A wind power tower structure provided with a high-strength steel constraint damping enhancement section and a design method thereof

Abstract

The application relates to a wind power tower structure provided with a high-strength steel constraint damping enhancement section and a design method thereof, wherein the high-strength steel constraint damping enhancement section comprises a high-strength material layer, a damping layer and a constraint layer, the upper and lower ends of the high-strength material layer are connected with a non-energy dissipation section of a tower body respectively, the damping layer and the constraint layer are not directly connected with the non-energy dissipation section, the damping layer is attached to the high-strength material layer on one side and is attached with the constraint layer on the other side; the design method comprises the following steps: firstly, performing preliminary design on a wind power tower and a foundation thereof and determining the arrangement position of the high-strength steel constraint damping enhancement section; using high-strength steel to process the high-strength material layer; through modal damping ratio calculation, performing parameter analysis and optimization on the high-strength steel constraint damping enhancement section, and determining corresponding structure schemes and additional damping. Compared with the prior art, the application can overcome the limitations of current inertia-based and material-based technologies, realize the synergistic enhancement effect of the additional damping, reduce the steel consumption and improve the damping effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power tower design, and particularly relates to a wind power tower structure provided with a high-strength steel constraint damping efficiency section and a design method thereof. BACKGROUND

[0002] In recent years, the development momentum of offshore wind power is strong, and the trend of large-scale is increasingly obvious. With the large-scale of wind power support structure, the wind power support structure evolves into higher tower and longer blades, and the design of single pile wind power tower faces unprecedented challenges in cost reduction and efficiency improvement and resistance to multiple dynamic actions. At present, material and structure form innovation, passive control and other vibration control technologies are important measures to cope with these challenges.

[0003] For example, in terms of material and structure form innovation, high-strength steel has great potential in realizing the lightweight of offshore wind power support structure. This is because high-strength steel has higher strength and better high-cycle fatigue performance. Public information shows that the Q420M+Q355 combination is used in the Guangdong Nuclear Huizhou Port Wind Power Project, which uses Q420 of 7500 tons to achieve a 10% weight reduction. Baowu officially obtained the "BWind500MD, BWind420MD high-strength steel butt joint fatigue performance evaluation" technical evaluation compliance certificate, which marks that Baowu has officially become the first material supplier in the industry to successfully break through the limitations of international standards and can apply high-strength steel to the lightweight and weight-reducing wind power tower design and manufacturing based on fatigue design. The 500Mpa high-strength steel wind power tower has been completed and hoisted, which can save 20% of steel and increase the fatigue life by 25% under the same installed capacity. Baosteel has obtained the first batch of 500Mpa wind power steel orders, which reduces the single tower weight from 308 tons to 277 tons, and has good weight reduction and cost reduction effect.

[0004] Among the existing passive control technologies, TMD (Tuned Mass Damper) and TLD (Tuned Liquid Damper) are two key inertia-based control means. They effectively reduce the vibration of wind power structures by installing specific devices at the top of the tower and using the principle of reaction force. TMD has been widely used in various engineering scenarios due to its simple principle and convenient manufacturing. To meet the special needs of wind power support structures, various improved TMDs have been developed, such as RID-TMD (Rotary Inertial Double Tuned Mass Damper), PS-TMD (Pre-stressed Tuned Mass Damper), PTMD (Suspension Tuned Mass Damper), and TMDI (Inertial Tuned Mass Damper). At the same time, TLD, as another important passive control device, ingeniously uses liquid as a counterweight and energy dissipation material to achieve multi-directional vibration reduction effect without additional energy-consuming equipment. It has a high cost-effectiveness and low maintenance cost, showing a broad application prospect. However, inertia-based technologies have limitations, such as the control effect may not be ideal for specific actions such as near-field earthquakes, and the calculation and analysis need to fully consider various complex working conditions.

[0005] In addition, material-based passive energy dissipation technology has also received some attention. This type of technology is usually installed at the lower part of the structure and dissipates energy through material deformation to provide additional damping to the structure to reduce vibration. Although related research is still insufficient, its great potential in reducing costs and increasing efficiency has been initially seen. Energy dissipation schemes using friction, viscosity, viscoelasticity, and other mechanisms are being explored in depth and are expected to effectively compensate for the shortcomings of inertia-based schemes in some areas, such as repairing and extending the service life of wind towers or foundations. However, technical maturity and practical applicability are key factors that restrict the application of material-based energy dissipation technology. Wind towers are high-soft and thin-walled conical structures, making it difficult to provide a stable support environment for material-based energy dissipation technology. Although some energy dissipation schemes and their amplification devices show certain vibration reduction effects in computational analysis, their installation methods may pose a serious challenge to the local stress control of the tower cylinder wall. At the same time, the existing few scale tests and computational analyses are still insufficient in examining the difficulty of connecting thin-walled structures and dampers.

[0006] Compared with other material-based energy dissipation schemes, constrained damping schemes (such as Figure 1The embodiment shown in the lower part of the wind tower is more convenient and does not cause complex local stress problems, and therefore has a significant advantage in practical application. The constrained damping layer is made of viscoelastic material as the constrained layer, and the outer layer is made of material with high modulus (such as steel) as the constrained layer, which can be attached to the surface of the cylindrical shell structure to provide damping performance. When the wind tower is bent and deformed, the constrained layer generates relative deformation between the base layer and the constrained layer, and then undergoes shear deformation to consume energy and provide additional damping to the structure. However, due to the limited deformation of the wind tower cylinder itself, how to amplify the deformation of the damping layer material through specific measures to achieve damping efficiency is a challenge.

[0007] In summary, there are still great challenges in reducing costs and increasing efficiency through material and structural form innovation, vibration control measures, mainly including the following three points. (1) The mixed tower commonly used in land-based wind turbines and other material-based wind turbine structures are restricted by transportation and installation conditions; high-strength steel has potential in lightweighting but no publicly reported research reports; (2) Passive control measures mainly focus on TMD and TLD based on inertia, while material-based damping measures are less researched due to installation space limitations, damping effects, and other factors, and have low technical maturity. (3) Research on new material-based wind turbine structures and passive control is often conducted independently, and the synergistic effect of the two has not been considered. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art and provide a wind tower structure provided with a high-strength steel constrained damping enhancement section and a design method thereof, which can overcome the limitations of current inertia-based and material-based technologies and achieve synergistic effect of additional damping while reducing steel consumption and improving damping effect.

[0009] The purpose of the present application can be achieved by the following technical solution: a wind tower structure provided with a high-strength steel constrained damping enhancement section, comprising a non-energy-consuming section and a high-strength steel constrained damping enhancement section, the high-strength steel constrained damping enhancement section comprising a high-strength material layer, a damping layer, and a constrained layer, wherein the upper and lower ends of the high-strength material layer are connected to the non-energy-consuming section of the tower body, the damping layer and the constrained layer are not directly connected to the non-energy-consuming section, the damping layer is attached to one side of the high-strength material layer, and the other side of the damping layer is attached to the constrained layer.

[0010] Further, the strength and high-cycle fatigue performance of the high-strength material layer is higher than that of the steel material used in the non-energy-consuming section.

[0011] Further, the thickness of the constrained layer is less than the thickness of the original energy-consuming section of the wind tower minus the thickness of the high-strength material layer, wherein the original energy-consuming section refers to the energy-consuming section of the traditional constrained damping measure;

[0012] The thickness of the high-strength material layer is less than or equal to the thickness of the non-energy-consuming section tower body connected above and below.

[0013] Further, the thickness of the constraint layer is 2-15 mm.

[0014] A wind turbine tower structure design method provided with a high-strength steel constraint damping enhancement section, comprising the following steps:

[0015] S1. Perform preliminary design of the wind turbine tower and its foundation according to the existing method;

[0016] S2. Determine the arrangement position of the high-strength steel constraint damping enhancement section according to the existing constraint damping optimization method;

[0017] S3. Process the high-strength material layer using high-strength steel to reduce the local cross-sectional size;

[0018] S4. Perform parameter analysis and optimization of the high-strength steel constraint damping enhancement section through modal damping ratio calculation to determine the structure scheme and additional damping of the high-strength steel constraint damping enhancement section.

[0019] Further, the calculation process of the modal damping ratio in step S4 comprises:

[0020] Neglecting the change of the bending moment of the constraint section range tower drum, the constraint tower wall with a width of b is taken for stress and deformation analysis; the two ends of the constraint damping section tower wall are subjected to bending axial force F, and part of the axial force is transmitted to the constraint layer through the shear stress of the damping layer through half of the constraint section length, combining the stress and strain distribution of the tower wall, the damping layer and the constraint layer, and considering the boundary conditions, the shear strain energy of the transmission section damping layer, the total strain energy of the transmission section damping layer, the shear strain energy ratio of the damping layer, the total strain energy of the wind turbine tower under the action of the tower top horizontal load P, the total strain energy of the constraint damping section, and the shear strain energy of the constraint damping section damping layer are calculated in sequence according to the balance condition, the geometric condition, the physical condition, and the boundary condition. According to the modal strain energy method, the first-order modal damping ratio of the wind turbine tower containing the constraint damping section is calculated.

[0021] Further, the process of performing parameter analysis and optimization of the high-strength steel constraint damping enhancement section in step S4 is specifically to analyze the influence of the damping layer thickness, the constraint layer thickness, and the tower wall thickness on the modal damping ratio to determine the thickness of each layer in the high-strength steel constraint damping enhancement section.

[0022] Further, the analysis of the influence of the damping layer thickness, the constraint layer thickness, and the tower wall thickness on the modal damping ratio comprises:

[0023] Analysis process 1, separately analyze the influence of the damping layer thickness on the modal damping ratio;

[0024] Analysis process 2, analyze the modal damping ratio when the damping layer thickness is optimal;

[0025] Analysis process 3, analyze the modal damping ratio when the damping layer thickness is optimal and the total thickness of the constraint layer and the tower wall is constant;

[0026] Analysis process 4, analyze the modal damping ratio when the damping layer thickness is optimal and the ratio of the constraint layer thickness to the tower wall thickness is constant;

[0027] Analysis process 5, analyze the maximum shear strain of the damping layer when the damping layer thickness is optimal.

[0028] Further, in the analysis process 1, the influence of the damping layer thickness t1 on the modal damping ratio is:

[0029]

[0030] When Λ = 1.639 The damping ratio ξ reaches the maximum value, that is, under the given other parameters, there is an optimal value of the damping layer thickness t1 Adjust t1 by adjusting the length of l, divide l into multiple segments to reduce the damping layer thickness;

[0031] Where H is the tower height, h is the height of the constraint damping section, which can be approximately taken as the height of the top of the constraint damping section, η dam is the loss factor of the damping material, η s is the loss factor of the original structure, D is the diameter of the constraint damping section tower, W0 is the bending section modulus of the constraint damping section tower, m is the tower top concentrated mass, f is the first order frequency of the wind tower, is a dimensionless parameter, l is the transition section length, that is, half of the constraint damping section length, G is the shear modulus of the damping material, E is the elastic modulus of the steel material, t0 and t2 are the thicknesses of the constraint damping section tower wall and the constraint layer, respectively;

[0032] In the analysis process 2, the modal damping ratio ξ is:

[0033]

[0034] At this time, the damping ratio increases with the increase of t2, and when t2 / t0 is greater than 3, the damping ratio will not be obviously improved by further increasing t2, so the design t2 / t0 is taken as 1-3; the damping ratio decreases with the increase of t0; the damping ratio increases linearly with the increase of l; the damping ratio decreases with the increase of h;

[0035] In the analysis process 3, the modal damping ratio ξ is:

[0036]

[0037] At this time, the damping ratio decreases rapidly with the increase of t0, T=t0+t2 is the total thickness of the constraint layer and the tower wall;

[0038] In the analysis process 4, the modal damping ratio ξ is:

[0039]

[0040] At this time, the damping ratio decreases with the increase of the total thickness T of the constraint layer and the tower wall, and alpha is the thickness ratio of the constraint layer and the tower wall;

[0041] In the analysis process 5, the maximum shear strain of the damping layer is:

[0042]

[0043] At this time, the maximum shear stress is inversely proportional to l, and l is too small to cause the maximum shear strain τ 1max of the damping layer to be too large.

[0044] Further, the step S4 further performs re-design of the wind power tower according to the additional damping after the additional damping is calculated, so as to convert the performance redundancy of the additional damping into the steel saving of the overall structure.

[0045] Compared with the prior art, the present application has the following advantages:

[0046] The present application proposes a new wind power tower structure integrating high-strength steel and constraint damping layer, which replaces the ordinary steel of the constraint damping section with high-strength steel material on the basis of ordinary constraint damping treatment, obtains a high-strength steel constraint damping efficiency section, and can realize the following three effects: Effect 1 - Since high-strength steel has higher strength and better high-cycle fatigue performance, after replacing the material of the constraint damping section with high-strength steel, only a smaller cross section is needed to meet the strength and fatigue performance requirements of the replacement section, thereby saving the steel of the replacement section;

[0047] Effect 2 - Like ordinary steel constraint damping, when the wind power tower is subjected to tensile and compressive deformation, the damping layer in the constraint damping treatment undergoes shear deformation, thereby dissipating vibration energy;

[0048] Effect 3 - Unlike ordinary steel constraint damping, the tower cylinder of the high-strength steel constraint damping section can reduce the cross-sectional size while meeting the strength and fatigue performance requirements, and the reduction of the cross-sectional size will make the tower wall made of high-strength steel deform more than the ordinary steel constraint damping section, and further amplify the strain of the damping material, thereby increasing the energy dissipation capacity.

[0049] Thus, the high-strength steel and the constraint damping are synergized, the high-strength steel is used to reduce the weight of the tower body, the deformation of the damping material of the constraint damping is enlarged, and the synergistic effect of the additional damping is realized, so that the damping effect is significantly improved, and the steel consumption is significantly reduced, and through the organic combination of the high-strength steel and the constraint damping layer, the double promotion of material lightening and structure high performance is realized.

[0050] In the design of the high-strength steel constraint damping synergistic section, the modal damping ratio is calculated by the designed simplified calculation, the parameter analysis and optimization of the damping enhancement section are carried out, and then the structure scheme of the high-strength steel constraint damping synergistic section and the additional damping are obtained. First, the first-order modal damping ratio of the wind power tower containing the constraint damping section is calculated by the designed simplified modal strain energy method, and then the influence of the damping layer thickness, the constraint layer thickness and the tower wall thickness on the modal damping ratio is analyzed, so as to determine the thickness of each layer in the high-strength steel constraint damping synergistic section. The accuracy of the structure design of the high-strength steel constraint damping synergistic section can be ensured, the influence law of each parameter on the performance can be accurately grasped, the damping ratio can be directly calculated by using the designed simplified formula, and the repeated trial calculation of the FEM optimization modal damping is avoided. In addition, the wind power tower can be further designed according to the additional damping, so that the performance redundancy of the additional damping is converted into the steel saving of the overall structure, that is, the steel cost is further saved. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is a schematic diagram of the existing constraint damping scheme;

[0052] Figure 2 It is a schematic diagram of the structure principle of the present application;

[0053] Figure 3 It is a schematic diagram of the design method flow of the present application;

[0054] Figure 4 It is a schematic diagram of the stress and deformation of the constraint damping section when the modal damping ratio is calculated;

[0055] Figure 5 It is a schematic diagram of the equivalent single degree of freedom system of the wind power tower when the modal damping ratio is calculated;

[0056] Figures 6a-6e It is a schematic diagram of the parameter analysis of the high-strength steel constraint damping synergistic section;

[0057] Figure 7 It is a schematic diagram of the damping arrangement area in the embodiment;

[0058] Figure 8a It is a schematic diagram of the NERL 5MW single pile offshore wind power tower model in the embodiment;

[0059] Figure 8b It is a simplified FEM model of the wind power tower in the embodiment;

[0060] Figure 9a and 9b This is a schematic diagram illustrating the influence of mesh size on modal results in the embodiment;

[0061] Figure 10 This is a schematic diagram of numerical analysis in the example;

[0062] Figure 11 This is a schematic diagram of the modal frequencies of each constraint damping scheme in the embodiments;

[0063] Figure 12 The modal damping ratios of each constraint damping scheme in the embodiments are shown.

[0064] Figures 13a-13d This is a schematic diagram of the strain energy density of each constraint damping scheme in the embodiments;

[0065] Figures 14a-14d This is a schematic diagram of the strain field for each constraint damping scheme in the embodiments. Detailed Implementation

[0066] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0067] Example

[0068] like Figure 2 As shown, a wind turbine tower structure with a high-strength steel confined damping enhancement section includes a non-energy-dissipating section and a lightweight damping enhancement section. The lightweight damping enhancement section includes a high-strength material layer, a damping layer, and a confining layer. The upper and lower ends of the high-strength material layer are connected to the non-energy-dissipating section of the tower body, while the damping section and the confining section are not directly connected to the non-energy-dissipating section. The damping layer is attached to the high-strength material layer on one side and the confining layer is attached to the other side.

[0069] In practical applications, the high-strength material layer can be made of high-strength steel, which has higher strength and high-cycle fatigue performance, while the steel used in the non-damping energy dissipation section must be of lower quality than that used in the high-strength material layer. For example, the high-strength material layer can be made of Q460, Q550, Q690, or Q960 steel. Alternatively, when Q550 steel is used for the high-strength material layer, Q355 steel can be used for other parts of the tower. Furthermore, the high-strength material layer can also be made of high-strength materials such as carbon fiber.

[0070] When the high-strength material layer is high-strength steel, the thickness of the damping layer is preferably 2-15 mm, and the damping layer should be as thin as possible under the condition of meeting the limit strain of the damping material (Note: this is the optimization rule, and the additional damping effect is better when the damping layer is thinner and the constraint layer is thicker); in particular, when the high-strength material layer is high-strength steel, the thickness of the constraint layer is less than the thickness of the original wind power tower after preliminary design minus the high-strength material layer (Note: based on this principle, the additional damping can be increased without increasing the amount of steel, and the additional damping will inevitably reduce the response of the structure, so the structure can be optimized based on the additional damping to ensure the inevitability of achieving the lightweight goal).

[0071] When the high-strength steel scheme is adopted, the thickness ratio of the constraint layer to the damping layer is in the range of 5-20; and under the condition of meeting other constraints, the thickness ratio in the range is preferably larger.

[0072] The application also provides a wind power tower structure design method with a high-strength steel constraint damping efficiency increasing section, as shown in Figure 3 The method comprises the following steps:

[0073] S1, performing preliminary design of the wind power tower and its foundation according to the existing method;

[0074] S2, determining the arrangement position of the high-strength steel constraint damping efficiency increasing section according to the existing constraint damping optimization method;

[0075] S3, using high-strength steel to process the high-strength material layer and reduce the local cross-sectional size;

[0076] S4, performing parameter analysis and optimization of the high-strength steel constraint damping efficiency increasing section through modal damping ratio calculation to determine the structure scheme and additional damping of the high-strength steel constraint damping efficiency increasing section.

[0077] The high-strength steel constraint damping provided by the application is based on the ordinary constraint damping treatment, and the ordinary steel of the constraint damping section is replaced by high-strength steel. The high-strength steel constraint damping has the following three effects: (1) Effect 1 - Since the high-strength steel has higher strength and better high-cycle fatigue performance, after replacing the material of the constraint damping section with high-strength steel, only a smaller cross section is needed to meet the strength and fatigue performance requirements of the replacement section, thereby saving the steel of the replacement section; (2) Effect 2 - Like ordinary steel constraint damping, when the wind power tower is subjected to tensile and compressive deformation, the damping layer in the constraint damping treatment undergoes shear deformation, thereby dissipating vibration energy; (3) Effect 3 - Unlike ordinary steel constraint damping, the tower cylinder of the high-strength steel constraint damping section can reduce the cross-sectional size while meeting the strength and fatigue performance requirements, and the reduction of the cross-sectional size will make the tower wall made of high-strength steel deform more than the ordinary steel constraint damping section, and further amplify the strain of the damping material, thereby increasing the energy dissipation capacity.

[0078] It is worth noting that in the high-strength steel constrained damping scheme, this additional energy dissipation phenomenon due to the strength and fatigue performance enhancement of high-strength steel with a damping layer is a synergistic effect between constrained damping and high-strength steel cylinder wall. This synergistic effect makes the combination of high-strength steel and constrained damping more effective than the superposition of the effects of the two alone, which is the mechanism of the synergistic effect of high-strength steel constrained damping. This feature of high-strength steel constrained damping is beneficial to achieving additional damping with lower cost, thereby achieving the purpose of cost reduction and efficiency improvement. To comprehensively evaluate the cost reduction and efficiency improvement caused by the three effects, the application of the above technical scheme is used, and a simplified method is used to quantitatively evaluate the cost and benefit of the high-strength steel constrained damping wind power tower compared with the traditional wind power tower.

[0079] First, introduce the damping composition and additional damping of the wind power tower containing the constrained damping section. The actual wind power structure has complex damping, including start-up damping, structural damping, hydrodynamic damping, soil damping, and additional damping contributed by the damper ξ ad . The composition of the total damping ξ total is shown in the following formula.

[0080] ξ total = ξ aero + ξ struc + ξ hydro + ξ soil + ξ ad

[0081] For the constrained damping wind power tower, the damping contributed by the energy dissipation of the viscoelastic material in the damping layer belongs to additional damping. In the subsequent evaluation, the damping excluding ξ ad is simplified to a fixed value ξ non , as shown in the following formula.

[0082] ξ total = ξ w / o + ξ ad

[0083] And according to the prior art, the damping cost of the uncontrolled structure and its value is a complex problem, and it is generally considered to be in the range of 1% to 5%.

[0084] Then the application proposes a simplified calculation theory of modal damping ratio of wind power tower containing constrained damping section. The tower cylinder mainly undergoes bending deformation under horizontal load, and the tower wall undergoes longitudinal tensile (compressive) deformation under the action of bending normal stress. After the tower wall is pasted with constrained damping, the longitudinal tensile (compressive) deformation of the tower wall causes the damping layer to produce shear deformation, as shown in Figure 4

[0085] ​Neglecting the change of bending moment of the tower wall in the constrained section, the stress and deformation of the tower wall with width b is analyzed; the two ends of the tower wall in the constrained damping section are subjected to bending axial force F, and part of the axial force is transmitted to the constraint layer through the shear stress of the damping layer through half of the length of the constrained section, and the stress and deformation mechanism of the transmission section is as shown in Figure 4 The stress and strain distribution of the tower wall, damping layer and constraint layer is as shown in Figure 4 .

[0086] According to the balance condition, it can be known that:

[0087] dF2(x)=τ1(x)bdx (1)

[0088] F1(x)+F2(x)=F (2)

[0089] According to the geometric condition, it can be known that:

[0090] γ1(x)t1=Δ0(x)-Δ2(x) (3)

[0091] According to the physical condition, it can be known that:

[0092] τ1(x)=Gγ1(x) (4)

[0093]

[0094] Solving equations (1)-(6) and considering the boundary condition τ1(l)=0, it can be obtained that:

[0095]

[0096] wherein: dimensionless parameter l is the length of the transition section, which is half of the length of the constrained damping section; G is the shear modulus of the damping material; E is the elastic modulus of the steel material; t0, t1 and t2 are the thicknesses of the tower wall, damping layer and constraint layer in the constrained damping section, respectively.

[0097] The shear strain energy of the damping layer in the transmission section:

[0098]

[0099] The total strain energy of the damping layer in the transmission section:

[0100]

[0101] The proportion of the shear strain energy of the damping layer:

[0102]

[0103] The first modal damping ratio of the wind turbine tower with the constrained damping section: (modal strain energy method)

[0104] The first modal of a wind turbine tower can be calculated by a single degree of freedom system with mass concentrated at the top of the tower (as shown in Fig. 1), so the first modal strain energy distribution is the same as that under the action of a horizontal force at the top of the tower. Figure 5

[0105] The total strain energy of the wind turbine tower under the action of a horizontal load P at the top of the tower is:

[0106]

[0107] wherein δ is the flexibility coefficient, m is the mass m RNA concentrated at the top of the tower, and f is the first frequency of the wind turbine tower.

[0108] The total strain energy of the constrained damping section is the work done by the bending moment M (M = P(H - h)) acting on both ends of the constrained damping section:

[0109]

[0110] wherein D is the diameter of the tower cylinder of the constrained damping section, W0 is the bending section modulus of the tower cylinder of the constrained damping section,

[0111] The shear strain energy of the damping layer of the constrained damping section is:

[0112]

[0113] The first modal damping ratio of the wind turbine tower with the constrained damping section is calculated according to the modal strain energy method:

[0114]

[0115] wherein H is the height of the top of the tower, h is the height of the constrained damping section, which can be approximately taken as the height of the top of the constrained damping section, η dam is the loss factor of the damping material, and η s is the loss factor of the original structure.

[0116] Through the above simplified calculation process, the modal damping can be directly and quickly calculated, which can greatly improve the calculation efficiency compared with the traditional finite element analysis calculation method, while ensuring the calculation accuracy.

[0117] Then, the modal damping ratio parameters of the wind turbine tower with the constrained damping section are analyzed, as shown in Fig. 2, which mainly include: Figures 6a-6e

[0118] 1. The influence of the thickness t1 of the damping layer on the modal damping ratio

[0119]

[0120] When Λ = 1.639 ​​The damping ratio ξ reaches the maximum value. That is, under the given other parameters, the damping layer thickness t1 has an optimal value The t1 can be adjusted by adjusting the length of l, and l can be divided into multiple sections to reduce the thickness of the damping layer.

[0121] 2. When the damping layer thickness takes the optimal value, the modal damping ratio ξ is:

[0122]

[0123] At this time, the damping ratio increases with the increase of t2, and when t2 / t0 is greater than 3, the damping ratio will not be obviously improved by further increasing t2. It is recommended that t2 / t0 takes 1-3; the damping ratio decreases with the increase of t0; the damping ratio increases linearly with the increase of l; and the damping ratio decreases with the increase of h.

[0124] 3. When the damping layer thickness takes the optimal value and the total thickness of the constraint layer and the tower wall (t0+t2=T) is constant, the modal damping ratio ξ is:

[0125]

[0126] At this time, the damping ratio decreases rapidly with the increase of t0.

[0127] 4. When the damping layer thickness takes the optimal value and the thickness ratio of the constraint layer to the tower wall is constant (t0=αT), the modal damping ratio ξ is:

[0128]

[0129] At this time, the damping ratio decreases with the increase of the total thickness T of the constraint layer and the tower wall.

[0130] 5. When the damping layer thickness takes the optimal value, the maximum shear strain of the damping layer is:

[0131]

[0132] At this time, the maximum shear stress is inversely proportional to l, and l should not be too small to avoid excessive maximum shear strain of the damping layer.

[0133] Therefore, reducing the thickness of the tower wall of the constraint damping section is the most effective measure to improve the modal damping ratio of the wind turbine tower. At the same time, the reduction of the tower wall thickness will result in the reduction of the static force and fatigue bearing capacity of the bottom section of the constraint damping section. In order to avoid the weak link in the constraint damping section, the thinned cylinder wall of the constraint damping section can be made of high-strength steel with higher static force and fatigue bearing capacity, i.e., the high-strength steel constraint damping section scheme.

[0134] To verify the effectiveness of the scheme, the embodiment applies the above technical scheme, adopts NREL 5MW wind tower model designed and published by the United States renewable energy laboratory and widely used in offshore wind energy technology concept research as a calculation model, and simultaneously refers to the single pile foundation with a diameter of 6m of the wind tower foundation of the OC3 project, the foundation enters the soil with a depth of 36m, and the average sea level is 20m away from the mud line. The main components of the model include the tower body, single pile, blade, hub and cabin, etc., the main characteristics are shown in Tables 1-3, and the damping material parameters of the damping layer of the constraint damping scheme are shown in Table 4.

[0135] Table 1

[0136]

[0137] Table 2

[0138] Component Material Young's modulus Poisson's ratio Density Tower Steel 210 GPa 0.3 8500 kg / m 3 ]] Single pile Steel 210 GPa 0.3 7850 kg / m 3 ]]

[0139] Table 3

[0140] Property Value Coordinate position (x, y, z) of the RNA (-0.417,0.00,1.967)m Moment of inertia of the RNA 350 000 kg Moment of inertia (Jxx, Jyy, Jzz) of the RNA <![CDATA[(4.370,2.353,2.542)×10 7 kg·m 2 ]]>

[0141] Table 4

[0142] Component Material Young's modulus Poisson's ratio Density Loss factor Viscoelastic layer Z1 2.61 MPa 0.49 1000 kg / m 3 ]] 1.06

[0143] Taking the 5MW standard wind turbine model as an example, the area above the average sea level by 10m is replaced by a high-strength steel constraint damping section, and the high-strength steel constraint damping section scheme shown in Fig. Figure 7 (b) is obtained. As a comparison, the constraint damping is additionally attached to the tower bottom 10m area where the wind tower deforms greatly, and the traditional constraint damping scheme shown in Fig. Figure 7 (a) is obtained.

[0144] The detailed parameters of each constraint damping scheme are shown in Table 5, wherein the tower wall thickness of the high-strength steel scheme is determined by replacing the cross-sectional bearing capacity, the constraint layer thickness ratio t2 / t0 is 1, and the damping layer thickness is the optimal thickness.

[0145] Table 5

[0146]

[0147] When the original tower damping ratio is 1%, the modal damping ratio of each constraint damping scheme is calculated according to formula (15) and shown in Table 6.

[0148] Table 6

[0149] Scheme Q355 Q460 Q550 Q690 Q960 First order modal damping ratio 1.47 1.70 1.83 2.04 2.38

[0150] After that, the numerical verification of the modal damping ratio calculation theory is carried out:

[0151] (1) Structure model and boundary conditions

[0152] The NERL 5MW single-pile offshore wind tower model shown in FIG. 1 is established by using ABAQUS software, and a simplified finite element model is shown in FIG. 2, wherein: the top head (RNA) is simulated by a concentrated inertia, and the inertia parameters are shown in Table 3; the tower body and the pile body are simulated by C3D8R solid elements, and the grid size is not greater than 0.5m; the influence of pile-water interaction on the dynamic characteristics of the wind tower is simulated by the added mass method; and the pile-soil interaction is simulated by a distributed soil spring, which is realized by a grounding spring in Abaqus. Figure 8a Figure 8b The NERL 5MW single-pile offshore wind tower model shown in FIG. 1 is established by using ABAQUS software, and a simplified finite element model is shown in FIG. 2, wherein: the top head (RNA) is simulated by a concentrated inertia, and the inertia parameters are shown in Table 3; the tower body and the pile body are simulated by C3D8R solid elements, and the grid size is not greater than 0.5m; the influence of pile-water interaction on the dynamic characteristics of the wind tower is simulated by the added mass method; and the pile-soil interaction is simulated by a distributed soil spring, which is realized by a grounding spring in Abaqus.

[0153] To ensure the accuracy of the simulation results, the model is verified in this embodiment. By comparing with the modal analysis results in the prior art (as shown in Table 7), the effectiveness and accuracy of the finite element model are verified.

[0154] Table 7

[0155]

[0156] (2) Load and damping parameters

[0157] The fluctuating wind load is the main dynamic load leading to the fatigue of the pile-tower part above sea level, and the fluctuating wind load is affected by environmental state parameters. In order to simplify the calculation, only the normal operation condition with a larger probability is calculated in this embodiment, wherein the average wind speed is taken as the rated wind speed 11.4m / s, and the turbulence intensity I is taken as 0.1. According to the wind environment parameters under the normal operation condition, the fluctuating wind load acting on the tower top can be calculated. As known from the foregoing, the modal damping ratio of the wind tower in the FA direction under the operation condition may be about 1% to 5%, and therefore the modal damping ratio is divided into 1% and 5% in the calculation of the dynamic response of the structure in the FA direction.

[0158] (3) Treatment of variable cross-section and mesh division

[0159] The different wall thickness sections of the wind tower are connected by rigid connection, and since the modal analysis mainly studies the overall characteristics of the tower drum, the variable cross-section can be simplified in modeling. In this embodiment, the wall thickness is linearly transitioned, and the slope of the transition section is 1:5.

[0160] In order to determine the grid size of the finite element model, taking the Q550 high-strength steel constrained damping scheme as an example, the influence of the grid size on the modal frequency is studied. First, only the damping layer is divided into three equal parts along the thickness direction, and the ring direction grid size is taken as 0.05m, then the constrained damping section and the sections 1m above and below it are taken as the grid encryption section, and the other sections are non-grid encryption sections, Figure 9a and Figure 9b ​The variation of the first order modal frequency of the FA direction with the vertical grid size of the encrypted and non-encrypted areas is shown. It can be seen that when the vertical grid size of the encrypted and non-encrypted areas is 0.1 m and 0.5 m respectively, the analysis result has sufficient accuracy, so in the subsequent analysis, this grid size will be used.

[0161] (4) Numerical analysis results

[0162] As shown in Figure 10 , the deviation of the formula calculation result from the finite element analysis result is not more than 10%, which fully shows that the simplified calculation formula proposed in the scheme can accurately calculate the modal damping ratio of the constraint damping wind power tower.

[0163] Further analysis of the influence of the high-strength steel constraint damping scheme on the dynamic characteristics:

[0164] (1) Influence on modal frequency

[0165] The modal frequency of each constraint damping scheme is shown in Figure 11 , the fundamental frequency of the traditional constraint damping scheme after adding damping and constraint layer is relatively increased by about 2% compared with the original tower, and the fundamental frequency of the high-strength steel constraint damping scheme is slightly reduced due to the reduction of the wall thickness of the cylinder, and the reduction amplitude is less than 10%. In summary, the influence of each constraint damping scheme on the modal frequency can be ignored, and the constraint damping scheme can be regarded as a damping vibration reduction scheme.

[0166] (2) Modal damping and damping effect

[0167] After obtaining the modal elastic strain energy (ELES) of each element through the field variable output result in the ABAQUS modal analysis, the modal damping ratio can be calculated according to the modal strain energy method. The calculation results of the modal damping ratio of each constraint damping scheme are shown in Figure 12 , the results show that the constraint damping scheme can effectively improve the first order modal damping ratio of the wind power tower, and the damping improvement effect of the high-steel constraint damping scheme is better than that of the traditional constraint damping scheme.

[0168] (3) Modal strain field and modal strain energy field distribution

[0169] The ABAQUS modal analysis result is the normalized result of the total strain energy, so the modal strain energy results of each scheme can be directly compared, and the size of the modal strain energy of the damping layer can directly reflect the advantages and disadvantages of the constraint damping scheme. At the same time, through the analysis of the modal strain field, the constraint damping deformation mechanism and amplification mechanism can be understood.

[0170] In order to facilitate the comparison of the modal result cloud chart between each scheme, the upper and lower limits of the Q960 high-strength steel constraint damping scheme result are used as the unified upper and lower limits of the legend. The modal strain energy density and longitudinal strain field of the uncontrolled structure and the constraint damping structure are respectively shown in Figures 13a-13d , Figures 14a-14dAs shown in the strain field distribution and strain energy density distribution of the tower drum, the tower drum section with reduced wall thickness is the deformation concentration area, and the constraint damping attached to the deformation concentration area can make the damping layer obtain greater shear strain and strain energy density. The shear strain field distribution of the damping layer is consistent with the aforementioned mechanism analysis. With the decrease of the wall thickness of the constraint section, the shear deformation of the damping layer increases, and the constraint effect of the constraint layer increases.

[0171] With the thinning of the wall thickness of the constraint section, the deformation of the constraint damping section gradually increases, the shear strain of the damping layer increases due to the compression deformation of the drum wall, the strain energy increases, and therefore the additional damping ratio increases.

[0172] With the decrease of the thickness of the damping layer, the shear stiffness of the damping layer increases, the composite cross-section effect is more obvious, and the constraint layer shares more tower load (the difference between the strain in the middle of the tower and the strain at both ends is more significant).

[0173] (4) Mechanism of damping enhancement effect

[0174] Effect on modal frequency: the constraint layer and the damping layer reduce the stiffness reduction caused by the decrease of the tower wall thickness to a certain extent, especially when the shear stiffness of the damping layer is large, the composite cross-section effect is more obvious.

[0175] Table 8

[0176] Modal frequency Q355-O / A Q960 constrained damping scheme Q960 high strength steel scheme 1st FA 0.245 0.224(-9％) 0.219(-11％)

[0177] Damping enhancement mechanism: tower bending model, resulting in tensile or compressive deformation of the drum wall, when the constraint damping is attached to the surface of the drum wall, the tensile or compressive deformation of the drum wall will cause shear deformation of the damping layer, and then cause shear energy dissipation. When the wall of the constraint damping section is thinned, the tensile or compressive deformation of the constraint damping section increases, which will increase the shear deformation of the damping layer and the shear energy dissipation, and the macroscopic performance is the increase of the damping ratio.

[0178] In summary, the present scheme aims at the dual challenges of cost reduction and wind load resistance faced by offshore wind towers in the trend of large-scale development, and innovatively proposes a new type of wind tower structure integrating high-strength steel and constraint damping layer, and systematically studies the potential of the structure in improving damping performance and lightweight level. Through theoretical analysis and numerical simulation, the following main conclusions are drawn:

[0179] (1) (Synergistic effect of high-strength steel and constraint damping layer technology) High-strength steel constraint damping achieves cost reduction and efficiency through three mechanisms, including the use of high-strength steel to reduce section size to directly save steel, the constraint damping layer to provide additional damping to the structure to indirectly achieve cost reduction and efficiency, and the synergistic efficiency mechanism in the high-strength steel constraint damping scheme. Among them, due to the higher strength and high-cycle fatigue performance than ordinary steel, local replacement of high-strength steel can achieve equivalent bearing capacity and fatigue performance of ordinary steel scheme with relatively small section, thereby saving steel; the constraint damping treatment measure can provide additional damping to the structure, thereby optimizing the space of the structure; therefore, the high strength and high-cycle fatigue performance of high-strength steel can effectively reduce the amount of steel, and the constraint damping layer can significantly enhance the wind vibration resistance of the structure through energy dissipation mechanism. The synergistic effect of the two amplifies the strain of the damping material, realizes damping efficiency, and provides a new idea for wind turbine tower design.

[0180] (3) (Additional damping performance and significant damping efficiency) Based on the modal strain energy method, the additional damping ratio of the ordinary steel constraint damping and high-strength steel constraint damping scheme is calculated. The results show that the high-strength steel constraint damping structure provides better additional damping to the structure. Compared with the uncontrolled structure and the ordinary constraint damping scheme, the high-strength steel constraint damping scheme can provide significant additional damping without increasing the amount of steel or even reducing the amount of steel.

[0181] Previous studies only focused on vibration control measures to improve structural damping or used new materials to reduce steel consumption. The wind turbine tower structure proposed in this scheme combines material innovation and passive control technology, realizes the synergistic mechanism between the structural bearing material and the damping energy dissipation material, and achieves the effect of one plus one greater than two. This synergistic effect includes: using high-strength steel to reduce section size to directly save steel; the constraint damping layer provides additional damping to the structure to indirectly achieve cost reduction and efficiency; more importantly, the strain of the thickened high-strength steel used in the tower body is greater than that of the original scheme, thereby amplifying the strain of the damping material and the damping of the structure. The damping amplification effect brought by this synergistic mechanism increases with the increase of the strength of high-strength steel.

[0182] In addition, this scheme significantly increases the damping without increasing the amount of steel used. Previous vibration reduction designs often increase the damping of the structure while also increasing the cost of steel consumption, making it difficult to evaluate the benefits of additional measures, and even having the risk of cost greater than benefit. However, by using this scheme, it is very easy to control and achieve "increasing additional damping without increasing the amount of steel" at the beginning of the design, and the positive gain is significant.

Claims

1. A wind turbine tower structure design method provided with a high-strength steel constraint damping enhancement section, characterized in that, The method comprises the following steps: S1, performing preliminary design of the wind power tower and its foundation according to an existing method; S2, determining the arrangement position of the high-strength steel constraint damping enhancement section according to an existing constraint damping optimization method; S3, processing the high-strength material layer by using high-strength steel, and reducing the local cross-sectional size; S4, performing parameter analysis and optimization of the high-strength steel constraint damping enhancement section through modal damping ratio calculation, and determining the structure scheme and additional damping of the high-strength steel constraint damping enhancement section. The parameter analysis and optimization of the high-strength steel constraint damping enhancement section in step S4 is specifically analyzing the influence of the damping layer thickness, the constraint layer thickness and the tower wall thickness on the modal damping ratio, so as to determine the thickness of each layer in the high-strength steel constraint damping enhancement section. The analysis of the influence of the damping layer thickness, the constraint layer thickness and the tower wall thickness on the modal damping ratio comprises: Analysis process 1, separately analyzing the influence of the damping layer thickness on the modal damping ratio; Analysis process 2, separately analyzing the modal damping ratio when the damping layer thickness takes an optimal value; Analysis process 3, analyzing the modal damping ratio when the damping layer thickness takes an optimal value and the total thickness of the constraint layer and the tower wall is unchanged; Analysis process 4, analyzing the modal damping ratio when the damping layer thickness takes an optimal value and the ratio of the constraint layer thickness to the tower wall thickness is unchanged; Analysis process 5, analyzing the maximum shear strain of the damping layer when the damping layer thickness takes an optimal value. In the analysis process 1, the influence of the damping layer thickness t1 on the modal damping ratio is: when hour Damping ratio The optimal value for the damping layer thickness t1 exists, given other parameters. By adjusting l Adjust t1 by its length. l Divide into multiple segments to reduce the thickness of the damping layer; wherein, H Htis the height of the tower, h Hc is the height of the constraint damping section, which is approximately the height of the top of the constraint damping section, η is the loss factor of the damping material, η0 is the loss factor of the original structure, D Dc is the diameter of the constraint damping section tower, Ec is the flexural modulus of the constraint damping section tower, m M is the concentrated mass at the top of the tower, f ω1 is the first order frequency of the wind turbine tower, ω1 is the first order frequency of the wind turbine tower, l Lc is the length of the transition section, i.e. half the length of the constraint damping section, and G is the shear modulus of the damping material, E E is the elastic modulus of the steel material, and t0 and t2 are the thicknesses of the constraint damping section tower wall and the constraint layer, respectively. In the analysis process 2, the modal damping ratio is: At this time, the damping ratio increases with the increase of t2, and when t2 / t0 is greater than 3, the increase of t2 continues, and the increase of the damping ratio will not be obvious, so t2 / t0 is designed to be 1-3; the damping ratio decreases with the increase of t0; the damping ratio increases linearly with the increase of l h; the damping ratio decreases with the increase of h; In the analysis process 3, the modal damping ratio is: At this time, the damping ratio decreases rapidly with the increase of t0, and T=t0+t2 is the total thickness of the constraint layer and the tower wall. In the analysis process 4, the modal damping ratio is: At this time, the damping ratio decreases with the increase of the ratio of the thickness of the constraint layer to the total thickness T of the tower wall, α is the ratio of the thickness of the constraint layer to the total thickness T of the tower wall. In the analysis process 5, the maximum shear strain of the damping layer is: At this time, the maximum shear stress is inversely proportional to l the thickness of the damping layer, l and too small will result in a maximum shear strain of the damping layer that is too large.

2. The design method of a wind power tower structure provided with a high-strength steel constraint damping enhancement section according to claim 1, characterized in that, The calculation process of the modal damping ratio in step S4 comprises: Ignoring the change of the tower cylinder bending moment in the constraint section range, the stress and deformation of the constraint tower wall with a width of b is analyzed; the two ends of the constraint damping section tower wall are subjected to bending axial force F, and part of the axial force is transmitted to the constraint layer through the shear stress of the damping layer through half of the constraint section length; combining the stress and strain distribution of the tower wall, the damping layer and the constraint layer, and considering the boundary conditions, the shear strain energy of the damping layer in the transmission section, the total strain energy of the damping layer in the transmission section, the ratio of the shear strain energy of the damping layer, the total strain energy of the wind power tower under the action of the tower top horizontal load P, the total strain energy of the constraint damping section, and the shear strain energy of the damping layer in the constraint damping section are calculated in turn according to the balance condition, the geometric condition, the physical condition, and the constraint damping section damping layer shear strain energy; and then the first-order modal damping ratio of the wind power tower containing the constraint damping section is calculated according to the modal strain energy method.

3. The method of claim 1, wherein the wind turbine tower structure is designed with a high-strength steel confinement and damping enhancement section. After the additional damping is calculated in step S4, the wind power tower is further designed again according to the additional damping, so as to convert the performance redundancy of the additional damping into the steel saving of the overall structure.

4. A wind turbine tower structure provided with a high-strength steel constraint-damping augmentation section, implemented based on the design method of claim 1, characterized in that, The wind power tower comprises a non-energy dissipation section and a high-strength steel constraint damping enhancement section, the high-strength steel constraint damping enhancement section comprises a high-strength material layer, a damping layer and a constraint layer, the upper and lower ends of the high-strength material layer are connected with the non-energy dissipation section of the tower body respectively, the damping layer and the constraint layer are not directly connected with the non-energy dissipation section, one side of the damping layer is attached to the high-strength material layer, and the other side of the damping layer is attached with the constraint layer; The strength and high-cycle fatigue performance of the high-strength material layer are higher than those of the steel material used in the non-energy dissipation section. The thickness of the constraint layer is less than the thickness of the original energy dissipation section of the wind power tower minus the thickness of the high-strength material layer, wherein the original energy dissipation section refers to the energy dissipation section of the traditional constraint damping measure; The thickness of the high-strength material layer is less than or equal to the thickness of the non-energy dissipation section tower body connected above and below.

5. A wind turbine tower structure provided with a high-strength steel confinement-damping- augmentation segment according to claim 4, characterized in that, The thickness of the constraint layer is 2-15 mm.

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