External prestressing CFRP (carbon fiber reinforced plastic) rib steel-concrete combined wind power tower drum and construction method thereof

Abstract

The invention discloses an external prestressing CFRP (carbon fiber reinforced plastic) rib steel-concrete combined wind power tower drum and a construction method thereof, the external prestressing CFRP rib steel-concrete combined wind power tower drum comprises a sectional concrete tower drum, a steel tower drum section, an external prestressing system and a sectional tensioning device, the sectional concrete tower drum is formed by connecting a plurality of prefabricated concrete drum sections through reducing sections; the bottom of the steel tower cylinder section is connected with the concrete cylinder section through a flange, the external prestress system comprises CFRP ribs which are evenly distributed in the longitudinal direction of the outer wall of the concrete cylinder section, the CFRP ribs are adopted to replace traditional steel strands, the surfaces of the CFRP ribs are coated with weather-resistant epoxy resin coatings, the anchoring ends are sealed through sealant, corrosion of complex environments such as seaborne and saline-alkali soil can be effectively resisted, and the service life of the steel tower is prolonged. And the CFRP ribs have the characteristics of light weight and high strength, and are combined with a steel-concrete combined structural form, the steel tower drum section is adopted at the upper part, and the concrete drum section is adopted at the lower part, so that the light weight of the wind power tower drum is realized on the premise of ensuring the overall rigidity and the anti-fatigue performance of the structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wind power generation tower drums, and particularly relates to an external prestressed CFRP tendon steel-concrete combined wind power generation tower drum and a construction method thereof. BACKGROUND

[0002] With the transformation of global energy structure to clean and low-carbon, wind power generation, especially offshore wind power generation, has become one of the core paths to achieve the "double carbon" goal. As a key structure supporting the unit, the wind power generation tower drum faces the stringent requirements of lightweight, high bearing capacity and long service life. The performance bottleneck of traditional tower drum materials and technologies under complex environment is increasingly prominent, and it is difficult to meet the future development needs.

[0003] When the height of the pure steel tower drum increases, the wall thickness needs to be greatly increased to meet the bending stiffness requirement, resulting in a sharp increase in the amount of steel. In addition, in the offshore environment, the steel tower is prone to corrosion and maintenance problems. The welds and connecting flanges of the steel tower drum are easily corroded by salt mist, and need to be maintained by anticorrosion coating every 5-8 years, which is high in operation and maintenance cost. The unit height weight of the pure concrete tower drum is 2-3 times that of the steel tower drum, and the self-weight is too large. The formwork needs to be set up for on-site pouring, and the maintenance period is long, which cannot meet the rapid installation demand of wind power.

[0004] The existing steel-concrete hybrid tower drum adopts internal post-tensioned steel strand, which needs to reserve a channel and grouting, and the process is complex and cannot realize prestress adjustment during the service period. The steel strand is prone to corrosion in the humid saline environment, and the service life is only 25-30 years. Moreover, the hybrid tower drum relies on the internal steel framework, and cannot fully utilize the lightweight and high-strength characteristics of high-performance composite materials (such as CFRP), resulting in high structural redundancy, transportation difficulty and high cost. SUMMARY

[0005] The purpose of the present application is to provide an external prestressed CFRP tendon steel-concrete combined wind power generation tower drum and a construction method thereof to solve the problems raised in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an external prestressed CFRP tendon steel-concrete combined wind power generation tower drum, comprising:

[0007] The segmented concrete tower drum is composed of multiple prefabricated concrete drum sections connected through variable diameter sections;

[0008] The steel tower drum section is rolled from a low-temperature ductile steel plate, and the bottom of the steel tower drum section is connected to the concrete drum section through a flange. The bolt spacing is adapted to the stress requirement. The steel-concrete transition section is provided with cylindrical head studs, which are distributed in a matrix. The embedded depth of the studs meets the interface shear requirement.

[0009] An external prestressing system comprises CFRP tendons longitudinally and uniformly distributed along the outer wall of a concrete cylinder section, the number of tendon bodies is arranged according to the circumference of the tower cylinder, and the two ends of the CFRP tendons are respectively connected with the foundation embedded steel anchor box and flange at the bottom of the concrete cylinder section through anchoring mechanisms, the anchoring mechanisms adopt a clamping type clamp or a bonding type anchor, and the bearing efficiency of the anchor meets the specification requirements;

[0010] A segmented tensioning device comprises an adjustable support screw, a steering mechanism and a hydraulic jack, the steering mechanism is arranged at a variable diameter section to guide the steering of the CFRP tendons and reduce local stress concentration.

[0011] Preferably, the anchoring mechanism comprises a flexible support block, the flexible support block is in an arc-shaped structure matched with the inner wall of the steel tower cylinder section, and a U-shaped groove is arranged on the inner wall of the flexible support block, a rubber pad layer is arranged in the U-shaped groove to prevent the corrosion-resistant coating of the CFRP tendons from being worn, the pad layer and the support block are bonded by an adhesive, the bonding strength meets the requirements, the flexible support block and the rubber pad layer of the anchoring mechanism jointly protect the corrosion-resistant coating of the CFRP tendons to ensure the corrosion resistance.

[0012] Preferably, the connecting section of the steel tower cylinder section and the concrete cylinder section is provided with an outer side circular truncated cone-shaped steel pipe and an inner side circular truncated cone-shaped steel pipe, the taper of the outer side circular truncated cone-shaped steel pipe and the inner side circular truncated cone-shaped steel pipe is consistent with that of the variable diameter section, the inner and outer side circular truncated cone-shaped steel pipes of the connecting section enhance the structural rigidity of the connection between the steel tower cylinder section and the concrete cylinder section, and are adapted to the variable diameter section to avoid stress concentration.

[0013] Preferably, an annular gap is formed between the outer side circular truncated cone-shaped steel pipe and the inner side circular truncated cone-shaped steel pipe, the annular gap is filled with high-strength grouting material, and a composite force transmission structure is formed through a vertical inner partition plate and a stud, the vertical inner partition plate is welded to the inner side circular truncated cone-shaped steel pipe, and the stud is embedded in the high-strength grouting material after penetrating the inner side circular truncated cone-shaped steel pipe, the annular gap filled with the grouting material and combined with the composite force transmission structure improve the integrity of the connecting section and the force transmission effect.

[0014] Preferably, the steering mechanism is a detachable pulley block, the surface of the pulley is coated with wear-resistant material; the detachable pulley block is fixed on the embedded steel plate of the variable diameter section and the adjustable support screw through bolts, the embedded depth of the bolts meets the anchoring requirements, anchor steel bars are arranged between the steel plate and the concrete, the detachable pulley block guides the steering of the CFRP tendons, reduces wear and tear, and is convenient to install and adjust, thereby reducing local stress concentration.

[0015] Preferably, the CFRP reinforcement surface is coated with a weather-resistant anti-corrosion coating and the anchoring ends of the CFRP reinforcement are sealed with sealant. A wireless sensor network is installed inside the steel tower section. The wireless sensor network includes CFRP reinforcement stress sensors, tilt sensors, crack gauges, etc. The data is transmitted wirelessly to a monitoring platform for long-term monitoring of CFRP reinforcement stress, steel tower section tilt, and crack development. In the over-tensioning compensation process, tensioning operations are suspended when the wind speed in the construction environment exceeds the limit. Before re-tensioning, the jacks need to be calibrated and the actual length of the CFRP reinforcement needs to be measured to correct the calculated tension force. After each section is tensioned, it needs to be left to stand for a certain period of time, and the stress loss needs to be monitored to ensure it is within the allowable range before the next section can be constructed.

[0016] Preferably, the concrete cylinder section is cast with high-performance concrete and polypropylene fiber is added to the concrete. The diameter decreases gradually from bottom to top with a certain slope. Adjacent concrete cylinder sections are connected by corbel steel. The high-performance concrete and polypropylene fiber improve the performance of the concrete cylinder section. The decreasing diameter is adapted to the stress. The corbel steel ensures the reliable connection of the cylinder sections.

[0017] A construction method for an externally prestressed CFRP reinforced steel-concrete composite wind turbine tower includes the following steps:

[0018] S1. Construction Section Division: The steel tower section is divided into several construction sections along the height direction. The height of each section is adapted to the construction and stress requirements. Each section corresponds to an independent CFRP reinforcement tensioning zone. Temporary anchoring devices are set at the junction of the sections.

[0019] S2, tensioning from bottom to top in stages:

[0020] a. Starting from the pre-embedded steel anchor box in the foundation, install the first section of CFRP bar and pass it through the reserved duct. The length of the CFRP bar exposed at the end of the anchor meets the anchorage requirements.

[0021] b. Apply initial tension to the CFRP reinforcement to 60%–70% of its tensile strength using a hydraulic jack and force sensor.

[0022] c. By using the over-tensioning compensation process, an additional 5% to 10% of the force is added to the initial tension force to offset creep and stress loss during construction of adjacent sections;

[0023] d. After tensioning this section is completed, the anchorage area is sealed with epoxy resin grout.

[0024] S3. Segmented connection and stress transfer: At the junction of adjacent construction sections, CFRP sleeves are used for mechanical connection or lap splicing to achieve the continuity of prestressed tendons.

[0025] S4, dynamic monitoring and adjustment: the strain data of each section of CFRP tendon is monitored in real time through the optical fiber grating sensor arranged in the steel tower section, and the subsequent tension force is adjusted combined with the feedback result to ensure that the stress deviation of each section is less than or equal to 15%.

[0026] Compared with the prior art, the beneficial effects of the present application are:

[0027] (1) CFRP tendon is used to replace traditional steel strand, the surface is coated with weather-resistant epoxy resin coating, and the anchoring end is sealed with sealant, which can effectively resist corrosion in complex environments such as sea and saline-alkali land, solve the problem of high corrosion risk and short service life of traditional steel strand in humid saline-alkali environment, greatly prolong the service life of the tower drum, at the same time, reduce the need for regular maintenance of anti-corrosion coating like pure steel tower drum, reduce the operation and maintenance cost, CFRP tendon has the characteristics of light weight and high strength, combined with the structure of steel and concrete, the upper part uses steel tower section, and the lower part uses concrete section, which fully utilizes the advantages of the two materials, realizes the light weight of the wind turbine tower drum under the premise of ensuring the overall rigidity and fatigue resistance of the structure, compared with the pure concrete tower drum, the weight per unit height is greatly reduced, and the load of the foundation is reduced; compared with the pure steel tower drum, the amount of steel is reduced under the condition of meeting the bending stiffness requirement.

[0028] (2) The lower concrete section adopts prefabricated hollow concrete section, which is prefabricated in the factory and transported to the site for assembly, reducing the need for formwork erection, curing and other links during site pouring, shortening the construction period, meeting the demand for rapid installation of wind power, and the segmented structure design and reasonable segmentation make transportation more convenient, and the construction process can be tensioned step by step from bottom to top, which is convenient to operate and improves the construction efficiency.

[0029] (3) Through the segmented tensioning construction method, the strain data of each section of CFRP tendon is monitored in real time by force sensor and optical fiber grating sensor, the subsequent tensioning force is adjusted combined with the feedback result, the stress deviation of each section is controlled in a reasonable range, the stress uniformity is realized, the external prestressed system is tensioned by CFRP tendon, the whole tower drum forms a whole stress system, the bearing capacity and crack resistance of the structure are improved, and the safety of the tower drum during service is enhanced.

[0030] (4) The wireless sensor network is arranged in the tower drum, including CFRP tendon stress sensor, inclination sensor, crack meter, etc., which can long-term monitor the CFRP tendon stress, tower inclination and crack development, and transmit wirelessly to the monitoring platform, at the same time, the anchor has a built-in hydraulic adjustment module, which can compensate when the prestress loss reaches a certain degree, so as to grasp the tower drum state in time and make maintenance and adjustment, and ensure the long-term stable operation of the tower drum. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1It is a structural schematic diagram of the whole tower drum of the application;

[0032] Figure 2 It is a layout diagram of the application of the CFRP tendon;

[0033] Figure 3 It is a structural schematic diagram of the outer circular truncated cone steel pipe and the inner circular truncated cone steel pipe of the application;

[0034] Figure 4 It is a top view of the outer circular truncated cone steel pipe and the inner circular truncated cone steel pipe of the application;

[0035] Figure 5 It is a structural schematic diagram of the flexible supporting block and the CFRP tendon of the application;

[0036] Figure 6 It is a process flow chart of the application;

[0037] Figure 7 It is a structural schematic diagram of the application.

[0038] In the figure: 1, concrete cylinder section; 2, steel tower drum section; 3, flange; 4, CFRP tendon; 5, foundation embedded steel anchor box; 6, adjustable supporting screw rod; 7, flexible supporting block; 8, U-shaped groove; 9, rubber pad layer; 10, connecting section; 11, outer circular truncated cone steel pipe; 12, inner circular truncated cone steel pipe; 13, annular gap; 14, high-strength grouting material; 15, detachable pulley block; 16, embedded steel plate. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0040] In the description of the application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved", "sleeved", "connected" and the like should be understood in a broad sense, for example, "connected" can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be the communication inside two elements; for those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0041] The application provides a kind of in-vitro prestressed CFRP tendon steel composite wind power tower drum as shown in Figures 1-7 , comprising:

[0042] The segmented concrete tower cylinder is composed of multiple prefabricated concrete cylinder segments 1 connected by variable-diameter segments, which are used to provide bottom support stiffness for the entire tower cylinder structure, bear and disperse the load transmitted from the upper part to the foundation, and adapt to the stress requirements and transportation and installation conditions of different heights through segmented prefabrication and variable-diameter segment connection.

[0043] The steel tower cylinder segment 2 is rolled from low-temperature ductile steel plates, which can maintain good brittle fracture resistance in low-temperature environments, and the bottom of the steel tower cylinder segment 2 is connected to the concrete cylinder segment 1 through a flange 3, which can realize reliable connection between the steel tower cylinder segment and the concrete cylinder segment, transmit axial force, shear force and bending moment, and ensure the sealing of the connection part.

[0044] The external prestressing system includes CFRP tendons 4 uniformly distributed along the longitudinal direction of the outer wall of the concrete cylinder segment 1, and the number of tendon bodies is arranged according to the circumference of the tower cylinder, which can apply circumferential and longitudinal prestress to the concrete cylinder segment, improve the overall crack resistance and carrying capacity of the tower cylinder, and the two ends of the CFRP tendon 4 are connected to the foundation embedded steel anchor box 5 at the bottom of the concrete cylinder segment 1 and the flange 3 through anchoring mechanisms, which can effectively transmit the prestress of the CFRP tendon 4 to the foundation and the steel tower cylinder segment 2.

[0045] The segmented tensioning device includes an adjustable support screw 6, a steering mechanism and a hydraulic jack, the steering mechanism is arranged at the variable-diameter segment, which is used to guide the steering of the CFRP tendon 4, so that the CFRP tendon 4 can adapt to the shape change of the variable-diameter segment, while reducing local stress concentration, the adjustable support screw 6 can adjust the position and angle of the steering mechanism, and the hydraulic jack is used to apply tension stress to the CFRP tendon 4.

[0046] The anchoring mechanism includes a flexible block 7 in the form of an arc structure that fits the inner wall of the steel tower cylinder segment 2, which can be in close contact with the inner wall of the steel tower cylinder segment to disperse the pressure transmitted by the CFRP tendon, and the inner wall of the flexible block 7 is provided with a U-shaped groove 8, in which a rubber pad layer 9 is arranged, which can buffer and protect the CFRP tendon 4 to prevent the corrosion-resistant coating of the CFRP tendon 4 from being worn, and ensure the corrosion resistance of the CFRP tendon 4.

[0047] The connecting segment 10 of the steel tower cylinder segment 2 and the concrete cylinder segment 1 is provided with an outer circular truncated cone steel pipe 11 and an inner circular truncated cone steel pipe 12, which can jointly enhance the structural stiffness of the connecting segment, and the taper of the outer circular truncated cone steel pipe 11 and the inner circular truncated cone steel pipe 12 is consistent with that of the variable-diameter segment, which ensures smooth transition of the connecting segment and the variable-diameter segment and avoids stress concentration.

[0048] The annular gap 13 is formed between the outer side frustoconical steel pipe 11 and the inner side frustoconical steel pipe 12, and the annular gap 13 is filled with high-strength grouting material 14, which can bond the outer side and the inner side frustoconical steel pipes into a whole, improve the integrity and carrying capacity of the connecting section, and form a composite force transmission structure through the vertical inner partition plate and the dowel, the vertical inner partition plate is welded with the inner side frustoconical steel pipe 12, which can enhance the stability and force transmission effect of the steel pipe, and the dowel is embedded in the high-strength grouting material 14 after penetrating the inner side frustoconical steel pipe 12, which can further strengthen the bonding force between the steel pipe and the grouting material, and realize effective force transmission.

[0049] The turning mechanism is a detachable pulley block 15, the surface of the pulley is coated with wear-resistant material, which can reduce the wear of the CFRP tendon 4 during turning; the detachable pulley block 15 is fixed on the pre-buried steel plate 16 of the variable diameter section and the adjustable support screw 6 through bolts, which is convenient for installation, disassembly and adjustment, and can adapt to different construction and use requirements, the bolt connection can ensure the fixing reliability of the turning mechanism, the surface of the CFRP tendon 4 is coated with a weather-resistant anticorrosive coating, which can resist the corrosion of the external environment and prolong the service life of the CFRP tendon, and the anchoring end of the CFRP tendon 4 is sealed with sealant, which further enhances the corrosion protection effect, and the wireless sensor network is arranged inside the steel tower section 2, which can monitor the operating state of the tower in real time, including the stress of the CFRP tendon 4, the inclination of the tower, etc., to provide data support for the safe operation of the tower.

[0050] The concrete section 1 is poured with high-performance concrete and polypropylene fibers are mixed in the concrete, the high-performance concrete can provide higher strength and durability, and the polypropylene fibers can improve the crack resistance of the concrete, the diameter decreases gradually from bottom to top according to a certain slope, which can adapt to the stress characteristics of the tower at different heights, reduce the weight of the upper structure, and the adjacent concrete sections 1 are connected through bracket steel, which can ensure the reliable connection and force transmission between the sections, and is convenient for installation and disassembly.

[0051] A construction method of an external prestressed CFRP tendon steel-concrete combined wind power tower, specifically comprising the following steps:

[0052] S1, construction section division: the steel tower section 2 is divided into several construction sections along the height direction, the height of each section is adapted to the construction and stress requirements, which is convenient for construction operation and control of structural stress, and each section corresponds to an independent CFRP tendon 4 tensioning interval, and a temporary anchoring device is arranged at the interval junction to ensure the stress stability of the CFRP tendon during tensioning and prevent stress transmission from affecting other sections;

[0053] S2, tensioning from bottom to top step by step:

[0054] a. From the base embedded steel anchor box 5, install the first section of CFRP tendon 4 and pass through the reserved hole, the exposed length of the CFRP tendon 4 end meets the anchoring requirements, ensuring that the CFRP tendon can be effectively anchored;

[0055] b. Use hydraulic jacks to apply initial tension to the CFRP tendon 4 with force sensors to 60% to 70% of the tensile strength, so that the CFRP tendon produces a predetermined prestress;

[0056] c. Through the super tension compensation process, increase 5% to 10% of the force on the basis of the initial tension to offset the stress loss of adjacent segment construction, ensure that the final prestress value of the CFRP tendon meets the design requirements;

[0057] d. After completing the tension of this section, seal the anchoring area 9 with epoxy grouting to enhance the sealing and corrosion resistance of the anchoring area, and protect the CFRP tendon and anchoring mechanism;

[0058] S3, segment connection and stress transfer: at the junction of adjacent construction sections, use CFRP sleeve mechanical connection or lap joint to realize the continuity of the prestressed tendon, ensure that the prestress can be effectively transmitted between the sections, and the entire tower structure forms a whole stress system;

[0059] S4, dynamic monitoring and adjustment: real-time monitoring of strain data of each section of CFRP tendon 4 through fiber Bragg grating sensors arranged in steel tower section 2, can timely grasp the stress change of CFRP tendon, adjust the subsequent tension force combined with the feedback results, ensure that the stress deviation of each section is ≤15%, ensure that the tower structure is uniformly stressed, and improve the safety and reliability of the structure.

[0060] The external prestressed CFRP tendon steel-concrete combined wind turbine tower adopts a hybrid structure form of "lower concrete-upper steel tower", which realizes efficient bearing through material performance complementation. The lower segmented concrete tower is composed of multiple prefabricated concrete cylinder sections 1 connected by variable diameter sections, which utilizes the excellent compression resistance of concrete to bear vertical load. Its diameter decreases from bottom to top according to the slope, which adapts to the stress characteristics of wind load increasing with height. The upper steel tower section 2 is made of low-temperature ductile steel plate, which resists the bending moment generated by horizontal wind load due to the high tensile strength of steel. The bottom is rigidly connected to the concrete cylinder section 1 through flange 3, forming a reasonable stiffness distribution of "upper soft and lower hard";

[0061] And the CFRP tendon 4 is longitudinally tensioned along the outer wall of the concrete cylinder section 1, and then a pre-compressive stress is applied to the lower concrete structure to offset part of the tensile stress caused by the wind load; at the same time, the pre-stress is transmitted to the steel tower section 2 through the anchoring mechanism, so that the upper steel structure and the lower concrete structure form a force community, and the overall anti-deformation capability is greatly improved; the segmented tensioning device applies a tensioning stress to the CFRP tendon 4 through a hydraulic jack, and the initial tensioning force is controlled at 60% to 70% of the tensile strength of the CFRP tendon 4, and a 5% to 10% over-tensioning compensation process is used to offset the creep and construction stress loss; during the tensioning process, the adjustable support screw and the detachable pulley set (steering mechanism) guide the CFRP tendon 4 to smoothly steer along the variable-diameter section, the wear-resistant material on the surface of the pulley reduces the abrasion of the tendon and reduces the local stress concentration coefficient; after tensioning, the CFRP tendon 4 forms a closed force system through the two end anchoring mechanisms: the bottom is anchored to the foundation embedded steel anchor box, the top is connected to the flange 3 of the steel tower section 2, and the middle is limited through the U-shaped groove rubber pad of the flexible support block; the pre-stress transmission path is: CFRP tendon 4→ foundation embedded steel anchor box→ concrete cylinder section 1→ flange 3→ steel tower section 2, which makes the entire structure produce a ring constraint effect, inhibits the cracking of concrete and improves the stability of the steel tower, and the weather-resistant epoxy resin coating on the surface of the CFRP tendon 4 and the sealant at the anchoring end form a double corrosion protection barrier, which can resist sea salt spray and saline soil erosion.

[0062] Example 1

[0063] Site survey and planning: conduct geological survey on the construction site to determine the bearing capacity of the foundation, plan the foundation construction area, material storage area, precast component storage area and tensioning operation area according to the design height and weight of the tower cylinder, and ensure that the site is flat and the drainage is smooth;

[0064] In the factory, a detachable steel formwork is used to manufacture the concrete tower cylinder by embedding distributed optical fiber sensors, transition section flanges 3 and stainless steel guide sleeves in the concrete inner cylinder;

[0065] Tower cylinder assembly and transition section connection: after the construction site is leveled, the concrete tower cylinder is installed by grouting connection from bottom to top, the transition section flange 3 is connected, and the steel tower section 2 is connected by anchor bolts;

[0066] CFRP tendon 4 threading: lay a slip pad in the guide groove, use a threading machine to pull the CFRP tendon 4 from the foundation section to the top of the tower, ensure that the tendon bundle slides freely and avoids bending;

[0067] Material and equipment preparation:

[0068] Preparation stage: precast concrete tower pieces in the factory, pre-embed stainless steel guide grooves and transition section flanges 3, and spray anticorrosive coating inside and outside the steel tower section;

[0069] On-site assembly: hoist the concrete segments and grout the joint, install the flange 3 of the transition section and the steel tower section, lay the CFRP tendon 4 bundles in the guide groove, and pass through the transition section hole;

[0070] Check the appearance quality of the CFRP tendon 4, ensure that the surface coating is not damaged, and the strength and elastic modulus meet the design requirements; the precast concrete cylinder segment 1 needs to be tested for compressive strength, the surface flatness and size deviation are within the allowable range; the welding quality of the steel tower cylinder section 2 needs to be tested by non-destructive testing, at the same time, the segmented tensioning device, fiber optic sensor, wireless transmission equipment, grouting equipment, etc. are prepared, and the tensioning equipment is calibrated and the sensor is tested for sensitivity.

[0071] Foundation construction

[0072] Foundation pouring: excavate the foundation pit according to the design drawings, bind the foundation steel reinforcement cage, and pre-set the embedded steel plate 16 connected with the concrete tower cylinder at the top of the foundation. The embedded steel plate 16 is welded and fixed with the foundation steel reinforcement to ensure its accurate position. When pouring concrete, use layered vibration to ensure the compactness of the concrete, and maintain to the design strength.

[0073] Anchor mechanism installation: install the bottom anchor mechanism on the foundation embedded steel plate 16, connect the anchor mechanism with the embedded steel plate 16 through bolts, and check the flatness and firmness of the anchor mechanism after installation.

[0074] Concrete tower cylinder assembly

[0075] Bottom cylinder segment installation: hoist the first precast concrete cylinder segment 1 above the foundation, connect it with the anchor mechanism on the foundation through the flange 3 disc at the bottom of the cylinder segment, adjust the verticality of the cylinder segment, tighten the connecting bolts, and lay rubber sealing pads between the flange 3 disc connecting surfaces to ensure good sealing.

[0076] Subsequent cylinder segment and variable diameter section installation: hoist the remaining precast concrete cylinder segments 1 in order from bottom to top, connect adjacent cylinder segments through embedded bolts on the corbel and the flange 3 disc at the bottom of the previous cylinder segment. After each connection node is installed, check the verticality and axis deviation of the cylinder segment, install the variable diameter section at the position where the diameter needs to be changed, and the connection method of the variable diameter section with the upper and lower cylinder segments is the same as that of the ordinary cylinder segment. Ensure that the taper of the variable diameter section meets the design requirements and the transition is smooth.

[0077] Steel tower cylinder section installation

[0078] Steel-concrete transition section treatment: install the annular embedded steel plate 16 at the pre-set position of the top concrete cylinder segment 1, weld the annular steel plate with the anchor steel reinforcement in the concrete, then weld the dowels on the flange 3 disc at the bottom of the annular steel plate and the steel tower cylinder section 2, and the dowels are distributed in a quincunx pattern.

[0079] Steel tower section 2 hoisting and connection: hoist the steel tower section 2 above the top concrete cylinder section 1, align the flange 3 disc at the bottom of the steel tower section 2 with the annular embedded steel plate 16 of the concrete cylinder section 1, connect through the flange 3 bolt assembly, after tightening the bolt, fill the high-strength grouting material 14 between the outer circular truncated cone steel pipe 11 and the inner circular truncated cone steel pipe 12, and use pressure grouting method to ensure that the grouting material fills the cavity without voids.

[0080] Installation of external prestressing system

[0081] CFRP tendon 4 arrangement: uniformly lay CFRP tendon 4 along the longitudinal wall of the tower cylinder, and guide the CFRP tendon 4 at the variable diameter section through a turning mechanism. The detachable pulley block of the turning mechanism is connected firmly to the tower cylinder outer wall through a support, ensuring that the CFRP tendon 4 is well attached to the pulley groove surface without deviation.

[0082] Installation of anchoring mechanism: install the top anchoring mechanism at the top of the tower cylinder, and fix the two ends of the CFRP tendon 4 to the anchoring mechanism at the bottom and top respectively. Ensure that the CFRP tendon 4 is in a straight state without twisting during anchoring. Apply sealant to the anchoring end to form a sealing barrier to prevent the intrusion of corrosive media.

[0083] Segmental tensioning construction

[0084] Tensioning interval division: according to the height and stress characteristics of the tower cylinder, divide the tower cylinder into several construction sections, and set up independent tensioning intervals in each section. Install a partition ring between the intervals to limit the lateral displacement of the CFRP tendon 4.

[0085] Tensioning operation: (1) First stage pre-tensioning: number the CFRP tendon 4 bundles from the top of the tower to the foundation section in turn, tension in symmetrical order, use hydraulic jacks to tension a single tendon bundle to the target force value, temporarily lock through the anchor, monitor the verticality deviation of the tower cylinder in real time, and adjust the tensioning force distribution when it exceeds the limit. Let stand for 24-48 hours, monitor the stress relaxation rate of the CFRP tendon 4 and the surface cracks of the concrete tower section;

[0086] (2) Second stage final tensioning: remove the temporary lock and re-tension to the final value. After tensioning is completed, inject modified epoxy resin into the gap after anchoring to form an integrated stress system, permanently lock the anchor and install a protective cover. Reach the design prestress to ensure structural stiffness and crack resistance.

[0087] (3) Stress compensation during service period: use the built-in hydraulic adjustment module in the anchor to compensate annually or when the detected prestress loss is greater than 10%. Wirelessly transmit to the monitoring platform to trigger automatic tensioning instructions;

[0088] In the first stage, the CFRP tendon 4 is tensioned to 0.4 times the ultimate stress to eliminate the structural assembly gap; in the second stage, after the tower cylinder is fully loaded, it is tensioned to 0.65 times the ultimate stress and locked; in the third stage, the tendon strain and tower deflection are monitored in real time by sensors.

[0089] Stress monitoring and adjustment: During tensioning, the strain data of each segment of the CFRP tendon 4 is monitored in real time by the fiber Bragg grating sensor, the data is transmitted to the on-site controller, the controller calculates the stress value of each segment, and when the stress deviation exceeds the reasonable range, the tensioning force of the tensioning equipment is adjusted to ensure uniform stress of each segment.

[0090] Monitoring system deployment

[0091] Sensor installation: Stress sensors are installed at key positions of the CFRP tendon 4, inclination sensors are installed at the top and middle of the tower cylinder, and crack meters are installed at weak parts of the concrete cylinder segment 1. The installation position of the sensor needs to be accurate and fixed firmly.

[0092] Data transmission debugging: Connect the sensor with the wireless transmission equipment, debug the wireless communication protocol, ensure that the sensor data can be accurately and real-time transmitted to the monitoring platform, test run the monitoring system, and check the stability and accuracy of the data.

[0093] Acceptance and commissioning

[0094] Acceptance check: After construction is completed, a comprehensive check is made on each connection node, the tensioning stress of the CFRP tendon 4, the grouting quality of the steel-concrete connection section 10, and the operation status of the monitoring system, to ensure that each index meets the design requirements.

[0095] Commissioning: A period of commissioning is carried out, the stress state, inclination and crack development of the tower cylinder under natural environment are monitored in real time, if problems are found, they are adjusted in time, and after the commissioning is qualified, the wind turbine tower can be formally put into use.

[0096] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A prestressed CFRP reinforced steel-concrete composite wind turbine tower, characterized in that, include: The segmented concrete tower is composed of multiple prefabricated concrete sections (1) connected by a variable diameter section. The steel tower section (2) is made of low-temperature tough steel plate and the bottom of the steel tower section (2) is connected to the concrete cylinder section (1) through flange (3); An external prestressing system, comprising CFRP bars (4) evenly distributed longitudinally along the outer wall of the concrete cylinder (1), wherein the number of CFRP bars (4) is arranged according to the circumference of the tower cylinder and the two ends of the CFRP bars (4) are respectively connected to the foundation embedded steel anchor box (5) and flange (3) at the bottom of the concrete cylinder (1) through anchoring mechanisms. The segmented tensioning device includes an adjustable support screw (6), a steering mechanism and a hydraulic jack. The steering mechanism is located at the diameter-changing section and is used to guide the CFRP tendon (4) to turn and reduce local stress concentration.

2. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 1, characterized in that: The anchoring mechanism includes a flexible support block (7), which has an arc-shaped structure that fits against the inner wall of the steel tower section (2) and has a U-shaped groove (8) on its inner wall. A rubber pad (9) is provided in the U-shaped groove (8) to prevent wear of the anti-corrosion coating of the CFRP reinforcement (4).

3. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 1, characterized in that: The connecting section (10) between the steel tower section (2) and the concrete cylinder section (1) is provided with an outer frustum-shaped steel pipe (11) and an inner frustum-shaped steel pipe (12), and the taper of the outer frustum-shaped steel pipe (11) and the inner frustum-shaped steel pipe (12) is consistent with that of the variable diameter section.

4. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 3, characterized in that: An annular gap (13) is formed between the outer frustum-shaped steel pipe (11) and the inner frustum-shaped steel pipe (12), and the annular gap (13) is filled with high-strength grout (14). A composite force transmission structure is formed by a vertical inner partition and studs. The vertical inner partition is welded to the inner frustum-shaped steel pipe (12), and the studs penetrate the inner frustum-shaped steel pipe (12) and are embedded in the high-strength grout (14).

5. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 1, characterized in that: The steering mechanism is a detachable pulley block (15), with the pulley surface covered with wear-resistant material; the detachable pulley block (15) is fixed to the pre-embedded steel plate (16) of the variable diameter section and the adjustable support screw (6) by bolts.

6. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 1, characterized in that: The CFRP reinforcement (4) is coated with a weather-resistant anti-corrosion coating and the anchoring end of the CFRP reinforcement (4) is sealed with sealant. A wireless sensor network is installed inside the steel tower section (2).

7. The externally prestressed CFRP reinforced steel-concrete composite wind turbine tower according to claim 1, characterized in that: The concrete cylinder section (1) is made of high-performance concrete and contains polypropylene fiber. The diameter decreases gradually from bottom to top according to the slope. Adjacent concrete cylinder sections (1) are connected by corbel steel.

8. A construction method for a prestressed CFRP reinforced steel-concrete composite wind turbine tower according to any one of claims 1-7, characterized in that: Specifically, the following steps are included: S1. Construction section division: The steel tower section (2) is divided into several construction sections along the height direction. The height of each section is adapted to the construction and stress requirements. Each section corresponds to an independent CFRP reinforcement (4) tensioning interval. Temporary anchoring devices are set at the junction of the sections. S2, tensioning from bottom to top in stages: a. Starting from the pre-embedded steel anchor box (5) in the foundation, install the first section of CFRP bar (4) and pass it through the reserved hole. The length of the CFRP bar (4) exposed at the end of the anchor meets the anchorage requirements. b. Using a hydraulic jack and a force sensor, apply an initial tension force to the CFRP reinforcement (4) to 60% to 70% of its tensile strength; c. By using the over-tensioning compensation process, an additional 5% to 10% of the force is added to the initial tension force to offset creep and stress loss during construction of adjacent sections; d. After completing the tensioning of this section, the anchorage area (9) is sealed with epoxy resin grouting; S3. Segmented connection and stress transfer: At the junction of adjacent construction sections, CFRP sleeves are used for mechanical connection or lap splicing to achieve the continuity of prestressed tendons. S4. Dynamic monitoring and adjustment: The strain data of each CFRP tendon (4) is monitored in real time by fiber optic grating sensors installed in the steel tower section (2), and the subsequent tension is adjusted in combination with the feedback results to ensure that the stress deviation of each section is ≤15%.

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