JPH054220A - Method of forming through holes in precast concrete members - Google Patents

Abstract

(57) [Summary] [Purpose] Through holes can be easily formed in advance in a precast concrete member that has been cured to a specified shape.
In addition, a method of forming a through hole in which the yield strength of a concrete member is not reduced is provided. [Structure] A through hole forming driving mold 3 formed by winding a mesh 2 around an outer circumference of a through hole forming frame member 1 is set at a position where a through hole E is formed, and the surrounding concrete D is poured. After curing to have sufficient strength, only the mold member 1 is removed. [Effect] Since the adhesion area between the through-hole forming mold member and the cast concrete is small, the adhesive force between them is also small, and only the mold member can be easily removed. Further, since the inner peripheral surface of the through hole is a rough surface composed of a mesh and concrete, the integrity of the grout mortar and the precast concrete member filled in the through hole is improved and sufficient proof stress is exhibited. It

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a through hole in a precast concrete member, in which a through hole is previously formed in a concrete member which has been hardened into a predetermined shape.

[0002]

2. Description of the Related Art For example, when a component of a concrete column is manufactured by precasting, a through hole (sheath hole) for penetrating a main bar must be formed in the precast concrete member in advance. There are various conventional methods for forming the sheath hole, and a typical method thereof is to use a thin steel sheath tube (corrugated tube) in the sheath hole forming portion as shown in FIG. In this forming method, for example, first, as shown in FIG. 4a, the corrugated pipe A is set at an interval where the through holes are to be formed, and necessary bar arrangements B such as hoop lines are formed on the corrugated pipe A. Concrete D is placed around these corrugated pipes A set in C while performing vibration compaction, and when the placed concrete D develops the required strength, only the outer formwork is removed as shown in FIG. It is a thing. In this forming method, the corrugated tube A remains around the sheath hole E.

As a special forming method, as shown in FIG. 5, a precast concrete member having a ring-shaped cross section is formed by a centrifugal forming method, and immediately after the centrifugal forming, a steel pipe or the like set in the sheath hole E forming portion. There is also one in which the driving mold F for forming the through hole is removed and the sheath hole E is formed in the extraction trace. In this forming method, the mold does not remain in the sheath hole E, and the sheath hole E itself is formed of concrete D.

After the main reinforcement is penetrated into the thus formed sheath hole, the gap between the main reinforcement and the sheath hole is filled with grout mortar to close the gap and fix both.

[0005]

However, in the former method of forming through-holes in a conventional precast concrete member, the former case is one in which the cured concrete is completely hardened by breathing, sinking and drying shrinkage of the concrete (hereinafter Since peeling occurs at the interface between the precast concrete) and the corrugated pipe, the integrity of the precast concrete and the corrugated pipe is impaired. In addition, in the precast concrete member manufactured by this method, since the adhesion between the corrugated pipe made of steel pipe and the precast concrete is extremely low, when bending stress acts on the concrete column, it is transmitted from the main bar to the grout mortar. The shearing force is hardly transmitted to the precast concrete on the outer periphery of the corrugated pipe as a whole, and a local stress concentration is caused to easily cause a splitting fracture along the main reinforcing bar. Therefore, there is a problem in that the yield strength is reduced at an early stage due to the structure, and a predetermined yield strength cannot be obtained as the pillar member.

On the other hand, in the latter method of forming the through holes of the conventional precast concrete member, the steel pipe of the driving mold for forming the through holes is removed, so that the above problems do not occur. . However, it is necessary to manufacture the precast concrete member by a special method such as the centrifugal molding method, which requires special equipment for the precast concrete member, resulting in lack of generality and high cost.

Therefore, it is conceivable that concrete is placed by the conventional vibration compaction method, and then the corrugated pipe is removed as a driving form. However, with this method, it is difficult to control the strength of the poured concrete when removing the corrugated pipe, and if the timing of the removal is too early and the strength of the poured concrete is too low, the concrete of the concrete will be removed along with the removal of the corrugated pipe. The sheath hole cannot be formed due to falling off. Further, if the removal timing is too late and the adhesive force between the corrugated pipe and the poured concrete becomes too high, it becomes difficult to remove the corrugated pipe.

The present invention was developed in order to solve these various problems. The former problem is eliminated by removing the driving mold for forming the through hole, and the driving mold is further removed. It is intended to provide a method of forming a through hole that is easy to remove and does not limit the method of manufacturing the precast concrete member itself.

[0009]

That is, a method for forming a through hole in a precast concrete member according to the present invention is a method for forming a through hole in a precast concrete member, wherein the through hole is formed in advance in a concrete member that has been hardened into a predetermined shape. In which a net-like material is wound around the outer periphery of a through-hole forming mold member having a cross-sectional outer shape corresponding to the inner shape of the through-hole to be formed to form a through-hole forming driving mold, and the driving mold After setting the frame at a predetermined position where a through hole should be formed, concrete is placed around the frame, and the concrete is cured until it has sufficient strength so that it does not lose its shape. It is characterized in that the net-like material is left and only the through-hole forming mold member is removed.

[0010]

In the method of forming a through hole of a precast concrete member according to the present invention, a through hole forming driving form formed by winding a mesh around the outer periphery of the through hole forming form member is placed at the position where the through hole is formed. After setting, concrete is cast around it, so that the cast concrete on the outer peripheral portion of the through hole is blocked by the net-like material and the adhesion area to the through hole forming frame member becomes small. Therefore, even after the casting concrete is hardened until it has sufficient strength to keep its shape, the adhesion between the casting concrete and the through-hole forming frame member is small, and the net-like material remains in the precast concrete. Only the through-hole forming mold member can be easily removed.

Further, since the inner peripheral surface of the through hole of the precast concrete member formed by this forming method is a rough surface composed of a mesh surface and a concrete surface, the inner peripheral surface of the through hole penetrates into the through hole. The adhesion with the grout mortar filled in between becomes extremely high, and the integrity of the mortar and the precast concrete is improved.

[0012]

EXAMPLE FIG. 1 shows an example of a method of forming a through hole in a precast concrete member according to the present invention. In this embodiment, four sheath holes are formed at four corners of a concrete column member having a rectangular cross section. First, as shown in FIG. 1a, as the through-hole forming frame member 1, a steel pipe having a strength that does not bend or break due to the load of the concrete to be placed or the impact at the time of placing the concrete is used. A wire mesh material 2 such as a lath net is wound around this, and a driving form 3 for forming a through hole is formed.
To create.

Next, as shown in FIG. 1b, the through-hole forming driving form 3 is set in the space between the sheath holes, and the bar arrangements 4 such as hoop lines are performed. Next, as shown in FIG. 1c, the driving mold 3 for forming through holes is set in the outer mold 5 of the precast concrete member, and thereafter, the driving mold 3 in the outer mold 5 is set. Concrete D is placed while vibrating and compacting the surroundings.

When the poured concrete D is hardened until it exhibits sufficient strength for demolding, transportation, etc., the outer mold 5 is removed as shown in FIG. 1d, and the through hole forming driving mold 3 is further removed. The steel pipe, which is the form member 1 for forming the through holes, is removed so that the net-like material 2 remains in the poured concrete D. In this case, as shown in FIG. 2, since the net-like material 2 is wound around the steel pipe which is the form member 1 for forming the through hole, it does not adhere to the cast concrete D entirely. Therefore, since the adhesion between the poured concrete D and the through hole forming frame member 1 is small, the through hole forming frame member 1 can be easily removed, and the sheath hole E formed after the removal is completed. Since the inner peripheral surface of is supported by the net-like material 2, it does not lose its shape.

FIG. 3 shows another embodiment of the method for forming the through hole of the precast concrete member of the present invention. In this embodiment, a rectangular through hole is formed through the central portion of a square concrete column member to form a thin hollow precast concrete column member. In this case, as shown in the same figure, a mold having a cross-sectional outer shape corresponding to the cross-sectional inner shape of the rectangular through hole is used as the through hole forming mold member 1, and the wire mesh product 2 is wound around it. Concrete D is cast around the through-hole forming driving mold 3 while performing vibration compaction, and the through-hole forming mold member 1 is set after the poured concrete D is hardened to a strength that does not collapse. It has been removed.

In each of the above examples, the concrete pouring is performed by the vibration compaction method, but the concrete pouring method is not limited to these. Of course, the shape of the precast concrete member and the shape of the through hole are not limited to the above, and in particular, when the internal shape of the through hole is different from the above, a form member having a cross sectional outer shape corresponding thereto may be used. The internal shape of the through hole referred to herein means the shape of all the inner peripheral surfaces of the horizontal and vertical cross sections of the through hole, and the cross-sectional outer shape of the form member means all of the horizontal and vertical cross sections of the form member. The shape of the outer peripheral surface is shown, and the fact that the cross-sectional outer shape corresponds to the cross-sectional inner shape means that their dimensions and shape are exactly the same.

[0017]

As described above, in the method of forming a through hole of a precast concrete member according to the present invention, a through hole forming driving die formed by winding a mesh around the outer periphery of the through hole forming frame member. After setting the frame at the formation position of the through hole,
Since the concrete is cast around it, the adhesive force between the cast concrete and the through-hole forming frame member is small even after the cast concrete is hardened until it has sufficient strength so that it does not lose its shape. It is possible to easily remove only the through hole forming mold member while leaving the net-like material.

Further, in the through hole of the precast concrete member formed by this forming method, even if the breathing, sedimentation and drying shrinkage of the concrete occur, the cross-sectional shape of the through hole is changed by that much, and the conventional corrugated pipe is used. There is no peeling of the corrugated pipe and no gap between the corrugated pipe and the precast concrete as in the case of use.

Furthermore, since the inner peripheral surface of the through hole of the precast concrete member formed by this forming method is a rough surface composed of the mesh surface and the concrete surface, the main reinforcing bar penetrated into the through hole is formed. The adhesiveness with the grout mortar filled in between becomes extremely high, and the integrity with the precast concrete member is improved. As mentioned above,
In the precast concrete member formed by the forming method of the present invention, the shearing force is distributed throughout the precast concrete around the main bar portion, and structural defects are less likely to occur.
Therefore, the structural strength can be as high as that of integrated driving,
Various problems in proof strength are eliminated.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a method of forming a through hole of a precast concrete member of the present invention.

FIG. 2 is a detailed cross-sectional view showing a state around a through hole in the forming method of FIG.

FIG. 3 is an explanatory view showing another embodiment of the method for forming the through hole of the precast concrete member of the present invention.

FIG. 4 is an explanatory view showing an example of a conventional method for forming a through hole in a precast concrete member.

FIG. 5 is an explanatory view showing another example of a method of forming a through hole of a conventional precast concrete member.

[Explanation of symbols]

 1 is a form member for forming a through hole 2 is a mesh 3 is a driving form for forming a through hole D is a cast concrete E is a through hole

Claims (1)

Claim: What is claimed is: 1. A method of forming a through hole of a precast concrete member, wherein a through hole is formed in advance in a concrete member that has been hardened to a predetermined shape. A net-like material is wound around the outer periphery of a through-hole forming mold member having a cross-sectional outer shape to form a through-hole forming driving mold, and the driving mold is set at a predetermined position where the through-hole should be formed. After that, concrete is poured around it, and after the poured concrete is hardened until it has a sufficient strength so that it does not lose its shape, the net-like material is left in the cast concrete to form the through hole forming frame member. A method for forming a through hole in a precast concrete member, characterized in that only the material is removed.