VLFS, Very Large Floating Structures


Very large floating structure(s) (VLFS(s)) (or, as some literature refers to them, very large floating platform(s), VLFP(s) for short) can be constructed to create floating airports, bridges, breakwaters, 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, mobile offshore structures and even for habitation.

VLFSs may be classified under two broad categories, namely the pontoon-type and the semi-submersible type. The former type is a simple box structure and features high stability, low manufacturing cost and easy maintenance and repair. In open sea, where the wave heights are relatively large, it is necessary to use the semi-submersible VLFS type to minimize the effects of waves while maintaining a constant buoyant force. VLFSs of the semi-submersible type are used for oil and gas exploration in seas and for other purposes. They are fixed in place by column tubes, piles, or other bracing systems.

In contrast, the pontoon-type VLFS just floats (lies) on the sea surface. The pontoon-type VLFS is very flexible compared to other kinds of offshore structures, so that the elastic deformations are more important than their rigid body motions. Thus, hydroelastic analysis takes center stage in the analysis of the pontoon-type VLFSs. Together with the motion of the floating structure, the response of the structure to water waves and the impact on the entire fluid domain have to be studied. Pontoon-type VLFSs are also known in the literature as mat-like VLFSs because of their small draft in relation to the length dimensions. They are suitable for use in only calm waters, often inside a cove or a lagoon and near the shoreline. Large pontoon-type floating structures have been termed Mega-Floats by Japanese engineers. The only Mega-Float created so far is the one installed at Yokosuka, Japan, for experiments from 1995 to 2000. Referring to the figure shown, a Mega-Float system consists of:

  1. a very large pontoon floating structure.
  2. mooring facility to keep the floating structure in place.
  3. an access bridge or floating road to get to the floating structure from shore.
  4. a breakwater (usually needed if the significant wave height is greater than 4 m) for reducing wave forces impacting the floating structure.

But appart from the Mega-Float  (that seems not to be very suitable for seasteading in open ocean) other conceptual structures, like the Mobile Offshore Base (M.O.B.) or the Pneumatically Stabilized Platform (PSP), are also included in this category of VLFS, and they do seem perfect for seasteading purposes. The several reasearch projects in this field of the VLFS are very promising for the future development of Seasteading, as a number of concepts o these structures have been proposed for building floating cities or huge living complexes.


  1. ellmer 4:22 am

    Miguel,  – This text must have been written before the Nkossa barge was created – floating flat raft structures are in use in open water – not in calm bays Nkossa is 80 miles off coast … as we speak.



  2. Miguel Lamas 1:56 pm

    Yes Eelmer, you are right. Also FPSOs or FSUs, that are not of the semi-submersible type, are used in deep and rough waters in the middle of the North Sea.

    But I could not consider a FPSO, a FSU or any concrete barge like Nkossa as a VLFS. A real VLFS, like the Mega-Float, need a very large surface without roll, heave and pitch movements to be able to install any insfraestructure similar to onshore, like an airport.

    But this is my thinking, of course…


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