STRUCTURE FOR SUPPORTING MARINE INSTALLATIONS AND PROCEDURE FOR THE EXECUTION THEREOF

Abstract

The invention relates to a structure (2) for supporting a wind turbine tower (1) provided with a housing (7) for fitting therein the foot of the tower (1), a main axis (Γ) being defined on the platform (2) which coincides with a main axis of the tower (1), and which comprises a body with a constant cross-section and internal walls (8) and intermediate walls (10) joined by internal radial ribs (11) perpendicular to the internal wall (8) whose plane passes through the main axis (Γ), such that at the intermediate wall (10) first joining nodes (12) are defined between the intermediate wall (10) and radial ribs (11), the intermediate wall (10) and an external wall (9) being joined by reticular ribs (14 and 15). This structure provides an optimal transmission of forces. The invention likewise relates to methods for manufacturing, assembling and installing the structure.

Claims

1. A structure (2) for supporting a wind turbine tower (1) provided with a housing (7) for fitting therein the foot of the tower (1), a main axis (Γ) being defined on the platform (2) which coincides a the main axis of the tower (1) when it is fitted in the housing (7), characterised in that it comprises a body with a constant cross-section along the direction of the main axis (Γ) in which the following are defined: an internal wall (8) that defines the housing (7) for fitting therein the foot of the tower (1); an external wall (9) that defines the outer perimeter of the body; an intermediate wall (10) arranged between the internal wall (8) and the external wall (9); the internal wall (8) and the intermediate wall (10) being joined by internal radial ribs (11) perpendicular to the internal wall (8) whose plane passes through the main axis (Γ), such that at the intermediate wall (10) first joining nodes (12) are defined between the intermediate wall (10) and radial ribs (11); the intermediate wall (10) and the external wall (9) being joined by reticular ribs (14 and 15) whose cross-section according to a plane perpendicular to the main axis (Γ) is a reticular structure (13), such that first reticular ribs (14) extend from the first joining nodes (12) perpendicularly to the external wall (9), and second reticular ribs (15) extend obliquely with respect to the first reticular ribs (14) from first joining nodes (12) to the external wall (9), second joining nodes (16) being defined on the external wall (9) where the external wall (9) and pairs of second reticular ribs (15) converge; wherein the walls and ribs are made of concrete; the housing being a housing for fitting therein the foot of the tower by inserting grout between the foot of the tower and the housing.

2. The structure according to claim 1, comprising n identical bodies (3), each body being delimited by: at least two joining walls (19) made up of an internal radial rib and a first reticular rib, the joining walls (19) being intended to be attached to joining walls (19) of the adjoining bodies (3), said two radial walls forming an angle α=360/n; and a central wall (8bis), so that the central walls (8bis) make up the nth fraction of the internal wall (8); an external wall (9bis) joining means between adjoining bodies (3), preferably bolts and grout.

3. The structure according to any of the preceding claim 1, wherein the reticular structure is of the Warren type with uprights.

4. The structure according to claim 1, wherein the angle between pairs of second reticular ribs (15) is 60°, so that a mesh of equilateral triangles (13 and 20) divided by the first reticular ribs (14) is configured.

5. The structure according to claim 1, wherein the distance (A) between each pair of second nodes (16) is comprised between 6 and 14 metres, and wherein the sides of the structure (2) measure from 1 to 10 times said distance (A).

6. The structure according to claim 1, wherein the following are defined: internal cells (17) which are those formed by at least one internal wall section, two radial ribs (11) and one intermediate wall section (10); and peripheral cells (18) are all the other cells that are not internal.

7. The structure according to claim 6, wherein some peripheral cells are capable of rising above the deck of the base, forming towers (55).

8. The structure according to claim 6, wherein the set of internal cells (17) is provided with a hydraulic communication system therebetween, including devices for emptying and filling which allow the level to be regulated, both for the anchoring thereof and for refloating.

9. The structure according to claim 1, wherein each body is closed at the lower portion thereof by a lower plate (4) perpendicular to the main axis (Γ), the structure (2) comprising an upper plate (6) provided with an opening (50) for the foot of the tower (1), the upper plate covering at least one body (3).

10. The structure according to claim 6, wherein some of the internal cells (17) comprise upper openings (51) and lower openings (52), so that they form a pneumatic damping system that allows for the shifting of the level of the internal cells (17) with respect to sea level, by means of limiting the inlet and outlet of air from the same.

11. The structure according to claim 1, wherein the housing (7) is cylindrical.

12. The structure according to claim 9, wherein the lower plates (4) protrude laterally from the respective external walls (9), so that damping tabs (53) are configured.

13. The structure according to claim 1, wherein the plates are made of concrete.

14. (canceled)

15. The structure according to claim 1, wherein the platform has a circular layout, with perimeter triangles similar to equilateral triangles, with the external and internal sides in the shape of an arc of a circle.

16. The structure according to claim 1, wherein three additional smaller circular cells are arranged, evenly distributed and located at uniform intervals with respect to the central circular cell and therebetween, to be able to house other supports of the superstructure.

17. A method for constructing a structure according to claim 6 by means of a floating dock, consisting of the following phases: Construction of a floating dock with sufficient dimensions to construct the platform; Placement of the reinforcement of the lower plate and concreting on the base of the floating dock; Placement of sliding formwork for the construction of the vertical facings; Concreting of the facings until the structure has sufficient buoyancy to have a safe freeboard to continue concreting outside the caisson plant; Ballasting of the caisson plant until the caisson is released and moored to the pier to continue concreting while floating; Once the entire strut of the structure has been concreted, the sliding formwork is removed, the pre-plates are placed, and the upper plate is concreted.

18. The method for constructing a structure according to claims 2, 6 and 7 by means of a floating dock, consisting of the following phases: Construction of the caissons on the floating dock; Preparation of the structure for subsequent assembly thereof; Creation of recesses for indicating the positioning of the possible perforations to be made for the insertion of pins; Insertion of cables in the sheaths that will be used to bring the caissons closer together; Arrangement of waterproof joints (23); Arrangement of gates (26) in the gaps of the lower plate; Assembly of a structure made up of three pieces, consisting of the following phases: Straightening of the caissons before joining them (to keep them in a horizontal position); Approaching with tugboats to the joining position thereof; Final approach and connection by means of cables previously inserted in the sheaths of the ends; Regularisation grouting (27) of the chambers located between caissons; Drilling in the cutouts that were arranged (22) and insertion of pins (28) in the holes made; Concreting of a circular lower plate (29); Installation of internal pipes for filling and emptying cells (30); Positioning of pre-plates (31) in the upper portion of the caisson and placement of reserves for passage of air outlet pipes (32) and ballast water (33); Placement of anchors for mooring lines (34); Concreting of the upper plate (35).

19. A method for assembling a wind turbine shaft on a structure according to claim 1, consisting of the following phases: Insertion of the superstructure (wind tower) (36) into the central gap that has been formed; Grouting of the space that remains between both (37).

20. A method for commissioning a structure according to claim 1 consisting of the following phases: Towing and positioning of the platform by means of three tugboats; Ballasting with water through the installed pumps; The central cells are filled until the internal water level is equal to sea level; Optionally: The lower gates are opened, joining the central cells with the sea; The upper air outlet required to achieve pneumatic damping adapted to the waves is adjusted; The cells located at the vertices of the base (44) are slightly filled for the operation of the variable ballast system that is carried out by the pipes (41); Connection of previously pre-installed mooring lines; Electric connection.

21. A method for uninstalling a structure according to claim 1 consisting of the following phases: Fixing of the platform by means of three tugboats. Electrical disconnection and fixation for subsequent use. Disconnection of mooring lines and fixation for subsequent use. Closing of the gaps in the lower plate. Emptying of the ballast water from the cells by means of the installed pumps, or by means of the injection of compressed air, which causes the structure to refloat. Towing of the structure to port.

22. (canceled)

23. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] FIG. 1a shows a perspective view of the structure according to the present invention, consisting of a single caisson. The following list includes the essential elements of the piece: [0090] 1. Superstructure (usually wind tower) [0091] 2. Base [0092] 3. Structure that makes up the base (caisson) [0093] 4. Lower plate of the caisson [0094] 5. Facings of the caisson [0095] 6. Upper plate [0096] 7. Housing for fitting therein the foot of the tower

[0097] FIG. 1b shows a perspective view of the structure according to the present invention, with the same essential elements except that the base is made up of three caissons instead of one.

[0098] FIG. 2a shows a plan view of the invention made up of a single caisson where the proposed structural system and the distribution of the loads transmitted by the wind turbine are shown. It is made up of the following elements: [0099] 8. Internal wall [0100] 9. External wall [0101] 10. Intermediate wall [0102] 11. Radial ribs [0103] 12. First joining nodes [0104] 13. Reticular structure [0105] 14. First reticular ribs [0106] 15. Second reticular ribs [0107] 16. Second joining nodes [0108] 17. Internal cells [0109] 18. External cells

[0110] FIG. 2b shows a plan view of the invention made up of three caissons where the proposed structural system and the distribution of the loads transmitted by the wind turbine are shown. It is made up of the same elements, except: [0111] 19. Joining walls between caissons [0112] 20. Reticular structure of each caisson [0113] 8bis. Central wall section [0114] 9bis. External wall section [0115] 10bis. Intermediate wall section

[0116] FIG. 3a shows a plan view of the invention made up of a single hexagonal caisson where the proposed structural system and the distribution of the loads transmitted by the wind turbine are shown. It is made up of the same elements as FIG. 2a.

[0117] FIG. 3b shows a plan view of the invention made up of three caissons that form a hexagonal base and where the proposed structural system and the distribution of the loads transmitted by the wind turbine are shown. It is made up of the same elements as FIG. 2b.

[0118] FIG. 4a shows a cross-sectional view of the invention where the modulation of the structure is shown, and a chamfered triangular base with three sides of 7 A and another 3 sides of A in length is represented.

[0119] FIG. 4b shows a plan view of the invention where the modulation of the structure is shown, and a chamfered triangular base with three sides of 7 A and another 3 sides of A in length is represented. The arrangement of the three highly rigid radial walls has been indicated, which, in the case of being made up of three caissons, are the double joining walls 54.

[0120] FIG. 5 shows a plan and cross-sectional view of the invention where the modulation of the structure is shown, and a hexagonal base with six sides of 3 A in length is represented.

[0121] FIG. 6 shows a perspective view indicating the external cells that can be increased to form towers 55.

[0122] FIG. 7 shows a bottom perspective view of the platform, in both configurations where the following elements stand out: [0123] 50. Opening in the upper plate to insert the foot of the tower [0124] 51. Openings in the upper plate located in the centre of the central cells [0125] 52. Openings in the lower plate of the single caisson or the three caissons, located in the centre of the central cells [0126] 53. Shock-absorbing tabs formed by the extension of the lower plate

[0127] FIG. 8 shows a plan view of an alternative of the invention with a circular shape of 6 A in diameter where the modulation of the structure is shown.

[0128] FIG. 9 shows a plan view of an alternative of the invention with a chamfered square shape of sides measuring 5 A where the modulation of the structure is shown.

[0129] FIG. 10 shows a plan view of the base configuration of the invention with three added circular cells 56 that are used to support buildings, substations or other installations that require more supports.

[0130] FIG. 11a shows a perspective view of a “caisson plant” floating dock constructed expressly for the construction of the platform in one piece.

[0131] FIG. 11b shows a perspective view of the construction of the platform in one piece, which, already having sufficient freeboard, is freed from the already submerged floating dock.

[0132] FIG. 11c shows a perspective view of the construction of the platform in single floating piece, where concreting continues on the sliding formwork.

[0133] FIG. 12 shows a perspective view of the construction of the platform in three pieces by means of a “caisson plant” floating dock with one of the three pieces already finished that is floating.

[0134] FIG. 13 shows a perspective view of one of the caissons that make up the structure, prepared for connection thereof. It consists of the following components: [0135] 21. Embedded sheaths for the joining cables [0136] 22. Side holes [0137] 23. Waterproof joints that dampen and make the connection between caissons watertight [0138] 24. Reinforcement bars

[0139] FIG. 14 shows a perspective view of the three sectioned and unsectioned caissons that are already joined, indicating the arrangement of hollow, preferably steel cylinders 25, and that of the corresponding closure 26 thereof, which can be of any type such as covers, gates, butterfly valves or the like.

[0140] FIG. 15 shows a perspective view of the joining process of the three caissons, where three tugboats are shown approaching the caissons while pulling the cables previously inserted in the sheaths of the ends.

[0141] FIG. 16 shows a perspective view of the regularisation grouting 27 that is carried out in the chambers located between caissons that are formed with the previously installed waterproof bands.

[0142] FIG. 17 shows a schematic perspective view of the insertion of the pins 28 into the holes of the joining walls.

[0143] FIG. 18 shows a perspective view of the three joined caissons, where the concreting area of the circular lower plate 29 stands out.

[0144] FIG. 19 shows a perspective view of the three joined caissons, where the internal pipes to be installed for filling and emptying cells 30 are located.

[0145] FIG. 20 shows a perspective view of the complete base where the following elements are represented: [0146] 31. Pre-plates for the upper portion of the caisson for subsequent concreting thereof [0147] 32. Air outlet pipes and valves [0148] 33. Ballast water pipes [0149] 34. Anchors for mooring lines [0150] 35. Concreting of the upper plate

[0151] FIG. 21 shows a perspective view showing how the superstructure (wind tower) (36) is installed in the central gap that has been formed.

[0152] FIG. 22 shows a perspective view where the grouting of the space left between the central circular cell and the shaft of the superstructure 37 is shown.

[0153] FIG. 23 shows a perspective view where the ballast system that is made up of the following elements is shown: [0154] 38. External water intake [0155] 39. Distribution ring [0156] 30. Pipes with valves for cell ballast [0157] 40. Pumps [0158] 41. Pipes for the active ballast system [0159] 42. Adjustable air outlet [0160] 43. Sliding gates for lower water connection

[0161] FIG. 24 shows a cross-sectional view showing the ballast system where the gates of the lower gaps are closed.

[0162] FIG. 25 shows a cross-sectional view showing the ballast system where the gates of the lower gaps are open, when the level of the central cells coincides with the outside.

[0163] FIG. 26a shows a perspective view showing the pneumatic damping system where the configuration of the internal cells is reflected when the platform is on the crest of the wave.

[0164] FIG. 26b shows a perspective view showing the pneumatic damping system where the configuration of the internal cells is reflected when the platform is in the valley of the wave.

[0165] FIG. 27 shows a perspective view where the decrease in the movement of the platform (dotted line) with respect to the profile of the wave (grey area) is represented.

[0166] FIG. 28 shows a perspective view where the platform is represented in service state.

[0167] FIG. 29 shows a plan and cross-sectional view where the location of the cells used for the variable ballast system 44 is represented.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A. Description of the Structure

[0168] The invention is a floating structure for the implementation of buildings, installations and wind turbines in the marine environment, which is distinguished by the two main features that follow: [0169] A structural system, easy to manufacture, totally safe, highly resistant, with very low bending stresses, low fatigue and great durability. [0170] A special hydrodynamic operation that captures a large mass of surrounding water, and which translates into optimal behaviour for wind energy production.

[0171] It consists of a base 2 formed by one concrete structure (FIG. 1a) or three concrete structures (FIG. 1b) in a prismatic shape, also called “caissons” made up of external vertical facings and an internal pattern of vertical facings that form cells 5 which are closed at the bottom 4 and at the top 6 by plates and which are constructed using floating docks (“caisson plants”), a widely used and proven methodology in the implementation of docks and piers. The caisson plant construction allows for quick and easy implementation of the structure and also leaves it afloat at the end of the process.

[0172] The caissons constructed in this way are closed around the entire perimeter thereof, are monolithic, have great resistance individually and float stably with reduced draught.

[0173] Any person skilled in port constructions is knowledgeable about what the structures of this type are like and how they are constructed, which usually have regularly arranged rectangular or circular internal cells. Nevertheless, the present invention includes a specific design for the use to which it will be subjected, which notably improves the operating properties, resistance and durability thereof.

[0174] One of the greatest structural problems when defining floating concrete platforms that support powerful wind turbines is distributing the great forces transmitted without concentrating the stresses at any point of the base, where the reinforcement would have to be greatly increased, and where a point with a high risk of fatigue and cracking would be established.

[0175] Instead of proposing a joining of the tower to the upper plate by means of a series of connection bolts (as is usually done), which would concentrate stresses in the area, the invention proposes completely inserting the shaft of the wind turbine 1 into the central cell 7 up to the lower plate of the platform 4 (FIG. 1a). It therefore consists of transmitting the forces produced by the wind exerted by the shaft of the wind turbine to the walls of the central cell, directly to very large radial screens 11 (FIG. 2a), which in turn are distributed over a very resistant perimeter formed by a mesh of smaller screens that form a grid of equilateral triangles 13. In this way, no part of the structure is over-stressed, which means safety and durability.

[0176] To do this, the invention, in the preferred configuration thereof, consists of a base that has a 6-sided polygonal layout, both regular and irregular, and the cells formed by the internal vertical facings have the following features: [0177] The perimeter of the base is made up of a mesh of equilateral triangles 15 and those that have a side on the outside of the base are divided by another vertical facing perpendicular to the midpoint 14 thereof. [0178] In the centre of the base there is a large circular cell 8 that will allow it to support the forces transmitted by the superstructure (mainly it will be a wind turbine). [0179] By connecting the two areas described above, radial facings 11 are arranged which connect the central cell with each of the internal vertices of the triangles on the perimeter.

[0180] FIGS. 2a and 2b show the essence of the proposed structural system, where the loads are distributed in a branched manner throughout the structure, without there being any node that is not branched. It is made up of the following elements: [0181] an internal wall 8 that defines the housing for fitting therein the foot of the tower [0182] an external wall 9 that defines the outer perimeter of the body [0183] an intermediate wall 10 arranged between the internal wall and the external wall [0184] internal radial ribs 11 that join the internal wall with the intermediate wall in the [0185] first joining nodes 12 [0186] primary reticular ribs 14 that perpendicularly join the first joining nodes with the external wall [0187] secondary reticular ribs 15 that obliquely join the first joining nodes with the external wall in the [0188] second joining nodes 16, the distance A that modulates the structure (FIG. 4b and FIG. 5) being the distance between them.

[0189] FIGS. 2b and 3b show the essence of the system in the invention consisting of three caissons. It is made up of the same elements, except: [0190] joining walls 19 intended to attach the caissons [0191] a central wall section (8bis) [0192] an external wall section (9bis) and [0193] an intermediate wall section (10bis)

[0194] In both cases, the internal wall 8 constitutes a housing for the foot of the tower 7, which in the preferred configuration will be cylindrical because it is what is needed to support wind turbines, but in general it can have any other polygonal-based prism shape to house other types of supports for other types of installations or buildings.

[0195] The previously described walls and ribbing configure cells that can be classified as internal and peripheral: [0196] The internal cells 17 are those formed by at least one internal wall section, two radial ribs and one intermediate wall section. [0197] The peripheral cells 18 are all the other cells that are not internal and are generally configured by an external wall section, first or second reticular ribs and an intermediate wall section.

[0198] The mesh of equilateral triangles on the perimeter forms a highly resistant closure of the platform. It also constitutes a double safety hull, such that any water leak that could be produced by an accidental impact would flood only a very small cell, without any repercussions for the whole.

[0199] As can also be seen, this system is in turn optimal for now transmitting the forces of the waves and currents towards the interior of the structure, resisting them without concentrations. The external spans of said mesh are of the order of 4 m with thicknesses of at least 50 cm, much smaller than the external spans of the rest of the existing concrete platforms, which are usually 8 m or more with thicknesses of around 40 cm. This significant difference translates into much lower bending stresses, more resistance and less reinforcement.

[0200] It could be argued that this feature is not an advantage because other platforms could do the same thing by simply introducing more facings and increasing thicknesses. But this being the case, it is not carried out in the other solutions because the weight would increase them so much that they would lose stability and all other naval properties.

[0201] This means that it is possible thanks to the proposed branched configuration and because the overall design of volumes and weights of the invention allows it.

[0202] The perimeter of the base formed by the mesh of equilateral triangles forms a 6-modulated side polygon with the parameter “A”, which is the distance between each pair of consecutive secondary nodes: [0203] If three sides have length A and the other three have nA, the result is a chamfered triangle like the one in FIG. 4b. [0204] If the 6 sides are equal with length nA, it is a regular hexagon like the one in FIG. 5.

[0205] Any other configuration of sides is possible, provided that the aforementioned structure is maintained. As a reference, it can be indicated that the module A can vary between 6 and 14 metres, and the sides of the base from 1 to 10 times A.

[0206] Another important aspect of the design of the structure to achieve exceptional resistance to the large actions to which it will be subjected with a low-stressed structure is the arrangement of three highly rigid radial walls 54 (FIG. 4b), which join the vertices with the central core.

[0207] This platform, as described, can be made up of one or three pieces. In the latter case, the joining walls thereof will be precisely the three large radial walls 54 (FIG. 4b). This accomplishes three things: [0208] That the double wall is a large wall with a “bracing” thickness of at least 1 m and with an exceptional rigidity to the structure, minimising the fatigue thereof. [0209] That there is a large contact surface between the caissons to achieve perfect monolithism in the joining [0210] That the mooring system can be attached to it and therefore distributed without affecting the rest of the structure (FIG. 22)

[0211] For the special hydrodynamic operation that captures a large mass of surrounding water, a series of perforations have been made in the lower plate, in the middle of the central cells 25 (FIG. 14) and pressure control valves in the upper plate 42 (FIG. 23).

[0212] As already indicated, almost all existing platforms have heave plates, because it is an effective system for trapping as much water as possible and thus optimising the operation thereof, but it is only used locally in the towers and on the perimeter of the bases. Precisely one of the strengths of the invention is the design of the platform as a gigantic heave plate that traps a large lower mass of water and also a large upper mass that is everything that enters the central cells and the path of the perimeter plate.

[0213] Moreover, the opening of the lower gaps in the central cells entails an increase of approximately one metre in the metacentric height of the platform (from 8.50 to 9.47 m), and when external water enters, the floating surface decreases. All of this translates into greater stability and optimal behaviour for wind energy production.

[0214] Additionally, it can incorporate an optional system, the pneumatic damping system, which enables the behaviour of the platform to be further improved, which is of great interest in very powerful seas:

[0215] The pneumatic damping system consists of shifting the level of the internal cells with respect to sea level by limiting their air inlet and outlet thereof through the passive or automated activation of the pressure control valves 42 (FIG. 23).

[0216] a) When the platform is on the crest of the wave (FIG. 26a), the central cells have a low level, because the limitation on the outlet of air inside it has slowed down the filling thereof. This implies a significant decrease in the elevation of the structure and therefore in the accelerations.

[0217] Over time, the central cells continue to fill, but out of phase with the wave.

[0218] b) When the platform is in the valley of the wave (FIG. 26b), the central cells have already been filled and have hardly been able to begin emptying because the inlet of the air has been impeded. This implies a significant decrease in the descent of the structure.

[0219] The inlet and outlet of air, depending on the wave conditions, can remain constant or can be regulated by a control system that optimises the operation thereof.

[0220] FIG. 27 shows the decrease in platform movement (dotted line) with respect to the wave profile (grey area).

[0221] The invention can present other configurations that, although with very similar properties, will allow it to adapt to very different scenarios and technical means of construction: [0222] Some peripheral cells are capable of rising above the deck of the base, forming towers that further increase stability. They will not always be necessary because with the base configuration all the required standards are amply covered, and it has the drawback of lacking a large useful deck for maintenance since in this case only the towers would emerge. However, the structural solution and water trapping work in the same way, and even the volume of water displaced can be greater, and therefore with lower accelerations.

[0223] FIG. 6 shows how the perimeter mesh of triangles allows for the construction of the towers 55. As already indicated, the preferred construction has sliding formwork in caisson plants and the construction thereof would not have any complexity since it is only necessary to continue concreting the facings that correspond to said towers. [0224] The platform can also have a circular layout, with the same features previously defined, but with perimeter triangles similar to equilateral triangles, with the external and internal sides in the shape of an arc of a circle (FIG. 8). [0225] The platform can also have a square layout (with chamfered corners), with the same features previously defined, but in this case divided into four prismatically shaped concrete structures (caissons) instead of three, and the division will be made by the diagonals thereof (FIG. 9). [0226] The structure, in addition to having a central circular cell, can have another three smaller ones, regularly distributed and with the same features defined previously to be able to house other supports of the superstructure (FIG. 10). These supports will be necessary when the structure to be supported is not a wind turbine but a building, a substation or any other type of installation. [0227] Another option is that the structure, once it is towed by flotation to the service area, is completely ballasted with seawater to rest on the seabed. [0228] When it is not possible to have a caisson plant floating dock with sufficient dimensions for the construction of the platform, it can be constructed, using prefabricated elements or with sliding formwork, on a pier with a launching system or on a dry dock capable of housing the construction.

[0229] Some values that can be used to assess the naval stability and suitability thereof for energy production are: [0230] Initial metacentric height=9.47 m [0231] Displacement=29,734 t [0232] Restoring torque for 5°=24,541 t m [0233] Restoring torque for 10°=48,896 t m [0234] Restoring torque for 20°=63,333 t m [0235] Every 170 m3 of transferred water expand=7,000 t m

[0236] Taking into account that the horizontal force exerted by the wind at maximum energy production on the hub of a 10 MW DTU turbine is 150 t, this would entail a destabilising moment of 18,000 t m, which can give us an idea of the small inclinations that the platform will undergo, and therefore the great energy production.

B. Description of the Construction, Assembly and Commissioning Method

[0237] The proposed construction system consists of two methods:

Method 1: “One Piece Construction”.

[0238] When it comes to large productions for wind farms of around 700-1000 MW, where the initial investment in constructing the infrastructure is divided into many units, the construction of a special caisson plant floating dock, with these unusual dimensions for the joint construction of the entire platform, is profitable.

Method 2: “Construction from Three Pieces”

[0239] When it comes to constructing a few units such as a prototype or nearshore power supply installations for ports or industries, and the investment in a very expensive caisson plant dock is not justifiable, it can be built in three pieces using existing caissons of smaller dimensions.

Method 1

[0240] The first method, used for mass production, consists of four blocks:

1. Construction of the structure in one piece
2. Assembly of the supporting superstructure (usually a wind turbine).
3. Commissioning suited to the conditions of implementation.
4. Disconnection and refloating for maintenance or dismantling.

1. Construction of the Structure in One Piece

[0241] When the construction volume justifies it, a floating dock of the necessary dimension for the construction of the platform will be previously constructed.

[0242] Said floating dock will preferably have a platform-like shape, somewhat larger in layout to save material, but it can also be made rectangular by joining existing pontoons. On the faces that are needed, guides would be fixed to the seabed which stabilise the dock when it is ballasted with water to release the structure (FIG. 11a). It can also be stabilised by flotation using submersible towers arranged in the corners.

[0243] The construction is carried out in the following phases: [0244] Placement of the reinforcement of the lower plate and concreting [0245] Placement of sliding formwork for the construction of vertical facings [0246] Concreting of the facings until the structure has sufficient buoyancy to have a safe freeboard to continue concreting outside the caisson plant [0247] Ballasting of the caisson plant until the caisson is released and moored to the pier to continue concreting while floating (FIG. 11b) [0248] Concreting while floating using sliding formwork for the rest of the structure (FIG. 11c) [0249] Once the entire strut of the structure has been concreted, the sliding formwork is removed, the pre-plates are placed, and the upper plate is concreted

[0250] This system allows for very efficient construction, being able to carry out this process in a single week, leaving the completely finished structure already floating.

2. Assembly of the Supporting Superstructure (Usually a Wind Turbine).

[0251] For the installation of the wind tower, substation or building that supports the platform, the following steps are followed: [0252] Insertion of the superstructure (wind tower) 36 into the central gap that has been formed (FIG. 21). This is an important innovation, since it involves replacing the usual joining of the tower that is usually carried out by means of a large flange that is screwed to a bolt cage embedded in the walls of the platform. This joining is highly complex, requiring great construction precision, and moreover, it entails a significant concentration of stresses in the area. On the other hand, this solution is extremely simple, requires much less restrictive tolerances, and distributes the loads without concentrations. [0253] Grouting of the space that remains between both 37 (FIG. 22). This step, which is similar to the one usually carried out for joining monopiles and the transition piece but is now used in joining the shaft with the platform, allows for integral joining between both elements.

3. Commissioning

[0254] The process consists of the following phases: [0255] Towing and positioning of the platform by means of three tugboats. The platform is moved with one or two conventional tugboats that pull it, and a third one that remains in the back to avoid possible side drifts that may occur during displacement. Subsequently, the same three tugboats will allow coupling to the previously installed moorings and positioning the platform in the service location thereof. [0256] Ballasting with water through the installed pumps

[0257] The ballast system will vary depending on the type and shape of the maritime structure in question, but it will always be made up of elements similar to those shown in FIG. 23:

[0258] External water intake 38

[0259] Distribution ring 39

[0260] Pipes with valves for cell ballast 30

[0261] Pumps 40

[0262] Pipes for the active ballast system 41

[0263] Adjustable air outlet 42

[0264] Sliding gates for lower water connection 43

[0265] Ballasting is carried out by introducing water from the outside by means of pumps 40 from the intake 38, and by means of the distribution ring 39 and the pipes with valves 30; the central cells are filled so that when the pressure is the same as the outside, the gaps arranged in the lower plate can be easily opened by means of sliding gates or the like 43 (FIG. 23).

[0266] The commissioning method is as follows: [0267] The central cells are filled until the internal water level is equal to sea level. [0268] The lower gates are opened, connecting the central cells with the sea. There is another possible configuration of the invention, where the central cells are not connected to the outside, such that the platform would not have gaps in the lower plate and therefore this point and the next would be omitted. [0269] The upper air outlet required to achieve pneumatic damping adapted to the waves is adjusted. [0270] The cells located at the vertices of the base 44 (FIG. 29) are slightly filled for the operation of the variable ballast system that is carried out by the pipes 41 (FIG. 23). [0271] Connection (plug and play) of the previously pre-installed mooring lines. One of the most important features of the invention is its ease of commissioning and removal since it is only ballasted with seawater. Moreover, the mooring lines can be easily connected and disconnected with the help of conventional tugboats alone. This allows the platform to be brought back to port whenever necessary. [0272] Electrical connection (plug and play). In the same way, the power line can be connected and disconnected by means of submarine electrical connection hubs that are also pre-installed to enable the uncoupling thereof.

4. Disconnection for Maintenance or Dismantling

[0273] The process consists of the following phases: [0274] Fixing of the platform by means of three tugboats. [0275] Electrical disconnection and fixation for subsequent use. [0276] Disconnection of mooring lines and fixation for subsequent use. [0277] Closing of the gaps in the lower plate. [0278] Emptying of the ballast water from the cells by means of the installed pumps, or by means of the injection of compressed air, which causes the structure to refloat. [0279] Towing of the structure to port.

Method 2

[0280] The second method, which allows for a few units to be produced, is a process similar to the previous one, with the difference that the base is constructed from three separate pieces that are subsequently connected monolithically by the concreting of the upper plate and a portion of the lower plate, also, if necessary, by means of joining bolts.

[0281] This method requires three specific processes:

1. Construction of the elements that make up the structure
2. Preparation of the structure for the subsequent assembly thereof
3. Assembly of the previous elements

[0282] The assembly of the superstructure (wind turbine), commissioning and disconnection would be identical to method 1.

1. Construction of the Elements that Make Up the Structure

[0283] As described above, the greatest difficulty encountered when constructing any of the existing platforms that have to support buildings, installations or 12 or 15 MW wind turbines is that they have enormous dimensions (around 50 m in diameter) and major actions to support.

[0284] Specialised shipyards and ports currently have means that could serve these purposes, such as: [0285] Syncrolift and launching ramps: they would allow the platform to be built on the pier and transported with a rail system, spmt trailers or very large cranes to the launch area, where they could be floated. It is a complex construction system, but it is the one proposed by several existing solutions. The fact is that none of these means are constructed with a beam of 50 m which is what would be required. [0286] Dry docks: in principle it is the simplest system to solve the problem, but currently there are very few dry docks that have the required dimensions. It would therefore be necessary to carry out a large excavation in a port area and provide a series of gates and waterproofing that would entail a high extra cost.

[0287] In any case, these means are very scarce and expensive, creating a bottleneck when it comes to meeting deadlines in large implementations.

[0288] For the manufacture thereof, it is therefore currently necessary to previously construct specific installations that allow the work to be carried out and allow for a transport and flotation system with a very high tonnage. This leads to repercussions on the cost of each unit, which could be compensated for in large wind farms, but never when it comes to manufacturing few platforms.

[0289] As explained, for concrete solutions, an ideal form of construction would be under the port caisson construction technique (using a “caisson plant”), but there exists the significant problem of not “fitting” in any of the existing floating docks.

[0290] For this reason, the present invention proposes breaking down the platform into several elements that are watertight, resistant and self-supporting, and which could be constructed in the numerous transferable floating docks existing for the construction of caissons.

[0291] For the construction of the previously defined caissons, the port caisson system will be used via the use of a floating dock. The construction may also be carried out both in dry dock or on a platform on the pier that will be subsequently floated, but in all cases the concreting would be carried out using the sliding formwork system (it could be constructed with prefabricated flat pieces and subsequently concreting the joints, but only if no other means are available).

[0292] The “caisson plant” floating dock has a perfectly designed infrastructure, which raises the formwork by means of a system of hydraulic jacks, such that it has the great advantage of being able to place the concrete in the formwork in small layers, in addition to being able to compact it and ensure the joining thereof with the previous layer under perfect conditions, removing the concreting joints. Moreover, once the caisson has been constructed, it floats in a stable way (FIG. 12), which is a very important operational advantage.

[0293] This entails great robustness and monolithism in the constructed structure, which makes it ideal for withstanding the pounding of waves and wind, as well as great resistance to accidental impacts from ships or icebergs. On the other hand, in the floating concrete platform solutions that are currently being designed on the market, to achieve performance that is somewhat similar to that of the caisson plant, prefabricated elements are used whose joints are susceptible to failure, and therefore have a much lower resistance.

2. Preparation of the Structure for the Subsequent Assembly Thereof

[0294] Each of the modules that make up the structure must be prepared for subsequent connection therebetween. For this, the side holes 22 (FIG. 13) and embedded sheaths 21 necessary to introduce the cables that will join them monolithically must be left. The position and quantity of the sheaths and holes will depend in each case on the stresses due to the superstructure and the environmental conditions where it is located. The position of the side joining holes has been provided in the arrangement of the reinforcement, but only a recess of about 5 cm is left on the facing, which serves as an indication of the position thereof. Inside this cutout, a perforation will subsequently be made when the caissons are firmly joined by the cables located at the ends thereof, and the gap that remains between the facings has been completely filled with grout (a process that will be explained later). Finally, the pins will be introduced, achieving an integral joining.

[0295] In some cases, if necessary, inside the lower plate or a side wall, a series of sheaths can also be arranged that would be used to introduce post-tensioning cables.

[0296] On the internal edge of the lower plate and on the external bands of the joining area, as can be seen in FIG. 13, waterproof joints 23 are arranged which allow the joining between caissons to be sealed. In the upper portion of the caisson and in the lower circular area, the bars of the required reinforcements 24 will be left so that later, when the upper plate and the small circle of the lower plate are concreted, an integral joining between the caissons is produced.

[0297] In the lower plate, in the area below the central cells, circular openings of about two metres in diameter will be left, which will allow water to pass to the inside.

[0298] To do this, on the lower plate, before concreting, hollow, preferably steel cylinders 25 (FIG. 14) will be arranged which will sufficiently protrude from the upper face thereof so that some type of closure 26 that closes said passage of water can later be coupled.

[0299] This closure must withstand the hydrostatic pressure existing on the lower face, and this pressure will always be less than two bars, perfectly bearable with a sheet that is not very thick. This means that many different types of closures, covers, gates, butterfly valves, etc. can be used.

[0300] A simple solution is guillotine gates such as those represented in FIG. 14, which can be remotely actuated by small hydraulic jacks to simplify the operation thereof.

3. Caisson Assembly

[0301] The objective of the assembly method is to carry out the operations in a reliable and safe way, ensuring the stability of the structure at all times and guaranteeing the robustness and monolithism of the resulting structure.

[0302] The process consists of the following phases: [0303] Straightening of the caissons before joining them (to keep them in a horizontal position). It consists of filling some cells of the caisson with a certain small amount of water so that it floats perfectly horizontal. [0304] Approaching with tugboats to the joining position thereof. Each caisson is moored to a tugboat that will position them until they are a short distance from each other, facing the facings where they will be joined. At this time, some cables are inserted through the sheaths located at the ends in such a way that when they are pulled from each of the tugboats, they are brought closer together (FIG. 15). [0305] Final approach and connection by tensioning the cables. When the caissons are already in the joining position thereof, they are tightened successively by means of jacks before being cut and disconnected from the tugs. [0306] Regularisation grouting 27 (FIG. 16) of the chambers located between caissons that are formed between the waterproof bands 23 (FIG. 13) that were installed on the side and lower edges of the facings to be joined. [0307] Drilling in the cutouts that were arranged 22 (FIG. 13) and insertion of pins 28 in the holes made (FIG. 17). Since the chamber that is formed between the caissons 27 is already completely filled with the grout, there will be no problem of water entering through the gaps and the support between caissons is perfectly regularised. [0308] Concreting of a circular lower plate 29 (FIG. 18). This step is very important since it entails the lower joining of the three caissons that will give great monolithism to the structure, and will serve as support for the wind turbine tower. In some cases, if necessary, this joining can be complemented with post-tensioning cables that further reinforce the joining of the lower plate and give it continuity. [0309] Installation of internal pipes for filling and emptying cells 30 (FIG. 19). They will allow for ballasting and deballasting with seawater for the commissioning thereof, as well as for water removal in emergencies. [0310] Positioning of pre-plates 31 in the upper portion of the caisson and placement of reserves for passage of air outlet pipes 32 and ballast water 33 (FIG. 20) [0311] Placement of anchors for mooring lines 34 (FIG. 20) [0312] Concreting of the upper plate 35 (FIG. 20). To do this, a perimeter formwork will be provided to cover the edge thereof, it being secured to the upper portion of the exterior facings. Another option is, in the caisson plant itself, to increase the external facings to the height of the edge of the plate so that they in turn serve as formwork for it.

Installation Example of a 10 MW Wind Turbine

[0313] For the installation of a 10 MW wind turbine, the preferred configuration would be made up of a polygonal base with 6 sides, 3 of 7 A in length and 3 of 1 A in length, which form a triangle truncated at the vertices and 20 m of strut with

TABLE-US-00001 the following features: Dimensions: 65.60 m length 56.80 m beam Dimensions of each caisson when 61.90 m length making it in three parts: 18.20 m beam Base height (H): 20.00 m Maximum external span (A/2): 4.10 m Thickness of external facings (E2): 0.50 m Thickness of internal facings (E1): 0.25 m Thickness of the lower plate (LI): 0.50 m Width of the heave plate (T): 2.20 m Thickness of the upper plate (LS): 0.80 m Weight of each caisson: 8,243 t Total weight of the structure: 28,460 t
Advantages Derived from the Invention

[0314] The proposed construction, assembly and commissioning method has great advantages over other systems that perform the same function:

1. The invention proposes a feasible solution in caisson plant floating docks that allows for quick and simple implementation of the structure in addition to leaving it afloat at the end of the process.
2. Being able to place concrete in the formwork in small layers, in addition to being able to compact it and ensure the joining thereof with the previous layer under perfect conditions, makes the caisson monolithic, without concrete joints. This makes it a structure that is highly resistant to the pounding of water and accidental impacts.
3. The manufacture of caisson plant structures is a highly tested technology with well-proven logistics. It is possible to manufacture 20,000 t parts in just 10 days. All this implies high quality implementation in record time.
4. Due to the easy construction, low cost and large dimensions and generated weight thereof, this construction system allows platforms to be built which support the largest wind turbines (10 MW, 12 MW or higher) that are currently being designed.
5. The superstructure (generally a wind tower) is not joined to the platform via a plate with bolts that supports all the torsion in that area, but rather it distributes it via a simple joining throughout the structure avoiding the concentration of stresses.
6. The external spans of the structure are of the order of four metres, with wall thicknesses of 50 cm, such the bending that can occur on the same is very small.
7. The force exerted by the mooring lines on the structure is directly absorbed and distributed by three large radial facings that stiffen the structure, without therefore affecting stresses on other facings. All this leads to a low reinforcement and minimisation of stresses.
8. Maintenance is almost zero due to low stresses and concentrations in a concrete that is hardly reinforced. Cracking is very low because, due to the structural type thereof, the concrete is mostly compressed, even where it is strained in other solutions. The useful life of the generated structure can exceed 50 years and could allow the wind turbine to be replaced after 20-25 years for another, more powerful one.
9. The structure is completely constructed and assembled in port, including the superstructure (usually a wind turbine), and it is moved by floating by means of conventional tugboats to the working position thereof. The low draught thereof allows it to be carried out in practically any conventional port close to implementation.
10. The anchoring process of the structure is carried out by exclusively ballasting the cells thereof with seawater, without the need for any additional means, or auxiliary vessels.
11. Due to the very large restoring torque thereof and therefore minimum operating inclination, the energy production of the turbine is guaranteed at full capacity at all times without reductions to carry out ballast transfer when the wind changes (as occurs with almost all other existing solutions).
12. All the installations subject to routine maintenance are located on the deck of the platform (there are no submerged equipment or metal structures), meaning the tasks are considerably simplified.
13. Since it is only ballasted with water, it enables easy emptying for transfer back to port and for more complex maintenance (onshore). In addition, it has a “plug and play” system for moorings and electrical connection, such that this process can be carried out with great agility.
14. The construction system using a caisson plant is the most environmentally friendly system for the construction of wind and port infrastructures, with a very notable decrease in polluting substances compared to traditional techniques. It is a foundation system that does not make noise which affects marine mammals and it can be carried out on practically all types of seabed without altering them. It requires a lower consumption of raw material resources which, depending on the features of each body, can lead to savings of 50%.
15. The low reinforcement that is required with the proposed method and the rapid implementation thereof represent a cost reduction of more than 50% compared to other similar metal structure.
16. The construction system used produces the same savings even when few units are produced, unlike current solutions that only produce savings in large productions since they require significant infrastructure whose cost has to be distributed among them.

[0315] In this text, the word “comprises” and its variants (such as “comprising”, etc.) should not be understood in an exclusive sense, i.e., they do not exclude the possibility of that which is described including other elements, steps, etc.

[0316] Moreover, the invention is not limited to the specific embodiments described herein, but rather encompasses, for example, the variations that a person skilled in the art could make, within the scope of what may be deduced from the claims.