Foundation in semi-submersible floating body type and construction method for foundation in semi-submersible floating body type

Abstract

To provide a foundation in a semi-submersible floating body type and a construction method for the foundation in the semi-submersible floating body type, allowing work load and cost upon construction to be reduced and resistance against repeated load like wave force to be secured, and maintenance cost to be reduced.SOLUTION: A foundation 2 in a semi-submersible floating body type is provided with: a center column 3 supporting a support rod 12 of a wind turbine 11; a plurality of side columns 4, 4, 4 arranged apart from the center column 3; and beams 5 connecting the center column 3 to the side columns 4. The center column 3 and the side column 4 respectively consist of a body part made of a cylindrical precast prestressed concrete member, a steel bottom plate, and a steel top plate. The beam 5, made of steel material, connects the bottom plates or the top plates of the center column 3 and the side column 4 to each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a semi-submersible floating foundation for an offshore wind power generation facility and a method for constructing a semi-submersible floating foundation. [Background technology]

[0002] Demand for renewable energy is increasing with the aim of reducing greenhouse gas emissions. Renewable energy sources include, for example, solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, and biomass power generation. Wind power generation facilities are often installed in mountainous areas away from residential areas because the noise and vibrations caused by wind turbines can affect the living environment and the impact on living spaces, etc. must be fully considered. However, it is difficult to secure land for installing large wind turbines in mountainous areas, and it is also difficult to secure transportation routes to wind power generation facilities and install transmission lines, etc. For this reason, installation of wind power generation facilities on the sea (on water) is being considered. When constructing a structure on water, a floating structure may be used as the foundation. Floating foundation structures include semi-submersible, spar, purge, and TLP types. Of these, semi-submersible foundations (semi-submersible floating foundations) are made up of a center column, multiple side columns spaced apart around the center column, and beams (pontoons) that connect the center column and the side columns, and have a relatively good track record due to their excellent stability against waves and wind.

[0003] Semi-submersible floating foundations are often composed mainly of steel members. However, costs can be reduced if all or part of the semi-submersible floating foundation is constructed from concrete. For example, Patent Document 1 discloses a semi-submersible floating foundation whose main structural elements are made of concrete. Patent Document 2 discloses a floating foundation whose center column and side columns are made of concrete, and the beams that connect the columns are composed of rigid members (fiber-reinforced plastic or steel).

[0004] Semi-submersible floating foundations made of concrete are generally constructed by integrating columns made of cylindrical reinforced concrete precast blocks and beams made of box-shaped reinforced concrete precast blocks with post-tensioning using prestressing steel. On the other hand, the prestressing steel is mainly arranged vertically in the columns and horizontally in the beams, and at the joints between the columns and beams, the vertical prestressing steel and horizontal prestressing steel are intertwined, resulting in a complex arrangement. This makes the arrangement of the prestressing steel time-consuming. In addition, the beams that connect the columns are subjected to large wave forces, so the thickness of the members must be large, which hinders cost reduction. In the floating foundation of Patent Document 2, the beam and the column are integrated by fixing the end of the beam inserted into the side wall of the column. However, the joint between the beam and the column is subject to a large load because repeated loads due to wave forces and the like act on the joint. In addition, the tip of the beam needs to be inserted into the column in which the PC steel is arranged, resulting in a complex joint structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2015-513046 [Patent Document 2] Special Publication No. 2013-545020 Summary of the Invention [Problem to be solved by the invention]

[0006] The objective of the present invention is to propose a semi-submersible floating foundation that reduces the effort and cost required for manufacturing, ensures resistance to repeated loads due to wave forces and the like, and reduces maintenance costs, as well as a method for constructing this semi-submersible floating foundation. [Means for solving the problem]

[0007] The present invention, which aims to solve the above problems, provides a semi-submersible floating foundation for a wind power generation facility, comprising a center column supporting a support for a wind turbine, a plurality of side columns spaced apart from the center column, and a beam connecting the center column and the side columns. The center column and the side columns each have a main body made of a cylindrical precast prestressed concrete member, a steel bottom plate, and a steel top plate. The beam is made of a steel member and connects at least one of the adjacent bottom plates and the adjacent top plates.

[0008] A first method for constructing a semi-submersible floating foundation includes the steps of forming the main body portion of the center column and the main body portion of the side column, fixing the bottom plate and the top plate to the main body portions, and connecting adjacent bottom plates and adjacent top plates with the beams. In addition, the second method of constructing a semi-submersible floating foundation includes the steps of forming a bottom structure connecting adjacent bottom plates via the beam, fixing the main body onto the bottom plate, and fixing the top plate to the upper end of the main body and connecting adjacent top plates via the beam.

[0009] According to this semi-submersible floating foundation and method for constructing a semi-submersible floating foundation, the bottom and top plates of the center column and side columns (hereinafter, when there is no need to distinguish between the two columns, they will simply be referred to as "columns") are made of steel and are joined to beams that are also made of steel members, so that the prestressing steel members do not become entangled at the joints between the columns and the beams. This reduces the amount of work required during manufacturing. It also ensures resistance to bending and twisting caused by external forces resulting from repeated loads caused by wave forces. Furthermore, because the beams are made of steel members, they can be connected to the bottom and top plates without being embedded in the side walls of the columns.

[0010] If the beam is formed by combining steel materials in a truss shape, higher rigidity can be ensured, making it easier to ensure sufficient resistance to wave forces. If the beam is bolted to the bottom plate and the top plate, even if the beam is damaged, it can be easily replaced. The bottom plate and the top plate preferably have a cover made of a circular steel plate in a plan view that can abut against the end face of the main body, and a wall that stands along the edge of the cover and is provided around the outer end face of the main body. In this case, it is preferable to bolt the wall to the outer end face of the main body via a water-stopping material. Such a bottom plate and top plate can be easily joined to the main body made of concrete, so there is no need to embed anchors or the like in the main body where many PC steel members are arranged, and the labor required for manufacturing can be reduced. Effect of the Invention

[0011] The semi-submersible floating foundation and the method for constructing this semi-submersible floating foundation of the present invention make it possible to reduce the effort and cost required during manufacturing, ensure resistance to repeated loads due to wave forces, etc., and reduce maintenance costs. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing an offshore wind power generation facility according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a perspective view showing a semi-submersible floating foundation according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a side view showing a portion of a semi-submersible floating foundation. [Figure 4] 1A is an enlarged cross-sectional view showing the joint between the bottom plate and the main body, and FIG. 1B is an enlarged cross-sectional view showing the joint between the top plate and the main body. [Diagram 5] FIG. 11 is a perspective view showing a main body forming step. [Figure 6] FIG. 11 is a perspective view showing a column forming step. [Figure 7] FIG. 11 is a perspective view showing a bottom structure forming step. [Figure 8] FIG. 11 is a perspective view showing a main body fixing step. [Figure 9]11 is an enlarged cross-sectional view showing another embodiment of the joint between the top plate and the main body portion. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First Embodiment In this embodiment, a foundation structure (semi-submersible floating foundation 2) of an offshore wind power generation facility (floor facility) 1 will be described. Fig. 1 is a perspective view of the offshore wind power generation facility 1. As shown in Fig. 1, the offshore wind power generation facility 1 includes a semi-submersible floating foundation 2, a pillar 12 erected on the semi-submersible floating foundation 2, and a wind turbine 11 rotatably provided on the upper end of the pillar 12. The wind turbine 11 and the pillar 12 are provided at a position higher than the water surface via the semi-submersible floating foundation 2. Figures 2 and 3 show a semi-submersible floating foundation 2. As shown in Figure 2, the semi-submersible floating foundation 2 comprises a center column 3 that supports the support pillars 12 of the wind turbine 11, three side columns 4, 4, 4 arranged at intervals from the center column 3, and beams 5, 5, ... that connect the center column 3 and the side columns 4. Note that the number and arrangement of the side columns 4 are not limited, and may be two, or four or more.

[0014] As shown in Figure 3, the center column 3 has a main body 31 made of a cylindrical precast prestressed concrete member, a steel bottom plate 32 provided at the lower end of the main body 31, and a steel top plate 33 provided at the upper end of the main body 31. The main body 31 is formed by connecting a plurality of (five in this embodiment) precast concrete members 34, 34, .... Tendons (not shown) are inserted through the precast concrete members 34. Prestress is introduced into the main body 31 in the vertical direction by the tendons.

[0015] FIG. 4 shows the bottom plate 32 and the top plate 33. As shown in FIG. 4(a), the bottom plate 32 has a cover 321 made of a steel plate having a circular shape in a plan view, and a wall 322 standing along the edge of the cover 321. The cover 321 has an outer diameter larger than that of the main body 31, and covers the end face of the main body 31 by abutting against the end face of the main body 31. A step 323 is formed on the periphery of the cover 321 in correspondence with the position of the inner surface of the main body 31. That is, when the cover 321 is abutted against the end face of the main body 31, the central portion is inserted into the hollow portion of the main body 31, and is engaged with the main body 31 at the step 323.

[0016] The wall portion 322 is erected on the peripheral edge of the lid portion 321. That is, the wall portion 322 is erected (vertically) on the upper surface of the lid portion 321 on the outer circumferential side by the thickness of the main body portion 31 from the step 323, and faces the outer surface of the main body portion 31. When the lid portion 321 is abutted against the end portion of the main body portion 31, the wall portion 322 is peripherally provided on the outer surface of the end portion of the main body portion 31. A plurality of female screw members 311 (e.g., nuts) are embedded in the lower end portion of the main body portion 31 in the circumferential direction. The wall portion 322 is formed with a through hole 324 corresponding to the position of the female screw member 311. With the wall portion 322 peripherally provided on the outer surface of the end portion of the main body portion 31, the bolt B inserted through the through hole 324 is screwed into the female screw member 311, thereby fixing the bottom plate 32 to the main body portion 31. A water-stopping material 6 (for example, water-stopping rubber or grout) is interposed between the wall portion 322 and the main body portion 31. Here, the through hole 324 is formed large relative to the axis of the bolt B, so that the positional deviation with respect to the female screw member 311 can be absorbed.

[0017] As shown in FIG. 4(b), the top plate 33 has a cover 331 made of a steel plate having a circular shape in plan view, a wall 332 erected along the edge of the cover 331, and a joint 335. The cover 331 has an outer diameter larger than that of the main body 31, and covers the end face of the main body 31 by abutting against the end face. A step 333 is formed on the periphery of the cover 331 in correspondence with the position of the inner surface of the main body 31. That is, when the cover 331 is abutted against the end face of the main body 31, the central portion is inserted into the hollow portion of the main body 31 and is engaged with the main body 31 at the step 333.

[0018] The wall portion 332 is erected on the periphery of the lid portion 331. That is, the wall portion 332 is erected (upright) on the lower surface of the lid portion 331 on the outer circumferential side by the thickness of the body portion 31 from the step 333, and faces the outer surface of the body portion 31. When the lid portion 331 is abutted against the end of the body portion 31, the wall portion 332 is circumferentially provided on the outer surface of the end of the body portion 31. A plurality of female screw members 311 (e.g., nuts) are embedded in the upper end of the body portion 31 in the circumferential direction. The wall portion 332 is formed with a through hole 334 corresponding to the position of the female screw member 311. The top plate 33 is fixed to the body portion 31 by screwing a bolt B inserted through the through hole 334 into the female screw member 311 with the wall portion 332 circumferentially provided on the outer surface of the end of the body portion 31. Note that a water stop material 6 is interposed between the wall portion 332 and the body portion 31. Here, the through hole 334 is formed large relative to the axis of the bolt B, so that any misalignment with the female screw member 311 can be absorbed.

[0019] The joint portion 335 is a flange formed to protrude from the periphery of the lid portion 331, and is connectable to the lower end portion of the support column 12. A plurality of through holes 336 are formed in the joint portion 335, and the joint portion 335 is joined to the flange 121 formed at the lower end of the support column 12 via the through holes 122 formed in the flange 121 and the bolts B inserted through the through holes 336 in a state of abutting (overlapping) the flange 121.

[0020] As shown in Figures 2 and 3, the side column 4 has a main body 41 made of a cylindrical precast prestressed concrete member, a steel bottom plate 42 provided at the lower end of the main body 41, and a steel top plate 43 provided at the upper end of the main body 41. The main body 41 is formed by connecting a plurality of (five in this embodiment) precast concrete members 44, 44, .... Tendons are inserted through the precast concrete members 44. That is, prestress is introduced into the main body 41 by the tendons.

[0021] 4(a), the bottom plate 42 has a lid portion 421 made of a steel plate having a circular shape in a plan view, and a wall portion 422 standing along the edge of the lid portion 421. The details of the lid portion 421 and the wall portion 422 are similar to those of the lid portion 321 and the wall portion 322 of the bottom plate 32 of the center column 3, and therefore a detailed description thereof will be omitted. 4(b), the top plate 43 has a cover portion 431 made of a steel plate having a circular shape in a plan view, and a wall portion 432 standing along the edge of the cover portion 431. The details of the cover portion 431 and the wall portion 432 are similar to those of the cover portion 331 and the wall portion 332 of the top plate 33 of the center column 3, and therefore a detailed description thereof will be omitted.

[0022] The beams 5 are made of steel members. As shown in Figs. 2 and 3, they are provided at the upper and lower parts of the semi-submersible floating foundation 2, respectively. The lower beam 5 connects the bottom plate 32 of the center column 3 to the bottom plate 42 of the side column 4. The upper beam 5 connects the top plate 33 of the center column 3 to the top plate 43 of the side column 4. The beam 5 is formed into a plate shape by combining steel materials in a truss shape. The beam 5 in this embodiment is bolted to the bottom plates 32, 42 or the top plates 33, 43.

[0023] A method for constructing the semi-submersible floating foundation 2 of this embodiment will be described below. The method for constructing the semi-submersible floating foundation 2 includes a main body forming step, a column forming step, and a beam connecting step. In the main body forming process, the main body 31 of the center column 3 and the main body 41 of the side column 4 are formed. Fig. 5 shows the main body forming process. In the main body forming process, as shown in Fig. 5, the precast concrete members 34, 44 are connected together and prestress is introduced by tension members to form the main bodies 31, 41. Note that when forming the main bodies 31, 41, the precast concrete members 34, 44 may be stacked one on top of the other, or may be connected together on the left and right and then erected.

[0024] In the column formation process, the bottom plates 32, 42 and the top plates 33, 43 are fixed to the main body parts 31, 41. The column formation process is shown in Figure 6. In the column formation process, the top plates 33, 43 are fixed to the upper ends of the main body parts 31, 41, and the bottom plates 32, 42 are fixed to the lower ends of the main body parts 31, 41, as shown in Figure 6.

[0025] In the beam connecting process, the bottom slab 32 of the center column 3 and the bottom slab 42 of the side column 4 are connected by the beam 5, and the top slab 33 of the center column 3 and the top slab 43 of the side column 4 are connected by the beam 5 to form the semi-submersible floating foundation 2. In the beam connecting process, as shown in Fig. 2, the bottom slabs 32, 42 of the center column 3 and the side column 4 (adjacent bottom slabs 32, 42) are connected by the beam 5, and the top slabs 33, 43 (adjacent top slabs 33, 43) are connected by the beam 5. The method of joining the beam 5 to the bottom slabs 32, 42 or the top slabs 33, 43 is not limited, and may be, for example, bolted or welded.

[0026] According to the semi-submersible floating foundation 2 and the method for constructing the semi-submersible floating foundation 2 of this embodiment, the bottom plates 32, 42 and top plates 33, 43 of the columns (center column 3 and side column 4) are made of steel and are joined to the beam 5, which is also made of a steel member, so that the PC steel members do not become entangled at the joints between the columns and the beam 5. This reduces the labor required for manufacturing. In addition, because the beam 5 is made of a plate-like member that has a truss shape in a plan view, it is possible to ensure resistance to bending and twisting caused by external forces acting due to repeated loads caused by wave forces.

[0027] In addition, the beam 5 is made of steel material and is not embedded in the side walls of the column, but is bolted to the bottom plates 32, 42 and top plates 33, 43, so that even if the beam 5 is damaged, it can be easily repaired. Since the beam 5 is formed by combining steel materials in a truss shape, higher rigidity can be ensured, and it is easy to ensure sufficient strength against wave forces. Furthermore, if the beam 5 is made into a truss-shaped member, the buoyancy will be lower than that of a hollow beam. However, the necessary buoyancy can be ensured by increasing the diameter of the main bodies 31, 41 of the center column 3 and the side column 4 and / or extending the length of the main bodies.

[0028] The bottom slabs 32, 42 and the top slabs 33, 43 have walls that are provided around the outer ends of the main body 31, 41, and therefore can be easily joined to the concrete main body 31, 41. This eliminates the need to embed anchors or the like in the main body 31, 41, which is provided with a large number of PC steel members, and reduces the labor required for production. Furthermore, by using a composite structure that combines concrete members and steel members, the structure of the connecting parts is simplified compared to a structure made entirely from concrete, reducing the amount of work required during production and ultimately enabling reductions in production costs.

[0029] Second Embodiment In the second embodiment, similarly to the first embodiment, a description will be given of a foundation structure (semi-submersible floating foundation 2) of an offshore wind power generation facility (water facility) 1. Details of the offshore wind power generation facility 1 are similar to those described in the first embodiment, and therefore detailed description will be omitted.

[0030] The method for constructing the semi-submersible floating foundation 2 of the second embodiment will be described below. The method for constructing the semi-submersible floating foundation 2 includes a bottom structure forming step, a main body fixing step, and a top plate connecting step. Figure 7 shows the bottom structure forming step, and Figure 8 shows the main body fixing step. In the bottom structure formation process, as shown in Fig. 7, a bottom structure 21 is formed by connecting the bottom plate 32 of the center column 3 and the bottom plates 42, 42, 42 of each side column 4, 4, 4 by a beam 5. The method of joining the beam 5 and the bottom plates 32, 42 is not limited, and may be, for example, bolted or welded.

[0031] In the main body fixing process, as shown in Fig. 8, the main bodies 31, 41 are fixed onto the respective bottom slabs 32, 42. The precast concrete members 34, 44 are vertically connected on the bottom slabs 32, 42, and prestress is introduced using tension members to form the main bodies 31, 41. At this time, of the precast concrete members 34, 44 constituting the main body 31, 41, the precast concrete member 34, 44 arranged at the bottom is bolted to the bottom slabs 32, 42 (see Fig. 4(a)). In the top plate connecting process, the top plates 33, 43 are fixed to the upper ends of the main bodies 31, 41, and the top plate 33 of the center column 3 and the top plate 43 of the side column 4 are connected by a beam 5 (see Figure 2). The top plates 33, 43 are bolted to the precast concrete members 34, 44 arranged in the uppermost stage among the precast concrete members 34, 44 constituting the main bodies 31, 41 (see Figure 4(b)).

[0032] According to the semi-submersible floating foundation 2 and the method for constructing a semi-submersible floating foundation 2 of the second embodiment, the same effects as those of the semi-submersible floating foundation 2 and the method for constructing a semi-submersible floating foundation 2 of the first embodiment can be obtained.

[0033] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention. For example, in the above embodiment, a flange-shaped joint 335 is formed on the top plate 33 and joined to the flange 121 formed on the lower end of the column 12, but if there is no flange 121 on the lower end of the column 12, a wall-like joint 337 that abuts against the inner surface of the column 12 may be formed on the top plate 33. In this case, the joint 337 may be friction-joined to the inner surface of the column 12 (see FIG. 9). There is no limitation on the method of forming the walls of the bottom plates 32, 42 and the top plates 33, 43. For example, the walls may be formed by fixing a steel plate to the lid, or by bending the edge portion of the lid. [Explanation of symbols]

[0034] 1. Offshore wind power generation facilities 11 Windmill 12 pillars 2. Semi-submersible floating foundation 3 Center Column 31 Main body 32 bottom plate 321 Lid 322 Wall 33 Top version 331 Lid 332 Wall 34 Precast concrete components 4 Side Column 41 Main body 42 bottom plate 421 Lid 422 Wall 43 Top version 431 Lid 432 Wall section 44 Precast concrete components 5 Beam 6. Water-stopping materials

Claims

1. A center column supporting the wind turbine support; a plurality of side columns disposed at intervals from the center column; A semi-submersible floating foundation comprising: a beam connecting the center column and the side columns, The center column and the side column each have a main body made of a cylindrical precast prestressed concrete member, a steel bottom plate, and a steel top plate; The beam is made of a steel member, A semi-submersible floating foundation, characterized in that at least one of adjacent bottom plates and adjacent top plates are connected by the beam.

2. 2. The semi-submersible floating foundation according to claim 1, wherein the beam is formed by combining steel members in a truss shape.

3. 2. The semi-submersible floating foundation according to claim 1, wherein the beams, the bottom plate and the top plate are connected by bolts.

4. The bottom plate and the top plate have a lid portion made of a steel plate having a circular shape in a plan view, and a wall portion erected along an edge portion of the lid portion, 2. A semi-submersible floating foundation as described in claim 1, characterized in that the wall portion is provided around the outer surface of the end portion of the main body portion with the lid portion abutting the end surface of the main body portion.

5. 5. A semi-submersible floating foundation according to claim 4, wherein the wall portion is bolted to the outer end surface of the main body portion via a water-stopping material.

6. A method for constructing a semi-submersible floating foundation according to any one of claims 1 to 5, comprising the steps of: forming the body portion of the center column and the body portion of the side column; fastening the bottom plate and the top plate to the body portion; and a step of connecting at least one of adjacent bottom slabs and adjacent top slabs with the beam.

7. A method for constructing a semi-submersible floating foundation according to any one of claims 1 to 5, comprising the steps of: forming a bottom structure by connecting adjacent bottom plates via the beam; Fixing the main body onto the bottom plate; a step of fixing the top plate to an upper end of the main body portion and connecting adjacent top plates via the beam.

Images