Wind power tower structure provided with high-strength steel constraint damping synergistic section and design method of wind power tower structure

Abstract

The invention relates to a wind power tower structure provided with a high-strength steel constraint damping synergistic section and a design method thereof.The high-strength steel constraint damping synergistic section comprises a high-strength material layer, a damping layer and a constraint layer, the upper end and the lower end of the high-strength material layer are connected with non-energy-consumption sections of a tower body respectively, the damping layer and the constraint layer are not directly connected with the non-energy-consumption sections, and the damping layer and the constraint layer are connected with the non-energy-consumption sections. One side of the damping layer is attached to the high-strength material layer, and the other side of the damping layer is attached to the restraint layer; the design method comprises the steps that firstly, the wind power tower and a foundation of the wind power tower are preliminarily designed, and the arrangement position of the high-strength steel constraint damping synergistic section is determined; the high-strength material layer is made of high-strength steel; and through modal damping ratio calculation, parameter analysis and optimization of the high-strength steel constrained damping synergistic section are carried out, and a corresponding structure scheme and additional damping are determined. Compared with the prior art, the method has the advantages that the limitation of the current inertia-based and material-based technology can be overcome, the synergistic interaction effect on additional damping is realized, and the damping effect is improved while the steel consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wind power tower design, and in particular to a wind power tower structure provided with a high-strength steel constrained damping efficiency enhancement section and a design method thereof. Background Art

[0002] In recent years, offshore wind power has developed rapidly, and the trend of large-scale development is becoming increasingly obvious. As wind power support structures become larger, they evolve into taller towers and longer blades. The design of single-pile wind power towers faces unprecedented challenges in terms of cost reduction, efficiency improvement, and resistance to multiple dynamic forces. At present, innovation in materials and structural forms, and vibration control technologies such as passive control are important measures to meet these challenges.

[0003] For example, in terms of innovation in materials and structural forms, high-strength steel has great potential in achieving lightweight offshore wind power support structures. This is because high-strength steel has higher strength and better high-cycle fatigue performance. Public information shows that CGN Huizhou Port Wind Power Project adopts a combination of Q420M+Q355, which uses 7,500 tons of Q420 to achieve a 10% weight reduction. Baowu was officially awarded the "BWind500MD, BWind420MD High-Strength Steel Butt Joint Fatigue Performance Evaluation" Technical Assessment 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 use high-strength steel for lightweight wind power tower design and manufacturing based on fatigue design. The 500Mpa high-strength steel wind power tower has also been hoisted, which can save 20% of steel and increase fatigue life by 25% under the same installed capacity. Baosteel Group received the first batch order of 500Mpa wind power steel, which reduced the weight of a single tower from 308 tons to 277 tons, achieving good weight reduction and cost reduction effects.

[0004] Among the many existing passive control technologies, TMD (Tuned Mass Damper) and TLD (Tuned Liquid Damper) are two key inertia-based control methods. They effectively reduce the vibration of wind power structures by cleverly installing specific devices on the top of the tower and using the principle of reaction force. TMD has been widely used in various engineering scenarios because of its simple and clear principle and convenient manufacturing. In order to meet the special needs of wind power support structures, a variety of improved TMDs have been developed, such as RID-TMD (rotational inertia dual tuned mass damper), PS-TMD (prestressed tuned mass damper), PTMD (suspended 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-consuming material to achieve multi-directional vibration reduction effects without the need for additional energy-consuming equipment. It is cost-effective and has low maintenance costs, showing broad application prospects. However, inertial-based technology has limitations. For example, the control effect on specific effects such as near-field earthquakes may not be ideal, and the computational analysis needs 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 bottom of the structure, dissipating energy through material deformation, providing additional damping for the structure to reduce vibration. Although relevant research is still insufficient, its great potential in reducing costs and increasing efficiency has begun to emerge. Energy dissipation schemes using various mechanisms such as friction, viscosity, and viscoelasticity are being explored in depth, and are expected to effectively make up for the shortcomings of inertia-based schemes in some aspects, such as repairing and extending the life of wind turbine towers or foundations. However, technical maturity and practical applicability have become key factors restricting the application of material-based energy dissipation technology. As a highly flexible and thin-walled conical structure, wind turbine towers are difficult to provide a stable support environment for material-based energy dissipation technologies. Although some energy dissipation schemes and their amplification devices have shown certain vibration reduction effects in computational analysis, their installation methods may pose severe challenges to the local stress control of the tower wall. At the same time, the existing small number of scaled tests and computational analyses are still insufficient in examining the difficulty of connecting thin-walled structures with dampers.

[0006] Compared with other material-based energy dissipation schemes, constrained damping schemes (such as Figure 1The implementation method of applying the constrained damping layer to the outer periphery of the lower part of the wind tower (as shown in the figure) is more convenient and will not cause complex local stress problems, so it has significant advantages in practical applicability. The constrained damping layer uses a viscoelastic material as the constrained layer, and the outer layer uses a material with a larger modulus (such as steel) as the constraining layer, which can be applied to the surface of the cylindrical shell structure to provide damping performance. When the wind tower is bent and deformed, the constrained layer produces relative deformation between the base layer and the constraining layer, and then deformation dominated by shear occurs to consume energy and provide additional damping for the structure. However, due to the limited deformation of the wind tower itself, how to amplify the deformation of the damping layer material through specific measures to achieve damping efficiency enhancement is a difficult point.

[0007] In summary, there are still huge challenges in reducing costs and increasing efficiency through innovation in materials and structural forms and vibration control measures, mainly including the following three points. (1) The material-based wind turbine structural forms such as hybrid towers commonly used in onshore wind power are restricted by factors such as transportation and installation conditions; high-strength steel has potential in lightweighting, but there are no publicly reported research reports; (2) Research on passive control measures mainly focuses on inertia-based measures such as TMD and TLD, while material damping-based measures are less studied due to factors such as installation space limitations and damping effects, and the technology maturity is low. (3) Research on wind turbine structural forms based on new materials and research on passive control are often carried out independently, and the synergistic effect of the two has not been paid attention to. Summary of the invention

[0008] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a wind turbine 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, achieve a synergistic enhancement effect on additional damping, and improve the damping effect while reducing the amount of steel used.

[0009] The purpose of the present invention can be achieved through the following technical scheme: a wind power tower structure provided with a high-strength steel constrained damping efficiency enhancement section, comprising a non-energy absorbing section and a high-strength steel constrained damping efficiency enhancement section, wherein the high-strength steel constrained damping efficiency enhancement section comprises 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 respectively connected to the non-energy absorbing section of the tower body, the damping layer and the constrained layer are not directly connected to the non-energy absorbing 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 to the constrained layer.

[0010] Furthermore, the strength and high cycle fatigue performance of the steel used in the high-strength material layer are higher than the strength and high cycle fatigue performance of the steel used in the non-energy absorbing section.

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

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

[0013] Furthermore, the thickness of the constrained layer is 2 to 15 mm.

[0014] A method for designing a wind power tower structure provided with a high-strength steel constrained damping efficiency enhancement section comprises the following steps:

[0015] S1. Carry out preliminary design of wind turbine tower and its foundation according to existing methods;

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

[0017] S3. Use high-strength steel to make and process high-strength material layers to reduce local cross-sectional dimensions;

[0018] S4. Through modal damping ratio calculation, parameter analysis and optimization of the high-strength steel constrained damping enhancement section are carried out to determine the structural scheme and additional damping of the high-strength steel constrained damping enhancement section.

[0019] Furthermore, the calculation process of the modal damping ratio in step S4 includes:

[0020] Ignoring the change of tower bending moment in the constraint section range, the constraint tower wall with a width of b is taken for force and deformation analysis; both ends of the tower wall of the constrained damping section are subjected to the bending axial force F, and part of the axial force is transferred to the constrained layer through the shear stress of the damping layer through half of the constraint section length. Combined with the stress and strain distribution of the tower wall, damping layer and constrained layer, the shear strain energy of the damping layer of the transfer section, the total strain energy of the damping layer of the transfer section, the shear strain energy proportion of the damping layer, the total strain energy of the wind tower under the horizontal load P on the tower top, the total strain energy of the constrained damping section, and the shear strain energy of the damping layer of the constrained damping section are calculated in turn according to the equilibrium conditions, geometric conditions, physical conditions, and boundary conditions. Then, the first-order modal damping ratio of the wind tower with the constrained damping section is calculated according to the modal strain energy method.

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

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

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

[0024] Analysis process 2: Analyze the modal damping ratio when the damping layer thickness takes the optimal value;

[0025] Analysis process 3: Analyze the modal damping ratio when the damping layer thickness takes the optimal value and the total thickness of the constraint layer and the tower wall remains unchanged;

[0026] Analysis process 4: Analyze the modal damping ratio when the damping layer thickness takes the optimal value and the ratio of the constraint layer to the tower wall thickness remains unchanged;

[0027] Analysis process 5: Analyze the maximum shear strain of the damping layer when the thickness of the damping layer takes the optimal value.

[0028] Furthermore, 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 its maximum value, that is, when other parameters are given, the damping layer thickness t1 has an optimal value t1 can be adjusted by adjusting the length of l, which can be divided into multiple segments to reduce the thickness of the damping layer;

[0031] Where H is the tower top height, h is the height of the restrained damping section, which can be approximated as the height of the top of the restrained damping section, and 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 tower of the restrained damping section, W0 is the bending section modulus of the tower of the restrained damping section, m is the concentrated mass at the top of the tower, f is the first-order frequency of the wind tower, is a dimensionless parameter, l is the length of the transition section, which is half the length of the constrained damping section, G is the shear modulus of the damping material, E is the elastic modulus of the steel, t0 and t2 are the thickness of the tower wall and the constrained layer of the constrained damping section respectively;

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

[0033]

[0034] At this time, the damping ratio increases at a slower rate with the increase of t2. When t2 / t0 is greater than 3 and t2 continues to increase, the damping ratio will not increase significantly. Therefore, t2 / t0 is designed to be 1 to 3; the damping ratio decreases faster with the increase of t0; the damping ratio increases linearly with the increase of l; the damping ratio decreases faster 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, which 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 constrained layer and the tower wall, where α is the ratio of the constrained layer to the tower wall thickness;

[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. If l is too small, the maximum shear strain τ of the damping layer will be 1max Too large.

[0044] Furthermore, after the additional damping is calculated in step S4, the wind turbine tower is further redesigned according to the additional damping to convert the performance redundancy of the additional damping into a saving in steel usage of the overall structure.

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

[0046] The present invention proposes a novel wind turbine tower structure integrating high-strength steel and a constrained damping layer. On the basis of ordinary constrained damping treatment, the ordinary steel of the constrained damping section is replaced with high-strength steel to obtain a high-strength steel constrained damping efficiency enhancement section, which can achieve the following three effects: Effect 1: Since high-strength steel has both higher strength and better high-cycle fatigue performance, after the material of the constrained damping section is replaced with high-strength steel, only a smaller cross-section is needed to simultaneously meet the strength and fatigue performance requirements of the replacement section, thereby saving steel for the replacement section;

[0047] Effect 2: Like ordinary steel constrained damping, when the wind tower undergoes tensile and compressive deformation, the damping layer in the constrained damping treatment undergoes shear deformation, thereby dissipating the vibration energy;

[0048] Effect 3 - Unlike ordinary steel constrained damping, the tower with high-strength steel constrained damping section can reduce the cross-sectional size while meeting the requirements of strength and fatigue performance. The reduction in cross-sectional size will make the tower wall made of high-strength steel material more deformed than the ordinary steel constrained damping section, and then amplify the strain of the damping material, bringing about an increase in energy dissipation capacity.

[0049] Thereby, the purpose of synergistic enhancement of high-strength steel constrained damping is achieved - while achieving lightweight of the tower body, high-strength steel can amplify the deformation of the damping material of the constrained damping measures, thereby achieving a synergistic effect on the additional damping, which not only achieves a significant improvement in the damping effect, but also can significantly reduce the amount of steel used. Through the organic combination of high-strength steel and the constrained damping layer, a double improvement is achieved: lightweight material and high performance structure.

[0050] When designing the high-strength steel constrained damping enhancement section, the present invention performs parameter analysis and optimization of the damping enhancement section through simplified calculation of the designed modal damping ratio, and then obtains the structural scheme and additional damping of the high-strength steel constrained damping enhancement section. First, the first-order modal damping ratio of the wind turbine tower containing the constrained damping section is calculated through the designed simplified modal strain energy method, and then the influence of the damping layer thickness, the constrained layer thickness, and the tower wall thickness on the modal damping ratio is analyzed to determine the thickness of each layer in the high-strength steel constrained damping enhancement section. The accuracy of the structural design of the high-strength steel constrained damping enhancement section can be ensured, the influence of each parameter on the performance can be accurately grasped, and the damping ratio can be directly calculated using the designed simplified formula, avoiding repeated trial calculations of FEM optimization modal damping. In addition, the wind turbine tower can be further redesigned according to the additional damping, so as to convert the performance redundancy of the additional damping into the steel saving of the overall structure, that is, further saving the steel cost. BRIEF DESCRIPTION OF THE 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 structural principle of the present invention;

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

[0054] Figure 4 It is the schematic diagram of the force and deformation of the constrained damping section when calculating the modal damping ratio;

[0055] Figure 5 Schematic diagram of the equivalent single degree of freedom system of the wind tower when calculating the modal damping ratio;

[0056] Figure 6a~6e It is a schematic diagram of parameter analysis of high-strength steel constrained damping enhancement section;

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

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

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

[0060] Figure 9a and 9b Schematic diagram of the effect of mesh size on modal results in the embodiment;

[0061] Fig.10 It is a numerical analysis schematic diagram in the embodiment;

[0062] Fig.11 Schematic diagram of modal frequencies of various constrained damping schemes in the embodiment;

[0063] Fig.12 is the modal damping ratio of each constrained damping scheme in the embodiment;

[0064] Figures 13a to 13d Schematic diagram of strain energy density of each constrained damping scheme in the embodiment;

[0065] Figures 14a to 14d Schematic diagram of strain field of each constrained damping scheme in the embodiment. DETAILED DESCRIPTION

[0066] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Example

[0068] like Figure 2 As shown, a wind power tower structure provided with a high-strength steel constrained damping efficiency enhancement section includes a non-energy absorbing section and a lightweight damping efficiency enhancement section, wherein the lightweight damping efficiency enhancement section includes a high-strength material layer, a damping layer, and a constrained layer, the upper and lower ends of the high-strength material layer are connected to the non-energy absorbing section of the tower body, while the damping section and the constrained section are not directly connected to the non-energy absorbing section; one side of the damping layer is attached to the high-strength material layer, and the other side is attached to the constrained layer.

[0069] In practical applications, the high-strength material layer can be made of high-strength steel with higher strength and high-cycle fatigue performance, while the steel of the non-damping energy-consuming section is lower than that of the high-strength material layer. For example, the high-strength material layer can be made of Q460, Q550, Q690, and Q960 steel. For another example, when the high-strength material layer is made of Q550, the other parts of the tower body are made of Q355 steel. In addition, 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 to 15 mm, and should be as thin as possible while satisfying the ultimate strain of the damping material (Note: this is the law of optimization, 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 original wind tower thickness after preliminary design minus the high-strength material layer (Note: based on this principle, additional damping can be increased without increasing the amount of steel used, and additional damping will inevitably reduce the response of the structure. The structure can be optimized based on the additional damping, thereby ensuring the necessity of achieving the lightweight goal).

[0071] When the high-strength steel solution is adopted, the thickness ratio of the constraining layer to the damping layer is in the range of 5 to 20; and if other constraints are met, a larger thickness ratio within this range should be taken.

[0072] The present invention also proposes a method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section, such as Figure 3 As shown, the following steps are included:

[0073] S1. Carry out preliminary design of wind turbine tower and its foundation according to existing methods;

[0074] S2. Determine the layout position of the high-strength steel constrained damping enhancement section according to the existing constrained damping optimization method;

[0075] S3. Use high-strength steel to make and process high-strength material layers to reduce local cross-sectional dimensions;

[0076] S4. Through modal damping ratio calculation, parameter analysis and optimization of the high-strength steel constrained damping enhancement section are carried out to determine the structural scheme and additional damping of the high-strength steel constrained damping enhancement section.

[0077] The high-strength steel constrained damping proposed in the present invention is based on the ordinary constrained damping treatment, and the ordinary steel of the constrained damping section is replaced with high-strength steel. High-strength steel constrained damping has the following three effects: (1) Effect 1 - Since high-strength steel has both higher strength and better high-cycle fatigue performance, after the material of the constrained damping section is replaced with high-strength steel, only a smaller cross-section is required to simultaneously 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 constrained damping, when the wind turbine tower undergoes tensile and compressive deformation, the damping layer in the constrained damping treatment undergoes shear deformation, thereby dissipating vibration energy; (3) Effect 3 - Unlike ordinary steel constrained damping, the tower tube of the high-strength steel constrained damping section can reduce the cross-sectional size while meeting the requirements of strength and fatigue performance, and the reduction in cross-sectional size will make the tower wall made of high-strength steel material deform more than that of the ordinary steel constrained damping section, and then amplify the strain of the damping material, bringing about an increase in energy dissipation capacity.

[0078] It is worth noting that in the high-strength steel constrained damping scheme, this phenomenon of additional energy consumption with a damping layer due to the enhanced strength and fatigue performance of high-strength steel is a synergistic effect between constrained damping and the 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 applied separately, which is the mechanism of synergistic efficiency enhancement of high-strength steel constrained damping. This feature of high-strength steel constrained damping is conducive to achieving additional damping at a lower cost, thereby achieving the purpose of reducing costs and increasing efficiency. In order to comprehensively evaluate the cost reduction and efficiency improvement caused by the combination of the three effects, this embodiment applies the above-mentioned technical solution and adopts a simplified method to quantitatively evaluate the cost and benefits of high-strength steel constrained damping wind towers compared to traditional wind towers.

[0079] First, the damping structure and additional damping of the wind turbine tower with constrained damping section are introduced. The damping in the actual wind turbine structure is relatively complex, including starting damping, structural damping, hydrodynamic damping, soil damping and additional damping contributed by the damper. ad Total damping ξ total The composition of is shown below.

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

[0081] For constrained damping wind towers, the damping contributed by the energy dissipation of viscoelastic materials in the damping layer belongs to additional damping. ad The damping outside is simplified to a fixed value ξ non , as shown below.

[0082] ξ total =ξ w / o +ξ ad

[0083] Furthermore, according to the prior art, the damping cost of an uncontrolled structure and its value are complex issues, and are generally considered to be in the range of 1% to 5%.

[0084] The present invention then proposes a simplified calculation theory of the modal damping ratio of a wind turbine tower with a constrained damping section. The tower tube mainly undergoes bending deformation under the action of horizontal loads, and the tower tube wall undergoes longitudinal tensile (compressive) deformation under the action of bending normal stress. After the constrained damping is applied to the outside of the tower wall, the longitudinal tensile (compressive) deformation of the tower wall causes the damping layer to produce shear deformation, such as Figure 4 shown.

[0085] Ignoring the change of tower bending moment in the constrained section, the constrained tower wall with a width of b is taken for stress and deformation analysis; both ends of the tower wall of the constrained damping section are subjected to the bending axial force F, and part of the axial force is transferred to the constrained layer through the shear stress of the damping layer through half the length of the constrained section. The stress deformation mechanism of the transfer section is as follows: Figure 4 As shown in the figure, the stress and strain distribution of the tower wall, damping layer and constraint layer is as follows: Figure 4 shown.

[0086] According to the equilibrium condition:

[0087] dF2(x)=τ1(x)bdx (1)

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

[0089] According to the geometric conditions:

[0090] γ1(x)t1=Δ0(x)-Δ2(x) (3)

[0091] According to physical conditions:

[0092] τ1(x)=Gγ1(x) (4)

[0093]

[0094] By combining equations (1) to (6) and considering the boundary condition τ1(l) = 0, we can obtain:

[0095]

[0096] Among them: dimensionless parameters 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; t0, t1, and t2 are the thicknesses of the tower wall, damping layer, and constrained layer of the constrained damping section, respectively.

[0097] Shear strain energy of the damping layer in the transfer section:

[0098]

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

[0100]

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

[0102]

[0103] The first-order modal damping ratio of a wind tower with a constrained damping section: (Modal strain energy method)

[0104] The first-order mode of a wind tower can be approximated by a single-degree-of-freedom system with mass concentrated at the top of the tower (e.g. Figure 5 Therefore, the first-order modal strain energy distribution is the same as the strain energy distribution under the horizontal force at the top of the tower.

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

[0106]

[0107] Where: δ is the flexibility coefficient, m is the concentrated mass at the top of the tower RNA , f is the first-order frequency of the wind tower.

[0108] The total strain energy of the constrained damping section is the work done by the bending moment M (M = P (Hh)) acting on its two ends:

[0109]

[0110] Where: D is the diameter of the tower of the restrained damping section; W0 is the bending section modulus of the tower of the restrained damping section,

[0111] Shear strain energy of the damping layer in the constrained damping section:

[0112]

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

[0114]

[0115] Where: H is the height of the tower top; h is the height of the constrained damping section, which can be approximated by the height of the top of the constrained damping section; η dam is the loss factor of the damping material; η s is the loss factor of the original structure.

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

[0117] Then the modal damping ratio parameters of the wind tower with constrained damping section are analyzed, such as Figure 6a~6e As shown, it mainly includes:

[0118] 1. Influence of damping layer thickness t1 on modal damping ratio

[0119]

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

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

[0122]

[0123] At this time, the damping ratio increases at a slower rate with the increase of t2. When t2 / t0 is greater than 3, the damping ratio will not increase significantly if t2 is continued to increase. It is recommended that t2 / t0 be 1 to 3; the damping ratio decreases at an accelerated rate with the increase of t0; the damping ratio increases linearly with the increase of l; the damping ratio decreases at an accelerated rate with the increase of h.

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

[0125]

[0126] At this time, the damping ratio decreases rapidly as t0 increases.

[0127] 4. When the damping layer thickness takes the optimal value and the ratio of the constraint layer to the tower wall thickness remains unchanged, 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 constrained layer and the tower wall.

[0130] 5. When the thickness of the damping layer 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] It can be seen that reducing the tower wall thickness of the constrained damping section is the most effective measure to improve the modal damping ratio of the wind tower. At the same time, the reduction of the tower wall thickness will lead to a reduction in the static and fatigue bearing capacity of the bottom section of the constrained damping section. In order to avoid weak links in the constrained damping section, the thinned cylinder wall of the constrained damping section can be made of high-strength steel with higher static and fatigue bearing capacity, that is, the high-strength steel constrained damping section solution.

[0134] To verify the effectiveness of this solution, this embodiment applies the above technical solution, adopts the NREL 5MW wind power tower model designed and released by the US Renewable Energy Laboratory and widely used in the conceptual research of offshore wind energy technology as the calculation model, and refers to the OC3 project wind power tower foundation using a single pile foundation with a diameter of 6m, a foundation burial depth of 36m, and an average sea level of 20m from the mud line. The main components of the model include the tower body, single pile, blades, hub and nacelle, etc. The main characteristics are shown in Tables 1 to 3, and the damping material parameters used in the damping layer of the constrained damping scheme are shown in Table 4.

[0135] Table 1

[0136]

[0137] Table 2

[0138] part Material Young's modulus Poisson's ratio density Tower Steel 210GPa 0.3 <![CDATA[8500kg / m 3 ]]> Single pile Steel 210GPa 0.3 <![CDATA[7850kg / m 3 ]]>

[0139] Table 3

[0140] property Numeric Coordinate position of RNA (x,y,z) (-0.417,0.00,1.967)m RNA's moment of inertia 350000kg RNA moment of inertia (Jxx, Jyy, Jzz <![CDATA[(4.370,2.353,2.542)×10 7 kg·m 2 ]]>

[0141] Table 4

[0142] part Material Young's modulus Poisson's ratio density Loss Factor Viscoelastic layer Z1 2.61MPa 0.49 <![CDATA[1000kg / m 3 ]]> 1.06

[0143] Taking the 5MW standard wind turbine model as an example, the area 10m above the average sea level is replaced by a high-strength steel constrained damping section, and the following is obtained: Figure 7 The high-strength steel restrained damping section scheme is shown in (b). As a comparison, restrained damping is added to the 10m area at the bottom of the wind tower where the deformation is larger. The following is obtained: Figure 7 The traditional constrained damping scheme shown in (a).

[0144] The detailed parameters of each constrained damping scheme are shown in Table 5, where the tower wall thickness of the high-strength steel scheme is determined by replacing the section 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 ratios of each constrained damping scheme are calculated according to formula (15) and are shown in Table 6.

[0148] Table 6

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

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

[0151] (1) Structural model and boundary conditions

[0152] ABAQUS software was used to build Figure 8a The NERL 5MW single pile offshore wind tower model shown in the figure is a simplified finite element model. Figure 8b As shown in the figure, the top nose (RNA) is simulated by concentrated inertia, and its inertia parameters are shown in Table 3; the tower body and pile body are simulated by C3D8R solid unit, and the grid size is not greater than 0.5m; the influence of pile-water interaction on the dynamic characteristics of wind tower is simulated by added mass method; the pile-soil interaction is simulated by distributed soil spring, which is realized by grounding spring in Abaqus.

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

[0154] Table 7

[0155]

[0156] (2) Load and damping parameters

[0157] Fluctuating wind load is the main dynamic load that causes fatigue of the pile tower above sea level. Fluctuating wind load is affected by environmental state parameters. To simplify the calculation, in this embodiment, only the normal operating conditions with a higher probability of occurrence are calculated, where the average wind speed is taken as the rated wind speed of 11.4m / s and the turbulence intensity I is taken as 0.1. According to the wind environment parameters under normal operating conditions, the fluctuating wind load acting on the top of the tower can be calculated. From the above content, it can be seen that the modal damping ratio in the FA direction under the operating condition of the wind tower may be around 1% to 5%. For this reason, this embodiment divides the modal damping ratio into two cases of 1% and 5% when calculating the dynamic response of the structure in the FA direction.

[0158] (3) Variable cross-section processing and meshing

[0159] The wind turbine tower has different wall thickness sections connected by rigid connection. Since the modal analysis mainly studies the overall characteristics of the tower, the variable cross-section can be simplified during modeling. This embodiment uses a linear transition method to handle the variable wall thickness of the cylinder wall, and the slope of the transition section is 1:5.

[0160] In order to determine the mesh size of the finite element model, the influence of mesh size on modal frequency was studied by taking the Q550 high-strength steel constrained damping scheme as an example. First, the damping layer was divided into three equal parts along the thickness direction, and the circumferential mesh size was 0.05m. Then, the constrained damping section and the 1m sections above and below it were used as mesh encryption sections, and the other sections were non-mesh encryption sections. Figure 9a and Figure 9bThe variation of the first-order modal frequency in the FA direction with the vertical grid size in the dense area and the non-densified area is shown. It can be seen that when the vertical grid sizes in the dense area and the non-densified area are 0.1m and 0.5m respectively, the analysis results have sufficient accuracy, so this grid size will be used in subsequent analysis.

[0161] (4) Numerical analysis results

[0162] like Fig.10 As shown, the deviation between the calculation result of the formula and the finite element analysis result does not exceed 10%, which fully demonstrates that the simplified calculation formula proposed in this scheme can more accurately calculate the modal damping ratio of the constrained damping wind tower.

[0163] Then analyze the influence of high-strength steel constrained damping scheme on dynamic characteristics:

[0164] (1) Impact on modal frequency

[0165] The modal frequencies of each constrained damping solution are as follows: Fig.11 As shown in the figure, the fundamental frequency of the traditional constrained damping scheme after adding damping and constrained layers is increased by about 2% compared with the original tower, and the fundamental frequency of the high-strength steel constrained damping scheme is slightly reduced compared with the original tower due to the reduction in the wall thickness of the cylinder, and the reduction is less than 10%. In summary, the influence of each constrained damping scheme on the modal frequency can be ignored, and the constrained damping scheme can be regarded as a damping vibration reduction scheme.

[0166] (2) Modal damping and damping enhancement

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

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

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

[0170] In order to facilitate the comparison of modal result cloud diagrams among various schemes, the upper and lower limits of the Q960 high-strength steel constrained damping scheme results are used as unified upper and lower limits of the legend. The modal strain energy density and longitudinal strain field of the uncontrolled structure and the constrained damping structure are shown in Figure 2. Figures 13a to 13d , Figure 14a to Figure 14dAs shown in the figure, the strain field distribution and strain energy density distribution of the tower indicate that the tower section with reduced wall thickness is the deformation concentration area. Applying constrained damping in the deformation concentration area can enable the damping layer to obtain greater shear strain and strain energy density. The shear strain field distribution of the damping layer is consistent with the aforementioned mechanism analysis. As the wall thickness of the constrained damping section decreases, the shear deformation of the damping layer increases, and the constraint effect of the constrained layer is enhanced.

[0171] As the wall thickness of the constrained section decreases, the deformation of the constrained damping section gradually increases, the shear strain of the damping layer caused by the compression deformation of the cylinder wall increases, the strain energy increases, and therefore the additional damping ratio increases.

[0172] As the thickness of the damping layer decreases, the shear stiffness of the damping layer increases, the effect of the composite section becomes more obvious, and the constrained layer shares the tower load more significantly (the difference between the strain in the middle of the tower and the strain at both ends becomes more significant).

[0173] (4) Mechanism of damping enhancement

[0174] Influence on modal frequency: By adding constraint layers and damping layers, the reduction in stiffness caused by the reduction in tower wall thickness is reduced to a certain extent. Especially when the shear stiffness of the damping layer is large, the composite section effect is more obvious.

[0175] Table 8

[0176] Modal frequency Q355-O / A Q960 Constrained Damping Scheme Q960 high strength steel solution 1st FA 0.245 0.224(-9％) 0.219(-11％)

[0177] Damping efficiency enhancement mechanism: The tower bending model causes the wall to stretch or compress. When the restrained damping is applied to the wall surface, the wall stretch or compress will cause the damping layer to shear, which will result in shear energy consumption. When the wall of the restrained damping section becomes thinner, the stretch or compressive deformation of the restrained damping section increases, which will increase the shear deformation of the damping layer and the shear energy consumption, which is manifested as an increase in the damping ratio in the macroscopic sense.

[0178] In summary, this proposal innovatively proposes a new wind turbine tower structure that combines high-strength steel and a constrained damping layer to address the dual challenges of cost reduction and efficiency improvement and wind load resistance faced by offshore wind turbines in the trend of large-scale construction, and systematically studies the potential of this structure in improving damping performance and lightweighting. Through theoretical analysis and numerical simulation, the following main conclusions are drawn:

[0179] (1) (Synergistic efficiency enhancement of high-strength steel and constrained damping layer technology) High-strength steel constrained damping achieves cost reduction and efficiency improvement through three mechanisms, including using high-strength steel to reduce the cross-sectional size to directly save steel, the constrained damping layer provides additional damping for the structure to indirectly achieve cost reduction and efficiency improvement, and the existence of a synergistic efficiency enhancement mechanism in the high-strength steel constrained damping scheme. Among them, due to its higher strength and high-cycle fatigue performance than ordinary steel, after partial replacement of high-strength steel, the equivalent bearing capacity and fatigue performance of the ordinary steel scheme can be achieved with a relatively small cross-section, thereby saving steel; the constrained damping treatment measures can provide additional damping for the structure, thereby leaving room for structural optimization; therefore, the high strength and high-cycle fatigue performance of high-strength steel can effectively reduce the amount of steel used, while the constrained damping layer significantly enhances the structure's wind vibration resistance through the energy dissipation mechanism. The synergistic effect of the two amplifies the strain of the damping material, achieves damping efficiency enhancement, and provides a new idea for wind turbine tower design.

[0180] (3) (Significant additional damping performance and damping enhancement effect) Based on the modal strain energy method, this scheme calculates the additional damping ratio of the ordinary steel constrained damping scheme and the high-strength steel constrained damping scheme. The results show that the high-strength steel constrained damping structure is better in providing additional damping for the structure. Compared with the uncontrolled structure and the ordinary constrained damping scheme, the high-strength steel constrained damping scheme can provide significant additional damping without increasing the amount of steel or even reducing the amount of steel used.

[0181] Previous studies have only focused on vibration control measures to improve structural damping, or on using new materials to reduce steel usage. The wind tower structure proposed in this proposal combines material innovation with passive control technology to achieve a synergistic mechanism between structural load-bearing materials and damping energy-consuming materials, achieving an effect of one plus one greater than two. This synergistic effect specifically includes: using high-strength steel to reduce the cross-sectional size to directly save steel usage; the constrained damping layer provides additional damping for the structure, thereby indirectly achieving cost reduction and efficiency improvement; more importantly, the tower body uses thinner high-strength steel, and its strain is greater than the original solution, which drives the strain of the damping material to be amplified, thereby amplifying the damping of the structure. The damping amplification effect brought about by this synergistic mechanism increases with the increase in the strength of the high-strength steel.

[0182] Moreover, this solution significantly increases damping without increasing the amount of structural steel. Previous vibration reduction designs often increase the cost of steel while increasing structural damping, and it is not easy to evaluate the benefits of additional measures, and there is even a risk that the cost will exceed the benefit. However, with this solution, it is very easy to control and achieve "increasing additional damping without increasing the amount of steel" at the beginning of the design, and its positive gain is significant.

Claims

1. A wind power tower structure provided with a high-strength steel constrained damping efficiency enhancement section, characterized in that: It includes a non-energy absorbing section and a high-strength steel constrained damping efficiency enhancement section, wherein the high-strength steel constrained damping efficiency enhancement section includes 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 respectively connected to the non-energy absorbing section of the tower body, the damping layer and the constrained layer are not directly connected to the non-energy absorbing 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 to the constrained layer.

2. A wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 1, characterized in that: The strength and high cycle fatigue performance of the steel used in the high-strength material layer are higher than the strength and high cycle fatigue performance of the steel used in the non-energy consuming section.

3. A wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 1, characterized in that: The thickness of the constrained layer is less than the thickness of the original energy-absorbing section of the wind power tower minus the thickness of the high-strength material layer, wherein the original energy-absorbing section refers to the energy-absorbing section of the traditional constrained damping measures; The thickness of the high-strength material layer is less than or equal to the thickness of the non-energy-consuming tower body connected above and below it.

4. A wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 3, characterized in that: The thickness of the constrained layer is 2 to 15 mm.

5. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section, characterized in that: The following steps are involved: S1. Carry out preliminary design of wind turbine tower and its foundation according to existing methods; S2. Determine the layout position of the high-strength steel constrained damping enhancement section according to the existing constrained damping optimization method; S3. Use high-strength steel to make and process high-strength material layers to reduce local cross-sectional dimensions; S4. Through modal damping ratio calculation, parameter analysis and optimization of the high-strength steel constrained damping enhancement section are carried out to determine the structural scheme and additional damping of the high-strength steel constrained damping enhancement section.

6. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 5, characterized in that: The calculation process of the modal damping ratio in step S4 includes: Ignoring the change of tower bending moment in the constraint section range, the constraint tower wall with a width of b is taken for force and deformation analysis; both ends of the tower wall of the constrained damping section are subjected to the bending axial force F, and part of the axial force is transferred to the constrained layer through the shear stress of the damping layer through half of the constraint section length. Combined with the stress and strain distribution of the tower wall, damping layer and constrained layer, the shear strain energy of the damping layer of the transfer section, the total strain energy of the damping layer of the transfer section, the shear strain energy proportion of the damping layer, the total strain energy of the wind tower under the horizontal load P on the tower top, the total strain energy of the constrained damping section, and the shear strain energy of the damping layer of the constrained damping section are calculated in turn according to the equilibrium conditions, geometric conditions, physical conditions, and boundary conditions. Then, the first-order modal damping ratio of the wind tower with the constrained damping section is calculated according to the modal strain energy method.

7. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 5, characterized in that: The process of performing parameter analysis and optimization of the high-strength steel constrained damping enhancement section in step S4 specifically analyzes the influence of the damping layer thickness, the constrained layer thickness, and the tower wall thickness on the modal damping ratio to determine the thickness of each layer in the high-strength steel constrained damping enhancement section.

8. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 7, characterized in that: The analysis of the influence of the damping layer thickness, the constraint layer thickness, and the tower wall thickness on the modal damping ratio includes: Analysis process 1. Analyze the influence of damping layer thickness on modal damping ratio separately; Analysis process 2: Analyze the modal damping ratio when the damping layer thickness takes the optimal value; Analysis process 3: Analyze the modal damping ratio when the damping layer thickness takes the optimal value and the total thickness of the constraint layer and the tower wall remains unchanged; Analysis process 4: Analyze the modal damping ratio when the damping layer thickness takes the optimal value and the ratio of the constraint layer to the tower wall thickness remains unchanged; Analysis process 5: Analyze the maximum shear strain of the damping layer when the thickness of the damping layer takes the optimal value.

9. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 8, characterized in that: In the analysis process 1, the influence of the damping layer thickness t1 on the modal damping ratio is: When Λ=1.639 The damping ratio ξ reaches its maximum value, that is, when other parameters are given, the damping layer thickness t1 has an optimal value t1 can be adjusted by adjusting the length of l, which can be divided into multiple segments to reduce the thickness of the damping layer; Where H is the tower top height, h is the height of the restrained damping section, which can be approximated as the height of the top of the restrained damping section, and 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 tower of the restrained damping section, W0 is the bending section modulus of the tower of the restrained damping section, m is the concentrated mass at the top of the tower, f is the first-order frequency of the wind tower, is a dimensionless parameter, l is the length of the transition section, which is half the length of the constrained damping section, G is the shear modulus of the damping material, E is the elastic modulus of the steel, t0 and t2 are the thickness of the tower wall and the constrained layer of the constrained damping section respectively; In the analysis process 2, the modal damping ratio ξ is: At this time, the damping ratio increases at a slower rate with the increase of t2. When t2 / t0 is greater than 3 and t2 continues to increase, the damping ratio will not increase significantly. Therefore, t2 / t0 is designed to be 1 to 3; the damping ratio decreases faster with the increase of t0; the damping ratio increases linearly with the increase of l; the damping ratio decreases faster with the increase of h; In the analysis process 3, the modal damping ratio ξ is: At this time, the damping ratio decreases rapidly with the increase of t0, T = t0 + t2, which is the total thickness of the constraint layer and the tower wall; In the analysis process 4, the modal damping ratio ξ is: At this time, the damping ratio decreases with the increase of the total thickness T of the constrained layer and the tower wall, where α is the ratio of the constrained layer to the tower wall thickness; 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. If l is too small, the maximum shear strain τ of the damping layer will be 1max Too large.

10. A method for designing a wind power tower structure provided with a high-strength steel constrained damping enhancement section according to claim 5, characterized in that: After the additional damping is calculated in step S4, the wind turbine tower is further redesigned according to the additional damping to convert the performance redundancy of the additional damping into a saving in steel usage of the overall structure.

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