JPH0751817B2 - Structure of unbonded filled steel pipe concrete column - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure of an unbonded filled steel pipe concrete column having improved structural strength against tensile axial force.

"Prior Art" As is well known, the filled steel pipe concrete structure adopted for columns and piles of a structure is one in which concrete is placed inside a steel pipe, and the steel pipe and the concrete are in a bonded state. That is, when an axial compressive force acts on a pillar of this type of structure, the steel pipe and the concrete are distorted integrally, so the steel pipe has an axial stress, an in-plane shearing force, and a circle from the concrete. Since it receives a stress in the circumferential direction, it tends to be in a plastic state due to the von Mises yielding condition, which may cause local buckling. Therefore, in the filled steel pipe concrete column having the above structure, the steel pipe reaches a considerable stress level due to the increased axial stress, etc., and the confined effect due to the circumferential stress (concrete expansion due to the circumferential stress of the steel pipe causes However, there was a drawback that the column could not be fully exerted, and as a result the column had a larger cross-sectional area than necessary.

Therefore, as a solution to such a drawback, the present inventors previously disclosed in Japanese Patent Application No. 60-45285, an unbonded filled steel pipe concrete column provided with a deformation absorbing portion (hereinafter simply referred to as an unbonded column). Abbreviated) is proposed. This unbonded column is provided with an unbonded treatment layer at the boundary surface between the steel pipe and concrete to eliminate the adhesion between concrete and steel pipe, and a large number of through holes are formed at appropriate positions of the steel pipe to provide a deformation absorbing part. is there.

In the unbonded column having the above structure, the steel pipe and the concrete are in a separated state, and even when the concrete is axially compressed and deformed, the steel pipe behaves as a separate body from the concrete, and further, the deformation absorbing portion is In order to absorb the axial deformation of the steel pipe, it was possible to increase the margin for the Mises yield condition.

Therefore, in the unbonded column of the above structure, the steel pipe receives only the ring tension from the concrete inside, and in order to exert an excellent confined effect with a sufficient circumferential stress, it is possible to significantly increase the yield strength of the concrete. It had an excellent feature that it was possible to reduce the cross-sectional area of the column as a result.

"Problems to be solved by the invention" However, in the unbonded column having the above-described structure, when the axial force or the shearing force acts, the steel pipe and the concrete behave separately, and the steel pipe is provided with the deformation absorbing portion. Because of
There was a problem that the structural strength against the tensile axial force acting during an earthquake was not sufficient.

The present invention has been made in view of the above problems, in addition to the excellent structural characteristics of the unbonded columns previously proposed by the present inventors, an unbonded filled steel tubular concrete column having an increased structural strength against tensile axial force. It is intended to provide a structure.

"Means for Solving Problems" In order to solve the above problems, the present invention provides a plurality of concrete parts by forming a plurality of annular notches at appropriate intervals in the lengthwise direction of a columnar concrete part. It is divided into concrete pillar parts, and a steel pipe is provided on the outside of each concrete pillar part through an unbonded treatment layer. This steel pipe has its upper and lower ends separated from the ends of other steel pipes above or below, The deformation absorbing portion is formed between the end portions of the upper and lower steel pipes, and at the upper end and the lower end of each steel pipe, inward flange-shaped bearing plates are formed by being inserted into the cutout portions, while the cutout portions are formed. In the concrete part inside, the reinforcing bars that span the upper and lower concrete columns are embedded.

"Action" The concrete column receives the compressive axial force, and the steel pipe receives the ring tension as a reaction that gives the concrete a confined effect. It is possible to improve the yield strength of the concrete column and reduce its cross-sectional area. Becomes

Furthermore, when a tensile axial force acts on the steel pipe, the bearing plate abuts against the end of the concrete column part and receives it, and in the concrete part inside the notch, the reinforcing bar reinforces the structural strength against the tensile axial force. Let

"Embodiment" FIGS. 1 to 3 show an embodiment of the present invention. An unbonded type filled steel pipe concrete column (hereinafter abbreviated as an unbond column) A of this example is shown in FIGS. It has the structure shown in the figure, and as shown in FIG.
It is used as a pillar for the building and is formed at a height corresponding to the height of the building.

In FIG. 1 and FIG. 2, reference numeral 1 is a steel pipe, and 2 is a concrete portion filled with concrete.

An annular notch 2a is formed on the outer periphery of the concrete portion 2 at intervals corresponding to the floor height of the building K, and each is located at a height near the center of each floor of the building. Then, a peripheral step portion 2b is formed, the concrete portion 2 is divided into a plurality of concrete pillar portions 2A by these cutout portions 2a, and a small diameter portion 2B is formed inside each cutout portion 2a.

Then, on the outside of each concrete pillar portion 2A, the steel pipe 1 forms a deformation absorbing portion H with a gap of a required width between the steel pipe 1 and the other steel pipes 1 above and below via the unbonded treatment layer 3. It is provided. Further, inward flange-shaped pressure-bearing plates 4 are provided at both upper and lower ends of each steel pipe 1, and each steel pipe 1 has upper and lower pressure-bearing plates 4 and 4 brought into contact with each circumferential step portion 2b of the concrete column portion 2A. It is provided so as to surround the concrete pillar portion 2A. In addition,
In the unbonded layer 3, the concrete column portion 2A is for separating the steel pipes 1 and causing them to behave separately, and a low friction material such as paraffin, asphalt, oil, grease, vaseline, or a powder for an organic solvent. It consists of dissolved separation material.

Further, inside the concrete column 2A inside the cutout portion 2a, a plurality of reinforcing reinforcing bars 6 such as reinforcing bolts (6 in the present embodiment) embedded with locking members 5 such as nuts at both ends are embedded. Has been done. The reinforcing bars 6 are arranged vertically with the locking members 5 at each end located inside the upper and lower concrete columns 2A, 2A, and on the inner circumference side of the pressure support plate 4, respectively. They are buried so that they are evenly spaced along the direction.

In addition, as shown in FIG. 3, a beam 8 for each floor is welded to the vicinity of the central portion in the height direction of each steel pipe 1 to form a skeleton of the structure A. Further, on the inner side of the steel pipe 1 to which the beam member 8 is joined, a steel stiffener 9 continuous with the beam member 8 may be provided in the concrete portion 2 as shown by a chain double-dashed line in FIG. it can.

Next, the operation of the unbonded pillar A having the above structure will be described.

In the unbonded column A having the above-mentioned structure, when a tensile axial force is applied, the bearing plate 4 of each steel pipe 1 abuts the circumferential step portion 2b to receive the tensile axial force and is embedded in the concrete column portion 2A. Since the reinforcing bar 6 receives the tensile axial force, it exhibits more excellent axial tensile proof strength as compared with the unbonded column previously proposed by the present inventors. Therefore, the building constructed by using the unbonded column A has a sufficiently high strength against the tensile axial force acting during the earthquake. When a tensile axial force is applied, in the peripheral step portion 2b of the concrete column portion 2A,
Since the annular pressure plate 4 presses the peripheral step portion 2b to generate stress in this portion, and also generates stress in the peripheral portion of the locking member 5 of the reinforcing bar 6, the periphery of the peripheral step portion 2b. The stress from the portion toward each locking member 5 is generated in an arch shape, and a good stress state can be obtained. Further, when a tensile shearing force acts on the unbonded column A, the reinforcing reinforcing bar 6 receives the shearing force.

On the other hand, when an axial compressive force acts on the unbonded pillar A to cause a large strain in the concrete portion 2, the steel pipe 1 and the concrete portion 2 are separated by the unbonded treatment layer 3,
Moreover, since the deformation absorbing portion H is provided between the steel pipe 1 and another steel pipe 1, each steel pipe 1 can move in the vertical direction by the distance allowed by the deformation absorbing portion H, This prevents buckling of the steel pipe 1. (Note that in view of this point, the gap between the upper and lower steel pipes 1 and 1 is set to a size capable of absorbing the movement amount of the steel pipe 1 due to the deformation of the concrete portion 2 due to the strain.) The confined effect can be exerted on the concrete pillar portion 2A with almost no axial force, and the ring tension is received as a reaction thereof. That is, the unbonded column A is subjected to an axial force by the concrete column portion 2A which is strong against compression and a ring tension by the steel pipe 1 which is strong against tension. As a result, the unbonded pillar A has the steel pipe 1 and the concrete portion 2
By virtue of the synergistic effect of and, a much higher compression strength is guaranteed compared to the conventional filled steel tube concrete column, and the cross-sectional area can be reduced accordingly.

Further, since a plurality of reinforcing reinforcing bars 6 are arranged on the inner peripheral side of the bearing plate 4 at a predetermined interval, the structural strength against the circumferential moment acting on the unbonded column A is also improved.

Furthermore, the problem of structural strength deterioration due to the formation of the notch 2a and loss of the cross-sectional area of the concrete pillar 2A is solved by the reinforcing bars 6 ... Reinforcing the concrete portion around the small diameter portion 2B. There is.

By the way, in order to construct the unbonded pillar A having the above-described structure, the steel pipes 1 and 1 are connected to each other through an annular discard form made of rubber, steel, or the like, and are erected at the construction site. It can be constructed by filling concrete with. Further, the abandoned form may be removed after the unbonded column A is constructed, or may be left between the steel pipes 1 and 1 if the form is deformable like soft rubber.

"Effects of the Invention" As described above, according to the present invention, the effects described below are achieved.

(1) When a tensile axial force acts on the unbonded column of the present invention, the pressure bearing plate of each steel pipe abuts against the end of the concrete column portion to counteract the tensile axial force, and is embedded in the concrete column portion. In order for the reinforcing bar to receive the tensile axial force,
The present invention exhibits superior axial tensile strength as compared with the unbonded column previously proposed by the present inventors. When a tensile axial force acts on the unbonded column as described above, at the end of the concrete column part, the annular pressure support plate presses the end of the concrete column part to generate stress in this part, and Since stress is generated also in the peripheral portion of the above, since a stress arch extending from the peripheral portion of the end portion to each reinforcing bar is generated, a good stress state can be obtained.

(2) Further, even if tensile shearing force acts on the notch of the unbonded column, the reinforcing bar opposes this, so the unbonded column has a structure that is also strong against tensile shearing resistance.

(3) On the other hand, when an axial compressive force acts on the unbonded column to cause a large strain in the concrete part, the steel pipe and the concrete part inside thereof are separated by the unbonded treatment layer, and the steel pipe is Since the deformation absorbing part is provided between the steel pipe and the steel pipe, the deformation absorbing part allows the deformation absorbing part to move in the vertical direction, and the steel pipe does not buckle. Therefore, the steel pipe can exert a confined effect on the concrete column portion with almost no axial force, and receives a ring tension as its reaction. That is, the unbonded column is subjected to an axial force by the concrete column portion that is strong against compression, and is subjected to ring tension by the steel pipe that is strong against tension. As a result, unbonded columns are guaranteed to have significantly higher compression strength than conventional filled steel pipe concrete columns due to the synergistic effect of the steel pipe and concrete part, and the cross-sectional area can be reduced accordingly. .

(4) Furthermore, the problem of structural strength deterioration due to the cross-section loss of the concrete column portion caused by forming the notch is
Since this can be solved by embedding a reinforcing bar in the concrete portion inside the cutout portion to improve the strength, the unbonded column of the present invention exhibits sufficient structural strength even if the concrete portion has the cutout portion.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a side view of a main part with a part broken away, FIG. 2 is a horizontal sectional view of the main part, and FIG. [Fig. 3] is a side view showing a part of a framework of a building constructed using unbonded columns. A: Unbonded columns (unbonded filled steel tube concrete columns), K: Frame, 1 ... Steel tube, 2 ... Concrete section, 2A ... Concrete column section, 2B ... Small diameter section, 2a ....
Notch part, 2b ... peripheral part, 3 ... unbonded layer, 4 ...
… Bearing plate, 5… Locking member, 6… Reinforcing bolt (reinforcing bar), 8… Beam material.

Claims (1)

[Claims] 1. A steel pipe, an unbonded treatment layer formed on the inner peripheral surface of the steel pipe, and a concrete portion formed inside the unbonded treatment layer. A deformation absorbing portion is provided at an appropriate position of the steel pipe. In the structure of an unbonded filled steel pipe concrete column, the concrete part is divided into a plurality of concrete column parts by forming a plurality of annular notches at appropriate intervals in the length direction of each concrete column part. On the outside, the steel pipe is separated by an unbonded layer from the upper and lower ends of the steel pipe to the ends of other steel pipes above or below to form a deformation absorbing portion between the ends of the upper and lower steel pipes. While being provided, at the upper end and the lower end of each steel pipe, an inward flange-shaped bearing plate is formed by being inserted into the notch,
The structure of an unbonded type filled steel pipe concrete column, wherein reinforcing concrete bars extending over the upper and lower concrete column parts are embedded in the concrete part inside the cutout part.