Offshore frame structure comprising structural components and structural joints connecting the structural components

Abstract

A structural joint for an offshore frame structure comprising structural components (1, 2) is disclosed. The structural joint between the structural components (1, 2) comprises a fork (3), an ear (4) and a pin (5). The fork and the ear comprise a hole, which is arranged to accommodate the pin. Also disclosed is a method for assembling an offshore frame structure comprising structural components (1, 2), and the use of the structural joint for connecting a column and a bracket of the structure in an offshore wind turbine foundation.

Description

Technical Field

[0001] The present invention relates to a structural joint for an offshore structure, in particular an offshore wind turbine structure.

[0002] Furthermore the invention relates to a method for assembling the offshore frame structure.

[0003] Furthermore, the present invention relates to the application of the structural joint. Background Art

[0004] Offshore wind turbines can be installed on different types of foundations. In shallow water depths, monopiles are usually preferred, but in greater water depths, the foundation needs to be a frame structure to provide sufficient rigidity. The foundation of a floating offshore wind turbine is also usually designed as a frame structure.

[0005] This frame structure can be made into a lattice structure or a "jacket" structure, such as a tripod, a tetrahedral floating device or other types of structures assembled at nodes by columns or brackets. Frame structures usually have good mechanical properties due to their high stiffness and material utilization, and they are more cost-effective than monopiles.

[0006] The connection of columns and brackets at the nodes is a challenge in offshore frame structures. In traditional offshore frame structures, columns and brackets are hollow steel tubes with cylindrical cross-sections, and the joints are welded. Due to the complex geometry of the non-axial pipe joints, welding can only be done manually, and welding cannot be done from both sides because the inside of the brackets is generally difficult to access. As a result, the welding quality is only mediocre. The geometric irregularities of the joints lead to significant geometric stress concentrations, and the combination of mediocre welds and geometric stress concentrations requires oversizing the structural members at the joints, resulting in a heavier weight than usual. In addition, although some parts can be prefabricated, most of the welding process in the entire construction process is carried out on-site, usually in expensive locations such as dry docks or quayside. Therefore, assembling offshore frame structures by welding is a long and expensive process, often occupying valuable space for weeks or even months.

[0007] EP2067914A1 discloses a pipe frame structure, comprising a plurality of columns and a plurality of brackets aligned at an angle, wherein the nodes are made of steel castings. As a result, the joints of the nodes themselves are not welded. The columns and brackets are connected to the node castings by welding, but the advantage over the joints of conventional welded pipes is that the welds are away from the locations where geometric stresses are concentrated and are welded with simple circumferential welds. Therefore, the manufacture of the frame structure can have higher weld quality and reduce the requirements for large dimensions. However, the device disclosed in EP2067914A1 does not significantly reduce the time of on-site manufacturing.

[0008] EP2535312B2 discloses a duct structure for offshore structures, in which the column and the bracket are connected by bolts. The connectors for the joints are preferably cast iron. This device eliminates the need for on-site welding, thereby greatly saving assembly time. However, due to its reliance on bolts, connection components that usually require maintenance are introduced. It is well known that the long-term serviceability of dynamically loaded bolted connections immersed in water is very problematic. Therefore, the solution to the challenge of easy assembly of nodes seems to be obtained at the cost of introducing additional maintenance.

[0009] One solution may be to use a pin joint connection between the column and the bracket. The pin joint includes an ear attached to one component and a fork attached to the other component. A pin passes through the ear and the fork to connect the two components. The connection components associated with the pin joint (ear or fork) can be pre-fabricated and incorporated into the column and bracket at appropriate locations, so that rapid assembly can be achieved at expensive loading locations such as dry docks or quayside.

[0010] Pin joints are widely used in onshore frame structures, such as the Centre Pompidou in Paris and Billund Airport. Pin joints are also used in more flexible structural arrangements, such as in the roof support structure above the Munich Airport Centre.

[0011] Pin joints are used in offshore applications that require maintenance, such as fairlead connections for mooring lines. However, pin joints are not used as structural joints for offshore frame structures.

[0012] Purpose of the Invention

[0013] The object of the present invention is to provide a structural joint for an offshore frame structure, such as a jacket, a tripod, a tetrahedron float or other types of offshore frame structures composed of columns and brackets assembled at nodes, and the structural joint can overcome the above-mentioned disadvantages.

[0014] In addition, an object of the present invention is to provide an assembling method of the offshore frame structure using the structural joint. Summary of the invention

[0015] These objects are achieved by the features described below and further set forth in the claims.

[0016] In a first aspect, the invention relates to a pin joint for use as a connection between structural components, which may be in the form of columns and brackets.

[0017] The structural joint according to the invention is special in that the structural joint between structural components comprises a fork, an ear and a pin, wherein the fork and the ear comprise a hole, which is arranged to receive the pin. The structural components are thus connected to each other. Such a structural joint can be denoted as a pin joint.

[0018] The structural joint is advantageously used in offshore wind turbine foundations for connecting columns and supports.

[0019] In a second aspect, the present invention relates to a method of assembling a pin joint for an offshore frame structure.

[0020] A method of assembling an offshore frame structure comprising structural components, typically comprising the following steps:

[0021] - placing structural components near the location where they are to be assembled;

[0022] - inserting the ear provided on the first structural component into the fork provided on the second structural component; and

[0023] - Assembly is accomplished by inserting a pin into aligned holes provided in the fork and the ears, the holes being arranged to receive the pin.

[0024] In one embodiment, the joint is similar to the pin joint used in land frame structures, with an ear attached to one component and a fork attached to the other component. The pin passes through the aligned holes provided in the ear and fork to join the two components. The associated joint components (ear or fork) of the pin joint can be prefabricated or incorporated into the column and bracket at a suitable location. This allows for rapid assembly at an expensive loading location, such as in a dry dock or at the quayside. The ear, fork and pin can be made of steel.

[0025] Hydrodynamic forces acting on structural components can cause micro-movements between pins and lugs and forks. Such micro-movements can cause wear and corrosion, and in a subsea environment, cathodic protection may not be effective due to shielding of the narrow gaps between components. This creates a risk of requiring extensive and costly maintenance, especially for subsea joints.

[0026] It will be understood by those skilled in the art that corrosion should be understood as corrosion in offshore environments including seabed environments. In addition, it will be understood by those skilled in the art that non-corrosive should be understood as non-corrosive in offshore environments including seabed environments.

[0027] This potential problem is alleviated in another embodiment of the invention. In this embodiment, the fork and the ears include sliding surfaces, which are equipped with bushings that act as bearings. The pin is made of a corrosion-resistant material and the sliding surfaces in the ears and / or fork are equipped with bushings that act as bearings. This avoids the risk of wear and corrosion on the mating surfaces.

[0028] The corrosion resistant pin may comprise a steel body which is partially or fully surrounded by a bushing made of a corrosion resistant material, or the corrosion resistant pin may be made entirely of a corrosion resistant material. Such a material may be a composite material or a metal, such as aluminum bronze or 625 alloy. The electrochemical potential of the corrosion resistant metal material is different from that of steel, and if the bushing used as a bearing is also metal, this may result in galvanic corrosion between the pin and the bushing and / or between the bushing and the lug or fork. The risk of such galvanic corrosion may be mitigated by using a bushing made of a non-conductive material, such as glass fiber reinforced plastic, PEEK (polyetheretherketone) or some other type of plastic, guaiac wood, rubber, or the like.

[0029] According to another embodiment, the structural joint is special in that the pin has a corrosion-resistant surface, which is made of a cladding or sleeve fixed to the pin made of a different material by welding or shrinking or gluing or otherwise, or the corrosion-resistant surface is continuous with the pin, and the pin is made of corrosion-resistant material as a whole.

[0030] Due to cyclic hydrodynamic loading, the pin joint may experience load reversals. As a result, wear between the bearing and the pin may occur, especially if there are a lot of particles in the water.

[0031] This potential problem has been alleviated in another embodiment of the present invention. In this embodiment, an interference fit is established between the pin and the bearing.

[0032] The interference fit can be formed by a variety of means, such as an expansion device, where the pin is expanded by axial movement of an internal tapered component, or by simply tapering the pin itself and pushing the pin axially into the bearing until the desired interference fit is obtained.

[0033] The ideal fit may be an interference fit where the surface pressure is sufficient to ensure that under extreme loads, the unloaded surface of the bearing will not fall off the pin. At this level of fit, the surface of the bearing never leaves the surface of the pin, thereby preventing any particles from entering the bearing. An alternative fit may be an interference fit where the surface pressure is sufficient to ensure that under normal loads, the unloaded surface of the bearing will not fall off the pin. At this level of fit, the surface of the bearing never leaves the surface of the pin under normal conditions, and particles enter the bearing only under extreme load conditions.

[0034] The bearings of the pin joint may be edge loaded in the event of out-of-plane loading of the joint, where the plane is defined as the plane perpendicular to the axis of the pin. Such out-of-plane loading may occur due to, for example, misalignment of the bearings, or as a result of hydrodynamic loading on the components joined by the pin joint.

[0035] This edge load can be reduced by properly forming the bearing raceways with end relief, or by making the pins slightly barrel-shaped, or by a combination of both.

[0036] In another embodiment of the invention, the bearing is a spherical bearing, thereby eliminating the risk of edge loading, except for the unavoidable loads due to friction in the bearing. The spherical bearing inserted into the ears is a spherical bearing comprising an outer spherical inner part and an inner spherical outer part.

[0037] In another embodiment of the invention, the bearing is made as an elastic bearing, for example a rubber sleeve. The sleeve can be inserted between the pin and the ear and / or between the pin and the fork. The sleeve can be inserted into the inner metal sleeve and / or the outer metal sleeve, or the sleeve can be vulcanized in the inner metal sleeve and / or the outer metal sleeve.

[0038] The pin joint can be made into a single joint, or can also be made into a double joint or multiple joints. In a preferred embodiment, the pin joint is made into a hinge. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Examples of preferred embodiments are described in the following drawings, in which:

[0040] Figure 1 A schematic structural diagram of an inventive structural joint according to a first exemplary embodiment of the present invention is shown;

[0041] Figure 2 A cross-sectional view showing an inventive structural joint according to a first exemplary embodiment of the present invention;

[0042] Figure 3 shows a cross-sectional view of an inventive structural joint according to a second exemplary embodiment of the present invention;

[0043] Figure 4 shows a cross-sectional view of an inventive structural joint according to a third exemplary embodiment of the present invention;

[0044] Figure 5 shows a cross-sectional view of an inventive structural joint according to a fourth exemplary embodiment of the present invention;

[0045] Figure 6 shows a cross-sectional view of an inventive structural joint according to a fifth exemplary embodiment of the present invention;

[0046] Figure 7 A cross-sectional view showing an inventive structural joint according to a sixth exemplary embodiment of the present invention;

[0047] Figure 8 A schematic diagram showing a first configuration of an inventive structural joint according to the present invention; and

[0048] Fig. 9 Schematic diagrams showing different configurations of the inventive structural joint according to the present invention. DETAILED DESCRIPTION

[0049] In the drawings, similar or corresponding elements are denoted by the same reference numerals.

[0050] Figure 1 The schematic diagram of the structure of the inventive structural joint according to the first exemplary embodiment of the present invention is shown. The column 1 and the bracket 2 are joined by a pin joint. The pin joint includes two forks 3 attached to the column 1, ears 4 attached to the bracket 2, and a pin 5.

[0051] Figure 2 A cross-sectional view of an inventive structural joint according to a first exemplary embodiment of the present invention is shown. The fork 3 is joined with the ear 4 by means of a pin 5. The fork 3, the ear 4 and the pin 5 may be made of steel.

[0052] Figure 3 A cross-sectional view of an inventive structural joint according to a second exemplary embodiment of the present invention is shown. Here, a bearing 6 is inserted into the ear 4. The pin can be made of steel or it can be made of a corrosion resistant material such as fiberglass reinforced plastic, aluminum bronze or 625 alloy. The corrosion resistant material can be a cladding shrunk, glued or otherwise attached to the steel pin, or the pin can be made entirely of the corrosion resistant material. The bearing can be metallic or can be made of a non-conductive composite material such as fiberglass reinforced plastic or polyetheretherketone (PEEK).

[0053] Figure 4A cross-sectional view of an inventive structural joint according to a third exemplary embodiment of the present invention is shown. As in the second exemplary embodiment of the present invention, a bearing 6 is inserted into the ear 4. In addition, a bearing 7 is inserted into the fork 3. Further, an axial bearing 8 is inserted between the fork 3 and the ear 4 to ensure that the pin joint can also withstand axial loads.

[0054] Figure 5 A cross-sectional view of an inventive structural joint according to a fourth exemplary embodiment of the present invention is shown. Here, the bearing inserted into the ear portion 4 is a spherical bearing, comprising an outer spherical inner component 9 and an inner spherical outer component 10.

[0055] Figure 6 A cross-sectional view of an inventive structural joint according to a fifth exemplary embodiment of the present invention is shown. Here, the bearing 6 inserted into the ear 4 and the bearing 7 inserted into the fork 3 are both tapered inside, and the pin 5 is also tapered. When inserted into the assembly position as shown in the figure, the pin 5 is strongly press-fitted into the bearings 6 and 7, thereby eliminating bearing play and preventing the infiltration of wear particles.

[0056] Figure 7 A cross-sectional view of an inventive structural joint according to a sixth exemplary embodiment of the present invention is shown. Here, an elastic bearing is used, which comprises a rubber sleeve 11 mounted between an outer metal sleeve 12 and an inner metal sleeve 13.

[0057] Figure 8 and Fig. 9 Two different configurations of the inventive structural joint according to the present invention are shown.

[0058] Figure 8 A single pin joint joining the post 1 and the bracket 2 is shown.

[0059] Fig. 9 There is shown a double pin joint joining the column 1 and the bracket 2. Here the pins have a common longitudinal axis 14, making the joint a hinge.

[0060] The above description of the preferred embodiments and other embodiments is not intended to limit or restrict the scope or applicability of the disclosed inventive concept. With the benefit of this application, it should be understood that the details described in one of the embodiments disclosed in this application can be combined with other embodiments of the application or used in other embodiments of the application, even if such combination or use may not be explicitly shown or described in other embodiments disclosed herein. In exchange for disclosing the inventive concept contained herein, the applicant hopes to obtain all patent rights provided by the attached claims. Therefore, the attached claims are intended to include all modifications and changes that fall within the scope of the attached claims or their equivalents.

Claims

1. An offshore frame structure comprising structural components (1, 2) and a structural joint connecting the structural components (1, 2), wherein the structural joint between the structural components (1, 2) comprises a fork (3), an ear (4) and a pin (5), wherein the fork (3) and the ear (4) comprise a hole, and the pin (5) is inserted into the hole, characterized in that: - the pin (5) has a corrosion-resistant surface, wherein the corrosion-resistant surface is made into a cladding or sleeve to be welded or shrunk or glued to a pin (5) made of a different material; or - wherein the corrosion-resistant surface is connected to a pin (5), and the pin (5) is entirely made of a corrosion-resistant material; and - the holes in the fork (3) and the ears (4) comprise sliding surfaces provided with bushings acting as bearings (6, 7), and - one or more axial bearings (8) are interposed between the ear and the fork, wherein the bearings (6, 7) disposed in the holes in the fork (3) and the ear (4) and one or more axial bearings (8) interposed between the ear and the fork are made of a non-conductive material, and The pin (5) has a body surrounded by bearings (6, 7) arranged in the holes in the fork (3) and the ear (4) and one or more axial bearings (8) inserted between the ear and the fork, and the non-conductive material of the bearings (6, 7) arranged in the holes in the fork (3) and the ear (4) and one or more axial bearings (8) inserted between the ear and the fork is selected from a combination including plastic, guaiac or rubber.

2. The offshore frame structure according to claim 1, characterized in that: The bearing inserted into the ear portion (4) is a spherical bearing (10), which comprises an outer spherical inner component (9) and an inner spherical outer component.

3. The offshore frame structure according to claim 1, characterized in that: The bearing is an elastic bearing, which comprises a rubber sleeve (11), the rubber sleeve (11) is inserted into an inner metal sleeve (13) and / or an outer metal sleeve (12), or the rubber sleeve (11) is vulcanized in the inner metal sleeve (13) and / or the outer metal sleeve (12).

4. The offshore frame structure according to claim 1, characterized in that: An interference fit is formed between the pin (5) and the bearing.

5. The offshore frame structure according to claim 4, characterized in that: The interference fit is formed by an expansion device in which the pin (5) is expanded.

6. The offshore frame structure according to claim 4, characterized in that: The interference fit is formed by the tapered shape of the pin (5).

7. The offshore frame structure according to claim 1, characterized in that: The joint of the pin is established as a single joint, multiple joints or a hinge.

8. The offshore frame structure according to claim 1, characterized in that: The corresponding fork portion (3) and the ear portion (4) are prefabricated components that are manufactured in advance and combined at the corresponding structural components (1, 2).

9. The offshore frame structure according to claim 1, characterized in that: One structural component (1) is a column, and the other structural component (2) is a bracket.

10. The offshore frame structure according to claim 1, characterized in that: The offshore frame structure is an offshore wind turbine foundation or a tetrahedron floating device.

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