Method for constructing a concrete floating body of an offshore floating wind power plant

Abstract

To improve the efficiency of assembling work by saving labor in the tensioning and fixing work of a PC steel material in a method for constructing a concrete floating body part.SOLUTION: A PC steel material 19 is previously divided into a PC steel rod 20 group used for temporarily assembling a precast cylindrical body in order and a PC steel stranded wire 23 group used for introducing prescribed tensile force after finishing the temporary assembly of a concrete floating body part. In the temporary assembly process of the 4A of the concrete floating body, the temporary assembly of the 4A of the concrete floating body is completed by assembling all the precast cylindrical bodies 15 and installing the floating body bottom 29 at the endmost part while introducing and fixing the tensile force to the PC steel bar 20 in the PC steel bar 20 group every time the precast cylindrical bodies 15 are sequentially connected, and in the tensile force introduction process, the PC steel strand 23 is inserted in the longitudinal direction over the entire length of the 4A of the concrete floating body in the PC steel strand 23 group, and the tensile force is introduced and fixed to the PC steel strand 23.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for efficiently constructing a concrete floating body section in a floating offshore wind power generation facility having a concrete floating body section 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. [Background technology]

[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 has the advantage of easily obtaining winds suitable for power generation and fewer restrictions on installation. For this reason, many different 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 have the lower part of the float submerged below the water surface and float in a semi-submerged state, 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 below an offshore wind power generation facility consisting of a float, mooring lines, a tower, a nacelle and multiple wind turbine blades installed at the top of the tower, wherein the float is made of concrete precast cylindrical bodies stacked vertically in multiple tiers, and the float is made of a lower concrete floating structure part (hereinafter referred to as the concrete floating body part) in which the precast cylindrical bodies are fastened together with PC steel to form a single unit, and an upper steel floating structure part (hereinafter referred to as the steel floating body part) connected to the above of the concrete floating body part (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.

[0007] To connect the precast cylindrical body 60 to the end of the assembled concrete floating body section 61, all of the numerous PC steel members arranged around the entire circumference of the precast cylindrical body are PC steel rods 62, 62..., 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. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5274329 [Patent Document 2] Japanese Patent Application Publication No. 2018-173011 Summary of the Invention [Problem to be solved by the invention]

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

[0010] Therefore, the main objective of this 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 portion of a floating offshore wind power generation facility, which has a concrete floating body portion in which multiple precast cylindrical bodies are connected and each precast cylindrical body is fastened and integrated with numerous PC steel members. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention according to claim 1 provides a method for constructing a concrete floating body portion of a floating offshore wind power generation facility, which has a concrete floating body portion formed by connecting a plurality of precast cylindrical bodies and fastening each precast cylindrical body to an integrated body using a large number of PC steel members, A large number of prestressing steel members arranged around the entire circumference of the precast cylindrical body are divided in advance into a group of prestressing steel rods to be used for temporarily assembling the precast cylindrical body in order, and a group of prestressing steel strands to be used for introducing a predetermined tension force after the temporary assembly of the concrete floating body section is completed, In the temporary assembly process of the concrete floating body part, each time the precast cylindrical bodies are connected in sequence, tension is introduced into the PC steel bars and fixed in place in the PC steel bar group, and all the precast cylindrical bodies are assembled and the bottom of the floating body is installed at the end, completing the temporary assembly of the concrete floating body part. 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 process, 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 to and fixed in 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 a 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 to and fixed in the PC steel rod group each time a precast cylindrical body is sequentially connected, and temporary assembly of all precast cylindrical bodies is completed by installing the floater bottom at the end.

[0014] On the other hand, PC steel strands are used in locations where PC steel members other than the PC steel bars are placed. In the tensioning process after the concrete floating body section has been temporarily assembled, the 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 to and fixed in the PC steel strands. Since tension is introduced to these PC steel strands after they have been inserted longitudinally through the concrete floating body section whose temporary assembly has been completed, tensioning and fixing only need to be done once, which saves labor in the prestressing and fixing work.

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

[0016] As a second aspect of the present invention, 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 set to 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 0.3 N / mm is required until the epoxy resin hardens. 2 In 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] As a third aspect of the present invention, 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 There is provided a method for constructing a concrete floating body portion of a floating offshore wind power generation facility as described in claim 1, in which 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 above specifies a method for determining the number of split PC steel bars in a cylindrical body formed by assembling arc-shaped split precast members, each of which is formed by splitting a precast cylindrical body in the circumferential direction. In this case, the compressive stress intensity at the joint surface between the precast cylindrical bodies is 0.2 to 0.4 N / mm 2In 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 rest are PC steel strand groups.

[0020] The present invention according to claim 4 provides a method for constructing a concrete floating body section 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 sequence horizontally in a horizontal position, or connected in sequence 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. [Effects of the Invention]

[0022] As explained above, according to the present invention, in a method for constructing a concrete floating body section of a floating offshore wind power generation facility 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 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. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is an overall view of a spar-type offshore wind power generation facility 1. [Figure 2] FIG. 2 is a vertical cross-sectional view of the floating body 4. [Figure 3] FIG. 2 is a perspective view showing the construction procedure of the spar-type offshore wind power generation facility 1. [Figure 4] 10 is a diagram showing how to connect precast cylindrical bodies 15 when constructing a concrete floating body section 4A in a horizontal position. [Figure 5] 1A shows a precast cylindrical body 15, where (A) is a front view, (B) is a cross-sectional view taken along line BB in (A), and (C) is a cross-sectional view taken along line CC in (A). [Figure 6] FIG. 10 is a diagram showing how the precast cylindrical bodies 15 are connected in the temporary assembly process. [Figure 7] 1A and 1B are diagrams showing how precast cylindrical bodies 15 are connected using PC steel bars 20. [Figure 8] These are diagrams (A) and (B) showing how to form sheath holes where PC steel strands are to be placed during the temporary assembly process. [Figure 9] FIG. 10 is a vertical cross-sectional view of a concrete floating body portion 4A after temporary assembly of the precast cylindrical bodies 15, 15... and the precast bottom slab 29 has been completed. [Figure 10] 10 is a diagram showing how to insert a PC steel strand 23 during the tension application process. FIG. [Figure 11] 10 is a diagram showing how to connect the precast cylindrical body 60. FIG. [Figure 12] FIG. 12 is a front view (view taken along XII-XII in FIG. 11) of a conventional precast cylindrical body 60. DETAILED DESCRIPTION OF THE INVENTION

[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. FIG.

[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 multiple blades 9, 9... installed on the top of the tower 6.

[0027] As shown in Figure 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 vertically in multiple layers, 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 materials such as water, gravel, fine or coarse aggregate, and metal particles can be introduced into or discharged from the hollow space of the floating body 4, thereby making it possible to adjust the buoyancy (draft). The introduction / discharge of ballast materials is possible by employing the fluid transport method previously proposed by the 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, 19... and the sheaths 21 will be described in more detail later.

[0031] On the other hand, the steel floating body section 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 at the mooring point P around the center of gravity G of the float 4 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] [Construction method of Floating Body 4] As a floating body construction method for completing the floating body 4 in a horizontally laid position at a quay yard, the method proposed by the present applicant in Patent Publication No. 2018-173011 can be suitably adopted.

[0037] As shown in Figure 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] In the steel ring connecting yard A, a first bridge crane 50 is installed so that it can travel freely in a fixed direction, and rotating platforms 52, 52... are installed at appropriate intervals in the direction of travel of the first bridge crane, and a mobile tent 56 is also installed so that it can move in the direction of travel of the first bridge crane. In the concrete ring manufacturing yard B, a mobile tent 57 is installed and a complete set of concrete ring manufacturing equipment is also installed. In the concrete ring connecting yard C, a second bridge crane 55 is installed so that it can travel freely in a fixed direction, and a mobile tent 58 is also installed so that it 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 covered with a mobile tent 56 if necessary, and the steel rings 51, 51... are connected by welding circumferentially while rotating them around 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 place, 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 covered with a mobile tent 58 if necessary, 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 floater 53.

[0040] [Construction method of concrete floating body 4A] <Preparation steps> 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] To be more specific, taking 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-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 up the 20, 20... PC steel bars, 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 should be 0.3N / 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). 2 , preferably 0.25 to 0.35N / 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 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 surfaces between the precast cylindrical bodies 15 would be 0.2 to 0.4 N / mm 2 If the range falls below this, the PC steel rods 20, 20... can be used at one location on each side of each of the arc-shaped divided precast members 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 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 connected horizontally in sequence, as shown in Figure 6. In this temporary assembly process, only the PC steel rods 20, 20... are used out of all the PC steel members 19, 19...

[0047] When connecting the precast cylindrical bodies 15 to be attached sequentially 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 placed adjacent to each other while the PC steel rods 20, 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] Next, as shown in Figure 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, and the PC steel rods 20 are assembled sequentially in the lengthwise direction in the same manner as described above, with the PC steel rods 20 tensioned and fixed in place. 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 locations for 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 application process.

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

[0052] <Tension force introduction process> In the tension introduction process after the temporary 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..., and tension is introduced to and fixed in these PC steel strands 23.

[0053] Specifically, as shown in Figure 10, the PC steel strand 23 is unwound from the reel 30 around which it is wound, and inserted into the sheath 21 for the PC steel strand 23 of the concrete floating body section 4A. Then, tension is introduced into the PC steel strand 23 and the strand is fixed between both ends of the concrete floating body section 4A. Also, grout material is injected into the sheath 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 embodiment, 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 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. [Explanation of symbols]

[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 portion of a floating offshore wind power generation facility having a concrete floating body portion in which a plurality of precast cylindrical bodies are connected and integrated by fastening each precast cylindrical body with a large number of PC steel members, A large number of PC steel members arranged around the entire circumference of the precast cylindrical body are divided in advance into a group of PC steel rods to be used for temporarily assembling the precast cylindrical body in order, and a group of PC steel strands to be used for introducing a predetermined tension force after the temporary assembly of the concrete floating body section is completed. In the temporary assembly process of the concrete floating body part, each time the precast cylindrical bodies are connected in sequence, tension is introduced into the PC steel bars and fixed in place in the PC steel bar group, and all the precast cylindrical bodies are assembled and the floating body bottom is installed at the end, completing the temporary assembly of the concrete floating body part. 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. In the temporary assembly process of the concrete floating body, the compressive stress of the joint surfaces between 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 rods is determined so that:

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 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. The 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, wherein the precast cylindrical bodies are connected in sequence in the horizontal direction while oriented horizontally, or connected in sequence in the vertical direction while oriented vertically.

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