BRIEF OUTLINE,DESIGN CHART

1. VERY LARGE FLOATING
STRUCTURES: APPLICATIONS
AND DESIGN ASPECTS
ARUNSREENATH A K
OFFSHORE STRUCTURES
M150152CE

2. INTRODUCTION
 Very large floating structures are manmade islands, which
may be constructed to create floating airports, storage facilities
(for oil & natural gas), for military purposes ,to create industrial
purposes
 They are easy and fast to construct
 VLFS’S can easily transported,removed,expanded
 Cost effective when water depth is large
 Do not damage marine eco-system
 Do not disrupt ocean currents
 They are immune to seismic shock
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3. To classify according to their geometry:
I. Pontoons.
II. Semisubmersibles.
To classify them by location:
I. CoastalVLFS.
Mega float
II. OffshoreVLFS
Mobile offshore base(MOB)
Pneumatically stabilized platform(PSP)
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4. MEGA FLOAT
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5.  Very large pontoon floating structure
 Suitable for use in calm water
 Provide break water if significant wave
height is greater than 4m
 Strong, reliable, lightweight
 Construction carried out with modules made
on land between 100 and 300 m in length
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6. Advantages
 Manufacturing and assembly easy and
inexpensive
 Unlimited size
 Capacity of positive load
Disadvantages
 suitable for inlets and bays
 Low mobility
 Ingress of water on deck
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7. Mobile offshore base
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8.  To support military operations wherever
convention all and bases are not available
 Providing a landing/takeoff area and
maintenance, as well as supply and other
advanced logistical, support operations
 Length of each module : 220 - 500 m
 width of each module : 120 - 170 m
 Numbers of each module : 3 - 5
 Total length of module completely aligned:upto
2km
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9.  Alignment is maintained by Dynamic positioning
thrusters
 Two types
Joint Mobile Offshore Base
Hybrid Mobile Offshore Base
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Joint Mobile Offshore Base module
five semi-submersible steel propelled ships
Track - mile(1800m)-long connected with non-load bearing
structures
A lightweight, collapsible draw bridge allows for transfer between
modules.

10.  Hybrid Mobile Offshore Base
 high strength, light weight LWC60 concrete in
the steel hull and superstructure deck
 fatigue is a major pitfall for a concrete hull with
a design life of 100 years.
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MOB semisubmersible hybrid concept: four modules together (left) and
a single module (right)

11. Advantages
 Mobility.
 Suitable for all types of water
 Deep and shallow waters
 Benign and harsh (conditions good behaviour
at sea).
Disadvantages
 Payload is limited, as is the case with all
semisubmersible vessels.
 Large internal movements: danger of fatigue in
the structure
 Connector technology still experimental.
 High construction and operational costs
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12. Pneumatically stabilized platform(psp)
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13.  Number of cylindrical components packaged
in a rectangular shape to form single module
 Each cylinder is sealed at the top and open to
the sea at it’s base
 It can handle loads and attenuate the wave
 Post tensioned cables used to help assemble
the components
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14. Advantages
 Manufacturing and installation process simple and
inexpensive
 Suitable for all types of water
 Unlimited size (modular)
 Low or almost zero maintenance
Disadvantages
 Experimental technology in its most basic principles:
indirect displacement.
 Joining technology with tensors in need of extensive
further development and study.
 Low mobility
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15. APPLICATIONS OF VLFS
 FLOATING AIRPORTS
The first sizeable floating runway
one-km long Mega-Float
Mega-Float in Tokyo Bay, Japan (1998)
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16. MOBILE OFFSHORE BASE
 large aircraft and ships may support
littoral combat operations from a secure
position without reliance on achieving
political support in other nations
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MOB,CHINA

17. FLOATING STORAGE FACILITIES
 used for storing fuel and keeping the
explosive, inflammable fluid from populated
areas on land.
 pontoon structure
 Japan has two major floating oil storage
systems.
in Shirashima with a capacity of 5.6
million kilolitres
in Kamigoto with a capacity of 4.4
million kilolitres.
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18. Kamigoto Floating Oil Storage Base,Japan
( 4.4million kilolitres)
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19. FLOATING DOCKS, PIERS, BERTHS AND
CONTAINER TERMINALS
The floating pier is 150 m x 30 m x4 m.
must allow smooth loading and unloading of cars
equal tidal rise and fall of the pier and ferries is
advantageous
Floating Pier at Ujina, Japan
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20. FLOATING EMERGENCY BASES
inherently base isolated from earthquakes
floating emergency rescue bases in earthquake
prone countries
Japan has a number of such floating rescue
bases
Emergency Rescue Base, Tokyo Bay10 November 2016
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21. FLOATING BRIDGES
1246-m long Nordhordland Floating Bridge built
in1994 at Salhus over a fjord depth of 500 m.
bridges are horizontally curved to better resist the
wave, the water current and wind forces
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Nordhordland Floating Bridge, Norway

22. Analysis and Design of Floating Structures
Characteristics to be considered :
 Horizontal forces due to waves much times greater than
the (non- seismic) horizontal loads on land-based
structures
 In framed, tower-like structures the horizontal wave
forces produce extreme bending and overturning
moments
 In a floating structure the static vertical self-weight and
payloads are carried by buoyancy.
 A particular type of structural system, denoted tension-
leg system, is achieved if a highly pre-tensioned
mooring system is applied.
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23.  Sizing of the floating structure and its mooring system
depends on its function
 VLFS’s usually constructed at shore-based building sites
remote from the deepwater installation area and without
extensive preparation of the foundation.
 Owing to the corrosive sea environment, floating
structures have to be provided with a good corrosion
protection system
 Possible degradation due to corrosion or crack growth
(fatigue) requires a proper system for inspection,
monitoring, maintenance and repair during use.
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24. LOAD TYPES AND COMBINATIONS
1) Permanent or dead loads
2) Variable or live loads
3) Frequent and Rare Environmental loads
4) operation loads
5) Cyclic loads
6) Accidental loads
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25. DESIGN PROCEDURE
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26. DESIGN PROCEDURE
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27. UNIQUENESS OF VLFS
1) Large Size
2) Environment Condition
3) Design and Analysis
4) Connection at Sea
5) Positioning
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28. CONCLUSION
 VLFS is a unique concept of ocean structures
because of their length,displacement,cost
 Requires massive investment and considered as a
mega project
 Cost of shore facilities is soaring , so offshore
floating facilities will become more attractive
 21 century there will undoubtedly be significant
developments in the field of VLFS
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29. REFERENCES
 Miguel Lamas-Pardo a,1, GregorioIglesias b,2, LuisCarral a,3,2015,
A review of Very Large Floating Structures (VLFS) for coastal and
offshore uses, Ocean Engineering109(2015)677–690
 Wanga C.M, Taya Z.Y,2011, Very Large Floating Structures:
Applications, Research and Development, Procedia Engineering 14
(2011) 62–72
 Masahiko Fujikubo,2005, Structural analysis for the design of VLFS,
Marine Structures 18 (2005) 201–226
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30. THANK YOU….
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