JP7337235B1 - jacket structure - Google Patents

Abstract

An object of the present invention is to provide an economical jacket structure while ensuring sufficient performance in terms of both fatigue strength and ultimate strength. [Solution] A transition piece 10 supporting an offshore wind turbine, a first steel pipe leg 21 supporting the transition piece 10, a second steel pipe leg 22 supporting the transition piece 10, a first steel pipe leg 21 and a first steel pipe leg 21 supporting the transition piece 10. A jacket structure 100 comprising: a diagonal brace 30 connecting two steel pipe legs 22; The fatigue load is dominant between the upper part U including the intersection point and the lower part L of the second steel pipe leg 22 including the intersection point between the second steel pipe leg 22 and the lower end of the diagonal brace 30. For those where the ultimate load is dominant, the first steel material is used, and for those where the ultimate load is dominant, the second steel material having higher strength than the first steel material is used. [Selection diagram] Figure 1

Description

The present invention relates to jacket structures.

BACKGROUND OF THE INVENTION A jacket structure that combines steel pipes is sometimes used in order to arrange wind turbines and the like used for wind power generation on the sea.
Patent Literature 1 discloses a jacket structure in which a reinforcing portion is provided inside a main member that also serves as a pile guide as a countermeasure against earthquakes.
Patent Literature 2 discloses a joint structure in which the number of welded portions between a steel pipe pile and a steel outer pipe is reduced as a countermeasure against repeated loads due to vibration of a wind turbine.
In Patent Document 3, in order to enable rational design of jackets and piles, a pile with a shear key that protrudes above the required height from the submerged ground is inserted into the lower part of the leg that has an inner diameter larger than the pile diameter, and this connection part is made. A structure is disclosed in which a predetermined length between the inner periphery of the leg and the outer periphery of the pile is filled with grout material and joined.

JP 2004-11363 A WO2012/118186 JP 2003-221816 A

The can of the jacket is often composed of one type of steel. In a jacket structure that supports an offshore wind turbine, there may be a mixture of a portion where fatigue strength is a dominant factor and a portion where ultimate strength is a dominant factor. By increasing the plate thickness of the can, both the ultimate strength and the fatigue strength can be improved. If the steel material of the can is changed to a higher strength one, the ultimate strength can be improved, but the fatigue strength cannot be improved. In order to improve the ultimate strength of the can, it is generally more economical to use a steel material with a higher strength than to increase the plate thickness. At this time, if a high-strength steel material is selected to meet the ultimate strength, and the plate thickness is increased to meet the fatigue strength, depending on the part, the steel will have excessive performance, which is uneconomical.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an economical jacket structure while securing sufficient performance in terms of both fatigue strength and ultimate strength.

In order to solve the above problems, the present invention proposes the following means.
A first aspect of the present invention includes a transition piece that supports an offshore wind turbine, a first steel pipe leg that supports the transition piece, a second steel pipe leg that supports the transition piece, the first steel pipe leg, and the a diagonal brace connecting a second steel pipe leg, the portion of the first steel pipe leg, the intersection of the first steel pipe leg and the upper end of the diagonal brace being and the lower portion of the second steel pipe leg, which includes the intersection of the second steel pipe leg and the lower end of the oblique brace, in which the fatigue load is dominant. is characterized in that a first steel material is used, and a second steel material having a strength higher than that of the first steel material is used when the ultimate load is dominant.

According to the present invention, the first steel material is used for the upper part and the lower part where the fatigue load is dominant, and the first steel material is used for the one where the ultimate load is dominant. A high-strength second steel material is used. As a result, for example, by forming the first steel pipe leg from one type of steel material, compared to the case where the upper part and the lower part are made of the same steel material, sufficient performance in both fatigue strength and ultimate strength can be obtained. while ensuring the performance of each part of the first steel pipe leg can be flexibly set. Therefore, excessive performance of the first steel pipe leg can be prevented, and an economical structure can be achieved.

Aspect 2 of the present invention is characterized in that, in the jacket structure of aspect 1, the thickness of the portion dominated by the ultimate load is greater than the thickness of the portion dominated by the fatigue load.

According to the invention, the thickness of which the ultimate load predominates is greater than the thickness of which the fatigue load predominates. Here, when using the high-strength second steel material for the one in which the ultimate load is dominant, it may rather be uneconomical depending on the price of the steel material to be applied. On the other hand, by increasing the thickness of the portion of the first steel pipe leg where the ultimate load is dominant, the necessary ultimate strength can be ensured without using unnecessarily expensive steel materials. In addition, for example, when it is not possible to obtain sufficient ultimate strength only by using a high-strength material due to structural reasons, etc., sufficient ultimate strength can be obtained.

Aspect 3 of the present invention is characterized in that, in the jacket structure of Aspect 1, the thickness of the portion dominated by the ultimate load is thinner than the thickness of the portion dominated by the fatigue load.

According to the invention, the thickness of which the ultimate load dominates is less than the thickness of which the fatigue load dominates. For example, when a high-strength material is used for the portion of the first steel pipe leg where the ultimate load is dominant, by making the thickness thinner than the portion where the fatigue load is dominant, the minimum necessary ultimate load strength. Therefore, the first steel pipe leg can be made more economical.

Aspect 4 of the present invention is the jacket structure according to any one of aspects 1 to 3, wherein the fatigue load is dominant in one of the upper portion and the lower portion, and the first steel material is used. , the other of the upper portion and the lower portion is dominated by the ultimate load and is made of the second steel material.

According to this invention, one of the upper part and the lower part is dominated by the fatigue load and the first steel material is used, and the other of the upper part and the lower part is dominated by the ultimate load. 2 steel materials are used. That is, a steel material having a higher strength than a portion where the fatigue load is dominant is used for the portion where the ultimate load is dominant. In this way, for example, by appropriately selecting the material to be used for each part according to design conditions including ground conditions, it is possible to efficiently ensure the performance required of the first steel pipe leg. Therefore, an economical first steel pipe leg can be obtained.

Aspect 5 of the present invention is the jacket structure according to Aspect 4, wherein the fatigue load is dominant in the upper portion, the first steel material is used, and the ultimate load is dominant in the lower portion. , wherein the second steel material is used.

For example, if the size of the offshore windmill is large, the shaking caused by the rotation of the offshore windmill becomes severe, so the fatigue load becomes dominant in the upper portion and the ultimate load becomes dominant in the lower portion. On the other hand, the first steel material is used for the upper part, and the second steel material is used for the lower part. Thereby, it is possible to cope with a case where the total weight of the offshore wind turbine and the transition piece is relatively large.

A sixth aspect of the present invention is the jacket structure according to the fourth aspect, wherein the upper portion is dominated by the ultimate load, the second steel material is used, and the lower portion is dominated by the fatigue load. , wherein the first steel material is used.

For example, if the size of the offshore wind turbine is small, the shaking caused by the rotation of the offshore wind turbine is small, so the ultimate load is dominant in the upper portion and the fatigue load is dominant in the lower portion. On the other hand, the second steel material is used for the upper part, and the first steel material is used for the lower part. Thereby, it is possible to cope with a case where the total weight of the offshore wind turbine and the transition piece is relatively small.

A seventh aspect of the present invention is characterized in that, in the jacket structure according to any one of the first to sixth aspects, the outer diameter of the lower portion is larger than the outer diameter of the upper portion.

According to this invention, the outer diameter of the lower portion is larger than the outer diameter of the upper portion. Thus, for example, the thickness of the lower portion is increased by increasing the outer diameter while maintaining the inner diameter of the lower portion. As a result, the ultimate strength can be improved more efficiently than in the case of increasing the thickness by reducing the inner diameter while maintaining the outer diameter of the lower portion.

Aspect 8 of the present invention is characterized in that, in the jacket structure according to any one of aspects 1 to 7, the second steel material is either SM490Y or SM520.

According to this invention, the second steel material is SM490Y or SN490Y. This allows the second steel material to have sufficient strength.

A ninth aspect of the present invention is characterized in that, in the jacket structure according to any one of the first to seventh aspects, the second steel material is BTHT-440.

According to this invention, the second steel material is BTHT-440. This allows the second steel material to have sufficient strength.

A tenth aspect of the present invention is the jacket structure according to any one of Aspects 1 to 9, wherein the lower portion comprises two arcuate members that are plate members having an arcuate cross section, and the two arcuate members. and a weld line that joins the two, and the weld line and the intersection point between the first steel pipe leg and the lower end of the oblique brace do not intersect.

According to this invention, the weld line does not intersect with the intersection of the first steel pipe leg and the lower end of the oblique brace. This makes it possible, for example, to avoid affecting the strength of the jacket structure due to the intersection of the weld line and the intersection point.

Aspect 11 of the present invention is the jacket structure according to any one of Aspects 1 to 10, wherein the outer diameter of the upper portion is the outer diameter of the portion of the first steel pipe leg and the peripheral portion of the upper portion. It is characterized in that the outer diameter of the lower portion is larger than the diameter of the portion of the second steel pipe leg and is larger than the outer diameter of the peripheral portion of the lower portion.

According to this invention, the outer diameter of the upper portion is larger than the outer diameter of the portion of the first steel pipe leg surrounding the upper portion, and the outer diameter of the lower portion is the portion of the second steel pipe leg. and is larger than the outer diameter of the peripheral portion of the lower portion. Thus, for example, when increasing the thickness of the upper and lower portions, the thickness can be increased by increasing the outer diameter while maintaining the inner diameter. Therefore, the ultimate strength can be improved more efficiently compared to the case of increasing the thickness by reducing the inner diameter while maintaining the outer diameter.

According to the present invention, it is possible to provide an economical jacket structure while ensuring sufficient performance with respect to both fatigue strength and ultimate strength.

1 is a perspective view of a jacket structure according to the invention; FIG. 1 is a front view of a jacket structure according to the present invention; FIG. It is a modification of the jacket structure according to the present invention. FIG. 10 is a first example of an enlarged view of a connecting portion between an oblique brace and a steel pipe leg; FIG. 11 is a second example of an enlarged view of the connecting portion between the oblique brace and the steel pipe leg;

A jacket structure 100 according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 and 2, the jacket structure 100 connects piles 200 driven into the seabed and the offshore wind turbine 300 . Thus, the jacket structure 100 has a role of supporting the offshore wind turbine 300 on the ocean.

(Overview of jacket structure 100)
As shown in FIG. 1 , the jacket structure 100 includes a transition piece 10 , steel pipe legs 20 and diagonal braces 30 .
The transition piece 10 supports an offshore wind turbine 300 . The transition piece 10 is a part that is arranged at the upper end of the jacket structure 100 and to which the lower end of the offshore wind turbine 300 is connected. The transition piece 10 is cross-shaped in plan view. The lower end of the offshore wind turbine 300 is arranged at the cross-shaped center of the transition piece 10 . A steel pipe leg 20 is arranged at each cross-shaped outer end of the transition piece 10 . Therefore, in this embodiment, four steel pipe legs 20 are provided. The transition piece 10 is not limited to this, and may be Y-shaped in plan view. That is, three steel pipe legs 20 may be provided.

A plurality of steel pipe legs 20 are provided over the substantially vertical direction of the jacket structure 100 . In this embodiment, the vertical direction refers to a direction orthogonal to the sea surface where the offshore wind turbine 300 is installed. A steel pipe, for example, is used for the steel pipe leg 20 . In this embodiment, four steel pipe legs 20 are provided. A transition piece 10 is connected to the upper end of the steel pipe leg 20 . A joining member 40 is connected to the lower end of the steel pipe leg 20 . Details of the steel pipe leg 20 will be described later.

The oblique braces 30 connect between the steel pipe legs 20 provided in the transition piece 10 . Specifically, the diagonal brace 30 connects a first steel pipe leg 21 and a second steel pipe leg 22, which will be described later. The diagonal braces 30 thereby reinforce the jacket structure 100 . A steel pipe, for example, is used for the oblique brace 30 . In the present embodiment, the diagonal brace 30 is configured in an X shape by two steel pipes between the steel pipe legs 20, for example. The oblique brace 30 may not be configured in the X shape by two steel pipes, but may be configured by only one steel pipe between the first steel pipe leg 21 and the second steel pipe leg 22 . As shown in FIGS. 1 and 2 , the X-shape is provided, for example, in one stage in the vertical direction of the jacket structure 100 . Alternatively, as shown in FIG. 3 , the diagonal braces 30 may be provided in two stages in the vertical direction of the jacket structure 100 . Two diagonal braces 30 each made of only one steel pipe may be provided in the vertical direction. The diagonal braces 30 may be provided in three or more stages in the vertical direction of the jacket structure 100 . Three or more stages of diagonal braces 30 each made of only one steel pipe may be provided in the vertical direction.

When the diagonal braces 30 are provided in two stages, the diagonal brace 30 located on the upper side in the jacket structure 100 is called an upper stage diagonal brace 31 as shown in FIG. Further, the diagonal brace 30 located on the lower side of the jacket structure 100 is called a lower stage diagonal brace 32 . Hereinafter, when the upper stage diagonal brace 31 and the lower stage diagonal brace 32 are not distinguished, they may be referred to as the diagonal brace 30 .

In this embodiment, each part of the oblique brace 30 is called as follows. That is, the upper portion of the connecting portion between the oblique brace 30 and the steel pipe leg 20 is referred to as the upper end of the oblique brace 30 . A lower portion of the connecting portion between the diagonal brace 30 and the steel pipe leg 20 is referred to as the lower end of the diagonal brace 30 .

The joining member 40 joins the jacket structure 100 to the plurality of piles 200 . The joint member 40 is provided at the lower end of the steel pipe leg 20 . The joining member 40 includes a sleeve 41 and a connecting member 42. As shown in FIG.
A plurality of sleeves 41 are provided for one of the plurality of steel pipe legs 20 provided in jacket structure 100 . A stake 200 is inserted into each of the plurality of sleeves 41 . Thereby, the jacket structure 100 and the pile 200 are connected.
The connection member 42 is a plate-like member that connects one of the steel pipe legs 20 and a plurality of sleeves 41 provided for one of the steel pipe legs 20 . That is, one and a plurality of sleeves 41 of the steel pipe leg 20 are connected by the connecting member 42 .

(Details of steel pipe leg 20)
Next, details of the steel pipe leg 20 will be described. Any one of the steel pipe legs 20 is hereinafter referred to as the first steel pipe leg 21 . Among the steel pipe legs 20 , the steel pipe leg 20 adjacent to the first steel pipe leg 21 in the circumferential direction is called a second steel pipe leg 22 . Here, the circumferential direction refers to the circumferential direction of the jacket structure 100 around the central axis of the lower end of the offshore wind turbine 300 connected to the transition piece 10 . The first steel pipe leg 21 and the second steel pipe leg 22 support the transition piece 10 . Hereinafter, the first steel pipe leg 21 and the second steel pipe leg 22 are referred to as a steel pipe leg 20 when not distinguished from each other.

As shown in FIGS. 1 and 2, the first steel pipe leg 21 has a first upper portion 21U and a first lower portion 21L.
The first upper portion 21U is a so-called leg can. That is, the first upper portion 21U is a portion of the first steel pipe leg 21 and includes the intersection of the first steel pipe leg 21 and the upper ends of the diagonal braces 30 . Specifically, the first upper portion 21U extends from the intersection point toward both sides in the length direction of the first steel pipe leg 21 so that the diameter of the diagonal brace 30 connected to the first steel pipe leg 21 is 1.5%. It refers to a region extending by a length of about 5 to 2.0 times.
The first lower portion 21L is a so-called leg can. That is, the first lower portion 21L is a portion of the first steel pipe leg 21 and includes the intersection of the first steel pipe leg 21 and the lower ends of the diagonal braces 30 . Specifically, the first lower portion 21L extends from the intersection toward both sides in the length direction of the first steel pipe leg 21 by a length of about three to five times the diameter of the first lower portion 21L. An extended area. The length of the first lower portion 21L is at least equal to or greater than that of the sleeve 41. As shown in FIG.

When the diagonal braces 30 are provided in two stages in the vertical direction, the first steel pipe leg 21 has the following configuration. That is, as shown in FIG. 3, the first steel pipe leg 21 has a first upper portion 21U, a first lower portion 21L, and a first middle portion 21M.
The first upper portion 21U is a portion of the first steel pipe leg 21 and includes an intersection point between the first steel pipe leg 21 and the upper end of the upper diagonal brace 31 .
The first lower portion 21</b>L is a portion of the first steel pipe leg 21 and includes an intersection point between the first steel pipe leg 21 and the lower end of the lower diagonal brace 32 .

The first middle section 21M is a so-called leg can. That is, the first middle portion 21M is a portion of the first steel pipe leg 21 and includes intersections between the first steel pipe leg 21 and the lower end of the upper diagonal brace 31 and the upper end of the lower diagonal brace 32, respectively. . Specifically, the first middle stage portion 21M extends 2.5 to 5.0 times the diameter of the first steel pipe leg 21 toward both sides in the length direction of the first steel pipe leg 21 from the intersection point. A region that extends for a certain length.
Note that when the diagonal brace 30 is composed of only one steel pipe, the first middle portion 21M is the portion of the first steel pipe leg 21, and is a portion of the first steel pipe leg 21 and the upper diagonal brace 31. It is a portion that includes an intersection with at least either the lower end or the upper end of the lower stage diagonal brace 32 .

As shown in FIGS. 1 and 2, the second steel pipe leg 22 has a second upper portion 22U and a second lower portion 22L.
The second upper portion 22U is a so-called leg can. That is, the second upper portion 22U is a portion of the second steel pipe leg 22 and includes the intersection of the second steel pipe leg 22 and the upper ends of the diagonal braces 30 . Specifically, the second upper stage portion 22U extends from the intersection point toward both sides in the length direction of the second steel pipe leg 22 so that the diameter of the oblique brace 30 connected to the second steel pipe leg 22 is 1.5%. It refers to a region extending by a length of about 5 to 2.0 times.
The second lower portion 22L is a so-called leg can. That is, the second lower portion 22</b>L is a portion of the second steel pipe leg 22 and includes the intersection of the second steel pipe leg 22 and the lower ends of the oblique braces 30 . Specifically, the second lower portion 22L extends from the intersection toward both sides in the length direction of the second steel pipe leg 22 by a length of about three to five times the diameter of the second lower portion 22L. An extended area. The length of the second lower portion 22L is at least equal to or greater than that of the sleeve 41. As shown in FIG.

When the diagonal brace 30 is provided in two stages in the vertical direction, the second steel pipe leg 22 has the following configuration. That is, as shown in FIG. 3, the second steel pipe leg 22 has a second upper portion 22U, a second lower portion 22L, and a second middle portion 22M.
The second upper portion 22U is a portion of the second steel pipe leg 22 and includes an intersection point between the second steel pipe leg 22 and the upper ends of the upper diagonal braces 31 .
The second lower portion 22</b>L is a portion of the second steel pipe leg 22 and includes an intersection point between the second steel pipe leg 22 and the lower ends of the lower diagonal braces 32 .

The second middle stage portion 22M is a so-called leg can. That is, the second middle portion 22M is a portion of the second steel pipe leg 22 and includes intersections of the second steel pipe leg 22 and the lower ends of the upper diagonal braces 31 and the upper ends of the lower diagonal braces 32, respectively. . Specifically, the second middle stage portion 22M is 2.5 to 5.0 times the diameter of the second steel pipe leg 22 from the intersection toward both sides in the length direction of the second steel pipe leg 22. A region that extends for a certain length.
In addition, when the diagonal brace 30 is composed of only one steel pipe, the second intermediate stage portion 22M is the portion of the second steel pipe leg 22, and is a portion of the second steel pipe leg 22 and the upper stage diagonal brace 31. It is a portion that includes an intersection with at least either the lower end or the upper end of the lower stage diagonal brace 32 .

When the diagonal braces 30 are provided in one stage in the vertical direction of the jacket structure 100, as shown in FIG. 1 upper part 21U, and the lower end is joined to the second lower part 22L. The second upper portion 22U and the first lower portion 21L of the diagonal brace 30 are joined to the second upper portion 22U at the upper end and to the first lower portion 21L at the lower end.
When the oblique braces 30 are provided in two stages in the vertical direction of the jacket structure 100, as shown in FIG. 3, the first upper stage portion 21U and the second middle stage portion 22M are connected by one steel pipe. The second upper portion 22U and the first middle portion 21M are connected by one steel pipe. The first middle portion 21M and the second lower portion 22L are connected by one steel pipe. The second middle section 22M and the first lower section 21L are connected by one steel pipe.

Hereinafter, the first upper portion 21U and the second upper portion 22U will be referred to as an upper portion U when not distinguished from each other. The first lower portion 21L and the second lower portion 22L are referred to as the lower portion L when not distinguished from each other. The first middle portion 21M and the second middle portion 22M are referred to as the middle portion M when not distinguished from each other. A portion of the steel pipe leg 20 that does not correspond to any of the upper portion U, the lower portion L, and the middle portion M will be referred to as a general portion G.

Here, regarding the loads that are dominant in the upper portion U, the lower portion L, and the middle portion M of the steel pipe leg 20, a portion where the fatigue load is dominant and a portion where the ultimate load is dominant coexist. There is In this embodiment, dominant means, for example, that each part of the steel pipe leg 20 can be the main cause of fracture. In other words, the fatigue load being dominant means that the structure determined from the viewpoint of fatigue has a higher ultimate strength than the structure ultimately determined. Ultimate load is dominant means that the structure determined by the ultimate point of view has a higher fatigue strength than the structure determined by fatigue.

In this embodiment, the fatigue load generated in the steel pipe leg 20, which is a factor for examining the fatigue strength, is due to, for example, a repeated load generated by vibration caused by the rotation of the offshore wind turbine. Also, the ultimate load on the steel pipe leg 20, which is the strength for which the ultimate strength is to be studied, is due to, for example, seismic input.

The steel pipe leg 20 needs to ensure both fatigue strength against vibrations of the offshore wind turbine 300 and ultimate strength against earthquake input. In the present embodiment, in order to deal with this, materials for forming each portion of the steel pipe leg 20 are properly used. As a result, the steel pipe leg 20 has an efficient structure, which contributes to making the steel pipe leg 20 economical. Specifically, it is as follows.

That is, for example, among the portions of the steel pipe leg 20, the first steel material is used for those portions where the fatigue load is dominant. Among the parts of the steel pipe leg 20, the second steel material having higher strength than the first steel material is used for those parts where the ultimate load is dominant. In the present embodiment, high strength means high yield stress.

The steel pipe leg 20 is formed, for example, by joining two arcuate members made of a first steel material or a second steel material by welding. The arc-shaped member is a plate-shaped member having an arc-shaped cross section. That is, the steel pipe leg 20 includes two arcuate members and a weld line (not shown) where the two arcuate members are joined. At this time, it is preferable that the welding line that joins the two arc-shaped members is arranged so as not to intersect with the intersection of the upper end and the lower end of the oblique brace 30 . The steel pipe leg 20 may be formed by bending a single steel plate to form an annular cross section. In this case, there may be only one weld line in the member axial direction.

For the first steel material, for example, 490N class carbon steel belonging to JIS G3106 is used as a steel material having relatively low strength. Specifically, for example, SM490 and SN490 are used.
For the second steel material, a steel material having a yield point of at least 325 N/mm ² or higher is used as a steel material having a relatively high strength. For the second steel material, for example, 490N class carbon steel belonging to JIS G3106 is used. Specifically, for example, SM490Y, SM520, and SM570 are used.
A high yield strength steel plate for building construction may be used as the second steel material. Specifically, for example, BTHT-440 may be used.
Further, when the fatigue strength is ensured by the first steel material, the fatigue strength may be improved by increasing the thickness of the steel material. In other words, the same steel material may be used for the first steel material and the second steel material, and the first steel material and the second steel material may be distinguished only by the difference in thickness.

In the present embodiment, as described above, the parts where the steel materials are selectively used are limited to the upper part U, the lower part L, and the middle part M. In other words, the general part G shall be unified with a common steel material. The first steel material is used for the general portion G, for example.
In addition, since the diagonal brace 30 has a role of reinforcing between the plurality of steel pipe legs, the fatigue load is dominant. Therefore, the first steel material is used for the diagonal brace 30 .

Which portion of the steel pipe leg 20 is dominated by the fatigue load or the ultimate load changes depending on design conditions including ground conditions, for example.
In this embodiment, for example, one of the upper portion U, the middle portion M, and the lower portion L is dominated by the fatigue load, and the first steel material is used. The other of the upper portion U, the middle portion M, and the lower portion L is dominated by the ultimate load, and the second steel material is used. Specifically, it is as follows.

For example, if the size of the offshore wind turbine is large, the shaking caused by the rotation of the offshore wind turbine becomes severe, so the fatigue load becomes dominant in the upper portion U and the middle portion M, and the ultimate load becomes dominant in the lower portion L. In this case, the first steel material is used for the upper portion U and the middle portion M, and the second steel material is used for the lower portion L.

For example, if the size of the offshore wind turbine is small, the shaking caused by the rotation of the offshore wind turbine is small, so the ultimate load becomes dominant in the upper portion U and the middle portion M, and the fatigue load becomes dominant in the lower portion L. In this case, the second steel material is used for the upper portion U and the middle portion M, and the first steel material is used for the lower portion L.

Also, as described above, the fatigue strength of each portion may be improved by increasing the thickness of the steel material. At this time, the specific plate thickness of each portion is appropriately determined in consideration of the specifications of the steel material to be used and the fatigue strength and ultimate strength required for each portion of the steel pipe leg 20 .
For example, the thickness of the one dominated by the ultimate load is made thicker than the thickness of the one dominated by the fatigue load. This aspect is suitable when sufficient ultimate strength cannot be obtained only by using a high-strength material for the required ultimate load.

Also, the thickness over which the ultimate load is dominant may be thinner than the thickness over which the fatigue load is dominant. This aspect is suitable for the case where the high-strength second steel material is used in the portion where the ultimate load is dominant, and the minimum required ultimate strength is used to further improve the economic efficiency.

Moreover, when increasing the thickness of the member in each of the upper portion U, the lower portion L, and the middle portion M, it is preferable to do as follows.
That is, for example, as shown in FIG. 4, it is preferable to make the outer diameter of the upper portion U larger than the outer diameter of the portion (general portion G) surrounding the upper portion U which is the portion of the steel pipe leg 20 . It is preferable to make the outer diameter of the middle step portion M larger than the outer diameter of the portion of the steel pipe leg 20 surrounding the middle step portion M (general portion G).

Further, as shown in FIG. 5, it is preferable that the outer diameter of the lower portion L is larger than the outer diameter of the portion (general portion G) surrounding the lower portion L, which is the portion of the steel pipe leg 20 .
That is, when increasing the thickness of the member, it is preferable to increase the outer diameter while maintaining the inner diameter.
Further, the outer diameters of the upper portion U, the lower portion L, and the middle portion M may be the same or different. For example, the outer diameter of the lower portion L may be larger or smaller than the outer diameters of the upper portion U and the middle portion M.

As described above, according to the jacket structure 100 according to the present embodiment, the first steel material is used for the upper part U and the lower part L where the fatigue load is dominant. For those where the ultimate load is dominant, a second steel material having a higher strength than the first steel material is used. As a result, for example, by forming the first steel pipe leg 21 with one type of steel material, both the fatigue strength and the ultimate strength are improved compared to the case where the upper part U and the lower part L are made of the same steel material. The performance of each portion of the first steel pipe leg 21 can be flexibly set while ensuring sufficient performance. Therefore, excessive performance of the first steel pipe leg 21 can be prevented, and an economical structure can be achieved.

Also, the thickness dominated by the ultimate load is thicker than the thickness dominated by the fatigue load. Here, when using the high-strength second steel material for the one in which the ultimate load is dominant, it may rather be uneconomical depending on the price of the steel material to be applied. On the other hand, by increasing the thickness of the portion of the first steel pipe leg 21 where the ultimate load is dominant, the necessary ultimate strength can be ensured without using unnecessarily expensive steel materials. In addition, for example, when it is not possible to obtain sufficient ultimate strength only by using a high-strength material due to structural reasons, etc., sufficient ultimate strength can be obtained.

Also, the thickness dominated by the ultimate load is thinner than the thickness dominated by the fatigue load. For example, when a high-strength material is used for the portion of the first steel pipe leg 21 where the ultimate load is dominant, by making the thickness thinner than the portion where the fatigue load is dominant, the minimum necessary It can be the ultimate strength. Therefore, the first steel pipe leg 21 can be made more economical.

One of the upper portion U and the lower portion L is dominated by the fatigue load and the first steel material is used, and the other of the upper portion U and the lower portion L is dominated by the ultimate load. 2 steel materials are used. That is, a steel material having a higher strength than a portion where the fatigue load is dominant is used for the portion where the ultimate load is dominant. In this way, for example, by appropriately selecting the material to be used for each part according to design conditions including ground conditions, it is possible to efficiently ensure the performance required of the first steel pipe leg 21 . Therefore, the first steel pipe leg 21 can be economical.

For example, if the size of the offshore wind turbine 300 is large, the shaking caused by the rotation of the offshore wind turbine 300 becomes severe. On the other hand, the upper part U uses the first steel material, and the lower part L uses the second steel material. Thereby, it is possible to cope with a case where the total weight of the offshore wind turbine 300 and the transition piece 10 is relatively large.

For example, if the size of the offshore wind turbine 300 is small, the shaking caused by the rotation of the offshore wind turbine 300 becomes small, so the ultimate load becomes dominant in the upper portion U and the fatigue load becomes dominant in the lower portion L. On the other hand, the upper portion U is made of the second steel material, and the lower portion L is made of the first steel material. Thereby, it is possible to cope with a case where the total weight of the offshore wind turbine 300 and the transition piece 10 is relatively small.

In addition, the outer diameter of the lower portion L is larger than the outer diameter of the upper portion U. Thus, for example, the thickness of the lower portion L is increased by increasing the outer diameter while maintaining the inner diameter of the lower portion L. As a result, the ultimate strength can be improved more efficiently than in the case of increasing the thickness by reducing the inner diameter while maintaining the outer diameter of the lower portion L.

Also, the second steel material is either SM490Y or SM520. This allows the second steel material to have sufficient strength.

The second steel material is BTHT-440. This allows the second steel material to have sufficient strength.

Also, the weld line does not intersect with the intersection of the first steel pipe leg 21 and the lower end of the oblique brace 30 . As a result, for example, it is possible to avoid affecting the strength of the jacket structure 100 due to the intersection of the weld line and the intersection point.

In addition, the outer diameter of the upper portion U is larger than the outer diameter of the portion of the first steel pipe leg 21 around the upper portion U, and the outer diameter of the lower portion L is larger than that of the second steel pipe leg 22. larger than the outer diameter of the portion surrounding the lower portion L. Thus, for example, when increasing the thickness of the upper portion U and the lower portion L, the thickness can be increased by increasing the outer diameter while maintaining the inner diameter. Therefore, the ultimate strength can be improved more efficiently compared to the case of increasing the thickness by reducing the inner diameter while maintaining the outer diameter.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, depending on design conditions including ground conditions, the same steel material may be used for the upper portion U and the lower portion L, and a different steel material may be used only for the middle portion M. Alternatively, the same steel material may be used for the middle portion M and the lower portion L, and a different steel material may be used for the upper portion U only.
In addition, different steel materials may be used in corresponding portions of the first steel pipe leg 21 and the second steel pipe leg 22 . For example, if the first upper portion 21U of the first steel pipe leg 21 and the second upper portion 22U of the second steel pipe leg 22 have different dominant factors, different steel materials may be used for each portion. .
In addition, not only the first steel material and the second steel material, but also a third steel material having a higher strength, for example, may be used.
The joining of the first steel pipe leg 21 and the second steel pipe leg 22 to the pile 200 may be performed without using the joining member 40 . For example, the lower ends of the first steel pipe leg 21 and the second steel pipe leg 22 are joined by being inserted into the pile 200 having an inner diameter larger than the outer diameter of the first steel pipe leg 21 and the second steel pipe leg 22. good too.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with well-known constituent elements without departing from the spirit of the present invention, and the modifications described above may be combined as appropriate.

10 Transition Piece 20 Steel Pipe Leg 21 First Steel Pipe Leg 22 Second Steel Pipe Leg 30 Diagonal Brace 31 Upper Diagonal Brace 32 Lower Diagonal Brace 100 Jacket Structure 300 Offshore Wind Turbine L Lower Part U Upper Part

Claims (9)

A transition piece that supports the offshore wind turbine,
a first steel pipe leg supporting the transition piece;
a second steel pipe leg supporting the transition piece;
a diagonal brace connecting the first steel pipe leg and the second steel pipe leg;
A jacket structure comprising:
an upper portion of the first steel pipe leg, the upper portion including the intersection of the first steel pipe leg and the upper end of the diagonal brace;
a lower portion of the second steel pipe leg, the lower portion including the intersection of the second steel pipe leg and the lower end of the diagonal brace;
Among them, the first steel material is used for the upper part where the fatigue load is dominant, and the second steel material having a higher strength than the first steel material is used for the lower part where the ultimate load is dominant ,
The first steel material and the second steel material are of different types,
A jacket structure characterized by: A transition piece that supports the offshore wind turbine,
a first steel pipe leg supporting the transition piece;
a second steel pipe leg supporting the transition piece;
a diagonal brace connecting the first steel pipe leg and the second steel pipe leg;
A jacket structure comprising:
an upper portion of the first steel pipe leg, the upper portion including the intersection of the first steel pipe leg and the upper end of the diagonal brace;
a lower portion of the second steel pipe leg, the lower portion including the intersection of the second steel pipe leg and the lower end of the diagonal brace;
Among them, the first steel material is used for the lower part where the fatigue load is dominant, and the second steel material having a higher strength than the first steel material is used for the upper part where the ultimate load is dominant ,
The first steel material and the second steel material are of different types,
A jacket structure characterized by: the thickness of which the ultimate load predominates is greater than the thickness of which the fatigue load predominates;
3. A jacket structure according to claim 1 or 2, characterized in that: the thickness of which the ultimate load predominates is less than the thickness of which the fatigue load predominates;
3. A jacket structure according to claim 1 or 2, characterized in that: The outer diameter of the lower portion is larger than the outer diameter of the upper portion,
3. A jacket structure according to claim 1 or 2, characterized in that: The second steel material is either SM490Y or SM520,
3. A jacket structure according to claim 1 or 2, characterized in that: The second steel material is BTHT-440,
3. A jacket structure according to claim 1 or 2, characterized in that: The lower portion includes two arc-shaped members that are plate-shaped members having an arc-shaped cross section;
a weld line where the two arc-shaped members are joined;
with
the weld line and the intersection of the first steel pipe leg and the lower end of the oblique brace do not intersect;
3. A jacket structure according to claim 1 or 2, characterized in that: The outer diameter of the upper portion is larger than the outer diameter of the portion of the first steel pipe leg and the peripheral portion of the upper portion,
The outer diameter of the lower portion is larger than the outer diameter of the portion of the second steel pipe leg surrounding the lower portion,
3. A jacket structure according to claim 1 or 2, characterized in that:

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