JPH09310448A - Concrete structure and work execution method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase tensile strength, bending strength, and shearing strength of a concrete structure by burying main reinforcements without restriction, and arranging steel fiber in the structure uniformly and dispersedly. SOLUTION: A plurality of main reinforcements are standingly provided on fixed positions of a base made of concrete without restriction. A formwork is assembled outside the main reinforcements 2, and concrete 6 mixed with a fixed quantity of steel fiber 5 of carbon steel, stainless steel, or the like is placed inside the formwork. After hardening of the concrete 6, the steel fiber 5 is arranged extending over the whole sectional territory of the pillar 7 of a concrete structure, uniformly and at random. Consequently, customary belt reinforcement restricting the main reinforcements is eliminated, customary steel fiber reinforced concrete is improved, and hence the tensile strength, the bending strength, and the shearing strength of the concrete structure can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves steel fiber reinforced concrete, dramatically improves the bending strength and toughness of a structure, abolishes band reinforcing bars, and eliminates the complexity of bar arrangement work. The present invention relates to a concrete structure capable of speeding up the work, reducing the construction cost, and obtaining a dense and smooth concrete surface, and a construction method thereof.

[0002]

2. Description of the Related Art Conventionally, in the case of constructing a concrete structure, a main reinforcing bar is assembled, band reinforcing bars are arranged at a predetermined pitch for the purpose of reinforcing shearing force, and a mold is assembled on the outside of the main reinforcing bar. It was pouring concrete on. In this case, with respect to the amount and arrangement of the strip reinforcing bars, generally, the shear strength is larger than the bending strength, so that the concrete structure is in the failure mode of bending failure precedent type, and the tensile strength of the main reinforcing bars is strengthened. Depending on the tensile toughness,
It is designed to maintain the load bearing capacity even after reaching the yield load.

However, this conventional method for constructing a concrete structure requires a band reinforcing bar and its reinforcement, and requires the production of the band reinforcing bar and the tight binding with a wire or a clip, which makes the work complicated and troublesome. Moreover, the concrete structure constructed in this way may be damaged by the shearing of the reinforcing bars depending on the location conditions, the amount of reinforcing bars, and the construction.This point is related to the previous Great Hanshin-Awaji Earthquake. Is illustrated in.

Therefore, as a means for strengthening the shearing force of a concrete structure, it is conceivable to increase the amount of reinforcing bars and weld all the intersections with the main reinforcing bars. But,
In this case, the work of arranging the strips is extremely complicated and time-consuming, resulting in a high construction cost and a long construction period. Is likely to occur.

By the way, conventionally, in roads, runways, tunnels, etc., in order to improve the tensile strength, bending strength, crack strength, toughness or impact resistance of concrete, short steel fibers such as carbon steel and stainless steel are used. Steel fiber reinforced concrete is used in which are evenly distributed.

However, this conventional steel fiber reinforced concrete is mainly for the purpose of improving cracks, and its strength is low depending solely on the strength of the steel fiber. It cannot be immediately applied to pillars, beams and walls.

[0007]

The present invention solves such problems, improves steel fiber reinforced concrete, dramatically improves the bending strength and toughness of a structure, and abolishes strip reinforcing bars. An object of the present invention is to provide a concrete structure which can eliminate the complexity of arranging work, speed up the construction and reduce the construction cost, and can obtain a dense and smooth concrete surface, and a construction method thereof.

[0008]

Therefore, according to the invention of claim 1, in a concrete structure in which main reinforcing bars are arranged, the main reinforcing bars are buried without restraint, and the steel fibers are uniformly distributed inside the structure. In order to provide a practical seismic resistant structure, the steel fiber reinforced concrete is improved and the bending strength and toughness rate of the structure are dramatically improved while the steel bars are abandoned. According to the invention of Item 2, in a construction method of a concrete structure in which a main reinforcing bar is arranged inside, a mold is assembled outside the reinforcing bar, and concrete is placed inside the mold, the main reinforcing bar is unconstrainedly assembled. At the same time, concrete containing a prescribed amount of steel fibers is placed in the formwork, the strip bar that has been frequently used in the past is abolished, and the complexity of the bar arrangement work is eliminated, speeding up the construction and reducing the construction cost. For precise and smooth concrete I'm trying to get a better look.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a description will be given of an illustrated embodiment in which the present invention is applied to a pillar of a building such as a building or a condominium which is a concrete structure. In FIGS. 1 to 6, 1 is a concrete base. On a table, a plurality of main reinforcing bars 2 are erected on predetermined positions in a predetermined position in an unrestrained state, that is, without reinforcing the conventional reinforcing bars 2 by the conventional band reinforcing bars. In this case, the material, size, arrangement, quantity and the like of the main rebar 2 are determined based on the architectural design standard in consideration of the maximum load acting on the column and the safety factor. Note that, as shown in FIG. 2, the reinforcing bars 3 may be arranged on the main reinforcing bars 2 at a coarse pitch and may be restrained as appropriate.

A mold 4 is assembled on the outside of the main rebar 2 on the base 1, and concrete 6 containing a predetermined amount of steel fibers 5 is placed inside the frame 4. The steel fiber 5 is formed by cutting carbon steel or stainless steel having a diameter of 0.6 mm into a length of 30 mm (aspect ratio 50), and forming the surface thereof in a sawtooth shape or a wavy shape, and the mixing ratio thereof is the total It is set to about 1.0% of the installed concrete volume.

The state after hardening of the concrete 6 is as shown in FIG. 4, in which the steel fibers 5 are arranged in a uniform and random direction over the entire cross section of the pillar 7 which is a concrete structure.

The pillar 7 thus constructed is constructed at the time of constructing a building such as a building or a condominium. First, concrete is placed on the constructed land to form the base 1, and at the same time, a plurality of bases 1 are formed. The main rebars 2 are arranged at predetermined intervals and assembled. When constructing beams and walls other than columns, the main rebars 2 are arranged at predetermined intervals in the length direction of the beams and assembled.

In this case, if necessary, a small amount of the band reinforcing bar 3 may be used to restrain the predetermined position of the main reinforcing bar 2, and by doing so, the main reinforcing bar 2 is shaken and the occupied space is expanded. It is possible to prevent the above-mentioned phenomenon and to make the strip reinforcing bar 3 bear the shearing force acting on the column 7 to enhance the shearing strength thereof. As described above, the present invention is a band reinforcing bar 3 which has been widely used in the past.
Is eliminated, and the production of the band reinforcing bar 3 and its complicated bar arrangement work are eliminated, and the construction can be speeded up and the construction cost can be reduced.

After assembling the main rebars 2 in this way, the mold 4 is assembled at the outer positions thereof, and the concrete 6 is placed inside the mold 4. A certain amount of steel fiber 5 is mixed in the concrete 6, and the mixing rate is set to about 1.0% of the total pouring concrete volume, and this is put together with the concrete 6 and moved in the form 4 Fill.

In this case, since only a plurality of main rebars 2 are arranged in the form 4, the wraparound and flowability of the concrete 6 are better than those of the main rebar 2 to which a large number of strip rebars 3 are attached. Well, the inside of the mold 4 is filled up precisely and surely. Therefore, the occurrence of junkers is prevented, and the concrete surface is formed smoothly to save the trouble of repairing them.

After the concrete 6 is hardened, the form 4 is removed and the surface thereof is appropriately finished, whereby a series of construction work of the pillar 7 is completed. The cross section of the pillar 7 constructed in this way is as shown in FIG. 4, and the steel fibers 5 are uniformly dispersed and arranged over the entire area of the pillar 7, and the directions thereof are randomly arranged.

Regarding the column 7 thus constructed, in order to examine the shear strength, the applicant made a test piece similar to this and conducted an experiment. In this shear strength test, the specimen was held vertically, a constant axial compressive stress was applied to the upper end of the specimen, and a horizontal load, that is, a shear load was alternately applied to the upper portion of the specimen, and the load was applied to the main rebar 2 The yield load of the column is set to 180 kN or more, and this is gradually increased to an integral multiple of the yield load of the column 7
The relationship between the displacement and the horizontal load was determined. On the other hand, the experiment was terminated when the horizontal load became 80% or less of the yield load or when the compression load could not be maintained.

Therefore, in this experiment, first, when a horizontal load equivalent to the yield load is applied to the specimen, cracks of about 0.1 mm are generated at several places on the surface of the specimen in a direction substantially perpendicular to the axial direction, These are distributed obliquely in the upper and lower positions of the test piece, and as the horizontal load increases, they gradually grow in the shearing direction, that is, approximately 45 ° with the axial direction of the test piece, widening the crack width, Gradually progress inside the specimen.

In this case, even if the cracks communicate with each other, the main rebar 2 and the steel fiber 5 retain the load while the main rebar 2 and the steel fiber 5 are soundly interposed, and thereafter the main rebar 2 has its own bending resistance. At the point of breakage, the specimen bends and breaks along the cutting plane perpendicular to its axial direction. The horizontal load at this time was about 200 kN. Therefore, the fracture mode in this case is a bending fracture precedent type, and the main reinforcing bar 2 and the steel fibers 5 absorb and sustain the shearing energy until this fracture, and suppress the rate of fracture.

FIG. 5 shows the results of the above experiment. After the yield of the main rebar 2, the displacement increases despite the load not increasing so much, so that the energy absorption capacity is large and its toughness and toughness ratio (load -The size of the area enclosed by the displacement curve and the horizontal axis is large. From the experimental results, it was found that 10 times the yield displacement of the main reinforcing bar 2 was below 80% of the yield horizontal load, and a toughness rate of about 10 could be expected.

Next, a test piece without the main rebar 2 was prepared, and a similar experiment was conducted. The toughness was zero and the horizontal load at the time of fracture was about 100 kN. Therefore, the concrete structure in which only the steel fibers 5 are arranged has less toughness than that of the structure in which the main reinforcing bars 2 are arranged, and corresponds to a substantially brittle member, and the bending strength is about 1/6 of the latter. Met. It is considered that this is because the connection between the steel fiber 5 and the concrete 6 lacks continuity and directionality, and as a result forms a mosaic-shaped combined body.

Further, when a similar experiment was conducted on plain concrete, the results shown in FIG. 6 were obtained. In this experiment,
After the main rebar 2 reached the yield displacement, diagonal cracks presumably due to shearing force occurred in the specimen at an early stage, which grew and the horizontal load was rapidly lost.

As described above, in the structure of the present invention in which the main rebars 2 are arranged in the steel fibers 5, the toughness rate is remarkably improved as compared with the concrete structure in which only the steel fibers 5 are arranged, and the fracture mode thereof. Since is a bending fracture type, it has significantly improved seismic strength and is suitable for columns, walls, floors, piers, etc. of buildings subject to shear load.

Therefore, if, for example, a large earthquake occurs after the pillar 7 is constructed and the pillar 7 is subjected to a shearing force in the horizontal direction,
The main rebars 2 and the steel fibers 5 resist shearing force and bending, prevent cracks in the columns 7, promote dispersion of the cracks, and suppress deformation and destruction of the columns 7.

Further, the toughness of the column 7 is improved by mixing the steel fiber 5, and the shock or shear load due to the earthquake is absorbed,
The deformation and the breaking speed of the pillar 7 are suppressed. Then, when the shock and amplitude of the earthquake gradually increase, cracks start to be dispersed and start to grow, and the opening width increases, and finally the main rebar 2 yields and bends. In this case, cracks grow and grow. The steel fiber 5 and the main rebar 2 endure the shock and vibration of the earthquake until the pillar 7 bends and breaks,
When the main rebar 2 yields and breaks, the column 7 bends and breaks. In addition, since the tensile stress is transmitted by the steel fiber 5 on the cracked surface, the shear strength of the concrete 6 itself is improved, promoting the fracture mode of bending fracture precedent type and enhancing the seismic strength.

As described above, according to the present invention, in the concrete structure subjected to the shearing force, the strip rebar which has been frequently used conventionally is abolished, so that the material cost of the rebar and the construction cost can be reduced, and the strip rebar can be manufactured. And the complicated work and labor of the bar arrangement work can be eliminated, and this can be done quickly, the construction period can be shortened and the construction cost can be reduced, and the concrete can be densely and surely placed.

Further, according to the present invention, steel fibers 5 are dispersed and arranged in concrete 6 instead of the strip reinforcing bars, and the fibers 5 and the main reinforcing bars 2 are
Since the shearing force and the bending acting on the structure are resisted by the above, the toughness and bending strength of the structure are dramatically improved, and a concrete structure having sufficient seismic strength can be obtained. Moreover, by arranging the steel fibers 5 and the main reinforcing bars 2, the strength of the conventional steel fiber reinforced concrete, particularly the toughness rate, is dramatically improved, and a practical earthquake-resistant concrete structure can be provided.

[0028]

As described above, according to the first aspect of the present invention, since the main rebars are embedded without restraint and the steel fibers are uniformly distributed inside the structure, the conventional strip rebars for restraining the main rebars are provided. While abolishing, the conventional steel fiber reinforced concrete was improved and the tensile strength, bending strength and shear strength of the concrete structure were strengthened to provide a practical seismic resistant structure, and the toughness rate was dramatically improved. As a result, it is possible to promote the pre-bending fracture type fracture mode and improve the earthquake resistance. In particular, by embedding the main rebar in concrete, the bending strength and toughness are dramatically improved as compared with the conventional steel fiber reinforced concrete, and a highly reliable seismic resistant structure can be provided. According to the invention of claim 2, since the main rebar is assembled without restraint and the concrete containing a predetermined amount of steel fibers is placed in the formwork, the use of the strip rebar, which has been widely used in the past, is eliminated, and the rebar is arranged. The complicated work can be eliminated, the construction can be speeded up and the construction cost can be reduced, and a dense and smooth concrete surface can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view sequentially showing a construction method according to the present invention.

FIG. 2 is a perspective view showing another embodiment of a construction method according to the present invention, showing a state in which main reinforcing bars are restrained by a small number of strip reinforcing bars.

FIG. 3 is a perspective view showing a situation of a structure constructed according to the present invention.

4 is a sectional view taken along the line AA of FIG.

[Fig. 5] In a shear strength test of a column to which the present invention is applied,
FIG. 4 is an experimental view showing a relationship between a load and a displacement.

FIG. 6 is an experimental diagram showing the relationship between load and displacement in a shear strength test of plain concrete.

[Explanation of symbols]

2 Main rebar 5 Steel fiber 6 Concrete 7 Concrete structure (column)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Matsuoka 2-3-5 Misakicho, Chiyoda-ku, Tokyo Iron Building Construction Co., Ltd.

Claims (2)

[Claims] 1. A concrete structure having a main reinforcing bar arranged therein, wherein the main reinforcing bar is embedded without restraint, and steel fibers are uniformly dispersed and arranged inside the structure. 2. A method for constructing a concrete structure, in which a main rebar is arranged inside, a form is assembled outside the rebar, and concrete is placed inside the form, while the main rebar is assembled without restraint. A method for constructing a concrete structure, wherein concrete containing a predetermined amount of steel fibers is placed in the formwork.