JPH0654050B2 - Structure for preventing cracks in the opening of reinforced concrete structures - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crack prevention structure that suppresses cracks that tend to occur at corners of openings such as concrete walls.

<< Prior Art >> A crack is likely to occur in a corner portion of a wall opening of a reinforced concrete structure (RC structure). The main cause of this is stress concentration in the corners of the opening due to drying shrinkage in the course of hardening of concrete. This stress was applied to each longitudinally and laterally inclined reinforcing bar arranged at the corners of the opening to suppress the occurrence of cracks, but no sufficient effect was obtained.

Therefore, there was also one in which a wire mesh streak or a ring stirrup spiral was arranged at the corner of the opening of the concrete wall.

<Problems to be solved by the invention> However, the tensile strain due to the reinforcing bar and the tensile strain of the concrete do not match, cracks occur in the concrete before the capacity of the reinforcing bar is fully utilized, and the effect corresponding to the amount of reinforcing bar It did not appear, and there were problems in terms of concrete packing density and workability at the time of concrete pouring because the reinforcing bars were intricate in the opening corners.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an effective crack preventing structure with a simple configuration without increasing the amount of reinforcing reinforcing bars used in the wall opening.

<< Means for Solving Problems >> In order to achieve the above object, the structure for preventing cracks in the opening of the reinforced concrete structure according to the present invention is for introducing prestress to the outer periphery of the opening formed in the reinforced concrete structure. While surrounding in a circular shape with the tension material, the both ends of the tension material are fixed to the opening edge surface of the opening by intersecting these ends in the radial direction of the closed circle drawn by the tension material with respect to the opening. It is characterized in that a tension member is arranged to generate compressive stress.

<Working> All the openings formed in the concrete wall are located within the circumference drawn by the tension material, and the centripetal force due to the prestress given by the tension material becomes an even biaxial compression action and surrounded by the tension material. A uniform compressive force is applied to the concrete within this range, and prestress is generated at any corner of the opening, canceling the tensile stress due to drying shrinkage.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the drawings. FIG. 1 exemplifies a wall surface side having an opening of a building for explaining the present invention, and one opening 2 is provided at a central portion of an outer wall 1 of the building.

Reinforcing bars 3 are arranged in the opening 2 in the vertical and horizontal directions along the edge of the opening. Then, in the outer wall 1 so as to surround the opening 2, the seast strands 5 fixed by the fixing tool 4-4 are circulated in a circular shape in the outer wall 1 while intersecting the upper end surface and the side surface of the opening with the respective end portions crossing each other. Prestressing is introduced by jacks at 4 points.

In the present embodiment, the outer periphery of the opening 2 is circularly surrounded by the castless strand 5 for introducing the pressless, and both ends of the cast strand 5 are fixed to the opening edge surface of the opening 2 by intersecting them. On the other hand, the configuration is such that the seast strands 5 are arranged to generate compressive stress in the radial direction of the closed circle drawn by the seast strands 5, so that even centripetal force is generated inside the seast strands 5. That is, the technique is not to introduce the tension material along the opening 2 but to generate a compressive stress based on the tension force in the radial direction of the circle drawn by the seast strand 5 with respect to the opening 2, whereby the seast strand 5 is formed. It is possible to achieve sufficient crack prevention while avoiding the complicated wiring form of

Further, since the fixing portion of the seast strand 5 is set to the opening edge surface of the opening 2 to be crack-prevented, not only the tensioning work is easy, but also the labor required for constructing the fixing portion completely separately, etc. Can be eliminated.

When there are many openings 2 adjacent to each other, the result is as shown in FIG. That is, the case where the outer wall 6 is provided with a plurality of openings 7, 7 '... When there are a plurality of openings 7, 7 '... In this way, the fixing ends of the seast strands 5 are placed in the openings 7, 7'adjacent to each other.

The fixing end of the seast strand 5 surrounding the outer periphery of the opening 7 is fixed by the fixing tool 4 to the opening edge surface 8'while crossing it before the latest opening edge surface 8'of the adjacent opening 7 '. . Similarly, the fixing end of the seast strand 5 ′ surrounding the outer periphery of the opening 7 ′ is fixed to the opening edge surface 8 of the adjacent opening 7.

When the cast strands 5 and 5'are placed around the openings 2, 7 and 7'respectively, the concrete is sequentially cast according to the construction procedure, and when the cast concrete reaches the required compressive strength. Prestressing may be introduced by providing tension jacks in the openings one after another. Since the fixing ends are tension-fixed so as to intersect with each other, uniform biaxial compression is imparted within the circumference drawn by the seast strands 5, 5 '.

Therefore, even in the middle portion of the outer wall of the adjacent openings 7 and 7 ', the compressive stress acts on this middle portion by taking the bearing stress to the adjacent opening. Does not occur.

<Effect> As described in detail above, according to the structure for preventing cracks in the opening of the reinforced concrete structure according to the present invention, the outer periphery of the opening formed in the reinforced concrete structure is circular with a tension material for introducing prestress. At the same time, both ends of the tension member are crossed with each other and fixed to the opening edge surface of the opening, and the tension member is generated in order to generate a compressive stress in the radial direction of the closed circle drawn by the tension member with respect to the opening. By arranging, a uniform centripetal force is generated inside the tension material, and furthermore, it is not necessary to dispose a large amount of reinforcing bars in the corners of the opening.
It has the effect of preventing the occurrence of cracks without impairing the filling properties of concrete. Particularly, in the present invention, since the uniform centripetal force is generated inside the tension member, that is, not the introduction of the tension force along the opening, but the radial direction of the circle drawn by the tension member with respect to the opening. This is a technique for generating a compressive stress based on the tension force, and by this, it is possible to achieve sufficient crack prevention while avoiding a complicated wiring form of the tension material.

Also, since the fixing part and the tensioned end are on the opening edge surface, not only the tensioning work but also the re-tensioning work is easy, and the construction labor etc. required when the fixing part is constructed separately is eliminated. The construction can be simplified.

Moreover, since the pre-stress can be sequentially applied from the hardened portion after the concrete is poured, it is not necessary to wait for the completion of the concrete pouring work of the entire structure, and the influence on the surroundings due to the introduction of the pre-stress is reduced.

[Brief description of drawings]

The drawings are all embodiments of the present invention, and FIG. 1 is a bar arrangement diagram when one opening is provided or when other openings are separated,
The figure is a bar arrangement diagram when a plurality of openings are adjacent to each other. 1 ... Outer wall, 2 ... Opening 3 ... Reinforcing bar, 4 ... Fixing tool 5 ... Seast strand 6 ... Outer wall, 7 ... Opening 8 ... Opening edge surface

Claims (2)

[Claims] 1. An outer periphery of an opening formed in a reinforced concrete structure is surrounded by a tension material for introducing a prestress in a circular shape, and both ends of the tension material are crossed with each other to form an opening edge surface of the opening portion. A structure for preventing cracks in an opening of a reinforced concrete structure, characterized in that a tension member is arranged so as to generate a compressive stress in a radial direction of a closed circle drawn by the tension member with respect to the opening. 2. When a pair of openings are adjacent to each other,
The structure for preventing cracking of an opening of a reinforced concrete structure according to claim 1, wherein the fixing portion of the tension member is formed on an opening edge surface of another adjacent opening.