JP2002266471A - Crack restraining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack restraining method for surely restraining a crack caused in a corner part of an opening part, capable of sufficiently securing the cover thickness of a wall reinforcement, without impairing filling performance of concrete. SOLUTION: A pipe 6 is arranged outside the opening part 3 of a concrete building frame 1 with its shaft tilted in relation to both edges of the opening part 3 forming the corner part 3a. A tension member 7 is inserted into the pipe 6 with its both end parts projected from the pipe 6. The concrete is placed, one end part 7a of the tension member 7 is fixed in the concrete, and the other end part 7b of the tension member 7 is projected from the concrete. After hardening the concrete, the other end part 7b of the tension member 7 is pulled, and is fixed in this state to restrain the crack.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing cracks at corners of an opening formed in a concrete body, for example.

[0002]

2. Description of the Related Art Concrete cracks occur when a concrete is subjected to a tensile force greater than its maximum tensile stress after hardening of the concrete. At the corners of the openings provided in concrete buildings, etc., tensile forces are likely to act due to, for example, drying shrinkage after concrete casting, uneven settlement of buildings, earthquakes acting on buildings, and therefore, cracks may occur. It is easier.

As a means for suppressing such cracks, there is a method disclosed in, for example, JP-A-08-246603. This is to provide an L-shaped reinforcing member at the corner of the opening, thereby suppressing deformation around the opening and suppressing cracks.

The most common method is to provide crack preventing bars 100 in the vertical, horizontal and oblique directions as shown in FIG. 3 at the corners of the opening. In this method, the tensile force generated at the corners of the opening is borne by the crack preventing streaks 100 to suppress cracks. In addition, in FIG. 3, the code | symbol 1 shows the outer wall of a concrete skeleton. The outer wall 1 is connected to columns 2, beams (not shown) and slabs. The outer wall 1 is provided with a rectangular opening 3. Reference numeral 3a denotes the opening 3
Are shown. The outer wall 1 is provided with a wall reinforcement 4 as a structure, and the wall reinforcement 4 is divided into a vertical reinforcement 4a arranged in a vertical direction and a horizontal reinforcement 4b arranged in a horizontal direction. ing. The vertical streak 4a and the horizontal streak 4b are tied by a binding wire 5 at a predetermined location.

[0005] Here, FIG.
This shows the state of cracks in the corners of the opening after a month. The cracks in the upper and lower corners on the left side of the opening indicate the state of cracking when cracks were not suppressed, and the cracks in the upper and lower right corners of the opening were provided with the crack prevention bars 100 shown in FIG. 5 shows a state of cracking when cracking is suppressed by the method described above. In FIG. 4, reference numeral 1 denotes an outer wall of the concrete body. The outer wall 1 is provided with a rectangular opening 3. Reference numeral 3a indicates a corner of the opening 3.

[0006]

However, Japanese Patent Application Laid-Open No.
In the method disclosed in Japanese Patent No. 246603 and the method of arranging the crack preventing bars 100, cracks generated at the corners of the opening can be suppressed to some extent, but it has been a problem that the cracks cannot be reliably suppressed.

In particular, in the method of arranging the crack preventing bars 100, it is hard to say that cracks occurring at the corners of the opening are suppressed as apparent from FIG. Further, in the method of arranging the crack preventing bars 100, the crack preventing bars 100 must be arranged in addition to the wall bars as a structure. Therefore, particularly for walls with small wall thickness, the covering thickness of the wall reinforcement cannot be sufficiently ensured, or the dense concrete reinforcement deteriorates the concrete filling property, and the concrete filling called so-called junka is incomplete. It has been a problem that some parts are generated and the construction quality is degraded. An object of the present invention is to provide a method for suppressing cracks, which reliably suppresses cracks occurring at the corners of an opening, and furthermore, can sufficiently secure a cover thickness of a wall streak and does not hinder the filling property of concrete. is there.

[0008]

Means for Solving the Problems In order to solve the above problems, the invention described in claim 1 is, for example, as shown in FIG.
A method for suppressing cracks at corners 3a of an opening 3 formed in a concrete skeleton 1 (for example, an outer wall), wherein a pipe 6 (for example, , A sheath tube) such that its axis is inclined with respect to both edges of the opening 3 forming the corner 3a, and a tension member 7 (for example, P
C steel rod) is inserted so that both ends thereof protrude from the pipe 6, and then concrete is poured into a portion where a concrete skeleton is to be constructed, whereby one end 7a of the tensile member 7 is formed. (E.g., the lower end) is fixed in the concrete, and the other end 7b (e.g., the upper end) of the tension member 7 is made to protrude from the concrete. The other end 7b
And is fixed in this state.

According to the first aspect of the present invention, one end of the tension member and a predetermined portion of the pipe are buried in the concrete by casting concrete. Therefore, when the concrete hardens, one end of the tensile member and a predetermined portion of the pipe are fixed to the concrete. Further, the other end of the tension member protrudes from the concrete. Therefore, after the concrete is hardened, by pulling the other end of the tensile member, concrete between the other end and the one end, that is, the concrete around the pipe in a portion where the pipe is buried is added to the concrete. A compressive force acts along the tube. Thereby, even after a concrete hardening, even when a tensile force is generated in the direction along the pipe at the corner of the opening due to the drying shrinkage, the differential settlement, the earthquake, etc., in the concrete around the pipe, The tensile force is offset by the compressive force. Therefore, after the concrete is hardened, it is possible to prevent a tensile force from acting on the concrete around the pipe, and it is possible to suppress cracks at the corners of the opening formed in the concrete skeleton.

According to the first aspect of the present invention, only the tension member and a pipe for inserting the tension member are provided at the corner of the opening in addition to the reinforcing bar as a structure. It is. Thereby, compared with the conventional method of arranging the anti-cracking bars, the corners of the opening are arranged with more room. Therefore, the covering thickness of the wall reinforcement is sufficiently ensured, and the concrete filling property at the corners of the opening is improved by not providing high-density reinforcement, so that the construction quality can be improved.

Here, as the concrete skeleton,
For example, there are an outer wall and a slab. Further, as the tensile member, there is, for example, a member made of a reinforcing steel or a PC steel. Further, the tube includes, for example, a sheath tube. The sheath tube may be made of metal, paper containing anticorrosive material or polyethylene.

According to a second aspect of the present invention, in the method for suppressing cracks according to the first aspect, a fixing means 8 () is provided at one end 7a of the tensile member 7 for fixing the tensile member 7 in concrete. (E.g., an iron plate).

According to the second aspect of the present invention, since one end of the tension member protruding from the pipe is provided with a fixing means for fixing the tension member in concrete, concrete hardening is performed. Later the tensile material is reliably settled in the concrete. Therefore, when the tension member is pulled after the concrete is hardened, the tension member can be reliably pulled without falling out of the concrete. Thus, a compressive force can be more reliably applied to the concrete in the portion where the pipe is embedded along the pipe. Therefore, after the concrete is hardened, it is possible to more reliably prevent the tensile force from acting on the concrete around the pipe, and it is possible to more reliably suppress cracks at the corners of the opening formed in the concrete skeleton. .

Here, as the fixing means, for example,
At one end of the tensile member protruding from the pipe, there is a method in which an iron plate is welded and fixed while being inserted through the tensile member.

The third aspect of the present invention provides the first or second aspect.
In the crack suppressing method described above, the other end portion 7b of the tension member 7 is held at the other end portion 7b of the tension member 7 after the other end portion 7b of the tension member 7 is stretched. It is characterized in that means 9 (for example, iron plate, screw thread, nut) are provided.

According to the third aspect of the present invention, after the other end of the tension member is pulled, the tension member is held in a stretched state by the holding means. A period of tensile force is provided. Thereby, a compressive force can be applied to the concrete in the portion where the pipe is embedded along the pipe for a long time. Therefore, after the concrete is hardened, it is possible to prevent a tensile force from acting on the concrete around the pipe for a long time, and it is possible to suppress cracks at the corners of the opening formed in the concrete skeleton for a long time.

Here, as one of the holding means, FIG.
As shown in (a), a thread is provided at the other end of the tensile member, and after the concrete is hardened, the other end is inserted into an iron plate while the tensile member is pulled, and the iron plate is supported by concrete. Then, there is a method in which the iron plate is used as a stopper and the other end is fixed with a nut. As another method, as shown in FIG. 2 (b), a hole is provided in the other end of the tensile member in a direction horizontal or in the same direction as the axial direction, and after the concrete is hardened, the tension member is pulled. There is a method in which an end is inserted into an iron plate and the iron plate is supported by concrete, and a wedge member is inserted into the hole using the iron plate as a stopper. Further, as another method, after hardening the concrete, grout is injected between a tension member in a stretched state and a pipe through which the tension member is inserted, and the grout material is cured, and the tension member, the tension member, There is a method in which the tension member is maintained in a stretched state by fixing a tube to the grout material.

According to a fourth aspect of the present invention, in the crack suppressing method according to any one of the first to third aspects, a PC steel material (for example, a PC steel rod) is used as the tensile member.

According to the fourth aspect of the present invention, a PC steel material is used as the tensile member. The PC steel material is obtained by rolling, heat-treating, drawing, and the like on a normal steel material, and has a greater axial rigidity and is less likely to be deformed than a normal steel material. Therefore, the stress relaxation phenomenon in which the tensile force gradually decreases as the tensile state of the tensile material continues for a long time is extremely small. This makes it possible to reliably apply a predetermined tensile force to the tensile member for a long period of time, so that a compressive force can be reliably applied to the concrete in the portion where the pipe is embedded along the pipe for a long time. Can be. Therefore, after the concrete is hardened, it is possible to reliably prevent a tensile force from acting on the concrete around the pipe for a long period of time, and it is possible to reliably suppress cracks at the corners of the opening formed in the concrete skeleton for a long period of time.

Here, the PC steel material includes, for example, PC
There is a steel rod or a PC steel stranded wire formed by combining a plurality of PC steel wires. Of the PC steel materials, those having a diameter of 9 to 33 mm are generally called PC steel bars, and those having a diameter of 2 to 8 mm are generally called PC steel wires. The stress relaxation phenomenon is also called relaxation.

According to a fifth aspect of the present invention, in the crack suppressing method according to any one of the first to fourth aspects, the tensile force applied to the tensile member 7 is set to a predetermined tensile force depending on the situation. Features.

According to the fifth aspect of the present invention, the tensile force generated by the deformation of the tensile member is freely set by adjusting the deformation according to the situation. That is, in a place where a large tensile force is likely to be generated due to the drying shrinkage, the differential settlement, the earthquake or the like, a place where a large tensile force is applied to the tensile material and a relatively small tensile force is considered to be generated. In the above, the magnitude of the tensile force can be freely set according to the situation, such that a small tensile force is applied to the tensile member. As a result, the concrete where the pipe is buried is
It is possible to freely apply a compressive force according to the situation such that a tensile force is not applied after the concrete is hardened. Therefore, after the concrete is hardened, it is possible to more reliably prevent the tensile force from acting on the concrete around the pipe, and it is possible to more reliably suppress the cracks at the corners of the opening formed in the concrete skeleton. .

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for suppressing cracks according to the present invention will be described in detail. First, the configuration of the means for realizing the crack suppression method of the present invention will be described.

In FIG. 1, reference numeral 1 denotes an outer wall (concrete skeleton) of a concrete skeleton. The outer wall 1
The column 2 is connected to a beam and a slab (not shown). The outer wall 1 is provided with a rectangular opening 3. The outer wall 1 is provided with a wall reinforcement 4 as a structure, and the wall reinforcement 4 is divided into a vertical reinforcement 4a arranged in a vertical direction and a horizontal reinforcement 4b arranged in a horizontal direction. ing. The vertical streak 4a is located closer to the outer surface of the outer wall 1 than the horizontal streak 4b, and the vertical streak 4a and the horizontal streak 4b
It is tied by a binding wire 5 at a predetermined location. Further, the wall reinforcement 4 has a double reinforcement arrangement in which a vertical reinforcement 4a and a horizontal reinforcement 4b are disposed on both sides of the outer wall 1, respectively.

On the outer wall 1, a sheath tube 6 (tube) passes near the corner 3a of the opening 3, and the axis of the sheath tube 6 defines the opening 3 forming the corner 3a. It is provided so as to be inclined with respect to both edges. The sheath tube 6 includes:
It is inserted between the double-arranged wall muscles 4 and is tied to the wall muscle 4 by a binding wire 5. A PC steel rod 7 (tensile material, PC steel) is inserted into the sheath pipe 6, and the PC steel rod 7 protrudes from both ends of the sheath pipe 6 by a predetermined length. A rectangular iron plate 8 having a predetermined thickness is provided at the lower end 7a (one end) of the PC steel bar 7.
The (fixing means) is inserted through the PC steel bar 7, and is fixed by welding the PC steel bar 7 and the iron plate 8 at the insertion portion. A rectangular iron plate 9 (9a) (holding means) is inserted through the PC steel bar 7 at the upper end 7b (the other end) of the PC steel bar 7, and further, the iron plate 9 (9a ) Are supported by the upper end of the outer wall 1.
The upper end portion 7b is provided with a thread 9 (9b) (holding means), and the PC steel bar 7 is fixed by a nut 9 (9c) (holding means) using the iron plate 9 (9a) as a stopper. I have.

Next, a construction method for realizing the crack suppression method of the present invention will be described. First, the vertical streak 4a and the horizontal streak 4b, which are the wall streaks 4, are arranged while being tightly bound to each other at a predetermined position by a binding wire 5. At this time, as shown in FIG. 1A, the vertical streak 4a is positioned closer to the outer surface of the outer wall 1 than the horizontal streak 4b. Further, a double bar arrangement is provided in which a vertical bar 4a and a horizontal bar 4b are arranged on both sides of the outer wall 1, respectively. By using the double bar arrangement, a sheath tube 6, a PC steel bar 7, and the like, which will be described later, can be inserted between the wall bars 4, so that the sheath tube 6, the PC steel bar 7, and the like can be more easily attached. It can be provided inside the outer wall 1. At this time, the vertical streak 4
a and the horizontal streak 4b are cut at predetermined locations so that a rectangular opening 3 is formed.

Next, a sheath tube 6 having a predetermined length is inserted between the double-arranged wall rebars 4, and the sheath tube 6 is tied to the wall rein 4 by a binding wire 5. At this time, the sheath tube 6 passes near the corner 3a of the opening 3 and the axis of the sheath tube 6 is inclined with respect to both edges of the opening 3 forming the corner 3a. To The upper end of the sheath tube 6 is located above the upper surface 1a of the concrete casting portion.

Next, a PC steel rod 7 is inserted into the sheath pipe 6 so that both ends of the PC steel rod 7 project from the sheath pipe 6 by a predetermined length. At this time, since the upper end of the sheath pipe 7 is located above the upper surface 1a of the concrete casting portion, the upper end portion 7b of the PC steel bar 7 is also located above the upper surface 1a of the concrete casting portion. Will be. Next, the lower end portion 7a of the PC steel bar 7 is inserted into the iron plate 8 provided with holes in advance, and the PC steel bar 7 and the iron plate 8 are welded and fixed at the insertion portion.

Next, a mold (not shown) is provided from both sides of the reinforcing bar 4. The molds on both sides are kept at a predetermined interval from each other by a separator (not shown) provided at a predetermined location. Further, a mold is also provided on the upper surface, the lower surface, the side surface, and the like of the opening 3 to be formed. No formwork is provided on the upper surface 1a of the concrete casting part. Next, concrete is cast to the upper surface 1a. At the time of concrete casting, a concrete casting pipe (not shown) is appropriately moved and compacted sufficiently by a vibrator (not shown). This prevents formation of a part called incompletely filled concrete called "junka" after concrete placement. After placing the concrete, the concrete is cured for a predetermined period to harden the concrete.

Next, an iron plate 9 (9a) having a predetermined thickness
Then, the upper end 7b of the PC steel rod 7 is connected to the iron plate 9 (9a).
After passing through the hole provided at the center of the
The nut 9 (9c) is turned on the lower end 7b of the PC steel bar 7 provided with (9b). And the iron plate 9
(9a) is stably brought into contact with the upper surface 1a, and the upper end 7 of the PC steel bar 7 is
b is gripped and pulled upward. This tensile machine has a function of measuring the tensile force acting on the PC steel 7. Then, in a state where a predetermined tensile force is applied to the PC steel bar 7, the nut 9 (9c) is tightened using the iron plate 9 (9a) as a stopper.

As described above, after the concrete is hardened, the cracks at the corners 3a of the opening 3 formed in the outer wall 1 due to the drying shrinkage, the uneven settlement, the earthquake, and the like can be suppressed.

According to the present embodiment, the following effects can be obtained. After the concrete is hardened, the concrete between the upper end 7b and the lower end 7a of the PC steel bar 7, that is, the portion where the sheath pipe 6 is embedded, is pulled by pulling the upper end 7b of the PC steel bar 7. A compressive force acts on the concrete around the sheath tube 6 along the sheath tube 6. Thereby, even if a tensile force is generated in the direction along the sheath pipe 6 around the opening 3 due to the drying shrinkage, the differential settlement, the earthquake, etc. after the concrete is hardened,
The tensile force is not applied to the concrete around the sheath tube 6, that is, the corner 3 of the opening 3 formed in the outer wall 1.
a can be suppressed.

Further, since the corners 3a of the opening 3 are loosely arranged, the cover thickness of the reinforcing bar is sufficiently ensured, and the corners 3a of the opening 3 are not formed by high-density reinforcement. In this case, the filling property of the concrete is improved, and the construction quality can be improved.

An iron plate 8 for securely fixing the PC steel bar 7 in concrete is welded and fixed to the lower end 7a of the PC steel bar 7, so that the PC steel bar 7 is hardened after concrete hardening. When the PC steel bar 7 is pulled, the PC steel bar 7 can be reliably pulled without falling out of the concrete.
Thereby, a compressive force can be more reliably applied to the concrete in the portion where the sheath tube 6 is embedded along the sheath tube 6. Therefore, after the concrete is hardened, the tensile force is not more reliably applied to the concrete around the sheath tube 6, that is, it is possible to more reliably suppress the cracks in the corners 3 a of the opening 3 formed in the outer wall 1. .

After the upper end 7b of the PC steel bar 7 is pulled, the PC steel bar 7 is pulled by the iron plate 9 (9a), the thread 9 (9b), and the nut 9 (9c). Is maintained, the PC steel rod 7 is given a tensile force for a long period of time. This allows a long-term compressive force to act on the concrete in the portion where the sheath tube 6 is embedded along the sheath tube 6, so that after concrete hardening, the concrete around the sheath tube 6 is pulled for a long period of time. No force is applied, that is, cracks at the corners 3a of the openings 3 formed in the outer wall 1 can be suppressed for a long time.

Since the stress relaxation phenomenon in which the tensile force gradually decreases as the tension is continued for a long time is extremely small, the PC steel rod 7 can be given a predetermined tensile force to the PC steel rod 7 for a long time. Can be given to. Accordingly, a compressive force can be reliably applied to the concrete in the portion where the sheath tube 6 is embedded along the sheath tube 6 for a long period of time. It is possible to reliably prevent a tensile force from being applied for a period, that is, to reliably suppress cracks in the corner 3a of the opening 3 formed in the outer wall 1 for a long period of time.

Since the tensile force applied to the PC steel bar 7 can be freely set according to the situation, the tensile force is not applied to the concrete in which the sheath pipe 6 is buried after the concrete is hardened. The compression force according to the situation can be freely applied. Therefore, after the concrete is hardened, it is possible to more reliably prevent a tensile force from acting on the concrete around the sheath tube 6, that is, it is possible to more reliably suppress cracks at the corners 3 a of the opening 3 formed in the outer wall 1. Become.

In the present embodiment, the wall reinforcement 4 as a structure is double-arranged. However, even in the case of so-called single reinforcement or staggered reinforcement, the sheath tube 6 or the tension member is used. 7 can be easily tied to the wall muscle 4 by the binding wire 5.

Further, in the present embodiment, in order to hold the tensioned state of the PC steel rod 7, the method uses the nut 9 (9c) shown in FIG. 2 (a). Without limitation, for example, as shown in FIG. 2 (b), a hole 9 (9d) is provided in the upper end 7b of the PC steel rod 7 in the same direction as the axial direction or in the same direction. The upper end 7b in the folded state is attached to the iron plate 9 (9
a), the iron plate 9 (9a) is supported by concrete, and the wedge member 9 (9e) is inserted into the hole 9 (9d) using the iron plate 9 (9a) as a stopper.

[0040]

According to the first aspect of the present invention, after the concrete is hardened, the other end of the tensile member is pulled, whereby the concrete between the tension point and the one end of the tensile member, that is, concrete, A compressive force acts along the pipe on the concrete around the pipe where the pipe is embedded.
Thereby, after concrete hardening, even when a tensile force is generated in the direction along the pipe at the corner of the opening due to the drying shrinkage, the differential settlement, the earthquake, etc.
It is possible to prevent a tensile force from acting on the concrete around the pipe, that is, to suppress cracks at the corners of the openings formed in the concrete skeleton. Also, since the corners of the opening are arranged with room, the cover thickness of the reinforcing bar is sufficiently ensured, and since it does not become high-density reinforcing, the filling property of the concrete at the corner of the opening is improved, The construction quality can be improved.

According to the second aspect of the invention, the same effects as those of the first aspect can be obtained, and the one end of the tension member protruding from the pipe is securely connected with the tension member. Since the fixing means for fixing the tension member in the concrete is provided, when the tension member is pulled after the concrete is hardened, the tension member can be reliably pulled without falling out of the concrete. Thus, a compressive force can be more reliably applied to the concrete in the portion where the pipe is embedded along the pipe. Therefore, after the concrete is hardened, the tensile force is not more reliably applied to the concrete around the pipe, that is, it is possible to more reliably suppress the cracks at the corners of the openings formed in the concrete skeleton.

According to the third aspect of the present invention, the same effects as those of the first or second aspect can be obtained, and after the other end of the tension member is pulled, the holding means is used. Since the tensioned state of the tension member is maintained,
The tensile member is given a tensile force for a long time. This allows
Since a long-term compressive force can be applied to the concrete in which the pipe is buried along the pipe, after the concrete is hardened, no tensile force is applied to the concrete around the pipe for a long period of time. It is possible to suppress cracks at the corners of the opening formed in the substrate for a long time.

According to the invention set forth in claim 4, claims 1 to 5
In addition to providing the same effect as the invention according to any one of (3) and (3), since the tensile material is made of a PC steel material having an extremely small stress relaxation phenomenon, a predetermined tensile force is applied to the tensile material. For a long time. As a result, the concrete where the pipe is buried is
Because it is possible to reliably apply a compressive force along the pipe for a long period of time, after hardening the concrete, the tensile force is not reliably applied to the concrete around the pipe for a long period of time,
Cracks at the corners of the opening formed in the concrete skeleton can be reliably suppressed for a long period of time.

According to the fifth aspect of the present invention, the first to fifth aspects are provided.
4. Needless to say, the same effects as those of the invention described in any one of 4 are obtained, and the tensile force applied to the tensile member can be freely set according to the situation. It is possible to freely apply a compressive force according to the situation such that no tensile force is applied after concrete hardening. Therefore, after the concrete is hardened, the tensile force is not more reliably applied to the concrete around the pipe, that is, it is possible to more reliably suppress the cracks at the corners of the opening formed in the concrete skeleton.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a state in which a method of a method for suppressing cracking of a corner of an opening of the present invention is applied to a corner of a rectangular opening of an outer wall, wherein FIG. () Is a side sectional view.

FIGS. 2A and 2B are diagrams showing an example of a holding means for holding a tensioned state of a PC steel rod, wherein FIG. 2A is a diagram of a method using a nut, and FIG. 2B is a diagram of a method using a wedge material. is there.

FIG. 3 is a view showing a state in which a crack preventing bar is arranged at a corner of a rectangular opening of an outer wall by a conventional method.

FIG. 4 is a diagram showing a state of cracks after concrete hardening when a crack preventing means is not provided at a corner of a rectangular opening of an outer wall and when a crack preventing bar is arranged by a conventional method.

[Explanation of symbols]

 Reference Signs List 1 outer wall (concrete body) 3 opening 6 sheath pipe (pipe) 7 PC steel rod (tensile material, PC steel) 7a lower end (one end) 7b upper end (other end)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Shiokawa 1-20-10 Toranomon, Minato-ku, Tokyo Nishimatsu Construction Co., Ltd. (72) Inventor Noriaki Nishiura 1-20-10 Toranomon, Minato-ku, Tokyo Nishimatsu F-term (reference) in Construction Corporation 2E164 AA21 AA31 DA03

Claims (5)

[Claims] 1. A method for suppressing cracks at corners of an opening formed in a concrete frame, comprising: a pipe having a shaft connected to a shaft outside the opening of the concrete frame to be constructed; Along with being provided so as to be inclined with respect to both edges of the opening to be formed, a tensile member is inserted through the pipe so that both ends thereof protrude from the pipe, and then the concrete body is to be constructed. By placing concrete, one end of the tensile member is fixed in the concrete, and the other end of the tensile member is projected from the concrete. Next, after the concrete is hardened, A method for suppressing cracks, wherein the other end is pulled and fixed in this state. 2. The crack suppressing method according to claim 1, wherein one end of said tensile member is provided with a fixing means for fixing said tensile member in concrete. Suppression method. 3. The method for suppressing cracks according to claim 1, wherein the other end of the tensile member is held in a tensioned state after the other end of the tensile member is pulled. A method for suppressing cracks, comprising a holding means for storing the crack. 4. The crack suppressing method according to claim 1, wherein a PC steel material is used as said tensile member. 5. The crack suppressing method according to claim 1, wherein the tensile force applied to the tensile member is set to a predetermined tensile force according to the situation.