JPH0647860B2 - Structure to prevent cracks in the corners of wall openings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to a crack prevention structure that suppresses cracks that are likely to occur at opening corners of a concrete wall.

<< Conventional Technology >> Cracks are likely to occur at the corners of the wall openings of concrete structures. 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. Although this stress was applied to each longitudinally and laterally inclined rebar arranged in the corners of the opening to suppress cracking, sufficient effect was not obtained.

Therefore, wire mesh streaks and ring stirrup spirals were placed in the opening corners 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 prevention structure without increasing the amount of reinforcing reinforcing bars used at the corners of wall openings.

<< Means for Solving the Problems >> In order to achieve the above object, the structure for preventing cracks at the corners of a wall opening according to the present invention is configured to have one opening or a plurality of openings formed in a concrete wall. PC steel materials are laid out in a substantially circular shape within the wall so as to surround them all together,
It is characterized in that the PC steel material is tensioned to generate compressive stress in the circular radial direction drawn by the PC steel material with respect to the opening.

<Action> All the openings formed in the concrete wall are located in the circle drawn by the PC steel material, and the centripetal force due to the prestress given by the PC steel material becomes a uniform biaxial compression action and PC
A uniform compressive force is applied to the concrete within the area surrounded by the steel material, and prestress occurs at any opening corner.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the drawings. FIG. 1 illustrates a side of a building having an opening for explaining the present invention, and one opening 2 is provided in 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, the seast strand 4 fixed to the upper end of the outer wall 1 is wound around the outer wall 1 so as to surround the opening 2 and is tense.

In this embodiment, the seast strands 4 are laid out in a substantially circular shape within the outer wall 1, and the seast strands 4 are tensioned to generate compressive stress in the radial direction of the circular shape drawn by the seast strands 4 with respect to the opening 2. Since a uniform centripetal force is generated on the inside of the seast strand 4 by providing the structure, that is, not by introducing a tension force along the opening 2, the radial direction of the circle drawn by the seast strand 4 with respect to the opening 2 Is a technique for generating an internal compressive stress based on a tension force, thereby avoiding a complicated wiring form of the seast strand 4,
Sufficient crack prevention can be achieved.

FIG. 2 shows a case where the building is a three-story building, and the outer wall 5 thereof is provided with a plurality of openings 6, 6 ... When there are a plurality of openings 6, 6 ... 6 in this way, unbonded tension members 7 such as seast strands should be surrounded from the first floor according to the concrete pouring procedure so as to surround these openings 6 collectively. Sequentially embed with a radius of curvature that becomes circular. The free end of the tension member 7 is fixed to the uppermost end of the outer wall 5. That is, the fixing ends 8 are tension-fixed at the upper end of the outer wall 5 so as to intersect with each other, and the outer wall 5 drawn by the tension members 7 is drawn.
The uniform biaxial compression is given within the circle.

<< Effects >> As described in detail above, according to the structure for preventing cracks in the corners of the wall opening according to the present invention, a single opening or a plurality of openings formed in the concrete wall are collectively compressed by PC steel material. As a result, a uniform centripetal force is generated inside the PC steel material, and cracking of the entire wall can be prevented.

Particularly, in the present invention, the PC steel material is laid out in a substantially circular shape in the wall, and the PC steel material is tensioned to generate a compressive stress in the circular radial direction drawn by the PC steel material with respect to the opening. Since a uniform centripetal force is generated inside the PC steel material, that is, tension is not introduced along the opening, but tension is applied toward the opening in the radial direction of the circle drawn by the PC steel material. This is a technique for generating internal compressive stress based on force, and by doing so, sufficient crack prevention can be achieved while avoiding the complicated wiring form of PC steel.

Further, since it is not necessary to dispose a large amount of reinforcing bars at the corners of the opening, there is an effect that the filling property of concrete becomes good.

[Brief description of drawings]

The drawings are embodiments of the present invention. FIG. 1 is a side view around one opening provided in an outer wall of a building, and FIG. 2 is an explanatory view illustrating the case of an outer wall having many openings. DESCRIPTION OF SYMBOLS 1 ... Outer wall, 2 ... Opening 3 ... Reinforcing bar, 4 ... Seast strand 5 ... Outer wall, 6 ... Opening 7 ... Unbond tension material, 8 ... Fixing end part

Claims (1)

[Claims] 1. A PC steel material is laid out in a substantially circular shape in a wall so as to enclose one opening or a plurality of openings formed in a concrete wall as a whole, and the PC steel material is placed around the opening. A structure for preventing cracks in a corner of a wall opening, wherein the PC steel material is tensioned so as to generate a compressive stress in a circular radial direction drawn by the PC steel material.