Method for manufacturing columnar floating structures

Abstract

To provide a columnar shape floating body capable of being manufactured at a lower cost and in a shorter period of time than before to solve problems of a conventional technology, and to provide its manufacturing method.SOLUTION: A columnar shape floating body of the present invention constitutes a floating offshore wind power generation facility and comprises a column body of a hollow columnar shape. The column body is formed by connecting multiple bending-planar members in a circumferential direction. The bending-planar member is constituted by including a planar section and a bent part formed on one end side, and a cross-sectional shape of the column body is a polygon with a curved apex.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a columnar floating body constituting a floating offshore wind power generation facility, and more specifically, to a columnar floating body provided with a column main body having a polygonal cross-sectional shape with a curved top and a method for manufacturing the same.

Background Art

[0002] Although the electricity consumption in Japan once decreased due to the impact of the global financial crisis in 2008, it has continued to increase since 1973 when there was an oil shock, and has expanded to 2.6 times between 1973 and 2007. The background includes the spread of so-called household appliances such as air conditioners and electric carpets due to the improvement of living standards, or the spread of OA (Office Automation) equipment and communication equipment due to the increase of office buildings.

[0003] Hitherto, such a huge amount of electricity demand has been mainly supported by power generation using so-called fossil fuels such as oil and coal. However, in recent years, the problem of depletion of fossil fuels and environmental problems associated with global warming have attracted attention, and accordingly, the power generation method has gradually changed. As a result, around 1973 as described above, power generation by oil and coal accounted for about 90% of the whole, whereas the proportion decreased to 66% in 2010. Instead, nuclear power generation, which accounts for slightly over 10% of the whole (in 2010), has increased. Nuclear power generation has contributed significantly to the electricity demand in Japan because it has a remarkable effect of reducing greenhouse gas emissions compared with conventional power generation methods and can provide power at low cost.

[0004] Also, in terms of being able to suppress the emission of greenhouse gases, power generation methods using renewable energy are being adopted. This renewable energy is energy that can be literally regenerated, such as sunlight, wind power, geothermal energy, small and medium-sized hydropower, and woody biomass, and is expected as promising low-carbon energy because it can suppress the emission of greenhouse gases and can be produced domestically.

[0005] Among renewable energy sources, wind power generation, in particular, is characterized by its high efficiency in converting electrical energy. Generally, the conversion efficiency of solar power generation is said to be about 20%, wood biomass power generation about 20%, and geothermal power generation 10-20%, while wind power generation is said to be 20-40%, meaning it can convert energy into electricity more efficiently than other power generation methods. In addition, unlike solar power generation, wind power generation can generate electricity day and night, which is another characteristic of wind power generation. Due to these characteristics, wind power generation is already widely used as a major power generation method in Europe, and in Japan, as part of the "energy mix" initiative, it is aimed to account for 1.7% of the power generation mix by 2030.

[0006] Wind power generation is broadly classified into onshore wind power generation and offshore wind power generation depending on the installation location. Onshore wind power generation has the advantage of being easier to install and therefore less expensive than offshore wind power generation. Offshore wind power generation, on the other hand, does not have the noise problems associated with onshore wind power generation, and the risk of damage from toppling etc. is avoided, and above all, it has the advantage of being able to obtain a large amount of wind power stably compared to onshore. Japan, which has the world's sixth-largest exclusive economic zone, is a suitable location for floating offshore wind power generation and is considered to have the potential to become a promising source of renewable energy in the future.

[0007] Furthermore, different types of offshore wind power generation are employed depending on the installation location. Fixed-bottom offshore wind power generation is suitable for sea areas shallower than 50m, while floating offshore wind power generation is suitable for sea areas deeper than 50m. Floating offshore wind power generation utilizes a floating structure that floats on seawater. The power generation mechanism is installed on the floating structure, which is connected by mooring lines, and this mechanism generates electricity. Examples of floating structure types include pontoon type (barge type), semi-submersible type, spar type (columnar type), and tensioned mooring type (TLP: Tension Leg Platform). In offshore areas far from land where large winds can be obtained, the columnar type tends to be mainly adopted.

[0008] Figure 16 is a schematic side view of a columnar offshore wind power plant. As shown in this figure, a columnar offshore wind power plant consists of a columnar floating body (spar-type floating body) that floats in the sea, and a tower, rotor, nacelle, etc. that are installed on top of it. The tower is a structure that supports the rotor and nacelle, and the columnar floating body functions as the base of the tower. The rotor, consisting of blades and a hub, converts wind into power, and the nacelle, which includes a gearbox, generator, transformer, etc., converts the power into electricity, which is then transmitted to land via a submarine cable. The columnar floating body is generally moored by the weight of a catenary-shaped mooring cable.

[0009] Incidentally, conventional columnar floating bodies, as shown in Patent Document 1, have a circular cross-section (i.e., a cylindrical tube), and are mainly manufactured by processing steel plates. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2013-141857 [Overview of the project] [Problems that the invention aims to solve]

[0011] Steel cylindrical pipes (i.e., steel pipes) are classified into seamless steel pipes and welded steel pipes depending on the manufacturing method. However, for large diameters (e.g., φ10m or more) such as columnar floating bodies, welded steel pipes are used, which are formed by shaping steel plates into a curved form and then welding them together. Here, the manufacturing process of columnar floating bodies will be explained with reference to Figure 17.

[0012] First, as shown in Figure 17(a), a predetermined size of plate piece (hereinafter referred to as "cut-out member" for convenience) is cut from a large steel plate that serves as the base material. This cut-out member is, so to speak, a part that constitutes the columnar floating body, and therefore, the necessary number of pieces (generally more than 1,000) required to constitute the columnar floating body are repeatedly cut out. Note that the cut-out member in the state cut out in Figure 17(a) is a plate material with a "flat" surface. Here, "flat" means not a curved surface, and refers to a shape that can be represented by the general formula for a plane in three-dimensional space, or a shape that approximates it. For convenience, here we will specifically refer to a plate material with a flat surface as a "flat material".

[0013] Once the cut-out members are cut, they are bent using methods such as "steel plate bending" or "roller bending," as shown in Figure 17(b). As mentioned above, conventional columnar floating bodies have a circular cross-section, and the cut-out members, which are the flat members, are bent to form a part of that circle. Of course, this bending process is performed on all the cut-out members. For convenience, here we will refer to plate materials with a curved surface as "curved materials."

[0014] Once the cut-out members have been bent, as shown in Figure 17(c), the curved cut-out members are placed on a mold jig, and adjacent cut-out members are joined together by welding. This forms a half-section structure of a predetermined length (hereinafter referred to as a "half-section segment"). As shown in Figure 17(d), separately prepared small assemblies (ribs) are then installed at predetermined intervals on the inner surface of the half-section segment.

[0015] Once the semi-section divisions are formed, as shown in Figure 17(e), the two semi-section divisions are joined by welding to form a circular cross-section "division." Then, as shown in Figure 17(f), the columnar floating body is completed by connecting multiple divisions in the axial direction.

[0016] Thus, the manufacture of columnar floating structures requires the use of large quantities of steel and involves a wide variety of processes. In particular, the bending process shown in Figure 17(b) is performed on large materials (cut-out members) with a plate length of about 5m, meaning that only about one piece (one sheet) can be processed per day, and moreover, a large number of cut-out members (for example, more than 1,000) must be processed. Therefore, bending processes incur significant costs such as labor costs, depreciation of processing machines, and fuel costs, and thus bending processes were a major factor driving up the manufacturing costs of columnar floating structures.

[0017] The object of the present invention is to solve the problems of the prior art, namely, to provide a columnar floating body that can be manufactured at a lower cost and in a shorter time than conventional methods, and a method for manufacturing the same. [Means for solving the problem]

[0018] The present invention focuses on the fact that the column body of a hollow tube is formed by leaving the cut-out member mostly as a straight material without bending the entire piece, and is based on an unprecedented idea.

[0019] The columnar floating body of the present invention constitutes a floating offshore wind power generation facility and comprises a hollow, columnar body. This columnar body is formed by connecting multiple bent-face members in the circumferential direction. The bent-face members consist of a "flat section" and a "bent section" formed on one end, and the cross-sectional shape of the columnar body is a polygon with a curved top.

[0020] The columnar floating body of the present invention may also be constructed using a bent-face material with a bent section formed in the middle. In this case, the bent-face material has two flat sections, and the bent section is positioned between these flat sections. The column body is constructed by butting adjacent bent-face materials together so that their flat sections are substantially on the same plane (including the same plane), and then connecting them in the circumferential direction.

[0021] The columnar floating body of the present invention can also be made using a bent flat material including two or more bent portions. In this case, the bent portions of the bent flat material are arranged at respective positions sandwiched by flat portions.

[0022] The columnar floating body of the present invention can further include a reduced-diameter body provided at one end of the column main body. This reduced-diameter body is formed by connecting a plurality of bent flat materials in the circumferential direction, has a frustum shape with a cross-sectional area decreasing outward from the column main body, and has a cross-sectional shape similar to the cross-sectional shape of the column main body.

[0023] The method for manufacturing a columnar floating body of the present invention is a method for manufacturing the columnar floating body of the present invention, and includes a cutting step, an end bending step, an arranging step, and a connecting step. In the cutting step, a flat material is cut out from a base material, and in the end bending step, a bent flat material is obtained by performing bending on one end of the flat material. In the arranging step, a plurality of bent flat materials are abutted and arranged at a predetermined crossing angle, and in the connecting step, the bent flat materials arranged in the arranging step are connected (joined) by welding. Note that a hollow columnar column main body is manufactured by abutting the flat portions and the bent portions of adjacent bent flat materials and then connecting a plurality of bent flat materials in the circumferential direction.

[0024] The method for manufacturing a columnar floating body of the present invention can also be a method including an intermediate portion bending step. In this intermediate portion bending step, a bent flat material is obtained by performing bending on the intermediate portion of the flat material. The bent flat material in this case includes flat portions arranged at two locations and a bent portion at a position sandwiched by these flat portions. Then, a hollow columnar column main body is manufactured by abutting the flat portions of adjacent bent flat materials so as to be substantially on the same surface (including the same surface) and then connecting a plurality of bent flat materials in the circumferential direction.

[0025] The method for manufacturing a columnar floating body according to the present invention can also be a method provided with a bending process. In this bending process, a bent facing material is obtained by performing bending on two or more locations of the facing material. The bent facing material in this case includes bent portions at respective positions sandwiched between flat portions. Then, after abutting the ends of adjacent bent facing materials against each other, a column main body that is hollow and columnar is manufactured by connecting a plurality of bent facing materials in the circumferential direction.

Effects of the Invention

[0026] The columnar floating body and the method for manufacturing a columnar floating body according to the present invention have the following effects. (1) Only bending is performed on the ends of the cut-out members, and compared with the conventional technology in which bending is performed on the entire cut-out members, the manufacturing cost of the columnar floating body is significantly reduced. As a result, it becomes easier to procure the columnar floating body, and it can be expected that the adoption of the columnar floating body will expand. (2) Since the burden on the workers involved in the bending process can be reduced, it can contribute to solving the problem of chronic labor shortages in recent years. (3) Also, since the consumption of various energies such as fuel and electricity required for bending can be reduced, the load on the environment can be suppressed compared to the conventional case. (4) If the top in a cross-sectional view is a "corner" where the structure is discontinuous, stress concentration is likely to occur. In contrast, in the present invention, since bending is performed on the top, stress concentration can be alleviated.

Brief Description of the Drawings

[0027] [Figure 1] A perspective view schematically showing the columnar floating body of the present invention. [Figure 2] (a) is a plan view for explaining the facing material, and (b) is a side view for explaining the facing material. [Figure 3] A cross-sectional view schematically showing the cross-sectional shape of the column main body. [Figure 4] A perspective view schematically showing the columnar floating body of the present invention with the facing materials arranged in a staggered pattern. [Figure 5](a) is a plan view illustrating the bending material, and (b) is a side view illustrating the bending material. [Figure 6] A schematic perspective view showing the columnar floating body of the present invention. [Figure 7] (a) is a plan view illustrating the bent surface material, and (b) is a side view illustrating the bent surface material. [Figure 8] A schematic cross-sectional view showing a portion of the column body formed by a bent, flat material. [Figure 9] (a) is a plan view illustrating a bent surface material having a bent section in the middle, and (b) is a side view illustrating a bent surface material having a bent section in the middle. [Figure 10] A schematic cross-sectional view showing a portion of a column body formed by a bent-processed flat material having a bent section in the middle. [Figure 11] A flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in the first embodiment. [Figure 12] A step diagram showing the main steps of the columnar floating body manufacturing method of the present invention in the first embodiment. [Figure 13] (a) is a plan view from above of two face materials positioned with a placement jig in contact with their inner circumferential surfaces, and (b) is a side view showing a face material placed on a placement jig that combines the function of adjusting the intersection angle with the function of a conventional mold jig. [Figure 14] A flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in a second embodiment. [Figure 15] A flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in the third embodiment. [Figure 16] A schematic side view illustrating a spar-type offshore wind power facility. [Figure 17] A step-by-step diagram illustrating the manufacturing process of a columnar floating structure. [Modes for carrying out the invention]

[0028] An example of an embodiment of the columnar floating body (spar-type floating body) and the method for manufacturing the columnar floating body of the present invention will be described with reference to the figures. The columnar floating body of the present invention is particularly suitable for use as a component of a floating offshore wind power generation facility, and the method for manufacturing the columnar floating body of the present invention is particularly suitable for manufacturing the columnar floating body of the present invention.

[0029] 1. Columnar floating body First, the columnar floating body of the present invention will be described in detail with reference to the diagram. The method for manufacturing the columnar floating body of the present invention is a method for manufacturing the columnar floating body of the present invention; therefore, the columnar floating body of the present invention will be described first, followed by a detailed explanation of the method for manufacturing the columnar floating body of the present invention.

[0030] Figure 1 is a schematic perspective view of the columnar floating body 100 of the present invention. As shown in this figure, the columnar floating body 100 of the present invention is composed of a column body 110, and may also be composed of a diameter-reducing body 120 and a base plate 130. The main elements constituting the columnar floating body 100 will be described below.

[0031] (Column body) As shown in Figure 1, the column body 110 is a long body in which the axial dimension (hereinafter referred to as "column axis") is larger than the cross-sectional dimension, and the interior is hollow, meaning that the outer shape is generally tubular. One of the features of the column body 110 is that it is formed from multiple face members FP.

[0032] Figure 2 illustrates a face material FP, where (a) is its plan view and (b) is its side view. As shown in this figure, a face material FP is a plate-shaped member with a thickness dimension smaller than its planar dimensions, and its surface is generally flat (including a flat surface). As previously stated, "flat" here means not a curved surface, and refers to a shape that can be represented by the general formula for a plane in three-dimensional space (ax+by+cz+d=0).

[0033] The column body 110 is formed, for example, by connecting multiple face members FP in the circumferential direction of the cross-section by welding. Therefore, the cross-sectional shape of the column body 110 is polygonal, as shown in Figure 3. In Figure 3, a regular dodecagon is formed by 12 face members FP having the same width, but of course, it is not limited to this and can be any number of n-sided polygons (where n is a natural number), and it can also be a polygon that is not a regular polygon (a polygon with all sides of equal length) (a polygon with different sides of different length). Also, as can be seen from Figure 1, depending on the column axis length of the column body 110, it is possible to form it by connecting multiple "divided bodies" (i.e., one ring) formed by connecting multiple face members FP in the circumferential direction of the cross-section in the direction of the column axis (12 stages in the figure). Alternatively, as shown in Figure 4, it is also possible to form it by connecting multiple face members FP in the direction of the column axis, such that the height of adjacent face members FP in the direction of the column axis is not the same (a so-called staggered arrangement).

[0034] The column body 110 can also be formed using a bent member RP instead of a flat member FP. Figure 5 is a diagram illustrating the bent member RP, where (a) is a plan view and (b) is a side view. As shown in this figure, the bent member RP is a plate material formed by bending a flat member FP at a predetermined angle of refraction. Here, the predetermined angle of refraction is the angle (i.e., the interior angle of the polygon) required for the cross-sectional shape (polygon) of the target columnar floating body 100 to be completed by multiple bent members RP. For example, if it is a regular dodecagon as shown in Figure 3, the angle of refraction of the bent member RP will be 150°. Note that the bent member RP is not limited to having one bend (hereinafter referred to as the "refraction line") as shown in Figure 5 (i.e., consisting of two flat members FP), but can also have two or more refraction lines (i.e., consisting of three or more flat members FP).

[0035] Although the column body 110 formed from the bent material RP requires slightly more effort than the case where it is formed from the flat material FP which does not require bending, it significantly reduces the effort required compared to conventional bending processes and also has the advantage of reducing the number of welds.

[0036] As shown in Figure 6, depending on the column axis length of the column body 110 formed by the bending material RP, it is preferable to form multiple "divided bodies" (i.e., one ring) by connecting multiple bending material RP in the circumferential direction of the cross-section, and connect them in multiple rows (four rows partially shown in the figure) in the column axis direction. At this time, it is preferable to avoid so-called "butt joints" where the connection positions (i.e., welding lines WL) of adjacent divided bodies in the column axis direction are continuous (connected), and instead to use a so-called "staggered arrangement" where the welding lines WL of adjacent divided bodies in the column axis direction (up and down in the figure) are discontinuous (staggered), as shown in Figure 6. Generally, welded areas tend to be structurally weaker than other parts, and by arranging the welding lines WL in a staggered pattern as shown in Figure 6, the overall structural fragility can be mitigated. Note that the divided bodies can be formed using only bending material RP, or they can be formed by combining bending material RP and face material FP.

[0037] Furthermore, the column body 110 can also be formed by a bent face member BP instead of a face member FP or a bent member RP. Figure 7 is a diagram illustrating the bent face member BP, where (a) is a plan view and (b) is a side view. As shown in this figure, the bent face member BP is formed by bending one end (right side in the figure) of a face member FP, and is a plate member having a flat "flat section SF" and a bent "bent section SR".

[0038] The main body 110, which uses bent face material BP, is also formed by connecting multiple bent face material BP in the circumferential direction of the cross-section, for example, by welding. In this case, adjacent bent face material BPs are arranged so that the end faces of the flat section SF and the bent section SR abut against each other, as shown in Figure 8. Therefore, the cross-sectional shape of the column body 110 is generally polygonal, but the top is curved (hereinafter, for convenience, this will be referred to as a "chamfered polygon"). In this case as well, it is preferable to form it by connecting multiple "divided bodies" (i.e., one ring) formed by connecting multiple bent face material BPs in the circumferential direction of the cross-section in the direction of the column axis. Note that the divided bodies can be formed using only bent face material BP, or they can be formed by combining face material FP and bent material RP.

[0039] As shown in Figure 7(b), the bent section is a so-called fan shape in cross-section, and its central angle is the angle (i.e., the interior angle of the polygon) required for the cross-sectional shape (chamfered polygon) of the target columnar floating body 100 to be completed by multiple bent face materials BP, similar to the refraction angle of the bending material RP. Generally, a smaller bending radius has the advantage of shorter working time, but the disadvantage of being prone to stress concentration, while a larger bending radius has the disadvantage of longer working time, but the advantage of improved structural continuity and reduced stress concentration. Therefore, the bending radius of the bent section SR (i.e., the fan shape) can be arbitrarily designed depending on the situation, and it is preferable to design it with a bending radius of 50 mm to 1000 mm, and more preferably 100 mm to 300 mm.

[0040] The bent face material BP can have a bent portion SR at the end (Figure 7), or, as shown in Figure 9, a bent portion SR in the middle (hereinafter referred to as "intermediate bent face material BPM"). Figure 9 is a diagram illustrating the intermediate bent face material BPM, where (a) is a plan view and (b) is a side view. As shown in Figure 9, this intermediate bent face material BPM is formed by bending the middle portion (approximately in the center in the figure) of a face material FP, and is a plate member in which two face material FPs are formed and a bent portion SR is formed in a position sandwiched between these face material FPs.

[0041] The main body 110, which uses intermediate-bent face members BPM, is also formed by connecting multiple intermediate-bent face members BPM in the circumferential direction of the cross-section, for example, by welding. In this case, adjacent bent face members BP are arranged so that the end faces of adjacent planar sections SF abut each other, as shown in Figure 10, and so that adjacent planar sections SF are substantially on the same plane (including the same plane). As a result, the cross-sectional shape of the column body 110 becomes a "chamfered polygon," similar to Figure 8. In this case as well, it is preferable to form it by connecting multiple "divided bodies" (i.e., one ring) formed by connecting multiple intermediate-bent face members BPM in the circumferential direction of the cross-section, in the direction of the column axis. Note that the divided bodies can be formed using only intermediate-bent face members BPM, or they can be formed by combining face members FP, bending members RP, and bent face members BP.

[0042] The intermediate bent face material BPM shown in Figures 9 and 10 has two flat sections SF and one bent section SR, but it is not limited to this and can also have three or more flat sections SF and two or more bent sections SR. For example, flat sections SF can be formed at n locations (where n is a natural number of 3 or more), and bent sections SR can be formed at n-1 locations between these flat sections SF. Furthermore, the intermediate bent face material BPM can also have bent sections SR at its ends (one end or both ends) (i.e., a combination of a bent face material BP and an intermediate bent face material BPM). Also, the bent face material BP shown in Figures 7 and 8 has a bent section SR at only one end, but it is not limited to this and can also have bent sections SR formed at both ends.

[0043] Although the column body 110 formed by the bent face material BP (including the intermediate bent face material BPM) requires slightly more effort than the case where it is formed by the face material FP which does not require end bending, the effort is significantly reduced compared to conventional bending processes. Furthermore, because the tops of the polygons are chamfered, it has the advantage of being less susceptible to damage such as chipping and denting.

[0044] (Reduced diameter body) The diameter-reducing section 120 is connected to the tower (Figure 16) that supports the rotor and nacelle, and is essentially an adjustment section for changing from the large diameter of the column body 110 to the smaller diameter of the tower. Therefore, as shown in Figure 1, the diameter-reducing section 120 is provided at the upper end of the column body 110 when in use (when installed underwater), and has a frustoconical shape (i.e., a tapered shape) in which the cross-sectional area decreases outward (upward in the figure) in the direction of the column axis from the column body 110.

[0045] The reduced-diameter body 120 is formed by connecting multiple face members FP in the circumferential direction of the cross-section, similar to the column body 110. More specifically, the face members FP are arranged so as to incline inward (towards the center) from the outward (upward in the figure) direction of the column axis from the column body 110, and then connected in the circumferential direction. Therefore, the cross-sectional shape of the reduced-diameter body 120 is polygonal, and it is preferable that it be similar in shape to the cross-sectional shape of the column body 110. Also, as can be seen from Figure 1, depending on the column axis length of the reduced-diameter body 120, it is preferable to form it by connecting multiple structures (i.e., one ring) of multiple face members FP connected in the circumferential direction in the column axis direction (two stages in the figure). The reduced-diameter body 120 can also be formed by bending members RP or bent face members BP (including intermediate bent face members BPM) instead of face members FP, similar to the column body 110, or by combining bending members RP, face members FP, and bent face members BP (including intermediate bent face members BPM). In Figure 4, a single diameter-reducing body 120 is installed on top of the column body 110, but it is not limited to this configuration; multiple diameter-reducing bodies 120 can also be installed on top of the column body 110. In this case, the diameter-reducing bodies 120 are stacked sequentially so that the cross-sectional area decreases as you move upwards.

[0046] (bottom plate) The columnar floating body 110 needs to float near the sea surface when in use, and therefore has a structure that receives buoyancy. Accordingly, a bottom plate 130 is provided at the lower end of the column body 110 when in use. By sealing with the bottom plate 130, seawater is prevented from entering the interior of the columnar floating body 110, that is, a pressure difference is created between the interior of the columnar floating body 110 and the sea. The bottom plate 130 should be polygonal in plan view and similar in cross-sectional shape to the column body 110.

[0047] 2. Method for Manufacturing Columnar Floating Bodies Next, the method for manufacturing the columnar floating body of the present invention will be explained in detail with reference to the diagram. Note that the method for manufacturing the columnar floating body of the present invention is the method for manufacturing the columnar floating body 100 described so far. Therefore, explanations that overlap with those described for the columnar floating body 100 will be avoided, and only the aspects specific to the method for manufacturing the columnar floating body of the present invention will be explained. In other words, anything not described here is the same as what was explained in "1. Columnar Floating Body".

[0048] Furthermore, the columnar floating body manufacturing method of the present invention can be broadly classified into three embodiments: one in which the columnar floating body 110 is formed using a flat material FP (hereinafter referred to as the "first embodiment"), one in which the columnar floating body 110 is formed using a bending material RP (or a combination of the bending material RP and the flat material FP) (hereinafter referred to as the "second embodiment"), and another in which the columnar floating body 110 is formed using a bent flat material BP (or a combination of the bending material RP and the flat material FP) (hereinafter referred to as the "third embodiment"). Each embodiment will be described in order below.

[0049] (First embodiment) Figure 11 is a flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in the first embodiment, and Figure 12 is a step diagram showing the main steps of the columnar floating body manufacturing method of the present invention in the first embodiment.

[0050] First, as shown in Figure 12(a), a predetermined size of plate piece (cut-out member) is cut from a large steel plate that serves as the base material (Step 101 in Figure 11). In this cutting process, the required number of cut-out members (generally more than 1,000) that constitute the columnar floating body 100 of the present invention are repeatedly cut. Since the cut-out members in the state shown in Figure 12(a) are face material FP, the cut-out members will be referred to as face material FP below.

[0051] Once the face material FP is cut out, it is arranged on a mold jig, for example, as shown in Figure 12(b) (Step 102 in Figure 11). At this time, two adjacent face material FPs are placed together so that they intersect at a predetermined angle. Here, the predetermined angle of intersection is the angle (i.e., the interior angle of the polygon) required for the cross-sectional shape (polygon) of the target columnar floating body 100 to be completed by the multiple face material FPs. For example, in the case of a regular dodecagon as shown in Figure 3, the intersection angle of two adjacent face material FPs is 150°. It should be noted that in the arrangement process in the present invention, it is essential to arrange the face material FPs as they are, that is, without bending the face material FPs (Figure 17(b)) as in the conventional technology (i.e., without processing them into curved materials), the face material FPs are arranged. This makes it possible to significantly reduce the manufacturing cost of the columnar floating body 100 compared to the conventional method.

[0052] By the way, it is not easy to position two facing members FP so that they meet a predetermined intersection angle by visual inspection. Therefore, as shown in Figure 13(a), it is advisable to position two adjacent facing members FP using a positioning jig AT. This positioning jig AT has a predetermined intersection angle (for example, 150° in Figure 3), and therefore, when this positioning jig AT is placed in contact with the inner circumferential surface of the facing members FP, the two adjacent facing members FP will be brought together at the predetermined intersection angle. In this case, if the facing members FP are placed on the floor surface, and their plate surfaces are in a nearly vertical (including vertical) position, it becomes relatively easy to adjust their position with the positioning jig AT in contact. However, it is advisable to suspend the facing members FP with a crane or the like to prevent them from tipping over, and to support them from the front and back with support materials.

[0053] Alternatively, two adjacent face material FPs can be positioned using the positioning jig AT shown in Figure 13(b). The positioning jig AT shown in Figure 13(b) also has a predetermined intersection angle (for example, 150° in the case of Figure 3), and as shown in this figure, simply by placing multiple (five in the figure) face material FPs on the positioning jig AT, two adjacent face material FPs are automatically butted together at the predetermined intersection angle. In other words, the positioning jig AT shown in Figure 13(b) is a jig that combines the function of adjusting the intersection angle with the function of a conventional mold jig. However, as shown in Figure 17(c), conventional mold jigs are used to place the cut-out member (curved material) with its inner circumferential surface facing upwards, whereas the positioning jig AT shown in Figure 13(b) is used to place the face material FP with its outer circumferential surface facing upwards. As can be seen from Figure 13(a), when two adjacent face materials FP are butted together, a "groove" is created on their outer surfaces. Therefore, when the face materials FP are placed on the placement jig AT shown in Figure 13(b), the next process of joining (welding) can be carried out in that state.

[0054] Once the face members FP are in place, adjacent cut members are joined (connected) by welding or the like (Step 103 in Figure 11), forming a semi-section divided body (a structure with a semi-section of a predetermined length). Also, as shown in Figure 12(c), separately prepared small assemblies (ribs) are installed at predetermined intervals on the inner surface of the semi-section divided body (Step 104 in Figure 11). Once the semi-section divided body is formed, as shown in Figure 12(d), two semi-section divided bodies are joined by welding or the like to form a polygonal cross-section "divided body" (i.e., one ring) (Step 105 in Figure 11). Then, as shown in Figure 12(e), the column body 110 is formed by connecting multiple (four stages in the figure) divided bodies in the axial direction (Step 106 in Figure 11).

[0055] Furthermore, the reduced-diameter body 120, formed in the same process as the column body 110, is attached to one end (upper end) of the column body 110 (Step 107 in Figure 11), and the bottom plate 130 is fixed to seal the other end (lower end) of the column body 110 (Step 108 in Figure 11), thereby completing the columnar floating body 100 of the present invention.

[0056] (Second embodiment) Figure 14 is a flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in a second embodiment.

[0057] First, as in the first embodiment, a flat sheet FP is cut from a large steel plate that serves as the base material (Step 201 in Figure 14). Once the flat sheet FP is cut, it is bent at a predetermined bending angle to obtain a bent sheet RP (Step 202 in Figure 14). This bending process is repeated for each cut flat sheet FP.

[0058] Once the bending members RP are obtained, the bending members RP are arranged in the same manner as in the first embodiment (Step 203 in Figure 14), and adjacent bending members RP are joined (connected) to each other by welding or the like (Step 204 in Figure 14) to form a semi-section division. In addition, separately prepared small sets (ribs) are installed at predetermined intervals on the inner surface of the semi-section division (Step 205 in Figure 14). Once the semi-section divisions are formed, two semi-section divisions are joined together by welding or the like to form a polygonal cross-section division (Step 206 in Figure 14). Then, the column body 110 is formed by connecting multiple divisions (four stages in the figure) in the axial direction (Step 207 in Figure 14). At this time, as shown in Figure 6, it is preferable to connect the divisions so that the welding lines WL of adjacent divisions in the column axis direction are discontinuous (staggered arrangement).

[0059] Furthermore, the reduced-diameter body 120, formed in the same process as the column body 110, is attached to one end (upper end) of the column body 110 (Step 208 in Figure 14), and the bottom plate 130 is fixed to seal the other end (lower end) of the column body 110 (Step 209 in Figure 14), thereby completing the columnar floating body 100 of the present invention.

[0060] (Third embodiment) Figure 15 is a flowchart showing the main steps of the columnar floating body manufacturing method of the present invention in a third embodiment.

[0061] First, as in the first and second embodiments, a face material FP is cut from a large steel plate that serves as the base material (Step 301 in Figure 15). Once the face material FP is cut, a bent face material BP is obtained by bending the ends (one end or both ends) of the face material FP to form a "bent section SR" and a "flat section SF" (Step 302 in Figure 15). As previously described, the bending process is performed so that the bent section SR has a predetermined central angle. This bending process is repeated for each cut face material FP. When manufacturing a columnar floating body 100 using an intermediate bent face material BPM, an intermediate bent face material BPM is obtained by bending the intermediate section of the cut face material FP (intermediate section bending process). Of course, if there are two or more bent sections SR, the bending process is performed only at those locations (bending process).

[0062] Once the bent face members BP are obtained, the bent face members BP are arranged as in the first and second embodiments (Step 303 in Figure 15), and adjacent bent face members BP are joined (connected) to each other by welding or the like (Step 304 in Figure 15) to form a half-section divided body. Separately prepared small assemblies (ribs) are also installed at predetermined intervals on the inner surface of the half-section divided body (Step 305 in Figure 15). Once the half-section divided body is formed, two half-section divided bodies are joined by welding or the like to form a divided body with a chamfered polygonal cross-section (Step 306 in Figure 15). Then, the column body 110 is formed by connecting multiple divided bodies in the axial direction (Step 307 in Figure 15).

[0063] Furthermore, the reduced-diameter body 120, formed in the same process as the column body 110, is attached to one end (upper end) of the column body 110 (Step 308 in Figure 15), and the bottom plate 130 is fixed to seal the other end (lower end) of the column body 110 (Step 309 in Figure 15), thereby completing the columnar floating body 100 of the present invention. [Industrial applicability]

[0064] The columnar floating structure and the method for manufacturing the columnar floating structure of the present invention can be particularly suitably used for floating offshore wind power generation in sea areas with a depth of 50m or more. Since the present invention allows for the construction of floating offshore wind power generation facilities at low cost, it can be expected to create a more positive incentive for offshore wind power generation. Furthermore, considering that it can stably supply energy while suppressing greenhouse gas emissions, the present invention is not only industrially applicable but can also be expected to make a significant contribution to society. [Explanation of Symbols]

[0065] 100 Columnar floating body of the present invention 110 (Columnar floating structure) Column body 120 (Reduced diameter body of a columnar float) 130 (Bottom plate of a columnar floating structure) AT placement jig BP bending surface material BPM Intermediate Bending Processed Face Material SF (flat surface of bent or intermediate bent surface material) SR (bent section of bent face material or intermediate bent face material) FP surface material RP bending material WL welding line

Claims

1. In a method for manufacturing columnar floating structures that constitute a floating offshore wind power generation facility, The cutting process involves cutting out a flat surface material from the base material, An end bending process is performed to obtain a bent face material including a flat portion and a bent portion by bending one end of the aforementioned face material, A placement step of arranging multiple bent surface materials so that they are butted together at a predetermined intersection angle, The system includes a connecting step of welding together the bent face materials that have been arranged in the arrangement step, By butting the flat portion and the bent portion of adjacent bent surface materials together and then connecting a plurality of these bent surface materials in the circumferential direction, a hollow columnar column body is manufactured. A method for manufacturing a columnar floating body, characterized by the features described herein.

2. In a method for manufacturing columnar floating structures that constitute a floating offshore wind power generation facility, The cutting process involves cutting out a flat surface material from the base material, An intermediate bending process is performed to obtain a bent face material that includes two flat sections and a bent section formed between the flat sections, by bending the intermediate section of the aforementioned face material. A placement step of arranging multiple bent face materials so that they are butted together, The system includes a connecting step of welding together the bent face materials that have been arranged in the arrangement step, A hollow, columnar column body is manufactured by butting together adjacent bent face materials such that their flat surfaces are on the same plane or substantially on the same plane, and then connecting a plurality of these bent face materials in the circumferential direction. A method for manufacturing a columnar floating body, characterized by the features described herein.

3. In a method for manufacturing columnar floating structures that constitute a floating offshore wind power generation facility, The cutting process involves cutting out a flat surface material from the base material, A bending process to obtain a bent face material including two or more bent sections by bending the aforementioned face material at two or more locations, A placement step of arranging multiple bent face materials so that they are butted together, The system includes a connecting step of welding together the bent face materials that have been arranged in the arrangement step, By butting the ends of adjacent bent face materials together and then connecting multiple bent face materials in the circumferential direction, a hollow columnar column body is manufactured. A method for manufacturing a columnar floating body, characterized by the features described herein.

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