Polygonal cylindrical structure, method for designing polygonal cylindrical structure, and foundation structure for offshore wind power plant using polygonal cylindrical structure

Abstract

The cross-sectional shape in the horizontal direction is formed by the same number of angles, and the polygonal columnar body (1) is formed by connecting steel flat plate members (10) in the circumferential direction and the columnar axis direction by welding. The cross-sectional shape of the polygonal columnar body (1) is a polygonal cross-sectional shape of a hexagon or more and twenty-four angles or less, and the plate thickness of the flat plate member (10) is 40 mm or more and 250 mm or less. The ratio of the outer diameter D of the polygonal cross section to the plate thickness t (outer diameter D / plate thickness t) is 200 or less.

Description

Technical Field

[0001] The present invention relates to a polygonal cylindrical structure, a design method of a polygonal cylindrical structure, and a foundation structure for an offshore wind power generation device using the polygonal cylindrical structure.

[0002] This application claims priority based on Japanese Patent Application No. 2022-199328 filed in Japan on December 14, 2022, the content of which is incorporated herein by reference. Background Art

[0003] Conventionally, in order to ensure the power generation amount of offshore wind power, the upscaling of wind turbines, towers supporting the wind turbines, and foundations has been promoted. Generally, the tower and the foundation mostly use a circular structure composed of cylindrical pipes, and as the cylindrical pipe for the foundation, it is expected that a large-diameter cylindrical pipe with an outer diameter exceeding 10 m, for example, will be used in the future. As the equipment becomes larger, it is necessary to improve the strength and rigidity, and the outer diameter and wall thickness also need to be increased. Usually, as shown in Patent Document 1, for example, short pipes are manufactured by bending a steel plate and welding the bent plates in the circumferential direction, and the tower and the foundation are constructed by further welding the short pipes in the column axis direction. In this case, there are the following problems: the capacity of the bending processing equipment has a limit and cannot cope with thickening and large diameter, and the cost also increases.

[0004] On the other hand, as a structure that does not perform bending processing, a structure having a polygonal cross section constructed by connecting a plurality of flat steel plates in the circumferential direction by welding in a columnar floating body constituting a floating type offshore wind power generation facility is known (for example, refer to Patent Document 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 4708365 Gazette

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2022-1474 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, in the above-described structure having a polygonal cross section, there are the following problems.

[0011] That is, in Patent Document 2, a polygon is constructed by connecting flat steel plates in the circumferential direction by welding, but since the number of corners is excessively increased, the cost may increase.

[0012] Moreover, in order to enable a polygonal structure to exhibit the same bending performance as a circular shape under the condition of the same cross-sectional area, it is generally considered to increase the outer diameter to increase the second moment of area of the cross-section. However, since the perimeter becomes longer and the plate thickness becomes relatively smaller, the local buckling resistance (load-carrying capacity) of the plate decreases.

[0013] In addition, the buckling mode that determines the limit state changes from the elephant foot buckling that occurs in circular members to the local buckling of the plate when changing from a circular shape to a polygonal shape. Therefore, it is necessary to increase the local buckling resistance by increasing the number of corners of the polygon and decreasing the width-thickness ratio of one side. However, if the number of corners increases, the length of the welding line and the assembly man-hours will increase, resulting in a problem of increased cost, and there is room for improvement in this regard.

[0014] The present invention has been completed in view of the above problems, and its object is to provide a polygonal cylindrical structure, a design method of a polygonal cylindrical structure, and a foundation structure for an offshore wind power generation device using the polygonal cylindrical structure that can well balance both the exhibition of the same bending performance as a circular shape and the reduction of cost by omitting the bending process and reducing the welding process.

[0015] Means for Solving the Problem

[0016] <1> A first aspect of the polygonal cylindrical structure of the present invention is a polygonal cylindrical structure in which the cross-sectional shape in the horizontal direction is formed by polygons having the same number of corners, and is characterized in that the polygonal cylindrical structure is constituted by connecting steel flat members in the circumferential direction and the column axis direction by welding, the cross-sectional shape is a polygonal cross-section of hexagon or more and icositetragon or less, the plate thickness of the flat member is 40 mm or more and 250 mm or less, and the ratio of the outer diameter to the plate thickness (outer diameter / plate thickness) of the polygonal cross-section is 200 or less.

[0017] <2> A first aspect of the design method of the polygonal cylindrical structure of the present invention is a design method of a polygonal cylindrical structure in which the cross-sectional shape in the horizontal direction is formed by polygons having the same number of corners, and is characterized in that the design is carried out in the following manner: the polygonal cylindrical structure is constituted by connecting steel flat members in the circumferential direction and the column axis direction by welding, the cross-sectional shape is a polygonal cross-section of hexagon or more and icositetragon or less, the plate thickness of the flat member is 40 mm or more and 250 mm or less, and the ratio of the outer diameter to the plate thickness (outer diameter / plate thickness) of the polygonal cross-section is 200 or less.

[0018] In the present invention, in a polygonal cross-section of a polygonal cylindrical structure where the horizontal cross-sectional shape is a polygon with 6 or more and 24 or fewer sides, by making the plate thickness of the flat plate member 40 mm or more and 250 mm or less and making the ratio of the outer diameter to the plate thickness (outer diameter / plate thickness) 200 or less, local buckling can be suppressed, a specification with the same cross-sectional area as a circle and capable of exhibiting the same bending performance as a circle can be selected, and it can be manufactured in a polygonal cylindrical structure capable of shortening the welding line length.

[0019] Thus, in the present invention, the configuration of the flat plate member can be constructed only by geometric adjustment, the bending process can be omitted, and the costly assembly welding process can be reduced. Therefore, in the present invention, it is possible to achieve a good balance between improving the bending performance in the same manner as a circle and suppressing the increase in cost. Moreover, in the present invention, since no reinforcing members such as ribs are required, a low-cost polygonal cylindrical structure can be provided.

[0020] <3>In the second aspect of the first aspect of the polygonal cylindrical structure subordinate to the present invention, preferably, the number of sides n of the polygonal cross-section satisfies formula (1) or formula (2).

[0021] <4>In the second aspect of the first aspect of the design method of the polygonal cylindrical structure subordinate to the present invention, preferably, the number of sides n of the polygonal cross-section satisfies formula (1) or formula (2).

[0022] n≥6 {when D / t≤80}…(1)

[0023] n≥(D / t) / 20 + 2 {when D / t>80}…(2)

[0024] Here, D is the outer diameter (mm), t is the plate thickness (mm), and n is the number of sides (natural number).

[0025] In this case, by specifying the minimum number of sides n with the same cross-sectional area as a circle and the same bending performance according to the diameter-thickness ratio D / t using formula (1) or formula (2), a polygonal cylindrical structure can be manufactured with the shortest welding line length.

[0026] <5>In the third aspect of the first or second aspect of the polygonal cylindrical structure subordinate to the present invention, preferably, the polygonal cross-section is a regular polygon.

[0027] <6>In the third aspect of the first or second aspect of the design method of the polygonal cylindrical structure subordinate to the present invention, preferably, the polygonal cross-section is a regular polygon.

[0028] In this case, since the cross-sectional shape is close to a circle, it is possible to manufacture a polygonal cylindrical structure with a specification of the minimum number of corners (i.e., the minimum length of the welding line) set to exhibit the same bending performance as a circle with higher precision as described above.

[0029] <7>The first aspect of the foundation structure for an offshore wind power generation device according to the present invention is characterized by including the polygonal cylindrical structure according to any one of the first to third aspects, and the polygonal cylindrical structure serves as the foundation of the offshore wind power generation device.

[0030] Advantages of the Invention

[0031] According to the polygonal cylindrical structure, the design method of the polygonal cylindrical structure, and the foundation structure for an offshore wind power generation device using the polygonal cylindrical structure of the present invention, it is possible to achieve a good balance between exhibiting the same bending performance as a circle and reducing costs by omitting the bending process and reducing the welding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a perspective view of a polygonal columnar body showing an embodiment of the present invention.

[0033] Figure 2 is Figure 1 a horizontal cross-sectional view of a part in the height direction of the shown polygonal columnar body.

[0034] Figure 3 is a horizontal cross-sectional view showing the welding state between adjacent flat members in the circumferential direction.

[0035] Figure 4 is a view showing an analysis model of an example.

[0036] Figure 5 Among them, (a) to (d) are views showing an example of a contour map of the distribution of the equivalent plastic strain at the maximum bending load based on the analysis results of the example.

[0037] Figure 6 is a view showing the relationship between the number of corners of the example and the bending performance of the polygonal cylindrical structure.

[0038] Figure 7 is a view showing the relationship between the number of corners having the same performance as a circle in the example and the diameter-to-thickness ratio.

[0039] Figure 8 is a perspective view of a polygonal columnar body showing an embodiment of the present invention.

[0040] Figure 9 is a perspective view of a polygonal columnar body showing an embodiment of the present invention.

[0041] Figure 10 It is a perspective view of a cylinder for explaining a structure. Detailed implementation mode

[0042] Hereinafter, a polygonal cylindrical structure of an embodiment of the present invention will be described based on the drawings.

[0043] As Figure 1 shown, the polygonal cylindrical structure of the present embodiment takes, for example, a tower (not shown) for fixing a rotor composed of blades, etc., and a foundation structure of a wind power generation device that supports the tower from below (hereinafter referred to as a polygonal column 1) as an example.

[0044] Here, in the polygonal column 1, the direction parallel to the central axis O is called the column axis direction, the direction around the central axis O is called the circumferential direction, and the direction orthogonal to the central axis O is called the radial direction. In addition, the direction going towards the central axis O in the radial direction is called the inner side, and the direction away from the central axis O is called the outer side.

[0045] As Figure 1 and Figure 2 shown, the polygonal column 1 is a polygonal cylindrical structure in which the cross-sectional shape in the horizontal direction is formed by the same number of corners (here, octagon). The polygonal column 1 is formed by connecting steel flat members 10 in the circumferential direction and the column axis direction by welding. The cross-sectional shape of the polygonal column 1 in the horizontal direction orthogonal to the column axis direction is a regular octagonal cross-section. In addition, the flat member 10 may be a single steel plate or a steel plate formed by welding a plurality of plates in the circumferential direction or the column axis direction.

[0046] In addition, the cross-sectional shape of the polygonal column 1 may be a polygon with 6 or more sides and 24 or fewer sides. In addition, it is not limited to a regular polygon with all side lengths equal, and a polygon with some or all of the side lengths different can also be used. In addition, it is not limited to a cylindrical structure of a polygon or a regular polygon with equal plate thickness in the column axis direction, and a polygon or a regular polygon with different plate thicknesses in the column axis direction can also be used. For example, it may be that starting from a predetermined height position in the column axis direction, the plate thickness of the flat plate member 10 becomes thinner as it goes upward (the upper part of the cylindrical structure). The predetermined height position may be, for example, any position above the lower end of the polygonal column 1. In the part where the plate thickness changes like this, compared with the plate thickness of a certain flat plate member 10, the plate thickness of the other flat plate member 10 adjacent above is thinner. In addition, it is not limited to a cylindrical structure of a polygon or a regular polygon with all the column axis directions of the flat plate members 10 having the same length, and a polygon or a regular polygon with different column axis directions of each annular body 10A can also be used. For example, it may be that starting from a predetermined height position in the column axis direction, the column axis direction length of the flat plate member 10 becomes longer as it goes upward (the upper part of the cylindrical structure). In the part where the length changes like this, compared with the column axis direction length of a certain flat plate member 10, the column axis direction length of the other flat plate member 10 adjacent above is longer. Moreover, it may be that as it goes upward (the upper part of the cylindrical structure) in the column axis direction, the plate thickness of the flat plate member 10 becomes thinner and the column axis direction length becomes longer. For example, it is not necessary for the plate thickness and length of the flat plate member 10 to gradually change as it goes upward (the upper part of the cylindrical structure) in the column axis direction, and it can also change from any height position in the column axis direction. In this case, compared with the plate thickness and the column axis direction length of a certain flat plate member 10, the plate thickness of the other flat plate member 10 adjacent above is thinner and the column axis direction length is longer.

[0047] Here, in the present invention, the following situation is treated as a regular polygon.

[0048] Among the circumferential dimensions of the flat plate member 10, the dimensions of all the flat plate members 10 fall within ±2% of the average value.

[0049] Among the angles formed with the adjacent flat plate members 10 (in the interior angles of the regular polygon, all the interior angles fall within ±2% of (180×(n−2)) / n).

[0050] The polygonal columnar body 1 is a long-sized body arranged with its column axis parallel to the up-and-down direction, and is in a hollow cylindrical shape. A device that does not contribute to the structural performance or the like may be provided in the hollow portion of the polygonal columnar body 1. Further, the polygonal columnar body 1 has a frustum shape (conical shape) in which the cross-sectional shape gradually shrinks upward, or only a part of the upper portion of the polygonal columnar body 1 has this frustum shape (conical shape). That is, the cross-sectional shapes at any height in the column axis direction are similar shapes. The polygonal body 1 may not have a conical shape in the column axis direction.

[0051] The flat plate member 10 constituting the polygonal columnar body 1 is a thick plate member without forming a bent portion or a bent-and-folded portion. The plate thickness t of the flat plate member 10 is 40 mm or more and 250 mm or less. For the polygonal cross-section of the polygonal columnar body 1 having the same bending performance as that of a circle, the ratio of the outer diameter D (mm) to the plate thickness t (mm) (outer diameter D / plate thickness t) is preferably set to 200 or less. When it exceeds 440, it is difficult to exhibit the same bending performance as that of a circle even for a 24-sided polygonal cross-section.

[0052] Figure 10 A cylinder 100 having the same perimeter as the perimeter of the cross-section of the polygonal columnar body 1 is shown. The outer diameter D of the polygonal columnar body 1 corresponds to the diameter D100 at the center line of the flat plate member 110 of the cylinder 100 having the same perimeter in the cross-section.

[0053] The number of corners n (natural number) of the polygonal cross-section of the polygonal columnar body 1 satisfies equation (1) or equation (2).

[0054] n≥6 {when D / t≤80}…(1)

[0055] n≥(D / t) / 20 + 2 {when D / t>80}…(2)

[0056] Here, D is the outer diameter (mm), t is the plate thickness (mm), and n is the number of corners (natural number).

[0057] Further, when the unit of the outer diameter D is meter (m), when calculating D / t, the units are unified to millimeter (mm) before calculation.

[0058] The flat plate members 10 connected to each other in the circumferential direction and the column axis direction are formed by being connected by welding. Figure 1 The reference sign W of represents the welded portion (welding part). The welded portion W has a transverse welded portion W1 extending in the circumferential direction and a longitudinal welded portion W2 extending in the column axis direction. In the present embodiment, by connecting 8 flat plate members 10 having the same shape in the circumferential direction, the cross-sectional shape of the polygonal columnar body 1 becomes a regular octagon.

[0059] The polygonal columnar body 1 of the present embodiment is formed by connecting one or more segments (six segments are described in Figure 1 in the axial direction of the column) of a ring body formed by connecting eight flat members 10 in the circumferential direction. In addition, the longitudinal weld portions W2 of the respective ring bodies 10A connected in the axial direction of the column are continuous with each other in the axial direction of the column. The transverse weld portions W1 of the respective ring bodies 10A may also be continuous with each other in the circumferential direction.

[0060] In addition, in the case of a so-called staggered arrangement in which the arrangement heights in the axial direction of the flat members 10 adjacent in the circumferential direction are different, the transverse weld portion W1 is not continuous in the circumferential direction, but the longitudinal weld portion W2 is continuous in the axial direction of the column.

[0061] Next, an explanation will be given of the manufacturing method of the polygonal columnar body 1 shown in Figure 1 and Figure 2 .

[0062] First, a plate piece (flat member 10) of a predetermined size is cut out from a large steel plate serving as a base material. Here, the plate piece (flat member 10) of a predetermined size is, for example, a plate piece having a length corresponding to the circumferential direction of 1.0 m or more and 5.0 m or less and a length corresponding to the axial direction of the column of 2.0 m or more and 15.0 m or less when constructing the polygonal columnar body. In this cutting process, the number of flat members 10 required to form the polygonal columnar body 1 is cut out. However, the large steel plate serving as the base material may also be directly used as the flat member 10 without going through the cutting process. In addition, the flat member 10 may be a cut plate piece or a single steel plate used without cutting, or may be a steel plate formed by welding the cut plate pieces or the steel plate used without cutting in the circumferential direction or the axial direction of the column. In the case where the flat member 10 is formed by welding a plurality of plate pieces in the circumferential direction or the axial direction of the column, if the angle formed between the plate pieces adjacent in the circumferential direction is within 1.0°, they can be treated as the same flat member 10.

[0063] After that, the flat member 10 is arranged, for example, on a stand (not shown). At this time, the flat member 10 is butt-arranged so that two flat members 10 adjacent in the circumferential direction form a predetermined crossing angle. Here, the predetermined crossing angle is the angle (that is, the interior angle of the polygon) for using a plurality of flat members 10 to complete the cross-sectional shape (polygon) of the polygonal columnar body 1 set as the purpose. If it is the Figure 1 shown regular octagon, the crossing angle at which the sides of two adjacent flat members 10 are perpendicular to each other is 135°. In this arrangement process, the flat member 10 is not bent as in the prior art, but is arranged as it is. In addition, the flat member 10 arranged on the stand is preferably arranged with the welding side facing up and welded with the torch facing down.

[0064] On the other hand, there is also the following situation: a plurality of flat members 10 are longitudinally arranged while ensuring a predetermined inner angle, and welding is performed with the torch facing sideways or downward. In this case, a pedestal may not be used.

[0065] In addition, when the flat member 10 is arranged on the pedestal, by using, for example, a positioning jig (not shown) having an abutting surface set to the above-mentioned predetermined crossing angle and arranging the flat member 10 in abutment with the abutting surface of the positioning jig, positioning between adjacent flat members 10 can be easily performed.

[0066] Next, since a groove shape is formed at the butting portion between the adjacent flat members 10 arranged, welding joining is performed on this groove portion, and the flat members 10 are connected to each other via the welded portion W. The flat member 10 is assembled into the above-mentioned annular body 10A or a partial cross-sectional annular body obtained by cross-sectionally dividing the annular body 10A. Then, the annular body 10A or the partial cross-sectional annular body is sequentially welded and connected upward in the column axis direction at a predetermined installation position of the polygonal columnar body 1 to construct the polygonal columnar body 1. In addition, as Figure 2 shown, the butting portion between the adjacent flat members 10 arranged may be a natural groove or a V-shaped groove, and welding joining may be performed from the outside of the cross-section to form the welded portion W. It is not limited to welding from one side (inner side or outer side), and the welded portion W may also be formed from both sides. In addition, as Figure 3 shown, X-shaped grooves 10c and 10d may be provided in advance at the respective ends of the flat members 10 adjacent in the circumferential direction, and welding joining is performed on the portion where the X-shaped grooves 10c and 10d are butted against each other from both the outside and the inside of the cross-section to form the welded portion W. It is not limited to welding from one side (inner side or outer side), and the welded portion W may also be formed from both sides.

[0067] In addition, the operation of manufacturing the segmented annular body 10A, etc. can be performed at a factory, site, etc. near the installation position of the polygonal columnar body 1, or after manufacturing at a processing factory far from the installation position of the polygonal columnar body 1, it can be transported to the installation position of the polygonal columnar body 1 by a truck, ship, etc.

[0068] According to the polygonal cylindrical structure, that is, the polygonal columnar body 1 described above, the cross-sectional shape in the horizontal direction is formed by the same number of angles. The polygonal columnar body 1 is formed by connecting steel flat members 10 in the circumferential direction and the column axis direction by welding. The cross-sectional shape of the polygonal columnar body 1 is a polygonal cross-section of hexagon or more and icositetragon or less, and the plate thickness of the flat member 10 is 40 mm or more and 250 mm or less. The ratio of the outer diameter D to the plate thickness t of the polygonal cross-section (outer diameter D / plate thickness t) is 200 or less.

[0069] By adopting such a configuration, under the condition that the cross-sectional shape in the horizontal direction of the polygonal cross-section of the polygonal column 1 is a polygonal cross-section with 6 or more and 24 or less sides and the same cross-sectional area, by making the plate thickness t of the flat plate member 10 be 40 mm or more and 250 mm or less and making the ratio of the outer diameter D to the plate thickness t (outer diameter D / plate thickness t) be 200 or less, local buckling can be suppressed. By selecting a specification with the smallest number of corners that has the same cross-sectional area as a circle and exhibits the same bending performance as a circle, the polygonal column 1 can be manufactured with the shortest welding line length. In addition, the above "equivalent" is defined, for example, as the case where the maximum endurance ratio of the polygonal cross-section to the circular cross-section is 0.9 (90%) or more.

[0070] Therefore, in the present embodiment, the configuration of the flat plate member 10 can be constructed only by geometric adjustment, the bending process can be omitted, and the increase in cost can be suppressed by minimizing the costly assembly welding process. Moreover, in the present embodiment, since no reinforcing members such as ribs are required, a low-cost polygonal column 1 can be provided.

[0071] In addition, in the present embodiment, the number of corners n of the polygonal cross-section satisfies the above formula (1) or (2).

[0072] In this case, by specifying the smallest number of corners n that has the same cross-sectional area as a circle and exhibits the same bending performance using formula (1) or (2) according to the diameter-thickness ratio D / t, the polygonal column 1 can be manufactured with the shortest welding line length.

[0073] The number of corners n (natural number) of the polygonal cross-section of the polygonal column 1 may also satisfy formula (3) or (4).

[0074] n ≥ 8 {when D / t ≤ 80} … (3)

[0075] n ≥ (D / t) / 20 + 4 {when D / t > 80} … (4)

[0076] When the number of corners n of the polygonal cross-section satisfies formula (3) or (4), the maximum endurance ratio is 0.95 (95%) or more.

[0077] The number of corners n (natural number) of the polygonal cross-section of the polygonal column 1 may also satisfy formula (5) or (6).

[0078] n ≥ 10 {when D / t ≤ 80} … (5)

[0079] n ≥ (D / t) / 20 + 6 {when D / t > 80} … (6)

[0080] When the number of corners n of the polygonal cross-section satisfies formula (5) or (6), the maximum endurance ratio is 0.99 (99%) or more.

[0081] The number of corners n (natural number) of the polygonal cross-section of the polygonal columnar body 1 may also satisfy formula (7) or formula (8).

[0082] 6 ≤ n ≤ 10 {when D / t ≤ 80} … (7)

[0083] (D / t) / 20 + 2 ≤ n ≤ (D / t) / 20 + 6 {when D / t > 80} … (8)

[0084] When the number of corners n of the polygonal cross-section satisfies formula (7) or formula (8), the maximum endurance ratio is 0.90 (90%) or more.

[0085] The number of corners n (natural number) of the polygonal cross-section of the polygonal columnar body 1 may also satisfy formula (9) or formula (10).

[0086] 8 ≤ n ≤ 12 {when D / t ≤ 80} … (9)

[0087] (D / t) / 20 + 4 ≤ n ≤ (D / t) / 20 + 8 {when D / t > 80} … (10)

[0088] When the number of corners n of the polygonal cross-section satisfies formula (9) or formula (10), the maximum endurance ratio is 0.95 (95%) or more.

[0089] The number of corners n (natural number) of the polygonal cross-section of the polygonal columnar body 1 may also satisfy formula (11) or formula (12).

[0090] 10 ≤ n ≤ 14 {when D / t ≤ 80} … (11)

[0091] (D / t) / 20 + 6 ≤ n ≤ (D / t) / 20 + 10 {when D / t > 80} … (12)

[0092] When the number of corners n of the polygonal cross-section satisfies formula (11) or formula (12), the maximum endurance ratio is 0.99 (99%) or more.

[0093] In the design method of the polygonal cylindrical structure of the present embodiment, the above-mentioned polygonal cylindrical structure is designed. For example, in the design method of the polygonal cylindrical structure, the ratio of the outer diameter D to the plate thickness t of the polygonal cross-section (outer diameter / plate thickness) is also designed to be 200 or less. In addition, the number of corners n of the polygonal cross-section is designed to satisfy formula (1) or formula (2). The polygonal cross-section is designed to be a regular polygon.

[0094] In addition, in the present embodiment, since the polygonal cross-section is a regular polygon and the cross-sectional shape is closer to a circle compared to a polygon with different side lengths, it is possible to manufacture a polygonal columnar body 1 with a specification of setting the minimum number of corners (i.e., the minimum length of the welding line) to exhibit the same bending performance as a circle with higher precision. That is, considering the generation of side length errors during manufacturing, compared with connecting flat members with different side lengths, when connecting flat members with the same side length, it is possible to manufacture a polygonal cylindrical structure with higher precision.

[0095] As described above, in the polygonal columnar body 1 of the wind power generation device, the design method of the polygonal cylindrical structure, and the foundation structure for an offshore wind power generation device using the polygonal cylindrical structure in the present embodiment, it is possible to achieve a good balance between exhibiting the same bending performance as a circle and reducing costs by omitting the bending process and reducing the welding process.

[0096] Figure 1 The polygonal columnar body 1 shown is in the shape of a frustum (conical shape) whose cross-sectional shape gradually shrinks as it goes upward. The Figure 1 Each flat member 10 constituting the polygonal columnar body 1 shown is in the shape of a trapezoid that shrinks as it goes upward when viewed from the front. It is also possible that, as Figure 8 shown, the polygonal columnar body 1' is in the shape of a cylinder. That is, it is also possible that the outer diameter of the cross-section of the polygonal columnar body 1' is substantially the same in the height direction. The Figure 8 Each flat member 10' constituting the polygonal columnar body 1' shown is in the shape of a rectangle when viewed from the front. By making the polygonal columnar body 1' in the shape of a cylinder, the process of cutting the flat member 10 into a trapezoidal shape is not required. Regarding the Figure 8 welding part W' of the polygonal columnar body 1' shown, similar to the welding part W of the polygonal columnar body 1 shown in Figure 1 , the longitudinal welding parts W2' of the respective annular bodies 10A' connected in the column axis direction are continuous with each other in the column axis direction, and the transverse welding parts W1' of the respective annular bodies 10A' may be continuous with each other in the circumferential direction or may be staggered.

[0097] In the polygonal cylindrical structure formed by the Figure 8 polygonal columnar body 1' shown, the same effects as those of the polygonal cylindrical structure formed by the Figure 1 polygonal columnar body 1 shown can also be obtained.

[0098] In addition, it is also possible that, as Figure 9 shown, in the polygonal columnar body 1B', only a part of the upper end portion is in the shape of a frustum, and the portion below it is in the shape of a cylinder. In Figure 9In [the figure], the ring body 10B' of the upper two segments has a frustum shape. The welding parts W' (W1', W2') at this time are the same as the above-mentioned welding part W.

[0099] In the case where the polygonal body 1 has a conical shape, preferably, the formula (1) or (2) is satisfied at the bottom part that is prone to buckling, and more preferably, the formula (1) or (2) is satisfied at any column axis height. As long as this is the case, the outer diameter D and the plate thickness t can also vary in the column axis direction.

[0100] Next, the embodiments for proving the effects of the polygonal cylindrical structure of the above-mentioned embodiments will be described below.

[0101] (Embodiment)

[0102] In the embodiment, using numerical simulation analysis (finite element analysis), a horizontal load F was applied to the vertex (upper part) of the cantilever beam model 2 obtained by modeling the polygonal cylindrical structure shown in Figure 4 , and the endurance of the polygonal cylindrical structure was evaluated.

[0103] As shown in Table 1, in the embodiment, in five analysis CASES (CASE1, CASE2, CASE3, CASE4, CASE5), the cantilever beam models 2 as shown in Figure 4 were respectively fabricated, and numerical simulation analysis was performed by changing the diameter-thickness ratio (D / t) of the polygonal shape for each of the analysis CASES 1 to 5. The specific conditions for each of the analysis CASES 1 to 5 are shown in Table 1. Regarding the diameter-thickness ratio (D / t) in the analysis CASE, it was 40 for CASE1, 80 for CASE2, 120 for CASE3, 160 for CASE4, and 200 for CASE5.

[0104] The "outer diameter" in Table 1 is the distance between the plate thickness centers of the flat member 10 of the center line of the cylinder that is the reference for the same perimeter in the cross section. The "perimeter" is the outer diameter (m) of the cylinder that is the reference for the same perimeter in the cross section × pi, that is, the plate width × the number of corners. The "area" is calculated as the plate thickness (mm) × the perimeter (m), that is, the perimeter × the plate thickness (plate width × the number of corners × the plate thickness).

[0105] [Table 1]

[0106]

[0107] In addition, Table 2 shows the side width B (m), the plate thickness t (mm), and the width-thickness ratio (B / t) of each of the 7 patterns in the analysis CASES 1 to 5 for the number of corners n (the number of corners n of the polygonal shape is 4, 6, 8, 10, 12, 16, 24).

[0108] In addition, as a comparative example for comparison with the polygonal cylindrical structure in this embodiment, a model of a circular cylindrical structure with a circular cross-section was fabricated and the same analysis was performed. For the analysis conditions of the circular cylindrical structure, in Analysis CASE1 to CASE5, the regular 256-gon, that is, the polygonal cylindrical structure with a side width of 0.123 m, was regarded as equivalent to a cylinder and the analysis was carried out.

[0109] The "side width" in Table 2 is the value of the perimeter / number of corners n.

[0110] [Table 2]

[0111]

[0112] In this embodiment, in Analysis CASE1 to CASE5, for the number of corners n of 7 patterns, the maximum stress (equivalent plastic strain, maximum endurance) acting when a horizontal load (bending load) was applied to each polygonal cylindrical structure was obtained by analysis. Similarly, the maximum stress (endurance) acting when a horizontal load was applied to the circular cylindrical structure of the comparative example was obtained by analysis.

[0113] Figure 5 (a) to (d) respectively show an example in which the cross-sectional shape of the cylindrical structure is shown on the left side of the paper surface and the distribution of the equivalent plastic strain at the maximum bending load based on the analysis results is shown in the form of an isogram on the right side of the paper surface. Figure 5 (a) is an example of the case of a quadrilateral with 4 corners. Figure 5 (b) is an example of the case of an octagon with 8 corners. Figure 5 (c) is an example of the case of a dodecagon with 12 corners. Figure 5 (d) is an example of the comparative example and is the case of a circular cross-section. Figure 5 The reference numeral K shown in (a) to (d) indicates the part (high stress part) where the equivalent plastic strain is generated in each isogram.

[0114] It can be seen that: Figure 5 In any of the diagrams (a) to (d), a large stress acts at the installation part (base end part) of the cylindrical structure. In addition, from the state of the isogram, it can be confirmed that: Figure 5 The number of corners 8 in (b) and Figure 5 the number of corners 12 in (c) have the same stress distribution and stress magnitude as Figure 5 (d) the comparative example of the circular cross-section. On the other hand, it can be seen that: in Figure 5 (a) the case of 4 corners, compared with Figure 5 (d) the comparative example of the circular cross-section, the range (area) of the stress distribution expands, and particularly in the vertical direction (column axis direction), the stress range expands significantly, so the endurance is insufficient.

[0115] Figure 6 and Figure 7 shows the analysis result.

[0116] Figure 6 shows the relationship between the number of corners n and the bending performance of the polygonal cylindrical structure, showing the case where the diameter-thickness ratio D / t is 80 (CASE2). In addition, in this embodiment, in Figure 6 , only the case where the diameter-thickness ratio D / t is 80 is typically shown, but in the cases where the diameter-thickness ratio D / t is 40 (CASE1), 120 (CASE3), 160 (CASE4), 200 (CASE5), the tendency is also roughly the same as a coordinate graph. In Figure 6 , the horizontal axis is the number of corners n, and the vertical axis is the ratio of the maximum endurance of the polygonal cylindrical structure (polygon) to the maximum endurance of the circular cylindrical structure (cylinder) (maximum endurance ratio). Here, as the evaluation criterion for the maximum endurance ratio, when the polygonal cylindrical structure has the same cross-sectional area as the circular cylindrical structure and the maximum endurance is 90% or more, it is defined as having the same endurance (bending performance).

[0117] As Figure 6 shown, it can be seen that: the number of corners n for which the maximum endurance ratio becomes 90% or more is 6 or more. Specifically, it can be confirmed that: when the number of corners is 6 (hexagon) or more, the maximum endurance ratio becomes 90% or more, when the number of corners is 8 (octagon) or more, the maximum endurance ratio becomes 95% or more, and when the number of corners is 10 (decagon) or more, the maximum endurance ratio becomes 99% or more. From this, it can be known that: the minimum number of corners n required to obtain a maximum endurance ratio of 90% or more equivalent to that of a circular cross-section becomes 6 (hexagon). Here, for example, a circular cylindrical structure with an outer diameter D of 8 to 12 m is taken as the object. If considering that the diameter-thickness ratio D / t for the polygonal cylindrical structure to exhibit bending performance equivalent (90% or more) to that of the circular cylindrical structure is in the range of 80 to 200, then when the outer diameter D is 8 to 12 m, the required plate thickness t is 40 mm or more. In addition, the plate thickness t can also be 50 mm or more, 60 mm or more, 65 mm or more, 70 mm or more, 75 mm or more, 80 mm or more. Starting from the increase in assembly cost caused by the increase in the weight of the plate, the upper limit of the plate thickness is set to 250 mm. In addition, as the upper limit value of the plate thickness, 200 mm is preferred, and 150 mm is more preferred.

[0118] Figure 7 shows the relationship between the number of corners n and the diameter-thickness ratio D / t that results in bending performance equivalent (90% or more) to that of the circular cylindrical structure. In Figure 7 , the horizontal axis is the number of corners n, and the vertical axis is the diameter-thickness ratio D / t. Moreover, in Figure 7In it, points at which, when the number of corners n is increased at a certain diameter-to-thickness ratio D / t, the number of corners n becomes 90% or more, 95% or more, and 99% or more of the maximum endurance ratio are respectively plotted. They represent a region (circular-equivalent region R1) capable of achieving bending performance equivalent to (90% or more) that of a circular cylindrical structure, and a buckling strength deficiency region R2 and a cross-sectional performance deficiency region R3 in a region where the maximum endurance ratio is less than 90%. The buckling strength deficiency region R2 is a region where the smaller the number of corners n, the longer the side width B and the thinner the plate thickness t, and consequently, the bending endurance decreases significantly due to local buckling of the plate. The cross-sectional performance deficiency region R3 is a region where, when the number of corners n is small, the second moment of area with respect to the bending load becomes small, and thus the cross-sectional performance cannot be obtained.

[0119] As Figure 7 shown, it can be seen that: when the number of corners is 6 (hexagon) and the diameter-to-thickness ratio D / t is 80 or less, the maximum endurance ratio is 90% or more, becoming the circular-equivalent region R1, and thus circular-equivalent performance can be obtained. On the other hand, it can be seen that: when the number of corners is 6 (hexagon) and the diameter-to-thickness ratio D / t is 120 (a case exceeding 80), the maximum endurance ratio is less than 90%, becoming the buckling strength deficiency region R2, and thus the endurance decreases significantly due to local buckling of the plate. In the cases of the number of corners 8 (octagon) and the number of corners 10 (decagon), compared with the case of the number of corners 6 (hexagon), even when the diameter-to-thickness ratio D / t is increased to 120, a maximum endurance ratio of 90% or more can be ensured.

[0120] In addition, in the case where the number of corners is 12 (dodecagon) or more, regardless of the diameter-to-thickness ratio D / t, the maximum endurance ratio is 90% or more and becomes the circular-equivalent region R1, and the maximum endurance ratio with respect to the diameter-to-thickness ratio D / t also increases. In particular, it can be seen that: in the case where the number of corners is 16 (hexadecagon) or more, regardless of the diameter-to-thickness ratio D / t, the maximum endurance ratio is 99% or more, and bending performance approximately the same as that of a circular cross-section can be obtained.

[0121] Moreover, in the case where the number of corners is 4 (quadrilateral), regardless of the diameter-to-thickness ratio D / t, the maximum endurance ratio is less than 90% and becomes the cross-sectional performance deficiency region R3. That is, it can be seen that: when only the number of corners n is small, the second moment of area with respect to the bending load becomes small, and thus the cross-sectional performance cannot be obtained.

[0122] According to the analysis results of this embodiment, when the diameter-thickness ratio D / t is 80 or less, the condition for the polygonal cylindrical structure to ensure more than 90% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 6 or more. When the diameter-thickness ratio D / t is 80 or less, the condition for the polygonal cylindrical structure to ensure more than 95% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 8 or more. When the diameter-thickness ratio D / t is 80 or less, the condition for the polygonal cylindrical structure to ensure more than 99% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 10 or more.

[0123] In addition, when the diameter-thickness ratio D / t is 120, the condition for the polygonal cylindrical structure to ensure more than 90% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 8 or more. In addition, when the diameter-thickness ratio D / t is 120, the condition for the polygonal cylindrical structure to ensure more than 95% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 10 or more. When the diameter-thickness ratio D / t is 120, the condition for the polygonal cylindrical structure to ensure more than 99% of the circular performance (maximum endurance ratio) of the circular cylindrical structure is that the number of corners n is 12 or more. The number of corners n can be an even number.

[0124] If the above is sorted out, the above formula (1) or (2) can be obtained.

[0125] The above has described the embodiments of the polygonal cylindrical structure of the present invention, but the present invention is not limited to the above embodiments and can be appropriately changed within the scope not departing from its gist.

[0126] For example, in the above embodiment, the basic structure of a wind power generation device is exemplified as the polygonal column 1 (polygonal cylindrical structure), but in other embodiments, the basic structure of an offshore wind power generation device using the above polygonal column 1 (polygonal cylindrical structure) is used. In this case, the polygonal column 1 becomes the foundation of an offshore wind power generation device, for example. Specifically, it can be used as a foundation structure of a monopile type, gravity type, or jacket type for offshore wind use or a foundation structure of a floating type TLP (Tension Leg Platform) type or semi-submersible type, and other structures for other uses can also be of a polygonal cylindrical structure.

[0127] In addition, in the present embodiment, the polygonal column 1 having a conical shape whose cross-sectional shape shrinks as it goes upward in the column axis direction is adopted, but it can also be a polygonal cylindrical structure having the same cross-sectional shape and the same cross-sectional dimensions at any height in the column axis direction, that is, a polygonal cylindrical structure having a non-reduced diameter shape as a whole.

[0128] In addition, in the present embodiment, there is also a mode in which the number of corners n of the polygonal cross-section of the polygonal columnar body 1 satisfies the above formula (1) or (2), but it is not limited to the number of corners n that satisfies these formulas (1) or (2).

[0129] In addition, the constituent elements in the above-described embodiment can be appropriately replaced with well-known constituent elements without departing from the gist of the present invention.

[0130] Industrial Applicability

[0131] According to the present invention, it is possible to achieve a good balance between exhibiting the same bending performance as that of a circle and reducing costs by omitting the bending process and reducing the welding process.

[0132] Explanation of Reference Numerals

[0133] 1 Polygonal columnar body (polygonal cylindrical structure)

[0134] 10 Flat plate member

[0135] 10A Ring body

[0136] W Welding part

Claims

1. A polygonal cylindrical structure, the cross-sectional shape of which in the horizontal direction is formed by the same number of angles, The polygonal cylindrical structure is formed by connecting steel flat members in the circumferential direction and the column axis direction by welding, The cross-sectional shape is a polygonal cross-section of hexagon or more and icositetragon or less, The plate thickness of the flat member is 40 mm or more and 250 mm or less, The ratio of the outer diameter to the plate thickness of the polygonal cross-section, i.e., outer diameter / plate thickness, is 200 or less.

2. The polygonal cylindrical structure according to claim 1, The number of angles n of the polygonal cross-section satisfies formula (1) or formula (2), n≥6 {when D / t≤80}…(1) n≥(D / t) / 20 + 2 {when D / t>80}…(2) Here, D is the outer diameter in mm, t is the plate thickness in mm, and n is the number of angles and is a natural number.

3. The polygonal cylindrical structure according to claim 1 or 2, The polygonal cross-section is a regular polygon.

4. A design method of a polygonal cylindrical structure, which is a design method of a polygonal cylindrical structure whose cross-sectional shape in the horizontal direction is formed by the same number of angles, The design is carried out in the following manner: The polygonal cylindrical structure is formed by connecting steel flat members in the circumferential direction and the column axis direction by welding, The cross-sectional shape is a polygonal cross-section of hexagon or more and icositetragon or less, The plate thickness of the flat member is 40 mm or more and 250 mm or less, The ratio of the outer diameter to the plate thickness of the polygonal cross-section, i.e., outer diameter / plate thickness, is 200 or less.

5. The design method of a polygonal cylindrical structure according to claim 4, The design is carried out in the following manner: The number of angles n of the polygonal cross-section satisfies formula (1) or formula (2), n≥6 {when D / t≤80}…(1) n≥(D / t) / 20 + 2 {when D / t>80}…(2) Here, D is the outer diameter in mm, t is the plate thickness in mm, and n is the number of angles and is a natural number.

6. The design method of a polygonal cylindrical structure according to claim 4 or 5, The design is carried out in the following manner: The polygonal cross-section is a regular polygon.

7. A foundation structure for an offshore wind power generation device, The foundation structure for an offshore wind power generation device has the polygonal cylindrical structure according to claim 1 or 2, The polygonal cylindrical structure serves as the foundation of the offshore wind power generation device.

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