Floating Platform

 The RFS’s platform consists of a Pneumatically Stabilized Basement Floor (PSBF)

Construction:

The basic construction method is to wet cast the individual cylinders with an integral top slab to be assembled into modules.These modules join with each other to form a complete platform structure as depicted below.  This modularity is a key aspect of the concept.

On -site module assembly

Underwater shape

The economics of casting a complete module is under study. The number of components in a module will depend on the selected construction and launching environment. A nine component module is considered adequate for maintaining stability during deployment. Generally, the larger the module, the lower the offshore labour cost. All joining of the manufactured units is with post-tensioned cables resulting in a monolithic structure.

How It Works:

Most conventional floating platforms acquire their floatation forces by directly displacing the water with their hulls. A pneumatic floating platform utilizes indirect displacement, in which the platform rests on trapped air that displaces the water, see figure. The primary buoyancy force is provided by air pressure acting on the underside of the deck.

The PSP is a distinct type of pneumatic platform, one in which the platform is composed of a number of cylindrical shaped components packed together in a rectangular pattern to form a module. Each cylinder is sealed at the top, open to the ocean at its base, and contains air at a pressure slightly above atmospheric pressure. Modules can be of a size that are relatively easy to manipulate, as shown in the simplified drawing below Another aspect of the PSP design is that, when needed, air is allowed to flow from a cylinder to its neighbours through a manifold or connecting orifices. The airflow provides a mechanism to help reduce the peaks in the pressure distribution beneath the structure and provide platform stability as well as a mechanism for dissipating wave energy. Directing the moving air through turbo-generators to produce electrical energy is a capability that is now generating considerable interest. See the "Wave Energy" page.

An assembly of cylinders results in enclosed interstitial regions between cylinders, which may be filled with air, foam or other material. These regions are isolated from the air pockets within the cylinders to provide additional buoyancy and righting moment. In comparison to conventional floating platforms, the designers of a pneumatic platform can modify the distribution of the flotation force as needed to minimize the hogging moment or in response to large concentrated loads on the deck. Further, it is possible, for a particular sea state, to tune the oscillation of the water columns inside the cylinders to minimize the overall hydrodynamic loading to which the platform is subjected.

This brings up the fact that the PSP, as with other floating platforms, is sensitive to its environment in form and function, and must be designed taking that into consideration. There is not a "one size fits all" PSP. However, that said, they can be segregated in two broad categories, open ocean platforms, and protected water platforms. These differ markedly in component size and complexity as illustrated in the following examples, see figures.

Figure: San Diego Prototype Component, 20 x 20 x 40 feet

Figure: North Sea Module