TW202428985A - Polygonal cylindrical structure, method for designing polygonal cylindrical structure, and foundation structure for ocean wind power generation facility using polygonal cylindrical structure - Google Patents

Abstract

According to the present invention, a cross-sectional shape in the horizontal direction is formed by the same number of corners, and a polygonal columnar body (1) is formed by steel flat plate members (10) being coupled by welding in the circumferential direction and column axis direction. The polygonal columnar body (1) forms a polygonal cross-section with a cross-sectional shape having 6-24 squares, and the plate thickness of the flat plate members (10) is 40-250 mm. The ratio of the outer diameter D to plate thickness t (outer diameter D/plate thickness t) of the polygonal cross-section is 200 or lower.

Description

Polygonal cylindrical structure, design method of polygonal cylindrical structure, and foundation structure for offshore wind power generation equipment using polygonal cylindrical structure

The present invention relates to a polygonal cylindrical structure, a design method of a polygonal cylindrical structure, and a foundation structure for offshore wind power generation equipment using a polygonal cylindrical structure. This case claims priority based on Special Application No. 2022-199328 filed in Japan on December 14, 2022, and its contents are cited here.

In the past, in order to ensure the amount of offshore wind power generated, the size of windmills and the towers or foundations supporting them has been increasing. Generally speaking, a circular structure composed of cylindrical tubes is often used in towers or foundations, and in the future, it is expected that large-diameter cylindrical tubes with an outer diameter of more than 10m will be used as cylindrical tubes for the foundation. As the equipment becomes larger, the strength and rigidity must be improved, and the outer diameter or wall thickness must also be increased. Generally speaking, as shown in Patent Document 1, a steel plate that has been bent is welded in the circumferential direction to produce a short tube, and the short tubes are further welded to each other in the column axis direction to construct a tower or foundation. In this case, the capacity of the bending processing equipment will be limited. In addition to being unable to cope with thicker walls or larger diameters, there will also be the problem of increased costs.

In contrast, as a structure that does not require bending, the following structure is known: In a columnar floating body constituting a floating offshore wind power generation facility, a plurality of flat steel plates are connected in the circumferential direction by welding to construct a polygonal cross-section (see, for example, Patent Document 2). Prior Art Document Patent Document

Patent document 1: Japanese Patent No. 4708365 Patent document 2: Japanese Patent No. 2022-1474

Invention Problems to be Solved

However, the above-mentioned polygonal cross-section structure has the following problems. That is, in Patent Document 2, although the polygon is constructed by connecting flat steel plates in the circumferential direction by welding, there is a concern that the cost will increase because the number of angles will increase excessively. In addition, in order to make the polygonal structure have the same bending performance as the circular structure under the condition of the same cross-sectional area, although it is generally possible to increase the cross-sectional secondary moment by increasing the outer diameter, the plate thickness will become relatively smaller due to the increase in the circumference, which will reduce the local buckling resistance of the plate. In addition, since the shape of the limit state of buckling is determined by changing from a circular shape to a polygon, the buckling of the elephant's foot generated in the circular member will change to the local buckling of the plate, so the number of polygon angles must be increased and the width-to-thickness ratio of one side must be reduced to improve the local buckling resistance. However, if the number of angles increases, the weld line length and the number of assembly steps will increase, which will increase the cost. There is still room for improvement in this regard.

The present invention is completed in view of the above-mentioned problems, and its purpose is to provide a polygonal cylindrical structure, a design method of a polygonal cylindrical structure, and a foundation structure for offshore wind power generation equipment using a polygonal cylindrical structure, which can balance the bending performance equivalent to that of a circular structure, and reduce costs by omitting the bending processing step and reducing the welding step. Means for solving the problem

<1> Aspect 1 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 the same number of angles, and is characterized in that: the cross-sectional shape is formed by connecting steel flat plate members by welding in the circumferential direction and the cylindrical axis direction, the cross-sectional shape is a polygonal cross-sectional shape of more than hexagonal and less than 24-sided, the plate thickness of the flat plate member is more than 40mm and less than 250mm, and the ratio of the outer diameter to the plate thickness (outer diameter/plate thickness) of the polygonal cross-sectional shape is less than 200. <2> Aspect 1 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 the same number of angles, and is characterized in that: the cross-sectional shape is formed by connecting steel flat plate members by welding in the circumferential direction and the column axis direction, the cross-sectional shape is a polygonal cross-section of more than hexagonal and less than 24-sided, the plate thickness of the flat plate member is more than 40mm and less than 250mm, and the ratio of the outer diameter to the plate thickness (outer diameter/plate thickness) of the polygonal cross-section is less than 200.

In the present invention, in a polygonal cross section whose horizontal cross section shape is a polygonal cross section of a polygonal cylindrical structure of at least 6-sided and at most 24-sided, the plate thickness of the flat plate member is set to at least 40 mm and at most 250 mm, and the ratio of the outer diameter to the plate thickness (outer diameter/plate thickness) is set to at most 200, thereby suppressing local buckling, selecting the specification of the number of angles that can achieve the same cross-sectional area as a circle and the same bending performance as a circle, and manufacturing with a polygonal cylindrical structure that can shorten the weld line length. In this way, in the present invention, the configuration of the flat plate member can be constructed only by geometric adjustment, the bending processing step can be omitted, and the cost-consuming assembly welding step can be reduced. Therefore, in the present invention, it is possible to balance the improvement of bending performance by making it equal to a circular shape and the suppression of cost increase. In addition, in the present invention, since reinforcing members such as ribs are not required, a low-cost polygonal cylindrical structure can be provided.

<3> In the aspect 1 and aspect 2 of the polygonal cylindrical structure of the present invention, it is more preferable that the angle number n of the polygonal cross section satisfies the formula (1) or the formula (2). <4> In the aspect 1 and aspect 2 of the design method of the polygonal cylindrical structure of the present invention, it is more preferable that the angle number n of the polygonal cross section satisfies the formula (1) or the formula (2).

n≧6　｛When D/t≦80｝　…(1) n≧(D/t)/20＋2　｛When D/t＞80｝　…(2) Here, D: outer diameter (mm), t: plate thickness (mm), n: angle (natural number).

In this case, the minimum number of angles n that can achieve the same cross-sectional area as a circle and the same bending performance can be determined according to the diameter-to-thickness ratio D/t using equation (1) or equation (2), and a polygonal cylindrical structure can be manufactured with the minimum weld line length.

<5> In the aspect 1 or aspect 2 of the polygonal cylindrical structure of the present invention, it is preferable that the aforementioned polygonal cross section is a regular polygon. <6> In the aspect 1 or aspect 2 of the design method of the polygonal cylindrical structure of the present invention, it is preferable that the aforementioned polygonal cross section is a regular polygon.

In this case, since the cross-sectional shape is close to a circle, a polygonal cylindrical structure set to the following specifications can be manufactured with better accuracy: as described above, the specification of the minimum angle (that is, the minimum weld line length) that exhibits bending performance equivalent to that of a circle can be manufactured.

<7> Aspect 1 of the foundation structure for offshore wind power generation equipment of the present invention is characterized in that it has a polygonal cylindrical structure described in any one of aspects 1 to 3, and the aforementioned polygonal cylindrical structure serves as the foundation of the offshore wind power generation equipment. Effect of the invention

According to the polygonal cylindrical structure, the design method of the polygonal cylindrical structure, and the foundation structure for offshore wind power generation equipment using the polygonal cylindrical structure of the present invention, it is possible to achieve a balanced bending performance equivalent to that of a circular shape, and to reduce costs by omitting the bending processing step and reducing the welding step.

The form used to implement the invention

The following is a description of the polygonal cylindrical structure of an embodiment of the present invention according to the drawings.

As shown in FIG. 1 , the polygonal cylindrical structure of the present embodiment is, for example, a tower (not shown) or a foundation structure of a wind power generation device (hereinafter referred to as a polygonal columnar body 1) as an example, wherein the tower is a rotor composed of fixed blades, etc., and the foundation structure supports the tower from below.

Here, in the polygonal columnar body 1, the direction parallel to the central axis O is called the columnar axis direction, the direction around the central axis O is called the circumferential direction, and the direction perpendicular to the central axis O is called the radial direction. In addition, the direction toward 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.

As shown in Fig. 1 and Fig. 2, the polygonal column 1 is a polygonal cylindrical structure formed by connecting the horizontal cross-sectional shape with the same number of angles (octagon in this case). The polygonal column 1 is formed by connecting the steel flat plate members 10 by welding in the circumferential direction and the column axis direction. The cross-sectional shape of the polygonal column 1 in the horizontal direction perpendicular to the column axis direction is a regular polygonal cross-sectional shape forming a regular octagon. In addition, the flat plate member 10 may be a single steel plate, or may be a steel plate formed by welding a plurality of plates in the circumferential direction or the column axis direction.

In addition, the cross-sectional shape of the polygonal column 1 can be any polygonal cross-section that is larger than a hexagon and smaller than a 24-gon. Furthermore, it is not limited to a regular polygon with all sides of equal length, and a polygon with a part or all of different sides may be used. Furthermore, it is not limited to a cylindrical structure of a polygon or regular polygon with equal thickness in the column axis direction, and a polygon or regular polygon with different thickness in the column axis direction may be used. For example, the thickness of the flat plate member 10 may be thinned upward from a predetermined height position in the column axis direction (the upper part of the cylindrical structure). The predetermined height position may also be, for example, any position above the lower end of the polygonal column 1. In a portion where the thickness changes like this, the thickness of other flat plate members 10 adjacent to the upper side will be thinner than the thickness of a certain flat plate member 10. Furthermore, the cylindrical structure is not limited to a polygonal or regular polygonal shape in which the lengths of the flat plate members 10 in the axial direction are all equal, and a polygonal or regular polygonal shape in which the lengths of the annular bodies 10A in the axial direction are different can also be adopted. For example, it can also be arranged so that the length of the flat plate member 10 in the axial direction becomes longer from a predetermined height position in the axial direction toward the upper side (the upper part of the cylindrical structure). In the portion where the length changes like this, compared with the length of a certain flat plate member 10 in the axial direction, the length of other flat plate members 10 adjacent to the upper side in the axial direction will be longer. In addition, it can also be arranged so that the thickness of the flat plate member 10 becomes thinner in the axial direction toward the upper side (the upper part of the cylindrical structure), and the length in the axial direction becomes longer. For example, it is not necessary to gradually change the thickness or length of the flat plate member 10 upward in the column axis direction (the upper part of the cylindrical structure), but it can also change from any height position in the column axis direction. In this case, compared with the thickness and column axis length of a certain flat plate member 10, the other flat plate members 10 adjacent to the upper side will have a thinner thickness and a longer length in the column axis direction.

Here, in the present invention, the following situations are treated as regular polygons. Among the dimensions of the flat plate member 10 in the circumferential direction, the dimensions of all the flat plate members 10 fall within ±2% of the average value. The angle with the adjacent flat plate member 10 falls within (among the internal angles of the regular polygon, all the internal angles are (180×(n-2))/n ±2%.

The polygonal column 1 is a long strip arranged with the column axis parallel to the up-down direction, and is formed into a hollow cylindrical shape. A device that does not contribute to the structural performance may be provided in the hollow portion of the polygonal column 1. In addition, the polygonal column 1 is provided in a pyramidal shape (conical shape) with only a portion of the top, or a cross-sectional shape that gradually decreases toward the top. That is, the cross-sectional shape at any height in the column axis direction is a similar shape. The polygonal body 1 may not be a conical shape in the column axis direction.

The flat plate member 10 constituting the polygonal column 1 is a thick plate member without a curved portion or a bent portion. The plate thickness t of the flat plate member 10 is greater than 40 mm and less than 250 mm. For the polygonal cross section of the polygonal column 1 having the same bending performance as a circle, it is ideal to set the ratio of the outer diameter D (mm) to the plate thickness t (mm) (outer diameter D/plate thickness t) to less than 200, because when it exceeds 440, even a 24-sided polygonal cross section still has difficulty in exerting the same bending performance as a circle. Figure 10 shows a cylinder 100 having the same circumference as the circumference of the cross section of the polygonal column 1. The outer diameter D of the polygonal column 1 is equivalent to the diameter D100 of the center line of the flat plate member 110 of the cylinder 100 with the same circumference in the cross section.

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 satisfies the formula (1) or the formula (2).

n≧6　{When D/t≦80}　…(1) n≧(D/t)/20＋2　{When D/t＞80}　…(2) Here, D: outer diameter (mm), t: plate thickness (mm), n: angle (natural number). In addition, when the unit of outer diameter D is meter (m), the unit will be unified into millimeter (mm) when calculating D/t.

The flat plate members 10 connected in the circumferential direction and the column axis direction are connected to each other by welding. The symbol W in Figure 1 shows the welding position (welding portion). The welding portion W has a transverse welding portion W1 extending along the circumferential direction and a longitudinal welding portion W2 extending along the column axis direction. In this embodiment, 8 flat plate members 10 of the same shape are connected in the circumferential direction, whereby the cross-sectional shape of the polygonal column 1 becomes a regular octagon.

The polygonal columnar body 1 of this embodiment is formed by connecting 8 flat plate members 10 in the circumferential direction and connecting one or more layers (six layers in FIG. 1 ) in the column axis direction. In addition, the longitudinal welds W2 of each of the ring-shaped bodies 10A connected in the column axis direction are continuous with each other. The transverse welds W1 of each of the ring-shaped bodies 10A can also be continuous with each other in the circumferential direction. In addition, when the arrangement heights of the adjacent flat plate members 10 in the column axis direction are different, that is, in the case of the so-called staggered arrangement, although the transverse weld W1 is not continuous in the circumferential direction, the longitudinal weld W2 is continuous in the column axis direction.

Next, the manufacturing method of the polygonal column 1 shown in Figures 1 and 2 is explained. First, a plate piece (flat plate member 10) of a predetermined size is cut out from a large steel plate of the parent material. Here, the plate piece (flat plate member 10) of a predetermined size is, for example, a plate piece whose length in the circumferential direction is greater than 1.0m and less than 5.0m when constructing a polygonal column, and whose length in the column axis direction is greater than 2.0m and less than 15.0m. In this cutting step, the number of flat plate members 10 required to construct the polygonal column 1 is cut out. However, the large steel plate of the parent material can be directly used as the flat plate member 10 without going through the cutting step. In addition, the flat plate member 10 may be a cut plate or a single steel plate used without cutting, or may be a steel plate formed by welding cut plates or steel plates used without cutting in the circumferential direction or the column axis direction. In this way, when the flat plate member 10 is formed by welding a plurality of plates in the circumferential direction or the column axis direction, as long as the angle formed by adjacent plates in the circumferential direction is within 1.0°, they can be regarded as the same flat plate member 10.

After that, for example, the flat plate member 10 is arranged on a stand not shown in the figure. At this time, the two adjacent flat plate members 10 in the circumferential direction are arranged butt-jointed at a predetermined intersection angle. Here, the predetermined intersection angle refers to the angle of the cross-sectional shape (polygon) of the polygonal columnar body 1 (i.e., the inner angle of the polygon) completed by a plurality of flat plate members 10. If it is a regular octagon as shown in FIG. 1, the intersection angle at which each side of the two adjacent flat plate members 10 is right angled is 135°. In this arrangement step, the flat plate member 10 is arranged as it is without bending the flat plate member 10 as in the conventional technology. In addition, the flat plate member 10 arranged on the stand is preferably arranged with the side to be welded facing upward, and welded with the welding gun facing downward. On the other hand, there are also cases where multiple flat plate components 10 are directly arranged vertically to ensure a predetermined inner angle, and the welding gun is welded horizontally or downward. In this case, the stand may not be used.

In addition, when the flat plate member 10 is arranged on the platform, for example, a configuration jig (not shown) having an abutment surface set to the above-mentioned predetermined intersection angle is used, and the flat plate member 10 is arranged to abut the abutment surface of this configuration jig, thereby easily positioning adjacent flat plate members 10 with each other.

Next, since grooves are formed in the butting portions of the adjacent flat plate members 10 that have been arranged, the grooves are welded and joined, and the flat plate members 10 are connected to each other through the welded portion W. The flat plate members 10 are assembled into, for example, the above-mentioned annular body 10A, or a partially cross-sectional annular body formed by dividing the cross section of the annular body 10A. Furthermore, the annular body 10A or the partially cross-sectional annular body is sequentially welded and joined on the upper side in the column axis direction at the predetermined setting position of the polygonal columnar body 1, thereby constructing the polygonal columnar body 1. In addition, as shown in FIG. 2 , the butted portions of the adjacent flat plate members 10 that have been arranged may also be natural grooves or V-shaped grooves, and may also be welded from the outer side of the cross section to form the welded portion W, and is not limited to welding from one side (inside or outside), and may also be formed from both sides. Also, as shown in FIG. 3 , X-shaped grooves 10c and 10d may be provided in advance at each end of the adjacent flat plate members 10 in the circumferential direction, and the butted portions of the X-shaped grooves 10c and 10d may be welded from both sides of the outer side and the inner side of the cross section to form the welded portion W, and is not limited to welding from one side (inside or outside), and may also be formed from both sides.

In addition, the operation of manufacturing the segmented ring body 10A etc. can also be carried out in a factory or site near the installation location of the polygonal column 1, or after manufacturing in a processing plant etc. far away from the installation location of the polygonal column 1, it can be transported to the installation location of the polygonal column 1 by a truck or ship etc.

According to the polygonal cylindrical structure described above, i.e., the polygonal columnar body 1, 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 the steel flat plate member 10 by welding in the circumferential direction and the column axis direction. The polygonal columnar body 1 is a polygonal cross-sectional shape with a cross-sectional shape of more than 6 angles and less than 24 angles, and the plate thickness of the flat plate member 10 is more than 40 mm and less than 250 mm. The polygonal cross-sectional shape is a ratio of the outer diameter D to the plate thickness t (outer diameter D/plate thickness t) of 200 or less.

By setting such a structure, under the condition that the cross-sectional shape of the polygonal cross section in the horizontal direction of the polygonal columnar body 1 is a polygonal cross section of more than 6 angles and less than 24 angles, the plate thickness t of the flat plate member 10 is set to more than 40 mm and less than 250 mm, and the ratio of the outer diameter D to the plate thickness t (outer diameter D/plate thickness t) is set to less than 200, thereby suppressing local buckling, and selecting the specification of the minimum number of angles that can achieve the same cross-sectional area as a circle and the same bending performance as a circle, thereby manufacturing the polygonal columnar body 1 with the minimum weld line length. In addition, the above-mentioned "same" is defined as, for example, the maximum endurance ratio of the polygonal cross section to the circular cross section is 0.9 (90%) or more. Therefore, in this embodiment, the configuration of the flat plate member 10 can be constructed only by geometric adjustment, the bending process step can be omitted, and the costly assembly welding step can be minimized, thereby suppressing the increase in cost. In addition, in this embodiment, since reinforcing members such as ribs are no longer required, a low-cost polygonal columnar body 1 can be provided.

Furthermore, in this embodiment, the number of angles n of the polygonal cross section satisfies the above formula (1) or formula (2). In this case, the minimum number of angles n that has the same cross-sectional area as a circle and the same bending performance can be determined by formula (1) or formula (2) according to the diameter-thickness ratio D/t, and the polygonal columnar body 1 can be manufactured with the minimum weld line length.

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 may also satisfy equation (3) or equation (4).

n≧8　｛When D/t≦80｝　…(3) n≧(D/t)/20＋4　｛When D/t＞80｝　…(4)

When the number of angles n of the polygonal cross section satisfies equation (3) or equation (4), the maximum endurance ratio is greater than 0.95 (95%).

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 may also satisfy equation (5) or equation (6).

n≧10　｛When D/t≦80｝　…(5) n≧(D/t)/20＋6　｛When D/t＞80｝　…(6)

When the number of angles n of the polygonal cross section satisfies equation (5) or equation (6), the maximum endurance ratio is greater than 0.99 (99%).

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 may also satisfy equation (7) or equation (8).

6≦n≦10　｛When D/t≦80｝　…(7) (D/t)/20＋2≦n≦(D/t)/20＋6　｛When D/t＞80｝　…(8)

When the number of angles n of the polygonal cross section satisfies equation (7) or equation (8), the maximum endurance ratio is greater than 0.90 (90%).

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 may also satisfy equation (9) or equation (10).

8≦n≦12　｛When D/t≦80｝　…(9) (D/t)/20＋4≦n≦(D/t)/20＋8　｛When D/t＞80｝　…(10)

When the number of angles n of the polygonal cross section satisfies equation (9) or equation (10), the maximum endurance ratio is greater than 0.95 (95%).

The number of angles n (natural number) of the polygonal cross section in the polygonal columnar body 1 may also satisfy equation (11) or equation (12).

10≦n≦14　｛When D/t≦80｝　…(11) (D/t)/20＋6≦n≦(D/t)/20＋10　｛When D/t＞80｝　…(12)

When the number of angles n of the polygonal cross section satisfies equation (11) or equation (12), the maximum endurance ratio is greater than 0.99 (99%).

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 polygonal cross section is also designed so that the ratio of the outer diameter D to the plate thickness t (outer diameter/plate thickness) is less than 200. In addition, the number of angles n of the polygonal cross section is designed to satisfy the formula (1) or the formula (2). The polygonal cross section is designed to be a regular polygon.

Furthermore, in the present embodiment, since the cross section of the polygon is a regular polygon and the cross section shape is closer to a circle than a polygon with different side lengths, the polygonal columnar body 1 can be manufactured with better accuracy as described above with the minimum angle (i.e., the minimum weld line length) that exhibits the same bending performance as a circle. That is, when the side length error generated during manufacturing is taken into account, the method of connecting flat plate members with the same side length can manufacture the polygonal cylindrical structure with better accuracy than connecting flat plate members with different side lengths.

As described above, in the polygonal columnar body 1 of the wind power generation equipment of this embodiment, the design method of the polygonal cylindrical structure, and the foundation structure for the offshore wind power generation equipment using the polygonal cylindrical structure, it is possible to balance the bending performance equivalent to that of a circle, and to seek cost reduction by omitting the bending processing step and reducing the welding step.

The polygonal column 1 shown in FIG. 1 is a pyramidal shape (cone shape) whose cross-sectional shape gradually decreases toward the upper side. Each flat plate member 10 constituting the polygonal column 1 shown in FIG. 1 is a trapezoid that decreases toward the upper side in a front view. As shown in FIG. 8 , the polygonal column 1' may also be cylindrical. That is, the outer diameter of the cross-section of the polygonal column 1' may also be roughly the same in the height direction. Each flat plate member 10' constituting the polygonal column 1' shown in FIG. 8 is rectangular in a front view. By setting the polygonal column 1' to be cylindrical, there is no need to cut the flat plate member 10 into a trapezoid. Regarding the welded portion W' of the polygonal columnar body 1' shown in FIG8, similarly to the welded portion W of the polygonal columnar body 1 shown in FIG1, the longitudinal welded portions W2' of each annular body 10A' connected in the column axis direction are continuous with each other in the column axis direction, and the transverse welded portions W1' of each annular body 10A' may be continuous with each other in the circumferential direction, or may be formed in a staggered manner. In the polygonal cylindrical structure formed by the polygonal columnar body 1' shown in FIG8, the same effect as that of the polygonal cylindrical structure formed by the polygonal columnar body 1 shown in FIG1 can also be obtained. In addition, as shown in FIG9, the polygonal columnar body 1B' may be a cone-shaped only at a part of the upper end, and a cylindrical shape may be formed below it. In FIG. 9 , the upper two-layer annular body 10B' is formed into a pyramid shape. The welded portion W' (W1', W2') at this time is the same as the welded portion W described above.

When the polygonal body 1 is a conical shape, it is desired that the bottom portion that is easily bent satisfies equation (1) or equation (2). It is more desired that as long as equation (1) or equation (2) is satisfied at any column axis height, the outer diameter D or plate thickness t in the column axis direction can also be changed.

Next, the following describes an embodiment carried out to verify the effect of the polygonal cylindrical structure of the above-mentioned embodiment.

(Example) In the example, numerical simulation analysis (finite element analysis) is used to apply a horizontal load F to the vertex (upper part) of the cantilever beam model 2 that has modeled the polygonal cylindrical structure shown in FIG. 4, and the endurance of the polygonal cylindrical structure is evaluated.

As shown in Table 1, in the embodiment, a cantilever beam model 2 as shown in FIG. 4 was prepared in 5 analytical cases (Case 1, Case 2, Case 3, Case 4, and Case 5), and numerical simulation analysis was performed by changing the diameter-to-thickness ratio (D/t) of the polygonal shape for each analytical case 1 to 5. The specific conditions of each analytical case 1 to 5 are shown in Table 1. The diameter-to-thickness ratio (D/t) in the analytical case is 40 for Case 1, 80 for Case 2, 120 for Case 3, 160 for Case 4, and 200 for Case 5. The "outer diameter" in Table 1 is the distance between the center of the plate thickness of the flat plate member 10 with the center line of the cylinder with the same circumference as the reference in the cross section. The "circumference" is the outer diameter (m) of the cylinder with the same circumference as the reference in the cross section × pi, that is, the plate width × the number of angles. "Area" is calculated by plate thickness (mm) × perimeter (m), that is, perimeter × plate thickness (plate width × number of corners × plate thickness).

[Table 1]

Table 2 shows the width B (m) and plate thickness t (mm), and the width-to-thickness ratio (B/t) of each angle number n (the angle number n of the polygon is 4, 6, 8, 10, 12, 16, and 24) of the 7 types in analysis cases 1 to 5. In addition, as a comparative example of the polygonal cylindrical structure in this embodiment, a model of a circular cylindrical structure with a circular cross section was made and the same analysis was performed. The analysis condition of the circular cylindrical structure is that the regular 256-polygon, that is, the polygonal cylindrical structure with a side width of 0.123m in analysis cases 1 to 5 is regarded as the same as a cylinder for analysis. The "side width" in Table 2 is the value of the circumference/angle number n.

[Table 2]

In this embodiment, the maximum stress (equivalent plastic strain, maximum bearing capacity) acting on each polygonal cylindrical structure when a horizontal load (bending load) is applied is obtained by analysis for each angle number n of the seven types of patterns in analysis cases 1 to 5. Similarly, the maximum stress (bearing capacity) acting on the circular cylindrical structure of the comparative example when a horizontal load is applied is obtained by analysis.

Figures 5(a) to (d) show the cross-sectional shape of the cylindrical structure on the left side of the paper, and the distribution of the equivalent plastic strain when the bending load of the analysis result is the maximum on the right side of the paper as an example of a contour map. Figure 5(a) is an example of a case of a quadrangle with an angle of 4. Figure 5(b) is an example of a case of an octagon with an angle of 8. Figure 5(c) is an example of a case of a dodecagon with an angle of 12. Figure 5(d) is an example of a comparative example and a case of a circular cross-section. The symbol K shown in Figures 5(a) to (d) shows the location (high stress area) where the equivalent plastic strain is generated in each contour.

It can be seen that in Figures 5(a) to (d), a relatively large stress acts in the setting part (base end) of the cylindrical structure. In addition, from the state of the contour lines, it can be confirmed that the angle number 8 in Figure 5(b) and the angle number 12 in Figure 5(c) are the same stress distribution and stress magnitude as the circular cross-section of the comparative example in Figure 5(d). On the other hand, when the angle number is 4 in Figure 5(a), compared with the circular cross-section of the comparative example in Figure 5(d), the range (area) of stress distribution is expanded, especially in the vertical direction (column axis direction), the stress range is greatly expanded, so it can be seen that the endurance is insufficient.

Figures 6 and 7 show the analysis results. Figure 6 shows the relationship between the angle number n and the bending performance of the polygonal cylindrical structure, and shows a case where the diameter-thickness ratio D/t is 80 (Case 2). In addition, although only the case where the diameter-thickness ratio D/t is 80 is shown in Figure 6 as a representative example in this embodiment, the cases where the diameter-thickness ratio D/t is 40 (Case 1), 120 (Case 3), 160 (Case 4), and 200 (Case 5) have roughly the same inclination in the graph. In Figure 6, the horizontal axis is the angle number n, and the vertical axis is the ratio (maximum endurance ratio) of the maximum endurance of the polygonal cylindrical structure (polygon) to the maximum endurance of the circular cylindrical structure (cylinder). Here, as the evaluation standard of 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 more than 90%, it is defined as the same endurance (bending performance).

As shown in FIG6 , it can be seen that the angle number n for which the maximum endurance ratio is 90% or more is 6 or more. Specifically, the following situations can be confirmed: the maximum endurance ratio is 90% or more when the angle number is 6 (hexagon) or more, the maximum endurance ratio is 95% or more when the angle number is 8 (octagon) or more, and the maximum endurance ratio is 99% or more when the angle number is 10 (decagon) or more. It can be seen that the minimum angle number n for obtaining a maximum endurance ratio of 90% or more, which is equivalent to a circular section, is 6 (hexagon). Here, for example, a circular cylindrical structure with an outer diameter D of 8 to 12 m is used as the object. If we consider that the polygonal cylindrical structure can exert the same (90%) or more bending performance as the circular cylindrical structure, the diameter-to-thickness ratio D/t is in the range of 80~200, then when the outer diameter D is 8~12m, the required plate thickness t is 40mm or more. In addition, the plate thickness t can also be 50mm or more, 60mm or more, 65mm or more, 70mm or more, 75mm or more, or 80mm or more. Since the increase in the weight of the plate will increase the assembly cost, the upper limit of the plate thickness is set to 250mm. In addition, the upper limit of the plate thickness is preferably 200mm, and more preferably 150mm.

Figure 7 shows the relationship between the angle n and the diameter-thickness ratio D/t for bending performance equivalent to or greater than (90%) that of a circular cylindrical structure. In Figure 7, the horizontal axis is the angle n and the vertical axis is the diameter-thickness ratio D/t. In addition, in Figure 7, the points where the angle n is greater than 90%, greater than 95%, and greater than 99% of the maximum endurance ratio are plotted when the angle n is increased at a certain diameter-thickness ratio D/t. These show the area (circular equivalent area R1) where bending performance equivalent to or greater than (90%) that of a circular cylindrical structure can be achieved, as well as the area R2 with insufficient buckling strength and the area R3 with insufficient section performance in the area less than 90% of the maximum endurance ratio. The buckling strength insufficient region R2 is a region where the side width B becomes longer as the angle n decreases, and the bending resistance caused by local buckling of the plate decreases significantly as the plate thickness t decreases. The section performance insufficient region R3 is a region where the section secondary moment relative to the bending load becomes smaller when the angle n is smaller, and the section performance cannot be obtained.

As shown in FIG7, it can be seen that when the diameter-to-thickness ratio D/t of the angle number 6 (hexagon) is 80 or less, the maximum endurance ratio is 90% or more, and it becomes the circle equivalent area R1, so the circle equivalent performance can be obtained. On the other hand, when the diameter-to-thickness ratio D/t of the angle number 6 (hexagon) is 120 (more than 80), the maximum endurance ratio is less than 90%, and it becomes the buckling strength insufficient area R2, so the endurance reduction caused by the local buckling of the plate is more significant. In the case of the angle number 8 (octagon) and the angle number 10 (decagon), compared with the case of the angle number 6 (hexagon), even if the diameter-to-thickness ratio D/t is increased to 120, the maximum endurance ratio of 90% or more can be ensured.

Furthermore, when the number of angles is 12 or more (12-sided), the maximum endurance ratio is more than 90% regardless of the diameter-thickness ratio D/t, and it becomes the circular equivalent area R1, and the maximum endurance ratio relative to the diameter-thickness ratio D/t is also larger. In particular, it can be seen that when the number of angles is 16 or more (16-sided), the maximum endurance ratio is more than 99% regardless of the diameter-thickness ratio D/t, and the bending performance almost the same as that of the circular section can be obtained. In addition, when the number of angles is 4 (4-sided), the maximum endurance ratio is less than 90% regardless of the diameter-thickness ratio D/t, and it becomes the section performance insufficient area R3. In other words, it can be seen that when the angle number n is small, the cross-sectional secondary moment relative to the bending load will become small, so the cross-sectional performance cannot be obtained.

According to the analysis results of this embodiment, when the diameter-thickness ratio D/t is less than 80, the polygonal cylindrical structure must ensure more than 90% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is greater than 6. When the diameter-thickness ratio D/t is less than 80, the polygonal cylindrical structure must ensure more than 95% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is greater than 8. When the diameter-thickness ratio D/t is less than 80, the polygonal cylindrical structure must ensure more than 99% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is greater than 10. Furthermore, when the diameter-to-thickness ratio D/t is 120, the polygonal cylindrical structure must ensure more than 90% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is 8 or more. Furthermore, when the diameter-to-thickness ratio D/t is 120, the polygonal cylindrical structure must ensure more than 95% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is 10 or more. When the diameter-to-thickness ratio D/t is 120, the polygonal cylindrical structure must ensure more than 99% of the circular performance (maximum endurance ratio) of the circular cylindrical structure when the angle number n is 12 or more. The angle number n can also be an even number. After sorting these out, the above formula (1) or formula (2) can be obtained.

Although the embodiments of the polygonal cylindrical structure of the present invention have been described above, the present invention is not limited to the above embodiments and can be appropriately modified within the scope of the gist thereof.

For example, in the above-mentioned embodiment, although the foundation structure of the wind power generation equipment is exemplified as a polygonal column 1 (polygonal cylindrical structure), other embodiments are foundation structures for offshore wind power generation equipment using the above-mentioned polygonal column 1 (polygonal cylindrical structure). In this case, the polygonal column 1, for example, will become the foundation of the offshore wind power generation equipment. Specifically, a grounded single-pile type, gravity type, or jacket type foundation structure, or a floating TLP (Tension Leg Platform) type or semi-submersible type foundation structure for offshore wind power can also be used, and structures for other purposes can also be set to a polygonal cylindrical structure.

Furthermore, in the present embodiment, although a polygonal columnar body 1 is adopted whose cross-sectional shape is tapered and decreases upward in the column axis direction, it may be a polygonal tubular structure having the same cross-sectional shape and the same cross-sectional size at any height in the column axis direction, that is, a polygonal tubular structure whose overall diameter does not decrease.

Furthermore, in the present embodiment, although there is a configuration in which the number of angles n of the polygonal cross section constituting the polygonal columnar body 1 satisfies the above-mentioned formula (1) or formula (2), it is not limited to the number of angles n satisfying these formulas (1) or formula (2).

Furthermore, the components in the above-mentioned embodiments may be appropriately replaced with known components without departing from the scope of the present invention. Industrial Applicability

According to the present invention, it is possible to achieve a balanced bending performance equivalent to that of a circular shape, and to reduce costs by omitting the bending process step and reducing the welding step.

1,1',1B': Polygonal column (polygonal cylindrical structure) 2: Cantilever beam model 10,10',110: Flat plate 10A,10A',10B': Ring 10c,10d: X-shaped slot 100: Cylinder B: Width (side width) D: Outer diameter D100: Diameter F: Horizontal load K: High stress area n: Angle R1: Circular equivalent area R2: Insufficient buckling strength area R3: Insufficient section performance area t: Plate thickness W,W': Welding area W1,W1': Horizontal welding area W2,W2': Longitudinal welding area O: Center axis

FIG. 1 is a three-dimensional view of a polygonal columnar body showing an embodiment of the present invention. FIG. 2 is a horizontal cross-sectional view of a portion of the polygonal columnar body shown in FIG. 1 in the height direction. FIG. 3 is a horizontal cross-sectional view showing the welding state of adjacent flat plate members in the circumferential direction. FIG. 4 is a diagram showing an analytical model of an embodiment. FIG. 5 (a) to (d) are diagrams showing an example of contour lines of the distribution of equivalent plastic strain when the bending load is maximum in the analytical results of the embodiment. FIG. 6 is a diagram showing the relationship between the angle number and the bending performance of the polygonal cylindrical structure of the embodiment. FIG. 7 is a diagram showing the relationship between the angle number and the diameter-thickness ratio of the embodiment with the same performance as the circle. FIG. 8 is a three-dimensional view of a polygonal columnar body showing an embodiment of the present invention. FIG. 9 is a three-dimensional diagram of a polygonal columnar body showing an embodiment of the present invention. FIG. 10 is a three-dimensional diagram of a cylinder for illustrating the structure.

1: Polygonal column (polygonal cylindrical structure)

10: Flat plate components

10A: Ring

W: Welding section

W1: horizontal welding section

W2: Longitudinal welding section

O: Center axis

Claims (7)

A polygonal cylindrical structure is a polygonal cylindrical structure in which the cross-sectional shape in the horizontal direction is formed by the same number of angles, and is formed by connecting steel flat plate members by welding in the circumferential direction and the column axis direction, the cross-sectional shape is a polygonal cross-sectional shape of more than hexagonal and less than 24-sided, the plate thickness of the flat plate member is more than 40 mm and less than 250 mm, the ratio of the outer diameter to the plate thickness (outer diameter/plate thickness) of the polygonal cross-sectional shape is less than 200. For example, in the polygonal cylindrical structure of claim 1, the angle number n of the aforementioned 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: outer diameter (mm), t: plate thickness (mm), n: angle number (natural number). A polygonal cylindrical structure as claimed in claim 1 or 2, wherein the polygonal cross-section is a regular polygon. A design method for a polygonal cylindrical structure is a design method for a polygonal cylindrical structure in which the cross-sectional shape in the horizontal direction is formed by the same number of angles. The design method is designed as follows: The structure is formed by connecting steel flat plate members by welding in the circumferential direction and the column axis direction. The cross-sectional shape is a polygonal cross-section of more than hexagonal and less than 24-sided. The plate thickness of the flat plate member is more than 40 mm and less than 250 mm. The ratio of the outer diameter to the plate thickness (outer diameter/plate thickness) of the polygonal cross-section is less than 200. The design method of the polygonal cylindrical structure of claim 4, wherein the angle number n of the polygonal section is designed to satisfy equation (1) or equation (2), n≧6 {when D/t≦80}　…(1) n≧(D/t)/20＋2 {when D/t＞80}　…(2) Here, D: outer diameter (mm), t: plate thickness (mm), n: angle number (natural number). A design method for a polygonal cylindrical structure as claimed in claim 4 or 5, wherein the polygonal cross-section is designed to be a regular polygon. A foundation structure for an offshore wind power generation device, which has a polygonal cylindrical structure as in claim 1 or 2, The aforementioned polygonal cylindrical structure serves as the foundation of the offshore wind power generation device.

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