Classification
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 sea and 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.
Read more about this topic: Very Large Floating Structure