Method of constructing concrete floating body for floating type offshore wind power generation facility

Abstract

[Problem] To improve the efficiency of assembly work by saving labor required for tensioning and anchoring work of PC steel material in a method of constructing a concrete floating body. [Solution] PC steel materials 19 are sorted in advance into a group of PC steel rods 20 to be used for temporarily assembling precast cylindrical bodies in order, and a group of PC steel strands 23 to be used for introducing predetermined tension after completing temporary assembly of a concrete floating body. In a temporary assembly step of a concrete floating body 4A, the temporary assembly of the concrete floating body 4A is completed by assembling all precast cylindrical bodies 15 while introducing tension to the PC steel rods 20 and anchoring the group of PC rods 20, each time the precast cylindrical bodies 15 are connected sequentially, and installing a floating body bottom part 29 on the endmost part. In a tension introduction step, the PC steel strands 23 are inserted in the longitudinal direction over the entire length of the concrete floating body 4A, and introduction of tension to the PC steel strands 23 and anchoring are performed for the group of PC steel strands 23.

Description

Construction method of concrete floating body of floating offshore wind power generation facility

[0001] The present invention relates to a method for efficiently constructing a concrete floating body portion in a floating offshore wind power generation facility having a concrete floating body portion in which concrete precast cylindrical bodies are stacked in multiple layers in the vertical direction and each precast cylindrical body is fastened and integrated with PC steel.

[0002] Traditionally, hydroelectric, thermal, and nuclear power generation have been the primary power generation methods, but in recent years, wind power generation, which utilizes natural wind to generate electricity, has been attracting attention from the perspective of environmental friendliness and the effective use of natural energy. Wind power generation facilities can be installed on land or on water (mainly offshore), but in Japan, which has mountainous terrain behind its coasts, there are few plains along the coast where stable winds can be expected. On the other hand, Japan is surrounded by sea on all sides, and the sea offers the advantage of easily obtaining winds suitable for power generation and fewer restrictions on installation. For this reason, various types of offshore wind power generation facilities and floating structures have been proposed in recent years.

[0003] The floating structure can be broadly classified into barge-type floats that float on the water surface, semi-submersible floats that float in a semi-submerged state with the lower part of the float submerged below the water surface, and spar-type floats that float in an upright position like a fishing float.

[0004] With regard to the spar-type float, the applicant has proposed in Patent Document 1 listed below an offshore wind power generation facility comprising a float, mooring lines, a tower, a nacelle and a plurality of wind turbine blades installed at the top of the tower, wherein the float is made of concrete precast cylindrical bodies stacked in multiple tiers in the height direction, and the float is made up of a lower concrete floating structure part (hereinafter referred to as the concrete floating structure part) in which the precast cylindrical bodies are fastened together with PC steel to form an integrated unit, and an upper steel floating structure part (hereinafter referred to as the steel floating structure part) connected to the upper side of the concrete floating structure (hereinafter referred to as the spar-type offshore wind power generation facility).

[0005] The method for constructing the float of the spar-type offshore wind power generation facility involves assembling the steel floating body section and the concrete floating body section in a horizontal position in a quay yard to complete the float (see Patent Document 2 below).

[0006] In particular, in assembling the concrete floating body section, as shown in Figure 11, in order to construct it in a horizontal position, the precast cylindrical body 50, which was manufactured vertically with its axial direction facing up and down, was erected so that it was in a horizontal position, and this erected precast cylindrical body 60 was lifted by a crane and sequentially connected to the ends of the assembled group of precast cylindrical bodies 61, thereby carrying out assembly.

[0007] To connect the precast cylindrical body 60 to the end of the assembled concrete floating body section 61, the numerous PC steel members arranged around the entire circumference of the precast cylindrical body are all PC steel rods 62, 62, etc., and as shown in Figure 12, each time a precast cylindrical body 60 is connected in sequence, tension is introduced into and fixed in all of the PC steel rods 62 while assembling all of the precast cylindrical bodies 61.

[0008] Japanese Patent No. 5274329 Japanese Patent Application Laid-Open No. 2018-173011

[0009] As described above, the concrete floating body section was assembled by tensioning and fixing all of the circumferential PC steel rods 62, 62... inserted into the precast cylindrical body 60 for each precast cylindrical body 60. Therefore, the number of times the PC steel rods 62 were tensioned and fixed when assembling the precast cylindrical body 61 was enormous, which took a lot of time and effort to assemble the precast cylindrical bodies 61, 61.... In the example shown in Figure 12, if the number of PC steel rods 62 per cross section of the precast cylindrical body 60 was 44 and there were 10 precast cylindrical bodies 60 to be assembled, the PC steel rods 62 would have to be tensioned and fixed 440 times (44 rods x 10 bodies = 440).

[0010] Therefore, the main objective of the present invention is to improve the efficiency of assembling precast cylindrical bodies by reducing the labor required for tensioning and fixing PC steel members in a method for constructing a concrete floating body section in a floating offshore wind power generation facility, which has a concrete floating body section in which multiple precast cylindrical bodies are connected and each precast cylindrical body is fastened and integrated with a large number of PC steel members.

[0011] In order to solve the above problems, the present invention according to claim 1 provides a method for constructing a concrete floating body section in a floating offshore wind power plant having a concrete floating body section in which a plurality of precast cylindrical bodies are connected and each precast cylindrical body is fastened and integrated with a plurality of PC steel members, the method comprising: dividing the plurality of PC steel members arranged around the entire circumference of the precast cylindrical bodies into a group of PC steel rods used to temporarily assemble the precast cylindrical bodies in order, and a group of PC steel strands used to introduce a predetermined tension after the temporary assembly of the concrete floating body section is completed; in the temporary assembly process of the concrete floating body section, tension is introduced to and fixed in the group of PC steel rods each time a precast cylindrical body is connected in order, and the temporary assembly of the concrete floating body section is completed by assembling all of the precast cylindrical bodies and placing a floating body bottom at the end; A method for constructing a concrete floating body section of a floating offshore wind power generation facility is provided, characterized in that in the tension introduction step, PC steel strands are inserted longitudinally through the entire length of the concrete floating body section in the PC steel strand group, and tension is introduced into and fixed to the PC steel strands.

[0012] In the invention described in claim 1 above, when constructing the concrete floating body section, the numerous PC steel members arranged around the entire circumference of the precast cylindrical body are divided in advance into a group of PC steel rods used to temporarily assemble the precast cylindrical bodies in sequence, and a group of PC steel strands used to introduce a predetermined tension force after the temporary assembly of all the precast cylindrical bodies has been completed.

[0013] The PC steel rod group is PC steel material for temporarily assembling a predetermined number of precast cylindrical bodies into a concrete floating body section, and PC steel rods that can be tensioned and fixed for each precast cylindrical body are used. In the precast cylindrical body temporary assembly process, tension is introduced into the PC steel rods in the PC steel rod group and fixed each time a precast cylindrical body is sequentially connected, and temporary assembly of all the precast cylindrical bodies is completed by installing the floating body bottom at the outermost end.

[0014] On the other hand, PC steel strands are used in the locations where PC steel members are arranged other than the PC steel bars. In the tensioning process after the completion of the temporary assembly of the concrete floating body section, PC steel strands are inserted longitudinally through the PC steel strand group over the entire length of the concrete floating body section, and tension is introduced to and fixed in the PC steel strands. Since tension is introduced into the PC steel strands after being inserted longitudinally through the concrete floating body section whose temporary assembly has been completed, tension introduction and fixation only need to be done once, which enables labor-saving in the prestressing and fixation work.

[0015] In addition, the tensioning force introduced per PC steel strand can be set to be greater for PC steel strands than for PC steel bars, so by reducing the number of PC steel strands, further labor savings can be expected in the prestressing and anchoring work.

[0016] In the present invention according to claim 2, in the temporary assembly process of the concrete floating body part, the compressive stress intensity of the joint surfaces of the precast cylindrical bodies is 0.2 to 0.4 N / mm 2 The method for constructing a concrete floating body portion of a floating offshore wind power generation facility according to claim 1 is provided, wherein the group of PC steel rods is determined so that:

[0017] The invention described in claim 2 above specifies a method for determining the number of PC steel bars. As will be described later, according to the "External Cable Structure / Precast Segment Construction Method Design and Construction Standards," when joining segments, the strength of the epoxy resin must be 0.3 N / mm until it hardens. 2In accordance with this, the compressive stress of the joint surfaces of the precast cylindrical bodies is set to 0.2 to 0.4 N / mm during the temporary assembly process of the concrete floating body. 2 The number of the PC steel rods is determined so that the number of the PC steel rods is equal to or greater than the number of the PC steel strands.

[0018] In the present invention according to claim 3, the precast cylindrical body is formed by assembling a plurality of arc-shaped divided precast members divided in the circumferential direction, and the compressive stress intensity of the joint surfaces of the precast cylindrical bodies is 0.2 to 0.4 N / mm 2 The present invention provides a method for constructing a concrete floating body portion of a floating offshore wind power generation facility as described in claim 1, wherein the group of PC steel rods is determined to include at least two locations, one on each side, in each arc-shaped divided precast member, and the remaining locations are the group of PC steel strands, provided that:

[0019] The invention described in claim 3 provides a method for determining the number of PC steel bars in a split type, in which a precast cylindrical body is split into a plurality of arc-shaped split precast members in the circumferential direction to form a cylindrical body. In this case, the compressive stress of the joint surfaces of the precast cylindrical bodies is 0.2 to 0.4 N / mm 2 In order to securely and balancedly fix each arc-shaped divided precast member, the number of PC steel rod groups is determined to include at least two locations, one on each side of each arc-shaped divided precast member, and the remaining locations are PC steel strand groups.

[0020] The present invention according to claim 4 provides a method for constructing a concrete floating body portion of a floating offshore wind power generation facility according to any one of claims 1 to 3, in which the precast cylindrical bodies are connected in succession horizontally in a horizontal position, or connected in succession vertically in a vertical position.

[0021] In the invention described in claim 4 above, when constructing the concrete floating body section, the direction in which the precast cylindrical bodies are connected may be horizontal construction, in which multiple precast cylindrical bodies are connected horizontally to construct the concrete floating body section in a laid-down position, or vertical construction, in which multiple precast cylindrical bodies are connected vertically to construct the concrete floating body section in an upright position.

[0022] As explained above, according to the present invention, in a method for constructing a concrete floating body section in a floating offshore wind power generation facility having a concrete floating body section in which multiple precast cylindrical bodies are connected and each precast cylindrical body is fastened and integrated with numerous PC steel members, it is possible to reduce the labor required for tensioning and fixing the PC steel members and improve the efficiency of the assembly work of the precast cylindrical bodies.

[0023] 1 is an overall view of a spar-type offshore wind power generation facility 1. It is a longitudinal cross-sectional view of a floater 4. It is a perspective view showing the construction procedure for a spar-type offshore wind power generation facility 1. It is a diagram showing how to connect precast tubular bodies 15 when constructing a concrete floating body section 4A in a horizontal position. (A) is a front view of the precast tubular body 15, (B) is a cross-sectional view along line BB in (A), and (C) is a cross-sectional view along line CC in (A). It is a diagram showing how to connect precast tubular bodies 15 in the temporary assembly process. It is a diagram (A) and (B) showing how to connect precast tubular bodies 15 using PC steel rods 20. It is a diagram (A) and (B) showing how to form sheath holes where PC steel strands are to be placed in the temporary assembly process. It is a longitudinal cross-sectional view of the concrete floating body section 4A after temporary assembly of the precast tubular bodies 15, 15, and the precast bottom slab 29 has been completed. It is a diagram showing how to insert PC steel strands 23 in the tensioning process. 12 is a diagram showing a connection procedure for the precast cylindrical body 60. FIG. 13 is a front view of the conventional precast cylindrical body 60 (view taken along XII-XII in FIG. 11 ).

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0025] [Hybrid Spar-Type Offshore Wind Power Generation Facility 1] First, a spar-type offshore wind power generation facility 1 to which the present invention is applied will be described in detail with reference to Figs. 1 and 2 .

[0026] As shown in Figure 1, the spar-type offshore wind power generation facility 1 is composed of a spar-type cylindrical floating body 4, mooring lines 5, 5..., a tower 6, and a wind turbine 7 consisting of a nacelle 8 and a plurality of blades 9, 9... installed on the top of the tower 6.

[0027] As shown in FIG. 2, the float 4 is made up of a concrete floating section 4A in which concrete precast cylindrical bodies 15, 15... (hereinafter also referred to as "concrete rings 15") are stacked in multiple layers in the vertical direction and each precast cylindrical body 15, 15... is fastened together with PC steel members 19, 19... to form an integrated body, and a steel floating section 4B connected to the upper side of this concrete floating section 4A.

[0028] Ballast material such as water, gravel, fine or coarse aggregate, or metal particles can be introduced into or discharged from the hollow portion of the floating body 4, thereby making it possible to adjust the buoyancy (draft). The introduction / discharge of ballast material is possible by employing the fluid transport method previously proposed by the present applicant in JP 2012-201217 A.

[0029] The concrete floating body section 4A is composed of concrete precast cylindrical bodies 15, 15 ... and a floating body bottom 29. The precast cylindrical bodies 15 are circular cylindrical precast members with the same cross section in the axial direction, and each is manufactured using the same formwork, or a hollow precast member manufactured by centrifugal molding is used.

[0030] Sheaths 21, 21 for passing PC steel members 19, 19 are embedded within the side wall of the precast cylindrical body 15. The PC steel members 19 and the sheaths 21 will be described in more detail later.

[0031] On the other hand, the steel floating body portion 4B is composed of a steel cylindrical body 17 located relatively on the lower side and a steel cylindrical body 18 located relatively on the upper side. The lower part of the lower steel cylindrical body 17 has the same outer diameter as the precast cylindrical body 15, and as shown in Figure 5, it is connected to the precast cylindrical body 15 by bolts or welding (bolt fastening in the illustrated example). The upper part of the steel cylindrical body 17 has a truncated conical shape with a gradually narrowing diameter.

[0032] The upper steel cylindrical body 18 is a cylindrical body with an outer diameter dimension that is continuous with the outer diameter of the upper part of the lower steel cylindrical body 17, and is connected to the lower steel cylindrical body 17 by bolts or welding (bolt fastening is used in the illustrated example). These steel cylindrical bodies 17, 18 are made up of steel rings divided into predetermined weights, and the steel rings are integrated by welding them circumferentially.

[0033] The tower 6 is made of steel, concrete, or PRC (prestressed reinforced concrete), but it is preferable to use one made of steel so that the total weight is small. The outer diameter of the tower 6 and the outer diameter of the upper steel cylindrical body 18 are approximately the same, and the outer shape is continuous in the vertical direction without any steps or the like.

[0034] As shown in Figure 1, the mooring point P of the mooring line 5 to the float 4 is set below the sea surface and at a position higher than the center of gravity G of the float 4. This prevents the ship from coming into contact with the mooring line 5. Also, a resistance moment is generated around the center of gravity G of the float 4 at the mooring point P to prevent the float 4 from tipping over too much, so that the tilting posture of the tower 6 can be maintained appropriately.

[0035] The nacelle 8 is a device equipped with a generator that converts the rotation of the wind turbine 7 into electricity, a controller that can automatically change the angle of the blades 9, and the like.

[0036] [Method for constructing the floating body 4] As a method for constructing the floating body in a quay yard by completing the floating body 4 in a sideways position, the method proposed by the present applicant and disclosed in Japanese Patent Application Laid-Open No. 2018-173011 can be suitably adopted.

[0037] As shown in FIG. 3, the floating structure construction method involves dividing a quay yard into a steel ring connection yard A, a concrete ring fabrication yard B, and a concrete ring connection yard C.

[0038] The steel ring connecting yard A is equipped with a first bridge crane 50 that can travel in a fixed direction, with rotating platforms 52, 52... installed at appropriate intervals in the direction of travel of the first bridge crane, and with a mobile tent 56 that can move in the direction of travel of the first bridge crane. The concrete ring manufacturing yard B is equipped with a mobile tent 57 and a complete set of concrete ring manufacturing equipment. The concrete ring connecting yard C is equipped with a second bridge crane 55 that can travel in a fixed direction, and with a mobile tent 58 that can move in the direction of travel of the second bridge crane.

[0039] The process then consists of a first step in which the steel rings 51, 51... are placed in order on the rotating platforms 52, 52... using the first bridge crane 50, and if necessary, covered with a mobile tent 56, and the steel rings 51, 51... are connected by welding in the circumferential direction while rotating them about their axes, thereby completing the steel floating body section 53B; and a second step in which the steel floating body section 53B is moved to the concrete ring connecting yard C and placed in a predetermined position, and then the concrete rings 15 fabricated in the concrete ring fabrication yard B are transported to the concrete ring connecting yard C in order, and if necessary, covered with a mobile tent 58, and the concrete rings 15 are connected to the steel floating body section 53B using the second bridge crane 55, and fastened together with PC steel members 19 to form a single unit, thereby completing the float 53.

[0040] [Method for constructing the concrete floating body section 4A] <Preparation procedure> In the preparation procedure, the numerous PC steel members 19, 19... arranged around the entire circumference of the precast cylindrical body 15 are divided in advance into a group of PC steel rods 20, 20... used to temporarily assemble the precast cylindrical body 15 in sequence, and a group of PC steel strands 23, 23... used to introduce a predetermined tension force after the temporary assembly of the concrete floating body section 4A is completed.

[0041] Specifically, referring to the precast cylindrical body 15 shown in Figure 5, this precast cylindrical body 15 is formed by assembling eight arc-shaped divided precast members 16A to 16H that are divided circumferentially. Within the wall surface of the precast cylindrical body 15, sheaths 21, 21... are embedded at predetermined intervals around the entire periphery to allow the installation of numerous PC steel members 19, 19...

[0042] When setting the PC steel bars 20, 20... group, according to the "External Cable Structure / Precast Segment Construction Method Design and Construction Standards" compiled by the Prestressed Concrete Technology Association, when joining the segments, the epoxy resin must be hardened at 0.3 N / mm 2 It is specified that a compressive stress of about 0.2 to 0.4 N / mm is applied to the joint surfaces of the precast cylindrical bodies 15 in the temporary assembly process of the precast cylindrical bodies 15 (Chapter 9 Considerations during construction, 9.3 Considerations during joining). In accordance with this guideline, the compressive stress of the joint surfaces of the precast cylindrical bodies 15, 15 is set to 0.2 to 0.4 N / mm 2 , preferably 0.25 to 0.35 N / mm 2 It is desirable to determine the number of the PC steel rods 20, 20... in the group so that

[0043] Therefore, in the precast cylindrical body 15 shown in FIG. 5, among all the PC steel members 19, 19, the group of PC steel rods 20, 20 used to temporarily assemble the precast cylindrical body 15 in order has a compressive stress intensity of 0.2 to 0.4 N / mm at the joint surface of the precast cylindrical bodies 15, 15. 2 If the size of the precast cylindrical body 15 were to increase and the precast cylindrical body 15 were to be constructed with PC steel bars 20, 20 only at two locations, one on each side of the precast cylindrical body 15, the compressive stress at the joint surface between the precast cylindrical body 15 would be 0.2 to 0.4 N / mm. 2 If the strength falls below this range, then the PC steel rods 20, 20... can be used at one location on each side of each arc-shaped divided precast member 16A to 16H, plus one or more intermediate locations.

[0044] As shown in Figure 5(C), the sheath 21 where the PC steel rods 20 are arranged has an expanded diameter section 21a (coupler sheath) formed at the lower end of the sheaths 21, 21... to accommodate nut members 25 for fastening the PC steel rods 19 and couplers 26 for connecting the PC steel rods together, and a box cutout section 22 formed at the top to fit a fastening anchor plate. There are a total of 72 PC steel members 19, 19..., and 16 of the PC steel rods 20, so that the PC steel rods 20, 20... account for approximately 22% of the total.

[0045] On the other hand, everything other than the group of PC steel rods 20, 20... is a group of PC steel strands 23, 23.... As shown in Figure 5(B), the sheaths 21 at the locations where these PC steel strands 23, 23... are arranged are sheaths 21 of the same diameter that are buried over the entire height of the locations where the PC steel strands 23 are arranged.

[0046] <Temporary Assembly Process of Concrete Floating Body Section 4A> The construction of the concrete floating body section 4A begins with a temporary assembly process in which the precast cylindrical bodies 15, 15... are placed sideways and sequentially connected in the horizontal direction, as shown in Figure 6. In this temporary assembly process, only the groups of PC steel rods 20, 20... are used out of all the PC steel members 19, 19...

[0047] When the precast cylindrical bodies 15 to be attached are sequentially connected to the end faces of the installed precast cylindrical bodies 15, 15, they are connected with the PC steel rods 20 aligned. Then, as shown in Figure 7(A), once the precast cylindrical bodies 15 are positioned adjacent to each other while the PC steel rods 20 extending from the assembled concrete floating body section are inserted into the sheaths 21, anchor plates 24 are fitted into the box cutout sections 22, prestress is introduced into the PC steel rods 20, and the precast cylindrical bodies are integrated by being fixed with nut members 25.

[0048] 7(B), a coupler 26 is screwed onto the protruding portion of the PC steel rod 20, and the next PC steel rod 20 is connected. The PC steel rod 20 is then inserted into the sheaths 21, 21 of the next precast cylindrical body 15 on the attachment side and placed adjacent to it. The PC steel rods 20 are then tensioned and fixed in place in the same manner as described above, and assembled sequentially in the lengthwise direction. Grout is injected into the sheaths 21 through the grout injection holes 27.

[0049] At the joint surface between the assembled precast cylindrical body 15 and the precast cylindrical body 15 on the mounting side, one gasket 28 is placed on the inside and one on the outside to ensure watertightness and to join the mating surfaces, and an adhesive such as an epoxy resin is applied to the joint surface.

[0050] On the other hand, at the planned placement locations of the PC steel strands 23, 23, as shown in Figure 8, the sheaths 21, 21 are aligned so that they are continuous in the vertical direction, and a long, narrow space is formed for inserting the PC steel strands 23 in the subsequent tension introduction process.

[0051] As shown in FIG. 9, once all the precast cylindrical bodies 15, 15, . . . have been connected, the float bottom 29 is connected to the outermost end, completing the temporary assembly of the concrete floating body portion 4A.

[0052] <Tensioning process> In the tensioning process after the preliminary assembly of the concrete floating body section 4A is completed, the PC steel strands 23 are inserted longitudinally through the entire length of the concrete floating body section 4A in each group of PC steel strands 23, 23, etc., and tensioning is introduced to and fixed in the PC steel strands 23.

[0053] Specifically, as shown in Figure 10, the PC steel strands 23 are unwound from the reels 30 around which they are wound, and inserted into the sheaths 21 for the PC steel strands 23 of the concrete floating body section 4A. Then, tension is introduced into the PC steel strands 23 between both ends of the concrete floating body section 4A, and the PC steel strands 23 are fixed in place. Also, grout material is injected into the sheaths 21. These operations are performed for all the PC steel strands 23, 23, ... to complete the concrete floating body section 4A.

[0054] [Other Examples] (1) In the above example, the float 4 is a spar-type float consisting of a concrete floating section 4A and a steel floating section 4B connected to the upper side of this concrete floating section 4A. However, it is also possible to construct a spar-type float consisting of only a concrete floating section 4A in which the float 4 is made up of precast cylindrical bodies 15, 15... stacked in multiple layers along its entire length, with each precast cylindrical body 15, 15... fastened together with PC steel members 19 to form a single unit, using the same procedure.

[0055] (2) In the above embodiment, the precast cylindrical bodies 15, 15... are completed by sequentially connecting them horizontally in a horizontal position, but the precast cylindrical bodies 15, 15... may also be completed by sequentially connecting them vertically in a vertical position.

[0056] 1...Spar-type offshore wind power generation facility, 4...Floating body, 4A...Concrete floating body section, 4B...Steel floating body section, 5...Mooring line, 6...Tower, 7...Wind turbine, 8...Nacelle, 9...Blade, 15...Precast cylindrical body (concrete ring), 19...PC steel material, 20...PC steel rod, 21...Sheath, 23...PC steel strand, 29...Precast bottom slab

Claims

1. A method for constructing a concrete floating body section of a floating offshore wind power generation facility, which has a concrete floating body section consisting of a plurality of connected precast cylindrical bodies, each of which is fastened and integrated with a number of prestressing steel members, in which the numerous prestressing steel members arranged around the entire circumference of the precast cylindrical bodies are previously divided into a group of prestressing steel rods used to temporarily assemble the precast cylindrical bodies in order, and a group of prestressing steel strands used to introduce a predetermined tension force after the temporary assembly of the concrete floating body section is completed, and in the temporary assembly process of the concrete floating body section, tension force is introduced to and fixed in the group of prestressing steel rods each time a precast cylindrical body is connected in order, and all of the precast cylindrical bodies are assembled, and the float bottom is placed at the end, completing the temporary assembly of the concrete floating body section, In the tension introduction step, a PC steel strand is inserted longitudinally through the entire length of the concrete floating body section in the PC steel strand group, and tension is introduced into and fixed to the PC steel strand.

2. During the temporary assembly process of the concrete floating body, the compressive stress of the joint surfaces of the precast cylindrical bodies is 0.2 to 0.4 N / mm 2 2. The method for constructing a concrete floating body portion of a floating offshore wind power generation facility according to claim 1, wherein the group of PC steel bars is determined so that:

3. The precast cylindrical body is formed by assembling arc-shaped divided precast members divided into multiple parts in the circumferential direction, and the compressive stress at the joint surfaces between the precast cylindrical bodies is 0.2 to 0.4 N / mm 2 2. A method for constructing a concrete floating body portion of a floating offshore wind power generation facility according to claim 1, wherein the group of PC steel rods is determined to include at least two locations, one on each side, in each arc-shaped divided precast member, and the remaining locations are the group of PC steel strands, under the condition that:

4. A method for constructing a concrete floating body portion of a floating offshore wind power generation facility as described in any one of claims 1 to 3, wherein the precast cylindrical bodies are connected in succession horizontally in a horizontal position, or connected in succession vertically in a vertical position.

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