JP2013083070A - Double pipe structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the buckling of steel plates forming a steel pipe, and to facilitate the joining of the steel plates by making them thin.SOLUTION: A support 1 of a double pipe structure is provided which consists of an inner pipe 2 and an outer pipe 3 coaxially provided outside the inner pipe 2 so as to be spaced with a certain distance from the inner pipe 2. Concrete 4 is injected between the inner pipe 2 and the outer pipe 3. The inner pipe 2 and the outer pipe 3 respectively have a certain length. First joint parts T1 each connecting the inner pipes 2, 2 to each other and second joint parts T2 each connecting the outer pipes 3, 3 to each other are arranged so as be alternately shifted in a longitudinal direction Y.

Description

  The present invention relates to a double tube structure applied to, for example, a prop of a wind turbine for wind power generation.

In a tower structure such as a windmill used for offshore wind power generation, the scale has been increased, and a steel pipe structure having a large cross section in which the thickness of a supporting column used reaches 100 mm (see, for example, Patent Document 1). . In such a large cross-section strut, in order to suppress buckling, the strut diameter / thickness ratio D / t (the ratio of the outer diameter dimension D to the plate thickness dimension t) is generally limited to approximately 50. Therefore, the outer diameter of the support is limited to about 5 m. For this reason, it is difficult to increase the size of the support with a steel structure from the viewpoint of steel sheet manufacture.
On the other hand, in order to increase the strength of the struts, a concrete-filled steel pipe (CFT) is also known.

JP 2010-223157 A

However, the conventional struts having a large-section steel pipe structure have the following problems.
That is, for example, when using a steel pipe having an outer diameter of 5 m, the joint portion in the extending direction of the column structure (length direction of the column) has a rolling width (for example, 5 m) in order to arrange the rolling direction in the circumferential direction of the column. ). Such a joint portion is usually bolted, but a steel pipe with a diameter of 5 m may have a plate thickness of 100 mm as described above, and it is difficult to join with a bolt. In addition, it is technically difficult to abut the steel plates having a thickness of 100 mm at the joints and weld all the cross sections, and there is a problem that the welding cost increases.

In general, the wind turbine support structure uses a steel material having a strength of about 500 MPa, and in the case of a structure to be a welded joint, it is difficult to reduce the weight of the steel using high strength steel. there were. That is, when 100 mm-thick steel plates are brought together at the joint portion and welded in all cross sections, it becomes difficult to ensure toughness, weld cracks occur, and weld strength decreases. It becomes more difficult.
Further, since the high strength steel has a smaller Σcr / σy (buckling stress / yield stress) than the low strength steel at the same diameter / thickness ratio D / t, the restriction of the diameter / thickness ratio on buckling becomes more severe. Yes. Therefore, there is room for improvement in that respect because the advantage of adopting high-strength steel cannot be obtained.

  The present invention has been made in view of the above-described problems, and can suppress buckling of a steel plate constituting a steel pipe, and can further easily join pipes by making the steel plate thinner. The object is to provide a tube structure.

  In order to achieve the above object, in the double pipe structure according to the present invention, the inner pipe and the outer pipe are doubled, and concrete is filled between the inner pipe and the outer pipe. Each has a fixed length and is a double pipe structure joined in the longitudinal direction, and the first joint part joining the inner pipes and the second joint part joining the outer pipes are long. It is characterized by being alternately displaced in the direction.

  In this invention, since the position of the 1st joint part which joins inner pipes and the 2nd joint part which joins outer pipes has shifted in the longitudinal direction of a pipe, either one of an inner pipe and an outer pipe The position of the joint portion of the pipe becomes the steel plate portion of the other pipe at the same position in the length direction, and the first joint portion of the inner pipe and the second joint portion of the outer pipe do not exist in the same cross section. Therefore, it is possible to disperse the stress concentration in the joint part where the ultimate strength may be low in the same cross section, and even if one of the inner pipe and the outer pipe breaks, a fail-safe structure is obtained. In addition, breakage of the steel pipe can be prevented.

Furthermore, by making the structure filled with concrete between the inner pipe and the outer pipe, the weight of the concrete is an increased part compared to the case consisting of only conventional steel pipes, but the steel has a higher specific gravity than concrete. However, the total weight is slightly increased. Reducing the thickness of the steel pipe can greatly reduce the cost of welding. If this characteristic is used in reverse, a pipe having a larger diameter double pipe structure can be formed.
Further, since the plate thickness can be reduced, it is possible to employ high-strength steel that is difficult to weld. In addition, since the concrete bears the compressive force, the strength of the steel material is determined by the tensile force in the cross-sectional design, so there is an advantage that the influence of the reduction of the buckling stress due to the high strength steel is eliminated.

  Moreover, in the double pipe structure which concerns on this invention, it is preferable that the 1st coupling part and the 2nd coupling part are joined by the friction bolt.

In this case, it is possible to reduce the welding work and improve the work efficiency by joining the joint portions with the friction bolts, so that the time and labor required for the joining work can be reduced.
And since the entire cross-section welding in the longitudinal direction of the inner tube and the outer tube is eliminated and the residual stress and welding deformation existing in these tubes are reduced, the buckling strength can be increased. Further, since the friction bolt exhibits an effect as a stopper, this can also improve the buckling strength. Furthermore, since the thickness of the portion is increased by the additional plate used for the friction bolt joining, there is an advantage that the structure becomes more difficult to buckle.

  In the double pipe structure according to the present invention, it is more preferable that high strength steel is used for each of the outer pipe and the inner pipe.

  In the present invention, it is possible to eliminate the entire cross-section welding in the longitudinal direction of the pipe, and by performing welding in a state where the pipe is laid down, the joint portion extending in a direction perpendicular to the longitudinal direction of the pipe is always directed downward. It can be performed by welding, and welding can be easily performed as compared with the joint portion in the longitudinal direction of the pipe.

  According to the double pipe structure of the present invention, the first joint part for joining the inner pipes and the second joint part for joining the outer pipes are not provided in the same cross section in the longitudinal direction of the pipes. The stress concentration generated in the joint portion is alternately shifted and dispersed in the longitudinal direction between the inner tube and the outer tube, and the buckling of the steel plate constituting the steel tube can be suppressed. Furthermore, there exists an advantage that joining of tubes can be performed easily by making a steel plate thin.

It is a partially broken perspective view which shows the structure of the support | pillar by embodiment of this invention. It is an elevation view shown in FIG. It is AA sectional view taken on the line shown in FIG. 1, Comprising: It is a longitudinal cross-sectional view of a support | pillar. FIG. 3 is a cross-sectional view taken along line B-B shown in FIG. 2, and is a horizontal cross-sectional view of a support column. It is an enlarged view of the joint part of the support | pillar shown in FIG.

  Hereinafter, a double tube structure according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 to 4, the strut 1 having a double pipe structure according to the present embodiment is used in a wind turbine for wind power generation, and is erected with the longitudinal direction Y directed in the vertical direction. That is, the support column 1 is composed of an inner tube 2 and an outer tube 3 that is coaxially provided outside the inner tube 2 at a predetermined interval, and the concrete 4 is placed between the inner tube 2 and the outer tube 3. It has a filled configuration.

  The inner tube 2 and the outer tube 3 each have a fixed length, and a first joint portion T1 that connects the inner tubes 2 and 2 and a second joint portion T2 that connects the outer tubes 3 and 3 to each other. Are alternately displaced in the longitudinal direction Y. The amount of displacement in the longitudinal direction Y between the first joint portion T1 and the second joint portion T2 at this time is not particularly limited, but the stress concentration of the joint portion having low rigidity is dispersed as will be described later. In consideration of the above, it is preferable that the position of the first joint portion T1 is a middle position between the second joint portions T2 and T2 in the length direction.

  The inner pipe 2 is a cylindrical steel pipe in which high-strength steel having a thickness dimension of, for example, 22 mm is used. As shown in FIG. 3 and FIG. 5, the first joint portion T <b> 1 is formed by applying an attachment plate 5 </ b> A having a plurality of bolt holes to the first joint portion T <b> 1 on the inner surface side of the inner tubes 2, 2. Are joined by fastening with friction bolts 6A. Note that the splicing plate 5A has a one-sided shear arrangement in these drawings, but can also be a two-sided shear if the distance between the double steel pipes permits. The single inner tube 2 is manufactured by rolling, and has a first joint R1 (see FIG. 4) in which both ends are joined by welding in a state in which the rolling direction is in the circumferential direction. And the inner pipes 2 and 2 joined to an up-down direction are joined in the position where each 1st junction part R1 mutually shifted | deviated to the circumferential direction.

  The outer tube 3 is a cylindrical steel tube in which high-strength steel having a thickness dimension of, for example, 25 mm is used. The second joint portion T2 is joined by applying an attachment plate 5B having a plurality of bolt holes to the second joint portion T2 on the outer surface side of the outer tubes 3 and 3 and fastening with the friction bolts 6B in these bolt holes. Has been. The single outer tube 3 is manufactured by rolling, and has a second joint portion R2 (see FIG. 4) in which both ends are joined by welding in a state where the rolling direction is in the circumferential direction. And the outer pipes 3 and 3 joined to the up-down direction are joined in the position where each 2nd junction part R1 mutually shifted | deviated to the circumferential direction.

  The concrete 4 is filled and integrated between the inner tube 2 and the outer tube 3 connected in a plurality in the longitudinal direction Y. At this time, since the concrete 4 has part of the friction bolts 6A and 6B of the first joint portion T1 and the second joint portion T2 projecting into the gap between the inner tube 2 and the outer tube 3, this projecting portion is It has a structure that is integrated with the concrete 4 by having a function of preventing slippage.

  For example, a comparative example 1 of an ordinary steel pipe having an outer diameter of 5 m and a thickness of 100 mm, a comparative example 2 of a CFT pipe in which concrete is filled in a steel pipe having an outer diameter of 5 m and a thickness of 65 mm, and a thickness of 25 mm made of ordinary steel Example 1 of the present invention in which concrete is filled between an outer tube of the present invention and an inner tube having a thickness of 22 mm, and Example 2 in which members of the outer tube and the inner tube of Example 1 are made of high-strength steel. Steel weight and total weight were compared. This is shown in Table 1.

As shown in Table 1, in the double pipe made of plain steel of Example 1, the bending strength can be achieved with a steel weight of 55% of the steel weight ratio as compared with Comparative Example 1 of the plain steel pipe alone. Furthermore, in the case of the high strength steel of BHS500 of Example 2, the steel weight can be reduced to 41% with respect to the steel weight ratio of 55% of Example 1 using ordinary steel. In addition, in this Example 2, since it becomes the structure filled with concrete, a weight increases only 17% compared with the comparative example 1 of a plain steel pipe single-piece | unit.
It can be confirmed from Table 1 that the CFT (concrete-filled steel pipe) of Comparative Example 2 increases in weight by 4 times or more and the steel weight ratio is reduced only to 65%.

Next, the effect | action of the support | pillar 1 (double-pipe structure) mentioned above is demonstrated in detail based on drawing.
As shown in FIG. 1, the positions of the first joint T1 that joins the inner tubes 2 and 2 and the second joint T2 that joins the outer tubes 3 and 3 are shifted in the longitudinal direction Y. The position of one joint part T1 (T2) of the first joint part T1 of the pipe 2 and the second joint part T2 of the outer pipe 3 becomes the steel plate part of the other pipe at the same position in the length direction Y, The joint portions T1 and T2 of the tube 2 and the outer tube 3 do not exist in the same cross section. Therefore, it is possible to disperse the stress concentration in the joint portion having a low ultimate strength in the same cross section, and even when one of the joint portions T1 (T2) of the inner tube 2 and the outer tube 3 is broken, the fail-safe structure. Thus, breakage of the steel pipe can be prevented.
In addition, by making a double pipe composed of the inner pipe 2 and the outer pipe 3, the compressive force generated in the steel sheet can be reduced because the concrete bears the compressive force, and the cross-sectional design based on the tensile force is performed. Can do. Therefore, buckling can be more reliably suppressed and the diameter / thickness ratio D / t can be reduced.

  Furthermore, by making the structure filled with concrete 4 between the inner pipe 2 and the outer pipe 3, the total weight tends to increase because the weight of concrete 4 minutes is increased as compared with the case where only the conventional steel pipe is used. However, since it is possible to reduce the plate thickness of the inner pipe 2 and the outer pipe 3, the steel weight can be reduced, so that the increase in the steel weight as a total is reduced. Furthermore, the cost for welding can be reduced. Furthermore, conversely, a larger-diameter support column 1 can be configured.

  Further, since the plate thickness can be reduced, it is possible to employ high-strength steel that is difficult to weld. In addition, since the concrete bears the compressive force, the strength of the steel material is determined by the tensile force in the cross-sectional design, so there is an advantage that the influence of the reduction of the buckling stress due to the high strength steel is eliminated.

  Further, since the first joint portion T1 and the second joint portion T2 are joined by the friction bolts 6A and 6B, welding work is reduced by joining the joint portions T1 and T2 with the friction bolts 6A and 6B. As a result, the work efficiency can be improved, and the time and labor required for the joining work can be reduced.

  And since the entire cross-section welding in the longitudinal direction Y of the inner tube 2 and the outer tube 3 is eliminated and the residual stress and welding deformation existing in these tubes are reduced, the buckling strength can be increased. In addition, since the friction bolts 6A and 6B exhibit the effect of preventing slippage, this can also improve the buckling strength. Furthermore, since the plate thickness of the portion is increased by the attachment plate 5 used for the friction bolt joining, there is an advantage that the structure becomes more difficult to buckle.

  Moreover, since high strength steel is used for each of the inner tube 2 and the outer tube 3, it is possible to eliminate the entire cross-sectional welding in the longitudinal direction Y, and by performing welding in a state where the tube is placed horizontally, The joint portion T1 (T2) extending in the direction perpendicular to the longitudinal direction Y of the pipe can always be downwardly welded and can be easily welded compared to the joint portions T1 and T2 in the longitudinal direction Y. it can.

  In the double pipe structure according to this embodiment described above, the first joint portion T1 of the inner pipe 2 and the second joint portion T2 of the outer pipe 3 are not provided in the same cross section in the longitudinal direction Y. Stress concentrations generated in the portions T1 and T2 are alternately shifted and dispersed in the longitudinal direction between the inner tube 2 and the outer tube 3, and buckling of the steel plates constituting the steel tube can be suppressed. Furthermore, there exists an advantage that joining of tubes can be performed easily by making a steel plate thin.

As mentioned above, although the embodiment of the double tube structure according to the present invention has been described, the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the scope of the present invention.
For example, in the above-described embodiment, the first joint portion T1 that joins the inner tubes 2 and 2 and the second joint portion T2 that joins the outer tubes 3 and 3 are frictioned via the attachment plates 5A and 5B. Although it is set as the structure fixed with volt | bolt 6A, 6B, it is not limited to such a joining means, The fixing means by welding may be sufficient. The splicing plate may be one-sided shear or two-sided shear.
Moreover, about thickness, the unit length dimension, an outer diameter dimension, etc. of the inner tube 2 and the outer tube 3, it can set suitably according to a material, required intensity | strength, etc.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention.

1 strut (double pipe structure)
2 inner pipe 3 outer pipe 4 concrete 5 additional plate 6A, 6B friction bolt T1 first joint part T2 second joint part R1 first joint part R2 second joint part

Claims (3)

The inner pipe and the outer pipe are doubled, and concrete is filled between the inner pipe and the outer pipe. Each of the inner pipe and the outer pipe has a certain length and is joined in the longitudinal direction. A double pipe structure,
The double pipe structure characterized by the 1st joint part which joins the said inner pipes, and the 2nd joint part which joins the said outer pipes mutually shifting in the longitudinal direction.   The double pipe structure according to claim 1, wherein the first joint portion and the second joint portion are joined by a friction bolt.   The double pipe structure according to claim 1 or 2, wherein high strength steel is used for each of the inner pipe and the outer pipe.

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