Design method for circumferential reinforcement of concrete tower sections for wind turbine generators

Abstract

This invention relates to the field of building engineering technology, specifically to a method for designing the circumferential reinforcement of a variable-diameter tower section in a wind turbine concrete tower. The method includes obtaining the structural parameters of the wind turbine concrete tower; calculating the design load of the variable-diameter tower section based on the structural parameters; calculating the circumferential tensile force at the bottom of the conical tower section and the bottom of the straight tower section of the variable-diameter tower section; calculating the design bending moment of the vertical sections of the conical and straight tower sections; calculating the amount of reinforcing steel at the bottom of the conical tower section; calculating the amount of reinforcing steel at the top and bottom of the straight tower section; and selecting the reinforcement design value for the connection area of ​​the variable-diameter tower section. This invention links load calculation, circumferential force analysis, model simplification, and reinforcement calculation into a complete and efficient closed-loop design chain, replacing the cumbersome finite element trial-and-error process, and solving the technical problems of high workload and high labor costs when designing the circumferential reinforcement of variable-diameter tower sections using a three-dimensional finite element model.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, and in particular to a design method for circumferential reinforcement of variable diameter concrete tower sections of wind turbine generators. Background Technology

[0002] With the increasing power output of individual wind turbine units and the rise in hub height, the problems of traditional steel towers—low natural frequency and susceptibility to resonance with wind frequencies—have become increasingly prominent. Steel-concrete hybrid towers, due to their superior economy and high rigidity, have become the main support structure for ultra-high-rise wind turbine units. To facilitate construction and save costs, concrete hybrid towers often employ segmented diameter variations to adapt to changes in bending stiffness.

[0003] However, engineering practice shows that, as Figure 2 As shown, the steel-concrete composite tower includes a C-shaped ring 4, a conical tower section 1, a straight tower section 2, and a far-end straight tower section 3. Under the combined action of complex wind loads and prestressing, the concrete variable-diameter tower section composed of the conical tower section 1 and the adjacent lower straight tower section 2 frequently exhibits multiple vertical joints 7 extending upward and downward along the horizontal construction joint. These vertical joints 7 not only extend vertically (up to 1.5~2.5m), but also penetrate both inside and outside and leak water, becoming a typical defect threatening the safety and durability of the tower structure.

[0004] Regarding the aforementioned cracking problem, relevant research revealed its mechanical root cause: under vertical pressure, the variable-diameter tower section experiences a significant circumferential tensile force at the horizontal crack due to the abrupt change in cross-section. ,like Figure 3 As shown, this resulted in vertical cracking of adjacent rings.

[0005] To address this issue, the commonly used technical solution in the engineering field is to rely on three-dimensional solid finite element analysis for reinforcement design and verification. The specific process involves: establishing a detailed solid model of the tower; importing design loads obtained from structural analysis software or engineering calculation methods; analyzing structural stress and crack distribution through complex nonlinear finite element calculations; and repeatedly adjusting the reinforcement scheme until it is verified to meet the ultimate limit and operational condition requirements. Figure 4 and Figure 5 As shown in the figure, 8 represents the distribution reinforcement.

[0006] However, this approach has led to a widespread perception in the engineering community that for complex structures like variable-diameter tower sections, only high-precision three-dimensional solid finite element analysis can ensure design safety; any simplified model is considered to be prone to design failure due to the loss of critical information. Finite element analysis is essentially a method of "verification" rather than "proactive design," its core being "trial and error." It fails to reveal the fundamental mechanical laws governing the variable-diameter effect, resulting in a lack of theoretical guidance in design and solidifying a mindset of "over-reliance on simulation and reluctance to effectively simplify," constituting a long-standing technical bias in the field and hindering the development of efficient design methods. Furthermore, building and calculating large-scale three-dimensional finite element models is extremely labor-intensive; a complete design verification cycle often lasts several weeks, severely slowing down project progress and incurring high human and time costs. In addition, the process demands extremely high levels of finite element theory, software operation, and engineering experience from designers, limiting the widespread application of the technology and easily leading to inconsistent design results due to differences in personnel skill levels. Finite element analysis is primarily used for "safety verification," not "performance optimization." It is difficult to intuitively guide designers on how to most effectively suppress cracks by adjusting reinforcement, often resulting in overly conservative reinforcement schemes or insufficient reinforcement in critical areas, failing to achieve the best balance between economy and safety.

[0007] Therefore, there is an urgent need for a precise and rapid design method for the reinforcement of variable diameter tower sections to solve the above-mentioned technical problems. Summary of the Invention

[0008] The main objective of this invention is to provide a design method for the circumferential reinforcement of variable-diameter concrete tower sections of wind turbine generators, aiming to solve the technical problems of high workload and high labor costs when designing the circumferential reinforcement of variable-diameter tower sections using existing three-dimensional finite element models.

[0009] To achieve the above objectives, this invention proposes a method for designing the circumferential reinforcement of variable-diameter concrete tower sections for wind turbine generators.

[0010] The method for designing the circumferential reinforcement of the variable-diameter tower section of the wind turbine concrete tower of the present invention is further improved by including the following steps:

[0011] S1. Obtain the structural parameters of the concrete tower of the wind turbine, and calculate the design load of the variable diameter tower section based on the structural parameters.

[0012] S2. Based on the structural parameters obtained in S1 and the design load of the variable diameter tower section, calculate the circumferential tension at the bottom of the conical tower section and the circumferential tension at the bottom of the straight tower section of the variable diameter tower section.

[0013] S3. Based on the circumferential tension at the bottom of each tower section obtained in S2, calculate the design bending moment of the vertical section of the conical tower section and the straight tower section respectively;

[0014] S4. Calculate the amount of reinforcing steel at the bottom of the conical tower section based on the design bending moment of the conical tower section obtained in S3; calculate the amount of reinforcing steel at the top and bottom of the straight tower section based on the design bending moment of the vertical section of the straight tower section obtained in S3; select the reinforcement design value for the connection area of ​​the variable diameter tower section.

[0015] A further improvement of the wind turbine concrete tower section circumferential reinforcement design method of the present invention is that the structural parameters of the wind turbine concrete tower include the height of each tower section, bottom diameter, top diameter, wall thickness, concrete strength grade and steel reinforcement material properties.

[0016] A further improvement to the design method for circumferential reinforcement of the variable-diameter concrete tower section of the wind turbine generator in this invention is that S2 specifically includes the following steps:

[0017] Calculate the circumferential tension at the bottom of the tapered tower section of the variable diameter tower segment. :

[0018] ;

[0019] in: The vertical force acting on the top of the conical tower section, This refers to the bending moment acting at the top of the conical tower section; The radius of the top section is... The radius of the bottom section; The distance from the center of the reinforced area at the bottom of the conical tower section to the top edge.

[0020] A further improvement to the design method for circumferential reinforcement of the variable-diameter concrete tower section of the wind turbine generator in this invention is that S2 specifically includes the following steps:

[0021] Calculate the circumferential tension at the bottom of the lower straight tower section adjacent to the tapered tower section of the variable-diameter tower section. :

[0022] ;

[0023] in: To calculate the distance between the center of the top reinforcement zone of the straight tower section and the bottom edge.

[0024] A further improvement to the design method for circumferential reinforcement of the variable-diameter concrete tower section of the wind turbine generator in this invention is that S2 specifically includes the following steps:

[0025] Calculate the circumferential tension at the bottom of the far-end straight tower section :

[0026] ;

[0027] in: The effective height of the cross-section of the far-end straight tower section.

[0028] A further improvement to the design method for circumferential reinforcement of the variable-diameter concrete tower section of the wind turbine in this invention is that S3 specifically includes the following steps:

[0029] Calculate the vertical bending moment of the conical tower section. :

[0030] ;

[0031] Calculate the vertical section bending moment of a straight tower section. :

[0032] .

[0033] A further improvement of the present invention on the design method of circumferential reinforcement of the variable diameter tower section of the concrete tower of the wind turbine is that the amount of reinforcing steel at the bottom of the conical tower section is calculated using the reinforcement calculation formula of a single-reinforced bending member. The calculation formula is as follows:

[0034] ;

[0035] in: This is the design value of the tensile strength of the steel reinforcement. The cross-section represents the height of the compression zone, and ξ represents the relative height of the compression zone. represents the elastic-plastic section modulus of the reinforced concrete section. For concrete strength grade coefficient, This is the design value for the compressive strength of concrete. The thickness of the ring sheet.

[0036] A further improvement of the present invention regarding the design method for the circumferential reinforcement of the variable-diameter tower section of the concrete tower of a wind turbine is that it employs a small eccentric tension member model and calculates the circumferential tension at the bottom of the conical tower section of the variable-diameter tower section based on S2. Circumferential tension at the bottom of the straight tower section adjacent to the tapered tower section of the variable diameter tower section. And the vertical section bending moment of the straight tower section was calculated using S3. Substitute into the formula to calculate the amount of reinforcing steel required at the top of the straight tower section. The amount of reinforcing steel bars used at the bottom of the straight tower section The expression is as follows:

[0037] ;

[0038] ;

[0039] in, This is the design value for the tensile strength of the reinforcing steel.

[0040] The technical solution of the present invention has the following beneficial effects:

[0041] The present invention proposes a novel design method for the circumferential reinforcement of variable-diameter concrete tower sections in wind turbine generators, which introduces a novel circumferential tensile force for straight tower sections. and the circumferential tension of the distal straight tower section The calculation formula precisely quantifies the attenuation law of the diameter variation effect with distance, providing a theoretical basis for differentiated and refined reinforcement. This invention links load calculation, circumferential force analysis, model simplification, and reinforcement calculation into a complete and efficient closed-loop design chain, replacing the cumbersome finite element trial-and-error process. It solves the technical problems of high workload and high manpower costs when designing the circumferential reinforcement of variable-diameter tower sections using existing three-dimensional finite element models. This invention reveals that the mechanical essence of cracking in variable-diameter tower sections lies in circumferential tension, and decouples the complex variable-diameter structure into a combined model of "conical tower section-bending member" and "straight tower section-eccentric tension member," breaking the technical bias of over-reliance on finite element analysis in this field. This invention proposes a reinforcement continuity principle to solve the problem of local stress concentration, clarifying the use of larger reinforcement values ​​in the tower section connection area, ensuring the overall continuity and safety of the structure, and effectively suppressing the initiation and propagation of cracks at the connection points. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0043] Figure 1 This is a flowchart of the design method for circumferential reinforcement of the variable diameter concrete tower section of the wind turbine unit according to the present invention.

[0044] Figure 2 This is a schematic diagram of the variable diameter section of a concrete tower.

[0045] Figure 3 This is a schematic diagram illustrating the mechanism of circumferential tension generation in a variable-diameter tower section.

[0046] Figure 4 Schematic diagram of reinforcement at the end of the tapered section;

[0047] Figure 5 Schematic diagram of reinforcement at the end of a straight tower section;

[0048] Figure 6 A flowchart for generating finite element analysis models of local tower sections (including variable diameter tower sections) is provided (TD1 is a conical tower section, and B1, A7, and A6 are straight tower sections).

[0049] Figure 7 A schematic diagram showing the crack distribution and development in traditional TD1 and A7 tower sections;

[0050] Figure 8 This is a schematic diagram showing the stress analysis results of the circumferential reinforcement in a traditional variable-diameter tower section.

[0051] Figure 9 This is a cloud diagram showing the overall deformation of the variable-diameter tower section under vertical load.

[0052] Figure 10 This is a simplified diagram of the lateral deformation of the vertical section under vertical load (TD1 is a conical tower section, and B1, A7, and A6 are straight tower sections).

[0053] Figure 11 A simplified schematic diagram of the tapered transition segment;

[0054] Figure 12 This is a schematic diagram for calculating the circumferential tensile force of the calculation unit;

[0055] Figure 13 This is a schematic diagram of the stress analysis model for a straight tower section;

[0056] Figure 14 This is a schematic diagram of the bending moment stress model for a conical tower section.

[0057] Figure 15 A schematic diagram of the reinforcement calculation model for flexural members;

[0058] Figure 16 This is a schematic diagram of a small-scale tension analysis model for a straight tower section.

[0059] Figure 17 A schematic diagram of a calculation model for reinforcement of a member with small eccentric tension.

[0060] Figure 18 This is a diagram showing the vertical crack distribution of the variable-diameter tower section under the reinforcement conditions of the circumferential reinforcement design method for the concrete tower section of the wind turbine of the present invention.

[0061] Figure 19 This is a diagram showing the stress distribution of the circumferential reinforcement in the variable-diameter tower section of the wind turbine concrete tower under the reinforcement design method of the present invention.

[0062] Explanation of icon numbers:

[0063] 1. Conical tower section; 2. Straight tower section; 3. Far-end straight tower section; 4. C-shaped ring plate; 5. Variable diameter tower section; 6. Horizontal joint; 7. Vertical joint; 8. Distributed reinforcement. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0065] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0066] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0069] like Figures 1-19 As shown, this invention proposes a design method for circumferential reinforcement of variable diameter concrete tower sections of wind turbines. The core idea is to identify and separate the key mechanical behavior that leads to cracking from the complex overall structure—circumferential tension—and transform it into a classic concrete component design problem, thereby achieving accurate and rapid design of the reinforcement of variable diameter tower section 5.

[0070] That is, through in-depth on-site testing and finite element parametric analysis, such as Figures 6-10As shown, the mechanical essence of the cracking in section 5 of the variable-diameter tower lies in the circumferential tensile force caused by the geometrical abrupt change. Based on this, this invention creatively decouples the complex variable-diameter structure into two classic mechanical models:

[0071] (1) Conical tower section 1, whose vertical cross-section stress distribution is compression at the top and tension at the bottom, can be precisely simplified as a "single-reinforced bending member", such as Figure 11 As shown. Figure 11 This is a simplified force diagram of a conical tower section. The main external load acting on the conical tower section is a vertical force. and bending moment It is applied at the center of the top surface. Given the low tensile strength of concrete, its contribution to the circumferential tensile force is ignored, and it is assumed that the circumferential tensile force is entirely borne by the circumferential reinforcement.

[0072] (2) Straight tower section, whose vertical cross-section stress distribution is non-uniform tension with larger stress at the top and smaller stress at the bottom, can be precisely simplified as a "small eccentric tension member", such as Figure 13 As shown. Figure 13 This is a schematic diagram of the force analysis model for a straight tower section, which is based on the analysis model of a conical tower section with the addition of a lower straight tower segment. The circumferential force is the same as that of the conical tower section. The derivation process, based on this diagram, yields the circumferential tension of the straight tower section in the variable diameter tower segment. .

[0073] This simplified paradigm breaks the technical bias of over-reliance on finite element analysis in this field, laying a theoretical foundation for establishing an efficient and reliable reinforcement design method.

[0074] Figure 6 To create a finite element analysis model of a local tower segment (the local tower segment created by the finite element software includes the tapered tower section TD1 and the straight tower section A7 of the variable diameter tower segment, as well as the vertically adjacent straight tower section B1 and the far-end straight tower section A6) using an existing finite element software, including the local concrete tower segment model, the steel cage model, and the boundary conditions and loading diagrams applied to the local concrete tower segment model. Figure 6 RP-1 is a reference point set at the top of the model, and a load is applied to the reference point. The reference point is associated with the surface of the analysis model through coupling constraints, thereby achieving uniform application and transfer of the upper load.

[0075] Figure 7The results of the tensile damage analysis of concrete in a local tower section under the design load are shown in the finite element model. Significant circumferential tensile stress appears at the connection joint between the conical tower section TD1 on the compression side of the variable-diameter tower section and the straight tower section below. This tensile stress exceeds the tensile strength of the tower section concrete, causing cracks to extend upward and downward from the connection joint. The location and direction of the cracks are basically consistent with the field observation results, which verifies the correctness of the finite element model of the variable-diameter tower section established in this invention and its reliability for analysis in actual engineering.

[0076] Figure 8 The stress analysis results of the circumferential reinforcement in the variable-diameter tower section under the design load show that the maximum stress of the circumferential reinforcement in the variable-diameter tower section is 393.5 MPa, which is less than the yield strength requirement of 400 MPa. This indicates that the bearing capacity meets the requirements under the ultimate load condition. However, the large stress in the circumferential reinforcement will lead to vertical cracking of the concrete, which will inevitably have a certain impact on normal operation.

[0077] Figure 9 This is a cloud diagram showing the overall deformation of the variable-diameter tower section under vertical load. Figure 10 This is a simplified diagram of the lateral deformation of a vertical section under vertical load. (Combined with two diagrams) Figure 1 From the analysis, we can see that:

[0078] (1) There is a transverse deformation inflection point in the middle of the conical tower section TD1. Its mechanical characteristics are that the lower section is under tension and the upper section is under compression. The maximum tensile deformation is located at the bottom of TD1, and the inflection point is roughly located at the midpoint of the tower section height. Based on this characteristic, the circumferential normal stress distribution of the conical tower section can be simplified to a pure bending model.

[0079] (2) Due to the coordinated deformation, the lateral deformation of the adjacent tower sections TD1 and A7 at the horizontal joint is completely consistent, indicating that A7 and TD1 both bear a large circumferential force at the horizontal joint position. They should be given special attention in the design to ensure the safety of the structure.

[0080] (3) At the far end of the horizontal joint, the straight tower section A7 is mainly subjected to tensile deformation of the entire cross section, but the value is significantly reduced. Therefore, the circumferential normal stress distribution of the straight tower section A7 can be simplified to an eccentric tensile analysis model.

[0081] (4) The straight tower section (B1) above TD1 has a deformation inflection point at about 1 / 3 of its bottom, meaning the lower section is under compression and the upper section is under tension. Its deformation is smaller than that of TD and A7. The straight tower section at the far end (A6) is under tension across the entire cross section, but because it is farther from the diameter change point, the circumferential deformation and stress decrease more significantly than those of A7. In actual engineering, no vertical cracks were detected on the straight tower sections (B1 and A6), indicating that the circumferential tensile stress on the tower sections far from the horizontal joint below the conical tower section is smaller, and its reinforcement can be significantly reduced.

[0082] The design method for circumferential reinforcement of variable diameter concrete tower sections of wind turbine generators includes the following steps:

[0083] S1. Obtain the structural parameters of the wind turbine concrete tower and calculate the design load of the variable-diameter tower section 5 based on the structural parameters. The structural parameters of the wind turbine concrete tower include the height, bottom diameter, top diameter, wall thickness, concrete strength grade, and steel reinforcement material properties of each tower section. Use general structural analysis software or engineering calculation methods to calculate the design load (including axial force, shear force, bending moment, torque, and prestress) of the variable-diameter tower section 5.

[0084] S2. Based on the structural parameters obtained in S1 and the design load of the variable-diameter tower section 5, calculate the circumferential tension at the bottom of the conical tower section and the circumferential tension at the bottom of the straight tower section of the variable-diameter tower section. Figure 11 and Figure 12 As shown in the figure, This is to transfer the vertical pressure from the upper tower section to the conical tower section. For the applied prestress, The circumferential width of the conical tower section used in the stress analysis model is... The infinitesimal element is used as the computational unit. The radial component of the circumferential tension. for balanced reaction force;

[0085] Calculate the circumferential tension at the bottom of the tapered tower section 1 of the variable diameter tower section. :

[0086] ;

[0087] in: The vertical force acting on the top of the conical tower section 1 The bending moment acting on the top of the conical tower section 1; The radius of the top section is... The radius of the bottom section; The distance from the center of the bottom reinforcement zone of the conical tower section 1 to the top edge;

[0088] Calculate the circumferential tension at the bottom of the straight tower section 2 adjacent to the tapered tower section 1 in the variable diameter tower section. :

[0089] ;

[0090] in: The distance from the center of the top reinforcement zone of the straight tower section 2 to the bottom edge.

[0091] like Figure 13 As shown in the figure, For the top of the analysis unit at Calculate the vertical downward force within the width range; calculate the circumferential tension at the bottom of the far-end straight tower section 3. :

[0092] ;

[0093] in: To calculate the distance from the center of the top reinforcement zone of the straight tower section 2 to the bottom edge, The effective height of section 3 of the far-end straight tower section.

[0094] Depend on and The calculation formula shows that as the distance from the horizontal joint 6 of the variable diameter tower section 5 increases (i.e., (Increase), the circumferential tensile force generated by the diameter change effect will be significantly reduced, and the circumferential reinforcement of the far-end straight tower section 3 can be configured according to the structural reinforcement requirements.

[0095] S3. Based on the circumferential tension at the bottom of each tower section obtained in S2, calculate the design bending moment of the vertical section of the conical tower section 1 and the straight tower section 2 respectively;

[0096] Calculate the vertical bending moment of section 1 of the conical tower. :

[0097] ;

[0098] Calculate the bending moment of the vertical section of the straight tower section 2. :

[0099] .

[0100] S4. Calculate the amount of reinforcing steel at the bottom of the conical tower section 1 based on the design bending moment of the conical tower section 1 obtained in S3; calculate the amount of reinforcing steel at the top and bottom of the straight tower section 2 based on the design bending moment of the vertical section of the straight tower section 2 obtained in S3; select the reinforcement design value for the connection area of ​​the variable diameter tower section.

[0101] Based on the vertical section bending moment of conical tower section 1 The amount of reinforcing steel bars at the bottom of section 1 of the conical tower is calculated according to the reinforcement calculation formula for single-reinforced bending members in the "Code for Design of Concrete Structures" (GB 50010-2010). ,like Figure 14 and Figure 15 As shown, Figure 14 This is a bending moment stress model for a conical tower section, representing the bending moment experienced by the vertical section of the conical tower section. Schematic diagram. Figure 15 This is a schematic diagram of the stress distribution in the reinforcement calculation model for a bending member. From this, the amount of reinforcing steel at the bottom of the conical tower section can be calculated. The formula for calculation is as follows:

[0102] ;

[0103] in: This is the design value of the tensile strength of the steel reinforcement. The cross-section represents the height of the compression zone, and ξ represents the relative height of the compression zone. represents the elastic-plastic section modulus of the reinforced concrete section. For concrete strength grade coefficient, This is the design value for the compressive strength of concrete. The thickness of the ring sheet.

[0104] Based on the vertical section bending moment of the straight tower section According to the equilibrium equation of small eccentric tension members in the "Code for Design of Concrete Structures" (GB 50010-2010), and based on the circumferential tension at the bottom of the conical tower section 1 of the variable-diameter tower section 5 calculated by S2, The bottom circumferential tension of the straight tower section 2 adjacent to the conical tower section 1 of the variable diameter tower section 5 and the circumferential tension of the circumferential tower section 2. And the vertical section bending moment of the straight tower section 2 was calculated using S3. Substitute into the formula to calculate the amount of reinforcing steel required at the top of section 2 of the straight tower. The amount of reinforcing steel bars used at the bottom of the straight tower section 2 ,like Figure 16 and Figure 17 As shown, the expression is as follows:

[0105] ;

[0106] ;

[0107] in, This is the design value for the tensile strength of the reinforcing steel. Figure 16 This is a stress analysis model for a straight tower section under small eccentric tension, representing the bending moment on the vertical section of the straight tower section. Schematic diagram. Figure 17 This is a schematic diagram of the reinforcement calculation model for a small-scale tension member, from which the circumferential tension at the upper and lower ends of the straight tower section can be calculated. and The resulting bending moment value And establish the equilibrium equations of force and bending moment for members under small eccentric tension.

[0108] Continuous reinforcement design in the connection area: For the connection area between different tower sections (i.e., near horizontal joint 6), in order to ensure the continuity of reinforcement and avoid stress concentration, the larger value (max value) of the calculated amount of reinforcing steel bars at the bottom of conical tower section 1 and the end of straight tower section 2 should be taken as the reinforcement design value for this connection area.

[0109] Compared with existing technologies (optimization methods based on complex three-dimensional finite element simulation), the main advantages of this invention are reflected in four aspects: design efficiency, ease of use, theoretical systematicity, and economic security. Its optimal technical effects are as follows:

[0110] I. Significantly improved efficiency: The design process is simplified from a time-consuming cycle of "modeling-simulation-trial and error" (lasting several days to several weeks) to direct calculation using formulas (lasting several hours), greatly shortening the design cycle.

[0111] Second, the threshold is significantly lowered: a clear formulaic process is provided, which can be operated by ordinary structural engineers without the need to become finite element experts, making it easy to promote.

[0112] III. Significantly Enhanced Safety: After applying the reinforcement scheme of this invention, the maximum stress of the circumferential reinforcement can be reduced from 393.5 MPa to 187.1 MPa (a reduction of >52%), effectively inhibiting crack propagation and improving structural durability. Figure 18 and Figure 19 As shown.

[0113] Fourth, better economic efficiency: The formula clarifies the key areas and areas that can be simplified in reinforcement, guides the rational allocation of materials, avoids conservative or weak design, and achieves a balance between safety and cost.

[0114] This invention has been verified by both systematic finite element analysis and engineering case studies, proving that it is completely feasible and has significant effects.

[0115] I. Finite Element Analysis Verification: A refined finite element model of the first variable-diameter tower section 5 of a 5MW unit's concrete tower was established. Calculation results show that under ultimate load, the location and direction of cracks are highly consistent with field observations, verifying the model's correctness. More importantly, the analysis reveals that the conical tower section 1 exhibits a reverse bending point (a characteristic of the bending model) and the straight tower section exhibits non-uniform tension (a characteristic of the eccentric tension model), providing a direct theoretical basis for simplifying the model in this invention.

[0116] II. Engineering Case Verification: Taking the aforementioned 5MW unit tower as an example, the reinforcement design was carried out using the method of this invention, and compared with the original actual reinforcement scheme:

[0117] (1) Conical tower section (TD1): Calculated reinforcement amount (14218.8 mm) 2 ) and the actual reinforcement amount (14477.4 mm) 2 The results showed a high degree of agreement (ratio 0.98), as shown in Table 1, demonstrating the accuracy of the method of the present invention.

[0118] Table 1 Comparison of calculated and actual reinforcement of conical tower section 1TD1

[0119]

[0120] (2) Straight tower section (A7): The reinforcement was calculated according to the method of the present invention and the finite element analysis was performed again. The results showed that the crack morphology was fundamentally improved and the steel stress was reduced by 46% (as mentioned above), which proved the superiority of the method of the present invention in improving structural safety and crack resistance.

[0121] III. Comparative Simulation Verification:

[0122] To highlight the non-obviousness of this invention, we conducted a comparative simulation: if traditional methods are used to design the reinforcement of a straight tower section, the calculation results will fail to reflect the actual situation of stress distribution, leading to unreasonable reinforcement. However, the "small eccentric tension" model of this invention precisely matches the finite element results. The significant difference in performance strongly demonstrates the originality and superiority of this invention, and is not an obvious choice for those skilled in the art.

[0123] Table 2 Geometric Dimensions of the Mixing Tower Section

[0124]

[0125] Table 3 Load values ​​at height 36.96

[0126]

[0127] Table 4 Calculated reinforcement and actual reinforcement results from drawings for straight tower sections

[0128]

[0129] Tables 1, 2, and 4 together form a rigorous logical chain of evidence, strongly supporting the practicality and inventiveness of this invention. Table 1 details the geometric abrupt changes in the conical tower section (TD1) and the straight tower section, establishing the physical basis for the generation of circumferential tensile force. Table 2 shows the ultimate design load value at the top section of tower section B1, confirming the rigor of the design background and the standardization of the input conditions. Most importantly, Table 4, by comparing the actual reinforcement of the straight tower section with the calculated values ​​of this invention, reveals the fatal flaw of insufficient reinforcement in existing designs due to neglecting the eccentric tensile effect (e.g., the calculated / actual ratio of the top section with greater stress in section A7 is 2.06). This directly explains the frequent occurrence of vertical cracks in the project. At the same time, the data in Table 4 also intuitively verifies the accuracy of the theoretical law of "variable diameter effect decays with distance" and the principle of continuous reinforcement design proposed in this invention, proving that this invention can accurately identify safety hazards and achieve refined reinforcement optimization.

[0130] The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention. All equivalent structural transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the protection scope of the present invention.

Claims

1. A method for designing circumferential reinforcement of a variable-diameter tower section of a concrete tower of a wind turbine generator, characterized in that, Includes the following steps: S1. Obtain the structural parameters of the concrete tower of the wind turbine, and calculate the design load of the variable diameter tower section (5) based on the structural parameters; S2. Based on the structural parameters obtained from S1 and the design load of the variable diameter tower section (5), calculate the bottom circumferential tension of the conical tower section (1) and the bottom circumferential tension of the straight tower section (2) of the variable diameter tower section (5). S3. Based on the circumferential tension at the bottom of each tower section obtained in S2, calculate the design bending moment of the vertical section of the conical tower section (1) and the straight tower section (2) respectively; S4. Calculate the amount of reinforcing steel at the bottom of the conical tower section (1) based on the design bending moment of the conical tower section (1) obtained from S3; calculate the amount of reinforcing steel at the top and bottom of the straight tower section (2) based on the design bending moment of the vertical section of the straight tower section (2) obtained from S3; select the reinforcement design value of the connection area of ​​the variable diameter tower section (5).

2. The method of designing the ring reinforcement of a variable diameter tower section of a concrete tower of a wind turbine generator according to claim 1, wherein, The structural parameters of the concrete tower of the wind turbine include the height of each tower section, the bottom diameter, the top diameter, the wall thickness, the concrete strength grade, and the steel reinforcement material properties.

3. The method of designing the ring reinforcement of a variable diameter tower section of a concrete tower of a wind turbine generator according to claim 1, wherein, S2 specifically includes the following steps: Calculate the circumferential tension at the bottom of the conical tower section (1) of the variable diameter tower section (5). : ； in: The vertical force acting on the top of the conical tower section (1) The bending moment acting on the top of the conical tower section (1); The radius of the top section is 1. The radius of the bottom section; The distance from the center of the bottom reinforcement zone of the conical tower section (1) to the top edge.

4. The method for designing circumferential reinforcement of the variable-diameter concrete tower section of a wind turbine according to claim 3, characterized in that, S2 specifically includes the following steps: Calculate the circumferential tension at the bottom of the straight tower section (2) adjacent to the conical tower section (1) of the variable diameter tower section (5). : ； in: The distance between the center of the top reinforcement zone of the straight tower section (2) and the bottom edge.

5. The method for designing circumferential reinforcement of the variable-diameter concrete tower section of a wind turbine according to claim 4, characterized in that, S2 specifically includes the following steps: Calculate the circumferential tension at the bottom of the far-end straight tower section (3) : ； in: The effective height of the cross section of the far-end straight tower section (3) is given.

6. The method for designing circumferential reinforcement of the variable-diameter concrete tower section of a wind turbine according to claim 5, characterized in that, S3 specifically includes the following steps: Calculate the vertical bending moment of the conical tower section (1). : ； Calculate the vertical section bending moment of the straight tower section (2). : 。 7. The method for designing circumferential reinforcement of the variable-diameter concrete tower section of a wind turbine according to claim 6, characterized in that, The amount of bottom reinforcing steel bars for a conical tower section (1) is calculated using the reinforcement calculation formula for a single-reinforced bending member. The calculation formula is as follows: ； in: This is the design value of the tensile strength of the steel reinforcement. The cross-section represents the height of the compression zone, and ξ represents the relative height of the compression zone. represents the elastic-plastic section modulus of the reinforced concrete section. For concrete strength grade coefficient, This is the design value for the compressive strength of concrete. The thickness of the ring sheet.

8. The method for designing circumferential reinforcement of the variable-diameter concrete tower section of a wind turbine according to claim 7, characterized in that, Using a small eccentric tension member model, and based on S2, the circumferential tension at the bottom of the conical tower section (1) of the variable-diameter tower section (5) is calculated. The bottom circumferential tension of the conical tower section (1) adjacent to the variable diameter tower section (5) and the straight tower section (2) And the vertical section bending moment of the straight tower section (2) calculated by S3. Substitute into the formula to calculate the amount of reinforcing steel at the top of the straight tower section (2). The amount of reinforcing steel bars at the bottom of the straight tower section (2) The expression is as follows: ； 。

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