How to assemble the jacket structure

Abstract

The objective is to provide a method for assembling a jacket structure that reduces the need to fix cylindrical legs lying on the ground together using components other than those that constitute the jacket structure. [Solution] The invention is characterized by comprising: a first placement step of laying each of 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 which is substantially parallel to the ground; and a first connection step of connecting the first leg 11 and the second leg 12, which were laid on the ground in the first placement step, with a cylindrical brace 20.

Description

Technical Field

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[0004]

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

Background Art

[0002] Conventionally, jacket structures have been assembled in the yard. Patent Document 1 discloses fixing legs to each other in a state where the legs are positioned horizontally on the ground. Patent Document 2 discloses that when constructing a jacket-type structure, two leg members are placed horizontally on the ground, a connecting member for connecting these leg members and a connecting member to another adjacent leg member are attached to fabricate a planar structure (hereinafter referred to as a panel), and a plurality of panels fabricated in this way are sequentially erected and the panels are joined to assemble the jacket-type structure, and an assembly jig that rotatably receives the lower chord member (the lowermost horizontal member) of the panel around its axis is used when erecting the panel. Patent Document 3 discloses a rotation receiving jig for a large planar structure that rotatably receives one side leg of a frame around a horizontal axis when assembling a large arrowhead-shaped structure used for oil drilling in the ocean, for example, in a state where the large structure is assembled horizontally using a plurality of planar structures (hereinafter referred to as frames) previously assembled on a horizontal plane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] To allow the jacket structure to be transported in a horizontal position after manufacturing, the jacket structure is sometimes manufactured in a horizontal position beforehand. Furthermore, during the assembly process of the jacket structure, when fixing the cylindrical legs together, it is necessary to streamline the work by avoiding the use of materials other than those that constitute the jacket structure. However, Patent Document 1 does not specifically disclose how to fix the legs together while they are positioned on the ground in a lying-down position. Furthermore, Patent Document 2 does not specifically disclose the connecting material used to connect the legs together. And Patent Document 3 does not disclose that the legs of the frame are cylindrical.

[0005] This disclosure is made in view of the circumstances described above, and aims to provide a method for assembling a jacket structure that can reduce the need to fix cylindrical legs lying on the ground together using members other than those constituting the jacket structure. [Means for solving the problem]

[0006] A method for assembling a jacket structure according to one aspect of the present disclosure is characterized by comprising: a first placement step of laying each of a cylindrical first leg and a cylindrical second leg on the ground so as to be substantially parallel to a predetermined direction substantially parallel to the ground; and a first connection step of connecting the first leg and the second leg, which were laid on the ground in the first placement step, with a brace. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a method for assembling a jacket structure that reduces the need to fix cylindrical legs lying on the ground together using members other than those constituting the jacket structure. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view of the jacket structure according to the embodiment. [Figure 2] This figure shows the first and second legs arranged so that they are approximately parallel to a predetermined direction. [Figure 3] This diagram shows the third and fourth legs positioned so as to sandwich the first and second legs, which are connected by diagonal braces. [Figure 4] This diagram shows the state in which the frame is joined to the first and second legs, and then the third and fourth legs are joined to the frame. [Figure 5] This diagram shows the deck slab being erected by a crane. [Figure 6] This diagram shows a state in which one floor slab is installed at one end of each of the first, second, third, and fourth legs, in a predetermined direction. [Figure 7] This figure shows the Madmat being raised by a crane. [Figure 8] This diagram shows a state in which one mat is installed at the other end of each of the first, second, third, and fourth legs in a predetermined direction. [Figure 9] This diagram shows the first, second, third, and fourth legs arranged to be approximately parallel to a predetermined direction. [Figure 10] This diagram shows the first and second legs, and the third and fourth legs, connected by braces. [Figure 11] This diagram shows the state in which the first and second legs are connected by a brace, and the third and fourth legs are connected by a brace, as they are being erected by a crane. [Figure 12] This diagram shows a configuration in which the first and second legs are connected by a brace, and a configuration in which the third and fourth legs are connected by a brace, both connected by a brace. [Figure 13] This diagram shows the first, second, fifth, and sixth legs arranged to be approximately parallel to a predetermined direction. [Modes for carrying out the invention]

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

[0010] (Regarding 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 or the like. As shown in FIG. 1, the jacket structure 1 includes legs 10, braces 20, a floor slab 30, and a mat 40.

[0011] (Regarding the Legs) The leg 10 is a cylindrical member 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. The four legs 10 all have the same configuration. Hereinafter, each of the four legs 10 included in the jacket structure 1 may be referred to as the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14. The floor slab 30 is installed at the upper end of the leg 10. Thus, the leg 10 supports the floor 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 distance between adjacent legs 10 is located so as to widen 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 with the direction from the upper end to the lower end of the jacket structure 1 as the axis. This makes it easier for the jacket structure 1 to support the floor slab 30 installed at the upper end of the leg 10. Also, the jacket structure 1 is structurally stabilized.

[0012] (Regarding the Brace) The brace 20 is a tubular member that connects multiple legs 10 of the jacket structure 1 to each other. The brace 20 reinforces the jacket structure 1. The brace 20 includes a horizontal brace 21 and a diagonal brace 22. Hereafter, the connection point between Leg 10 and Brace 20 is sometimes referred to as Leg Can.

[0013] (Regarding horizontal bracing) The horizontal braces 21 extend horizontally within the jacket structure 1. More specifically, in the first embodiment, the horizontal braces 21 are arranged horizontally between the four legs 10. Multiple horizontal braces 21 are provided at intervals in the height direction of the jacket structure 1. In the first embodiment, the horizontal braces 21 positioned between each leg 10 are provided at the same height. This forms the horizontal braces 21 in a rectangular shape, and the legs 10 are connected to each of the corners of the rectangular shape. Hereinafter, the rectangular shape formed by the horizontal braces 21 will be referred to as the frame 21F. The frame 21F may further include horizontal braces 21 connecting the diagonal corners of the rectangular shape. This may reinforce the structure of the frame 21F. In the first embodiment, it is preferable that the frame 21F is composed of at least three or more horizontal braces 21, including horizontal braces 21 connecting the legs 10 to each other.

[0014] (Regarding diagonal braces) The diagonal brace 22 extends diagonally to the horizontal in the jacket structure 1. The diagonal brace 22 connects, for example, two leg cans in two adjacent legs 10 in the circumferential direction of the jacket structure 1. The leg cans connected by the diagonal brace 22 are at different positions in the height direction, and are adjacent to each other in the height direction of the jacket structure 1. In this way, the diagonal brace 22 further reinforces the jacket structure 1.

[0015] As shown in Figure 1, for example, multiple diagonal braces 22 are provided between legs 10, extending vertically. In this case, the multiple diagonal braces 22 are arranged in a wave-like pattern in the vertical direction of the jacket structure 1. That is, adjacent diagonal braces 22 in the vertical direction of the jacket structure 1 are tilted in different directions. The leg camber to which adjacent diagonal braces 22 in the vertical direction of the jacket structure 1 are connected is common. As shown in Figure 1, the directions in which each of the diagonal braces 22 that are located at the same height and facing each other in the jacket structure 1 extend may be different. That is, the direction in which the diagonal brace 22 connecting one pair of two adjacent legs 10 in the circumferential direction extends may be different from the direction in which the diagonal brace 22 connecting the pair opposite to the aforementioned pair extends. In this case as well, however, it is preferable that the leg camber positions in the vertical direction are the same.

[0016] Alternatively, the diagonal braces 22 may all be tilted in the same direction, or two diagonal braces 22 may be placed at the same height to form an X shape. Furthermore, if the distance between the legs 10 is large, for example, as shown in Figure 1 for the lowest diagonal brace 22 of the jacket structure 1, the lower ends of the diagonal braces 22 may be positioned between the legs 10 so that two diagonal braces 22 are placed at the same height.

[0017] (Regarding the deck slab) The deck slab 30 is connected to the upper end of the leg 10. The deck slab 30 is, for example, a place where workers stand and work in the jacket structure 1. Alternatively, the deck slab 30 may be provided with superstructures that constitute an oil platform or the like. The shape of the floor slab 30 is determined appropriately according to the number of legs 10. That is, for example, if there are three legs 10, the floor slab 30 is triangular. In this case, each vertex of the triangle is connected to the upper end of the legs 10. As described above, in the first embodiment there are four legs 10. Therefore, in the first embodiment the floor slab 30 is quadrilateral. In this case, each corner of the floor slab 30 is connected to the upper end of each of the four legs 10.

[0018] (About Madmat) The Madmat 40 is connected to the lower end of the Leg 10. When the jacket structure 1 is erected on the seabed, the Madmat 40 is in contact with the seabed. In this way, the Madmat 40 increases the 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 mat 40 is determined appropriately according to the number of legs 10. That is, for example, if there are three legs 10, the mat 40 is triangular. In this case, each vertex of the triangle is connected to the upper end of the legs 10. As described above, in the first embodiment there are four legs 10. Therefore, in the first embodiment the mat 40 is a square. In this case, each corner of the mat 40 is connected to the lower end of each of the four legs 10. Furthermore, the shape of the Madmat 40 may be appropriately determined according to the soil properties of the seabed where the jacket structure 1 is installed. For example, if the seabed where the jacket structure 1 is installed is relatively soft, the Madmat 40 may be kept in the aforementioned triangular or rectangular shape to ensure sufficient contact area. For example, if the seabed where the jacket structure 1 is installed is relatively hard, the Madmat 40 may be made lighter by cutting out a portion of the aforementioned triangular or rectangular shape, while leaving a relatively large area around the connection point with the leg 10. The jacket structure 1 in the first embodiment is configured with the above-described components.

[0019] (Regarding the assembly method of the jacket structure) Next, the assembly method of the jacket structure 1 according to the first embodiment will be described. In the first embodiment, the jacket structure 1 is assembled in a horizontal position in a yard Y on the ground. The completed jacket structure 1 is then transported in a horizontal position by a transport ship (not shown) or the like, and installed by being raised upright at the installation site. The assembly method for the jacket structure 1 according to the first embodiment comprises a first placement step, a first connection step, a second placement step, a first joining step, a lifting step, a second joining step, a third joining step, a first installation step, and a second installation step.

[0020] (Regarding the first placement process) Figure 2 shows the state in which the first leg 11 and the second leg 12 are arranged to be approximately parallel to a predetermined direction D. The first placement step is to lay each of the cylindrical first leg 11 and the cylindrical second leg 12 on the ground so that they are approximately parallel to a predetermined direction D which is approximately parallel to the ground. The predetermined direction D being approximately 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, for example, from conditions such as the layout of the yard Y where the jacket structure 1 is manufactured. In this embodiment, the predetermined direction D is the direction in which the centerlines of the first leg 11 and the second leg 12 of the surface formed by the laid-down first leg 11 and second leg 12 are vertically upward in Figure 1. Furthermore, the first leg 11 and the second leg 12 being approximately parallel to the predetermined direction D means that the intersection angle between each of the first leg 11 and the second leg 12 and the predetermined direction D is 10° or less. Furthermore, when the first leg 11 and the second leg 12 are laid down, it is preferable that the angle of intersection between the pipe axes of the first leg 11 and the second leg 12 and the ground is 5° or less. In this embodiment, with the first leg 11 and the second leg 12 lying down as described above, the direction on which the floor slab 30 is attached is referred to as one of the predetermined directions D, and the direction on which the mat 40 is attached is referred to as the other of the predetermined directions D.

[0021] When the first leg 11 and the second leg 12 are laid down in the first placement process, the distance between one end of the first leg 11 and one end of the second leg 12 in a 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 ensures that, in the circumferential direction of the fabricated jacket structure 1, the distance between adjacent legs 10 increases as you move from the upper end to the lower end of the legs 10.

[0022] In the first placement process, the first leg 11 and the second leg 12 are supported by the first frame T1 and the second frame T2, as shown in Figure 2. Multiple first support frames T1 are provided at intervals along the longitudinal direction of the first leg 11 and the second leg 12. The first support frames T1 are provided, for example, to allow the jacket structure 1 to 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 support frames T1 can be lifted by a dolly (not shown). At this time, the dolly (not shown) moves under a support portion (not shown) provided on the first support frame T1 and lifts the first support frame T1. As a result, the dolly lifts the jacket structure 1 together with the first support frames T1, allowing the jacket structure 1 to be moved by the dolly. The second support frames T2 are provided in multiples with spacing between them, such as between the multiple first support frames T1 arranged as described above. If the first legs 11 and 2 legs 12 are supported only by the first support frames T1 before they are connected by the braces 20, the first legs 11 and 2 legs 12 may deform due to their own weight and the weight of the frame 21F. By providing the second support frames T2 between the first support frames T1, deformation of the first legs 11 and 2 legs due to their own weight and the weight of the frame 21F is suppressed. It is preferable that the second support frames T2 be removed when the assembly of the jacket structure 1 is completed and the dolly lifts the jacket structure 1 together with the first support frames T1. This is preferable to prevent the second support frames T2 from interfering with the dolly.

[0023] (Regarding the first connection process) Figure 3 shows a configuration in which the third leg 13 and the fourth leg 14 are positioned so as to sandwich the first leg 11 and the second leg 12, which are connected by the diagonal brace 22. The first connection step is the step of connecting the first leg 11 and the second leg 12, which are laid on the ground in the first placement step, with a brace 20. In the first connection step, for example, the first leg 11 and the second leg 12 and the brace 20 are connected by welding. In the first connection step, for example, the first leg 11 and the second leg 12 are connected by both an oblique brace 22 and a horizontal brace 21.

[0024] (Second placement process) The second placement step is to lay 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, as shown in Figure 3, and the third leg 13 is approximately parallel to a predetermined direction D. At this time, the third leg 13 is positioned such 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 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 installed parallel to the first leg 11, and the fourth leg 14 is installed parallel to the second leg 12. Here, scaffolding used for working at heights during the second joining process, which will be described later, may be pre-installed on the third leg 13 and the fourth leg 14. In this case, during the second placement process, the scaffolding provided 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 in order to prevent interference between the scaffolding and the ground. In the first embodiment, in the second positioning step, in addition to positioning the third leg 13 as described above, the fourth leg 14 is laid on the ground such that the second leg 12 is sandwiched between the first leg 11 and the fourth leg 14, and the fourth leg 14 is substantially parallel to the predetermined direction D. At this time, the fourth leg 14 is positioned such 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 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 will allow the subsequent processes, such as the lifting process described later, to proceed smoothly. In the first embodiment, the second placement step is performed before the first joining step and the lifting step. The second placement step may be performed after the first joining step, but it is preferable that it be performed at least before the lifting step.

[0025] (Regarding the first joining process) Figure 4 shows the state in which the frame 21F is joined to the first leg 11 and the second leg 12, and further, the third leg 13 and the fourth leg 14 are joined to the frame. The first joining step is to join a frame 21F, which is 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 such that the frame 21F is aligned substantially vertically. In the first embodiment, the frame 21F being aligned substantially vertically means that the angle of intersection between the frame 21F and the vertical direction is 10° or less. As mentioned above, the frame 21F is formed by horizontal braces 21. That is, the three or more braces 20, including the brace 20 connecting the legs 10, are all 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 the first joining step. In the first connection 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 Figure 1, when the jacket structure 1 is positioned at sea, the legs 10 are inclined with respect to the vertical. Then, as shown in Figure 4, in the first positioning step, the first legs 11 and 2 legs 12 are laid on the ground so as to be approximately parallel to a predetermined direction D which is approximately parallel to the ground. In the first joining step, the frame 21F is made to be approximately aligned with the vertical direction, in other words, the frame 21F is tilted appropriately with respect to the vertical direction by the angle of intersection between the first legs 11 and 2 legs 12 and the frame 21F in the completed jacket structure 1, so that when the jacket structure 1 is positioned at sea, the horizontal braces 21 are aligned with the horizontal direction and the legs 10 are inclined with respect to the vertical direction. In this embodiment, the frame 21F being approximately aligned with the vertical direction may mean that the frame 21F is tilted appropriately as described above.

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

[0028] (Regarding the second joining process) The second joining process involves joining the third leg 13, which is lifted in the lifting process, to the frame 21F, which is joined in the first joining process. In the second joining process, for example, the third leg 13 and the frame 21F are joined by welding. In the first embodiment, the fourth leg 14 is joined to the frame 21F in the same way as the third leg 13 by performing the lifting process and the second joining process multiple times. Note that the lifting process of the third leg 13 and the joining process of the fourth leg 14 may be performed simultaneously. Alternatively, the fourth leg 14 may be lifted and joined to the frame 21F after the third leg 13 has been lifted and joined to the frame 21F.

[0029] (Regarding the third joining process) Figure 5 shows the state in which the deck slab 30 is being raised by the crane CL. The third joining process is a process in which braces 20 are joined to the third leg 13 and fourth leg 14, which are lifted in the lifting process after the second joining process, and to the first leg 11 or second leg 12, which is laid on the ground in the first placement process. The horizontal brace 21 is joined to the first leg 11 and second leg 12 as a frame 21F in the first joining process. In other words, the brace 20 that is joined to the first leg 11 and second leg 12 in the third joining process is the diagonal brace 22, as shown in Figure 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] (Regarding the first installation step) Figure 6 shows a state in which one floor slab 30 is installed at one end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14, in a predetermined direction D. The first installation step is to install one floor slab 30 at one end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14, in a predetermined direction D. That is, the first installation step is to attach the floor slab 30 to a configuration in which each of the first leg 11, second leg 12, third leg 13, and fourth leg 14 is joined to each other by braces 20. In the first embodiment, the first installation step is carried out as follows.

[0031] In other words, first, the floor slab 30 is laid flat on the ground. At this time, as described above, one side 30S of the floor slab 30, which is a rectangle, is laid flat on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. As shown in Figure 5, one side 30S is the side of the floor slab 30 whose ends are joined to the first leg 11 and the second leg 12. Furthermore, the state in which one side 30S of the floor slab 30 is approximately perpendicular to the first leg 11 and the second leg 12 means that the intersection angle between one side 30S and the first leg 11 and the second leg 12 is in the range of 85° to 95°. Here, as shown in Figure 1, when the jacket structure 1 is positioned at sea, the legs 10 are inclined with respect to the vertical. In contrast, when the jacket structure 1 is positioned at sea, the deck slab 30 is positioned horizontally. That is, when the jacket structure 1 is positioned at sea, the legs 10 and the deck slab 30 are joined at an inclination relative 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 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 positioned at sea.

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

[0033] (Regarding the second installation step) Figure 7 shows the state in which the Madmat 40 is being erected by the crane CL. Figure 8 shows a state in which one Madmat 40 is installed at the other end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14 in a predetermined direction D. The second installation step is to install one Madmat 40 at each end of the first leg 11, second leg 12, third leg 13, and fourth leg 14, on the other end in a predetermined direction D. That is, the second installation step is to attach the Madmat 40 to a configuration in which each of the first leg 11, second leg 12, third leg 13, and fourth leg 14 is joined to each other by a brace 20. In the first embodiment, the second installation step is carried out as follows.

[0034] Specifically, first, the Madmat 40 is laid flat on the ground. At this time, one side 40S of the rectangular Madmat 40 is laid flat on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. As shown in Figure 7, one side 40S is the side of the Madmat 40 whose ends are joined to the first leg 11 and the second leg 12. Furthermore, the state in which one side 40S of the Madmat 40 is approximately perpendicular to the first leg 11 and the second leg 12 means that the intersection angle between one side 40S and the first leg 11 and the second leg 12 is in the range of 85° to 95°. Here, as shown in Figure 1, when the jacket structure 1 is positioned on the open sea, the leg 10 is inclined with respect to the vertical. In contrast, when the jacket structure 1 is positioned on the open sea, the madmat 40 is positioned horizontally along the seabed. That is, when the jacket structure 1 is positioned on the open sea, the leg 10 and the madmat 40 are joined at an angle to each other. In this embodiment, the state in which one side 40S of the madmat 40 is approximately perpendicular to the first leg 11 and the second leg 12 may mean that one side 40S of the madmat 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 positioned on the open sea.

[0035] In the second installation step, the Madmat 40 is rotated from the state described above, using one side 40S as the axis of rotation. That is, as shown in Figure 7, the side of the Madmat 40 that is opposite to one side 40S is lifted by the crane CL. This causes the Madmat 40 to be erected while one side 40S of the Madmat 40 remains in contact with the ground. After the Madmat 40 is erected, as shown in Figure 8, the Madmat 40 is installed at the ends of the first leg 11, second leg 12, third leg 13, and fourth leg 14, on the other end in the predetermined direction D. The legs 10 and the Madmat 40 are joined together, for example, by welding.

[0036] The assembly of the jacket structure 1 according to the first embodiment is carried out by the above steps. In addition, the third leg 13 or fourth leg 14 that is lifted in the lifting step may be fitted with a boat landing, for example. This makes it possible to reduce interference between the boat landing, etc., and the ground during the manufacturing of the jacket structure 1, compared to, for example, the case where the boat landing, etc., is fitted to the first leg 11 or second leg 12 that is laid on the ground.

[0037] As described above, the assembly method for the jacket structure 1 according to the first embodiment comprises a first placement step and a first connection step. In the first placement step, the cylindrical first leg 11 and the cylindrical second leg 12 are laid on the ground so as to be substantially parallel to a predetermined direction D substantially parallel to the ground. In the first connection step, the first leg 11 and the second leg 12, which were laid on the ground in the first placement step, are connected with a cylindrical brace 20. This allows the legs 10, which are laid on the ground, to be fixed together by the brace 20. Therefore, for example, when assembling the jacket structure 1, compared to the case where the first leg 11 and the second leg 12 are connected to the brace 20 while they are upright, it is possible to eliminate the need for large-scale configurations necessary to support the legs 10 in an upright position, such as assembly jigs. Therefore, the scale of the configuration used to assemble the jacket structure 1 can be reduced. Therefore, waste when assembling the jacket structure 1 can be reduced.

[0038] The assembly method further comprises a first joining step. In the first joining step, a frame 21F, which is composed of three or more braces 20 including the brace 20 that connected the first leg 11 and the second leg 12 in the first connection step, is joined to the first leg 11 and the second leg 12 so that the frame 21F is aligned approximately vertically. This allows the legs 10 lying on the ground to be fixed together using the frame 21F composed of multiple braces 20. At this time, by aligning the frame 21F approximately vertically, the ends of the frame 21F that are not connected to the first leg 11 and the second leg 12 are located away from the ground. This allows a new leg 10 (for example, a third leg 13) to be connected to the ends of the frame 21F that are not connected to the first leg 11 and the second leg 12. Therefore, it is possible to easily connect a 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 comprises a lifting step and a second joining step. Specifically, in the lifting step, the third leg 13 is lifted. Then, in the second joining step, the third leg 13, which was lifted in the lifting step, is joined to the frame 21F, which 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 configuration in which the first leg 11 and the second leg 12 are fixed to the frame 21F. Thus, the space required for assembling the jacket structure 1 can be reduced.

[0040] Furthermore, the assembly method further includes a third joining step. In the third joining step, after the second joining step, the diagonal brace 22 is joined to the third leg 13, which is lifted in the lifting step, and to the first leg 11 or second leg 12, which is laid on the ground in the first placement step. This allows the jacket structure 1 to be equipped with the diagonal brace 22. Thus, the jacket structure 1 can be reinforced more reliably.

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

[0042] Furthermore, the shape of the deck slab 30 is either triangular or quadrilateral. This allows, for example, a triangular deck slab 30 to be used when there are three legs 10, and a quadrilateral deck slab 30 to be used when there are four legs 10. Thus, the shape of the deck slab 30 can be better matched to the number of legs 10. Furthermore, one side of the floor slab 30 is laid flat on the ground and is approximately perpendicular to the first leg 11 and the second leg 12. Then, in the first installation step, the floor slab 30 is installed at one end of the first leg 11, the second leg 12, and the third leg 13, which are in a predetermined direction D, by rotating the floor slab 30 using the side that is laid flat on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 as the axis of rotation. In other words, when attaching the floor slab 30 to the jacket structure 1 which is under assembly, the floor slab 30 is raised from a state where it is laid flat on the ground. When raising the floor slab 30, the side that is laid flat on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 is used as the axis of rotation. This allows, for example, the floor slab 30 to be transported to the vicinity of the jacket structure 1, which is still under assembly, while lying down. Therefore, the transportation of the floor slab 30 can be performed more stably. In addition, by using one side of the floor slab 30 as the axis of rotation, the floor slab 30 can be raised with less force. Therefore, the work of raising the floor slab 30 can be made more efficient.

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

[0044] Furthermore, the shape of the window mat 40 is either triangular or square. This allows, for example, a triangular window mat 40 to be used when there are three legs 10, and a square window mat 40 to be used when there are four legs 10. Thus, the shape of the window mat 40 can be better matched to the number of legs 10. Furthermore, one side of the Madomat 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 Madomat 40 is installed at the ends of the first leg 11, the second leg 12, and the third leg 13, on the other end in a predetermined direction D, by rotating the Madomat 40 using the side of the Madomat 40 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 as the axis of rotation. In other words, when attaching the Madomat 40 to the jacket structure 1 that is under assembly, the Madomat 40 is raised from a state where it is laid on the ground. When raising the Madomat 40, the side of the Madomat 40 that is laid on the ground and is approximately perpendicular to the first leg 11 and the second leg 12 is used as the axis of rotation. This allows, for example, the Madomat 40 to be transported to the vicinity of the jacket structure 1 that is in the process of being assembled while lying down. Therefore, the transport of the Madomat 40 can be performed more stably. In addition, by using one side of the Madomat 40 as the axis of rotation, the Madomat 40 can be raised upright with less force. Therefore, the work of raising the Madomat 40 can be performed more efficiently.

[0045] Furthermore, 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 the third leg 13 is approximately parallel to a predetermined direction D. This reduces the distance the third leg 13 needs to be moved when connecting the third leg 13 to the jacket structure 1 during assembly, thereby shortening the time the third leg 13 is lifted by the crane CL. Thus, the lifting step can be performed efficiently. In addition, the restraining time of the crane CL can be reduced.

[0046] (Second Embodiment) Next, the assembly method of the jacket structure 1 of the second embodiment according to this disclosure will be described with reference to Figures 9 to 12. In this second embodiment, the same reference numerals are used for parts that are the same as those in the first embodiment, and their descriptions are omitted. Only the differences will be described. In the second embodiment, the jacket structure 1 shown in Figure 1 is assembled in a horizontal position in a yard Y on land. The completed jacket structure 1 is then transported in a horizontal position by a transport ship and installed by being raised upright at the installation site. In the second embodiment, the jacket structure 1 comprises at least four legs 10: a first leg 11, a second leg 12, a third leg 13, and a fourth leg 14. The floor slab 30 and the mat 40 are both rectangular in shape.

[0047] The assembly method for the jacket structure 1 according to the second embodiment comprises a first placement step, a first connection step, a second placement step, a second connection step, a first lifting step, a second lifting step, a third connection step, a fourth connection step, a floor slab installation step, and a mat installation step (installation step).

[0048] Figure 9 shows a state in which the first leg 11, the second leg 12, the third leg 13, and the fourth leg 14 are arranged to be substantially parallel to a predetermined direction D. As will be described later, in the second embodiment, the first leg 11 and the second leg 12 are connected to each other by braces 20 in the first connection step. The third leg 13 and the fourth leg 14 are connected to each other by braces 20 in the second connection step. At this time, as described above, in the jacket structure 1, the distance between adjacent legs 10 is positioned to increase from the upper end to the lower end of the leg 10. For this reason, in the second embodiment, when the legs 10 are positioned to be substantially parallel to a predetermined direction D, it may also mean that each of the legs 10 is positioned along the predetermined direction D and in accordance with the state in which the jacket structure 1 is positioned on the sea. Figure 10 shows the 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 the brace 20. In the second embodiment, the first placement step is performed in the same manner as in the first embodiment, so its description is omitted. In the second embodiment, when the first leg 11 and the second leg 12 are laid down, the direction on which the Madmat 40 is attached is referred to as one of the predetermined directions D, and the direction on which the floor slab 30 is attached is referred to as the other of the predetermined directions D.

[0049] (Regarding the first connection process) The first connection step is the step of connecting the first leg 11 and the second leg 12, which are laid on the ground in the first placement step, with a brace 20, as shown in Figure 10. In the first connection step, for example, the first leg 11 and the second leg 12 and the brace 20 are connected by welding. In the first connection 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 placement step is the step of placing the third leg 13 and the fourth leg 14 in the same manner as the first placement step. That is, the second placement step is the 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 Figure 9. Details of the second placement step are the same as those of the placement of the first leg 11 and the second leg 12 in the first placement step, so the explanation will be omitted.

[0051] (Regarding the second connection process) The second connection step is the process of connecting the third leg 13 and the fourth leg 14 with the brace 20, in the same manner as the first connection step. That is, the second connection step is the process of connecting the third leg 13 and the fourth leg 14, which were laid on the ground in the second placement step, with the brace 20, as shown in Figure 10. Details of the second connection step are the same as the connection of the first leg 11 and the second leg 12 in the first connection step, so the explanation will be omitted.

[0052] In the second embodiment, the order of the first placement step, the first connection step, the second placement step, and the second connection step is not limited to the order described above. That is, as long as the first placement step is performed before the first connection step, and the second placement step is performed before the second connection step, the order of the four steps described above can be determined arbitrarily.

[0053] (Regarding the first lifting process) Figure 11 shows the state in which the first leg 11 and the second leg 12 are connected by a brace 20, and the third leg 13 and the fourth leg 14 are connected by a brace 20, as they are erected by the crane CL. In Figure 11, four cranes CL simultaneously erect two configurations: one in which the first leg 11 and the second leg 12 are connected by a brace 20, and another in which the third leg 13 and the fourth leg 14 are connected by a brace 20. However, the configurations may also be erected separately by two or one crane CL, with the first leg 11 and the second leg 12 connected by a brace 20 and the third leg 13 and the fourth leg 14 connected by a brace 20. The first lifting process is the process of raising the configuration in which the first leg 11 and the second leg 12 are connected by a brace 20, as shown in Figure 11, using a crane CL. In other words, the first lifting process is the process in which one of the first leg 11 and the second leg 12, which are connected by the brace 20 in the first connection process, is laid on the ground, and the other is lifted so that the planes containing the respective pipe axes of the first leg 11 and the second leg 12 are aligned approximately vertically. In the first lifting process, the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is raised as described above, so that the completed jacket structure 1 is laid down 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. It is preferable that the first leg 11 remains supported by the first frame T1 even after the second leg 12 has been lifted. In this case, the second frame T2 is removed as appropriate after the completion of the first connection step. Alternatively, the first leg 11 may be supported by both the first frame T1 and the second frame T2 even after the second leg 12 has been lifted. In the first lifting process, the first leg 11, which is one of the two legs 12, is rotated around the axis of rotation. That is, in the first lifting process, by lifting the second leg 12, 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 axis of rotation. In this way, the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is raised upright while the first leg 11 remains supported by the first frame T1 or the second frame T2 or both. After the configuration in which the first leg 11 and the second leg 12 are connected by the brace 20 is raised upright by the crane CL, it may be fixed by a wire (not shown). 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) The second lifting process, as shown in Figure 11, is the process of raising the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 using the crane CL. In other words, the second lifting process is the process in which one of the third leg 13 and the fourth leg 14, which are connected by the brace 20 in the second connection process, is laid on the ground, and the other is lifted so that the planes containing the respective pipe axes of the third leg 13 and the fourth leg 14 are aligned approximately vertically. In the second lifting process, the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is raised as described above, so that the completed jacket structure 1 is laid down 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. It is preferable that the third leg 13 remains supported by the first frame T1 even after the fourth leg 14 has been lifted. In this case, the second frame T2 is removed as appropriate after the completion of the second connection step. Alternatively, the third leg 13 may be supported by both the first frame T1 and the second frame T2 even after the fourth leg 14 has been lifted. In the second lifting process, the third leg 13, which is the other of the third leg 13 and the fourth leg 14, is rotated around the third leg 13 as the axis of rotation. That is, in the second lifting process, by lifting the fourth leg 14, the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is rotated around the third leg 13 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 raised upright while the third leg 13 remains supported by the first frame T1 or the second frame T2 or both. After the configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20 is raised upright by the crane CL, it may be fixed by a wire (not shown). At this time, the crane CL may be removed 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 shows a configuration in which the first leg 11 and the second leg 12 are connected by the brace 20, and a configuration in which the third leg 13 and the fourth leg 14 are connected by the brace 20, both connected by the brace 20. The third connection step, as shown in Figure 12, is the step of connecting the other end of the first leg 11 and second leg 12, which are lifted in the first lifting step, with the other end of the third leg 13 and fourth leg 14, which are lifted in the second lifting step, using 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 by the brace 20. At this time, the second leg 12 and the fourth leg 14 and the brace 20 are connected 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. In this way, a configuration in which the first leg 11 and the second leg 12 are connected by the brace 20, and a 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 connection step, the second leg 12 and the fourth leg 14 are first connected by the diagonal brace 22. After that, 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. Or, the formation of the frame 21F may be carried out from the third connection step to the fourth connection step described below. Furthermore, at the time of the second lifting process, before the third connection process, the brace 20 connecting the fourth leg 14 to the second leg 12 may be pre-attached to the fourth leg 14, which is structured in such a way that the third leg 13 and the fourth leg 14 are connected by the brace 20. This may reduce or eliminate the need for high-altitude work to connect the brace 20 to the fourth leg 14 when connecting the fourth leg 14 to the second leg 12 in the third connection process.

[0058] (Regarding the fourth connection process) The fourth connection step, as shown in Figure 12, is the step of connecting one of the first leg 11 and the second leg 12, which are laid on the ground in the first lifting step, with one of the third leg 13 and the fourth leg 14, which are laid on the ground in the second lifting step, using a brace 20. That is, in the fourth connection step, after the first and second lifting steps, 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 a brace 20. At this time, the first leg 11 and the third leg 13 and the brace 20 are connected 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 floor slab installation step described below.

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

[0060] In other words, first, the floor slab 30 is laid on the ground. At this time, as described above, one side 30S of the rectangular floor slab 30 is laid on the ground and is approximately perpendicular to one of the first leg 11 and the second leg 12, which are laid on the ground in the first lifting process, and to one of the third leg 13 and the fourth leg 14, which are laid on the ground in the second lifting process. In other words, in the second embodiment, one side 30S of the floor slab 30 is approximately perpendicular to the first leg 11 and the third leg 13. As shown in Figure 5, one side 30S of the floor slab 30 is the side of the floor slab 30 whose ends are joined to the first leg 11 and the third leg 13. Furthermore, the condition in which one side 30S of the floor slab 30 is approximately perpendicular to the first leg 11 and the third leg 13 means that the intersection angle between one side 30S and the first leg 11 and the third leg 13 is in the range of 85° to 95°. Here, as shown in Figure 1, when the jacket structure 1 is positioned at sea, the legs 10 are inclined with respect to the vertical. In contrast, when the jacket structure 1 is positioned at sea, the deck slab 30 is positioned horizontally. That is, when the jacket structure 1 is positioned at sea, the legs 10 and the deck slab 30 are joined at an angle 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 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 positioned at sea.

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

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

[0063] In other words, first, the Madomat 40 is laid down on the ground. At this time, one side 40S of the rectangular Madomat 40 is laid down on the ground and is approximately perpendicular to one of the first leg 11 and the second leg 12, which are laid down on the ground in the first lifting process, and to one of the third leg 13 and the fourth leg 14, which are laid down on the ground in the second lifting process. In other words, in the second embodiment, one side 40S of the Madomat 40 is approximately perpendicular to the first leg 11 and the third leg 13. As shown in Figure 7, one side 40S of the Madomat 40 is the side of the Madomat 40 whose ends are joined to the first leg 11 and the third leg 13. Furthermore, the state in which one side 40S of Madmat 40 is approximately perpendicular to the first leg 11 and the third leg 13 means that the intersection angle between one side 40S and the first leg 11 and the third leg 13 is in the range of 85° to 95°. Here, as shown in Figure 1, when the jacket structure 1 is positioned on the open sea, the legs 10 are inclined with respect to the vertical. In contrast, when the jacket structure 1 is positioned on the open sea, the madmat 40 is positioned horizontally along the seabed. That is, when the jacket structure 1 is positioned on the open sea, the legs 10 and the madmat 40 are joined at an angle to each other. In this embodiment, the state in which one side 40S of the madmat 40 is approximately perpendicular to the first leg 11 and the third leg 13 may mean that one side 40S of the madmat 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 positioned on the open sea.

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

[0065] As described above, the assembly method for the jacket structure 1 according to the second embodiment further comprises a second placement step and a second connection step. In the second placement step, the cylindrical third leg 13 and the cylindrical fourth leg 14 are laid on the ground so as to be substantially parallel to a predetermined direction D. In the second connection step, the third leg 13 and the fourth leg 14, which were laid on the ground in the second placement step, are connected with a brace 20. Thus, for example, 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 can be erected and connected to each other to form the jacket structure 1. Therefore, compared to 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, for example, the amount of work at height can be reduced.

[0066] Furthermore, the assembly method further comprises a first lifting step, a second lifting step, and a third connection step. In the first lifting process, one of the first leg 11 and the second leg 12, which are connected by the brace 20 in the first connection process, is laid on the ground, and the other is lifted so that the plane containing the axis of each pipe is aligned approximately vertically. In the second lifting process, one of the third leg 13 and the fourth leg 14, which are connected by the brace 20 in the second connection process, is laid on the ground, and the other is lifted so that the plane containing the axis of each pipe is aligned approximately vertically. In the third connection process, the other end of the first leg 11 and the second leg 12, which are lifted in the first lifting process, and the other end of the third leg 13 and the fourth leg 14, which are lifted in the second lifting process, are connected by a brace 20. Specifically, in the first lifting process, the configuration in which the first leg 11 and the second leg 12 are connected by a brace 20 is erected. In the second lifting process, the configuration in which the third leg 13 and the fourth leg 14 are connected by a brace 20 is erected. Then, in the third connection process, the configuration in which the first leg 11 and the second leg 12 are connected by a brace 20 is connected to the configuration in which the third leg 13 and the fourth leg 14 are connected by a brace 20. 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] Furthermore, the assembly method further includes a fourth connection step. In the fourth connection step, one of the first leg 11 and the second leg 12, which are laid on the ground in the first lifting step, and one of the third leg 13 and the fourth leg 14, which are laid on the ground in the second lifting step, are connected 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. Thus, the jacket structure 1 can be reinforced more reliably.

[0068] Furthermore, the assembly method further includes an installation step. In the installation step, one Madmat 40 is installed at one end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14 in a predetermined direction D. This allows the Madmat 40 to be installed on the jacket structure 1. In addition, the first leg 11, second leg 12, third leg 13, and fourth leg 14 can be more securely fixed to each other using the Madmat 40. Furthermore, one side of the Madomat 40 is laid on the ground and is approximately perpendicular to one of the first leg 11 and second leg 12, which are laid on the ground in the first lifting process, and to one of the third leg 13 and fourth leg 14, which are laid on the ground in the second lifting process. Then, in the installation step, the Madomat 40 is installed on one end of each of the first leg 11, second leg 12, third leg 13, and fourth leg 14 by rotating the side of the Madomat 40 that is approximately perpendicular to one of the first leg 11 and second leg 12, and to one of the third leg 13 and fourth leg 14, which are laid on the ground, using this side as the axis of rotation. In other words, when attaching the Madomat 40 to the jacket structure 1 during assembly, the Madomat 40 is raised from a state where it is laid on the ground. When the Madmat 40 is erected, one side of the Madmat 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, which are laid on the ground, is used as the axis of rotation. This allows, for example, the Madomat 40 to be transported to the vicinity of the jacket structure 1 that is in the process of being assembled while lying down. Therefore, the transport of the Madomat 40 can be performed more stably. In addition, by using one side of the Madomat 40 as the axis of rotation, the Madomat 40 can be raised upright with less force. Therefore, the work of raising the Madomat 40 can be performed more efficiently.

[0069] (Third embodiment) Next, the assembly method of the jacket structure 1 of the third embodiment according to this disclosure will be described with reference to Figure 13. In this third embodiment, the same reference numerals are used for parts that are the same as those in the first and second embodiments, and their descriptions are omitted. Only the differences will be described. In the third embodiment, multiple jacket structures 1 are manufactured simultaneously in a single yard Y.

[0070] Hereinafter, the jacket structure 1 in the first and second embodiments (see Figure 1) will be referred to as the first jacket structure. A jacket structure 1 with the same configuration as the first jacket structure, but manufactured simultaneously with the first jacket structure, will be referred to as the second jacket structure (not shown). In the following description, the configurations in the second jacket structure corresponding 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, and 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 on which the floor slab 30 is attached is referred to as one of the predetermined directions D, and the direction on which the madomatt 40 is attached is referred to as the other of the predetermined directions D.

[0071] The fabrication of the multiple jacket structures 1 in the third embodiment is carried out 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 process corresponding to the first placement process and the first connection process in the first or second embodiment will be described. The other processes are carried out in the same manner as in the first or second embodiment, and therefore their description is omitted. The assembly method for the jacket structure 1 according to the third embodiment comprises at least a first placement step, a second placement step, a first connection step, and a second connection step.

[0072] (Regarding the first placement process) Figure 13 shows a state in which the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 are arranged to be approximately parallel to a predetermined direction D. The first placement step is the same as in the first and second embodiments. That is, the first placement step is to lay the first leg 11 and the second leg 12, which will become part of the first jacket structure, on the ground so that they are substantially parallel to a predetermined direction D which is substantially parallel to the ground. The details of the first placement step are the same as in the first embodiment, so the explanation will be omitted.

[0073] (Regarding the second placement process) The second placement step in the third embodiment corresponds to the first placement step in the second jacket structure. That is, the second placement step is the step of laying the fifth leg 15 and the sixth leg 16, which will become part of the second jacket structure, on the ground so that they are substantially parallel to a predetermined direction D. The details of the second placement step are the same as those of the first placement step, so the explanation will be omitted.

[0074] (Regarding the first connection process) The first connection step is the same as in the first and second embodiments. That is, the first connection step is the step of connecting the first leg 11 and the second leg 12, which were laid on the ground in the first placement step, with the first horizontal brace. The details of the first connection step are the same as in the first embodiment, so the explanation is omitted.

[0075] (Regarding the second connection process) The second connection step in the third embodiment corresponds to the first connection step in the second jacket structure. That is, the second connection step is the 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 connection step are the same as those of the first connection step, so the explanation will be omitted.

[0076] (Regarding the placement of the legs) 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 one end of the first leg 11 in a predetermined direction D and one end of the second leg 12 is shorter than the distance between the other end of the first leg 11 in a predetermined direction D and the other end of the second leg 12. Furthermore, the distance between one end of the fifth leg 15 in a predetermined direction D and one end of the sixth leg 16 is longer than the distance between the other end of the fifth leg 15 in a predetermined direction D and the other end of the sixth leg 16. In other words, in the first and second placement steps, when placing the first leg 11, second leg 12, fifth leg 15, and sixth leg 16 respectively, the top and bottom of the first jacket structure and the top and bottom of the second jacket structure are arranged in an alternating pattern. This allows the first jacket structure and the second jacket structure to be assembled in closer proximity. Furthermore, in the third embodiment, as shown in Figure 13, the area A3 between the area A1 sandwiched by the first leg 11 and the second leg 12 laid on the ground in the first placement step and the area A2 sandwiched by the fifth leg 15 and the sixth leg 16 laid on the ground in the second placement step is secured to a degree that allows a crawler crane (not shown) to pass through. This makes it possible to use the same crawler crane for assembling the first jacket structure using the first leg 11 and the second leg 12 and for assembling the second jacket structure using the fifth leg 15 and the sixth leg 16. Thus, the number of crawler cranes used can be reduced. In the third embodiment, the first jacket structure and the second jacket structure are assembled simultaneously by arranging the first leg 11, the second leg 12, the fifth leg 15, and the sixth leg 16 as described above. The assembly of the jacket structure 1 according to the third embodiment is carried out in the manner described above.

[0077] As described above, the assembly method for the jacket structure 1 according to the third embodiment comprises a first placement step, a second placement step, a first connection step, and a second connection step. In the first placement step, the first leg 11 and the second leg 12, which will become part of the first jacket structure, are laid on the ground so that they are approximately parallel to a predetermined direction D which is approximately parallel to the ground. In the second placement step, the fifth leg 15 and the sixth leg 16, which will become 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 step, the first leg 11 and the second leg 12, which were laid on the ground in the first placement step, are connected with a first horizontal brace. In the second connection step, the fifth leg 15 and the sixth leg 16, which were laid on the ground in the second placement step, are connected with a second horizontal brace. This allows the legs 10, which are lying on the ground, to be fixed together by the brace 20. Therefore, when assembling the jacket structure 1, for example, compared to connecting the first leg 11 and the second leg 12, and the fifth leg 15 and the sixth leg 16 to the brace 20 while they are upright, the need to fix them together using components other than those that make up the jacket structure 1, such as assembly jigs, can be reduced. Therefore, waste during the assembly of the jacket structure 1 can be reduced. Furthermore, the distance between one end of the first leg 11 in the predetermined direction D and one end of the second leg 12 is shorter than the distance between the other end of the first leg 11 in the predetermined direction D and the other end of the second leg 12. And the distance between one end of the fifth leg 15 in the predetermined direction D and one end of the sixth leg 16 is longer than the distance between the other end of the fifth leg 15 in the predetermined direction D and the other end of the sixth leg 16. In other words, 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 proximity. Therefore, the space required when assembling multiple jacket structures 1 can be reduced.

[0078] Furthermore, the area A3 between area A1, which is sandwiched between the first leg 11 and the second leg 12 laid on the ground in the first placement process, and area A2, which is sandwiched between the fifth leg 15 and the sixth leg 16 laid on the ground in the second placement process, is passable by a crawler crane. 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. Thus, the assembly of multiple jacket structures 1 can be performed efficiently.

[0079] The technical scope of this disclosure is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of this disclosure. For example, using the method described above, a third jacket structure may be manufactured simultaneously with the first and second jacket structures. However, four or more jacket structures 1 may be manufactured simultaneously. In this case, it is preferable that adjacent jacket structures 1 be arranged so that their tops and bottoms are staggered during manufacturing.

[0080] Furthermore, it is possible to replace the components in the above embodiments with well-known components as appropriate, without departing from the spirit of this disclosure, and the above-described modifications may be combined as appropriate.

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

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

[0083] The above method for assembling the jacket structure comprises a first placement step and a first connection step. In the first placement 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 approximately parallel to the ground. In the first connection step, the first leg and the second leg, which were laid on the ground in the first placement step, are connected with a cylindrical brace. This allows the legs, which were laid on the ground, to be fixed together by the brace. Therefore, compared to, for example, when assembling the jacket structure, it is possible to eliminate the need for large-scale configurations, such as assembly jigs, that are necessary to support the first leg and the second leg in an upright position. Therefore, the scale of the configuration used to assemble the jacket structure can be reduced. Therefore, waste when assembling the jacket structure can be reduced.

[0084] <2> the above <1> The method for assembling the jacket structure may further include a first joining step of joining a frame, which is composed of three or more braces including the brace, to the first leg and the second leg, such that the frame is aligned substantially vertically.

[0085] Furthermore, the assembly method further comprises a first joining step. In the first joining step, a frame consisting of three or more braces, including the brace that connected the first and second legs in the first connection step, is joined to the first and second legs so that the frame is aligned approximately vertically. This allows the legs, which are lying on the ground, to be fixed together using a frame composed of multiple braces. At this time, by aligning the frame approximately vertically, the ends of the frame that are not connected to the first and second legs are located away from the ground. This allows a new leg (for example, a third leg) to be connected to the ends of the frame that are not connected to the first and second legs. Therefore, it is possible to easily connect a new leg without moving the first and second legs. Thus, the jacket structure can be assembled efficiently.

[0086] <3> the above <2> In the method for assembling the jacket structure relating to the present invention, a configuration may be adopted that further comprises 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 that is joined in the first joining step.

[0087] Furthermore, the assembly method further comprises a lifting step and a second joining step. Specifically, in the lifting step, the third leg is lifted. Then, in the second joining step, the third leg, which was lifted in the lifting step, is joined to the frame that was joined to the first and second legs in the first joining step. This allows the third leg to be fixed to the first and second legs. Also, by lifting the third leg, for example, the third leg can be joined without rotating or moving the configuration in which the first and second legs are fixed by the frame. Therefore, the space required for assembling the jacket structure can be reduced.

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

[0089] Furthermore, the assembly method includes a third joining step. In the third joining step, after the second joining step, a diagonal brace is joined to the third leg, which is lifted in the lifting step, and to the first or second leg, which is laid on the ground in the first placement step. This allows a diagonal brace to be provided to the jacket structure, thereby reinforcing the jacket structure more reliably.

[0090] <5> the above <3> or <4> The method for assembling the jacket structure may further include a first installation step of installing a floor slab at one end of each of the first, second, and third legs, in the predetermined direction.

[0091] Furthermore, the assembly method further comprises a first installation step. In the first installation step, one floor slab is installed at one end of each of the first, second, and third legs, in a predetermined direction. This allows the floor slab to be installed on the jacket structure. In addition, the first, second, and third legs can be more securely fixed to each other using the floor slab.

[0092] <6> the above <5> In the method for assembling the jacket structure relating to the present invention, the shape of the floor slab may be triangular or quadrilateral, one side of the floor slab may be laid on the ground and be approximately perpendicular to the first leg and the second leg, and in the first installation step, the floor slab may be installed at the end of each of the first leg, the second leg and the third leg, on one end in the predetermined direction, by rotating the floor slab around one side as the axis of rotation.

[0093] Furthermore, the shape of the deck slab is either triangular or quadrilateral. This allows for, for example, using a triangular deck slab when there are three legs, and a quadrilateral deck slab when there are four legs. Thus, the shape of the deck slab can be better matched to the number of legs. Furthermore, one side of the floor slab is laid flat on the ground and is approximately perpendicular to the first and second legs. Then, in the first installation step, the floor slab is installed at one end of the first, second, and third legs in a predetermined direction by rotating the side of the floor slab that is laid flat on the ground and is approximately perpendicular to the first and second legs as the axis of rotation. In other words, when attaching the floor slab to the jacket structure that is under construction, the floor slab is raised from a state where it is laid flat on the ground. When raising the floor slab, the side of the floor slab that is laid flat on the ground and is approximately perpendicular to the first and second legs is used as the axis of rotation. This allows, for example, the floor slab to be transported to the vicinity of the jacket structure under assembly while lying down. Therefore, the transportation of the floor slab can be performed more stably. In addition, by using one side of the floor slab as the axis of rotation, the floor slab can be raised with less force. Therefore, the work of raising the floor slab can be made more efficient.

[0094] <7> the above <5> or <6> The method for assembling the jacket structure may further include a second installation step of installing a madmat at the other end of each of the first leg, the second leg, and the third leg in the predetermined direction.

[0095] Furthermore, the assembly method further includes a second installation step. In the second installation step, one Mad Mat is installed at the end of each of the first, second, and third legs, on the other end in a predetermined direction. This allows the Mad Mat to be installed on the jacket structure. In addition, the first, second, and third legs can be more securely fixed to each other using the Mad Mat.

[0096] <8> the above <7> In the method for assembling the jacket structure relating to the present invention, the shape of the window mat may be triangular or square, one side of the window mat may be laid on the ground and approximately perpendicular to the first leg and the second leg, and in the second installation step, the window mat may be installed on the end of the first leg, the second leg and the third leg, on the other end in the predetermined direction, by rotating the window mat with one side of the window mat as the axis of rotation.

[0097] Furthermore, the shape of the mat is either triangular or square. This allows for, for example, using a triangular mat when there are three legs, and a square mat when there are four legs. Thus, the shape of the mat can be better matched to the number of legs. Furthermore, one side of the Madomat is laid on the ground and is approximately perpendicular to the first and second legs. Then, in the second installation step, the Madomat is installed at the ends of the first, second, and third legs, on the other end in a predetermined direction, by rotating the Madomat using the side that is laid on the ground and is approximately perpendicular to the first and second legs as the axis of rotation. In other words, when attaching the Madomat to the jacket structure during assembly, the Madomat is raised from a state where it is laid on the ground. When raising the Madomat, the side that is laid on the ground and is approximately perpendicular to the first and second legs is used as the axis of rotation. This allows, for example, the Madomat to be transported while lying down near the jacket structure that is still being assembled. Therefore, the transport of the Madomat can be performed more stably. In addition, by using one side of the Madomat as the axis of rotation, the Madomat can be raised upright with less force. Therefore, the process of raising the Madomat can be performed more efficiently.

[0098] <9> the above <3> from <8> A method for assembling a jacket structure according to any one of the embodiments may further include a second positioning step, before the lifting step, in which the third leg is laid on the ground such that the first leg is sandwiched between the second and third legs, and the third leg is substantially parallel to the predetermined direction.

[0099] Furthermore, the assembly method 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 and third legs, and the third leg is approximately parallel to a predetermined direction. This reduces the distance the third leg needs to be moved when connecting it to the jacket structure during assembly, thereby shortening the time the third leg is lifted by the crane. Thus, the lifting step can be performed efficiently. In addition, the crane's restraint time can be reduced.

[0100] <10> the above <1> The method for assembling the jacket structure may further include 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, and a second connection step of connecting the third leg and the fourth leg, which were laid on the ground in the second placement step, with a brace.

[0101] Furthermore, the assembly method further comprises 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 as to be approximately parallel to a predetermined direction. In the second connection step, the third leg and the fourth leg, which were laid on the ground in the second placement step, are connected with braces. In this way, for example, a configuration in which the first leg and the second leg are connected with braces and a configuration in which the third leg and the fourth leg are connected with braces can be erected and connected to each other to form a jacket structure. Therefore, compared to a method in which the third and fourth legs are lifted and connected to a configuration in which the first leg and the second leg are connected by a frame, for example, the amount of work at height can be reduced.

[0102] <11> the above <10> The assembly method for the jacket structure may further include a configuration comprising: a first lifting step in which one of the first and second legs connected by a brace in the first connection step is laid on the ground and the other is lifted so that the plane containing the respective pipe axis is aligned substantially vertically; a second lifting step in which one of the third and fourth legs connected by a brace in the second connection step is laid on the ground and the other is lifted so that the plane containing the respective pipe axis is aligned substantially vertically; and a third connection step in which the other lifted in the first lifting step and the other lifted in the second lifting step are connected by a brace.

[0103] Furthermore, the assembly method further comprises a first lifting step, a second lifting step, and a third connection step. In the first lifting process, one of the first and second legs, which are connected by braces in the first connection process, is laid on the ground, and the other is lifted so that the plane containing the axis of each pipe is aligned approximately vertically. In the second lifting process, one of the third and fourth legs, which are connected by braces in the second connection process, is laid on the ground, and the other is lifted so that the plane containing the axis of each pipe is approximately aligned vertically. In the third connection process, the other half of the first and second legs, which are lifted in the first lifting process, and the other half of the third and fourth legs, which are lifted in the second lifting process, are connected by braces. In other words, in the first lifting process, the structure in which the first and second legs are connected by braces is erected. In the second lifting process, the structure in which the third and fourth legs are connected by braces is erected. Then, in the third connecting process, the structure in which the first and second legs are connected by braces and the structure in which the third and fourth legs are connected by braces are connected to each other. This reduces the amount of work at heights compared to, for example, a method in which the third and fourth legs are lifted and connected to a structure in which the first and second legs are connected by a frame.

[0104] <12> the above <11> The assembly method for the jacket structure may further include a fourth connection step in which one of the first and second legs, which are laid on the ground in the first lifting step, and one of the third and fourth legs, which are laid on the ground in the second lifting step, are connected by a brace.

[0105] Furthermore, the assembly method includes a fourth connection step. In the fourth connection step, one of the first and second legs, which are laid on the ground in the first lifting step, is connected with one of the third and fourth legs, which are laid on the ground in the second lifting step, using a brace. This allows the first, second, third, and fourth legs to be connected to each other by braces. Thus, the jacket structure can be reinforced more reliably.

[0106] <13> the above <11> or <12> The method for assembling the jacket structure may further include an installation step of installing a single window mat at one end of each of the first, second, third, and fourth legs in the predetermined direction, wherein the shape of the window mat is rectangular, and one side of the window mat is laid on the ground and is approximately perpendicular to one of the first and second legs and one of the third and fourth legs that are laid on the ground in the first lifting step, and the window mat is installed at one end of each of the first, second, third, and fourth legs by rotating the window mat around one side as the axis of rotation in the installation step.

[0107] Furthermore, the assembly method includes an installation step. In the installation step, one Mad Mat is installed at one end of each of the first, second, third, and fourth legs in a predetermined direction. This allows the Mad Mat to be installed on the jacket structure. In addition, the first, second, third, and fourth legs can be more securely fixed to each other using the Mad Mat. Furthermore, one side of the Madomat is laid on the ground and is approximately perpendicular to one of the first and second legs, and one of the third and fourth legs, which are laid on the ground in the first lifting process. Then, in the installation step, the Madomat is rotated using the side of the Madomat that is approximately perpendicular to one of the first and second legs, and one of the third and fourth legs, as the axis of rotation, thereby installing the Madomat at one end of each of the first, second, third, and fourth legs. In other words, when attaching the Madomat to the jacket structure during assembly, the Madomat is raised from a state where it is laid on the ground. When setting up the Madmat, one side of the Madmat that is approximately perpendicular to one of the first and second legs, and one of the third and fourth legs, which are laid on the ground, serves as the axis of rotation. This allows, for example, the Madomat to be transported while lying down near the jacket structure that is still being assembled. Therefore, the transport of the Madomat can be performed more stably. In addition, by using one side of the Madomat as the axis of rotation, the Madomat can be raised upright with less force. Therefore, the process of raising the Madomat can be performed more efficiently.

[0108] <14> A method for assembling a jacket structure according to one aspect of the present disclosure includes: a first placement step of laying a first leg and a second leg, each to 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 placement step of laying a fifth leg and a sixth leg, each to 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 placement 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 placement step, with a second horizontal brace. The invention provides a structure wherein 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.

[0109] The above method for assembling the jacket structure comprises a first placement step, a second placement step, a first connection step, and a second connection step. In the first placement step, the first and second legs, which will become part of the first jacket structure, are laid on the ground so that they are approximately parallel to a predetermined direction approximately parallel to the ground. In the second placement step, the fifth and sixth legs, which will become part of the second jacket structure, are laid on the ground so that they are approximately parallel to a predetermined direction. In the first connection step, the first and second legs, which were laid on the ground in the first placement step, are connected with the first horizontal brace. In the second connection step, the fifth and sixth legs, which were laid on the ground in the second placement step, are connected with the second horizontal brace. This allows the legs, which are lying on the ground, to be fixed together with braces. Therefore, for example, when assembling a jacket structure, compared to connecting the first and second legs, and the fifth and sixth legs, with braces while they are standing upright, the need to fix them together using components other than those that make up the jacket structure, such as assembly jigs, can be reduced. Thus, waste during the assembly of the jacket structure can be reduced. Furthermore, the distance between one end of the first leg in a predetermined direction and one end of the second leg is shorter than the distance between the other end of the first leg in a predetermined direction and the other end of the second leg. And the distance between one end of the fifth leg in a predetermined direction and one end of the sixth leg is longer than the distance between the other end of the fifth leg in a predetermined direction and the other end of the sixth leg. In other words, 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 and second jacket structures to be assembled in closer proximity. Therefore, the space required when assembling multiple jacket structures can be reduced.

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

[0111] Furthermore, the area between the region enclosed by the first and second legs, which are laid on the ground in the first placement process, and the region enclosed by the fifth and sixth legs, which are laid on the ground in the second placement process, is passable by the crawler crane. This makes it easier to assemble the first jacket structure using the first and second legs, and the second jacket structure using the fifth and sixth legs, using a single crawler crane. Thus, the assembly of multiple jacket structures can be performed efficiently. [Explanation of Symbols]

[0112] 1. Jacket structure 10 Legs 11 Leg 1 12 Leg 2 13. Third Leg 14. Leg 4 15. Leg 5 16. Leg 6 20 braces 21 Horizontal brace 21F Frame 22 Diagonal braces 30 Floor slab 40 Madmat CL Crane D Specified direction T1 First mounting base T2 Second mounting base Y Yard

Claims

1. A first placement step involves laying each of 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, The first connection step involves connecting the first leg and the second leg, which are laid on the ground in the first placement step, with a cylindrical brace, A method for assembling a jacket structure, characterized by comprising the following:

2. A first joining step involves joining a frame, which is composed of three or more braces including the aforementioned brace, to the first leg and the second leg such that the frame is aligned substantially vertically. The method for assembling a jacket structure according to claim 1, further comprising the above.

3. The lifting process involves lifting the third leg, A second joining step is performed to join the third leg, which is lifted in the lifting step, to the frame, which is joined in the first joining step. The method for assembling a jacket structure according to claim 2, further comprising the above.

4. A third joining step is performed to join an oblique brace to the third leg, which is lifted in the lifting step, and to the first leg or second leg, which is laid on the ground in the first placement step, after the second joining step. The method for assembling a jacket structure according to claim 3, further comprising the above.

5. A first installation step involves installing a floor slab at one end of each of the first, second, and third legs, in the predetermined direction. The method for assembling a jacket structure according to claim 3, further comprising the above.

6. The shape of the aforementioned deck slab is triangular or quadrilateral. One side of the aforementioned floor slab lies flat on the ground and is approximately perpendicular to the first and second legs. In the first installation step, the floor slab is installed on one end of each of the first, second, and third legs, in the predetermined direction, by rotating it with one side of the floor slab as the axis of rotation. The method for assembling the jacket structure according to feature 5.

7. A second installation step involves installing a single mat at the end of each of the first leg, the second leg, and the third leg, on the other end in the predetermined direction. The method for assembling a jacket structure according to claim 5, further comprising the above.

8. The shape of the aforementioned mat is triangular or square. One side of the aforementioned mat is laid on the ground and is approximately perpendicular to the first and second legs. In the second installation step, the mat is installed on the ends of the first leg, the second leg, and the third leg, on the other end in the predetermined direction, by rotating the mat around one side of the mat as the axis of rotation. The method for assembling the jacket structure according to feature 7.

9. Prior to the lifting process, a second positioning step is performed in which the third leg is laid on the ground so that the first leg is sandwiched between the second and third legs, and the third leg is substantially parallel to the predetermined direction. A method for assembling a jacket structure according to any one of claims 3 to 8, further comprising the above.

10. A second arrangement step involves laying the cylindrical third leg and the cylindrical fourth leg on the ground so that they are substantially parallel to the predetermined direction, The second connection step involves connecting the third and fourth legs, which were laid on the ground in the second placement step, with braces, The method for assembling a jacket structure according to claim 1, further comprising the above.

11. In the first connection step, one of the first and second legs, which are connected by a brace, is laid on the ground, and the other is lifted up in a first lifting step in which the plane containing the axis of each pipe is aligned approximately vertically, In the second connection step, one of the third and fourth legs, which are connected by a brace, is laid on the ground, and the other is lifted up in a second lifting step in which the plane containing the axis of each pipe is aligned approximately vertically. A third connecting step involves connecting the other object lifted in the first lifting step with the other object lifted in the second lifting step using a brace. The method for assembling a jacket structure according to claim 10, further comprising the above.

12. A fourth connecting step involves connecting one of the first and second legs, which are laid on the ground in the first lifting step, with one of the third and fourth legs, which are laid on the ground in the second lifting step, using a brace. The method for assembling a jacket structure according to claim 11, further comprising the above.

13. Installation step of installing one mat mat at one end of each of the first, second, third, and fourth legs in the predetermined direction, Furthermore, The shape of the aforementioned madonna is rectangular. One side of the Mad Mat is laid on the ground and is approximately perpendicular to one of the first and second legs, which are laid on the ground in the first lifting process, and to one of the third and fourth legs, which are laid on the ground in the second lifting process. In the installation step, the Mad Mat is installed on one end of each of the first, second, third, and fourth legs by rotating it around one side as the axis of rotation. A method for assembling a jacket structure according to any one of claims 11 to 12.

14. A first placement step involves laying the first and second legs, which will become part of the 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 involves laying the fifth and sixth legs, which will become part of the second jacket structure, on the ground so that they are substantially parallel to the predetermined direction, The first connection step involves connecting the first and second legs, which were laid on the ground in the first placement step, with a first horizontal brace. The second connection step involves connecting the fifth and sixth legs, which were laid on the ground in the second placement step, with a second horizontal brace. Equipped with, 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. 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. A method for assembling a jacket structure characterized by the following features.

15. The area between the region sandwiched by the first and second legs laid on the ground in the first placement step and the region sandwiched by the fifth and sixth legs laid on the ground in the second placement step is passable by a crawler crane. The method for assembling the jacket structure according to feature 14.

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