JPH07103638B2 - Reinforced reinforced concrete column structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reinforced concrete column structure for reinforcement. More specifically, the present invention relates to a high-rise building, an earthquake-resistant building, and a reinforced concrete column structure with a steel pipe restraint useful for lateral reinforcement and shear reinforcement of short columns.

(Prior art and its problem) As a conventional reinforcing method for a reinforced concrete column, a method of restraining the outside of the reinforced concrete column with a cylindrical steel pipe or a flat plate rectangular steel pipe has been known.

The structure by this reinforcement method has the effect of preventing the concrete from falling out of the reinforced concrete column, restraining the crushing of the concrete and the buckling of the reinforcing bar to enhance the proof strength of the column, and it has attracted attention as a reinforcing method for reinforced concrete. It is what

However, in the case of these steel pipe restrained reinforced concrete column structures which have been conventionally considered, there still remain problems to be solved. The main issues are:
In the case of a reinforced concrete column having a rectangular cross section, there are drawbacks that the restraining action is insufficient and the bending strength is small.

For example, in the case of flat plate rectangular steel pipe, since it is constrained by out-of-plane bending of the pipe wall, if the main bar ratio is high, bond splitting cracks and crushing of compressed edge concrete and buckling of compressed rebars that cause large strain are sufficiently restricted. It was not possible, and it was unavoidable that the proof stress of the column would decrease. For this reason, a thick steel pipe is required to restrain the column having a large amount of main reinforcement, which is not economical as an actual construction method.

Further, when the column is a column and is reinforced with a cylindrical steel pipe, the structure and construction of the joint between the column and the beam are troublesome.

Further, in all of the conventional restraint structures, since the steel pipe bears the axial stress, the yielding occurs early and the restraining effect and the shear reinforcing effect cannot be sufficiently exhibited.

This invention has been made in view of the circumstances as described above, and improves the drawbacks of the reinforced concrete columnar structure of the reinforced concrete by the steel pipe restraint considered so far, and has excellent restraint properties,
A new steel pipe constraint useful for super high-rise buildings, which not only exhibits improved compressive strength of concrete columns, but also exerts large bending strength and shear strength, and can exhibit extremely tough behavior even after reaching shear strength. It is intended to provide a reinforced reinforced concrete column structure.

(Means for Solving the Problems) As a means for solving the above problems, the present invention is characterized in that the surface portion of a reinforced concrete column is externally restrained by a folded plate or corrugated steel pipe having a rectangular cross section. Provide reinforced reinforced concrete column structure.

FIG. 1 shows an example of the reinforced concrete structure of the present invention. As shown in FIG. 1, in the structure of the present invention, the reinforced concrete column (2) is externally restrained by the steel pipe (1) having a rectangular cross section with the surface being a folded plate. The arrangement of the main bars (3) may be set appropriately as in the conventional case, and the shape, size and arrangement of the main bars for obtaining the required proof stress can be set appropriately.

It goes without saying that the angle (α) of the folded plate of the folded plate steel pipe (1) and the thickness (t) thereof can be appropriately designed. About the angle (α), about 40 to 65 ° can be used as a guide.

Further, FIG. 2 shows another example. In this case, unlike the example shown in FIG. 1, adjacent edges (A)
(B) has a relationship of receding and projecting, and has a characteristic that the circumferential length and the cross-sectional area of the steel pipe are the same and the cross-sectional area of the concrete is almost the same for any cross-section of the column. Therefore, there is little difference in the proof stresses due to the difference in the position of the cross section, and a large proof stress as a column can be exhibited.

FIG. 3 shows the example of FIG. 2 as an exploded view of the folded plate. It can be seen that by bending one flat plate, a member having a shape that restrains half the circumference of a reinforced concrete column can be obtained.

The excellent characteristics of the folded plate steel pipe restraint will be explained by a concrete experiment.

The test piece corresponds to the shape of the flat steel pipe shown in FIG. The following numbers are shown as dimensionless characteristic values.

(Outer diameter) D = 185, α = 45 ° (Thickness) t = 3, (Length) l = 340, Weight 0.67 Face bending rigidity 8.57 Folded plate steel pipe is made from L-30 × 30 × t, The angle was welded. Then, it is annealed. The yield stress after annealing was 3100 kg / cm ² .

The cement used was ordinary Portland cement, the fine aggregate was sea sand with a grain size of 2.5 mm or less, and the coarse aggregate was river gravel with a grain size of 10 mm or less. As the reinforcing bar, a deformed reinforcing bar of D13 ( _a σy = 3560 kg / cm ² ) was used.

(1) Center compression test A center compression force was applied using a 500 ton tester under the material end condition of the one end fixed other end pin.

At the end of the material, only concrete was compressed. Axial strain degree of concrete in the center section of the column (measurement length 60 mm)
Was measured with a measuring pipe embedded in the center of the column. The amount of axial contraction of the entire column length was measured using four displacement gauges.

As shown in Fig. 4 a) and b), regarding the relationship between the axial strain degree _c ε and the axial force N of the concrete in the central part of the column, the steel amount of the steel pipe in the case of the folded plate is the case of the flat plate. About 60%
Despite this, the maximum yield strength (19
2ton) is larger than the proof strength (190ton) of flat plate reinforcement. In addition, the degree of strain at the point where the proof stress begins to decrease is about three times that of the flat plate in the case of the folded plate.

(2) Bending shear test under constant axial force A column is subjected to antisymmetric deformation. For loading, the displacement amplitude was increased by ± 0.005 rad at each member angle to ± 0.03 rad, and three cycles were performed at the same amplitude, and a total of 18 cycles were repeated by displacement control. After that, loading was performed for one cycle with a large displacement of the member angular amplitude of 0.06 rad.

When the amount of main bars is large (Pg = 6.64%), the proof stress begins to decrease when the member angle exceeds 0.02rad, but the deterioration of the restoring force characteristics is not so remarkable. A pillar with a small amount of main muscle (Pg = 3.
In the case of 32%), the folded steel pipe yielded at the end of the column, but at the center of the column, it behaved in the elastic range until the end.

In the recent design of reinforced concrete structures in Japan, regarding the restriction of member deformation at the time of a large earthquake, the deformation of the member angle
Since it is considered that the deformation performance of 0.02 rad is sufficient, the restoring force characteristic of this test piece was sufficiently satisfactory.

5 and 6 show another example of the present invention corresponding to FIGS. 1 and 2.

In this example, a corrugated plate is used instead of the folded plate.
In the case of this corrugated plate, it is easy to mold it with a press roll, and either the corrugated steel pipe can be easily manufactured by welding the corrugated plates that are orthogonal to each other at the corners, or by applying internal pressure to the cylindrical steel pipe to integrate it. It can be manufactured by mechanically pressing. Further, unlike the case of a folded plate, there is no sharply bent top portion, so that stress concentration can be easily avoided. The corrugated plate tops (5) on the adjacent surfaces of the corrugated steel pipe (4) are coincident in FIG. 5 and deviated in FIG.
With regard to reinforced concrete columns reinforced with these corrugated steel pipes, a central compression test and a bending shear test under constant axial force or fluctuating axial force were performed, and it was confirmed that the reinforcing effect was almost the same as that when reinforced with folded plate steel pipes. It was

As is apparent from the above description, the following remarkable effects are realized in the structure of the present invention.

1) The strength of the reinforced concrete columns is excellently restrained, and the internal concrete strength is greatly improved. Therefore, it becomes possible to put many main points.

2) High flexural strength and shear strength are exhibited.

3) All of the internal concrete can be used for strength.

4) Even after reaching shear strength, it exhibits extremely tough behavior.

5) The steel pipe also serves as a concrete pouring frame.

The above effects cannot be realized by the steel pipe reinforcement structure considered so far.

[Brief description of drawings]

FIG. 1 is a front view of a partial cross-sectional disclosure showing a structural example of the present invention. FIG. 2 is a perspective view showing another example,
FIG. 3 is a partially developed view of the folded plate of this example. FIG. 4 is a) b), which is a correlation diagram between axial strain and proof stress showing the results of the central compression test. 5 and 6 are perspective views showing another example of the present invention using a corrugated plate. 1 ... Folded plate steel pipe 2 ... Reinforced concrete column 3 ... Main bar 4 ... Corrugated steel pipe 5 ... Corrugated plate top

Claims (1)

[Claims] 1. A reinforced reinforced concrete column structure, characterized in that the surface portion of the reinforced concrete column is externally restrained by a bent plate or corrugated steel pipe having a rectangular cross section.