Semi-submersible floating foundation

Abstract

To propose a semi-submersible floating foundation capable of being reduced in weight and being constructed in a relatively simple way.SOLUTION: A semi-submersible floating foundation 2 for a wind power generation facility comprises a center column 3 supporting a support 12 for a wind turbine 11, three side columns 4, 4, 4 arranged at intervals around the center column 3, and a beam 5 connecting the center column 3 and the side columns 4. The center column 3 comprises a steel slab 31 and a cylindrical body part 32 erected from the slab 31. The slab 31 comprises a bottom steel plate 33 for slab provided on a bottom surface, and a top steel plate 34 for slab provided on a top surface. The body part 32 is made of prestressed concrete, and passes through the top steel plate 34 for slab, and the lower end of the body part 32 is in contact with the bottom steel plate 33 for slab.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] For the purpose of reducing the emission amount of greenhouse gases, the demand for renewable energy is increasing. Renewable energy includes, for example, solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, biomass, etc. Wind power generation facilities may have noise and vibration caused by wind turbines affecting the living environment, and it is necessary to fully consider the impact on living spaces, etc., so they are often installed in mountainous areas away from residential areas. 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 the wind power generation facilities and install power transmission lines, etc. Therefore, it has been considered to install wind power generation facilities on the sea (water). When constructing a structure on water, a floating structure may be adopted as the foundation structure. As the floating foundation structure, there are a semi-submersible type, a spar type, a barge type, a TLP type, etc. Among these, the semi-submersible type foundation (semi-submersible floating foundation) includes a center column, a plurality of side columns arranged at intervals around the center column, and a beam connecting the center column and the side columns, and has excellent stability performance against waves and wind, so there are relatively many achievements. The semi-submersible floating foundation is often mainly composed of steel members. On the other hand, if the semi-submersible floating foundation is constructed of concrete, the cost can be reduced. For example, Patent Document 1 discloses a semi-submersible floating foundation in which the main structural elements are made of concrete. For the purpose of reducing the construction cost of an offshore wind power generation facility, there is a case where the semi-submersible floating foundation is moored to a quay wall in a floating state and the wind turbine is installed by a crane on the quay wall. In this case, it is necessary to make the draft smaller than the water depth of the quay wall. Also, the semi-submersible floating foundation adjusts the draft so that the sway caused by waves and wind can be effectively restricted by arranging ballast. Because concrete is heavier than steel, if the main structural elements of a semi-submersible floating foundation are made of concrete, the area that provides buoyancy needs to be larger, which in turn increases the amount of concrete required. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2015-513046 [Overview of the project] [Problems that the invention aims to solve]

[0004] The objective of this invention is to propose a semi-submersible floating foundation that is lightweight and can be constructed relatively easily. [Means for solving the problem]

[0005] The present invention, for solving the aforementioned problems, is a semi-submersible floating foundation for a wind power generation facility, comprising a center column supporting the wind turbine's support structure, a plurality of side columns arranged at intervals around the center column, and beams connecting the center column and the side columns. The center column comprises a steel slab and a cylindrical main body erected on the slab. The slab comprises a bottom steel plate for the slab provided on its bottom surface and an upper steel plate for the slab provided on its top surface. The main body is made of prestressed concrete and penetrates the upper steel plate for the slab, with the lower end of the main body in contact with the bottom steel plate for the slab. . before Steel plate frame members are erected at the corners between the main body and the bottom steel plate for the slab, and at the corners between the main body and the top steel plate for the slab, and steel connecting members are provided on the peripheral wall of the main body to connect the frame members that are opposite each other across the peripheral wall. ru. With this semi-submersible floating foundation, by making at least a portion of the center column out of steel, it is possible to reduce the weight compared to a case where the entire structure is made of concrete, and also reduce the amount of concrete required. Furthermore, even if the main body of the center column is made of concrete, the main body is made continuous (integrated) with the bottom steel plate and the top steel plate, so the required strength can be obtained in the ultimate limit state and fatigue limit state. [Effects of the Invention]

[0006] The semi-submersible floating foundation of the present invention can be constructed relatively easily, thereby shortening the construction period and reducing costs. Furthermore, its lightweight design allows for the securing of the desired buoyancy with the minimum necessary size. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view showing an offshore wind power generation facility according to an embodiment of the present invention. [Figure 2] This figure shows a semi-submersible floating foundation according to an embodiment of the present invention, where (a) is a plan view and (b) is a cross-sectional view of (a) IIB. [Figure 3] This figure shows a part of the center column, where (a) is a cross-sectional view showing the joint structure between the main body and the bottom steel plate for the slab, (b) is a longitudinal section showing the joint structure between the main body and the bottom steel plate for the slab, and (c) is a longitudinal section showing the joint structure between the main body and the top steel plate for the slab. [Figure 4] This figure shows a composite precast segment, where (a) is a longitudinal section and (b) is an IVB section of (a). [Figure 5] This is a flowchart showing the method for constructing a semi-submersible floating foundation. [Modes for carrying out the invention]

[0008] In this embodiment, the foundation structure (semi-submersible floating foundation 2) of the offshore wind power generation facility (floating facility) 1 will be described. Figure 1 is a perspective view of the offshore wind power generation facility 1. As shown in Figure 1, the offshore wind power generation facility 1 has a wind turbine 11 and a support column 12 that supports the wind turbine 11, and is installed at a position higher than the water surface via a semi-submersible floating foundation 2. The wind turbine 11 is rotatably mounted on the upper end of the support column 12. The support column 12 is erected on the semi-submersible floating foundation 2. The semi-submersible floating foundation 2 comprises a center column 3 that supports the support column 12 of the wind turbine 11, three side columns 4, 4, 4 arranged at intervals around the center column 3, and beams 5, 5, 5 that connect the center column 3 and the side columns 4.

[0009] Figure 2 shows the semi-submersible floating foundation 2. The center column 3 comprises a slab 31 and a cylindrical main body 32 erected on the slab 31, as shown in Figures 2(a) and (b). The slab 31 is formed by combining steel plates and includes a bottom steel plate 33 for the slab provided on the bottom surface and an upper steel plate 34 for the slab provided on the top surface. The slab 31 has an outer shape that is sufficiently larger than the outer shape of the main body 32. The slab 31 also has a beam joint portion 35 that protrudes toward the beam 5. The beam joint portion 35 is made of steel material that has an outer shape similar to that of the beam 5 (a rectangular tube shape in this embodiment). As shown in Figure 2(b), the main body 32 penetrates the central part of the upper steel plate 34 for the slab, and the lower end of the main body 32 abuts against the bottom steel plate 33 for the slab. A part of the main body 32 is shown in Figure 3. The main body 32 is made of prestressed concrete, and as shown in Figure 3(a), a PC steel member (column tensioning member 321) is provided in the center in the thickness direction. The column tensioning member 321 is arranged in the vertical direction of the main body 32. As shown in Figure 3(b), a steel frame member 36 is erected at the corner between the main body 32 and the bottom steel plate 33 for the slab. Also, as shown in Figure 3(c), a steel frame member 36 is erected at the corner between the main body 32 and the upper steel plate 34 for the slab. Multiple frame members 36 are provided at intervals around the circumferential direction of the main body 32, as shown in Figure 3(a). Steel cylindrical bodies 37 are provided around the outer and inner surfaces of the main body 32, corresponding to the positions of the frame members 36. The frame members 36 are fixed (welded) to the cylindrical bodies 37. As shown in Figures 3(b) and (c), steel vertical connecting members 38 are provided on the peripheral wall of the main body 32. As shown in Figure 3(b), the vertical connecting member 38 positioned above the slab bottom steel plate 33 is located at the corner between the main body 32 and the slab bottom steel plate 33, connecting the opposing structural members 36 across the peripheral wall. As shown in Figure 3(c), the vertical connecting member 38 positioned below the slab top steel plate 34 is located at the corner between the main body 32 and the slab top steel plate 34, connecting the opposing structural members 36 across the peripheral wall. Both ends of the vertical connecting member 38 are fixed (welded) to the cylindrical body 37, corresponding to the positions of the structural members 36. Furthermore, as shown in Figure 3(b), a horizontal connecting member 39 is fixed to the lower end of a vertical connecting member 38 that connects the structural members 36, which are installed on the bottom steel plate 33 for the slab.

[0010] As shown in Figure 2(a), three side columns 4 are arranged around the center column 3. The spacing between adjacent side columns 4 is the same. The side columns 4 are connected to the center column 3 via beams 5. As shown in Figures 2(a) and (b), the side column 4 is cylindrical. The side column 4 is made of concrete, and its upper end is shielded by a top plate 41.

[0011] Beam 5 is made of prestressed concrete with PC steel members (beam tensioning members 55) installed. As shown in Figures 2(a) and (b), one end of beam 5 is connected to the slab 31 of the center column 3, and the other end of beam 5 is connected to the side column 4. Beam 5 has a rectangular tubular shape with a top plate 51, a bottom plate 52, and left and right side walls 53, 53. Beam 5 is formed by connecting a plurality of beam segments 54, 54, ... in the lateral direction. The beam segments 54 are precast concrete members. Also, as shown in Figure 4(a), beam tensioning members 55 are installed in the top plate 51 and the bottom plate 52. Figure 4 is a diagram showing the joint between the center column 3 and beam 5. The beam tensioning members 55 are installed along the longitudinal direction of beam 5 and penetrate the plurality of beam segments 54. One end of the beam tensioning member 55 is fixed to the side column 4, and the other end of the beam tensioning member 55 is fixed to a composite precast segment 6 interposed between the beam 5 and the slab 31.

[0012] As shown in Figure 4(a), the composite precast segment 6 is made by combining concrete and steel, and includes a steel section 61, an anchoring section 62, and a beam connection section 63. The steel section 61 has a bottom steel plate 64 for segments and an upper steel plate 65 for segments that is spaced apart above the bottom steel plate 64 for segments. The steel section 61 is welded to the slab 31 of the center column 3. The anchoring portion 62 is positioned in accordance with the beam tensioning member 55. In this embodiment, the anchoring portion 62 is formed at the beam 5 side end of the segment bottom steel plate 64 and at the beam 5 side end of the segment upper steel plate 65, respectively. The anchoring portion 62 is made of concrete, and a pressure receiving plate 67 is fixed to the end face of the anchoring portion 62. A segment vertical steel plate 66 is fixed to the beam 5 side end of the segment bottom steel plate 64. The segment vertical steel plate 66 is formed perpendicular to the segment bottom steel plate 64. Similarly, a segment vertical steel plate 66 is also fixed to the segment upper steel plate 65.

[0013] In the fixing portion 62, as shown in FIGS. 4(a) and (b), perforated steel sheet diver 621 is fixed to the bottom steel sheet 64 for segments at a predetermined interval. In the present embodiment, a pair of perforated steel sheet divers 621 are provided so as to sandwich the beam tension member 55 in a plan view. Reinforcing bars 622 arranged in a direction orthogonal to the beam tension member 55 penetrate the perforated steel sheet diver 621. One end of the perforated steel sheet diver 621 is fixed to the pressure receiving plate 67, and the other end is fixed to the end portion of the vertical steel sheet 66 for segments. Similarly, the perforated steel sheet diver 621 is also fixed to the upper steel sheet 65 for segments, and the reinforcing bars 622 penetrating the perforated steel sheet diver 621 are arranged. Further, a diver 623 is fixed to the vertical steel sheet 66 for segments corresponding to the position of the fixing portion 62. The fixing portion 62 is formed in a state of enclosing the perforated steel sheet diver 621 and the diver 623, thereby ensuring the integrality with the steel portion 61.

[0014] The beam connection portion 63 is a concrete portion formed on the end face of the steel portion 61 on the beam 5 side. The beam connection portion 63 of the present embodiment includes a lower joint portion 631 and an upper joint portion 632 formed at positions facing the fixing portion 62 with the vertical steel sheet 66 for segments interposed therebetween, and a partition portion 633 interposed between the lower joint portion 631 and the upper joint portion 632. Through holes through which the beam tension member 55 is inserted are formed in the lower joint portion 631 and the upper joint portion 632. A diver 634 is fixed to the vertical steel sheet 66 for segments corresponding to the position of the beam connection portion 63. The beam connection portion 63 is formed in a state of enclosing the diver 634, thereby ensuring the integrality with the steel portion 61.

[0015] The construction method of the semi-submersible floating body type foundation of the present embodiment will be described. As shown in FIG. 5, the construction method of the semi-submersible floating body type foundation includes a segment manufacturing process S1, a beam forming process S2, a composite precast segment installation process S3, a center column connection process S4, and a side column connection process S5. The segment manufacturing process S1 is a process of manufacturing the composite precast segment 6 and the beam segments 54 that make up the beam 5. In the segment manufacturing process S1, an operation S11 of manufacturing the steel part 61 by combining steel plates, an operation S12 of manufacturing the fixing part 62 and the beam connection part 63 with the steel part 61 as a female mold, and an operation S13 of manufacturing the beam segment 54 with the composite precast segment 6 as a female mold are performed. The beam forming process S2 is a process of forming the beam 5 by arranging a plurality of beam segments 54, 54,... at predetermined positions. A water stop material (not shown) is interposed between the beam segments 54. At this time, the beam segments 54 are temporarily joined by introducing a compressive force with PC steel bars.

[0016] The composite precast segment installation process S3 is a process of installing the composite precast segment 6 at the base end of the beam 5. In the composite precast segment installation process S3, the installation error is measured, and an adjustment steel member 68 is fixed (welded) to the steel part 61 of the composite precast segment 6. The center column connection process S4 is a process of connecting the composite precast segment 6 to the center column 3. In the center column connection process S4, the composite precast segment 6 (adjustment steel member 68) is welded to the slab 31 of the center column 3 to integrate the center column 3 and the beam 5. The side column connection process S5 is a process of connecting the side column 4 to the tip of the beam 5. At this time, a tensile force is introduced into the beam 5 by the post-tensioning method. That is, one end of the beam tension member 55 (multi-strand or single-strand) through which the beam 5 is inserted is fixed (anchored) to the composite precast segment 6, and the other end is fixed (anchored) to the side column 4.

[0017] According to the semi-submersible floating foundation 2 and the construction method of the semi-submersible floating foundation 2 of this embodiment, by making the slab 31 of the center column 3 out of steel, it is possible to reduce the weight compared to when the entire center column is made of concrete, and it is also possible to reduce the amount of concrete required. Furthermore, since the beam tensioning members 55 of the beam 5 are fixed to the composite precast segment 6, it is possible to suppress the entanglement of reinforcing bars and beam tensioning members 55 in the center column 3. As a result, the labor involved in construction can be reduced.

[0018] Furthermore, since steel plate frame members 36 are erected at the corners between the main body 32 and the bottom steel plate 33 for the slab, and at the corners between the main body 32 and the top steel plate 34 for the slab, and steel vertical connecting members 38 are provided on the peripheral wall of the main body 32 to connect the frame members 36 facing each other across the peripheral wall, even if the main body 32 of the center column 3 is made of concrete, the main body 32 and the bottom steel plate and top steel plate are made continuous (integrated). As a result, the required strength can be obtained in the ultimate limit state and fatigue limit state. Furthermore, the composite precast segment 6 ensures stress transfer performance between the steel slab 31 and the concrete beam 5. Anchoring the beam tensioning members 55 of beam 5 into the composite precast segment 6 offers superior workability compared to anchoring the beam tensioning members 55 into the center column 3. Specifically, when anchoring the beam tensioning members 55 of beam 5 into the center column 3, where multiple beams 5 are connected, it becomes necessary to cross the beam tensioning members 55 three times within the center column 3, resulting in a tangled arrangement of beam tensioning members 55. On the other hand, anchoring the beam tensioning members 55 into the composite precast segment 6 can suppress this tangled arrangement of beam tensioning members 55. Furthermore, in the main body 32 of the center column 3, large sectional forces are generated due to wind loads and inertial forces caused by the swaying of the beams 5, so there are generally many vertical reinforcements. Therefore, when anchoring the beam tensioners 55 to the main body 32, the beam tensioners 55 extending from each beam 5 and the vertical reinforcements are arranged in the main body 32, making the arrangement of reinforcements and beam tensioners 55 complex. As a result, construction efficiency is poor. On the other hand, in the semi-submersible floating foundation 2 of this embodiment, the beam tensioners 55 are anchored to the composite precast segments 6, so there is no interference between the reinforcements of the main body 32 and the beam tensioners 55.

[0019] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and each of the above-mentioned components can be modified as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, a case was described in which the beam 5 is formed by combining a plurality of beam segments 54, 54, ... but the beam 5 may also be formed by cast-in-place concrete. Furthermore, in the above embodiment, the vertical segment steel plates 66 are fixed to the ends of the bottom segment steel plate 64 and the top segment steel plate 65. However, the vertical segment steel plates 66 may also be formed by bending the ends of the bottom segment steel plate 64 or the top segment steel plate 65. Alternatively, the vertical segment steel plates may be steel plates fixed across the bottom segment steel plate 64 and the top segment steel plate 65. In the above embodiment, the case where there are three side columns 4 was described, but the number of side columns 4 is not limited, and for example, there may be four or more. Furthermore, in the above embodiment, a perforated steel plate dowel 621 is provided at the anchoring portion 62 of the composite precast segment 6, but the perforated steel plate dowel 621 may be provided only as needed. Also, the dowel structure used for joining the steel portion 61 (steel material) and the anchoring portion 62 (concrete) is not limited to the use of a perforated steel plate dowel 621. [Explanation of Symbols]

[0020] 1. Offshore wind power generation facilities 11 Windmill 12 pillars 2. Semi-submersible floating foundation 3 Center Column 31 Slab 32 Main body 33. Steel plate for slab base 34 Upper steel plate for slab 35 Beam junction 36. Structural members 37 Cylinder 38 Vertical connecting members 4 Side Columns 5 beams 51 Top version 52 bottom plate 53 Side wall 54 Beam Segments 55. Beam tensioning material (PC steel) 6. Composite precast segments 61 Steel Department 62 Fixing section

Claims

[Claim 1] A center column supporting the support structure of a wind turbine, Multiple side columns are arranged at intervals around the aforementioned center column, A semi-submersible floating foundation for a wind power generation facility comprising a beam connecting the center column and the side columns, The aforementioned center column comprises a steel slab and a cylindrical main body erected on the slab. The slab comprises a bottom steel plate for the slab provided on the bottom surface and an upper steel plate for the slab provided on the top surface. The main body is made of prestressed concrete and penetrates the upper steel plate for the slab, and the lower end of the main body abuts against the bottom steel plate for the slab. A structural member made of steel plate is erected at the corners between the main body and the bottom steel plate for the slab, and at the corners between the main body and the upper steel plate for the slab, respectively. A semi-submersible floating foundation characterized in that steel connecting members are provided on the peripheral wall of the main body to connect the skeletal members that are opposite each other on either side of the peripheral wall.

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