Manufacturing method for cylindrical structures of offshore wind turbines, floating foundation and floating offshore wind turbine

Abstract

This method allows for the manufacture of cylindrical structures for offshore wind turbines using simpler equipment compared to conventional methods. [Solution] A method for manufacturing a cylindrical structure for an offshore wind turbine, comprising the steps of: placing a steel plate on an arc-shaped jig; bending the steel plate by its own weight, causing the plate surface of the steel plate to conform to the jig; pulling the steel plate towards the jig to bend the steel plate into an arc shape; and fixing a shape-retaining member to the arc-shaped bent steel plate.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a cylindrical structure of an offshore windmill, a floating foundation, and a floating offshore windmill.

Background Art

[0002] In a columnar floating body constituting a floating offshore wind power generation facility, a columnar floating body is disclosed which includes a column main body that is hollow and columnar, and the column main body is formed by connecting a plurality of straight members whose plate surfaces are flat in the circumferential direction, and the cross-sectional shape is polygonal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When manufacturing a cylindrical structure of an offshore windmill, there is a process of bending a steel plate used for the outer plate of a column into an arc shape in order to manufacture the cylindrical structure. Conventionally, in this process of bending the steel plate, for example, equipment such as a large bending roller is used to bend the steel plate. However, in the conventional method using this bending roller, it is impossible to manufacture a column in a factory that does not have a bending roller. Further, there is a problem that this bending roller is very expensive.

[0005] An object of the present invention is to manufacture a cylindrical structure of an offshore windmill with simpler equipment than in the prior art.

Means for Solving the Problems

[0006] A method for manufacturing a cylindrical structure of an offshore wind turbine to which the present invention applies comprises the steps of: placing a steel plate on an arc-shaped jig; bending the steel plate by its own weight so that the surface of the steel plate conforms to the jig; pulling the steel plate towards the jig to bend it into an arc shape; and fixing a shape-retaining member to the arc-shaped bent steel plate. Furthermore, the process of bending the steel plate into an arc shape is carried out in a direction along the surface of the steel plate, and gripping portions are attached to each end of the steel plate in a direction perpendicular to the arc direction of the steel plate, and the surface of the steel plate is brought to conform to the jig by pulling the gripping portions in the radial direction of the radius of curvature of the arc of the jig. Furthermore, the position where the gripping portion is attached may be characterized in that it is located towards the end of the jig in the arc direction from the position where the size of the gap between the jig and the steel plate is maximum. Furthermore, the position where the gripping portion is attached can be characterized by being determined by numerical analysis using finite element analysis.

[0007] From another perspective, the floating foundation to which the present invention applies is a floating foundation that uses the cylindrical structure formed by combining steel plates manufactured by the manufacturing method described above. From another perspective, the floating offshore wind turbine to which the present invention applies is a floating offshore wind turbine having the floating foundation described above and a wind power generation device attached to the floating foundation. [Effects of the Invention]

[0008] According to the present invention, cylindrical structures for offshore wind turbines can be manufactured using simpler equipment compared to conventional methods. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a floating offshore wind turbine manufactured by the cylindrical structure manufacturing method to which the embodiment is applied. [Figure 2]Figures (a) to (c) show an example of the manufacturing process for a cylindrical structure. [Figure 3] This figure shows an example of a curved sheet metal produced in the bending process. [Figure 4] This is a flowchart showing an example of a sheet metal bending process. [Figure 5] This figure shows an example of the steel plate arrangement process. [Figure 6] This figure shows an example of the load application process. [Figure 7] (a) and (b) are diagrams showing examples of initial conditions for numerical analysis. [Figure 8] This graph shows an example of the numerical analysis results of a hypothetical steel plate bending under its own weight, compared to the actual measurement results of a real steel plate. [Figure 9] (a) and (b) are diagrams showing examples of numerical analysis of load application. [Figure 10] (a) and (b) are figures illustrating further examples of numerical analysis of load application. [Figure 11] This graph shows an example of the numerical results of a numerical analysis. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the attached drawings. [Floating offshore wind turbine] Figure 1 shows an example of a floating offshore wind turbine 1 manufactured by the cylindrical structure manufacturing method to which the embodiment is applied. The floating offshore wind turbine 1 comprises a wind power generation device 2 that converts wind power into electrical energy, and a floating foundation 3 that floats on the sea.

[0011] The wind power generation device 2 includes a rotor 23, a nacelle 24, and a tower 25. The rotor 23 includes a plurality of blades 21 which are blades that receive wind power, and a hub 22 that serves as a rotating shaft. The nacelle 24 is a housing that stores a speed increaser, a generator, etc. inside. The tower 25 is a support column that supports the rotor 23 and the nacelle 24. In the wind power generation device 2, when the blades 21 receive wind power, the blades 21 rotate around the hub 22. This rotational energy is converted into electrical energy by a generator in the nacelle 24, thereby performing wind power generation. As shown in FIG. 1, the direction in which the tower 25 extends is referred to as the vertical direction, the one end side where the rotor 23 and the nacelle 24 are provided is referred to as the upper side, and the other end side opposite to this one end side may be referred to as the lower side.

[0012] 〔Floating foundation〕 The floating foundation 3 is where the wind power generation device 2 is arranged. The floating foundation 3 includes one or more columns 30. In the present embodiment, the floating foundation 3 includes three columns 30. Further, the floating foundation 3 includes braces 41 that connect the columns 30, and reinforcing members 42 that reinforce the structure of the columns 30 and the braces 41.

[0013] The column 30 has a cylindrical shape with a hollow interior and is an example of a cylindrical structure. Buoyancy is generated by the air inside the hollow of the column 30, and the floating foundation 3 floats on the water. The material of the column 30 is, for example, a steel plate.

[0014] The braces 41 connect adjacent columns 30. The braces 41 are provided respectively on the upper side and the lower side of the facing surfaces of adjacent columns 30. The shape of the braces 41 is, for example, a hollow pipe-shaped member having a circular or rectangular cross-section. Also, the shape of the braces 41 may be, for example, an I-shaped or H-shaped steel material. One end side of the reinforcing member 42 that extends in the longitudinal direction is attached to the upper brace 41, and the other end side is attached to the lower brace 41. The shape of the reinforcing member 42 is, for example, a hollow pipe-shaped member having a circular or rectangular cross-section. Also, the shape of the reinforcing member 42 may be, for example, an I-shaped or H-shaped steel material.

[0015] [Column manufacturing process] Next, the manufacturing process of column 30 will be described with reference to FIG. 2. FIGS. 2(a) to (c) are diagrams showing an example of the manufacturing process of column 30. In the plate bending process shown in FIG. 2(a), the flat steel plate 31 is bent to manufacture an arc-shaped curved plate 33. Also, since a plurality of such curved plates 33 are used for column 30, a plurality of curved plates 33 are manufactured in this plate bending process. Note that this plate bending process will be described in more detail later with reference to FIGS. 4, 5, and 6.

[0016] In the ring assembly process shown in FIG. 2(b), three arc-shaped curved plates 33 are combined in three in the circumferential direction of the arc to form a cylindrical shape and are joined by welding to manufacture a ring 34. In this ring assembly process, a plurality of rings 34 are manufactured. The curved plate 33 is manufactured to be a fan-shaped curved plate with a central angle of the arc of 120 degrees. However, the size of the central angle of the arc of the curved plate 33 is not limited to this. For example, the curved plate 33 may be manufactured such that the size of the central angle of the arc of the curved plate 33 is 90 degrees, and four curved plates 33 may be combined to manufacture one ring 34.

[0017] In the column assembly process shown in FIG. 2(c), a column 30 is manufactured by combining a plurality of rings 34 and two bottom plates 35 that close the upper or lower surface of column 30. The bottom plate 35 is, for example, a steel plate and is a circular plate-shaped member having substantially the same shape as the opening of the ring 34. These rings 34 and bottom plates 35 are joined by welding.

[0018] [Plate bending process] Next, the curved plate 33 will be described with reference to FIG. 3. FIG. 3 is a diagram showing an example of the curved plate 33 manufactured in the bending process. As shown in Figure 3, the curved plate 33 comprises a steel plate 31 and a structural member 32. A structural member 32, which is an example of a shape-retaining member for maintaining the shape of the steel plate 31, is fixed to the inner surface 31a, which is the concave side of the steel plate 31. The structural member 32 fixed to the steel plate 31 may be singular or multiple. The curved plate 33 is curved in an arc shape. Hereinafter, the circumferential direction of the arc of this curved plate 33 may be referred to as the arc direction. Also, the direction perpendicular to the arc direction and along the plate surface of the curved plate 33 may be referred to as the width direction. In the example shown in Figure 3, three structural members 32 are arranged on one steel plate 31 along the arc direction of the curved plate 33 and fixed parallel to each other with spacing in the width direction of the curved plate 33. The structural member 32 is a rod-shaped steel material having an arc-shaped surface. As a method of fixing the structural member 32 to the steel plate 31, welding can be used, for example. The fixing of the structural members 32 to the steel plate 31 prevents the steel plate 31 from returning to its flat shape.

[0019] Next, the sheet metal bending process will be explained with reference to Figures 4, 5, and 6. Figure 4 is a flowchart showing an example of a sheet metal bending process. Figure 5 shows an example of the steel plate arrangement process. Figure 6 shows an example of the load application process.

[0020] In the cutting process (step 101), the steel plate 31 is cut from the base steel plate to the dimensions of the curved plate 33.

[0021] In the steel plate placement process (step 102), the steel plates 31 are placed on an arc-shaped jig 50 (see Figure 5). As shown in Figure 5, the cut steel plates 31 are rigged using a lifting beam 61, and the lifting beam 61 is moved by a crane (not shown) to place the steel plates 31 on the arc-shaped jig 50. The jig 50 comprises an arc-shaped curved bar 51, a plurality of jig legs 52 that support the bar 51, and a base 53 to which the jig legs 52 are fixed. The plurality of bars 51 are arranged parallel to each other with intervals between them. In this embodiment, three bars 51 are arranged.

[0022] In the self-weight bending process (step 103), the self-weight of the steel plate 31 causes its surface to conform to the jig 50, causing the steel plate 31 to bend into an arc shape. When the steel plate 31 is placed on the jig 50, it may not form an arc shape by its own weight alone. In other words, a gap may occur between the steel plate 31 and the bar 51 of the jig 50. Hereinafter, the gap between the steel plate 31 and the bar 51 may be referred to as the gap, and the size of this gap may be referred to as the gap amount. This gap amount is the distance from the bar 51 to the steel plate 31 in the radial direction of the arc of the bar 51.

[0023] In the load application process (step 104), as shown in Figure 6, the gripping part 81 is fixed to the steel plate 31 at the location of the gap, and the steel plate 31 is pulled towards the bar 51 by operating the lever hoist 83. More specifically, the gripping part 81 and the lever hoist 83 are connected by a wire rope 85. The end of the chain 86 extending from the lever hoist 83 is hooked onto an embedded anchor 82 fixed to the ground. In this state, by operating the lever of the lever hoist 83 and winding up the chain 86, the tension on the wire rope 85 increases. As a result, the gripping part 81 is pulled towards the embedded anchor 82 by the tension of the wire rope 85, and the steel plate 31 is pulled towards the bar 51. The gripping part 81 can be exemplified by a clamp such as a C-clamp or an F-clamp. The lever hoist 83 is an example of a manually operated hoisting machine. Furthermore, when pulling in the gripping section 81, an electric hoist may be used instead of the lever hoist 83.

[0024] Furthermore, the position at which the steel plate 31 is pulled towards the bar 51 may be determined, for example, by conducting experiments and based on the experimental results. Alternatively, the position at which the steel plate 31 is pulled towards the bar 51 may be determined, for example, by numerical analysis results from the numerical analysis device 10. Alternatively, the position at which the steel plate 31 is pulled towards the bar 51 may be determined, for example, by both experimental results and numerical analysis results. In other words, the position at which the gripping portion 81 is attached to the steel plate 31 may be determined based on at least one of the experimental results and the numerical analysis results. The experiments and numerical analyses for pre-determining this pulling position will be described later.

[0025] Note that Figure 6 is a view of the steel plate 31 from the width direction (see Figure 5), and only one end of the steel plate 31 in the width direction is shown. A similar gap exists on the other end relative to this one end. In the load application process, the gripping part 81 is fixed on the other end of the steel plate 31 in the width direction, and the steel plate 31 is pulled towards the bar 51 by operating the lever hoist 83. In other words, in the load application process, both ends of the steel plate 31 in the width direction are gripped, and a load is applied in the radial direction of the arc of the bar 51. To put it another way, gripping parts 81 are attached to each end of the steel plate 31 in a direction along the surface of the steel plate 31 and perpendicular to the arc direction of the steel plate 31. Then, by pulling the gripping parts 81 in the radial direction of the radius of curvature of the arc of the bar 51, the surface of the steel plate 31 is bent into an arc shape along the bar 51. Furthermore, a gap also occurs on the opposite side in the arc direction (see Figure 3) between the steel plate 31 and the bar 51. Therefore, to address the gap on the opposite side in the arc direction, both ends of the steel plate 31 in the width direction are gripped, and a load is applied to the bar 51 in the radial direction of the arc.

[0026] In the shape-maintaining member fixing process (step 105), the structural members 32 (see Figure 3) are fixed to the steel plate 31, which has been bent into an arc shape to eliminate the gap. Here, "eliminating the gap" means that the gap has been reduced to a degree that allows the structural members 32 to be welded. The amount of gap that can be welded is determined by the material of the steel plate 31 and structural members 32, and the welding method. In this embodiment, welding is possible when the gap between the bar 51 and the steel plate 31 is, for example, less than 5 mm.

[0027] In the transport process (step 106), the curved plate 33, which was completed in the shape-maintaining member fixing process (step 105), is transported from the jig 50 using the suspension beam 61. The above process is repeated to manufacture multiple curved plates 33.

[0028] [Method for pre-determining the position to be attracted] Next, we will explain how to pre-determine the position at which the steel plate 31 is pulled towards the bar 51. For example, in the load application process (step 104), when the steel plate 31 is pulled towards the bar 51, depending on the position where the steel plate 31 is pulled towards the bar 51, the gap between the steel plate 31 and the bar 51 may not be a weldable gap (for example, less than 5 mm). Therefore, it is desirable to predetermine the position at which the steel plate 31 is pulled towards the bar 51 so that the gap is weldable. As mentioned above, one example of how the position at which the steel plate 31 is pulled towards the bar 51 can be determined is based on experiments or numerical analysis.

[0029] As an experiment to pre-determine the position for pulling the steel plate 31 towards the bar 51, for example, the steel plate 31 is actually placed on the jig 50, the gripping part 81 is attached to the steel plate 31 and a load is applied, and the position of the gripping part 81 and the maximum gap amount are recorded in correspondence. Here, the maximum gap amount refers to the largest value among the gap amounts that occur between the steel plate 31 and the bar 51. Furthermore, the position of the gripping part 81 attached to the steel plate 31 is changed, and the position of the gripping part 81 and the maximum gap amount are recorded in correspondence at multiple positions. Then, for example, one can exemplify a method in which the record with the smallest maximum gap amount is obtained from among the multiple records, and the position of the gripping part 81 associated with the record with the smallest maximum gap amount is set as the position for pulling the steel plate 31 towards the bar 51. Furthermore, for example, one can illustrate a method in which the position of the gripping portion 81 associated with the record in which the maximum gap amount is a weldable gap amount (e.g., less than 5 mm) is set to the position where it is pulled closer.

[0030] As a numerical analysis to pre-determine the position at which the steel plate 31 is pulled towards the bar 51, for example, a finite element analysis using the finite element method can be exemplified. The numerical analysis is performed, for example, by the control of a numerical analysis device 10 (see Figure 6). The numerical analysis device 10 consists of a computer device such as a desktop PC or a notebook PC. The numerical analysis device 10 has software installed on it, such as Abaqus®, which performs finite element analysis using the finite element method. Below, an example of a numerical analysis for pre-determining the position at which the steel plate 31 is pulled towards the bar 51 will be described.

[0031] First, using Figures 7 and 8, we will explain the numerical analysis in the case where a steel plate 31 is placed on a bar 51 and the steel plate 31 is bent by its own weight. Figures 7(a) and 7(b) show examples of initial conditions for numerical analysis. Figure 7(a) shows the state in which the virtual steel plate 131 is placed relative to the virtual bar 151. Figure 7(b) shows Figure 7(a) viewed from the z-axis direction. Here, the virtual bar 151 is a model of the bar 51, and the virtual steel plate 131 is a model of the steel plate 31. Figure 8 is a graph showing an example of the numerical analysis results of a virtual steel plate 131 that bends due to its own weight, and the actual measurement results of the steel plate 31.

[0032] As shown in Figure 7(a), the virtual bar 151 is positioned parallel to the x-axis, with the center of the arc of the virtual bar 151 being at the origin of the x-axis. Furthermore, the virtual bar 151 is positioned so that its convex surface faces the negative direction of the y-axis. Multiple virtual bars 151 are arranged in the same number as the bars 51 in the jig 50 (see Figure 5), and are positioned parallel to each other at predetermined intervals in the z-axis direction. When modeling, an R-shape is provided at the arc-direction end of the virtual bar 151. This R-shape allows the virtual steel plate 131 to bend smoothly when its weight is applied to it after being placed on the virtual bar 151. Furthermore, to prevent the virtual bar 151 from moving during the numerical analysis modeling process, the virtual bar 151 was completely fixed at multiple positions. The positions where it is completely fixed correspond to the positions of the jig legs 52 (see Figure 5). For example, the virtual bar 151 is completely fixed at the origin in the x-axis direction, at positions of ±3750 mm and ±7500 mm in the x-axis direction. In Figure 7(b), the positions where the virtual bar 151 is completely fixed are indicated by triangular marks 152. The distance between adjacent marks 152 in the x-axis direction is, for example, 3750 mm, which is shown as length K in Figure 7(b).

[0033] The dimensions of the virtual steel plate 131 are set to match the dimensions of the steel plate 31. For example, the dimensions of the virtual steel plate 131 are set to a width of 3200 mm, a length of 18000 mm, and a thickness of 15 mm. Here, the width of the virtual steel plate 131 is shown as W in Figure 7(a). The length of the virtual steel plate 131 is shown as L in Figure 7(b). The thickness of the virtual steel plate 131 is shown as D in Figure 7(b).

[0034] Numerical analysis was performed by placing the virtual steel plate 131 to be bent on the virtual bar 151 under the initial conditions shown in Figures 7(a) and (b). In this numerical analysis, all solid elements were modeled, and a load equivalent to the self-weight was input to the entire model in the negative direction of the y-axis. This load equivalent to the self-weight was obtained by inputting the acceleration due to gravity into the element whose density was defined. As a result of performing the numerical analysis under these conditions, the numerical analysis results shown in Figure 8 were obtained.

[0035] The graph shown in Figure 8 has the position on the arc of the virtual bar 151 in the x-axis direction (mm) on the horizontal axis, and the gap amount (mm) on the vertical axis, which is the size of the gap between the virtual bar 151 and the virtual steel plate 131, which is subjected to a load equivalent to its own weight in the negative y-axis direction. In Figure 8, the numerical analysis results are shown as black circles, and the actual measured results are shown as white circles. The actual measured results are the result of measuring the gap amount by placing the actual steel plate 31 in the jig 50. As shown in Figure 8, it was confirmed that the numerical analysis results and the actual measured results are in general agreement.

[0036] Next, using Figure 9, we will explain the numerical analysis of applying a load diagonally to the position with the largest gap in the measured results shown in Figure 8. More specifically, we will explain the numerical analysis of applying a load diagonally to a position where the position on the arc is ±6900 mm. Figures 9(a) and 9(b) show examples of numerical analysis of load application. Figure 9(a) shows a virtual steel plate 131 that is curved under its own weight alone, and shows the position where the load is applied. Figure 9(b) shows the results of the numerical analysis after the load has been applied. Numerical analysis revealed that welding was impossible because the gap size exceeded 5 mm. As shown in Figure 9(b), at the position where the load was applied (6900 mm on the arc), the gap size became 0 and the gap disappeared. However, at positions greater than 6900 mm on the arc, a gap occurred, and the gap size exceeded 5 mm. This is because, when a gap exists on the end side of the arc position from the position where the load was applied, the virtual steel plate 131 and the virtual bar 151 are in contact at the position where the load was applied, and the load does not exert a sufficient effect on the end side beyond that position. In this experiment, we actually fixed the gripping part 81 (see Figure 6) to the steel plate 31 at a position of 6900 mm on the arc and applied a load, confirming that the gap amount was not less than 5 mm.

[0037] Next, using Figures 10(a), (b) and 11, we will explain the results of a numerical analysis performed by applying a load diagonally at a position of 7500 mm on the arc. Figures 10(a) and (b) show further examples of numerical analysis of load application. Figure 10(a) shows a virtual steel plate 131 that is curved under its own weight alone, and shows the position where the load is applied. Figure 10(b) shows the results of the numerical analysis of load application. Figure 11 is a graph showing an example of the numerical results of the numerical analysis.

[0038] As shown in Figure 10(a), numerical analysis was performed by applying loads at positions ±7500 mm on the arc. When numerical analysis was performed by applying a load diagonally at the position 7500 mm on the arc, the numerical analysis result obtained showed that there was no gap between the virtual steel plate 131 and the virtual bar 151, as shown in Figure 10(b). More specifically, a graph of the specific numerical results of the numerical analysis was obtained as shown in Figure 11. The dashed line in Figure 11 shows the numerical analysis result before applying the load, and the solid line in Figure 11 shows the numerical analysis result after applying the load at the position 7500 mm on the arc. After applying a load at a position of 7500 mm on the arc, no gap is observed from 0 mm to 7500 mm on the arc, but a gap is present in the range greater than 7500 mm on the arc. As shown in Figure 11, even at the position with the largest gap (8400 mm on the arc), the gap does not exceed the weldable gap amount (e.g., 5 mm).

[0039] In this experiment, the gripping part 81 was fixed to the steel plate 31 at a position of 7500 mm on the arc, and a load was applied. The gap amount was less than 5 mm, confirming that the structural members 32 (see Figure 3) were in a state where welding was possible. Thus, it was confirmed that the fixing position of the gripping part 81 can be predetermined based on the results of numerical analysis.

[0040] Furthermore, as mentioned above, the appropriate position for applying the load in the load application process (step 104) is not necessarily the position with the largest gap before the load is applied. In other words, the position where the gripping portion 81 is attached may be closer to the end in the arc direction of the jig 50 than the position where the gap between the jig 50 and the steel plate 31 is largest.

[0041] Furthermore, this numerical analysis only needs to be performed before the gripping portion 81 is fixed to the steel plate 31 in the load application process (step 104), and the timing of the numerical analysis is not particularly limited. For this reason, for example, when selecting the material of the steel plate 31 or designing the dimensions of the steel plate 31, numerical analysis of the self-weight bending process and the load application process may be performed to determine the position where the gripping portion 81 is attached, and the material or dimensions of the steel plate 31 may be selected based on the results of the numerical analysis.

[0042] As detailed above, in this embodiment, the steel plate 31 is bent by its own weight using the jig 50. In this embodiment, if the steel plate 31 does not bend into an arc shape by its own weight alone, the gripping part 81 and the lever hoist 83 are used to pull the steel plate 31 towards the arc-shaped surface of the jig 50. The gripping part 81 can use a general tool such as a clamp, and the steel plate 31 is bent into an arc shape without using special tools. As a result, the bending process of the steel plate 31 can be performed with simpler equipment, without using expensive equipment such as a bending roller. In this embodiment, the columns 30 of the floating foundation 3 are manufactured with simpler equipment compared to conventional methods.

[0043] [Other forms] In this embodiment, a semi-submersible floating offshore wind turbine 1 is described as an example, and a semi-submersible floating foundation 3 is described as an example. Here, the floating foundation 3 may be, for example, a semi-submersible type with a wind power generation device 2 at the center of three columns 30. The floating foundation 3 may also use more than three columns, for example, four columns 30. Furthermore, the floating foundation 3 may be not only a semi-submersible type but also a barge type, TLP type, spar type, etc. Furthermore, this embodiment can also be applied to bottom-fixed offshore wind turbines, such as those in which cylindrical monopiles are fixed to the seabed. This allows for the manufacture of monopiles without the use of equipment such as large bending rollers. This embodiment may also be used for cylindrical structures used in offshore wind turbines, for example, when manufacturing the cylindrical tower 25 of a wind power generation device 2. [Explanation of symbols]

[0044] 1…Floating offshore wind turbine, 2…Wind power generation device, 3…Floating foundation, 10…Numerical analysis device, 30…Column, 31…Steel plate, 32…Aggregate, 33…Bent plate, 34…Ring, 50…Jig, 51…Bar, 60…Lifting part, 81…Gripping part, 82…Embedded anchor, 83…Lever hoist, 85…Wire rope, 86…Chain, 131…Virtual steel plate, 151…Virtual bar

Claims

1. The process involves placing a steel plate on an arc-shaped jig, The process of bending the steel plate by aligning its surface with the jig using the weight of the steel plate, The process of pulling the steel plate towards the jig and bending the steel plate into an arc shape, A step of fixing a shape-retaining member to the steel plate that has been bent into an arc shape, A method for manufacturing a cylindrical structure for an offshore wind turbine equipped with [a specific component].

2. The process of bending the steel plate into an arc shape is carried out in a direction along the surface of the steel plate, and gripping portions are attached to each of the ends of the steel plate in a direction perpendicular to the arc direction of the steel plate. The gripping portion is pulled in the radial direction of the radius of curvature of the arc of the jig, thereby bringing the surface of the steel plate along the jig. A method for manufacturing a cylindrical structure for an offshore wind turbine according to claim 1.

3. The position where the gripping portion is attached is characterized in that it is located towards the end of the jig in the arc direction from the position where the gap between the jig and the steel plate is at its largest. A method for manufacturing a cylindrical structure for an offshore wind turbine according to claim 2.

4. The position where the gripping portion is attached is determined by numerical analysis using finite element analysis. A method for manufacturing a cylindrical structure for an offshore wind turbine according to claim 3.

5. A floating foundation using the cylindrical structure formed by combining steel plates manufactured by the manufacturing method described in claim 1.

6. A floating foundation according to claim 5, The wind power generation device attached to the floating foundation, A floating offshore wind turbine having [a specific feature / feature].

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