may include human error, malfunctions, exceptional weather conditions or a combination of these factors. The abnormal energy to be absorbed by the fender can be calculated as:

EA = FS × EN

PIANC Factors of Safety (FS) Vessel type

Size

FS

Tanker, bulk, cargo

Largest Smallest

1.25 1.75

Container

Largest Smallest

1.5 2.0

General cargo

Where, EA = Abnormal berthing energy to be absorbed by the fender (kNm) FS = Safety factor for abnormal berthings

1.75

RoRo, ferries

≥ 2.0

Tugs, workboats, etc

2.0

Choosing a suitable safety factor (FS) will depend on many factors:

Source: PIANC 2002; Table 4.2.5.

B B B B B B

PIANC recommends that ‘the factor of abnormal impact when derived should be not be less than 1.1 nor more than 2.0 unless exception circumstances prevail’. Source: PIANC 2002; Section 4.2.8.5.

The consequences a fender failure may have on berth operations. How frequently the berth is used. Very low design berthing speeds which might easily be exceeded. Vulnerability to damage of the supporting structure. Range of vessel sizes and types using the berth. Hazardous or valuable cargoes including people.

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SHIP DEFINITIONS Many different definitions are used to describe ship sizes and classes. Some of the more common descriptions are given below. Vessel Type

DWT

10,000–40,000 dwt 130,000–200,000 dwt >200,000 dwt 200,000–300,000 dwt >300,000 dwt

Comments 1st Generation container 8,000 teu All vessel types in Suez Canal All vessel types in St Lawrence Seaway Bulk carrier Bulk carrier Bulk carrier Oil tanker Oil tanker

2. Suez Canal The canal, connecting the Mediterranean and Red Sea, is about 163km long and varies from 80–135m wide. It has no lock chambers but most of the canal has a single traffic lane with passing bays.

3. St Lawrence Seaway The seaway system allows ships to pass from the Atlantic Ocean to the Great Lakes via six short canals totalling 110km, with 19 locks, each 233m long, 24.4m wide and 9.1m deep.

Length × Beam × Draft

Small feeder

200m × 23m × 9m

Feeder

215m × 30m × 10m

Panamax1

290m × 32.3m × 12m

Post-Panamax

305m × >32.3m × 13m

Super post-Panamax (VLCS) Suezmax 2 Seaway-Max3 Handysize Cape Size Very large bulk carrier (VLBC) Very large crude carrier (VLCC) Ultra large crude carrier (ULCC)

500m × 70m × 21.3m 233.5m × 24.0m × 9.1m

1. Panama Canal Lock chambers are 305m long and 33.5m wide. The largest depth of the canal is 12.5–13.7m. The canal is about 86km long and passage takes eight hours.

The ship tables show laden draft (DL) of vessels. The draft of a partly loaded ship (D) can be estimated using the formula below: LWT

MD = LWT + DWT

+

DWT

= MD

D≈

DL × LWT

=

MD

D

DL × (MD – DWT) MD

DL

USING SHIP TABLES 50%

75%

Ship tables originally appeared in PIANC 2002. They are divided into Confidence Limits (CL) which are defined as the proportion of ships of the same DWT with dimensions equal to or less than those in the table. PIANC considers 50% to 75% confidence limits are the most appropriate for design. Please ask Trelleborg Marine Systems for supplementary tables of latest and largest vessel types including Container, RoRo, Cruise and LNG.

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12–14 50%

SHIP TABLES smaller

Type

General cargo ship

Bulk carrier

Container ship

Oil tanker

DWT/GRT

Displacement M50

LOA

LBP

B

FL

DL

larger

Wind area Lateral Front Full Load Ballast Full Load Ballast

1000

1580

63

58

10.3

1.6

3.6

227

292

59

88

2000

3040

78

72

12.4

1.9

4.5

348

463

94

134

3000

4460

88

82

13.9

2.1

5.1

447

605

123

172

5000

7210

104

96

16.0

2.3

6.1

612

849

173

236

7000

9900

115

107

17.6

2.5

6.8

754

1060

216

290

10000

13900

128

120

19.5

2.7

7.6

940

1340

274

361

15000

20300

146

136

21.8

3.0

8.7

1210

1760

359

463

20000

26600

159

149

23.6

3.1

9.6

1440

2130

435

552

30000

39000

181

170

26.4

3.5

10.9

1850

2780

569

709

40000

51100

197

186

28.6

3.7

12.0

2210

3370

690

846

5000

6740

106

98

15.0

2.3

6.1

615

850

205

231

7000

9270

116

108

16.6

2.6

6.7

710

1010

232

271

10000

13000

129

120

18.5

2.9

7.5

830

1230

264

320

15000

19100

145

135

21.0

3.3

8.4

980

1520

307

387

20000

25000

157

148

23.0

3.6

9.2

1110

1770

341

443

30000

36700

176

167

26.1

4.1

10.3

1320

2190

397

536

50000

59600

204

194

32.3

4.8

12.0

1640

2870

479

682 798

70000

81900

224

215

32.3

5.3

13.3

1890

3440

542

100000

115000

248

239

37.9

5.9

14.8

2200

4150

619

940

150000

168000

279

270

43.0

6.6

16.7

2610

5140

719

1140

200000

221000

303

294

47.0

7.2

18.2

2950

5990

800

1310

250000

273000

322

314

50.4

7.8

19.4

3240

6740

868

1450

7000

10200

116

108

19.6

2.4

6.9

1320

1360

300

396

10000

14300

134

125

21.6

3.0

7.7

1690

1700

373

477

15000

21100

157

147

24.1

3.9

8.7

2250

2190

478

591

20000

27800

176

165

26.1

4.6

9.5

2750

2620

569

687

25000

34300

192

180

27.7

5.2

10.2

3220

3010

652

770

30000

40800

206

194

29.1

5.8

10.7

3660

3370

729

850

40000

53700

231

218

32.3

6.8

11.7

4480

4040

870

990

50000

66500

252

238

32.3

7.7

12.5

5230

4640

990

1110

60000

79100

271

256

35.2

8.5

13.2

5950

5200

1110

1220

1000

1450

59

54

9.7

0.5

3.8

170

266

78

80

2000

2810

73

68

12.1

0.7

4.7

251

401

108

117

3000

4140

83

77

13.7

1.0

5.3

315

509

131

146

5000

6740

97

91

16.0

1.4

6.1

419

689

167

194

7000

9300

108

102

17.8

1.7

6.7

505

841

196

233

10000

13100

121

114

19.9

2.0

7.5

617

1040

232

284

15000

19200

138

130

22.5

2.6

8.4

770

1320

281

355

20000

25300

151

143

24.6

3.1

9.1

910

1560

322

416

30000

37300

171

163

27.9

3.7

10.3

1140

1990

390

520

50000

60800

201

192

32.3

4.9

11.9

1510

2690

497

689

70000

83900

224

214

36.3

5.7

13.2

1830

3280

583

829

100000

118000

250

240

40.6

6.8

14.6

2230

4050

690

1010

150000

174000

284

273

46.0

8.3

16.4

2800

5150

840

1260

200000

229000

311

300

50.3

9.4

17.9

3290

6110

960

1480

300000

337000

354

342

57.0

11.4

20.1

4120

7770

1160

1850

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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12–15 50%

SHIP TABLES smaller

larger

Type

RoRo ship

Passenger (cruise) ship

DWT/GRT

Displacement M50

LOA

LBP

B

FL

DL

1000

1970

66

60

13.2

2.0

3.2

2000

3730

85

78

15.6

2.9

3000

5430

99

90

17.2

3.6

5000

8710

119

109

19.5

Wind area Lateral Front Full Load Ballast Full Load Ballast 700

810

216

217

4.1

970

1110

292

301

4.8

1170

1340

348

364

4.7

5.8

1480

1690

435

464

7000

11900

135

123

21.2

5.5

6.6

1730

1970

503

544

10000

16500

153

141

23.1

6.7

7.5

2040

2320

587

643

15000

24000

178

163

25.6

8.2

8.7

2460

2790

701

779

20000

31300

198

182

27.4

9.5

9.7

2810

3180

794

890

30000

45600

229

211

30.3

11.7

11.3

3400

3820

950

1080

1000

850

60

54

11.4

2.2

1.9

426

452

167

175

2000

1580

76

68

13.6

2.8

2.5

683

717

225

234

3000

2270

87

78

15.1

3.2

3.0

900

940

267

277

5000

3580

104

92

17.1

3.9

3.6

1270

1320

332

344

7000

4830

117

103

18.6

4.5

4.1

1600

1650

383

396

10000

6640

133

116

20.4

5.0

4.8

2040

2090

446

459

15000

9530

153

132

22.5

5.9

5.6

2690

2740

530

545

20000

12300

169

146

24.2

5.2

7.6

3270

3320

599

614

30000

17700

194

166

26.8

7.3

7.6

4310

4350

712

728

50000

27900

231

197

30.5

10.6

7.6

6090

6120

880

900

70000

37600

260

220

33.1

13.1

7.6

7660

7660

1020

1040

1000

810

59

54

12.7

1.9

2.7

387

404

141

145

2000

1600

76

69

15.1

2.5

3.3

617

646

196

203

3000

2390

88

80

16.7

2.8

3.7

811

851

237

247

5000

3940

106

97

19.0

3.3

4.3

1150

1200

302

316

7000

5480

119

110

20.6

3.7

4.8

1440

1510

354

372

10000

7770

135

125

22.6

4.2

5.3

1830

1930

419

442

15000

11600

157

145

25.0

4.7

6.0

2400

2540

508

537

20000

15300

174

162

26.8

5.2

6.5

2920

3090

582

618

30000

22800

201

188

29.7

5.9

7.4

3830

4070

705

752

40000

30300

223

209

31.9

6.5

8.0

4660

4940

810

860

1000

2210

68

63

11.1

1.0

4.3

350

436

121

139

2000

4080

84

78

13.7

1.6

5.2

535

662

177

203

3000

5830

95

89

15.4

2.0

5.8

686

846

222

254

5000

9100

112

104

17.9

2.7

6.7

940

1150

295

335

7000

12300

124

116

19.8

3.2

7.4

1150

1410

355

403

10000

16900

138

130

22.0

3.8

8.2

1430

1750

432

490

15000

24100

157

147

24.8

4.6

9.3

1840

2240

541

612

20000

31100

171

161

27.1

5.4

10.0

2190

2660

634

716

30000

44400

194

183

30.5

6.1

11.7

2810

3400

794

894

50000

69700

227

216

35.5

9.6

11.7

3850

4630

1050

1180

70000

94000

252

240

39.3

12.3

11.7

4730

5670

1270

1420

100000

128000

282

268

43.7

15.6

11.7

5880

7030

1550

1730

Ferry

Gas carrier

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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12–16 75%

SHIP TABLES smaller

Type

General cargo ship

Bulk carrier

Container ship

Oil tanker

DWT/GRT

Displacement M75

LOA

LBP

B

FL

DL

larger

Wind area Lateral Front Full Load Ballast Full Load Ballast

1000

1690

67

62

10.8

1.9

3.9

278

342

63

93

2000

3250

83

77

13.1

2.3

4.9

426

541

101

142

3000

4750

95

88

14.7

2.5

5.6

547

708

132

182

5000

7690

111

104

16.9

2.8

6.6

750

993

185

249

7000

10600

123

115

18.6

3.0

7.4

922

1240

232

307

10000

14800

137

129

20.5

3.3

8.3

1150

1570

294

382

15000

21600

156

147

23.0

3.6

9.5

1480

2060

385

490

20000

28400

170

161

24.9

3.9

10.4

1760

2490

466

585

30000

41600

193

183

27.8

4.3

11.9

2260

3250

611

750

40000

54500

211

200

30.2

4.6

13.0

2700

3940

740

895

5000

6920

109

101

15.5

2.4

6.2

689

910

221

245

7000

9520

120

111

17.2

2.6

6.9

795

1090

250

287

10000

13300

132

124

19.2

2.9

7.7

930

1320

286

340

15000

19600

149

140

21.8

3.3

8.6

1100

1630

332

411

20000

25700

161

152

23.8

3.6

9.4

1240

1900

369

470

30000

37700

181

172

27.0

4.1

10.6

1480

2360

428

569

50000

61100

209

200

32.3

4.7

12.4

1830

3090

518

723

70000

84000

231

221

32.3

5.2

13.7

2110

3690

586

846

100000

118000

255

246

39.2

5.9

15.2

2460

4460

669

1000

150000

173000

287

278

44.5

6.7

17.1

2920

5520

777

1210

200000

227000

311

303

48.7

7.3

18.6

3300

6430

864

1380

250000

280000

332

324

52.2

7.8

19.9

3630

7240

938

1540

7000

10700

123

115

20.3

2.6

7.2

1460

1590

330

444

10000

15100

141

132

22.4

3.3

8.0

1880

1990

410

535

15000

22200

166

156

25.0

4.3

9.0

2490

2560

524

663

20000

29200

186

175

27.1

5.0

9.9

3050

3070

625

771

25000

36100

203

191

28.8

5.7

10.6

3570

3520

716

870

30000

43000

218

205

30.2

6.4

11.1

4060

3950

800

950

40000

56500

244

231

32.3

7.4

12.2

4970

4730

950

1110

50000

69900

266

252

32.3

8.4

13.0

5810

5430

1090

1250

60000

83200

286

271

36.5

9.2

13.8

6610

6090

1220

1370

1000

1580

61

58

10.2

0.5

4.0

190

280

86

85

2000

3070

76

72

12.6

0.8

4.9

280

422

119

125

3000

4520

87

82

14.3

1.1

5.5

351

536

144

156

5000

7360

102

97

16.8

1.5

6.4

467

726

184

207

7000

10200

114

108

18.6

1.8

7.1

564

885

216

249

10000

14300

127

121

20.8

2.1

7.9

688

1090

255

303

15000

21000

144

138

23.6

2.7

8.9

860

1390

309

378

20000

27700

158

151

25.8

3.2

9.6

1010

1650

355

443

30000

40800

180

173

29.2

3.9

10.9

1270

2090

430

554

50000

66400

211

204

32.3

5.0

12.6

1690

2830

548

734

70000

91600

235

227

38.0

6.0

13.9

2040

3460

642

884

100000

129000

263

254

42.5

7.1

15.4

2490

4270

761

1080

150000

190000

298

290

48.1

8.5

17.4

3120

5430

920

1340

200000

250000

327

318

42.6

9.8

18.9

3670

6430

1060

1570

300000

368000

371

363

59.7

11.9

21.2

4600

8180

1280

1970

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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SHIP TABLES smaller

larger

Type

RoRo ship

Passenger (cruise) ship

DWT/GRT

Displacement M75

Wind area Lateral Front Full Load Ballast Full Load Ballast

LOA

LBP

B

FL

DL

73

66

14.0

2.7

3.5

880

970

232

232

1000

2190

2000

4150

94

86

16.6

3.9

4.5

1210

1320

314

323

3000

6030

109

99

18.3

4.7

5.3

1460

1590

374

391

5000

9670

131

120

20.7

6.1

6.4

1850

2010

467

497

7000

13200

148

136

22.5

7.3

7.2

2170

2350

541

583

10000

18300

169

155

24.6

8.8

8.2

2560

2760

632

690

15000

26700

196

180

27.2

10.7

9.6

3090

3320

754

836

20000

34800

218

201

29.1

12.4

10.7

3530

3780

854

960

30000

50600

252

233

32.2

15.2

12.4

4260

4550

1020

1160

1000

1030

64

60

12.1

2.3

2.6

464

486

187

197

2000

1910

81

75

14.4

2.9

3.4

744

770

251

263

3000

2740

93

86

16.0

3.4

4.0

980

1010

298

311

5000

4320

112

102

18.2

4.2

4.8

1390

1420

371

386

7000

5830

125

114

19.8

4.7

5.5

1740

1780

428

444

10000

8010

142

128

21.6

5.3

6.4

2220

2250

498

516

15000

11500

163

146

23.9

6.2

7.5

2930

2950

592

611

20000

14900

180

160

25.7

7.3

8.0

3560

3570

669

690

30000

21300

207

183

28.4

9.8

8.0

4690

4680

795

818

50000

33600

248

217

32.3

13.7

8.0

6640

6580

990

1010

70000

45300

278

243

35.2

16.6

8.0

8350

8230

1140

1170

1000

1230

67

61

14.3

2.1

3.4

411

428

154

158

2000

2430

86

78

17.0

2.6

4.2

656

685

214

221

3000

3620

99

91

18.8

2.9

4.8

862

903

259

269

5000

5970

119

110

21.4

3.5

5.5

1220

1280

330

344

7000

8310

134

124

23.2

3.9

6.1

1530

1600

387

405

10000

11800

153

142

25.4

4.3

6.8

1940

2040

458

482

15000

17500

177

164

28.1

5.0

7.6

2550

2690

555

586

20000

23300

196

183

30.2

5.5

8.3

3100

3270

636

673

30000

34600

227

212

33.4

6.2

9.4

4070

4310

771

819

40000

45900

252

236

35.9

6.9

10.2

4950

5240

880

940

1000

2480

71

66

11.7

1.1

4.6

390

465

133

150

2000

4560

88

82

14.3

1.5

5.7

597

707

195

219

3000

6530

100

93

16.1

2.0

6.4

765

903

244

273

5000

10200

117

109

18.8

2.6

7.4

1050

1230

323

361

7000

13800

129

121

20.8

3.2

8.1

1290

1510

389

434

10000

18900

144

136

23.1

3.9

9.0

1600

1870

474

527

15000

27000

164

154

26.0

4.8

10.1

2050

2390

593

658

20000

34800

179

169

28.4

5.5

11.0

2450

2840

696

770

30000

49700

203

192

32.0

6.7

12.3

3140

3630

870

961

50000

78000

237

226

37.2

10.5

12.3

4290

4940

1150

1270

70000

105000

263

251

41.2

13.4

12.3

5270

6050

1390

1530

100000

144000

294

281

45.8

16.9

12.3

6560

7510

1690

1860

Ferry

Gas carrier

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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12–18

APPROACH VELOCITY (VB) Berthing speeds depend on the ease or difficulty of the approach, the exposure of the berth and the vessel’s size. Conditions are normally divided into five categories as shown in the chart’s key table. The most widely used guide to approach speeds is the Brolsma table, adopted by BS1, PIANC2 and other standards. For ease of use, speeds for the main vessel sizes are shown at the bottom of this page.

0.8 a b c d e

0.7

VB

Approach velocity, VB (m/s)

e 0.6

Berthing condition Easy berthing, sheltered Difficult berthing, sheltered Easy berthing, exposed Good berthing, exposed Difficult berthing, exposed

d 0.5 c

0.4

most commonly used conditions

0.3 b 0.2 a 0.1 USE WITH CAUTION 0 1,000

10,000

100,000

500,000

Deadweight (DWT)* * PIANC suggests using DWT from 50% or 75% confidence limit ship tables.

Velocity, VB (m/s) DWT

a

b

c

d

e

1,000

0.179

0.343

0.517

0.669

0.865

2,000

0.151

0.296

0.445

0.577

0.726

3,000

0.136

0.269

0.404

0.524

0.649

4,000

0.125

0.250

0.374

0.487

0.597

5,000

0.117

0.236

0.352

0.459

0.558

10,000

0.094

0.192

0.287

0.377

0.448

20,000

0.074

0.153

0.228

0.303

0.355

30,000

0.064

0.133

0.198

0.264

0.308

40,000

0.057

0.119

0.178

0.239

0.279 0.258

50,000

0.052

0.110

0.164

0.221

100,000

0.039

0.083

0.126

0.171

0.201

200,000

0.028

0.062

0.095

0.131

0.158

300,000

0.022

0.052

0.080

0.111

0.137

400,000

0.019

0.045

0.071

0.099

0.124

500,000

0.017

0.041

0.064

0.090

0.115

B Approach velocities less than 0.1m/s should be used with caution. B Values are for tug-assisted berthing. B Spreadsheets for calculating the approach velocity and berthing energy are available at www.trelleborg.com/marine . B Actual berthing velocities can be measured, displayed and recorded using a SmartDock Docking Aid System (DAS) by Harbour Marine.† †

Harbour Marine is part of Trelleborg Marine Systems.

Caution: low berthing speeds are easily exceeded.

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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12–19

BLOCK COEFFICIENT (CB) The block coefficient (CB) is a function of the hull shape and is expressed as follows:

CB =

Typical block coefficients (CB)

MD LBP × B × D × ρSW

Container vessels General cargo and bulk carriers Tankers Ferries RoRo vessels

where, MD = displacement of vessel (t) LBP = length between perpendiculars (m) B = beam (m) D = draft (m) ρSW = seawater density ≈ 1.025t/m3

0.6–0.8 0.72–0.85 0.85 0.55–0.65 0.7–0.8

Source: PIANC 2002; Table 4.2.2

Given ship dimensions and using typical block coefficients, the displacement can be estimated:

LBP

D

MD ≈ CB × LBP × B × D × ρSW

B

ADDED MASS COEFFICIENT (CM) B The added mass coefficient allows for the body of water carried along with the ship as it moves sideways through the water. As the ship is stopped by the fender, the entrained water continues to push against the ship, effectively increasing its overall mass. The Vasco Costa method is adopted by most design codes for ship-to-shore berthing where water depths are not substantially greater than vessel drafts. Shigera Ueda (1981)

PIANC (2002)

for

KC

≤ 0.1

for

KC D

KC D

≥ 0.5

VB

D KC

Vasco Costa* (1964)

CM = 1.8

D

for 0.1 ≤

Quay

≤ 0.5

KC D

CM = 1.875 – 0.75

CM = 1.5

CM =

π×D 2 × CB × B

2D CM = 1 +

B

where, D = draft of vessel (m) B = beam of vessel (m) LBP = length between perpendiculars (m) KC = under keel clearance (m)

* valid where VB ≥ 0.08m/s, KC ≥ 0.1D

Special case – longitudinal approach

V

CM = 1.1 Recommended by PIANC.

12–19

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12–20

ECCENTRICITY COEFFICIENT (CE) The Eccentricity Coefficient allows for the energy dissipated by rotation of the ship about its point of impact with the fenders. The correct point of impact, berthing angle and velocity vector angle are all important for accurate calculation of the eccentricity coefficient. In practice, CE often varies between 0.3 and 1.0 for different berthing cases. Velocity (V) is not always perpendicular to the berthing line.

LBP y x B 2

ϕ

R

α berthing line VB

V VL VL = longitudinal velocity component (forward or astern)

x+y=

R=

LBP 2

y2 +

(assuming the centre of mass is at mid-length of the ship)

B 2

Common berthing cases

2

Quarter-point berthing K = (0.19 × CB + 0.11) × LBP x=

K + R cos ϕ 2

CE =

2

LBP 4

CE ≈ 0.4–0.6

2

Third-point berthing

K2 + R2

x= where, B = beam (m) CB = block coefficient LBP = length between perpendiculars (m) R = centre of mass to point of impact (m) K = radius of gyration (m)

LBP 3

CE ≈ 0.6–0.8

Midships berthing x=

LBP 2

CE ≈ 1.0

Caution: for ϕ < 10º, CE J 1.0 Lock entrances and guiding fenders

Tug

ϕ V R

Dolphin berths ϕ

α R

α V a

Where the ship has a significant forward motion, PIANC suggests that the ship’s speed parallel to the berthing face (Vcosα) is not decreased by berthing impacts, and it is the transverse velocity component (Vsinα) which much be resisted by the fenders. When calculating the eccentricity coefficient, the velocity vector angle (ϕ) is taken between V and R.

Ships rarely berth exactly midway between dolphins. ROM 0.2-90 suggests a=0.1L, with a minimum of 10m and maximum of 15m between the midpoint and the vessel’s centre of mass. This offset reduces the vector angle (ϕ) and increases the eccentricity coefficient.

M1100-S12-V1-3-EN © Trelleborg AB, 2011

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12–21

ECCENTRICITY COEFFICIENT (CE) Special cases for RoRo Terminals Modern RoRo terminals commonly use two different approach modes during berthing. PIANC defines these as mode b) and mode c). It is important to decide whether one or both approach modes will be used, as the berthing energies which must be absorbed by the fenders can differ considerably.

Mode b)

Mode c)

α ≤ 15º

Breasting dolphins

Outer end

A A

R

V1

Breasting dolphins

≤0.25LS

R

ϕ

Approach

ϕ

V1

≥ 1.05LL

≤0.25LS

α ≤ 15º

V2

≤0.25LS

V2

B

B

≤0.25LS Inner end

V3

V3

≤0.25LS

≤0.25LS

End fender and shore based ramp

A

Fender Side

B C

Side End

C

Typical values 100mm/s ≤ V1 ≤ 300mm/s 60° ≤ ϕ ≤ 90° N/A 300mm/s ≤ V2 ≤ 500mm/s 200mm/s ≤ V3 ≤ 500mm/s 0° ≤ ϕ ≤ 10°

RoRo vessels with bow and/or stern ramps make a transverse approach to the berth. The ships then move along the quay or dolphins using the side fenders for guidance until they are the required distance from the shore ramp structure. B Lower berthing energy B Reduced speeds may affect ship manoeuvrability B Increased turn-around time B CE is smaller (typically 0.4–0.7)

α

End fender and shore based ramp

C

A

Fender Side

Typical values 1000mm/s ≤ V1 ≤ 3000mm/s

0° ≤ ϕ ≤ 50°

B C

Side End

500mm/s ≤ V2 ≤ 1000mm/s 200mm/s ≤ V3 ≤ 500mm/s

0° ≤ ϕ ≤ 50° 0° ≤ ϕ ≤ 10°

RoRo vessels approach either head-on or stern-on with a large longitudinal velocity. Side fenders guide the vessel but ships berth directly against the shore ramp structure or dedicated end fenders. B Quicker berthing and more controllable in strong winds B High berthing energies B Risk of vessel hitting inside of fenders or even the dolphins B CE can be large (typically 0.6–0.9)

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BERTH CONFIGURATION COEFFICIENT (CC) When ships berth at small angles against solid structures, the water between hull and quay acts as a cushion and dissipates a small part of the berthing energy. The extent to which this factor contributes will depend upon several factors: B B B B B

Closed structure

Quay structure design Underkeel clearance Velocity and angle of approach Projection of fender Vessel hull shape

Semi-closed structure PIANC recommends the following values:

CC = 1.0

B B B B

CC = 0.9

B Solid quay structures B Berthing angles > 5º

Open structures including berth corners Berthing angles > 5º Very low berthing velocities Large underkeel clearance

Note: where the under keel clearance has already been considered for added mass (CM), the berth configuration coefficient CC =1 is usually assumed.

SOFTNESS COEFFICIENT (CS) Where fenders are hard relative to the flexibility of the ship hull, some of the berthing energy is absorbed by elastic deformation of the hull. In most cases this contribution is limited and ignored (CS =1). PIANC recommends the following values: CS = 1.0

Soft fenders (δf > 150mm)

CS = 0.9

Hard fenders (δf ≤ 150mm)

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Every type and size of fender has different performance characteristics. Whatever type of fenders are used, they must have sufficient capacity to absorb the normal and abnormal energies of berthing ships. When selecting fenders the designer must consider many factors including: B B B B B B

Single or multiple fender contacts The effects of angular compressions Approach speeds Extremes of temperature Berthing frequency Fender efficiency

Reaction

FENDER SELECTION

ENERGY = area under curve

Deflection

Comparing efficiency Fender efficiency is defined as the ratio of the energy absorbed to the reaction force generated. This method allows fenders of many sizes and types to be compared as the example shows. Comparisons should also be made at other compression angles, speeds and temperatures when applicable.

R

R

E

E

D

This comparison shows Super Cone and SeaGuard fenders with similar energy, reaction and hull pressure, but different height, deflection and initial stiffness (curve gradient).

D

Super Cone SCN 1050 (E2)

SeaGuard SG 2000 × 3500 (STD)

E = 458kNm R = 843kN D = 768mm P = 187kN/m2 *

E = 454kNm R = 845kN D = 1200mm P = 172kN/m2

E = 0.543 kNm/kN R

E = 0.537 kNm/kN R

* for a 4.5m2 panel

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FENDER PITCH

B Smaller ships have smaller bow radius but usually cause smaller fender deflection. B Clearance distances should take account of bow flare angles. B Bow flares are greater near to the bow and stern. B Where ship drawings are available, these should be used to estimate bow radius.

Bow radiu

s, RB

Fenders spaced too far apart may allow ships to hit the structure. A positive clearance (C) should always be maintained, usually between 5–15% of the uncompressed fender height (H). A minimum clearance of 300mm inclusive of bow flare is commonly specified.

α

θ

δF

H

θ

P/ 2

Fender pitch

1

B

2

2

+

LOA2 8B

where, RB = bow radius (m) B = beam of vessel (m) LOA = vessel length overall (m) The bow radius formula is approximate and should be checked against actual ship dimensions where possible.

Caution Large fender spacings may work in theory but in practice a maximum spacing of 12–15m is more realistic.

As a guide to suitable distance between fenders on a continuous wharf, the formula below indicates the maximum fender pitch. Small, intermediate and large vessels should be checked.

P ≤ 2 RB2 – (RB – h + C)2 where, P = pitch of fender RB = bow radius (m) h = fender projection when compressed, measured at centreline of fender a = berthing angle C = clearance between vessel and dock (C should be 5–15% of the undeflected fender projection, including panel) θ = hull contact angle with fender According to BS 6349: Part 4: 1994, it is also recommended that the fender spacing does not exceed 0.15 × L S, where L S is the length of the smallest ship. Bow radius (metres)

RB ≈

P/ 2

h = H – δF

h

C

P

Bow radius

θ

Cruise liner

Container ship

200

Bulk carrier/ general cargo

150 100 50 0 0

65 Displacement (1000 t)

0

140 0 425 Displacement (1000 t) Displacement (1000 t)

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MULTIPLE CONTACT CASES 3-fender contact

RB

δF2

RB

RB

δF1

P

B B B B

2-fender contact

δF2

P

RB

δF

Berthing H line

P

P

B B B B

Energy absorbed by three (or more) fenders Larger fender deflection likely Bow flare is important 1-fender contact also possible for ships with small bow radius

P/ 2

P/ 2

Berthing line

P

Energy divided over 2 (or more) fenders Smaller fender deflections Greater total reaction into structure Clearance depends on bow radius and bow flare

ANGULAR BERTHING The berthing angle between the fender and the ship’s hull may result in some loss of energy absorption. Angular berthing means the horizontal and/or vertical angle between the ship’s hull and the berthing structure at the point of contact. There are three possible conditions for the effects of angular berthing: flare, bow radius and dolphin.

Flare

Bow radius

Dolphin

Bow

α us,

radi RB

θ

α

β P sin θ =

P 2RB

where RB = bow radius

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FENDER PANEL DESIGN 3 design cases

Fender panels are used to distribute reaction forces into the hulls of berthing vessels. The panel design should consider many factors including: B B B B B B B B B B B B B B B B B

Full-face contact

Hull pressures and tidal range Lead-in bevels and chamfers Bending moment and shear Local buckling Limit state load factors Steel grade Permissible stresses Weld sizes and types Effects of fatigue and cyclic loads Pressure test method Rubber fender connections UHMW-PE attachment Chain connections Lifting points Paint systems Corrosion allowance Maintenance and service life

Low-level impact

Double contact

n×T F

F1

R

R

R1

F

R2

F2

Steel Properties PIANC steel thicknesses Standard

EN 10025

JIS G-3101

Grade

Yield Strength (min)

Tensile Strength (min)

Temperature

N/mm²

psi

N/mm²

psi

°C

°F

S235JR (1.0038)

235

34 000

360

52 000

–

–

S275JR (1.0044)

275

40 000

420

61 000

–

–

S355J2 (1.0570)

355

51 000

510

74 000

-20

-4

S355J0 (1.0553)

355

51 000

510

74 000

0

32

SS41

235

34 000

402

58 000

0

32

SS50

275

40 000

402

58 000

0

32

SM50

314

46 000

490

71 000

0

32

A-36

250

36 000

400

58 000

0

32

A-572

345

50 000

450

65 000

0

32

PIANC recommends the following minimum steel thicknesses for fender panel construction: Exposed both faces Exposed one face Internal (not exposed)

≥ 12mm ≥ 9mm ≥ 8mm

Source: PIANC 2002; Section 4.1.6. Corresponding minimum panel thickness will be 140–160mm (excluding UHMW-PE face pads) and often much greater.

Typical panel weights ASTM

The national standards of France and Germany have been replaced by EN 10025. In the UK, BS4360 has been replaced by BS EN 10025. The table above is for guidance only and is not comprehensive. Actual specifications should be consulted in all cases for the full specifications of steel grades listed and other similar grades.

The table can be used as a guide to minimum average panel weight (excluding UHMW-PE face pads) for different service conditions: Light duty Medium duty Heavy duty Extreme duty

200–250kg/m2 250–300kg/m2 300–400kg/m2 ≥400kg/m2

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HULL PRESSURES W

Allowable hull pressures depend on hull plate thickness and frame spacing. These vary according to the type of ship. PIANC gives the following advice on hull pressures: Size/class

Hull pressure (kN/m2)

< 1 000 teu (1st/2nd generation) < 3 000 teu (3rd generation) < 8 000 teu (4th generation) > 8 000 teu (5th/6th generation)

< 400 < 300 < 250 < 200

General cargo

≤ 20 000 DWT > 20 000 DWT

400–700 < 400

Oil tankers

≤ 20 000 DWT ≤ 60 000 DWT > 60 000 DWT

< 250 < 300 150–200

Gas carriers

LNG/LPG

< 200

Vessel type

R P=

H

Container ships

W×H

P = average hull pressure (kN/m2) R = total fender reaction (kN) W = panel width, excluding bevels (m) H = panel height, excluding bevels (m)

Bulk carriers

< 200

RoRo Passenger/cruise SWATH

Usually fitted with beltings (strakes)

Source: PIANC 2002; Table 4.4.1

BELTINGS

Belting types

Most ships have beltings (sometimes called belts or strakes). These come in many shapes and sizes – some are well-designed, others can be poorly maintained or modified. Care is needed when designing fender panels to cope with beltings and prevent snagging or catching which may damage the system. Belting line loads exert crushing forces on the fender panel which must be considered in the structural design. Application Light duty Medium duty Heavy duty

Vessels

Belting Load (kN/m)

Aluminium hulls

150–300

Container RoRo/Cruise

Belting range

1

2

h 3

500–1 000 1 000–1 500

Belting range is often greater than tidal range due to ship design, heave, roll, and changes in draft.

≥h

1

2

Common on RoRo/Cruise ships. Projection 200–400mm (typical).

3

Common on LNG/Oil tankers, barges, offshore supply vessels and some container ships. Projection 100–250mm (typical).

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FRICTION Typical friction design values

Friction has a large influence on the fender design, particularly for restraint chains. Low friction facing materials (UHMW-PE) are often used to reduce friction. Other materials, like polyurethanes (PU) used for the skin of foam fenders, have lower friction coefficients than rubber against steel or concrete. The table can be used as a guide to typical design values. Friction coefficients may vary due to wet or dry conditions, local temperatures, static and dynamic load cases, as well as surface roughness.

Materials UHMW-PE HD-PE Polyurethane Rubber Timber Steel

Steel Steel Steel Steel Steel Steel

Friction Coefficient (μ) 0.2 0.3 0.4 0.7 0.4 0.5

CHAIN DESIGN Chains can be used to restrain the movements of fenders during compression or to support static loads. Chains may serve four main functions: B Weight chains support the steel panel and prevent excessive drooping of the system. They may also resist vertical shear forces caused by ship movements or changing draft. B Shear chains resist horizontal forces caused during longitudinal approaches or warping operations. B Tension chains restrict tension on the fender rubber. Correct location can optimise the deflection geometry. B Keep chains are used to moor floating fenders or to prevent loss of fixed fenders in the event of accidents.

1 3

Factors to be considered when designing fender chains: B Corrosion reduces link diameter and weakens the chain. B Corrosion allowances and periodic replacement should be allowed for. B A ‘weak link’ in the chain system is desirable to prevent damage to more costly components in an accident.

SWL =

2

μR + W n cosθ

MBL ≥ FC × SWL θ

where, SWL = safe working load (kN) FC = safety factor μ = coefficient of friction R = fender reaction (kN) W = gross panel weight (kg) (for shear chains, W = 0) n = number of chains θ = effective chain angle (degrees)

μR

1

Tension chains

2

Weight chains

3

Shear chains

W

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UHMW-PE FACING The contact face of a fender panel helps to determine the lifetime maintenance costs of a fender installation. UHMW-PE (FQ1000) is the best material available for such applications. It uniquely combines low friction, impact strength, non-marking characteristics and resistance to wear, temperature extremes, seawater and marine borers. Sinter moulded into plates at extremely high pressure, UHMW-PE is a totally homogeneous material which is available in many sizes and thicknesses. These plates can be cut, machined and drilled to suit any type of panel or shield.

Fastening example

W t

Always use oversize washers to spread the load.

Application Light duty Medium duty

Heavy duty

Extreme duty

t (mm)

W* (mm)

Bolt

30

3–5

M16

40

7–10

50

10–15

60

15–19

70

18–25

80

22–32

90

25–36

100

28–40

M16–M20

M24–M30

M30–M36

* Where allowances are typical values, actual wear allowance may vary due fixing detail.

The standard colour is black, but UHMW-PE is available in many other colours if required.

Large pads vs small pads Larger pads are usually more robust but smaller pads are easier and cheaper to replace.

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CORROSION PREVENTION Fenders are usually installed in corrosive environments, sometimes made worse by high temperature and humidity. Corrosion of fender accessories can be reduced with specialist paint coatings, by galvanising or with selective use of stainless steels. Paint coatings and galvanising have a finite life. Coating must be reapplied at intervals during the life of the fender. Galvanised components like chains or bolts may need periodic re-galvanising or replacement. Stainless steels should be carefully selected for their performance in seawater.

Paint coatings ISO EN 12944 is a widely used international standard defining the durability of corrosion protection systems in various environments. The C5-M class applies to marine coastal, offshore and high salinity locations and is considered to be the most applicable to fenders. The life expectancy or ‘durability’ of coatings is divided into three categories which estimate the time to first major maintenance: Low Medium High

2–5 years 5–15 years >15 years

Durability range is not a guarantee. It is to help operators estimate sensible maintenance times.

The table gives some typical C5-M class paint systems which provide high durability in marine environments. Note that coal tar epoxy paints are not available in some countries. Priming Coat(s)

Top Coats

Paint System

Paint Surface System Preparation

Binder

Primer

No. coats

NDFT

Binder

No. coats

NDFT

No. coats

NDFT

Expected durability (C5-M corrosivity)

S7.09

Sa 2.5

EP, PUR

Zn (R)

1

40

EP, PUR

3-4

280

4-5

320

High (>15y)

S7.11

Sa 2.5

EP, PUR

Zn (R)

1

40

CTE

3

360

4

400

High (>15y)

S7.16

Sa 2.5

CTE

Misc

1

100

CTE

2

200

3

300

Medium (5-15y)

Sa 2.5 is defined in ISO 8501-1 NDFT = Nominal dry film thickness Zn (R) = Zinc rich primer

Misc = miscellaneous types of anticorrosive pigments EP = 2-pack epoxy

PUR = 1-pack or 2-pack polyurethane CTE = 2-pack coal tar epoxy

Design considerations Other paint systems may also satisfy the C5-M requirements but in choosing any coating the designer should carefully consider the following: B B B B B B B

Corrosion protection systems are not a substitute for poor design details such as re-entrant shapes and corrosion traps. Minimum dry film thickness >80% of NDFT (typical) Maximum film thickness