JPH04363454A - Prestressed concrete - Google Patents

Abstract

PURPOSE:To prevent distortion cracking at both end portions of concrete without using hoop reinforcement. CONSTITUTION:In prestressed concrete which uses a stress member 1 made of braided fibers and which is formed by applying prestress to concrete using pretension method, smooth portions 6 are formed partially at both end portions of the stress member 1 embedded in the concrete.

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 that applies prestress to concrete using a pretensioning method using tendons made of braided fibers.

0002

[Prior Art] Conventionally, this type of prestressed concrete is produced by applying tensile force to tendons a and pulling them, as shown in Figure 2, placing concrete b after erecting the formwork, and curing the tendons a. is loosened, and the tensile force of the tendon a is transmitted to the concrete b through the adhesion between the tendon a and the concrete b, thereby applying prestress to the concrete b.

0003

[Problems to be Solved by the Invention] However, since the tension material a made of a braided fiber body is extremely irregular in shape, the adhesion force between the tension material a and the concrete b is too large.
When the tension material a is loosened, a large tensile force is concentrated at both ends of the concrete b, and the concrete b
Strain cracks were likely to occur at both ends of the concrete b, and it was necessary to provide hoop reinforcements around the ends of the concrete b and the tendon a.

[0004] An object of the present invention is to provide prestressed concrete that does not require the provision of such hoop reinforcements.

[0005]

[Means for Solving the Problems] The prestressed concrete of the present invention uses a tension material made of braid-like fibers, and is buried in the prestressed concrete to apply prestress to the concrete by a pretensioning method. It is characterized by partially forming smooth parts at both ends of the tension material.

[0006] In this case, it is preferable to wind the tape around both ends of the tendon material at intervals to form partially smooth portions at both ends.

[0007]

[Operation] The edges of the tendon and concrete are cut by the smooth parts partially formed at both ends of the tendon, and the adhesion between the tendon and concrete becomes appropriate at both ends of the concrete. This prevents distortion and cracking in the parts.

[0008]

[Example] Next, an example of the prestressed concrete of the present invention will be described.

In the figure, 1 shows a tendon material made of a braided fiber body, in which eight strands 3 of fibers 2 having high tensile strength such as aromatic polyamide fibers or carbon fibers are knitted into a round string shape. In the illustrated embodiment, these fibers 2 were bound together with an epoxy resin (not shown).

[0010] This is similar to conventional prestressed concrete in that the tension material 1 is used to apply prestress to the concrete 10 using a pretension method.
In the embodiment shown in the first figure, a vinyl tape 4 is wound around both ends of the tendon 1 to be buried at a distance 5 at both ends of the concrete 10 to partially form smooth portions 6 at both ends.

More specific examples will be explained below along with comparative examples.

Example 8 strands of aromatic polyamide fibers were knitted into a round string shape, each fiber was bound with epoxy resin, and the diameter was 1.6 cm.
Prepare a 2cm wide tension material, wrap vinyl tape 2cm wide around each end three times with an interval of about 2cm, then apply a tensile force of 12.8 tons to create tension, and then pour concrete. A concrete specimen measuring 21 cm in height, 12 cm in width, and 2.4 m in length was prepared, and when the concrete reached a predetermined strength, both ends of the tendons were cut.

When the specimen was observed, no cracks were found at all.

Comparative Example A specimen was prepared in the same manner as in the above Example except that the tape was not wound. When observed in the same manner, cracks were found at both ends.

[0015]

As described above, the prestressed concrete of the present invention has the effect of preventing strain cracking at both ends of the concrete without using hoop reinforcements.

[Brief explanation of drawings]

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

[Fig. 2] An enlarged explanatory diagram of conventional prestressed concrete.

[Explanation of symbols]

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

Claims (2)

[Claims] Claim 1: In prestressing concrete that applies prestress to concrete using a pretensioning method using tendons made of braided fiber bodies, there is a partially smooth portion at both ends of the tendons buried in the concrete. Prestressed concrete characterized by forming. 2. The prestressed concrete according to claim 1, wherein a tape is wound around both ends of the tendon at intervals to form a partially smooth portion at both ends.