JPS5965140A - Prevention of crack in concrete structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an embedding piece 1 of a predetermined shape near a corner 15 of an opening provided in a concrete structure in a fixed position. crack of yb 41:,
This relates to a method that can effectively prevent (7). In general, in concrete structures such as reinforced concrete, concrete IJ- during construction. Is it inevitable that shrinkage will occur inside the concrete, especially in concrete structures? Since tensile stress is concentrated near the corners of rectangular openings that are intended to be windows, entrances, etc., cracks are likely to occur inward from the corners. By the way, the shrinkage of concrete due to solidification generally decreases by 1 in the first 6 years.
Approximately Q for 000mm, 57+J or 1/2
00.0, and if this amount of contraction occurs, if we consider it as a rod-shaped concrete, it will be approximately 105/cg/C.
A tensile stress of up to 7N is induced, which is more than enough to cause cracks to form at the corners, considering that the tensile strength of concrete is about 20kQlC-. In fact, in buildings, etc., many cracks are seen that occur at the corners of rectangular openings such as windows, and once the cracks have formed on the surface, they not only impair the aesthetic appearance, but are rarely repaired. It becomes difficult.

111, which causes cracks near the corners of such rectangular openings.
・In order to alleviate the occurrence of force concentration, it is effective to form the angle smoothly by υ processing or radius processing, etc., but Functionally, such radius treatments are often difficult in practice, and therefore it is necessary to alleviate stress concentration and prevent cracking without changing the shape of the corners. 1.

The present invention was developed as a result of careful consideration in view of the above-mentioned circumstances, and the idea of embedding a predetermined embedded material for crack prevention near the corner of a rectangular opening of a concrete structure. The purpose of this invention was to provide a method for effectively suppressing the occurrence of cracks without impeding the function of the opening. .

Therefore, the feature of the present invention is that a predetermined length formula σ) is provided near the corner of the opening provided in the concrete structure.
At least one of the embedded portions having a single straight part is embedded in a fixed position so that the center of the 9\Sls is approximately located at the extension pole of the straight part, and a tensile force is applied near the corner. 115 so that the stress is separated by the direct weir sweat 1S of the embedding), and thus the fixed embedding island phase is cut into an opening piece such as a rectangle) 115 Nearby Conch IJ
) By being embedded inside, as the concrete solidifies and contracts, the tensile force generated near the corner S161 will be located radially from the center of the embedded part It. The stress concentration is effectively alleviated by the straight line portion S, and as a result, the occurrence of cracks near the beveled angle 1tIS can be effectively suppressed.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

First, FIGS. 1 to 3 show an example of an embedded part used in the present invention, and the embedded piece IS 2 is formed in a concrete structure 1 as shown in FIG. rectangle σ)
It is embedded in the concrete near the corner of the opening 4, for example, the corner of the opening 4, which is to be used as an anchor for a reinforced concrete building. As is clear from FIGS. 1 to 31-1, the implantable head 2 includes a plate-shaped head Ffl', 6 of a predetermined length and a predetermined width constituting a straight portion, and a curved head. A rib 8 is erected on one side of the rib 6 in its length direction, and an appropriate number (in this case, two) of pick-up levers 10 are integrally fixed to the rib 8. Cage embedded part kidnapping 2
When disposing it near the corner of the opening 4, it can be fixed in position by an appropriate fixing method such as welding (q), for example, to the reinforcing bars arranged via the mounting rod 10. It has become. This makes it possible to easily perform 19 positioning during construction.

Note that the upper surface of the head piece 156 of the embedded piece 15 (2), in other words, the surface opposite to the side on which the rib 8 is formed, has r'
& Vl-j A large number of grooves 12 are formed in the direction perpendicular to the longitudinal direction of the part 6, and in the vertical width direction, and the entire surface is uneven, thereby reducing the contact area with the concrete. It's been made bigger. In this way, by making the surface that comes into contact with the concrete as large as possible compared to a flat surface, the adhesion of the concrete to this area, or in other words, the adhesive strength, is increased and the layer It is.

In addition, such an embedded sound can be relatively easily manufactured by, for example, casting, and cast products do not corrode as much in Funkri-1.
1. Ductile cast iron, which has a higher yield strength (strength) than other preparations, can also be used, and since there is a greater degree of freedom in the surface shape, even the above and 1412 etc. can be molded without using machining. This gives rise to the advantage that it is possible to form.

As shown in FIG. 4, the embedded part 2 is installed by welding or the like through the mounting rod 10 using a reinforcing steel frame that has been arranged and assembled. The movable layer J is temporarily fixed near the angle, and concrete is poured and buried in that state. At least 1 fine fiber per corner - 1-1 Generally used at a ratio of 2 (IM or more), when one piece is arranged in the depth direction (thickness direction) of the soft opening 4 If the concrete wall is very thick, they will be buried in the center of the concrete wall, and if the concrete wall is very thick, they will be buried at an appropriate number at regular intervals in the depth direction. An appropriate number of embedding members 2 will be embedded in the vicinity of the part in the same manner.

Further, as clearly shown in FIG. 4, the embedded members 2 embedded at a ratio of two for each corner are the same as the embedded members 2 at the embedding step 1. In such a state that the center A of the corner piece IS is approximately located on the straight line, that is, the extension line of the head 6, and the head Ffls6 is placed on each side 14, 16 of the rectangular opening 4.
It is embedded in a fixed position so that it is located at J-,
The Funkley-1 portion forming the corner is divided into roughly three equal parts.

In such a state, the bisector p? of the angle formed by the corner of the opening 4? The two heads 6 (straight line parts) are located at symmetrical positions on both sides of the extended straight line A-B'ff, so that the angle is approximately 1s till.
The eight parts are divided into three parts d, e, and f in the figure.

Then, during the solidification process of concrete, embedding! lS
Assuming that the hole 2 is not buried, the shrinkage stress as shown by the arrow in FIG. The tensile stress generated inside the concrete and caused by the contraction will be most concentrated approximately on the extension line A-13 of the above-mentioned bisector of the corner of the opening 4, and in the vicinity of the corner. Since this is also the weakest point under tension, the stress increases as the concrete shrinks, making it extremely easy for cracks to form near the A-B line.

However, as shown in FIG. 4, when the embedded member 2 is placed near the corner of the opening HIS4, the embedded member 2 has sufficient strength and rigidity to withstand the stress caused by concrete shrinkage. 9, a +J'74 force is ensured that does not cause peeling or peeling between the broken concrete and the embedded member 2, and is especially formed on the surface i/f1 of the head piece 1 of the embedded member 2. By further increasing the bonding strength between concrete and concrete by grooves 2 and 1, it is possible to effectively prevent the concrete from breaking off at 6 places due to the above-mentioned tensile force, and furthermore, ” - The tensile stress that causes the crack is at the head of the embedded member 2 (as shown by the arrow in the figure).
As a result of being divided by the straight line part) 6, the corner part of the opening 4 (
The stress concentration that occurs in A) is alleviated, and there is almost no stress concentration that exceeds the strength limit of the concrete shearing and tension shield, and as a result of the assimilation of the concrete σ) This means that the occurrence of cracks, which frequently occurred in the past, can be effectively suppressed.

In addition to the assimilation process of concrete, tensile stress is generated near the A-13 line at the corner of opening iM4 even when a horizontal load is applied due to wind (especially in high-rise buildings), which is the cause of earthquakes. However, in the case of reinforced concrete, it can be treated as a rigid frame without concrete, but since concrete is brittle against strain, it cannot withstand relatively light vibrations even when horizontal loads are applied. Therefore, it is safe to assume that a stress state approximately equal to 17 will occur in the case of solidification, and therefore, even when stress concentration is induced at the corner of the opening 40 due to such horizontal load, the embedded member 2 will not crack. It can work effectively in -1- to reduce the amount of money generated. Moreover, regardless of the cause of the stress, the embedded member 2 has high rigidity in the direction in which the stress acts, but can follow the concrete and reinforcing bars in other directions.

As is clear from the above description, the embedding members 2 to be embedded according to the present invention are preferably used in two or more pieces, and the plurality of embedding members 2 are located at the corners of the opening 81S4. By arranging them symmetrically with respect to a straight line extending the bisector β of the angle at the corner, the stress generated near the corner can be more effectively divided (- to suppress the occurrence of cracks). This works effectively, especially when the corner of the opening 1s4 is 900i as in the above example.
In this case, each head (straight line ff1s) 6 of the two embedded members 2 is positioned approximately on the extension line of each of the two sides 14 and 16 forming the corner of the opening S4. It is desirable that the That way i
ll, the entire length of each straight portion (6) will function most effectively in dividing the tensile force 11C1 generated near the corner 164, and its influence will be exerted over a wide range. Because it can be done.

Note that when the opening 4 is rectangular as shown above,
Generally, it is desirable that the two embedded members be arranged at right angles to each other, as shown on the upper side, but the opening provided in the concrete structure should be rectangular as shown on the upper side. For example, as shown in FIG. It can be arranged in various forms. Therefore, the angle formed by the corner of the opening is 90
Even in cases other than angles, it is desirable that the concrete part forming such an angle be equally divided by the embedded member 2 to be embedded, as this will achieve effective division of stress concentration. be.

In addition, regarding placing and fixing all the embedded members 2 in advance near the corner of the opening IS4 during concrete pouring...J
In the example, the mounting body 10 is integrally provided on the rib 8 of the embedded member 2 and is fixed to the reinforcing steel by welding or the like. Included part 2
If it is formed by casting, as shown in Fig. 7(a)
, (1)), and (C). For example, FIG. 7(a),
In (b), the mounting bodies 22, 24 are fixed by screwing or engaging with the rib 8 through the connecting member 18.2 (l) by a known cast-in method. In addition, in Fig. 7(C), the mounting body 2
6 is directly fixed to the rib 8s by casting. In addition, each mounting body has a rib of 8mj.
The direction is not limited to the direction parallel to , but may be perpendicular thereto, and can be appropriately selected depending on the arrangement form and fixing manner of the embedded member 2 . In addition, it is also possible to use a method in which mounting holes are provided in the 8 portions of the ribs described in Ill. and fixed to the reinforcing bars using wire or the like. The stop part is integrally formed,
It is also possible to fix the frame by fixing such a latching portion to a reinforcing frame or the like, or by using a fixing means such as a hook bolt in addition to the latching portion B'ls.

In addition, in the explanation so far, it has been mentioned that cast products are suitable for embedded parts, but it is not limited to cast products.
It is also possible to use a cast product or one in which each component sound IS (fJA) is integrated by welding, etc.
Although it is not necessarily made of such a metal, as long as it has a strength of (+i+7) to withstand the internal stress of concrete, the embedded GLS phase can be made of a non-metallic material such as ceramics, for example.

Further, according to the present invention, the predetermined embedded member is not limited to reinforced concrete structures, but can also be installed in steel frame concrete structures, etc.
Substantially the same effect as described above can be obtained even if it is embedded in other concrete structures.

In addition, although specific descriptions are omitted, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention.9 .

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the embedded member used in the present invention, and FIGS. 2 and 3 are front views thereof, respectively.
It is a bottom view. Fig. 4 is an explanatory diagram schematically showing how the embedded member is placed near the S corner of the opening, and Fig. 5 shows the stress distribution generated around the opening due to assimilation of concrete. The theory is that there are four walls. FIG. 6 is an explanatory diagram corresponding to FIG. 4 showing another cast form of embedded Fflj interest. Figure 7 (a). (b) and (e) are partial cross-sectional explanatory views showing various attachment forms of the attachment body to the embedded member, respectively. 2: Embedded member 4: Rectangular opening piece S6: Head piece Is
(Straight section ~) 8: Rib 10.22, 24.26
: Mounting rod 12: Groove 14, 16: Sides 18, 20: Connecting member Presenter Okamoto Co., Ltd. Figure 7

Claims (3)

[Claims] (1) Concrete 1: In the vicinity of the opening 15 of the opening provided in the structure, at least one embedded part having a single straight part of a predetermined length bag is placed on the extension line of the straight part. A method for preventing cracks in a concrete structure, characterized by embedding in a fixed position so that the center of the part is approximately located, and tensile stress acting near the corner is divided by a straight part of the embedded member. . (2) The two pieces of +iii embedded in the concrete structure that form the entire corner of the opening r4'J are embedded in the position where the corner is roughly divided into three equal parts at their front lines. The method according to claim 1. (3) The method according to claim 1 or 2, wherein the straight line portion of the embedded groove is constituted by a plate-like portion having a predetermined width.