Literature study about_lng_jetty

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LITERATURE STUDY
Final Project Report : Design of LNG Jetty 2 in LNG Tangguh to accommodate LNG Tanker with
capacity more than 150.000 m3
2.1 Port and Harbour
2.1.1 General
Definition of harbour by Carl A.Thorensen which are some protected water area to provide safe
and suitable accommodation for ships for transfer of cargo, refueling, repairs etc. Harbours may
be subdivided into:
• Natural harbours: harboms protected from storms and wave by the natural configuration
of the land.
• Seminatural harbours: harbours with both natural send artificial protection.
• Artificial harbours: harbours protected from the effect of waves by means of
breakwaters, or harbours created by dredging.
Definition of port by Carl A. Thorensen is a sheltered place where the ship may receive or
discharge cargo. It includes the harbour with its approach channels and anchorage places. The
port may be subdivided into:
• Ocean ports: ports located on coasts, tidal estuaries or river mouths where the port can
be reached directly by oceangoing ships.
• Inland waterway ports: ports located on navigable rivers channels and lakes.
To design port, there are some stages like surveying to get enviromental data consist of: hydro-
oceanography survey, topography bathymetric survey and geotechnical survey. After gathetring
the data, port engineer can analyze data to determine the suitable design for this project.
There are three main component that we must consider to design harbour facilities which are:
• Navigation Channel
• Harbour Basin
• Port
The three main component will be explain clearly in next sub chapter 2.4 Port Planning.
2

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2.1.2 Port
2.1.2.1 Berthing Layout
The layout of berthing area can be dividing into:
2.1.2.1.1. Long Pier
This pier structure usually used for container port. The illustrations for long pier see Figure 2.1.
Figure 2. 1 Long Piers
Source: Port Design Guide and Recommendations Carl A.Thorensen
2.1.2.1.2. Finger Type Wharf
This type will be used for the different depth seabed. Finger type wharf usually use for general
cargo port. The illustrations for finger type wharf see Figure 2.2.
Figure 2. 2 Finger Type Piers
2.1.2.1.3. Pier
This pier type that suitable for oil and gas terminal, between port and land connect by approach
trestle. It’s suitable for the bathymetric far away from land.The illustration for pier type see
Figure 2.3

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Figure 2. 3 Pier
Sumber: US DoD (Department of Defense), 2005. Design: Piers and Wharfs, Unified Facilities
Criteria (UFC) 4-152-01, 28 July 2005
2.1.2.2 Berthing Structure
There are four main type of berthing structure which are:
2.1.2.2.1 Deck on Pile
The structure use pile as foundation for the deck. For LNG Jetty, we use steel pile. The pile
receives all vertical load. Sometimes we use revetment to strength the dtructure foundation.
Ilustration for deck on pile see Figure 2.4.
Figure 2. 4 Deck On Pile
Source: US DOD (Department of Defense), 2005. Design: Piers and Wharfs, Unified Facilities

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2.1.2.2.2 Sheet Pile
The bulkhead consists of a flexible wall formed of steel or concrete sheet piling with interlocking
tongue and groove joints and a cap of steel or concrete construction. The bulkhead is restrained
from outward movement by placing an anchorage system above the low water level. Sheet pile
can hold the lateral load because of berthing force from the ship. It usually use for steep beach.
The illustration of sheet pile bulkhead see Figure 2,5
Figure 2. 5 Sheet Pile Bulkhead
Source: US DoD (Department of Defense),2005. Design: Piers and Wharfs, Unified Facilities
2.1.2.2.3 Diaphragm Wall
This type consists of two series of circular arcs connected together by diaphragms perpendicular
to the axis of the cellular structure. The width of cells may be widened by increasing the length
of the diaphragms without raising interlock stress, which is a function of the radius of the arc
portion of the cell. Cells must be filled in stages so that the heights of fill in adjoining cells are
maintained at equal levels to avoid distortion of the diaphragm walls. Diaphragm type cells
present a flatter faced wall than circular cells and are considered more desirable for marine,
structures. Ilustration for diaphragm wall see Figure 2.6 and Figure2.7.
Figure 2. 6 Diaphragm Type Cell
Source: US DoD (Department of Defense),2005. Design: Piers and Wharfs, Unified Facilities

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Figure 2. 7 Struktur Dermaga Diafragma Wall
2.1.2.2.3 Caisson
The caissons are usually made ashore and then launched, towed out and sunk in position on
a prepared gravel and/or rubble base. Thus the underwater work is reduced to a minimum. It is
both very economic and convenient if the caissons can be made on an existing slipway or in
a dry dock, from which they can easily be launched. The caissons are usually placed on a firm
base of gravel and/or rubble, well compacted and accurately levelled. It is very important that
before placing ofthe caissons, most of the settlements are brought to a minimum, particularly
any uneven settlement. If the site is exposed to waves and currents, the baseand the caissons
should be designed in such a way that the time required for launching, towing and placing of
the caissons is as short as possible. After the placing of the caissons they are filled with
suitable material, and a reinforced concrete cap is provided on top, as it is done on block wall
quays.
Figure 2. 8 Caisson

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2.2 Liquified Natural Gas
2.2.1 Characteristic LNG
Liquefied Natural Gas is a gaseous substance at ambient temperature and pressure, but liquefied
by pressurization or refrigeration - sometimes a combination of both. Virtually all liquefied gases
are hydrocarbons and flammable in nature. Liquefaction itself packages the gas into volumes well
suited to international carriage - freight rates for a gas in its non-liquefied form would be normally
far too costly. The principal gas cargoes are LNG, LPG and a variety of petrochemical gases. All
have their specific hazards.
LNG is liquefied natural gas and methane naturally occurring within the earth, or in association
with oil fields. It is carried in its liquefied form at its boiling point of -162ºC. Depending on the
standard of production at the loading port, the quality of LNG can vary but it usually contains
fractions of some heavier ends such as ethane (up to 5%) and traces of propane. LNG is sharply
clear and colorless. It comprises mainly methane but has a percentage of constituents such as
ethane, butane and propane together with nitrogen. It is produced from either gas wells or oil
wells. In the case of the latter it is known as associated gas. At the point of production the gas is
processed to remove impurities and the degree to which this is achieved depends on the facilities
available. Typically this results in LNG with between 80% and 95% methane content. The resulting
LNG can therefore vary in quality from loading terminal to loading terminal or from day-to-day.
Other physical qualities that can change significantly are the specific gravity and the calorific
value of the LNG, which depend on the characteristics of the gas field. The specific gravity affects
the deadweight of cargo that can be carried in a given volume, and the calorific value affects
both the monetary value of the cargo and the energy obtained from the boil off gas fuel.
These factors have significance in commercial arrangements and gas quality is checked for each
cargo, usually in a shore-based laboratory by means of gas chromatography. LNG vapor is
flammable in air and, in case of leakage; codes require an exclusion zone to allow natural
dispersion and to limit the risk of ignition of a vapor cloud. Fire hazards are further limited by
always handling the product within oxygen-free systems. Unlike oil tankers under inert gas, or in
some cases air, LNG carriers operate with the vapor space at 100% methane. LNG vapour is non-
toxic, although in sufficient concentration it can act as an asphyxiant.
Gas quality is also significant from a shipboard perspective. LNG’s high in nitrogen, with an
atmospheric boiling point of -196ºC, naturally allow nitrogen to boil-off preferentially at voyage
start thus lowering the calorific value of the gas as a fuel. Towards the end of a ballast passage,
when remaining 'heel' has all but been consumed, the remaining liquids tend to be high on the
heavier components such as the LPG’s. This raises the boiling point of the remaining cargo and
has a detrimental effect on tank cooling capabilities in readiness for the next cargo.
The second main cargo type is LPG (liquefied petroleum gas). This grade covers both butane and
propane, or a mix of the two. The main use for these products varies from country to country but
sizeable volumes go as power station or refinery fuels. However LPG is also sought after as a
bottled cooking gas and it can form a feedstock at chemical plants. It is also used as an aerosol

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propellant (with the demise of CFCs) and is added to gasoline as a vapor pressure enhancer.
Whereas methane is always carried cold, both types of LPG may be carried in either the
pressurized or refrigerated state. Occasionally they may be carried in a special type of carrier
known as the semi-pressurized ship. When fully refrigerated, butane is carried at -5ºC, with
propane at -42ºC, this latter temperature already introducing the need for special steels.
Ammonia is one of the most common chemical gases and is carried worldwide in large volumes,
mainly for agricultural purposes. It does however have particularly toxic qualities and requires
great care during handling and carriage. By regulation, all liquefied gases when carried in bulk
must be carried on a gas carrier, as defined by the IMO. IMO’s Gas Codes (see next section -
Design of gas carriers) provide a list of safety precautions and design features required for each
product. The principal hydrocarbon gases such as butane, propane and methane are non-toxic in
nature and a comparison of the relative hazards from oils and gases is provided in the Table 2.1.
Table 2. 1 Comparative Hazards of some liquified gases and oils.
Source: LNG and its carriers from UK PI document.
Comparative Hazards of some liquified gases and oil
Gases Oil
Hazards LNG LPG Gasoline Fuel Oil
Toxic No No Yes Yes
Carsinogenic No No Yes Yes
Asphyxiant Yes Yes No No
Others Low Temperature
Low
Temperature
Narkotics, Eye Iritant,
Nausea
Narkotics, Eye
Iritant, Nausea
Flammability
Limit in Air(%)
5-15 2-10 1-6 N/A
Storage
Pressure
Atmosferic
Often
Pressurized
Atmosferic Atmosferic
Behaviour if it
split
Evaporates forming
a visible cloud that
dispersed readily
and is non
explosive, unless
contained
Evaporates
forming &
explosive
vapour cloud
Forms a flammable pool
which if ignited would burn
with explosive
force,enviromental clean
up may be required
Forms a
flammable pool,
enviromental
clean up may be
required
2.2.2 The Gas Carrier
The regulations for the design and construction of gas carriers stem from practical ship designs
codified by the International Maritime Organization (IMO). However all new ships (from June
1986) are built to the International Code for the Construction and Equipment of Ships Carrying

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Liquefied Gases in Bulk (the IGC Code). This code also defines cargo properties and documentation,
provided to the ship (the Certificate of Fitness for the Carriage of Liquefied Gases in Bulk), shows
the cargo grades the ship can carry.
In particular this takes into account temperature limitations imposed by the metallurgical
properties of the materials making up the containment and piping systems. It also takes into
account the reactions between various gases and the elements of construction not only on tanks
but also related to pipeline and valve fittings.
When the IGC Code was produced an intermediate code was also developed by the IMO - the Code
for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (the GC Code). This
covers ships built between 1977 and 1986.
As alluded to above, gas carriers were in existence before IMO codification and ships built before
1977 are defined as 'existing ships' within the meaning of the rules. To cover these ships a
voluntary code was devised, again by the IMO - the Code for Existing Ships Carrying Liquefied Gases
in Bulk (the Existing Ship Code).Considering the fleet of gas carriers of over 1,000 m3
capacity, the
total of nearly 1,000 ships can be divided into five major types according to the following Table
2.2.
Table 2. 2 The gas carrier fleet
Cargo carriage in the pressurized fleet comprises double cargo containment - hull and tank. All
other gas carriers are built with a double hull structure and the distance of the inner hull from the
outer is defined in the gas codes. This spacing introduces a vital safety feature to mitigate the
consequences of collision and grounding. Investigation of a number of actual collisions at the
time the gas codes were developed drew conclusions on appropriate hull separations which were
then incorporated in the codes. Collisions do occur within the class and, to date, the codes'
recommendations have stood the test of time, with no penetrations of cargo containment having
been reported from this cause. The double hull concept includes the bottom areas as a
protection against grounding and, again, the designer's foresight has proven of great value in
several serious grounding incidents, saving the crew and surrounding populations from the
consequences of a ruptured containment system.
Herein lays a distinctive difference between gas carriers and their sisters, the oil tankers and
chemical carriers. Cargo tanks may be of the independent self-supporting type or of a membrane
design. The self-supporting tanks are defined in the IGC Code as type A, B and C, these are the
explanation:

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1. Type- A containment comprises box shaped or prismatic tanks (shaped to fit the hold).
2. Type- B comprises tanks where fatigue life and crack propagation analyses have shown
improved characteristics. Such tanks are usually spherical but occasionally may be of
prismatic types.
3. Type-C tanks are the pure pressure vessels, often spherical or cylindrical, but sometimes
bi-lobe in shape to minimize broken stowage.
Figure 2. 9 Gas Carriers
The fitting of one system in preference to another tends towards particular trades. For example,
Type-C tanks are suited to small volume carriage. They are therefore found most often on coastal
or regional craft. The large international LPG carrier will normally be fitted with Type-A Tanks.
Type-B tanks and tanks following membrane principles are found mainly within the LNG fleet.
There are some gas carrier with different function will be list below:

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• The pressurized fleet
Figure 2. 10 Pressurised LPG carrier with cylindrical tanks
Figure 2.2 show a small fully pressurized carrier. Regional and coastal cargoes are often carried in
such craft with the cargo fully pressurized at ambient temperature. Accordingly, the tanks are
built as pure pressure vessels without the need for any extra metallurgical consideration
appropriate to colder temperatures. Design pressures are usually for propane (about 20 bar) as
this form of LPG gives the highest vapor pressure at ambient temperature. As described above,
ship design comprises outer hull and an inner hold containing the pressure vessels. These rests in
saddles built into the ship's structure. Double bottoms and other spaces act as water ballast
tanks and if problems are to develop with age then the ballast tanks are prime candidates. These
ships are the most numerous classes, comprising approximately 40% of the fleet. They are
nevertheless relatively simple in design yet strong of construction.
Cargo operations that accompany such ships include cargo transfer by flexible hose and in certain
areas, such as China, ship-to-ship transfer operations from larger refrigerated ships operating
internationally are commonplace. Records show that several ships in this class have been lost at
sea because of collision or grounding, but penetration of the cargo system has never been
proven.

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• The semi pressurized fleet
Figure 2. 11 Semi-pressurised LPG carrier
Ships on the Figure 2.3 sometimes referred to as 'semi-refrigerated', the cargo is carried in
pressure vessels usually bi-lobe in cross section, designed for operating pressures of up to 7 bars.
The tanks are constructed of special grade steel suitable for the cargo carriage temperature. The
tanks are insulated to minimize heat input to the cargo. The cargo boils off causing generation of
vapor, which is reliquefied by refrigeration and returned to the cargo tanks. The required cargo
temperature and pressure is maintained by the reliquefaction plant.
These ships are usually larger than the fully pressurized types and have cargo capacities up to
about 20,000 m3
. As with the fully pressurized ship, the cargo tanks are of pressure vessel
construction and similarly located well inboard of the ship's side and also protected by double
bottom ballast tanks. This arrangement again results in a very robust and inherently buoyant
ship.
• The ethylene fleet
Ethylene, one of the chemical gases, is the premier building block of the petrochemicals industry.
It is used in the production of polyethylene, ethylene dichloride, ethanol, styrene, glycols and
many other products. Storage is usually as a fully refrigerated liquid at -104ºC.
Ships designed for ethylene carriage also fall into the semi-pressurized class. They are relatively
few in number but are among the most sophisticated ships afloat. In the more advanced designs
they have the ability to carry several grades. Typically this range can extend to ethane, LPG,
ammonia, propylene butadiene and vinyl chloride monomer (VCM), all featuring on their
certificate of fitness. To aid in this process several independent cargo systems co-exist onboard
to avoid cross contamination of the cargoes, especially for the reliquefaction process.
The ships range in size from about 2,000 m3
to 15,000 m3
although several larger ships now trade
in ethylene. Ship design usually includes independent cargo tanks (Type-C), and these may be
cylindrical or bi-lobe in shape constructed from stainless steel. An inert gas generator is provided
to produce dry inert gas or dry air. The generator is used for inerting and for the dehydration of
the cargo system as well as the inter barrier spaces during voyage. For these condensation occurs
on cold surfaces with unwanted build-ups of ice. Deck tanks are normally provided for
changeover of cargoes.

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The hazards associated with the cargoes involved are obvious from temperature, toxic and
flammable concerns. Accordingly, the safety of all such craft is critical with good management
and serious personnel training remaining paramount.
• The fully refrigerated fleet
Figure 2. 12 Fully refrigerated LPG carrier
These are generally large ships, up to about 100,000 m3
cargo capacity, those above 70,000 m3
being designated as VLGC’s. Many in the intermediate range (say 30,000 m3
to 60,000 m3
) are
suitable for carrying the full range of hydrocarbon liquid gas from butane to propylene and may
be equipped to carry chemical liquid gases such as ammonia. Cargoes are carried at near ambient
pressure and at temperatures down to -48ºC.
Reliquefaction plants are fitted, with substantial reserve plant capacity provided. The cargo tanks
do not have to withstand high pressures and are therefore generally of the free standing
prismatic type. The tanks are robustly stiffened internally and constructed of special low
temperature resistant steel.
All ships have substantial double bottom spaces and some have side ballast tanks. In all cases the
tanks are protectively located inboard. The ship's structure surrounding or adjacent to the cargo
tanks is also of special grade steel, in order to form a secondary barrier to safely contain any cold
cargo should it leak from the cargo tanks. All cargo tanks, whether they be of the pressure vessel
type or rectangular, are provided with safety relief valves amply sized to relieve boil-off in the
absence of reliquefaction and even in conditions of surrounding fire.
• The LNG fleet
Although there are a few exceptions, the principal ships in the LNG fleet range from 75,000m3
to
150,000m3
capacity, with ships of up to 265,000 m3
expected by the end of the decade. The cargo
tanks are thermally insulated and the cargo carried at atmospheric pressure. Cargo tanks may be
free standing spherical, of the membrane type, or alternatively, prismatic in design. In the case of
membrane tanks, the cargo is contained within thin walled tanks of invar or stainless steel. The
tanks are anchored in appropriate locations to the inner hull and the cargo load is transmitted to
the inner hull through the intervening thermal insulation.

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Figure 2. 13 LNG carrier with Type-B tanks (Kvaerner Moss system)
Figure 2. 14 LNG carrier with membrane tanks
All LNG carriers have a watertight inner hull and most tank designs are required to have a
secondary containment capable of safely holding any leakage for a period of 15 days. Because of
the simplicity and reliability of stress analysis of the spherical containment designs, a full
secondary barrier is not required but splash barriers and insulated drip trays protect the inner hull
from any leakage that might occur in operation.
2.2.3 The LNG Carrier
It was as far back as 1959 that the Methane Pioneer carried the first experimental LNG cargo, and
40 years ago, in 1964, British Gas at Canvey Island received the inaugural cargo from Arzew on
the Methane Princess. Together with the Methane Progress these two ships formed the core of
the Algeria to UK project. And the project-based nature of LNG shipping was set to continue until
the end of the 20th century. LNG carriers only existed where there were projects, with ships built

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specifically for employment within the projects. The projects were based on huge joint ventures
between cargo buyers, cargo sellers and shippers, all in themselves large companies prepared to
do long term business together.
The projects were self-contained and operated without much need for outside help. They
supplied gas using a purpose-built fleet operating like clockwork on a CIF basis. Due to
commercial constraints, the need for precisely scheduled deliveries and limited shore tank
capacities, spot loadings were not feasible and it is only in recent years that some projects now
accept LNG carriers as cross-traders, operating more like their tramping cousins - the oil tankers.
Doubtless the trend to spot trading will continue. However, the co-operative nature of LNG's
beginnings has led to several operational features unique to the ships. In particular there is the
acceptance that LNG carriers burn LNG cargo as a propulsive fuel. They also retain cargo onboard
after discharge as an aid to keeping the ship cooled down and ready to load on arrival at the load
port. Thus matters that would be anathema to normal international trades are accepted as
normal practice for LNG.
2.2.3.1 Cargo Handling
The process of liquefaction is one of refrigeration and, once liquefied, the gas is stored at
atmospheric pressure at its boiling point of -162ºC and where it condenses to a liquid at
atmospheric pressure shrinking to approximately 1/600 of its original volume with a density of
420 to 490 kg/m3.At loading terminals any boil-off from shore tanks can be reliquefied and
returned to storage. However, on ships this is almost certainly not the case. According to design,
it is onboard practice to burn boil-off gas (often together with fuel oil) in the ship's boilers to
provide propulsion. In the general terms of seaborne trade this is an odd way to handle cargo and
is reminiscent of old tales of derring-do from the 19th century when a cargo might have been
burnt for emergency purposes. It is nevertheless the way in which the LNG trade operates. Boil-
off is burnt in the ship's boilers to the extent that it evaporates from its mother liquid. Clearly
cargo volumes at the discharge port do not match those loaded.
Cargo tank design requires carriage at atmospheric pressure and there is little to spare in tank
design for over or under pressures. Indeed, the extent to which pressure build-up can be
contained in a ship's tanks is very limited in the case of membrane cargo tanks, although less so
for Type-B tanks. Normally this is not a problem, as at sea the ship is burning boil-off as fuel or in
port has its vapor header connected to the terminal vapor return system. Clearly, however, there
are short periods between these operations when pressure containment is necessary. This can be
managed. So taken together, shipboard operations efficiently carried out succeed in averting all
possible discharges to atmosphere, apart that is from minor escapes at pipe flanges, etc.
Certainly this is part of the design criteria for the class as it is recognized that methane is a
greenhouse gas.
Boil-off gas (BOG) is limited by tank insulation and new building contracts specify the efficiency
required. Usually this is stated in terms of a volume boil-off per day under set ambient conditions
for sea and air temperature. The guaranteed maximum figure for boil-off would normally be
about 0.15% of cargo volume per day.

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While at sea, vapors bound for the boilers must be boosted to the engine room by a low-duty
compressor via a vapor heater. The heater raises the temperature of the boil-off to a level suited
for combustion and to a point where cryogenic materials are no longer required in construction.
The boil-off then enters the engine room suitably warmed but first passes an automatically
controlled master gas valve before reaching an array of control and shutoff valves for direction to
each burner. As a safety feature, the gas pipeline through the engine room is of annular
construction, with the outer pipe purged and constantly checked for methane ingress. In this
area, operational safety is paramount and sensors cause shutdown of the master gas valve in
alarm conditions. A vital procedure in the case of a boiler flameout is to purge all gas from the
boilers before attempting re-ignition. Without such care boiler explosions are possible and
occasional accidents of this type have occurred.
2.2.3.2 Cargo Care
The majority of LNG shippers and receivers have a legitimate concern over foreign bodies getting
into tanks and pipelines. The main concern is the risk of valve blockage if an old welding rod
becomes lodged in a valve seat. Such occurrences are not unknown with a ship discharging first
cargoes after new building or recently having come from dry dock. Accordingly, and despite
discharge time diseconomies, it is common practice to fit filters at the ship's liquid manifold
connections to stop any such material from entering the shore system. The ship normally
supplies filters fitting neatly into the manifold piping.
In a similar vein, even small particulate matter can cause concerns. The carryover of silica gel dust
from inert gas driers is one such example. Another possible cause of contamination is poor
combustion at inert gas plants and ships tanks becoming coated with soot and carbon deposits
during gas freeing and gassing up operations. Subsequently, the contaminants may be washed
into gas mains and, accordingly, cargoes may be rejected if unfit. Tank cleanliness is vital and,
especially after dry-docks; tanks must be thoroughly vacuumed and dusted. A cargo was once
rejected in Japan when, resulting from a miss operation, steam was accidentally applied to the
main turbine with the ship secured alongside the berth. The ship broke out from the berth, but
fortunately the loading arms had not been connected. This action was sufficient however for
cargo receivers to reject the ship, and the cargo could only be delivered after a specialized ship-
to-ship transfer operation had been accomplished. The ship-to-ship transfer of LNG has only ever
been carried out on a few occasions and is an operation requiring perfect weather, great care
and specialist equipment.
2.2.3.3 LNG Cargo Tank
A temperature of -162ºC is astonishingly cold. Most standard materials brought into contact with
LNG become highly brittle and fracture. For this reason pipelines and containment systems are
built from specially chosen materials that do not have these drawbacks. The preferred materials
of construction are aluminium and stainless steel. However these materials do not commonly
feature over the ship's weather decks, tank weather covers or hull. These areas are constructed
from traditional carbon steel. Accordingly, every care is taken to ensure that LNG is not spilt. A
spill of LNG will cause irrevocable damage to the decks or hull normally necessitating emergency

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dry docking. Accidents of this nature have occurred, fortunately none reporting serious personal
injury, but resulting, nevertheless, in extended period’s off-hire.
LNG carriers are double-hulled ships specially designed and insulated to prevent leakage and
rupture in the event of accident such as grounding or collision. That aside, though sophisticated
in control and expensive in materials, they are simple in concept. Mostly they carry LNG in just
four, five or six centre line tanks. Only a few have certification and equipment for cross trading in
LPG. The cargo boils on passage and is not re-liquefied onboard - it is carried at atmospheric
pressure. There are four LNG containment systems, which are:
1. IHI prismatic
Ishikawajima-Harima Heavy Industries has developed a self supporting tank type. This tank type is
very similar to the ones used on the first ship, Methane Princess. The tank is made of aluminum.
Figure 2. 15 IHI prismatic system 87.500 m3
Source: LNG Tanker Ship Presentation of Wisnu Mustapha
2. Moss tanks
This design is owned by the Norwegian company Moss Maritime and it is a spherical aluminum
tank. It was developed in 1971 by Kvaerner.
Figure 2. 16 Kvaerner Moss system 137.000 m3
3. TGZ Mark III
This design was developed by Technigaz and it is of the membrane type. The membrane consists
of stainless steel with 'waffles' to absorb the thermal contraction when the tank is cooled down.
Figure 2. 17 Technigaz system 18.900 m3

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4. GT96
This is Gaz Transport's tank design. The tanks consist of a primary and secondary thin membrane
made of the material Invar, which has almost no thermal contraction. The insulation is
constructed of plywood boxes filled with Perlite, a lightweight insulating material.
Figure 2. 18 Gaz Transport system 135.000 m3
Source : LNG Tanker Ship Presentation of Wisnu Mustapha
The most common in used are the spherical tanks of Moss design and the membrane tanks from
Gaz Transport refer to Figure 2.18 or Technigaz refer to Figure 2.17 (two French companies, now
amalgamated as GTT). Each is contained within the double hull where the water ballast tanks
reside. The world fleet divides approximately 50/50 between the two systems.
There are two system tanks, which are:
1. Spherical Tank
Regarding spherical tanks, a very limited number were constructed from 9% nickel steel, the
majority are constructed from aluminium. A disadvantage of the spherical system is that the
tanks do not fit the contours of a ship's hull and the consequent 'broken stowage' is a serious
diseconomy. In general terms, for two LNG ships of the same carrying capacity, a ship of Moss
design will be about 10% longer. It will also have its navigating bridge set at a higher level to allow
good viewing for safe navigation. On the other hand the spherical tanks are simple in design and
simple to install in comparison to the membrane system, with its complication of twin barriers
and laminated-type construction. Tank designs are often a controlling factor in building an LNG
carrier. Shipyards usually specialise in one type or the other. Where a yard specialises in the Moss
system, giant cranes are required to lift the tanks into the ships and limits on crane outreach and
construction tooling facilities currently restrict such tanks to a diameter of about 40 metres.
Figure 2. 19 Spherical Tank (Moss Design)
2. Membrane Tank

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The cargo is contained within thin walled tanks of invar or stainless steel.LNG carriers have a
watertight inner hull and most tank designs are required to have a secondary containment
capable of safely holding any leakage for a period of 15 days. The tanks fits the contours of a
ship's hull and navigating bridge set at a lower level
Figure 2. 20 LNG carrier with membrane tanks
Figure 2. 21 Membrane design (GTT)
Comparison between spherical tank and membrane tank shown at Table 2.3
Table 2. 3 Comparison between spherical tank and membrane tank
Spherical Tank Membrane Tank
Material Aluminium & 9% nickel steel invar or stainless steel
Install Simple to install Little bit difficult
Navigating bridge Higher level Lower level
Ship hull Not fit the contour Fit the contour

Oktaviani T 2-19
Nowaday, the membrane tanks is commonly used because of it’s advantages.Some of the
advantages compare with the spherical tanks are :
More efficient in space utilization
More compact in size with same DWT
Less wind catchments area
Lower bridge, less obstruction for sight to bow from bridge
Lower bridge, she can sail underneath low existing bridges
Maintain draft, increase beam to accommodate larger DWT
Less cost overall
Table 2. 4 LNG Tanker Ship
Source: LNG Tanker ship for BPMIGAS Kebandran June 25 2009

Oktaviani T 2-20
2.3 LNG Loading Terminal
2.3.1 Standard and Code
1.3.1.1 Standard for LNG Loading Terminal
British Standard Code of Practice for Marine Structures - Part 1-6. BS6349: British Standards
Institution.
Technical Standards and Commentaries for Port and Harbour Facilities in Japan – TSCPHFJ
Permanent International Association of Navigation Congresses (PIANC): Guideline for the
Design of Fenders Systems (2002)
Society of International Gas Tankers and Terminal Operators, Ltd (SIGTTO): Site Selection
and Design for LNG Ports and Jetties, Information Paper No. 14
Oil Companies International Marine Forum (OCIMF): Mooring Equipment Guidelines
Oil Companies International Marine Forum (OCIMF) and SIGTTO: Prediction of Wind Loads
on Large Liquefied Gas Carriers
Oil Companies International Marine Forum (OCIMF): Prediction of Wind and Current Loads
on VLCC's (current forces only)
National Fire Protection Association (NFPA): NFPA 59A, Production, Storage and Handling of
Liquefied Natural Gas (LNG)
1.3.1.2 Standard for Sructural Design
The American Association of State Highway and Transportation Officials (AASHTO) Standard
Specifications for Highway Bridges.
American Petroleum Institute (API): RP2A Recommended Practice for Planning; Design and
Constructing Fixed Offshore Platforms.
American Concrete Institute (ACI): ACI 318-95, Building Code Requirements for Structural
Concrete.
Precast / Prestressed Concrete Institute (PCI): PCI Design Handbook.
American Institute of Steel Construction (AISC): Manual of Steel Construction.
American Welding Society (AWS): AWS D1.1 Structural Welding Code.
International Conference of Building Officials: Uniform Building Code 97 .
2.3.2 LNG Loading Arm
2.3.2.1 General
The marine transfer arm or loading arm is the key link for cargo transfer between the jetty piping
and the vessel. Arms must be able to transfer products without leakage, move as the vessel's
manifold position changes, and support the imposed dead load, fluid, ice and wind loads. Design
will depend on the type of fluid being transferred and on vendor’s own technology. Continued

Oktaviani T 2-21
reliability of operation is essential to maintain supply of products and to expedite vessel
turnaround and avoid demurrage costs, and minimize risks of flammable products and pollution.
The use of loading arms for the large gas carrier is now quite common and, if not a national
requirement, is certainly an industry recommendation. The alternative use of hoses is fraught
with concerns over hose care and maintenance, and their proper layout and support during
operations to prevent kinking and abrasion.
As ships have grown in size the installation of vapour return lines interconnecting ship and shore
vapour systems has become more common. Indeed, in the LNG industry it is required, with the
vapour return being an integral part of the loading or discharging system. In the LPG trades,
vapour returns are also common, but are only opened in critical situations such as where onboard
reliquefaction equipment is unable to cope with the loading rate and boil-off. A feature common
to both ship and shore is that both have emergency shutdown systems. It is now common to
interconnect such systems so that, for example, an emergency on the ship will stop shore-based
loading pumps. One such problem may be the automatic detection of the ship moving beyond
the safe working envelope for the loading arms. A further refinement at some larger terminals is
to have the loading arms fitted with emergency release devices, so saving the loading arms from
fracture (refer to Figure 2.22 until Figure 2.23).
Figure 2. 22 Hard arms at cargo manifold, including vapour return line

Oktaviani T 2-22
Figure 2. 23 Hard arm quick connect/disconnect coupler (QCDC)
For conventional product transfer system, there are two many types of loading arm technology.
These are:
Solid Link System
Pantograph (Cable) System
The pantograph system at Figure 2.24 has been chosen because of it’s inherent flexibility and it’s
resulting ability to absorb the forces associated with relatively rapid changes in arm direction that
result from the movement of LNG Carrier.
Figure 2. 24 Pantograph System
Source: LNG Loading Arms Wisnu Presentation Dec 2006.
Loading arm has function to transfer cargo between jetty piping and LNG carrier. Arm must
capable to transfer LNG without any leakage, and moves appropriate with ship manifold and
capable to hold the load from the structure, fluid, wind and ice.
The design of loading arm depends on variety of cargo and vendor technology.
Loading arm selection depend on strength of ship’s manifold which are load that can be hold by
presentation flange see Table 2. 5

Oktaviani T 2-23
Table 2. 5 Presentation Flange Loading
Source: Recommendations for Manfold for Refrigerates LIquified Natural Gas Carrierrs
Ship Category A B C
Vertical Force (ton) 5 5 10
Lateral Force (ton) 2 2 3
Axial Force (ton) 5 5 7
Moment
(ton/meter)
5 5 10
Forces based on
maximum loads
imposed by
unsupportes loading
arms of stated size
12” 16” 20”
The ship should be able to present the following vertical flanges for loading or discharging at the
cargo manifold on each side of the ship see Table 2.6.
Table 2. 6 Spacing and Principal Flange Size
Source: Recommendations for Manfold for Refrigerates LIquified Natural Gas Carrierrs
Ship Volume H*
Liquid Lines Vapour Lines
Flange Size Flange Size
Category A 2,5 m 12” 12”
Category B 3,0 m 16” 16”
Category C 3,5 m 20” 20”
H* = minimum distance recommended between the manifold flange centres. The distances
should not be exceeded by more than half a metre

Oktaviani T 2-24
2.3.3 Emergency Release System
The Emergency Release System (ERS) provides a positive means of releasing the transfer arms
and providing safe isolation between ship and shore with minimal product spillage. Additionally
the ERS is the ultimate protection of the transfer arms as it allows stopping of the cargo transfer
and quick disconnection of the arms from the tanker manifold either by pressing the ERS button
or in case of excessive drift of the ship.
Typically the ERS system consists of an emergency release coupling (ERC) and one or two
interlocked valves (depending on the product). Hydraulic actuation is on the upper part of the
coupler, operating both valves via special linkage and the ERC. On release, the lower part of the
assembly and its attendant valve remain attached to the ship’s manifold whilst the arm, with the
upper part of the system and its valve is free to rise clear from the ship. Mechanical or electro-
hydraulic interlocks prevent the coupling from release before the valves are closed.
The speed of operation of the opening/closure of valves and disconnection of the ERC is adjusted
and verified during commissioning. The speed of closure of the valves is critical in order to
prevent surge pressure in the piping. Preferably transfer of liquid should be stopped prior to ERS
activation by using the pre-alarm signal if available. In case of emergency, loading pumps are
stopped concurrently with closure of the ERS valves to limit surge pressure.
1. First step: Emergency stop of loading
Stop all cargo transfer pumps and close liquid/gas emergency shut-off ESD valves (onshore and
on the LNG vessel).
2. Second step: Emergency release
a. Close ERS valve(s) – may be carried out during first step.
b. Open ERC.
c. Withdrawal of the arm.
2.3.4 PERC
Each loading arm completed with Double Ball Valves (DBV) and PERC (Powered Emergency Release
Coupler) as part of ERS (Emergency Release System) from loading arm show in Figure 2.25. DBV
and PERC have function to protect loading arm from vessel movements in LNG Jetty and
decrease LNG gas spilled. ERS has 2 system controls which are:
DBV system
System control PERC

Oktaviani T 2-25
Figure 2. 25 Hard arm connection to manifold, double ball valve safety release.
2.3.5 Quick Release Hooks (QRH)
The provision of quick-release mooring hooks at many terminals, particularly those handling large
vessels, reduces both manpower requirements and the need for mooring gangs to handle large
diameter wires and ropes, with the risk of personal injury. Additionally they can assist in the rapid
and orderly disconnection of lines to permit the vessel to depart in an emergency.
The release mechanism is locally initiated usually by a lever (sometimes with a safety lanyard) on
pneumatic or hydraulic powered assistance. Furthermore they have the ability to be released
remotely. Some terminals may have a system whereby one switch releases all of the hooks. This
type of system is not recommended and can lead to dangerous situations where the ship may
suddenly be released and drift away from the terminal.
The design of the QRH incorporates two rotation pins to ensure that the hooks remain oriented
in line with the mooring ropes/wires throughout the design sector. The structure is fixed to the
jetty and may support a single, double, triple or quadruple arrangement of hooks. There is a
vertically oriented rotation pin to permit horizontal rotation (needed because of different ship
sizes and layout of shipboard mooring equipment). There is also a horizontally oriented rotation
pin to permit vertical rotation (needed because of ship deck elevation changes due to tide and
draft). The hook must also be able to freely rotate in order to release the line. There are also
moving parts associated with the release mechanism. Lubricated non-sealed pins/bushings are
typically used. QRH’s require a high degree of maintenance.

Oktaviani T 2-26
Figure 2. 26 QRH
Sumber: LNG Loading Arms Wisnu Presentation Dec 2006.
1.3.6 Quick Connect / Disconnect Coupler (QC / DC)
The Quick Connect/Disconnect Coupler (QC/DC) can reduce the time and effort required
connecting and disconnecting the transfer arms to the ship’s manifold, compared with bolted
flanges. The coupler can be manually or hydraulically operated. A QC/DC coupler is not part of the
emergency release system.
If a QC/DC coupling failed there is the potential for full bore discharge of product. Therefore the
design must ensure that the probability of failure is negligible. A high quality inspection and
maintenance regime for these items is therefore imperative.
Due to the above, it is essential to include interlock mechanisms that prevent operation of the
QC/DC coupler during cargo transfer. This interlock mechanism should be easily understood and
of the most simple nature.
Manual couplers are of two basic designs, either using friction locks or mechanical methods
(usually hand wheel manual coupling: as the hand wheel is rotated, the clamping hooks close
simultaneously, applying the load evenly to the ships presentation flange).
The hydraulic QC/DC coupler consists of a main fluid carrying body that has, at the rear, a flange
for connection to the transfer arm. At the front of the QCDC body is a face flange, which houses
the seals that ensure a leak tight connection to the ships presentation flange.
Usually there is a visual indicator showing when the opening or closing operation is complete.
Hydraulic couplers are equipped with an emergency release mechanism in case of power failure.
1.3.7 Capstans
The primary purpose of capstans is to facilitate the line handling activities and reduce the
potential for personnel injuries. The capstan is used to haul in the first line or messenger line,
which will have the main mooring wire or rope attached to its seaward end.

Oktaviani T 2-27
The vast majority of capstans will be electrical operated and approved for use in hazardous areas.
QRH units will usually incorporate an integral capstan. A geared reducer is used to provide an
output speed between 20 and 30 meters per minute, with a pull of 1 to 3 tons.
The capstan rotation may be single direction with a brake, or reversible. Operation of the capstan
is usually by way of a footswitch pedal, which allows the operator to handle the first line.
1.3.8 Dock Hoses
Hoses are in regular use at smaller terminals and although not seen as the optimum method of oil
and liquefied gas cargo transfer it is accepted that there will always be a need for these items.
They are, however, susceptible to damage through misuse during handling and storage and
guidance is provided on this, along with the breakaway couplings with which they should be
fitted.
Hose systems can range from such simple systems as single hose strings handled by the ship's
derrick and single strings handled by a shore crane to more complex systems found in multi-
string hose towers. Hoses can also be used in conjunction with swivels and piping to form half-
metal/half-hose system (commonly referred to as a ‘flow boom’).
Each hose should be provided with a permanent tag plate showing pressure range (including
vacuum where applicable), temperature range, production date, material, electrical discontinuity
(whether or not electrically conductive), re-testing date, etc.
There are some hose types are:
The guidelines presented in this section are applicable to both rubber (smooth and rough bore)
and composite hoses used in the following product services: Oil and Petroleum Products at
temperatures ranging from -20°C (-4°F) to 82°C (180°F) for rubber hose assemblies (refer to
EN1765) and from -30°C (-22°F) to 150°C (302°F) for composite hose assemblies (refer to EN13765).
a. Composite Hose
Composite hose provides a lightweight alternative to rubber hoses. Although not as robust nor
having the durability of rubber hoses, composite hoses being lighter offer easier handling and
lower initial cost. Composite hose is a tubeless hose made up of several layered components
between internal and external spiral wire reinforcement show at Figure 2.27. The hose is
manufactured on a mandrel, first with the internal wire reinforcement, followed by several layers
of synthetic films (polypropylene, polyester, synthetic fabrics), with a PVC impregnated cover,
and finally the external spiral wire that lies between the spirals of the internal wire. The resulting
hose construction has a corrugated appearance.
Composite hoses must always be considered electrically continuous since the reinforcement
wires can not be effectively insulated from end fittings.

Oktaviani T 2-28
Figure 2. 27 Composite Hoses
Source: SIGTTO OCMIF Jetty Inspection Maintenance Draft
b. Rubber Hose
Standard rubber hose contains a tube or inner rubber liner and reinforcing components show at
Figure 2.28. The tube is the innermost part of the rubber hose body and protects the outer layers
and carcass from contact by the product. An inner steel reinforcement wire is often placed in the
rubber hose to add strength and resist delaminating of inner layers. When the tube is placed over
the wire reinforcement or the wire reinforcement is imbedded in the inner lining, the hose is
referred to as a rough bore hose. When the inner steel reinforcement is not employed, the hose
is referred to as a smooth bore hose.
The core of the hose is referred to as the carcass and provides the hose strength against internal
pressures, longitudinal tension, and other loads occurring from the handling and support of the
hose. The carcass consists of combinations of fabric and/or metal elements. The outermost layer
of the hose construction is called the cover and protects the carcass from abrasion, wear, and
attack from the elements and/or chemical action. When the carcass does not use any wire
reinforcement or steel rings but gains its strength from fabrics or woven cords, the hose is
referred to as a soft-wall rubber hose.
Rough bore hoses are to be considered electrically continuous in that it is not practical to ensure
electrical insulation of the internal reinforcement wire. Smooth-bore and soft-wall hoses can be
manufactured either electrically continuous or electrically discontinuous.
End fittings are vulcanized into the hose body or swaged.
Figure 2. 28 Rubber Hoses
Source: SIGTTO OCMIF Jetty Inspection Maintenance Draft

Oktaviani T 2-29
1.3.9 Safety System pada Transfer LNG
There’s one thing we must do in process LNG transfer is to prevent LNG spill. When the LNG
transfer process is analyzed, three potential sources of product spillage are identified. In order of
probability and risk, these are:
Connection/disconnection of the ship to shore connection
Swivel leakage
During emergency disconnect
The above safety related risks of operations led to development of PMS (Position Monitoring
System). The PMS enable operators to:
Permanently monitor the position of the loading arm at the jetty, and hence of the
LNG carrier, including measurement of the velocity of the LNG carrier drift in order to
anticipate/ bring forward disconnection of the ERS.
Accurately position the LNG Carrier along the spotting line required to maximize fore
and aft drift.
Link the PMS to the maximum allowable tension in the mooring lines to give advance
warning to operatorsbefore the dedicated LNg carrier breaks away and
Enable continuos monitoring of operations from the berth and from the central
control room of the terminal.
Figure 2. 29 Tangguh Loading Arm Envelope
Source: LNG Loading Arms Wisnu Presentation Dec 2006.
By contrast, modern day emergency shut down occurs in a more controllable fashion. All alarm
stages a result of a comparison between predetermined limits and the arms positions

Oktaviani T 2-30
communicated by sensors to a Position Monitoring System, are specific to the jetty and are
generally determined in conjuction with the operator. These are:
1 Pre-alarm
A preliminary, passive alarm stage only, this warns the operator that corrective action (tension
ship mooring) must be taken to bring the LNG Carrier under control. No action is taken by the
loading arm control system.
2 First Stage Alarm
Should the carrier continue to drift, the first stage alarm is sounded. At this point, the pumps are
stopped, the (MOV) valve at the foot at the base riser is shut and the two ball valves in the ERS
system are closed. Product transfer is stopped and the system is safe. Site actions necessary to
bring carrier movement under control continue. The sequence continues to be reversible at thios
point. If the carrier is brought under control, transfer can be restarted immediately.
3 Second Stage Alarm
Finally, should carrier movement continue outward from the alarm zones, the second and final
alarm stage is reached. This stage result in physical connection and is irreversible. Once this point
is reached, restart of product transfer requires a time consuming process including draining of
the arm, return to ambient temperature, the onshore connection of the lower part of thre ERS
system that is left with the carrier manifold during emergency disconnection and the
recommencement of the transfer start up sequence from the beginning.
2.4 Port Planning
2.4.1 Principal Recommendation for Port Planning from SIGGTO
2.3.1.1 Port Design
2.3.1.1.1 Approach Channels.
Harbour channels should be of uniform cross-sectional depth and have a minimum width, equal
to five times the beam of the largest ship.
2.3.1.1.2 Turning Circles.
Turning circles should have a minimum diameter of twice the overall length of the largest ship,
where current effect is minimal. Where turning circles are located in areas of current, diameters
should be increased by the anticipated drift.
2.3.1.1.3 Tug Power.
Available tug power, expressed in terms of effective bollard pull, should be sufficient to
overcome the maximum wind force generated on the largest ship using the terminal, under the
maximum wind speed permitted for harbour manoeuvres and with the LNG carrier's engines out
of action.

Oktaviani T 2-31
2.3.1.1.4 Traffic Control.
A Vessel Traffic Service (VTS) System should be a port requirement and this should be able to
monitor and direct the movement of all ships coming within the operating area of LNG carriers.
2.3.1.1.5 Operating Limits.
Operating criteria, for maximum wind speed, wave height, and current, should be established for
each terminal and port approach. Such limits should match LNG carrier size, manoeuvring
constraints, and tug power.
2.3.1.1.6 Speed Limits.
Speed limits should be set for areas in the port approach presenting either collision or grounding
risks. These limits should apply not only to LNG carriers but also to any surrounding traffic.
2.3.1.2 Jetty Design
2.3.1.2.1 Exclusion of Ignition Sources.
No uncontrolled ignition source should be within a predetermined safe area centred on the LNG
carrier's cargo manifold.
2.3.1.2.2 Mooring Layout.
The terminal should provide mooring points of a strength and in an array which permits all LNG
carriers using the terminal to be held alongside in all conditions of wind and current.
2.3.1.2.3 Quick Release Hooks.
All mooring points should be equipped with quick release hooks. Multiple hook assemblies
should be provided at those points where multiple moorings lines are deployed so that not more
than one mooring line is attached to a single hook.
2.3.1.2.4 Emergency Release System.
At each hard arm the terminal should fit an ERS system, able to be interlinked to the ship's ESD
system.
This system must operate in two stages:
• the first stage stops: LNG pumping and closes block valves in the pipelines
• the second stage: entails automatic activation of the dry-break coupling at the PERC
together with its quick-acting flanking valves.
2.3.1.2.5 Powered Emergency Release Couplers (PERCs).
The terminal should fit a PERC in each hard arm together with quick-acting flanking valves so that
a dry-break release can be achieved in emergency situations.

Oktaviani T 2-32
2.3.1.2.6 Terminal Security.
An effective security regime should be in place to enforce the designated ignition exclusion zone
and prevent unauthorised entry into the terminal and jetty area, whether by land or by sea.
2.3.1.2.7 Operating Limits.
Operating criteria, expressed in terms of wind speed, wave height, and current, should be
established for each jetty. Such limits should be developed according to ship size, mooring
restraint, and hard arm limits. Separate sets of limits should be established for berthing,
stopping cargo transfer, hard arm disconnection and departure from the berth.
2.4.2 Elevation of LNG Jetty
Elevation of LNG Jetty based on Us DoD (Department of Defense), 2005. Design: Piers and
Wharfs, Unified Facilities Criteria (UFC) 4-152-01, 28 July 2005 which are given by equation
E = MHHW + maximum wave crest height + air gap + structure depth (2. 1)
Where:
E = elevation of LNG Jetty ( LAT)
MHHW = mean highest high water level (m)
Maximum wave crest height = wave crest height (50 years period)
Structure depth = the depth of deck
2.4.3 Turning Basin
In determination of the area of basin used for bow turning, due consideration shall be given to
the method of bow turning, the vessel bow turning performance, the layout of mooring facilities
and navigation channel, and meteorological and marine conditions.
It is recommended that turning basins be located appropriately in front of mooring facilities in
consideration of the layout of other navigation channels and basins.
The standard area of turning basin according to ‘Technical Standard and Commentaries for Port
and Harbour Facilities in Japan, The Overseas Coastal Area Development Institute of Japan’ is as
follow:
• Bow turning without assistance of tugboats: Circle having a diameter of 3L
• Bow turning using tugboats: Circle having a diameter of 2L
To enable to turn the bow of the ship (hereafter to be called bow turning) by using an anchor or
using tugboats, the area should exceed an area of the circle with a radius of the overall length of
the ship. However, for a very calm basin and for ships with high bow turning capability, the area
can be reduced to the extent not to hinder the bow turning.
This scheme will be applied if the vessel targeted to leave the berth in same path with the enter
of vessel. In case of otherwise, the turning basin may not provided except the access channel.
Depth of basin usually ranges from 1.05 to 1.15 of full loaded draft of the maximum target vessel.

Oktaviani T 2-33
2.4.4 Navigation Channel
In planning and design of a navigation channel, considerations shall be given to the safety of
navigation, the easiness of ship maneuvering, the topographic, meteorological and marine
conditions, and the conformity with related facilities.
A navigation channel can be difined as a waterway with sufficient depth and width to allow the
smooth passage of vessels. A good navigation channel should satisfy the following requirements:
The alignment of the navigation channel is close to a straight line.
The width and depth are sufficient in consideration of the effects of the shape of the channel’s
bank, the sea bottom topography, and ship-generated waves on the navigation of other vessels.
Meteorological and marine conditions including winds and tidal currents are good for safe
navigation.
A sufficient number of good navigation aids and signaling facilities have been provided.
Figure 2. 30 Depth of Navigation Channel
Source: Port Engineering Book Carl A.Thorensen
Squat or the reduction of underkeel clearance is due to the suction effect induced by the higher
current velocity between the sea bottom and the ship. This causes a reduction in the water level
near the ship and the ship therefore sinks bodily in the water. The squat increases with the
length of the ship, with the increase in the ship speed, and with reduction in underkeel
clearance and narrowness of a channel. In addition, the water depth is also affected by the
water density and must be greater in freshwater than in seawater importance for river or
estuary.
Ship movements due to waves can be up to 2/3 of the significant wave height for smaller ships.
VLCC and large ore carriers, due to their huge size, are only susceptible to waves with a period
of more than 10 seconds. Waves with a shorter period will scarcely result in vertical motions for
these ships.

Oktaviani T 2-34
The rise or fall of the water level due to change in the atmospheric pressure is approximately
equal to 0,9 cm in rise/ fall of the water level for 1 mmbar fall /rise in atmospheric pressure. The
fall and rise in the atmospheric pressure can in Nor- way give a variation of about 550 cm.
Where the bottom is composed of soft materials (sand etc.) the minimum net underkeel
clearance should be 0.5 m and for rocky bottom 1.0 m. The water depth must during
construction dredging be reasonable to avoid both possible error in dredging and yearly
excessive cost for maintenance dredging due to possibility of silting up.
When setting a navigation channel, it is necessary to analyze the tracks of vessels entering and
leaving the port using examples of similar existing ports and harbors as references. It is also
necessary to hear opinions from the people in the local maritime organizations. Further
considerations should be given to the status of provisions of navigation aids and the marine
traffic control system within the harbor, the distances from the adjacent basins to the harbor, the
navigation channel division methods employed for the harbor (e.g., large and small ships,
inbound and outbound traffic), the angle of approach to the harbor, and whether or not
tugboats are used.
For the area of water that is mainly used for the navigation of vessels, measures should be taken
to avoidanchorage or turning of vessels within such waters even when there is no designation for
navigation channels.
The width of the manoeuvering lane will generally vary from 1.6 to 2.0 times the beam of the
largest ship using the channel, depending on wind, current and the manoeuverability of the ship.
The very high superstructures on containerships, car carriers, passenger ships and tankers in
ballast present considerable windage area and may therefore require more channel width than
their beam would suggest. Allowance for yaw of the ship must be made if the channel is
exposed to crosscurrents and/or winds. The angle of yaw can be between 5" to 10". For a
largeship an angle of yaw of 5" can add an extra width equivalent to half the beam to the
manoeuvering lane. Ships displaced from the channel centre line towards the banks of the
channel will experience a bank suction effect due to the assymmetrical flow of water round
the ship and this will cause a yawing movement. To counteract this effect on the ship an
additional bank clearance width usually between 1 to 2 times the beam of largest ship must be
added. A steepsided channel section produces more bank suction than a channel with a
trapezoidal section. Bank suction also increases when the underked clearance decreases.
To avoid excessive interaction between two ships travelling past one another, either in the
same or in the opposite direction in a two lane channel, it is necessary to separate the two
manoeuvering lanes by a ship clearance lane. To minimise the suction and repulsion forces
between the ships, a clearance lane equal to minimum 30 m or the beam of the largest ship
should be provided. Figure 2.31 will show the single lane navigation channel and Figure 2.32 show
us the width of two lane navigation channel.

Oktaviani T 2-35
Figure 2. 31 Single Lane Navigation Channel
Figure 2. 32 Two Lane Navigation Channel
Width of navigation channel for single lane based on 'Port Engineering', Per Bruun, given by
equation:
( )W= 2*BC +ML   (2. 2)
Width of navigation channel for two lane based on 'Port Engineering', Per Bruun, given by
equation:
( )W= 2* BC+ML +SC   (2. 3)
where:
W = width of navigation channel
B = beam of ship
BC = Bank Clearance
ML = Maneuvering Lane
SC = Ship Clearance

Oktaviani T 2-36
2.5 Mooring
2.5.1 General
Moorings are provided to prevent vessels from drifting away from a berth or from colliding with
adjacent moored vessels. Movement should be restrained by means of an adequate number of
mooring lines, which can be readily handled by the operating personnel, compatible with the
conditions of winds, tides, waves and other effects likely to be experienced during the period a
vessel is berthed. The mooring layout is dependent on the size and type of vessel using the
berth, and the position, spacing and strength of the moorings on the pier. The following points
should be noted when designing the mooring system (see Figure 2.33)
Figure 2. 33 Typical Mooring Pattern
Source: Mooring Equipment Guideline
The mooring system should be symmetrical to ensure even distribution of the restraining forces
on the vessel. The mooring lines should not be too short to avoid steep angles of the lines, which
will result in poor load distribution. The mooring lines should not be too long to avoid excessive
movement of the vessel. The spring lines should be aligned as close to the longitudinal direction
of the vessel as possible to provide the maximum restraint against the vessel surging along the
pier. The breast lines should be roughly aligned perpendicular to the longitudinal direction of the
vessel to provide the maximum restraint against the vessel from being moved broadside from
the pier. Head and stern lines are generally not necessary provided that mooring points are
suitably designed and arranged. Head and stern lines may however be required to provide
assistance in ship manoeuvring in some situations, for example, where a vessel is being moved
along a pier without use of main engine or where there is exceptional asymmetrical current or
wind loads. The vertical mooring angle should be as small as practicable and preferably not
greater than 25º. The mooring system should be able to cater for various sizes and types of
vessels using the jetty. Mooring loads from vessels’ lines are applied through pier fittings such as
bollards fixed to the top of the deck. A bollard is usually in the form of a short metal column
fixed on the surface of the pier deck for the purpose of securing and belaying wire ropes or
hawsers to refrain movement of the vessels at the pier. Bollards made of cast iron collar infilled
with reinforced concrete are commonly used at the pier.

Oktaviani T 2-37
2.5.2 Forces Acting on the Ship
The moorings of a ship must resist the forces due to some, or possibly all, of the following
factors:
wind
current
tides
surges from passing ships
waves/swell/seiche
ice
changes in draft, trim or list.
2.4.2.1 Wind
The force effect of wind is greater on a large ship than on a small ship in a similarly loaded
condition as it has more exposed area. Figure 2.34 demonstrates how the resultant wind force on
a ship varies with wind velocity and direction. For simplicity, wind forces on a ship can be broken
down into two components: longitudinal force acting parallel to the longitudinal axis of the ship
and a transverse force acting perpendicular to the longitudinal axis. The resultant force initiates a
yawing moment. Wind force on the ship also varies with the exposed area of the ship. Since a
head wind only strikes a small portion of the total exposed area of the ship, the longitudinal force
is relatively small. A beam wind, on the other hand, exerts a very large transverse force on the
exposed side area of the ship. If the wind hits the ship from any quartering direction between the
beam and ahead (or astern), it will exert both a transverse and longitudinal force, since it is
striking both the bow (and stern) and the side of the ship. For any given wind velocity, both the
transverse and longitudinal force components of a quartering wind will be smaller than the
corresponding forces caused by the same wind blowing abeam or head on.
Figure 2. 34 Wind Forces on a Ship

Oktaviani T 2-38
The calculation for wind and current force based on Oil Companies International Marine Forum
(OCIMF): Prediction of Wind and Current Loads on VLCC's.
2.4.2.1.1 Lateral Wind Force.
Lateral wind force is determined from the equation:
2
yw yw w w L
1
F = C ρ V A
2
(2. 4)
CyW = lateral force coefficient,
AL = longitudinal area projection
ρw = mass density of water (kg/m3
)
VW = wind speed (m/s)
2.4.2.1.2 Longitudinal Wind Force.
2
xw xw w w T
1
F = C ρ V A
2
(2. 5)
Dimana:
CXW = longitudinal force coefficient
ρU = mass density of water (kg/m3
)
= wind speed (m/s)
= transversal projected area of the ship (m)
= transverse wind force drag coefficient
2.4.2.1.2 Wind Yaw Moment.
2
XYw XYw w w L BP
1
M = C ρ V A L
2
(2. 6)
Dimana:
CXYW = longitudinal force coefficient ,
AL = longitudinal area projection (m2
).
)
VW = wind speed (m/s)
The conversion for wind speed for elevation 10 m given by equation
1/7
w w
10
V =u ( )
h
(2. 7)
where:
VW = wind speed at elevation 10 m (m/s)
uw = wind speed at elevation h(m/s)
h = survey elevation (m)

Oktaviani T 2-39
Figure 2. 35 Longitudinal Force Coefficient
Source: Oil Companies International Marine Forum (OCIMF): Prediction of Wind and Current
Loads on VLCC's
Figure 2. 36 Lateral wind coefficient
Loads on VLCC's

Oktaviani T 2-40
Figure 2. 37 Yaw Moment Coefficient
Loads on VLCC's
2.4.2.2 Current
Water current force considerations are similar to those of wind force. The magnitude of current
forces on a ship depends on the velocity of the current, the hull area exposed to the current and
the under keel clearance of the vessel. As with wind, current forces are directly related to the
area of the ship exposed to them. The maximum force of the current will be experienced when
the vessel is in a loaded condition and the current is acting directly on the beam. The force is
minimised if the ship is light in the water and its bow is headed into the current.
Current force increases with the square of the current velocity. If the current velocity doubles,
the current force is four times larger. If the velocity triples, the force is nine times larger. Since
current forces act on the submerged portion of the ship, they are likely to be most critical when
the ship is loaded. While it is usually evident when the wind is blowing at or near gale force, high
current velocities are not as noticeable to the ship’s personnel. Only a review of the current
information for the terminal is reliable.
2.4.2.2.1 Lateral Current Force.
Lateral current force is determined from the equation:
2
yc yc w Bp
1
F = C ρ Vc L T
2
(2. 8)
Dimana:
CYC = lateral current coefficient
).
T = draft of LNG Tanker (m)

Oktaviani T 2-41
VC = current speed (m/s)
LBP = length between perpendicular (m)
2.4.2.2.2 Longitudinal Current Force.
Longitudinal current force is determined from the equation:
2
xc xc w Bp
1
F = C ρ Vc L T
2
(2. 9)
where:
CXC = longitudinal current coefficient
).
2.4.2.2.2 Current Yaw Moment
2 21
2
XYc XYc w c BPM C V L Tρ= (2. 10)
CXYW = current force coefficient
).
Figure 2. 38 Current Longitudinal Coefficient for(WD/T=1.2)
Loads on VLCC's

Oktaviani T 2-42
Figure 2. 39 Lateral Current Coefficient
Loads on VLCC's
Figure 2. 40 Yaw Moment Coefficient
Loads on VLCC's

Oktaviani T 2-43
2.6 Berthing
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 recognized deterministic methods as outlined in the
following sections.
Most berthing 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, and experience of the operators, berth type, wind and current
exposure.
The normal energy to be absorbed by the fender can be calculated as:
CSEM
D
CCCC
VM
E ⋅⋅⋅⋅
⋅
=
2
2
(2. 11)
Where,
E = Normal berthing energy to be absorbed by the fender (kNm)
MD = Mass of the vessel (displacement in tons)
V = Approach velocity component perpendicular to the berthing line (m/s).
CM = Added mass coefficient
CE = Eccentricity coefficient
CC = Berth configuration coefficient
CS = Softness coefficient
1. Eccentricity Factor
The eccentricity factor shall be calculated by the following:
2
E 2 2
K
C =
K +R
(2. 12)
( )0,19 0,11B ppr C L= + (2. 13)
where
r = radius of gyration; this is related to the moment of inertia around the vertical axis of
the vessel by the relationship
Lpp = length between perpendiculars (m)
Cb = block coefficient = /( LppBd)

Oktaviani T 2-44
= Volume of water displaced by the vessel (m3
)
B = moulded breadth (m),
D = draft (m)
2. Mass Coefficient
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.
B
D
CM
2
1+= (2. 14)
Where,
D= loaded draft
B= breadth moulded
3. Sotness Coefficient
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).
4. Berth Configuration Coefficient
When a ship 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:
• Quay structure design
• Under keel clearance
• Velocity and angle of approach
• Projection of fender
• Vessel hull shape
Table 2. 7 Berth configuration factor

Oktaviani T 2-45
2.7 Force Analysis in Jetty
2.7.1 General
Design of LNG Jetty as plan based on the structure and the function of it’s port. There are two
kind of analysis which are force analysis and loading analysis. The analyses are:
a) Wave Analysis
b) Vertical Loading Analysis
c) Seismic Analysis
d) Foundation Analysis
e) Structural Analysis
2.7.2 Wave Load
Wave load on a pile is calculated using Morison’s equation when the wave length is larger than
five times the pile diameter. This equation is based on the assumption that the cross-sectional
dimension of the pile is sufficiently small and the local gradient of the water practical acceleration
and velocity along the pile is to be neglected. The Morison’s equation is expressed as follows:
2
1
2 4
D M
D du
f C D u u C
dt
π
ρ ρ= ⋅ ⋅ ⋅ ⋅ + ⋅ ⋅ ⋅ (2. 15)
where,
F = horizontal force per unit length of pile (kN/m)
Fi = inertial force per unit length of pile (kN/m)
Fd = drag force per unit length of pile (kN/m)
ρ = density of fluid (1.025 t/m3
for the sea water)
D = diameter of pile (m) + allowance for marine growth 0.1m
(marine growth thickness is assumed as 50mm)
u =horizontal water particle velocity at the axis of the pile (m/sec)
du/dt = horizontal water particle acceleration at the axis of the pile (m/s2
)
Ci = inertia or mass coefficient (see Table 2.10)
Cd = drag coefficient (see Table 2.11)
L = wave length
Total wave force is obtained by the said Morison’s equation (F=Fi+Fd) and the drag force Fd
depends on wave particle velocity and the inertia force Fi depends on wave particle acceleration.

Oktaviani T 2-46
Table 2. 8 Inertia Coefficient
Source: Technical Standards for Port and Harbour Facilities in Japan
Table 2. 9 Drag Coefficient
Source: Technical Standards for Port and Harbour Facilities in Japan

Oktaviani T 2-47
2.7.3 Current Load
There are two current load to be considered in the detail design stage that is the current load
directly on the construction and current load on the ship hull. The Morrison equation for calculate
the current load but only drag forge which impact on this jetty.
2
D D n
1
F = .C ρV A
2
(2. 16)
Fd = drag force per unit length of pile (kN/m)
ρ0 = density of fluid (1.025 t/m3
for the sea water)
D = diameter of pile (m) + allowance for marine growth 0.1m
(marine growth thickness is assumed as 50mm)
u = horizontal water particle velocity at the axis of the pile (m/sec)
2.7.4 Vertical Loading Analysis
Vertical loading in jetty structure can be determine as dead load and live load. Dead load is self
weight of structure. Dead load calculated by equation:
GCS WWWDL ++= (2. 17)
Where,
WS = self weight (ton)
WC = crane weight(ton)
WG = storage and shelter weight (ton)
Live load in jetty consists of distributed load, point load, and others.
2.7.5 Seismic Analysis
Seismic design condition is that the structure will have minor damage after earthquake taken
place. This is obtained by limiting the structural deflection due to seismic load to 7.5 cm.
The seismic loading to be determined in accordance to Standar Nasional Indonesia, Tata Cara
Perencanaan Ketahanan Gempa Untuk Bangunan Gedung, Badan Standardisasi Nasional, 2003,
SND-03-1726-2002. The loading will be in static equivalent approach.
tI W
R
I
CV =
(2. 18)
Where,
T = Natural Frequency
C = seismic coefficient

Oktaviani T 2-48
I = importance faktor
R = seismic reduction factor
W = total weight of structure
Figure 2. 41 Indonesia Areal Seismic Map
Source: SNI 02-1729
Based on seismic map shown at Figure 2.41 LNG Tangguh, Papua Provice include in Seismic Areal
no 3 and the chart comparasion natural frequency of structure in Areal 6 on the picture below.

Oktaviani T 2-49
Figure 2. 42 Diagram C vs T
Table 2. 10 Seismic Reduction Coefficient
Source: SNI 0279
Table 2.10 shown the reduction seismic factor. We assume that the structure will be fully elastic
so the R=1,6. On the Table 2.11 shown the seismic importance factor.

Oktaviani T 2-50
Table 2. 11 Seismic Importance Factor
Source: SNI 0279
2.7.6 Pile Foundation
2.7.6.1 Axially Loaded Piles
Steel pipe pile is recommended to be used in supporting structure load for heavy and settlement
sensitive structures.
The ultimate soil bearing capacity in compression and tension is calculated using API RP 2A by
using the following equation:
d f p s pQ Q Q fA qA= + = +
(2. 19)
where:
Qf = skin friction resistance, lb (kN),
Qp = total end bearing, lb (kN),
f = unit skin friction capacity, lb/ft2
(kPa),
As = side surface area of pile, ft2
(m2
),
q = unit end bearing capacity, lb/ft2
(kPa),
Ap = gross end area of pile, ft2
(m2
).
For uplift (tensile) capacity, only the first term (fs.As) is used in the calculation and multiflied by
0.65. The weight of pile and soil plug within steel pipe is neglected in tensile capacity.

Oktaviani T 2-51
Cohesive soil
We follow APIRP2A (1987) method for computation of the unit skin friction for pile in cohesive
soils. The unit skin friction may be expressed as:
f cα=
where:
α = dimensionless factor,
c = undrained shear strength of the soil at the point in question.
The factor, α, can be computed by the equations:
α = 0.5 ψ–0.5 ψ ≤ 1.0
α = 0.5 ψ–0.25 ψ > 1.0
with the constraint that, α ≤ 1.0,
where:
ψ = c/p’
0 for the point in question,
p´0 = effective overburden pressure at the point in question lb/ft2
(kPa).
Cohesionless soil
The unit skin friction on cohesionless soils according API RP2A (1987) method expressed as:
0. tansf k p d=
where:
k = coefficient of lateral earth pressure
= 0.8 for open ended pile
= 1.0 for full displacement pile
p0= effective overburden pressure
d = the friction angle between the soil and the pile wall which is estimated to be 0.75 f.
The unit skin friction cannot increase without limit because of arching characteristic of
cohesionless soil as p0 will reach the maximum value at a critical depth Zc. The critical depths Zc
depend on the relative density, thus angle of internal friction f of the soil. Zc varies from 10 D to
20 D with D being the pile diameter.
For piles end bearing the unit end bearing q in lb/ft2
(kPa) may be computed by the equation:
• Cohesive soils

Oktaviani T 2-52
We follow API RP2A (1987) method for computation of the unit end bearing for pile in cohesive
soils, expressed as:
p c uq N s=
where:
pq = unit end bearing, kN/m2
Nc = a non dimensional factor end bearing,
Su = undrained shear strength of the soil at point of question.
• Cohesionless soils
0q p Nq=
where
p0 = effective overburden pressure lb/ft2
(kPa) at the pile tip,
Nq = dimensionless bearing capacity factor
The value of po be limited to the value at the critical depth as described for unit skin friction
above. The value of Nq depends on the Ø of the soil. The internal friction angle f value of
cohesionless soil is estimated from SPT N value using the following formula:
20 15Nφ = +
Where:
N = corrected standard penetration test
The design limiting parameters for cohesionless soil presented in the following Table 2.12.

Oktaviani T 2-53
Table 2. 12 Design Parameters for Cohesionless Siliceous Soil
Source: API RP 2A WSD
2.7.6.2 Capacity Lateral Piles
Response of pile under lateral loading is calculated using p-y method. From the curve of pile
response under lateral loading, lateral pile capacity for allowable deflection then be determined.
Finite difference approximation method is implemented in the computer program for iteration
process of this non-linier problem, and p-y curves are generated internally by the program. Inputs
for the computer programs are undrained shear strength (su) and e50 for clay and internal
friction angle (f) and relative density (Dr) for cohesionless soil. Basic equation for calculating pile
lateral capacity is:
4
2
4 4
0
d yd x
EI Px P
d y dx
= + − = (2. 20)
Density
Soil
Description
Soil Pile, Friction
angle Degrees
Limiting Skin,
Friction Values
kips/ft2
Nq
Limiting Unit End
Bearing Values kips/ft2
Very
loose
Sand
15 1.0 (47.8) 8 40(1.9)
Loose Sand-silt
Medium Sand
Loose Sand
20 1,4(67.0) 12 60(2.9)Medium Sand-silt
Dense Sand
Medium Sand-silt
25 1,7(81,3) 20 100(4,8)
Dense Sand
Dense Sand
30 2.0(95.7) 40 200(9.6)
Very
Dense
Sand-silt
Dense Gravel
35 2.4(114.8) 50 250(12.0)
Very
Dense
Sand

Oktaviani T 2-54
Where:
EI = flexural rigidity of pile
y = deflection of pile
x = length along pile
px = axial load
p = soil reaction per unit length
2.7.6.3 Pile Capacity
The passive resistance provided by the soil to the yielding of an infinitely long pile is infinite. Thus
the ultimate lateral load which can be carried by the pile is determined solely from the ultimate
moment of resistance Mu of the pile shaft. The maximum negative bending moment occurs at the
pile head and at the ultimate load it is equal to the ultimate moment of resistance of the pile
shaft. The ultimate lateral load is given by the following equation:
uH =
u
p
M
H
e 0.54
BK
+
γ
(2. 21)
For a pile of uniform cross-section.
uH = u
u
p
2M
H
e 0.54
BK
+
γ
(2. 22)
The ultimate moment resistance of piles is taken by the yield moment of pile that is by fy*Z.
2.8 Reinforcement Design
The reinforcement design based on BS 8110-1:1997. Figure 2.35 show us the flowchart to design
concrete strength.
Table 2. 13 Strength of Reinforcement
Source: BS 8110-1:1997
Material Yield Strength,fy (N/mm2
)
Hot rolled mild steel 250
High Yield steel( hot rolled or cold worked) 460

Oktaviani T 2-55
Figure 2. 43 Flowchart of Design Procedure
Suource : BS 8110-1: 1997 Structural Use of Concrete

Oktaviani T 2-56
Nominal cover is the design depth of concrete cover to all steel reinforcement, including links. It
is the dimension used in design and indicated on the drawings. The actual cover to all
reinforcement should never be less than the nominal cover minus 5 mm. The nominal cover
should:
a) be in accordance with the recommendations for bar size and aggregate size for concrete cast
against uneven surfaces
b) protect the steel against corrosion
c) protect the steel against fire
d) allow for surface treatments such as bush hammering.
There are some criteria to choose the nominal cover:
1. Bar size
The nominal cover to all steel should be such that the resulting cover to a main bar should not be
less thanthe size of the main bar or, where bars are in pairs or bundles, the size of a single bar of
cross-sectional areaequal to the sum of their cross-sectional areas. At the same time the nominal
cover to any links should bepreserved.
2. Nominal maximum size of aggregate
Nominal covers should be not less than the nominal maximum size of the aggregate. The nominal
maximum size of coarse aggregate should not normally be greater than one-quarter of the
minimum thickness of the concrete section or element. For most work, 20 mm aggregate is
suitable. Larger sizes should be permitted where there are no restrictions to the flow of concrete
into sections. In thin sections or elements with closely spaced reinforcement, consideration
should be given to the use of 14 mm or 10 mm nominal maximum size.
3. Concrete cast against uneven surfaces
In such cases the specified nominal cover should generally be increased beyond the values given
in specified case where concrete is cast directly against the earth should generally be not less
than 75 mm. Where concrete is cast against an adequate blinding, a nominal cover of less than 40
mm (excluding blinding) should not generally be specified.
4. Ends of straight bars
Cover is not required to the end of a straight bar in a floor or roof unit where its end is not
exposed to theweather or to condensation.
5. Cover against corrosion
The cover required to protect the reinforcement against corrosion depends on the exposure
conditions and the quality of the concrete as placed and cured immediately surrounding the
reinforcement.

Oktaviani T 2-57
Table 2.12 gives limiting values for the nominal cover of concrete made with normal-weight
aggregates as a function of these factors.
Table 2. 14 Pemilihan Nominal Cover
Sumber: BS 8110-1:1997
2.8.1 Beam Reinforcement
2.8.1.1 Design Limitation
2.8.1.1.1 Simply Supported Beams
The effective span of a simply-supported beam may be taken as the smaller of the distance
between the centres of bearings, or the clear distance between supports plus the effective
depth.
2.8.1.1.2 Continuos Beam
The effective span of a continuous member should be taken as the distance between centres of
supports. The centre of action of support at an encastré end should be taken to be at half the
effective depth from the face of the support.

Oktaviani T 2-58
2.8.1.1.3 Cantilever
The effective length of a cantilever should be taken as its length to the face of the support plus
half its effective depth except where it forms the end of a continuous beam where the length to
the centre of the support should be used.Flange Beam
2.8.1.1.4 Slenderness limit
The clear distance between restraints should not exceed:
a) for simply-supported or continuous beams: 60bc or 250b2
c/d if less;
b) for cantilevers with lateral restraint only at support: 25bc or 100b2
c/d if less;
where
bc is the breadth of the compression face of the beam, measured mid-way between restraints (or
the breadth of the compression face of a cantilever)
d is the effective depth (which need not be greater than whatever effective depth would be
necessary to withstand the design ultimate load with no compression reinforcement)
2.8.1.2 Rectangular Beam
The following equations, which are based on the simplified stress block of Figure 3.3, are also
applicable to flanged beams where the neutral axis lies within the flange:
K’ = 0,156 (2. 23)
where redistribution does not exceed 10 % (this implies a limitation of the neutral axis
depth to d/2) or
K’ = 0.402(βb – 0.4) – 0.18(βb – 0.4)2
(2. 24)
where redistribution exceeds 10 %;
Figure 2. 44 Stress concrete block
Sumber: BS 8110-1:1997

Oktaviani T 2-59
where
K = M/bd2fcu·
βb = (moment at the section after redistribution)
(moment at the section before redistribution)
d = effective depth of the tension reinforcement.
M = moment ultimate
x = depth to the neutral axis.
Table 2.13 ditunjukkan nilai βf yang dipergunakan untuk desain penulangan ini
Table 2. 15 βf Value
If K < K, compression reinforcement is not required and:
K
z=d 0,5+ (0.25- )
0.9
  
 
 
(2. 25)
but not greater than 0.95d.
where
x=(d-z)/0,45
s yA =M/0.95f z
If K > K, compression reinforcement is required and:
K'
z=d 0,5+ (0,25- )
0,9
  
 
 
(2. 26)
Where:
x=(d-z)/0,45

Oktaviani T 2-60
2
s cuA '=(K-K')f bd 0.95fy(d-d')
2
s cuA =K'f bd 0.95fyz+As'
If d/x exceeds 0.37 (for fy = 460 N/mm2), the compression stress will be less than 0.95fy and
should be obtained from Figure 2.37.
Figure 2. 45 Short term design stress-strain curve for reinforcement
Source: BS 8110-1:1997
Dimana:
As = area of tension reinforcement.
As´ = area of compression reinforcement.
B = width or effective width of the section or flange in the compression zone.
Bw = average web width of a flanged beam.
d = effective depth of the tension reinforcement.
d’ = depth to the compression reinforcement.
hf = thickness of the flange.
2.8.2 Shear Reinforcement
The design shear stress v at any cross-section should be calculated from:
V
v=
bd
(2. 27)
In no case should v exceed 0.8√fcu or 5 N/mm2, whichever is the lesser, whatever shear
reinforcement is provided. (This limit includes an allowance for of 1.25).

Oktaviani T 2-61
At a monolithic beam-column junction where the beam has been designed on the assumption
that the column provides a simple support but where some nominal top steel has been provided
to control cracking vc may be calculated on the basis of the area of the bottom steel at the
support. If this anchorage has not been provided then vc should be calculated on the basis of the
topsteel. This steel should extend into the span for a distance of at least three times the effective
depth fromthe face of the support. The calculation for sherar resistance from bent up bars which
are:
b
b sb
d-d'
V =A (0,95fyv)(cosα+sinαcotβ)
s
(2. 28)
Asb = cross-sectional area of bent-up bars.
d = effective depth.
fyv =characteristic strength of links (not to be taken as more than 460 N/mm2).
Vb = design shear resistance of bent-up bars.
α = angle between a bent-up bar and the axis of a beam.
β = angle between the “compression strut” of a system of bent-up bars and the axis of the
beam.
Table 2.16 dan Table 2.17 will be used to calculate design shear resistance.
Table 2. 16 Form and area shear reinforcement
Source: BS 8110-1:1997

Oktaviani T 2-62
Table 2. 17 Concrete Design Shear Stress
Source: BS 8110-1:1997
2.9 Material
2.9.1 Concrete
Concrete structural components may include deck structure, pile caps and coping beams.
Concrete and steel structure shown at Figure 2.30. Failures in marine concrete structures may be
through a wide range of mechanisms and initiators. There are some failures that might happen in
concrete structure.
2.9.1.1 Chloride Attack
Chlorides attack the reinforcement of concrete resulting in a progressive deterioration of
appearance and strength ultimately ending in collapse. Chloride ions are present in all coastal
structures from salt in the seawater and use of de-icing salts on the deck during winter months.
Chloride ions seep into the concrete, gradually penetrating through to the reinforcement. When
the concentration of the ions reaches a sufficient level the reinforcement begins to rust. As well
as reducing the strength of the steel, rusting causes an expansion in volume which forces the
concrete out and spalling occurs. The time required for chlorides to penetrate the concrete can
ranges from 5 to 15 years and depends on many factors; environmental conditions, thickness of
concrete cover, concrete quality and presence of surface defects (formwork tie holes,
construction joints, honeycombing, etc).
Chloride attack may be identified by observation of rust stains on the bottom and side faces of
the member. Corrosion is distinguished from other causes of deterioration (overload,
temperature, shrinkage, etc.) by cracks parallel rather than perpendicular to the reinforcing steel.

Oktaviani T 2-63
Often this occurs with internal de-bonding of the outer concrete cover. The internal de-bonding
can be detected by the "hollow" sound when faces are tapped with a hammer.
Inadequate drainage can increase the risk of corrosion. Intermittent ponding or continual flow of
water focuses the environment for corrosion on a particular part of the structure. Under these
severe conditions, the timescale for chloride penetration and reinforcement corrosion can be
significantly reduced.
2.9.1.2 Cracking and Spalling
Cracking is sometimes a sign of a loss of strength in the concrete matrix. The structure is then
operating at less than its design capacity and may fail under an extreme event. Cracking can
occur due to a multitude of reasons; design details, construction practices, drying shrinkage,
thermal stresses, incompatibility of concrete materials, freeze-thaw weathering, impact, overload
or corrosion. Cracking to some degree is inherent in the design of reinforced concrete and is
therefore not always a problem although this should always be checked by an engineer. Crack
widths of 0.1-0.25 mm are typically allowed by industry design codes for marine structures.
Rectified in a timely manner, corrosion of the reinforcing steel will occur due to intrusion of water
and chlorides into the crack. Overload cracking can occur to the deck if it is loaded beyond its
design capacity. Cracks created by an overload condition are usually oriented diagonally across
the member (shear cracks) or perpendicular to the reinforcing steel and often penetrate across
the full member section.
Accidental impact, either by a vessel or a vehicle can cause local cracks or spalling. Corners and
edges of platform decks and pile caps are particularly susceptible. Localized cracking can occur
adjacent to an expansion joint or bearing, if expansion joints and bearings are constricted and do
not permit sufficient differential movement. Degradation of concrete by reoccurring thermal
cycles can increase its vulnerability to corrosion. Repeated freeze-thaw can result in scaling of
exterior concrete paste resulting in a rough exposed aggregate surface. Eventually, the
aggregate becomes dislodged and the exterior concrete cover is worn down such that chlorides
reach the reinforcing steel and corrosion of rebar occurs. Freeze-thaw conditions can also
aggravate cracking of structural members.
2.9.1.3 Sulphates
Sulphates attack the matrix of concrete itself resulting in degradation of appearance and
strength and ultimately collapse. Sulphates react with the concrete to produces products that
are voluminous and soft. The type of cement and the quality and composition of the aggregate
stone used in the concrete can influence this chemical attack.

Oktaviani T 2-64
Figure 2. 46 Concrete Deteriotation Symptoms
Source: SIGTTO OCIMF Jetty Inspection Maintenance draft 2006

Oktaviani T 2-65
Figure 2. 47 Steel and Concrete Structure
Source: SIGTTO OCIMF Jetty Inspection Maintenance draft 2006
2.9.2 Steel
Steel structural components may include piling and platform. There are five major causes of
deterioration of steel jetty members; corrosion, abrasion, loosening of structural connections,
fatigue, and impact or collision.
2.9.2.1 Corrosion
Corrosion is the most common cause of deterioration in waterfront steel structures. It is a
chemical reaction, which converts steel into an oxide compound, which generally, is loosely
bonded to the base metal in the form of scale that will peel or fall off easily. Over a period of
time, corrosion will reduce the cross sectional areas of steel components and hence their load
bearing capacity. The rusting surface may or may not be pitted and usually loose scales or layers
of oxides are evident on the surface.
2.9.2.2 Abrassion
Abrasion of steel structures can generally be recognized by a worn, smooth, polished appearance
of the abraded surface caused by continual rubbing of adjacent moving surfaces. In cases where
one of the abrasive members of adjacent rubbing steel surfaces has been removed and corrosion
has taken over, the abrasive action can generally be recognized by a depression in the abraded
area when compared to the surrounding surfaces.
2.9.2.3 Structural Connection Failure
Structural steel members are joined by means of welds, bolts or (in older structures) rivets.
Rivets and ordinary bolts have a tendency to work loose over an extended period of time when
subjected to repeat transitory loading such as impact loading of a vessel on a fender system or
wave action. Corrosion of welds bolts or rivets, nuts, washers and holes can exacerbate the
problem. Loosening of connections will tend to produce slip in mating connection surfaces. This
changes the load paths through the structure resulting in members carrying loads other than

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