Anchoring floating structural body in deep water

Disclosed is a deep water anchoring system including a structural body floating at the surface of a body of water and with an intermediate floating member directly under and spaced from the floating structural body, the intermediate floating member being submerged below the surface of the water a distance sufficient to be unaffected directly by surface winds and waves. A gravity anchor along the bed of the body of water is coupled to the intermediate floating member via multiple cables which perferably extend angularly outwardly from the intermediate floating member. The anchoring system is provided with at least three separate and rigid rods, each of which are rotatably coupled at one end to the intermediate floating member and rotatably coupled at the other end to the floating structural body.

FIELD OF THE INVENTION 
This invention relates to anchoring the floating structural bodies such as 
an oil drilling platform, floating ports and the like in deep water so 
that the floating structural body is kept in elastically safe working 
conditions and minimizing swinging. 
BACKGROUND OF THE INVENTION 
In U.S. Pat. No. 3,986,367 filed Oct. 1, 1975 owned in common with this 
invention. The floating structural body has RIGID HANGING ELEMET hanging 
by flexible cables. The rigid hanging element is anchored to the ground 
foundation by slope cables which hold the rigid hanging element and 
floating structural body in position, but do not transfer the horizontal 
ground motion (earthquake) to the floating structural body. The floating 
structural body under wave, windstorm, hurricanes, tornadoes pressure can 
move horizontally, twist and swing independently from the rigid hanging 
element. 
The present invention is concerned with minimizing the swinging of the 
floating structural body. The INTERMEDIATE FLOATING ELEMENT is not hanging 
but supporting the floating structural body. The rods join the floating 
structural body and intermediate floating element and have ball joints at 
the top and bottom. The intermediate element is held by sloped cables 
anchored in sealed gravity foundation in horizontal and vertical position. 
The floating structural body under wave, windstorm, hurricanes, tornadoes 
pressure can move elastically horizontally and twist independently from 
the intermediate floating element, but cannot swing. The floating 
structural body can move only parallel to the intermediate floating 
element. 
WAVE ACTION TO THE FLOATING STRUCTURAL BODY 
Water waves may be caused by earthquakes, bom explosions in water, tides or 
winds. It is the latter which produce the waves which enginiers are most 
interested. 
WAVE GENERATION FROM WIND 
Waves are generated by the transfer of energy from air moving over the 
water surface. The transfer is effected in two ways: 
FIRST: The water surface reacts to small differces in pressure of the 
moving air, which creates the first variation in the water level. These 
are increased differences in pressure exerted by the moving wind on the 
back and on the front of the wave. 
SECOND: Tangential stress ocours between the two fluids, air and water, 
which are in contact and moving at different speeds relative to each 
other. Since both normal pressure and tangential stress are functions of 
the wind velocity it follows that wave characteristics also are functions 
of wind velocity. 
WAVE FORM 
Waves manifest themselves by curved undulation of the surface of the water 
occurring at periodic intervals, it is the wave form and not the water 
which moves over surface as a result of the orbital motion of surface 
water particles, which oscillate back and forth, but do not advance. The 
floating object in deep water will rise and fall with the undulation of 
the waves, but will not move horizontally unless it is moved by wind, 
current or other forces, except for a small back and forth motion caused 
by the orbital motion of the water particles. 
The size of a wave for a particular location will depend upon the velocity 
of the wind, the duration of the wind, the direction of the wind, the 
greatest distance over which the wind can act, and depth of the water. 
WAVE ACTION TO THE FLOATING STRUCTURAL BODY 
The wave pressure against the floating structural body consists of: (a) 
hydrostatic pressure which varies as the wave rises and falls. The waves 
act on both sides of the floating structural body, maximum net horizontal 
force will occur when the crest acts against one side when the trough acts 
against the other. (b) The dynamic pressure acts near the region where the 
wave crest hits the floating structural body. The floating structural body 
under the wave hydrostatic and dynamic loads moves horizontally, 
vertically, swings and posibly twists. 
WIND ACTION TO THE FLOATING STRUCTURAL BODY 
The circulation of masses air mor less paralel to the earth's surface is 
known as wind. The side of a structure facing the direction from which the 
wind comes is the windward side and the opposite side is the leeward side. 
The wind loads to the floating structural body are assumed to act from the 
water level up. The total wind pressure on a floating structural body 
varies with shape. Winds, impinging on the varied surfaces offered by the 
floating structural body, could develop large forces on the windward side, 
but considerably less than those produced by a tornado. 
The tornado is defined as a moving spiral of air, spinning in a vertical 
cylinder with wind velocities at the cylinder wall of up to 300 m.p.h. and 
reduced air pressure inside the cylinder. The action of a tornado that 
moves directly into a floating structural body produces very large lateral 
and rotational forces, followed by a powerful lift, as the center of the 
tornado moves forward accross the floating structural body. 
The floating structural body under dynamic and static wind load moves 
horizontally, swings and possibly twists. 
BRIEF SUMMARY OF THE INVENTION 
The present invention contemplates a new anchoring system in deep water in 
wich the floating structural body is not directly supported or anchored in 
seabed. New is the introduction of an INTERMEDIATE FLOATING ELEMENT 
between the floating structural body and seabed close and directly under 
the floating structural body. The new anchoring system generally consists 
of two parts. 
The FIRST is an intermediate floating element, slope cables under tension 
force and gravity foundation on seabed. There is no direct wave, wind and 
tornado action to the intermediate floating element. The weight of the 
intermediate floating element is less than the weight of the displaced 
water, therefore there is hydrostatic upward force-uplift force. The slope 
cables, under tension force, anchored by conventional methods, on sealed 
concrete gravity foundation hold the intermediate floating element in 
horizontal and vertical position. 
The SECOND part is platform, hull and rods. The hull is for two reasons: 
(a) to rise the uplift force in rods. The weight of the hull is less than 
the displaced water. (b) the instalations facilities. After the hull is 
instaled in its position it will be made permanent with platform by bolts, 
welding or otherwise and both called FLOATING STRUCTURAL BODY. 
The vertical and equally long peripherial placed rods join the floating 
structural body and intermediate floating element and have conventional 
ball bearing joints at the top and bottom. The floating structural body 
under wave, windstrom, hurricanes, tornadoes pressure can move 
horizontally in all directions independently from the intermediate 
floating element holding by slope cables in horizontal and vertical 
position, but can not swing. The floating structural body can move only 
paralel to the intermediate floating element.

DETAILED DESCRIPTION OF PREFERED EMBODIMENT 
Referring to FIGS. 1, 2 and 3 a floating structural body 11, 12 shown 
floating in natural deep water 10. The present invention contemplates a 
new anchoring system in deep water 10 in which the floating structural 
body 11, 12 is not directly supported or anchored in deep sealed 23 
gravity foundation 22. New is the introduction of an INTERMEDIATE FLOATING 
ELEMENT 18. The intermediate floating element 18 is directly and close to 
the bottom of the floating structural body 11, 12. The new anchoring 
system generally consists of two parts. 
The FIRST part consists of the intermediate floating element 18, slope 
cables 21, gravity foundation 22, and seabed 23. The object of the 
invention is to construct intermediate floating element 18 which remains 
substantionally in vertical and horizontal position during wave, windstorm 
and tornado action to the floating structural body 11, 12. There is not 
direct wave, windstorm and tornado action to the intermediate floating 
element 18, it can be any convenient shape or material: steel, concrete or 
other. The weight of the intermediate floating element is less than the 
weight of the displaced water, therefore there is hydrostatic 
upward-uplift force. The minimum necessary uplift force is that, which can 
full the cables 21 tight. 
The horizontal and vertical stability of intermediate floating element 
depends on its own 18 and the deep forced floating structural body's 12, 
11 uplift force, anchored by slope cables 21 in gravity foundation 22 
placed on the seabed 23. More uplift force, more vertical and horizontal 
stability. Mor sloping of the cables, more horizontal stability. 
19-structural cross beams to horizontal strength. 
20-watertight cells. 
The SECOND part consists of floating platform 11, hull 12 and rods 15. 
The hull 12 is for two reasons: first to raise the uplift force in rods 15. 
The weight of the hull 12 is less than the displaced water, therefore 
there is hydrostatic upward-uplift force. Second: for the installation 
facilities. By gradually pumping the water in and out in the cells 14 
There is the necessary depth for the installation of the rods 15. After 
the hull 12 is installed in its position it will be made permanent with 
floating platform 11 by bolts, welding or otherwise. The two structures 11 
and 12 together form floating structural body. 
13-structural cross beams to horizonta strength. 
14-watertight cells. 
The rods 15 join the floating structural body 11, 12 with the intermediate 
floating element 18 for compresion and tension forces. The rods 15 through 
the conventional ball joints 16 and 17 on both ends have complete freedom 
of rotation, so the relative horizontal and corresponding vertical 
movement between the floating structural body 11, 12 and intermediate 
floating element 18 can take place in all directions. The rods are the 
same length and cannot move axially, therefore the floating structural 
body 11, 12 can move only parallely to intermediate floting element 18 
without swinging. 
It is to be understood that the form of my invention herewith shown and 
described is to be taken as a preferred example of the same and that 
various changes relative to the material, size, shape and arrangements of 
parts may be resorted to without departing from the spirit of the 
invention or the scope of the subjoined.