Floating offshore structure foundation

Abstract

To provide a floating type offshore structure foundation that can stably support a floating structure for a long period.SOLUTION: A floating type offshore structure foundation 1 mainly comprises a floating body part 3, a bottom slab 5, a supporting wall 7, an offshore structure attachment part 9, a lid part 11, etc. The floating body part 3, the bottom slab 5, the supporting wall 7, the offshore structure attachment part 9, and the lid part 11 are all made of reinforced concrete, are desirably made of, for example, prestressed concrete, and may be partially made of steel. The floating body part 3 has an approximately round bowl shape opened upward. A top end of the floating body part 3 is covered and closed by the lid part 11. For example, a water stop member is arranged between the lid part 11 and the floating body part 3. In other words, a closed space is formed inside the floating body part 3. The bottom slab 5 is arranged and fixed on a lower part of the floating body part 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foundation structure for a floating offshore structure that supports a floating structure on the ocean. [Background technology]

[0002] For offshore structures such as offshore wind turbines, floating towers and other structures have been proposed. Steel floats are generally used as support structures for such floating structures. However, steel floats deteriorate over time, such as rusting, and require regular inspection and repair. After 20 to 30 years of use, they require inspection and repair work in a dock, similar to that required for ships.

[0003] In response to this, methods using a concrete floating body have been proposed (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2014-503424 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-129061 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, such hollow concrete floaters have a box-shaped hollow space surrounded by side walls, a bottom slab, and a top slab, which creates corners between the side walls and the bottom slab, and between adjacent side walls. This creates large shear forces around the corners, making them prone to cracking. Furthermore, because the side walls are constructed on the bottom slab, thermal cracks (which can become through cracks) can occur in the side walls that are restrained by the bottom slab. The occurrence of cracks formed in this manner is particularly serious for offshore wind power floaters, which must function as floaters for long periods of time, such as 20 years or more.

[0006] Additionally, while the introduction of prestressing is considered as a measure to prevent cracks in reinforced concrete, it is difficult to place PC steel tendons at the corners of a box-shaped structure.Furthermore, barge-type floating structures with a shallow draft have little resistance to waves and tend to move significantly, which can cause fatigue loads and other long-term durability issues for the wind power generation equipment (wind turbines) installed on them.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a foundation structure for a floating offshore structure that can stably support a floating structure over the long term. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a foundation structure for a floating offshore structure, characterized by comprising a floating body whose main member is made of concrete, which is open at the top and has at least the lower part roughly bowl-shaped, a bottom slab arranged at the bottom of the floating body body, a plurality of support walls arranged between the side of the floating body body and the upper surface of the bottom slab, an offshore structure mounting part formed inside the floating body body, and a lid part covering the top end of the floating body body.

[0009] In a plan view, it is desirable that the float body portion does not protrude from the bottom slab, and that at least a portion of the bottom slab protrudes from the float body portion.

[0010] The offshore structure mounting portion may be made of approximately cylindrical prestressed concrete, a steel ring-shaped member may be placed on the top of the offshore structure mounting portion, and one end of the tension member may be fixed to the ring-shaped member.

[0011] The floating body may be made of prestressed concrete, and tendons may be helically arranged at least below the floating body.

[0012] One end of a tendon arranged in the floating body main body may be fixed to the bottom slab.

[0013] A mooring line may be attached to the lid portion or the upper portion of the floating body main body portion.

[0014] A plurality of columns are arranged around the floating body main body part, the columns are made of concrete, and are provided with another floating body main body part having an approximately circular bowl shape with an open top, another bottom plate arranged at the bottom of the other floating body main body part, another lid part that covers the top of the other floating body main body part, and a plurality of other support walls arranged approximately radially in a planar view between the side of the other floating body main body part and the upper surface of the other bottom plate, and the floating body main body part or the bottom plate may be connected to the other floating body main body part or the other bottom plate.

[0015] The support walls may be arranged radially in a plan view, or at least some of the support walls may be arranged parallel to each other in a plan view.

[0016] A seaweed bed fixing portion for fixing the seaweed bed may be arranged on the support wall.

[0017] The interior of the floating body main body may be divided by a partition wall.

[0018] According to the present invention, the float is made of prestressed concrete, and compressive stress is applied in advance to offset the maximum tensile stress generated by external forces, etc., so there are no problems with rust, as there are with steel floats. Furthermore, unlike steel floats, there is no need for welding or other work at a special shipyard, so they can be assembled on the coast near the installation site. This simplifies the assembly and transportation of the foundation structure for a floating offshore structure.

[0019] Furthermore, because the floating body is approximately bowl-shaped and has no corners, the occurrence of cracks can be suppressed. Furthermore, because the floating body is approximately bowl-shaped, it is less susceptible to the effects of tidal currents and waves. Furthermore, because a plate-shaped base plate is placed under the approximately bowl-shaped floating body, the foundation structures for floating offshore structures can be stably arranged and positioned, for example, in coastal areas.

[0020] Furthermore, by disposing a support wall that separates the floating body and the bottom slab, it is possible to form multiple spaces surrounded by the floating body, the bottom slab, and the support wall. Therefore, for example, when the floating structure tilts due to waves or currents, the water in the space on the lifted side can be kept within the space, and the weight of this water can prevent further tilting of the floating structure.

[0021] In addition, since the central part has an offshore structure mounting part, the offshore structure can be easily fixed to the floating body.

[0022] In addition, by making the size of the bottom plate larger than the size of the float body main body and making at least a portion of the bottom plate extend beyond the float body main body when viewed in a plane, a portion of the bottom plate can function as a rocking suppression function.

[0023] In addition, by placing a steel ring-shaped member at the top of the offshore structure mounting part, the ring-shaped member can be used as an anchoring point for the tendon of the offshore structure mounting part, and the ring-shaped member can also be used as a joint with the offshore structure.

[0024] Furthermore, by making the floating body main body from prestressed concrete with helically arranged tendons, prestressing force can be efficiently applied to the floating body main body.

[0025] Furthermore, by fixing one end of the tendon arranged in the floating body main body to the bottom slab, the bottom slab and the floating body main body can be efficiently integrated.

[0026] In addition, by fixing the mooring line to the top of the lid or the floating body main body, it is easy to fix the mooring line.

[0027] Furthermore, by arranging multiple columns around the floating body, it is possible to exert greater buoyancy and suppress rocking. This allows the individual structures to be made smaller. In this case, if each column is also composed of the floating body, bottom slab, support wall, lid, etc., the same effects as those described above can be obtained. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a foundation structure for a floating offshore structure that can stably support a floating structure over a long period of time. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective view showing a foundation structure 1 for a floating offshore structure. [Figure 2] FIG. 1 is a plan view showing a foundation structure 1 for a floating offshore structure. [Figure 3] Cross section of line AA in Figure 2. [Figure 4] 1(a) is a conceptual diagram showing the arrangement of tendons in the floating body main body 3, and FIG. 1(b) is a conceptual diagram showing the arrangement of tendons relative to the bottom slab 5 and the floating body main body 3. FIG. [Figure 5] FIG. 2 is a diagram showing the state in which the foundation structure 1 for a floating offshore structure is in use. [Figure 6] An enlarged view of the joint between the floating offshore structure foundation structure 1 and the offshore structure 19. [Figure 7] FIG. 2 is a plan view showing the foundation structure 1a for a floating offshore structure. [Figure 8] 3A to 3C are diagrams showing an example of a manufacturing process for the foundation structure 1a of a floating offshore structure. [Figure 9] 3A to 3C are diagrams showing an example of a manufacturing process for the foundation structure 1a of a floating offshore structure. [Figure 10] FIG. 2 is a plan view showing the foundation structure 1b for a floating offshore structure. [Figure 11] FIG. 2 is a diagram showing an example of a manufacturing process for the foundation structure 1b of a floating offshore structure. [Figure 12] 1(a) is a cross-sectional view showing the foundation structure 1c for a floating offshore structure, and FIG. 1(b) is a plan view showing the foundation structure 1c for a floating offshore structure. [Figure 13] 1(a) is a diagram showing the positional relationship of the foundation structure 1 for a floating offshore structure on the quay, and FIG. 1(b) is a diagram showing the positional relationship of the foundation structure 1d for a floating offshore structure on the quay. [Figure 14] A diagram showing the foundation structure 1d of a floating offshore structure. [Figure 15]10A and 10B are diagrams showing another embodiment using the foundation structure 1 for a floating offshore structure, in which (a) is an overall plan view and (b) is a perspective view of a column 23. [Figure 16] Cross-sectional view taken along line BB in Figure 15(a). [Figure 17] A diagram showing the state in which a net 37 for attaching sporophytes and gametophytes is attached to the supporting wall of the foundation structure 1 of the floating offshore structure. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a perspective view showing a foundation structure 1 for a floating offshore structure, Fig. 2 is a plan view showing the foundation structure 1 for a floating offshore structure, and Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. The foundation structure 1 for a floating offshore structure is a foundation structure for supporting an offshore structure while it is floating on the ocean. Note that, although this embodiment shows a case where the offshore structure is a wind turbine for offshore wind power generation, other structures may also be used as the offshore structure.

[0031] The floating offshore structure foundation structure 1 is mainly composed of a floating body main body 3, a bottom slab 5, a support wall 7, an offshore structure mounting portion 9, a cover portion 11, etc. The floating body main body 3, bottom slab 5, support wall 7, offshore structure mounting portion 9, and cover portion 11 are all made of reinforced concrete, preferably prestressed concrete, but some may be made of steel. For example, the main components (the floating body main body 3 and bottom slab 5) may be made of concrete, and some of the structure, such as the offshore structure mounting portion 9, support wall 7, or cover portion 11, may be made of steel (or a composite of steel and concrete) with a corrosion-resistant coating.

[0032] In addition, the floating body main body 3 may be made of short fiber mixed concrete such as vinylon short fiber, or alternative reinforced concrete for corrosion resistance using AFRP (aramid fiber reinforced plastic) or CFRP (carbon fiber reinforced plastic).

[0033] If the floating body 3 is made of prestressed concrete, the manufacturing method can be to pour the concrete at the manufacturing site or to manufacture it in sections as precast members and assemble them. If it is made of short fiber mixed concrete, the dispersed short fibers suppress the occurrence of cracks in various directions, providing the same effect as prestressed concrete. If it is made of alternative reinforced concrete, there is no rusting and expansion of the reinforcing bars, so it has the effect of suppressing through cracks that cause water leakage.

[0034] The float body main body 3 has a generally circular bowl shape that is open at the top. Here, the generally circular bowl shape refers to a shape that has a generally circular horizontal cross section, is closed at the bottom, has a portion whose outer diameter gradually increases from the bottom end toward the top, and is open at the top. The vertical cross section at the center of the float body main body 3 may be entirely curved (arcuate), such as a semicircular or semielliptical shape, or may be linear, such as a triangle or trapezoid, or may be a combination of linear and curved shapes.

[0035] Furthermore, the diameter of the approximately bowl-shaped floater main body 3 does not have to gradually change from the bottom to the top. For example, the diameter may gradually change in a curved or linear manner from the bottom to a predetermined height, and the diameter may be constant from the predetermined height to the top (i.e., cylindrical). Furthermore, the upper end of the floater main body 3 does not have to have the maximum diameter (maximum diameter in a plan view). For example, when a member (the long diameter side of which has a vertical cross-sectional shape such as a substantially circular, elliptical, egg-shaped, or teardrop-shaped member) is erected, the shape may be such that it is cut at a position above the maximum diameter in a plan view. In this way, the floater main body 3 may have a portion where the diameter gradually increases in a linear or curved manner from the bottom to the height where the diameter is maximum, and may include a shape where the diameter gradually decreases in a linear or curved manner from that portion to the top.

[0036] The top end of the floating body main body 3 is covered and sealed by the lid 11. For example, a water-stopping member is disposed between the lid 11 and the floating body main body 3. In other words, an enclosed space is formed inside the floating body main body 3.

[0037] Furthermore, an offshore structure mounting portion 9 is formed approximately at the center inside the floating body main body portion 3. The offshore structure mounting portion 9 is made of, for example, approximately cylindrical prestressed concrete with a diameter that gradually decreases as it goes upward. The upper end of the offshore structure mounting portion 9 protrudes above the cover portion 11. Watertightness is also ensured between the cover portion 11 and the offshore structure mounting portion 9. The lower end of the offshore structure is joined to the upper part of the offshore structure mounting portion 9. Details of the joint with the offshore structure will be described later.

[0038] A slab 5 is disposed and fixed to the lower part of the floating body main body 3. The slab 5 is a solid plate, and as shown in FIG. 2, it is desirable that the slab 5 be equal to or larger than the size of the floating body main body 3. For example, when the floating body main body 3 is substantially circular and the slab 5 is polygonal (rectangle in the figure) in a plan view, it is desirable that the minimum diameter of the slab 5 be equal to or larger than the outer diameter of the floating body main body 3. In this way, by making the floating body main body 3 not protrude from the slab 5 in a plan view and making at least a portion of the slab 5 protrude from the floating body main body 3, the protruding portion from the floating body main body 3 provides resistance to rocking when the foundation structure 1 for a floating offshore structure is floated on the ocean, thereby suppressing rocking.

[0039] Support walls 7 are arranged between the side surfaces of the floating body main body 3 and the upper surface of the slab 5. In plan view, the multiple support walls 7 are arranged in a generally radial pattern at predetermined intervals in the circumferential direction (i.e., so as to divide the space between the side surfaces of the floating body main body 3 and the upper surface of the slab 5 into multiple spaces in the circumferential direction). In addition to reinforcing the joint structure between the floating body main body 3 and the slab 5, the support walls 7 also have the function of dividing the space between the floating body main body 3 and the slab 5 in the circumferential direction, forming independent spaces.

[0040] By dividing the structure into multiple spaces in this way, when the foundation structure 1 for a floating offshore structure is floated on the ocean and rocked, for example, water in the space being lifted is prevented from flowing out of the space. Therefore, the water in each space acts as a weight to resist rocking, and rocking of the foundation structure 1 for a floating offshore structure can be suppressed.

[0041] The support wall 7 does not have to be disposed up to the upper end of the floater main body 3 as shown in Figure 3, but may be formed up to a predetermined height of the floater main body 3 that is lower than the upper end. Furthermore, the outer edge of the support wall 7 may not be perpendicular to the bottom slab 5, but may be formed in a shape that flares from the top toward the bottom slab 5. Furthermore, to reduce resistance when subjected to waves or tidal currents, through holes may be provided in the bottom slab 5 and the support wall 7.

[0042] Next, the arrangement of tendons in prestressed concrete will be described. FIG. 4(a) is a conceptual diagram showing the arrangement of tendons 13 in the floater body 3. The sheath pipes and anchoring members for arranging the tendons 13 are not shown. As described above, the floater body 3 is prestressed by the tendons 13. It is desirable to arrange multiple tendons 13 in a helical (spiral) shape at predetermined intervals in the circumferential direction in both the clockwise and counterclockwise directions. This allows for efficient prestressing. The helical arrangement of the tendons 13 may be a combination of a lattice arrangement in the meridian direction and the circumferential direction above the floater body 3, particularly if they are arranged below the floater body 3.

[0043] As mentioned above, it is also desirable that the bottom slab 5 be prestressed by the tendons 13. In this case, as shown in Figure 4(b), for example, one end of the tendon 13 may be fixed near the upper edge of the floating body main body 3, and the other end of the tendon 13 may be fixed near the outer edge of the bottom slab 5. In this way, by tensioning the floating body main body 3 and the bottom slab 5 together, they can be more reliably joined and integrated.

[0044] Next, we will explain how the foundation structure 1 for a floating offshore structure is used. The foundation structure 1 for a floating offshore structure can be assembled on the coast near the ocean where it will be installed. At this time, the base slab 5 allows for stable storage and transportation. The assembled foundation structure 1 for a floating offshore structure is floated on the sea and then towed to the installation site.

[0045] FIG. 5 shows the foundation structure 1 for a floating offshore structure in place. The foundation structure 1 for a floating offshore structure is moored to the seabed by mooring lines 15. The mooring lines 15 are attached to the cover 11 or the upper part of the floating body main body 3. This facilitates fastening of the mooring lines 15. If the mooring lines 15 interfere with the bottom slab 5, notches may be formed in the bottom slab 5. Alternatively, a tension mooring method may be used. In this case, the support wall 7 may be extended to the side of the floating body main body 3, and the mooring lines may be fastened to the upper part of the support wall 7 so as to penetrate the bottom slab 5 and the support wall 7. In addition, iron pipes or iron plates may be attached to the penetrations or the areas where the mooring lines 15 interfere with the notches and the concrete. In addition, the length between the waterline and the bottom of the base (draft) may be a so-called semi-submersible type as shown in the illustration, or an appropriate draft such as a so-called barge type or spar type can be adopted depending on the wave conditions at the installation site and the characteristics of the offshore structure.

[0046] As described above, the offshore structure 19 is joined to the offshore structure mounting portion 9 of the floating offshore structure foundation 1. The offshore structure 19 may be towed while fixed to the offshore structure mounting portion 9, or the offshore structure 19 may be fixed to the offshore structure mounting portion 9 after the floating offshore structure foundation 1 is installed at the installation site.

[0047] Figure 6 is an enlarged cross-sectional view of part B in Figure 5. There is no particular limitation on the method of fixing the offshore structure 19 to the offshore structure mounting portion 9, but for example, as shown in Figure 6, a ring-shaped member 21 may be placed on the top of the offshore structure mounting portion 9. The ring-shaped member 21 is made of steel, for example, and is a member with a roughly U-shaped cross section. That is, the ring-shaped member 21 is provided with flange-shaped fixing portions with fixing holes parallel to each other on the top and bottom. Note that the cross-sectional shape is not limited to a U-shape and may be other shapes.

[0048] As mentioned above, the offshore structure mounting portion 9 is made of approximately cylindrical prestressed concrete. One end of the tendon 13a that applies prestressing force to the offshore structure mounting portion 9 is fixed to the ring-shaped member 21. In addition, the offshore structure 19 is fixed to the top of the ring-shaped member 21 with bolts or the like. In this way, the tendon 13a can be easily fixed and the offshore structure 19 can be easily secured.

[0049] As described above, according to the foundation structure 1 for a floating offshore structure of this embodiment, the outer surface of the floating body 3 supporting the offshore structure 19 is substantially circular, and therefore there are no corners, unlike a box-shaped structure with a rectangular cross-section, and prestressing force can be applied by placing tendons over almost the entire surface. This allows for long-term durability. Note that, although the cross-sectional shape forms corners at the boundary between the floating body 3 and the cover 11, since the floating body 3 and the cover 11 are separate bodies, there are no problems such as cracks caused by the placement of tendons at the corners.

[0050] Furthermore, by helically arranging the tendons 13 of the floating body main body 3, prestressing force can be applied efficiently to the entire floating body main body 3.

[0051] Furthermore, by placing the bottom slab 5 under the floating body main body 3, it becomes easier to store and transport the floating offshore structure foundation 1. Also, a part of the bottom slab 5 can function as a member for suppressing the rocking motion of the floating body main body 3. Furthermore, by applying prestress force to the floating body main body 3 and the bottom slab 5 integrally with each other using the tendons 13, they can be efficiently fixed together.

[0052] In addition, by providing a support wall 7 between the floating body main body 3 and the bottom slab 5, it can function as a reinforcing structure for the floating body main body 3 and the bottom slab 5, and can also divide the area around the floating body main body 3 into multiple spaces, functioning as a rocking suppression member for the floating body main body 3.

[0053] Furthermore, by providing the offshore structure mounting portion 9, the offshore structure 19 can be easily fixed. In this case, by using the ring-shaped member 21, it is easy to fix the tendon 13a of the offshore structure mounting portion 9 and to fix it to the offshore structure 19.

[0054] Next, a second embodiment will be described. Figure 7 is a plan view showing a foundation structure 1a for a floating offshore structure. In the following description, components that have the same functions as those of the foundation structure 1 for a floating offshore structure according to the first embodiment will be assigned the same reference numerals as those in Figures 1 to 6, and redundant description will be omitted.

[0055] The foundation structure 1a for a floating offshore structure has a structure that is almost the same as the foundation structure 1 for a floating offshore structure, but differs in the arrangement of the support walls 7. In the foundation structure 1a for a floating offshore structure, at least some of the support walls 7 are arranged parallel to each other. In the example shown, the support wall 7 is arranged in a straight line at approximately the center of the floating body main body 3 (vertical direction in the figure), and multiple support walls 7 in the width direction (horizontal direction in the figure) are arranged on both sides so as to be perpendicular to the central support wall 7. The multiple support walls 7 in the width direction are arranged parallel to each other.

[0056] Next, a manufacturing method for the foundation structure 1a for a floating offshore structure will be described. First, as shown in Fig. 8(a), the bottom slab 5 is formed. As described above, the bottom slab 5 is made of, for example, reinforced concrete or prestressed concrete, and may be a cast-in-place or precast bottom slab.

[0057] Next, as shown in Figure 8(b), multiple segments 33 are placed on top of the bottom slab 5. The segments 33 have insertion sections for the tendons provided inside. As shown in Figure 8(c), the segments are assembled into a cylindrical shape with the same diameter and fixed to the bottom slab 5 with vertical tendons, and the upper and lower segments are integrated to form the offshore structure mounting section 9. Note that water-stopping members, positioning keyways, etc. may be formed between the segments 33, and prestressing force may be introduced circumferentially using tendons. In the example described above, multiple segments 33 divided circumferentially were used, but ring-shaped members may also be stacked. Alternatively, a single cylindrical precast tube may be used.

[0058] Figure 9(a) is a cross-sectional view showing the state in which the offshore structure mounting portion 9 is fixed onto the bottom slab 5. From this state, the support walls 7 are installed as shown in Figure 9(b). In this case, the support walls 7 are arranged in a straight line in the center of the width direction (direction perpendicular to the figure), and multiple support walls 7 are further arranged in the width direction (left and right direction in the figure). The support walls 7 in the width direction are arranged parallel to each other. As mentioned above, the support walls 7 may be made of precast concrete or steel with a corrosion-resistant coating.

[0059] Next, as shown in Figure 9(c), the upper formwork 25 and the lower formwork 27 are placed. At this time, the lower formwork 27 is supported by shoring 29 and inserted into the gap between the support walls 7 from the side, while the upper formwork 25 is inserted from above. The floating body main body 3 can be formed by pouring concrete between the upper formwork 25 and the lower formwork 27 thus placed. The lower formwork 27 and the shoring 29 can then be removed from the side. Concrete can be poured in lots from below. This method can also be applied to a form in which the support walls 7 are placed radially. Furthermore, if the lower formwork 27 is an embedded formwork that remains in place and does not require removal, and has the strength and rigidity to withstand reinforced concrete pouring, the formwork itself, and the working load, and is self-sustaining in terms of strength and deformation, shoring 29 can be eliminated.

[0060] According to the second embodiment, the floating body main body 3 can be manufactured integrally on-site. As described above, the support walls 7 are arranged to divide the space between the side of the floating body main body 3 and the top surface of the base slab 5 into multiple sections. By dividing the space into multiple sections in this manner, when the foundation structure 1a for a floating offshore structure is floated on the ocean and rocked, for example, water in the space on the side being lifted is prevented from flowing out of the space. Therefore, the water in each space acts as a weight to resist rocking, thereby suppressing rocking of the foundation structure 1a for a floating offshore structure. In this case, as shown in FIG. 7 , the space closer to the center of the foundation structure 1a for a floating offshore structure (C in the figure) is larger than the space on the edge (D in the figure). This provides a more effective rocking prevention function, for example, against rocking in the left-right direction in FIG. 7 . The arrangement of the support walls 7 in the left-right direction is anisotropic, which differs from the isotropy of the arrangement of the support walls 7 in the radial direction. However, by aligning the left-right direction with the main direction of waves and wind, the structure has excellent resistance to rocking. In addition, the formwork supporting the floating body main body 3 in FIG. 7 can be easily installed and removed from the left and right in the figure, allowing for compact flow work by moving it up and down in the figure.

[0061] Next, a third embodiment will be described. Fig. 10 is a plan view (perspective view of the lid) showing a foundation structure 1b for a floating offshore structure. The foundation structure 1b for a floating offshore structure has a structure similar to that of the foundation structure 1 for a floating offshore structure, but differs in that the inside of the floating body main body 3 is partitioned by bulkheads 31.

[0062] In this way, by dividing the inside of the floating body main body 3 with the bulkheads 31, it becomes possible to inject or drain water into each space. Such intentional injection of a certain amount of water into the inside of the floating body main body 3 is called ballast, and by lowering or raising the center of gravity of the floating offshore structure foundation 1 by injecting or draining water, it becomes possible to control the degree of stability against tipping of the entire floating structure, including before and after the installation of the wind turbines and auxiliary equipment.

[0063] Next, a manufacturing method of the floating offshore structure foundation 1b will be described. As in the second embodiment, first, the offshore structure mounting portion 9 is installed on the bottom slab 5. Next, as shown in FIG. 11(a), plate-like members are arranged radially around the offshore structure mounting portion 9. In the illustrated example, the number of plate-like members is four, but the number is not particularly limited as long as multiple members are arranged at predetermined intervals. Since this plate-like member serves as both the bulkhead 31 and the support wall 7, in the following description, this plate-like member will be referred to as the bulkhead 31 or the support wall 7 as appropriate. In this embodiment, the bulkhead 31 (support wall 7) is connected to the bottom slab 5 and the offshore structure mounting portion 9 to promote strong self-supporting. However, it is also possible to use only the support wall 7 standing up from the bottom slab 5 without a bulkhead structure (not connected to the offshore structure mounting portion 9).

[0064] Next, as shown in Figure 11(b), the divided main body portion 35 having a curved surface is placed between the partition walls 31. The divided main body portion 35 is made of precast concrete and has an insertion portion for the tendon provided inside. Note that a receiving portion for receiving the divided main body portion 35 from below may be provided on the surface of the support wall 7. That is, a protrusion or a temporary receiving metal fitting may be provided on the surface of the support wall 7, and the divided main body portion 35 may be placed on this protrusion.

[0065] When the divided main body portions 35 are arranged between the respective bulkheads 31, the entire divided main body portions 35 (and the bulkheads 31 sandwiched between the divided main body portions 35) form a floating body portion 3 having an approximately bowl-like shape. In this state, the tendons are tensioned in the vertical and circumferential directions (or helically arranged). At the lower end of the divided main body portions 35, the tendons may be fixed to the bottom slab 5 or to the offshore structure mounting portion 9.

[0066] According to the third embodiment, the foundation structure 1b for a floating offshore structure can be efficiently manufactured on-site. In addition, by dividing the inside of the floating body main body 3 with bulkheads 31, it becomes possible to use ballast. This makes it possible to adjust the waterline and balance of the foundation structure 1b for a floating offshore structure.

[0067] In the above description, the approximately bowl-shaped floating body main body 3 is exemplified by an example having a curved surface overall, but this is not limiting. Figure 12(a) is a cross-sectional view of a floating offshore structure foundation 1c, and Figure 12(b) is a plan view (perspective view of the lid) of the floating offshore structure foundation 1c. As shown in the floating offshore structure foundation 1c, the floating body main body 3 may be formed by stacking multiple divided main body sections 35a. Each divided main body section 35a is a planar plate-like member, but its horizontal cross-section is approximately circular, closed at the bottom, and has a portion whose outer diameter gradually increases from the bottom end upward, forming an open shape at the top. Therefore, such a shape is also considered to be approximately bowl-shaped. As such, as long as the overall shape is approximately bowl-shaped, a partially linear structure may also be used. This folded plate structure consisting of small flat slabs can also be made of steel instead of concrete to form a similar shape.

[0068] Furthermore, the above-described approximately bowl-shaped floating body main body 3 has been shown to have a form in which the outer diameter gradually increases from bottom to top over its entire height, but as mentioned above, this is not limited to this. Figure 13(a) is a diagram showing the state in which an offshore structure 19 is installed on a quay on the foundation structure 1 for a floating offshore structure. For example, if the offshore structure 19 is made larger, the foundation structure, that is, the foundation structure, of the floating offshore structure 1, must also be made larger. This increases the distance E from the quay. In this case, the boom of the crane that lifts the offshore structure 19 must be extended farther, and the crane used must also be larger.

[0069] Therefore, the floating body foundation 1d shown in Figure 13(b) has a vertically elongated shape for the floating body main body 3 and adjusts its height with ballast, thereby ensuring stability against buoyancy and rolling that accompanies an increase in the size of the offshore structure 19, and enabling the distance F from the quay to be set at a constant distance without extending it. In other words, the floating body main body 3 of the floating body foundation 1d has a floating body main body 3 (Figure 1, etc.) on the bottom of the floating body main body 3 of the floating body foundation 1 etc. described above, and a cylindrical shape extended upward while maintaining a substantially constant diameter.

[0070] Figure 14 is a diagram showing the floating body main body 3 of the floating offshore structure foundation 1d. In this case, the height can be easily adjusted by stacking ring members 41 above the curved floating body main body 3. Therefore, even if the size of the offshore structure 19 changes, it can be easily accommodated by changing the number of stacked ring members 41. In other words, the floating body main body 3 has a depth dimension that is larger than its diameter, and the lower part of the floating body main body 3 can be approximately bowl-shaped, while the upper part of the floating body main body 3 can be cylindrical.

[0071] In this case, the tendons 13 may be arranged helically in the lower, approximately circular bowl-shaped member, and the tendons 13 may be arranged both circumferentially and vertically in the upper ring member 41. Depending on the shape and dimensions of the upper ring member 41, compressive force may be generated in the circumferential direction even if the tendons 13 are arranged only vertically, so that the circumferential tendons 13 may be omitted.

[0072] In the above-described embodiment, an example has been shown in which only one foundation structure 1 for a floating offshore structure is used for one offshore structure 19, but this is not limiting. FIG. 15(a) shows an example of a foundation structure that uses a plurality of columns 23 in addition to the foundation structure 1 for a floating offshore structure. A plurality of columns 23 are arranged at regular intervals around the periphery of the foundation structure 1 for the floating offshore structure (floater main body 3). For example, three or more columns 23 are arranged.

[0073] 15(b) is a diagram showing the column 23. The column 23 is composed of a floater main body 3a having a generally circular bowl shape with an open top, a bottom slab 5a disposed at the bottom of the floater main body 3a, a lid 11a covering the top of the floater main body 3a, and a plurality of support walls 7a disposed generally radially in a plan view between the side of the floater main body 3a and the top surface of the bottom slab 5a. The floater main body 3a, bottom slab 5a, support walls 7a, 7b, and lid 11a are made of prestressed concrete.

[0074] The floating body main body 3a, bottom slab 5a, support walls 7a and 7b, and cover 11a of the column 23 correspond to the floating body main body 3, bottom slab 5, support walls 7, cover 11, etc. of the foundation structure 1 for a floating offshore structure. In other words, the column 23 has substantially the same configuration as the foundation structure 1 for a floating offshore structure, except for the offshore structure mounting portion 9.

[0075] Figure 16 is a cross-sectional view taken along line BB in Figure 15(a). As described above, in the foundation 1 for a floating offshore structure, the support walls 7 are arranged at predetermined intervals around the periphery of the floating body main body 3, but in this embodiment, the foundation 1 for a floating offshore structure and the adjacent column 23 are connected by a support wall 7b. The support wall 7b is thicker than the support walls 7 and 7a, and one end side is joined to the floating body main body 3 and the slab 5 of the foundation 1 for a floating offshore structure, and the other end side is joined to the floating body main body 3a and the slab 5a of the column 23.

[0076] The method of connecting the foundation structure 1 for a floating offshore structure and the column 23 is not particularly limited, and the bottom slab 5 and the bottom slab 5a may be connected with other members, or the floating body main body portion 3 and the floating body main body portion 3a may be connected with other members, without using the support wall 7b. In other words, it is sufficient that the floating body main body portion 3 or the bottom slab 5 of the foundation structure 1 for a floating offshore structure and the floating body main body portion 3a or the bottom slab 5a of the column 23 are connected.

[0077] In this way, by using a plurality of columns 23, it is possible to reduce the size of the foundation structure 1 for a floating offshore structure. Although the floating body main body portion 3a of the column 23 is illustrated as being approximately the same size as the floating body main body portion 3 of the foundation structure 1 for a floating offshore structure, the floating body main body portion 3a may be smaller than the floating body main body portion 3. Alternatively, the floating body main body portion 3a may be larger than the floating body main body portion 3.

[0078] Furthermore, a portion of the foundation of the floating offshore structure can also be used as a fishing reef. In the example shown in FIG. 17, a net 37 is fixed to a portion of the support wall 7. The net 37 serves as a seaweed bed fixing portion, and can be used to fix ropes or the like with seaweed sporophytes or gametophytes attached. The support wall reduces the effects of waves and tidal currents and promotes the growth of seaweed, seafood, and their fry and larvae. Note that, in shallow waters, sunlight reaches the net, so it may be placed on the top surface of the base 5 rather than on the support wall 7. When the net 37 is fixed to the side of the support wall 7, a scaffolding 39 may be provided below it. That is, the scaffolding 39 may be protruding from the side of the support wall 7, and the net 37 may be fixed above it. The scaffolding may be removable. Eye bolts, U-shaped fixing members, or the like can be used to fix the net 37. Furthermore, the surface of the support wall 7 may be formed with irregularities in advance to facilitate the attachment of seaweed and the like. Furthermore, the seaweed may be artificial, which will encourage the growth of seaweed after the floating body is installed.

[0079] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not limited to the above-described embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention.

[0080] For example, it goes without saying that the configurations in the respective embodiments can be combined with each other. [Explanation of symbols]

[0081] 1, 1a, 1b, 1c, 1d....Floating offshore structure foundation structure 3, 3a... Floating body main body 5, 5a……Bottom plate 7, 7a, 7b……Supporting wall 9....Offshore structure mounting section 11, 11a……Lid part 13, 13a……Tension material 15……Mooring rope 19...Offshore structure 21...Ring-shaped member 23...Column 25...Upper formwork 27...Lower formwork 29……Shoring 31……Bulkhead 33...segment 35, 35a……Split main body part 37...Net 39...Scaffolding 41...Ring member

Claims

1. a floating body made of concrete, the floating body having an opening at the top and at least a substantially bowl-shaped lower portion; a concrete bottom slab disposed under the floating body; A plurality of support walls arranged between the side surface of the floating body main body and the upper surface of the bottom plate; An offshore structure mounting portion formed inside the floating body main body portion; A lid portion that covers the top end of the floating body main body portion; A foundation structure for a floating offshore structure comprising:

2. 2. The foundation structure for a floating offshore structure according to claim 1, wherein, in a plan view, the floating body main body does not protrude from the bottom slab, and at least a portion of the bottom slab protrudes from the floating body main body.

3. 2. A floating offshore structure foundation structure as described in claim 1, characterized in that the offshore structure mounting portion is made of approximately cylindrical prestressed concrete, a steel ring-shaped member is placed on the top of the offshore structure mounting portion, and one end of a tension member is fixed to the ring-shaped member.

4. 2. The foundation structure for a floating offshore structure according to claim 1, wherein the floating body is made of prestressed concrete, and tension members are helically arranged at least below the floating body.

5. 5. The foundation structure for a floating offshore structure according to claim 4, wherein one end of a tendon arranged in the floating body portion is fixed to the bottom slab.

6. 2. The foundation structure for a floating offshore structure according to claim 1, wherein a mooring line is attached to the top of the lid portion or the floating body main body portion.

7. A plurality of columns are arranged around the floating body, The column is made of concrete and includes another floating body main body part having a substantially circular bowl shape with an opening at the top, another bottom plate arranged at the bottom of the other floating body main body part, another lid part that closes the top of the other floating body main body part, and a plurality of other support walls arranged substantially radially in a plan view between the side surface of the other floating body main body part and the upper surface of the other bottom plate, 2. The foundation structure for a floating offshore structure according to claim 1, wherein the floating body main body or the bottom slab is connected to another floating body main body or the other bottom slab.

8. 2. The foundation structure for a floating offshore structure according to claim 1, wherein the support walls are arranged in a substantially radial pattern in a plan view.

9. The foundation structure for a floating offshore structure according to claim 1, wherein at least some of the support walls are arranged parallel to each other in a plan view.

10. 2. The foundation structure for a floating offshore structure according to claim 1, wherein a seaweed bed fixing portion for fixing the seaweed bed is disposed on the support wall.

11. 2. The foundation structure for a floating offshore structure according to claim 1, wherein the inside of the floating body is divided by bulkheads.

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