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VERY LARGE FLOATING STRUCTURES Presented by:- A.Prabhakar Reddy 11001D1102ABSTRACT: Many developed island countries and countries with long coastlines in need of land have for some time now been successfully reclaiming land from the sea to create new space and, correspondingly, to ease the pressure on their heavily-used land space. The older idea is to build a big ship to accommodate the excess population of the country and the other solutions are Ocean colonization and land reclamation.Engineers resort to land reclamation to ease the pressure on existing heavily-used land and underground spaces. Using fill materials from seabed, hills, deep underground excavations, and even construction debris, engineers are able to create relatively vast and valuable land from the sea. Countries such as the Netherlands, Singapore and Japan, have expanded their land areas significantly through aggressive land reclamation programs INTRODUCTION: The population of the world is increasing day to day, today the population of our world is nearly seven billions. Due to the increase of population many problems are being arise in the world the major problem that will arise is the accommodation of people on the land. We all know that 71% of the earths surface is covered with oceans and other water bodies, so only 29% of the earths surface can be used for acquisition of people. As the population of the world is increasing day to day the land resources which are very small compared to water resources on the earth that can be used for the people are being depleted so there is an urgent need to find a solution to this problem.So the very new idea for this problem is Very Large Floating Structures (VLFS).

Very large floating structures (VLFSs) or, as some literature refers to them, very large floating platforms (VLFPs) can be constructed not only for the human habitation but they can also be used to create floating airports, bridges, piers and docks, storage facilities (for oil & natural gas), wind and solar power plants, for military purposes, to create industrial space, emergency bases, entertainment facilities (such as casinos), recreation parks etc. HISTORY OF VLFS:About 480 BC, King Xerxes of Persia led his army across the Hellespont, now called the Dardanelles, using two rows of floating bridges, each consisting of about 300 boats laid side by side as shown in following figure.

In 1874, a 124-m long floating wooden railroad bridge was constructed over the Mississippi River in Wisconsin.TYPES OF VERY LARGE FLOATING STRUCTURES: There are basically two types of very large floating structures (VLFSs). They are: Semisubmersible Type, Pontoon Type. Semi-submersible type floating structures are raised above the sea level using column tubes or ballast structural elements to minimize the effects of waves while maintaining a constant buoyancy force. 1.SEMISUBMERSIBLE TYPE: 2.PONTOON TYPE: Pontoon-type floating structures lie on the sea level like a giant plate floating on water. Pontoon-type floating structures are suitable for use in only calm waters. Large pontoon-type floating structures have been termed Mega-Floats by Japanese engineers.Horizontally large floating structures can be from 500 to 5000 meters in length and 100 to 1000 meters in width, while their thickness can be of the order of about 2-10 meters.

COMPONENTS OF A VERY LARGE FLOATING STRUCTURE:

The following shows the various components of the VLFS. MATERIALS USED FOR THE CONSTRUCTION OF LARGE FLOATING STRUCTUES: The materials used for the floating body may be steel, or concrete or steel-concrete composite water tightness of concrete is important to avoid or limit corrosion of the reinforcement, either watertight concrete or offshore concrete should be used. High-performance concrete containing fly ash and silica fume is most suitable for floating structures.

BASIC PRINCIPLE FOR THE DESIGN OF VLFS: A floating body can exhibits three types of equilibriums. They are:

Stable equilibriumUnstable equilibriumNeutral equilibrium Depending on the position of META CENTRE with respect to the Centre of gravity it can be decided that whether the body exhibits the stable equilibrium or unstable equilibrium or neutral equilibrium. The basic principle underlying in the design of the VLFS to be in the stable condition i.e to regain its original position even after it is subjected to angular displacement. The condition for the body to be in the stable equilibrium is the Metacentre(M) of the body should be above the Centre of Gravity(G) of the body.PRESENT AND FUTURE APPLICATIONS OF VLFS:Floating Bridges:The bridge is constructed across a water channel, and it floats on two hollow steel pontoons (each of dimensions 58 m x 58 m x 8 m.)

Yumemai Bridge, JapanThe 1246-m long Nordhordland Floating Bridge built in 1994 at Salhus over a fjord depth of 500 m (see Fig).

Nordhordland Floating Bridge, NorwayFloating Entertainment Facilities:In 1991, Japan built a floating restaurant (on a 24 m x 24 m x 3.2 m pontoon) in Yokohoma

Floating storage facilities:Japan has two major floating oil storage systems. One oil storage facility is located in Shirashima (Fig 1) with a capacity of 5.6 million kilolitres while the other is at Kamigoto (Fig 2) with a capacity of 4.4 million kilolitres.

Floating Airports and Mobile Offshore Base:Kansai International Airport at Osaka is an example of an airport constructed in the sea, albeit on a reclaimed island.The first sizeable floating runway is the one-km long Mega-Float test model built in 1998 in the Tokyo bay.

Floating docks, piers, berths and container terminals: An example of a floating pier is the one located at Ujina Port, Hiroshima. The floating pier is 150 m x 30 m x4 m.

Floating Power Plants:In 1985, Jamaica acquired a 45 m x 30.4 m x 10m floating power plant. This plant was built in Japanese shipyards and towed to Jamaica and moored by a dolphin-rubber fender system.

Concept Design of a Clean Energy Plant by Floating Structure Association of JapanADVANTAGES OF VERY LARGE FLOATING STURUCTURES: They are easy and fast to construct.

They can be easily relocated, expanded, or removed.

VLFSs are cost effective when the water depth is quite large.

The construction of VLFSs is not greatly affected by the depth of the water, sea bed profile, etc.

The facilities and structures on VLFSs are protected from sesmic shocks since the energy is dissipated by the sea.DISADVANTAGES OF VLFS:(Might be) not sufficient stability for the airport control systems

Mat like VLFSs are only suitable for use in calm waters associated with naturally sheltered coastal formationsCONCLUSIONS:To overcome the problems that are arising due to rapid increase in the population VLFS are very effective.Through VLFS independent states can be developed and the Micro Economy states can be established.A lot of economy can be obtained by the country by constructing floating recreation centers and tourist spots.Coastal regions of the country can be protected from invasion by setting up of marine stations.

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