Method and structure used in attaching a superstructure to a foundation pile

Abstract

A method for attaching a superstructure to an upper end of a foundation pile, the upper end having a truncated cone shape, the superstructure having an opening that fits over the upper end, and the opening having a truncated cone shaped outer peripheral surface that fits over the upper end, comprising: placing a guide structure including at least one inclined guide surface on the upper end, and then lowering the superstructure over the guide structure onto the upper end of the foundation pile.

Description

[Technical field]

[0001] The present invention relates to a method for attaching a superstructure to a foundation pile, to a method for attaching the superstructure to the upper end of the foundation pile and forming a slip joint between the upper end of the foundation pile and the superstructure, and further to a structure for use in such an attachment. [Background technology]

[0002] For example, in onshore and offshore constructions, slip joints are used to attach superstructures to foundation piles, such as monopiles driven into the ground or seabed. This usually means that a superstructure with a suitable attachment opening is slid onto the frusto-conical upper end of the pile. This opening has an inner surface shaped according to the frusto-conical upper end, so that the upper end can slide onto it and be pressed against it by the force of gravity. In this assembly, the superstructure is kept from slipping out by gravity and by friction between the outer surface of the upper end of the pile and the inner surface of the superstructure. This allows it to be kept from slipping out even in the case of high loads acting on the superstructure and the foundation, for example wave and / or wind loads. Such slip joints are known, for example, from WO2020 / 106146 or WO2018 / 070868.

[0003] Conventionally, when a superstructure is installed on the top of a foundation pile to form a slip joint, the superstructure is lifted by a crane to a position above the top of the foundation pile so that the opening of the superstructure can be lowered onto the top of the foundation pile. The opening is generally not much larger than the cross section of the top of the foundation pile to be fitted, as seen from above, so this operation has relatively high accuracy requirements. When installing a superstructure, such as a platform, the superstructure is suspended by a crane and is therefore susceptible to external forces such as wind. Furthermore, when the superstructure is an offshore structure that is installed using a lifting ship, the accuracy of lowering the structure onto the foundation pile also depends on the waves. That is, the installation of the superstructure is largely dependent on favorable weather conditions, such as no or limited wind and no or limited waves. This significantly limits the time frame in which such installation operations can be carried out, which can result in relatively long waiting times for personnel and equipment, making it very cost-inefficient. Therefore, the time period in which such projects can be carried out can also be limited to a relatively short period of time. Also, during such installation operations, sudden wind or wave events, for example, may occur that may cause sudden and uncontrollable movement of the suspended superstructure relative to the foundation piles, resulting in a collision, which may result in damage to the superstructure and / or the foundation piles.

[0004] In offshore installation operations, it is known to use installation platforms that are fixed to the seabed near the foundation piles to minimize wave effects, but this requires equipment and personnel, which is time consuming and costly, and the use of such platforms does not eliminate the effects of wind on the suspended superstructure. Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for improvements in methods and apparatus for attaching superstructures to foundation piles. [Means for solving the problem]

[0006] In one aspect of the disclosure, a method for attaching a superstructure to an upper end of a foundation pile is disclosed. The upper end has a frusto-conical shape, and the superstructure has an opening that fits over the upper end. In one aspect of the disclosure, a guide structure having at least one inclined guide surface is placed on the upper end. The superstructure is then lowered over the guide structure onto the upper end of the foundation pile. During the lowering of the superstructure onto the foundation pile, the guide surface of the guide structure can guide the superstructure, thereby reducing the effect of wind and / or waves on the positioning of the superstructure.

[0007] The opening preferably has an outer peripheral surface in the shape of a truncated cone that fits over the upper end of the foundation pile.

[0008] When using the method according to the present disclosure, lateral movement of the superstructure relative to the foundation pile is prevented or at least limited by the guide surfaces of the guide structure. As the superstructure is lowered further, the inclined guide surfaces further center the superstructure relative to the upper ends of the foundation piles, making positioning of the superstructure easier to achieve even in relatively high wind and / or wave conditions.

[0009] In the method according to the present disclosure, after the superstructure is attached, the guide structure is preferably removed from the foundation pile. The guide structure can be reused, for example, to attach another superstructure to another foundation pile. Furthermore, removing the guide structure allows the upper end of the foundation pile, in particular the upper surface of the upper end, to be attached another superstructure, such as, but not limited to, a tower of a wind turbine, for example as disclosed in WO 2020 / 106146.

[0010] The upper part of the guide structure usable in one aspect of the present disclosure has a cross section whose dimensions, in particular the diameter, increase along a downward direction, i.e., in the direction towards the foundation pile in use. The upper part is preferably substantially conical or frusto-conical. The lower part of such a guide structure usable in one aspect of the present disclosure is connected to the upper part, and the cross section of the lower part decreases as it moves away from the upper part. The lower part preferably has a substantially conical or frusto-conical configuration.

[0011] In a very preferred arrangement, a guide structure is used with an upper part having a conical or frusto-conical shape and a lower part also having a conical or frusto-conical shape, the upper and lower parts decreasing in cross section in opposite directions. The upper and lower parts in such an embodiment preferably abut at an interface plane. The upper part extends radially outward relative to the lower part to provide a support element. The support element supports the guide structure on the upper end of the foundation pile. The lower part fits into the open upper end of the foundation pile and the upper part extends upward from said end.

[0012] The guide structure according to such an embodiment has the advantage that it can center itself by lowering it towards the foundation pile. The lower part in such an embodiment preferably has a maximum cross-section at or near the interface plane between the upper and lower parts, said maximum cross-section being substantially equal to the inner cross-section of the open end of the foundation pile.

[0013] The method according to one aspect of the present disclosure is further characterized in that, at least in use, the guide structure and the superstructure are suspended from the support frame, preferably such that the guide structure is suspended so as to extend at least partially below the superstructure. According to such a method, the superstructure and the guide structure can be lifted together and lowered together to the foundation pile, thereby further reducing the time required for installation of the superstructure. In such a method, when suspended from the support frame, the guide structure preferably extends partially below the superstructure, so that the aforementioned portion of the guide structure is attached to the open end of the open end of the foundation pile, specifically entering the open end, before the superstructure moves above the upper end of the foundation pile.

[0014] In an embodiment of the method according to the present disclosure, the guide structure and the superstructure suspended from the support frame are raised to a position above the upper end of the foundation pile, such that the guide structure, particularly its lower portion, is suspended directly above the upper end of the foundation pile, particularly the open upper end of the foundation pile. The support frame is then lowered, and the guide structure is at least partially inserted into the open upper end of the foundation pile. The support frame is then further lowered, and the superstructure is lowered onto the outer surface of the upper end of the foundation pile to form a slip joint with the foundation pile. The superstructure is then removed from the support frame, and the support frame is again raised, and the guide structure is pulled away from the foundation pile.

[0015] The method of the present disclosure is particularly suited, but not limited to, for mounting a platform having an upper surface and a lower surface. An opening extends through the platform from the upper surface to the lower surface. In such a method, the guide structure can be easily suspended from a hanging element that passes through the opening. The hanging element is connected to a support frame that extends above the platform and the guide structure.

[0016] In embodiments according to the present disclosure, the guide structure may be a relatively open structure to allow most of the wind to pass through.

[0017] The present disclosure further relates to a new guide structure for use in attaching a superstructure to a foundation pile.

[0018] In one aspect of the disclosure, a guide structure has an upper portion and a lower portion, the upper portion including or forming a guide surface and the lower portion designed to engage an upper end of a foundation pile, wherein, in use, the lower portion allows centering of the guide structure relative to the upper end of the foundation pile and the guide surface extends above the upper end of the foundation pile to guide the upper structure during lowering of the upper end of the foundation pile.

[0019] The present disclosure further relates to an assembly of a guide structure and an upper structure according to the present disclosure, the assembly further comprising a support frame, the upper structure and the guide structure being supported by and preferably suspended from the support frame.

[0020] The disclosure further relates to a foundation pile for supporting at least one superstructure, in particular a monopile for mounting at least a platform by means of a slip joint, the upper end of which is provided with a removable guide structure, which guides the superstructure relative to the upper end when the superstructure is mounted. [Brief description of the drawings]

[0021] Methods, structures and assemblies according to embodiments of the present disclosure are described below with reference to the drawings, which are given by way of example only and should not be understood as limiting the scope of the present disclosure or protection in any way. The following examples are given to enhance the understanding of the present invention, but are not intended to be limiting. The drawings are as follows: [Figure 1] 1A-1D are schematic diagrams showing four steps of attaching a superstructure, shown as a platform by way of example, to foundation piles. [Diagram 2]1A-1D are schematic diagrams showing four steps of attaching a superstructure, shown as a platform by way of example, to foundation piles. [Diagram 3] 1A-1D are schematic diagrams showing four steps of attaching a superstructure, shown as a platform by way of example, to foundation piles. [Figure 4] 1A-1D are schematic diagrams showing four steps of attaching a superstructure, shown as a platform by way of example, to foundation piles. [Diagram 5] 4 is a partial cross-sectional view showing a schematic diagram of a guide structure attached to the upper end of a foundation pile. FIG. [Figure 6A] FIG. 2 is a schematic diagram showing a three-dimensional view of a guide structure. [Figure 6B] FIG. 2 is a schematic diagram showing in three dimensions a guide structure attached to the upper end of a foundation pile. [Figure 7] FIG. 1 is a schematic diagram showing a method cq for offshore application of an assembly according to the present disclosure. [Figure 8A] 1 is a schematic diagram showing a general configuration of an embodiment of a guide structure according to the present disclosure. [Figure 8B] 1 is a schematic diagram showing a general configuration of an embodiment of a guide structure according to the present disclosure. [Figure 8C] 1 is a schematic diagram showing a general configuration of an embodiment of a guide structure according to the present disclosure. [Figure 8D] 1 is a schematic diagram showing a general configuration of an embodiment of a guide structure according to the present disclosure. [Figure 9A] FIG. 13 is a schematic diagram illustrating a guide structure and a platform that utilizes the guide structure for alignment, according to one embodiment of the present disclosure. [Figure 9B] FIG. 13 is a schematic diagram illustrating a guide structure and a platform that utilizes the guide structure for alignment, according to one embodiment of the present disclosure. [Figure 9C] FIG. 13 is a schematic diagram illustrating a guide structure and a platform that utilizes the guide structure for alignment, according to one embodiment of the present disclosure. [Figure 9D]FIG. 13 is a schematic diagram illustrating a guide structure and a platform that utilizes the guide structure for alignment, according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In this specification, the same or similar components are given the same or similar reference numerals. Although different embodiments or portions thereof are shown, combinations of the embodiments of the methods and structures or portions thereof should also be considered as disclosed herein.

[0023] In this specification, an offshore structure is understood to include at least any structure driven into or placed on the bottom of a body of water. "Bottom of a body of water" includes but is not limited to the ocean floor. In the present disclosure, an offshore structure may be, for example, a wind turbine, a drilling rig, an electrical device such as a transformer, etc., and is preferably supported at least in part above the water level of the body of water in which it is located. An onshore structure is a structure that is identical or similar in structure but located on land.

[0024] A platform attached to or to be attached to a pile as disclosed herein is understood to mean at least, but not limited to, a platform that at least partially surrounds the pile. The platform is preferably combined with the pile to form a slip joint, but may alternatively be attached in other ways, for example bolted to the pile. The provision of such a platform provides a structure suitable for docking vessels for transferring people and / or products to and from the offshore structure, and / or for safe movement of people around the pile and / or tower or foot attached to the pile. In the present disclosure, the platform, when used with a tower also attached to the pile, is installed before fastening the tower to the pile, allowing personnel to enter the platform and engage in positioning and fastening operations, for example bolting the tower to the pile.

[0025] It is to be understood that the words "substantially" or "about" are used herein to mean that for a given value or aspect, some deviation is acceptable, for example, less than 20% deviation from a given value, e.g., less than 15%, less than 10%, or minimal deviation due to normal tolerances such as manufacturing tolerances.

[0026] Although embodiments are disclosed and described herein, it is to be understood that portions of those embodiments may be combined to form different embodiments.

[0027] In the present specification, the term "foundation pile" should be understood to mean at least a pile such as, for example, but not limited to, a monopile, which is known and used as a foundation pile for wind power generators, landing platforms, artificial islands, etc., installed on land or offshore. The foundation pile according to the present disclosure preferably has a truncated cone-shaped upper end with an open upper end. More preferably, the pile is a substantially hollow monopile, for example, mainly composed of metal and / or concrete. In the present specification, the term "slip joint" should be understood in a general sense. The slip joint can be formed directly between the inner surface of the opening of the superstructure and the outer surface of the foundation pile or the transition piece of the foundation pile. The slip joint may also be formed between the surfaces. At least one filler element is provided between the surfaces, for example, bonded to one of the surfaces, and the at least one filler element may be formed, for example, but not limited to, from a material that is more compressible than the material of the superstructure and the foundation pile, for example, a plastic material, for example, PU.

[0028] 1 to 4 show diagrammatically four steps of attaching a superstructure, shown as a platform 1, to an upper end 2 (sometimes called upper tip 2) of a foundation pile 3. The foundation pile 3 in this embodiment is shown as a monopile, formed as a generally hollow pile, made of metal, for example steel. The foundation pile 3 has an upper end 2 that is substantially frustoconical in shape, and therefore has an outer surface 4 that is frustoconical in shape. The outer surface 4 is inclined at an angle α to a longitudinal axis XX of the pile 3. The longitudinal axis XX preferably extends substantially vertically. In this embodiment, the upper surface 5 of the upper end 2 is provided with an edge 6 that extends substantially parallel to a lower portion 7 of the pile 3. This edge 6 is considered to form part of the upper end 2 and may be omitted, for example as shown diagrammatically in FIG. 5, or may extend radially inwards.

[0029] 1 and 2, the platform 1 is suspended from a support frame 8 by a series of first suspension elements 9. The first suspension elements 9 may be, for example, wires, ropes, chains, rods, etc. The suspension elements 9 may be flexible or relatively rigid elements. The suspension elements 9 are preferably sufficiently flexible or pliable so that the support frame 8 can be lowered further towards the piles 3 as the platform 1 is lowered onto the upper ends 2 of the piles 3. By way of example, the support frame 8 may be suspended from a crane by one or more suitable suspension elements 10 and may be raised and lowered by the crane C, as can be seen, for example, in FIG. 7.

[0030] The platform 1 has an opening 13 passing through it from the upper surface 1A to the lower surface 1B. The opening 13 has an inner peripheral surface 14, which in this embodiment has a frusto-conical shape. The inner peripheral surface 14 may mate with an outer surface 4 of the upper end 2 of the pile 3 to form a slip joint, as is known in the art.

[0031] Further referring to FIG. 1, a guide structure 11 is suspended from the support frame 8 by at least one second suspension element 12 in this embodiment, which extends through the opening 13. The guide structure 11 includes at least one inclined guide surface 15 inclined downwards and outwardly at an angle β to the longitudinal axis XX. In the embodiment shown in FIGS. 1 to 4, the guide structure 11 has an upper part 11A and a lower part 11B. The upper part 11A constitutes or forms the guide surface 15, while the lower part 11B is designed to engage the upper end 2 of the foundation pile 3. In use, the lower part 11B allows for centering of the guide structure 11 relative to the upper end 2 of the foundation pile 3, while the guide surface 15 extends above the upper end 2 of the foundation pile 3 to guide the platform 1 as it descends to the upper end 2 of the foundation pile 3.

[0032] The upper portion 11A is configured to increase in cross section towards the lower portion 11B, which in this embodiment is shown as a substantially conical or frusto-conical portion 11A. A The diameter D is a circle with a vertex angle twice the angle β. A is preferably configured to be continuously larger towards the lower portion 11B. The lower portion 11B is preferably configured to have a decreasing cross section moving away from the upper portion 11A, and in this embodiment is shown as a substantially conical or frusto-conical portion 11B. The lower portion 11B also has a cross section of diameter D B of circle with diameter D B decreases away from the upper portion 11A and is preferably continuously smaller. The lower portion 11B also has an inwardly and downwardly sloping outer surface 16 with an apex 17 facing downwards. The outer surface 16 is also a guide surface and forms an angle γ with the axis XX, the angle of the apex 17 being twice γ. The angle β, and preferably both angles β and γ, are greater than the angle α, so that the inclination of the outer surface 4 is at least greater than the inclination of the surface 15.

[0033] The interface between the upper portion 11A and the lower portion 11B is located at an interface plane 18, where the upper portion 11A extends radially outward from the lower portion 11B, and where an end 20 of the upper portion 11A at the interface plane 18 forms a support portion 19. In this embodiment, the support portion 19 is substantially ring-shaped and has a width W that is equal to or greater than the maximum diameter D of the upper portion 11A. A(max) to the maximum diameter D of the lower part 11B B(max) It is defined as the value minus

[0034] The guide structure 11 is suspended from the support frame 8. The top 21 is within or below the opening 13, with most or all of the guide structure below the underside 1B of the platform 1. The piles 3 are open at their upper faces 22. The edge 6 has a ring shape and has an inner diameter D in is the maximum outer diameter D of the lower part 11B of the guide structure 11 B(max) substantially the same as or slightly larger than the outer diameter D out is the maximum outer diameter D of the upper part 11A of the guide structure 11 A(max) It is preferable that the value is substantially the same as that of the

[0035] As can be seen in FIG. 2, the support frame 8 can be lowered towards the pile 3. By lowering, the lower part 11B of the guide structure 11 is lowered into the open top surface 22 of the pile until the support part 19 abuts against the edge 6 of the pile 3. During this delivery, the guide surface 16 abuts against the edge 6, or at least can abut against it, so that the guide structure is further lowered and centered inside the end 22. This means that if there is not a proper alignment between the guide structure 11 and the XX axis of the pile 3, for example because wind pushes the guide structure 11 sideways, waves affect the alignment, or even because the crane is not properly positioned, the guide surface 16 will force the guide structure 11 to be properly aligned, using gravity.

[0036] 2, when the guide structure 11 is properly lowered inside the pile 3, the support portion 19 rests on the edge 6 and the upper or first portion 11A extends upwardly from the upper end 2 of the pile 3. In this position, the platform is still suspended from the support frame 8 and is not fixed to the pile 3.

[0037] Further lowering of the support frame 8 also lowers the platform 1 further, and the opening 13 moves over the upper part 11A of the guide structure 11 to a position on the upper end 2 of the pile 3 as shown diagrammatically in FIG. 3. If the opening 13 of the platform 1 is not properly aligned with the XX axis of the pile 3, for example because wind pushes the platform 1 sideways, waves affect the alignment, or even because the crane is not properly positioned, the guide surface 15 forces the platform 1 to be properly aligned by using gravity. A part of the peripheral surface 14 of the opening 13 engages with the guide surface 15 of the upper part 11A, and gravity forces the platform 1 to be centered with respect to the guide structure 11, in particular its upper part 11A, and thus with respect to the pile 3. The guide structure 3 preferably remains attached to the support frame 8 by at least one suspension element 12 as shown in FIG. 3.

[0038] After the platform 1 is properly positioned on the upper end 2 of the pile 3 and a slip joint is formed, the first suspension element 9 is removed from the platform 1. The guide structure 11 can then be raised from the pile 3 by moving the support frame 8 upwards again, as shown in FIG. 4. The guide structure 3 can then be removed and used for other purposes, for example for mounting another superstructure, such as the platform 1, on another pile 3. The upper end of the pile, in particular its end face 22, can then be used for mounting another structure, such as but not limited to a wind turbine tower, on the pile 3 by means of bolting or another slip joint.

[0039] 9A to 9D show diagrammatically by way of example the forces acting on the guide structure 11 and the platform 1 when the guide structure is lowered onto the pile 3 and when the platform is lowered towards the pile 3. In FIG.

[0040] Figure 9A shows the platform 1 and guide structure 11 suspended from the support frame 8, with the centre line 24 of the guide structure 11 and the centre line 25 of the opening 13 in the platform 1 not aligned with the XX axis of the pile 3. Both centre lines are shown displaced to the right of the XX axis in Figures 9A to 9C. Figure 9A shows the position where the guide surface 16 of the lower part 11B is in contact with the inside of the edge 6. Gravity F acting on the guide structure 11 zw(11) As a result, when the support frame 8 is lowered in the direction M, the guide structure further descends, so that a reaction force F in As a result, the guide structure 11 moves toward the XX axis of the pile, and the center line 24 of the guide structure 11 and the XX axis coincide with each other.

[0041] From FIG. 9B it can be seen that the guide structure 11 is properly centered with respect to the XX axis and therefore with respect to the pile 3. According to FIG. 9B, the platform 1 is not properly aligned with respect to the XX axis and therefore with respect to the pile 3. In the figure, as an example, the center line 25 of the opening 13 has been displaced to the right of the XX axis. If the platform were to be lowered straight down from this position, as in the prior art, without the guide structure 11 as shown, the underside 1B of the platform 1 would hit the edge 6 of the pile and would not be able to be properly attached. In such a case, it would be necessary to apply an external force to the platform 1 to move it laterally, to the left in FIG. 9B, in order to move the opening 13 above the upper end of the pile 3. Applying such an external force in the prior art, even if possible, would be very cumbersome, time-consuming and costly. On the other hand, there is a high risk of damage to the platform and / or the pile, and there is also a risk of the platform being unsuccessfully attached.

[0042] The above problem is prevented in a surprising manner by providing the guide structure 11 by adopting the method according to the present disclosure. As shown in FIG. 9C, when the platform 1 is further lowered, a part of the inner surface 14 of the opening 13 may engage with the guide surface 15 of the upper part 11A of the guide structure 11. Then, the gravity F acting on the platform 1 decreases. zw(1) When the support frame 8 is further lowered along the direction M, a horizontal force F is applied to push the platform 1 to the left in FIG. 9C so that the alignment is completed. hor As a result, the center line 25 of the opening 13 is aligned with the XX axis of the pile 3. This is shown diagrammatically in FIG. 9D.

[0043] In Fig. 5 an embodiment of a guide structure 11 is shown diagrammatically, which is attached to the upper end 2 of the pile 3. Figs. 6A and 6B show the same or a similar guide structure in three dimensions. In this embodiment, the guide structure has a substantially open configuration, e.g. wind can pass through the guide structure relatively easily. It should be noted that the guide structures 11 shown in Figs. 1 to 8 can obviously have the same or similar configuration. In this embodiment, the guide structure 11 is mainly composed of profiles 30, such as metal profiles or beams. The profiles may for example be welded or bolted together to form a rigid structure.

[0044] In the embodiments shown in Figures 5, 6A and 6B, the guide structure has a central profile 30A that extends from the apex 21 to the lower end 17 (also called apex 17). In these embodiments, the guide structure has an upper part 11A with a conical shape and a lower part 11B with a frustoconical shape. The upper part 11A and the lower part 11B each consist of a series of inclined profiles 30B. The inclined profiles essentially define the guide surfaces 15 and 16 of the upper part 11A and the lower part 11B, respectively. In these embodiments, a ring-shaped profile 30C consisting of a series of radial spokes 30D connected to the central profile 30A essentially forms the interface 18. The suspension element 12 is connected to the upper end of the central profile 30A.

[0045] In these embodiments, the guide surfaces 15 and 16 are formed by outwardly facing portions 31 of the inclined profile 30B forming a substantially conical or frustoconical surface, as shown for example in Figures 1 and 2. Between the profiles 30A to 30D, open areas 32 are provided, for example to allow wind to pass through, reducing the wind effect on the guide structure. This also reduces the contact surface between the openings of the superstructure, such as but not limited to the platform 1, and the guide structure. The surface portions 31 can be provided with a friction reducing coating, coating or finish. For example, materials such as ridges, plastic strips, pastes, fluids, etc. can be used, as known in the art of tribology.

[0046] Figure 7 shows a schematic diagram of an assembly 33 consisting of a guide structure 11 and a platform 1 forming a superstructure for use at sea. The assembly 33 is suspended from a support frame 8 supported by hoisting lines 10 and raised in a known manner by a crane C on a ship 34. The assembly is suspended above the upper ends 22, 2 of the piles 3, as shown diagrammatically in Figure 1, and is lowered by the crane to attach the platform 1 to the piles 3, for example according to the steps described with reference to Figures 1 to 4 and 9.

[0047] The method according to the present disclosure has the advantage that the guide structure 11 is installed only at the top of the foundation pile 3 after it has been driven into the ground, for example, into a water bottom or a coastal area leading to land, so that the guide structure can be engaged with a known pile driver or similar driving means at the top of the pile and driven into the ground without risk of damaging the guide structure. If piles that are engaged at the top and driven into the ground are not used, for example foundation piles constructed from multiple segments, the guide structure can be removably attached to the top as a separate entity.

[0048] 8A-8D show various configurations of the guide structure 11 according to the present disclosure in a schematic manner, by way of example only. FIG. 8A shows the embodiment described above, with upper and lower portions 11A, 11B, both of which are conical in shape. FIG. 8B shows an embodiment in which the lower portion 11B is conical, but the upper portion 11B forms a substantially hemispherical, or at least curved, guide surface 15. FIG. 8C shows an embodiment in which the lower portion 11B is still conical, but the upper portion 11A is substantially frustoconical. FIG. 8D shows an embodiment in which both the upper portion 11A and the lower portion 11B are substantially frustoconical.

[0049] In the illustrated embodiment, the pile 3 and the guide structure 11 are circular in cross section perpendicular to the XX axis. This means that the guide structure 11 can be attached to the top end 2 of the pile 3 in any rotational position about the longitudinal axis XX axis, cq, the center line 24. However, in some embodiments, the pile 3, and in particular the edge 6 and the opening 6A which it defines, can be other than circular, for example elliptical or formed with partially straight edges, and the guide structure, and in particular its lower part 11B, can have a corresponding shape. Thus, when the guide structure is lowered into the opening 6A, it is forced to rotate about the center line 24 until it fits into the opening. In such an embodiment, for example, the opening 13 of the platform is also formed non-circular and the upper part 11A of the guide structure is formed accordingly. Thus, the platform is also forced to lower above the guide structure to reach a suitable position relative to the guide structure and thus relative to the pile 3. This is useful, for example, when it is desired to rotate the platform to a specific predetermined position relative to the pile.

[0050] The disclosed embodiments are presented by way of example only and should not be construed as limiting the scope of the present disclosure. Many variations are possible within the scope of the present invention as defined by the claims. For example, the superstructure attached to the piles can be of different construction, for example supported by a series of piles as disclosed. The guide structure can be formed in different ways, for example using multiple plates to form a skeleton, rather than multiple adjacent profiles as shown. The superstructure, such as a platform, and the guide structure can be installed in separate steps. For example, the guide structure is first raised onto the piles, and then the superstructure is raised onto the piles. This is useful for superstructures that do not have openings through them, such as towers. The guide structure can be easily disassembled so that individual parts can be removed.

[0051] These and other modifications, including but not limited to combinations of the disclosed embodiments or portions thereof, are also contemplated as being disclosed within the scope of the following claims.

Claims

1. A method for attaching a superstructure to an upper end of a foundation pile, the upper end having a truncated cone shape, the superstructure having an opening that fits into the upper end, the opening preferably having a truncated cone shaped outer peripheral surface that fits into the upper end, the method including: placing a guide structure including at least one inclined guide surface on the upper end, and then lowering the superstructure above the guide structure onto the upper end of the foundation pile.

2. The method of claim 1 , further comprising: removing the guide structure from the upper end of the foundation pile after positioning the superstructure on the upper end of the foundation pile.

3. 3. The method according to claim 1, wherein a guide structure is used which has a conical or frusto-conical guide surface.

4. The method according to claim 1 , wherein the guide structure has an upper portion constituting or forming the guide surface and a lower portion, the lower portion being inserted into an open end of the upper end.

5. 5. The method of claim 4, wherein the lower portion has a substantially conical or truncated shape and is provided with at least one support element extending outwardly at the interface between the upper portion and the lower portion, and the guide structure is lowered onto the open end of the foundation pile such that the at least one support element rests on the foundation pile.

6. 6. The method of claim 1, wherein the guide structure and the upper structure are suspended from a support frame, the guide structure suspended such that it extends at least partially below the upper structure.

7. The method of claim 6 , wherein the guide structure is suspended from the support frame by at least one hanging element that extends through the opening in the upper structure.

8. 8. The method according to claim 6 or 7, wherein the guide structure and the superstructure suspended from the support frame are raised to a position above the upper end of the foundation pile, the guide structure, in particular the lower part of the guide structure, is suspended directly above the upper end of the foundation pile, in particular the open upper end of the foundation pile, then the support frame is lowered and the guide structure is at least partially inserted into the open upper end of the foundation pile, then the support frame is further lowered and the superstructure is lowered onto an outer surface of the upper end of the foundation pile to form a slip joint with the foundation pile, then the superstructure is removed from the support frame, the support frame is re-raised and the guide structure is moved away from the foundation pile.

9. 9. The method of claim 1, wherein the superstructure is a platform having an upper surface and a lower surface, and the opening extends through the platform from the upper surface to the lower surface.

10. The method according to any one of claims 1 to 9, wherein an aperture structure is used as the guide structure.

11. 11. The method according to claim 1, wherein a slip joint is formed between the superstructure and the upper end of the foundation pile by lowering the superstructure onto the upper end of the foundation pile.

12. A guide structure for use in mounting a superstructure on a foundation pile according to any one of claims 1 to 11.

13. 13. The guide structure of claim 12, wherein the guide structure has an upper portion and a lower portion, the upper portion including or forming a guide surface, the lower portion designed to engage an upper end of a foundation pile, and in use, the lower portion allows centering of the guide structure relative to the upper end of the foundation pile, and the guide surface extends above the upper end of the foundation pile to guide the upper structure during lowering of the upper structure onto the upper end of the foundation pile.

14. 14. A guide structure according to claim 13, wherein the upper portion has a configuration of increasing cross section towards the lower portion, preferably being substantially conical or frusto-conical.

15. 15. A guide structure according to claim 13 or 14, wherein the lower portion has a configuration of decreasing cross section moving away from the upper portion, preferably having a substantially conical or frusto-conical shape.

16. 16. The guide structure of claim 13, wherein an interface plane exists at the interface between the upper portion and the lower portion, and at the interface plane, the upper portion projects radially outwardly from the lower portion, such that a support portion is provided at the interface plane by an end of the upper portion.

17. 17. A guide structure according to any one of claims 12 to 16, wherein the guide structure has a substantially open configuration.

18. 17. An assembly of a guide structure and an upper structure as claimed in any one of claims 12 to 16, said assembly further comprising a support frame, said upper structure and said guide structure being supported on, and preferably suspended from, said support frame.

19. 20. The assembly of claim 18, wherein the upper structure has an opening therethrough, at least one suspension element extending from the support frame through the opening, and the guide structure is suspended from the at least one suspension element such that the guide structure extends at least partially below the opening.

20. 20. The assembly of claim 19, wherein said upper structure is a platform and said opening extends from an upper surface to a lower surface of said platform.

21. 21. An assembly as claimed in any one of claims 18 to 20, wherein the guide structure has a maximum cross-section perpendicular to a vertical axis of the guide structure, the maximum cross-section being smaller than the minimum cross-section of the opening measured in a direction perpendicular to the vertical axis of the opening such that the guide structure moves vertically through the opening, and wherein the maximum cross-section of the guide structure is preferably substantially the same as the minimum outer cross-section of the upper end of the foundation pile, and more preferably the guide structure does not extend radially beyond the outer surface of the upper end of the foundation pile.

22. A foundation pile for supporting at least one superstructure, in particular a monopile for attaching at least a platform by means of a slip joint, the upper end of the foundation pile being provided with a removable guide structure, which guides the superstructure relative to the upper end when the superstructure is attached.

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