2. Positive Buoyancy . The platform supports its own self-weight, the 

 cold water pipe, thermal and electrical equipment, and vertical 

 component of the mooring force. 



3. Controlled Variable Buoyancy. Platform buoyancy will need to be 

 constantly compensated for changes in the density of ambient seawater, 

 vertical forces due to waves, and - most important - the vertical component 

 of the mooring force, which is influenced by currents, wind, and waves. 

 Long-term increases in weight will also need to be considered because of 

 biofouling and seawater saturation of concrete. 



4. Pressure Resistant Hull . The platform will need to be pressure 

 resistant to depths of several hundred feet in order to provide the 

 buoyancy and the one-atmosphere housing for men and equipment. 



The structural requirements to provide "System Availability" are: 



1. Design and Engineering . Design requires a knowledge of the loadings, 

 the structure's capability to resist the loadings, and analysis methods 



to relate the loadings to the structure's resistance. 



2. Loadings. The structure will be subjected to a variable hydro- 

 static head* repetitive loadings and vibrations from waves, machinery, 

 and mooring lines* and dynamic, concentrated loads at the cold water pipe 

 connection. The cold water pipe will be subjected to tensile loads by 

 its own weight and to significant bending and shear forces (and possibly 

 large and small amplitude vibrations) by currents and, perhaps, internal 

 waves. Contingent loadings such as impact due to collision and grounding 

 must be considered. 



3. Load -Resistance Capacity . To resist service and environmental 

 loadings, the structure must provide adequate strength to bending, tensile^ 



