Floating enclosed offshore support structure

• US 4,984,935 A
• Filed: 12/22/1987
• Issued: 01/15/1991
• Est. Priority Date: 12/22/1986
• Status: Expired due to Fees

• Current Assignee: Empresa de Portos Do Brasil SA, Petróleo Brasileiro SA (Campo de Azulão)
• Original Assignee: Empresa de Portos Do Brasil SA -Portobras, Petrã“Leo Brasileiro SA - Petrobras (Presidãªncia Da Repãºblica)
• Inventors: Pires, Valtair P. L., de Oliveira Filho, Florencio
• Primary Examiner(s): CORBIN, DAVID
• Application Number:
  US07/136,324
• Time in Patent Office: 1,120 Days
• Field of Search: 405/195, 405/200, 405/203, 405/26, 405/27, 405/30, 405/31, 405/75, 405/76, 405/211, 405/219, 405/224, 114/264, 114/45, 114/263, 114/266, 114/267, 114/265
• US Class Current: 405/224
• CPC Class Codes: B63B 35/44 Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices construction methods for floating offshore platforms B63B75/00

Abstract

A floating structure to support maritime operations is constituted by a metallic platform, in the shape of an internally open square (10) floating in the ocean being moored to the bottom of the ocean by a cable system (C₁, C₂, C₃ . . . C_n) tied to a pile system (E₁, E₂, E₃ . . . E_n). It retains in its interior a portion of the sea which is communicated to the outside ocean through an opening (11) in the walls of the said metallic platform (10) in such a way that, in that confined part of the ocean, the support boats to the sea work, may be moored due to the fact the interior of the open square is calm in respect to the rough sea outside the structure (10). For the confined sea body to be calm contributes the resistance offered to the wave impact by the lateral walls (16, 18, 19) of structure (10), which are submerged down to a wet depth of more than 30 meters and also because the wall (18) possess deflecting devices (20) of the water and chambers (21) to dampen the wave impact.

Claims

1. A floating enclosed offshore support structure for stabilized mooring at any point in the ocean by fastening the support structure to the bottom of the sea, said structure comprising:

an upper metallic platform (10) taking the shape of an open square in plan configuration defining an internally open interior (17) and having at least one entrance opening communicating the interior (17) to the exterior ocean, said at least one entrance opening being within a face facing the direction of oncoming waves, said platform face being defined by three distinct parts;

(a) a vertical flat wall (16) located in an upper part of said face;

(b) an intermediate wall (18) formed by a plurality of protruding elements (20) shaped as a section of a tetrahedron as seen by the oncoming waves and by openings (21) between said protruding elements and limited on both sides by lateral walls of adjacent, laterally spaced protruding elements (20), said openings (21) communicating the exterior ocean with, a vertical inner channel (23) within the portion of the platform formed by said vertical flat wall, each inner channel corresponding to each opening and cut in the interior of the platform, through which the water may penetrate violently under the effect of the waves, said inner channel being partially defined by an inner wall shaped to absorb and dampen the force of the incoming water into the opening (21) and the inner channel (23), and at least one special opening (24) communicating with said inner channel (23) to let the water penetrating into the open space (23) to flow through said at least one special opening (24) onto the exterior face of the vertical flat wall (16); and

(c) a lower wall (19), flat and vertical, located immediately under the intermediate wall (18) and which, when the structure is positioned in the ocean, stays fully submerged;

said structure further comprising a float system (13) for supporting the platform (10) including floats and spaced columns (14) connecting said floats to said platform such that the floating platform (10) is stabilized over an ocean spot with said floats remaining fully submerged;

a cable system comprising multiple cables (C₁, C₂, C₃ . . . C_n) linking said floating structure to mooring piles (E₁, E₂, E₃ . . . E_n) fastened to the bottom of the sea, said cables having upper ends fastened to points in the bottom of the floats, and lower ends tied to respective mooring piles.

2. The floating enclosed offshore support structure as claimed in claim 1, wherein the inner channel (23) which communicate with the ocean through openings (21) have inner walls rounded up to deviate the water, forced by the impact of the waves, through said inner channel (23) and through said special opening (24) to return to the ocean.

3. The floating enclosed offshore support structure, as claimed in claim 2, further comprising a ballasted piston (25) mounted in the platform inner channel (23) for vertical movement within said inner channel (23) under the force of the wave for performing useful work.

4. The floating enclosed offshore support structure as claimed in claim 1, wherein the upper metallic platform is submerged to a wet depth of approximately 30 meters.

5. The floating enclosed offshore support structure, as claimed in claim 2, wherein upper metallic platform is defined by lateral walls forming the open interior having a lateral width of about 20 meters.

6. The floating enclosed offshore support structure, as claimed in claim 2, wherein the interior (17) of the platform serves as a boat shelter;

with the waves within the open interior being greatly damped in comparison to the rough ocean waters outside said support structure.

7. The floating enclosed offshore support structure, as claimed in claim 4, defined by the expression "H_t /H_i ×

100", where H_t is the height of the transmitted wave within the open interior (17) of the platform;

H_i is the height of the wave impacting said face from the open ocean, and within the range of 4 to 55 for wave periods of 8.0 to 12.0 seconds and external wave heights of 2.0 to 6.0 meters.

8. The floating enclosed offshore support structure, as claimed in claim 4, wherein the water retained within the opening of the upper metallic platform is totally dampened relative to the waves external of the support structure.

9. The floating enclosed offshore support structure, as claimed in claim 1, wherein said the cables (C₁, C₂, C₃, . . . C_n) tying said structure to said piles (E₁, E₂, E₃ . . . E_n) forming a reticulated system with multiple nodes, each occupied by a secondary floating element in a manner whereby the catenary effect is alternated over the extent of the cable system.

10. The floating enclosed offshore support structure as claimed in claim 1, wherein the upper metallic platform is provided with at least one lateral vertical opening (12) on each face, and wherein closing gates (11) are provided for each opening whereby only one of the openings may be selectively maintained open for convenience of operation and to maximize the dampening effect of the ocean waves entering the open interior of the upper metallic platform through said one opening.

11. The floating enclosed offshore support structure as claimed in claim 8, wherein the entrance opening to the open interior (17) of the upper metallic platform is at right angles to the plane of the face on the platform which receives direct impact of oncoming sea waves.