JP2021042582A - Thin column cft diaphragm - Google Patents

Abstract

To provide a diaphragm of a thin column CFT which does not collect air at a lower peripheral edge of the diaphragm and improves filling property of concrete even if a steel pipe has a small diameter which increases the concrete ascending speed.SOLUTION: A planar diaphragm 11 partitions an inside space by fixing a peripheral edge part inside a small-diameter steel pipe 12. The diaphragm is formed by arranging a placing hole 13 for passing concrete 17 placed by being pressed from below in the steel pipe in a central part of the diaphragm and a plurality of air vent small holes 14 for releasing air to an upper part in a peripheral part of the diaphragm. A rising portion 15 protruding upward from an upper surface of the diaphragm is erected along the vicinity of a peripheral edge part 13a of the placing hole, for the purpose of temporarily storing concrete overflowing from the placing hole and delaying a time until the concrete reaches the air vent small hole through the diaphragm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a diaphragm of steel pipe concrete (CFT: Concrete Filled stell Tube, the same applies hereinafter) in which concrete is filled inside a small diameter steel pipe, and in short, it relates to a diaphragm of a thin pillar CFT.

Conventionally, as a diaphragm of this kind of steel pipe concrete, a diaphragm of steel pipe concrete disclosed in Japanese Patent No. 4767715 is known.

As shown in FIG. 5, the diaphragm of the steel pipe concrete is formed in the center portion of the diaphragm 1 in the placement hole 4 for passing the concrete 3 to be cast by being press-fitted into the steel pipe 2 from below, and also in the peripheral portion. An air vent hole 5 for letting air escape to the upper part is provided, and the concrete overflowing from the casting hole 4 to the upper surface of the diaphragm 1 prevents the concrete overflowing from the casting hole 4 from blocking the air vent hole 5 in the air vent hole 5. It has a configuration in which a tubular rising portion 6 is provided so as to project upward from the upper surface (see Patent Document 1).

In the steel pipe concrete diaphragm 1 having such a configuration, when the concrete 3 cast in the steel pipe 2 rises and reaches the diaphragm 1, the concrete 3a in the central portion, which is raised above the surroundings, is placed in the casting hole 4. Even if the concrete overflows from the upper surface of the diaphragm 1 and flows out to the surroundings, the time until the overflowed concrete reaches the air vent hole 5 and closes the air vent hole 5 is delayed and lengthened due to the presence of the rising portion 6.
In the meantime, the concrete 3b at the peripheral edge of the cast concrete rises and passes through the air vent hole 5 while pushing air upward from the air vent hole 5 to reach the upper end of the rising portion 6 or the upper surface of the diaphragm 1.
Therefore, air does not collect in the vicinity 7 of the peripheral edge on the lower side of the diaphragm 1, and the generation of voids is prevented.

On the other hand, as a means for achieving both high earthquake resistance and design in a steel structure, a thin column CFT in which concrete is filled inside a small diameter steel column is adopted as a column.

Japanese Patent No. 4767715

In the thin pillar CFT, when concrete is filled as in the past, the ascending speed (filling speed) of concrete is increased because the pillar has a small diameter.
In this case, in the case of the conventional steel pipe concrete diaphragm 1, a large amount of concrete 3 overflows from the large-diameter casting hole 4 at a high speed, and before the concrete 3b at the peripheral edge reaches under the air vent hole 5. The start-up portion 6 will be closed from above.
Therefore, as a result, it is not possible to solve the problem that air is accumulated in the vicinity 7 of the peripheral edge portion on the lower side of the diaphragm 1 and the filling property of the concrete is lowered.

Therefore, in the steel pipe concrete diaphragm of the conventional example, even if the thin column CFT has a high concrete ascending speed, the problem of air accumulating near the peripheral edge 7 on the lower side of the diaphragm 1 is solved and the concrete filling property is solved. There is a problem that must be solved to improve.

The gist of the present invention for solving the above-mentioned problems of the conventional example is a flat plate-shaped diaphragm in which a peripheral edge portion is fixed inside a small-diameter steel pipe to partition an internal space, and the inside of the steel pipe is located at the center of the diaphragm. In a diaphragm in which a casting hole for passing concrete to be cast by press-fitting from below and a plurality of air venting small holes for allowing air to escape to the upper part are provided in a peripheral portion of the diaphragm. In order to temporarily store the concrete overflowing from the casting hole along the vicinity of the peripheral edge of the casting hole and delay the time for the concrete to reach the air venting small hole through the diaphragm. This is because a rising portion protruding upward from the upper surface of the diaphragm was erected.

The rising portion has a circular shape or a polygonal shape in a plan view;
Is included.

According to the diaphragm of the thin column CFT according to the present invention, the concrete in the central portion, which is press-fitted into the steel pipe from below and is raised above the periphery, temporarily stays inside the rising portion, so that the concrete overflows to the upper surface of the diaphragm. It is possible to delay the time required to reach the air vent small hole.
In the meantime, the concrete at the peripheral edge of the cast concrete rises, pushes air upward from the air bleeding small hole, passes through the air bleeding small hole, and reaches the upper surface of the diaphragm.
Therefore, even in the case of a small-diameter steel pipe in which the ascending speed of concrete is high, air does not collect in the vicinity of the peripheral edge on the lower side of the diaphragm, and the concrete filling property is improved.

It is a top view which shows the diaphragm of the thin column CFT which concerns on this invention. It is explanatory drawing which shows the state at the time of concrete placing of the diaphragm of the thin column CFT in the cross section. It is explanatory drawing which shows the state at the time of concrete placing of the diaphragm of the thin column CFT in the cross section. It is explanatory drawing which shows the state at the time of concrete placing of the diaphragm of the thin column CFT in the cross section. It is a vertical cross-sectional view of the steel pipe explaining the diaphragm of the steel pipe concrete which concerns on the prior art.

Next, an embodiment of the present invention will be described with reference to the drawings. First, in FIGS. 1 to 4, reference numeral 11 indicates a diaphragm of a thin pillar CFT, and the diaphragm 11 of the thin pillar CFT has a flat plate shape in which a peripheral edge portion is fixed inside a small diameter steel pipe 12 to partition an internal space. It is formed, and a casting hole 13 for passing concrete is provided in the central portion (see FIGS. 1 and 2), and a plurality of small air vent holes 14 are provided in the peripheral portion (FIGS. 1 and 2). (See), a rising portion 15 projecting upward from the upper surface of the diaphragm 11 is erected along the vicinity of the peripheral edge portion 13a of the driving hole 13.

The small column CFT or the small diameter steel pipe 12 has a diameter of about 440 to 460 mm, preferably about 450 mm, and realizes high earthquake resistance and design.

The diaphragm 11 is provided so as to project inside and outside the steel pipe 12, and serves to transmit stress to a structure 16 such as a steel beam.

The casting hole 13 is formed in a circular shape at the center of the diaphragm 11 and is provided to pass the concrete 17 to be cast by press-fitting into the steel pipe 12 from below (see FIGS. 1 and 2). ).

The rising portion 15 is erected in a state of protruding upward from the upper surface of the diaphragm 11 along the vicinity of the peripheral edge portion 13a of the driving hole 13, and is attached by a fixing means such as welding.
The material of the rising portion 15 is preferably a steel pipe material, and the thickness of the rising portion 15 is about 4.5 mm.
As an example, the shape of the rising portion 15 has a diameter dimension of about 60 mm larger than the diameter dimension of the casting hole 13, and the height is about 50 mm. Further, the rising portion 15 has a circular shape or a polygonal shape in a plan view.
The rising portion 15 is a portion for temporarily fixing the concrete 17a in the central portion, which is pressed into the steel pipe 12 from below and is raised above the periphery.
Of course, the height of the riser portion 15 may be formed higher than 50 mm with a margin in order to further delay the storage time of concrete in the riser portion 15.

The air bleeding small holes 14 are provided at eight or a plurality of locations at equal intervals around the diaphragm 11, and the diameter dimension thereof is about 8 to 30 mm or more.
The small air vent 14 is provided to allow air to escape to the upper part and prevent the air from staying in the vicinity of the peripheral edge 18 on the lower side of the diaphragm 11 to prevent the generation of voids.

In the diaphragm 11 of the thin column CFT configured as described above, the concrete 17a in the central portion, which is press-fitted into the steel pipe 12 from below and is raised above the periphery, temporarily stays inside the rising portion 15 (see FIG. 3). ), The time until the concrete 17 overflows to the upper surface of the diaphragm 11 and reaches the air venting small hole 14 can be delayed.
During that time, the concrete 17b at the peripheral edge of the cast concrete rises, pushes air upward from the air bleeding small hole 14, passes through the air bleeding small hole 14, and reaches the upper surface of the diaphragm 11.
Therefore, even in the case of the small-diameter steel pipe 12 in which the ascending speed of the concrete 17 is increased, air does not collect in the vicinity of the peripheral edge portion 18 on the lower side of the diaphragm 11, and the filling property of the concrete is improved.

1 Diaphragm 2 Steel pipe 3 Concrete 3a Concrete in the center 3b Concrete in the peripheral part 4 Casting hole 5 Air vent hole 6 Rising part 7 Near the peripheral edge 11 Diaphragm of thin pillar CFT 12 Steel pipe 13 Casting hole 13a Peripheral part 14 For air venting Small hole 15 Rising part 16 Structure such as steel beam 17 Concrete 17a Central part concrete 17b Peripheral part concrete 18 Near the peripheral part

Claims (2)

It is a flat plate-shaped diaphragm whose peripheral edge is fixed to the inside of a small-diameter steel pipe to partition the internal space, and is used to pass concrete to be cast by press-fitting into the steel pipe from below into the central portion of the diaphragm. In a diaphragm provided with an installation hole and a plurality of small air vent holes for allowing air to escape to the upper part in the peripheral portion of the diaphragm.
In order to temporarily store the concrete overflowing from the casting hole along the vicinity of the peripheral edge of the casting hole and delay the time for the concrete to reach the air venting small hole through the diaphragm. A thin pillar CFT diaphragm characterized in that a rising portion protruding upward from the upper surface of the diaphragm is erected. The diaphragm of the thin column CFT according to claim 1, wherein the rising portion has a circular shape or a polygonal shape in a plan view.

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