TOWING, MOTIONS, AND STABILITY 

 CHARACTERISTICS OF OCEAN PLATFORMS 



Robert H. Macy 

 Naval Architect and Marine Engineer 

 Pascagoula, Mississippi 



GENERAL 



For the purposes of this paper an ocean platform is defined as a floating 

 unit which can be towed or in some cases self-propelled to a location where it 

 is anchored or dynamically positioned to fulfill its function. In special cases 

 platforms are propelled slowly while working. However, in general, an ocean 

 platform is considered to be a unit which is designed for performing some type 

 of work in a more or less fixed location rather than one that is engaged in trans- 

 porting commodities. While single hulls such as ships or barges may be posi- 

 tioned for a working assignment, these are not considered as true platforms, 

 although they are mentioned in the paper. A platform is envisioned as a unit 

 that has a relatively large working deck of considerable width in respect to its 

 length, where the length to width ratio of the platform itself may be anything 

 from 1.0 to 3.0. 



Such platforms have a variety of uses, and with modern technology new uses 

 are being developed. Some of these are as follows: oil well drilling; oil well 

 producing; oil well workover; oil storage; undersea mining; heavy lifting; pipe 

 laying; oceanographic research; weather stations; missile launching; beacons - 

 visual, radar, loran, etc.; landing platforms - air or water vehicles. 



Ocean platforms fall principally into the following categories: fixed pile 

 structures having built-in buoyancy for towing only; single hulls - ship or barge; 

 catamarans - floating or submerged; fixed height noncolumn stabilized struc- 

 tures; jack-up platforms with or without bottom hull; column stabilized plat- 

 forms; and special types: (a) deadweight anchor type platforms and (b) spar 

 vessels. 



Many of the types of platforms listed above are shown in Figs. 1 through 15. 

 Fixed pile structures such as that shown in Fig. 1 are not properly a part of this 

 paper as they are ordinarily transported to location on the deck of barges. How- 

 ever, a few have been towed either with the use of attached pontoons to provide 

 stability or by having at least two of the corner tubular members made suffi- 

 ciently large to provide stability and buoyancy. Such pontoons are lowered into 

 position by selective flooding. Once in position on the bottom, they are ordi- 

 narily regarded as being permanently placed, although it is not inconceivable 



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