Method for assembling a jacket structure

Abstract

To provide a method for assembling a jacket structure capable of suppressing the necessity of fixing cylindrical legs laid on the ground by using a member other than a member constituting the jacket structure.SOLUTION: The method includes a first arrangement step of laying each of a cylindrical first leg 11 and a cylindrical second leg 12 on the ground so as to be substantially parallel to a predetermined direction D substantially parallel to the ground, and a first connection step of connecting the first leg 11 and the second leg 12 laid on the ground in the first arrangement step by a cylindrical brace 20.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for assembling a jacket structure. [Background technology]

[0002] Conventionally, the jacket structure is assembled in a yard. Patent Document 1 discloses that the legs are fixed to each other while being positioned on the ground in a horizontal position. Patent Document 2 discloses that when constructing a jacket-type structure, two leg members are placed horizontally on the ground, and connecting members that connect these leg members and connecting members that connect them to other adjacent leg members are attached to create a planar structure (hereinafter referred to as a panel), and the multiple panels created in this way are erected in sequence to join the panels and assemble the jacket-type structure, and that when erecting the panels, an assembly jig is used to support the lower chord member (the lowest horizontal member) of the panel so that it can rotate around its axis. Patent document 3 discloses a rotation support jig for large planar structures that supports the legs of one side of a frame rotatably around a horizontal axis so that each frame can be rotated upright when assembling a large, arrow-shaped structure, for example, used for offshore oil drilling, using multiple planar structures (hereinafter referred to as frames) that have been pre-assembled on a horizontal surface to lay the large structure on its side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-46721 [Patent Document 2] Japanese Utility Model Application Publication No. 5-22628 [Patent Document 3] Jikko No. 60-33190 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to enable the jacket structure to be transported in a laid-down state after fabrication, the jacket structure is sometimes fabricated in a laid-down state in advance. Also, when fastening the cylindrical legs together in the process of assembling the jacket structure, it is desired to improve the efficiency of the work by not using any materials other than those constituting the jacket structure. However, Patent Document 1 does not specifically disclose how the legs are fixed to each other while they are positioned on the ground in a reclined position. Patent Document 2 does not specifically disclose a connecting member that connects the legs to each other. And Patent Document 3 does not disclose that the legs of the frame are cylindrical.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a method for assembling a jacket structure that can reduce the need to fasten cylindrical legs laid on the ground together using members other than those that constitute the jacket structure. [Means for solving the problem]

[0006] A method for assembling a jacket structure according to one embodiment of the present disclosure is characterized by comprising a first placement process in which a cylindrical first leg and a cylindrical second leg are each laid on the ground so that they are approximately parallel to a predetermined direction that is approximately parallel to the ground, and a first connection process in which the first leg and the second leg laid on the ground in the first placement process are connected with a brace. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a method for assembling a jacket structure that can reduce the need to fasten cylindrical legs laid on the ground together using components other than those that constitute the jacket structure. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a front view of the jacket structure according to the embodiment. [Figure 2] FIG. 10 is a diagram showing a state in which the first leg and the second leg are arranged so as to be substantially parallel to a predetermined direction. [Figure 3] FIG. 10 is a diagram showing a state in which the third leg and the fourth leg are arranged to sandwich the first leg and the second leg connected by a diagonal brace. [Figure 4] FIG. 10 is a diagram showing a state in which a frame is joined to the first leg and the second leg, and further, a third leg and a fourth leg are joined to the frame. [Figure 5] FIG. 10 is a diagram showing the state in which the deck slab is being raised by a crane. [Figure 6] FIG. 10 is a diagram showing a state in which one deck slab is installed at each end of the first leg, second leg, third leg, and fourth leg, that is, at the end on one side in a predetermined direction. [Figure 7] This is a diagram showing the state in which the mud mat is being erected by a crane. [Figure 8] FIG. 10 is a diagram showing a state in which one mud mat is installed at each end of the first leg, second leg, third leg, and fourth leg, the end on the other side in a predetermined direction. [Figure 9] FIG. 2 is a diagram showing a state in which the first leg, the second leg, the third leg, and the fourth leg are arranged so as to be substantially parallel to a predetermined direction. [Figure 10] FIG. 10 is a diagram showing a state in which the first leg and the second leg, and the third leg and the fourth leg are connected by a brace. [Figure 11] FIG. 10 is a diagram showing a configuration in which the first leg and the second leg are connected by a brace, and a configuration in which the third leg and the fourth leg are connected by a brace, being erected by a crane. [Figure 12] FIG. 10 is a diagram showing a state in which a configuration in which the first leg and the second leg are connected by a brace and a configuration in which the third leg and the fourth leg are connected by a brace are connected by a brace. [Figure 13] FIG. 10 is a diagram showing a state in which the first leg, second leg, fifth leg, and sixth leg are arranged substantially parallel to a predetermined direction. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) Hereinafter, a method for assembling a jacket structure according to an embodiment of the present disclosure will be described with reference to the drawings. In describing the method for assembling a jacket structure, first, a jacket structure according to a first embodiment will be described.

[0010] (About the jacket structure) FIG. 1 is a front view of a jacket structure 1 according to an embodiment. The jacket structure 1 in the first embodiment is used, for example, in an offshore oil platform, etc. As shown in FIG. 1 , the jacket structure 1 includes legs 10, braces 20, a deck slab 30, and a mud mat 40.

[0011] (Regarding Reg) The legs 10 are cylindrical members extending in the vertical direction. The jacket structure 1 includes at least three legs 10. In the first embodiment, the jacket structure 1 includes four legs 10. All four legs 10 have the same configuration. Hereinafter, the four legs 10 included in the jacket structure 1 may be referred to as a first leg 11, a second leg 12, a third leg 13, and a fourth leg 14, respectively. A deck slab 30 is installed on the upper end of the leg 10. As a result, the leg 10 supports the deck slab 30 at sea. In the first embodiment, the leg 10 is inclined with respect to the vertical direction as shown in FIG. 1. That is, for example, in the circumferential direction of the jacket structure 1, the legs 10 are positioned so that the distance between adjacent legs 10 increases from the upper end to the lower end of the leg 10. Note that in the first embodiment, the circumferential direction of the jacket structure 1 is the circumferential direction whose axis is the direction from the upper end to the lower end of the jacket structure 1. This makes it easier for the jacket structure 1 to support the deck slab 30 installed on the upper end of the leg 10. It also makes the jacket structure 1 structurally stable.

[0012] (About braces) The braces 20 are tubular members that connect the multiple legs 10 included in the jacket structure 1 to each other. The braces 20 reinforce the jacket structure 1. The braces 20 include horizontal braces 21 and diagonal braces 22. Hereinafter, the portion of the leg 10 that is connected to the brace 20 may be referred to as a leg can.

[0013] (About horizontal braces) The horizontal braces 21 extend in the horizontal direction in the jacket structure 1. More specifically, in the first embodiment, the horizontal braces 21 are arranged along the horizontal direction between four legs 10. A plurality of horizontal braces 21 are provided at intervals in the height direction of the jacket structure 1. In the first embodiment, the horizontal braces 21 arranged between the legs 10 are each provided at the same height. As a result, the horizontal braces 21 are formed in a rectangular shape, and the legs 10 are connected to each corner of the rectangle. Hereinafter, the rectangular shape formed by the horizontal braces 21 will be referred to as a frame 21F. The frame 21F may further include horizontal braces 21 connecting diagonal corners of the rectangle. This may reinforce the structure of the frame 21F. In the first embodiment, the frame 21F is preferably composed of at least three horizontal braces 21, including horizontal braces 21 connecting legs 10 to each other.

[0014] (About diagonal braces) The diagonal braces 22 extend diagonally relative to the horizontal direction in the jacket structure 1. The diagonal braces 22 connect, for example, the leg cans of two legs 10 that are adjacent in the circumferential direction of the jacket structure 1. The leg cans connected by the diagonal braces 22 are located at different height positions and are adjacent to each other in the height direction of the jacket structure 1. In this way, the diagonal braces 22 further reinforce the jacket structure 1.

[0015] 1, for example, a plurality of diagonal braces 22 are provided between legs 10 in the up-down direction. At this time, the plurality of diagonal braces 22 are provided in a wave-like pattern in the up-down direction of the jacket structure 1. That is, the diagonal braces 22 adjacent to each other in the up-down direction of the jacket structure 1 have different tilt directions. The leg cans to which the diagonal braces 22 adjacent to each other in the up-down direction of the jacket structure 1 are connected are the same. 1, the directions in which the diagonal braces 22 that are positioned at the same height in the jacket structure 1 and that face each other may be different, for example. That is, the direction in which the diagonal brace 22 connecting one pair of two circumferentially adjacent legs 10 extends may be different from the direction in which the diagonal brace 22 connecting the pair opposite that pair extends. Even in this case, it is preferable that the positions of the leg cans in the vertical direction are the same.

[0016] Alternatively, the diagonal braces 22 may all be inclined in the same direction, or two diagonal braces 22 may be arranged at the same height to form an X-shape. Furthermore, when the distance between the legs 10 is large, for example, like the diagonal brace 22 located at the bottom of the jacket structure 1 shown in FIG. 1, the two diagonal braces 22 may be arranged at the same height with the lower end of the diagonal brace 22 positioned between the legs 10.

[0017] (About the deck) The deck 30 is connected to the upper end of the leg 10. The deck 30 is, for example, a place where workers stand and perform work in the jacket structure 1. Alternatively, a superstructure constituting an oil platform or the like may be provided on the deck 30. The shape of the deck slab 30 is determined appropriately according to the number of legs 10. That is, for example, if there are three legs 10, the deck slab 30 is triangular. As a result, each vertex of the triangle is connected to the upper end of a leg 10. As described above, in the first embodiment, there are four legs 10. Therefore, in the first embodiment, the deck slab 30 is quadrangular. As a result, each corner of the deck slab 30 is connected to the upper end of each of the four legs 10.

[0018] (About Madmat) The mud mat 40 is connected to the lower end of the leg 10. When the jacket structure 1 is erected on the seabed, the mud mat 40 comes into contact with the seabed. In this way, the mud mat 40 increases the ground contact area of ​​the jacket structure 1 and reduces the surface pressure acting on the seabed due to the weight of the jacket structure 1. The shape of the window mat 40 is determined appropriately according to the number of legs 10. That is, for example, if there are three legs 10, the window mat 40 is triangular. As a result, each vertex of the triangle is connected to the upper end of a leg 10. As described above, in the first embodiment, there are four legs 10. Therefore, in the first embodiment, the window mat 40 is quadrangular. As a result, each corner of the window mat 40 is connected to the lower end of each of the four legs 10. Furthermore, the shape of the mud mat 40 may be determined appropriately according to the soil properties of the seabed on which the jacket structure 1 is to be installed. For example, if the seabed on which the jacket structure 1 is to be installed is relatively loose, the mud mat 40 may remain in the triangular or rectangular shape described above to ensure a sufficient ground contact area. For example, if the seabed on which the jacket structure 1 is to be installed is relatively hard, the mud mat 40 may be made lighter by cutting out a portion of the triangular or rectangular shape described above while leaving a relatively large area around the connection portion with the leg 10. The jacket structure 1 in the first embodiment is configured with the above components.

[0019] (How to assemble the jacket structure) Next, a method for assembling the jacket structure 1 according to the first embodiment will be described. In the first embodiment, the jacket structure 1 is assembled in a lying state in a yard Y on the ground. Then, the completed jacket structure 1 is transported in a lying state by a transport ship (not shown) or the like, and is installed at the installation site by standing upright. The method for assembling the jacket structure 1 according to the first embodiment includes a first arrangement process, a first connection process, a second arrangement process, a first joining process, a lifting process, a second joining process, a third joining process, a first installation step, and a second installation step.

[0020] (Regarding the first placement process) FIG. 2 is a diagram showing a state in which the first leg 11 and the second leg 12 are arranged so as to be substantially parallel to a predetermined direction D. As shown in FIG. The first arrangement step is a step of laying the cylindrical first leg 11 and the cylindrical second leg 12 on the ground so that they are substantially parallel to a predetermined direction D that is substantially parallel to the ground. The predetermined direction D being substantially parallel to the ground means that the intersection angle between the ground and the predetermined direction D is 5° or less. The predetermined direction D is arbitrarily determined based on conditions such as the layout of the yard Y where the jacket structure 1 is fabricated. In this embodiment, the predetermined direction D is a direction in which the center lines of the first leg 11 and the second leg 12 on a plane consisting of the laid-down first leg 11 and the second leg 12 are vertically upward in FIG. 1 . Furthermore, the first leg 11 and the second leg 12 being substantially parallel to the predetermined direction D means that the intersection angle between the first leg 11 and the second leg 12 and the predetermined direction D is 10° or less. In addition, when the first leg 11 and the second leg 12 are laid down, the crossing angle between the tube axes of the first leg 11 and the second leg 12 and the ground is preferably 5° or less. In this embodiment, when the first leg 11 and the second leg 12 are laid down as described above, the direction to which the deck slab 30 is attached is referred to as one side of the specified direction D, and the direction to which the window mat 40 is attached is referred to as the other side of the specified direction D.

[0021] When the first leg 11 and the second leg 12 are laid down in the first arrangement step, the distance between one end of the first leg 11 and one end of the second leg 12 in the predetermined direction D is shorter than the distance between the other end of the first leg 11 and the other end of the second leg 12. This positions the legs 10 so that the distance between adjacent legs 10 in the circumferential direction of the manufactured jacket structure 1 increases from the upper end to the lower end of the legs 10.

[0022] In the first arrangement step, the first leg 11 and the second leg 12 are supported by the first mount T1 and the second mount T2, as shown in FIG. A plurality of first frames T1 are provided at intervals along the longitudinal direction of the first leg 11 and the second leg 12. The first frames T1 are provided, for example, so that the jacket structure 1 can be transported while supporting the first leg 11 and the second leg 12 after the fabrication of the jacket structure 1 is completed. In the first embodiment, the first frame T1 can be lifted by a dolly (not shown). At this time, the dolly (not shown) enters under a support portion (not shown) provided on the first frame T1 and lifts the first frame T1. In this way, the dolly lifts the jacket structure 1 together with the first frames T1, and the jacket structure 1 can be moved by the dolly. A plurality of second mounts T2 are provided at intervals between the plurality of first mounts T1 arranged as described above. Here, if the first legs 11 and the second legs 12 were supported only by the first mounts T1 before the first legs 11 and the second legs 12 were connected by the braces 20, the first legs 11 and the second legs 12 could be deformed due to the weight of the first legs 11 and the second legs 12 and the weight of the frame 21F. By providing the second mounts T2 between the first mounts T1, deformation of the first legs 11 and the second legs 12 due to their weight and the weight of the frame 21F is suppressed. Note that the second mounts T2 are preferably removed when the jacket structure 1 is assembled and the dolly lifts the jacket structure 1 together with the first mounts T1. This prevents the second mounts T2 from interfering with the dolly.

[0023] (Regarding the first connection process) FIG. 3 is a diagram showing a state in which the third leg 13 and the fourth leg 14 are arranged to sandwich the first leg 11 and the second leg 12 connected by the diagonal brace 22. The first connection step is a step of connecting the first leg 11 and the second leg 12, which are laid on the ground in the first placement step, with the braces 20. In the first connection step, for example, the first leg 11 and the second leg 12 are connected to the braces 20 by welding. In the first connection step, for example, the first leg 11 and the second leg 12 are connected by both the diagonal braces 22 and the horizontal braces 21.

[0024] (Second placement process) 3, the second placement step is a step of laying the third leg 13 on the ground so that the first leg 11 is sandwiched between the second leg 12 and the third leg 13 and so that the third leg 13 is approximately parallel to the predetermined direction D. At this time, the third leg 13 is placed so that the distance between the third leg 13 and the first leg 11 is smaller than the distance between the second leg 12 and the first leg 11 and so that the angle between the third leg 13 and the first leg 11 is closer to parallel than the angle between the second leg 12 and the first leg 11. In the second placement step, it is preferable that the third leg 13 is placed parallel to the first leg 11 and the fourth leg 14 is placed parallel to the second leg 12. Here, scaffolding to be used for work at height that occurs in the second joining step described later may be installed in advance on the third leg 13 and the fourth leg 14. In this case, in the second placement step, the scaffolding installed on the third leg 13 and the fourth leg 14 may be installed at a higher position than the first leg 11 and the second leg 12 to prevent the scaffolding from interfering with the ground. In the first embodiment, in the second placement step, in addition to placing the third leg 13 as described above, the fourth leg 14 is laid on the ground so that the second leg 12 is sandwiched between the first leg 11 and the fourth leg 14 and so that the fourth leg 14 is approximately parallel to the predetermined direction D. At this time, the fourth leg 14 is placed so that the distance between the fourth leg 14 and the second leg 12 is smaller than the distance between the first leg 11 and the second leg 12 and so that the angle between the fourth leg 14 and the second leg 12 is closer to parallel than the angle between the first leg 11 and the second leg 12. This allows the lifting process and subsequent processes described below to be carried out smoothly. In the first embodiment, the second arranging step is performed before the first joining step and the lifting step. Note that the second arranging step may be performed after the first joining step, but is preferably performed at least before the lifting step.

[0025] (Regarding the first joining process) FIG. 4 is a diagram showing a state in which a frame 21F is joined to the first leg 11 and the second leg 12, and further, a third leg 13 and a fourth leg 14 are joined to the frame. The first joining step is a step of joining a frame 21F composed of three or more braces 20 including a brace 20 connecting the legs 10 to the first leg 11 and the second leg 12 so that the frame 21F is aligned approximately vertically. In the first embodiment, the frame 21F being aligned approximately vertically means that the crossing angle between the frame 21F and the vertical direction is within 10°. As described above, the frame 21F is formed by the horizontal braces 21. That is, all three or more braces 20, including the brace 20 connecting the legs 10, are horizontal braces 21. In the first embodiment, joining the frame 21F to the first leg 11 and the second leg 12 means, for example, forming the frame 21F by appropriately joining a plurality of horizontal braces 21 in a first joining step. In the first connecting step, for example, the first leg 11 and the second leg 12 are joined to the frame 21F by welding.

[0026] Here, as shown in FIG. 1 , when the jacket structure 1 is placed offshore, the legs 10 are inclined with respect to the vertical direction. Then, as shown in FIG. 4 , in a first placement step, the first legs 11 and the second legs 12 are laid on the ground so as to be approximately parallel to a predetermined direction D that is approximately parallel to the ground. In a first joining step, the frame 21F is aligned with the approximately vertical direction. In other words, the frame 21F is appropriately inclined with respect to the vertical direction by an angle corresponding to the intersection between the frame 21F and the first legs 11 and second legs 12 in the completed jacket structure 1. This ensures that, when the jacket structure 1 is placed offshore, the horizontal brace 21 is aligned with the horizontal direction and the legs 10 are inclined with respect to the vertical direction. In this embodiment, the frame 21F being aligned with the approximately vertical direction may mean that the frame 21F is appropriately inclined as described above.

[0027] (About the lifting process) The lifting process is a process of lifting the third leg 13. In the lifting process, the third leg 13 is lifted by a crane CL, for example, as shown in FIG. 4. This allows the third leg 13 to be joined to the frame 21F in the second joining process described next. In this embodiment, for example, a crawler crane is used as the crane CL. Alternatively, a gantry crane may be used as the crane CL.

[0028] (Regarding the second joining process) The second joining step is a step of joining the third leg 13 lifted in the lifting step to the frame 21F joined in the first joining step. In the second joining step, the third leg 13 and the frame 21F are joined by welding, for example. In the first embodiment, the above-described lifting step and second joining step are performed multiple times to join the fourth leg 14 to the frame 21F in the same manner as the third leg 13. Note that the operation of lifting the third leg 13 and joining it to the frame 21F and the operation of lifting the fourth leg 14 and joining it to the frame 21F may be performed simultaneously. Alternatively, after the third leg 13 is lifted and joined to the frame 21F, the fourth leg 14 may be lifted and joined to the frame 21F.

[0029] (Regarding the third joining process) FIG. 5 is a diagram showing a state in which the deck slab 30 is being erected by the crane CL. The third joining process is a process of joining braces 20 to the third leg 13 and the fourth leg 14 that are lifted in the lifting process after the second joining process, and to the first leg 11 or the second leg 12 that is laid on the ground in the first placement process. Note that the horizontal brace 21 is joined to the first leg 11 and the second leg 12 as a frame 21F in the first joining process. That is, the brace 20 joined to the first leg 11 and the second leg 12 in the third joining process is a diagonal brace 22, as shown in FIG. 5 . In the third joining process, the first leg 11, the second leg 12, and the third leg 13 are joined to the diagonal brace 22 by welding.

[0030] (About the first installation step) Figure 6 is a diagram showing a state in which one deck slab 30 is installed at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on one side in the specified direction D. The first installation step is a process of installing one deck slab 30 at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on one side in the predetermined direction D. That is, the first installation step is a process of attaching the deck slab 30 to a configuration in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are joined to each other by braces 20. In the first embodiment, the first installation step is performed as follows.

[0031] That is, first, the deck slab 30 is laid on the ground. At this time, as described above, one side 30S of the deck slab 30, which is, for example, rectangular, is laid on the ground and is set to a state in which it is approximately perpendicular to the first leg 11 and the second leg 12. Note that, as shown in FIG. 5 , the one side 30S is a side of the deck slab 30 whose both ends are joined to the first leg 11 and the second leg 12. Furthermore, the state in which the one side 30S of the deck slab 30 is approximately perpendicular to the first leg 11 and the second leg 12 means that the crossing angle between the one side 30S and the first leg 11 and the second leg 12 is in the range of 85° to 95°. 1, when the jacket structure 1 is placed offshore, the leg 10 is inclined relative to the vertical direction. In contrast, when the jacket structure 1 is placed offshore, the deck slab 30 is positioned horizontally. That is, when the jacket structure 1 is placed offshore, the leg 10 and the deck slab 30 are joined at an inclination to each other. In this embodiment, the state in which one side 30S of the deck slab 30 is approximately perpendicular to the first leg 11 and the second leg 12 may mean that the one side 30S of the deck slab 30 and the first leg 11 and the second leg 12 are positioned in accordance with the state in which the jacket structure 1 is placed offshore.

[0032] In the first installation step, from the above-described state, the deck slab 30 is rotated around one side 30S as a rotation axis. That is, as shown in FIG. 5, the side of the deck slab 30 that is paired with the side 30S is lifted by a crane CL. In this way, the deck slab 30 is erected while the side 30S of the deck slab 30 remains in contact with the ground. After the deck slab 30 is erected, as shown in FIG. 6, the deck slab 30 is installed at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on one side in the predetermined direction D. The legs 10 and the deck slab 30 are joined, for example, by welding.

[0033] (About the second installation step) FIG. 7 is a diagram showing the state in which the window mat 40 is being erected by the crane CL. Figure 8 is a diagram showing a state in which one mud mat 40 is installed at the end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14, that is, at the end on the other side in the specified direction D. The second installation step is a process of installing one mud mat 40 at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on the other side in the predetermined direction D. That is, the second installation step is a process of attaching the mud mat 40 to a configuration in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are joined to each other by the braces 20. In the first embodiment, the second installation step is performed as follows.

[0034] That is, first, the mud mat 40 is laid on the ground. At this time, one side 40S of the mud mat 40, which is rectangular as described above, is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. As shown in FIG. 7 , the one side 40S is a side of the mud mat 40 whose both ends are joined to the first leg 11 and the second leg 12. The state in which the one side 40S of the mud mat 40 is approximately perpendicular to the first leg 11 and the second leg 12 means that the crossing angle between the one side 40S and the first leg 11 and the second leg 12 is in the range of 85° to 95°. 1, when the jacket structure 1 is placed offshore, the legs 10 are inclined relative to the vertical. In contrast, when the jacket structure 1 is placed offshore, the mud mats 40 are placed horizontally along the seabed. That is, when the jacket structure 1 is placed offshore, the legs 10 and the mud mats 40 are joined at an inclination to each other. In this embodiment, the state in which one side 40S of the mud mat 40 is approximately perpendicular to the first leg 11 and the second leg 12 may mean that the one side 40S of the mud mat 40 and the first leg 11 and the second leg 12 are positioned in accordance with the state in which the jacket structure 1 is placed offshore.

[0035] In the second installation step, the mud mat 40 is rotated from the above-described state around one side 40S as a rotation axis. That is, as shown in FIG. 7, the side of the mud mat 40 that is paired with the side 40S is lifted by a crane CL. In this way, the mud mat 40 is erected while the side 40S of the mud mat 40 remains in contact with the ground. After the mud mat 40 is erected, as shown in FIG. 8, the mud mat 40 is installed at the end of each of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on the other side in the predetermined direction D. The legs 10 and the mud mat 40 are joined by, for example, welding.

[0036] The jacket structure 1 according to the first embodiment is assembled through the above steps. Note that a boat landing or other configuration may be attached to the third leg 13 or the fourth leg 14 that is lifted in the lifting step. This makes it possible to prevent the boat landing or other configuration from interfering with the ground during fabrication of the jacket structure 1, compared to when a boat landing or other configuration is attached to the first leg 11 or the second leg 12 that is laid on the ground.

[0037] As described above, the method for assembling the jacket structure 1 according to the first embodiment includes a first arrangement step and a first connection step. In the first arrangement step, the cylindrical first leg 11 and the cylindrical second leg 12 are laid on the ground so as to be approximately parallel to a predetermined direction D that is approximately parallel to the ground. In the first connection step, the first leg 11 and the second leg 12 laid on the ground in the first arrangement step are connected with a cylindrical brace 20. This allows the legs 10 laid on the ground to be fixed together by the brace 20. Therefore, for example, when assembling the jacket structure 1, a large-scale configuration, such as an assembly jig, required to support the legs 10 in an upright state is not required compared to connecting the first leg 11 and the second leg 12 to the brace 20 in an upright state. This therefore reduces the scale of the configuration used to assemble the jacket structure 1. This therefore reduces waste when assembling the jacket structure 1.

[0038] The assembly method further includes a first joining step. In the first joining step, a frame 21F composed of three or more braces 20, including the brace 20 connecting the first leg 11 and the second leg 12 in the first connecting step, is joined to the first leg 11 and the second leg 12 so that the frame 21F is aligned in a substantially vertical direction. This allows the legs 10 laid on the ground to be fixed together using the frame 21F composed of multiple braces 20. Furthermore, by aligning the frame 21F in a substantially vertical direction, the end of the frame 21F not connected to the first leg 11 and the second leg 12 is positioned away from the ground. This allows a new leg 10 (e.g., the third leg 13) to be connected to the end of the frame 21F not connected to the first leg 11 and the second leg 12. This makes it easy to connect the new leg 10 without moving the first leg 11 and the second leg 12. Therefore, the jacket structure 1 can be assembled efficiently.

[0039] The assembly method further includes a lifting step and a second joining step. That is, in the lifting step, the third leg 13 is lifted. Then, in the second joining step, the third leg 13 lifted in the lifting step is joined to the frame 21F that is joined to the first leg 11 and the second leg 12 in the first joining step. This allows the third leg 13 to be fixed to the first leg 11 and the second leg 12. Furthermore, by lifting the third leg 13, for example, the third leg 13 can be joined without rotating or moving the structure in which the first leg 11 and the second leg 12 are fixed by the frame 21F. This allows the space required for assembling the jacket structure 1 to be reduced.

[0040] The assembly method further includes a third joining step. In the third joining step, diagonal braces 22 are joined to the third leg 13 that is lifted in the lifting step after the second joining step, and to the first leg 11 or the second leg 12 that is laid on the ground in the first placement step. This allows the diagonal braces 22 to be provided in the jacket structure 1. This allows the jacket structure 1 to be reinforced more reliably.

[0041] The assembly method further includes a first installation step. In the first installation step, one deck slab 30 is installed at each end of the first leg 11, the second leg 12, and the third leg 13, that is, at an end on one side in the predetermined direction D. This allows the deck slab 30 to be installed in the jacket structure 1. Furthermore, the first leg 11, the second leg 12, and the third leg 13 can be more reliably fixed together using the deck slab 30.

[0042] The shape of the deck slab 30 is triangular or rectangular. This allows, for example, a triangular deck slab 30 to be used when there are three legs 10, and a rectangular deck slab 30 to be used when there are four legs 10. Therefore, the shape of the deck slab 30 can be made to better suit the number of legs 10. One side of the deck slab 30 is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. Then, in a first installation step, the deck slab 30 is installed at the end of each of the first leg 11, the second leg 12, and the third leg 13, which is on one side in the predetermined direction D, by rotating the deck slab 30 around the side of the deck slab 30 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 as a rotation axis. That is, when the deck slab 30 is attached to the jacket structure 1 in the middle of assembly, the deck slab 30 is raised from a state where it is laid on the ground. When raising the deck slab 30, the side of the deck slab 30 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 serves as the rotation axis. This allows, for example, the deck slab 30 to be transported in a lying state near the jacket structure 1 that is in the middle of being assembled. Therefore, the deck slab 30 can be transported more stably. Also, by using one side of the deck slab 30 as the rotation axis, the deck slab 30 can be erected with less force. Therefore, the work of erecting the deck slab 30 can be made more efficient.

[0043] The assembly method further includes a second installation step. In the second installation step, one mud mat 40 is installed at each end of the first leg 11, the second leg 12, and the third leg 13, the end on the other side in the predetermined direction D. This allows the mud mat 40 to be installed in the jacket structure 1. Furthermore, the first leg 11, the second leg 12, and the third leg 13 can be more reliably fixed together using the mud mat 40.

[0044] The shape of the window mat 40 is triangular or rectangular. This allows, for example, a triangular window mat 40 to be used when there are three legs 10, and a rectangular window mat 40 to be used when there are four legs 10. Therefore, the shape of the window mat 40 can be made to better match the number of legs 10. One side of the window mat 40 is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. Then, in the second installation step, the window mat 40 is installed at the end of each of the first leg 11, the second leg 12, and the third leg 13, which is the other end in the predetermined direction D, by rotating the window mat 40 around the side of the window mat 40 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 as the rotation axis. That is, when the window mat 40 is attached to the jacket structure 1 in the middle of assembly, the window mat 40 is erected from its state of being laid on the ground. When erecting the window mat 40, the side of the window mat 40 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 serves as the rotation axis. This allows, for example, the window mat 40 to be transported in a lying state near the jacket structure 1 that is in the middle of being assembled. Therefore, the window mat 40 can be transported more stably. Also, by using one side of the window mat 40 as the rotation axis, the window mat 40 can be erected with less force. Therefore, the work of erecting the window mat 40 can be made more efficient.

[0045] The assembly method further includes a second placement step. In the second placement step, before the lifting step, the third leg 13 is laid on the ground so that the first leg 11 is sandwiched between the second leg 12 and the third leg 13 and so that the third leg 13 is approximately parallel to the predetermined direction D. This reduces the distance the third leg 13 needs to be moved when connecting it to the jacket structure 1 in the middle of assembly, thereby shortening the time it takes for the crane CL to lift the third leg 13. This allows the lifting step to be performed efficiently. Also, the time the crane CL is tied up can be shortened.

[0046] (Second embodiment) Next, a method for assembling the jacket structure 1 of the second embodiment according to 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. In the second embodiment, a jacket structure 1 as shown in Fig. 1 is assembled in a lying state in a ground yard Y. Then, the completed jacket structure 1 is transported in a lying state by a transport ship and installed at the installation site by standing upright. In the second embodiment, the jacket structure 1 includes at least four legs 10: a first leg 11, a second leg 12, a third leg 13, and a fourth leg 14. The deck slab 30 and the mud mat 40 are both rectangular.

[0047] The assembly method of the jacket structure 1 according to the second embodiment includes a first placement process, a first connection process, a second placement process, a second connection process, a first lifting process, a second lifting process, a third connection process, a fourth connection process, a deck slab installation step, and a mud mat installation step (installation step).

[0048] FIG. 9 is a diagram showing a state in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are arranged so as to be substantially parallel to the predetermined direction D. As shown in FIG. As will be described later, in the second embodiment, the first leg 11 and the second leg 12 are connected to each other by the brace 20 in a first connecting step. The third leg 13 and the fourth leg 14 are connected to each other by the brace 20 in a second connecting step. At this time, as described above, in the jacket structure 1, the distance between adjacent legs 10 increases from the upper end to the lower end of the legs 10. Therefore, in the second embodiment, arranging the legs 10 so that they are approximately parallel to the predetermined direction D may also mean that each of the legs 10 is arranged along the predetermined direction D and in accordance with a state in which the jacket structure 1 is arranged offshore. FIG. 10 is a diagram showing a state in which the first leg 11 and the second leg 12, and the third leg 13 and the fourth leg 14 are connected by a brace 20. As shown in FIG. In the second embodiment, the first arrangement step is performed in the same manner as in the first embodiment, and therefore a description thereof will be omitted. In the second embodiment, when the first leg 11 and the second leg 12 are laid down, the direction to which the window mat 40 is attached is referred to as one side of the specified direction D, and the direction to which the deck slab 30 is attached is referred to as the other side of the specified direction D.

[0049] (Regarding the first connection process) 10, the first connecting step is a step of connecting the first leg 11 and the second leg 12, which are laid on the ground in the first placing step, with the brace 20. In the first connecting step, for example, the first leg 11 and the second leg 12 are connected to the brace 20 by welding. In the first connecting step of the second embodiment, the first leg 11 and the second leg 12 are connected using the diagonal brace 22 and the horizontal brace 21.

[0050] (Regarding the second placement process) The second arranging step is a step of arranging the third leg 13 and the fourth leg 14 in the same manner as the first arranging step. That is, the second arranging step is a step of laying the cylindrical third leg 13 and the cylindrical fourth leg 14 on the ground so that they are approximately parallel to the predetermined direction D, as shown in Fig. 9. Details of the second arranging step are similar to the arrangement of the first leg 11 and the second leg 12 in the first arranging step, and therefore will not be described here.

[0051] (Regarding the second connection process) The second connection step is a step of connecting the third leg 13 and the fourth leg 14 with the brace 20, similar to the first connection step. That is, the second connection step is a step of connecting the third leg 13 and the fourth leg 14, which have been laid on the ground in the second placement step, with the brace 20, as shown in Fig. 10. Details of the second connection step are similar to those of the connection of the first leg 11 and the second leg 12 in the first connection step, and therefore will not be described here.

[0052] In the second embodiment, the order of the first arrangement step, first connection step, second arrangement step, and second connection step can be carried out regardless of the order described above. That is, as long as the first arrangement step is performed before the first connection step, and the second arrangement step is performed before the second connection step, the order of the above four steps can be determined arbitrarily.

[0053] (Regarding the first lifting process) Figure 11 is a diagram showing a configuration in which the first leg 11 and the second leg 12 are connected by a brace 20, and a configuration in which the third leg 13 and the fourth leg 14 are connected by a brace 20, being erected by a crane CL. 11, four cranes CL simultaneously erect a configuration in which the first leg 11 and the second leg 12 are connected by the braces 20 and a configuration in which the third leg 13 and the fourth leg 14 are connected by the braces 20. However, this is not limiting, and two or one cranes CL may separately erect a configuration in which the first leg 11 and the second leg 12 are connected by the braces 20 and a configuration in which the third leg 13 and the fourth leg 14 are connected by the braces 20. 11, the first lifting step is a step of using a crane CL to erect the structure in which the first leg 11 and the second leg 12 are connected by the brace 20. That is, the first lifting step is a step in which one of the first leg 11 and the second leg 12 connected by the brace 20 in the first connecting step is laid on the ground, and the other is lifted so that the plane including the pipe axis of each of the first leg 11 and the second leg 12 is aligned approximately vertically. In the first lifting step, the structure in which the first leg 11 and the second leg 12 are connected by the brace 20 is erected as described above, so that the completed jacket structure 1 is laid on the ground.

[0054] In the first lifting step of the second embodiment, one of the first leg 11 and the second leg 12 is the first leg 11. That is, in the first lifting step of the second embodiment, the second leg 12 is lifted by the crane CL. Note that even after the second leg 12 is lifted, it is preferable that the first leg 11 remains supported by the first frame T1. In this case, the second frame T2 is removed as appropriate after the first connection step is completed. Alternatively, even after the second leg 12 is lifted, the first leg 11 may be supported by both the first frame T1 and the second frame T2. In the first lifting step, the first leg 11, which is one of the first leg 11 and the second leg 12, is rotated around the rotation axis. That is, in the first lifting step, the second leg 12 is lifted, and the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is rotated around the first leg 11 as the rotation axis. In this way, the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is erected while the first leg 11 remains supported by the first frame T1, the second frame T2, or both. Note that the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 may be fixed with a wire (not shown) after being erected by the crane CL. At this time, the crane CL may be detached from the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20.

[0055] (Regarding the second lifting process) 11, the second lifting step is a step of using a crane CL to erect the configuration in which the third leg 13 and the fourth leg 14 are connected by the braces 20. That is, the second lifting step is a step in which one of the third leg 13 and the fourth leg 14 connected by the braces 20 in the second connecting step is laid on the ground, and the other is lifted so that the plane including the pipe axis of each of the third leg 13 and the fourth leg 14 is aligned substantially vertically. In the second lifting process, the structure in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is erected as described above, so that the completed jacket structure 1 is laid on the ground.

[0056] In the second lifting step of the second embodiment, one of the third leg 13 and the fourth leg 14 is the third leg 13. That is, in the second lifting step of the second embodiment, the fourth leg 14 is lifted by the crane CL. Note that even after the fourth leg 14 is lifted, it is preferable that the third leg 13 remains supported by the first frame T1. In this case, the second frame T2 is removed as appropriate after the second connection step is completed. Alternatively, even after the fourth leg 14 is lifted, the third leg 13 may be supported by both the first frame T1 and the second frame T2. In the second lifting step, the third leg 13, which is the other of the third leg 13 and the fourth leg 14, is rotated as the axis of rotation. That is, in the second lifting step, the fourth leg 14 is lifted, and the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is rotated as the axis of rotation. In this way, the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is erected while the third leg 13 remains supported by the first frame T1, the second frame T2, or both. Note that the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 may be fixed by a wire (not shown) after being erected by the crane CL. At this time, the crane CL may be detached from the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20.

[0057] (Regarding the third connection process) Figure 12 is a diagram showing a configuration in which the first leg 11 and the second leg 12 are connected by a brace 20 and a configuration in which the third leg 13 and the fourth leg 14 are connected by a brace 20, both connected by a brace 20. As shown in Fig. 12 , the third connection step is a step of connecting the other of the first leg 11 and the second leg 12, which are lifted in the first lifting step, to the other of the third leg 13 and the fourth leg 14, which are lifted in the second lifting step, with a brace 20. That is, in the third connection step, the second leg 12 and the fourth leg 14, which are lifted in the first lifting step and the second lifting step, respectively, are connected with the brace 20. At this time, the second leg 12 and the fourth leg 14 are connected to the brace 20 by welding. In the third connection step, the second leg 12 and the fourth leg 14 are connected using a diagonal brace 22 and a horizontal brace 21. As a result, the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 and the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 are connected by the brace 20. In the third connecting step, the second leg 12 and the fourth leg 14 are first connected by the diagonal brace 22. Then, the horizontal brace 21 is attached as appropriate. In this way, the frame 21F is formed by the horizontal brace 21. Alternatively, the frame 21F may be formed first by the horizontal brace 21, and then the second leg 12 and the fourth leg 14 may be connected by the diagonal brace 22. Alternatively, the formation of the frame 21F may be performed from the third connecting step to the fourth connecting step described next. Note that, at the time of the second lifting step before the third connection step, the brace 20 connecting the fourth leg 14 and the second leg 12 may be attached in advance to the fourth leg 14 having a structure in which the third leg 13 and the fourth leg 14 are connected by the brace 20. This may reduce or eliminate the need for work at height to connect the brace 20 to the fourth leg 14 when connecting the fourth leg 14 and the second leg 12 in the third connection step.

[0058] (Regarding the fourth connection step) As shown in Fig. 12, the fourth connection step is a step of connecting one of the first leg 11 and the second leg 12, which is laid on the ground in the first lifting step, to one of the third leg 13 and the fourth leg 14, which is laid on the ground in the second lifting step, with a brace 20. That is, in the fourth connection step, after the first lifting step and the second lifting step, the first leg 11 and the third leg 13, which are supported by the first frame T1 or the second frame T2, or both, are connected with the brace 20. At this time, the first leg 11 and the third leg 13 are connected with the brace 20 by welding. In the fourth connection step, the first leg 11 and the third leg 13 are connected using a diagonal brace 22 and a horizontal brace 21. In the second embodiment, the frame 21F of the jacket structure 1 is formed at least before the deck slab installation step described next.

[0059] (About the deck installation steps) The deck slab installation step corresponds to the first installation step in the first embodiment. That is, the deck slab installation step is a process of installing one deck slab 30 at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on the other side in the predetermined direction D. That is, the deck slab installation step is a process of attaching the deck slab 30 to a configuration in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are joined to each other by the braces 20. In the first embodiment, the deck slab installation step is performed as follows.

[0060] That is, first, the deck slab 30 is laid on the ground. At this time, as described above, one side 30S of the deck slab 30, which is rectangular, is laid on the ground and is approximately perpendicular to one of the first leg 11 and the second leg 12 that is laid on the ground in the first lifting step, and one of the third leg 13 and the fourth leg 14 that is laid on the ground in the second lifting step. That is, in the second embodiment, the one side 30S of the deck slab 30 is approximately perpendicular to the first leg 11 and the third leg 13. Note that, as shown in FIG. 5 , the one side 30S of the deck slab 30 is the side of the deck slab 30 whose both ends are joined to the first leg 11 and the third leg 13. In addition, when one side 30S of the deck slab 30 is approximately perpendicular to the first leg 11 and the third leg 13, the intersection angle between the one side 30S and the first leg 11 and the third leg 13 is in the range of 85° or more and 95° or less. 1, when the jacket structure 1 is placed offshore, the leg 10 is inclined relative to the vertical direction. In contrast, when the jacket structure 1 is placed offshore, the deck slab 30 is positioned horizontally. That is, when the jacket structure 1 is placed offshore, the leg 10 and the deck slab 30 are joined at an incline to each other. In this embodiment, the state in which one side 30S of the deck slab 30 is approximately perpendicular to the first leg 11 and the third leg 13 may mean that the one side 30S of the deck slab 30 and the first leg 11 and the third leg 13 are positioned in accordance with the state in which the jacket structure 1 is placed offshore.

[0061] In the deck installation step, the deck slab 30 is rotated from the above-described state around one side 30S as the rotation axis. That is, as shown in FIG. 5, the side of the deck slab 30 that is paired with the side 30S is lifted by a crane CL. In this way, the deck slab 30 is erected while the side 30S of the deck slab 30 remains in contact with the ground. After the deck slab 30 is erected, the deck slab 30 is installed at the end of each of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, which is the end on the other side in the predetermined direction D, as shown in FIG. 6. The legs 10 and the deck slab 30 are joined, for example, by welding.

[0062] (Mat installation steps) The mud mat installation step (installation step) corresponds to the second installation step in the first embodiment. That is, the mud mat installation step is a process of installing one mud mat 40 at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at the end on one side in the predetermined direction D. That is, the mud mat installation step is a process of attaching the mud mat 40 to a configuration in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are joined to each other by the braces 20. In the first embodiment, the mud mat installation step is performed as follows.

[0063] That is, first, the window mat 40 is laid on the ground. At this time, one side 40S of the window mat 40, which is rectangular as described above, is laid on the ground and is approximately perpendicular to one of the first leg 11 and the second leg 12 that is laid on the ground in the first lifting step, and one of the third leg 13 and the fourth leg 14 that is laid on the ground in the second lifting step. That is, in the second embodiment, the one side 40S of the window mat 40 is approximately perpendicular to the first leg 11 and the third leg 13. Note that, as shown in FIG. 7 , the one side 40S of the window mat 40 is the side of the window mat 40 whose both ends are joined to the first leg 11 and the third leg 13. In addition, when one side 40S of the mud mat 40 is approximately perpendicular to the first leg 11 and the third leg 13, the intersection angle between the one side 40S and the first leg 11 and the third leg 13 is in the range of 85° or more and 95° or less. 1, when the jacket structure 1 is placed offshore, the legs 10 are inclined relative to the vertical. In contrast, when the jacket structure 1 is placed offshore, the mud mats 40 are placed horizontally along the seabed. That is, when the jacket structure 1 is placed offshore, the legs 10 and the mud mats 40 are joined at an incline to each other. In this embodiment, the state in which one side 40S of the mud mat 40 is approximately perpendicular to the first leg 11 and the third leg 13 may mean that the one side 40S of the mud mat 40 and the first leg 11 and the third leg 13 are positioned in accordance with the state in which the jacket structure 1 is placed offshore.

[0064] In the mud mat installation step, the mud mat 40 is rotated from the above-described state around one side 40S as the rotation axis. That is, as shown in FIG. 7, the side of the mud mat 40 that is paired with the side 40S is lifted by the crane CL. In this way, the mud mat 40 is erected while the side 40S of the mud mat 40 remains in contact with the ground. After the mud mat 40 is erected, as shown in FIG. 8, a mud mat 40 is installed at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at one end in the predetermined direction D. The legs 10 and the mud mat 40 are joined, for example, by welding. The jacket structure 1 according to the second embodiment is assembled through the above steps.

[0065] As described above, the method for assembling the jacket structure 1 according to the second embodiment further includes a second arrangement step and a second connection step. In the second arrangement step, the cylindrical third leg 13 and the cylindrical fourth leg 14 are laid on the ground so that they are approximately parallel to the predetermined direction D. In the second connection step, the third leg 13 and the fourth leg 14 laid on the ground in the second arrangement step are connected with the brace 20. As a result, for example, the jacket structure 1 can be formed by connecting a configuration in which the first leg 11 and the second leg 12 are connected with the brace 20 and a configuration in which the third leg 13 and the fourth leg 14 are connected with the brace 20. Therefore, for example, work at height can be reduced compared to a method in which the third leg 13 and the fourth leg 14 are hoisted and connected to a configuration in which the first leg 11 and the second leg 12 are connected with a frame 21F.

[0066] The assembly method further includes a first lifting step, a second lifting step, and a third connecting step. In the first lifting step, one of the first leg 11 and the second leg 12 connected by the brace 20 in the first connecting step is laid on the ground, and the other is lifted so that the plane containing each pipe axis is aligned approximately vertically. In the second lifting step, one of the third leg 13 and the fourth leg 14, which are connected by the brace 20 in the second connecting step, is laid on the ground, and the other is lifted so that the plane containing each pipe axis is aligned approximately vertically. In the third connecting step, the other of the first leg 11 and the second leg 12, which are lifted in the first lifting step, is connected by the brace 20 to the other of the third leg 13 and the fourth leg 14, which are lifted in the second lifting step. That is, in a first lifting step, a configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is erected. In a second lifting step, a configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is erected. Then, in a third connecting step, the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 and the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 are connected to each other. This reduces the amount of work at height compared to, for example, a method in which the third leg 13 and the fourth leg 14 are lifted and connected to a configuration in which the first leg 11 and the second leg 12 are connected by a frame 21F.

[0067] The assembly method further includes a fourth connecting step in which one of the first leg 11 and the second leg 12, which is laid on the ground in the first lifting step, is connected to one of the third leg 13 and the fourth leg 14, which is laid on the ground in the second lifting step, by a brace 20. This allows the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 to be connected to each other by the brace 20. This allows the jacket structure 1 to be reinforced more reliably.

[0068] The assembly method further includes an installation step. In the installation step, one window mat 40 is installed at each end of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14, that is, at one end in the predetermined direction D. This allows the window mat 40 to be installed in the jacket structure 1. Furthermore, the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 can be more reliably fixed together using the window mat 40. One side of the window mat 40 is laid on the ground and is approximately perpendicular to one of the first leg 11 and the second leg 12 laid on the ground in the first lifting step and one of the third leg 13 and the fourth leg 14 laid on the ground in the second lifting step. Then, in the installation step, the window mat 40 is installed at one end of each of the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 by rotating the window mat 40 about the side that is approximately perpendicular to one of the first leg 11 and the second leg 12 and one of the third leg 13 and the fourth leg 14 laid on the ground as the axis of rotation. In other words, when the window mat 40 is attached to the jacket structure 1 in the middle of assembly, the window mat 40 is erected from its state of being laid on the ground. When the mud mat 40 is erected, one side of the mud mat 40 that is approximately perpendicular to one of the first leg 11 and the second leg 12, and one of the third leg 13 and the fourth leg 14 that are laid on the ground, serves as the axis of rotation. This allows, for example, the window mat 40 to be transported in a lying state near the jacket structure 1 that is in the middle of being assembled. Therefore, the window mat 40 can be transported more stably. Also, by using one side of the window mat 40 as the rotation axis, the window mat 40 can be erected with less force. Therefore, the work of erecting the window mat 40 can be made more efficient.

[0069] (Third embodiment) Next, a method for assembling the jacket structure 1 of the third embodiment according to the present disclosure will be described with reference to FIG. In this third embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted, with only the differences being described. In the third embodiment, a plurality of jacket structures 1 are manufactured at the same time in one yard Y.

[0070] Hereinafter, the jacket structure 1 (see FIG. 1) in the first and second embodiments will be referred to as a first jacket structure. A jacket structure 1 having the same configuration as the first jacket structure and manufactured simultaneously with the first jacket structure will be referred to as a second jacket structure (not shown). In the following description, the components of the second jacket structure that correspond to the first leg 11 and the second leg 12 of the first jacket structure are referred to as the fifth leg 15 and the sixth leg 16, respectively. Also, the horizontal brace 21 provided in the first jacket structure is referred to as the first horizontal brace. The horizontal brace 21 provided in the second jacket structure is referred to as the second horizontal brace. In the third embodiment, when the first leg 11 and the second leg 12 are laid down, the direction to which the deck slab 30 is attached is referred to as one side of the specified direction D, and the direction to which the window mat 40 is attached is referred to as the other side of the specified direction D.

[0071] In the third embodiment, the multiple jacket structures 1 are manufactured by appropriately selecting either the process described in the first embodiment or the process described in the second embodiment. In the third embodiment, only the processes corresponding to the first arrangement process and the first connection process in the first or second embodiment will be described. The other processes are performed in the same way as in the first or second embodiment, and therefore descriptions thereof will be omitted. The method for assembling the jacket structure 1 according to the third embodiment includes at least a first arranging step, a second arranging step, a first connecting step, and a second connecting step.

[0072] (Regarding the first placement process) FIG. 13 is a diagram showing a state in which the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 are arranged so as to be substantially parallel to the predetermined direction D. As shown in FIG. The first arrangement step is the same as in the first and second embodiments. That is, the first arrangement step is a step of laying the first leg 11 and the second leg 12, which are parts of the first jacket structure, on the ground so that they are approximately parallel to a predetermined direction D that is approximately parallel to the ground. The details of the first arrangement step are the same as in the first embodiment, and therefore will not be described again.

[0073] (Regarding the second placement process) The second arranging step in the third embodiment corresponds to the first arranging step in the second jacket structure. That is, the second arranging step is a step of laying the fifth leg 15 and the sixth leg 16, which are parts of the second jacket structure, on the ground so that they are approximately parallel to the predetermined direction D. The details of the second arranging step are the same as those of the first arranging step, and therefore will not be described again.

[0074] (Regarding the first connection process) The first connecting step is the same as in the first and second embodiments. That is, the first connecting step is a step of connecting the first leg 11 and the second leg 12, which have been laid on the ground in the first placing step, with a first horizontal brace. The details of the first connecting step are the same as in the first embodiment, and therefore will not be described again.

[0075] (Regarding the second connection process) The second connecting step in the third embodiment corresponds to the first connecting step in the second jacket structure. That is, the second connecting step is a step of connecting the fifth leg 15 and the sixth leg 16, which were laid on the ground in the second placement step, with the second horizontal brace. The details of the second connecting step are the same as those of the first connecting step, and therefore will not be described here.

[0076] (Regarding leg placement) In the first and second arrangement steps of the third embodiment, the arrangement of the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 is as follows. The distance between the end of the first leg 11 on one side in the predetermined direction D and the end of the second leg 12 on one side is shorter than the distance between the end of the first leg 11 on the other side in the predetermined direction D and the end of the second leg 12 on the other side. The distance between the end of the fifth leg 15 on one side in the predetermined direction D and the end of the sixth leg 16 on one side is longer than the distance between the end of the fifth leg 15 on the other side in the predetermined direction D and the end of the sixth leg 16 on the other side. That is, in the first and second arranging steps, when the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 are arranged, the top and bottom of the first jacket structure and the top and bottom of the second jacket structure are arranged alternately, thereby enabling the first jacket structure and the second jacket structure to be assembled in closer positions. 13, in the third embodiment, an area A3 between an area A1 sandwiched between the first leg 11 and the second leg 12 laid on the ground in the first placement step and an area A2 sandwiched between the fifth leg 15 and the sixth leg 16 laid on the ground in the second placement step is secured to an extent that a crawler crane (not shown) can pass through. This makes it possible to use the same crawler crane to assemble the first jacket structure using the first leg 11 and the second leg 12 and to assemble the second jacket structure using the fifth leg 15 and the sixth leg 16. This reduces the number of crawler cranes used. In the third embodiment, the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 are arranged as described above, so that the first jacket structure and the second jacket structure are assembled simultaneously. In the manner described above, the jacket structure 1 according to the third embodiment is assembled.

[0077] As described above, the method for assembling the jacket structure 1 according to the third embodiment includes the first arranging step, the second arranging step, the first connecting step, and the second connecting step. In the first placement process, the first leg 11 and the second leg 12, which will be part of the first jacket structure, are laid on the ground so that they are approximately parallel to a predetermined direction D that is approximately parallel to the ground. In the second placement process, the fifth leg 15 and the sixth leg 16, which will be part of the second jacket structure, are laid on the ground so that they are approximately parallel to the predetermined direction D. In the first connection process, the first leg 11 and the second leg 12 laid on the ground in the first placement process are connected with a first horizontal brace. In the second connection process, the fifth leg 15 and the sixth leg 16 laid on the ground in the second placement process are connected with a second horizontal brace. This allows the legs 10, which are laid on the ground, to be fixed together by the braces 20. Therefore, for example, when assembling the jacket structure 1, compared to connecting the first leg 11 and the second leg 12, and the fifth leg 15 and the sixth leg 16 to the braces 20 in an upright state, it is possible to reduce the need to fix them together using members other than the members that make up the jacket structure 1, such as assembly jigs. Therefore, it is possible to reduce waste when assembling the jacket structure 1. Furthermore, the distance between an end of the first leg 11 on one side in the predetermined direction D and an end of the second leg 12 on one side is shorter than the distance between an end of the first leg 11 on the other side in the predetermined direction D and an end of the second leg 12 on the other side. The distance between an end of the fifth leg 15 on one side in the predetermined direction D and an end of the sixth leg 16 on one side is longer than the distance between the end of the fifth leg 15 on the other side in the predetermined direction D and an end of the sixth leg 16 on the other side. That is, the first leg 11 and the second leg 12, and the fifth leg 15 and the sixth leg 16 are arranged so that the top and bottom of the first jacket structure and the top and bottom of the second jacket structure are staggered. This allows the first jacket structure and the second jacket structure to be assembled in closer positions. Therefore, the space required for assembling multiple jacket structures 1 can be reduced.

[0078] Furthermore, a crawler crane can pass through an area A3 between an area A1 sandwiched between the first leg 11 and the second leg 12 laid on the ground in the first placement step, and an area A2 sandwiched between the fifth leg 15 and the sixth leg 16 laid on the ground in the second placement step. This makes it easier to assemble the first jacket structure using the first leg 11 and the second leg 12, and the second jacket structure using the fifth leg 15 and the sixth leg 16, using a single crawler crane. This allows the assembly of multiple jacket structures 1 to be performed efficiently.

[0079] 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. For example, using the above-described method, in addition to the first jacket structure and the second jacket structure, a third jacket structure may be simultaneously produced. Not limited to this, four or more jacket structures 1 may also be simultaneously produced. In this case, it is preferable that adjacent jacket structures 1 are arranged in a staggered arrangement during production.

[0080] 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.

[0081] (Addendum) The method of assembling the jacket structure according to the embodiment can be understood, for example, as follows.

[0082] <1> A method for assembling a jacket structure according to one embodiment of the present disclosure is characterized by comprising a first placement process in which a cylindrical first leg and a cylindrical second leg are each laid on the ground so that they are approximately parallel to a predetermined direction that is approximately parallel to the ground, and a first connection process in which the first leg and the second leg laid on the ground in the first placement process are connected with a cylindrical brace.

[0083] The above-described jacket structure assembly method includes a first arrangement step and a first connection step. In the first arrangement step, the cylindrical first leg and the cylindrical second leg are laid on the ground so that they are approximately parallel to a predetermined direction that is approximately parallel to the ground. In the first connection step, the first leg and the second leg laid on the ground in the first arrangement step are connected with a cylindrical brace. This allows the legs laid on the ground to be fixed together by the brace. Therefore, for example, when assembling the jacket structure, a large-scale configuration, such as an assembly jig, required to support the first leg and the second leg in an upright state is not required, compared to when the first leg and the second leg are connected to the brace in an upright state. This allows the scale of the configuration used to assemble the jacket structure to be reduced. This allows for less waste when assembling the jacket structure.

[0084] <2> the above <1> The method for assembling a jacket structure according to the above may further include a first joining step of joining a frame made up of three or more braces including the brace to the first leg and the second leg so that the frame is aligned in a substantially vertical direction.

[0085] The assembly method further includes a first joining step. In the first joining step, a frame made up of three or more braces, including the brace whose first and second legs were connected in the first connecting step, is joined to the first and second legs so that the frame is aligned in a substantially vertical direction. This allows the legs laid on the ground to be fixed together using a frame made up of multiple braces. Also, by aligning the frame in a substantially vertical direction, the end of the frame not connected to the first and second legs is located away from the ground. This allows a new leg (e.g., a third leg) to be connected to the end of the frame not connected to the first and second legs. This makes it easy to connect the new leg without moving the first and second legs. This allows for efficient assembly of the jacket structure.

[0086] <3> the above <2> The method for assembling a jacket structure according to the above may further include a lifting step of lifting a third leg, and a second joining step of joining the third leg lifted in the lifting step to the frame joined in the first joining step.

[0087] The assembly method further includes a lifting step and a second joining step. That is, in the lifting step, the third leg is lifted. Then, in the second joining step, the third leg lifted in the lifting step is joined to the frame joined to the first leg and the second leg in the first joining step. This allows the third leg to be fixed to the first leg and the second leg. Furthermore, by lifting the third leg, for example, the third leg can be joined without rotating or moving the structure in which the first leg and the second leg are fixed by the frame. This reduces the space required for assembling the jacket structure.

[0088] <4> the above <3> In the method for assembling a jacket structure according to the above, a configuration may be adopted in which, after the second joining step, a third joining step is further provided in which a diagonal brace is joined to the third leg that is lifted in the lifting step and to the first leg or the second leg that is laid on the ground in the first placement step.

[0089] The assembly method further includes a third joining step. In the third joining step, diagonal braces are joined to the third leg that is lifted in the lifting step after the second joining step and to the first leg or the second leg that is laid on the ground in the first placement step. This allows the jacket structure to be provided with diagonal braces. This allows the jacket structure to be reinforced more reliably.

[0090] <5> the above <3> or <4> The method for assembling a jacket structure according to the present invention may further include a first installation step of installing one deck slab at each end of the first leg, the second leg, and the third leg, the end on one side in the predetermined direction.

[0091] The assembly method further includes a first installation step. In the first installation step, one deck slab is installed at each end of the first leg, the second leg, and the third leg, the end being on one side in the predetermined direction. This allows the deck slab to be installed in the jacket structure. Furthermore, the first leg, the second leg, and the third leg can be more reliably fixed together using the deck slab.

[0092] <6> the above <5> In the method for assembling a jacket structure according to the above, the deck slab may have a triangular or rectangular shape, one side of the deck slab is laid on the ground and is approximately perpendicular to the first leg and the second leg, and in the first installation step, the deck slab is installed at the end of each of the first leg, the second leg, and the third leg, which is on one side of the specified direction, by rotating the deck slab around one side of the deck slab as a rotation axis.

[0093] The shape of the deck is either triangular or rectangular. This allows, for example, a triangular deck to be used when there are three legs, and a rectangular deck to be used when there are four legs. This allows the shape of the deck to be more closely matched to the number of legs. Furthermore, one side of the deck slab is laid on the ground and is approximately perpendicular to the first leg and the second leg. Then, in a first installation step, the deck slab is installed at the end of each of the first leg, the second leg, and the third leg, which is one end on one side in a predetermined direction, by rotating the deck slab around the side of the deck slab that is laid on the ground and is approximately perpendicular to the first leg and the second leg as a rotation axis. In other words, when the deck slab is attached to the jacket structure in the middle of assembly, the deck slab is raised from a state where it is laid on the ground. Then, when the deck slab is raised, the side of the deck slab that is laid on the ground and is approximately perpendicular to the first leg and the second leg serves as the rotation axis. This allows, for example, the deck slab to be transported in a lying position near the jacket structure that is in the process of being assembled. This allows the deck slab to be transported more stably. Also, by using one side of the deck slab as the rotation axis, the deck slab can be erected with less force. This makes the work of erecting the deck slab more efficient.

[0094] <7> the above <5> or <6> The method for assembling the jacket structure according to the present invention may further include a second installation step of installing one mud mat at the end of each of the first leg, the second leg, and the third leg, which is on the other side in the specified direction.

[0095] The assembly method further includes a second installation step. In the second installation step, one mud mat is installed at each end of the first leg, the second leg, and the third leg that is on the other side in the predetermined direction. This allows the mud mat to be installed in the jacket structure. Furthermore, the first leg, the second leg, and the third leg can be more reliably fixed together using the mud mat.

[0096] <8> the above <7> In the method for assembling a jacket structure according to the above, the shape of the mud mat may be a triangle or a rectangle, one side of the mud mat is laid on the ground and is approximately perpendicular to the first leg and the second leg, and in the second installation step, the mud mat is installed at the end of each of the first leg, the second leg, and the third leg that is on the other side in the predetermined direction by rotating the mud mat around one side of the mud mat as a rotation axis.

[0097] The shape of the mud mat is triangular or rectangular. This allows, for example, a triangular mud mat to be used when there are three legs, and a rectangular mud mat to be used when there are four legs. This allows the shape of the mud mat to be more closely matched to the number of legs. Furthermore, one side of the mud mat is laid on the ground and is approximately perpendicular to the first leg and the second leg. Then, in the second installation step, the mud mat is installed at the end of each of the first leg, the second leg, and the third leg that is on the other side in the predetermined direction by rotating the mud mat around the side that is laid on the ground and is approximately perpendicular to the first leg and the second leg as the rotation axis. In other words, when attaching the mud mat to the jacket structure in the middle of assembly, the mud mat is erected from its state of being laid on the ground. When erecting the mud mat, the side that is laid on the ground and is approximately perpendicular to the first leg and the second leg serves as the rotation axis. This allows the mat to be transported in a lying position near the jacket structure being assembled, for example. This makes it possible to transport the mat more stably. Also, by using one side of the mat as the rotation axis, the mat can be erected with less force. This makes the work of erecting the mat more efficient.

[0098] <9> the above <3> from <8> In the method for assembling a jacket structure according to any one of the above aspects, a configuration may be adopted which further includes a second placement step of laying the third leg on the ground before the lifting step so that the first leg is sandwiched between the second leg and the third leg and so that the third leg is approximately parallel to the predetermined direction.

[0099] The assembly method further includes a second placement step. In the second placement step, before the lifting step, the third leg is laid on the ground so that the first leg is sandwiched between the second leg and the third leg and so that the third leg is approximately parallel to the predetermined direction. This reduces the distance the third leg needs to be moved when connecting it to the jacket structure in the middle of assembly, thereby shortening the time it takes to lift the third leg with the crane. This allows the lifting step to be performed efficiently. It also reduces the time the crane is required to be tied up.

[0100] <10> the above <1> The method for assembling a jacket structure according to the above aspect may further include a second placement step of laying each of the cylindrical third leg and the cylindrical fourth leg on the ground so that they are approximately parallel to the predetermined direction, and a second connection step of connecting the third leg and the fourth leg laid on the ground in the second placement step with a brace.

[0101] The assembly method further includes a second placement step and a second connection step. In the second placement step, the cylindrical third leg and the cylindrical fourth leg are laid on the ground so that they are approximately parallel to a predetermined direction. In the second connection step, the third leg and the fourth leg laid on the ground in the second placement step are connected with braces. This allows, for example, a jacket structure to be formed by standing and connecting a configuration in which the first leg and the second leg are connected with a brace and a configuration in which the third leg and the fourth leg are connected with a brace. Therefore, for example, work at height can be reduced compared to a method in which the third leg and the fourth leg are hoisted and connected to a configuration in which the first leg and the second leg are connected with a frame.

[0102] <11> the above <10> The jacket structure assembly method according to the above may further include a first lifting step in which one of the first leg and the second leg connected by a brace in the first connecting step is laid on the ground and the other is lifted so that a plane including the pipe axis of each leg is aligned approximately vertically; a second lifting step in which one of the third leg and the fourth leg connected by a brace in the second connecting step is laid on the ground and the other is lifted so that a plane including the pipe axis of each leg is aligned approximately vertically; and a third connecting step in which the other leg lifted in the first lifting step and the other leg lifted in the second lifting step are connected by a brace.

[0103] The assembly method further includes a first lifting step, a second lifting step, and a third connecting step. In the first lifting step, one of the first leg and the second leg connected by the brace in the first connecting step is laid on the ground, and the other is lifted so that the plane containing each pipe axis is aligned approximately vertically. In the second lifting step, one of the third leg and the fourth leg connected by the brace in the second connecting step is laid on the ground, and the other is lifted so that the plane containing each pipe axis is aligned approximately vertically. In the third connecting step, the other of the first leg and the second leg lifted in the first lifting step and the other of the third leg and the fourth leg lifted in the second lifting step are connected by a brace. That is, in a first lifting step, a configuration in which the first leg and the second leg are connected by a brace is erected. In a second lifting step, a configuration in which the third leg and the fourth leg are connected by a brace is erected. Then, in a third connecting step, the configuration in which the first leg and the second leg are connected by a brace and the configuration in which the third leg and the fourth leg are connected by a brace are connected to each other. This reduces the amount of work at height compared to, for example, a method in which the third leg and the fourth leg are hoisted and connected to a configuration in which the first leg and the second leg are connected by a frame.

[0104] <12> the above <11> The jacket structure assembly method according to the present invention may further include a fourth connection step of connecting, with a brace, one of the first leg and the second leg that is laid on the ground in the first lifting step and one of the third leg and the fourth leg that is laid on the ground in the second lifting step.

[0105] The assembly method further includes a fourth connecting step. In the fourth connecting step, one of the first leg and the second leg laid on the ground in the first lifting step is connected with a brace to one of the third leg and the fourth leg laid on the ground in the second lifting step. This allows the first leg, the second leg, the third leg, and the fourth leg to be connected to each other with a brace. This allows the jacket structure to be reinforced more reliably.

[0106] <13> the above <11> or <12> The method for assembling a jacket structure according to the above aspect may further include an installation step of installing one mud mat at one end of each of the first leg, the second leg, the third leg, and the fourth leg in the predetermined direction, wherein the mud mat has a rectangular shape, one side of which is laid on the ground and is approximately perpendicular to one of the first leg and the second leg laid on the ground in the first lifting step and one of the third leg and the fourth leg laid on the ground in the second lifting step, and wherein the installation step may involve rotating the mud mat around one side of the mud mat as an axis of rotation, thereby installing the mud mat at the one end of each of the first leg, the second leg, the third leg, and the fourth leg.

[0107] The assembly method further includes an installation step. In the installation step, one mud mat is installed at each end of the first leg, the second leg, the third leg, and the fourth leg, which is on one side in the predetermined direction. This allows the mud mat to be installed in the jacket structure. Furthermore, the first leg, the second leg, the third leg, and the fourth leg can be more reliably fixed together using the mud mat. One side of the mud mat is laid on the ground and is approximately perpendicular to one of the first leg and the second leg laid on the ground in the first lifting step and one of the third leg and the fourth leg laid on the ground in the second lifting step. Then, in the installation step, the mud mat is installed at one end of each of the first leg, the second leg, the third leg, and the fourth leg by rotating the mud mat about the side that is approximately perpendicular to one of the first leg and the second leg and one of the third leg and the fourth leg laid on the ground as the rotation axis. In other words, when the mud mat is attached to the jacket structure in the middle of assembly, the mud mat is erected from its state of being laid on the ground. When the mud mat is erected, one side of the mud mat that is approximately perpendicular to one of the first leg and the second leg and one of the third leg and the fourth leg that are laid on the ground serves as the axis of rotation. This allows the mat to be transported in a lying position near the jacket structure being assembled, for example. This makes it possible to transport the mat more stably. Also, by using one side of the mat as the rotation axis, the mat can be erected with less force. This makes the work of erecting the mat more efficient.

[0108] <14> A method for assembling a jacket structure according to one embodiment of the present disclosure includes a first arrangement step of laying a first leg and a second leg, which will be part of a first jacket structure, on the ground so that they are substantially parallel to a predetermined direction substantially parallel to the ground; a second arrangement step of laying a fifth leg and a sixth leg, which will be part of a second jacket structure, on the ground so that they are substantially parallel to the predetermined direction; a first connection step of connecting the first leg and the second leg laid on the ground in the first arrangement step with a first horizontal brace; and a second connection step of connecting the fifth leg and the sixth leg laid on the ground in the second arrangement step with a second horizontal brace. a distance between an end of the first leg that is on one side in the predetermined direction and an end of the second leg that is on the one side is shorter than a distance between an end of the first leg that is on the other side in the predetermined direction and an end of the second leg that is on the other side; and a distance between an end of the fifth leg that is on the one side in the predetermined direction and an end of the sixth leg that is on the one side is longer than a distance between an end of the fifth leg that is on the other side in the predetermined direction and an end of the sixth leg that is on the other side.

[0109] The above-described jacket structure assembling method includes a first arranging step, a second arranging step, a first connecting step, and a second connecting step. In the first placement process, the first leg and the second leg that will become part of the first jacket structure are laid on the ground so that they are approximately parallel to a predetermined direction that is approximately parallel to the ground. In the second placement process, the fifth leg and the sixth leg that will become part of the second jacket structure are laid on the ground so that they are approximately parallel to the predetermined direction. In the first connection process, the first leg and the second leg that were laid on the ground in the first placement process are connected with a first horizontal brace. In the second connection process, the fifth leg and the sixth leg that were laid on the ground in the second placement process are connected with a second horizontal brace. This allows the legs laid on the ground to be fixed together with the braces. Therefore, for example, when assembling the jacket structure, compared to connecting the first and second legs and the fifth and sixth legs with the braces in an upright state, it is possible to reduce the need to fix them together using members other than the members that make up the jacket structure, such as assembly jigs. This reduces waste when assembling the jacket structure. The distance between the end of the first leg on one side in the predetermined direction and the end of the second leg on one side is shorter than the distance between the end of the first leg on the other side in the predetermined direction and the end of the second leg on the other side, and the distance between the end of the fifth leg on one side in the predetermined direction and the end of the sixth leg on one side is longer than the distance between the end of the fifth leg on the other side in the predetermined direction and the end of the sixth leg on the other side. That is, the first and second legs, and the fifth and sixth legs are arranged so that the top and bottom of the first jacket structure and the top and bottom of the second jacket structure are staggered. This allows the first jacket structure and the second jacket structure to be assembled in closer positions. Therefore, the space required for assembling multiple jacket structures can be reduced.

[0110] <15> the above <14> In the jacket structure assembling method according to the present invention, a configuration may be adopted in which a crawler crane can pass through an area between the area sandwiched between the first leg and the second leg laid on the ground in the first placement step and an area sandwiched between the fifth leg and the sixth leg laid on the ground in the second placement step.

[0111] Furthermore, a crawler crane can pass through the area between the area sandwiched between the first leg and the second leg laid on the ground in the first placement step and the area sandwiched between the fifth leg and the sixth leg laid on the ground in the second placement step. This makes it easier to assemble the first jacket structure using the first leg and the second leg, and the second jacket structure using the fifth leg and the sixth leg, using a single crawler crane. This allows for efficient assembly of multiple jacket structures. [Explanation of symbols]

[0112] 1. Jacket structure 10 Legs 11 First Leg 12 Second Leg 13 Third Leg 14 Fourth Leg 15 5th Leg 16 6th Leg 20 braces 21 Horizontal brace 21F slot 22 Diagonal brace 30 Floor slab 40 Madmat CL Crane D Specified direction T1 First Mount T2 Second Mount Y yard

Claims

1. a first placement step of laying the cylindrical first leg and the cylindrical second leg on the ground so that they are approximately parallel to a predetermined direction that is approximately parallel to the ground; a first connecting step of connecting the first leg and the second leg laid on the ground in the first placing step with a cylindrical brace; A method for assembling a jacket structure, comprising:

2. a first joining step of joining a frame composed of three or more braces including the brace to the first leg and the second leg so that the frame is aligned in a substantially vertical direction; 2. The method for assembling a jacket structure according to claim 1, further comprising:

3. a lifting step of lifting the third leg; a second joining step of joining the third leg lifted in the lifting step to the frame joined in the first joining step; The method for assembling a jacket structure according to claim 2, further comprising:

4. a third joining step of joining a diagonal brace to the third leg lifted in the lifting step and the first leg or the second leg laid on the ground in the first placement step after the second joining step; 4. The method for assembling a jacket structure according to claim 3, further comprising:

5. a first installation step of installing one deck slab at each end of the first leg, the second leg, and the third leg, the end being on one side in the predetermined direction; 4. The method for assembling a jacket structure according to claim 3, further comprising:

6. The shape of the deck is triangular or rectangular, One side of the deck is laid on the ground and is approximately perpendicular to the first leg and the second leg; In the first installation step, the deck slab is installed at an end of each of the first leg, the second leg, and the third leg, which is on one side in the predetermined direction, by rotating the deck slab around one side of the deck slab as a rotation axis.

6. A method for assembling a jacket structure according to claim 5.

7. a second installation step of installing one mud mat at each end of the first leg, the second leg, and the third leg, the end being on the other side in the predetermined direction; 6. The method for assembling a jacket structure according to claim 5, further comprising:

8. The shape of the mud mat is triangular or rectangular, One side of the mud mat is laid on the ground and is approximately perpendicular to the first leg and the second leg; In the second installation step, the mud mat is installed at the end of each of the first leg, the second leg, and the third leg, which is on the other side in the predetermined direction, by rotating the mud mat around one side of the mud mat as a rotation axis.

8. A method for assembling a jacket structure according to claim 7.

9. a second placement step of laying the third leg on the ground so that the first leg is sandwiched between the second leg and the third leg and so that the third leg is approximately parallel to the predetermined direction before the lifting step; The method for assembling a jacket structure according to any one of claims 3 to 8, further comprising:

10. a second placement step of laying the cylindrical third leg and the cylindrical fourth leg on the ground so that they are substantially parallel to the predetermined direction; a second connecting step of connecting the third leg and the fourth leg laid on the ground in the second placing step with a brace; 2. The method for assembling a jacket structure according to claim 1, further comprising:

11. a first lifting step in which one of the first leg and the second leg connected by the brace in the first connecting step is laid on the ground and the other is lifted so that a plane including each pipe axis is aligned substantially vertically; a second lifting step in which one of the third leg and the fourth leg connected by the brace in the second connecting step is laid on the ground and the other is lifted so that a plane including each pipe axis is aligned substantially vertically; a third connecting step of connecting the other part lifted in the first lifting step and the other part lifted in the second lifting step with a brace; The method of assembling a jacket structure according to claim 10, further comprising:

12. a fourth connecting step of connecting, with a brace, one of the first leg and the second leg that is laid on the ground in the first lifting step and one of the third leg and the fourth leg that is laid on the ground in the second lifting step; 12. The method of assembling a jacket structure according to claim 11, further comprising:

13. an installation step of installing one mud mat at each end of the first leg, the second leg, the third leg, and the fourth leg, the end being on one side in the predetermined direction; Further provided with The shape of the mud mat is quadrangular, One side of the mud mat is laid on the ground and is approximately perpendicular to one of the first leg and the second leg that is laid on the ground in the first lifting step, and one of the third leg and the fourth leg that is laid on the ground in the second lifting step; In the installation step, the mud mat is installed at the end of each of the first leg, the second leg, the third leg, and the fourth leg, which is one of the ends, by rotating the mud mat around one side of the mud mat as a rotation axis. A method for assembling the jacket structure according to any one of claims 11 to 12.

14. a first placement step of laying the first leg and the second leg, which will be part of the first jacket structure, on the ground so that they are substantially parallel to a predetermined direction that is substantially parallel to the ground; a second placement step of laying the fifth leg and the sixth leg, which will be part of the second jacket structure, on the ground so that they are approximately parallel to the predetermined direction; a first connecting step of connecting the first leg and the second leg laid on the ground in the first placing step with a first horizontal brace; a second connecting step of connecting the fifth leg and the sixth leg laid on the ground in the second placing step with a second horizontal brace; Equipped with a distance between an end of the first leg that is on one side in the predetermined direction and an end of the second leg that is on the one side is shorter than a distance between an end of the first leg that is on the other side in the predetermined direction and an end of the second leg that is on the other side; a distance between an end of the fifth leg on one side in the predetermined direction and an end of the sixth leg on the one side is longer than a distance between an end of the fifth leg on the other side in the predetermined direction and an end of the sixth leg on the other side; A method for assembling a jacket structure.

15. a crawler crane can pass through an area between the area sandwiched between the first leg and the second leg laid on the ground in the first placement step and the area sandwiched between the fifth leg and the sixth leg laid on the ground in the second placement step; 15. A method for assembling a jacket structure according to claim 14.

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