JPH0447745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure for controlling cracks in openings in concrete walls.

Generally, cracks occur in openings in concrete walls due to drying shrinkage of the concrete wall, and the amount of shrinkage is particularly concentrated at the corners, making cracks more likely to occur as shown in FIG.

In other words, the free shrinkage strain of a concrete wall is generally 5
It has ^been found through actual measurements that the
×1/2×5×10 ^-4 = 0.75mm shrinkage amount. on the other hand,
The cracks mentioned above are caused by the restraint of the pillars and grains around the wall, and the degree of restraint is generally 0.2~
It is said to be 0.6. Therefore, the opening should be 0.75mm×
There is always a contraction of about 0.2~0.6=0.15~0.45mm,
Cracks are starting to appear.

Conventionally, in order to prevent the above-mentioned cracks, a method of arranging reinforcing bars at the corners of the opening has been adopted, but if the reinforcing bars are not placed accurately, the cracks tend to widen.
Moreover, no matter what measures are taken, it is currently impossible to prevent this type of cracking 100%.

In addition, research to date has shown that the crack width is 0.1 mm.
It has been found that if the depth exceeds 0.2 to 0.3 mm, water will leak, and if it exceeds 0.2 to 0.3 mm, the reinforcing bars inside the concrete wall will rust.

As mentioned above, it is almost impossible to completely prevent cracks in openings in concrete walls, but even if cracks occur, if the width does not exceed a certain limit, problems such as water leakage and corrosion of reinforcing bars may occur. It is also true that this will not occur.

The present invention was made in view of the above circumstances, and
The purpose of this is to allow cracks to occur to a certain extent, and to actively disperse and control the cracks to multiple pieces at predetermined intervals.
It is inexpensive and easy to construct, suppressing the width of cracks per wire within a predetermined limit depending on the use and conditions of the building, increasing the precision of reinforcing bar arrangement, preventing water leakage and reinforcing steel rust, and increasing the durability of the building. To provide a crack control structure in concrete wall openings.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, 1 is a concrete wall, 2 is an opening, and in the concrete wall 1 near the opening corner 2a is an inducing jig 3 for inducing cracks.
is installed. As shown in FIG. 3, the inducing jig 3 is composed of a substrate 3a and two inducing pieces 3b bent at substantially right angles to both ends of the substrate 3a. Then, when the back surface of the substrate 3a is arranged along the inner surface of the opening corner 2a and the triggering piece 3b is oriented from the opening corner toward the inside of the concrete wall, as shown in FIG. 2A. A crack C is induced from the tip of the inducing piece 3b toward the inside of the concrete wall 1.

A plurality of reinforcing bars 4 are arranged in a direction substantially perpendicular to the crack C, and are integrally assembled by fixing reinforcing bars 4a.
The reinforcing bars 4 are also held in accurate positions by a holding jig 5. The holding jig 5
As shown in FIG. 4, it is composed of a substrate 5a, an arm plate 5b erected from the substrate 5a, and a grip portion 5c provided at the tip of the arm plate 5b. The reinforcing bar 4 is disposed along the inner surface of the opening corner 2a, and the reinforcing bar 4 is fitted into the grip part 5c.

Since this embodiment is configured as described above, for example, if the interval between the induction plates 3b is 50 mm, the amount of shrinkage of concrete will be 50 x 5 x 10 ^-4 = 0.025 mm,
Also, if the tensile stress of the reinforcing bar is 2100Kg/cm ² , the elongation strain of the reinforcing bar 4 will be 1000×10 ^-6 and the amount of elongation will be 50×1000×10 ^-6 = 0.05mm, so in the end 1 The width of the crack in the book is 0.025 + 0.05 = 0.075mm, preventing water leakage and reinforcing steel rust. In addition, when preventing only reinforcing steel rust, the pitch of the crack-inducing pieces 2b and the anchoring reinforcing bars 4a should be doubled, or the stress level of the reinforcing bars 4 should be doubled, compared to the case where the purpose is to prevent water leakage.
Can be doubled.

Next, the construction procedure of the above-mentioned crack control structure will be explained.

First, the formwork for the opening 2 is attached to the outer formwork for the concrete wall 1, and the substrate 3a of the induction jig 3 and the substrate 5 of the holding jig 5 are attached to the formwork for the opening.
Attach a with nails, screws, adhesive, etc. Subsequently, the reinforcing bars 4, which are integrally assembled with the fixing reinforcing bars 4a by welding or the like, are fitted into the gripping portions 5c of the holding jig 5, and arranged at accurate positions. Once the reinforcement is completed, the inner formwork is installed and concrete is poured.

Next, FIG. 5 shows another embodiment in which another induction jig 6 is installed in place of the above-mentioned induction jig 3, and reinforcing bars 4 are double reinforced in the thickness direction of the concrete wall 1. As is clear from FIG. 6, the inducing jig 6 is composed of a substrate 6a and a inducing piece 6b, and the inducing piece 6b is inclined in one direction with respect to the substrate 6a (approximately in this embodiment). 45°).

Further, FIG. 7 shows a third embodiment of the crack control structure, in which ladder reinforcements as reinforcing reinforcements 7 are oriented obliquely so as to be almost perpendicular to the cracks C induced by the induction jig 6, and The reinforcing bar 7 is held in an accurate position by a holding jig 8 as shown in FIG.

Furthermore, FIG. 9 shows a fourth embodiment in which the reinforcing bars 7 are arranged in the thickness direction of the concrete wall 1 and held by a holding jig 9 shown in FIG. 10.

Furthermore, FIG. 11 shows a fifth embodiment in which the reinforcing bar 7 is held by another holding jig 10. In this embodiment, the gripping part 1 of the holding jig 10 is
Although cracks are induced from 0a, the above-mentioned inducing jigs 3, 6, etc. may be attached. Note that the holding jig 10 may be replaced with a holding jig 11 shown in FIG. 12.

In FIG. 13, the reinforcing bars 7 are double reinforced, and these reinforcing bars 7 are held by a holding jig 12 as shown in FIG. 14. in this case,
The inner reinforcing bars 7 are held by the first gripping part 12a of the holding jig 12, and the outer reinforcing bars 7 are held by the second gripping part 12b.
In this embodiment as well, cracks are induced from the first gripping portion 12a of the holding jig 12, but a separate induction jig may be provided.

Although the triggering jig of the above embodiment has two triggering pieces arranged at both ends of the board, the present invention is not limited to this, and a plurality of triggering pieces can be arranged side by side at a predetermined interval. It's okay.

Next, the effects of the present invention will be listed.

(1) Multiple trigger pieces are placed in parallel at a predetermined interval in the concrete wall near the corner of the opening, from the opening corner of the wall toward the inside of the concrete wall, ensuring that cracks do not start from the tips of the trigger pieces. At the same time, it is possible to suppress the crack width within a predetermined range and prevent water leakage and reinforcing steel rust from occurring.

(2) The holding jig not only allows reinforcing bars to be placed in accurate positions, but also has the effect of simplifying reinforcing bar construction management.

(3) Combination structure of induction jig, reinforcing bars, and holding jig (3) Combination structure of induction jig, reinforcing bars, and holding jig allows crack locations and number of cracks to be distributed almost systematically to improve the building's intended use. The crack width can be set according to the conditions.

(4) The crack control structure of the present invention can be applied to areas where shrinkage joints cannot be applied.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the state of cracks at the corner of an opening in a concrete wall, Figures 2A and B are diagrams showing the first embodiment of the crack control structure of the present invention, and Figure 3 is a perspective view of the induction jig. , FIGS. 4A and B are front and side views of the holding jig, FIGS. 5A and B are views showing a second embodiment of the crack control structure, and FIG. 6 is a diagram showing another embodiment of the inducing jig. 7A and B are views showing the third embodiment of the crack control structure, FIGS. 8A and B are views showing the second embodiment of the holding jig, and FIGS. 9A and B are views showing the second embodiment of the holding jig. 10A and 10B are diagrams showing the third embodiment of the holding jig;
Figures A and B are views showing a fifth embodiment of the crack control structure, Figure 12 is a view showing a modified example of the holding jig shown in Figure 11, and Figure 13 is a view showing a sixth embodiment of the crack control structure.
FIGS. 14A and 14B are diagrams showing still another embodiment of the holding jig. 1... Concrete wall, 2... Opening, 2a...
...Corner, 3...Induction jig, 3a...Substrate, 3b...
...Trigger piece, 4...Reinforcement muscle, 4a...Anchor reinforcement muscle,
5... Holding jig, 5a... Board, 5b... Arm plate,
5c... Gripping part, 6... Induction jig, 6a... Board, 6b... Induction piece, 7... Reinforcement bar, 8, 9, 1
0... Holding jig, 10a... Gripping part, 11, 12
...Holding jig, 12a...First gripping part, 12b...
...Second gripping part, C...Crack.

Claims (1)

[Claims] 1. An inducing jig consisting of a substrate and inducing pieces formed by bending both ends of the substrate is arranged with the back side of the substrate along the inner surface of an opening corner of a concrete wall, and the inducing pieces are Oriented from the corner of the opening toward the inside of the concrete wall; the back side of the substrate of a holding jig consisting of a substrate, an arm plate erected from the substrate, and a grip provided at the tip of the arm plate; The gripping portion is placed along the inner surface of the corner of the opening, and the gripping portion is positioned inside the concrete wall; reinforcing bars are fitted into the gripping portion, and the reinforcing bars are orthogonal to the direction of the triggering piece. A crack control structure in an opening in a concrete wall, characterized in that reinforcement is arranged in a direction.