JP6372422B2 - Steel pipe joint structure - Google Patents

Description

  The present invention relates to a steel pipe joining structure that is employed in a wind power generation facility or the like and joins two steel pipes having different diameters by filling a grout between the steel pipes.

  In Japan, wind power generation as a renewable energy has attracted attention. There are two types of wind power generation: onshore wind power and offshore wind power. Offshore wind power has an advantage that a large-scale site can be secured and stable wind can be obtained compared with onshore wind power. In Japan, empirical research on offshore wind has been conducted and is being put to practical use.

  Offshore wind power generation facilities are installed on the sea, and there are two types of foundation structures: stationary and floating. Examples of the bottoming type structure include a gravity type, a jacket type, and a monopile type (single pile type).

  FIG. 3 shows an offshore wind power generation facility having a monopile basic structure. As shown in FIG. 3, this offshore wind power generation facility 10 first places a single pile steel pipe pile 11 called monopile on the seabed ground, and then has a transition piece having a diameter larger than that of the steel pipe pile (monopile) 11. Is covered with a steel pipe pile (monopile) 11. Since there is a gap between the steel pipe pile (monopile) 11 and the steel pipe (transition piece) 12, both are integrated by filling with grout (not shown here) (hereinafter referred to as a grout joint). . A tower 15 and a blade 16 are installed at the upper end of the steel pipe 12.

  As a result, the offshore wind power generation facility 10 receives wind power from the blade 16, and the force is transmitted from the tower 15 to the steel pipe 12 and is transmitted to the steel pipe pile 11 through the grout joint.

  At that time, the offshore wind power generation facility 10 has a structure that is constantly subjected to vibrations caused by wind and waves, and the design assumes that the number of stress vibrations is about 200 million times in a service period of 20 years. Fatigue accumulates due to this repeated load acting on the grout joint that transmits the load. FIG. 4 shows that the stress generated by the grout is particularly high at the lower end of the grout joint. Incidentally, the vertical axis | shaft of FIG. 4 has shown the height direction position which made the height position of the grout junction lowest end zero.

  FIG. 5 is a longitudinal sectional view of a steel pipe joint structure (grouting joint) for joining two steel pipes having different diameters by filling the gap between the steel pipes with a grout at the axial position in the pipe axis direction. It is.

  As shown in FIG. 5, the inner pipe 1 (corresponding to the steel pipe pile 11 in FIG. 3) is inserted into the outer pipe 2 (corresponding to the steel pipe 12 in FIG. 3) with the axial center aligned by a predetermined length, A grout joint 4 is formed by filling the grout 3 between the tube 1 and the outer tube 2.

  However, in the case of the steel pipe joint structure as shown in FIG. 5, the load transmission from the outer pipe 2 to the inner pipe 1 is expected only from the surface friction between the steel pipe (the inner pipe 1 and the outer pipe 2) and the grout 3. Therefore, the surface friction force between the steel pipe (inner pipe 1 and outer pipe 2) and the grout 3 is reduced during long-term service, and load transmission from the outer pipe 2 to the inner pipe 1 is not smoothly performed. There is a possibility that the tube 2 may shift downward in the vertical direction (downward in the tube axis direction).

  Therefore, in order to smoothly transmit the load from the outer tube 2 to the inner tube 1 even in a long-term service, as shown in FIG. 6, the outer surface of the inner tube 1 and the outer tube at the grout joint 4. A shear key (shearing force transmission member) 9 may be attached to the inner surface of 2 (see Non-Patent Document 1). Mounting the shear key 9 in this manner is effective in preventing the outer tube 2 from shifting downward in the vertical direction.

  However, since the shear key 9 is attached by welding, there is a tensile residual stress in the weld due to heat input, and the fatigue strength decreases. In addition, when the shape of the weld toe portion changes suddenly, stress concentration occurs and the fatigue strength further decreases. Therefore, it is common to adopt a steel pipe joint structure in which the shear key 9 is not installed.

  On the other hand, in Patent Document 1, either the inner diameter of the outer tube or the outer diameter of the inner tube at the grout junction is changed in the tube axis direction, and the cross section in the tube axis direction of the grout is changed to the outer tube side or the inner tube. A steel pipe joining structure having a wedge shape with an inclined side is disclosed, and it is described that the downward displacement of the outer pipe 2 in the vertical direction can be prevented without attaching a shear key.

  Further, Patent Document 2 discloses a steel pipe joint structure in which band-shaped steel plates with protrusions are welded to the inner surface of the outer tube and the outer surface of the inner tube, and the residual stress due to heat input can be reduced as compared with the case where a shear key is welded. In addition, it is described that sufficient shear strength can be ensured after improving fatigue performance.

JP2013-53425A Japanese Patent No. 5136726

2011 DNV-OS-J101 Design of Offshore Wind Turbine Structures Sec. 9-Page 143

  In the above-mentioned Patent Document 1, in order to prevent the displacement between the inner tube and the outer tube in the tube axis direction, either the inner diameter of the outer tube or the outer diameter of the inner tube at the grout joint is changed in the tube axis direction. The cross section in the tube axis direction of the grout has a wedge shape in which the outer tube side or the inner tube side is slanted, but in the wedge-shaped grout joint in which either the outer tube side or the inner tube side is slanted, It is not always sufficient to prevent the displacement of the tube and the outer tube in the tube axis direction.

  Further, in the above-mentioned Patent Document 2, in order to prevent the displacement of the inner tube and the outer tube in the tube axis direction, the strip-shaped steel plates with protrusions are welded to the inner surface of the outer tube and the outer surface of the inner tube. A time-consuming process such as butt welding the band-shaped steel sheet with protrusions is required.

  The present invention has been made in view of the circumstances as described above, and the inner tube is inserted into the outer tube, and the grout is filled between the inner tube and the outer tube, thereby forming a grout joint. It is an object of the present invention to provide a steel pipe joint structure that can accurately and efficiently prevent the displacement of the inner pipe and the outer pipe in the pipe axis direction.

  In order to solve the above problems, the present invention has the following features.

  [1] A steel pipe joint in which the inner pipe is inserted into the outer pipe by a predetermined length with the axial center aligned, and the grout is filled between the inner pipe and the outer pipe, thereby forming a grout joint. A steel pipe joint structure, wherein the outer diameter of the inner pipe changes in the pipe axis direction and the inner diameter of the outer pipe changes in the pipe axis direction in the grout joint.

  [2] The steel pipe joint structure according to [1], wherein a grout width at an end portion in the tube axis direction is larger than a grout width at an intermediate portion in the tube axis direction in the grout joint portion.

  [3] The steel pipe joint structure according to the above [2], wherein the grout width of the intermediate part in the pipe axis direction is constant in the grout joint part.

  In the present invention, the inner pipe and the outer pipe are formed as a steel pipe joining structure in which the inner pipe is inserted into the outer pipe and the grout is filled between the inner pipe and the outer pipe to form a grout joint. Can be prevented accurately and efficiently.

It is a longitudinal cross-sectional view which shows the steel pipe joining structure which concerns on Embodiment 1 of this invention. It is a longitudinal cross-sectional view which shows the steel pipe joining structure which concerns on Embodiment 2 of this invention. It is a figure which shows a monopile type offshore wind power generation installation. It is a figure which shows the stress distribution of a grout junction part. It is a figure which shows the conventional steel pipe junction structure (there is no shear key). It is a figure which shows the conventional steel pipe junction structure (with a shear key).

  Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a longitudinal sectional view of a steel pipe joint structure according to Embodiment 1 of the present invention cut at an axial center position in the pipe axis direction.

  As shown in FIG. 1, in the steel pipe joint structure according to the first embodiment, the inner pipe 1 is inserted into the outer pipe 2 by a predetermined length with the axial center aligned, and between the inner pipe 1 and the outer pipe 2. The grout joint 4 is formed by being filled with the grout 3.

  In the grout joint 4, the outer diameter of the inner tube 1 changes (expands) in part in the tube axis direction, and the inner diameter of the outer tube 2 changes (reduces diameter) in part in the tube axis direction. .

  That is, in FIG. 1, 1a is an inner tube outer diameter enlarged portion 1a in which the outer diameter of the inner tube 1 is increased, and 2a is an outer tube inner diameter reduced portion 2a in which the inner diameter of the outer tube 2 is reduced.

  In the grout joint 4, the inner diameter of the inner tube 1 and the outer diameter of the outer tube 2 are constant in the tube axis direction.

  Thus, in the steel pipe joint structure according to the first embodiment, the groove 3 is in the pipe axis direction on both the inner tube side (inner tube outer diameter enlarged portion 1a) and the outer tube side (outer tube inner diameter reduced portion 2a). Therefore, it is possible to accurately prevent the displacement of the inner tube 1 and the outer tube 2 in the tube axis direction as compared with Patent Document 1.

  Moreover, the outer diameter is increased in part in the tube axis direction and the inner tube 1 has a constant inner diameter in the tube axis direction, and the inner diameter is reduced in part in the tube axis direction. In the outer tube 2 having a constant outer diameter, a steel tube manufactured using a single-sided difference thickness steel plate whose thickness is changed in the longitudinal direction on one side may be used. It is possible to efficiently prevent the displacement of 1 and the outer tube 2 in the tube axis direction.

  Here, the tube axis direction end of the grout joint 4 is set in the tube axis direction starting from the foremost end of the grout joint 4 in the tube axis direction (the top end and the bottom end of the grout joint 4 in FIG. 1). It is set as a part to 300-1000 mm, and let the pipe-axis direction intermediate part of the grout junction part 4 be a part except the pipe-axis direction edge part of the grout junction part 4 in the pipe-axis direction of the grout joint part 4.

  At that time, in FIG. 1, regarding the thickness (grout width) W of the grout 3 in the tube radial direction, the grout width at the end in the tube axis direction of the grout joint 4 is the middle of the grout joint 4 in the tube axis direction. It is preferable to make it larger than the grout width. As a result, the stress concentration on the grout 3 at the end in the tube axis direction of the grout joint 4 can be reduced.

  Moreover, it is preferable that the grout width of the intermediate portion in the tube axis direction of the grout joint 4 is uniform. As a result, the stress transmission between the outer tube 2 and the inner tube 1 is made smoother.

  In addition, the fact that the grout width in the intermediate portion in the tube axis direction is uniform means that the grout width in the intermediate portion in the tube axis direction is within a range of 80 to 120% with respect to the average value of the grout width in the intermediate portion in the tube axis direction. Alternatively, the target value of the grout width at the intermediate portion in the tube axis direction may be determined, and may be within a range of 80 to 120% with respect to the target value.

  In other words, the outer diameter expansion amount of the inner pipe outer diameter expanded portion 1a and the inner diameter decreased diameter of the outer tube inner diameter decreased diameter portion 2a are excessively large, or the inner tube outer diameter expanded portion 1a and the outer tube inner diameter decreased. A portion where the grout width becomes extremely small, for example, by wrapping with the diameter portion 2a in the tube axis direction (for example, 30% or less of the average value or the target value of the grout width in the tube axis direction intermediate portion) It is not preferable that this occurs.

  Further, in FIG. 1, one inner tube diameter-enlarged portion 1a and one outer tube diameter-reduced portion 2a are provided, but one or both of them may be provided at a plurality.

[Embodiment 2]
FIG. 2 is a longitudinal sectional view of a steel pipe joint structure according to Embodiment 2 of the present invention cut at the axial center position in the pipe axis direction.

  As shown in FIG. 2, the steel pipe joint structure according to the second embodiment has the same basic configuration as the steel pipe joint structure according to the first embodiment, and the outer diameter of the inner pipe 1 is the grout joint 4. However, the inner diameter of the outer tube 2 is changed (reduced diameter) in a part in the tube axis direction.

  That is, in FIG. 2, 1a is an inner tube outer diameter enlarged portion 1a in which the outer diameter of the inner tube 1 is increased, and 2a is an outer tube outer diameter reduced portion 2a in which the inner diameter of the outer tube 2 is reduced. .

  In addition, in the steel pipe joint structure according to the second embodiment, the inner diameter of the inner pipe 1 is reduced in the inner pipe outer diameter enlarged portion 1a, and the outer diameter of the outer pipe 2 is reduced in the outer pipe inner diameter reduced portion 2a. Is expanded.

  Thereby, also in the steel pipe joint structure according to the second embodiment, the groove 3 is arranged in the pipe axis direction on both the inner tube side (inner tube outer diameter enlarged portion 1a) and the outer tube side (outer tube inner diameter reduced portion 2a). Therefore, it is possible to accurately prevent the displacement of the inner tube 1 and the outer tube 2 in the tube axis direction as compared with Patent Document 1.

  In addition, the inner tube 1 whose outer diameter is increased in part in the tube axis direction and whose inner diameter is reduced, and the inner diameter is reduced in part in the tube axis direction, and the outer diameter is increased. Since the outer pipe 2 that is used may be a steel pipe manufactured using a double-sided difference thickness steel plate whose thickness changes in the longitudinal direction on both sides, the inner pipe 1 and the outer pipe are compared with Patent Document 2. 2 can be effectively prevented from shifting in the tube axis direction.

[Embodiment 3]
In the first and second embodiments of the present invention described above, in the grout joint 4, the location where the outer diameter of the inner tube 1 is increased (the inner diameter of the outer diameter of the inner tube) and the location where the inner diameter of the outer tube 2 is reduced. (Outer pipe inner diameter reduced diameter part) In addition to this, the third embodiment of the present invention further includes a part where the outer diameter of the inner pipe 1 is reduced (inner pipe outer diameter reduced diameter part) and The steel pipe joining structure is provided with a portion (outer pipe inner diameter enlarged portion) where the inner diameter of the outer pipe 2 is increased.

  For example, when an inner tube outer diameter enlarged portion and an outer tube inner diameter reduced portion are provided, when an inner tube outer diameter reduced portion and an outer tube inner diameter enlarged portion are provided, an inner tube outer diameter reduced portion and an outer tube inner diameter reduced portion are provided. For example, when the diameter portion is provided, the inner tube outer diameter enlarged portion, the outer tube inner diameter enlarged portion, the inner tube outer diameter reduced portion, and the outer tube inner diameter reduced portion are provided.

  In the inner tube outer diameter reduced diameter part and the outer pipe inner diameter enlarged diameter part, since the tube thickness of the inner tube or the outer pipe is reduced as it is, the inner tube outer diameter reduced diameter part is located in the same position in the tube axis direction. It is preferable to provide an inner tube inner diameter reduced portion and an outer tube outer diameter enlarged portion with respect to the outer tube inner diameter enlarged portion.

DESCRIPTION OF SYMBOLS 1 Inner pipe 2 Outer pipe 3 Grout 4 Grout joint part 9 Shear key 10 Offshore wind power generation equipment 11 Steel pipe pile (monopile)
12 Steel pipe (transition piece)
15 tower 16 blade

Claims (2)

It is a steel pipe joint structure in which the inner pipe is inserted into the outer pipe by a predetermined length with the axial center aligned, and the grout is filled between the inner pipe and the outer pipe to form a grout joint. In the grout joint, the outer diameter of the inner tube changes in the tube axis direction, and the inner diameter of the outer tube changes in the tube axis direction. A steel pipe joint structure characterized in that the grout width of the entire direction intermediate portion is uniform .   2. The steel pipe joint structure according to claim 1, wherein a grout width at an end portion in the tube axis direction is larger than a grout width at an intermediate portion in the tube axis direction in the grout joint portion.

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