JP2000096712A - Concrete filled steel pipe beam and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend an application range of a concrete filled steel pipe material for a structural material such as a beam acting bending shearing force by introducing the prestress of compression in the direction of a steel pipe axial line on only filling concrete. SOLUTION: A concrete adhesion prevention agent 4 is applied on an inner peripheral face, and the inside of a steel pipe material 2 penetrating sheath pipes 6, 6 in the inside is filled with concrete 3. After the concrete 3 is hardened, the prestress of compression in the direction of the axial line of the steel pipe material 2 is introduced on only the concrete 3 by prestress imparting tension materials 7, 7 in the sheath pipe 6 in the state where adhesion between the filling concrete 3 and the steel pipe material 2 is cut. Thereby the application range of a concrete filling steel pipe material can be widened advantageously on structure and effectively even for the structural material acting bending shearing force or the like, for instance, a beam or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete-filled steel pipe used in the construction field and the like.

[0002]

2. Description of the Related Art For example, a concrete-filled steel pipe (CFT) in which steel pipe is filled with concrete is sometimes used as a structural material for building. When this concrete-filled steel pipe is used as a column on which an axial compressive force acts, the following mechanical advantages can be exhibited. That is, compared to the case of steel pipe material not filled with concrete, since the axial compression force is shared and received by the filled concrete and the steel pipe material, the axial force share of the steel pipe material can be reduced. Local buckling of the steel pipe material can be prevented by the filled concrete. The filled concrete can be brought into a triaxial stress state by the restraint by the steel pipe material, and the proof strength of the filled concrete can be increased by this confined effect.

[0003] Further, since the concrete-filled steel pipe material is formed by filling concrete, which is a refractory material, inside the steel pipe material, it also has an advantage of being excellent in fire resistance.

[0004]

However, although the conventional concrete-filled steel pipe is effective as described above as a structural material on which an axial compressive force acts, for example, it mainly has little effect on the axial compressive force. When it is used as a structural material such as a beam on which bending and shearing force acts, it is not economical in design because concrete is not expected to increase the strength due to the confined effect and the weight of the member increases. Therefore, the concrete-filled steel pipe material has the advantage of being excellent in fire resistance as described above, but its use is limited to the structural material in which the axial compressive force acts as described above, that is, the column material. And its application range was narrow. By the way, steel was used for the beam, which still required a fireproof coating, which was troublesome to construct.

[0005] In view of the above-mentioned conventional problems, the present invention is intended to limit the application range of concrete-filled steel tubing having an advantage in terms of fire resistance in that almost no axial compressive force acts, mainly bending shear force acts. It is an object of the present invention to be able to expand to structural materials such as beams and beams.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to fill concrete inside a steel pipe, and to cut off the adhesion between the filled concrete and the steel pipe so that only the filled concrete has a steel pipe. The problem is solved by a concrete-filled steel tubing characterized by the introduction of an axial compression prestress.

That is, in this concrete-filled steel pipe,
The filling concrete and the steel pipe material are cut off from each other, and a compressive prestress is introduced only into the filling concrete. Therefore, even if bending and shearing force is applied to this concrete-filled steel pipe, the tensile stress generated in the cross section of the filled concrete is small, or only the compressive stress is generated in the cross section, improving the properties of the filled concrete that is vulnerable to tension. can do. Moreover, the filled concrete in which the prestress has been introduced is restrained by the steel pipe material, and can be in a three-dimensional stress state, and the strength of the filled concrete is increased by the confined effect. Further, since the filled concrete and the steel pipe material are cut off from each other, the prestress does not act on the steel pipe material, and the prestress can be effectively introduced only into the filled concrete.

Therefore, the concrete-filled steel pipe having such a structure advantageously and effectively expands the scope of application of the concrete-filled steel pipe to structural materials that act on bending and shearing forces, such as beams. Therefore, when such a structural material is used for construction, it is possible to exhibit a fire-resistant advantage and reduce or eliminate the troublesomeness of the fire-resistant coating.

As a method for producing the above-mentioned concrete-filled steel pipe material, concrete is filled into a steel pipe material in which a concrete adhesion inhibitor is applied to the inner peripheral surface and a sheath pipe is passed through, and concrete is hardened. With a tendon material for applying prestress in the sheath pipe, a so-called post-tension method of introducing a prestress of compression in the axial direction of the steel pipe material only to concrete,
Alternatively, a concrete adhesion preventing agent is applied to the inner peripheral surface, and a tension member for applying a prestress is passed through the inside, and concrete is filled inside the steel pipe material in a state where a tensile force is applied to the tension member. Alternatively, a so-called pretension method may be used, in which after the concrete is hardened, the tensile force of the tendon is released to introduce a compressive prestress in the axial direction of the steel pipe material only to the concrete. Since the adhesion between the steel pipe material and the filled concrete is cut by the adhesion preventing agent, the prestress can be effectively introduced only into the filled concrete.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a post-tensioned concrete-filled steel pipe 1. Reference numeral 2 denotes a square steel pipe as a steel pipe, reference numeral 3 denotes a filled concrete, and asphalt 4 on the inner surface of the square steel pipe 2 as a concrete adhesion preventing agent.
Coated concrete 3 and square steel pipe 2
And the bond between them has been cut. Then, high-strength steels 7 as tension members passed through the sheath tube 6 are drawn out from both ends of the filled concrete 3, passed through the end plates 8 and 9, and are subjected to the tip. Nuts 10 are screwed into the screw portions 7a. By tightening the nuts 10, a tensile force is applied to the high-tensile steels 7, and a prestress of axial compression is introduced into the filled concrete 3 through the end plates 8, 9.

The above concrete-filled steel pipe 1 can be manufactured, for example, as follows. That is, first,
As shown in FIG. 2A, an asphalt 4 for insulation is applied to the inner surface of the square steel pipe 2 to prevent concrete from adhering.

Thereafter, as shown in FIG. 2 (b), an end plate 8 is set only at one end opening of the rectangular steel pipe material 2, and a high tensile steel 7 is passed through the rectangular steel pipe material 2 in advance. Insert the sheathed tubes 6 and put one end through the end plate 8
.. Are screwed into screws 7a at the ends of the high-tensile steel 7.
The end plates 8 and 9 are preferably designed to have a shape and a size that allow the end plates 8 and 9 to fit into the opening at the end of the rectangular steel tube material 2 in order to impart prestress to the filled concrete 3. By doing so, as shown in the figure, the end plate 8 is set so as to fit within the end of the rectangular steel pipe 2 so that the end face position of the filled concrete 3 is more inward than the end face position of the square steel pipe 2. Can be set.

The high-strength steel 7... Drawn outward from the other end opening of the square steel pipe 2 is not shown,
It is preferable to use a spacer or the like so as to be positioned coaxially with the square steel pipe 2.

Then, as shown in FIG. 2 (C-1), the concrete 3 is filled in the square steel pipe material 2 through the other end opening. The filling of the concrete 3 may be performed from above with the rectangular steel pipe 2 with the open end facing upward, standing upright.

Then, after the concrete is hardened, as shown in FIG. 1, an end plate 9 is also set on the other end of the rectangular steel pipe material 2, and high-strength steel 7 is passed through this end plate 9, and The nuts 10 are screwed into the end screws 7a and tightened.
This tightening introduces a compressive prestress into the filled concrete 3 as described above. Filled concrete 3
Since the insulating asphalt 4 is present between the rectangular steel pipe 2 and the
Has been cut off, and the prestress is
, And is effectively introduced only into the filled concrete 3.

As shown in FIG. 2C, the end plate 8 is in contact with the end plate main body projecting inward from the end of the rectangular steel pipe 2 and the end face of the rectangular steel pipe 2. By using the shape having the brim-like part integrally, the inner end face of the end plate 8 can be set at a predetermined position inside the end of the rectangular steel pipe material 2 so as to be positioned. Can be accurately set inward by a predetermined dimension from the end face position of the rectangular steel pipe material 2. in this case,
By using the same end plate 9 as that shown in FIG. 1, a compressive prestress can be introduced into the filled concrete 3 without any trouble.

The concrete-filled steel pipe 1 functions effectively as a beam in a building. That is, since a compressive prestress is introduced into the filled concrete 3, even if a bending shear force acts, the tensile stress generated in the cross section of the filled concrete 3 is small, or only the compressive stress is generated in the cross section. The properties of the filled concrete, which is vulnerable to tension, are improved and can effectively resist bending and shearing forces. Moreover, since the compressive prestress is introduced only into the filled concrete 3, the strength of the filled concrete 3 is increased by the confined effect.
Therefore, by using the concrete-filled steel pipe 1 having such a structure, the concrete-filled steel pipe can be advantageously used as a beam in a building. By using the steel pipe material 1, it is possible to exhibit a fire-resistant advantage, and it is possible to reduce or eliminate troublesome fire-resistant coating in a building.

FIG. 3 shows a concrete-filled steel pipe 1 of the pretension type. Reference numeral 2 denotes a square steel pipe as a steel pipe, 3 denotes a filled concrete, and asphalt 4 as a concrete adhesion preventing agent is applied to an inner surface of the square steel pipe 2, and the filled concrete 3 and the square steel pipe 2 The bond between has been cut. The tensile strength is given to the high-tensile steel 7... As the tendon material passed through the filled concrete 3, and this tensile force is applied to the high-tensile steel 7 by the adhesion between the high-tensile steel 7 and the filled concrete 3. 3, a prestress of axial compression is introduced only into the filled concrete 3.

A concrete-filled steel pipe 1 of this type is
For example, it can be manufactured as follows. That is, as shown in FIG. 4 (a), an asphalt 4 for insulation is applied to the inner surface of the square steel pipe material 2 to prevent concrete from adhering.

Thereafter, as shown in FIG.
The high-strength steel 7 is passed through the inside of the rectangular steel pipe 2, and the end plates 11, 12 are set at both ends of the square steel pipe 2. The nuts 10 are screwed into the screws 7a at the end of the nut 7 and tightened to apply a tensile force to the high-tensile steels 7. Therefore, in this case, the end plates 11 and 12 used are those having a size to be brought into contact with the end surface of the high-tensile steel 7. In the present embodiment, the high-tensile steel 7
Needless to say, a structure having a structure that easily adheres to concrete is used.

In this state, as shown in FIG. 4C, concrete 3 is filled in the rectangular steel pipe 2. For this concrete filling, as shown in FIG. 4 (b-2), a hole 12a for concrete filling is formed in one end plate 12 so that concrete can be filled through the hole 12a. Has become. The filling of the concrete 3 may be performed from above with the end on the side of the end plate 12 having the hole 12a facing upward and standing upright.

After the concrete is hardened, as shown in FIG.
The nut 10 and both end plates 11 and 12 are removed. Thereby, the tensile force applied to the high-tensile steel 7 as described above is transmitted to the filled concrete 3 by the adhesion between the high-tensile steel 7 and the filled concrete 3, and the compressed concrete 3 is compressed in the axial direction. A prestress is introduced. Since the insulating asphalt 4 exists between the filled concrete 3 and the square steel pipe 2, the adhesion between the filled concrete 3 and the square steel pipe 2 is cut off, and the prestress is introduced into the steel pipe 2. Instead, it is effectively introduced only into the filled concrete 3.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, a case where a square steel pipe material is used as the steel pipe material is described, but a steel material having various cross-sectional shapes having an annular wall portion for concrete filling, such as a circular steel pipe material, is used. It may be configured in a structure. Further, in the above embodiment, the case where asphalt material is used as the concrete adhesion preventing agent has been described. However, what is necessary is just to cut off the adhesion between the steel pipe material 2 and the filled concrete 3. An anti-adhesion agent may be used.

[0025]

As described above, according to the concrete-filled steel pipe of the present invention, concrete is filled inside the steel pipe,
This filled concrete and the steel pipe material are cut off the adhesion between them, and only the filled concrete is introduced with the prestress of compression in the axial direction of the steel pipe material. In addition, it is possible to improve the strength of the filled concrete by confining the filled concrete to the steel pipe material to make it into a three-dimensional stress state, and to improve the strength of the filled concrete by the confined effect. Prevents and effectively introduces prestress only to filled concrete, and makes the application range of concrete-filled steel pipes structurally advantageous and effective for structural materials that act on bending and shear forces, such as beams. Can be expanded. When used as a beam, vertical deflection is also reduced. Therefore, when such a structural material is used for construction, it can exhibit a fire-resistant advantage and reduce or eliminate troublesome fire-resistant coating,
The construction period can be shortened and costs can be reduced. Further, according to the manufacturing method of the present invention, the concrete-filled steel pipe as described above can be easily manufactured.

[Brief description of the drawings]

1 shows a first embodiment of a concrete-filled steel pipe material, wherein FIG. 1A is a longitudinal sectional view, FIG. 1B is an end view, and FIG. 1C is a sectional view taken along line II of FIG. 1A. FIG.

FIGS. 2 (a), 2 (b) and 2 (c-1) are longitudinal sectional views sequentially showing a manufacturing method thereof, and FIG. 2 (c-2) is a longitudinal sectional view showing a modification of an end plate. is there.

FIG. 3 shows a second embodiment of a concrete-filled steel pipe material, in which FIG. 1A is a longitudinal sectional view, and FIG.
FIG. 2 is a sectional view taken along line I-II.

FIGS. 4A, 4B and 4C are longitudinal sectional views sequentially showing the manufacturing method, and FIG. 5B is a sectional view of FIG.
It is an end elevation of 1).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1: Concrete-filled steel pipe material 2: Steel pipe material 3: Filled concrete 4: Asphalt (concrete adhesion preventive agent) 6: Sheath pipe 7: High tensile steel (tensile material)

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[Procedure amendment]

[Submission date] July 9, 1999 (July 7, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Concrete-filled steel pipe beam and method for producing the same

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (3)

[Claims] A concrete is filled in a steel pipe material, the adhesion between the filled concrete and the steel pipe material is cut off, and only the filled concrete is subjected to a compressive prestress in the axial direction of the steel pipe material. Concrete-filled steel pipe material characterized by being made. 2. Concrete is filled into a steel pipe material in which a concrete adhesion inhibitor is applied to an inner peripheral surface thereof and a sheath pipe is passed through the inside, and after the concrete is hardened, tension for applying a prestress in the sheath pipe is provided. A method for producing a concrete-filled steel pipe material, wherein a prestress of compression in the axial direction of the steel pipe material is introduced into concrete only in the material. 3. A concrete anti-adhesive agent is applied to the inner peripheral surface, and a tension member for applying a prestress is passed through the inside, and concrete is applied to the inside of the steel pipe in a state where a tensile force is applied to the tension member. A method of manufacturing a concrete-filled steel pipe, characterized by introducing a prestress of compression in the axial direction of steel pipe material only to concrete by releasing the tension of the tendon after hardening the concrete and releasing the tension.