JPH07103642B2 - Prestressed concrete - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prestressed concrete, and more particularly to prestressed concrete which uses a tension material made of braided fibrous body to prestress concrete by a pretensioning method.

[0002]

2. Description of the Related Art Conventionally, in this type of prestressed concrete, a tension member a is stretched by applying a tensile force to the tension member a as shown in FIG. The tension force of the tension material a is transmitted to the concrete b by the adhesion of the tension material a and the concrete b to prestress the concrete b.

[0003]

However, since the tension member a made of the braided fiber body is extremely irregular, the adhesion force between the tension member a and the concrete b is too large.
When the tension member a is loosened, a large tensile force is concentrated and applied to both ends of the concrete b too much.
Strain cracks tend to occur at both ends of the concrete, and it was necessary to dispose hoop streaks around the ends of the concrete b and the tendons a.

An object of the present invention is to provide prestressed concrete that does not require such hoop streak arrangement.

[0005]

The prestressed concrete of the present invention uses a tension material composed of a braided fibrous body and is embedded in the prestressed concrete for prestressing the concrete by the pretensioning method. It is characterized in that smooth portions are partially formed at both ends of the tension member.

In this case, it is preferable that the tape is wound around both ends of the tension member with a space therebetween to partially form smooth portions at the both ends.

[0007]

[Function] The edges of the tension material and the concrete are cut by the smooth portions partially formed at both ends of the tension material, and the adhesion force between the tension material and the concrete becomes appropriate at both ends of the concrete. Distortion cracks in the part are prevented.

[0008]

EXAMPLES Next, examples of the prestressed concrete of the present invention will be described.

In the figure, reference numeral 1 denotes a tension member composed of a braided fibrous body. For example, eight strands 3 of a fiber 2 having a large tensile strength such as an aromatic polyamide fiber or a carbon fiber are knitted in a round striking string shape. In the illustrated embodiment, these fibers 2 are bound to each other with an epoxy resin (not shown).

Like the conventional prestressed concrete, the prestressing is applied to the concrete 10 by the pretensioning method using the tension material 1.
In the first embodiment shown in the drawings, vinyl tapes 4 were wound around both ends of the concrete material 10 at both ends of the tension material 1 to be embedded at intervals 5 to form smooth portions 6 at both ends.

Hereinafter, more specific examples will be described together with comparative examples.

EXAMPLE A strand of aromatic polyamide fiber was knitted into a shape of 8 round punched strings, and each fiber was bound with an epoxy resin to give a diameter of 1.6c.
m tension material is prepared, and vinyl tape with a width of 2 cm is wound around the ends 3 times with a space of about 2 cm, and tension is applied by applying a tensile force of 12.8 tons, and then concrete is poured. A concrete test piece having a height of 21 cm, a width of 12 cm, and a length of 2.4 m was prepared, and both ends of the tension material were cut when the concrete reached a predetermined strength.

When the specimen was observed, no cracks were found.

Comparative Example A test piece was prepared in the same manner as in the above-mentioned example except that the tape was not wound, and the same observation was performed. As a result, cracks were found at both ends.

[0015]

As described above, according to the prestressed concrete of the present invention, it is possible to prevent distortion cracks at both ends of the concrete without using hoop reinforcements.

[Brief description of drawings]

FIG. 1 is an enlarged explanatory diagram of an example of prestressed concrete of the present invention.

FIG. 2 is an enlarged explanatory diagram of conventional prestressed concrete.

[Explanation of symbols]

 1 Tension material 4 Tape 5 Spacing 6 Smooth part 10 Concrete

Claims (2)

[Claims] 1. A tension member made of a braided fiber body is used.
A prestressing concrete for prestressing concrete by a pretensioning method, characterized in that smooth portions are partially formed at both ends of a tension material embedded in the concrete. 2. The prestressed concrete according to claim 1, wherein tapes are wound around both ends of the tension material with a space therebetween to partially form smooth portions at the both ends.