Lightweight wind power cable bent tower composite structure of high-power fan and design method thereof

Abstract

The invention provides a lightweight wind power cable tower combined structure of a high-power fan and a design method of the lightweight wind power cable tower combined structure, and belongs to the technical field of fan equipment designing.The lightweight wind power cable tower combined structure comprises the steps that firstly, tower parameters are determined according to wind field conditions, load data are collected, and then a three-dimensional finite element analysis model is established to set material parameters and initial cable force; then determining the arrangement of supporting components and optimizing connecting nodes, and determining the optimal cable section and cable force through a pre-stressed cable section optimization equation set; then drawing a deepened detailed drawing to design connection nodes, and carrying out component splitting and connection scheme design according to transportation conditions; and finally, on-site construction and installation are conducted, a staged tensioning process is adopted, and the structural performance is verified after the wind turbine generator is installed. The problem that a high-power wind power tower tube structure is insufficient in lateral force resistance can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind turbine equipment design, and in particular relates to a lightweight wind turbine tower combination structure for a high-power wind turbine and a design method thereof. Background Art

[0002] With the advancement of wind power technology, high-power wind turbines have gradually become the mainstream choice for wind farms. Traditional wind turbine tower structures primarily utilize steel conical cylinders or concrete towers. While steel conical towers are convenient to construct, the lateral loads they bear significantly increase with increasing height and wind turbine power, making deformation control difficult. Concrete towers, while heavier, lack the lateral load resistance required for high-power wind turbines, especially in areas prone to high-intensity earthquakes.

[0003] Existing wind turbine tower designs typically rely on increasing tower wall thickness or using higher-strength materials to improve lateral load resistance, resulting in overall structural system inefficiency. In particular, as wind turbine power and tower height increase, the wind loads and overhead equipment loads on the tower increase significantly. Traditional single-material structures struggle to effectively handle the increasing lateral forces, and under extreme wind conditions or earthquakes, they may experience excessive deformation or even overturning risks.

[0004] Currently, the wind power industry urgently needs a structural system that can effectively improve the tower's ability to resist lateral loads, in order to solve the technical problem of insufficient lateral force resistance of high-tower structures of large-power wind turbines. However, the existing technical system has not yet provided a systematic solution. Summary of the Invention

[0005] In view of this, the present invention provides a lightweight wind turbine tower combination structure for a high-power wind turbine and a design method thereof, which can solve the technical problem in the prior art that the high-power wind turbine tower structure has insufficient lateral force resistance.

[0006] The present invention is achieved in that:

[0007] The present invention provides a lightweight wind power cable tower combination structure for a high-power wind turbine, which includes: determining the tower height and wind turbine model according to wind field conditions, collecting load data and wind load and earthquake information; establishing a three-dimensional finite element analysis model of a hollow sandwich steel tube concrete component, setting material parameters and initial cable forces of prestressed cables; determining the number and layout positions of supporting components, optimizing the design of connection nodes, and adjusting the cable shape so that the prestressed cables can withstand tension; and determining the optimal prestressed cable cross-section and initial cable force using a group of prestressed cable cross-section optimization equations based on cable force distribution and deformation analysis results, so that the structure meets strength requirements and displacement constraints, and the design scheme is completed.

[0008] On the basis of the above technical solution, the lightweight wind power tower combination structure of a high-power wind turbine of the present invention can also be improved as follows:

[0009] Among them, the prestressed cable section optimization equation group includes an objective function equation, a strength constraint equation, a displacement constraint equation and a cable force balance equation; the objective function equation is used to minimize the total weight of the structural system; the strength constraint equation is used to ensure that each component is not damaged under the ultimate load condition; the displacement constraint equation is used to control the displacement of the tower top to meet the wind turbine operation requirements; the cable force balance equation is used to establish the relationship between the initial cable force of the prestressed cable and its balanced tower lateral load.

[0010] Furthermore, the input of the objective function equation includes the cross-sectional area of the prestressed cable, the length of the prestressed cable obtained by cable shape calculation, the density of the prestressed cable material, the volume of the hollow sandwich steel tube concrete component and the density of the hollow sandwich steel tube concrete component, and the output is the total weight function of the structural system used for optimization design.

[0011] Furthermore, the input of the strength constraint equation includes the cross-sectional area of the prestressed cable, the tensile strength of the prestressed cable material, the compressive strength of the hollow sandwich steel tube concrete component, the design load and the safety factor, and the output is the constraint condition of the ratio of the component stress to the allowable stress used to optimize the design.

[0012] Furthermore, the input of the displacement constraint equation includes the maximum allowable displacement of the tower top corresponding to the wind turbine model, the initial tension of the prestressed cable, the load condition combination, the tower stiffness and the position of the supporting components, and the output is the ratio constraint condition of the tower top displacement and the allowable displacement used for optimizing the design.

[0013] Furthermore, the input of the cable force balance equation includes the wind load distribution function, the geometric dimensions of the tower, the position of the supporting components and the angle between the prestressed cable and the tower obtained by cable shape calculation, and the output is the initial cable force design value of the prestressed cable used for optimization design and tensioning control.

[0014] Furthermore, the hollow sandwich steel tube concrete component is a composite component formed by an outer steel tube, an inner steel tube and concrete filled therebetween. The outer steel tube provides restraint to improve the compressive strength of the concrete, and the inner layer forms a hollow structure to reduce its own weight. The prestressed cable is a tension member made of high-strength steel strands, which is fixed to the anchor end after being prestressed by tensioning equipment, and is used to bear the lateral load of the wind turbine tower and provide stability. The inter-tower support member is a secondary structural member connecting the main tower and the prestressed cable, which is used to adjust the cable shape and provide intermediate support points, thereby reducing the free length of the prestressed cable and reducing wind vibration fatigue damage.

[0015] Furthermore, the nonlinear analysis condition considers the calculation model of large structural geometric deformation and nonlinear material characteristics, which is used to accurately simulate the actual stress state of prestressed cables and hollow sandwich steel tube concrete components under various loads.

[0016] Furthermore, the cable shape refers to the geometric shape of the prestressed cable from the top of the tower to the ground anchor point, which is adjusted by the supporting components to form a broken line shape rather than a straight line shape, which is used to optimize the cable force distribution and reduce the footprint.

[0017] Furthermore, the designed lightweight wind turbine tower composite structure system of the high-power wind turbine is composed of a composite load-bearing system consisting of a hollow sandwich steel tube concrete main tower, multiple prestressed cables and several tower support components. The main tower bears pressure, the prestressed cables bear tension, and the support components provide lateral support.

[0018] The present invention proposes a lightweight wind turbine tower combination structure for high-power wind turbines. By organically combining hollow sandwich steel tube concrete components, prestressed cables and supporting components, a composite load-bearing structure system is formed, which achieves a significant improvement in the lateral force resistance performance.

[0019] This design approach rationally configures the collaborative working mechanism of hollow sandwich steel tube concrete components and prestressed cables, ensuring that the main tower primarily bears compressive forces and the prestressed cables bear tensile forces, fully leveraging the mechanical properties of each material. Simultaneously, by optimizing the arrangement of supporting components and the shape of the prestressed cables, and establishing a set of equations for optimizing the prestressed cable cross-section, the goal is to maximize the lateral stiffness of the structural system while satisfying displacement constraints, effectively addressing the insufficient lateral force resistance of traditional tower structures.

[0020] The method of the present invention significantly improves the structure's ability to resist wind loads and earthquakes through the lateral support force provided by prestressed cables, ensures that the top displacement of the tower under various load combinations meets the wind turbine operation requirements, solves the technical problem of insufficient lateral force resistance of high-power wind turbine tower structures, and provides reliable protection for the safe and stable operation of high-power wind turbines.

[0021] Compared with the prior art, the lightweight wind power tower assembly structure for a high-power wind turbine provided by the present invention has the following beneficial effects: BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of a lightweight wind power tower assembly structure for a high-power wind turbine;

[0023] Figure 2 This is a schematic diagram of a lightweight wind power tower assembly structure for a high-power wind turbine;

[0024] Figure 3 It is a cross-sectional view of a hollow sandwich steel tube concrete component;

[0025] Figure 4 A cross-sectional view of a main tower of a lightweight wind power cable tower combination structure for a high-power wind turbine;

[0026] Figure 5A schematic diagram of a lightweight wind power tower combined structure anchoring device for a high-power wind turbine;

[0027] Figure 6 Calculate and analyze deformation diagrams for structural systems;

[0028] Figure 7 Calculate and analyze mode shape diagrams for structural systems;

[0029] Figure 8 A side view of the wind power tower combined structure system of Example 2;

[0030] Figure 9 This is a front view of the wind power tower combined structure system of Example 2;

[0031] Figure 10 A top view of the wind power tower combined structure system of Example 2;

[0032] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0033] 10. Wind turbine; 20. Main tower; 30. Support member; 40. Prestressed cable; 50. Anchoring device; 52. Anchor plate; 53. Anchor; 54. Tensioning equipment; 60. Hollow sandwich steel tube concrete member; 61. Outer steel tube; 62. Inner steel tube; 63. Concrete. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] like Figure 2-5 The figure shows a lightweight wind turbine tower assembly structure for a high-power wind turbine according to the present invention. This structure illustrates the entire wind turbine tower structure, including the positional relationships of the hollow sandwich steel tube concrete main tower 20, prestressed cables 40, support members 30, foundation, and wind turbine 10. The figure clearly illustrates how the prestressed cables travel from the tower top through the support members 30 to the ground anchorage points.

[0036] It includes: determining the tower height and wind turbine model according to wind field conditions, collecting load data and wind load and earthquake information; establishing a 60-degree three-dimensional finite element analysis model of hollow sandwich steel tube concrete components, setting material parameters and initial cable tension of prestressed cables; determining the number and layout of supporting components, optimizing the connection node design, and adjusting the cable shape so that the prestressed cables can withstand tension; based on the cable force distribution and deformation analysis results, using the prestressed cable section optimization equation group to determine the optimal prestressed cable section and initial cable tension, so that the structure meets the strength requirements and displacement constraints, and completes the scheme design.

[0037] Among them, in the above technical scheme, the prestressed cable section optimization equation group includes the objective function equation, the strength constraint equation, the displacement constraint equation and the cable force balance equation; the objective function equation is used to minimize the total weight of the structural system; the strength constraint equation is used to ensure that each component is not damaged under the extreme load condition; the displacement constraint equation is used to control the displacement of the tower top to meet the wind turbine operation requirements; the cable force balance equation is used to establish the relationship between the initial cable force of the prestressed cable and its balanced tower lateral load.

[0038] Furthermore, in the above technical solution, the input of the objective function equation includes the cross-sectional area of the prestressed cable, the length of the prestressed cable obtained by cable shape calculation, the density of the prestressed cable material, the volume of the hollow sandwich steel tube concrete component and the density of the hollow sandwich steel tube concrete component, and the output is the total weight function of the structural system used for optimization design.

[0039] Furthermore, in the above technical solution, the input of the strength constraint equation includes the cross-sectional area of the prestressed cable, the tensile strength of the prestressed cable material, the compressive strength of the hollow sandwich steel tube concrete member, the design load and the safety factor, and the output is the ratio constraint condition of the member stress and the allowable stress used to optimize the design.

[0040] Furthermore, in the above technical solution, the input of the displacement constraint equation includes the maximum allowable displacement of the tower top corresponding to the wind turbine model, the initial tension of the prestressed cable, the load condition combination, the tower stiffness and the position of the supporting components, and the output is the ratio constraint condition of the tower top displacement and the allowable displacement used for optimizing the design.

[0041] Furthermore, in the above technical solution, the input of the cable force balance equation includes the wind load distribution function, the geometric dimensions of the tower, the position of the supporting components and the angle between the prestressed cable and the tower obtained by cable shape calculation, and the output is the initial cable force design value of the prestressed cable used for optimized design and tensioning control.

[0042] Furthermore, in the above technical solution, the hollow sandwich steel tube concrete member 60 is a composite member formed by an outer steel tube 61, an inner steel tube 62 and concrete 63 filled therebetween. The outer steel tube provides a restraining force to improve the compressive strength of the concrete, and the inner layer forms a hollow structure to reduce its own weight. The prestressed cable is a tension member made of high-strength steel strands, which is fixed to the anchor end after being prestressed by tensioning equipment, and is used to bear the lateral load of the wind turbine tower and provide stability. The inter-tower support member is a secondary structural member connecting the main tower and the prestressed cable, which is used to adjust the cable shape and provide an intermediate support point, thereby reducing the free length of the prestressed cable and reducing wind vibration fatigue damage.

[0043] Furthermore, in the above technical solution, the nonlinear analysis condition considers the calculation model of large structural geometric deformation and nonlinear material characteristics, which is used to accurately simulate the actual stress state of prestressed cables and hollow sandwich steel tube concrete components under various loads.

[0044] Furthermore, in the above technical solution, the cable shape refers to the geometric shape of the prestressed cable from the top of the tower to the ground anchor point, which is adjusted by the supporting structure to form a broken line shape rather than a straight line shape, which is used to optimize the cable force distribution and reduce the footprint.

[0045] Furthermore, in the above technical solution, the designed lightweight wind turbine tower composite structure system of the large-power wind turbine is composed of a composite load-bearing system consisting of a hollow sandwich steel tube concrete main tower, multiple prestressed cables and several tower support components. The main tower bears pressure, the prestressed cables bear tension, and the support components provide lateral support.

[0046] like Figure 1 FIG. 1 is a flow chart of a lightweight wind power tower assembly structure for a high-power wind turbine provided by the present invention. The method includes the following steps:

[0047] S01. Determine the tower height and wind turbine model based on wind field conditions, collect data on the load generated by the wind turbine on the tower top, obtain earthquake information on the project address, including earthquake grouping and seismic intensity, and collect wind load information, including basic wind pressure, gust coefficient, and wind pressure height variation coefficient;

[0048] S02. Establish a three-dimensional finite element analysis model based on the cross-sectional parameters of the hollow sandwich steel tube concrete component, set the material parameters and the initial cable force of the prestressed cable, add wind load, seismic load and tower top load, and select nonlinear analysis conditions to simulate the actual stress state;

[0049] S03. Determine the number and layout of support components. Optimize the design of the connection nodes between the support components and the main tower through finite element analysis. Adjust the cable shape so that the prestressed cables bear tension, the hollow sandwich steel tube concrete components bear compression, and the support components bear axial force.

[0050] S04. Based on the cable force distribution and tower deformation analysis results, the optimal prestressed cable cross-section and initial cable force are determined using the prestressed cable cross-section optimization equations to minimize the total weight of the structural system while meeting strength requirements and displacement constraints. This ensures that the maximum displacement of the tower top under each load combination meets the wind turbine operating requirements.

[0051] S05. Draw detailed drawings, design the welding connection nodes between the support components and the tower, design the cable clamps connecting the prestressed cables and support components, and perform segmented design of the hollow sandwich steel tube concrete components based on the transportation conditions;

[0052] S06. Optionally, this also includes disassembling components based on the load and size restrictions of the transport vehicle, determining the on-site assembly sequence and node connection method, and formulating a tower segment bolt connection plan and a prestressed cable installation and tensioning plan;

[0053] S07. Optionally, the on-site construction further includes first connecting the tower base to the foundation, using lifting equipment to sequentially hoist the prefabricated hollow sandwich steel tube concrete segmented components and connecting them with bolts, and then installing the supporting components and arranging the prestressed cables;

[0054] S08. Optionally, the prestressed cables are tensioned in stages, with the first tensioning being performed after the tower is assembled to secure the structural system, and the second tensioning being performed after the wind turbine is installed to ensure that the prestressed cable force meets the design requirements;

[0055] S09. Optional: Installing the wind turbine and verifying the actual performance of the structural system, measuring and recording the displacement of the tower top, verifying the deviation between the actual prestressed cable force and the designed cable force, and adjusting the tension force if necessary;

[0056] The prestressed cable section optimization equation group includes an objective function equation, a strength constraint equation, a displacement constraint equation and a cable force balance equation;

[0057] The objective function equation is used to minimize the total weight of the wind turbine tower structure system. The input includes the cross-sectional area of the prestressed cable determined in step S03, the length of the prestressed cable calculated from the cable shape determined in step S03, the material density of the prestressed cable set in step S02, the volume of the hollow sandwich steel tube concrete component established in step S02, and the density of the hollow sandwich steel tube concrete component set in step S02. The output is the total weight function of the structure system used for the optimization design in step S04.

[0058] The strength constraint equation is used to ensure that each component does not fail under the ultimate load condition. The input includes the cross-sectional area of the prestressed cable optimized in step S04, the tensile strength of the prestressed cable material set in step S02, the compressive strength of the hollow sandwich steel tube concrete component set in step S02, the design load collected in step S01, and the safety factor set in step S02. The output is the constraint condition of the ratio of component stress to allowable stress used in the optimized design in step S04.

[0059] The displacement constraint equation is used to control the displacement of the tower top to meet the wind turbine operation requirements. The input includes the maximum allowable displacement of the tower top corresponding to the wind turbine model determined in step S01, the initial cable force of the prestressed cables optimized in step S04, the load condition combination set in step S02, the tower stiffness established in step S02, and the support member position determined in step S03. The output is the constraint condition of the ratio of the tower top displacement to the allowable displacement used in the optimized design in step S04.

[0060] The cable force balance equation is used to establish the relationship between the initial cable force of the prestressed cable and its balanced tower lateral load. The input includes the wind load distribution function collected in step S01, the tower geometry established in step S02, the support member position determined in step S03, and the angle between the prestressed cable and the tower calculated from the cable shape determined in step S03. The output is the design value of the initial cable force of the prestressed cable used for the optimization design in step S04 and the tension control in step S08.

[0061] Among them, hollow sandwich steel tube concrete components specifically refer to composite components formed by an outer steel tube, an inner steel tube and concrete filled between the two. The outer steel tube provides restraint to increase the compressive strength of the concrete, and the inner layer forms a hollow structure to reduce its own weight.

[0062] Among them, prestressed cables specifically refer to tensioned components made of high-strength steel strands, which are fixed at the anchor end after being prestressed by tensioning equipment. They are used to bear the lateral load of the wind turbine tower and provide stability.

[0063] Among them, the inter-tower support member specifically refers to the secondary structural member connecting the main tower and the prestressed cable, which is used to adjust the cable shape and provide intermediate support points, reduce the free length of the prestressed cable and reduce wind vibration fatigue damage.

[0064] Among them, the nonlinear analysis condition specifically refers to a calculation model that takes into account the large geometric deformation of the structure and the nonlinear characteristics of the material, which can accurately simulate the actual stress state of prestressed cables and hollow sandwich steel tube concrete components under various loads.

[0065] Among them, the cable shape specifically refers to the geometric shape of the prestressed cable from the top of the tower to the ground anchor point. After adjustment through the supporting components, it forms a broken line shape instead of a straight line shape, which can optimize the cable force distribution and reduce the footprint.

[0066] Among them, the designed lightweight wind turbine tower composite structural system for large-power wind turbines is a composite load-bearing system consisting of a hollow sandwich steel tube concrete main tower, multiple prestressed cables and several tower support components. The main tower bears pressure, the prestressed cables bear tension, and the support components provide lateral support, forming an efficient structural system that works in coordination.

[0067] The specific implementation of the above steps is described in detail below.

[0068] The specific implementation of step S01 is to determine the optimal tower height using a wind energy resource assessment and analysis method based on the wind farm's geographic location, terrain characteristics, and wind resource conditions. Typically, a height within the range of 70 to 150 meters is selected, ensuring that the lowest point of the turbine blades is at least 50 meters above the ground. A matching wind turbine model is selected based on the tower height, typically a high-power turbine of 3 to 10 megawatts. Data on the vertical load, horizontal load, and bending moment generated by the turbine on the tower top during normal operation, extreme wind conditions, and emergency shutdown are obtained from the manufacturer's technical manual. Seismic microzoning analysis is used to determine the project site's earthquake classification (typically Class I, II, III, and IV) and seismic intensity (typically 6 to 9 degrees). Extreme value statistics are used to analyze wind speed observations from local meteorological stations for at least 20 years to determine a 50-year return period basic wind pressure, typically between 0.45 and 0.85 kPa. The gust coefficient (typically 2.1 to 2.5) and the wind pressure height variation coefficient are calculated based on the terrain roughness.

[0069] like Figure 6 As shown, the specific implementation method of step S02 is to use finite element analysis software to establish a three-dimensional model of the tower structure, and use geometric nonlinear large deformation theory to consider the second-order effect of the structure under large displacement conditions. For hollow sandwich steel tube concrete components, the diameter of the outer steel tube is usually 3.5 to 5.0 meters, the wall thickness is 20 to 40 mm, the diameter of the inner steel tube is usually 0.4 to 0.6 times the diameter of the outer steel tube, the wall thickness is 16 to 30 mm, and the strength grade of the filled concrete is C50 to C60. In the material parameter setting, the steel adopts a bilinear constitutive model with a yield strength of 345 to 420 MPa, the concrete adopts a damage plasticity model, and the compressive strength of the cylinder is 50 to 60 MPa. The prestressed cable material adopts high-strength steel strand with an ultimate tensile strength of 1860 MPa and an elastic modulus of 1.95×10 5 MPa. The initial cable tension was set at 30% to 40% of the cable's tensile strength. Load application followed the principle of step-by-step loading, first applying the structure's deadweight, then prestressing, and finally superimposing wind loads (distributed along the tower height using the Gaussian integral method), seismic loads (calculated using the response spectrum method), and wind turbine top loads. A nonlinear explicit dynamic analysis solver was selected to simulate the actual stress state, and a Rayleigh damping model with a damping ratio of 5% was used to account for structural damping effects.

[0070] The specific implementation of step S03 is based on structural optimal design theory, comprehensively considering load-bearing capacity, stiffness, and construction feasibility to determine the optimal arrangement of support components. The number of support components is typically 4 to 8, evenly distributed along the tower height or appropriately increased in areas of concentrated wind loads. Finite element mesh refinement techniques are used to analyze stress concentration at the connection points between the support components and the main tower. The node design utilizes the principle of smooth cross-section transitions to reduce the stress concentration factor to no more than 2.0. A parametric design approach is used to optimize the support component angles. By varying the angle between the support components and the horizontal plane, the prestressed cables form a broken line rather than a straight line. Cable shape optimization utilizes a force balance iteration method to adjust the inclination angle and support point locations of each cable segment, ensuring that the cables are in tension under all load conditions, with the tension value not less than 50% of the initial cable force and not exceeding 60% of the cable material's ultimate tensile strength. Furthermore, the maximum compressive stress of the hollow sandwich steel-concrete-filled tube component under the ultimate load condition does not exceed 85% of the design compressive stress, and the axial force of the support component does not exceed 70% of its critical buckling load.

[0071] The specific implementation of step S04 is to obtain cable force distribution and tower deformation data based on the structural sensitivity analysis method. The maximum allowable horizontal displacement of the tower top is usually limited to 1 / 100 to 1 / 150 of the tower height. A sequential quadratic programming algorithm is used to construct a set of equations for optimizing the prestressed cable cross-section. The objective function is to minimize the total weight of the structural system. The constraints include cable stress limits, tower compressive stress limits, support member stress limits, and tower top displacement limits. The optimal prestressed cable cross-sectional area and initial cable force values are determined by solving this nonlinear programming problem. Modal analysis is used to verify the structural fundamental frequency during the optimization process, ensuring that the fundamental frequency is greater than 0.3 Hz to avoid resonance with the wind turbine operating frequency. Fatigue life assessment is also performed to ensure that the cumulative fatigue damage coefficient of key nodes does not exceed 0.8 under the action of the design wind speed spectrum, and the expected service life is not less than 25 years.

[0072] The specific implementation method of step S05 is to use parametric modeling technology to draw detailed drawings and use three-dimensional solid modeling software to accurately model the structural components. The welding connection nodes between the support components and the tower use full penetration welds. The welding process requires the weld quality grade to be no less than level 2. Ultrasonic non-destructive testing is performed after welding to ensure the quality of the welds. Customized cable clamps are used to connect the prestressed cables to the support components. The cable clamp design is based on the principle of frictional force transmission. High-strength bolts are used to connect the clamps. The bolt preload torque is designed according to 1.2 times the nominal torque to prevent the cable clamps from slipping. The segmented design of the hollow sandwich steel tube concrete components is based on the modular concept. Considering the transportation conditions, the length of a single segment is usually controlled at 10 to 15 meters, and the weight of a single segment does not exceed 80 tons. The segmented connection uses high-strength bolts with flanges. The flange thickness is not less than 50 mm, and the bolt grade is not less than 10.9.

[0073] Step S06 is an optional step, and its specific implementation method is to plan the component splitting and on-site assembly based on logistics and transportation constraints. According to road transportation restrictions, the maximum outer diameter of the component shall not exceed 4.5 meters, the maximum length shall not exceed 30 meters, and the maximum weight shall not exceed 100 tons. The finite element cutting optimization algorithm is used to determine the optimal cutting line position for complex-shaped components to minimize the stress on the cutting surface. The on-site assembly sequence follows the bottom-up principle. The bottom section of the tower is installed first and connected to the foundation. The connection adopts the embedded bolt ring and the bottom flange high-strength bolt connection method, and the bolt pre-tightening force is controlled by hydraulic synchronous tensioning technology. The tower sections are connected with flange bolts, and the bolt holes are precisely aligned with locating pins. The bolts are tightened with a hydraulic wrench in diagonal order, and the torque control accuracy is ±5%. A tensioning force verification test is carried out before the installation of the prestressed cable to verify that the cable clamp sliding force is not less than 1.5 times the design cable force.

[0074] Step S07 is optional. Its specific implementation involves connecting the tower base with a pile foundation or box foundation. This connection utilizes a pre-buried bolt ring, whose diameter matches the tower base diameter. The number of bolts is determined by uniform circumferential distribution, typically ranging from 36 to 48. A crawler crane is used to hoist the prefabricated hollow sandwich steel tubular concrete segments into place according to the construction sequence drawings. Temporary positioning fixtures are used between segments to ensure centering accuracy. Metal gaskets are placed between flanges to ensure planar contact. Bolt connections utilize a tensioning stress control method, with bolt stress reaching 70% to 75% of the yield strength. The support structure is installed by welding the aerial work platform to the tower using a combination of manual arc welding and semi-automatic gas shielded welding. Welding parameters are controlled according to the welding procedure qualification report. Before prestressed cable placement, cableway measurements and layout are performed to ensure cableway positioning accuracy. Tensioning equipment is installed and calibrated, ensuring an accuracy of no less than 1%.

[0075] Step S08 is an optional step, and its specific implementation method is to use a staged tensioning process to control the construction quality of the prestressed cables. The first stage of tensioning is carried out after the tower is assembled. The tensioning force is 60% to 70% of the design cable force. Synchronous tensioning equipment is used to simultaneously and symmetrically tension multiple cables, controlling the displacement of the tower top to no more than 30% of the design displacement. During the tensioning process, load-displacement real-time monitoring technology is used to monitor the relationship between cable force and displacement to verify consistency with theoretical calculation results. After tensioning is completed, the cable force is locked. The locking is carried out using wedge anchoring technology to ensure that the cable force loss after locking does not exceed 5% of the design cable force. The second stage of tensioning is carried out after the wind turbine is installed. The tensioning force reaches 100% of the design cable force. The relationship between the tower top displacement and cable force is monitored to verify the consistency of the actual cable force-displacement curve with the theoretical curve, with a deviation of no more than 10%. After the second stage of tensioning is completed, the cable force is locked and protective measures are installed, including anti-corrosion, lightning protection, and anti-vibration measures.

[0076] Step S09 is an optional step, and its specific implementation method is to verify the actual performance of the structural system through a structural health monitoring system. After the wind turbine is installed, a comprehensive inspection is carried out, including vibration testing, displacement measurement and cable tension testing. A three-dimensional acceleration sensor is installed on the top of the tower to measure the acceleration response of the structure under different wind speeds. The actual damping ratio and fundamental frequency of the structure are determined by frequency domain analysis, and the deviation between the fundamental frequency and the theoretical calculation is verified to be no more than 5%. A total station is used to monitor the displacement of the top of the tower in real time to verify that the displacement does not exceed the design limit at the design wind speed. A magnetic elastic dynamometer is used to measure the actual cable tension of the prestressed cable to verify that the deviation from the design cable tension does not exceed 8%. The tensioning force of the prestressed cable whose deviation exceeds the allowable value is adjusted using fine tensioning equipment, and the cable tension adjustment accuracy is controlled within ±3%. At the same time, a long-term monitoring system is established to continuously monitor key parameters to ensure the long-term safe operation of the structure.

[0077] The method for fitting the optimal set of equations for prestressed cable sections first uses finite element analysis to obtain stress and displacement data sets for prestressed cables of different cross-sections under different load conditions, including parameters such as axial force, stress, nodal displacement, and frequency response. The least squares method is then used to fit the objective function and constraint expressions. The objective function is fitted using a linear polynomial model to describe the relationship between the total weight of the structure and the dimensions of each component. The strength constraint equations are fitted using a nonlinear expression based on the stress influence surface method to establish the functional relationship between the stress and cross-sectional parameters of each component under the ultimate load condition. The displacement constraint equations are fitted using the principles of structural elastic mechanics to establish the functional relationship between the tower top displacement and the cable force, tower stiffness, and support location. The cable force equilibrium equations are fitted using the principles of static equilibrium, establishing the functional relationship between the initial cable force and the external loads balanced by it through mechanical analysis. An iterative optimization algorithm is used in the fitting process, with coefficients continuously adjusted until the fitting error is less than 5%. The resulting set of equations comprehensively considers the principles of structural mechanics and practical engineering constraints, accurately describing the mechanical behavior and optimization objectives of the wind turbine cable-tower composite structure.

[0078] The mathematical model or calculation process involved in the present invention is described in detail below.

[0079] In step S01, the wind load calculation adopts the basic principles of wind engineering and takes into account the height variation coefficient, which is specifically expressed as follows:

[0080] F w (z)=μ s μ z μ c ·w0·A(z);

[0081] Where, F w (z) is the wind load at height z, in kilonewtons; μ s is the wind load shape coefficient, dimensionless, ranging from 0.8 to 1.2; μ zis the wind pressure height variation coefficient, dimensionless, calculated using the power law: μ z =(z / 10) 2α , where α is the surface roughness index, ranging from 0.12 to 0.30; μ c is the gust coefficient, dimensionless, ranging from 2.1 to 2.5; w0 is the basic wind pressure, in kPa, ranging from 0.45 to 0.85; A(z) is the windward area at height z, in square meters.

[0082] This equation, based on the principles of fluid mechanics, accounts for the variation of wind load with height. It uses a power-exponential relationship to describe the height variation of wind pressure, which better reflects actual wind field characteristics than a linear relationship. The gust coefficient is derived from meteorological data using extreme value statistics, and the shape coefficient is determined based on the tower shape. The multiplication relationship between the various parameters in the equation reflects the physical process of load transfer. It is an improved form of the classic equation in wind engineering, adding nonlinear characteristics to account for height variations.

[0083] The earthquake load calculation adopts the response spectrum method, which is expressed as follows:

[0084] F e =γ·M·S a (T);

[0085] Where, F e is the equivalent lateral force vector of the structure under earthquake action, in kilonewtons; γ is the earthquake action adjustment coefficient, dimensionless, ranging from 1.0 to 1.3; M is the structural mass matrix, in tons; S a (T) is the design acceleration response spectrum, in meters per square second, which can be expressed as: S a (T) = α max ·η(T,ξ)·g, where α max is the maximum horizontal earthquake influence coefficient, ranging from 0.05 to 0.40; η(T, ξ) is the design response spectrum curve, which is a function of the structural period T and the damping ratio ξ; g is the gravitational acceleration constant, which is 9.81 m / s2.

[0086] This equation, based on structural dynamics theory, employs the matrix product of a mass matrix and an acceleration response spectrum to accurately describe the dynamic response of a structure under earthquake action. The response spectrum, a characteristic description of the seismic action, combines the earthquake intensity with the structural periodicity, while the mass matrix reflects the structural mass distribution. This calculation method is more accurate than the traditional equivalent static method and can account for the participation of multiple modes of the structure.

[0087] In step S02, the nonlinear constitutive model of the hollow sandwich steel tube concrete member is specifically expressed as follows:

[0088] Bilinear constitutive model for steel:

[0089]

[0090] Where σ s is the stress of steel, in MPa; E s is the elastic modulus of steel, in MPa, with a typical value of 2.1×10 5 ; ε s is the steel strain, dimensionless; ε y is the yield strain of steel, dimensionless, ε y =f y / E s ;f y is the yield strength of steel, in MPa, ranging from 345 to 420; E st is the tangent modulus of steel after yield, in MPa, E st =β·E s , where β is the hardening coefficient, ranging from 0.01 to 0.05.

[0091] Damage plasticity model of concrete:

[0092]

[0093] Where σ c is the concrete stress, in MPa; d is the damage variable, ranging from 0 to 1, which is a function of strain; E c is the initial elastic modulus of concrete, in MPa, which can be measured by Calculate, where f c ' is the compressive strength of the concrete cylinder, in MPa, ranging from 50 to 60; ε c is the total strain of concrete, dimensionless; is the plastic strain of concrete, dimensionless.

[0094] These two constitutive model equations describe the nonlinear mechanical behavior of materials under large deformation conditions. The steel model uses bilinear simplification to account for the hardening effect after yielding, while the concrete model takes into account the damage evolution process, which can more accurately simulate the nonlinear characteristics of concrete under compression. The model parameters are obtained through standard material tests, including uniaxial tension tests, uniaxial compression tests, and triaxial compression tests. These constitutive models are more accurate than traditional linear elastic models and can simulate the nonlinear response of structures in limit states, providing a reliable basis for structural safety assessment.

[0095] In step S03, the optimization of the support members and prestressed cables involves the following calculations:

[0096] Calculation of critical buckling load of supporting members:

[0097]

[0098] Where, P cr is the critical buckling load of the supporting member, in kN; E b is the elastic modulus of the supporting member, in MPa; I b is the moment of inertia of the supporting member, expressed in the fourth power of centimeters; K is the effective length coefficient, which depends on the constraint conditions of the supporting member and ranges from 0.5 to 1.0; L b is the length of the supporting member in meters.

[0099] This equation, based on Euler's buckling theory, describes the instability of slender members subjected to axial compression. The equation uses an inverse square relationship to express the effect of length on the buckling load, highlighting the critical influence of a member's slenderness on stability. The effective length factor, K, accounts for the correction of theoretical lengths due to practical constraints, making the results more consistent with engineering practice.

[0100] Iterative force balance equation for cable shape optimization:

[0101]

[0102] Where, T i+1 is the cable force vector of the i+1th iteration, in kilonewtons; T i is the cable force vector of the i-th iteration, in kilonewtons; K T is the tangent stiffness matrix, in kN / m; F is the external load vector, in kN; F i is the internal force vector generated by the cable tension at the i-th iteration, in kilonewtons.

[0103] This iterative equation, based on the Newton-Raphson method, continuously modifies the cable force vectors to achieve force equilibrium in the structure. The equation uses a matrix representation to express the interactions between multiple cables. The tangent stiffness matrix incorporates geometric nonlinear effects, accurately describing the structural response under large deformations. This iterative algorithm converges faster than simple linear iterations and is particularly well-suited for optimizing highly nonlinear cable structures.

[0104] In step S04, the prestressed cable section optimization equations are expressed in detail as follows:

[0105] Objective function equation:

[0106]

[0107] Where W total is the total weight of the structural system, in tons; ρ s is the density of the prestressed cable material, in tons / cubic meter, with a typical value of 7.85; A iis the cross-sectional area of the i-th prestressed cable, in square centimeters; L i is the length of the i-th prestressed cable, in meters; n is the total number of prestressed cables; ρ c V is the equivalent density of the hollow sandwich steel tube concrete component, in tons / cubic meter, ranging from 2.5 to 3.5; c is the volume of the hollow sandwich steel tube concrete component, in cubic meters; ρ b V is the density of the supporting structure, in tons / cubic meter, with a typical value of 7.85; b is the total volume of the supporting structure in cubic meters.

[0108] This equation, based on the principle of mass accumulation, calculates the overall weight by linearly adding the weights of the individual components. Its concise form facilitates optimization. All parameters can be directly calculated from design parameters and material density, eliminating the need for empirical coefficients. This direct accumulation formulation lends the optimization problem excellent mathematical properties, facilitating the search for a global optimal solution.

[0109] Strength constraint equation:

[0110]

[0111] Where g1 is the strength constraint function; A is the cross-sectional area vector of the prestressed cable, in square centimeters; T0 is the initial cable force vector of the prestressed cable, in kilonewtons; σ i is the maximum stress of the i-th component, in MPa; σ allow is the allowable stress of the corresponding component, in MPa, for prestressed cable σ allow =f pk / γ m , where f pk is the characteristic strength of the cable, in MPa, γ m It is the material partial coefficient, ranging from 1.15 to 1.25.

[0112] This constraint equation ensures that stress levels in all components do not exceed allowable values. Using a maximum value formulation simplifies the expression of multiple constraints. The use of stress ratios in the equation makes strength constraints for different components comparable, facilitating the handling of constraints for different materials within a unified framework. The calculation of allowable stresses incorporates material partial factors, embodying the principle of safety reserves in structural design.

[0113] Displacement constraint equation:

[0114]

[0115] Where g2 is the displacement constraint function; δ top is the maximum horizontal displacement of the tower top, in millimeters, which can be calculated using the following equation: where K sys is the system stiffness matrix considering the prestressing effect, with the unit of kN / m, e is the displacement influence vector corresponding to the unit load; δ allow It is the allowable horizontal displacement of the tower top, in millimeters, usually taken as H / 100 to H / 150 of the tower height, where H is the tower height, in millimeters.

[0116] This constraint equation ensures that the tower top displacement meets the wind turbine's operational requirements. Using a displacement ratio makes the constraint dimensionless, facilitating its processing within the optimization algorithm. The system stiffness matrix in this equation incorporates the contribution of prestressing to the structural stiffness, reflecting the reinforcement of the prestressed cables on the overall structural stiffness. The displacement calculation utilizes the energy equivalence principle, enabling efficient processing of the displacement response of complex structures.

[0117] Cable force equilibrium equation:

[0118]

[0119] Where Q is the geometric matrix of the prestressed cable, and its element q ij represents the effect of the unit force of the j-th prestressed cable in the i-th direction; T0 is the initial force vector of the prestressed cable, in kilonewtons; F w (z) is the wind load function at height z, in kN / m; is the modal shape function at height z, dimensionless; h is the tower height, in meters; F top is the load vector generated by the tower top wind turbine, in kilonewtons.

[0120] The cable force balance equation, based on the principle of static equilibrium, describes how a prestressed cable system balances external loads. The left side of the equation represents the internal forces generated by the prestressed cables, while the right side represents the external loads that need to be balanced, including wind loads distributed along the height and concentrated loads at the tower top. The integral term accounts for the distribution of wind loads along the height, using modal shape functions as weights to reflect the varying degrees of influence of wind loads at different heights on the structure. The geometric matrix Q, determined by the spatial arrangement of the prestressed cables, reflects the influence of the cable system's geometric configuration on the force balance.

[0121] In step S08, the cable force control equation during the prestressed cable tensioning process is:

[0122] T i (t) = T 0i -ΔT creep (t)-ΔT relax (t)-ΔT temp (t);

[0123] Where, T i (t) is the actual cable force of the i-th prestressed cable at time t, in kilonewtons; T0i is the design initial cable force of the i-th prestressed cable, in kilonewtons; ΔT creep (t) is the cable force loss caused by concrete creep, in kilonewtons, which can be expressed as ΔT creep (t) = φ(t, t0)·E s ·A s ·ε init , where φ(t, t0) is the creep coefficient of concrete, ε init is the initial strain; ΔT relax (t) is the loss of cable force due to strand relaxation, in kilonewtons, which can be expressed as ΔT relax (t) = ρ 1000 ·T 0i (t / 1000) k , where ρ 1000 is the relaxation rate after 1000 hours, ranging from 2.5% to 4.0%, k is the time index, ranging from 0.15 to 0.25; ΔT temp (t) is the change in cable tension due to temperature change, in kilonewtons, which can be expressed as ΔT temp (t) = E s ·A s α s ΔT(t), where α s is the linear expansion coefficient of steel, with a typical value of 1.2×10 -5 / ℃, ΔT(t) is the temperature change value, unit is ℃.

[0124] This equation, based on prestress loss theory, comprehensively considers various factors influencing the long-term tension in prestressed cables. The equation employs a superposition of losses, with each loss term based on a different physical mechanism. Creep loss accounts for the effect of concrete deformation on cable tension, relaxation loss accounts for the stress relaxation characteristics of the strand itself, and temperature loss accounts for thermal expansion and contraction. The inclusion of a time function enables the equation to describe the temporal evolution of cable tension, providing a theoretical foundation for long-term cable tension control.

[0125] In step S09, the performance evaluation equation of the structural health monitoring system is:

[0126]

[0127] Where RI is the structural reliability index, ranging from 0 to 1; n is the number of monitoring parameters; w i is the weight coefficient of the i-th parameter, satisfying M i is the measured value of the i-th parameter; C i Calculate the design value for the ith parameter.

[0128] This evaluation equation, based on the weighted average principle, assesses structural performance by comparing measured and calculated values. Its concise form facilitates engineering implementation, and the weighted treatment of parameters accounts for the varying degrees of impact on structural safety. Measured values are directly acquired through the monitoring system, while calculated values are derived using the aforementioned theoretical model. The ratio of the two reflects the degree of consistency between theory and practice, providing a quantitative basis for structural safety assessment.

[0129] The sequential quadratic programming algorithm is used to solve the prestressed cable section optimization equations. The specific calculation process is as follows:

[0130] x k+1 =x k +α k ·d k ;

[0131] Where x k is the design variable vector for the kth iteration, including the cross-sectional area of the prestressed cable and the initial cable force; x k+1 is the design variable vector for the k+1th iteration; α k is the step size coefficient of the kth iteration, determined by one-dimensional search; d k is the search direction for the kth iteration, obtained by solving the following quadratic programming subproblem:

[0132]

[0133] Constraints:

[0134]

[0135] Where H k is the objective function at point x k The Hessian matrix at or its approximation; is the objective function at point x k The gradient vector at g j (x k ) is the jth constraint function at point x k The value at is the jth constraint function at point x k The gradient vector at ; m is the number of constraints.

[0136] This optimization algorithm is based on local quadratic approximations of the objective function and constraint functions, and gradually approaches the optimal solution through iteration. The algorithm uses gradient information to guide the search direction, converges quickly, and is particularly suitable for dealing with complex optimization problems with nonlinear constraints. The introduction of the Hessian matrix takes into account the second-order derivative information of the objective function, giving the algorithm superlinear convergence characteristics when approaching the optimal solution. The linearization of the constraint conditions simplifies the solution of subproblems while ensuring the satisfaction of the constraints. Compared with traditional linear programming methods, this algorithm is more efficient and can handle highly nonlinear engineering optimization problems such as wind turbine tower structures.

[0137] Optional, fundamental frequency calculation equation in structural frequency analysis:

[0138]

[0139] Where, f is the fundamental frequency of the structure, in Hertz; K eq is the equivalent stiffness of the structure, in kN / m, which can be extracted from the finite element analysis results; M eq is the equivalent mass of the structure, in tons, calculated from the mass matrix and mode shape vector: M eq =Φ T ·M·Φ, where Φ is the vibration mode vector corresponding to the fundamental frequency and M is the structural mass matrix.

[0140] This equation, based on the dynamics of single-degree-of-freedom systems, calculates the fundamental frequency of a structure using equivalent stiffness and equivalent mass. The equation uses a square root relationship to express the effects of stiffness and mass on frequency, reflecting fundamental dynamic laws. The introduction of equivalent parameters simplifies complex multi-degree-of-freedom systems into equivalent single-degree-of-freedom systems, facilitating engineering applications. This equation verifies that the fundamental frequency of a structure meets the requirement of being greater than 0.3 Hz to avoid resonance with the wind turbine's operating frequency.

[0141] Optionally, fatigue life assessment uses the cumulative damage equation:

[0142]

[0143] Where D is the cumulative fatigue damage coefficient, dimensionless and controlled below 0.8; k is the stress cycle amplitude level number; n i is the actual number of cycles of the i-th stress cycle, determined by the wind speed probability distribution and structural dynamic response analysis; N i is the allowable number of cycles of the material corresponding to the i-th level stress cycle, which is determined by the material SN curve: Where C and m are material constants, Δσ i is the stress cycle amplitude of the ith level, in MPa.

[0144] This equation, based on Miner's linear cumulative damage theory, estimates the fatigue life of a structure by accumulating damage at each stress cycle. Its concise form makes it easy to apply in engineering applications, with parameters derived from wind speed statistics and structural analysis results. The material SN curve, a classic model in fatigue research, uses a power function to describe the relationship between stress amplitude and life. This equation ensures that the structure's expected service life under the design wind speed spectrum is at least 25 years.

[0145] Optional, calculation equation for stress concentration factor of welded nodes:

[0146]

[0147] Where K t is the stress concentration factor, dimensionless, controlled below 2.0; t is the plate thickness, in millimeters; r is the transition fillet radius, in millimeters; a and b are empirical coefficients, which are related to the joint form. Usually a ranges from 0.1 to 0.3, and b ranges from 0.3 to 0.5.

[0148] This equation, based on elasticity theory, describes stress concentration at welded joints using geometric parameters. It uses a power function to express the effects of plate thickness and fillet radius on stress concentration, reflecting the fundamental laws of stress distribution at geometric discontinuities. The inclusion of empirical coefficients accounts for the differences in properties of different joint types, enhancing the applicability of the equation. This equation is used to optimize the design of the connection between support members and the main tower, ensuring that the stress concentration factor does not exceed 2.0.

[0149] Optionally, the bolt connection preload calculation equation is:

[0150] F p =α p ·A s ·f y，b ;

[0151] Where, F p is the bolt preload, in kN; α p is the preload coefficient, ranging from 0.7 to 0.75; A s is the bolt stress cross-sectional area, in square millimeters; f y，b It is the yield strength of the bolt material, in MPa. The yield strength of 10.9 grade high-strength bolts is 900 MPa.

[0152] This equation, based on the principles of bolt connection mechanics, calculates the appropriate preload force using material strength parameters. The equation is concise and clear, with parameters easily accessible. The selection of the preload factor considers a balance between safety margin and connection reliability. This equation is used in the design of tower segment bolt connections to ensure that the connection strength and stiffness meet requirements.

[0153] Optional, cable clamp slip force verification equation:

[0154] F slip =μ·n·F c ;

[0155] Where, F slip is the cable clamp sliding force, in kN, which is required to be no less than 1.5 times the design cable force; μ is the friction coefficient, ranging from 0.15 to 0.25, depending on the contact surface treatment method; n is the number of friction surfaces; F c is the clamping force of the splint, in kilonewtons, provided by high-strength bolts: Where T is the bolt torque in kN·m, λ is the torque coefficient, typically 0.2, and d is the bolt diameter in meters.

[0156] This equation, based on Coulomb's friction law, calculates the anti-slip capacity of a cable clamp using friction. The equation uses a linear relationship to describe the relationship between the compressive force and the slipping force, reflecting the fundamental characteristics of the friction mechanism. The conversion between bolt torque and compressive force accounts for the effects of thread friction and head friction, making the calculation more realistic. This equation is used in the design of cable clamps connecting prestressed cables to supporting structures to ensure that they do not slip under extreme loads.

[0157] Specifically, the principle of this invention is: based on the composite force system and prestressed equilibrium theory in structural mechanics, it optimizes the structural lateral force resistance by establishing a mechanism for the coordinated operation of hollow sandwich steel tube concrete components and prestressed cables. Its principle is mainly reflected in the following aspects:

[0158] First, a hollow sandwich steel tubular concrete-filled structure is used as the main tower. The "constraint effect" principle, whereby the outer steel tube provides lateral restraint on the concrete, significantly improves the concrete's axial bearing capacity and bending resistance. While maintaining high bending stiffness, this composite structure exhibits greater toughness than traditional concrete towers, enabling it to more effectively resist wind loads and seismic events.

[0159] Secondly, prestressed cables are introduced as the primary lateral force-resisting component. Based on the principle of "cable stability," the prestressed cables and the main tower form a coordinated tension-compression system. The initial tension generated by the prestressed cables balances the external lateral loads. When subjected to wind loads or earthquakes, the prestressed cables immediately respond and provide tension to resist lateral displacement, creating effective lateral restraint and enhancing overall structural stability.

[0160] Thirdly, by adjusting the cable shape through the support members, based on the "zigzag cable" theory, the prestressed cables are formed into a zigzag line rather than a straight line, increasing the angle between the cables and the wind direction and improving lateral stiffness. This arrangement provides sufficient lateral support in all directions, giving the structure a comprehensive resistance to wind loads from various directions.

[0161] Finally, a mathematical optimization model including the objective function equation, strength constraint equation, displacement constraint equation and cable force equilibrium equation was established. The optimal prestressed cable cross-section and initial cable force were determined through nonlinear analysis, so that the structural system can achieve the best lateral force resistance performance while satisfying the displacement constraint conditions, reflecting the scientific principles of structural optimization design.

[0162] The comprehensive application of these principles enables the present invention to effectively solve the technical problem of insufficient lateral force resistance of high-power wind turbine towers, and achieves high-efficiency lateral force resistance of the structural system.

[0163] A specific embodiment 1 of the present invention is provided below. The specific implementation of each step in this embodiment 1 is described in detail as follows.

[0164] The specific implementation method of step S01 is to determine the optimal tower height by using the wind energy resource assessment analysis method based on the geographical location, terrain characteristics and wind resource conditions of the wind farm, and usually select a height value within the range of 70 to 150 meters to meet the requirement that the lowest point of the wind turbine blade is not less than 50 meters from the ground. According to the tower height, a matching wind turbine model is selected, and the wind turbine model is usually a high-power wind turbine of 3 to 10 megawatts. The vertical load, horizontal load and bending moment data generated by the wind turbine on the tower top under normal operation, extreme wind conditions and emergency shutdown conditions are obtained through the technical manual provided by the wind turbine manufacturer. The earthquake grouping (usually Class I, II, III, IV) and seismic intensity (usually 6 to 9 degrees) of the project location are obtained using the earthquake micro-zoning analysis method. The extreme value statistical method is used to analyze the wind speed observation data of the local meteorological station for more than 20 consecutive years to obtain the basic wind pressure once in 50 years, with a typical value of 0.45 to 0.85 kPa. The wind load calculation adopts the basic principles of wind engineering and takes into account the height variation coefficient, which is specifically expressed as follows: F w (z)=μ s μ z μ c ·w0·A(z); where F w (z) is the wind load at height z, in kilonewtons; μ s is the wind load shape coefficient, dimensionless, ranging from 0.8 to 1.2; μ z is the wind pressure height variation coefficient, dimensionless, calculated using the power law: μ z =(z / 10) 2α , where α is the surface roughness index, ranging from 0.12 to 0.30; μ cis the gust coefficient, dimensionless, ranging from 2.1 to 2.5; w0 is the basic wind pressure, in kPa, ranging from 0.45 to 0.85; A(z) is the windward area at height z, in square meters. The gust coefficient (typical value is 2.1 to 2.5) and the wind pressure height variation coefficient are calculated based on the terrain roughness. The response spectrum method is used for earthquake load calculation, which is specifically expressed as follows: F e =γ·M·S a (T); where F e is the equivalent lateral force vector of the structure under earthquake action, in kilonewtons; γ is the earthquake action adjustment coefficient, dimensionless, ranging from 1.0 to 1.3; M is the structural mass matrix, in tons; S a (T) is the design acceleration response spectrum, in meters per square second, which can be expressed as: S a (T) = α max ·η(T,ξ)·g, where α max is the maximum horizontal earthquake influence coefficient, ranging from 0.05 to 0.40; η(T, ξ) is the design response spectrum curve, which is a function of the structural period T and the damping ratio ξ; g is the gravitational acceleration constant, which is 9.81 m / s2.

[0165] The specific implementation of step S02 is to use finite element analysis software to establish a three-dimensional model of the tower structure, and adopt geometric nonlinear large deformation theory to consider the second-order effects of the structure under large displacement conditions. For hollow sandwich steel tube concrete components, the outer steel tube diameter is usually 3.5 to 5.0 meters, the wall thickness is 20 to 40 mm, the inner steel tube diameter is usually 0.4 to 0.6 times the outer steel tube diameter, the wall thickness is 16 to 30 mm, and the filling concrete strength grade is C50 to C60. In the material parameter setting, the steel adopts a bilinear constitutive model: Where σ s is the stress of steel, in MPa; E s is the elastic modulus of steel, in MPa, with a typical value of 2.1×10 5 ; ε s is the steel strain, dimensionless; ε y is the yield strain of steel, dimensionless, ε y =f y / E s ;f y is the yield strength of steel, in MPa, ranging from 345 to 420; E st is the tangent modulus of steel after yield, in MPa, E st =β·E s , where β is the hardening coefficient, ranging from 0.01 to 0.05. The concrete adopts the damage plasticity model: Where σ cis the concrete stress, in MPa; d is the damage variable, ranging from 0 to 1, which is a function of strain; E c is the initial elastic modulus of concrete, in MPa, which can be measured by Calculate, where f c ' is the compressive strength of the concrete cylinder, in MPa, ranging from 50 to 60; ε c is the total strain of concrete, dimensionless; is the plastic strain of concrete, dimensionless. The prestressed cable material is high-strength steel strand with an ultimate tensile strength of 1860 MPa and an elastic modulus of 1.95×10 5 MPa. The initial cable tension was set at 30% to 40% of the cable's tensile strength. Load application followed the principle of step-by-step loading, first applying the structure's deadweight, then prestressing, and finally superimposing wind loads (distributed along the tower height using the Gaussian integral method), seismic loads (calculated using the response spectrum method), and wind turbine top loads. A nonlinear explicit dynamic analysis solver was selected to simulate the actual stress state, and a Rayleigh damping model with a damping ratio of 5% was used to account for structural damping effects.

[0166] The specific implementation method of step S03 is to determine the optimal arrangement of support components based on the structural optimal design theory, taking into account the bearing capacity, stiffness and construction feasibility. The number of support components is usually 4 to 8, evenly distributed along the height of the tower or appropriately increased in areas with concentrated wind loads. The connection nodes between the support components and the main tower are subjected to stress concentration analysis using finite element mesh refinement technology. The node design adopts the principle of smooth section transition to reduce the stress concentration factor so that the stress concentration factor does not exceed 2.0. Calculation of critical buckling load of support components: Where, P cr is the critical buckling load of the supporting member, in kN; E b is the elastic modulus of the supporting member, in MPa; I b is the moment of inertia of the supporting member, expressed in the fourth power of centimeters; K is the effective length coefficient, which depends on the constraint conditions of the supporting member and ranges from 0.5 to 1.0; L b is the length of the support member in meters. The support member angle optimization adopts parametric design method, by changing the angle between the support member and the horizontal plane, the prestressed cable forms a broken line state instead of a straight line state. The cable shape optimization adopts the force balance iteration method: Where, T i+1 is the cable force vector of the i+1th iteration, in kilonewtons; T i is the cable force vector of the i-th iteration, in kilonewtons; K T is the tangent stiffness matrix, in kN / m; F is the external load vector, in kN; F iis the internal force vector generated by the i-th iteration of the cable tension, in kilonewtons. Adjust the inclination angle and support point locations of each cable segment so that the cable is in tension under all load conditions, with the tension being no less than 50% of the initial cable tension and no more than 60% of the ultimate tensile strength of the cable material. Furthermore, ensure that the maximum compressive stress of the hollow sandwich concrete-filled steel tubular member under the ultimate load condition does not exceed 85% of the design compressive stress, and that the axial force of the supporting member does not exceed 70% of its critical buckling load.

[0167] The specific implementation of step S04 is to obtain cable force distribution and tower deformation data based on structural sensitivity analysis. The maximum allowable horizontal displacement of the tower top is usually limited to 1 / 100 to 1 / 150 of the tower height. A sequential quadratic programming algorithm is used to construct the prestressed cable cross-section optimization equations, and the objective function is to minimize the total weight of the structural system: Where W total is the total weight of the structural system, in tons; ρ s is the density of the prestressed cable material, in tons / cubic meter, with a typical value of 7.85; A i is the cross-sectional area of the i-th prestressed cable, in square centimeters; L i is the length of the i-th prestressed cable, in meters; n is the total number of prestressed cables; ρ c V is the equivalent density of the hollow sandwich steel tube concrete component, in tons / cubic meter, ranging from 2.5 to 3.5; c is the volume of the hollow sandwich steel tube concrete component, in cubic meters; ρ b V is the density of the supporting structure, in tons / cubic meter, with a typical value of 7.85; b is the total volume of the supporting structure in cubic meters. The constraints include the strength constraint equation: Where g1 is the strength constraint function; A is the cross-sectional area vector of the prestressed cable, in square centimeters; T0 is the initial cable force vector of the prestressed cable, in kilonewtons; σ i is the maximum stress of the i-th component, in MPa; σ allow is the allowable stress of the corresponding component, in MPa, for prestressed cable σ allow =f pk / γ m , where f pk is the characteristic strength of the cable, in MPa, γ m is the material partial coefficient, ranging from 1.15 to 1.25. Displacement constraint equation: Where g2 is the displacement constraint function; δ top is the maximum horizontal displacement of the tower top, in millimeters, which can be calculated using the following equation: where K sysis the system stiffness matrix considering the prestressing effect, in kN / m, e is the displacement influence vector corresponding to the unit load; δ allow The allowable horizontal displacement of the tower top is in millimeters, usually taken as H / 100 to H / 150 of the tower height, where H is the tower height in millimeters. Cable force equilibrium equation: Where Q is the prestressed cable geometry matrix, and its element q ij represents the effect of the unit force of the j-th prestressed cable in the i-th direction; T0 is the initial force vector of the prestressed cable, in kilonewtons; F w (z) is the wind load function at height z, in kN / m; is the modal shape function at height z, dimensionless; H is the tower height, in meters; F top is the load vector generated by the tower top wind turbine, in kilonewtons. The solution of the prestressed cable section optimization equations adopts the sequential quadratic programming algorithm. The specific calculation process is: k+1 =x k +α k ·d k Where x k is the design variable vector for the kth iteration, including the cross-sectional area of the prestressed cable and the initial cable force; x k+1 is the design variable vector for the k+1th iteration; α k is the step size coefficient of the kth iteration, determined by one-dimensional search; d k is the search direction for the kth iteration, obtained by solving the following quadratic programming subproblem: Constraints: j=1,2,...,m;where H k is the objective function at point x k The Hessian matrix at or its approximation; is the objective function at point x k The gradient vector at g j (x k ) is the jth constraint function at point x k The value at is the jth constraint function at point x k The gradient vector at ; m is the number of constraints. Modal analysis is used to verify the fundamental frequency of the structure during the optimization process: Where, f is the fundamental frequency of the structure, in Hertz; K eq is the equivalent stiffness of the structure, in kN / m, which can be extracted from the finite element analysis results; M eq is the equivalent mass of the structure, in tons, calculated from the mass matrix and mode shape vector: M eq =Φ TM·Φ, where Φ is the mode shape vector corresponding to the fundamental frequency and M is the structural mass matrix. Ensure that the fundamental frequency is greater than 0.3 Hz to avoid resonance with the wind turbine operating frequency. Simultaneously, fatigue life assessment is performed using the cumulative damage equation: Where D is the cumulative fatigue damage coefficient, dimensionless and controlled below 0.8; k is the stress cycle amplitude level number; n i is the actual number of cycles of the i-th stress cycle, determined by the wind speed probability distribution and structural dynamic response analysis; N i is the allowable number of cycles of the material corresponding to the i-th level stress cycle, which is determined by the material SN curve: Where C and m are material constants, Δσ i is the stress cycle amplitude at level i, in MPa. Ensure that under the design wind speed spectrum, the cumulative fatigue damage factor of key nodes does not exceed 0.8, and the expected service life is not less than 25 years.

[0168] The specific implementation of step S05 is to use parametric modeling technology to draw detailed drawings and use 3D solid modeling software to accurately model the structural components. The welding connection nodes between the support components and the tower use full penetration welds. The welding process requires the weld quality grade to be no less than level 2. Ultrasonic non-destructive testing is performed after welding to ensure weld quality. The equation for calculating the stress concentration factor of the weld node is: Where K t is the stress concentration factor, dimensionless, and controlled below 2.0; t is the plate thickness, in millimeters; r is the transition fillet radius, in millimeters; a and b are empirical coefficients related to the joint type, usually a range of 0.1 to 0.3, and b range of 0.3 to 0.5. Customized cable clamps are used to connect the prestressed cables to the supporting members. The cable clamp design is based on the principle of frictional force transmission. The cable clamp slip force verification equation is: F slip =μ·n·F c Where, F slip is the cable clamp sliding force, in kN, which is required to be no less than 1.5 times the design cable force; μ is the friction coefficient, ranging from 0.15 to 0.25, depending on the contact surface treatment method; n is the number of friction surfaces; F c is the clamping force of the splint, in kilonewtons, provided by high-strength bolts: Where T is the bolt torque in kNm, λ is the torque coefficient with a typical value of 0.2, and d is the bolt diameter in meters. High-strength bolts are used to connect the splints, and the bolt pre-tightening torque is designed according to 1.2 times the nominal torque to prevent the cable clamp from slipping. The segmented design of hollow sandwich steel tube concrete components is based on the modular concept. Considering the transportation conditions, the length of a single segment is usually controlled at 10 to 15 meters, and the weight of a single segment does not exceed 80 tons. The segmented connection adopts high-strength bolts with flanges. The thickness of the flange is not less than 50 mm, and the bolt grade is not less than 10.9. Bolt connection pre-tightening force calculation formula: F p =α p ·A s ·f y，b Where, F p is the bolt preload, in kN; α p is the preload coefficient, ranging from 0.7 to 0.75; A s is the bolt stress cross-sectional area, in square millimeters; f y，b It is the yield strength of the bolt material, in MPa. The yield strength of 10.9 grade high-strength bolts is 900 MPa.

[0169] The specific implementation of steps S06-S07 is the same as above and will not be repeated here.

[0170] The specific implementation of step S08 is to use a staged tensioning process to control the construction quality of the prestressed cables. The first stage of tensioning is carried out after the tower is assembled. The tensioning force is 60% to 70% of the designed cable force. Synchronous tensioning equipment is used to simultaneously and symmetrically tension multiple cables, controlling the displacement of the tower top to no more than 30% of the designed displacement. The cable force control equation during the prestressed cable tensioning process is: T i (t) = T 0i -ΔT creep (t)-ΔT relax (t)-ΔT temp (t); where T i (t) is the actual cable force of the i-th prestressed cable at time t, in kilonewtons; T 0i is the design initial cable force of the i-th prestressed cable, in kilonewtons; ΔT creep (t) is the cable force loss caused by concrete creep, in kilonewtons, which can be expressed as ΔT creep (t) = φ(t, t0)·E s ·A s ·ε init , where φ(t, t0) is the creep coefficient of concrete, ε init is the initial strain; ΔT relax (t) is the loss of cable force due to strand relaxation, in kilonewtons, which can be expressed as ΔT relax (t) = ρ 1000 ·T0i (t / 1000) k , where ρ 1000 is the relaxation rate after 1000 hours, ranging from 2.5% to 4.0%, k is the time index, ranging from 0.15 to 0.25; ΔT temp (t) is the change in cable tension due to temperature change, in kilonewtons, which can be expressed as ΔT temp (t) = E s ·A s α s ΔT(t), where α s is the linear expansion coefficient of steel, with a typical value of 1.2×10 -5 / ℃, ΔT(t) is the temperature change value in ℃. During the tensioning process, real-time load-displacement monitoring technology is used to monitor the relationship between cable force and displacement to verify consistency with theoretical calculation results. After tensioning is completed, the cable force is locked, and the locking adopts wedge anchoring technology to ensure that the cable force loss after locking does not exceed 5% of the design cable force. The second stage of tensioning is carried out after the installation of the wind turbine is completed. The tensioning force reaches 100% of the design cable force. At the same time, the relationship between the displacement of the tower top and the cable force is monitored to verify the consistency of the actual cable force-displacement curve with the theoretical curve, with a deviation of no more than 10%. After the second stage of tensioning is completed, the cable force is locked and protective measures are installed, including anti-corrosion, lightning protection and anti-vibration measures.

[0171] The specific implementation of step S09 is to verify the actual performance of the structural system through the structural health monitoring system. After the wind turbine is installed, a comprehensive inspection is carried out, including vibration testing, displacement measurement, and cable tension testing. A three-dimensional acceleration sensor is installed on the top of the tower to measure the acceleration response of the structure under different wind speeds. The actual damping ratio and fundamental frequency of the structure are determined through frequency domain analysis, and the deviation between the fundamental frequency and the theoretical calculation is verified to be no more than 5%. The performance evaluation equation of the structural health monitoring system is: Where RI is the structural reliability index, ranging from 0 to 1; n is the number of monitoring parameters; w i is the weight coefficient of the i-th parameter, satisfying M i is the measured value of the i-th parameter; C i is the calculated design value of the i-th parameter. A total station is used to monitor the displacement of the tower top in real time to verify that it does not exceed the design limit at the design wind speed. A magnetoelastic dynamometer is used to measure the actual prestressed cable tension to verify that the deviation from the design tension does not exceed 8%. Prestressed cables with deviations exceeding the allowable value are tensioned using precision tensioning equipment, with an accuracy of ±3%. A long-term monitoring system is also established to continuously monitor key parameters to ensure the long-term safe operation of the structure.

[0172] A specific embodiment 2 of the present invention is provided below. The specific implementation of each step in this embodiment 2 is described in detail as follows.

[0173] like Figure 8-10 As shown, the overall steps of a lightweight wind power tower assembly design method for a large-power wind turbine are as follows:

[0174] Structural System: The entire system comprises a stable concrete-filled steel tube tower, prestressed cables, steel supports, and bottom anchor points. The concrete-filled steel tube tower bears compression, while the prestressed cables bear tension. This structural system effectively transmits force, fully utilizing the compression of the concrete structure and the tension of the prestressed cables, improving material efficiency.

[0175] Component connection: The concrete-filled steel tube tower column is connected to the wind turbine foundation. This connection can be made using pre-buried anchor bolts. One end of the prestressed cable is connected to the upper part of the tower, and the other end is anchored to the ground. The steel support in the middle secures the cable to the tower.

[0176] Structural Construction: Conventional construction methods are used for the concrete-filled steel tube tower columns. Prestressed cables undergo secondary tensioning. The initial tensioning occurs before turbine installation to stabilize the structure. The secondary tensioning occurs after turbine installation, reaching the designed cable tension value to ensure structural stability during turbine operation. Cable clamps are installed on the steel supports to connect the prestressed cables to the tower.

[0177] Structural system verification: Midas software was used to analyze the stress and deformation of a 100m high tower under the operation of a 5MW wind turbine. The calculation results showed that the structural system has good stiffness, strength and stability under the working conditions of high-power wind turbines.

[0178] It should be noted that the variables involved in the present invention are explained in detail as shown in Table 1-2 below.

[0179] Table 1 Variable explanation table a

[0180]

[0181] Table 2 Variable explanation table b

[0182]

[0183] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A lightweight wind power tower assembly structure for a high-power wind turbine, characterized in that: include: Determine tower height and wind turbine model based on wind field conditions, and collect load data, wind load, and earthquake information; Establish a three-dimensional finite element analysis model of the hollow sandwich steel tube concrete component, set the material parameters and the initial cable force of the prestressed cable; Determine the number and layout of supporting components, optimize the design of connection nodes, and adjust the cable shape so that the prestressed cables can withstand tension; According to the cable force distribution and deformation analysis results, the optimal prestressed cable cross-section and initial cable force are determined using the prestressed cable cross-section optimization equation group, so that the structure meets the strength requirements and displacement constraints, and the scheme design is completed.

2. A lightweight wind power tower assembly structure for a high-power wind turbine according to claim 1, characterized in that: The prestressed cable section optimization equation group includes an objective function equation, a strength constraint equation, a displacement constraint equation and a cable force balance equation; the objective function equation is used to minimize the total weight of the structural system; the strength constraint equation is used to ensure that each component does not fail under the ultimate load condition; the displacement constraint equation is used to control the displacement of the tower top to meet the wind turbine operation requirements; the cable force balance equation is used to establish the relationship between the initial cable force of the prestressed cable and its balanced tower lateral load.

3. The lightweight wind power tower assembly structure for a high-power wind turbine according to claim 2, characterized in that: The inputs of the objective function equation include the cross-sectional area of the prestressed cable, the length of the prestressed cable obtained by cable shape calculation, the density of the prestressed cable material, the volume of the hollow sandwich steel tube concrete component and the density of the hollow sandwich steel tube concrete component. The output is the total weight function of the structural system used for optimization design.

4. A lightweight wind power tower assembly structure for a high-power wind turbine according to claim 3, characterized in that: The input of the strength constraint equation includes the cross-sectional area of the prestressed cable, the tensile strength of the prestressed cable material, the compressive strength of the hollow sandwich steel tube concrete component, the design load and the safety factor, and the output is the constraint condition of the ratio of the component stress to the allowable stress used for optimizing the design.

5. The lightweight wind power tower assembly structure for a high-power wind turbine according to claim 4, characterized in that: The input of the displacement constraint equation includes the maximum allowable displacement of the tower top corresponding to the wind turbine model, the initial tension of the prestressed cables, the load condition combination, the tower stiffness and the position of the supporting components. The output is the ratio constraint condition of the tower top displacement to the allowable displacement used for the optimized design.

6. A lightweight wind power tower assembly structure for a high-power wind turbine according to claim 5, characterized in that: The input of the cable force balance equation includes the wind load distribution function, the geometric dimensions of the tower, the position of the supporting components, and the angle between the prestressed cable and the tower obtained by cable shape calculation. The output is the initial cable force design value of the prestressed cable used for optimization design and tensioning control.

7. A lightweight wind power tower assembly structure for a high-power wind turbine according to claim 6, characterized in that: The hollow sandwich steel tube concrete component is a composite component formed by an outer steel tube, an inner steel tube and concrete filled between the two. The outer steel tube provides restraint to improve the compressive strength of the concrete, and the inner layer forms a hollow structure to reduce its own weight; the prestressed cable is a tension member made of high-strength steel strands, which is fixed to the anchor end after being prestressed by tensioning equipment, and is used to bear the lateral load of the wind turbine tower and provide stability; the inter-tower support member is a secondary structural member connecting the main tower and the prestressed cable, which is used to adjust the cable shape and provide intermediate support points, thereby reducing the free length of the prestressed cable and reducing wind vibration fatigue damage.

8. The lightweight wind power tower assembly structure for a high-power wind turbine according to claim 7, characterized in that: The nonlinear analysis condition takes into account the calculation model of large structural geometric deformation and nonlinear material characteristics, and is used to accurately simulate the actual stress state of prestressed cables and hollow sandwich steel tube concrete components under various loads.

9. The lightweight wind power tower assembly structure for a high-power wind turbine according to claim 8, characterized in that: The cable shape refers to the geometric shape of the prestressed cable from the top of the tower to the ground anchor point, which is adjusted by the supporting components to form a broken line shape instead of a straight line shape, which is used to optimize the cable force distribution and reduce the footprint.

10. The method for designing a lightweight wind power tower assembly for a high-power wind turbine according to claim 9, characterized in that: The designed lightweight wind turbine tower composite structural system for high-power wind turbines is a composite load-bearing system consisting of a hollow sandwich steel tube concrete main tower, multiple prestressed cables and several tower support components. The main tower bears pressure, the prestressed cables bear tension, and the support components provide lateral support, forming an efficient structural system that works in coordination.

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