Semi-submersible floating fan foundation, system and design method

Abstract

The invention relates to the technical field of offshore wind power generation, in particular to a semi-submersible floating fan foundation, a system and a design method. The semi-submersible floating fan foundation comprises a middle buoy and at least three side buoys arranged around the middle buoy, bases are poured at the bottoms of the side buoys, and prestressed concrete box girders are connected between the adjacent side buoys. The semi-submersible type floating fan foundation provided by the invention can be used for bearing an offshore fan, and the effective displacement of the fan foundation can be greatly improved by adopting a form of combining the floating barrels and the box girders, so that the fan foundation has higher bearing capacity; the box girders are prestressed concrete box girders, so that the higher structural strength and rigidity and excellent crack resistance and durability of the prestressed concrete box girders can be utilized to save part of steel bar and concrete cost under the condition of meeting the bearing requirement and the stability requirement of the offshore wind turbine, thereby being beneficial to improving the overall economic benefit of offshore wind turbine engineering; and large-scale commercial use of the offshore wind turbine can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power generation, and in particular to a semi-submersible floating wind turbine foundation, system and design method. Background Art

[0002] At present, the fixed foundation commonly used in offshore wind power is suitable for shallow beaches. As the development of offshore wind energy resources tends to be saturated, it is a general trend for offshore wind power to move to deep seas. Seas with a water depth of more than 60 meters are suitable for floating offshore wind power. At present, floating wind power at home and abroad is still in the exploratory demonstration stage. In order to meet the stability requirements, the wind power foundation uses a large amount of steel, and the economic benefits have not reached the requirements of large-scale commercial use. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of large steel consumption and low economic benefits in wind power foundations in the background technology, and to provide a semi-submersible floating wind turbine foundation, system and design method.

[0004] In a first aspect, the present invention provides a semi-submersible floating wind turbine foundation, comprising: a middle pontoon and at least three side pontoons arranged around the middle pontoon, a base is cast at the bottom of the side pontoon, and prestressed concrete box beams are connected between adjacent bases.

[0005] A semi-submersible floating wind turbine foundation provided by the present invention can be used to carry offshore wind turbines. By adopting a combination of pontoons and box girders, the effective drainage of the wind turbine foundation can be greatly improved, so that the wind turbine foundation has a greater bearing capacity; the box girder adopts a prestressed concrete box girder, which can save part of the steel bar and concrete costs while meeting the offshore wind turbine bearing demand and stability requirements by utilizing the higher structural strength, rigidity and excellent crack resistance and durability of the prestressed concrete box girder, thereby greatly reducing the steel consumption and part of other costs of the wind turbine foundation, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0006] Preferably, the prestressed concrete box girder is provided with prestressed tendons along its length direction, and anchors are provided at both ends of the prestressed tendons.

[0007] Preferably, the prestressed tendons include a bonding section and a non-bonding section, the bonding section is located in the middle of the prestressed concrete box girder, and the non-bonding section is located at the end of the prestressed concrete box girder.

[0008] The bonding section of the prestressed tendons can be bonded to the prestressed concrete box girder through cement slurry, which is beneficial to improve the tightness of the connection between the prestressed tendons and the prestressed concrete box girder, thereby improving the bearing capacity of the prestressed concrete box girder; the non-bonded section of the prestressed tendons is not bonded to the prestressed concrete box girder, and is set at the end, so that the connection between the prestressed concrete box girder and the base can be slightly opened under extremely unfavorable conditions to release the internal force, thereby maintaining the safety of the overall structure.

[0009] Preferably, a steel base is provided inside the base, and a concrete shell is cast and covered on the outer side of the steel base, and the concrete shell is cast and connected to the prestressed concrete box girder.

[0010] Preferably, at least part of the anchor extends into the base; at least part of the anchor or at least part of the prestressed tendons are connected to the steel base; and the side buoy is connected to the steel base.

[0011] Preferably, the prestressed tendons are prestressed steel strands.

[0012] Preferably, the prestressed concrete box girder is cast using ultra-high performance concrete.

[0013] Preferably, the concrete shell and the prestressed concrete box girder are connected by pouring ultra-high performance concrete.

[0014] Preferably, the prestressed concrete box girder comprises a bottom plate, a top plate and side plates, and the prestressed tendons are distributed in the middle of the bottom plate, the middle of the top plate and four corners.

[0015] Preferably, there are three bases in total and they are distributed in a triangle.

[0016] Preferably, the semi-submersible floating wind turbine foundation is constructed by the following steps:

[0017] Step 1: Casting the prestressed concrete box girder and leaving a hole in the prestressed concrete box girder;

[0018] Tensioning the prestressed tendons passing through the hole, grouting into the hole, so that the middle of the prestressed tendons are bonded to the concrete, and the two ends of the prestressed tendons are not bonded to the concrete, and anchoring the prestressed tendons with anchors;

[0019] Step 2: Install the steel base;

[0020] Step 3: Connecting the steel base with the prestressed concrete box beam by pouring, wherein the anchor is buried in the concrete of the base during pouring, leaving a position for installing the buoy;

[0021] Step 4: Install the side buoys.

[0022] In a second aspect, the present invention provides a floating wind turbine system, comprising a wind turbine and a semi-submersible floating wind turbine foundation as described above, wherein the wind turbine is installed on the middle buoy, and a connecting rod assembly is connected between the side buoy and the middle buoy, and the connecting rod assembly comprises an upper cross bar and a lower cross bar, and a diagonal rod located between the upper cross bar and the lower cross bar.

[0023] The floating wind turbine system provided by the present invention can save part of the steel bar and concrete costs while meeting the load-bearing requirements and stability requirements of the offshore wind turbine by using the semi-submersible floating wind turbine foundation as described above, thereby greatly reducing the steel consumption of the wind turbine foundation and part of other costs, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0024] In a third aspect, the present invention provides a floating wind turbine foundation design method, which is applied to the floating wind turbine system as described above, and comprises the following steps:

[0025] S1. constructing a finite element model of the wind turbine foundation and the wind turbine according to the draft and displacement of the wind turbine foundation, wherein the wind turbine is located on the intermediate buoy;

[0026] S2. Calculate the equivalent design wave using the finite element model:

[0027] Obtain the maximum vertical static bending moment Mxy1_s of the prestressed concrete box girder under still water conditions and the maximum vertical dynamic bending moment Mxy1_d under wave conditions, and combine Mxy1_s and Mxy1_d to obtain the maximum vertical bending moment Mxy1 of the prestressed concrete box girder;

[0028] Obtain the maximum vertical static bending moment Mxy2_s of the connecting rod assembly under still water conditions and the maximum vertical dynamic bending moment Mxy2_d under wave conditions, and combine Mxy2_s and Mxy2_d to obtain the maximum vertical bending moment Mxy2 of the connecting rod assembly;

[0029] S3. Determine whether the ratio of Mxy1 to Mxy2 meets the design requirements, wherein the maximum vertical bending moment of the prestressed concrete box girder is Mxy1=Mxy1_s+Mxy1_d, and the maximum vertical bending moment of the connecting rod assembly is Mxy2=Mxy2_s+Mxy2_d.

[0030] A floating wind turbine foundation design method provided by the present invention can be used to evaluate whether the base and prestressed concrete box girder are the main bodies that bear wave loads, thereby serving as a design basis for the floating wind turbine foundation; the design method uses finite element analysis to perform equivalent design wave calculations, simulates and analyzes and obtains the vertical bending moments of the prestressed concrete box girder and the connecting rod assembly under still water conditions and wave conditions, and by combining the vertical bending moments and comparing the combined Mxy1 and Mxy2, it can more intuitively reflect the role of the lower floating body in bearing wave loads.

[0031] Preferably, S2 comprises the following steps:

[0032] S21. Select a significant wave height Hs and at least two wave periods Tn (n=1, 2, ...) according to the engineering environment;

[0033] S22. Calculate the vertical bending moment at the end of the prestressed concrete box girder in the static water condition, and select the maximum value as Mxy1_s;

[0034] Calculate the vertical bending moment at the end of the prestressed concrete box girder in at least two wave directions in each wave period Tn, and select the maximum value as Mxy1_d;

[0035] Calculate the vertical bending moment at the end of the lower crossbar under still water conditions, and select the maximum value as Mxy2_s;

[0036] Calculate the vertical bending moment at the end of the lower crossbar in at least two wave directions in each wave period Tn, and select the maximum value as Mxy2_d.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. A semi-submersible floating wind turbine foundation provided by the present invention can be used to carry offshore wind turbines. By adopting a combination of pontoons and box beams, the effective drainage of the wind turbine foundation can be greatly improved, so that the wind turbine foundation has a greater bearing capacity; the box beam adopts a prestressed concrete box beam, which can save part of the steel bar and concrete costs while meeting the bearing requirements and stability requirements of the offshore wind turbine by utilizing the higher structural strength, rigidity, excellent crack resistance and durability of the prestressed concrete box beam, thereby greatly reducing the steel consumption and part of other costs of the wind turbine foundation, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0039] 2. The floating wind turbine system provided by the present invention can save part of the steel bar and concrete costs while meeting the load-bearing requirements and stability requirements of the offshore wind turbine by using the semi-submersible floating wind turbine foundation as described above, thereby greatly reducing the steel consumption and part of other costs of the wind turbine foundation, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0040] 3. A floating wind turbine foundation design method provided by the present invention can be used to evaluate whether the base and prestressed concrete box girder are the main bodies that bear wave loads, thereby serving as a design basis for the floating wind turbine foundation; this design method uses finite element analysis to perform equivalent design wave calculations, simulates and analyzes and obtains the vertical bending moments of the prestressed concrete box girder and the connecting rod assembly under still water conditions and wave conditions, and by combining the vertical bending moments and comparing the combined Mxy1 and Mxy2, it can more intuitively reflect the role of the lower floating body in bearing wave loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of the floating wind turbine system of the present invention;

[0042] Figure 2 It is a front view of the floating wind turbine system of the present invention;

[0043] Figure 3 A top view of the floating wind turbine system of the present invention;

[0044] Figure 4 is a schematic cross-sectional view of the prestressed concrete box girder of the present invention;

[0045] Figure 5 It is a schematic diagram of the arrangement of the prestressed tendons of the present invention;

[0046] Figure 6 This is a schematic diagram of the optimization of the floating wind turbine foundation of the present invention;

[0047] Figure 7 A schematic diagram of the selection of control points in the design method of the present invention;

[0048] Figure 8 It is a parameter chart of the floating wind turbine foundation of the present invention under a specific working condition;

[0049] Fig. 9 It is a schematic diagram of the force results of the floating wind turbine foundation under typical dynamic load conditions of the present invention;

[0050] Fig.10 This is the wet surface model and mass model of the floating wind turbine foundation and the wind turbine described in the present invention.

[0051] Markings in the figure:

[0052] 1-lower floating body;

[0053] 11- Prestressed concrete box girder;

[0054] 111-prestressed tendons; 112-anchors; 113-bonding sections; 114-unbonded sections;

[0055] 12-bottom plate; 13-top plate; 14-side plate; 15-hole position; 16-base;

[0056] 2-Floating body;

[0057] 21-middle buoy; 22-side buoy;

[0058] 3-Connecting rod assembly;

[0059] 31-upper horizontal bar; 32-lower horizontal bar; 33-diagonal bar;

[0060] 4- Fan. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0062] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or position relationship such as "up", "down", "left", "right", "center", "inside", "outside", etc. are all based on the expression of the orientation or position relationship shown in the drawings, or are the orientation or position relationship when the invented product / equipment / device is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the present invention or simplifying the description in the specific embodiments, so as to facilitate the technicians to quickly understand the scheme, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore cannot be understood as a limitation on the present invention.

[0063] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the scheme of the present invention.

[0064] In addition, the expressions “first”, “second”, “third”, etc., which appear in the terms, are merely used to distinguish the description of the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0065] In addition, in the description of the embodiments of the present invention, "several", "plurality" and "a number" represent at least 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0066] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0067] Example 1

[0068] like Figure 1-5 As shown, the present embodiment provides a semi-submersible floating wind turbine foundation, comprising an upper buoy 2 and a lower buoy 1, wherein the upper buoy 2 comprises a middle buoy 21 and at least three side buoys 22 arranged around the middle buoy 21; the lower buoy 1 comprises a base 16 arranged at the bottom of the side buoy 22, and a prestressed concrete box girder 11 located between adjacent bases 16.

[0069] The upper buoy 2 and the lower buoy 1 are both floating structures that can float on the surface of liquid. The upper buoy 2 and the lower buoy 1 are fixedly connected so that the two can float on the surface of liquid (such as seawater) as a whole, and can serve as the installation basis of the fan 4, so that the fan 4 can float on the sea.

[0070] The middle buoy 21 and the side buoy 22 are both buoy structures, which have the characteristics of large volume and small mass, so that they can float on the water surface; when they are connected to the lower buoy 1 as the upper buoy 2, the middle buoy 21 and the side buoy 22 can increase the bearing capacity of the wind turbine foundation to meet the installation requirements of the large-mass wind turbine 4. Preferably, the middle buoy 21 and the side buoy 22 are both cylindrical.

[0071] The prestressed concrete box girder 11 is a box girder with prestress. On the one hand, the prestressed concrete box girder 11 is a hollow structure that can increase the volume of the water displaced and increase the buoyancy it is subjected to. On the other hand, the prestressed concrete box girder 11 is a prestressed structure, which not only has a high structural strength and can achieve a higher bearing capacity with less material, but also has excellent crack resistance and durability. Especially in a seawater environment, the excellent crack resistance can make the surface of the prestressed concrete box girder 11 almost free of cracks, thereby preventing seawater from invading and corroding the internal steel bars.

[0072] The prestressed concrete box girder 11 is a box girder type component, and a hollow chamber inside it can increase the volume of the prestressed concrete box girder 11, so that the prestressed concrete box girder 11 as the lower floating body 1 can provide greater buoyancy, thereby increasing the bearing capacity of the wind turbine foundation; the cross-section of the prestressed concrete box girder 11 (cut with a surface perpendicular to its longitudinal direction) is relatively large, so that it has a larger moment of inertia and thus has greater bending resistance; moreover, the prestressed concrete box girder 11 has a large vertical projection area, and when it is located in the water, it has a larger waterline area, and the floating wind turbine foundation has a sufficiently large restoring torque so that it has a better ability to suppress heave, sway, and pitch, which can improve stability and reduce the risk of capsizing.

[0073] A semi-submersible floating wind turbine foundation provided by the present invention can be used to carry offshore wind turbines. By adopting a combination of pontoons and box beams, the effective drainage of the wind turbine foundation can be greatly improved, so that the wind turbine foundation has a greater bearing capacity; the box beam adopts a prestressed concrete box beam 11, and by utilizing the higher structural strength, rigidity, excellent crack resistance and durability of the prestressed concrete box beam 11, while meeting the bearing requirements and stability requirements of the offshore wind turbine, part of the steel and concrete costs can be saved, thereby greatly reducing the steel consumption and part of other costs of the wind turbine foundation, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0074] Figure 6This is a schematic diagram of the optimization of the floating wind turbine foundation of the present invention. The present invention adds a prestressed concrete box beam 11 on the basis of the prior art, which can reduce the draft and increase the stability of the overall structure without affecting the overall width.

[0075] Preferably, the prestressed concrete box girder 11 is cast using ultra-high performance concrete, which has ultra-high durability and ultra-high mechanical properties and can adapt to the stress requirements of severe sea conditions.

[0076] The design theory of ultra-high performance concrete is the maximum packing density theory (densified particle packing), and its constituent materials have particles of different sizes that form the densest packing in the best proportion. The differences between ultra-high performance concrete and ordinary concrete or high-performance concrete include: no coarse aggregate is used, silica fume and fiber (steel fiber or composite organic fiber) must be used, the amount of cement used is large, and the water-cement ratio is very low.

[0077] Under the condition of meeting the load-bearing requirements and stability requirements, the use of prestressed concrete box beam 11 as the lower floating body 1 can reduce the deadweight of the structure and greatly reduce the amount of steel used in the wind turbine foundation. The inventor has confirmed through experiments that the use of a large amount of ultra-high performance prestressed concrete can make the amount of steel used in the wind turbine foundation less than 300t / MW (less than 300 tons of steel per megawatt of power generation), which greatly reduces the cost and is conducive to improving the economic benefits of the overall project. Figure 8 As shown, Figure 8 Parameter diagram for the design of a floating wind turbine foundation under a specific working condition, where the steel structure usage is 213t / MW.

[0078] In one or several preferred embodiments, the prestressed concrete box girder 11 is provided with prestressed tendons 111 along its length direction, and anchors 112 are provided at both ends of the prestressed tendons 111 .

[0079] For this embodiment, the prestressed tendons 111 can be tensioned by a post-tensioning process: during construction, a corrugated tube arranged along the length direction of the box girder can be embedded in the steel mesh of the box girder. After the concrete pouring of the box girder is completed and reaches 75% or more of the design strength, the prestressed tendons 111 passing through the corrugated tube are tensioned by tensioning at both ends, and the tensioned prestressed tendons 111 can be connected to the box girder by anchoring at both ends or grouting in the corrugated tube, thereby making a prestressed concrete box girder 11.

[0080] Preferably, the prestressed tendons 111 are prestressed steel strand bundles; the prestressed steel strand bundles include a plurality of steel strands, and the steel strand models can be high-strength, low-relaxation prestressed steel strands with a diameter of 15.2 mm and a standard strength of 1860 MPa; during tensioning, the tensioning stress under the anchor can be controlled to be 1265 MPa.

[0081] Optionally, the prestressed steel strand bundle is a straight bundle parallel to the structural center line of the prestressed concrete box girder 11 .

[0082] Preferably, the prestressed tendon 111 includes a bonding section 113 and a non-bonding section 114, wherein the bonding section 113 is located in the middle of the prestressed concrete box girder 11, and the non-bonding section 114 is located at the end of the prestressed concrete box girder 11. Figure 5 shown.

[0083] In the exemplary embodiment, the bonding section 113 of the prestressed tendon 111 is bonded to the prestressed concrete box girder 11 by cement slurry, and the cement slurry can improve the tightness of the connection between the prestressed tendon 111 and the prestressed concrete box girder 11 at that position, so that the prestressing force can act better on the prestressed concrete box girder 11. The unbonded section 114 of the prestressed tendon 111 is not bonded to the box girder by cement slurry, so that relative displacement between the prestressed tendon 111 and the prestressed concrete box girder 11 can occur; the unbonded section 114 is set at the two ends of the prestressed concrete box girder 11, so that the connection between the prestressed concrete box girder 11 and the base 16 can be slightly opened to release stress under extremely unfavorable conditions, thereby maintaining the overall structural safety of the lower floating body 1.

[0084] The length of the unbonded section 114 at each end of the prestressed concrete box girder 11 is preferably 2 to 5 meters, more preferably 2 to 4 meters, more preferably 3 to 4 meters, and more preferably 2.5 to 3.5 meters.

[0085] In one or several preferred embodiments, a steel base is provided inside the base 16 , and a concrete shell is cast and covered on the outer side of the steel base, and the concrete shell is cast and connected to the prestressed concrete box girder 11 .

[0086] The concrete shell is preferably cast with ultra-high performance concrete; under some working conditions, the base 16 can also be designed as a prestressed concrete structure. The ultra-high performance concrete and prestressing force can make the base 16 have higher structural strength, crack resistance and durability.

[0087] Preferably, at least part of the anchor 112 extends into the base 16; at least part of the anchor 112 or at least part of the prestressed tendons 111 are connected to the steel base; and the side buoy 22 is connected to the steel base.

[0088] By connecting at least part of the anchor 112 or at least part of the prestressed tendons 111 to the steel base, the connection strength between the base 16 and the prestressed concrete box girder 11 can be increased; by connecting the side pontoon 22 through the steel base, the connection strength between the base 16 and the side pontoon 22 can be increased, which is beneficial to improving the integrity of the floating wind turbine foundation.

[0089] Preferably, the concrete shell and the prestressed concrete box beam 11 are connected by pouring ultra-high performance concrete, which can further improve the integrity of the lower floating body 1.

[0090] Preferably, the prestressed concrete box girder 11 includes a bottom plate 12 , a top plate 13 and side plates 14 , and the prestressed tendons 111 are distributed in the middle of the bottom plate 12 , the middle of the top plate 13 and four corners.

[0091] Several holes 15 may be arranged in the middle of the bottom plate 12 and the top plate 13 , and several holes 15 may also be arranged at the corners where the bottom plate 12 and the side plate 14 intersect, and at the corners where the top plate 13 and the side plate 14 intersect, so that the prestressed tendons 111 are passed through the holes 15 .

[0092] like Figure 4 As shown, taking a preferred working condition as an example: 56 hole positions 15 are arranged in a ring shape on the prestressed concrete box girder 11, wherein two groups of holes 15 are symmetrically arranged in the middle of the bottom plate 12, with 7 holes in each group; two groups of holes 15 are symmetrically arranged in the middle of the top plate 13, with 7 holes in each group; and one L-shaped group of holes 15 is arranged at each of the four corners, with 7 holes in each group.

[0093] Preferably, there are three bases 16 in total and they are distributed in a triangle shape.

[0094] The three bases 16 may be located at the three vertices of the triangle respectively, and the prestressed concrete box girder 11 is connected to the bases 16 as the three sides of the triangle; the base 16 may be a solid or hollow structure made of concrete.

[0095] Further preferably, the three bases 16 are distributed in a regular triangle, the three bases 16 are respectively located at the three vertices of the equilateral triangle, and the three prestressed concrete box girders 11 are located at the three sides of the equilateral triangle.

[0096] The equilateral triangle distribution can make the wind turbine foundation have a high degree of symmetry, improve the uniformity of internal force distribution, reduce stress concentration as much as possible, and make full use of the materials of each part, thereby reducing costs and improving the economic benefits of the project while meeting the load-bearing requirements.

[0097] In one or more preferred embodiments, the prestressed concrete box girder 11 is a flat structure; Figure 4 As shown, the lateral dimension of the flat prestressed concrete box girder 11 cross section is much larger than the vertical dimension, generally 2 times or more. The flat structure can lower the center of gravity of the prestressed concrete box girder 11, thereby lowering the center of gravity of the entire wind turbine foundation, making the wind turbine foundation have a higher anti-overturning ability, which is beneficial to improving the stability of the entire system.

[0098] Since the prestressed concrete box girder 11 has excellent crack resistance, the flat design will not significantly increase the thickness of the top plate 13 and the bottom plate 12 of the prestressed concrete box girder 11, and the increase in the manufacturing cost of the prestressed concrete box girder 11 is limited, but it can significantly improve the overall stability.

[0099] Optionally, the transverse width of the cross section of the prestressed concrete box girder 11 is 2 to 4 times the vertical height.

[0100] In one or several preferred embodiments, at least two compartments are provided inside the prestressed concrete box girder 11; at least part of the compartments are ballast water tanks.

[0101] The ballast water tanks can be used to store seawater. The ballast water tanks are distributed at different positions of the prestressed concrete box girder 11. The inclination angle, draft and center of gravity distribution of the prestressed concrete box girder 11 can be adjusted by filling or draining water into different ballast water tanks to maintain the stability of the posture of the prestressed concrete box girder 11. When floating in the dock, the ballast water tanks can be in an empty state to reduce the draft of the prestressed concrete box girder 11, thereby reducing the requirements for the water depth in the dock; when transported to the pre-loading water area, water can be filled into the ballast water tanks to reduce the center of gravity of the entire system to improve the overall stability.

[0102] Under some working conditions, all compartments inside the prestressed concrete box girder 11 are used as ballast water tanks.

[0103] Preferably, a plurality of drain valves can be provided at the bottom of the prestressed concrete box girder 11, and the drain valves can be opened and closed. A temporary power supply and an air compressor can be installed on the upper part of the prestressed concrete box girder 11. The air compressor can blow air into the ballast water tank through a pipeline to discharge the water in the ballast water tank from the drain valve.

[0104] In some preferred working conditions, after the prestressed concrete box girder 11 is installed in place, in principle, dynamic load adjustment by injection and drainage is no longer performed, and the air compressor can be removed.

[0105] Example 2

[0106] A semi-submersible floating wind turbine foundation provided in this embodiment is constructed by the following steps:

[0107] Step 1: Casting a prestressed concrete box girder 11, and leaving a hole in the prestressed concrete box girder 11;

[0108] Tension the prestressed tendons 111 passing through the hole, grouting into the hole so that the middle of the prestressed tendons 111 are bonded to the concrete, and the two ends of the prestressed tendons 111 are not bonded to the concrete, and the prestressed tendons 111 are anchored by anchors 112;

[0109] Step 2: Install the steel base;

[0110] Step 3: Connect the steel base with the prestressed concrete box beam 11 by pouring, wherein the anchor 112 is buried in the concrete of the base 16 during pouring, leaving a position for installing the buoy;

[0111] Step 4: Install the side buoy 22.

[0112] In step 1, the steel mesh of the prestressed concrete box girder 11 can be tied first, and a corrugated pipe can be inserted into the steel mesh to form a channel through the corrugated pipe; the steel mesh of the prestressed concrete box girder 11 can include elongation bars extending from both ends for fixing the connection base 16.

[0113] After the strength of the prestressed concrete box beam 11 reaches 75% or more, the prestressed tendons 111 can be inserted into the corrugated pipe, and then tensioned, grouted, and anchored. During grouting, some cement slurry test blocks can be reserved for strength testing, so as to infer the solidification status of the cement slurry in the corrugated pipe by measuring the strength of the cement slurry test blocks.

[0114] In step 2, the steel base may be connected to the elongation ribs.

[0115] In one or more preferred embodiments, step 1 comprises the following steps:

[0116] Step 11: Check the strength of the prestressed concrete box girder 11 and make prestressed tendons 111;

[0117] After the strength of the prestressed concrete box beam 11 reaches the design strength, the prestressed tendons 111 are installed;

[0118] Inspect anchor 112, install anchor 112 and tensioning equipment, and pre-inspect tensioning equipment;

[0119] Step 12: tensioning the prestressed tendons 111;

[0120] Grouting of holes and making cement slurry test blocks;

[0121] Step 13: Measure the strength of the slurry in the channel by pressing the cement slurry test block. When the expected strength is reached, it can be lifted and transported.

[0122] Example 3

[0123] A floating wind turbine system provided in this embodiment includes a wind turbine 4 and a semi-submersible floating wind turbine foundation as described in Example 1 or 2, wherein the wind turbine 4 is installed on an intermediate buoy 21, and a connecting rod assembly 3 is connected between the side buoy 22 and the intermediate buoy 21, wherein the connecting rod assembly 3 includes an upper cross bar 31 and a lower cross bar 32, and a diagonal rod 33 located between the upper cross bar 31 and the lower cross bar 32.

[0124] The upper cross bar 31 and the lower cross bar 32 may be connected to the middle buoy 21 at one end and connected to the side buoy 22 at the other end.

[0125] The floating wind turbine system provided by the present invention can save part of the steel bar and concrete costs while meeting the load-bearing requirements and stability requirements of the offshore wind turbine by using the semi-submersible floating wind turbine foundation as described above, thereby greatly reducing the steel consumption of the wind turbine foundation and part of other costs, which is beneficial to improving the overall economic benefits of the offshore wind turbine project and enabling large-scale commercial use of offshore wind turbines.

[0126] Preferably, the middle buoy 21 and the side buoy 22 are both steel structures, such as steel buoys; the upper cross bar 31, the lower cross bar 32 and the diagonal bar 33 are all steel structures, such as steel pipes.

[0127] Preferably, the three side buoys 22 and the three bases 16 are distributed in an equilateral triangle, and the middle buoy 21 is located at the center of the equilateral triangle.

[0128] Preferably, when constructing the base 16, a section of a buoy unit can be pre-buried on the base 16, and the buoy unit is connected to the steel base of the base 16 through anchor bars; in subsequent construction, other buoy units are constructed above the buoy unit, and the buoy units on each base 16 together constitute a side buoy 22.

[0129] Example 4

[0130] This embodiment provides a floating wind turbine system, comprising a wind turbine 4 and a semi-submersible floating wind turbine foundation as described in Embodiment 1 or 2, wherein:

[0131] The upper floating body 2 includes a middle buoy 21 and three side buoys 22 arranged around the middle buoy 21. The three side buoys 22 are distributed in an equilateral triangle. The middle buoy 21 is located at the center of the equilateral triangle. The fan 4 is installed on the middle buoy 21. The side buoy 22 is connected to the middle buoy 21 through a connecting rod assembly 3. The connecting rod assembly 3 includes an upper cross bar 31 and a lower cross bar 32 arranged vertically at intervals, and an inclined rod 33 located between the upper cross bar 31 and the lower cross bar 32. The two ends of the inclined rod 33 are respectively connected to the side buoy 22 and the middle buoy 21.

[0132] The lower floating body 1 includes three bases 16 distributed in an equilateral triangle, the side pontoons 22 are connected to the bases 16, and prestressed concrete box girders 11 are connected between the bases 16; the prestressed concrete box girder 11 is provided with prestressed tendons 111, and the prestressed tendons 111 are prestressed steel strand bundles; the prestressed concrete box girder 11 includes a bottom plate 12, a top plate 13 and side plates 14, and the prestressed tendons 111 are distributed in the middle of the bottom plate 12, the middle of the top plate 13 and the four corners.

[0133] Example 5

[0134] A floating wind turbine foundation design method provided in this embodiment can be applied to the semi-submersible floating wind turbine foundation described in Embodiment 3 or 4, comprising the following steps:

[0135] S1. According to the draft depth and displacement of the wind turbine foundation, a finite element model of the wind turbine foundation and the wind turbine 4 is constructed, wherein the wind turbine 4 is located on the middle buoy 21;

[0136] S2. Calculate the equivalent design wave using the finite element model:

[0137] Obtain the maximum vertical static bending moment Mxy1_s of the prestressed concrete box girder 11 under still water conditions and the maximum vertical dynamic bending moment Mxy1_d under wave conditions, and combine Mxy1_s and Mxy1_d to obtain the maximum vertical bending moment Mxy1 of the prestressed concrete box girder 11;

[0138] Obtain the maximum vertical static bending moment Mxy2_s of the connecting rod assembly 3 under still water conditions and the maximum vertical dynamic bending moment Mxy2_d under wave conditions, and combine Mxy2_s and Mxy2_d to obtain the maximum vertical bending moment Mxy2 of the connecting rod assembly 3;

[0139] S3. Determine whether the ratio of Mxy1 to Mxy2 meets the design requirements, wherein the maximum vertical bending moment of the prestressed concrete box girder 11 is Mxy1=Mxy1_s+Mxy1_d, and the maximum vertical bending moment of the connecting rod assembly 3 is Mxy2=Mxy2_s+Mxy2_d.

[0140] A floating wind turbine foundation design method provided by the present invention can be used to evaluate whether the base 16 and the prestressed concrete box girder 11 are the main bodies that bear wave loads, thereby serving as a design basis for the floating wind turbine foundation; the design method uses finite element analysis to perform equivalent design wave calculations, simulates and analyzes and obtains the vertical bending moments of the prestressed concrete box girder 11 and the connecting rod assembly 3 under still water conditions and wave conditions, and by combining the vertical bending moments and comparing the combined Mxy1 and Mxy2, it can more intuitively reflect the role of the lower floating body in bearing wave loads.

[0141] In the demonstration example, when the value of Mxy1 / Mxy2 is between 1.5 and 3, the bending moment and shear force distribution of the wind turbine foundation is more uniform, and there are fewer stress concentration points in the structure.

[0142] Preferably, S2 comprises the following steps:

[0143] S21. Select a significant wave height Hs and at least two wave periods Tn (n=1, 2, ...) according to the engineering environment;

[0144] S22. Calculate the vertical bending moment at the end of the prestressed concrete box girder 11 in the static water condition, and select the maximum value as Mxy1_s;

[0145] Calculate the vertical bending moment at the end of the prestressed concrete box girder 11 in at least two wave directions in each wave period Tn, and select the maximum value as Mxy1_d;

[0146] Calculate the vertical bending moment at the end of the lower crossbar 32 under still water conditions, and select the maximum value as Mxy2_s;

[0147] The vertical bending moment at the end of the lower cross bar 32 in at least two wave directions in each wave period Tn is calculated, and the maximum value thereof is selected as Mxy2_d.

[0148] Take an optimal working condition as an example: the draft depth of the wind turbine foundation is 20 meters, the displacement is 20,000 tons, and the following can be constructed: Fig.10 The wet surface model and mass model are shown; when performing equivalent design wave calculations, the significant wave height Hs≈10m is selected, and 5 wave periods are selected, namely T=10.47s, 11.42s, 12.57s, 13.96s, and 15.71s, and the wave directions are selected as 0 degrees and 90 degrees.

[0149] The end of the prestressed concrete box beam 11 is selected as the force control point of the lower floating body 1 (such as Figure 7 The end of the lower cross bar 32 is selected as the force control point of the upper floating body 2 (such as point A in FIG. Figure 7 point B in the figure).

[0150] The ends of the three prestressed concrete box girders 11 are numbered as NO.1167, NO.1237, NO.3139, NO.3209, NO.3320, and NO.3391, and the following data can be obtained by calculation:

[0151]

[0152] Among them: LC1_Static is the vertical bending moment under the condition of still water, LC2_Dynamic is the vertical bending moment under the condition of wave period T = 15.71s, LC3_Dynamic is the vertical bending moment under the condition of wave period T = 13.96s, LC4_Dynamic is the vertical bending moment under the condition of wave period T = 12.57s, LC5_Dynamic is the vertical bending moment under the condition of wave period T = 11.42s, and LC6_Dynamic is the vertical bending moment under the condition of wave period T = 10.47s.

[0153] From the above table, it can be found that the maximum vertical static bending moment Mxy1_s of the prestressed concrete box girder 11 under static water conditions is 4.07×10 7 N·m.

[0154] When the wave direction is 0 degrees, the maximum vertical dynamic bending moment Mxy1_d of the prestressed concrete box girder 11 under the above five wave conditions is 1.11×10 8 N·m, it can be obtained that when the wave direction is 0 degrees, the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 is: Mxy1_d / Mxy1_s=2.73.

[0155] When the wave direction is 90 degrees, the maximum vertical dynamic bending moment Mxy1_d of the prestressed concrete box girder 11 under the above five wave conditions is 8.91×10 7 N·m, it can be obtained that when the wave direction is 90 degrees, the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 is: Mxy1_d / Mxy1_s=2.19.

[0156] In summary, when the wave direction is 0 degrees, Mxy1_d=1.11×10 8 N·m is taken as the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 under wave conditions.

[0157] Fig. 9 This is a schematic diagram of the force results under the conditions of wave direction of 0 degrees and wave period T = 15.71s.

[0158] The ends of the three lower cross bars 32 are numbered as NO.312, NO.335, NO.2970, NO.2993, NO.3502, and NO.3525, respectively, and the following data can be calculated:

[0159]

[0160] It can be found from the above table that the maximum vertical static bending moment Mxy2_s of the lower crossbar 32 under static water conditions is 2.13×10 7 When the wave direction is 0 degrees, the maximum vertical dynamic bending moment Mxy2_d of the lower cross bar 32 under the above five wave conditions is 5.28×10 7 N·m; it can be obtained that when the wave direction is 0 degrees, the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the lower cross bar 32 is: Mxy2_d / Mxy2_s=2.47.

[0161] When the wave direction is 90 degrees, the maximum vertical dynamic bending moment Mxy2_d of the lower cross bar 32 under the above five wave conditions is 5.14×10 7N·m; it can be obtained that when the wave direction is 90 degrees, the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the lower cross bar 32 is: the ratio of Mxy2_d / Mxy2_s is 2.41.

[0162] In summary, when the wave direction is 0 degrees, Mxy2_d=5.28×10 7 N·m is taken as the maximum vertical dynamic bending moment of the connecting rod assembly 3 under wave conditions.

[0163] Combining Mxy1_s and Mxy1_d gives:

[0164] Mxy1=Mxy1_s+Mxy1_d=4.07×10 7 +1.11×10 8 =1.52×10 8 N·m;

[0165] Combining Mxy2_s and Mxy2_d gives:

[0166] Mxy2=Mxy2_s+Mxy2_d=2.13×10 7 +5.28×10 7 =7.41×10 7 N·m.

[0167] The ratio of the maximum vertical bending moment of the prestressed concrete box girder 11 to the connecting rod assembly 3 is:

[0168] Mxy1 / Mxy2=1.52×10 8 / 7.41×10 7 =2.05; meets the design standards.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A semi-submersible floating wind turbine foundation, characterized in that: include: A middle buoy (21) and at least three side buoys (22) arranged around the middle buoy (21), a base (16) is cast at the bottom of the side buoy (22), and prestressed concrete box beams (11) are connected between adjacent bases (16).

2. The semi-submersible floating wind turbine foundation according to claim 1, characterized in that: The prestressed concrete box girder (11) is provided with prestressed tendons (111) along its length direction, and anchors (112) are provided at both ends of the prestressed tendons (111).

3. The semi-submersible floating wind turbine foundation according to claim 2, characterized in that: The prestressed tendons (111) comprise a bonding section (113) and a non-bonding section (114); the bonding section (113) is located in the middle of the prestressed concrete box girder (11); and the non-bonding section (114) is located at the end of the prestressed concrete box girder (11).

4. The semi-submersible floating wind turbine foundation according to claim 3, characterized in that: A steel base is arranged inside the base (16), and a concrete shell is cast and covered on the outer side of the steel base, and the concrete shell is cast and connected to the prestressed concrete box beam (11).

5. The semi-submersible floating wind turbine foundation according to claim 4, characterized in that: At least part of the anchor (112) extends into the base (16); at least part of the anchor (112) or at least part of the prestressed tendons (111) are connected to the steel base; and the side buoy (22) is connected to the steel base.

6. The semi-submersible floating wind turbine foundation according to claim 4, characterized in that: The prestressed tendons (111) are prestressed steel strand bundles; The prestressed concrete box girder (11) is cast using ultra-high performance concrete; The concrete shell and the prestressed concrete box beam (11) are connected by pouring ultra-high performance concrete; The prestressed concrete box girder (11) comprises a bottom plate (12), a top plate (13) and a side plate (14); the prestressed tendons (111) are distributed in the middle of the bottom plate (12), the middle of the top plate (13) and four corners; There are three bases (16) in total, and they are distributed in a triangle shape.

7. The semi-submersible floating wind turbine foundation according to claim 4, characterized in that: The construction is carried out by the following steps: Step 1: Casting the prestressed concrete box girder (11), and leaving a hole in the prestressed concrete box girder (11); The prestressed tendons (111) passing through the hole are tensioned, grouting is poured into the hole, so that the middle of the prestressed tendons (111) is bonded to the concrete, and the two ends of the prestressed tendons (111) are not bonded to the concrete, and the prestressed tendons (111) are anchored by anchors (112); Step 2: Install the steel base; Step 3: Connecting the steel base with the prestressed concrete box girder (11) by pouring, wherein the anchor (112) is buried in the concrete of the base (16) during pouring, leaving a position for installing the buoy; Step 4: Install the side buoy (22).

8. A floating wind turbine system, characterized in that: It comprises a wind turbine (4) and a semi-submersible floating wind turbine foundation as described in any one of claims 1 to 7, wherein the wind turbine (4) is installed on the middle buoy (21), a connecting rod assembly (3) is connected between the side buoy (22) and the middle buoy (21), and the connecting rod assembly (3) comprises an upper cross bar (31) and a lower cross bar (32), and an inclined rod (33) located between the upper cross bar (31) and the lower cross bar (32).

9. A floating wind turbine foundation design method, characterized in that: The floating wind turbine system as claimed in claim 8 comprises the following steps: S1. constructing a finite element model of the wind turbine foundation and the wind turbine (4) according to the draft and displacement of the wind turbine foundation, wherein the wind turbine (4) is located on the intermediate buoy (21); S2. Calculate the equivalent design wave using the finite element model: Obtaining the maximum vertical static bending moment Mxy1_s of the prestressed concrete box girder (11) under still water conditions and the maximum vertical dynamic bending moment Mxy1_d under wave conditions, and combining Mxy1_s and Mxy1_d to obtain the maximum vertical bending moment Mxy1 of the prestressed concrete box girder (11); Obtaining the maximum vertical static bending moment Mxy2_s of the connecting rod assembly (3) under still water conditions and the maximum vertical dynamic bending moment Mxy2_d under wave conditions, and combining Mxy2_s and Mxy2_d to obtain the maximum vertical bending moment Mxy2 of the connecting rod assembly (3); S3. Determine whether the ratio of Mxy1 to Mxy2 meets the design requirements, wherein the maximum vertical bending moment Mxy1 of the prestressed concrete box girder (11) is Mxy1=Mxy1_s+Mxy1_d, and the maximum vertical bending moment Mxy2 of the connecting rod assembly (3) is Mxy2=Mxy2_s+Mxy2_d.

10. The floating wind turbine foundation design method according to claim 9, characterized in that: The S2 comprises the following steps: S21. Select a significant wave height Hs and at least two wave periods Tn (n=1, 2, ...) according to the engineering environment; S22. Calculate the vertical bending moment at the end of the prestressed concrete box girder (11) in the static water condition, and select the maximum value as Mxy1_s; Calculating the vertical bending moment at the end of the prestressed concrete box girder (11) in at least two wave directions in each wave period Tn, and selecting the maximum value therebetween as Mxy1_d; Calculate the vertical bending moment at the end of the lower crossbar (32) under still water conditions, and select the maximum value as Mxy2_s; The vertical bending moment at the end of the lower crossbar (32) in at least two wave directions in each wave period Tn is calculated, and the maximum value thereof is selected as Mxy2_d.

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