Polygonal cylindrical structure

Abstract

To provider a polygonal cylindrical structure capable of reducing cost for construction by maintaining equal yield strength and reducing weight.SOLUTION: This polygonal cylindrical structure is formed by polygonal shapes having the same number of corners and the same sectional shape in the horizontal direction. Each polygonal shape is formed with 6 to 24 corners and includes a plurality of flat plate members 10 made of steel material. A yield stress value calculated by a metal material tensile test is used as the material strength of the steel material. The flat plate members 10 are composed of at least two types of members whose material strengths differ by 10% or more. Among the flat plate members 10 arranged in the circumferential direction, plate materials (high-strength plate material 11 and low-strength plate material 12) having different material strengths are arranged adjacent to each other on at least one side, and the circumferential ends on both sides are joined to each other by welding.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a polygonal tubular structure. [Background technology]

[0002] Conventionally, wind turbines and the towers and foundations that support them have become larger in size in order to secure the amount of power generation from offshore wind power. Generally, circular structures made of cylindrical tubes are widely used for towers and foundations, and it is expected that cylindrical tubes with a large diameter, for example, an outer diameter of more than 10 m, will be adopted as foundations in the future. As the size of the equipment increases, the strength and rigidity must be increased, and the outer diameter and wall thickness must also be increased. Usually, as shown in Patent Document 1, for example, short tubes are manufactured by bending steel plates and welding the curved plates in the circumferential direction, and the towers and foundations are constructed by further welding the short tubes together in the axial direction. In this case, there is a problem that the bending equipment has a limited capacity, cannot handle thicker walls or larger diameters, and costs also increase.

[0003] In contrast, a structure that does not involve bending is known in which a polygonal cross section is constructed by connecting multiple flat steel plates circumferentially by welding in a columnar float that constitutes a floating offshore wind power generation facility (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4708365 [Patent Document 2] Patent Publication No. 2022-1474 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the past, polygonal cylindrical structures made of connected flat plates have been proposed, but to achieve the same performance as a cylinder, it is necessary to increase the number of corners to improve the local buckling resistance or to add stiffening members to increase rigidity. However, increasing the number of corners leads to an increase in the number of manufacturing steps, and the method of installing stiffening members requires bending or welding, which reduces the economic efficiency. In addition, there is a problem that the weight increases as the cylindrical structure becomes thicker and larger, which increases the costs of construction such as assembly and transportation, and there is room for improvement in this regard.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a polygonal tubular structure that can reduce construction costs by making it lighter while maintaining the same strength. [Means for solving the problem]

[0007] (1) A first aspect of the polygonal tubular structure of the present invention is a polygonal tubular structure whose horizontal cross-sectional shape is formed by polygons with the same number of corners, the polygons being formed of at least 6 sides and at most 24 sides, the structure comprising a plurality of flat plate members made of steel, the flat plate members being composed of at least two types of members whose material strengths differ by 10% or more when the yield stress value obtained in a metal material tensile test is taken as the material strength of the steel, the flat plate members being characterized in that the flat plate members arranged in the circumferential direction are arranged adjacent to at least one side with plate members having different material strengths, and the circumferential both side ends are connected to each other by welding.

[0008] In the present invention, in polygonal cross sections having a horizontal cross-sectional shape of 6 to 24 sides, the plate thickness can be reduced by using high-strength plate material in part, and therefore weight can be reduced at the converted cross-sectional area ratio for the same strength. In addition, in the present invention, by arranging two types of flat plate members with different strengths, a stiffening effect can be achieved without the need for processing. Therefore, by adjusting to achieve the same strength, the cross-sectional area can be kept small, and weight and cost can be reduced. In addition, an increase in maximum strength can be expected by indicating the range of strength ratios in which the stiffening effect can be obtained. As a result, in the present invention, by increasing the maximum strength, it is possible to obtain performance that is equal to or greater than the maximum strength of a cylinder with the same amount of steel, or performance that is equal to or greater than a cylindrical structure with a fewer number of corners compared to a polygonal structure using plate material of the same thickness. Furthermore, in the present invention, the flat plate members are connected to each other by welding, and the bending process can be omitted, which allows for a reduction in manufacturing costs. Furthermore, in the present invention, since reinforcing members such as ribs are not required, a low-cost polygonal tubular structure can be provided.

[0009] (2) A second aspect of the present invention may be characterized in that, in the polygonal cylindrical structure of the first aspect, the flat plate members constituting the polygon among the flat plate members are composed of two types of plate members: a first plate member having high strength, and a second plate member having lower strength than the first plate member.

[0010] In this case, the stiffening effect can be achieved by using only flat plate members having two different material strengths, a high-strength first plate member and a low-strength second plate member, thereby enabling costs to be reduced.

[0011] (3) A third aspect of the present invention may be characterized in that in the polygonal tubular structure of the second aspect, a portion of the circumferential direction of the polygon has a location where the first plate material and the second plate material are arranged alternately.

[0012] In this case, the high-strength first plate material and the low-strength second plate material are arranged in a balanced manner in a portion of the circumferential direction, so that the stiffening effect of the high-strength first plate material to suppress deformation of the low-strength second plate material is more reliably exerted.

[0013] (4) In a fourth aspect of the present invention, in the polygonal tubular structure of any one of the first to third aspects, the horizontal cross-sectional shape is preferably an even-numbered polygon.

[0014] In the present invention, by making the cross-sectional shape of the polygonal cylindrical structure an even-numbered polygon, high-strength plate materials and low-strength plate materials can be arranged alternately in the circumferential direction in a balanced manner, and a stiffening effect can be achieved in which the high-strength plate materials suppress deformation of the low-strength plate materials.

[0015] (5) In aspect 5 of the present invention, in a polygonal cylindrical structure according to any one of aspects 1 to 3, when the plate thickness t and material strength σ of the lowest strength plate material among two or more types of plate materials having different material strengths are used as a basis and the strength ratio between the low-strength plate material and a plate material with a higher strength than the low-strength plate material is expressed as equation (1), it is preferable that when α is in the range of 0.5 to 1, the strength ratio is 0.25 to 4.

[0016]

number

[0017] In the present invention, when α in formula (1) is in the range of 0.5 to 1 and the strength ratio is in the range of 0.25 to 4, the thickness can be reduced by using high-strength plate materials in part by making the plate thickness of the low-strength plate material different from the equivalent plate thickness. Therefore, weight reduction is possible with the same converted cross-sectional area ratio of strength. In addition, by forming a polygonal shape by combining plate materials with thick and thin equivalent thicknesses, the adjacent thick plate materials suppress the large deformation of the plate materials with thin equivalent thickness after buckling, and exert a stiffening effect, so that the cross-sectional area can be further reduced and weight can be reduced when the same strength is achieved.

[0018] (6) In aspect 6 of the present invention, in a polygonal cylindrical structure according to any one of aspects 1 to 3, when the equivalent thickness of a high-strength plate material is determined based on the lowest strength plate material among two or more types of plate materials having different material strengths, it is preferable that the thickness of the low-strength plate material differs from the equivalent thickness in the range of α of 0.5 to 1.

[0019]

number

[0020] In the present invention, the material strength ratio is replaced with the plate thickness and defined as the equivalent plate thickness. By making the plate thickness of the low-strength plate material and the equivalent plate thickness different when α in formula (2) is in the range of 0.5 to 1, the thickness can be reduced by using a high-strength plate material in part. Therefore, weight reduction is possible with the same converted cross-sectional area ratio of strength. In addition, by forming a polygonal shape by combining plates with thick and thin equivalent thicknesses, the adjacent thick plates suppress the large deformation of the plates with thin equivalent thickness after buckling, and exert a stiffening effect, so that the cross-sectional area can be further reduced and weight can be reduced when the same strength is achieved. Effect of the Invention

[0021] According to the polygonal tubular structure of the present invention, the weight can be reduced while maintaining the same strength, thereby reducing the cost of construction. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a perspective view showing a polygonal column according to an embodiment of the present invention. [Diagram 2] 2 is a horizontal cross-sectional view of a portion of the polygonal column shown in FIG. 1 in the height direction. [Diagram 3] 4 is a horizontal cross-sectional view showing a welding state between circumferentially adjacent flat plate members. FIG. [Figure 4] FIG. 1 is a diagram explaining the section modulus, where (a) is a diagram for a regular rectangular steel pipe, and (b) is a diagram for a cylindrical steel pipe. [Diagram 5] FIG. 1 is a diagram showing an analytical model according to an embodiment. [Figure 6] 3A to 3C are diagrams showing the cross-sectional shapes of each case according to the first embodiment. [Figure 7] FIG. 4 is a diagram showing an analysis result according to the first embodiment. [Figure 8] FIG. 4 is a diagram showing an analysis result according to the first embodiment. [Figure 9] FIG. 4 is a diagram showing an analysis result according to the first embodiment. [Figure 10] FIG. 4 is a diagram showing an analysis result according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a polygonal tubular structure according to an embodiment of the present invention will be described with reference to the drawings.

[0024] As shown in Figure 1, the polygonal cylindrical structure of this embodiment is exemplified by a tower (not shown) for fixing a rotor made of blades in a wind power generation facility, and a foundation structure (hereinafter referred to as a polygonal columnar body 1) for supporting the tower from below.

[0025] Here, in the polygonal columnar body 1, the direction parallel to the central axis O is called the column axis direction, the direction going around the central axis O is called the circumferential direction, and the direction perpendicular to the central axis O is called the radial direction. Additionally, the radial direction toward the central axis O is called the inner side, and the direction away from the central axis O is called the outer side.

[0026] As shown in Figures 1 and 2, the polygonal columnar body 1 is a polygonal cylindrical structure whose horizontal cross-sectional shape is formed with the same number of corners (here, octagonal) at any height. The polygonal columnar body 1 is formed by connecting steel flat plate members 10 in the circumferential direction and the column axial direction by welding. The horizontal cross-sectional shape of the polygonal columnar body 1 perpendicular to the column axial direction forms a regular octagonal polygonal cross section.

[0027] The cross-sectional shape of the polygonal columnar body 1 may be a polygonal cross section having 6 or more sides and 24 or less sides. The polygonal columnar body 1 is not limited to a regular polygon having the same side length, and it is also possible to adopt a polygon having a different side length in part or in whole. If the number of corners is 6 or more, the polygonal columnar body 1 can obtain a performance equivalent to or greater than the maximum strength of a cylinder with the same amount of steel material due to an increase in maximum strength, or a performance equivalent to or greater than that of a cylindrical structure with a smaller number of corners compared to a polygonal structure using flat plate members of the same thickness. The above "equivalent" is defined as, for example, a maximum load cylinder ratio of the polygonal cross section to a circular cross section of 0.9 (90%) or more. That is, in the case of a quadrangle, the maximum load cylinder ratio is less than 0.8, and therefore, as described above, performance equivalent to or greater than that of a cylindrical structure cannot be obtained. Furthermore, if the number of corners of the polygonal columnar body 1 exceeds 24, the length of the weld line increases, which increases the manufacturing time and costs, so the polygonal cross section of the polygonal columnar body 1 is set to 24 or less. It is more preferable that the cross-sectional shape of the polygonal column 1 is 16 or less sides, since the load increases gradually after buckling and tends to decrease gradually after the maximum load, providing a stiffening effect.

[0028] The polygonal column 1 is a long body that is installed with its column axis oriented parallel to the vertical direction, and has a hollow cylindrical shape. The polygonal column 1 has a truncated pyramid shape (tapered shape) whose cross-sectional shape gradually decreases toward the top. In other words, the cross-sectional shapes at any height in the column axis direction are similar.

[0029] The flat plate member 10 constituting the polygonal columnar body 1 is a two-sided body with no curved or bent parts. The flat plate member 10 has an even-numbered polygonal cross-sectional shape in the horizontal direction. The plate thickness of the flat plate member 10 is, for example, 40 mm to 250 mm.

[0030] When the yield stress value obtained by JIS Z 2241 Metallic Material Tensile Test Method is taken as the material strength, the flat plate member 10 is composed of two types of members with material strengths differing by 10% or more. The flat plate member 10 is composed of two types of members: a high-strength first plate member (high-strength plate member 11) and a second plate member (low-strength plate member 12) with lower strength than the high-strength plate member 11.

[0031] For tensile testing of metal materials, the 0.2% proof stress and lower yield stress are measured using a tensile testing machine in accordance with JIS-Z2241 (2011), and the smaller of these is taken as the material strength of the steel. The testing machine used for the tensile test shall be Class 1 or higher according to JIS B 7721. Test pieces shall be taken in accordance with the method for steel plates in JISG 0416 (2014) "Steel and steel products - Location and preparation of test pieces and specimens for mechanical testing", and JIS No. 14B test pieces shall be prepared as described in Appendix D of JIS-Z2241 (2011) "Types of test pieces for plates with a thickness of 3 mm or more and wire and rods with a diameter or face-to-face distance of 4 mm or more" so that the tensile direction is parallel to the rolling direction. The conditions for the tensile test shall be room temperature of 15 to 30°C, tensile speed of 5 mm / min, and gauge length of 50 mm. The test shall be performed on two test pieces, and the average value of the two data shall be taken.

[0032] Regarding plate thickness tolerances, JIS G 3196 (2019) "Shape, dimensions, mass and tolerances thereof for hot-rolled steel plates and strips" allows, for example, a tolerance of ±1.5 mm (maximum of 4.8% in thickness ratio) for plate thicknesses of 63 mm or more and less than 100 mm, and ±1.5 mm (maximum of 3.8% in thickness ratio) for plate thicknesses of 100 mm or more and less than 160 mm. If a similar tolerance is allowed for material strength based on the idea of ​​strength ratio between high strength and low strength materials, the strength ratio (σ 高強度 / σ 低強度 ) is considered to exceed the margin of error if it differs by 5% or more. However, the greater the difference in material strength between high-strength and low-strength materials, the more clearly the effect is manifested, so it is preferable for the material strength ratio to differ by 10% or more.

[0033] The flat plate members 10 arranged in the circumferential direction have plate materials with different material strengths arranged adjacent to each other on at least one side (both sides in this embodiment), and both circumferential ends are connected to each other by welding. That is, high-strength plate materials 11 and low-strength plate materials 12 are arranged alternately in the circumferential direction of the polygon.

[0034] A shape connecting a center line 11c in the thickness direction of the high-strength plate material 11 and a center line 12c in the thickness direction of the low-strength plate material 12 forms a regular octagon. That is, the high-strength plate material 11 has a smaller outer diameter than the low-strength plate material 12, and an outer surface 11a of the high-strength plate material 11 and an outer surface 12a of the low-strength plate material 12 are shifted in the radial direction. Both circumferential ends of these circumferentially adjacent flat plate members 10 are connected to each other by welding. A plate thickness t2 of the low-strength plate material 12 is larger than a plate thickness t1 of the high-strength plate material 11.

[0035] Among two or more types (here, two types) of flat plate members 10 having different material strengths, the plate thickness t and material strength σ of the lowest strength plate material (here, low-strength plate material 12) are taken as the basis, and the strength ratio (high-strength material-low-strength material strength ratio) to a plate material having higher strength than the low-strength plate material 12 (high-strength plate material 11) is expressed by equation (1).When α is in the range of 0.5 or more and 1 or less, the above strength ratio is 0.25 or more and 4 or less.

[0036]

number

[0037] Furthermore, when the converted thickness of a high-strength plate material among two or more types (here, two types) of flat plate members 10 having different material strengths is calculated using the lowest-strength plate material as a reference, the thickness of the low-strength plate material differs from the above-mentioned converted thickness when α is in the range of 0.5 to 1.

[0038]

number

[0039] As the polygonal columnar body, it is also possible to employ a polygonal shape in which adjacent sides in the circumferential direction have different lengths, such as a modified polygonal columnar body 1A shown in FIG.

[0040] Here, the α value in the converted plate thickness shown in the above formulas (1) and (2) will be specifically described. First, we will explain the case where the α value is set to 0.5. In a polygonal cylindrical structure, the ultimate state is local buckling of the plates that make up the polygon. Here, the width-thickness ratio parameter is given by Equation (3). Here, B is the width of the plate, t is the plate thickness, ν is the Poisson's ratio, k is the buckling coefficient, σ y is the yield strength and E is Young's modulus.

[0041]

number

[0042] Karman's ultimate buckling strength evaluation formula is expressed by formulas (4) and (5), where σu is the limit value of the mean stress of the plate material.

[0043]

number

[0044] From the above, if B / t is used as a variable, it can be transformed into equation (6) or (7). That is, the yield stress σ y and plate thickness t have a 1 / 2 power to 1 relationship, and the yield stress σ y By increasing , the plate thickness t can be made thinner, which may result in higher strength and lighter weight than if the same thickness and strength material were used.

[0045]

number

[0046]

number

[0047] Next, the case where the α value is 1 will be described. When a cantilever model of a cylindrical steel pipe is used as shown in Fig. 5, the horizontal load when the yield stress is reached can be expressed as equation (8). Here, σ y is the yield stress, Z is the section modulus, L is the length of the cylindrical steel pipe, and M is the bending moment. In the case of a regular rectangular steel pipe as shown in Figure 4(a), the relationship between the plate thickness, outer diameter, and inner diameter is given by equation (9), so the section modulus is given by equation (10). In other words, when rearranged using an approximation formula, the section modulus Z is roughly proportional to the plate thickness of the steel pipe. In the case of a cylindrical steel pipe as shown in Figure 4(b), the relationship between the plate thickness, outer diameter, and inner diameter is given by equation (11). Therefore, the section modulus Z is given by equation (12), and in the case of a cylindrical pipe, the section modulus Z is roughly proportional to the plate thickness as well. From equations (8), (10), and (12), under the same load, the yield stress σ y and plate thickness t have a one-to-one relationship.

[0048]

number

[0049]

number

[0050]

number

[0051] The flat plate members 10 connected in the circumferential and column axis directions are formed by connecting them together through welding. The symbol W in Fig. 2 indicates a welded portion (weld portion). The weld portion W has a horizontal weld portion W1 extending along the circumferential direction and a vertical weld portion W2 extending along the column axis direction. In this embodiment, eight flat plate members 10 of the same shape are connected in the circumferential direction, so that the cross-sectional shape of the polygonal columnar body 1 is a regular octagon.

[0052] The polygonal columnar body 1 of this embodiment is formed by connecting multiple stages (six stages are shown in FIG. 1) of ring bodies, each of which is made of eight flat plate members 10 connected in the circumferential direction, in the column axial direction. In addition, the vertical welds W2 of each of the ring bodies 10A connected in the column axial direction are continuous with each other in the column axial direction. Furthermore, even in the case where the arrangement heights in the column axis direction of the circumferentially adjacent flat plate members 10 are not the same, that is, in a so-called staggered arrangement, the vertical welds W2 are continuous in the column axis direction.

[0053] Next, a method for manufacturing the polygonal columnar body 1 shown in FIG. 1 and FIG. 2 will be described. First, a plate piece (flat plate member 10) of a predetermined size is cut out from a large steel plate that serves as the base material. In this cutting process, a necessary number of high-strength plate materials 11 and low-strength plate materials 12 are cut out to form the polygonal columnar body 1. However, the large steel plate that serves as the base material can also be used as the flat plate member 10 as is without going through the cutting process.

[0054] Thereafter, the flat plate members 10 are arranged, for example, on a stand (not shown). At this time, the high-strength plate members 11 and the low-strength plate members 12 adjacent in the circumferential direction are arranged so as to butt against each other at a predetermined crossing angle. Here, the predetermined crossing angle is an angle (i.e., an interior angle of a polygon) at which the cross-sectional shape (polygon) of the intended polygonal columnar body 1 is completed by the plurality of flat plate members 10. In the case of a regular octagon as shown in FIG. 1, the crossing angle between two adjacent flat plate members 10 is 135°. In this arrangement process, the flat plate members 10 are arranged as they are, without bending the flat plate members 10 as in the conventional technology. It is preferable that the flat plate members 10 arranged on the stand are arranged with the side to be welded facing upward, and are welded in a state in which the welding torch faces downward. On the other hand, there is also a case where a plurality of flat plate members 10 are arranged vertically while maintaining a predetermined interior angle, and welding is performed in a state where the welding torch is oriented horizontally. In this case, it is not necessary to use a stand.

[0055] When placing the flat plate members 10 on the stand, for example, a placement jig (not shown) having an abutment surface set at the above-mentioned specified intersection angle can be used, and the flat plate members 10 can be placed by abutting them against the abutment surface of this placement jig, thereby easily positioning adjacent flat plate members 10 relative to each other.

[0056] Next, a groove shape is formed at the butt joint between the adjacent high-strength plate material 11 and low-strength plate material 12, and the groove is welded to connect the flat plate members 10 together via the welded part W. The flat plate members 10 are assembled, for example, into the above-mentioned ring body 10A, or a half-section ring body obtained by dividing the cross section of the ring body 10A into two. The ring body 10A or the half-section ring body are then welded and connected in sequence to the upper side in the column axis direction at predetermined installation positions of the polygonal columnar body 1, thereby constructing the polygonal columnar body 1.

[0057] In addition, the work of manufacturing the divided ring bodies 10A etc. may be carried out near the installation position of the polygonal columnar body 1, or they may be manufactured in a processing factory or the like away from the installation position of the polygonal columnar body 1, and then transported by truck or the like to the installation position of the polygonal columnar body 1.

[0058] According to the polygonal cylindrical structure (polygonal columnar body 1) described above, the horizontal cross-sectional shape is formed by a polygon with the same number of corners. The polygonal shape is formed of a hexagon or more and 24 or less sides, and includes a plurality of flat plate members 10 made of steel. When the yield stress value obtained by a metal material tensile test is taken as the material strength, the flat plate members 10 are composed of at least two types of members (high strength plate member 11, low strength plate member 12) whose material strengths differ by 10% or more. The flat plate members 10 arranged in the circumferential direction are arranged such that plate members with different material strengths are adjacently arranged on at least one side, and both circumferential side ends are connected to each other by welding.

[0059] With this configuration, in polygonal cross sections whose horizontal cross-sectional shape is hexagonal or more and 24 or less sides, the plate thickness can be reduced by using high-strength plate material in part, so that weight can be reduced with the converted cross-sectional area ratio of the same strength. In addition, in this embodiment, by arranging two types of flat plate members 10 (high-strength plate material 11, low-strength plate material 12) with different strengths, a stiffening effect can be achieved without the need for processing. Therefore, by adjusting to achieve the same strength, the cross-sectional area can be kept small, and weight and cost can be reduced. In addition, an increase in maximum strength can be expected by indicating the range of the strength ratio in which the stiffening effect can be obtained.

[0060] As a result, in this embodiment, by increasing the maximum strength, it is possible to obtain performance that is equal to or greater than the maximum strength of a cylinder with the same amount of steel, or performance that is equal to or greater than a cylindrical structure with fewer corners compared to a polygonal structure using flat plate members of the same thickness. Furthermore, in this embodiment, the flat plate members 10 are connected to each other by welding, and the bending process can be omitted, which allows for a reduction in manufacturing costs. Furthermore, in this embodiment, since reinforcing members such as ribs are not necessary, a low-cost polygonal columnar body 1 can be provided.

[0061] Furthermore, in this embodiment, since the polygonal cross-section structure has different thicknesses and different strengths, the weight can be adjusted, and the natural frequency can be easily adjusted. For example, in an offshore wind power generation facility, the design is such that the vibrations caused by the rotation of the wind turbine blades and the natural frequency of the wind turbine are prevented from resonating. Therefore, the natural frequency is generally adjusted by changing the height of the wind turbine, but especially when the offshore wind farm is inclined like the seabed ground in Japan, the height of the foundation structure differs among the offshore wind farms, and the natural frequency is adjusted in the design, so the polygonal cylindrical structure of the present invention, which is easy to adjust the natural frequency, is suitable.

[0062] In this embodiment, the flat plate members constituting the polygon are made up of two types of plate members: high-strength plate members 11 and low-strength plate members 12. In this manner, in this embodiment, a stiffening effect can be achieved by using only the flat plate member 10 having two different types of material strength, that is, the high-strength plate material 11 and the low-strength plate material 12, and therefore costs can be reduced.

[0063] In this embodiment, the polygon has a portion in the circumferential direction where the high-strength plate materials and the low-strength plate materials are alternately arranged. Therefore, the high-strength plate materials 11 and the low-strength plate materials 12 are arranged in a well-balanced manner in the circumferential direction, and the stiffening effect of suppressing the deformation of the high-strength plate materials 11 by the low-strength plate materials 12 as described above is more reliably exerted.

[0064] In addition, in this embodiment, since the horizontal cross-sectional shape is an even-numbered polygon, the high-strength plate materials 11 and the low-strength plate materials 12 can be arranged alternately in the circumferential direction in a balanced manner, and a stiffening effect can be achieved that suppresses deformation of the low-strength plate materials 12 by the high-strength plate materials 11.

[0065] In addition, in this embodiment, when the plate thickness and material strength of the lowest strength plate material among two or more types of plate materials having different material strengths is used as a standard and the strength ratio of the low-strength plate material to a plate material with a higher strength is expressed by equation (1), when α is in the range of 0.5 to 1, the strength ratio is 0.25 to 4. In addition, in this embodiment, when the converted thickness of a high-strength plate material is calculated based on the lowest-strength plate material among two or more types of plate materials having different material strengths, the converted thickness differs from the plate thickness of the low-strength plate material when α is in the range of 0.5 to 1.

[0066] Therefore, by making the thickness of low-strength plate materials different from the equivalent plate thickness, it is possible to use high-strength plate materials in some parts and reduce the thickness. This makes it possible to reduce the weight at the same equivalent cross-sectional area ratio for the same strength. Also, by combining plates with thick and thin equivalent thicknesses into a polygon, the adjacent thick plates suppress the large deformation of the plate with the thin equivalent thickness after buckling, providing a stiffening effect, making it possible to further reduce the cross-sectional area and reduce the weight when the same strength is achieved.

[0067] As described above, the polygonal columnar body 1 according to this embodiment can be made lighter while maintaining the same strength, thereby reducing the cost of construction.

[0068] Next, examples carried out to verify the effects of the polygonal tubular structure according to the above-described embodiment will be described below.

[0069] (First embodiment) In the first embodiment, a numerical simulation analysis (finite element analysis) was used to apply a horizontal load F to the vertex 2a (upper part) of a cantilever beam model 2 that models a polygonal cylindrical structure (corresponding to the polygonal columnar body 1 described above) as shown in Figure 5, and the strength of the polygonal cylindrical structure was evaluated.

[0070] The subjects of this analysis are polygonal tubular structures and cylindrical structures. The polygonal cylindrical structure used in this analysis is based on a cylindrical structure with a steel pipe diameter (D) of 10.0 m, length (L) of 50.0 m, diameter-thickness ratio (D / t) of 80.0, and Young's modulus of steel (E) of 205,000 MPa. Assuming a cylindrical structure with a diameter-thickness ratio of 80.0, six cases were set for a regular octagon, as shown in Table 1 and Figure 6, in which the cross-sectional area, thickness of adjacent plates, and steel strength were changed. The steel types assumed were SM490 and SM570, with the former set to a yield strength of 325 MPa and the latter to a yield strength of 460 MPa. Note that the slope of the material curve after yielding for both was set to 1 / 100 of the slope before yielding.

[0071] [Table 1]

[0072] Specifically, as shown in Figure 6, we first considered regular octagons (cases 1 and 2) with the same thickness and different strength (SM490, SM570), and in each of cases 1 and 2, we set cases where the thickness of the thick plate material was kept at 125 mm but the thickness of the thin plate material was reduced (cases 3 and 4) so ​​that the cross-sectional area was not changed. Furthermore, we set different strength cases (cases 5 and 6) where the strength of the thin plate material in the different thickness cases was different from that of the thick plate material. Figure 6 shows a list of the cross sections of regular octagons in each of cases 1 to 6. As shown in Table 1, the cross-sectional area was based on the ratio to the cross-sectional area when D / t was 80.0, and eight patterns were implemented where the ratio was set to be in increments of 0.05 from 1 to 0.65.

[0073] Here, in cases 5 and 6 where the cross-sectional area ratio is 1, the thicknesses are set to be the same but the strengths are different. That is, cases 5 and 6 correspond to the polygonal columnar body 1 according to the above-mentioned embodiment. In this embodiment, the plate thickness arrangement was set so that the plate thickness centers coincided. As described above, a total of 48 cases were examined for the regular octagon, with 8 patterns for the cross-sectional area ratio (≒D / t) and 6 patterns for the plate thickness and plate strength (cases 1 to 6).

[0074] Figure 7 shows the analysis results, with the horizontal axis representing the polygonal cross-sectional area (m 2 ) and the vertical axis is the maximum load (kN). As shown in Fig. 7, the maximum loads obtained from the analysis results were plotted, and the polygonal cross-sectional areas of Case 1 (same thickness and strength - SM490), Case 2 (same thickness and strength - SM570), and Case 5 (different strength and thickness polygon (thick - SM490, thin - SM570)) where the maximum loads are the same were calculated by linearly interpolating between the plots.

[0075] Figure 8 is a graph plotting the diameter-thickness ratio of Case 1 as the standard on the horizontal axis and the steel weight ratio at the same yield strength on the vertical axis. Figure 9 is a graph plotting the diameter-thickness ratio of Case 1 as the standard on the horizontal axis and the steel price ratio on the vertical axis. Here, it is assumed that the price ratio of SM490 to SM570 is 1.44 times.

[0076] The steel weight ratio shown in Figure 8 is Case 2 (SM570) < Case 5 (different strength polygon) < Case 1 (SM490). In other words, when comparing at the same strength, the higher the proportion of high strength material used, the smaller the steel weight becomes. In the case of the different strength polygon, the steel weight is 9% smaller than the case of the same material SM490.

[0077] On the other hand, the price ratio shown in Figure 9 is Case 1 (SM490) < Case 5 (different strength polygon) < Case 2 (SM570). As the proportion of high strength materials used increases, the steel price rises for the same strength, but as the diameter-thickness ratio increases, the price of the different strength polygon in Case 5 falls to the same level as that of the SM490 material in Case 1.

[0078] Figure 10 is a graph showing the relationship between the strength ratio of high strength material to low strength material and the maximum load ratio in the converted cross-sectional area. The horizontal axis of Figure 10 is formula (1) for the strength ratio of high strength material to low strength material mentioned above. In Figure 10, a maximum load ratio of 1 indicates a state in which there is no stiffening effect, and a maximum load ratio greater than 1 indicates an increase in strength (increase in maximum load) due to the stiffening effect. As Figure 10 shows, it can be confirmed that the stiffening effect is caused by the strength ratio of the plate materials, which is determined by the plate thickness and the material strength of the steel material.

[0079] (Second Example) In the second embodiment, a structural example was considered that took into consideration the deformation of a cantilever beam that applies a horizontal load as shown in FIG. As shown in formula (8) above, the theoretical yield load is calculated based on the section modulus and yield stress calculated for each polygon. In other words, the horizontal strength is the theoretical value of the horizontal load when the lower end of the steel pipe reaches the yield stress. The specifications for polygonal steel pipes are mainly based on the values ​​mentioned above. However, calculations were performed using the following steel materials: low strength plate material: SM400 (yield stress 205 MPa) and high strength plate material: SM490 (yield stress 285 MPa). The α value was calculated as 1.

[0080] Tables 2 and 3 show the results of calculations for the second example. Table 2 shows the horizontal strength and steel pipe weight for a regular hexagon, a regular octagon, and a regular decagon. Table 3 shows the horizontal strength and steel pipe weight for a regular dodecagon, a regular hexagon, and a regular 24-gon.

[0081] [Table 2]

[0082] [Table 3]

[0083] From the calculation results in Tables 2 and 3, it was confirmed that in a model in which high-strength materials are used in some parts and the thickness of the high-strength materials is appropriately adjusted, the overall weight of the steel pipe can be reduced by 6 to 19% while maintaining the same horizontal strength, compared to when steel materials of the same strength are used.

[0084] Although the embodiment of the polygonal tubular structure according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit of the present invention.

[0085] In addition, in this embodiment, a tapered polygonal columnar body 1 is used, whose cross-sectional shape tapers upward in the column axis direction, but it may also be a polygonal structure that has the same cross section at any height in the column axis direction, that is, a polygonal tubular structure that does not taper overall.

[0086] Moreover, the polygonal shape includes not only regular polygons but also polygons whose sides have different lengths.

[0087] Furthermore, this embodiment is not limited to the arrangement of high-strength plate materials and low-strength plate materials alternately in the circumferential direction of the polygon.

[0088] In this embodiment, the horizontal cross-sectional shape is not limited to an even-numbered polygon.

[0089] Furthermore, when the thickness and material strength of the lowest-strength plate material among two or more types of plate material having different material strengths is used as a standard and the strength ratio to a plate material having a strength higher than the low-strength plate material is expressed by the above formula (1), the strength ratio is 0.25 to 4 when α is in the range of 0.5 to 1. Furthermore, when the converted thickness of a high-strength plate material among two or more types of plate material having different material strengths is used as a standard and the converted thickness is expressed by the above formula (2), the thickness of the low-strength plate material and the converted thickness are different when α is in the range of 0.5 to 1. However, the present invention is not limited to such a range of strength ratios or a configuration in which the thickness of the low-strength plate material and the converted thickness are different.

[0090] As shown in this embodiment, it is preferable that the polygonal cross section is formed by members having two types of plate thickness, the high-strength plate material 11 and the low-strength plate material 12, but the types are not limited to two.

[0091] Furthermore, within the scope of the present invention, the components in the above-described embodiments can be appropriately replaced with well-known components. [Explanation of symbols]

[0092] 1. Polygonal columnar body (polygonal cylindrical structure) 10 Flat plate members 10A Ring body 11 High strength plate material (first plate material) 12 Low strength plate material (second plate material)

Claims

1. A polygonal cylindrical structure in which the horizontal cross-sectional shape is formed by polygons with the same number of corners, The polygonal shape is formed with a number of sides of 6 to 24, A plurality of flat plate members made of steel are provided, The yield stress value obtained in the tensile test of metal materials is taken as the material strength of the steel material. The flat plate member is made of at least two types of members having material strengths that differ by 10% or more; The flat plate members arranged in the circumferential direction have a polygonal cylindrical structure in which plate members having different material strengths are arranged adjacent to each other on at least one side, and both circumferential ends are connected to each other by welding.

2. Among the flat plate members, the flat plate members constituting a polygon are 2. The polygonal tubular structure according to claim 1, comprising two types of plate material: a first plate material having high strength, and a second plate material having a strength lower than that of the first plate material.

3. The polygonal cylindrical structure according to claim 2 , wherein a circumferential portion of the polygon has a portion where the first plate members and the second plate members are arranged alternately.

4. The polygonal cylindrical structure according to claim 1 , wherein the horizontal cross-sectional shape is an even-numbered polygon.

5. When the plate thickness t and material strength σ of the lowest strength plate material among two or more types of plate materials having different material strengths are used as a standard and the strength ratio of the plate material having a higher strength than the low strength plate material is expressed by the formula (1), The polygonal tubular structure according to claim 1 , wherein when α is in the range of 0.5 to 1, the strength ratio is 0.25 to 4. [0010]

6. When the conversion plate thickness t of the high-strength plate material is expressed by the formula (2) when the lowest-strength plate material among two or more types of plate materials having different material strengths is used as the standard, The polygonal tubular structure according to claim 1 , wherein the plate thickness of the low-strength plate material is different from the equivalent plate thickness when α is in the range of 0.5 to 1. [0025]

Images