Design method for circular reinforcement of variable-diameter tower section of concrete tower drum of wind turbine generator

Abstract

The invention relates to the technical field of constructional engineering, in particular to a wind turbine generator concrete tower tube variable-diameter tower section annular reinforcement design method which comprises the steps that structural parameters of a wind turbine generator concrete tower tube are obtained, and the design load of a variable-diameter tower section is calculated according to the structural parameters; calculating the bottom circumferential tension of the tapered tower section of the variable-diameter tower section and the bottom circumferential tension of the straight tower section of the variable-diameter tower section; calculating the design bending moment of the vertical sections of the conical tower section and the straight tower section; calculating the use amount of conical tower section bottom reinforcing steel bars; calculating the use amount of reinforcing steel bars at the top and the bottom of the straight tower section; and selecting a reinforcement design value of the connecting area of the variable-diameter tower section. Load calculation, toroidal force analysis, model simplification and reinforcement calculation are connected in series to form a complete and efficient closed-loop design chain, the tedious finite element trial and error process is replaced, and the technical problems that when a three-dimensional finite element model is used for designing toroidal reinforcement of the variable-diameter tower section of the tower drum, the workload is large, and the labor cost is high are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of construction engineering, and particularly relates to a design method for circumferential reinforcement of a variable-diameter tower section of a wind turbine concrete tower. BACKGROUND

[0002] With the increase of single machine power of wind turbines and the increase of hub height, the traditional steel tower has increasingly prominent problems of low natural frequency and easy resonance with wind vibration frequency. Steel-concrete hybrid tower, with its superior economy and high stiffness performance, has become the main support structure form of super-high wind turbines. In order to facilitate construction and save cost, the concrete hybrid tower often adopts a segmented variable-diameter scheme to adapt to the change in bending stiffness.

[0003] However, engineering practice shows that, as shown in Figure 1 The steel-concrete hybrid tower includes a C-shaped ring piece 4, a tapered tower section 1, a straight tower section 2, and a distal straight tower section 3. Under the combined action of complex wind load and prestress, the concrete variable-diameter tower section composed of the tapered tower section 1 and the adjacent straight tower section 2 below frequently appears multiple vertical joints 7 extending upwards and downwards along the horizontal construction joint. The vertical joint 7 not only extends up and down (up to 1.5-2.5m), but also penetrates inside and outside and seeps water, which has become a typical disease threatening the safety and durability of the tower structure.

[0004] In view of the above crack problem, relevant research reveals the mechanical root cause: under the action of vertical pressure, the variable-diameter tower section generates significant circumferential tension at the horizontal joint due to the geometric mutation of the cross section , which further causes vertical cracking of the adjacent ring piece. Figure 2

[0005] To solve this problem, the technical solution commonly used in the existing engineering field is to rely on three-dimensional solid finite element analysis for reinforcement design and verification. The specific process is as follows: a detailed tower entity model is established, the design load obtained by a structural analysis software or an engineering calculation method is imported, the structure stress and crack distribution are analyzed through complex nonlinear finite element calculation, and the reinforcement scheme is repeatedly adjusted until it meets the requirements of the ultimate and operating conditions, as shown in Figure 3 and Figure 4 In the figure, 8 is a distributed steel bar.

[0006] ​However, this scheme leads to the engineering community to form a general recognition that for such a complex structure as the variable-diameter tower section, only relying on high-precision three-dimensional solid finite element analysis can ensure the safety of the design, and any form of simplified model is considered to cause design failure due to the loss of key information. The finite element analysis method is essentially a "verification" rather than a "proactive design" method, and its core is the "trial and error method". It fails to reveal the law of variable-diameter effect from the essence of mechanics, leading to a lack of theoretical guidance in design, and solidifying the thinking of "over-reliance on simulation and unwilling to effectively simplify", which constitutes a long-standing technical bias in this field, hindering the development of efficient design methods. Moreover, the establishment and calculation of large three-dimensional finite element models require a huge amount of work, and a complete design verification cycle often takes several weeks, seriously delaying project progress and incurring high labor and time costs. In addition, the process requires high requirements for the finite element theory, software operation and engineering experience of the designer, limiting the popularization and application of the technology, and easily leading to inconsistent design results due to differences in personnel levels. Finite element analysis is mainly used for "safety verification", rather than "performance optimization". It is difficult to directly guide the designer to effectively suppress cracks by adjusting the reinforcement, often resulting in overly conservative reinforcement schemes or insufficient reinforcement in critical areas, and failing to achieve the best balance between economy and safety.

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

[0008] The main purpose of the present application is to provide a wind turbine concrete tower variable-diameter tower section ring reinforcement design method, which aims to solve the technical problems of large workload and high labor cost in the design of the existing three-dimensional finite element model for the ring reinforcement of the tower variable-diameter tower section.

[0009] To achieve the above purpose, the present application provides a wind turbine concrete tower variable-diameter tower section ring reinforcement design method, The wind turbine concrete tower variable-diameter tower section ring reinforcement design method of the present application is further improved and comprises the following steps: S1, obtaining the structural parameters of the wind turbine concrete tower, and calculating the design load of the variable-diameter tower section according to the structural parameters; S2, calculating the bottom ring tension of the conical tower section and the bottom ring tension of the straight tower section of the variable-diameter tower section according to the structural parameters and the design load of the variable-diameter tower section obtained in S1; S3, calculating the design bending moment of the vertical section of the conical tower section and the straight tower section according to the bottom ring tension of each tower section obtained in S2; S4, the amount of reinforcing steel at the bottom of the tapered tower section is calculated according to the design bending moment of the tapered tower section obtained in S3; the amount of reinforcing steel at the top and bottom of the straight tower section is calculated according to the design bending moment of the vertical section of the straight tower section obtained in S3; and the design value of the reinforcement at the connection area of the variable-diameter tower section is selected.

[0010] The wind turbine concrete tower variable-diameter tower section ring reinforcement design method further improves the structure parameters of the wind turbine concrete tower, including the height, bottom diameter, top diameter, wall thickness, concrete strength grade and reinforcement material properties of each tower section.

[0011] The wind turbine concrete tower variable-diameter tower section ring reinforcement design method further improves S2, which specifically includes the following steps: Calculate the bottom ring tension of the tapered tower section of the variable-diameter tower section Wherein: is the vertical force acting on the top of the tapered tower section, is the bending moment acting on the top of the tapered tower section; is the top section radius, is the bottom section radius; is the distance from the center of the reinforced area at the bottom of the tapered tower section to the edge of the top.

[0012] The wind turbine concrete tower variable-diameter tower section ring reinforcement design method further improves S2, which specifically includes the following steps: Calculate the bottom ring tension of the straight tower section adjacent to the tapered tower section of the variable-diameter tower section Wherein: is the distance from the center of the reinforced area at the top of the straight tower section to the edge of the bottom.

[0013] The wind turbine concrete tower variable-diameter tower section ring reinforcement design method further improves S2, which specifically includes the following steps: Calculate the bottom ring tension of the straight tower section at the far end Wherein: is the effective height of the section of the straight tower section at the far end.

[0014] The wind turbine concrete tower variable-diameter tower section ring reinforcement design method further improves S3, which specifically includes the following steps: Calculate the vertical section bending moment of the tapered tower section ​​​​​​​ ; Calculate straight tower section vertical section bending moment : .

[0015] Further improvement of the wind turbine concrete tower variable diameter tower section ring reinforcement design method of the application is that the single reinforcement bending member reinforcement calculation formula is used to calculate the amount of reinforcing steel at the bottom of the conical tower section The calculation formula is as follows: ; Among them: The design value of the tensile strength of the reinforcing steel, The section is the height of the compression zone, and ξ is the relative compression zone height, The elastic-plastic resistance moment coefficient of the reinforced concrete section, The concrete strength grade coefficient, The design value of the compressive strength of the concrete, The thickness of the ring piece.

[0016] Further improvement of the wind turbine concrete tower variable diameter tower section ring reinforcement design method of the application is that the small eccentric tension member model is used, and the conical tower section bottom ring tension of the variable diameter tower section is calculated according to S2 And the straight tower section bottom ring tension adjacent to the conical tower section of the variable diameter tower section And the vertical section bending moment of the straight tower section calculated by S3 The amount of reinforcing steel at the top of the straight tower section is calculated by substituting the formula And the amount of reinforcing steel at the bottom of the straight tower section The expression is as follows: ; ; Among them, The design value of the tensile strength of the reinforcing steel.

[0017] The technical scheme of the application has the following beneficial effects: The wind turbine concrete tower variable diameter tower section ring reinforcement design method of the application proposes a new straight tower section ring tension And the far-end straight tower section ring tension The calculation formula accurately quantifies the law of the diameter change effect with distance attenuation, and provides a theoretical basis for differentiation and fine reinforcement. The load calculation, hoop force analysis, model simplification and reinforcement calculation are connected in series to form a complete and efficient closed-loop design chain, which replaces the tedious finite element trial and error process, and solves the technical problems of large workload and high labor cost of the existing three-dimensional finite element model for designing the hoop reinforcement of the variable-diameter tower section of the tower drum. The application discloses that the mechanical nature of the cracking of the variable-diameter tower section is the hoop tension, and the complex variable-diameter structure is decoupled into a combined model of a conical tower section-bending member and a straight tower section- eccentric tension member, which breaks the technical prejudice of excessive dependence on finite element analysis in the field. The application proposes a reinforcement continuity principle, solves the local stress concentration problem, and clearly defines a larger reinforcement value in the tower section connection area, ensuring the continuity and safety of the structure as a whole, and effectively inhibiting the initiation and expansion of cracks at the connection. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the drawings shown.

[0019] Figure 1 The flow chart of the wind turbine concrete tower variable-diameter tower section hoop reinforcement design method of the present application; Figure 2 The schematic diagram of the variable-diameter tower section of the concrete tower; Figure 3 The schematic diagram of the hoop tension generation mechanism of the variable-diameter tower section; Figure 4 The schematic diagram of the reinforcement at the end of the conical section; Figure 5 The schematic diagram of the reinforcement at the end of the straight tower section; Figure 6 The flow chart of the finite element analysis model generation of the local tower section (including the variable-diameter tower section) (TD1 is a conical tower section, B1, A7 and A6 are straight tower sections); Figure 7 The schematic diagram of the crack distribution and development of the traditional TD1 and A7 tower sections; Figure 8 The schematic diagram of the hoop reinforcement stress analysis result of the traditional variable-diameter tower section; Figure 9 The overall deformation cloud chart of the variable-diameter tower section under the action of the vertical load; Figure 10Fig. 1 is a schematic diagram of a vertical cross-section transverse deformation diagram under vertical load (TD1 is a conical tower section, B1, A7, A6 are straight tower sections); Figure 11 Fig. 2 is a schematic diagram of a simplified model of a conical transition section; Figure 12 Fig. 3 is a schematic diagram of a calculation of a unit ring tension; Figure 13 Fig. 4 is a schematic diagram of a stress analysis model of a straight tower section; Figure 14 Fig. 5 is a schematic diagram of a bending moment stress model of a conical tower section; Figure 15 Fig. 6 is a schematic diagram of a reinforcement calculation model of a bending member; Figure 16 Fig. 7 is a schematic diagram of a stress analysis model of a small eccentric tension of a straight tower section; Figure 17 Fig. 8 is a schematic diagram of a reinforcement calculation model of a small eccentric tension member; Figure 18 Fig. 9 is a vertical crack distribution diagram of a variable-diameter tower section under a reinforcement condition of a wind turbine generator concrete tower variable-diameter tower section ring reinforcement design method of the application; Figure 19 Fig. 10 is a ring reinforcement stress distribution diagram of a variable-diameter tower section under a reinforcement condition of a wind turbine generator concrete tower variable-diameter tower section ring reinforcement design method of the application.

[0020] Explanation of reference numerals: 1, conical tower section; 2, straight tower section; 3, distal straight tower section; 4, C-shaped ring piece; 5, variable-diameter tower section; 6, horizontal joint; 7, vertical joint; 8, distribution reinforcement. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0022] It should be noted that all directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directionality indications also change accordingly.

[0023] In addition, the descriptions such as "first", "second" and the like in the present application are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0024] In the present application, unless otherwise specifically defined and limited, the terms "connection", "fixation" and the like should be understood broadly, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, can be internal communication of two elements or interaction relationship of two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] In addition, the technical solutions of various embodiments of the present application can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection required by the present application.

[0026] As shown in Figures 1-19 , the present application proposes a design method for circumferential reinforcement of variable-diameter tower section of wind turbine tower, the core idea of which is: identifying and separating the key mechanical behavior of crack-causing circumferential tension from the complex overall structure, and converting it into a classic concrete member design problem, so as to realize accurate and rapid design of reinforcement of variable-diameter tower section 5.

[0027] That is, through in-depth field detection and finite element parameterized analysis, as shown in Figures 6-10 , it is revealed that the mechanical essence of cracking of variable-diameter tower section 5 lies in the circumferential tension caused by geometric mutation. Based on this, the present application creatively decouples the complex variable-diameter structure into two classic mechanical models: (1) the conical tower section 1, whose vertical section stress distribution is upper compression and lower tension, which can be accurately simplified as "single-reinforced flexural member", as shown in Figure 11 . Figure 11 The simplified model of the conical tower section is a force diagram, the main external load acting on the conical tower section is vertical force and bending moment , which are applied to the center of the top surface. Since the tensile strength of concrete is low, its contribution under the action of circumferential tension is ignored, and it is assumed that the circumferential tension is completely borne by the circumferential steel bars.

[0028] (2) Straight tower section, the vertical section stress distribution is non-uniform tension from big to small, which can be accurately simplified as "small eccentric tension member", as shown in Figure 13 Figure 13 The figure is a schematic diagram of the stress analysis model of the straight tower section, which is based on the analysis model of the conical tower section, and the lower straight tower section is added. The ring force of the straight tower section of the variable-diameter tower section is The derivation process, and the ring tension of the straight tower section of the variable-diameter tower section can be obtained from the figure

[0029] This model simplification paradigm breaks the technical bias of excessive reliance on finite element analysis in the field, and lays a theoretical foundation for establishing an efficient and reliable reinforcement design method.

[0030] Figure 6 The finite element analysis model of the local tower section (the local tower section includes the conical tower section TD1 and the straight tower section A7 of the variable-diameter tower section, as well as the upper and lower adjacent straight tower sections B1 and the remote straight tower section A6) is established by using an existing finite element software, including a local concrete tower section model, a reinforcement cage model, and a schematic diagram of boundary conditions and loading applied by the local concrete tower section model. Figure 6 RP-1 is a reference point provided at the top of the model, and a load is applied at the reference point. The reference point is associated with the surface of the analysis model through coupling constraints, so as to realize uniform application and transmission of the upper load.

[0031] Figure 7 The concrete tension damage analysis result of the finite element model of the local tower section under the design load shows that the connecting joint between the conical tower section TD1 of the compression side of the variable-diameter tower section and the lower straight tower section has a significant ring tension stress, and the tension stress has exceeded the tensile strength of the tower section concrete, resulting in cracks extending upward and downward from the connecting joint, respectively. The position and direction of the cracks are basically consistent with the field observation results, which verifies the correctness of the variable-diameter tower section finite element model established by the application and has the reliability of being analyzed in actual engineering.

[0032] Figure 8 The ring reinforcement stress analysis result of the variable-diameter tower section under the design load shows that the maximum stress of the ring reinforcement of the variable-diameter tower section is 393.5 MPa, which is less than the yield strength requirement of 400 MPa, indicating that the bearing capacity under the limit load condition meets the requirements, but the larger ring reinforcement stress will cause vertical cracking of the concrete, which will inevitably have a certain impact on normal operation.

[0033] Figure 9 The figure is a vertical load action variable-diameter tower section overall deformation cloud picture, Figure 10 The figure is a vertical load action vertical section transverse deformation schematic diagram. Combined with the two Figure 1 The analysis shows that: ​​(1) The transverse deformation inflection point exists in the middle of the conical tower segment TD1, and its mechanical characteristics are that the lower segment is in tension and the upper segment is in compression. The maximum tensile deformation is located at the bottom of TD1, and the inflection point is approximately at the midpoint of the tower segment height. Based on this feature, the ring stress distribution of the conical tower segment can be simplified as a pure bending model.

[0034] (2) Due to deformation coordination, the transverse deformation of the adjacent TD1 and A7 tower segments is completely consistent, indicating that at the horizontal joint location, A7 and TD1 also bear a large ring force, and key design should be performed to ensure the safety of the structure.

[0035] (3) At the far end of the horizontal joint, the straight tower segment A7 is mainly in full-section tensile deformation, but the value is significantly reduced. Therefore, the ring stress distribution of the straight tower segment A7 can be simplified as an eccentric tensile analysis model.

[0036] (4) The straight tower segment (B1) above TD1 has a deformation inflection point at about 1 / 3 of its bottom, i.e., the lower segment is in compression and the upper segment is in tension, and its deformation is smaller than that of TD and A7. The far-end straight tower segment (A6) is in full-section tensile deformation, but due to its distance from the variable-diameter section, the ring deformation and stress are significantly lower than those of A7. In actual projects, no vertical cracks are detected on the straight tower segments (B1 and A6), indicating that the ring tensile stress on the tower segments far from the lower horizontal joint of the conical tower segment is small, and the reinforcement can be significantly reduced.

[0037] The method for designing the ring reinforcement of the variable-diameter tower section of the wind turbine concrete tower includes the following steps: S1, obtaining the structural parameters of the wind turbine concrete tower, and calculating the design load of the variable-diameter tower section 5 according to 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 material properties of each tower segment. The design load (including axial force, shear force, bending moment, torque, and prestress) of the variable-diameter tower section 5 is calculated using a general structural analysis software or engineering calculation method.

[0038] S2, calculating the ring tension at the bottom of the conical tower segment and the ring tension at the bottom of the straight tower segment of the variable-diameter tower section according to the structural parameters and the design load of the variable-diameter tower section 5 obtained in S1, as shown in Figure 11 and Figure 12 , wherein is the vertical pressure transmitted to the conical tower segment by the upper tower section, is the received prestress, is a microelement with a circumferential width of taken as the calculation unit in the force analysis model, is the radial component of the ring tension, is the counterforce in balance; calculating the ring tension at the bottom of the conical tower segment 1 : ; wherein: is the vertical force acting on the top of the conical tower segment 1, is the bending moment acting on the top of the conical tower segment 1; is the top section radius, is the bottom section radius; is the distance from the center of the reinforcement zone at the bottom of the conical tower segment 1 to the edge of the top; calculating the circumferential tensile force of the bottom of the straight tower segment 2 adjacent to the variable-diameter tower segment 1 : ; wherein: is the distance from the center of the reinforcement zone at the top of the straight tower segment 2 to the edge of the bottom.

[0039] As shown in FIG. 1, Figure 13 is the vertical force acting on the top of the analysis unit in the range of the width; calculating the circumferential tensile force of the bottom of the distal straight tower segment 3 : ; wherein: is the distance from the center of the reinforcement zone at the top of the straight tower segment 2 to the edge of the bottom, is the effective height of the section of the distal straight tower segment 3.

[0040] As can be seen from the calculation formulas of and , with the increase of the distance from the horizontal joint 6 of the variable-diameter tower segment 5 (i.e. the increase of ), the circumferential tensile force caused by the variable-diameter effect will be significantly reduced, and the circumferential reinforcement of the distal straight tower segment 3 can be configured according to the structural reinforcement requirements.

[0041] S3, calculating the design bending moment of the vertical section of the conical tower segment 1 and the straight tower segment 2 respectively according to the circumferential tensile force of the bottom of each tower segment obtained in S2; calculating the bending moment of the vertical section of the conical tower segment 1 : ; calculating the bending moment of the vertical section of the straight tower segment 2 : .

[0042] ​S4, the design moment of the conical tower section 1 is calculated according to the design moment of the conical tower section 1 obtained in S3, the design moment of the vertical section of the straight tower section 2 is calculated according to the design moment of the vertical section of the straight tower section 2 obtained in S3, and the reinforcement design value of the connecting area of the variable diameter tower section is selected.

[0043] According to the bending moment of the vertical section of the conical tower section 1 , the reinforcement amount of the bottom of the conical tower section 1 is calculated according to the reinforcement calculation formula of the bending member in the Code for Design of Concrete Structures (GB 50010-2010) , as shown in Figure 14 and Figure 15 , the bending moment stress model of the conical tower section is shown in Figure 14 , which represents the bending moment of the vertical section of the conical tower section schematic diagram. Figure 15 The reinforcement calculation model of the bending member is shown in the stress schematic diagram, and the formula for calculating the reinforcement amount of the bottom of the conical tower section is listed, and the calculation formula is as follows: ; Among them: is the design value of the tensile strength of the steel bar, is the compressive zone height of the section, and ξ is the relative compressive zone height, is the elastic-plastic resistance moment coefficient of the reinforced concrete section, is the concrete strength grade coefficient, is the design value of the compressive strength of the concrete, is the thickness of the ring piece.

[0044] According to the bending moment of the vertical section of the straight tower section , the balance equation of the small eccentric tension member in the Code for Design of Concrete Structures (GB 50010-2010) is used, and the bottom ring tension of the conical tower section 1 of the variable diameter tower section 5 and the bottom ring tension of the straight tower section 2 adjacent to the conical tower section 1 of the variable diameter tower section 5 are calculated according to S2, and the vertical section bending moment of the straight tower section 2 is calculated according to S3, and the reinforcement amount of the top position of the straight tower section 2 and the reinforcement amount of the bottom position of the straight tower section 2 are calculated, as shown in Figure 16 and Figure 17 , and the expressions are as follows: ; ; Among them, is the design value of the tensile strength of the steel bar. Figure 16It is a small eccentric tension member force analysis model of straight tower segment, which represents the bending moment of vertical section of straight tower segment Schematic diagram. Figure 17 It is a force schematic diagram of the reinforcement calculation model of the small eccentric tension member, so that the circumferential tension of the upper and lower ends of the straight tower segment can be calculated And The bending moment value caused by And the balance equation of force and bending moment of the small eccentric tension member is established.

[0045] Continuous design of reinforcement in the connection area: for the connection area between different tower segments (i.e. near the horizontal joint 6), in order to ensure the continuity of reinforcement and avoid stress concentration, the larger value (max value) of the reinforcement amount calculation results of the bottom of the tapered tower segment 1 and the end of the straight tower segment 2 should be taken as the reinforcement design value of the connection area.

[0046] Compared with the prior art (an optimization method based on complex three-dimensional finite element simulation), the main advantages of the present application are reflected in four aspects of design efficiency, method usability, theoretical systematicness and economic safety, and the optimal technical effects are as follows: I. Efficiency is significantly improved: the design is simplified from the time-consuming "modeling-simulation-trial and error" cycle (several days to several weeks) to direct calculation by formula (within several hours), which greatly shortens the design cycle.

[0047] II. The threshold is greatly reduced: a clear formulaic process is provided, which can be operated by ordinary structural engineers without becoming a finite element expert, and is easy to popularize.

[0048] III. Safety is significantly enhanced: after applying the reinforcement scheme of the present application, the maximum stress of the circumferential reinforcement can be reduced from 393.5 MPa to 187.1 MPa (decrease > 52%), effectively inhibiting crack propagation and improving structural durability, as shown in Figure 18 And Figure 19 .

[0049] IV. Economic efficiency is better: the formula clearly defines the key reinforcement area and the simplified area, guides the reasonable allocation of materials, avoids conservative or weak design, and achieves a balance between safety and cost.

[0050] The present application has been verified by systematic finite element analysis and engineering cases, which proves that it is completely feasible and has remarkable effects.

[0051] I. Finite element analysis verification: A refined finite element model of the first variable-diameter tower section 5 of the concrete tower drum of a certain 5MW unit is established. The calculation results show that under the ultimate load, the position and direction of the cracks are highly consistent with the field observation results, verifying the correctness of the model. More importantly, the analysis results reveal the mechanical behavior of the conical tower section 1 with a bending point (bending model feature) and the straight tower section with non-uniform tension (eccentric tension model feature), providing a direct theoretical basis for the model simplification of the invention.

[0052] II. Engineering case verification: Taking the aforementioned 5MW unit tower drum as an example, the reinforcement design is carried out using the method of the invention, and compared with the original actual reinforcement scheme: (1) Conical tower section (TD1): The calculated reinforcement amount (14218.8 mm 2 ) is highly consistent with the actual reinforcement amount (14477.4 mm 2 ) (ratio 0.98), as shown in Table 1, proving the accuracy of the method of the invention.

[0053] Table 1 Comparison of calculated reinforcement and actual reinforcement of conical tower section 1 TD1

[0054] (2) Straight tower section (A7): The reinforcement is calculated according to the method of the invention and re-analyzed by finite element method, the results show that the crack pattern is fundamentally improved and the steel stress is reduced by 46% (as mentioned before), proving the superiority of the method of the invention in improving structural safety and crack resistance.

[0055] III. Comparative simulation verification: To highlight the non-obviousness of the invention, we conducted a comparative simulation: if the traditional method is used to design the reinforcement of the straight tower section, the calculation results will not reflect the true situation of stress increasing from top to bottom, leading to unreasonable reinforcement. While using the "small eccentric tension" model of the invention, it accurately matches the finite element results. The difference between the two is obvious, which strongly proves the originality and superiority of the invention, and it is not an obvious choice for those skilled in the art.

[0056] Table 2 Geometric size parameters of tower section

[0057] Table 3 Load values at height 36.96

[0058] Table 4 Calculated reinforcement and actual reinforcement of straight tower section

[0059] Table 1, Table 2 and Table 4 jointly constitute a rigorous logical evidence chain, which strongly supports the practicality and creativity of the present application. Table 1 details the geometric mutation characteristics of the conical tower segment (TD1) and the straight tower segment, establishing the physical basis for generating the ring tension; Table 2 shows the limit working condition design load values at the top section of B1 tower segment, confirming the severity of the design background and the standardization of the input conditions; the most critical Table 4 reveals the fatal flaw of insufficient reinforcement caused by the neglect of eccentric tension effect in the existing design (such as the top of A7 segment with large stress, the calculated / actual ratio is 2.06) by comparing the actual reinforcement of the straight tower segment with the calculated value of the present application, which directly explains the reason for the frequent occurrence of vertical cracks in engineering; at the same time, the data in Table 4 also directly verifies the accuracy of the theoretical law of "diameter variation effect decaying with distance" and the reinforcement continuous design principle proposed by the present application, proving that the present application can accurately identify safety hazards and achieve fine reinforcement optimization.

[0060] The above only describes the preferred embodiments of the present application, and does not limit the scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or direct / indirect application in other related technical fields within the inventive concept of the present application, as described in the specification and drawings of the present application, are included in the protection scope of the present application.

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, The method comprises the following steps: S1, obtaining the structural parameters of the concrete tower of the wind turbine, and calculating the design load of the variable-diameter tower section (5) according to the structural parameters; S2, calculating the bottom ring tension of the conical tower section (1) and the bottom ring tension of the straight tower section (2) of the variable-diameter tower section (5) according to the structural parameters and the design load of the variable-diameter tower section (5) obtained in S1; S3, calculating the design bending moment of the vertical section of the conical tower section (1) and the straight tower section (2) respectively according to the bottom ring tension of each tower section obtained in S2; S4, calculating the amount of reinforcing steel at the bottom of the conical tower section (1) according to the design bending moment of the conical tower section (1) obtained in S3, calculating the amount of reinforcing steel at the top and bottom positions of the straight tower section (2) according to the design bending moment of the vertical section of the straight tower section (2) obtained in S3, and selecting 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, bottom diameter, top diameter, wall thickness, concrete strength grade and steel material properties of each tower section.

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 comprises the following steps: calculating the hoop tension at the bottom of the conical tower segment (1) of the variable-diameter tower segment (5) : ； wherein: M is the vertical force acting on the top of the tapered segment (1), M is the bending moment acting on the top of the tapered segment (1); R is the radius of the top section, R is the radius of the bottom section; L is the distance from the center of the reinforcement zone at the bottom of the tapered segment (1) to the edge of the top.

4. The wind turbine generator concrete tower variable diameter tower section ring reinforcement design method of claim 3, wherein, S2 specifically comprises the following steps: Calculate the hoop tension at the bottom of a straight section (2) adjacent to a conical section (1) of a variable diameter column (5) : ； wherein: is the distance from the center of the top reinforcement zone of the straight tower segment (2) to the edge of the bottom.

5. 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 4, wherein, S2 specifically comprises the following steps: calculating the hoop tension at the bottom of the far-end straight tower segment (3) : ； wherein: is the effective height of the far-end straight tower section (3) cross-section.

6. 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 5, wherein, S3 specifically comprises the following steps: Calculating the vertical section bending moment of a conical tower segment (1) : ； calculating the vertical section bending moment of the straight tower segment (2) : 。 7. 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 6, wherein, 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: ； wherein: is the design value of tensile strength of steel, is the compressive zone height of the cross section, and ξ is the relative compressive zone height, is the elastic-plastic resistance moment coefficient of the reinforced concrete cross section, is the concrete strength grade coefficient, is the design value of compressive strength of concrete, is the thickness of the ring.

8. 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 7, wherein, The bottom ring tension of the conical tower section (1) of the variable-diameter tower section (5) is calculated according to S2 and the bottom ring tension of the straight tower section (2) adjacent to the conical tower section (1) of the variable-diameter tower section (5) and the vertical section bending moment of the straight tower section (2) calculated according to S3 The amount of reinforcing steel at the top of the straight tower section (2) is calculated by substituting the formula and the amount of reinforcing steel at the bottom of the straight tower section (2) The expression is as follows: ； 。

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