JPH01158154A - Cracking preventive structure of opening section made of rc - Google Patents

Abstract

PURPOSE: To generate uniform centripetal force at the inside of a tendon and to prevent generation of a crack without preventing concrete filling property by surrounding and compressing an opening part formed on concrete by the tendon. CONSTITUTION: A sheathed strand 5 is circularly laid within an outer wall 1 so as to surround an opening 2 in which reinforcing bars 3 are longitudinally and latitudinally arranged. This sheathed strand 5 is fixed by a fixing tool 4-4, making each tip part intersect an upper end face and a side surface of the opening 2 and prestress is introduced at the portion of the fixing tool 4-4. Therefore, because uniform centripetal force is generated at the inside of the sheathed strand 5, generation of a crack can be prevented, and because a fixing part and a tension tip part exist on an opening surface, a tension work can be easily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crack-preventing structure that suppresses cracks that tend to occur at the corners of openings in concrete walls and the like.

(Prior Art) Cracks are likely to occur at the corners of wall openings in reinforced concrete structures (RC construction). The main reason for this is stress concentration at the opening corners due to drying shrinkage during the hardening process of concrete. This stress was applied to the vertical, horizontal and diagonal reinforcing bars placed at the corners of the opening to suppress the occurrence of cracks, but this has not been sufficiently effective.

For this reason, some have wire mesh reinforcements or ring reinforcement spirals placed at the corners of openings in concrete walls.

(Problem to be solved by the invention) However, the tensile strain caused by the reinforcing bars does not match the tensile strain of the concrete, and cracks occur in the concrete before the capacity of the reinforcing bars is fully utilized, resulting in an effect corresponding to the amount of reinforcing bars. In addition, reinforcing bars were intricately placed at the corners of the openings, which caused problems in terms of concrete filling density and workability during concrete pouring.

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

(Means for Solving the Problems) In order to achieve the above object, the crack prevention structure of the RC open opening according to the present invention is provided by surrounding the outer periphery of the opening with a tension material for introducing prestress. Both ends of the tension material are crossed over each other and each end is fixed to the opening surface to absorb tension reaction force.

(Function) All openings formed in the concrete wall are located within the circumference drawn by the tendons, and the centripetal force due to the prestress applied by the tendons becomes an even biaxial compression action, which causes the openings surrounded by the tendons to A similar compressive force is applied to the concrete within the area, and prestress is generated at every corner of the opening, which offsets the tensile stress caused by drying shrinkage.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In order to explain the present invention, FIG. 1 illustrates a wall side of a building where an opening is located, and one opening 2 is provided in the center of an outer wall 1 of this building.

In this opening 2, reinforcing reinforcing bars 3 are arranged vertically and horizontally along the edge of the opening. Then, in the outer wall 1 surrounding the opening 2, the sheath strands 5 fixed by the fixing device 4-4 are hung and turned in a circular shape, with each end crossing the upper end surface and the side surface of the opening. Prestress is introduced at the part of tool 4 by jacking.

If there are a large number of adjacent openings 2, the result will be as shown in FIG. r, and the outer wall 6 has a plurality of open lowers.

7'... is provided. In this way, when there are a plurality of open lowers 7', the fixing ends of the sheath strands 5 are placed in the adjacent open lowers 7'.

The fixing ends of the sheath strands 5 surrounding the outer periphery of the open lower are crossed in front of the nearest side 8' of the adjacent open lower' and are fixed to this side 8' by the fixing device 4. Similarly, the anchoring ends of the sheath strands 5' surrounding the outer periphery of the open lower core are anchored to the side surface 8 of the adjacent open lower core.

Place concrete strands 5, 5' around each opening 2, 7.7', etc., and pour concrete in sequence according to the construction procedure, and when the poured collectrete reaches the required compressive strength. For example, tension jacks may be provided in the openings one after another to introduce prestress. Since the fixing ends are tension-fixed so as to cross each other, uniform two-wheel compression is applied within the circumference drawn by the sheath strands 5, 5'.

Therefore, even if there is a middle part of the outer wall of the adjacent openings 7, 7', by taking the bearing stress to the adjacent opening, compressive stress will also act on this middle part, so that the open lower parts 7' will be drawn together and cracks will occur. It never happens.

(Effects) As explained in detail above, according to the crack prevention structure of the RC building according to the present invention, one or more openings formed in concrete are individually surrounded and compressed with tendons. As a result, an even centripetal force is generated inside the tension material, and there is no need to place a large amount of reinforcing bars at the corners of the opening, so cracks can be prevented without impeding the filling properties of the concrete. It has the effect of preventing

In addition, since the fixing portion and the tensioning end are located on the opening surface, not only the first tensioning operation but also the re- tensioning operation is easy. Furthermore, after pouring concrete, prestress can be sequentially applied starting from the hardened parts, so there is no need to wait until the concrete pouring work for the entire structure is completed, and the impact on the surrounding area due to the introduction of prestress is reduced.

[Brief explanation of the drawing]

The figures are all examples of the present invention, and Figure 1 is a reinforcement diagram when the opening is in one place or other openings are far apart, and Figure 2
The figure is a reinforcement arrangement diagram when there are a plurality of adjacent openings. 1... Outer wall 2... Opening 3.
...Reinforcement reinforcing bar 4...Fixing tool 5...
... Seast strand 6 ... Outer wall 7 ... Opening 8.
...Inner surface of the opening

Claims (2)

[Claims] (1) A structure for preventing cracks in reinforced concrete openings, in which the outer periphery of the opening is surrounded with tension material for introducing prestress, and each end of the tension material is fixed to the opening surface while crossing both ends of the tension material. (2) The structure for preventing cracks in a reinforced concrete opening according to claim 1, wherein the fixing portion of the tendon material is formed on an adjacent opening surface.