FR2995871A1 - FLOATING SUPPORT WITH SELF-LOCKING FLOATS - Google Patents

Abstract

Floating support for offshore structure, comprising: - a support mast (12), - a floating structure (14) on which the support mast (12) is fixed, said floating structure (14) comprising at least one floating cage ( 24) extending along a longitudinal axis (Xi) and a plurality of buoyancy chambers stacked in stages in the buoyancy cage (24), at least two adjacent buoyancy chambers belonging respectively to distinct stages each comprise at least one surface stop, the abutment surfaces cooperating with each other so as to immobilize said two buoyancy chambers relative to each other.

Description

The present invention relates to a floating support for offshore structure, comprising: - a support mast, - a floating structure on which the support mast is fixed, said floating structure comprising at least one floating cage s extending along a longitudinal axis and a plurality of buoyancy chambers stacked in stages in the buoyancy cage. The field of the invention relates to floating supports intended to be implemented at sea or on the high seas, for example in the field of petrochemical exploitation, in the sector of the marking of the sea lanes or in that of offshore wind turbines. Each floatation cage provided with its buoyancy chambers defines a buoyancy module of the floating support. These modules have the effect of increasing the stability performance of the support and the offshore structure that is fixed. The dimensions of the buoyancy modules and the number of buoyancy chambers they comprise are then predetermined according to the performance required to ensure the good stability and good buoyancy of the offshore structure, and are then easily adaptable to the latter because of their simple structure.

Each floatation cage is in the form of a metal frame, so that the cost associated with the buoyancy modules is relatively low. Several types of buoyancy modules are known to those skilled in the art. They are generally in the form of a floatation cage filled caissons shaped to be juxtaposed to each other and stacked on each other along the longitudinal axis of the float cage. The modules are held in position by the frame of the cage with which the buoyancy modules cooperate for their centrifugal radial immobilization and in rotation with respect to the longitudinal axis of the floating cage. However, this is not entirely satisfactory.

Indeed, in the configuration described, the buoyancy chambers are not immobilized relative to each other, and, under the effect of movements of the floating support, tend to clash and move because of existing games between the different components of the buoyancy modules. However, these shocks and these movements tend to accelerate the wear of the boxes and thus reduce their service life.

One of the objects of the invention is therefore to provide a floating support for offshore structure does not have this disadvantage. To this end, the invention relates to a floating support for offshore structure of the aforementioned type, characterized in that at least two adjacent buoyancy chambers belonging respectively to distinct stages each comprise at least one abutment surface, the abutment surfaces co-operating between them so as to immobilize said two buoyancy chambers relative to each other. According to other embodiments, the invention comprises one or more of the following technical characteristics, taken separately or in any combination (s) technically possible (s): - one of the two buoyancy chambers comprises a tenon having an inner surface forming said abutment surface of this box, and the other of the two boxes comprises a mortise delimiting an internal lateral surface forming said abutment surface of this other box; each buoyancy chamber comprises a mortise delimiting two internal lateral surfaces and two tenons respectively received in the mortise of two adjacent caissons, each tenon having an internal surface, the mortise of a given buoyancy chamber being disposed astride two tenons belonging each to one of two adjacent buoyancy chambers; for each buoyancy chamber, the inner surfaces converge towards each other in the centripetal direction, and the inner lateral surfaces are also convergent towards each other in the centripetal direction; each buoyancy chamber has two lateral surfaces each cooperating with a lateral surface of one of two adjacent buoyancy chambers of the same stage; the lateral surfaces of each buoyancy chamber converge towards each other in the centripetal direction; each stage of buoyancy chambers is rotated by a half angle of opening of the caissons with respect to the adjacent stages; The floatation cage delimits side windows, and the maximum width of the buoyancy chambers is less than the width of said windows; the buoyancy cage comprises a plurality of braces regularly spaced along the longitudinal axis; two successive braces define a chamber of the floatation cage comprising several stages of buoyancy chambers, each pair of adjacent buoyancy chambers of the upper stage of each chamber delimiting a space in which is received a beam of the upper brace to immobilize the upper tier of boxes rotating about the longitudinal axis and in translation along the longitudinal axis; - With the possible exception of the lower cross, each beam comprises a wedge perpendicular to said beam and located at the end of the beam which is opposite to the longitudinal axis, each buoyancy chamber of the upper stage, respectively lower, caissons of each chamber being in abutment against at least one wedge of the upper spider, respectively lower; - The floating structure comprises a support column on which the floatation cage is fixed, said support column having an own axis parallel to the longitudinal axis of the float cage and inclined relative to the support mast. The invention will be better understood on reading the following detailed description, given by way of example and with reference to the appended figures, in which: FIG. 1 is a diagrammatic perspective illustration of a floating support according to the invention; Figure 2 is a perspective view of four float chamber stages of the floating support of Figure 1; Figure 3 is a top perspective view of a buoyancy chamber of the support of Figure 1; Figure 4 is a perspective bottom view of the buoyancy chamber of Figure 3; Figure 5 is a schematic illustration of a buoyancy chamber of the floating support of Figure 2; and Figure 6 is a side view of a buoyancy module of the floating support of Figure 1; and With reference to FIG. 1, the floating support 10 according to the invention, hereinafter support 10, is associated with an offshore structure whose support it carries out. It is intended to be implemented at sea. The support 10 comprises a support mast 12 as well as a floating structure 14.

The support mast 12 is firstly fixed to the floating structure 14 at its base, and is integral at its upper part of the offshore structure in question (not shown). The offshore structure is for example a wind turbine, a petrochemical equipment, or a seaway beacon. The floating structure 14 is able to stabilize the movements of the offshore structure induced by waves, wind, etc.

For this purpose, the floating structure 14 comprises a float 16, beams 18, support columns 20 and buoyancy modules 22. The float 16 is adapted to ensure the floatation of the support 10 and the offshore structure.

The beams 18 are adapted to secure the support mast 12 to the float 16 and the support columns 20, and stiffen the support 10 generally. The support columns 20 are adapted to increase the stability of the support 10. For this purpose, they are regularly spaced around the support mast 12, and each extend along a proper axis T, inclined relative to the support mast 12.

The buoyancy modules 22 are adapted to increase the buoyancy and the stability of the support 10 and are respectively fixed to the support columns 20. In the example of FIG. 1, the support 10 comprises three support columns 20 of respective own axes. T1, 12 and 13, and three buoyancy modules 22 respectively attached to one of the support columns 20.

Alternatively, the support 10 comprises two, three or more buoyancy modules 22 attached to each of the support columns 20. The number of support columns 20 may also be greater than three. Each buoyancy module 22 is intended to be at least partially immersed and comprises a floatation cage 24, hereinafter cage 24, and a plurality of buoyancy chambers 26, hereinafter boxes 26, arranged in stages 27 in the defined volume. by the cage 24. The cage 24 extends along a longitudinal axis X, parallel to the proper axis T, of the support column 20 to which the buoyancy module 22 is fixed. The cage 24 has a general shape of hexagonal prism and comprises a frame 28 made from metal, and more particularly from steel. The frame 28 comprises six spars 29 extending parallel to the longitudinal axis X ,, connected by groups of six crosspieces 31. Each group forms a frame 131 (Figure 2) hexagonal substantially contained in a plane perpendicular to the axis X. In this example, there are five frames 131, including a frame at each end of the cage 24 and three regularly spaced between these two frames. In each of these planes, there is further provided a spider 30 shaped six-pointed star comprising six spokes attached to the frame 131 corresponding. This fixing is done by bolting for the four upper braces, and by welding for the lower brace.

The rails 29 and the cross members 31 define side windows 290 of the frame 28 each having a width L, and through which the boxes 26 are adapted to be inserted, as will be seen later. Two successive braces 30 delimit a chamber 301 of the cage 24 in which there are several stages 27 of boxes 26, including an upper stage 27 in contact with the upper brace 30. As illustrated in FIG. 1, each buoyancy module 22 comprises five braces 30 which delimit four chambers 301 each having four floors 27 of boxes 26.

Each chamber 301 has a height, along the longitudinal axis X ,, substantially equal to the height of four floors 27 of boxes 26. With reference to Figure 2, the radii of a spider 30 are formed by six beams 32 integral with each other at one of their ends, in the center of the spider, and each of which is intended to be fixed by bolting to a spar 29 at the other of its ends. Each beam 32 has a height h, along the longitudinal axis X, and a width 2d complementary to the receiving space dimensions and a groove that the boxes 26 delimit. This is described in more detail in the following. The beams all have substantially the same length.

In the four upper braces, each carries at its outer end a wedge 320 comprising a flat wall both disposed perpendicularly and welded to the corresponding beam 32. The wedges 320 are at a distance from the center of the spider 30 substantially equal to the radial dimension of the caissons 26. These wedges 320 are used for bolting the beams 32 on the frames 131 and blocking the caissons 26, as will be seen later . With reference to Figures 1 to 4, the boxes 26 are adapted to increase the buoyancy and stability of the support 10. Each box 26 is intended to be stacked on other boxes 26 or on the lower cross 30, or floor, of the cage 24 to fill the volume of the cage 24.

This stack is described in more detail in the following. Referring to Figures 3 and 4, each box 26 has a general shape of hexagonal prism sector and has a plane of symmetry SJ. More precisely, each box 26 has a general shape of isosceles trapezoidal prism.

For a given box 26, the smaller of the two bases of the trapezoidal base, hereinafter small base, generates the front face 33 of the box 26.

The larger of the two bases of the trapezoidal base, hereinafter large base, generates the rear face 35 of the box 26 and has a bevel 37 at each of its ends. These bevels have the effect of reducing the maximum width 1'x of the caissons 26 with respect to a non-beveled configuration of the caissons 26. The maximum width 1'x of the caissons 26 is less than the width L of the side windows 290. Referring to the orientation of Figures 3 and 4, each box 26 also has an upper face 38, a lower face 40, and two side faces 42. The bevels 37 also have the effect that the radial length Lp of the faces 42 is substantially equal to the radial dimension of the box 26 in its plane of symmetry SJ, as shown in Figure 3. The box 26 comprises two pins 44 projecting on the upper face 38 and located near one of the edges of the upper face 38 and one of the lateral faces 42. Each tenon 44 has a general shape of hexahedron extending in a direction substantially parallel to the nearest lateral surface 42, and having, along its directio n, a trapezoidal section converging towards the front face 33. Each post 44 has a constant height h and comprises an inner surface 46, a substantially trapezoidal front surface 47 and an outer surface 48. In addition, each post 44 comprises a parallel top surface. at the upper surface 38 of the box 26 and a substantially trapezoidal rear surface parallel to its front surface 47. The outer surface 48 and the inner surface 46 are slightly inclined relative to the side face 42 of the box 26 near which it is located , and the base of the outer surface 48 extends parallel and at a distance d from the edge of the upper face 38 and this side face 42. The inner surfaces 46 of a box 26 converge towards one another in direction of the front face 33 of the box 26. Each pin 44 defines a space 50 of minimum width d, of height equal to h and located between its outer surface 48 and the edge of the f upper ace 38, said space 50 being adapted to be juxtaposed to a second space 50 delimited by an adjacent chamber 26 of the same stage 27 to receive one of the beams 32 of a spider 30, as will be seen later. The two pins 44 of each box 26 are opposite and symmetrical to one another relative to the plane of symmetry SJ of the box 26 considered.

Due to the presence of the tenons 44, the upper face 38 of each box 26 has a general shape of arrow oriented towards the front face 33 and symmetrical with respect to the plane of symmetry S. On its lower face 40, each box 26 comprises a mortise 52 and a groove 53 which delimit two lateral shoes 54 of the box 26. Each mortise 52 has a general shape of isosceles trapezoidal base prism Si plane of symmetry and has dimensions complementary to those of two studs 44 of two boxes 26 juxtaposed . It has a particular depth h.

Each mortise 52 delimits two mortise front surfaces 521 perpendicular to the plane Si and respectively carried by the one and the other of the shoes 54. Each mortise 52 also delimits two internal lateral surfaces 55 opposite to each other and respectively worn. by both hooves 54. As illustrated in Figure 4, the inner side surfaces 55 of a box 26 converge towards each other in the direction of the front face 33 of the box 26. The groove 53 has a general shape of bowl extending along the plane of symmetry Si of the box 26 between the mortise 52 and the front face 33 and opens into both the mortise 52 and the front face 33. The groove 53 has a depth substantially equal to h and a minimum width substantially equal to 2.

The shoes 54 of a box 26 given are symmetrical to each other with respect to the plane of symmetry Si of the box and are respectively intended to be in contact with the upper face 38 of one of two adjacent boxes 26 of the lower floor 27. Because the tenons 44 and mortises 52 have complementary dimensions, the upper face 38 of each box 26 has a shape complementary to that of the shape of two shoes 54 contiguous to each other, for example by setting and then contacting the side surfaces 42 of two boxes 26. The two side surfaces 42 of a box 26 are substantially flat and respectively included in a plane. The planes of the lateral surfaces 42 of the same box 26 thus define an opening angle a of the box 26. The lateral surfaces 42 of a box 26 thus converge towards each other in the direction of the front face 33 of the box 26. Box 26. In the example of Figures 3 and 4, the opening angle a is substantially equal to 60 °.

The boxes 26 are made from plastic material by rotational molding, that is to say by injection of plastic material into a rotating mold.

More precisely, the boxes 26 are made from polyethylene. Each box 26 has a mass of between 250 kg and 400 kg, and preferably substantially equal to 350 kg, a length of between 2 m and 3 m, and preferably equal to 2.5 m, a maximum width I'x appreciably equal to its length, and a height of between 1 m and 1.4 m, and preferably substantially equal to 1.2 m. The stacking of the boxes 26 in the cage 24 and the operation of the support 10 will now be described in more detail with reference to FIGS. 1 to 6. As indicated above, the boxes 26 are arranged in stages 27 in the cage 24. At least a plurality of stages 27 is immersed.

Each floor 27 comprises six boxes 26 juxtaposed to each other, having all the same dimensions and the same shape. Two adjacent caissons 26 have one of their two lateral surfaces 42 in contact with each other. Each stage 27 is rotated by a half-angle of opening with respect to the two adjacent stages 27, that is to say 30 ° in this example.

With the exception of the caissons 26 of the first and the last stages 27 of the cage 24, which have no respectively directly lower and directly higher stage 27, each caisson 26 cooperates with two adjacent caissons 26 belonging to the same stage 27, two adjacent caissons 26 belonging to the directly lower stage 27, and two adjacent caissons 26 belonging to the directly higher stage 27.

The boxes 26 are regularly arranged around the longitudinal axis X, and are centered on the longitudinal axis X. The front face 33 of the boxes 26 is oriented towards the longitudinal axis X. Referring to FIGS. 2 and 5, FIG. except for the boxes included in the floor 27 in contact with the floor of the cage 24, each box 26 straddles the two adjacent boxes 26 belonging to the floor 27 directly below. In this configuration, for each box 26, the lateral surfaces 42, the internal surfaces 46 of each pin 44 and the internal lateral surfaces 55 form abutment surfaces cooperating with those carried by the adjacent boxes 26 to immobilize the box 26 considered by relative to the casings 26 adjacent in rotation and radially with respect to the longitudinal axis X. More specifically, the mortise 52 of a box 26 given receives two studs 44 juxtaposed each belonging to one of the two boxes 26 on which the box 26 considered is on horseback. The two internal lateral surfaces 55 of the box 26 cooperate with the inner surface 46 of one of the two pins 44 that the mortise 52 receives, which has the effect of immobilizing the box 26 in rotation around the longitudinal axis X, relative to the caissons 26 on which it is on horseback, and this in both directions. Simultaneously, the orientation and the convergent disposition towards each other in the centripetal direction of the two internal lateral surfaces 55 oppose the radial movement in the centrifugal direction of the box 26.

In addition, the two shoes 54 of the box 26 are respectively in contact with the upper surface 28 of one of the two adjacent boxes 26 of the directly lower stage 27. In this configuration, the upper face 38 of each box 26 is in contact with two shoes 54 each belonging to one of the two adjacent boxes 26 of the directly higher stage 27. The inner surface 46 of each of the tenons 44 abuts against the internal lateral surface 55 of the mortise 52 of one of the two adjacent caissons 26 of the directly upper stage 27, which has the effect of immobilizing the casing 26. in rotation about the longitudinal axis X, relative to the boxes 26 which it receives the shoes 54, and in both directions of rotation. Similarly, because of the shape of the pins 44 and the convergence of the inner surfaces 46 of a box 26 towards each other in the centripetal direction, the simultaneous cooperation of the inner surfaces 46 with one of the lateral surfaces internal 55 of the mortise of two adjacent boxes 26 opposes any radial displacement in the centrifugal direction of the box 26. In addition, the side faces 42 of each box 26 are respectively in contact with the side faces 42 of the two adjacent boxes 26 of same stage 27. Due to the trapezoidal prismatic shape of the caissons 26, the lateral faces 42 of the adjacent caissons 26 of the same stage 27 converge towards each other in the centripetal direction and oppose the radial displacement of the caisson 26 by relative to the longitudinal axis X, in the centripetal direction. In other words, each box 26 is immobilized radially in the centripetal direction because of the cooperation of its lateral faces 42 with the corresponding lateral face 42 of the adjacent boxes 26 of the same stage 27.

In addition, the lateral surfaces 42 of these boxes 26 also oppose the rotation of the box 26 around the longitudinal axis X ,, and in both directions. Referring to Figures 2 and 5, the two pins 44 respectively belonging to one of two adjacent boxes 26 of the same floor 27 define a receiving space 56 consisting of two spaces 50 delimited by each of the two pins 44 and set look at each other.

Each receiving space 56 has a height equal to h and a minimum width equal to 2d and is thus adapted to ensure the reception of a beam 32 of brace 30. However, the receiving spaces 56 do not all receive a beam 32.

Indeed, only the six receiving spaces 56 delimited by the six boxes 26 of the upper stage 27 of each chamber 301 each receive a beam 32. Each of these beams 32 is then also received in the groove 53 of the boxes 26 on horseback on the boxes 26 defining the corresponding receiving spaces 56.

The bevels of the rear faces 35 of the six boxes 26 of the upper stage 27 of each chamber 301 are then each bearing against a shim 320. In addition, the rear faces 35 of the boxes 26 of the lower stage 27 of each chamber 301 (With the exception of the lower chamber 301), are also in contact with a shim 320 belonging to the beam 32 on which they are respectively on horseback.

Each shim 320 thus directly opposes the displacement of one or three of the boxes 26 radially in the centrifugal direction relative to the longitudinal axis X ,, and therefore to the displacement of all the boxes 26 in the same direction because the boxes 26 are immobilized relative to each other. In practice, the braces 30 are mounted prestressed, that is to say that their beams 32 are supported on the bottom of the receiving space 56 in which each of them is received. Each spider 30 then tends to press the four stages 27 of the underlying chamber 301 against the immediately lower caissons 26 and / or against the immediately lower spider 30.

Because of the complementary dimensions of the beams 32 and the receiving spaces 56 and the prestressed mounting of the beams 32, each spider 30 immobilizes the boxes 26 in translation along the longitudinal axis X, and in rotation relative to the same axis X. In addition, because the beams 32 have dimensions complementary to those of the grooves 53 and receiving spaces 56, the braces 32 do not interfere with the relative arrangement of the boxes relative to each other. Finally, because of the relative immobilization of the boxes relative to each other, each spider 30 immobilizes the entirety of the caissons 26 of the cage 24 in rotation about the longitudinal axis X ,, as well as the entirety of the caissons 26 of the floors 27 lying below it in translation along the longitudinal axis X. In summary, each box 26 is immobilized: in translation along the longitudinal axis X ,, at least by a cross 30 of the chamber 301 in which the casing 26 considered is located, and / or by caissons 26 of the adjacent stage or stages 27 of this chamber, in simultaneous rotation around the longitudinal axis X, of all the caissons 26 of at least the chamber 301, at the less by said spider 30, in rotation in both directions relative to the adjacent caissons 26 by cooperation of the internal surfaces 46 of its tenons 44 with one of the internal lateral surfaces 55 of the mortise 52 of the two adjacent caissons 26 straddling said box 26 ; by cooperation of its lateral surfaces 42 with the lateral surfaces 42 of the adjacent caissons 26 of the same stage 27; and by cooperation of the internal lateral surfaces 55 of its mortise 52 with an inner surface 46 of a stud 44 of each of the two boxes 26 on which the box 26 considered is astride, radially in the centripetal direction at least by cooperation of its surfaces lateral 42 respectively with a lateral surface 42 of one of the two adjacent boxes 26 of the same stage 27, and radially in the centrifugal direction by cooperation of the inner surfaces 46 of its tenons 44 with the internal lateral surfaces 55 of the shoes 54 of the boxes 26 adjacent to the upper stage 27; by cooperation of the internal lateral surfaces 55 of its mortise 52 with the internal surfaces 46 of the tenons 44 that receives its mortise 52; and / or by abutment on a shim 320. In other words, according to the invention, the shape, the nesting of the boxes 26, the arrangement of the boxes 26 in the cage 24 in contact with braces 30 rigidly fixed to the cage 24, as well as the cooperation of the different abutment surfaces that they have with complementary abutment surfaces carried by the adjacent caissons 26 or wedges 320, have the effect that the caissons 26 are immobilized relative to one another and relative to each other. at the cage 24, so that the movements of the boxes 26 resulting from games tending to wear them are substantially reduced. Furthermore, each box 26 is immobilized relative to the adjacent boxes 26 by means of several abutment surfaces in the direction of movement, which has the effect of guaranteeing this immobilization in the event of deformation or damage occurring on one of the stop surfaces. In particular, in the event of failure of the lateral surfaces 42, internal 46 and internal lateral surfaces 55, the front surfaces 47 abut against the mortise front surfaces 521 to block any radial displacement.

Referring to Figure 6, which illustrates a buoyancy module 22 immersed in the case of calm water (solid line) and agitated water (dashed lines), the immersion of the buoyancy module 22 results in a hydrostatic pressure applied to the caissons 26 having a component along the longitudinal axis X ,, and a component orthogonal to the longitudinal axis X. Due to the presence of the braces 30 every four floors 27 of boxes 26, each spider 30 recovers the part of the hydrostatic forces applied to the caissons 26 of the four floors 27 of the chamber 301 that it delimits beneath it. In other words, each spider 30 allows the recovery of a portion of the hydrostatic force applied to the module 22, so that this force is applied to the cage 24 and to its frame 28 in a more homogeneous manner, which has for the effect of limiting the fatigue of the frame 28, to increase the life of the buoyancy module 22 as well as to increase the stability of the support 10 in general. In addition, because of the inclination of the longitudinal axis T, relative to the vertical, the orthogonal component of the hydrostatic force applied to the boxes 26 is transmitted by the boxes 26 to the longitudinal members 29 via shims 320 closest of the support column 20 to which the floatation module 22 is attached, rather than to the braces 30. This further improves the homogeneity of the recovery of the hydrostatic force applied to the caissons 26 and reduces the fatigue of the braces 30.

Furthermore, all the caissons 26 have an identical shape, which does not require to have molds of different shapes during their manufacture and does not require to nest the boxes in each other in a particular order. Finally, the immobilization of the boxes 26 in the cage 24 and with respect to each other is not ensured by the frame 28 of the cage 24.

This allows a slight oversizing of the frame 28 with respect to the floors 27 of boxes 26. Coupled with the bevels which reduce the maximum width I'x of the boxes 26, this oversizing allows the passage of the boxes 26 radially through the windows 290, and not necessarily by the top of the cage 24, which facilitates the mounting of the buoyancy modules 22 on the support 10.

In practice, the boxes are located at a distance from the longitudinal members 29 of the cage 24 in which they are received between 15 cm and 40 cm, and preferably equal to 25 cm. The method of mounting a support 10 according to the invention will now be described.

During a fixing step, a cage 24 is fixed to one of the support columns 20 of the support 10.

During a step of laying the boxes 26, four stages 27 of boxes 26 are successively mounted in the cage 24. To do this, the boxes 26 that comprise four stages 27 are successively introduced by one of the windows 290 of the cage 24, then translated along the longitudinal axis X ,, and then arranged next to each other and on the adjacent boxes 26 of the lower stage 27 or on the floor 24, so that their abutment surfaces come to cooperate with the abutment surfaces of adjacent wells 27 of the same floor 27 and adjacent floors 27 of the same floor and adjacent floors. Following the step of laying the boxes 26, during a step of placing a spider, a spider 30 is fixed to the cage 24 in contact with the upper stage 27 of the four floors 27 of boxes 26 placed during from the previous step. This fixing is done by bolting shims 320 on the frame 131 associated. This step of laying a cross leads to a new step of laying cans 26, which itself gives rise to a new step of installation of a spider 30, and so on until the volume of the cage 24 is completely filled with boxes 26 and then closed by a spider 30. In a variant, each cage 24 comprises one, two or three chambers 301, or else comprises more than four chambers 301. In a variant, each chamber 301 comprises an even number As a variant, each cage 24 has any form of polygonal prism. In this variant, the boxes 26 have a general shape of polygon sector associated with the shape of the cage 24.

Claims (12)

CLAIMS1.- Floating support for offshore structure, comprising: - a support mast (12), - a floating structure (14) on which the support mast (12) is fixed, said floating structure (14) comprising at least one cage flotation device (24) extending along a longitudinal axis (X,) and a plurality of stacked buoyancy chambers (26) stacked in stages (27) in the buoyancy cage (24), characterized in that at least two caissons of adjacent buoyancy (26) each of which comprises at least one abutment surface (42, 46, 55), the abutment surfaces (42, 46, 55) cooperating with one another so as to immobilize said two buoyancy chambers (26) relative to each other. 2. Floating support according to claim 1, characterized in that one of the two buoyancy chambers (26) comprises a pin (44) having an inner surface (46) forming said abutment surface of this housing, and in that that the other of the two boxes comprises a mortise (52) delimiting an inner lateral surface (55) forming said abutment surface of the other box. 3. Floating support according to claim 2, characterized in that each buoyancy chamber (26) comprises a mortise (52) delimiting two internal lateral surfaces (55) and two pins (44) respectively received in the mortise (52) of two adjacent caissons, each tenon (44) having an inner surface (46), the mortise (52) of a given buoyancy chamber (26) being disposed astride two studs (44) each belonging to one of two adjacent buoyancy chambers (26). 4. Floating support according to claim 3, characterized in that for each buoyancy chamber (26), the inner surfaces (46) are convergent towards each other in the centripetal direction, and the internal lateral surfaces (55) ) are also convergent towards each other in the centripetal sense. 5. Floating support according to any one of the preceding claims, characterized in that each buoyancy chamber (26) has two lateral surfaces (42) each cooperating with a lateral surface (42) of one of two buoyancy chambers. (26) adjacent the same floor (27). 6. Floating support according to claim 5, characterized in that the lateral surfaces (42) of each buoyancy chamber (26) are convergent towards each other in the centripetal direction. 7. Floating support according to any one of the preceding claims, characterized in that each stage (27) of buoyancy chambers (26) is rotated by a half-angle of opening (a) of the caissons relative to the stages (27) adjacent. 8. Floating support according to any one of the preceding claims, characterized in that the flotation cage (24) delimits side windows (290), and in that the maximum width (I'x) of the buoyancy chambers ( 26) is less than the width (L) of said windows (290). 9. Floating support according to any one of the preceding claims, characterized in that the flotation cage (24) comprises a plurality of braces (30) regularly spaced along the longitudinal axis (X,). 10. Floating support according to claim 9, characterized in that two successive braces (30) define a chamber (301) of the floating cage (24) comprising several stages (27) of buoyancy chambers (26), each pair of buoyancy chambers (26) adjacent to the upper stage (27) of each chamber (301) delimiting a space (50) in which is received a beam (32) of the upper brace (30) to immobilize the stage (27). ) of caissons in rotation about the longitudinal axis (X,) and in translation along the longitudinal axis (X,). 11. Support according to claim 10, characterized in that, with the possible exception of the lower cross (30), each beam (32) comprises a wedge (320) perpendicular to said beam (32) and located at the end. of the beam (32) which is opposite the longitudinal axis (X), each buoyancy chamber (26) of the upper (respectively lower) stage (27) of caissons of each chamber (301) bearing against at least one shim (320) of the upper and lower crosspieces (30). 12- floating support according to any one of the preceding claims, characterized in that the floating structure (14) comprises a support column (20) on which the floating cage (24) is fixed, said support column (20) having a clean axis (T,) parallel to the longitudinal axis (X,) of the floatation cage (24) and inclined with respect to the support mast (12).