Prefabricated assembly type uplifted steel pipe concrete wind power tower foundation and construction method thereof

Abstract

The application discloses a prefabricated lifting steel pipe concrete wind power tower foundation and a construction method thereof, and relates to the technical field of wind power generation. The foundation comprises a transfer ring, is a hollow columnar steel pipe concrete structure, is arranged at the top of the foundation, and is used for connecting an upper steel tower drum; a plurality of inclined braces are arranged between the transfer ring and a foundation pile cap, are uniformly distributed in a ring direction, and each inclined brace is a steel pipe concrete component; and a central drum is a reinforced concrete structure, is arranged at the lower part of the transfer ring, and is arranged on the foundation pile cap. The prefabricated lifting steel pipe concrete wind power tower foundation and the construction method thereof can be assembled in a full dry mode through high-strength bolts and tensioning screw rods, and do not need wet work on site. The application realizes full prefabricated assembly construction of the wind power tower foundation, greatly shortens the construction period, and improves the fatigue performance and durability of the connecting joint.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to a prefabricated assembled raised steel pipe concrete wind turbine tower foundation and its construction method. Background Technology

[0002] As the capacity of individual wind turbine units continues to increase, as do the tower height and load, higher demands are placed on the safety, economy, and construction speed of the foundations. High-power wind turbine tower foundations not only need to withstand enormous overturning moments and vertical loads, but also need to be constructed within a short construction window, especially in complex sites such as mountainous areas and coastal regions.

[0003] Currently, most wind turbine tower foundations utilize cast-in-place reinforced concrete structures, connected to the bottom flange of the upper steel tower via numerous long anchor bolt cages embedded in the foundation. Anchor bolts require precise on-site positioning, assembly, multiple tensioning, and grouting, involving numerous procedures, lengthy on-site concrete pouring and curing times, high labor and formwork consumption, and are severely affected by weather conditions due to wet construction. With the development of prefabricated building technology, some projects have begun to experiment with prefabricated foundation components; however, connection nodes still largely rely on on-site welding or secondary casting, failing to achieve truly dry assembly connections. Furthermore, traditional anchor bolt connections are prone to prestress loss, anchor bolt breakage, and localized concrete crushing under alternating fatigue loads, affecting structural durability. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the above-mentioned technologies.

[0005] Therefore, one objective of this invention is to propose a prefabricated assembled steel-concrete composite wind turbine tower foundation and its construction method. By prefabricating all core components in the factory and achieving full bolted dry assembly connection on site using high-strength bolts and tie rods, and by introducing prestressing technology to put the foundation under full compression, the construction efficiency and structural reliability are significantly improved.

[0006] To achieve the above objectives, the first aspect of this invention proposes a prefabricated assembled raised steel-concrete composite wind turbine tower foundation, comprising a transition ring, which is a hollow cylindrical steel-concrete composite structure, disposed at the top of the foundation for connecting the upper steel tower; multiple diagonal braces, disposed between the transition ring and the foundation platform, evenly distributed along the circumferential direction, each of the diagonal braces being a steel-concrete composite component; a central cylinder, which is a reinforced concrete structure, disposed below the transition ring and resting on the foundation platform; and a foundation platform, which is a reinforced concrete platform, disposed at the bottom of the foundation; the transition ring, the diagonal braces, and the central cylinder are all prefabricated components in the factory and are dry-assembled and connected on site using high-strength bolts and tie rods.

[0007] In addition, the prefabricated assembled steel pipe concrete wind turbine tower foundation proposed above according to the present invention may also have the following additional technical features: Specifically, the transition ring includes an outer steel pipe, an inner steel pipe, a bottom steel plate, a radial stiffening plate, a circumferential stiffening plate, a prestressed duct steel pipe, and core concrete filled between the inner and outer steel pipes; the outer steel pipe extends upward to form an integral T-shaped flange at the top, and bolt holes are provided on the T-shaped flange, which is connected to the tower flange at the bottom of the steel tower by high-strength bolts.

[0008] Specifically, the radial stiffening plates are connected to the inner steel pipe, the outer steel pipe, and the bottom steel plate respectively; the circumferential stiffening plates are arranged in sections between adjacent radial stiffening plates; the bottom steel plate has holes and is connected to the prestressed duct steel pipe; and a steel mesh is arranged inside the transition ring in the prestressed anchorage area.

[0009] Specifically, the diagonal brace is a square steel tube concrete component or a circular steel tube concrete component, with an upper end plate welded to its upper end and a lower end plate welded to its lower end. Bolt holes are provided on both the upper end plate and the lower end plate. The upper end plate is connected to the outer steel tube of the transition ring through a tie rod, and the lower end plate is connected to the embedded part pre-embedded on the foundation platform through a tie rod.

[0010] Specifically, the outer steel pipe of the adapter ring has a through hole corresponding to the bolt hole position of the upper end plate, and the hole position is based on the thickness of the steel pipe wall with equal cross-sectional area.

[0011] Specifically, the outer diameter of the central cylinder is the same as the outer diameter of the transition ring; the central cylinder is equipped with horizontal circumferential steel bars and vertical steel bars, and multiple bundles of prestressed tendons are evenly arranged circumferentially along the pre-set channels in the wall of the central cylinder. The upper end of the prestressed tendons is anchored to the top of the transition ring, and the lower end is anchored to the foundation platform.

[0012] Specifically, the prestressing tendons are high-strength steel strands, which, after tensioning, put the central cylinder, the transition ring, and the diagonal brace under compression, forming a self-balancing prestressing system.

[0013] Specifically, the T-shaped flange is annular, with its extended flange and web forming a T-shaped cross-section, and the bolt holes are arranged in a double ring along the circumferential direction; the transition ring is a polygonal steel-concrete composite ring beam.

[0014] Another aspect of this invention proposes a construction method for a prefabricated assembled raised steel-concrete wind turbine tower foundation, comprising the following steps: Step 1: Pour reinforced concrete foundation cap and pre-embed embedded parts on the top surface of the cap for connecting the lower end of the diagonal brace; Step 2: After the foundation platform reaches the design strength, the prefabricated diagonal brace is hoisted into place, and the lower end of the diagonal brace is initially connected to the embedded part through tie rods; Step 3: Hoist the precast center tube and position it in the center of the foundation platform; Step 4: Hoist the prefabricated adapter ring to the top of the central cylinder, and connect the upper end of the diagonal brace to the adapter ring via tie rods; Step 5: Tighten the nuts at all joints in stages; Step 6: Tension the prestressing tendons inside the central tube and anchor them to the top of the transition ring; Step 7: Place the bottom flange of the steel tower onto the T-flange of the transition ring and tighten it with high-strength bolts.

[0015] Specifically, in step one, the embedded part is a downwardly extending screw, a reserved through hole, or a sleeve with internal threads; in step two, the nut of the tie rod at the lower end of the diagonal brace is not completely locked, leaving an adjustment margin; after step four is completed, all node nuts are tightened uniformly in stages; in step three, the central cylinder is positioned by the positioning plate or insert bar embedded in the top surface of the foundation platform.

[0016] The beneficial effects of this invention are: (1) Fully prefabricated assembly, high construction efficiency: the transition ring, diagonal brace and central tube are all prefabricated in the factory. Only the component hoisting and bolt tightening work is carried out on site. The on-site pouring and curing of large volume concrete is completely eliminated, which greatly shortens the construction cycle and greatly reduces the on-site formwork, support and labor. Moreover, the construction quality is still controllable in winter or rainy season.

[0017] (2) Direct force transmission path, eliminating vulnerable anchor bolts: The transition ring is directly connected to the steel tower tube with high-strength bolts through the integrated T-shaped steel flange of the outer steel pipe. Bending moment, shear force and axial force are continuously transmitted through steel components, avoiding stress concentration, relaxation and fatigue fracture problems in traditional anchor bolt connections. The connection reliability is significantly improved, and the bolts can be inspected and replaced.

[0018] (3) Achieve fully dry bolt connection of diagonal bracing: The upper and lower ends of the diagonal bracing adopt the assembly node of end plate + tie rod, which has high rigidity and good ductility. No on-site welding or grouting is required, and the installation accuracy is adjustable, which is convenient for maintenance and replacement, and truly realizes the bolt assembly of all components.

[0019] (4) Prestressing technology optimizes the stress state: The prestressing tendons of the central tube are anchored to the top of the transition ring, which not only puts the central tube itself under pressure, but also introduces prestress in the transition ring and the diagonal brace, so that the entire foundation system is basically under full cross-section pressure under all working conditions, effectively suppressing concrete cracking and improving the fatigue resistance and overall stiffness of the structure.

[0020] (5) Balancing economy and safety: The use of steel-concrete composite members has high load-bearing capacity, good ductility, and the cross-sectional dimensions can be optimized. Calculations show that the transition ring and diagonal bracing schemes meet the requirements and have sufficient safety reserves, achieving a balance between lightweight and high reliability.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 A cross-sectional structural schematic diagram of a prefabricated assembled raised steel-concrete composite wind turbine tower foundation according to an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the transition ring structure of a prefabricated assembled steel-concrete composite wind turbine tower foundation according to an embodiment of the present invention. Figure 3 This is a top view of the transition ring structure of a prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to an embodiment of the present invention. Figure 4 This is a schematic cross-sectional view of the inclined strut structure of a prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to an embodiment of the present invention. Figure 5 This is a schematic cross-sectional view of the central tube structure of a prefabricated assembled steel-concrete composite wind turbine tower foundation according to an embodiment of the present invention. Figure 6 This is a top view of the central tube structure of a prefabricated assembled steel-concrete composite wind turbine tower foundation according to an embodiment of the present invention. Figure 7 A top view of a T-flange structure of a prefabricated assembled steel-concrete composite wind turbine tower foundation according to an embodiment of the present invention. Figure 8 This is a cross-sectional structural diagram of a T-flange of a prefabricated assembled steel pipe concrete wind turbine tower foundation according to an embodiment of the present invention.

[0023] Figure label: 11. Adapter ring; 12. Outer steel pipe; 13. Inner steel pipe; 14. Bottom steel plate; 15. Radial stiffening plate; 16. Circumferential stiffening plate; 17. Prestressed duct steel pipe; 18. Core concrete; 19. T-flange; 20. Reinforcing mesh; 21. Diagonal brace; 22. Upper end plate; 23. Lower end plate; 34. Tie rod; 35. Central tube; 36. Circumferential reinforcement; 37. Vertical reinforcement; 38. Pre-set duct; 39. Prestressed tendon; 40. Foundation cap; 51. High-strength bolts. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] The following description, with reference to the accompanying drawings, illustrates an embodiment of the present invention: a prefabricated assembled raised steel pipe concrete wind turbine tower foundation and its construction method.

[0026] like Figure 1 - Figure 8 As shown, an embodiment of the present invention provides a prefabricated assembled steel pipe concrete wind turbine tower foundation and its construction method, which may include: a transition ring 1, multiple diagonal braces 2, a central tube 3, and a foundation platform 4.

[0027] The transition ring 1 is a hollow cylindrical steel-concrete structure, located at the top of the foundation, used to connect to the upper steel tower. Multiple diagonal braces 2 are evenly distributed circumferentially between the transition ring 1 and the foundation platform 4; each diagonal brace 2 is a steel-concrete component. The central tube 3 is a reinforced concrete structure, located below the transition ring 1 and resting on the foundation platform 4. The foundation platform 4 is a reinforced concrete platform located at the bottom of the foundation. The transition ring 1, diagonal braces 2, and central tube 3 are all prefabricated components, assembled on-site using high-strength bolts 5 and tie rods 23 in a completely dry assembly manner, eliminating the need for on-site wet work and secondary concrete pouring.

[0028] like Figure 2 and Figure 3 As shown, the transition ring 1 includes an outer steel pipe 11, an inner steel pipe 12, a bottom steel plate 13, a radial stiffening plate 14, a circumferential stiffening plate 15, a prestressed duct steel pipe 16, and a core concrete 17 filled between the inner and outer steel pipes 11.

[0029] The outer steel pipe 11 extends upwards, forming an integral T-shaped flange 18 at the top. The T-shaped flange 18 is annular, with its extended flange and web forming a T-shaped cross-section. Bolt holes are provided on it, and it is connected to the tower flange at the bottom of the steel tower using high-strength bolts 5. Preferably, the bolt holes are arranged in a double ring along the circumferential direction, forming a friction-type connection with the bottom flange of the steel tower using double-layer high-strength bolts 5. The high-strength bolts 5 are inserted into the corresponding bolt holes of the T-shaped flange 18 from above or below the tower flange, and a reliable bending-resistant connection is formed after applying pre-tightening force, thus completely eliminating the need for traditional pre-embedded anchors.

[0030] Radial stiffening plates 14 are connected to the inner steel pipe 12, outer steel pipe 11, and bottom steel plate 13 respectively, and circumferential stiffening plates 15 are arranged in segments between adjacent radial stiffening plates 14. The bottom steel plate 13 has holes and is connected to the prestressed duct steel pipe 16. A steel mesh 19 is arranged inside the transition ring 1 in the prestressed anchorage area to ensure the safety of the core concrete 17 under local pressure. The core concrete 17 is poured and filled between the inner steel pipe 12, outer steel pipe 11, and bottom steel plate 13. Through holes are opened on the outer steel pipe 11 at the bolt hole positions corresponding to the upper end plate 21 of the diagonal brace 2. The wall thickness of the steel pipe is thickened according to the equal cross-sectional area at the opening position to ensure that the load-bearing capacity of the steel pipe is not reduced after the opening.

[0031] like Figure 4 As shown, the diagonal brace 2 is a square steel tube concrete component or a circular steel tube concrete component. Taking square steel tube concrete as an example, the diagonal brace 2 includes a square steel tube and the concrete filling inside. An upper end plate 21 is welded to its upper end, and a lower end plate 22 is welded to its lower end. Bolt holes are provided on both the upper end plate 21 and the lower end plate 22. The upper end plate 21 is connected to the corresponding through hole on the outer steel tube 11 of the transition ring 1 via tie rods 23, and both ends are tightened with nuts, reliably connecting the upper end of the diagonal brace 2 to the transition ring. The lower end plate 22 is connected to the embedded parts pre-embedded on the foundation pedestal 4 via tie rods 23, and nuts are tightened from above and the side, reliably connecting the root of the diagonal brace 2 to the pedestal. Both the upper and lower nodes are pure bolt connections of end plates and tie rods 23, without any on-site welding, and can be repeatedly disassembled and reassembled.

[0032] like Figure 5 and Figure 6As shown, the outer diameter of the central cylinder 3 is the same as that of the transition ring 1. The central cylinder 3 is equipped with horizontal circumferential reinforcing bars 31 and vertical reinforcing bars 32, forming a reinforced concrete cylinder structure. Multiple bundles of prestressing tendons 34 are evenly arranged circumferentially along pre-set channels 33 inside the wall of the central cylinder 3. The prestressing tendons 34 are high-strength steel strands, with their upper ends anchored to the top of the transition ring 1 and their lower ends anchored to the foundation cap 4. After tensioning the prestressing tendons 34, the central cylinder 3, transition ring 1, and diagonal brace 2 are under compression, forming a self-balancing prestressed system. Because the outer diameter of the central cylinder 3 is the same as that of the transition ring 1, compared to traditional designs, the diameter of the concrete cylinder below the central cylinder 3 is significantly reduced, and the diameter of the circle where the prestressing tendons 34 are arranged is also correspondingly reduced, saving the amount of concrete and prestressing materials used, and making assembly and construction easier.

[0033] The foundation cap 4 is a large-volume reinforced concrete platform at the bottom, used to bear and distribute the load. The top surface of the foundation cap 4 has embedded parts at the connection with the diagonal brace 2. The embedded parts are downward-extending screws, reserved through holes, or embedded sleeves with internal threads, used to connect with the lower end plate 22 on the diagonal brace 2 through tie rods 23.

[0034] Specific implementation methods of construction This invention also provides a construction method for a prefabricated assembled steel-concrete composite wind turbine tower foundation, comprising the following steps: Step 1: Pour the reinforced concrete foundation cap 4, and pre-embed embedded parts on the top surface of the cap for connecting the lower end of the diagonal brace 2. The embedded parts can take the form of downward-extending screws, reserved through holes, or embedded sleeves with internal threads, etc.

[0035] Step Two: After the foundation cap 4 reaches its design strength, hoist the precast diagonal brace 2 into place and initially connect the lower end of the diagonal brace 2 to the embedded part via tie rod 23. In this step, the nut of the tie rod 23 at the lower end of the diagonal brace 2 is not completely locked, leaving an adjustment margin for subsequent adjustments.

[0036] Step 3: Hoist the precast center tube 3 and position it in the center of the foundation cap 4. The center tube 3 is precisely positioned using the positioning plate or reinforcing bar pre-embedded on the top surface of the foundation cap 4.

[0037] Step 4: Hoist the prefabricated adapter ring 1 to the top of the central cylinder 3, and connect the upper end of the diagonal brace 2 to the adapter ring 1 through the tie rod 23.

[0038] Step 5: After all components are aligned, tighten the nuts at all joints in stages. Preferably, tighten in stages from bottom to top and from inside to outside, with each stage torque controlled at 30%, 70%, and 100% of the final tightening torque.

[0039] Step Six: Tension the prestressing tendons 34 inside the central tube 3 and anchor them to the top of the transition ring 1. Post-tensioning in stages is used, with a tensioning control stress of 0.75fptk.

[0040] Step 7: Place the bottom flange of the steel tower onto the T-flange 18 of the transition ring 1, and tighten it with high-strength bolts 5 to complete the connection between the foundation and the tower.

[0041] As an alternative to the assembly sequence, the central cylinder 3 and the transition ring 1 can be pre-assembled into one unit at the factory and connected to the diagonal brace 2 and the bearing platform as a single component on site, further reducing the number of on-site hoisting operations.

[0042] As one possible implementation example: Example 1: This example provides a prefabricated assembled steel pipe concrete wind turbine tower foundation.

[0043] Adapter ring: Material is Q355 steel pipe, core concrete is C80, component height: H=2420mm, outer diameter: Dout=4400mm, outer steel pipe wall thickness is 60mm, core concrete thickness is 500mm, inner steel pipe wall thickness is 10mm.

[0044] The flange is a T-type flange, connected with double-layer high-strength bolts.

[0045] Diagonal bracing: The material is Q355 steel pipe, and the core concrete is C80. The cross-sectional parameters of the steel pipe concrete diagonal bracing are: outer side length 700mm, steel pipe wall thickness 25mm, and length 10.7m.

[0046] Central tube: height 7280mm, wall thickness 500mm, made of C80 concrete, circumferential reinforcement: E16@100, vertical reinforcement: E16@150, outer diameter of central tube is 4400mm (to be consistent with the outer diameter of the upper transition ring).

[0047] Diagonal bracing and transition joint: Uses end plates and continuous threaded rods. Material: Q355 steel. End plate dimensions: length 1225mm, radial width 1700mm, end plate thickness 30mm. Threaded rods: M42, 36 rods, 700mm long.

[0048] Diagonal brace and foundation joint: Uses end plates and threaded rods. Material: Q355 steel. End plate dimensions: 1225mm long, 1700mm wide, 65mm thick. Threaded rods: M42, 36 rods, 700mm long.

[0049] Example 2: The diagonal brace uses a circular steel-concrete composite member with an outer diameter of 550mm and a wall thickness of 18mm, filled with C50 concrete. The shape of the upper and lower end plates of the diagonal brace is adjusted accordingly to circular end plates with a diameter of 650mm and a thickness of 30mm, with 12 bolt holes evenly opened along the circumference.

[0050] Example 3: The difference between this example and Example 1 is that the central cylinder and the transition ring are pre-assembled into one unit in the factory, and then hoisted into place as a whole component on site, and then connected to the diagonal brace and the bearing platform, further reducing the number of on-site hoisting operations.

[0051] Example 4: The difference between this example and Example 1 is that the transition ring adopts an octagonal steel pipe concrete ring beam with an outer circle diameter of 4.5m and an inner circle diameter of 3.2m. T-type flanges are continuously set along each side of the octagon.

[0052] In summary, this invention, a prefabricated assembled steel-concrete composite wind turbine tower foundation and its construction method, allows for the factory prefabrication of core components such as transition rings, diagonal braces, and central tubes. On-site assembly is achieved solely through high-strength bolts and tie rods, completely eliminating the need for large-volume on-site concrete pouring and curing, significantly shortening the construction cycle. Furthermore, the transition ring is directly connected to the steel tower via an integrated T-shaped steel flange, avoiding stress concentration, relaxation, and fatigue fracture problems associated with traditional anchor bolt connections, effectively improving structural reliability and durability. The diagonal braces utilize end plates and tie rods at both ends, eliminating the need for on-site welding or grouting, and offering adjustable installation precision for easy maintenance and replacement. The prestressed tendons of the central tube are anchored to the top of the transition ring, ensuring the entire foundation system is essentially under full-section compression under all working conditions, effectively suppressing concrete cracking and improving structural fatigue resistance and overall stiffness. This invention achieves fully prefabricated assembly construction of wind turbine tower foundations, yielding significant economic and social benefits.

[0053] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A prefabricated assembled steel-concrete composite wind turbine tower foundation, characterized in that, include: The transition ring (1) is a hollow cylindrical steel pipe concrete structure, which is set on the top of the foundation and used to connect the upper steel tower. Multiple diagonal braces (2) are set between the transition ring (1) and the foundation platform (4) and are evenly distributed along the circumferential direction. Each diagonal brace (2) is a steel pipe concrete component. The central tube (3) is a reinforced concrete structure, located at the lower part of the transition ring (1) and situated on the foundation platform (4); The foundation cap (4) is a reinforced concrete platform located at the bottom of the foundation. The adapter ring (1), the diagonal brace (2) and the central cylinder (3) are all prefabricated components in the factory and are assembled and connected on site using high-strength bolts and tie rods.

2. The prefabricated assembled steel-concrete composite wind turbine tower foundation according to claim 1, characterized in that, The transition ring (1) includes an outer steel pipe (11), an inner steel pipe (12), a bottom steel plate (13), a radial stiffening plate (14), a circumferential stiffening plate (15), a prestressed duct steel pipe (16), and core concrete (17) filled between the inner and outer steel pipes; the outer steel pipe (11) extends upward and forms an integral T-shaped flange (18) at the top end. The T-shaped flange (18) is provided with bolt holes and is connected to the tower flange at the bottom of the steel tower by high-strength bolts (5).

3. The prefabricated assembled steel-concrete composite wind turbine tower foundation according to claim 2, characterized in that, The radial stiffening plate (14) is connected to the inner steel pipe (12), the outer steel pipe (11), and the bottom steel plate (13) respectively. The circumferential stiffening plate (15) is arranged in sections between adjacent radial stiffening plates (14). The bottom steel plate (13) has holes and is connected to the prestressed duct steel pipe (16). The transition ring (1) has a steel mesh (19) arranged inside the prestressed anchorage area.

4. The prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to claim 1, characterized in that, The diagonal brace (2) is a square steel tube concrete component or a circular steel tube concrete component. It has an upper end plate (21) welded to its upper end and a lower end plate (22) welded to its lower end. Bolt holes are provided on both the upper end plate (21) and the lower end plate (22). The upper end plate (21) is connected to the outer steel tube (11) of the transition ring (1) through a tie rod (23). The lower end plate (22) is connected to the embedded parts pre-embedded on the foundation platform (4) through a tie rod (23).

5. A prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to claim 4, characterized in that, The outer steel pipe (11) of the adapter ring (1) has a through hole at the bolt hole position of the upper end plate (21), and the hole position is made up of the steel pipe wall thickness according to the equal cross-sectional area.

6. A prefabricated assembled steel-concrete composite wind turbine tower foundation according to claim 1, characterized in that, The outer diameter of the central cylinder (3) is the same as the outer diameter of the transition ring (1); the central cylinder (3) is equipped with horizontal circumferential steel bars (31) and vertical steel bars (32), and multiple bundles of prestressed tendons (34) are evenly arranged in the circumferential direction along the pre-set channel (33) inside the central cylinder wall. The upper end of the prestressed tendon (34) is anchored to the top of the transition ring (1), and the lower end is anchored to the foundation platform (4).

7. A prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to claim 6, characterized in that, The prestressing tendon (34) is a high-strength steel strand. After tensioning, the central cylinder (3), the transition ring (1) and the diagonal brace (2) are under pressure, forming a self-balancing prestressing system.

8. A prefabricated assembled raised steel pipe concrete wind turbine tower foundation according to claim 2, characterized in that, The T-shaped flange (18) is annular, with its extended flange and web forming a T-shaped cross section, and the bolt holes are arranged in a double ring along the circumferential direction; the transition ring (1) is a polygonal steel pipe concrete ring beam.

9. A construction method for a prefabricated assembled raised steel-concrete wind turbine tower foundation according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Pour the reinforced concrete foundation cap (4) and pre-embed the pre-embedded parts on the top surface of the cap for connecting the lower end of the diagonal brace (2); Step 2: After the foundation platform (4) reaches the design strength, the prefabricated diagonal brace (2) is hoisted into place, and the lower end plate (22) of the diagonal brace (2) is initially connected to the embedded part through the tie rod (23); Step 3: Hoist the precast center tube (3) and position it in the center of the foundation platform (4); Step 4: Hoist the prefabricated adapter ring (1) to the top of the central cylinder (3), and connect the upper end plate (21) of the diagonal brace (2) to the adapter ring (1) through the tie rod (23); Step 5: Tighten the nuts at all joints in stages; Step 6: Tension the prestressed tendons (34) inside the central tube (3) and anchor them to the top of the transition ring (1); Step 7: Place the bottom flange of the steel tower onto the T-flange (18) of the transition ring (1) and fasten it with high-strength bolts (5).

10. The construction method according to claim 9, characterized in that, In step one, the embedded part is a downward-extending screw, a reserved through hole, or a sleeve with internal threads; in step two, the nut of the tie rod (23) at the lower end of the diagonal brace (2) is not completely locked, leaving an adjustment margin; after step four is completed, all node nuts are tightened uniformly in stages; in step three, the central cylinder (3) is positioned by the positioning plate or insert bar embedded in the top surface of the foundation platform (4).

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