JPH0365449B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a PC with an end buried in concrete.
PC buried in the concrete when introducing prestress by post tension into the concrete product by pulling the other end of the steel strand wire one-sidedly
The present invention relates to a structure for fixing the end of a stranded steel wire.

(Prior art) For example, when applying prestress to a concrete product using a so-called unbonded PC steel stranded wire, the surroundings of which are coated with lubricating oil such as grease and the coated surface is covered with a synthetic resin tube. Now, peel off the tube on the end side of the PC steel stranded wire, remove the lubricating oil from the peeled part, and either fix the PC steel stranded wire itself in the concrete at that part, or remove the lubricating oil. At the same time, fix the fixing plate to the PC steel strand,
The fixing plate serves as a fixing section structure.

(Problem to be Solved by the Invention) However, with the former fixing means, since there is only a small fixing surface between the prestressed steel strand and the concrete product, the stress of large displacement due to the post tension is applied to the fixing surface. As a result, it is difficult to introduce a strong prestress, and there is a risk that the prestress will be released over time.

On the other hand, according to the latter fixing means, although it is easy to provide a large bearing surface that resists the post tension, it has the disadvantage that the concrete is divided at that part, and is expensive, and The disadvantage was that it was difficult to fix in the area.

The present invention aims to solve the above-mentioned drawbacks by a simple improvement of the structure of the fixing section.

(Means for Solving the Problems) In order to achieve the above object, the structure of the end anchoring part of the PC steel stranded wire according to the present invention untwists the end strand of the PC steel stranded wire and expands it into a conical shape. The present invention is characterized in that the strands are opened, and conical spiral reinforcements are arranged around the outside of the strands, and the spiral reinforcements and the expanded strands are buried in concrete.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows an end fixing part A of a PC steel stranded wire 1.

To explain an example of the manufacturing procedure of this end fixing part A, as shown in Fig. 2, first, a lubricating oil such as grease is applied around the prestressed steel stranded wire 1, and this is coated with a synthetic resin tube. A so-called unbonded PC steel stranded wire B coated with b is prepared, and the resin tube b on the end side thereof is peeled off, and the lubricating oil on the peeled part is wiped off to expose the PC steel stranded wire 1.

Next, as shown in FIG. 3, a conical spiral wire 2 is placed over the exposed PC steel stranded wire 1 from its top side, and the top wire portion 2a is placed at the end of the resin tube b. It is fastened by wrapping it around the area.

Then, as shown in FIG.
Untwist strand a of wire 1 from PC steel,
The strands a... are expanded into a conical shape with the apex at the attachment portion by the top muscle portion 2a.

The unbonded PC steel strand B, whose end has been processed in this way, is placed, for example, in the slab molding part C, as shown in FIG. 5, and the expanded strand a... Concrete D is placed in the slab molded portion C while embedding the spiral reinforcing bars 2 placed around the outside of a.

When the concrete D hardens, an end fixing part A shown in FIG. 1 is formed in which the conical expansion strand a and the spiral reinforcement 2 are restrained by the concrete D. Yes, and unbond with the fixing part A as the reaction force point.
By pulling the other end of the wire B from the PC steel, prestress due to post tension can be introduced into the slab version E.

According to the structure of the end fixing section A having the above configuration, the PC
Since the strands a of the steel wire 1 are loosened, the surface of the strands a to be fixed with the concrete D is increased, and the pull-out strength of the strands a against the post tension is increased.

Furthermore, as shown in FIG. 6, a conical structure F is formed in the vicinity of the fixing section by conical strands a... and concrete D surrounded by the conical strands a. A cone-shaped structure G is formed around the cone-shaped spiral reinforcement 2 and the concrete D restrained by this, so the large pulling force due to the post tension is applied to the cone-shaped structure G. Even if it acts on the structure F, the cone-shaped structure F is firmly held by the cone-shaped structure G due to the development of a wedge effect, and the fixing surface is expanded by the expansion of the strands a. In addition to the increase, the pull-out strength becomes strong.

As explained based on FIG. 3, the spiral reinforcement 2 is placed over the wire 1 made of PC steel, and the top reinforcement portion 2a of this is fixed to the end of the resin tube b. As shown in , the spiral thread 2 is placed over the side of the resin tube b, and if necessary, the end of the resin tube b is wrapped around and fixed with a wire c, and in this state, the strands a... are untwisted. After expanding into a conical shape, the spiral striations 2 may be placed around the outside of the expanded strand a, or alternatively, the spiral striations 2 may be placed around the outside of the expanded strand a, or the spiral striations 2 may not be covered in advance, but they may be stranded with unbonded PC steel. B
It is also possible to cover it from the other end and position it at a predetermined location.

Other embodiments are shown from FIG. 8 onwards. What is shown in FIG. 8 is a structure in which a plurality of reinforcing bars 3 having different diameters are bound to strands a with wires d, so that the strands a are maintained in a conically expanded state.

What is shown in Fig. 9 is the expanded strand a.
...is tied to the spiral muscle 2 with a wire d.

The one shown in FIG.
It is unique in that it is constructed so that it can be embedded in cast-in-place concrete, such as a floor, and fixed.
In this case, the conical concrete mass H
is formed, it is possible to bring forward the timing of prestress introduction, and moreover, it is possible to use high-strength concrete only for the anchoring part.

In addition, in the examples, the present invention was explained using unbonded PC steel stranded wire B, but a metal or resin sheath tube was arranged and lubricating oil was applied to it.
A means for inserting the PC steel stranded wire 1 may be adopted, and in this case, a fixing portion A is formed at the end of the PC steel stranded wire 1 prior to insertion.

Further, the spiral muscle 2 may be arranged in a completely free state around the outside of the expanded strand a, or the spiral muscle 2 may be fixed to other reinforcements.

(Effects of the Invention) As explained above, according to the structure of the end fixing part of the PC steel stranded wire according to the present invention, since the strand at the end of the PC steel stranded wire is loosened, the fixing surface for concrete products is increased. However, the pull-out strength of the strand against post tension is increased.

In addition, the loosened strands are expanded into a conical shape, conical spiral reinforcements are placed around the outside of the strands, these are buried in concrete, and the conical reinforcement is restrained by the spiral reinforcements in the area. It forms a concrete mass, and this concrete mass becomes a large anchoring surface material, and even if an excessive pulling force is applied to the concrete mass, the concrete mass and the cone-shaped concrete product around it This concrete mass is firmly held by the cone-shaped concrete product due to the wedge action between the concrete blocks, and there is no concrete separation as with conventional fixing plates, and the fixation at the thin plate part is In other words, there are no restrictions on the fixing target, and overall, although it is a simple improvement, it has been possible to achieve a fixing effect that is greater than that achieved by the fixing plate.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view of the end fixing section, FIGS. 2 to 4 are explanatory diagrams showing an example of the procedure for manufacturing the end fixing section, and FIG. 5 is slab molding. FIG. 6 is a functional explanatory diagram of the fixing section, and FIGS. 7 to 10 are explanatory diagrams of another embodiment. 1...PC steel stranded wire, 2...Spiral wire, 3
... Expansion ring, a... Strand.

Claims (1)

[Claims] 1 An end fixing part structure of a PC steel stranded wire for introducing prestress by post tension, which has the above-mentioned structure.
The end strands of the PC steel strands are untwisted and expanded into a conical shape, and conical spiral reinforcements are placed around the outer circumference of the strands, and the spiral reinforcements and the expansion strands are connected to concrete. An end anchoring structure for a PC steel stranded wire, characterized by being embedded in the PC steel strand.