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MARINE TERMINAL DESIGN PRACTICES

FENDER SYSTEM SectionXXXI-M

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PROPRIETARY INFORMATION - For Authorized Company Use OnlyDate

December, 1998

EXXON RESEARCH AND ENGINEERING COMPANY - FLORHAM PARK, N.J.

EXXONENGINEERING

CONTENTSSection Page

SCOPE ....................................................................................................................................................3

REFERENCES .........................................................................................................................................3

INTERNATIONAL PRACTICE...........................................................................................................3

OTHER REFERENCES ....................................................................................................................3

DEFINITIONS...........................................................................................................................................3

INTRODUCTION......................................................................................................................................4

GENERAL STEPS IN DESIGNING A FENDER SYSTEM ..........................................................................4

EXISTING FACILITIES .....................................................................................................................4

NEW FACILITIES.............................................................................................................................5

CALCULATION OF BERTHING IMPACT ENERGY ..................................................................................5

IMPACT ENERGY ............................................................................................................................5

ARRIVAL DISPLACEMENT..............................................................................................................5

BERTHING VELOCITY.....................................................................................................................5

CONSTANT OF PROPORTIONALITY ..............................................................................................6

VESSEL OFFSET ............................................................................................................................7

TYPES OF FENDER SYSTEMS ...............................................................................................................9

SELECTION OF A FENDER SYSTEM .....................................................................................................11

DESIGN OF FENDER SYSTEM...............................................................................................................13

ENERGY ABSORPTION OF FENDERS...........................................................................................13

VESSEL ANGLE OF IMPACT..........................................................................................................14

HULL PRESSURE OF THE VESSEL ...............................................................................................15

CURVATURE OF THE HULL OF THE VESSEL...............................................................................15

FENDER SPACING .........................................................................................................................16

PIER ORIENTATION AND SUPPORT STRUCTURE .......................................................................17

WATER ELEVATION CHANGE (TIDE)............................................................................................17

SHEAR CAPACITY OF FENDERS ..................................................................................................17

TENSION CAPACITY OF FENDERS ...............................................................................................18

WEIGHT CHAINS............................................................................................................................19

ANCHOR BOLTS............................................................................................................................19

NOMENCLATURE ..................................................................................................................................21

DESIGN PRACTICES MARINE TERMINAL

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FENDER SYSTEM

DateDecember, 1998 PROPRIETARY INFORMATION - For Authorized Company Use Only


EXXONENGINEERING

CONTENTS (Cont)Section Page

EXAMPLES ............................................................................................................................................22

EXAMPLE 1 SAMPLE CALCULATION OF BERTHING IMPACT ENERGY....................................22

EXAMPLE 2 SAMPLE FOR SPECIFYING A FENDER SYSTEM ...................................................22

EXAMPLE 3 SAMPLE FENDER SYSTEM WITH BRIDGESTONE SUPER CELL FENDERS .........26

COMPUTER TOOLS ...............................................................................................................................31

TABLESTable 1 Berthing Velocities for Breasting Dolphins and Marginal Piers.........................................8Table 2 General Types of Fender Systems..................................................................................9Table 3 Major Advantages/Disadvantages of Fender System Alternatives..................................12

FIGURESFigure 1 Constant of Proportionality.............................................................................................6Figure 2 Vessel Offset.................................................................................................................7Figure 3 Types of Common Fender System Designs..................................................................10Figure 4 Deflection/Reaction Force Curve..................................................................................13Figure 5 Vessel Berthing Angle and Direction of Motion..............................................................14Figure 6 Effect of Vessel Hull Curvature on Fender Spacing.......................................................16Figure 7 Fender System in Compression....................................................................................18Figure 8 Effect of Tensile Force on a Fender Element.................................................................19Figure 9 Chain Assembly...........................................................................................................20Figure 10Anchor Bolt..................................................................................................................20Figure 11Correction Factor for Angular Berthing Trellex Fender Systems.....................................24Figure 12Performance Data Trellex Fender Systems...................................................................25Figure 13Fender System with Two Bridgestone Fender Units......................................................26Figure 14Performance Data Bridgestone SUC1250H Fender.......................................................26Figure 15Performance Curve Bridgestone SUC1250H Fender.....................................................27Figure 16Fender System in Compression....................................................................................28Figure 17Angular Performance Data Bridgestone Suc1250H Fender...........................................29Figure 18Correction Factor for Reaction Force Bridgestone 1250H Fender ..................................30Figure 19Correction Factor for Energy Absorption Bridgestone 1250H Fender.............................31

Revision Memo

12/98 Initial issue of this Design Practice.



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EXXONENGINEERING

SCOPE

This practice covers fender systems for the berthing of ships and barges at conventional marine pier and sea island facilities. Itcovers the design of fender systems through the Design Basis Memorandum and Design Specification stage. It does not coverNPQC, Commissioning, or Start-up of the fenders.

REFERENCES

INTERNATIONAL PRACTICE

IP 4-4-1, Marine Piers and Mooring Facilities

OTHER REFERENCES

Beazley, R. A. and Forester, G. L. Jr., Marine Fender and Dolphin Systems for Very Large Crude Carriers, EE1TTR.72,January 1972.Bruun, P., Port Engineering-Harbor Planning, Breakwaters, and Marine Terminals, Gulf Publishing, Company, Houston, (1989).

Bridgestone Cell Fender Series Catalog.

Bridgestone Marine Fender Design Manual.British Standard, BS 6349, Part 4, Code of Practice for Design of Fendering and Mooring Systems, BSI Standards, SecondEdition, October 1994.Dorsch, R. E., Designing: The Cost Effective Marine Fender System, World Dredging and Marine Construction, Volume 19Number 8, August 1983.Feinberg, A. S. and Mascenik, J., Evaluation of Full Scale Tanker Berthing Impact Forces, EE.16ER.67, June 1967.Gaythwaite, J. W., Design of Marine Facilities for Berthing, Mooring and Repair of Vessels, Van Nostrand Reinold, New York(1990).Marketing Engineering Standards, Marine Facilities Design Specification and Evaluation, EE.3M.86.

Sandstrom, R. E., Fender Analysis - Oblique Loads, 95 CMS2 065, April 1995.Trellex Application Manual - Trellex MV Elements.

Zwinklis, V. C., Modular Fender Systems for Barge and Coaster, EE.9TT.80, July 1980.

Zwinklis, V. C., Survey of Synthetic Fender Facing Material, EE.10TT.80, November 1980.

DEFINITIONS

Dead Weight Tonnage - Tonnage expressed by the weight actually loaded on the vessel, such as cargo, fuel, bunker oil,water, passengers and food.Full Load Displacement - Tonnage expressed by the total weight of the vessel body, engine, cargo (where the cargo is loadeduntil the draft line reaches the full draft line of the vessel) and all other materials loaded in it.Light Displacement - Tonnage expressed by the total weight of the vessel before cargo has been loaded.


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INTRODUCTION

Fender systems at a marine pier serve three distinct purposes. The primary function of a fender system is to reduce the loadsdistributed to the pier and vessel by absorbing some or all of the kinetic energy of berthing vessels. Fendering also distributesberthing and breasting loads along the pier and over a large surface of the ships hull. Finally, fendering provides a rubbingsurface between the pier face and vessel hull, preventing abrasion or other damage from vessel maneuvering or vesselmovement due to tides, the environment, or draft changes. Fender systems should be designed to: 1) prevent direct contactbetween vessels and fixed structures, 2) ensure berthing impact energies are acceptable for berthing structures and fendersystems in normal and extreme cases so that risk of vessel and pier damage is minimized, and 3) ensure berthing and mooringloads are within the structural capacity of the individual facilities.The degree of fendering required depends on many variables, the most important of which are vessel size and approachvelocity. The size or mass of a vessel and the speed in which it contacts the pier are directly related to the amount of berthingimpact energy that must be absorbed through deflection of the fender system. The selected fender system must be effectivelycapable of absorbing most of the berthing energy and transmitting as minimal reaction force to the fixed structure as possible.Energy absorption is a function of load and deflection. The larger the deflection, the lower the resulting load to absorb thesame amount of energy. Stiff fenders, which are only designed for small deflections, will result in relatively high loadstransferred into the structure and ship's hull. Soft fenders, which allow for large deflections will result in relatively low loads.The tradeoff between fender softness and pier strength should be carefully evaluated when designing a new structure,upgrading an existing berth, or assessing alternatives to accommodate decreased structural capacity from damage ordeterioration.

GENERAL STEPS IN DESIGNING A FENDER SYSTEM

EXISTING FACILITIES

Many fender system projects involve the design, manufacture and installation of new fender systems on existing marine berths.This type of project often involves the replacement of existing fenders that are severely damaged or no longer adequate for therange of vessels calling at the facility. In some cases, a risk assessment of the facility's operations indicates that new fendersare required to improve the safety of the operations.

Generally, new fender system projects for an existing facility include the following steps through to the Design Specification:

1. Screening Study or DBMa. Develop Alternative Cases for Type, Number, Size and Layout of Fender System.

(1) Establish the maximum and minimum vessel sizes to be considered.(2) Determine the load capacity of the berth structure.

(3) Consider the layout of the dock facility (i.e., fender spacing, pier orientation and support structure, and tidalelevation changes).

(4) Calculate the berthing impact energy.(5) Select a fender system and evaluate the reaction loads (based on catalog information on the selected fender

system).b. Determine Requirements for Ancillary Equipment.

(1) Size and select materials for construction of the frontal panel.(2) Calculate the shear and tension capacity of the fender system.

(3) Determine the requirements for weight chains.

c. Gather Budgetary Quotes for Various Alternative Cases.d. Select Best Case and Confirm with Affiliate or Local Project Team.

(1) Estimate the investment required for the fender system.(2) Calculate the expected maintenance costs.

(3) Develop a schedule for the installation of the fender system, and estimate the length of time the berth will be outof service.

(4) Note any safety considerations.2. Design Specification and Recommended Vendors List

a. Develop a Design Specification based on the International Practice - Fender Systems (Future).

b. Provide a list of vendors based on consultations with ER&E Marine Terminal Engineering Section.



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GENERAL STEPS IN DESIGNING A FENDER SYSTEM (Cont)

NEW FACILITIES

New (grassroots) facilities generally follow the same steps as existing facilities except the design of the fender system is part ofthe overall design of the berth. In a new facility, the fender system and berth structure shall be optimized based on costs, loadcapacities, and possible future expansion.

CALCULATION OF BERTHING IMPACT ENERGY

The impact energy of a berthing vessel is used in the design or evaluation of the pier or dolphin structure and its fender system.This section presents guidelines for determining the value of parameters used to calculate the design berthing impact energy.The values presented herein are based mainly on the conclusions developed in Exxon Engineering Report No. EE.16ER.67.The requirements for existing structures should also incorporate previous berthing experience when determining appropriatevelocities for use in energy calculations.The impact energy of a berthing vessel is calculated by multiplying the total kinetic energy of the vessel by a constant ofproportionality, as given by the following equation:

g2VWc

E2

= Eq. (1)

where: E = Impact energy of the berthing vessel, ton-ft (tonne-m)W = Actual arrival displacement of the berthing vessel, ton (tonne)V = Berthing velocity of the vessel perpendicular to the marine terminal berthing line, ft/sec

(m/sec)c = Constant of proportionality, dimensionlessg = Acceleration of gravity, typically 32.2 ft/sec2 (9.8 m/s2)

IMPACT ENERGY

The berthing impact energy, E, for any particular portion of a structure is typically controlled by the vessel with the largestdisplacement upon berthing which will contact that portion. However, there are situations when this is not the case. Forexample, smaller vessels may berth at higher velocities than larger vessels, and may also contact berthing points closer to theircenter of gravity. Both of these effects increase the berthing energy to be absorbed. Thus, a full range of vessels that expectto use the berth should be considered.

ARRIVAL DISPLACEMENT

The actual arrival displacement, W, of the berthing vessel, which depends on the vessel draft condition (i.e., quantity of cargoonboard), should be used with the above equation. Typically, the displacement governing the design berth impact energy is fora fully loaded draft, even at loading terminals where the vessel arrives in a ballasted condition. This is to allow for the situationwhen a fully loaded vessel departs the berth and then has to return due to an onboard emergency. In some cases, partiallyloaded vessels may control the design berthing energy at facilities where the vessel's draft is restricted by the water depth.

BERTHING VELOCITY

The berthing velocity, V, with which a vessel approaches a berth is a significant factor in the calculation of the energy to beabsorbed by the fendering system as the energy is proportional to the square of the velocity. The design berthing velocity of avessel should be based on consideration of the vessel size, load condition, location and layout of berthing facilities,meteorological and sea conditions, the availability and size of tugboats, and on any existing records of berthing velocities.Table 1 lists design berthing velocities for vessels. These velocities are recommended for facilities where no previous recordsof berthing velocities exist. Judgement is required for applying these velocities at a specific location, particularly whenevaluating the adequacy of an existing fender system where previous experience indicates different berthing velocities wouldbe appropriate.


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CALCULATION OF BERTHING IMPACT ENERGY (C ont)

CONSTANT OF PROPORTIONALITY

The constant of proportionality, c, indicates the portion of the normal kinetic energy of the vessel that is to be dissipated by thefender system. It also includes an allowance for energy absorbed by structural deflections of the ship's hull, berthing structureand foundation soils, the damping effect of water between the pier and vessel and the hydrodynamic added mass of the vessel.The added mass can be thought of as the amount of water that moves with the vessel as it approaches the pier. This addedmass contributes to the amount of energy the pier must dissipate. The magnitude of "c" will vary according to the followingfactors:

Location of the point of contact on the vessel with the fender system (Vessel Offset)

Depth of water under the keel

Current direction and speedThe location of the point of contact on the vessel with the fender system affects the amount of vessel rotation after initial impactand thus the portion of the normal kinetic energy that is dissipated by the structure during initial contact and by water resistanceduring subsequent rotation. The depth of water under the keel (underkeel clearance) and current direction and speed affect thehydrodynamic mass. The value of "c" is directly taken from Figure 1 when the underkeel clearance is between 4 and 10 ft (1.2and 3.0 m) and the current is approximately parallel to the pier. For other conditions, adjustments to the constant ofproportionality are required as noted in Figure 1.

FIGURE 1CONSTANT OF PROPORTIONALITY

DP31Mf01

Notes:(1) a = Distance of impact point from center of gravity of vessel (assumed to be on transverse centerline).(2) L = Vessel length, overall (LOA).(3) Increase "c" by 15% if underkeel clearance is less than 4 ft (1.2 m).(4) Decrease "c" by 10% if underkeel clearance is 10 to 25 ft (3 to 7.5 m), and decrease by 15% if the clearance

is greater than 25 ft (7.5 m).(5) Add 0.1 to all values of "c" when the current is pushing the ship towards the pier with an aspect angle

between 5 and 10. Add 0.2 when the angle is greater than 10.

a/L

CO

NSTA

NT O

F PR

OPO

RTIO

NA

LITY

"c"

0.5 0.4 0.3 0.2 0.1 0.00.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1



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VESSEL OFFSET

Ideally, the manifold of a berthing vessel would line up with the pier loading equipment which is generally centered on the berthstructure. However, experience has shown that the tanker manifold and pier loading point can be offset at initial impact. Formarginal piers, an offset distance of 30 - 50 ft (10 - 15 m) is usually used in determining the distance "a" between vessel impactpoint on the fender system and the vessel's center of gravity as shown in Figure 2. This distance generally increases from 30 -50 ft (10 - 15 m) as vessel size increases. However, local conditions and berthing procedures must be evaluated indetermining this value for each individual location.

FIGURE 2VESSEL OFFSET

Pier

PierDistance from pier

center of manifold tofirst point of contact

VesselVesselOffset

"a" = Distance fromvessel center of

gravity to first point ofcontact

Berthing Angle

Vessel BerthingVelocity

CL

CL

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CALCULATION OF BERTHING IMPACT ENERGY (C ont)

TABLE 1BERTHING VELOCITIES, V(1)

BREASTING DOLPHINS AND MARGINAL PIERS (2)

PROTECTED HARBOR

BERTHING SITUATION VESSEL (3)

Vessel LoadCondition Tugs

PierParallelsCurrent

Barges,Coasters,

Tankers lessthan 15,000

dwt

Tankers15,001 dwt

through30,000 dwt

Tankers30,001 dwt

through50,000 dwt

Tankers50,001 dwt

through90,000 dwt

Over90,000 dwt

Full Load Yes Yes 0.550 0.450 0.350 0.325 0.300

No Yes 0.650 0.550 0.450 0.425 0.400

Yes No 0.650 0.550 0.450 0.425 0.400

No No 0.700 0.600 0.500 0.475 0.450

Ballasted Yes Yes 0.650 0.525 0.425 0.375 0.350

No Yes 0.750 0.625 0.525 0.475 0.450

Yes No 0.750 0.625 0.525 0.475 0.450

No No 0.800 0.675 0.575 0.525 0.500

MODERATELY EXPOSED LOCATION

BERTHING SITUATION VESSEL (3)

Vessel LoadCondition Tugs

PierParallelsCurrent

Barges,Coasters,

Tankers lessthan 15,000

dwt

Tankers15,001 dwt

through30,000 dwt

Tankers30,001 dwt

through50,000 dwt

Tankers50,001 dwt

through90,000 dwt

Over90,000 dwt

Full Load Yes Yes 0.650 0.550 0.450 0.400 0.375

No Yes 0.750 0.650 0.550 0.500 0.475

Yes No 0.750 0.650 0.550 0.500 0.475

No No 0.800 0.700 0.600 0.550 0.525

Ballasted Yes Yes 0.750 0.625 0.525 0.450 0.425

No Yes 0.850 0.725 0.625 0.550 0.525

Yes No 0.850 0.725 0.625 0.550 0.525

No No 0.900 0.775 0.675 0.600 0.550

Notes:

(1) In units of ft/sec (1 ft/sec = 0.3 m/sec)

(2) For finger piers reduce the berthing velocity, V, by 20 - 25%. For turning dolphins increase the berthing velocity, V, by 0.050 -0.100 ft/sec (0.015 - 0.030 m/sec)

(3) dwt = Dead Weight Tons



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TYPES OF FENDER SYSTEMS

There are many different types and configurations of fender systems available for marine piers. Fender systems can bebroadly categorized into three types as listed in Table 2 and shown in Figure 3.

TABLE 2GENERAL TYPES OF FENDER SYSTEMS

FENDER SYSTEM DESCRIPTION

Rubbing Strips

Rubbing Strips are timbers or high-density polyethylene materialdirectly attached to a pier face to provide a smooth rubbing surfacebetween the pier and hull of a ship. Rubbing strips absorb almostno energy and therefore must be used on flexible piers that aredesigned to deflect and absorb the impact energy of berthingvessels. Rubbing strip fender systems are generally limited tosmall wooden pier or bulkhead type barge facilities.

Flexible Pile Systems

Flexible Pile Systems are steel or timber piles designed to bend inflexure to absorb berthing impact energy. There are many differentconfigurations and a wide range of ship sizes that can beaccommodated by flexible pile systems. These systems can rangefrom a single or multiple steel pile breasting dolphin which acts likea cantilever and is entirely independent of any other structure, to aseries of angled timber piles attached to the pier which bow in themiddle when impacted to absorb energy.

Resilient Buffer Systems

Resilient Buffer Systems are comprised of flexible buffers, such assteel springs, rubber tubes or columns, which are mounted on theface of a platform or dolphin and absorb impact energy bycompressing. There are many different configurations and a widerange of ship sizes that can be accommodated by resilient buffersystems. Resilient buffer systems can range from unfaced bufferunits which come in direct contact with the ship, to systems whichuse panels to distribute loads amongst several buffers and over alarge area of the ship hull. These panels can either be hung bychains off the pier, supported by the buffers themselves, orsupported by piles which can also assist in energy absorption.

Typically, two or three of these general types of fender systems are combined to work together in order to capitalize on eachindividual system's advantages. A common example of this is a single steel pile flexible dolphin outfitted with a buckling typerubber buffer and a steel framed panel faced with synthetic rubbing strips.


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TYPES OF FENDER SYSTEMS (C ont)

FIGURE 3TYPES OF COMMON FENDER SYSTEM DESIGNS

Suspended Panel

Resilient Buffer Fender

Rubbing

Strip

Flexible Pile Fender ( Attached

To Breasting Face System)

Unfaced Resilient

Buffer System

Flexible Dolphin

.

DP31MF03

Pile Supported Panel


Pneumatic or foam filled




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SELECTION OF A FENDER SYSTEM

Once the energy absorption requirements and the load limitations of the pier facility and vessels are determined, an appropriatefendering system can be designed. The selection of the best fender system for a particular application depends on:

Energy absorption requirements.

Maximum reaction force.

Maximum deflection and load deflection characteristics.

Effect of angular impact on performance.

Coefficient of friction and vertical and longitudinal rubbing forces.

The range of vessels to be handled, the types of vessels, their hull size and shape.

Distance requirements between the vessel and pier structure.

Range of tide and exposure conditions.

Environmental exposure effects.

Frequency of berthing and wear considerations.

Factor of safety and overload capacity.

Cost and long-term maintenance/repair costs.

Local availability, costs, and construction practices.It is impractical to suggest a standardized fender system because local conditions are rarely identical. Because every facilityvaries, the design must be tailored for that specific terminal. However, if past experience has proven that a particular fenderdesign is effective and economical for a site, it should be considered for other sites with similar conditions. In general, the bestfender system will absorb the required amount of energy while minimizing the reaction forces to the pier structure and vesselhull, at the lowest cost.Table 3 lists the major advantages and disadvantages of the various types of available fender systems to assist in the optimalselection. New or used truck tires are occasionally installed at Marketing facilities to serve as the fender system. While thesetype systems have performed well in some situations, many have experienced considerable wear and damage of the tires, aswell as structural damage to the pier. This damage is primarily due to their lack of energy absorption capacity or inadequaterestraint systems that expose the pier face. Tires have not been engineered for this application, and there is little datasupporting the use of tires as an effective fender system. Locations utilizing these type systems should ensure fender andberth capacity has been adequately considered.


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SELECTION OF A FENDER SYSTEM (Cont)

TABLE 3MAJOR ADVANTAGES/DISADVANTAGES OF FENDER SYSTEM ALTERNATIVES

TYPE OF FENDER SYSTEM ADVANTAGES DISADVANTAGES

Rubbing StripsAs total fendering system Lowest Cost Limited to small barge berths with structures

designed to absorb energy through deflection

Generally results in high loads into the shipand pier

As facing for other systems:

Wood Low initial cost compared with synthetic facings

Helps distribute point loads

Requires periodic replacement

Synthetic Durable, low maintenance Higher initial Cost than wood

Resilient Buffer SystemsGeneral/Unfaced High energy/reaction force ratio

Can accommodate a large range of ship sizes

Moderate cost

Can be installed quickly

Well suited for barge berths

Moderate to high cost

Results in high vessel hull pressures

Easily damaged by protrusions from ship hull

Only portion of the buffer is contact effective

Load is not distributed along pier

Pile supported panel systems Ideal for locations with large tide variation

Results in low hull pressures

Applicable on almost all types of piers

Distributes contact amongst multiple buffers

Maintenance of piles, chains, and facingmaterials

Difficult to install

Moderate distance between vessel and pierface

Suspended panel systems Eliminates pile cost and maintenance

Can be installed quickly

Maintenance of chains and facing materials

Moderate distance between vessel and pierface

Floating pneumatic/foam systems Produces low hull pressures and loads into pier

Can usually be installed very quickly

Requires large backing surface

Pneumatic types susceptible topuncture/deflation

Large distance between vessel and pier

Not good for large tidal or ship size range

Flexible Pile SystemsSingle pile breasting dolphin Low cost for a dolphin structure May require high strength steels and large

pile driving equipment

Limited to certain soil conditions

Multiple pile breasting dolphin Uses smaller lower strength piles Limited to certain soil conditions

Welded connections critical

Independent multiple pilebreasting face systems

Protects entire platform face

No resultant loads into the platform

Good for large range of ship sizes and tides

Most suited to barges

Limited to certain soil conditions

Difficult to maintain

Attached multiple pile breastingface systems

Protects entire platform face

Good for large range of ships sizes and tides

Difficult to maintain



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DESIGN OF FENDER SYSTEM

Regardless of the type of fender system chosen for a particular location, it should be designed to ensure adequate protection ofthe pier and vessel, minimize operating restrictions and problems, and reduce and simplify required maintenance. This sectiondescribes design criteria that should be considered when designing or specifying a fender system. In general, the followingshould be considered when selecting a fender system: the required energy capacity, configuration of the fender system andsupport structure, and the fender panel requirements.

After determining the requirements for the fender system, design information can be obtained from manufacturer's catalogswhich can be found in the Marine Terminal Engineering Library. There are many different options when selecting a fendersystem. The size, shape, and material of a fender system determine its energy absorption capacity and reaction force.Therefore, each manufacturer supplies the required design data about each fender system that they offer. The catalogprovides information about a fender system's physical size and shape, the material composition, the energy absorption capacityand reaction forces at specific deflections, and effect of angular berthing on the fender. Based on the required performancecriteria determined in this section and the information supplied in the fender catalogs, the best fender system for the applicationcan be selected.

ENERGY ABSORPTION OF FENDERS

For a given vessel impact energy, the selected fender system must be capable of effectively absorbing most of the berthingenergy and transmitting as minimal reaction force to the fixed structure as possible. The work done by deflecting the fendersystem is equal to the area under the load deflection curve as given by the integral:

d

=

o

n dx)x(RE Eq. (2)

where: En = Energy absorbed by the fender systemR = Reaction forcex = Deflectiond = Deflection at the rated or desired energy level

This is expressed graphically as the area under the deflection/reaction force curve as shown in Figure 4.

FIGURE 4DEFLECTION/REACTION FORCE CURVE

10% 20% 30% 40% 50% 60% 70%

20%

40%

60%

80%

100%

120%

Reac

tion F

orce

Cur

ve

DEFLECTION, % OF FENDER ELEMENT HEIGHT

% O

F R

ATED

REA

CTIO

N F

OR

CE

0%0%

130%

DP31Mf04


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DESIGN OF FENDER SYSTEM (Cont)

The selected fender system should have greater energy absorption at normal compression than the berthing impact energy,and the reaction force should be less than the maximum allowable reaction force of the pier structure. The calculated designenergy should be absorbed within 67 percent of the ultimate energy capacity of the fender system, which is referred to as therated energy capacity. Typically, the information provided by fender manufacturers refers to the rated performance of thefender system. The rated performance is typically based on the rated deflection, which ranges from 45 to 60%, depending onthe manufacturer. Elastomeric and pneumatic fender manufacturers typically supply fender performance curves for each modelthey supply. Precautions should be taken to insure that the most current information is being used.The berthing energy, as calculated using Eq. (2), is based on normal operations and may be exceeded due to accidentaloccurrences such as the following:1. A change in wind or current conditions greater than the design limits.

2. An engine or steering gear failure of the ship or tug.3. Human error.

In order to provide a margin of safety for such accidental occurrences, the ultimate energy capacity of the fender should be upto one and a half times (safety factor of 1.5) the calculated berthing energy for normal impacts.

VESSEL ANGLE OF IMPACT

The angle of approach is the angle that the vessel's hull makes with the berthing structure and should not be confused with thedirection of the vessel motion as shown in Figure 5. Energy loss of the fender system can occur under angular approachesdue to the non-uniform deflections and energy absorption by each fender in the system. This energy loss should be consideredin the analysis. Vessels should be assumed to approach at angles up to 10 for tankers and 15 for coasters and barges.

FIGURE 5VESSEL BERTHING ANGLE AND DIRECTION OF MOTION

Pier

Pier

Fender

Vessel

Berthing Angle= 10

Vessel BerthingVelocity

CL

CL

DP31Mf05

Depending on the berthing angle, an angular correction factor will need to be applied to the energy absorption capacity of theselected fender system at normal (berthing angle of zero degrees) compression, as shown by the following equation:

eana FEEE =< Eq. (3)

where: E = Berthing impact energyEa = Energy absorption of the fender at angular compressionEn = Energy absorption of the fender at normal compressionFea = Angular correction factor for energy absorption



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If there is any limit in the allowable reaction force to the pier structure, the following equation should be utilized:

Rmax > Rn and Ra = Rn Fra Eq. (4)

where: Rmax = Maximum allowable reaction forceRn = Reaction force at normal compressionRa = Reaction force at angular compressionFra = Angular correction factor for reaction force

Typically, most manufacturers of elastomeric and pneumatic fender systems provide correction factors to the performance dataof their units for use in angular berthing conditions.

HULL PRESSURE OF THE VESSEL

Large vessels with large areas of vertical and parallel sides are vulnerable to local point loads on the shell plating andstiffeners, which are designed for local hydrostatic pressure. For smaller vessels, however, the local hull strength is not usuallya problem because of the closer frame spacing, greater curvature and inherently greater stiffness. The ratio between the widthof the fender contact area and the vessel transverse frame spacing should not be less than 0.5 to 0.65, and the ratio betweenthe height and the side longitudinal spacing not less than about two. Because of the wide variety of vessel construction, it isdifficult to determine the transverse spacing for a particular design. Therefore, to simplify the design process, the fender facingcontact area should be sized such that the maximum hull pressure does not exceed 2 tons/ft2 (20 tonnes/m2). From themaximum hull pressure, the minimum required fender contact area is obtained by the following equation:

hull

max

PR

AreaContactFacing Fender = Eq. (5)

where: Rmax = Maximum reaction force of fenderPhull = Maximum hull pressure

Typically for elastomeric fender systems, a fender panel is utilized to reduce the contact pressure to the vessel's hull or tobridge a series of units into a single fender. The fender panels are usually of steel construction with a timber or polymer facingmaterial to minimize abrasive contact with the hull of the vessel. In addition, the edges of the fender panel are chamfered sothat the panel's edges do not damage the hull or scrape off the paint.

CURVATURE OF THE HULL OF THE VESSEL

Vertical curvature of the hull and hull flare, and overhang or projection such as bulbous bows, must be considered in fendersystem layout. The standoff distance from the face of the pier to the face of the fender should be minimized in the interest ofincreasing the effective reach of loading equipment and gangways, but should also provide a sufficient buffer zone to preventcontact of any part of the vessel with the pier face with fenders at their maximum rated deflection. The effect of the verticalcurvature is shown in Figure 6a. The standoff distance usually ranges from 3 to 6 ft (1 to 2 m) for most seagoing terminalfacilities. At offshore installations, this distance will be close to 10 ft (3 m) or more.The minimum standoff is dependent on the curvature of the vessel's hull, angle of the pile structure, the loading equipmentoperating envelope, and the energy absorption requirements of the fender system. In order to calculate the minimum offsetdistance associated with the curvature of the hull the following formula can be used:

aa

=> sincos

hDStandoff Eq. (6)

where: D = The distance from the centerline of the fender element face to the point of contact between the vessel's hull and the berthing structure.

h = The vertical distance from the fender centerline to the point of contact between the vessel's hull and the berthing structure.

a = The angle of the vessel hull.

For pile supported structures, the fender standoff distance should account for the pile's slope angle. The vessel's hull shouldnot come into contact with the piles (see Figure 6a-II). The piles slope angle should be determined before the design of thefender system standoff. The vertical line from the compressed fender face to the piles should be larger than the molded depthof the largest calling ship. This is to prevent ships from contacting the piles at the time of berthing.


Section

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FENDER SYSTEM



EXXONENGINEERING


FIGURE 6EFFECT OF VESSEL HULL CURVATURE ON FENDER SPACING

b. Horizontal Curvaturea. Vertical Curvature DP31Mf06

Vessel Hull

Structure

D

ha

LWLHWL

Berth

DeballastedVessel

Loading Arms

Fully LoadedVessel

II

I

r

O

P

HH/2

Fender

Vessel

Wharf

q

FENDER SPACING

Fender spacing depends upon the type of fender system and structural support, the range of vessel size to be accommodated,the curvature of the vessel's hull and the type and arrangement of berth and mooring loads. Fenders are typically spaced onthe order of 25% to 50% of the vessel's Length overall (LOA). The vessel overhang beyond the end of the breasting faceshould be minimized (less than 33% of the vessel's LOA). A vessel alongside only requires two points of contact while in berth,but three or more contact points are recommended. The length of the vessel parallel sides controls the maximum spacingbetween fenders. The ratio of a vessel's parallel midbody length is on the order of 35% to 55% of its LOA, usually being largerfor longer vessels. This ratio often determines the point of first contact with the vessel's hull, which is usually at the end of theparallel midbody and also the length of vessel available to contact fenders under moored conditions. The fender spacing mustalso prevent the horizontal curvature of the vessel's hull near the bow or stern from contacting the loading platform or otherfixed structure as shown in Figure 6b. The fender spacing should be based on the smallest vessel that is expected to call atthe terminal. The following equation can be used to determine the adequate spacing between fenders for vessels approachingat angles up to 10 degrees for tankers:

2HHr4P -= Eq. (7)

where: P = Fender spacingH = Fender heightr = Vessel hull radius of curvature

For coasters and barges where the bow and stern are typically squared, a continuous fender face is recommended to preventany contact with the pier structure.



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PIER ORIENTATION AND SUPPORT STRUCTURE

The choice of fender type is also dependent on the orientation and type of structure to which it will be attached. The ability ofthe pier or berthing structure to distribute the load and resist all berthing and mooring reaction forces must be carefullychecked. Fenders with large deflection are more energy absorbent than fenders with less deflection, and in turn provide moreprotection to the support structure.

WATER ELEVATION CHANGE (TIDE)

The tidal elevation variation from the high-high water to the low-low water shall be taken into consideration when designing afender system. The fender system must prevent the smallest vessel, loaded, and arriving at the lowest tide from travelingunderneath the fender. The fender system may partially be submerged, but shall not be completely submerged during thehigh-high water. This will ease the task of maintenance.

SHEAR CAPACITY OF FENDERS

Shear forces are forces exerted on the fender element as a result of friction between the vessel's hull and the fender face.These forces, if not kept within acceptable limits, will induce shear deformations in the fender. The shear forces aremathematically expressed as the product of the normal force and the coefficient of friction.

frictionnormalshear fFS = Eq. (8)

where: Sshear = Shearing reaction force of fender (ton)Fnormal = Normal Compression Force on fender face (ton)ffriction = Coefficient of friction of fender face material (supplied by manufacturer)

The size of the shear chain is determined by the maximum tension on the shear chain which can be calculated by the followingformula:

fm+f-m

=sincos

SRT shearn Eq. (9)

where: T = Tension on shear chainm = Friction coefficient between ship and fenderRn = Axial reaction force of fenderSshear = Shearing reaction force of fenderf = Angle between the chain and the face of the structure

Figure 7 depicts the movement of the shear chain.


Section

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FENDER SYSTEM



EXXONENGINEERING


FIGURE 7FENDER SYSTEM IN COMPRESSION

Max. ShearDeflection

Frontal Frame

Shear Chain Max.

Com

pre

ssio

nD

eflect

ion

Fender

Heig

ht

f

DP31Mf07

Fender

TENSION CAPACITY OF FENDERS

Tension forces are the forces exerted on the fender element as a result of tensile deflections of the fender due to unbalancedcontact with the fender frontal panel due to low tide or small vessel berthing. This berthing creates high tension on the upperfender element. This tension can only be maintained within the allowable limit by the design of an adequate tension chain.The allowable deflection of the fender is as follows:1. Deflection in the middle part of the fender: Max. allowable tensile deflection: 5%.

2. Deflection in the peripheral area: Max. allowable tensile deflection: 10%.The following are the calculations to determine the proper size chain. Figure 8 depicts the effect of tensile force on the fenderelement and the parameters of the equations:

1. Find reaction force of the fender (R2) from its performance curve where (B) receives maximum deflection (d2) based on thedesign impact energy.

2. Calculate the deflection of the fender (d1) at (A) with the following formula and then find the reaction force of the fender(R1) from its performance curve:

221

11 d

+=d

lll

Eq. (10)

3. Substitute the values of reaction force arrived at in 1 and 2, the (R1 and R2) in the following formula (Moment Balanceformula) and obtain the tensile strength to be applied to the chain

( )l

lll 32321 RRT++

= Eq. (11)

where: T = Tension force on the chainR1 = Reaction force of fender at d1R2 = Reaction force of fender at d2F = Berthing force of vesseld1 = Deflection at (A)d2 = Max. deflection at (B)l = Distance between point of contact and tension chain

1l = Distance between tension chain and Point (A)

2l = Distance between Points (A) and (B)

3l = Distance between Point (B) and point of contact



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EXXONENGINEERING


FIGURE 8EFFECT OF TENSILE FORCE ON A FENDER ELEMENT

Tension Chain

Wharf

l

l1

l2

l3

R2

R1

F

d2d1

Vessel

W.L.

(A)

(B)

DP31Mf08

WEIGHT CHAINS

The purpose of the weight chains is to support the weight of the fender facing panel cantilever deadweight when the system isnot in use. In the case of severe vertical shear, the chains may serve both functions. The weight chains strength is determinedbased on:1. Panel weight

2. Number of panels3. The standoff of the fender

4. The shear force (Shear force = Normal force x Coefficient of friction)

The chain design load is determined based on all these factors. The chains must be designed to have breaking strength atleast three times greater than their maximum design load.A chain assembly consists of shackles on both sides, end link, rubber flex (for some chains), common links, and turn buckles.Normally, shackles and common links are made of carbon steel. The end link and turn buckles are made of mild steel. Therubber flex assembly consists of rubber and mild steel. All steel components are galvanized per ASTM A123 or A153 asapplicable. Figure 9 depicts a typical chain assembly. The choice of the chain type is dependent on the type of service andthe applied load. Some manufacturers for the weight chain recommend rubber flex chains.

ANCHOR BOLTS

Anchor bolts are steel bars cast into new concrete or bolted into existing concrete for the purpose of attaching the chain end tothe fixed structure as shown in Figure 10. The bolts cast into new concrete are usually of the U type unless otherwisespecified by the designer. The concrete embedments (anchor bolts, anchor bolt inserts, and chain anchors) shall be no closerthan 10 in. (250 mm) to an edge and designed to resist a pull out 1.25 times greater than the breaking strength of the malethreads or chain attached to them. Threaded embedments for attaching rubber elements to concrete must have Type 316stainless steel, female threads. The selection of bolts depends on the design load. The breaking or the pull out strength mustbe four times greater than the design load.


Section

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FENDER SYSTEM



EXXONENGINEERING


FIGURE 9CHAIN ASSEMBLY

DP31Mf09

LEGEND

1 Shackle

2 End Link

3 Rubber flex

4 Common Link

5 Turn Buckle

45

2 1

1 2 3 4

FIGURE 10ANCHOR BOLT

DP31Mf10



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EXXONENGINEERING

NOMENCLATURE

a = Distance from vessel center of gravity to first point of contact with the berth as used in Figures 1 and 2, ft (m)

c = Constant of proportionality, dimensionlessD = Distance from the centerline of the fender element face to the point of contact between the vessel's hull and

the berthing structure, ft (m)E = Impact energy of a berthing vessel, ton-ft (tonne-m)

Ea = Energy absorption of the fender at angular compression, ton-ft (tonne-m)En = Energy absorption of the fender at normal compression, ton-ft (tonne-m)

F = Berthing force of vessel, ton (tonne)

ffriction = Coefficient of friction of fender face materialFea = Angular correction factor for energy absorption, dimensionless

Fnormal = Normal Compression Force on fender face, ton (tonne)Fra = Angular correction factor for reaction force, dimensionless

g = Acceleration of gravity, typically 32.2 ft/sec2 (9.8 m/s2)

h = Vertical distance from the fender centerline to the point of contact between the vessel's hull and the berthingstructure, ft (m)

H = Fender height, ft (m)

L = Vessel Length, Overall (LOA), ft (m)

l = Distance between point of vessel contact and fender tension chain as used in Figure 8

1l = Distance between tension chain and Point (A) as used in Figure 8

2l = Distance between Points (A) and (B) as used in Figure 8

3l = Distance between Point (B) and point of contact as used in Figure 8

P = Fender spacing, ft (m)Phull = Maximum hull pressure, ton/ft2 (tonne/m2)

r = Vessel hull radius of curvature, ft (m)

R = Reaction force, ton (tonne)Ra = Reaction force at angular compression, ton (tonne)

Rmax = Maximum allowable reaction force, ton (tonne)Rn = Reaction force at normal compression, ton (tonne)

R1 = Reaction force of fender at d1, ton (tonne)

R2 = Reaction force of fender at d2, ton (tonne)Sshear = Shearing reaction force of fender, ton (tonne)

T = Tension force on the shear chain, ton (tonne)V = Berthing velocity of the vessel perpendicular to the marine terminal berthing line, ft/sec (m/sec)

W = Actual arrival displacement of the berthing vessel, ton (tonne)X = Deflection, ft (m)

a = Angle of the vessel hull as used in Figure 6a

d = Deflection at the rated or desired energy level, ft (m)

d1 = Max. deflection at Point (A) as used in Figure 8, ft (m)

d2 = Deflection at Point (B) as used in Figure 8, ft (m)

m = Friction coefficient between ship and fender

f = Angle between the chain and the face of the structure as used in Figure 7

q = Vessel approach angle as used in Figure 6b


Section

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FENDER SYSTEM



EXXONENGINEERING

EXAMPLES

The following examples represent only a few fender system layouts. Depending on the specific needs of the facility, therecould be numerous options for the design of the fender system. The size, shape, placement and materials which make up thefender are critical factors in the selection process. Because of the uniqueness of each manufacturer's fender system(s), oneshould consult the manufacturer's catalogs, application/design manuals and/or representative for assistance when designing afender system for a facility.

EXAMPLE 1 SAMPLE CALCULATION OF BERTHING IMPACT ENERGY

Given: A loaded 27,000 DWT Tanker (Displacement = 35,000 tonnes) is berthing at an angle of 5 to a marginal pier in aprotected harbor. Adequate tug assistance is available and currents are parallel to the pier. The pier length is 200ft (60 m) and the underkeel clearance is 5 ft (1.5 m). The overall vessel length is 630 ft (192 m). What is theberthing impact energy?

Solution:Using Table 1, determine the berthing velocity, V, for a fully loaded 27,000 DWT tanker (15,001 - 30,000 DWTcategory), with tugs and currents parallel to the pier.

V = 0.450 ft/sec (0.135 m/s)

Note: No adjustment to V is required for a marginal pier.

Assume a maximum manifold offset of 40 ft (12 m) from the pier centerline.Distance "a" = 100 - 40 = 60 ft (30 - 12 = 18 m)

a/L = 60/630 or 18/192 = 0.095

From Figure 1, c = 0.90. No corrections are necessary on "c" for this case since the underkeel clearance of thevessel, 5 ft (1.5 m), is greater than 4 ft (1.2 m) but less than 10 ft (3 m) and currents are parallel to the pier.

Using Eq. (1) for the berthing impact energy:

g2VWc

E2

=

)2.32(2)450.0()tonnes/tons9842.0x000,35()9.0(

E2

= or)8.9(2

)135.0()000,35()9.0(E

2=

ftton98E -= or mtonne30E -=

EXAMPLE 2 SAMPLE FOR SPECIFYING A FENDER SYSTEM

Given: Using the information and results given in the example for calculating berthing impact energy (Example 1), specify afender system for this application. The following is additional information about the design criteria for the pierfacility:

Dock Type Continuous, Open Pile

Maximum Dock Reaction 180 tonnes

Maximum Berthing Angle 5

Maximum Hull Pressure 20 tonne/m2

Maximum Undeflected Standoff 1.0 m

Berthing Speed 0.135 m/s

Elevation of Top Mounting Area 6.0 m

Elevation of Bottom Mounting Area 1.0 m

Width of Mounting Area 3.5 m

Elevation of Top of Panel 3.75 m

Elevation of Bottom of Panel 0.25 m

Special Conditions Tide 0.0 - 1.92 m



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EXXONENGINEERING

EXAMPLES (Cont)

Solution:

From Example 1, the required energy dissipation is 30 tonne-m. Including a safety factor of 1.5, the design energydissipation is 45 tonne-m.For this example, the following catalog data, Figures 11 and 12, from Trellex Fender Systems will be used.

Using the maximum standoff distance of 1.0 m and selecting fender panel with a thickness of 0.178 m, the height ofthe fender, H, must be less than 1.178 m.

Therefore, two examples of acceptable fender systems would be:

Option 1 - (2) MV1000 x 1000 A : E = 50.0 tonne-m and R = 108.8 tonnes

or

Option 2 - (2) MV 800 x 2000 A : E = 64.0 tonne-m and R = 174.4 tonnes

Choosing to mount the fenders one over the other as shown in Figure 11 and using the chart, L = 0.9H and L =1.9H, respectively. Therefore, based on a maximum berthing angle of 5o, the energy absorption including theeffects of angular berthing are as follows:

Option 1 - MV1000 x 1000 A : E(@5o) = (0.97)(50.0) = 48.5 tonne-m

or

Option 2 - MV800 x 2000 A : E(@5o) = (0.88)(64.0) = 56.3 tonne-m

As specified, the fender panel must be 3.5 m tall, therefore, the panel's width, W is as follows [using Eq. (5)]:

HPR

WHull

=

Option 1: 6.1)5.3)(20(

8.108W == m (use 2.0 m)

Option 2: 4.2)5.3)(20(

4.174W == m (use 2.5 m)

Next, we need to calculate the spacing between fenders [using Eq. (7)].

2HHr4P -= , where r is the radius of curvature of the hull (for this example r = 98 m). Therefore,

Option 1: 2)178.00.1()98)(178.00.1(4P +-+= = 21.5 m

or

Option 2: 2)178.08.0()98)(178.08.0(4P +-+= = 19.5 m


Section

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FENDER SYSTEM



EXXONENGINEERING

EXAMPLES (Cont)

Recommendation:

Option 1: (2) MV1000 x 1000 A Trellex Fender elements with E(@5o) = 48.5 tonne-m and R = 108.8 tonnes(1) 3.5 m by 2.0 m fender panel, anda Fender Spacing = 20 m on center

Option 2: (2) MV800 x 2000 A Trellex Fender elements with E(@5o) = 56.3 tonne-m and R = 174.4 tonnes(1) 3.5 m by 2.5 m fender panel, anda Fender Spacing = 18 m on center

FIGURE 11CORRECTION FACTOR FOR ANGULAR BERTHING

TRELLEX FENDER SYSTEMS

100

90

80

70

60

50

40

30

20

10

0

Reduct

ion F

act

or,

RI %

15 a1050

L = 4.0 H

L = 2.0 H

L = 0.625 H

L = 1.0 H

a

H

L

DP31Mf11



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December, 1998


EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 12PERFORMANCE DATA

TRELLEX FENDER SYSTEMS

MV 300 x 600Bx 600Ax 900Bx 900A

x 1200Bx 1200Ax 1500Bx 1500A

MV 400 x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000Ax 2500Bx 2500Ax 3000Bx 3000A

MV 500 x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

MV 550 x 1000Bx 1000Ax 1500Bx 1500A

MV 600 x 1000Bx 1000Ax 1500Bx 1500A

MV 750 x 1000Bx 1000Ax 1500Bx 1500A

MV 800 x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

MV 1000 x 900Bx 900A

x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

MV 1250 x 900Bx 900A

x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

MV 1450 x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

MV 1600 x 1000Bx 1000Ax 1500Bx 1500Ax 2000Bx 2000A

0.91.31.42.01.82.62.38.32.84.04.26.05.68.07.0

10.08.4

12.04.36.26.59.38.7

12.45.37.68.0

11.46.39.09.5

13.59.8

14.014.721.011.216.016.824.022.432.015.822.517.525.026.337.535.050.024.635.127.339.041.058.554.678.036.852.655.278.973.6

105.244.864.067.296.089.6

128.0

6.89.8

10.314.718.719.617.224.515.321.822.932.730.643.638.254.545.865.419.027.228.640.838.254.421.030.031.545.022.832.634.248.928.741.043.161.530.543.645.865.461.087.234.349.038.154.457.181.676.2

108.842.861.247.668.071.4

102.095.2

136.055.379.083.0

118.5110.6158.061.087.291.6

130.8122.1174.4

152122323043385434485072679684

1201011444260639084

12046666999507276

108639095

1356796

10114413419276

10884

12012618016824095

135105150158225210300122174183261244348135192202288269384

913142018262232273941595578689883

1174361649185

122527578

112628893

13296

137144206110157165235220314155221172245258368343490241344268383402574536766361516542774722

1032440628659942879

1256

6696

101144134192168240150214224321300428375535449642187267280400374534206294309441224320336480282402423603299428449642599856337481374534560800748

1068420600467667701

1001934

1334543775813

116210851550599855898

128311971710

69

10141319162420293043415851726187324547676390385558824665699871

10110615281

116122174162232113162126180189270262360177253197282296423395564266380399570532760323462485693647924

Element size H x LCompound A or B

Rated performance for one elementRTonne

ETonne-m

RKips

EkNm

RkN

EFt-kips

Single element may be used, but they are normallyplaced in pairs of 2, 4, 6 or more elements behind ashield or panel.

Other lengths L are available on request.Ask your nearest Trellex Office for advise.

PERFORMANCE VALUES IN THE TABLE AREVALID FOR ONE SINGLE ELEMENT

MV ELEMENT SELECTION

STANDARD SIZES

E = Energy absorptionR = Reaction forceF = Compression forceR = Fr = Rated deflection

Trellex MV elements are available intwo standard compounds A and B.

The softer compound B gives lowervalues E and R than compound A forthe same size of element.

The rated values in the table arevalid for a deflection of 57.5% of H.

For performance rating at otherdeflections, use the curves on page9 in conjunction with the ratings inthe table.

When selecting a MV element it willminimize reaction force, panel sizeand often cost if the element chosenhas the maximum H permitted andthe application.

For use of single elements, oddnumber of elements and otherspecial applications contact yournearest Trellex office.

L

r

H

F

R

DP31Mf12


Section

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FENDER SYSTEM



EXXONENGINEERING

EXAMPLES (Cont)

EXAMPLE 3 SAMPLE FENDER SYSTEM WITH BRIDGESTONE SUPER CELL FENDERS

Given: A loaded 60,000 DWT Tanker is berthing at an angle of 9o to a marginal pier at a berthing speed of 0.15 m/s. Thedesign berthing energy has been calculated to be 63.8 tonne-m. Recommend a fender system utilizing twoBridgestone Super Cell fenders connected with a single fender panel as shown in Figure 13.

FIGURE 13FENDER SYSTEM WITH TWO BRIDGESTONE FENDER UNITS

1250mm

Minimum Spacing

Super Cell FenderSUC1250H (RS)

Compression

9

Plan View

DP31Mf13

Solution:

For this example, a fender system will be selected from the Bridgestone - Cell Fender Series Catalog.Based on the design berthing energy, a candidate for the fender system is the Super Cell Fender SUC1250H (RS).

At normal berthing (at 0o), the rated energy absorption and reaction force of the fender systems (see Figures 14and 15) are:

6.1143.572En == tonne-m

6.2083.1042Rn == tonne

FIGURE 14PERFORMANCE DATA

BRIDGESTONE SUC1250H FENDER

Rubber gradeRated reaction

forceTonsKips

Maximum energyabsorption

Ton - MFt - Kips

Maximum reactionforceTonsKips

Rated energyabsorption

Ton - MFt - Kips

RE

RS

RH

RO

R1 55.6122.6

117.6259.3104.3230.090.4

199.369.6

153.559.2

130.5

125.0275.6110.9244.596.1

211.973.9

162.930.5

220.7

64.5466.757.3

414.649.6

358.938.2

276.432.3

233.7

68.3494.260.6

438.452.6

380.640.4

292.3

Tolerance: 10%Rated deflection: 52.5%Maximum deflection 55% DP31Mf14



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EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 15PERFORMANCE CURVE


Energy Absorption

Reaction Force RE

RS

RH

R1

RD

RO

RSRE

RHR1

(Ton

M)

90

60

20

0

200

100

0

Energ

y A

bso

rpti

on

(Ft

K

ips)

555040302010

120

90

60

30

0

250

200

150

100

50

0

Deflection (%)

React

ion F

orc

e

(Tons)

(K ips)

DP31Mf15

The energy absorption and reaction force at an angular berthing of 9o is the summation of the energy absorptionand reaction forces from each individual fender cell.

eay

N

1yny

N

1yaya FEEE

==

== and ray

N

1yny

N

1yaya FRRR

==

== ,

where: N = number of fender cells

For this example, using Figure 16:

)FE()FE(E 2ea2n1ea1na += and )FR()FR(R 2ra2n1ra1na +=

To determine the maximum energy and reaction force, Fender 1 will be compressed to its rated deflection at anangle of 9o. Using Figure 17, the following information is obtained:

Rated Deflection of Fender 1, d1 = 47.5%

6.49FEE 1ea1n1a == tonne-m

5.101FRR 1ra1n1a == tonnes

Assuming a rigid fender panel connects the two fender cells, the deflection of the fender cells due to angularberthing are proportional, as shown in Figure 16. Using trigonometry, the deflection of Fender 2 is

%8.23tanP12 =a-d=d

where: P = minimum spacing between fender cells and can be obtained from the catalog.


Section

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FENDER SYSTEM



EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 16FENDER SYSTEM IN COMPRESSION

9

P

P

d1

d2a

D

DP31Mf16

Based on this deflection, the energy absorption, reaction force and associated angular correction factors can beobtained using Figures 18-19 or from the manufacturer's representative. For this example, the following informationcan be used:

0.1995.00.20FEE 2ea2n2a === tonne-m

and

0.9595.00.100F RR 2ra2n2a === tonnes

Therefore,

6.680.196.49EEE 21a =+=+= tonne-m

and

5.1960.955.101RRR 21a =+=+= tonne

From the calculations, the selected fender cells can absorb the berthing energy of the vessel. However, thereaction forces are relatively high. If the dock structure is capable of handling these forces, it is acceptable to usethis design. If the reaction forces are too high, then another option should be looked at. For example, if a singleSUC1450H (RH) fender cell is used, the reaction forces are significantly smaller (118.4 tonnes) while stillmaintaining an energy absorption of 65.9 tonne-m.



Page

29 of 31


December, 1998


EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 17ANGULAR PERFORMANCE DATA


ANGLEDeg.

MAX.DEFLECTION

LIMIT.%

RUBBERGRADE

ANGLEDeg.

RUBBERGRADE

ENERGYABSORPTIONMetric Tons

Ft Kips

REACTIONFORCE

Metric TonsKips

MAX.DEFLECTION

LIMIT.%

ENERGYABSORPTIONMetric Tons

Ft Kips

REACTIONFORCE

Metric TonsKips

0 7

3 8

4 9

5 10

6 15

55.0 49.1

52.5 48.3

51.6 47.5

50.8 46.7

50.0 42.6

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

RE

RS

RH

RO

R1

125.0275.6

68.3494.2

110.9244.5

60.6438.4

96.1211.9

52.6380.6

73.9162.9

40.4292.3

59.2130.5

32.3233.7

119.9264.4

106.4234.6

92.2203.3

71.0156.6

56.8125.2

64.0463.0

56.8410.9

49.2356.0

37.9274.2

30.3219.2

115.4254.5

58.4422.5

102.5226.0

51.9375.5

88.8195.8

44.9324.9

68.3150.6

34.6250.3

54.6120.4

27.6199.7

115.4254.5

102.5226.0

88.8195.8

68.3150.6

54.6120.4

57.1413.1

50.7366.8

43.9317.6

33.8244.5

27.1196.1

117.4258.9

62.5452.2

104.2229.8

55.5401.5

90.3199.1

48.1348.0

69.5153.2

36.9267.0

55.6122.6

29.6214.2

116.6257.1

103.5228.2

89.7197.8

69.0152.1

55.2121.7

60.9440.6

54.1391.4

46.9339.3

36.1261.2

28.9209.1

114.4252.3

55.9404.4

101.5223.8

49.6358.9

88.8195.8

43.0311.1

67.7149.3

33.1239.5

54.1119.3

26.5191.7

112.7248.5

100.1220.7

86.7191.2

66.7147.1

53.4117.7

55.0397.9

48.8353.1

42.2305.3

32.5235.1

26.0188.1

112.3247.6

99.6219.6

86.4190.5

66.4146.453.1

117.1

49.3356.7

43.8316.9

37.9274.2

29.2211.323.4

169.3

116.3256.4

103.2227.6

89.4197.1

68.8151.755.0

121.3

59.7431.9

53.0383.5

46.0332.8

35.4256.128.2

204.0

DP31Mf17


Section

XXXI-M

Page

30 of 31

FENDER SYSTEM



EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 18CORRECTION FACTOR FOR REACTION FORCE

BRIDGESTONE 1250H FENDER

50403020100

0.9

1.0

Corr

ect

ion F

act

or

1.1

SU Series

Cell Series

q = 9

q = 6

q = 9

q = 3

q = 6

q = 3

Deflection (%)DP31Mf18



Page

31 of 31


December, 1998


EXXONENGINEERING

EXAMPLES (Cont)

FIGURE 19CORRECTION FACTOR FOR ENERGY ABSORPTION

BRIDGESTONE 1250H FENDER

5040302010

Deflection (%)

0.9

1.0

Corr

ect

ion F

act

or

SU Series

Cell Series

q = 3

q = 6

q = 9

DP31Mf19

COMPUTER TOOLS

Using the same principles as demonstrated in the examples, more complex fender systems can be designed such as acontinuous fender face system in which multiple fender units are connected by a single fender facing or multiple fender panelshinged together to form a continuous facing. For reference, there are two (2) computer tools that are available to assist in thedesign of fender systems.One computer tool is an Excel spreadsheet that was developed to assess oblique loading of a cylindrical fender. Thespreadsheet is available through ER&E's Marine Terminal Engineering Section. The spreadsheet can be used to asses thesensitivity of fender characteristics, tension chain placement and load distribution in cylindrical fenders. The spreadsheetapproximates fender reaction forces and moments due to a user specified angular rotation and zero displacement location. Inaddition, it calculates the resultant load in the Tension Chain and the Ship Impact Force using static equilibrium principles.Another tool that can be used to evaluate a potential fender system configuration is ABAQUS. ABAQUS is a Finite ElementAnalysis program that is located on the VAX maintained by the Mechanical Engineering Section. In order to use ABAQUS, theuser must be trained and authorized to use the program or must have someone with access to it perform the analysis.

DP MANUALS INDEXMARINE TERMINAL DPs INDEXSCOPEREFERENCESINTERNATIONAL PRACTICEOTHER REFERENCES

DEFINITIONSINTRODUCTIONGENERAL STEPS IN DESIGNING A FENDER SYSTEMEXISTING FACILITIESNEW FACILITIES

CALCULATION OF BERTHING IMPACT ENERGYIMPACT ENERGYARRIVAL DISPLACEMENTBERTHING VELOCITYCONSTANT OF PROPORTIONALITYVESSEL OFFSET

TYPES OF FENDER SYSTEMSSELECTION OF A FENDER SYSTEMDESIGN OF FENDER SYSTEMENERGY ABSORPTION OF FENDERSVESSEL ANGLE OF IMPACTHULL PRESSURE OF THE VESSELCURVATURE OF THE HULL OF THE VESSELFENDER SPACINGPIER ORIENTATION AND SUPPORT STRUCTUREWATER ELEVATION CHANGE (TIDE)SHEAR CAPACITY OF FENDERSTENSION CAPACITY OF FENDERSWEIGHT CHAINSANCHOR BOLTS

NOMENCLATUREEXAMPLESEXAMPLE 1 -SAMPLE CALCULATION OF BERTHING IMPACT ENERGYEXAMPLE 2 -SAMPLE FOR SPECIFYING A FENDER SYSTEMEXAMPLE 3 -SAMPLE FENDER SYSTEM WITH BRIDGESTONE SUPER CELL FENDERS

COMPUTER TOOLSTABLESTable 1 Berthing Velocities for Breasting Dolphins and Marginal PiersTable 2 General Types of Fender SystemsTable 3 Major Advantages/ Disadvantages of Fender System Alternatives

FIGURESFigure 1 Constant of ProportionalityFigure 2 Vessel OffsetFigure 3 Types of Common Fender System DesignsFigure 4 Deflection/ Reaction Force CurveFigure 5 Vessel Berthing Angle and Direction of MotionFigure 6 Effect of Vessel Hull Curvature on Fender SpacingFigure 7 Fender System in CompressionFigure 8 Effect of Tensile Force on a Fender ElementFigure 9 Chain AssemblyFigure 10 Anchor BoltFigure 11 Correction Factor for Angular Berthing Trellex Fender SystemsFigure 12 Performance Data Trellex Fender SystemsFigure 13 Fender System with Two Bridgestone Fender UnitsFigure 14 Performance Data Bridgestone SUC1250H FenderFigure 15 Performance Curve Bridgestone SUC1250H FenderFigure 16 Fender System in CompressionFigure 17 Angular Performance Data Bridgestone Suc1250H FenderFigure 18 Correction Factor for Reaction Force Bridgestone 1250H FenderFigure 19 Correction Factor for Energy Absorption Bridgestone 1250H Fender

dp31m

Documents

fender systems

berthing impact energy

authorized company

angle of impact

exxon research

proprietary information

absorption of fenders