Installation method

Abstract

To provide an installation method for an offshore wind turbine jacket structure that allows the offshore wind turbine jacket structure to be laid down and placed on a barge.SOLUTION: The installation method includes a placement step of laying down and placing an offshore wind turbine jacket structure 1 on a barge S.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an installation method. [Background technology]

[0002] Conventionally, jacket structures for offshore wind turbines have been installed in the sea. Patent Document 1 discloses that the steel jacket is loaded onto a barge and towed to the planned installation location by a tugboat, and that the steel jacket is then lifted vertically by an offshore crane and sunk into a predetermined position on the seabed or replaced sand. Patent Document 2 discloses assembling an offshore structure in advance in a factory or on a ship, laying the offshore structure on a barge and transporting it to the installation area, erecting the offshore structure, and lowering the offshore structure from the barge into the sea using a crane and setting it down on the seabed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 63-103112 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-76240 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Documents 1 and 2 do not anticipate the jacket structure for an offshore wind turbine being laid on a barge.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a method for installing a jacket structure for an offshore wind turbine, which allows the jacket structure for an offshore wind turbine to be laid down on a barge. [Means for solving the problem]

[0006] <1> The installation method according to the first aspect of the present disclosure is characterized by including an arrangement step of laying the jacket structure for an offshore wind turbine on a barge. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a method for installing an offshore wind turbine jacket structure, which allows the jacket structure for an offshore wind turbine to be laid out on a barge. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing a state in which the jacket structure for an offshore wind turbine is laid down on a barge. [Figure 2] FIG. 2 is a view of FIG. 1 as seen from above. [Figure 3] FIG. 2 is an enlarged view of part III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along the arrow IV in FIG. 3. [Figure 5] FIG. 10 is a view showing the state in which the jacket structure for an offshore wind turbine is lifted from the barge in the lifting process. [Figure 6] FIG. 6 is a view of FIG. 5 seen from above. [Figure 7] 7 is an enlarged view of the periphery of the connection portion between the first leg can and the first rope-like body, taken along the arrow VII in FIG. 6. [Figure 8] 8 is an enlarged view of the periphery of the connection portion between the second leg can and the second rope-like body, taken along the arrow VIII in FIG. 6. [Figure 9] FIG. 1 is a first diagram of the sinking process. [Figure 10] FIG. 2 is a second diagram of the sinking process. [Figure 11] FIG. 3 is a third diagram of the sinking process. [Figure 12] FIG. 4 is a fourth diagram of the sinking process. [Figure 13] FIG. 1 is a first diagram of the pulling process. [Figure 14] FIG. 2 is a second diagram of the pulling process. [Figure 15] FIG. 3 is a third diagram of the pulling process. [Figure 16] FIG. 4 is a fourth diagram of the pulling process. [Figure 17] FIG. 10 is a diagram showing a pulling-up step in the second embodiment. [Figure 18] FIG. 18 is a view of FIG. 17 seen from above. [Figure 19] FIG. 10 is a first diagram of a sinking step in the second embodiment. [Figure 20] FIG. 10 is a second diagram of the sinking step in the second embodiment. [Figure 21] FIG. 10 is a third diagram of the sinking step in the second embodiment. [Figure 22] FIG. 4 is a schematic diagram showing the periphery of a connection between a center pipe of a transition piece and a first rope-like body. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) Hereinafter, a method for installing an offshore wind turbine jacket structure according to an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a front view showing a state in which an offshore wind turbine jacket structure 1 is laid on a barge S. FIG. FIG. 2 is a view of FIG. 1 seen from above. FIG. 3 is an enlarged view of part III in FIG. FIG. 4 is a cross-sectional view taken along the arrow IV in FIG. The offshore wind turbine jacket structure 1 in this embodiment is fabricated in a yard on land. The fabricated offshore wind turbine jacket structure 1 is placed in a lying state on a barge S, as shown in Figures 1 and 2. The offshore wind turbine jacket structure 1 is placed on the barge S by, for example, a crane, dolly, skid beam, or the like, which are not shown in Figures 1 and 2. As shown in Figs. 3 and 4, the offshore wind turbine jacket structure 1 is placed on a mount T provided on the barge S, and is thereby disposed on the barge S. Therefore, the weight of the offshore wind turbine jacket structure 1 is transmitted to the barge S via the mount T. For this reason, it is preferable that the mount T be provided, for example, in a portion of the barge S that has a relatively high strength. In other words, it is preferable that the mount T be provided, for example, on a bulkhead, transbeam, or the like of the barge S. The offshore wind turbine jacket structure 1 arranged on the barge S in this way is transported by the barge S to an installation site on the sea (details will be described later). Note that, as shown in FIG. 1 or FIG. 2, the offshore wind turbine jacket structure 1 may protrude from the longitudinal or lateral direction of the barge S when arranged on the barge S. Even in such a case, it is preferable that the mounting frame T is provided only on the floor of the barge S. In other words, it is preferable that the mounting frame T is not provided in a position that protrudes from the floor of the barge S. An outline of the jacket structure 1 for an offshore wind turbine will be described below.

[0010] (Outline of jacket structure for offshore wind turbines) The jacket structure 1 for an offshore wind turbine in this embodiment is installed on the sea and supports an offshore wind turbine (not shown). As shown in FIG. 1, the jacket structure 1 for an offshore wind turbine includes a transition piece 11, a leg 12, and a brace 13.

[0011] (Transition Piece) The transition piece 11 is the part to which the lower end of the tower of the offshore wind turbine is connected. The lower end of the tower of the offshore wind turbine is connected to a center pipe 11a, which is a cylindrical member provided in the transition piece 11. Loads acting on the offshore wind turbine due to wind force and the like are transmitted to the transition piece 11. The transition piece 11 is formed to have an internal space by, for example, combining a plurality of plate-shaped members around a center pipe 11a. The space provided in the transition piece 11 accommodates, for example, a converter that converts electricity generated by the offshore wind turbines, a storage battery that stores electricity generated by the offshore wind turbines (neither of which are shown), and the like. In this embodiment, the transition piece 11 is watertight. That is, the space provided in the transition piece 11 is formed watertight. This prevents, for example, the devices housed inside the transition piece 11 from being affected by water. Furthermore, as will be described later, when the jacket structure 1 for an offshore wind turbine is floated on the sea, the watertight transition piece 11 provides buoyancy. In this embodiment, multiple floors are provided inside the transition piece 11. That is, for example, there is a first floor located above the transition piece 11 for connecting the offshore wind turbine and the transition piece 11, a second floor located below the first floor where converters, storage batteries, etc. are located, and a third floor located below the second floor where a submarine cable extending from the seabed is connected (all not shown).

[0012] (Reg) The legs 12 are connected at their upper ends to the transition piece 11 and at their lower ends to piles driven into the seabed. This supports the transition piece 11 at sea. The legs 12 are formed, for example, from steel pipes. A plurality of legs 12 are provided in the offshore wind turbine jacket structure 1. In this embodiment, four legs 12 are provided in the offshore wind turbine jacket structure 1. In this case, the distance between adjacent legs 12 in the circumferential direction of the offshore wind turbine jacket structure 1 increases from the upper end to the lower end, as shown in FIG. 1, for example. This preferably makes it easier to withstand loads acting on the transition piece 11 via the offshore wind turbine when the offshore wind turbine jacket structure 1 is placed at sea.

[0013] (Brace) The braces 13 are steel pipes that connect adjacent legs 12 in the circumferential direction of the offshore wind turbine jacket structure 1. By providing the braces 13, the structure of the offshore wind turbine jacket structure 1 is reinforced. The braces 13 are arranged, for example, like the horizontal brace 13a shown in Fig. 1, so as to be horizontal when the jacket structure 1 for an offshore wind turbine is placed on the sea. Alternatively, the braces 13 may be arranged, for example, like the diagonal brace 13b shown in Fig. 1, so as to be oblique to the horizontal direction when the jacket structure 1 for an offshore wind turbine is placed on the sea. In this case, the diagonal brace 13b is arranged, for example, to form an X-shape 13X as shown in Fig. 1. Alternatively, the diagonal brace 13b may be arranged, for example, so as to form a triangle 13T with two diagonal braces 13b and one horizontal brace 13a.

[0014] (Leg Camp) In this embodiment, the connection portion between the leg 12 and the brace 13 is referred to as a leg can 12C. In the jacket structure 1 for an offshore wind turbine, a plurality of leg cans 12C are provided. 1, among the multiple leg cans 12C provided, the leg can 12C directly below the transition piece 11 is referred to as the first leg can 12Ca. The leg can 12C directly below the transition piece 11 refers to the leg can 12C that is closest to the connection between the leg 12 and the transition piece 11 in the extension direction of the leg 12. 1, among the multiple leg cans 12C provided, a leg can 12C different from the first leg can 12Ca is referred to as a second leg can 12Cb. In other words, among the leg cans 12C, those other than the leg can 12C directly below the transition piece 11 are referred to as the second leg can 12Cb.

[0015] (Installation method of jacket structure for offshore wind turbine) Next, a method for installing the offshore wind turbine jacket structure 1 according to this embodiment will be described. That is, each step from transporting the manufactured offshore wind turbine jacket structure 1 to the installation site on the sea to erecting and installing it will be described. FIG. 5 is a diagram showing the state in which the offshore wind turbine jacket structure 1 is lifted from the barge S in the lifting process. FIG. 6 is a view of FIG. 5 seen from above. FIG. 7 is an enlarged view of the periphery of the connection portion between the first leg can 12Ca and the first rope-shaped body W1, taken along the arrow VII in FIG. FIG. 8 is an enlarged view of the periphery of the connection portion between the second leg can 12Cb and the second rope-shaped body W2, taken along the arrow VIII in FIG. FIG. 9 is a first diagram of the sinking process. FIG. 10 is a second diagram of the sinking process. FIG. 11 is a third diagram of the sinking process. FIG. 12 is a fourth diagram of the sinking process. FIG. 13 is a first diagram of the pulling process. FIG. 14 is a second view of the pulling step. FIG. 15 is a third diagram of the pulling step. FIG. 16 is a fourth diagram of the pulling step. The method for installing the jacket structure 1 for an offshore wind turbine according to this embodiment includes a placement step, a transportation step, a connection step, a lifting step, a lowering step, a lifting step, and a release step.

[0016] (Placement process) The placement step is a step of placing the jacket structure 1 for an offshore wind turbine on a barge S, as shown in FIGS. That is, first, the jacket structure 1 for an offshore wind turbine fabricated in a yard on land is transported to a quay by a dolly or the like. Next, the jacket structure 1 for an offshore wind turbine transported to the quay is hoisted up by a crane (not shown in Figures 1 and 2). Then, the jacket structure 1 for an offshore wind turbine is placed on a pedestal T provided on the barge S, thereby laying the jacket structure 1 for an offshore wind turbine on the barge S. In the placement step in this embodiment, as shown in Figs. 3 and 4, the leg cans 12C of the jacket structure 1 for an offshore wind turbine are placed on the pedestal T provided on the barge S, thereby laying the jacket structure 1 for an offshore wind turbine on the barge S. Although Figs. 3 and 4 illustrate the second leg can 12Cb as an example, the same applies to the first leg can 12Ca. Here, the leg cans 12C in the offshore wind turbine jacket structure 1 have a relatively high strength compared to other parts of the offshore wind turbine jacket structure 1. Therefore, it is preferable to mount the leg cans 12C on the frame T so that the leg cans 12C can more easily withstand the load of the offshore wind turbine jacket structure 1.

[0017] When the offshore wind turbine jacket structure 1 is transported by the barge S, if the offshore wind turbine jacket structure 1 is not fixed to the cradle T, the cradle T and the leg cans 12C may become misaligned due to the rocking of the barge S caused by waves or the like. Therefore, when the offshore wind turbine jacket structure 1 is placed on the cradle T in the placement process, it is preferable to fix the cradle T and the leg cans 12C by welding. If the cradle T and the leg cans 12C are directly welded together, this may affect the leg cans 12C when they are detached from the cradle T during installation of the offshore wind turbine jacket structure 1. To avoid this, a doubler plate (not shown) is provided on the leg cans 12C. In this way, the leg cans 12C can be fixed to the cradle T by welding the cradle T and the doubler plate together. Furthermore, it is preferable that the doubler plate be separated from the mounting base T when the offshore wind turbine jacket structure 1 is installed, so that the leg can 12C can be protected by the doubler plate.

[0018] (Transportation process) The transportation process is a process in which the jacket structure 1 for an offshore wind turbine, which was placed on the barge S in the placement process, is transported to an installation site on the sea by the barge S. After the jacket structure 1 for an offshore wind turbine has been transported to the installation site, the barge S is moored to a crane ship CS (e.g., a floating crane) shown in Fig. 5, and the process moves to the connection process.

[0019] (Connection process) The connecting step is a step of connecting the first rope-like body W1 and the second rope-like body W2 to the jacket structure 1 for an offshore wind turbine that is placed on the barge S in the placing step. This makes it possible to lift the jacket structure 1 for an offshore wind turbine from the barge S by the crane CL, as shown in Fig. 5 . In this embodiment, the crane CL is provided on a crane ship CS, for example, as shown in Fig. 5. The crane CL is one that can lift the first rope-like body W1 and the second rope-like body W2 individually.

[0020] The first rope-like body W1 is connected to the first leg can 12Ca. The first rope-like body W1 is pulled up by a crane CL shown in Figures 5 to 16 in a pulling-up process described later. The first rope-like body W1 is used to erect the jacket structure 1 for an offshore wind turbine on the sea. 5 and 6, a plurality of first rope-like bodies W1 are provided in the short side direction of the offshore wind turbine jacket structure 1. Each of the plurality of first rope-like bodies W1 is connected to a first hook H1 suspended from the boom CLA of the crane CL. Each of the plurality of first rope-like bodies W1 is connected to two upper first leg cans 12Ca in the laid-down offshore wind turbine jacket structure 1. This enables the offshore wind turbine jacket structure 1 to be stably erected during the lifting process. In this embodiment, the first rope-like body W1 is connected to a lifting jig 12Ca1 provided on the first leg can 12Ca as shown in Fig. 7. For example, as shown in Fig. 7, the first rope-like body W1 is connected to the lifting jig 12Ca1 at an engaging portion W1a provided at the end thereof via a connecting portion 12Ca2.

[0021] The second rope-like body W2 is connected to the second leg can 12Cb. The second rope-like body W2 is provided to support the offshore wind turbine jacket structure 1 in the lifting step and the lowering step, which will be described later. 5 and 6, a plurality of second rope-like bodies W2 are provided in the longitudinal and lateral directions of the offshore wind turbine jacket structure 1. Each of the second rope-like bodies W2 is connected to a second hook H2 suspended from the boom CLA of the crane CL. The second rope-like bodies W2 are connected to the two second leg cans 12Cb located on the upper side of the offshore wind turbine jacket structure 1 in the laid-down state, as well as to the two first leg cans 12Ca located on the upper side of the offshore wind turbine jacket structure 1 in the laid-down state.

[0022] As shown in FIG. 8, the second rope-shaped body W2 is connected to the leg can 12C, for example, by being connected to a hooking portion 12Cb1 provided on the second leg can 12Cb. The hooking portion 12Cb1 is an L-shaped member provided on the leg can 12C. One end of the hooking portion 12Cb1 is connected to the leg can 12C and extends upward in the offshore wind turbine jacket structure 1 laid on the barge S. The other end of the hooking portion 12Cb1 extends along the longitudinal direction of the leg 12. In this case, the extending direction of the other end of the hooking portion 12Cb1 is a direction away from the boom CLA of the crane CL in the plan view shown in FIG. 8. As a result, an opening 12Cb2 is formed between the second leg can 12Cb and the other end of the hooking portion 12Cb1, as shown in FIG. 8. As a result, the second rope-like body W2 is connected to the hooking portion 12Cb1 by having its end passed through the opening 12Cb2 and hooked onto the hooking portion 12Cb1. That is, the second rope-like body W2 is connected by being hooked onto the hooking portion 12Cb1. For this reason, it is preferable that the end of the second rope-like body W2 be formed in a loop or hook shape.

[0023] With this structure, when tension is generated in the second rope-like body W2 due to the load of the offshore wind turbine jacket structure 1, the second rope-like body W2 remains connected to the hanging portion 12Cb1. Then, as will be described later, when the load of the offshore wind turbine jacket structure 1 no longer acts on the second rope-like body W2 because the offshore wind turbine jacket structure 1 sinks into the sea, the tension in the second rope-like body W2 no longer occurs. Then, as shown by the two-dot chain line in FIG. 8, the second rope-like body W2 moves away from the hanging portion 12Cb1. As a result, when the load of the offshore wind turbine jacket structure 1 no longer acts on the second rope-like body W2, the second rope-like body W2 comes off the hanging portion 12Cb1. In order to prevent the second rope-shaped body W2 from accidentally coming off the hooking portion 12Cb1, it is preferable to provide a stopper 12Cb3 that closes the opening 12Cb2, as shown in Fig. 8. The stopper 12Cb3 is fixed to the hooking portion 12Cb1 and the second leg can 12Cb by, for example, bolting. When removing the second rope-shaped body W2 from the hooking portion 12Cb1, the stopper 12Cb3 is removed by a diver or an ROV (Remote Operating Vehicle). In this embodiment, the operation of removing the stopper 12Cb3 is performed in a release process, which will be described later.

[0024] In the connection process, after the barge S has been moved to the installation site in the transportation process, the first rope-like body W1 is connected to the first leg can 12Ca as described above, and the second rope-like body W2 is connected to the second leg can 12Cb as described above. Then, the leg can 12C of the offshore wind turbine jacket structure 1 is removed from the frame T of the barge S. This makes it possible to lift the offshore wind turbine jacket structure 1 by the crane CL.

[0025] (Lifting process) 5 and 6, the lifting process is a process of lifting the offshore wind turbine jacket structure 1, which is laid on a barge S, by a crane CL. At this time, the second rope-like body W2 is used to lift the offshore wind turbine jacket structure 1. Therefore, as shown in FIGS. 5 and 6, the first rope-like body W1 may be in a slack state when the lifting process is performed. In the lifting process, after the offshore wind turbine jacket structure 1 is lifted by the crane CL, the offshore wind turbine jacket structure 1 is moved from the barge S onto the sea surface in a laid-down state, as shown in Figures 5 and 6. Note that Figures 5 and 6 show the barge S after it has moved from under the offshore wind turbine jacket structure 1 after it has been lifted. Note that the lifting process is preferably performed with the boom CLA of the crane CL in an upright position, in order to fully utilize the lifting performance of the crane CL and to stably lift the offshore wind turbine jacket structure 1. Furthermore, in order to be able to lift the offshore wind turbine jacket structure 1 with the boom CLA in an upright position, in the lifting process, the offshore wind turbine jacket structure 1 is preferably positioned so that the longitudinal direction of the offshore wind turbine jacket structure 1 intersects with the extension direction of the boom CLA in the plan view shown in Fig. 6.

[0026] (Subsidence process) The lowering step is a step of submerging the jacket structure 1 for an offshore wind turbine, to which the first rope-like body W1 and the second rope-like body W2 are connected in the connecting step, into the sea, as shown in Figures 9 and 10. In this embodiment, the lowering step is performed with the jacket structure 1 for an offshore wind turbine lying down. In addition, the second rope-like body W2 is used in the lowering step, continuing from the lifting step. Therefore, as shown in Figures 9 and 10, the first rope-like body W1 may be in a slack state when the lowering step is performed. As shown in Fig. 9, the boom CLA of the crane CL is kept upright until the offshore wind turbine jacket structure 1 is fully submerged in the sea in order to fully utilize the lifting performance of the crane CL. As the offshore wind turbine jacket structure 1 is submerged in the sea during the submersion process, buoyancy is generated in the offshore wind turbine jacket structure 1. This reduces the load acting on the crane CL. After the jacket structure 1 for an offshore wind turbine has been fully submerged in the sea and the weight acting on the crane CL has been reduced, the boom CLA of the crane CL is laid down as shown in Figure 10. This ensures a sufficient distance between the crane ship CS and the jacket structure 1 for an offshore wind turbine before the lifting process described next is carried out.

[0027] (Pulling process) The lifting process is a process of lifting up the first rope-like body W1 connected in the connecting process after the lowering process. This causes the first leg can 12Ca to the transition piece 11, i.e., the upper part of the offshore wind turbine jacket structure 1, to move upward by the first rope-like body W1. As a result, the offshore wind turbine jacket structure 1 is erected on the sea.

[0028] When the first rope-shaped body W1 is pulled up in the pulling-up step, the offshore wind turbine jacket structure 1 may be rotated in advance by 90° on the sea with the vertical direction as the rotation axis, as shown in Fig. 11. This allows the lower part of the offshore wind turbine jacket structure 1 to face the crane CL, and the crane CL to be positioned on an extension of the offshore wind turbine jacket structure 1 in the longitudinal direction. This is preferable because it makes it possible to prevent the load of the offshore wind turbine jacket structure 1 from being biased in the left-right direction when the first rope-shaped body W1 is pulled up, with the direction in which the boom CLA of the crane CL extends being the front. As described above, the first rope-like body W1 and the second rope-like body W2 are arranged side by side along the longitudinal direction of the offshore wind turbine jacket structure 1. Here, before the lifting step is performed, the center of gravity of the offshore wind turbine jacket structure 1 is located directly below the second rope-like body W2 suspended from the boom CLA of the crane CL. The connection part between the offshore wind turbine jacket structure 1 and the first rope-like body W1 is located at a position moved in the longitudinal direction of the offshore wind turbine jacket structure 1 from directly below the boom CLA of the crane CL, as shown in Fig. 6, for example. In this state, if the load of the offshore wind turbine jacket structure 1 is applied to the first rope-like body W1 from a state in which the offshore wind turbine jacket structure 1 is lifted only by the second rope-like body W2 without rotating the offshore wind turbine jacket structure 1 as described above (i.e., leaving it in the state shown in Fig. 10), the offshore wind turbine jacket structure 1 may suddenly rotate around the rotation axis in the vertical direction or the longitudinal direction of the offshore wind turbine jacket structure 1. By rotating the offshore wind turbine jacket structure 1 as described above before lifting the offshore wind turbine jacket structure 1 by the first rope-like body W1, it is possible to prevent the offshore wind turbine jacket structure 1 from rotating suddenly.

[0029] After rotating the jacket structure 1 for an offshore wind turbine as shown in Figure 11, the jacket structure 1 for an offshore wind turbine is further submerged in the sea as shown in Figure 12. Note that in order to properly submerge the jacket structure 1 for an offshore wind turbine in the sea, a step of attaching a valve (not shown) to the legs 12 and injecting water into a part of the lower side of the legs 12 may be further included in the submerging step or the subsequent lifting step. By appropriately submerging the jacket structure 1 for an offshore wind turbine in the sea, sufficient buoyancy is generated in the jacket structure 1 for an offshore wind turbine. From this state, the first rope-like body W1 starts to be pulled up. For example, the first hook H1 of the first rope-like body W1 is pulled up by the crane CL.

[0030] When the pulling up of the first rope-like body W1 begins, a portion of the upper part of the jacket structure 1 for an offshore wind turbine is pulled up above the water surface, as shown in FIG. 13 . At this time, the load is no longer applied to the portion of the second rope-like body W2 connected to the first leg can 12Ca, and the portion becomes slack. Even in this state, the load remains applied to the portion of the second rope-like body W2 connected to the second leg can 12Cb. At this time, the second hook H2 to which the second rope-like body W2 is connected is further lowered, causing the lower part of the jacket structure 1 for an offshore wind turbine to sink into the sea. This ensures that the jacket structure 1 for an offshore wind turbine is always held by the first rope-like body W1 and the second rope-like body W2 when the first rope-like body W1 is pulled up and the second rope-like body W2 is pulled down during the pulling up process, preventing the lower part of the jacket structure 1 for an offshore wind turbine from suddenly sinking into the sea, contributing to the stable erection of the jacket structure 1 for an offshore wind turbine.

[0031] As the first rope-like body W1 continues to be pulled up and the second rope-like body W2 continues to be pulled down, the lower part of the jacket structure 1 for an offshore wind turbine is fully submerged in the sea, as shown in Fig. 14. After this state is reached, the jacket structure 1 for an offshore wind turbine is rotated 180° around the vertical direction as the rotation axis, as shown in Fig. 15. Before the jacket structure 1 for an offshore wind turbine is rotated, it is preferable that the second rope-like body W2 is removed by a release step. By rotating the offshore wind turbine jacket structure 1 as described above, the upper part of the offshore wind turbine jacket structure 1 faces the crane CL, and the crane CL is positioned on the longitudinal extension of the offshore wind turbine jacket structure 1. This is preferable to prevent the lower part of the offshore wind turbine jacket structure 1 from interfering with the crane ship CS when the offshore wind turbine jacket structure 1 is completely erected.

[0032] As shown in Fig. 15, after the rotation of the offshore wind turbine jacket structure 1 is completed, the lifting of the first rope-like body W1 continues. As a result, the offshore wind turbine jacket structure 1 is completely erected as shown in Fig. 16. At this time, by lifting the offshore wind turbine jacket structure 1 with the crane CL, the longitudinal direction of the offshore wind turbine jacket structure 1 is aligned with the vertical direction, so that a third rope-like body W3 may be separately attached to the first leg can 12Ca located on the opposite side of the first leg can 12Ca on the side of the offshore wind turbine jacket structure 1 to which the first rope-like body W1 is connected, as shown in Fig. 16. When the third rope-like body W3 is attached, it is preferable that the third rope-like body W3 be attached after the offshore wind turbine jacket structure 1 has been rotated 180° around the vertical direction as the rotation axis, for example, as described above.

[0033] (Release process) The releasing step is a step of releasing the connection of the second rope-like body W2 that was connected to the offshore wind turbine jacket structure 1 in the connecting step after the lowering step. In the releasing step, a diver, an ROV, or the like removes the stopper 12Cb3 shown in Fig. 8. This causes the tension in the second rope-like body W2 to be lost, and the second rope-like body W2 is released from the hooking portion 12Cb1. In this embodiment, the releasing step is preferably performed during the lifting step as described above. Through the above steps, the jacket structure 1 for an offshore wind turbine is installed on the sea.

[0034] As described above, the installation method according to this embodiment includes an arrangement step of arranging the offshore wind turbine jacket structure 1 lying on the barge S. This allows the offshore wind turbine jacket structure 1 to be arranged lying on the barge S. Furthermore, by arranging the offshore wind turbine jacket structure 1 lying on the barge S, when transporting the offshore wind turbine jacket structure 1 by the barge S, the center of gravity of the offshore wind turbine jacket structure 1 can be positioned lower than when the offshore wind turbine jacket structure 1 is arranged upright on the barge S. Therefore, the offshore wind turbine jacket structure 1 can be transported stably by the barge S. Furthermore, this makes it easier to place the offshore wind turbine jacket structure 1 on the barge S. Here, for example, if the offshore wind turbine jacket structure 1 is large, the lifting height of the crane CL may not be sufficient, making it difficult to lift the offshore wind turbine jacket structure 1 in an upright position. In such a case, by laying the offshore wind turbine jacket structure 1 down, the offshore wind turbine jacket structure 1 can be lifted by an existing crane CL. Therefore, for example, it is possible to suppress increases in costs.

[0035] In the placement step, the offshore wind turbine jacket structure 1 is placed on a mounting stand T provided on the barge S, and the offshore wind turbine jacket structure 1 is placed lying on the barge S. By placing the offshore wind turbine jacket structure 1 via the mounting stand T in this way, it is possible to prevent parts of the offshore wind turbine jacket structure 1, such as the transition piece 11, from coming into contact with the floor of the barge S. Therefore, the offshore wind turbine jacket structure 1 can be placed on the barge S without being affected by the shape of the offshore wind turbine jacket structure 1.

[0036] In the placement step, the leg cans 12C of the offshore wind turbine jacket structure 1 are placed on a mounting stand T provided on the barge S, so that the offshore wind turbine jacket structure 1 is placed lying on the barge S. In this way, when the offshore wind turbine jacket structure 1 is placed on the barge S, the load of the offshore wind turbine jacket structure 1 acts on the leg cans 12C. Here, the leg cans 12C of the offshore wind turbine jacket structure 1 have a strength that is relatively high compared to other parts of the offshore wind turbine jacket structure 1. Therefore, by placing the offshore wind turbine jacket structure 1 on the barge S in the above-mentioned manner, it is possible to make it easier to withstand the load of the offshore wind turbine jacket structure 1.

[0037] The installation method according to this embodiment further includes a connecting step. In the connecting step, first, a first rope-like body W1 is connected to a first leg can 12Ca, which is the leg can 12C immediately below the transition piece 11 of the jacket structure 1 for an offshore wind turbine that is placed on the barge S in the placing step. Furthermore, a second rope-like body W2 is connected to a second leg can 12Cb, which is a leg can 12C different from the first leg can 12Ca and is the leg can 12C of the jacket structure 1 for an offshore wind turbine that is placed on the barge S in the placing step. This allows the first rope-like body W1 and the second rope-like body W2 to support multiple locations of the jacket structure 1 for an offshore wind turbine when the jacket structure 1 for an offshore wind turbine is lifted from the barge S by a crane CL or the like. Furthermore, for example, by supporting the jacket structure 1 for an offshore wind turbine with the second rope-like body W2 while winding up the first rope-like body W1, the jacket structure 1 for an offshore wind turbine can be erected stably. Furthermore, by connecting each of the first rope-like body W1 and the second rope-like body W2 to the leg can 12C having a relatively high strength, the load of the jacket structure 1 for an offshore wind turbine can be easily withstood.

[0038] The installation method according to this embodiment further includes a lowering step. In the lowering step, the offshore wind turbine jacket structure 1 to which the first rope-like body W1 and the second rope-like body W2 are connected in the connecting step is submerged in the sea. This allows the offshore wind turbine jacket structure 1 to be erected using the first rope-like body W1 and the second rope-like body W2 while utilizing the buoyancy of the offshore wind turbine jacket structure 1. This makes it possible to stably erect the offshore wind turbine jacket structure 1 while reducing the burden on the first rope-like body W1 and the second rope-like body W2 and the crane CL to which the first rope-like body W1 and the second rope-like body W2 are connected.

[0039] The installation method according to this embodiment further includes a lifting step. In the lifting step, after the lowering step, the first rope-like body W1 that will be connected in the connecting step is lifted up. In this way, by lifting up the first rope-like body W1 connected to the first leg can 12Ca, which is the leg can 12C directly below the transition piece 11 of the offshore wind turbine jacket structure 1 while the jacket structure 1 for an offshore wind turbine is submerged in the sea in the lowering step, the transition piece 11 of the jacket structure 1 for an offshore wind turbine can be moved upward while the lower part of the jacket structure 1 for an offshore wind turbine is further submerged in the sea due to the weight of the jacket structure 1 for an offshore wind turbine. Therefore, the lifting step makes it possible to more efficiently erect the jacket structure 1 for an offshore wind turbine.

[0040] The transition piece 11 is watertight. This allows buoyancy to be generated in the transition piece 11 of the offshore wind turbine jacket structure 1. This makes it difficult for the transition piece 11 to sink in the sea. Also, it makes it relatively easy for the lower part of the offshore wind turbine jacket structure 1 to sink in the sea. This allows the offshore wind turbine jacket structure 1 to be erected more efficiently.

[0041] (Second embodiment) Next, a method for installing the offshore wind turbine jacket structure 1 according to the second embodiment of the present disclosure will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, with only the differences being described. FIG. 17 is a diagram showing a pulling-up step in the second embodiment. FIG. 18 is a view of FIG. 17 seen from above. FIG. 19 is a first view of the sinking step in the second embodiment. FIG. 20 is a second view of the sinking step in the second embodiment. FIG. 21 is a third view of the sinking step in the second embodiment.

[0042] (Differences from the first embodiment) The installation method according to the second embodiment differs from the first embodiment in that two cranes CL are used to erect the offshore wind turbine jacket structure 1. That is, as shown in FIGS. 17 and 18 , a first crane CL1 and a second crane CL2 are used to erect the offshore wind turbine jacket structure 1 in the second embodiment. By using two cranes CL for one offshore wind turbine jacket structure 1 in this way, it is possible to cope with, for example, a case where the offshore wind turbine jacket structure 1 is large and difficult to lift with one crane CL. Furthermore, by using two cranes CL for one offshore wind turbine jacket structure 1, it is possible to cope with, for example, a case where watertightness cannot be ensured in the transition piece 11 of the offshore wind turbine jacket structure 1 and the upper part of the offshore wind turbine jacket structure 1 cannot be completely submerged.

[0043] The first crane CL1 is mounted on the first ship CS1, and the second crane CL2 is mounted on the second ship CS2. That is, two crane ships, the first ship CS1 and the second ship CS2, are used to install the offshore wind turbine jacket structure 1 in the second embodiment. In the second embodiment, a first rope W1 is connected to a first crane CL1. That is, the first rope W1 is operated by the first crane CL1. A second rope W2 is connected to a second crane CL2. That is, the second rope W2 is operated by the second crane CL2. The uses of the first rope W1 and the second rope W2 are the same as in the first embodiment.

[0044] In the second embodiment, the performance of the first crane CL1 and the second crane CL2, including the lifting height and the rated total load, may be the same or different. If the performance of the first crane CL1 and the second crane CL2 is different, it is preferable to use the crane with the greater lifting capacity as the second crane CL2. This preferably allows the second crane CL2 to stably lift the offshore wind turbine jacket structure 1 in a laid-down state.

[0045] (Installation method of jacket structure for offshore wind turbine) The method for installing an offshore wind turbine jacket structure 1 according to the second embodiment further includes a barge placement step in addition to the steps in the first embodiment. That is, the installation method for the jacket structure 1 for an offshore wind turbine according to the second embodiment includes a placement process, a transportation process, a barge placement process, a connection process, a lifting process, a raising process, a lowering process, and a release process. The placement process and the transportation process are performed in the same manner as in the first embodiment, and therefore a description thereof will be omitted.

[0046] (Barge placement process) The barge placement process is a process of placing a barge B between a first ship CS1 having a first crane CL1 and a second ship CS2 having a second crane CL2, as shown in Figures 17 and 18. By being placed between the first ship CS1 and the second ship CS2, barge B acts as a spacer that keeps the distance between the first ship CS1 and the second ship CS2 constant.

[0047] In the barge positioning process, the first vessel CS1 and the second vessel CS2 are positioned so that they sandwich the barge B. At this time, the first vessel CS1 and the second vessel CS2 are positioned as follows: That is, as shown in Figs. 17 and 18, the first crane CL1 is positioned near the upper end of the offshore wind turbine jacket structure 1 so that the offshore wind turbine jacket structure 1 can be erected by the first crane CL1. Then, the second crane CL2 is positioned near the center of gravity CG of the offshore wind turbine jacket structure 1 so that the second crane CL2 can stably lift the laid-down second crane CL2. For example, if the offshore wind turbine jacket structure 1 can be lifted by only the second crane CL2, the distance between the rotation center of the first crane CL1 and the rotation center of the second crane CL2 is set to approximately match the distance D1 from the upper end of the offshore wind turbine jacket structure 1 to the center of gravity CG. In other words, in the barge placement step, the center of gravity CG of the offshore wind turbine jacket structure 1 may be positioned at the rotation center of the second crane CL2 in the longitudinal direction of the offshore wind turbine jacket structure 1. That is, the second crane CL2 may be placed, for example, directly above the center of gravity CG. For example, if the weight of the offshore wind turbine jacket structure 1 exceeds the lifting capacity of the second crane CL2 and the offshore wind turbine jacket structure 1 cannot be lifted by the second crane CL2 alone, it is preferable to make the distance between the rotation center of the first crane CL1 and the rotation center of the second crane CL2 longer than the distance D1 from the upper end of the offshore wind turbine jacket structure 1 to the center of gravity CG. In other words, in the barge placement step, the center of gravity CG of the offshore wind turbine jacket structure 1 in the longitudinal direction of the offshore wind turbine jacket structure 1 may be positioned between the rotation center of the first crane CL1 and the rotation center of the second crane CL2. This preferably enables the offshore wind turbine jacket structure 1 to be lifted together by the first crane CL1 and the second crane CL2. By appropriately adjusting the positions of the first ship CS1 and the second ship CS2 as described above and then sandwiching the barge B between the first ship CS1 and the second ship CS2, the jacket structure 1 for the offshore wind turbine can be lifted or erected stably. After the positions of the first ship CS1 and the second ship CS2 have been adjusted, the first ship CS1, the second ship CS2 and the barge B are preferably fixed to each other, for example. The barge positioning step is performed at least before the lifting step. The barge positioning step may be performed, for example, before the connection step.

[0048] (Connection process) 17 and 18, the connecting step is a step of connecting the first rope-like body W1 and the second rope-like body W2 to the jacket structure 1 for an offshore wind turbine that is placed on the barge S in the placing step. The connecting step in the second embodiment differs from the first embodiment in that the first rope-like body W1 is provided on the first ship CS1 and the second rope-like body W2 is provided on the second ship CS2. Furthermore, in the second embodiment, since the jacket structure 1 for an offshore wind turbine is large as described above, the second rope-like body W2 may be connected only to the second leg can 12Cb, and only the first rope-like body W1 may be connected to the first leg can 12Ca.

[0049] (Pulling process) The lifting process is a process in which the first rope-shaped body W1, which will be connected to the offshore wind turbine jacket structure 1 in the connection process, is lifted by the first crane CL1, and the second rope-shaped body W2, which will be connected to the offshore wind turbine jacket structure 1 in the connection process, is lifted by the second crane CL2. The lifting process in the second embodiment corresponds to the lifting process in the first embodiment. The second embodiment differs from the first embodiment in that both the first rope-shaped body W1 and the second rope-shaped body W2 are used to lift the offshore wind turbine jacket structure 1. That is, in the second embodiment, the first crane CL1 and the second crane CL2 simultaneously lift the first rope-shaped body W1 and the second rope-shaped body W2, respectively, making it possible to lift a large offshore wind turbine jacket structure 1. This makes it possible to lift the offshore wind turbine jacket structure 1 using an existing crane CL, contributing to suppressing increases in costs. After the lifting step in the second embodiment is completed, the barge S that has been supporting the offshore wind turbine jacket structure 1 moves from under the offshore wind turbine jacket structure 1. This allows the transition to the subsidence step to occur without moving the first ship CS1 and the second ship CS2.

[0050] (Subsidence process) 19 , after the lifting step, the lowering step is a step of lowering the second rope-like body W2 with the second crane CL2 and submerging the offshore wind turbine jacket structure 1 to which the second rope-like body W2 is connected in the connecting step into the sea. That is, in the second embodiment, the second crane CL2 is lowered, and the first crane CL1 maintains the height of the upper part of the offshore wind turbine jacket structure 1 near the sea surface while submerging the lower part of the offshore wind turbine jacket structure 1 into the sea, thereby erecting the offshore wind turbine jacket 1 on the sea. This prevents the large offshore wind turbine jacket structure 1 from being lifted upward. Furthermore, in this embodiment, by always maintaining the upper part of the offshore wind turbine jacket structure 1 near the sea surface, the transition piece 11 does not need to be watertight. Furthermore, in order to properly submerge the lower part of the jacket structure 1 for an offshore wind turbine in the sea, the submerging process or the subsequent erection process may further include a process of attaching a valve (not shown) to the leg 12 and injecting water into a portion of the lower side of the leg 12. In the lowering process in the second embodiment, the offshore wind turbine jacket structure 1 is maintained in the orientation in which it was lifted in the lifting process without being rotated about the vertical axis. In the second embodiment, the lowering process is performed while the booms CLA of the first crane CL1 and the second crane CL2 remain upright. First, as shown in Fig. 20, the second rope-like body W2 is pulled down to move the lower part of the jacket structure 1 for an offshore wind turbine downward. At this time, the upper part of the jacket structure 1 for an offshore wind turbine is supported by the first rope-like body W1. Then, the load is no longer applied to the part of the second rope-like body W2 connected to the side closer to the first leg can 12Ca, and the part becomes loose. Even in this state, the load remains applied to the part of the second rope-like body W2 connected to the side farther from the first leg can 12Ca. By continuing to pull up the first rope-like body W1 and hang down the second rope-like body W2, the offshore wind turbine jacket structure 1 is completely erected as shown in Fig. 21. At this time, by supporting the upper part of the offshore wind turbine jacket structure 1 with the first crane CL1, in order to make the longitudinal direction of the offshore wind turbine jacket structure 1 follow the vertical direction, as shown in Fig. 21, in the offshore wind turbine jacket structure 1, a third rope-like body W3 may be separately attached to the first leg can 12Ca located on the opposite side to the first leg can 12Ca on the side to which the first rope-like body W1 is connected. In the second embodiment, the removal of the second rope-like body W2 from the jacket structure 1 for an offshore wind turbine by the releasing step described next is preferably carried out during the submerging step.

[0051] (Release process) In the releasing step, the second rope-like body W2 connected to the offshore wind turbine jacket structure 1 in the connecting step is released after or during the lowering step. The releasing step is performed in the same manner as in the first embodiment. That is, for example, in the middle of the lifting step, a diver, ROV, or the like removes the stopper 12Cb3 shown in FIG. 8. As a result, the tension of the second rope-like body W2 is lost, and the second rope-like body W2 is released from the hooking portion 12Cb1. Through the above steps, the jacket structure 1 for an offshore wind turbine is installed on the sea.

[0052] As described above, according to the installation method of the second embodiment, in the lifting step, the first rope-like body W1, which will be connected to the offshore wind turbine jacket structure 1 in the connecting step, is lifted by the first crane CL1, and the second rope-like body W2, which will be connected to the offshore wind turbine jacket structure 1 in the connecting step, is lifted by the second crane CL2. In this way, by lifting one offshore wind turbine jacket structure 1 with multiple cranes, it is possible to easily accommodate large offshore wind turbine jacket structures 1. Furthermore, by eliminating the need for a crane with a large lifting height, it is possible to suppress increases in costs, for example.

[0053] In the lowering step, after the lifting step, the second rope-like body W2 is lowered by the second crane CL2, and the jacket structure 1 for an offshore wind turbine to which the second rope-like body W2 is connected in the connecting step is submerged in the sea. This allows the lower part of the jacket structure 1 for an offshore wind turbine to be submerged in the sea more stably. Therefore, the jacket structure 1 for an offshore wind turbine can be erected more stably.

[0054] The installation method according to the second embodiment further includes a releasing step. In the releasing step, after the lowering step, the second rope-like body W2 connected to the offshore wind turbine jacket structure 1 in the connecting step is released from connection. This allows the offshore wind turbine jacket structure 1 to be erected on the sea.

[0055] The installation method according to the second embodiment further includes a barge positioning step. In the barge positioning step, before the lifting step, the first ship CS1 having the first crane CL1 and the second ship CS2 having the second crane CL2 are positioned so that the barge B is sandwiched between them, so that the distance between the rotation center of the first crane CL1 and the rotation center of the second crane CL2 is approximately the same as the length from the upper end of the offshore wind turbine jacket structure 1 to the center of gravity CG of the offshore wind turbine jacket structure 1. In the barge positioning step, the first ship CS1 having the first crane CL1 and the second ship CS2 having the second crane CL2 may be positioned so that the barge B is sandwiched between them, so that the center of gravity CG of the offshore wind turbine jacket structure 1 is located between the rotation center of the first crane CL1 and the rotation center of the second crane CL2 in the longitudinal direction of the offshore wind turbine jacket structure 1, or at the rotation center of the second crane CL2. In addition, in the barge placement process, the first ship CS1 having the first crane CL1 and the second ship CS2 having the second crane CL2 may be placed so as to sandwich the barge B between them, so that the distance between the center of the first crane CL1 and the center of the second crane CL2 is approximately the same as the length from the top end of the jacket structure 1 for an offshore wind turbine to the center of gravity of the jacket structure 1 for an offshore wind turbine. This prevents changes in the distance between the first ship CS1 and the second ship CS2 when lifting or erecting the offshore wind turbine jacket structure 1, thereby preventing changes in the relative positions of the offshore wind turbine jacket structure 1 and the first ship CS1 and second ship CS2. This makes it possible to more stably and easily lift or erect the offshore wind turbine jacket structure 1 using the first crane CL1 and the second crane CL2.

[0056] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. Fig. 22 is a schematic diagram showing the periphery of the connection between the center pipe 11a and the first rope-shaped body W1 of the transition piece 11. Note that Fig. 22 shows only the center pipe 11a. For example, when connecting the first rope-like body W1 to the offshore wind turbine jacket structure 1, instead of connecting it to the first leg can 12Ca as described above, it may be connected to a gripping tool 11H attached to the center pipe 11a of the transition piece 11, as shown in FIG. 22 . The gripping tool 11H is fixed to the inner circumferential surface of the center pipe 11a, for example, by contacting the inner circumferential surface of the center pipe 11a and by friction with the inner circumferential surface or by holding a flange protrusion 11aF on the upper part of the center pipe 11a of the transition piece 11. The first rope-like body W1 may be attached to the gripping tool 11H attached in this manner via a connecting part 12Ca2, thereby enabling the transition piece 11 to be lifted. Furthermore, it is preferable that the gripping tool 11H be detached from the center pipe 11a after erection of the offshore wind turbine jacket structure 1 is completed.

[0057] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

[0058] (Addendum) The installation method according to the embodiment can be understood as follows, for example.

[0059] <1> An installation method according to one aspect of the present disclosure is characterized by including an arrangement step of laying the jacket structure for an offshore wind turbine on a barge.

[0060] The method includes a placement step of placing the jacket structure for an offshore wind turbine lying down on a barge. This allows the jacket structure for an offshore wind turbine to be placed lying down on the barge. Furthermore, by placing the jacket structure for an offshore wind turbine lying down on the barge, the center of gravity of the jacket structure for an offshore wind turbine can be positioned lower when transporting the jacket structure for an offshore wind turbine by barge compared to when the jacket structure for an offshore wind turbine is placed upright on the barge. Therefore, the jacket structure for an offshore wind turbine can be transported stably by barge. Furthermore, it is possible to easily place the jacket structure for an offshore wind turbine on the barge. Here, for example, if the jacket structure for an offshore wind turbine is large, the lifting height of the crane may be insufficient, making it difficult to lift the jacket structure in an upright position. In such cases, by laying the jacket structure for an offshore wind turbine in a lying position, the jacket structure for an offshore wind turbine can be lifted by an existing crane. Therefore, for example, an increase in costs can be suppressed.

[0061] <2> the above <1> In the installation method according to the above, the placement step may be configured to place the jacket structure for the offshore wind turbine on a platform provided on the barge, thereby placing the jacket structure for the offshore wind turbine lying on the barge.

[0062] In the placement process, the jacket structure for an offshore wind turbine is placed on a mount provided on a barge, and the jacket structure for an offshore wind turbine is placed lying on the barge. By placing the jacket structure for an offshore wind turbine via the mount in this way, it is possible to prevent parts of the jacket structure for an offshore wind turbine, such as a transition piece, from coming into contact with the floor of the barge. Therefore, the jacket structure for an offshore wind turbine can be placed on the barge without being affected by the shape of the jacket structure for an offshore wind turbine.

[0063] <3> the above <1> or <2> In the installation method according to the above, the arranging step may be configured to place leg cans of the jacket structure for an offshore wind turbine on a platform provided on the barge, thereby arranging the jacket structure for an offshore wind turbine lying on the barge.

[0064] In the placement process, the leg cans of the offshore wind turbine jacket structure are placed on a mount provided on the barge, and the offshore wind turbine jacket structure is placed lying on the barge. In this way, when the offshore wind turbine jacket structure is placed on the barge, the load of the offshore wind turbine jacket structure acts on the leg cans. Here, the leg cans in the offshore wind turbine jacket structure have relatively high strength compared to other parts of the offshore wind turbine jacket structure. Therefore, by placing the offshore wind turbine jacket structure on the barge in the above-mentioned manner, it is possible to make it easier to withstand the load of the offshore wind turbine jacket structure.

[0065] <4> the above <1> from <3> In the installation method according to any one of the above aspects, a configuration may be adopted that further includes a connection step of connecting a first rope-shaped body to a first leg can that is a leg can directly below the transition piece of the offshore wind turbine jacket structure that is placed in the placement step, and connecting a second rope-shaped body to a second leg can that is a leg can different from the first leg can and is a leg can of the offshore wind turbine jacket structure that is placed in the placement step.

[0066] The installation method according to the present disclosure further includes a connecting step. In the connecting step, first, a first rope-shaped body is connected to a first leg can, which is a leg can immediately below the transition piece of the offshore wind turbine jacket structure that is to be placed on the barge in the placing step. Furthermore, a second rope-shaped body is connected to a second leg can, which is a leg can different from the first leg can and is a leg can of the offshore wind turbine jacket structure that is to be placed on the barge in the placing step. This allows the first and second rope-shaped bodies to support multiple locations of the offshore wind turbine jacket structure when the offshore wind turbine jacket structure is lifted from the barge by a crane or the like. Furthermore, for example, by supporting the offshore wind turbine jacket structure with the second rope-shaped body and then winding up the first rope-shaped body, the offshore wind turbine jacket structure can be erected stably. Furthermore, by connecting each of the first and second rope-shaped bodies to a leg can with a relatively high strength, the offshore wind turbine jacket structure can more easily withstand the load.

[0067] <5> the above <4> The installation method according to the present invention may be configured to further include a submerging process in which the jacket structure for an offshore wind turbine to which the first rope-like body and the second rope-like body are connected in the connection process is submerged in the sea.

[0068] The installation method according to the present disclosure further includes a lowering step. In the lowering step, the jacket structure for an offshore wind turbine to which the first and second rope-like bodies are connected in the connecting step is submerged in the sea. This allows the offshore jacket structure for an offshore wind turbine to be erected using the first and second rope-like bodies while utilizing the buoyancy of the jacket structure for an offshore wind turbine. Therefore, it is possible to stably erect the jacket structure for an offshore wind turbine while reducing the burden on the first and second rope-like bodies and the crane to which the first and second rope-like bodies are connected.

[0069] <6> the above <5> The installation method according to the above aspect may further include, after the lowering step, a lifting step of lifting up the first rope-shaped body connected in the connecting step.

[0070] The installation method according to the present disclosure further includes a lifting step. In the lifting step, after the lowering step, the first rope-shaped body connected in the connecting step is lifted. In this way, by lifting the first rope-shaped body connected to the first leg can, which is the leg can directly below the transition piece of the offshore wind turbine jacket structure, while the jacket structure for an offshore wind turbine is submerged in the sea in the lowering step, the lower part of the jacket structure for an offshore wind turbine can be further submerged in the sea due to the weight of the jacket structure for an offshore wind turbine, while the transition piece of the jacket structure for an offshore wind turbine can be moved upward. Therefore, the lifting step makes it possible to more efficiently erect the jacket structure for an offshore wind turbine.

[0071] <7> the above <4> In the installation method according to the above aspect, a configuration may be adopted in which the transition piece is watertight.

[0072] The transition piece is watertight. This allows buoyancy to be generated in the transition piece of the jacket structure for an offshore wind turbine. This makes it difficult for the transition piece to sink in the sea. Also, it makes it relatively easy for the lower part of the jacket structure for an offshore wind turbine to sink in the sea. This allows the jacket structure for an offshore wind turbine to be erected more efficiently.

[0073] <8> the above <4> The installation method according to the present invention may further include a lifting step in which the first rope-like body connected to the offshore wind turbine jacket structure in the connection step is lifted by a first crane, and the second rope-like body connected to the offshore wind turbine jacket structure in the connection step is lifted by a second crane.

[0074] In the lifting process, the first rope-like body that will be connected to the jacket structure for an offshore wind turbine in the connecting process is lifted by a first crane, and the second rope-like body that will be connected to the jacket structure for an offshore wind turbine in the connecting process is lifted by a second crane. In this way, lifting one jacket structure for an offshore wind turbine with multiple cranes makes it easier to accommodate large jacket structures for offshore wind turbines. Furthermore, by eliminating the need for a crane with a large lifting height, it is possible to suppress increases in costs, for example.

[0075] <9> the above <8> In the installation method according to the above, a configuration may be adopted which further comprises a lowering process in which, after the lifting process, the second rope-like body is lowered by the second crane, and the jacket structure for the offshore wind turbine to which the second rope-like body is connected in the connection process is submerged into the sea.

[0076] In the lowering step, after the lifting step, the second rope-like body is lowered by the second crane, and the jacket structure for an offshore wind turbine to which the second rope-like body is connected in the connecting step is submerged in the sea. This allows the lower part of the jacket structure for an offshore wind turbine to be submerged in the sea more stably. Therefore, the jacket structure for an offshore wind turbine can be erected more stably.

[0077] <10> the above <9> The installation method according to the present invention may further include a disconnection process for disconnecting the second rope-like body that is connected to the offshore wind turbine jacket structure in the connection process after the lowering process.

[0078] The installation method according to the present disclosure further includes a releasing step in which, after the lowering step, the second rope-like body connected to the jacket structure for an offshore wind turbine in the connecting step is released from connection, thereby allowing the jacket structure for an offshore wind turbine to be erected on the sea.

[0079] <11> the above <8> from <10> In the installation method according to any one of the above aspects, a configuration may be adopted which further comprises, before the lifting step, a barge positioning step of positioning a first ship having the first crane and a second ship having the second crane so that a barge is sandwiched between them, so that the center of gravity of the offshore wind turbine jacket structure is located between the center of rotation of the first crane and the center of rotation of the second crane in the longitudinal direction of the offshore wind turbine jacket structure, or is located at the center of rotation of the second crane.

[0080] The installation method according to the present disclosure further includes a barge positioning step. In the barge positioning step, before the lifting step, a first ship having a first crane and a second ship having a second crane are positioned so that the barge is sandwiched between them, so that the center of gravity of the offshore wind turbine jacket structure is located between the rotation center of the first crane and the rotation center of the second crane in the longitudinal direction of the offshore wind turbine jacket structure, or is located at the rotation center of the second crane. This prevents changes in the distance between the first ship and the second ship when lifting or erecting the offshore wind turbine jacket structure, thereby preventing changes in the relative positions of the offshore wind turbine jacket structure and the first and second ships. This makes it possible to more stably and easily lift or erect the offshore wind turbine jacket structure using the first and second cranes. [Explanation of symbols]

[0081] 1 Jacket structure for offshore wind turbines 11 Transition Piece 12th Leg 12C leg camping 12Ca 1st leg camp 12Cb 2nd leg camp 12Cb1 Latch part 12Cb2 opening 12Cb3 Stopper 13 Brace 13a Horizontal brace 13b Diagonal brace 13T triangle 13X X-shape B Barge CL Crane CL1 No. 1 crane CL2 No. 2 crane CLA Boom CS Crane Ship CS1 1st ship CS2 Second Ship S barge T frame W1 First plexiform body W2 Second plexiform body W3 Third plexiform body

Claims

1. an arrangement step of laying the jacket structure for the offshore wind turbine on a barge; An installation method comprising:

2. The placing step places the jacket structure for an offshore wind turbine lying on the barge by placing the jacket structure for an offshore wind turbine on a rack provided on the barge.

2. The installation method according to claim 1 .

3. the placing step includes placing leg cans of the jacket structure for an offshore wind turbine on a frame provided on the barge, so that the jacket structure for an offshore wind turbine is laid down on the barge.

3. The installation method according to claim 2.

4. a connecting step of connecting a first rope-shaped body to a first leg can that is a leg can immediately below a transition piece of the jacket structure for the offshore wind turbine that is placed in the placing step, and connecting a second rope-shaped body to a second leg can that is a leg can different from the first leg can and is a leg can of the jacket structure for the offshore wind turbine that is placed in the placing step; 4. The installation method according to claim 1, further comprising:

5. a submerging step of submerging the jacket structure for an offshore wind turbine, to which the first rope-shaped body and the second rope-shaped body are connected in the connecting step, into the sea; 5. The installation method of claim 4, further comprising:

6. a lifting step of lifting up the first rope-shaped body connected in the connecting step after the lowering step; 6. The installation method of claim 5, further comprising:

7. The transition piece is watertight.

6. The installation method according to claim 5.

8. a lifting step of lifting the first rope-shaped body connected to the offshore wind turbine jacket structure in the connecting step with a first crane, and lifting the second rope-shaped body connected to the offshore wind turbine jacket structure in the connecting step with a second crane; 5. The installation method of claim 4, further comprising:

9. a lowering step of lowering the second rope-like body by the second crane after the lifting step, and submerging the jacket structure for an offshore wind turbine to which the second rope-like body is connected in the connecting step into the sea; The installation method of claim 8 further comprising:

10. a disconnecting step of disconnecting the second rope-shaped body connected to the offshore wind turbine jacket structure in the connecting step after the lowering step; 10. The installation method of claim 9, further comprising:

11. a barge positioning step of positioning a first ship having the first crane and a second ship having the second crane so that a barge is sandwiched between them, such that the center of gravity of the jacket structure for an offshore wind turbine is located between the center of rotation of the first crane and the center of rotation of the second crane, or is located at the center of rotation of the second crane, in the longitudinal direction of the jacket structure for an offshore wind turbine, before the lifting step; The installation method of claim 8 further comprising:

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