JPH10325211A - Infilled type steel-pipe reinforced concrete column and improving method of strength and ductility of reinforced concrete column - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excite a mode, in which a yield line is formed in an X shape or expanded to the outside, to display the constraint effect of column concrete in a steel pipe or a hoop effectively, to increase the mean strength of column concrete and to improve ductility capacity in not only normal-strength concrete but also extra-high strength concrete and lightweight concrete, and to elevate the mean compressive strength of column concrete further while enhancing ductility capacity even when normal-strength high-strength concrete having normal specific gravity is used. SOLUTION: In the infilled type steel-pipe column (a CFT column) and a reinforced concrete RC column, X-shaped shear compressive fracture inducing solids 1 consisting of concrete having strength higher than column concrete 3 are disposed into column concrete at one or several places in the central height direction of the column or at the intervals of cross-sectional size. Accordingly, a mode, in which the yield line of column concrete is formed in an X shape or expanded to the outside, is excited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the strength and toughness of a filled steel pipe concrete column and a reinforced concrete column which are classified as a steel reinforced concrete structure among column members of a structure in the construction field. is there.

[0002]

2. Description of the Related Art Conventional filled steel pipe concrete columns (CF)
In (T column), only the concrete is filled in the steel pipe, and there are no other components. Also, a known reinforced concrete column (RC column) is composed of a main bar and a band bar, and has a bar-shaped, a rice-shaped, a box-shaped, and an X-shaped reinforcing bar as a reinforcing method. There are no other components.

[0003]

In the case of the above-mentioned concrete column filled with steel pipe, it is known that the compressive strength of concrete is higher than that of concrete without steel pipe due to the restraining effect of steel pipe on concrete. Have been. It is also known that, in a reinforced concrete column, an increase in the compressive strength of the column and an increase in toughness as a column member are caused by a reinforcing bar (hoop bar) arranged as a shear reinforcing bar. However, focusing on the compressive strength of concrete cylinders and the specific gravity of concrete, the following is generally known. (1) Compressive strength of concrete is 600 kgf / cm ²
The average compressive strength of column concrete increases linearly with the strength and cross section of steel pipes or stirrups, but the compressive strength of concrete is 600 kgf. In ultra-high-strength concrete exceeding / cm ² , an increase in the average compressive strength of columns cannot be expected as compared with ordinary to high-strength concrete. (2) In the case of lightweight concrete, the increase in the average compressive strength of the column due to the restraining effect of the steel pipe or the tie bar on the concrete is smaller than that of the concrete having the normal specific gravity.

[0004] These factors are considered as follows. (1 ') According to the results of the center compression test of the column, the fracture line is a cone shape, that is, an oblique crack crossing the column axis is formed in an X shape on average, according to the results of the center compression test of the column. As the compressive axial force or the vertical deformation increases, the steel pipe or the stirrup restrains the concrete on the left and right of the X-shaped crack from being pushed outward and trying to expand, resulting in an increase in strength and an increase in toughness. Is considered to be achieved. (See FIGS. 5 (a) and (c).) (2 ') On the other hand, in ultra-high-strength concrete or lightweight concrete, a fracture line is not always formed in an X-shape, and as shown in FIGS. A | -shaped fracture line is formed due to the shape or split, and the concrete is not extruded outward and does not expand, and an effective restraining effect of the steel pipe or the strip bar on the concrete is not exhibited. As a result, it is considered that an increase in strength and an increase in toughness cannot be expected. (3 ′) Particularly, in ultra-high-strength concrete or lightweight concrete, an X-shaped breaking line is not necessarily formed.
The ratio of tensile strength to compressive strength is lower than that of concrete of normal strength or normal specific gravity, and concrete aggregate is cracked at the fracture surface (cracked surface) when it is formed in a | It is presumed that the fracture surface has almost no shear resistance, and the fracture surface slips before the crack is formed in an X-shape, and the expansion mode is hardly generated.

[0005] The present invention has been proposed in view of the above-mentioned problems, and the object thereof is to make the fracture line X-shaped or outward not only in ordinary-strength concrete but also in ultra-high-strength concrete and lightweight concrete. Exciting the expansion mode, effectively exerting the restraining effect of the steel pipe or stirrup, increasing the average strength of the column concrete, improving the toughness, and further increasing the ordinary strength and ordinary strength of ordinary specific gravity. Even when concrete is used, the point is to further increase the average compressive strength of the column concrete and to improve the toughness.

[0006]

According to the present invention, there is provided a method for improving the strength and toughness of a concrete-filled steel tube column and a reinforced concrete column according to the present invention.
An X-shaped shear compression failure-inducing solid of concrete having a strength higher than the cylinder compressive strength of the column concrete is disposed in the column concrete at one or several places in the center height direction of the column or at intervals of the cross-sectional dimension. This excites a mode in which the breaking line of the column concrete is expanded in an X shape or outward.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings showing preferred embodiments of the present invention. Fig. 1 (a)
(B) and (c) show conventional RC columns, (a) and (b)
Shows a plan sectional view, and (c) shows a longitudinal sectional view. In a column concrete a, a column main bar b extending in the height direction of the column and a band bar c surrounding the column main bar b are arranged.

FIGS. 2A, 2B and 2C show a conventional CF.
5 shows a T column, in which a round concrete pipe d or a square steel pipe d ′ is filled with column concrete a. At this time, when ultra-high strength concrete or lightweight concrete is used as the concrete, the ratio of the tensile strength to the compressive strength is small, the aggregate is cracked at the fracture surface (cracked surface), the shear resistance of the fracture surface is almost eliminated, and the X-shaped The slippage occurs before the fracture surface is formed, and the expansion mode is difficult to come out.

In this method, one or several pieces or a cross section having a cross-sectional dimension in the height direction of the column having a compressive strength higher than the compressive strength of the concrete cylinder and having a spherical or upper and lower cross-sectional dimension at the center are provided. 1 comprising an X-shaped shear compression fracture-inducing solid smaller than the cross-sectional dimension of the surface
Is disposed in the column concrete a via the reinforcing material fixing iron wire 2. The reinforcing material 1 is not limited to concrete and mortar materials.

Accordingly, concrete of RC column and CFT column using high-strength concrete or lightweight concrete 3
In this case, the reinforcing material 1 excites a fracture mode in which the fracture line is expanded in an X-shape or outwards, and thus the restraining action of the column concrete a by the circular steel pipe d, the square steel pipe d 'or the strip c is effectively applied. Things. In addition, the above-mentioned method is mainly used for filled steel pipe concrete columns classified as steel reinforced concrete column structures, in steel pipes of filled coated steel pipe columns, and for reinforced concrete columns,
Application to beam members to improve toughness is also conceivable. It is also used to maintain long-term loads that support the weight of buildings and to ensure the safety of buildings during earthquakes and storms.

[0011]

According to the method of the present invention, X-type shear compression fracture of concrete having higher strength than the cylinder compressive strength of column concrete in filled steel tubular concrete columns and reinforced concrete columns classified as steel reinforced concrete structures. By disposing solids in the column concrete at one or several places in the column height direction or at intervals of the cross-sectional dimension in the column concrete, the breaking line of the column concrete is expanded in an X shape or outward. Exciting the mode that causes the steel pipe or band reinforcing steel to increase the binding strength to the column concrete,
Improve toughness.

As a result, it is possible to stably hold the weight of the building, that is, the column under a long axial force and a high axial force during a large earthquake, and to secure the stability of the building during an earthquake or a storm. .

[Brief description of the drawings]

1 (a), (b) and (c) show conventional RC columns, respectively. (A) and (b) are plan sectional views of a circular RC column and a rectangular RC column, respectively, and (c) is a longitudinal sectional view. It is.

FIGS. 2 (a), (b) and (c) show conventional CFT columns, respectively, and FIGS. (A), (b) and (c) are a cross-sectional plan view and a longitudinal sectional view of a circular steel pipe column and a square column, respectively. It is.

FIGS. 3A and 3B show RC columns constructed by the method of the present invention, respectively. FIGS. 3A and 3B are plan sectional views of a circular column and a rectangular column, respectively. Is a longitudinal sectional view.

FIGS. 4A and 4B show CFT columns constructed by the method of the present invention, respectively. FIGS. 4A and 4B are plan sectional views of a circular column and a rectangular column, respectively. Is a longitudinal sectional view.

5 (a) and (b) are schematic diagrams showing a failure mode of a conventional RC column, (c) and (d) are schematic diagrams showing a failure mode of a conventional CFT column, and (a) is a normal concrete column. , (B)
Shows the case of high-strength concrete and lightweight concrete columns, (c) shows the case of ordinary concrete columns, and (d) shows the case of high-strength concrete and lightweight concrete columns.

6 (a) and 6 (b) are explanatory views showing the reinforcing effect of RC columns and CFT columns constructed by the method of the present invention.

FIGS. 7 (a) and 7 (b) are explanatory views showing fixing means at the time of construction of an X-shaped shear compression failure inducing solid of concrete, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-type shear compression fracture induction solid 2 Iron wire for fixation 3 Column concrete a Column concrete b Column main bar c Band bar d Round steel pipe d 'Square steel pipe

Claims (1)

[Claims] 1. A concrete-filled steel tubular concrete column and a reinforced concrete column having a strength higher than a cylinder compressive strength of a column concrete at one to several places in a center height direction of the column or at intervals of a cross-sectional dimension. Filled steel tubular concrete columns and reinforced concrete columns, characterized in that an X-shaped shear compression failure-inducing solid is arranged in column concrete to excite a mode in which the fracture line of the column concrete is expanded in the X-shape or outward. For improving the strength and toughness of steel.