Ground Build Methodology for Crude Oil Tankers -...
Transcript of Ground Build Methodology for Crude Oil Tankers -...
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Ground Build Methodology for Crude Oil Tankers
Youngtae Yang*, Kiyoung Yoon
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Hyundai Heavy Industries Inc. *
Abstract
This paper presents the design consideration, methodology and results of successful execution of
first attempt to build conventional Crude Oil Tanker (COT) of 105,000T capacity, entirely on the
ground and transversely load-out and float-off using the semi-submersible barges. The loading and
environmental conditions considered for the load-out and float off are explained. This paper also
provide the details of development of various techniques and facilities like multi-barge load-
out/float-off operation using semi-submersible barges, quay wall & skid way verification, new kind
of pulling &skidding system for load-out.
Even though Ground build methodologies have been adopted widely for offshore structures,
adopting it to the conventional ships requires additional consideration and development for the
load-out system and operation. One of the major concerns is the duration for load-out preparation
and execution, since it directly relates to the downtime of 1500T Gantry crane which has been used
for the assembly of hull blocks on ground. Another major concern is the verification of the
structural integrity with sufficient contingency of the conventional ship which is very long and
curved outer surface compared to common offshore structure. Hence the special considerations
such as low friction Air Pressure system (APS), Push-Pull units (PPU) and Cross Over Bridge
above the Gantry crane tracks were adopted first time for such heavy load-out.
Most importantly, the concept has been developed by considering its adopting to build series of
projects rather than one time project. It makes a lot of system design and operation change. First,
make them easy and minimize the repetitive works such as temporary works at quay wall area,
positioning / leveling / supporting of sea-fastening and removal / installation of Double Barge Unit
(DBU) casings.
Korean Chem. Eng. Res., Vol. 43, No. 2, April, 2005
2005년도 한국해양과학기술협의회 공동학술대회
The strength and longitudinal deflection of COT has been verified through detail analysis
considering various parameters and HAZOP studies to make this operation safe and reliable. The
load-out & float-off concept and methodologies given here are verified through successful
operation of 105K COT projects.
Keywords : Semi-submersible Double Barge Unit ( ), Air Pad System(
), Push-Pull system( ),
INTRODUCTION
Hyundai Heavy Industries Co., Ltd (HHI)
opens up the new shipbuilding method to build its
commercial ships on the ground instead of
conventional dry docks. Starting from last year,
HHI began to build sixteen 105,000 DWT crude
oil tankers ordered by shipping companies.(i.e.
NOVOSHIP, QSC, Teekay) on the ground
without using dry docks.
HHI had already developed a unique technology
for constructing large offshore structures on the
yard ground instead of in dry dock. HHI's so-
called "On-ground Build" method has already
been verified by oil majors through the
construction of drilling rigs and other huge
offshore facilities. Now, HHI has extended this
technique to build ships for the first time in the
world, as shown in Fig. 1. At present, HHI has an
order backlog of 206 ships, worth of 15.08
million GT. Such a large order book will make
HHI‘s nine dry docks full and busy for three and
half years. HHI expects that on-ground
construction will contribute to operate the
currently crowded dry docks smoothly [1].
The key technical process of "On-ground
Build" method for the 105K COT are as follows
and it is also shown in Fig. 2. [1]
(1) Two ships are assembled simultaneously on
load-out track using 1500T gantry crane
(2) DBU is moored to quay: Load-out step-1
(3) Ship is load-out on to the DBU transversely
by skidding system
(4) Stability casings of DBU are installed for
float-off stability: Load-out step-2
(5) DBU is towed out to float-off site, using
tugboats: Towing step
(6) DBU is anchored on float-off site: Float-off
step-1
(7) DBU is ballasted and submerged to allow the
ship to self float: Float-off step-2
(8) Ship is towed back to quay
Fig. 1. Final Load out Position
HHI’s ground-build method which has been
adopted for the construction of 105K COT has the
following major changes and developments
corresponded to the previous load-outs of
offshore structures.
- New load out system such as skid shoe, skid
rail, dynamic jacking system, push-pull
system, cross-over bridge, link beam and
easy jack down and sea fastening in order to
minimize down time of 1500 ton gantry
crane.
- DBU’s fixed casings, which block the ship
being loaded out transversely had been
modified as “Movable type”.
- The hull has been fabricated in large sizes
block weighing up to 1300 Ton. Outfitting
works has been maximized during the block
fabrication period.
In this method, the hull can be fabricated in large
size blocks weighing up to 1500T and assembled
using 1500T gantry crane. After the hull is
assembled and fully commissioned, it has been
loaded-out transversely on to the DBU using APS
modules placed on eight skid ways. Since the APS
module reduces the friction between loaded-out
object and skid ways to very small level (1%),
few numbers of small capacities PPU are
adequate to move the Hull on to the semi-
submersible barge. After the load-out, the hull is
set down on the pre-equipped supporting and sea
fastening system and taken to the float-off
location. By ballasting the DBU, the DBU is
submerged to allow the hull to float-off. All the
above mentioned key features of this techniques,
has been evolved from the experience of various
projects and after detail theoretical and
experimental verifications. This paper describes
the details of various components and operation
from load-out to float-off.
OVERVIEW OF LOAD-OUT & FLOAT-OFF
PLAN
Characteristics of 105K COT
The 105K COT, the loaded-out object, has the
light weight of 18000T and additional ballast of
1 2
3 4
5 6
7 8
Fig. 2 Process of Load out, Towing and Float
off
3000T, in total 21000T during the load-out. The
3000T ballast has been considered in order to
have even heel during the float-off operation.
The LCG with the ballast is 4370mm from mid
ship towards bow direction, mainly due to
accommodation module. The Principal dimension
of COT is given below.
Item HDB-1011 HDB-1012 105K COT
Length 140.0 m 140.0 m 244.0 m
Breadth 37.0 m 37.0 m 42.0 m
Depth 12.0 m 12.0 m 20.2 m
Design Draft 9.0 m 9.0 m 13.6 m
Submersed Draft 25.5 m 25.5 m -
An additional contingency over the load-out
weight of 21,000 ton has been considered in order
to account the followings.
Possible COG shifts along longitudinal up to
2.0m.
Possible unexpected winds up to 40knots
Possible changes in hydraulic grouping of
APS modules and accommodation of
load/level difference between groups.
DBU & hull deflections for load-out, tow and
float off
load-out plan
105K COT has been constructed in Hyundai
Offshore fabrication yard in Ulsan, South Korea.
The Quay wall and the soil along the load-out
tracks had been verified for the maximum
expected line loads. The concentrated loads that
come from the cross-over bridges and on-shore
bridges are transferred to large area of ground
through concrete mats. Fig.3. shows the general
arrangement of 105K COT location, DBU and
load-out systems, such as skid way, cross-over
bridge, on-shore bride and link beams. [2]
Fig. 3. Yard Layout & General Arrangement
Load-out design basis
The hull has been loaded-out by skidding
transversally over eight (8) skid ways placed on
the yard (189m) to the skid ways placed on the
DBU (57.25m). In order to reduce the force
required to skid the hull and to have effective
control over skidding forward as well as
backward, APS modules have been adopted. The
main advantage of APS is the very low friction
(less than 1% of static friction) generated between
the load-out object and skid ways. Hence only
very less push is required. More over the entire
load-out process is reversible
Static Loads
The expected load-out weight of hull including
ballast is 21000T. The skid shoe length is 36 m
along 6 Frames, namely FR-63, FR-64, Fr-78, Fr-
79, FR-81 and FR-82 and 32m along the skid
ways at the forward side of hull namely FR-60
and Fr-61. The over all length of skid shoe is
280m and fitted with 140 numbers of APS
modules at a spacing of 2.0m. These APS
modules distribute the COT weight evenly as line
load over the eight skid ways and COT bottom
structure. The maximum expected line load is 94
ton/m. The frictional forces between skid way and
skid shoe which are to be overcome by Push-Pull
units are estimated 3 times the maximum friction
of 1%. In addition to the estimated weight, 20%
contingency has been considered and the entire
load-out system has been checked for the
maximum load of 25,000 ton. This 20%
contingency has been estimated from the detail
parametric study. The effect of DBU deflections
and COT deflections are also taken in to account
in the parametric study.
Dynamic Load
The design environmental criteria is given in
Table 1.The maximum motions and accelerations
during load-out, tow and float-off have been
estimated from the detail motion response
analysis and conservative design values(Table.2)
have been considered throughout the design.
Other limitations
Even though, this load-out is similar to previous
load-out of conventional offshore structures, the
incorporation of APS system to reduce the load-
out duration leads to very stringent requirements.
The Air seal of the APS module demand
fluctuations on the skid surface within 1mm and
more over no gap on the skid surface is permitted
even at the link beam interface. The other critical
parameters are as follows.
1. APS Hydraulic jack capacity to
accommodate unexpected failures of few
jacks in a group and maximum stroke height
to accommodate foundation settlement and
DBU/COT deflections.
2. Push-Pull Unit Capacity to operate even at
partial failures and speed of pushing to meet
the time required to cross the critical areas
like link beam.
3. Strength of COT hull to accommodate the
maximum stresses that occurs during the
operation and deflections that are within the
limit of stroke of APS modules
4. Ballasting capacity and speed of load-out
barges to meet the speed of movement that
can be achieved by PPU.
5. Strength of load-out barges including rigid
connectors
6. Capacity of ground and quay wall
7. Other load-out facilities like link beam,
onshore bridge, cross-over bridges and etc.
Even though the PPU unit can work at 1m/min
speed, the ballasting capacity of DBU could not
meet to compensate the line load on DBU at the
same rate. Hence DBU ballasting speed
determines the load-out duration.
Table.2 Motion Response Summary
Actual Value Design Value
ForcesLoad-
OutTow
Float-
Off
Load-
OutTow
Float-
Off
Ver. 1.005g 1.05g 1.05g 1.1g
Longi. 0.005g 0.04g 0.04g 0.1g
Trans. 0.004g 0.16g 0.16g 0.2g
Table.1 Environment Criteria
Description Wind
(knots)
Wave
Hs
(m)
Wave
Tz
(sec)
Current
(knots)
Design 25 0.5 3~6 0.6 Load-
out Operaion 20 0.34 4 0.6
Design 40 1.0 6~10 0.6 Moor
ings Operaion 32 0.8 10 0.48
LOAD-OUT SYSTEM DESIGN [5]
Skid-way on ground & Barge
The entire skid way has been divided in to the
following segments based on its position along
the load-out track.
a) Skid way on ground
b) Skid way on cross-over bridge
c) Skid way on onshore bridge
d) Skid way on link beam
e) Skid way on barge
Even though the segments “a” to “c” are on the
yard, each one is provided with different purpose.
The cross over bridge is provided over the exiting
gantry crane and zip crane rails to avoid crane
down time during load-out preparation. The
onshore bridge is provided to transfer the load-out
weight directly to Quay wall and on to the piles
behind Quay wall in order to avoid any lateral
pressure on Quay.
The skid way on ground “a” to “c” and barge skid
way “e” have been supported by rigid foundation
consisting of concrete mat / pile foundations and
grillage beam foundation respectively.
To have skid ways without any gap, long
continuous base plates have been attached to the
skid way beams. The significant gap which may
arise at the each sides of link beam due to the
level difference between yard and barge has been
avoided by attaching smooth profiled plates on to
the base plate. Silicone oil has been used as
lubricant over the skid surface.
Skid Shoe and hydraulic jacking system
Each row of skid shoe consists of either eight (8)
or nine (9) numbers of 4m long skid shoe
segments (Table.3). Each row of skid shoe has
been controlled as single group in terms of
hydraulic and pneumatic control. Each skid shoe
segments consists of two (2) APS modules with
330mm stroke (excluding air stroke of 30mm),
both attached to the skid shoe beam (Fig.4).
The rollers are provided to the skid shoe for the
purpose of easy insertion on to the skid way,
Table.3 Skidding Arrangement
AFT FWD
Hull
Frame
Number
60 61 63 64 78 79 81 82
No. of
Skid shoe
segments
8 8 9 9 9 9 9 9
Skid shoe
length32 32 36 36 36 36 36 36
No. of
Push Pull
Units
1 1 1 1
Fig.4 Skidshoe Details
when the hull is on the fabrication supports. These
rollers do not carry any loads or touches the skid
way once the skid shoe is extended from its fully
retracted position. The skid shoe top longitudinal
beam consist of “ ” shaped frame in transverse
direction at every 2m (i.e., at every APS module
location). This is to facilitate the removal of APS
modules after the load-out and after connecting
the “ ” frame to the support columns provided
on the load-out barges. The 4m skid show
segments are connected as follows to make rows
of skid-shoes.
Details of skid shoe:
Total length of skid shoe: 2x32 +6x36 = 280m
Number of APS module/Hydraulic Jacks:
280/2 = 140
Total capacity APS system and Hydraulic
jacks: 140 x 250 ton = 35,000T
Ratio between actual weight and capacity :
(21,000/35,000) x 100 = 60%
Jack stroke : 330mm (excluding air stroke of
20~30mm)
The hydraulic system of 8 skid shoes has been
arranged in to four (4) hydraulic groups namely
Group A, B, C and D in order to have statically
determinate system that can actively respond
against any load variation and longitudinal /
transverse tilts during load-out(fig.5).
Depending upon the field requirement the groups
can be controlled from1 to 16 numbers of groups
by dividing each lie as two separate port and
starboard group. Additional two rows of hydraulic
jack groups (Group M) have been added on to the
DBU, near to the mid ship parallel to the skid
ways in order to distribute the COT load to large
are of DBU after the load-out is completed and
during the jack-down.
All the APS modules are designed to be
controlled as individual as well as part of the
group through central computer. By adjusting the
jack strokes, the possibilities of concentrated
loads were avoided.
Fig.6 APS Module
Fig.6 shows APS module. The capacity and the
stroke height had been determined based on the
maximum expected load and the required height
to lift the hull over its fabrication supports and to
achieve the hull natural deflection during the
load-out through compensating foundation
settlement and DBU deformation. During its
operation, compressed air is supplied to air
chamber of APS modules at 30~40 bar to lift an
equivalent load of 250 ton. During the movement,
the air leakage due to undulation in the skid
surface or any tilt has been compensated
continuously by automatic air control valve. All
the hydraulic jacks are fitted with pipe burst
valves which can maintain the last load even if the
hydraulic lines are closed.
Fig.5 Hydraulic Groups
Push-Pull System
The horizontal movement of hull has been
achieved by means of push-pull system attached
to the four skid ways. The maximum force
required to break the initial static friction is
equivalent to 1% of weight (21000x1/100 =210T).
Details of Push-Pull system:
Number of Push-Pull unit : 4
Longitudinal dimension :
3957mm (retracted position) and
5823mm (extended position)
Pushing capacity : 160 ton x 4 = 640 ton
Ratio between total static friction and
Pushing capacity: (210/640) x 100= 33%
Pulling Capacity : 80 ton x 4 = 320 ton
Ratio between total static friction and
Pulling capacity : (210/320) x 100=66%
One end of the push pull system is attached to the
skid shoe and the other end is clamped to the skid
way. The hull on the skid shoe has been pushed
by longitudinal extension (stroke) of push-pull
system with respect to the skid way. After each
stroke, push-pull unit will be retracted by
loosening of connection with skidway after then
attached to the new position automatically.
Since all these sequence are automatic the entire
load-out process is continuous and fast.
Two PPU is adequate to overcome the frictional
forces and wind forces generated during load-out
and the balances are provided as back-up.
Symmetry in PPU unit has to be maintained in
order to avoid skewing.
Foundation and Quay Wall
The foundations for the fabrication supports, skid
ways, piles supporting onshore and cross-over
bridge have been verified for the bearing capacity,
settlement and various failure modes based on the
maximum expected load conditions. The Quay
wall has been checked for the following loads.
Earth Pressure
Differential water pressure
Concentrated load from link beam and
onshore bridge
Pulling forces
Barge berthing/Mooring loads
The safety margins shown in Table.4 for the
various failure modes have been determined. The
major concern was the pulling loads from barge
Fig.7 Push Pull System
Table.4 Foundation FOS of Settlement
FOS
Analysis Bearing
CapacitySliding Overturning
Settlement
(mm)
Fabrication
support
2.30 - - 25~30
Concrete
Mat
foundation
below skid
way
3.90 - - 25~35
Pile
foundation
below
Bridge
supports
3.6~4.0 - - 7~10
Quay Wall
stability
3.78~6.2
1
4.6~4.7 6.4~6.5 25~35
when the link beams are installed immediately
after berthing and before installing the mooring
lines. It has been successfully solved by
interconnecting the Quay wall with pile caps of
nearby gantry crane tracks.
Moorings, Fenders and Link Beams
The DBU has been kept in position by barge’s
mooring system during load-out. The numbers
and capacity of mooring lines have been
determined based on 10 year return environmental
conditions. Emergency mooring system has also
been prepared considering the 100 year storm
condition in order to meet the typhoon conditions.
The mooring wires have been kept in tension
using stand jacks in order to limit the barge
movement within the gap permitted at link beam
ends.
Fender system has been arranged between the
load-out barge and quay wall in order to provide
temporary berth through direct contact between
DBU and Quay wall and to keep the barge
perfectly aligned perpendicular to the load-out
track.
Eight numbers of rigid link beams were used for
linking each ground skid way to barge. These
link beams not only carry the line load from
skidding operation but also the compressive load
from the barge. The link beams also laterally
restrained in order to keep the barge skid ways
perfectly aligned with skid ways on ground.
Monitoring System
The following critical points are continuously
monitored and kept within the design limitations
during the entire operation.
1. Foundation settlements
2. APS module alignments with respect to
skid way and link beam
3. COT Hull deflections
4. DBU draft level and positioning
5. DBU deflections particularly at rigid link
interface between barges
6. APS module hydraulic jack loads, stroke
height, air seal failures
7. PPU jack loads
FLOAT-OFF SYSTEM DESIGN [5]
Ballast Header
To increase the ballasting/de ballasting capacity
during the load out temporary ballast header
which extend the ballast capacity by 50%.is
installed.
Ballast Control System
DBU is ballasted to the required load-out draft
and moored along the quayside. To control the
ballasting of two barges at one location the
control room is moved and cables are connected,
which is make all the ballasting operation at one
location.
Fig. 8 ballast Header Diagram
Fig. 9 Water ballast control system
Tide Gauge System
The real-time tide level measuring device is used
to check tide-variation (about 600 mm at HHI
offshore yard), as shown in Figure 10. This way
possible more accurate tide compensation is
achieved.
The figures 11 shows that the real time tide gauge
readings are more accurate than the estimated tide
curve and this is very convenient for the tide
compensation during the Load out.
Motion Gauge System
The motion measuring system is used to check the
motion of DBU during the entire process from the
load-out to the float-off, which is consisted of
motion monitoring system, fiber optic gyro and
accelerometer. The roll, pitch and vertical
acceleration of DBU can be checked through the
motion monitoring system in the control room, as
shown in Figure 12
Figure 12 DBU Motion Monitoring System
It is found out that the maximum motion,
constraint forces and relative motions for the
actual environment condition is lower than the
operation criteria as show below table. 5. So, the
entire process from the load-out to the float-off
was completed safely.
Table. 5 Result of Motion [3]
Fig.10 Real Time Tide Gauge
Fig.11. Comparison Curve of Actual Tide
0 500 1000 1500 2000 2500
0
0.04
0.08
0.12
0.16
0.2
Roll(D
eg)
0 500 1000 1500 2000 2500
-0.15
-0.1
-0.05
0
0.05
0.1
Pitch(D
eg)
0 500 1000 1500 2000 2500
1
1.002
1.004
1.006
1.008
Heave(m
/s2)
1500 2000 2500 3000 3500
-0.8
-0.4
0
0.4
0.8
1.2
Roll(D
eg)
1500 2000 2500 3000 3500
-0.2
0
0.2
0.4
0.6
Pitch(D
eg)
1500 2000 2500 3000 3500
0.99
0.995
1
1.005
1.01
1.015
1.02
Heave(m
/s2)
Fig. 13 Motion responses measured at L/O step-1
Fig. 14 Motion responses measured at L/O step-2
Fig. 15 Motion responses measured at F/O step-
1(Towing)
Fig. 16 Motion responses measured at F/O step-2
STRUCTURAL ANALYSIS [6]
The strength of COT structure has been verified
through detail 3D FEM analysis for the load-out,
jack-down, tow and float-off conditions. The
load-out condition is an active condition in which
the hull natural defection is maintained by
maintaining the stroke height the hydraulic jacks
of APS close to the hull natural deflection and
distributes the load more evenly as line. In the
other conditions which are called passive
conditions, the natural deflected shape of hull is
maintained by adjusting the support column
heights as per the pre-determined shape of
hull(Fig.17). Shimming plates made up of timber
and steel had been used to maintain the natural
deflected shape of hull. By maintaining the
natural hull deflected, the local concentrated loads
at skid ways are avoided. The deformation of
DBU due to still water and wave bending moment
had been taken in to account in the total
deformation, which were compensated by stroke
height during active condition and adjusted
support level during passive conditions.
The Von-Mises stress, buckling capacity and
deformation had been checked against the
0 400 800 1200 1600
0
0.04
0.08
0.12
0.16
0.2
Roll(D
eg)
0 400 800 1200 1600
-0.05
0
0.05
0.1
0.15
0.2
Pitch(d
eg)
0 400 800 1200 1600
1
1.002
1.004
1.006
1.008
Heave(m
/s2)
2280 2320 2360
-0.4
-0.2
0
0.2
0.4
0.6
Roll(D
eg)
2280 2320 2360
-0.05
0
0.05
0.1
0.15
0.2
0.25
Pitch(D
eg)
2280 2320 2360
0.996
1
1.004
1.008
1.012
Heave(m
/s2)
maximum possible line load that can come from
the APS modules. The results had shown that the
stress level and deflection levels are below the
maximum expected during the COT voyage
conditions. The maximum Von-Mises stress was
found as 210MPa and 224MPa during load-out
and jack-down conditions at skid way support
frames No.64 and Fr. No. 60 respectively. The
maximum buckling unity check value of 0.71 and
0.69 has been found at Fr.64 and Fr.60
respectively. All the stiffeners and plates were
found to be well within the allowable limit for
both yield and buckling verifications. The
maximum vertical deflection of 210mm had been
noticed at the center bulkhead.
Fig.17 and fig.18 show the deformation during
and after load-out.
Fig.17 Hull Deflection for Load out (Active)
Fig.18 Hull Deflection for Final Jack Down With Additional Support (with DBU Deflection)
HAZOP STUDY
Detail HAZOP study had been performed in detail
during the design phase in order to identify,
quantify and minimize the risk level. The
following are the main concerns for the HAZOP
study.
1) Failure of hydraulic jacks and air pad in
the APS module
2) Failure of Push-Pull Units
3) Failure of Hydraulic Power Packs
4) Failure of Air Supply Units
5) Failure of DBU ballast pumps
6) Failure of Mooring lines
7) Weather conditions beyond design limits.
8) Misalignment in skid way.
9) Barge interconnecting rigid frame
relative deflections
10) Distribution of vertical and horizontal
loads to Quay
After detail HAZOP study, the risk levels were
reduced to the acceptable level and careful
monitoring system had been developed where the
probabilities of risks are high.
CONCLUSION
The design methodology described in this paper
had been successfully demonstrated through the
load-out and float-off of 105K COT, the world
first conventional Cargo Oil Tanker built on
ground. Usage of this technique for the
conventional ships leads to paradigm shift in
shipbuilding and provides many advantageous.
Independent of dock facilities and no size
restrictions. Ships can be built, commissioned
and launched anywhere and at any time. No
need to wait for free dock slots and hence
Production capacity of yard becomes
practically enlarged.
Can meet the current and expected
increased in conventional ship building
orders and fully utilize the offshore facilities
during dull offshore market
Improves the safety level of workers since
most of blocks are built at or near to ground
level with large open accessible area.
Hull blocks can size up to 1,300 ton. It leads
to lower number of blocks and maximize
outfitting work, piping and equipment
installation before hull assembly.
Reduces the block integration time and
maximize the usage of gantry crane.
Efficient usage of yard facilities and
resources
Flexibility to accommodate design changes
during construction
Possibility of significant amount of time
saving, approximately three to four months
Significant amount of cost saving, when it is
applied in multiple project
This technology can be easily extended to any
kind of offshore/ship type structure of any size
which are not feasible with current dry dock
limitations.
[1] Hyundai Heavy Industries, 2004, “October IR
News,” IR Team, HHI (http://www.hhiir.com).
[2] Yang, Y. T., Cho, H. G., Yoon, K. Y., Ha, S.
S. and Kang, H. S., 2003, “ Development of
Load-out Methodology for On-Ground-Build
FPSO”, OTC 2003.
[3] , 2004, “LOAD-OUT, TOWING AND
FLOAT-OFF ANALYSIS FOR THE 105K
COT(CASE2)”
[4] Yang, Y.T., Kang, H.S., Park, B.N., 2003,
"Numerical Strength Evaluation of FSO Ground
Build Load-out," International Society of Offshore
and Polar Engineers
[5]Yoon.K.Y., Kim. B.M., Bae S.H., 2004“Load out
Procedure of 105K COT” Hyundai Heavy
Industries
[6]Yoon.K.Y., Kim. B.M., Shin M.K., 2004, “Hull
Strength Analysis For Load-out & Float-off”
Hyundai Heavy Industries