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A unique aspect of floating structures is that, in addition to the applied

functional deck gravity loads and environmental forces acting on the body, it is

necessary to determine the inertial loads due to acceleration of the body in motion.

A floating structure responds dynamically to wave, wind and current forces in a

complicated way involving translation and rotation of the floater.

Thus, while fixed structures in shallow and moderate water may be designed

by applying the laws of static equilibrium to the structure, most fixed structures in

deep water and all floating structures require the application of the laws of

dynamics. Weight control is more important to the design of floating structures

than to the fixed structures.

Mooring and station-keeping are unique requirements of floating structures.

“Mooring” refers to the means for providing a connection between the structure

and the seafloor for the purposes of securing the structure against environmental
loads. “Station-keeping” is a term used to define a system for keeping the facility

within a specified distance from a desired location. This is typically a requirement
of drilling or riser connections to the seafloor, or for running equipment to the sea

floor. The station-keeping requirement may be achieved by means of mooring
lines, which may be adjustable. or by means of a dynamic positioning system using

thrusters, or a combination of the two.

Another unique characteristic of the floating structure is that typically it can be

decommissioned readily and moved to another site for reuse. A decommissioned

fixed platform has to be removed in whole or in part, requiring the use of heavy lift

equipment and the reverse of the installation procedure. Typically, such a structure

has to be taken to shore for use as scrap steel or possibly modified and given a

second life. Thus, the capital expenditures (CAPEX) for fixed platforms need to

allocate substantial sums to cover future decommissioning costs.

2.2 Classification of Loads.

“Metocean” refers to the combined effect of the meteorology and

oceanography.
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