External work platform, marine structure, and marine structure assembly method

Abstract

The present invention provides an external work platform, a marine structure, and a method for assembling a marine structure, which enable efficient construction. [Solution] An external work floor 30 provided on an offshore structure 20 that supports an offshore wind turbine 10, which is configured to be divisible into multiple floor sections 31, and which are configured to surround the outer periphery of the tower 14 of the offshore wind turbine 10 when viewed vertically by combining the multiple floor sections 31.

Description

[Technical Field]

[0001] The present disclosure relates to an external working platform, an offshore structure, and a method for assembling an offshore structure. [Background technology]

[0002] Patent Document 1 discloses a platform formed by connecting two floating bodies, each of which surrounds the outer periphery of a tower when viewed in the vertical direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-239370 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the floating body bodies described in Patent Document 1 are not configured to be separable. Here, there has been a demand for a smaller external work platform so that it can be easily transported and construction can be carried out efficiently.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide an external working platform, an offshore structure, and an assembly method for an offshore structure that enable construction to be carried out efficiently. [Means for solving the problem]

[0006] In order to solve the above problems, the present disclosure proposes the following means. The external work floor of the present disclosure is an external work floor provided on an offshore structure that supports an offshore wind turbine, and is configured to be divisible into multiple floor sections, and by combining the multiple floor sections, is configured to surround the outer periphery of the tower of the offshore wind turbine when viewed vertically. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an external work platform, an offshore structure, and an assembling method for an offshore structure that allows construction to be carried out efficiently. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of a first example of an offshore wind power system according to a first embodiment. [Figure 2] FIG. 1 is a front view of a first example of an offshore wind power system according to a first embodiment. [Figure 3] FIG. 2 is a plan view of the transition piece in FIG. 1. [Figure 4] FIG. 2 is a cross-sectional view showing the internal structure of the transition piece in FIG. [Figure 5] FIG. 1 is a plan view showing an external work platform according to a first embodiment. [Figure 6] FIG. 2 is a plan view showing the transition piece according to the first embodiment. [Figure 7] FIG. 2 is a front view showing an example in which the external work platform according to the first embodiment is provided on a transition piece. [Figure 8] FIG. 8 is a plan view showing the installation locations of the legs of the external work platform in FIG. 7. [Figure 9] FIG. 2 is a front view showing the positional relationship between the external work platform and the support members according to the first embodiment. [Figure 10] FIG. 10 is a plan view showing an external work platform according to a second embodiment. [Figure 11] FIG. 10 is a plan view showing a transition piece according to a second embodiment. [Figure 12] FIG. 10 is a front view showing an example in which legs of an external work platform according to a second embodiment are provided on a transition piece. [Figure 13] FIG. 13 is an enlarged view showing the installation locations of the legs of the external work platform in FIG. [Figure 14] FIG. 13 is a plan view showing the installation locations of the legs of the external work platform in FIG. [Figure 15] FIG. 10 is a front view of a second example of an offshore wind power system according to an embodiment. [Figure 16] FIG. 10 is a front view of a third example of an offshore wind power system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) Hereinafter, an external work platform according to a first embodiment of the present disclosure will be described with reference to the drawings.

[0010] (About offshore wind turbines) The offshore wind turbine 10 included in the offshore wind power system 1 has a known configuration. As shown in Fig. 1, the offshore wind turbine 10 is made up of blades 11, a hub 12, a nacelle 13, and a tower 14. The offshore wind turbine 10 is placed on the ocean, and generates electricity by transmitting the rotation of the blades 11 to a generator (not shown).

[0011] (Regarding offshore structures) The offshore structure 20 is a structure that supports the offshore wind turbine 10. For example, a known configuration may be suitably used for the offshore structure 20. In this embodiment, the offshore structure 20 is a jacket-type foundation, as shown in Figs. 1 and 2. That is, the offshore structure 20 includes at least a transition piece 21 to which the lower end of the tower 14 of the offshore wind turbine 10 is connected and which supports the tower 14 of the offshore wind turbine 10, legs 22 that support the transition piece 21, and an external working platform 30. As shown in Fig. 2, the offshore structure 20 is placed offshore by connecting the legs 22 to piles P driven into the seabed.

[0012] (About the transition piece) 2, the transition piece 21 includes a center pipe 21a whose upper end is connected to the lower end of the tower 14 of the offshore wind turbine 10. As shown in FIGS. 3 and 4, the transition piece 21 also includes an upper flange 21b and a lower flange 21c disposed above and below the center pipe 21a, respectively, and a first web 21d and a second web 21e that reinforce the connections between the center pipe 21a and the upper flange 21b and the lower flange 21c, respectively.

[0013] As shown in Fig. 3, the center pipe 21a is provided in the center of the transition piece 21. The center pipe 21a is a tubular member, and its pipe axis extends in the vertical direction. The diameter of the center pipe 21a is the same as the diameter of the part of the tower 14 of the offshore wind turbine 10 that is connected to the center pipe 21a. In this embodiment, the upper end of the center pipe 21a is located, for example, above the upper flange 21b, which will be described below. This preferably makes it easier to connect the center pipe 21a to the tower 14 of the offshore wind turbine 10.

[0014] As shown in Figures 3 and 4, the upper flange 21b is a plate-like member provided on the upper part of the center pipe 21a. The upper flange 21b connects the center pipe 21a to the legs 22 at the upper part of the center pipe 21a. In this embodiment, the marine structure 20, which is a jacket-type foundation, has four legs 22. For this reason, in this embodiment, the upper flange 21b is preferably formed in a cross shape, for example, as shown in Figure 3. 3 and 4, the lower flange 21c is a plate-like member provided at the lower part of the center pipe 21a. The lower flange 21c connects the center pipe 21a to the leg 22 at the lower part of the center pipe 21a. In this embodiment, the lower flange 21c is preferably formed in a cross shape, similar to the upper flange 21b, as shown in FIG. 2, the leg 22 is inclined downward and away from the center of the marine structure 20. Therefore, the upper flange 21b and the lower flange 21c each have a shape that can accommodate the inclination of the leg 22. That is, the shape of the lower flange 21c is similar to the shape of the upper flange 21b and is larger than the shape of the upper flange 21b.

[0015] The first web 21d and the second web 21e reinforce the connections between the center pipe 21a and the upper flange 21b and the lower flange 21c, and the connections between the upper flange 21b and the lower flange 21c and the legs 22. In this way, the first web 21d and the second web 21e reinforce the connections between the center pipe 21a and the legs 22, and also reinforce the structure of the entire transition piece 21. As shown in FIG. 3, each of the first web 21d and the second web 21e is provided between the center pipe 21a and one of the legs 22.

[0016] (Outline of external work platform) 1 and 5, the external work floor 30 is provided on the transition piece 21. As shown in Fig. 5, the external work floor 30 includes a plurality of steel members 28. The plurality of steel members 28 are, for example, beams, and form the framework of the external work floor 30.

[0017] In this embodiment, a grating 41 is provided on the upper surface of the external work floor 30. However, the grating 41 does not have to be provided. The grating 41 may be provided, for example, on the entire surface of the external work floor 30. By providing the grating 41 on the external work floor 30 instead of a steel plate, for example, the weight of the external work floor 30 can be reduced and workability can be improved, for example.

[0018] As shown in FIG. 5, the external work floor 30 has a first opening 32 through which the center pipe 21a can be inserted. The first opening 32 has a substantially circular shape, which may be, for example, a perfect circle or an ellipse. The shape of the first opening 32 may be, for example, a regular polygon, as long as the center pipe 21a can be inserted therethrough.

[0019] Furthermore, in addition to the external work floor 30, the first opening 32 may be provided in the grating 41. In this case, the first opening 32 can be formed, for example, by processing the grating 41. It is preferable that the first opening 32 provided in the grating 41 is provided at a position that overlaps with the first opening 32 of the external work floor 30.

[0020] 5, the external work floor 30 has a second opening 34 for attaching a davit crane 33. The davit crane 33 is installed on the external work floor 30. The davit crane 33 can be used to hoist materials and the like on the external work floor 30 during maintenance work on the offshore wind turbine 10, for example.

[0021] The second opening 34 has, for example, a substantially circular shape and is provided so as to penetrate vertically through the external work floor 30. The substantially circular shape may be, for example, a perfect circle or an ellipse. The shape of the second opening 34 may also be, for example, a regular polygon. The second opening 34 may be, for example, a space between the steel members 28 among the multiple steel members 28 that make up the framework of the external work floor 30. The second opening 34 is provided, for example, at the end of the external work floor 30. The second opening 34 is provided in a position that does not overlap with the transition piece 21 in a plan view.

[0022] Furthermore, in addition to the external work floor 30, the grating 41 may be provided with a second opening 34. In this case, the second opening 34 can be formed, for example, by processing the grating. The second opening 34 provided in the grating 41 is preferably provided at a position overlapping with the second opening 34 of the external work floor 30.

[0023] As shown in Figure 5, the external work floor 30 is configured to be divisible into multiple floor sections 31. Here, the longitudinal direction of the external work floor 30 is defined as a first direction X, and the lateral direction is defined as a second direction Y. The size of the external work floor 30 in the first direction X is greater than the size of the external work floor 30 in the second direction Y. The first direction X and the second direction Y are perpendicular to each other.

[0024] As shown in Figure 5, the external work floor 30 according to this embodiment is divided into three sections: a first floor section 31A, a second floor section 31B, and a third floor section 31C. Of these multiple floor sections 31, one floor section 31 (the first floor section 31A) has a second opening 34. Hereinafter, the floor section 31 of the external work floor 30 that has the second opening 34 will be referred to as the first floor section 31A. When the second opening 34 is formed in one floor section 31 in this way, the second opening 34 can be formed more easily than, for example, when the second opening 34 is formed across multiple floor sections 31.

[0025] 5, the external work floor 30 is divided into a plurality of floor sections 31 in the first direction X on a straight line L1 that runs along the second direction Y and passes through the center O (central axis) of the first opening 32. In this case, one of the plurality of floor sections 31 divided in the first direction X is the first floor section 31A. Of the external work floor 30 divided as described above, the floor portion 31 on the side not including the second opening 34 is further divided in the second direction Y on a line L2 that runs along the first direction X and passes through the center O of the first opening 32, into two floor portions 31. Here, of the floor portion 31 on the side not including the second opening 34, the floor portion 31 on the same side as the second opening 34 with respect to the center O of the first opening 32 in the second direction Y is referred to as the second floor portion 31B. Meanwhile, the floor portion 31 located on the diagonal line based on the center O of the first opening 32 with respect to the second opening 34 is referred to as the third floor portion 31C. The multiple floor portions 31 may be a collective term for, for example, the first floor portion 31A, the second floor portion 31B, and the third floor portion 31C.

[0026] The external work floor 30 does not have to be divided along the center O of the first opening 32, and the division position does not have to be a straight line. Furthermore, the number of divisions of the external work floor 30 is not limited to three, and the division positions are not limited to those described above.

[0027] The multiple floor sections 31 are arranged so as to surround the outer periphery of the tower 14 when viewed in the vertical direction. This allows the multiple floor sections 31 to function as a single external work floor 30.

[0028] As described above, the external work floor 30 is configured to be divisible into a plurality of floor sections 31. This makes the external work floor 30 smaller, and makes it easier to transport the external work floor 30.

[0029] The grating 41 is provided on the multiple floor sections 31. In this embodiment, the grating 41 is provided, for example, over the entire surface of the multiple floor sections 31, but such grating 41 is configured to be divisible into multiple grating sections 42. This allows the grating 41 to be made compact, making it easier to transport the grating 41. The dividing positions of the grating 41 may be the same as or different from the dividing positions of the external work floor 30.

[0030] Each of the multiple grating portions 42 is fixed to at least one of the multiple floor portions 31. The at least one floor portion 31 may be, for example, one of the first floor portion 31A, the second floor portion 31B, and the third floor portion 31C, or may be more than one of them. This allows the grating portions 42 to be fixed using the floor portions 31.

[0031] Adjacent grating portions 42 among the multiple grating portions 42 are not connected to each other. In other words, each grating portion 42 is supported only by the corresponding floor portion 31, and adjacent grating portions 42 do not have to be in contact with each other. This makes it possible to omit work such as welding to connect the grating portions 42 to each other.

[0032] (For details on external work platforms) 5, the external work floor 30 is configured to be divisible into multiple floor sections 31 at positions on a line passing through the tower 14 when viewed vertically. In other words, the external work floor 30 is divided at a position where the first opening 32 is divided. This makes it easier to combine the floor sections 31, for example. More preferably, the external work floor 30 is divided so that the perimeter length of the first opening 32 in each floor portion 31 is equal to or less than half the total perimeter length of the first opening 32. This eliminates the need to fit the external work floor 30 from above the tower 14 during assembly, and allows it to be positioned to surround the perimeter of the tower 14. As long as the position is on a line passing through the tower 14, the division may be made at a position passing through the center O of the tower 14, or at a position not passing through the center O of the tower 14.

[0033] Adjacent floor portions 31 among the plurality of floor portions 31 do not have to be connected to each other. That is, each floor portion 31 may be supported only by the transition piece 21 via legs 35 described below.

[0034] The multiple floor portions 31 according to this embodiment are a first floor portion 31A, a second floor portion 31B, and a third floor portion 31C. As shown in Fig. 5, the first floor portion 31A is adjacent to the second floor portion 31B and the third floor portion 31C at the end portion on the side having the first opening 32. In this case, the first floor portion 31A does not have to be connected to the second floor portion 31B and the third floor portion 31C. Furthermore, the second floor portion 31B is adjacent to the first floor portion 31A as well as the third floor portion 31C. In this case, the second floor portion 31B and the third floor portion 31C do not have to be connected to each other.

[0035] That is, the first floor section 31A, the second floor section 31B, and the third floor section 31C are supported only by the transition piece 21 via their respective legs 35. This makes it possible to omit work such as welding to connect the floor sections 31 together.

[0036] The multiple floor sections 31 may be arranged spaced apart from one another. That is, the first floor section 31A, the second floor section 31B, and the third floor section 31C may be adjacent to one another but spaced apart from one another. Also, the second floor section 31B and the third floor section 31C may be adjacent to one another but spaced apart from one another. This makes it possible to prevent a load acting on one floor portion 31 from affecting other floor portions 31, for example.

[0037] As shown in FIG. 5, the floor portion 31 adjacent to the tower 14 among the plurality of floor portions 31 is disposed with a gap 27 from the outer periphery of the tower 14 . Here, it is preferable that the gap 27 between the floor portion 31 and the outer periphery of the tower 14 is provided to an extent that the floor portion 31 and the outer periphery of the tower 14 do not come into contact with each other. Furthermore, it is more preferable to provide a wider gap 27 to an extent that the floor portion 31 and the tower 14 do not come into contact with each other even when the tower 14 is subjected to vibrations due to the influence of the external environment. This makes it possible to prevent the load acting on the floor portion 31 from reaching the tower 14. It is also possible to prevent the load acting on the tower 14 from reaching the floor portion 31.

[0038] The gap 27 between the outer periphery of the tower 14 and the external work floor 30 is formed in a substantially circular shape when viewed in the vertical direction. The substantially circular shape may be, for example, a perfect circle or an ellipse. By forming the gap 27 in a substantially circular shape, it is possible to, for example, make it easier to set the gap 27 between the floor portion 31 and the outer periphery of the tower 14 uniformly.

[0039] (Support structure for external work floor) 5, the plurality of floor sections 31 are each supported while being placed on the transition piece 21. That is, each of the plurality of floor sections 31 is individually placed on the transition piece 21. This allows the floor sections 31 to be installed in a stable state.

[0040] As described above, the transition piece 21 has a center pipe 21a at its center. The upper flange 21b and the lower flange 21c are formed in a cross shape. That is, the transition piece 21 has four protrusions. Here, by placing the external work floor 30 as shown in FIG. 5 , when viewed from above the tower 14, one of the four protrusions is entirely covered by the external work floor 30, and each of the remaining three protrusions is partially exposed from the external work floor 30. The protrusion covered by the external work floor 30 is referred to as protrusion 21A. Two of the four protrusions protrude in the first direction X, and the remaining two protrude in the second direction Y. Protrusion 21A protrudes in the first direction X.

[0041] 5 to 7, the plurality of floor sections 31 include legs 35 that are placed on the transition piece 21. This makes it easier for the floor sections 31 to be supported by the transition piece 21, for example. The leg portions 35 may be, for example, steel pipes or H-shaped steel. The leg portions 35 extend downward from the plurality of floor portions 31. One floor portion 31 may be provided with, for example, a plurality of leg portions 35. The leg portions 35 are provided so as to overlap the transition pieces 21. 5 and 6, for example, the transition piece 21 has leg arrangement areas 23 at a total of 15 locations on four protruding portions. Specifically, legs 35 are placed at four locations on each of the three protruding portions excluding protruding portion 21A. Furthermore, legs 35 are placed at three locations on protruding portion 21A, and support members 24 that support the davit crane 33 are provided in the portions corresponding to the portions on which the legs 35 are not placed. In other words, as shown in FIG. 6, the first floor portion 31A has seven legs 35, and the second floor portion 31B and the third floor portion 31C each have four legs 35.

[0042] The leg portion 35 may be welded to, for example, the transition piece 21. For example, the leg portion 35 may be welded to the upper surface of the transition piece 21. 7 and 8, the transition piece 21 includes a support plate 36 in the leg arrangement region 23. The support plate 36 is a plate-shaped steel member, and for example, a steel plate is preferably used. The support plate 36 is attached to the lower end of the leg 35 by welding. The support plate 36 is placed on the upper surface of the transition piece 21, and, for example, the outer periphery of the support plate 36 is welded to the upper surface of the transition piece 21. This allows the leg 35 to be firmly fixed to the transition piece 21. As the welding method, any known method can be suitably adopted. As shown in Fig. 8, the leg portion 35 is preferably disposed and welded so as to be positioned at the center of the support plate 36.

[0043] (About davit cranes) 9, the marine structure 20 may further include a davit crane 33 and a support member 24 that supports the davit crane 33. In addition, a second opening 34 for passing the support member 24 is formed in at least one floor portion 31 of the plurality of floor portions 31.

[0044] The support member 24 is made of, for example, steel, and the davit crane 33 is attached to the offshore structure 20 via the support member 24. One end of the support member 24 is connected to the side surface of the transition piece 21, and the other end passes through a second opening 34 formed in the floor portion 31 and is connected to the davit crane 33. The support member 24 has a one end portion 24a located on one end side of the support member 24 that is inclined, and an other end portion 24b located on the other end side that extends vertically. The one end portion 24a is connected to the side surface of the transition piece 21 (leg 22), and the other end portion 24b passes through a second opening 34 formed in the floor portion 31 and is connected to a davit crane 33. That is, the floor portion 31 is not in contact with the support member 24. This makes it possible to prevent interference between the floor portion 31 and the support member 24 even when the davit crane 33 is provided.

[0045] As shown in FIG. 9 , the offshore structure 20 includes a horizontal support member 25 that spans between the transition piece 21 and the support member 24. The horizontal support member 25 includes a steel pipe 26. The steel pipe 26 extends upward from a midpoint in the longitudinal direction of the horizontal support member 25. The steel pipe 26 has a protrusion 26a at its upper part. The external work platform 30 is installed on the protrusion 26a. Note that the horizontal support member 25 does not necessarily have to include the steel pipe 26.

[0046] The davit crane 33 is supported by the support member 24 that passes through the second opening 34, and the floor portion 31 and the support member 24 are not in contact with each other. In other words, the davit crane 33 is not supported by any of the multiple floor portions 31. This makes it possible to prevent a load acting on one of the multiple floor portions 31 and the davit crane 33 from affecting the other. The second opening 34 may also be provided in the grating 41 as in this embodiment. The support member 24 penetrates the floor portion 31 and the grating portion 42 and can support the davit crane 33. This prevents interference between the grating 41 and the support member 24.

[0047] As explained above, the external work platform 30 according to this embodiment is configured to be divisible into multiple floor sections 31, and by combining the multiple floor sections 31, it is configured to surround the outer periphery of the tower 14 of the offshore wind turbine 10 when viewed in the vertical direction. This makes it easy to transport the external work platform 30 and allows for efficient construction.

[0048] (Regarding offshore structures) The marine structure 20 according to this embodiment includes the external working floor 30 according to the present disclosure. This allows the marine structure 20 to enjoy the above-described effects. For example, because the marine structure 20 includes the external working floor 30 that can be separated, the external working floor 30 can be easily transported. This allows the construction of the marine structure 20 to be carried out efficiently.

[0049] (Method of assembling marine structures) Next, an assembly method of this embodiment will be described. The assembly method is a method for assembling the marine structure 20. The method for assembling the marine structure 20 according to this embodiment is a method for assembling the marine structure 20 including an external working platform 30, a transition piece 21, and a substructure 50. The substructure 50 is, for example, a jacket-type foundation. The assembly method includes a first installation step, a second installation step, and a third installation step.

[0050] (First installation process) The first installation step can be carried out in a yard on land or the like. In the first attachment step, some of the floor portions 31 are attached to the transition piece 21 placed on the ground (for example, a yard on land, etc.). Here, the some of the floor portions 31 of the plurality of floor portions 31 may be, for example, the second floor portion 31B and the third floor portion 31C. The second floor portion 31B and the third floor portion 31C are even smaller than the first floor portion 31A, and therefore can be easily transported and carried on land. More specifically, in the first attachment step, the legs 35 provided on the second floor section 31B and the third floor section 31C are attached to the upper surface of the transition piece 21. In the first attachment step, the transition piece 21 is placed on the ground, such as in a yard on land, so that the work can be carried out at a low altitude. As a result, the offshore structure 20 can be assembled more efficiently.

[0051] (Second installation process) The second installation step can be carried out in a yard on land, as in the first installation step. In the second installation step, the transition piece 21 to which the floor section 31 has been attached in the first installation step is installed by a crane onto the upper part of the substructure 50 placed on the ground. Here, the crane is different from the davit crane 33 and refers to a crane that is capable of assembling the marine structure 20 on land. In the second installation step, the work using the crane can be performed in a yard or the like. This allows the crane to work in a stable state compared to construction on the sea. Therefore, the marine structure 20 can be assembled more efficiently.

[0052] (Third installation process) The third installation step can be carried out in a yard on land or the like, similar to the first installation step and the second installation step. In the third installation step, for example, a crane is used to install the remaining floor portion 31 of the multiple floor portions 31 to the transition piece 21 that was installed on the upper part of the lower structure 50 in the second installation step. Here, the remaining floor portion 31 in this embodiment is, for example, the first floor portion 31A.

[0053] In the assembly method according to this embodiment, in the second attachment step, the remaining floor portion 31 is not attached to the transition piece 21. The remaining floor portion 31 according to this embodiment is, for example, the first floor portion 31A. Therefore, the lifting load of the crane in the second attachment step can be reduced.

[0054] As described above, according to the external work floor 30, marine structure 20, and method for assembling the marine structure 20 of this embodiment, the external work floor 30 is divided, making it easy to transport the external work floor 30 and allowing construction to be carried out efficiently.

[0055] (Second embodiment) Next, an external work platform 30 according to a second embodiment of the present disclosure will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, with only the differences being described.

[0056] 10, the external work floor 30 according to the second embodiment includes a plurality of steel members 28. The plurality of steel members 28 are, for example, beams, and form the framework of the external work floor 30.

[0057] 10, the external work floor 30 is divided into a fourth floor section 31D and a fifth floor section 31E. Specifically, it is divided into two floor sections 31 in the first direction X on a straight line L1 that runs along the second direction Y and passes through the center O of the first opening 32. In this case, the external work floor 30 does not have to be divided so as to pass through the center of the first opening 32, and the division position does not have to be a straight line. Here, the floor portion 31 on the side having the second opening 34 is referred to as a fourth floor portion 31D, and the floor portion 31 on the side not having the second opening 34 is referred to as a fifth floor portion 31E.

[0058] 10, the plurality of floor sections 31 include legs 35 that are placed on the transition piece 21. As shown in FIG. 11, for example, the legs 35 are placed at a total of 12 locations on four protruding portions of the transition piece 21. Specifically, the legs 35 are placed at four locations on two protruding portions of the transition piece 21 that protrude in the first direction X, and at two locations on two protruding portions that protrude in the second direction Y. In other words, as shown in Fig. 10, the fourth floor portion 31D and the fifth floor portion 31E each have six legs 35. This makes it easier for the transition piece 21 to support the floor portion 31.

[0059] The legs 35 of the external work platform 30 according to the second embodiment are not rigidly connected to the transition piece 21. In this embodiment, the legs 35 are not welded to the transition piece 21. Furthermore, as shown in FIG. 12 , the legs 35 are installed on the transition piece 21 via a position restriction mechanism 45. The position restriction mechanism 45 restricts vertical and horizontal movement of the legs 35 relative to the transition piece 21. As shown in Figure 12, the position restriction mechanism 45 is provided on the leg arrangement area 23 where the leg 35 is installed. The position restriction mechanism 45 includes a support plate 36, a base plate 37, an L-shaped hook 38 (hook), a retaining plate 39, and a spacer 40. One position restriction mechanism 45 restricts the vertical and horizontal movement of one leg 35 relative to the transition piece 21. A plurality of position restriction mechanisms 45 are provided corresponding to the legs 35.

[0060] As shown in FIG. 12, the base plate 37 is a plate-shaped steel member welded to the upper surface of the transition piece 21. The support plate 36 is a plate-shaped steel member having the legs 35 attached to its upper surface, and is placed on the upper surface of the base plate 37. The support plate 36 is fixed to the legs 35 by welding. It is preferable that the support plate 36 is smaller than the base plate 37. The L-shaped hook 38 is an L-shaped steel member having a protruding portion 38a that faces the leg portion 35 in the horizontal direction. 14, the L-shaped hooks 38 are provided at positions corresponding to two adjacent sides of the support plate 36. In this embodiment, two L-shaped hooks 38 are provided per side of the support plate 36, but one or three or more L-shaped hooks 38 may be provided per side of the support plate 36. 12 and 13, the L-shaped hook 38 is provided at one end of the base plate 37 so as to hold down the support plate 36. The protrusion 38a is located above the end of the support plate 36. Therefore, the protrusion 38a can prevent the support plate 36 from floating up.

[0061] The pressing plate 39 is a plate-shaped steel member provided at the end (other end) of the base plate 37 on the side where the L-shaped hook 38 is not installed. 14, the pressure plates 39 are provided on two adjacent sides of the support plate 36, that is, on two sides opposite to the side on which the L-shaped hooks 38 are provided. In this embodiment, one pressure plate 39 is provided per side of the support plate 36, but multiple pressure plates 39 may be provided per side of the support plate 36. The side of the pressure plate 39 is provided at the other end of the base plate 37 so as to press down on the support plate 36. The spacer 40 is provided between the L-shaped hook 38 and pressure plate 39, and the support plate 36. The spacer 40 is, for example, a plate-shaped steel member, and its front surface is in contact with the support plate 36. By arranging the L-shaped hook 38, pressure plate 39, and spacer 40 in this manner, horizontal displacement of the leg 35 can be suppressed. Here, the L-shaped hooks 38, the retaining plate 39, and the spacer 40 are welded to the upper surface of the base plate 37. On the other hand, the contact surfaces of the support plate 36 and the spacer 40 and the contact surfaces of the support plate 36 and the base plate 37 are not welded. As a result, the legs 35 are not rigidly connected to the transition piece 21, and therefore it is not necessary to take the external work platform 30 into consideration in the structural analysis. This simplifies the structural analysis. The legs 35 of the external work platform 30 according to the first embodiment may be placed on the transition piece 21 by a position restriction mechanism 45. Furthermore, the legs 35 of the external work platform 30 according to the second embodiment may be welded to the transition piece 21, as in the first embodiment.

[0062] Here, a method for attaching the position restriction mechanism 45 according to the second embodiment will be described. First, before attaching the external work platform 30 to the transition piece 21, a support plate 36 is welded to the leg 35 of the external work platform 30, a base plate 37 is welded to the underside of the support plate 36, and an L-shaped hook 38, a retaining plate 39, and a spacer 40 are welded to the upper surface of the base plate 37. Note that the contact surfaces of the support plate 36 and the spacer 40 and the contact surfaces of the support plate 36 and the base plate 37 are not welded to each other. Next, the external work platform 30 is lifted up by a crane, and the base plate 37 is placed on the transition piece 21 (the detailed method of attaching the external work platform 30 according to the second embodiment will be described later). Finally, the base plate 37 is welded to the upper surface of the transition piece 21. With the above steps, the position restriction mechanism 45 can be attached to the transition piece 21.

[0063] The method of attaching the position restriction mechanism 45 is not limited to the above method. For example, before attaching the external work platform 30 to the transition piece 21, the support plate 36 is welded to the leg 35 of the external work platform 30. Furthermore, before attaching the external work platform 30 to the transition piece 21, the base plate 37 is welded to the upper surface of the transition piece 21. At this time, the L-shaped hook 38, the retaining plate 39, and the spacer 40 are not provided on the base plate 37. Next, the external work platform 30, with the support plate 36 attached to the legs 35, is lifted by a crane, and the support plate 36 attached to the legs 35 is placed on the base plate 37. Finally, the L-shaped hook 38, the presser plate 39, and the spacer 40 are welded to the upper surface of the base plate 37. Note that the contact surfaces of the support plate 36 and the spacer 40 and the contact surfaces of the support plate 36 and the base plate 37 are not welded to each other. In this manner, the position restriction mechanism 45 can be attached to the transition piece 21.

[0064] Next, a method for assembling the marine structure 20 equipped with the external working platform 30 according to the second embodiment will be described. The assembly method according to the second embodiment includes a first attachment step and a second attachment step. Here, the lower structure 50 is, for example, a jacket-type foundation.

[0065] (First installation process) The first installation step can be carried out in a yard on land or the like. In the first installation step, the transition piece 21 is installed by a crane on top of the lower structure 50 placed on the ground. Here, the crane refers to a crane capable of assembling the marine structure 20 on land, as in the first embodiment. The first installation step can be carried out in a yard or the like, and compared to construction on the sea, it is possible to work in a stable state with the crane. Therefore, the marine structure 20 can be assembled more efficiently.

[0066] (Second installation process) The second installation step can be carried out in a yard on land or the like. In the second attachment step, a plurality of floor sections 31 are attached by a crane to the transition piece 21 attached to the upper part of the lower structure 50. The plurality of floor sections 31 are, for example, the fourth floor section 31D and the fifth floor section 31E.

[0067] In the assembly method of the first embodiment, a portion of the floor portion 31 is attached to the transition piece 21 in the first attachment step, and the transition piece 21 with the attached floor portion 31 is attached to the lower structure 50 in the second attachment step. On the other hand, in the assembly method of the second embodiment, the floor portion 31 is not attached to the transition piece 21 in the first attachment step. This makes it possible to reduce the lifting load of the crane when attaching the transition piece 21 to the lower structure 50.

[0068] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0069] For example, the external work floor 30 does not have to be supported while placed on the transition piece 21. The external work floor 30 does not have to be provided with legs 35 that are placed on the transition piece 21. The external work floor 30 does not have to be configured so that it can be divided into multiple floor sections 31 at a position on a line that passes through the tower 14 when viewed along the vertical direction. Among the multiple floor portions 31, adjacent floor portions 31 may be connected to each other. The multiple floor portions 31 do not have to be arranged spaced apart from each other. Among the multiple floor portions 31, the floor portion 31 adjacent to the tower 14 does not have to be arranged with a gap 27 from the outer periphery of the tower 14. The gap 27 between the floor portion 31 and the outer periphery of the tower 14 does not have to be approximately circular. The grating 41 does not have to be provided on the multiple floor portions 31. The grating 41 does not have to be configured so as to be divisible into multiple grating portions 42. The offshore structure 20 may not include the davit crane 33 and the support member 24. The second opening 34 for passing the support member 24 may not be formed in at least one floor portion 31 of the multiple floor portions 31. The second opening 34 may be formed in the multiple floor portions 31. The offshore structure 20 may not include the grating 41 on the floor portion 31, and the second opening 34 for passing the support member 24 may not be formed in the grating 41. The davit crane 33 may be supported on any one or more of the multiple floor sections 31.

[0070] Furthermore, the substructure 50 according to this embodiment may be a monopile foundation, which is a fixed-bottom foundation different from a jacket-type foundation, or a floating foundation different from a fixed-bottom foundation, in addition to the jacket-type foundation. The monopile foundation shown in Fig. 15 is configured by providing a transition piece 21 on top of a monopile 20M driven into the seabed. The monopile foundation shown in Fig. 15 has a configuration corresponding to a center pipe 21a. The center pipe 21a in the monopile foundation shown in Fig. 15 is, for example, cylindrical. Alternatively, the center pipe 21a in the monopile foundation shown in Fig. 15 may have a shape whose diameter increases from top to bottom. The floating foundation shown in Fig. 16 is configured by supporting a floating body 20F floating on the sea with wires 20W connected to the seabed. The floating foundation shown in Fig. 16 has a configuration equivalent to a center pipe 21a. The center pipe 21a in the floating foundation shown in Fig. 16 is supported on the sea by the buoyancy acting on the floating body 20F.

[0071] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

[0072] (Addendum) The embodiment can be understood, for example, as follows.

[0073] <1> An external work floor according to one aspect of the present disclosure is an external work floor provided on an offshore structure that supports an offshore wind turbine, and is configured to be divisible into multiple floor sections, and by combining the multiple floor sections, is configured to surround the outer periphery of the tower of the offshore wind turbine when viewed vertically.

[0074] The external work floor is configured to be divisible into a plurality of floor sections, which allows the external work floor to be made compact and easy to transport. By combining the multiple floor sections, the structure is configured to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction, which makes it possible to configure an external work floor that surrounds the outer periphery of the tower using compact floor sections. Therefore, construction can be carried out efficiently.

[0075] <2> the above <1> In the external working platform according to the above, the offshore structure may be provided with a transition piece, and each of the plurality of floor sections may be supported while being placed on the transition piece.

[0076] Each of the plurality of floor sections is supported while being placed on the transition piece, which allows, for example, the floor sections to be installed in a stable state.

[0077] <3> the above <2> In the external work platform according to the above, a configuration may be adopted in which each of the plurality of floor sections includes a leg section that is placed on the transition piece.

[0078] Each of the floor sections includes a leg portion that rests on the transition piece, which makes it easier for the floor sections to be supported by the transition piece, for example.

[0079] <4> the above <3> In the external work platform according to the above, a configuration may be adopted in which the legs are welded to the transition pieces.

[0080] The legs are welded to the transition piece, which allows, for example, the legs to be firmly fixed to the transition piece.

[0081] <5> the above <3> In the external work platform according to the above, a configuration may be adopted in which the legs are not rigidly connected to the transition piece.

[0082] The legs are not rigidly connected to the transition piece, which simplifies the structural analysis, for example, because there is no need to consider the external work platform in the structural analysis.

[0083] <6> the above <1> from <5> The external work platform according to any one of the above aspects may be configured to be divisible into a plurality of floor sections at a position on a line passing through the tower when viewed vertically.

[0084] The external work platform is configured to be divisible into a plurality of floor sections at positions on a line passing through the tower when viewed vertically, which makes it easier to combine the floor sections, for example.

[0085] <7> the above <1> from <6> In the external work floor according to any one of the above aspects, a configuration may be adopted in which adjacent floor sections among the plurality of floor sections are not connected to each other.

[0086] Adjacent floor sections among the plurality of floor sections are not connected to each other, which makes it possible to omit work such as welding for connecting the floor sections to each other, for example.

[0087] <8> the above <1> from <7> In the external work platform according to any one of the above aspects, a configuration may be adopted in which the plurality of floor sections are arranged spaced apart from each other.

[0088] The plurality of floor sections are arranged spaced apart from one another, which makes it possible to prevent, for example, a load acting on one floor section from affecting the other floor sections.

[0089] <9> the above <1> from <8> In any one of the above-mentioned external work floors, a configuration may be adopted in which the floor portion adjacent to the tower among the plurality of floor portions is positioned with a gap from the outer periphery of the tower.

[0090] Of the multiple floor sections, the floor section adjacent to the tower is arranged with a gap from the outer periphery of the tower. This prevents the floor section from coming into contact with the tower. Therefore, the load acting on the floor section can be prevented from being applied to the tower. Also, the load acting on the tower can be prevented from being applied to the floor section.

[0091] <10> the above <9> In the external work platform according to the above, a configuration may be adopted in which the gap is formed in a substantially circular shape when viewed in the vertical direction.

[0092] The gap at the outer periphery of the tower is formed in a substantially circular shape when viewed in the vertical direction, which makes it easier to set the gap between the floor portion and the outer periphery of the tower uniform, for example.

[0093] <11> the above <1> from <10> In the external work platform according to any one of the above aspects, a configuration may be adopted in which gratings are provided on a plurality of the floor portions.

[0094] The external work floor is provided with gratings installed on multiple floor sections, which makes it possible to reduce the weight of the external work floor and improve workability compared to when steel plates are installed on the external work floor, for example.

[0095] <12> the above <11> In the external work platform according to the above, a configuration may be adopted in which the grating is configured to be divisible into a plurality of grating sections.

[0096] The grating is configured to be separable into a plurality of grating sections, which allows the grating to be made compact and easy to transport.

[0097] <13> the above <12> In the external work platform according to the present invention, a configuration may be adopted in which each of the plurality of grating sections is fixed to at least one of the plurality of floor sections.

[0098] Each of the grating sections is fixed to at least one of the plurality of floor sections, which allows the grating sections to be fixed using the floor sections, for example.

[0099] <14> the above <12> or <13> In one aspect of the external work platform, a configuration may be adopted in which adjacent grating sections among the plurality of grating sections are not connected to each other.

[0100] Adjacent grating sections among the plurality of grating sections are not connected to each other, which makes it possible to omit work such as welding for connecting the grating sections to each other, for example.

[0101] <15> The marine structure according to one aspect of the present disclosure is <1> from <14> The present invention is provided with an external work floor according to any one of the above aspects.

[0102] The marine structure is equipped with an external working platform according to the present disclosure. This allows the marine structure to enjoy the above-mentioned effects. For example, because the marine structure is equipped with a separable external working platform, the external working platform can be easily transported. This allows for efficient construction of the marine structure.

[0103] <16> the above <15> The marine structure according to the present invention may be configured to include a davit crane provided on the external work platform, and a support member supporting the davit crane, and an opening for passing the support member is formed in at least one of the plurality of floor portions.

[0104] An opening for passing the support member is formed in at least one of the floor sections. This allows the opening to be formed in a compact floor section, improving workability. In addition, even when a davit crane is installed, interference between the floor section and the support member can be prevented.

[0105] <17> the above <16> In the marine structure according to the above, a configuration may be adopted in which the opening is formed in one of the floor portions.

[0106] The opening is formed in one floor portion, which makes it easier to form the opening compared to, for example, a case where the opening is formed across a plurality of floor portions.

[0107] <18> the above <16> In the marine structure according to the above, a configuration may be adopted in which the davit crane is not supported by any of the plurality of floor portions.

[0108] The davit crane is not supported by any of the floor sections, which prevents a load acting on one of the floor sections and the davit crane from affecting the other.

[0109] <19> the above <16> from <18> In any one of the above embodiments, the marine structure may have a configuration characterized in that it includes gratings provided on a plurality of the floor portions, and openings are formed in the gratings to allow the support members to pass through.

[0110] The apparatus includes a grating provided on the plurality of floor sections, and openings are formed in the grating to allow the support members to pass through. This prevents interference between the grating and the support members.

[0111] <20> A method for assembling a marine structure according to one aspect of the present disclosure includes the steps of: <1> ~ <14> A method for assembling an offshore structure comprising an external work floor, a transition piece, and a lower structure according to any one of the above embodiments, comprising: a first attachment step of attaching some of the floor sections to the transition piece placed on the ground; a second attachment step of attaching the transition piece to which the floor sections have been attached in the first attachment step, by a crane, to an upper part of the lower structure placed on the ground; and a third attachment step of attaching the remaining floor sections of the plurality of floor sections to the transition piece attached to the upper part of the lower structure in the second attachment step, by a crane.

[0112] In the first attachment step, some of the floor sections are attached to the transition piece placed on the ground, which allows the first attachment step to be performed at a low elevation. In the second attachment step, the transition piece to which the floor portion was attached in the first attachment step is attached by a crane to the top of the lower structure placed on the ground, and in the third attachment step, the remaining floor portions of the multiple floor portions are attached by a crane to the transition piece that was attached to the top of the lower structure in the second attachment step. In this way, because the remaining floor portions are not attached to the transition piece in the second attachment step, the lifting load of the crane can be reduced.

[0113] <21> A method for assembling a marine structure according to one aspect of the present disclosure includes the steps of: <1> ~ <14> A method for assembling an offshore structure comprising an external work floor, a transition piece, and a lower structure according to any one of the above embodiments, comprising a first installation step of installing the transition piece by a crane on top of the lower structure placed on the ground, and a second installation step of installing a plurality of the floor sections by a crane on the transition piece installed on top of the lower structure in the first installation step.

[0114] In a first attachment step, the transition piece is attached by a crane to the top of the lower structure placed on the ground. In a second attachment step, multiple floor sections are attached by a crane to the transition piece attached to the top of the lower structure in the first attachment step. In this way, because the floor sections are not attached to the transition piece in the first attachment step, the lifting load of the crane can be reduced. [Explanation of symbols]

[0115] 1. Offshore wind power systems 10 Offshore wind turbines 11 Blades 12 Hub 13 Nacelle 14. Tower 20 Marine structures 21 Transition Piece 21a center pipe 21b Upper flange 21c Lower flange 21d Web 1 21e Second Web Leg 22 23 Leg placement area 24 Support member 25 Horizontal support member 26 Steel pipe 27 Gap 30 External work floor 31 Floor part 31A 1st floor section 31B 2nd floor part 31C 3rd floor section 31D 4th floor section 31E 5th floor section 32 First opening 33 Davit crane 34 Second Opening 35 Legs 36 Support plate 37 Base Plate 38 L-shaped hooks 39 Retaining plate 40 spacer 41 Grating 42 Grating part 45 Position regulation mechanism 50 Undercarriage X 1st direction Y Second direction P pile

Claims

1. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; each of the plurality of floor sections includes a steel member; The steel members are beams on the external work floor.

2. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; Equipped with grating, The plurality of floor sections and the grating are different, The grating is an external work floor provided on a plurality of the floor sections.

3. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; The marine structure is a jacket-type foundation, The jacket type foundation includes a transition piece, An external work floor in which each of the plurality of floor sections is supported while being placed on the upper surface of the transition piece.

4. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; the offshore structure includes a transition piece; Each of the plurality of floor sections is supported in a state of being placed on the transition piece, Each of the plurality of floor sections includes a leg portion that is placed on the transition piece, An external work platform in which the legs are not rigidly connected to the transition piece.

5. the offshore structure includes a transition piece; The external work platform according to any one of claims 1 to 3, wherein each of the plurality of floor sections is supported while being placed on the transition piece.

6. The external work floor according to claim 5 , wherein each of the plurality of floor sections includes a leg portion that rests on the transition piece.

7. The external work platform of claim 6 , wherein the legs are welded to the transition pieces.

8. The external work floor according to any one of claims 1 to 4, wherein the external work floor is configured so as to be divisible into a plurality of floor sections at positions on a line passing through the tower when viewed along the vertical direction.

9. The external work floor according to any one of claims 1 to 4, wherein adjacent floor sections among the plurality of floor sections are not connected to each other.

10. 5. An external work floor according to claim 1, wherein the plurality of floor sections are arranged spaced apart from each other.

11. 5. An external work platform according to claim 1, wherein the floor section adjacent to the tower among the plurality of floor sections is arranged with a gap from the outer periphery of the tower.

12. The external work platform according to claim 11, wherein the gap is formed in a substantially circular shape when viewed in the vertical direction.

13. The external work platform according to claim 2, wherein the grating is configured to be divisible into a plurality of grating sections.

14. The external work floor according to claim 13, wherein each of the plurality of grating sections is fixed to at least one of the plurality of floor sections.

15. The external work platform according to claim 13, wherein adjacent grating sections among the plurality of grating sections are not connected to each other.

16. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; An offshore structure comprising the external working platform, a davit crane provided on the external work platform; a support member for supporting the davit crane, An offshore structure, wherein the plurality of floor sections are formed to allow the support members to pass through.

17. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; An offshore structure comprising the external working platform, a davit crane provided on the external work platform; a support member for supporting the davit crane, An offshore structure in which an opening for passing the support member is formed in at least one of the plurality of floor portions.

18. 18. The offshore structure according to claim 17, wherein the opening is formed in one of the floor portions.

19. 19. The marine structure according to any one of claims 16 to 18, wherein the davit crane is not supported on any of the plurality of floor portions.

20. gratings provided on the plurality of floor portions; 19. The marine structure according to any one of claims 16 to 18, wherein an opening is formed in the grating for passing the support member therethrough.

21. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; A method for assembling an offshore structure comprising the external working floor, a single transition piece, and a substructure, comprising: a first attachment step of attaching some of the floor sections to the single transition piece placed on the ground; a second installation step of installing the single transition piece to which the floor section has been attached in the first installation step, to an upper portion of the lower structure placed on the ground, by using a crane; a third installation step of installing the remaining floor sections of the plurality of floor sections to the single transition piece installed on the upper part of the lower structure in the second installation step by using a crane; A method for assembling a marine structure comprising:

22. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; A method for assembling an offshore structure comprising the external working platform, a transition piece, and a substructure which is a monopile foundation or a floating foundation, comprising: a first attachment step of attaching some of the floor sections to the transition piece placed on the ground; a second installation step of installing the transition piece, to which the floor portion has been attached in the first installation step, to an upper portion of the lower structure placed on the ground by a crane; a third installation step of installing the remaining floor sections of the plurality of floor sections to the transition piece installed on the upper part of the lower structure in the second installation step by using a crane; A method for assembling a marine structure comprising:

23. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; A method for assembling an offshore structure comprising the external working floor, a single transition piece, and a substructure, comprising: a first installation step of installing the single transition piece on an upper portion of the lower structure placed on the ground by a crane; a second installation step of installing the plurality of floor sections by a crane to the single transition piece installed on the upper part of the lower structure in the first installation step; A method for assembling a marine structure comprising:

24. An external work platform provided on an offshore structure supporting an offshore wind turbine, It is configured to be divisible into multiple floor sections, a plurality of the floor sections are combined together to surround the outer periphery of the tower of the offshore wind turbine when viewed along the vertical direction; A method for assembling an offshore structure comprising the external working platform, a transition piece, and a substructure which is a monopile foundation or a floating foundation, comprising: a first installation step of installing the transition piece on an upper portion of the lower structure placed on the ground by a crane; a second installation step of installing the plurality of floor sections to the transition piece installed on the upper part of the lower structure in the first installation step by using a crane; A method for assembling a marine structure comprising:

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