Semi-submersible floating wind turbine foundation, system and design method

Abstract

The present application relates to offshore wind power generation technology field, especially to a kind of semi-submersible floating wind turbine foundation, system and design method.Semi-submersible floating wind turbine foundation includes: intermediate pontoon and at least three edge pontoon arranged around intermediate pontoon, the bottom of edge pontoon is poured with base, and prestressed concrete box girder is connected between adjacent edge pontoon.The semi-submersible floating wind turbine foundation provided by the present application can be used to bear offshore wind turbine, by adopting the form of pontoon and box girder combination, the effective displacement of wind turbine foundation can be greatly improved, so that wind turbine foundation has greater carrying capacity;Box girder adopts prestressed concrete box girder, can be used by the higher structural strength, stiffness and excellent crack resistance, durability of prestressed concrete box girder, under the condition of meeting the load demand and stability requirement of offshore wind turbine, save part of reinforcement and concrete cost, it is favorable to improve the overall economic benefit of offshore wind turbine engineering, so that offshore wind turbine can be large-scale commercial use.

Description

TECHNICAL FIELD

[0001] The present application relates to the offshore wind power technology field, in particular to a semi-submersible floating wind turbine foundation, system and design method. BACKGROUND

[0002] At present, the fixed foundation commonly used in offshore wind power is suitable for shallow beach. With the offshore wind energy resource development tending to saturation, offshore wind power is moving towards deep sea, and the sea area with water depth exceeding 60 meters is suitable for floating offshore wind power. At present, the floating wind power at home and abroad is still in the exploration and demonstration stage. In order to meet the stability requirements, a large amount of steel is used in the wind power foundation, and the economic benefit has not reached the large-scale commercial requirements. SUMMARY

[0003] The present application aims to overcome the problem of large amount of steel used in the wind power foundation in the background art and low economic benefit, and provides a semi-submersible floating wind turbine foundation, system and design method.

[0004] In a first aspect, the present application provides a semi-submersible floating wind turbine foundation, comprising: a middle floating cylinder and at least three edge floating cylinders arranged around the middle floating cylinder, the bottom of the edge floating cylinder being poured with a base, and a pre-stressed concrete box girder being connected between adjacent bases.

[0005] The semi-submersible floating wind turbine foundation provided by the present application can be used to bear offshore wind turbines. By adopting the combination of floating cylinders and box girders, the effective displacement of the wind turbine foundation can be greatly improved, so that the wind turbine foundation has greater bearing capacity. The pre-stressed concrete box girder is used, so that the higher structural strength, stiffness, excellent crack resistance and durability of the pre-stressed concrete box girder can be utilized to save part of the steel and concrete cost under the condition of meeting the bearing demand and stability requirement of offshore wind turbines, thereby greatly reducing the steel consumption and part of the other costs of the wind turbine foundation, which is beneficial to improve the overall economic benefit of offshore wind turbine engineering and make offshore wind turbines large-scale commercial.

[0006] Preferably, the pre-stressed concrete box girder is provided with a pre-stressed tendon along the length direction thereof, and the pre-stressed tendon is provided with an anchor at both ends.

[0007] Preferably, the pre-stressed tendon comprises a bonded section and an unbonded section, the bonded section is located in the middle of the pre-stressed concrete box girder, and the unbonded section is located at the end of the pre-stressed concrete box girder.

[0008] The bonding section of the prestressed tendon can be bonded with the prestressed concrete box girder through the cement slurry, which is beneficial to improve the connection tightness of the prestressed tendon and the prestressed concrete box girder, and further improve the bearing capacity of the prestressed concrete box girder; the unbonding section of the prestressed tendon is not bonded with the prestressed concrete box girder, and is arranged at the end part, so that the connection part of the prestressed concrete box girder and the base can be slightly opened to release the internal force in the extreme adverse conditions, thereby maintaining the safety of the overall structure.

[0009] Preferably, a steel base is arranged in the base, and a concrete shell is cast on the outer side of the steel base.

[0010] Preferably, at least part of the anchor is inserted into the base; at least part of the anchor or at least part of the prestressed tendon is connected with the steel base; and the side buoy is connected with the steel base.

[0011] Preferably, the prestressed tendon is a prestressed steel strand bundle.

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

[0013] Preferably, the concrete shell and the prestressed concrete box girder are connected by using 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 part of the bottom plate, the middle part of the top plate and the four corner parts.

[0015] Preferably, the base is three in number and is distributed in a triangular shape.

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

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

[0018] tensioning the prestressed tendon arranged in the hole, grouting into the hole, bonding the middle part of the prestressed tendon with the concrete, not bonding the two ends of the prestressed tendon with the concrete, and anchoring the prestressed tendon by using an anchor;

[0019] Step 2: installing the steel base;

[0020] Step 3: casting and connecting the steel base with the prestressed concrete box girder, wherein the anchor is embedded in the concrete of the base during casting, and a position for installing a buoy is reserved;

[0021] Step 4: installing the side buoy.

[0022] In a second aspect, the present application provides a floating wind turbine system, comprising a wind turbine and a semi-submersible floating wind turbine foundation as described above, the wind turbine being mounted on the middle pontoon, and a linkage assembly being connected between the side pontoons and the middle pontoon, the linkage assembly comprising an upper crossbar and a lower crossbar, and diagonal bars between the upper crossbar and the lower crossbar.

[0023] The present application provides a floating wind turbine system, by using the semi-submersible floating wind turbine foundation as described above, the steel consumption and part of the other costs of the wind turbine foundation can be greatly reduced to improve the overall economic benefits of offshore wind turbine engineering, so that offshore wind turbines can be commercially used on a large scale, while meeting the load-bearing requirements and stability requirements of offshore wind turbines.

[0024] In a third aspect, the present application provides a floating wind turbine foundation design method, applied to the floating wind turbine system as described above, comprising 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 middle pontoon;

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

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

[0028] Obtaining the maximum vertical static bending moment Mxy2_s of the linkage assembly under static water working conditions, and the maximum vertical dynamic bending moment Mxy2_d of the linkage assembly under wave working conditions, and combining Mxy2_s and Mxy2_d to obtain the maximum vertical bending moment Mxy2 of the linkage assembly;

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

[0030] The application provides a floating wind turbine foundation design method, which can be used for evaluating whether a base and a prestressed concrete box girder are main bodies for bearing wave loads, thereby serving as a design basis of the floating wind turbine foundation; the design method uses finite element analysis to calculate equivalent design waves, simulates and analyzes vertical bending moments of the prestressed concrete box girder and a connecting rod assembly under static water conditions and wave conditions, combines the vertical bending moments, and compares Mxy1 and Mxy2 obtained by the combination, so that the role of a lower floating body under wave loads can be directly reflected.

[0031] Preferably, S2 comprises the following steps:

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

[0033] S22. Calculating vertical bending moments of the prestressed concrete box girder end under static water conditions, and selecting a maximum value as Mxy1_s;

[0034] S23. Calculating vertical bending moments of the prestressed concrete box girder end in at least two wave directions under each wave period Tn, and selecting a maximum value as Mxy1_d;

[0035] S24. Calculating vertical bending moments of the lower cross bar end under static water conditions, and selecting a maximum value as Mxy2_s;

[0036] S25. Calculating vertical bending moments of the lower cross bar end in at least two wave directions under each wave period Tn, and selecting a maximum value as Mxy2_d.

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

[0038] 1. The semi-submersible floating wind turbine foundation provided by the application can be used for bearing offshore wind turbines, and by adopting a combination of a buoy and a box girder, the effective displacement of the wind turbine foundation can be greatly improved, so that the wind turbine foundation has greater bearing capacity; the box girder is a prestressed concrete box girder, and by using the high structural strength, rigidity, excellent crack resistance and durability of the prestressed concrete box girder, part of the steel and concrete cost can be saved under the condition of meeting the bearing demand and stability requirement of offshore wind turbines, so that the steel consumption and part of other costs of the wind turbine foundation are greatly reduced, the overall economic benefit of offshore wind turbine engineering is improved, and offshore wind turbines can be used on a large scale.

[0039] 2. The floating wind turbine system provided by the present application can meet the load bearing demand and stability requirement of offshore wind turbine, save part of the cost of steel and concrete, greatly reduce the steel consumption and other costs of the wind turbine foundation, improve the overall economic benefit of offshore wind turbine engineering, and make offshore wind turbine commercially available on a large scale.

[0040] 3. The floating wind turbine foundation design method provided by the present application can be used to evaluate whether the base and the prestressed concrete box girder are the main body of wave load bearing, thereby serving as the design basis of the floating wind turbine foundation. The design method uses finite element analysis to calculate equivalent design waves, simulates and analyzes the vertical bending moment of the prestressed concrete box girder and the connecting rod assembly under static water conditions and wave conditions, combines the vertical bending moments, and compares Mxy1 and Mxy2 obtained by the combination, so that the role of the lower floating body under wave load can be more directly reflected. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 FIG. 1 is a structural schematic diagram of the floating wind turbine system according to the present application;

[0042] Figure 2 FIG. 2 is a front view of the floating wind turbine system according to the present application;

[0043] Figure 3 FIG. 3 is a top view of the floating wind turbine system according to the present application;

[0044] Figure 4 FIG. 4 is a cross-sectional schematic diagram of the prestressed concrete box girder according to the present application;

[0045] Figure 5 FIG. 5 is a schematic diagram of the arrangement of the prestressed tendon according to the present application;

[0046] Figure 6 FIG. 6 is an optimization schematic diagram of the floating wind turbine foundation according to the present application;

[0047] Figure 7 FIG. 7 is a schematic diagram of the selection of control points in the design method according to the present application;

[0048] Figure 8 FIG. 8 is a parameter diagram of the floating wind turbine foundation under a specific working condition according to the present application;

[0049] Figure 9 FIG. 9 is a schematic diagram of the stress result of the floating wind turbine foundation under a typical dynamic load working condition according to the present application;

[0050] Figure 10 FIG. 10 is a wet surface model and a mass model of the floating wind turbine foundation and the wind turbine according to the present application.

[0051] Markings in the figure:

[0052] 1-floater body;

[0053] 11-prestressed concrete box girder;

[0054] 111-prestressed tendon; 112-anchor; 113-bonding section; 114-unbonding section;

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

[0056] 2-floater body;

[0057] 21-intermediate floater; 22-side floater;

[0058] 3-link assembly;

[0059] 31-upper cross bar; 32-lower cross bar; 33-inclined bar;

[0060] 4-fan. DETAILED DESCRIPTION

[0061] The application will be further described in conjunction with specific embodiments. However, it should not be understood that the above-mentioned subject matter of the application is limited to the following embodiments only, and any technology realized based on the content of the application falls within the scope of the application.

[0062] In the description of the specific embodiments of the application, the orientation or position relationship terms such as "up", "down", "left", "right", "center", "inner", "outer", and the like, are expressed based on the orientation or position relationship shown in the drawings, or the orientation or position relationship when the product / device / apparatus of the application is usually used. These orientation or position relationship terms are only used to facilitate the description of the application scheme or simplify the description in the specific embodiments, to facilitate the quick understanding of the scheme by the technicians, and are not intended to 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 application.

[0063] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or overhanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Alternatively, it can be simplified to understand that the corresponding device / component / element is arranged in the direction of "horizontal", "vertical", "overhanging", "parallel" and the like, and can have an error / deviation of ±10% relative to the corresponding direction, more preferably an error / deviation of ±8% or less, more preferably an error / deviation of ±6% or less, more preferably an error / deviation of ±5% or less, and more preferably an error / deviation of ±4% or less. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the present application.

[0064] In addition, the terms "first", "second", "third", and the like in the description of the present application are only used to distinguish the same or similar components, and should not be understood as emphasizing or implying the relative importance of the specific components.

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

[0066] In addition, in the description of the technical solutions of the present application, unless otherwise specified / limited / limited, the terms "arrangement", "installation", "connection", "connection", "provided with", "laid", "arrangement" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, which can be welding, riveting, bolting, screwing, etc. Common connection means in the art. Such connection can be mechanical connection, electrical connection or communication connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the communication between two elements.

[0067] Embodiment 1

[0068] As shown in Figures 1-5 The semi-submersible floating wind turbine foundation provided by the embodiment includes an upper floating body 2 and a lower floating body 1. The upper floating body 2 includes a middle floating cylinder 21 and at least three edge floating cylinders 22 arranged around the middle floating cylinder 21. The lower floating body 1 includes a base 16 arranged at the bottom of the edge floating cylinder 22 and a prestressed concrete box girder 11 located between adjacent bases 16.

[0069] The upper floating body 2 and the lower floating body 1 are both floating body structures capable of floating on the surface of a liquid, and the upper floating body 2 and the lower floating body 1 are fixedly connected to enable the two to float on the surface of a liquid (such as seawater) as a whole and to serve as a mounting base for the wind turbine 4, enabling the wind turbine 4 to float on the sea.

[0070] The intermediate pontoon 21 and the side pontoon 22 are both pontoon structures, have a large volume and a small mass, and can float on the surface of water. When the intermediate pontoon 21 and the side pontoon 22 are connected to the upper floating body 2 and the lower floating body 1, the intermediate pontoon 21 and the side pontoon 22 can increase the load-carrying capacity of the wind turbine base to meet the installation requirements of the large-mass wind turbine 4. Preferably, the intermediate pontoon 21 and the side pontoon 22 are both cylindrical.

[0071] The prestressed concrete box girder 11 is a box girder with prestress. On the one hand, the hollow structure of the prestressed concrete box girder 11 can increase the volume of the displaced water and improve the buoyancy. On the other hand, the prestressed concrete box girder 11 is a prestressed structure, which not only has a high structural strength, can realize a high load-carrying capacity with less material, but also has good crack resistance and durability. In particular, in the seawater environment, the excellent crack resistance can make the surface of the prestressed concrete box girder 11 almost free of cracks, thereby avoiding the corrosion of seawater into the internal steel bars.

[0072] The prestressed concrete box girder 11 is a box girder component, which has a hollow chamber inside to 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 and further increase the load-carrying capacity of the wind turbine base. The prestressed concrete box girder 11 has a relatively large cross-sectional size (cut by a surface perpendicular to the longitudinal direction thereof), so that it has a large moment of inertia and thus has a large bending resistance. Moreover, the prestressed concrete box girder 11 has a large vertical projection area, so that when it is located in water, it has a large waterplane area, and the floating wind turbine base has a large restoring moment to have better ability to suppress heave, surge and pitch, and can improve stability and reduce the risk of capsizing.

[0073] The semi-submersible floating wind turbine base provided by the application can be used to carry a wind turbine on the sea. By adopting the combination of a pontoon and a box girder, the effective displacement of the wind turbine base can be greatly increased, and the wind turbine base has a larger load-carrying capacity. The box girder is a prestressed concrete box girder 11, which can save part of the steel and concrete costs by utilizing the high structural strength, stiffness, excellent crack resistance and durability of the prestressed concrete box girder 11 to meet the load-carrying demand and stability requirement of the offshore wind turbine, thereby greatly reducing the steel consumption and part of the other costs of the wind turbine base and being beneficial to improving the overall economic benefit of the offshore wind turbine project, so that the offshore wind turbine can be commercially used on a large scale.

[0074] Figure 6For the optimization schematic of the floating wind turbine foundation described in the present application, the prestressed concrete box girder 11 is added on the basis of the prior art, which can reduce the draft depth without affecting the overall width and can increase the stability of the overall structure.

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

[0076] The design theory of ultra-high performance concrete is the densified particle packing theory, in which particles of different sizes of constituent materials form the closest 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 fibers (steel fibers or composite organic fibers) must be used, the cement dosage is larger, and the water-cement ratio is very low.

[0077] Under the conditions of meeting the bearing requirements and stability requirements, using the prestressed concrete box girder 11 as the lower floating body 1 can reduce the structural self-weight and greatly reduce the steel consumption of the wind turbine foundation. The inventor has confirmed through tests that the use of a large amount of ultra-high performance prestressed concrete can make the steel consumption of the wind turbine foundation less than 300 t / MW (the steel consumption required for each megawatt of power generation is less than 300 tons), greatly reducing the cost and improving the economic benefits of the overall project. Figure 8 As shown in Figure 8 For the parameter diagram of the floating wind turbine foundation designed for a specific working condition, the steel consumption is 213 t / MW.

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

[0079] For this embodiment, the prestressed tendons 111 can be tensioned by the post-tensioning process: during construction, corrugated pipes arranged along the length direction can be pre-buried in the reinforcement 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 penetrating the corrugated pipes are tensioned by the two-end tensioning method, and the tensioned prestressed tendons 111 can be connected to the box girder by two-end anchoring or grouting in the corrugated pipes, thereby forming the prestressed concrete box girder 11.

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

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

[0082] Preferably, the prestressed tendon 111 comprises a bonded section 113 and an unbonded section 114, the bonded section 113 is located in the middle of the prestressed concrete box girder 11, and the unbonded section 114 is located at the end of the prestressed concrete box girder 11, as shown. Figure 5

[0083] In the exemplary embodiment, the bonded section 113 of the prestressed tendon 111 is adhered to the prestressed concrete box girder 11 by cement paste, which can improve the tightness of the connection between the prestressed tendon 111 and the prestressed concrete box girder 11 at this location, so that the prestress can better act on the prestressed concrete box girder 11. The unbonded section 114 of the prestressed tendon 111 is not adhered to the box girder by cement paste to allow relative displacement between the prestressed tendon 111 and the prestressed concrete box girder 11; by arranging the unbonded section 114 at both ends of the prestressed concrete box girder 11, the connection between the prestressed concrete box girder 11 and the base 16 can be slightly opened to release stress under extremely adverse conditions, thereby maintaining the overall structural safety of the floating body 1.

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

[0085] In one or more preferred embodiments, a steel base is provided inside the base 16, the outer side of the steel base is coated with a concrete shell, and the concrete shell is cast connected with 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, which can have high structural strength, crack resistance and durability through ultra-high performance concrete and prestress.

[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 tendon 111 is connected to the steel base; and the side float 22 is connected to the steel base.

[0088] By connecting at least part of the anchor 112 or at least part of the prestressed tendon 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 float 22 to the steel base, the connection strength between the base 16 and the side float 22 can be increased, which is beneficial to improve the integrity of the floating wind turbine foundation.

[0089] ​Preferably, the concrete shell and the prestressed concrete box girder 11 are connected by casting with ultra-high performance concrete. This can further improve the overall integrity of the lower buoy 1.

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

[0091] Several holes 15 can be arranged in the middle of the bottom plate 12 and the top plate 13, and several holes 15 can 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 prestressing tendons 111 can be inserted into the holes 15.

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

[0093] Preferably, there are three bases 16, which are arranged in a triangular pattern.

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

[0095] More preferably, the three bases 16 are arranged in an equilateral triangle, with the three bases 16 located at the three vertices of the equilateral triangle, and the three prestressed concrete box girders 11 located on the three sides of the equilateral triangle.

[0096] An equilateral triangular distribution can give the wind turbine foundation a high degree of symmetry, improve the uniformity of internal force distribution, minimize stress concentration, and make full use of materials in each part. This reduces costs and improves the economic benefits of the project while meeting load-bearing requirements.

[0097] In one or more preferred embodiments, the prestressed concrete box girder 11 has a flat structure; such as Figure 4 As shown, the transverse dimension of the flat, prestressed concrete box girder 11 section is much larger than its vertical dimension, generally twice 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, which can give the wind turbine foundation a higher resistance to overturning and improve the stability of the entire system.

[0098] Due to the excellent crack resistance of the prestressed concrete box girder 11, the flat design does not substantially increase the thickness of the top plate 13 and the bottom plate 12 of the prestressed concrete box girder 11, and the manufacturing cost of the prestressed concrete box girder 11 is limited, but the overall stability is substantially improved.

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

[0100] In one or more preferred embodiments, the prestressed concrete box girder 11 is internally provided with at least two compartments; at least part of the compartments are ballast water compartments.

[0101] The ballast water compartments can be used to store seawater, and the ballast water compartments are distributed at different positions of the prestressed concrete box girder 11. By injecting water or draining water into different ballast water compartments, the inclination, draft and gravity center distribution of the prestressed concrete box girder 11 can be adjusted to maintain the attitude stability of the prestressed concrete box girder 11. When floating in the dock, the ballast water compartments can be in an empty state to reduce the draft of the prestressed concrete box girder 11, thereby reducing the requirement for water depth in the dock; when transported to the pre-loading water area, the ballast water compartments can be injected with water to reduce the gravity center of the entire system, thereby improving the overall stability.

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

[0103] Preferably, a plurality of water inlet and outlet valves can be arranged at the bottom of the prestressed concrete box girder 11, the water inlet and outlet 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, and the air compressor can blow air into the ballast water compartments through pipelines to drain the water in the ballast water compartments through the water inlet and outlet valves.

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

[0105] Embodiment 2

[0106] The semi-submersible floating wind turbine foundation provided in the embodiment is formed by the following steps:

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

[0108] Tensioning the prestressed tendon 111 arranged in the hole, grouting into the hole, bonding the middle part of the prestressed tendon 111 with the concrete, and not bonding the two ends of the prestressed tendon 111 with the concrete, and anchoring the prestressed tendon 111 by the anchor 112;

[0109] Step 2: installing a steel base;

[0110] Step 3: Pouring the steel base and the prestressed concrete box girder 11, wherein the anchorage 112 is embedded in the concrete of the base 16 during pouring, and the position of the installation of the pontoon is reserved;

[0111] Step 4: Installing the side pontoon 22.

[0112] In step 1, the steel reinforcement net of the prestressed concrete box girder 11 can be bound first, and the corrugated pipe is arranged in the steel reinforcement net to form a hole channel. The steel reinforcement net of the prestressed concrete box girder 11 can include the elongated tendon, which extends from both ends for fixed connection with the base 16.

[0113] After the strength of the prestressed concrete box girder 11 reaches 75% or above, the prestressed tendon 111 is arranged in the corrugated pipe, and then tensioned, grouted and anchored. During grouting, part of the cement paste test block can be reserved for strength detection, so as to determine the solidification condition of the cement paste in the corrugated pipe by measuring the strength of the cement paste test block.

[0114] In step 2, the steel base can be connected with the elongated tendon.

[0115] In one or several preferred embodiments, step 1 includes the following steps:

[0116] Step 11: checking the strength of the prestressed concrete box girder 11, and making the prestressed tendon 111;

[0117] After the strength of the prestressed concrete box girder 11 reaches the design strength, the prestressed tendon 111 is arranged;

[0118] The anchorage 112 is inspected, the anchorage 112 and the tensioning equipment are installed, and the tensioning equipment is pre-tested;

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

[0120] The hole is grouted, and the cement paste test block is made;

[0121] Step 13: measuring the strength of the slurry in the hole by pressing the cement paste test block, and lifting and transporting after reaching the expected strength.

[0122] Embodiment 3

[0123] The floating wind turbine system provided in the embodiment includes the wind turbine 4 and the semi-submersible floating wind turbine foundation as described in embodiment 1 or 2, the wind turbine 4 is installed on the middle pontoon 21, the side pontoon 22 is connected with the middle pontoon 21 through the connecting rod assembly 3, the connecting rod assembly 3 includes the upper horizontal rod 31 and the lower horizontal rod 32, and the inclined rod 33 between the upper horizontal rod 31 and the lower horizontal rod 32.

[0124] The upper horizontal rod 31 and the lower horizontal rod 32 can be connected with the middle pontoon 21 at one end and connected with the side pontoon 22 at the other end.

[0125] The floating wind turbine system provided by the present application can save part of the cost of steel and concrete 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, improving the overall economic benefit of the offshore wind turbine project, and making the offshore wind turbine commercially available on a large scale.

[0126] Preferably, the intermediate buoy 21 and the edge buoy 22 are steel structures, such as steel buoys; and the upper crossbar 31, the lower crossbar 32 and the inclined bar 33 are steel structures, such as steel pipes.

[0127] Preferably, the three edge buoys 22 and the three bases 16 are arranged in a regular triangle, and the intermediate buoy 21 is located at the center of the regular triangle.

[0128] Preferably, when the base 16 is constructed, a buoy unit is pre-buried on the base 16, the buoy unit is connected to the steel base of the base 16 through anchor reinforcement, and other buoy units are constructed above the buoy unit in subsequent construction, and the buoy units on each base 16 collectively form the edge buoy 22.

[0129] Embodiment 4

[0130] The floating wind turbine system provided by the present embodiment comprises a wind turbine 4 and a semi-submersible floating wind turbine foundation as described in Embodiment 1 or 2, wherein:

[0131] The floating body 2 comprises an intermediate buoy 21 and three edge buoys 22 arranged around the intermediate buoy 21, the three edge buoys 22 are arranged in a regular triangle, the intermediate buoy 21 is located at the center of the regular triangle, and the wind turbine 4 is installed on the intermediate buoy 21; the edge buoy 22 is connected to the intermediate buoy 21 through the connecting rod assembly 3, the connecting rod assembly 3 comprises vertically spaced upper crossbars 31 and lower crossbars 32, and inclined bars 33 located between the upper crossbars 31 and the lower crossbars 32, and the two ends of the inclined bars 33 are connected to the edge buoy 22 and the intermediate buoy 21, respectively.

[0132] The lower floating body 1 comprises three bases 16 arranged in a regular triangle, the edge buoy 22 is connected to the base 16, and the pre-stressed concrete box girder 11 is connected between the bases 16; the pre-stressed concrete box girder 11 is provided with pre-stressed tendons 111, the pre-stressed tendons 111 are pre-stressed steel strand bundles; the pre-stressed concrete box girder 11 comprises a bottom plate 12, a top plate 13 and side plates 14, and the pre-stressed tendons 111 are distributed in the middle of the bottom plate 12, the middle of the top plate 13 and the four corners.

[0133] Embodiment 5

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

[0135] S1. According to the draft 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 pontoon 21;

[0136] S2. Equivalent design wave calculation is performed by using the finite element model:

[0137] The maximum vertical static bending moment Mxy1_s of the prestressed concrete box girder 11 under the static water working condition and the maximum vertical dynamic bending moment Mxy1_d of the prestressed concrete box girder 11 under the wave working condition are obtained, and the maximum vertical bending moment Mxy1 of the prestressed concrete box girder 11 is obtained by combining Mxy1_s and Mxy1_d;

[0138] The maximum vertical static bending moment Mxy2_s of the connecting rod assembly 3 under the static water working condition and the maximum vertical dynamic bending moment Mxy2_d of the connecting rod assembly 3 under the wave working condition are obtained, and the maximum vertical bending moment Mxy2 of the connecting rod assembly 3 is obtained by combining Mxy2_s and Mxy2_d;

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

[0140] The design method of the floating wind turbine foundation provided in the embodiment can be used to evaluate whether the base 16 and the prestressed concrete box girder 11 are the main body to bear the wave load, thereby serving as the design basis of the floating wind turbine foundation; the design method uses finite element analysis to perform equivalent design wave calculation, simulates and analyzes the vertical bending moments of the prestressed concrete box girder 11 and the connecting rod assembly 3 under the static water working condition and the wave working condition, combines the vertical bending moments, and compares Mxy1 and Mxy2 obtained by the combination, so that the role of the lower floating body when bearing the wave load can be more directly reflected.

[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, the S2 comprises the following steps:

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

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

[0145] Calculate the vertical bending moment of 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 of the end of the lower crossbar 32 in the static water working condition, and select the maximum value as Mxy2_s;

[0147] Calculate the vertical bending moment of the end of the lower crossbar 32 in at least two wave directions in each wave period Tn, and select the maximum value as Mxy2_d.

[0148] For example, in a preferred working condition, the draft of the fan foundation is 20 meters, and the displacement is 20000 tons, and the wet surface model and mass model can be constructed as shown in Figure 10 When calculating the equivalent design wave, the significant wave height Hs is selected to be about 10m, and 5 wave periods are selected, which are T=10.47s, 11.42s, 12.57s, 13.96s, 15.71s, and the wave direction is selected to be 0 degrees and 90 degrees.

[0149] The end of the prestressed concrete box girder 11 is selected as the stress control point of the lower floating body 1 (such as point A in Figure 7 ), and the end of the lower crossbar 32 is selected as the stress control point of the upper floating body 2 (such as point B in Figure 7 ).

[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 calculated:

[0151]

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

[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 the static water working condition is 4.07x10 7 N.m.

[0154] When the wave direction is 0 degree, the maximum vertical dynamic bending moment Mxy1_d of the prestressed concrete box girder 11 under the above five wave working conditions is 1.11x10 8 N.m, and the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 when the wave direction is 0 degree can be obtained as follows: 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 working conditions is 8.91x10 7 N.m, and the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 when the wave direction is 90 degrees can be obtained as follows: Mxy1_d / Mxy1_s=2.19.

[0156] In summary, Mxy1_d=1.11x10 8 N.m when the wave direction is 0 degree is selected as the maximum vertical dynamic bending moment of the prestressed concrete box girder 11 under the wave working condition.

[0157] Figure 9 The force result schematic diagram under the working condition of the wave direction being 0 degree and the wave period T=15.71s is shown.

[0158] The end portions of the three lower cross bars 32 are labeled as NO.312, NO.335, NO.2970, NO.2993, NO.3502, and NO.3525, and the following data can be obtained by calculation:

[0159]

[0160] From the above table, it can be found that the maximum vertical static bending moment Mxy2_s of the lower cross bar 32 under the static water working condition is 2.13x10 7 N.m. When the wave direction is 0 degree, the maximum vertical dynamic bending moment Mxy2_d of the lower cross bar 32 under the above five wave working conditions is 5.28x10 7 N.m; and the ratio of the maximum vertical static bending moment to the maximum vertical dynamic bending moment of the lower cross bar 32 when the wave direction is 0 degree can be obtained as follows: 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 working conditions is 5.14x10 7N·m; the ratio of the maximum vertical static bending moment and the maximum vertical dynamic bending moment of the lower cross bar 32 when the wave direction is 90 degrees can be obtained as follows: the ratio of Mxy2_d / Mxy2_s is 2.41.

[0162] In summary, the Mxy2_d=5.28×10 7 N·m is selected as the maximum vertical dynamic bending moment of the connecting rod assembly 3 under the wave condition.

[0163] Mxy1_s and Mxy1_d are combined to obtain:

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

[0165] Mxy2_s and Mxy2_d are combined to obtain:

[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 and the connecting rod assembly 3 is:

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

[0169] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A floating wind turbine foundation design method, characterized by, The wind turbine (4) and the semi-submersible floating wind turbine foundation, the semi-submersible floating wind turbine foundation comprising: a middle pontoon (21) and at least three edge pontoons (22) arranged around the middle pontoon (21), the bottom of the edge pontoons (22) being poured with a base (16), and prestressed concrete box girders (11) being connected between adjacent bases (16); The prestressed concrete box girders (11) are provided with prestressed tendons (111) along the length direction thereof, and the prestressed tendons (111) are provided with anchorage devices (112) at both ends thereof; The prestressed tendons (111) comprise bonded sections (113) and unbonded sections (114), the bonded sections (113) being located in the middle of the prestressed concrete box girders (11), and the unbonded sections (114) being located at the ends of the prestressed concrete box girders (11); The base (16) is provided with a steel base, and the outer side of the steel base is poured with a concrete shell, and the concrete shell is connected with the prestressed concrete box girders (11) by pouring; At least part of the anchorage devices (112) extends into the base (16), and at least part of the anchorage devices (112) or at least part of the prestressed tendons (111) are connected with the steel base; the edge pontoons (22) are connected with the steel base; The prestressed tendons (111) are prestressed steel strand bundles; The prestressed concrete box girders (11) are poured with ultra-high performance concrete; The concrete shell and the prestressed concrete box girders (11) are connected by pouring with ultra-high performance concrete; The prestressed concrete box girders (11) comprise 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; The base (16) is in a triangular distribution and comprises three bases; The wind turbine (4) is installed on the middle pontoon (21), and a connecting rod assembly (3) is connected between the edge pontoons (22) and the middle pontoon (21), the connecting rod assembly (3) comprising upper cross bars (31) and lower cross bars (32), and inclined rods (33) located between the upper cross bars (31) and the lower cross bars (32); The floating wind turbine foundation design method comprises the following steps: S1. According to the draft 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 pontoon (21); S2. The equivalent design wave calculation is performed by using the finite element model: The maximum vertical static bending moment Mxy1_s of the prestressed concrete box girders (11) under the static water condition and the maximum vertical dynamic bending moment Mxy1_d under the wave condition are obtained, and Mxy1_s and Mxy1_d are combined to obtain the maximum vertical bending moment Mxy1 of the prestressed concrete box girders (11); Obtaining the maximum vertical static bending moment Mxy2_s of the connecting rod assembly (3) in the still water working condition, the maximum vertical dynamic bending moment Mxy2_d of the connecting rod assembly (3) in the wave working condition, 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 and Mxy2 meets the design requirements, wherein the maximum vertical bending moment Mxy1 of the prestressed concrete box girder (11) is Mxy1_s+Mxy1_d, and the maximum vertical bending moment Mxy2 of the connecting rod assembly (3) is Mxy2_s+Mxy2_d.

2. The floating wind turbine foundation design method of claim 1, wherein, The semi-submersible floating wind turbine foundation is formed by the following steps: Step 1: pouring and forming the prestressed concrete box girder (11), and leaving a hole in the prestressed concrete box girder (11); Tensioning the prestressed tendon (111) arranged in the hole, grouting into the hole, bonding the middle part of the prestressed tendon (111) with the concrete, and not bonding the two ends of the prestressed tendon (111) with the concrete, and anchoring the prestressed tendon (111) by using the anchor (112); Step 2: installing the steel base; Step 3: pouring and connecting the steel base and the prestressed concrete box girder (11), wherein the anchor (112) is embedded in the concrete of the base (16) during pouring, and a floating position is reserved; Step 4: installing the side pontoon (22).

3. The floating wind turbine foundation design method of claim 1, wherein, The S2 includes the following steps: S21. Select the 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 of the end of the prestressed concrete box girder (11) in the still water working condition, and select the maximum value as Mxy1_s; Calculate the vertical bending moment of 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; Calculate the vertical bending moment of the end of the lower cross bar (32) in the still water working condition, and select the maximum value as Mxy2_s; Calculate the vertical bending moment of the end of the lower cross bar (32) in at least two wave directions in each wave period Tn, and select the maximum value as Mxy2_d.

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