JP6641907B2 - Steel pipe coupler structure - Google Patents

Description

  The present invention relates to a coupler structure of a steel pipe provided with a plurality of recesses on an outer peripheral surface, and more particularly to a coupler structure of a steel pipe used for a steel pipe pile or a steel pipe column.

  BACKGROUND ART Steel pipes are used in various applications such as pile foundations and column structures because they have a circular cross section and can be variously constructed and processed and have high efficiency in cross section performance. In order to enhance the performance according to each of these utilization methods, the steel pipe is not utilized as it is, but processing is often required according to the utilization method.

  For example, in a steel pipe pile, a concave portion is provided on the outer peripheral surface of the steel pipe in order to improve peripheral friction force and prevent the steel pipe pile from shifting when buried in the ground or concrete. Patent Literature 1 proposes that a steel pipe pile is driven by a press-fitting method so that a hollow portion comes into contact with the ground.

  Patent Literature 2 proposes that a steel pipe for reinforcing ground is provided with a plurality of ridges on an outer peripheral surface of the steel pipe in order to improve peripheral frictional force. It has been proposed to form a concave groove on the outer peripheral surface of the steel pipe as the ridge, and fit a ring made of another member into the concave groove to fix the groove.

  In addition, Patent Document 3 proposes that a steel pipe pile for liquefied ground be provided with a ground disturber that disturbs the ground in order to recover horizontal resistance that has disappeared due to liquefaction. As this ground disrupter, for example, it has been proposed to alternately form a concave surface (dent surface) and a convex surface on the outer peripheral surface of a steel pipe.

Japanese Patent No. 5365462 Japanese Patent No. 5470212 Japanese Patent No. 2715261

  However, in the steel pipe pile described in Patent Literature 1, the concave portion on the outer peripheral surface of the steel pipe is structurally weak. For this reason, especially at a location where the axial force applied to the steel pipe pile is large, the steel pipe may buckle starting from the recessed portion, and the compression strength and bending strength of the steel pipe may be reduced.

  Further, in the steel pipe for ground reinforcement described in Patent Document 2, a ring is fixed to a concave groove on the outer peripheral surface of the steel pipe. However, such a configuration is intended to provide a ridge protruding from the outer peripheral face of the steel pipe. This is just one of the ways to achieve it. That is, although a ring is provided in the groove, the ring does not structurally sufficiently reinforce the groove.

  Further, in the liquefied ground steel pipe pile described in Patent Literature 3, when a depression is provided on the outer peripheral surface of the steel pipe, similarly to the steel pipe pile described in Patent Literature 1, the axial force applied to the steel pipe pile is particularly large. At a large portion, the steel pipe may buckle starting from the depression.

  The present invention has been made in view of such a point, and an object of the present invention is to propose, in a steel pipe provided with a plurality of recesses on an outer peripheral surface, suppressing buckling of the steel pipe using a simple structure. I do.

In order to achieve the above object, the present invention relates to a steel pipe coupler structure, wherein a plurality of depressions are provided on an outer peripheral surface of the steel pipe, and a coupler is attached to the outer peripheral surface of the steel pipe, and the coupler is a steel pipe. has an outer diameter substantially the same inner diameter, and a frame portion provided along the outer peripheral surface of the steel pipe, protruding from the inner peripheral surface of the frame portion, have a, a protrusion fitted into the recess, the The recess is provided to extend in a direction inclined in the circumferential direction or the axial direction on the outer peripheral surface of the steel pipe. It is characterized by the fact that some parts remain .

  ADVANTAGE OF THE INVENTION According to this invention, even if the axial force of a steel pipe is large, it can suppress that a steel pipe buckles from a depression part because a protrusion part of a coupler is fitted in the hollow part of a steel pipe. In addition, since the frame portion of the coupler is provided around the depression on the outer peripheral surface of the steel pipe, the periphery of the depression can be reinforced. Therefore, with the coupler structure of the present invention, buckling of the steel pipe can be suppressed, and the compressive strength and bending strength of the steel pipe can be improved.

  In the structure described in Patent Literature 2 described above, the ring is simply provided in the groove on the outer peripheral surface of the steel pipe, so that the periphery of the groove cannot be reinforced, and the effects of the present invention described above can be enjoyed. Can not.

  Conventionally, when processing steel pipes, for example, welding and grout joining using a cement-based material were often used, but these processes required welding time and grout solidification time, There has been a demand for further improvement in on-site productivity. In this regard, the present invention has a simple structure in which a coupler is fitted into a steel pipe, so that processing can be performed in a short time and processing cost can be reduced. Therefore, the processing of the steel pipe can be performed efficiently, and the productivity on site can be improved.

  The coupler may be divided into a plurality in the circumferential direction, and the coupler may be provided with a jig for fastening the frame in the circumferential direction when the coupler is mounted on a steel pipe. In such a case, the jig may be made of a tubular or ring-shaped steel material.

  The coupler structure may be applied to a joint structure of two steel pipes. That is, the coupler is attached to a joint portion that vertically joins two steel pipes, the frame portion is provided across an end of one steel pipe and an end of another steel pipe, and the protrusion is formed of a steel pipe. It may be provided at at least two places in the axial direction, and may be fitted into the recess provided at the end of one steel pipe and fitted into the recess provided at the end of another steel pipe.

  The coupler structure may be applied to a steel pipe pile. That is, a blade portion protruding from the outer peripheral surface may be provided on the outer peripheral surface of the frame portion. In such a case, the blade portion may be provided spirally with respect to the outer peripheral surface of the frame portion. Moreover, the said blade | wing part may be provided so that the distance between the one end part and the other end part of the said blade | wing part may be 1.5 times or more of the outer diameter of a steel pipe in side view.

  The coupler structure may be applied to a beam / column joint structure. That is, the steel pipe is used as a column member through which the pipe material provided at the end of the beam material is inserted, and the outer peripheral surface of the frame portion has a taper whose diameter increases from one end to the other end on the pipe material side. The coupler may have a shape, and one end of the coupler may be fitted into the tube. In such a case, the inner peripheral surface of the tube material may have a tapered shape adapted to the outer peripheral surface of the frame portion.

  The steel pipe may be formed by hot treatment or warm treatment together with the depression.

  ADVANTAGE OF THE INVENTION According to this invention, the buckling of a steel pipe can be suppressed using the coupler structure of a simple structure in the steel pipe with which several recessed parts were provided in the outer peripheral surface.

It is a figure showing some composition of a steel pipe concerning this embodiment. It is AA sectional drawing of FIG. It is a figure showing the coupler structure of the steel pipe concerning this embodiment. It is a figure explaining the effect of the coupler structure of a steel pipe, (a) shows a part of steel pipe, (b) is a mimetic diagram showing signs that an axial force acts on a steel pipe, (c) is a hollow part FIG. 6 is a schematic view showing a state in which an axial force acts on a steel pipe when a coupler is attached to the steel pipe. It is a figure showing some composition of a steel pipe concerning other embodiments. It is a figure showing some composition of a steel pipe concerning other embodiments. It is a figure which shows the example which applied the coupler structure to the joint structure of a steel pipe. It is a figure which shows the example which applied the coupler structure to a steel pipe pile, (a) shows a steel pipe pile, (b) shows the axial force distribution which acts on a steel pipe, (c) shows the bending moment distribution which acts on a steel pipe. Show. It is a figure which shows the example which provided the blade part in the coupler in the example which applied a coupler structure to a steel pipe pile. It is a figure which shows the example which applied the coupler structure to the beam / column joint structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

<1. Coupler structure>
First, a coupler structure of a steel pipe according to the present embodiment will be described. FIG. 1 is a diagram showing a part of a main body of a steel pipe 10 used in the present embodiment. As shown in FIG. 1, a plurality of depressions 11 are provided on the outer peripheral surface of the steel pipe 10. The plurality of recesses 11 are provided at predetermined intervals in the axial direction of the steel pipe 10 (hereinafter, simply referred to as “axial direction”), and are provided at a plurality of positions symmetrical to each other on the same circumference. In addition, as shown in FIG. 6 described later, the depression 11 may be provided to extend in a direction inclined in the axial direction of the steel pipe 10.

  FIG. 2 is a sectional view taken along line AA of FIG. As shown in FIG. 2, the pair of recesses 11 provided on the same circumference are provided to extend in the circumferential direction, respectively. Between one dent 11 and another dent 11, an unformed part 12 in which these dents 11 are not provided remains. In addition, as shown in FIG. 6 described later, even when the recess 11 is provided to extend in the direction inclined in the axial direction of the steel pipe 10, the unformed portion 12 remains between the recesses 11.

  The steel pipe 10 is formed together with the recess 11 by hot treatment or warm treatment. A general production line for the steel pipe 10 is used, and for example, a steel pipe production line described in Japanese Patent No. 5365462 can be used. The concave portion 11 is provided by pressing the outer peripheral surface of the steel pipe 10 by a roll in a hot or warm state after the pipe forming step in the production line. For this reason, the steel pipe 10 can be manufactured on a manufacturing line, and is easily and economically manufactured by a normal pipe forming process as compared with, for example, a case where the recessed portion 11 is formed by machining performed separately.

  FIG. 3 is a view showing a coupler structure of the steel pipe 10. As shown in FIG. 3, a coupler 20 is attached to the outer peripheral surface of the steel pipe 10. The coupler 20 has a frame 21 and a protrusion 22. A material that can be freely molded, for example, a casting such as cast iron or cast steel is used for the coupler 20.

  The frame portion 21 has the same inner diameter as the outer diameter of the steel pipe 10 and is provided along the outer peripheral surface of the steel pipe 10. That is, the frame portion 21 is provided in contact with the outer peripheral surface of the steel pipe 10. The tolerance between the steel pipe 10 and the frame portion 21 is naturally allowable, and the outer diameter of the steel pipe 10 and the inner diameter of the frame portion 21 may be substantially the same.

  The protruding portion 22 protrudes from the inner peripheral surface of the frame portion 21 and has a shape adapted to the recessed portion 11. Then, the protrusion 22 is fitted into the recess 11. In addition, a tolerance is naturally allowed between the protrusion 22 and the recess 11, and the shape of the protrusion 22 and the shape of the recess 11 may be substantially matched.

  Then, by fitting the protruding portion 22 into the recessed portion 11 in this manner, the coupler 20 is fixed without moving in the axial direction. In addition, since the unformed portion 12 exists between the recessed portions 11, the protrusion 22 comes into contact with the unformed portion 12 and is caught, and the coupler 20 is fixed without rotating in the circumferential direction.

  The coupler 20 is divided into a plurality in the circumferential direction, that is, the frame 21 and the protrusion 22 are each divided into a plurality in the circumferential direction. By splitting the coupler 20 in this manner, the protrusion 22 can be fitted into the recess 11 and the coupler 20 can be attached to the steel pipe 10. When attaching the coupler 20 to the steel pipe 10, a jig 23 made of a ring-shaped steel material is attached to an end of the frame 21 and the frame 21 is fastened in the circumferential direction. The configuration of the jig 23 is not limited to the present embodiment, and may be, for example, a tubular steel material or a bolt.

  The coupler 20 is provided on substantially the entire outer circumferential surface of the steel pipe 10 in the circumferential direction. However, a slight gap between the divided couplers 20 is acceptable.

  Next, the operation and effect of the coupler structure of the steel pipe 10 configured as described above will be described with reference to FIG. 4 (b) and 4 (c), only one outer peripheral surface of the steel pipe 10 is shown for ease of explanation.

  When an axial force Np acts on the steel pipe 10 provided with the depression 11 shown in FIG. 4A as shown in FIG. 4B, the steel pipe 10 buckles from the depression 11 as a starting point, and the steel pipe 10 buckles. Is deformed like a dotted line. On the other hand, when the coupler 20 is attached to the steel pipe 10 as shown in FIG. 4C, the protrusion 22 is fitted into the recess 11. Then, since the force acting on the depression 11 can be received by the projection 22, the deformation of the depression 11 due to buckling can be suppressed.

  Moreover, since the frame 21 is provided around the recess 11 on the outer peripheral surface of the steel pipe 10, the periphery of the recess 11 can be reinforced. Therefore, according to the coupler structure of the present embodiment, buckling of the steel pipe 10 can be suppressed, and the compressive strength and bending strength of the steel pipe 10 can be improved.

  In addition, since it has a simple structure in which the coupler 20 is fitted into the steel pipe 10, processing can be performed in a short time, and the processing cost can be reduced. Therefore, the processing of the steel pipe 10 can be performed efficiently, and the on-site productivity can be improved.

  In addition, the arrangement of the recess 11 with respect to the steel pipe 10 is not limited to the present embodiment, and the coupler structure of the present embodiment can be applied to the recess 11 having an arbitrary arrangement. For example, as shown in FIG. 5, a plurality of depressions 11 may be provided at positions symmetrical to each other at a predetermined interval in the axial direction, that is, a plurality of depressions 11 in a staggered shape in a side view. Alternatively, as shown in FIG. 6, the depression 11 may be provided to be inclined in the axial direction of the steel pipe 10.

  In addition, the shape of the depression 11 is not limited to the present embodiment, and the shape in a side view can be a triangle, a square, a trapezoid, a semicircle, or the like.

  Further, the depression 11 may be formed on the entire circumference on the same circumference, and the unformed part 12 may be omitted. However, as described above, if there is an unformed portion 12, the coupler 20 is fixed without rotating in the circumferential direction, so that the unformed portion 12 is preferably left.

  As described above, the coupler structure of the present embodiment has a simple structure, and the steel pipe 10 can be processed according to various uses. Hereinafter, an example in which the coupler structure is applied to the joint structure of the steel pipe 10, an example in which the coupler structure is applied to a steel pipe pile, and an example in which the coupler structure is applied to a beam / column joint structure will be described.

<2. Steel Pipe Joint Structure>
First, an example in which the coupler structure according to the present embodiment is applied to a joint structure of a steel pipe 10 will be described. As shown in FIG. 7, the coupler 20 is attached to a joint portion that vertically connects the two steel pipes 10.

  The frame 21 is provided so as to straddle the end of one steel pipe 10 and the end of another steel pipe 10. The protrusions 22 protrude from the inner peripheral surface of the frame 21 at two locations in the axial direction. One protruding portion 22 is fitted into the recess 11 provided at the end of one steel pipe 10, and the other protruding portion 22 is fitted into the recess 11 provided at the end of the other steel pipe 10. .

  The coupler 20 is divided into a plurality in the circumferential direction, the jig 23 is attached to an end of the frame 21, and the frame 21 is fastened in the circumferential direction. The coupler 20 is provided on substantially the entire circumference in the circumferential direction on the outer circumference of the steel pipe 10.

  In such a case, the coupler 20 is fixed without being moved in the axial direction by the protrusion 22 being fitted into the recess 11, and the coupler 20 is brought into contact with the unformed portion 12 and is caught in the circumferential direction. Is fixed without rotating. Therefore, the two steel pipes 10 are appropriately cascaded by the coupler structure.

  Further, the joint structure of the steel pipe 10 is constituted only by the coupler 20 and the jig 23, and since the coupler 20 is also provided only with the protrusion 22 on the frame portion 21, the working degree is extremely small, and the existing joint is not provided. As compared with the structure, the processing cost can be significantly reduced.

<3. Steel Pipe Piles>
Next, an example in which the coupler structure of the present embodiment is applied to a steel pipe pile will be described. FIG. 8A is a diagram illustrating a steel pipe pile in which a plurality of couplers 20 are attached to the outer peripheral surface of the steel pipe 10. The steel pipe pile is a foundation pile. The base end of the steel pipe 10 is embedded in the concrete foundation 30, and the other part is embedded in the ground. The dimensions of such a steel pipe pile are as follows. The length of the steel pipe 10 is, for example, 2 m to 20 m. The outer diameter of the steel pipe 10 is, for example, 40 mm to 200 mm. The thickness (plate thickness) of the steel pipe 10 is, for example, 2.3 mm to 9 mm. The axial interval between the depressions 11 is, for example, 200 mm to 300 mm. The depth of the depression 11 is, for example, 7 mm to 11 mm. The length in the circumferential direction of the unformed portion 12 is, for example, 10 mm to 20 mm.

  FIG. 8B shows the distribution of axial force acting on the steel pipe 10, and FIG. 8C shows the distribution of bending moment acting on the steel pipe 10. In the steel pipe 10, the coupler 20 is attached to a place where the axial force is large and the stress state is severe. Specifically, for example, when the distance from the ground surface to the tip of the steel pipe 10 is L, the coupler 20 is attached to the depression 11 provided between the ground surface and the distance L / 3. .

  In such a case, the dent portion 11 where the stress state is severe and buckling is likely to occur is reinforced by the coupler 20, and buckling of the steel pipe 10 can be suppressed. On the other hand, it is not necessary to provide the coupler 20 for the recessed portion 11 provided at the place where the stress state is loose. The depression 11 exhibits a function of improving the frictional force on the peripheral surface, and can suppress the displacement of the steel pipe pile when buried in the ground. Therefore, according to the steel pipe pile of the present embodiment, the function of the depression 11 can be exhibited while the structurally weak point is reinforced by the coupler 20.

  When the coupler structure is applied to a steel pipe pile, the coupler 20 may be provided with a blade 24 as shown in FIG. The blade portion 24 is provided so as to project from the outer peripheral surface of the frame portion 21. With the blades 24, the pull-out resistance of the steel pipe 10 can be improved.

  Here, conventionally, the blade portion is provided by directly welding to the steel pipe. In such a case, the thickness (plate thickness) of the steel pipe at the welded portion between the steel pipe and the blade portion is small, so that it is structurally weak and has low yield strength. Then, there is a possibility that the welded portion may be damaged by, for example, a pulling force. In this regard, since the blade portion 24 of the present embodiment is provided on the coupler 20, the portion where the blade portion 24 is provided is reinforced by adding the thickness of the coupler 20 (frame portion 21) to the thickness of the steel pipe 10. Therefore, the pull-out resistance of the steel pipe 10 can be improved.

  Further, it is not necessary to weld the blades directly to the steel pipe as in the related art, and the coupler 20 provided with the blades 24 can be mass-produced. Therefore, the steel pipe 10 and the coupler 20 can be transported separately. Here, conventionally, when transporting a steel pipe provided with a blade portion to a site, the blade takes up space and hinders transportation, resulting in poor transport efficiency. In this regard, according to the present embodiment, the transport efficiency can be significantly improved by transporting the steel pipe 10 and the coupler 20 separately. Further, at the site, it is only necessary to attach the coupler 20 to the steel pipe 10, so that the productivity at the site can be improved. Further, it is possible to easily add or delete the blade portions 24 to or from the coupler 20 according to the ground conditions at the site.

  In the coupler 20, the protrusion 20 is fitted into the recess 11, so that the coupler 20 is fixed without moving in the axial direction. For this reason, even if a pulling force acts on the blade portion 24, the pulling force is transmitted in the axial direction of the steel pipe 10.

  In addition, since the unformed portion 12 exists between the recessed portions 11, the protrusion 22 comes into contact with the unformed portion 12 and is caught, and the coupler 20 is fixed without rotating in the circumferential direction. The steel pipe 10 is driven into the ground while being rotated. At this time, a rotational force acts on the coupler 20. Even in such a case, since the coupler 20 does not rotate, the rotational force is transmitted to the steel pipe 10, and it is possible to exhibit rotational resistance.

  The shape of the blade portion 24 is not particularly limited, but is preferably provided spirally with respect to the outer peripheral surface of the frame portion 21, that is, the blade portion 24 is provided to be inclined from the axial direction in side view. In such a case, the workability when driving the steel pipe 10 into the ground while rotating it can be improved.

  In a side view, the distance S between one end and the other end of the blade portion 24 is preferably 1.5 times or more the outer diameter D of the steel pipe. In such a case, the pull-out resistance of the steel pipe 10 can be further improved.

  In addition, in such a steel pipe pile, when vertically joining two steel pipes 10, the joint structure shown in FIG. 7 may be used.

<4. Beam-column joint structure>
Next, an example in which the coupler structure of the present embodiment is applied to a beam / column joint structure will be described. As shown in FIG. 10, the steel pipe 10 is used as a column member through which a pipe member 41 provided at an end of a beam member 40 is inserted. In addition, a steel pipe is used for the pipe material 41, for example.

  The outer diameter C1 of one end (the end on the tube material 41 side) of the frame portion 21 is smaller than the outer diameter C2 of the other end. That is, the outer peripheral surface of the frame portion 21 has a tapered shape whose diameter increases from one end to the other end. Then, when the steel pipe 10 is inserted through the pipe 41 and the frame 21 is fitted into the pipe 41, the frame 21 is locked to the pipe 41. Thus, a column / beam joint structure is formed.

  In the beam / column joint structure of the present embodiment, a plurality of divided frame portions 21 are fastened in the circumferential direction by fitting frame portion 21 into tube 41. For this reason, the above-mentioned jig 23 becomes unnecessary.

  The shape of the inner peripheral surface of the tube material 41 is not particularly limited, but preferably has a taper tendency adapted to the outer peripheral surface of the frame portion 21. In such a case, since the outer peripheral surface of the frame portion 21 is in surface contact with the inner peripheral surface of the tube 41, the frame 21 is appropriately locked by the tube 41.

  In the coupler 20, the protrusion 20 is fitted into the recess 11, so that the coupler 20 is fixed without moving in the axial direction. Therefore, the vertical load received from the beam member 40 is transmitted in the axial direction of the steel pipe 10.

  In addition, since the unformed portion 12 exists between the recessed portions 11, the protrusion 22 comes into contact with the unformed portion 12 and is caught, and the coupler 20 is fixed without rotating in the circumferential direction. Therefore, the beam member 40 and the steel pipe 10 are appropriately joined by the coupler structure.

  As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the concept described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  INDUSTRIAL APPLICABILITY The present invention is useful when a steel pipe provided with a plurality of depressions on the outer peripheral surface is used for a steel pipe pile or a steel pipe column.

DESCRIPTION OF SYMBOLS 10 Steel pipe 11 Depressed part 12 Unformed part 20 Coupler 21 Frame part 22 Projection part 23 Jig 24 Blade part 30 Concrete foundation 40 Beam material 41 Tube material

Claims (10)

A steel pipe coupler structure,
A plurality of depressions are provided on the outer peripheral surface of the steel pipe, and a coupler is attached to the outer peripheral surface of the steel pipe,
The coupler is
A frame having substantially the same inner diameter as the outer diameter of the steel pipe, and provided along the outer peripheral surface of the steel pipe;
Projecting from the inner peripheral surface of the frame portion, it has a, a protrusion fitted into the recess,
The recess is provided to extend in a direction inclined in a circumferential direction or an axial direction on an outer peripheral surface of the steel pipe,
A coupler structure for a steel pipe, characterized in that an unformed part in which the depression is not provided remains on the outer peripheral surface of the steel pipe on substantially the same circumference as the depression. The coupler is divided into a plurality in the circumferential direction,
Wherein the coupler, when the coupler is attached to the steel pipe, characterized in that the jig for fastening the frame section in the circumferential direction is attached, the coupler structure of the steel pipe according to claim 1. The coupler structure for a steel pipe according to claim 2 , wherein the jig is made of a tubular or ring-shaped steel material. The coupler is attached to a joint portion connecting two steel pipes vertically,
The frame portion is provided across the end of one steel pipe and the end of another steel pipe,
The protrusions are provided at at least two places in the axial direction of the steel pipe, and are fitted into the recesses provided at the end of one steel pipe, and are fitted into the recesses provided at the end of another steel pipe. The coupler structure for a steel pipe according to any one of claims 1 to 3 , wherein the coupler structure is provided. The coupler structure for a steel pipe according to any one of claims 1 to 4 , wherein a blade portion protruding from the outer peripheral surface is provided on an outer peripheral surface of the frame portion. The coupler structure for a steel pipe according to claim 5 , wherein the blade portion is provided spirally with respect to an outer peripheral surface of the frame portion. The said blade part is provided so that the distance between the one end part and the other end part of the said blade part may be 1.5 times or more of the outer diameter of a steel pipe in a side view, The claim characterized by the above-mentioned. Item 7. A coupler structure for a steel pipe according to item 5 or 6 . The steel pipe is used as a pillar for inserting the pipe provided at the end of the beam,
The outer peripheral surface of the frame portion has a tapered shape whose diameter increases from one end to the other end on the tube material side,
The coupler structure of a steel pipe according to any one of claims 1 to 3 , wherein one end of the coupler is fitted into the pipe material. The coupler structure for a steel pipe according to claim 8 , wherein an inner peripheral surface of the pipe material has a tapered shape that fits an outer peripheral surface of the frame portion. The coupler structure for a steel pipe according to any one of claims 1 to 9 , wherein the steel pipe is formed by hot treatment or warm treatment together with the depression.

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