JPS6131262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PC (prestressed concrete) structure for preventing cracks at the opening corners of a concrete wall.

Generally, stress is concentrated at the corner of an opening in a concrete wall due to drying shrinkage of the concrete, making cracks more likely to occur. In order to keep such cracks as small as possible, conventional methods have been to embed vertical, horizontal, or diagonal wire meshes in the opening corners of concrete walls, or to arrange diagonal reinforcements, ring reinforcement spirals, etc., as shown in Figure 1. It was hot. However, it has been impossible to actively eliminate cracks by simply placing reinforcing bars in this way.

Recently, as shown in Figure 2, methods to proactively prevent cracks have been developed, such as burying a large number of ring reinforcements in a concentrated manner, and applying tension to the diagonal reinforcements to prestress the concrete at the corners. A construction method has been developed.

However, using a large amount of the above-mentioned ring muscles not only increases the material cost, but also
It is not possible to completely prevent cracks, and the prestressing method using diagonal reinforcement requires a complicated structure in which both ends of the reinforcing bars are anchored to the concrete, and a member is pre-installed to tension the middle part of the diagonal reinforcement after the concrete hardens. As a result, it is not only expensive and requires special techniques for construction, but also has the disadvantage that it is not possible to select the most suitable prestress depending on the condition of the corner.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to provide a new method for opening corners of concrete walls that is easy to construct, has low material cost, and can proactively prevent cracks.
Located in providing PC structure.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3, 1 is a concrete wall in which an opening 2 is formed. Inside the concrete wall 1, reinforcing bars 3 are arranged vertically and horizontally along the edge of the opening 2, and intersect at the corner 1a.

A PC steel wire 4 is bent into a ring shape 4a at the upper right corner 1a of FIG. 3, and its one end anchoring portion 4b is anchored to concrete. The ring-shaped portion 4a of the PC steel wire 4 is inserted into a sheath (not shown) or has its surface coated with grease so that its outer peripheral surface does not adhere to concrete. PC
The tension portion 4c on the other end side of the steel wire 4 is attached to the concrete wall 1
It is exposed in the opening 2 of the corner 1a and is connected to a tensioning device 5 such as a jack or screw, which applies prestress to the concrete at the corner 1a by tensioning the ring-shaped portion 4a.

Next, a construction method for the PC structure of the above embodiment will be explained. First, a prestressed steel wire 4 of a desired length is prepared and inserted into the sheath, leaving the fixed portion 4b, or its surface is coated with grease. next,
The PC steel wire 4 is bent into a ring shape 4a together with reinforcing bars 3, etc., and the fixing part 4b is stretched diagonally with respect to the side edge of the opening 2, and the tension part 4c is attached to the opening 2. Place it so that it protrudes inward and pour concrete. When the concrete reaches the required compressive strength and the fixing portion 4b is fixed to the concrete, a tensioning device 5 such as a jack is attached to the tensioning portion 4c to tension the PC steel wire 4 and tighten the corner 1.
Apply prestress to the concrete in a. Due to this prestress, the concrete at corner 1a is
The tensile stress caused by the drying shrinkage is canceled out and no cracks occur.

In addition, in the above example, the ring-shaped portion 4 of the PC steel wire 4
Although a is arranged in a circular shape, the present invention is not limited to this. For example, it may be formed in a circular shape as shown in the upper left corner 1a of FIG. 3, or as shown in the lower right corner 1a in FIG. Figure 8 shape, furthermore the lower left corner 1
As shown in a, the term "ring shape" in this specification, such as a spiral shape, can be used for each of the above embodiments and any shape similar to these shapes, as long as it does not prevent tensioning of the PC steel wire. good.

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

(b) Prestressing the concrete in the corners actively prevents cracks caused by drying shrinkage, prevents water leakage from the outside, and is aesthetically pleasing.

(b) General PC steel wire can be used as is, so
The cost of materials is low, and construction can be done simply and quickly by simply bending it into a ring shape and exposing the tensioned part within the opening in the concrete wall.

(c) The length of the PC steel wire, the shape of the ring, the direction of the anchoring part, etc. can be freely set according to the stress state of the corner, and the optimal prestress can be applied.

[Brief explanation of the drawing]

Figures 1 and 2 are reinforcement diagrams of a conventional crack prevention structure at the corner of an opening in a concrete wall.
The figure is a reinforcement diagram showing each embodiment of the PC structure according to the present invention. 1... Concrete wall, 1a... Corner, 4...
PC steel wire, 4a...ring-shaped part, 4b...fixing part, 4c...tensioning part, 5...tensioning device.

Claims (1)

[Claims] 1 Place the PC steel wire under tension in a ring shape at the corner of the opening of the concrete wall, and
1. A PC structure at an opening corner of a concrete wall, characterized in that one end tensioned part of the PC steel wire is exposed inside the opening of the concrete wall to apply prestress to the concrete at the corner.