JPH1161736A - Concrete-filled steel column - Google Patents

Abstract

(57) [Problem] To provide a concrete-filled steel column which has a simple structure, is easy to construct, prevents a stiffener from coming off during an earthquake, and has a large effect of improving strength and toughness. SOLUTION: A plurality of stiffeners 7 provided with a plurality of through holes 8 in an inner periphery of a lower portion of a column having an outer peripheral wall portion 1 made of steel.
Are fixed in the radial direction, and the concrete 2 is further filled with the concrete 2, thereby filling the inside of the through hole 8 with the concrete 2, thereby preventing the stiffener 7 from coming out of the concrete 2 during an earthquake.

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 column, such as a highway bridge pier, and more particularly to a structure of the column base.

[0002]

2. Description of the Related Art For example, as shown in FIG. 4, a cantilever-type circular steel pier for roads is formed by bending a thin steel plate into a cylindrical shape and welding a butt portion thereof in a vertical direction. It has a column base structure including a steel outer peripheral wall section 1 and concrete 2 filled in a lower portion (column base section) inside the outer peripheral wall section 1. However, when a seismic load is applied, local buckling may occur in the column base 3, which is problematic in terms of earthquake resistance.

In order to improve the seismic resistance of such steel columns, various proposals have conventionally been made.
Among them, the simplest and representative one is a stiffener (stiffener) 4a made of a rectangular steel plate as shown in FIG.
Is fixed radially to the inner periphery of the steel outer peripheral wall 1 of the column base 3. However, a flat stiffener 4a
In this case, the stiffener 4a slips between the stiffener 4a and the concrete 2 during an earthquake because the bonding strength with the concrete 2 is weak.
Get out of Therefore, this method cannot prevent local buckling 5 from occurring in the column base 3.

Further, in place of the flat plate stiffener 4a,
There is also a method using a stiffener 4b having an L-shaped cross section or a T-shaped cross section as shown in FIG. When the stiffener 4b having an L-shaped cross section or a T-shaped cross section is used, it is possible to prevent the stiffener 4b from coming off in the radial direction. However, in this method, the stiffener 4b comes off in the axial direction at the time of an earthquake. Therefore, the stiffener 4b is prevented from coming out in the axial direction by attaching the diaphragm 6 to the upper portion of the column base 3 and pressing the upper surface of the concrete 2.
It is difficult to reduce the gap between the diaphragm 6 and the upper surface of the concrete 2, and it is necessary to use expanded concrete or the like.
Further, a stiffener having an L-shaped cross section or a T-shaped cross section requires a high material cost and a high processing cost, resulting in a high cost.

[0005]

As described above, the conventional concrete-filled steel column has a problem that the stiffener cannot be prevented from coming off during an earthquake. Therefore, the cast concrete did not contribute to the increase in strength and toughness of the column. In addition, diaphragms and expansive concrete must be used, and the structure is complicated and seismic resistance cannot be expected sufficiently.
The construction was troublesome.

The present invention has been made to solve the above-mentioned problems, and has a simple structure, is easy to construct, prevents the stiffener from coming off during an earthquake, and improves strength and toughness. It is an object of the present invention to provide a concrete-filled steel column having a large effect.

[0007]

According to the present invention, there is provided a concrete-filled steel column having a plurality of stiffeners provided radially on an inner periphery of a lower portion of a column having an outer peripheral wall made of steel. By providing a plurality of through-holes in the stiffener and filling the concrete in the through-hole in a portion filled with concrete, preventing the stiffener from slipping out of the concrete during an earthquake. It is characterized by the following.

In the present invention, by providing a plurality of through-holes in a flat plate stiffener (stiffener) and filling the through-holes with concrete, it is possible to enhance the integrity of the stiffener and concrete. Therefore, the stiffener does not come off during an earthquake, and thus the strength and toughness of the concrete-filled steel column are improved.

[0009]

FIG. 1 is a sectional side view of a concrete-filled steel column according to the present invention, and FIG. 2 is a sectional plan view. As shown in these figures, a plurality of stiffeners 7 made of a flat plate provided with a plurality of through holes 8 are attached to the inner periphery of the steel outer peripheral wall portion 1 by welding on the column base 3 of the concrete-filled steel column. Further, concrete 2 is filled. In addition, the size of the through hole 8 is a size in which the aggregate, the fiber, and the like included in the concrete 2 can enter. By filling the concrete 2, the inside of each through hole 8 of each stiffener 7 is filled with the concrete 2, and the integrity of each stiffener 7 and the concrete 2 is increased.

As described above, as a result of filling the inside of each through hole 8 with the concrete 2, the stiffener 7 and the concrete are improved in unity, and the stiffener 7 is prevented from coming off in the radial and axial directions during an earthquake. Can be. As a result, the buckling of the steel outer peripheral wall can be delayed, and the strength and toughness of the concrete-filled column can be improved.

Further, since it is not necessary to use a diaphragm or an expansive concrete for pressing down the upper surface of the filled concrete 2 as in the prior art, the construction becomes easy.
And cost can be reduced.

FIG. 3 shows an example of actual design dimensions. The material of the outer peripheral wall steel plate and the stiffener is SS400, and the specifications are as follows. Number of stiffeners: n = 8 Column height: h = 4500 mm Concrete height: hc = 2250 mm Column radius: R = D / 2 = 400 mm Outer wall steel plate thickness: t = 9 mm Stiffener width: bs = 90 mm Stiffener thickness: ts = 9 mm Stiffener length: a = 2R = 800 mm Through hole diameter: φ = 40 mm Through hole pitch: c = 130 mm, c-φ >> bs SS400: Yield strength: σy = 235 MPa Young's modulus: E = 2.06 × 10 ⁵ MPa Poisson Ratio: ν = 0.3 It has been confirmed that the strength and toughness of this column are sufficiently high.

The above description has been given of the embodiment in which the column has a circular cross section. However, the present invention is not limited to this, and a polygonal column having a triangular, quadrangular, hexagonal or octagonal cross section, or a non-elliptical column such as an elliptical cross section is used. It can also be performed on circular columns.

[0014]

As described above, according to the present invention, a through hole is provided in a flat plate stiffener, and concrete is filled in the through hole, so that the stiffener does not come off during an earthquake and the column base buckles. Thus, the strength and toughness of the concrete-filled steel column are improved. In addition, the construction of the column base is simple, and there is no need to use a diaphragm or expansive concrete to hold down the concrete surface as in the past, so construction is very easy and contributes to cost reduction. It is.
Furthermore, even if the surface of the stiffener is not provided with unevenness or the like, the stiffener can be manufactured at low cost and using a thin-walled material because the integration with concrete is enhanced.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a concrete-filled steel column of the present invention.

FIG. 2 is a sectional plan view of FIG.

FIG. 3 is a diagram showing an example of design dimensions in the embodiment.

FIG. 4 is a sectional front view of a conventional concrete-filled steel column.

FIG. 5 is a cross-sectional plan view of a column base provided with a conventional flat plate stiffener.

FIG. 6 is an explanatory view showing buckling of a column base portion and escape of a stiffener during an earthquake.

FIG. 7 is a sectional plan view of a column base provided with a conventional stiffener having a T-shaped cross section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel outer peripheral wall 2 Concrete 3 Column base 7 Stiffener (stiffener) 8 Through hole

Claims (2)

[Claims] A plurality of longitudinal stiffeners provided on an inner periphery of a lower portion of a column having an outer peripheral wall made of steel, and a lower portion of the column is filled with concrete; A concrete-filled steel column, wherein the through hole is filled with the concrete, thereby preventing the stiffener from falling out of the concrete during an earthquake. 2. The concrete-filled steel column according to claim 1, wherein the stiffener is made of a rectangular steel plate.