JP2888239B1 - Unbonded anticorrosion PC steel strand - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a required fixing length portion by simply peeling off a polyethylene sheath 25 at the time of installation, in which a PC steel wire 21 itself has a high anticorrosion property and a high adhesive force to cement grout. The present invention provides an unbonded anticorrosion-protected PC stranded wire, which can form a steel wire and can secure free elongation at a free length. SOLUTION: A resin coating layer 23 of an epoxy resin or a polyethylene resin is formed on the surface of a PC steel strand 21a to give the strand 21a itself a high anticorrosion property and a high adhesive force to cement grout, By providing a polyethylene sheath 25 having a predetermined inner diameter on the outer periphery of the stranded wire 21b on which the resin coating layer was formed, a free extension in the free length portion was secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
That is, the present invention relates to a cable that prestresses a concrete structure as an anchor for preventing landslides such as rocks and slopes, or for stabilizing a concrete structure such as a dam or a pier. In particular, having a high adhesive force to cement grout in the fixing length part, and after fixing the fixing length part with cement grout, when tensioning, it is easy to freely stretch in the free length part and to apply tension, It concerns unbonded anticorrosion PC steel strands.

[0002]

2. Description of the Related Art As a typical conventional unbonded anticorrosive PC steel strand, a grease is applied to the bare surface of a PC strand as shown in JP-B-53-47609. There is a cable whose outer periphery is covered with a polyethylene sheath, and other cables having the following structure are known.

[0003] One of them is shown in FIG.
In this cable, a coating layer 3 having a simple rust-preventing effect is formed on each of the strands 2, and a grease 4 is applied to the surface of the strand 1 and a polyethylene sheath 5 is coated on the outer periphery thereof.

[0004] As shown in FIG. 8, after the stranded wire 1 is formed, a coating is applied to the outside of the bare stranded wire 1 to form a coating layer 3, and grease 4 is applied thereon. Some cables have a polyethylene sheath 5 provided on the outer periphery.

By the way, these P shown in FIG. 7 or FIG.
When a cable in which grease is applied around a C steel strand is used as an anchor, for example, as shown in FIG. 10, the cement grout 6 and the strand 1 are fixed at the anchoring length A fixed with the cement grout 6. To adhere, the polyethylene sheath 5 must be removed and the grease 4 applied to the strand 1 must be removed.

Therefore, in the fixing length portion A, since the strand 1 is only protected by the cement grout 6 and protected from corrosion, there is a problem that if the cement grout 6 is cracked, it is immediately exposed to a corrosive environment. .

In the cable shown in FIG. 7 in which grease is applied around the PC steel stranded wire, the grease 4 is
It is necessary to untwist the stranded wire 1 in order to completely remove the stranded wire, and there is a problem that the operation is difficult.

In addition, when a long time has passed since installation,
The grease 4 of the free length portion B hangs down on the fixing length portion A, and the grease 4 penetrates into the interface between the cement grout 6 and the strand 1 of the fixing length portion A, and the adhesive force between the strand 1 and the cement grout 6. May be reduced.

For this reason, without using grease, FIG.
As shown in FIG. 1, there is also proposed a cable in which each strand 2 of the stranded wire 1 is coated with a coating layer 3 of a thin film of a fluororesin, which is a plastic having a small coefficient of friction, and a polyethylene sheath 5 is adhered to the outer periphery thereof.

However, this method has a problem that the processing of the fluororesin coating layer 3 is troublesome.

Next, as a method of protecting a cable from a corrosive environment, an installation method as shown in FIG. 11 has been proposed.

In this method, a plurality of cables are bundled and wrapped with a protective tube 7 to form a free length B, and a polyethylene sheath 5 and a grease 4 of each strand 1 protruding from the tip of the free length B. The fixing portion A is formed by covering a protective tube 8 having an uneven surface on the portion where the fixing portion has been removed.
And the protective tubes 7 and 8 are also filled with cement grout 6.

The method of using the protective tubes 7 and 8 has the effect of preventing corrosion of the outside of the protective tubes 7 and 8 but has the problem of corrosion and dripping of the grease 4 inside the protective tubes 7 and 8. There is also the problem of removal.

Further, when the protective tubes 7 and 8 are used, the diameter of the whole becomes large. Therefore, the boring diameter of the hole C to be installed at the time of the installation work must be increased, and the construction cost increases accordingly. There is also a problem.

Next, a cable having extremely high corrosion resistance of a PC steel stranded wire and also having a high adhesive force with cement grout, having an epoxy coating formed on the surface of the stranded wire with an enhanced adhesive force with cement grout. There is also (Tokuhei 3
-28551, JP-A-8-85946).

[0016] However, a PC steel strand having an epoxy coating on the surface has a high adhesive force to cement grout, but a plurality of cables are bundled in a bundle in order to secure elongation at the free length when tensioned. Therefore, there is a problem that the diameter of the boring becomes large when the installation work is performed.

In FIGS. 10 and 11, reference numeral 9 denotes a support plate, 10 denotes a fixing device, and 11 denotes a wedge.

[0018]

SUMMARY OF THE INVENTION The present invention has solved various problems of the conventional cable as described above.
In other words, it has excellent anticorrosion properties, does not require grease to be removed during installation, and can easily form a required fixing length, and accommodates in a protective tube to form a free length. It is intended to provide an unbonded anticorrosion PC steel stranded wire that does not need to be performed.

[0019]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cable, that is, an unbonded anticorrosion P
The steel C strand was constructed as follows.

First, a resin coating layer 23 having an epoxy resin or a polyethylene resin having a thickness of at least 0.4 mm or more is formed on the surface of the stranded wire 21 so that the stranded wire 21a itself has a sufficient anticorrosion property. It was made to give.
Hereinafter, the stranded wire 21a formed with the resin coating layer 23 is referred to as
It is called anticorrosion strand 21b.

As shown in FIG. 2, the resin coating layer 23 may be formed on the surface of the stranded wire 21a and then provided on the surface thereof. Alternatively, as shown in FIG. The resin coating layer 23 may be provided on the wire 22. In addition, the gap between the strands 22 forming the strands 21a may be filled with an epoxy resin or a polyethylene resin.

The resin coating layer 23 needs to have a thickness of at least 0.4 mm in order to obtain a sufficient anticorrosion property, and in order to obtain a sufficient adhesive force with the cement grout 6, It is necessary that the thickness of the stranded wire 21a be large enough to leave eyes. Further, in order to increase the adhesive force with the cement grout 6, solid particles such as silica sand are embedded in the resin forming the resin coating layer 23, or the resin coating layer 2
It is desirable to form the surface of No. 3 as a rough surface.

The present invention relates to the above resin coating layer 23
The outer diameter of the stranded wire 21a, ie, the anticorrosion stranded wire 21b, is 0.6 m larger than the outer diameter of the resin coating layer of the anticorrosion stranded wire 21b
A polyethylene sheath 25 having an inner diameter larger by m to 6 mm is provided. As a method of providing the polyethylene sheath 25, there is a method of coating the outer periphery of the anticorrosion stranded wire 21b with the resin coating layer formed thereon by extruding polyethylene, or a method of covering a hollow polyethylene tube.

As described above, according to the present invention, the polyethylene sheath 25 having an inner diameter that is 0.6 mm to 6 mm larger than the outer diameter of the resin coating layer of the anticorrosion stranded wire 21b is used.
b is provided on the outer circumference because the difference between the outer diameter and the inner diameter is 0.6
mm, the resin coating layer 23 of the anticorrosion stranded wire 21b
In particular, when the surface is roughened, a large frictional force is generated between the anticorrosive strand 21b and the polyethylene sheath 25 during tensioning.
This is because it becomes impossible to secure free growth.

On the other hand, as the difference between the outer diameter and the inner diameter is larger,
Although the frictional force between the anticorrosion twisting wire 21b and the polyethylene sheath 25 is reduced, when the size exceeds 6 mm, the outer diameter of the polyethylene sheath 25 increases, and when a plurality of bundled bundles are used, the overall outer diameter is reduced. As the diameter increases and the cable is transported as a coil from the factory to the construction site, the polyethylene sheath 25 having a circular cross section
As shown in (1), a problem of deformation into an elliptical shape arises.
If the cross section of the polyethylene sheath 25 is deformed into an elliptical shape, as shown in FIG. 1, at the time of the installation work, the mesh plate 13 on the bottom surface of the anticorrosion material-filled case 12 installed on the back surface of the support plate 9.
It becomes difficult to pass the cable through the circular cable insertion hole formed in the above, and the workability deteriorates.

(Test Example) Like the cable according to the present invention, the outer diameter of the resin coating layer of the anticorrosive strand 21b is 0.6 m.
When the polyethylene sheath 25 having an inner diameter larger than m is provided on the outer periphery of the stranded wire 21b on which the resin coating layer 23 is formed, the frictional force generated between the polyethylene sheath 25 and the anticorrosion stranded wire 21b during tension is small, It was confirmed by performing the following friction measurement test that it can function as a free length portion as it is.

First, the cable having the structure shown in FIG.
The test was performed with a resin coating layer 23 formed on the surface of the stranded wire 21a and a polyethylene sheath 25 provided on the outer periphery thereof.

In the test, a plurality of cables having a difference between the outer diameter of the resin coating layer of the anticorrosion strand 21b and the inner diameter of the polyethylene sheath were prepared, and each cable was 10 m long and 70 mm inside diameter.
Insert the cement grout to be used as an anchor into the space between the cable and the steel pipe, and after the cement grout has solidified, tighten the cable in a vertical state and tighten the cable on the fixed side. The measurement was performed by measuring the decrease in load, and the results shown in FIG. 5 were obtained.

The fixed side load P was determined by the following equation.

Fixed-side load P = ^tensile -side load P ₀ × e- ^λl λ: Friction coefficient in a straight line state 1: Cable length The specific dimensions and the like of each cable used in the test are as follows.

In any case, before the resin coating layer 23 is formed, the outer diameter of the stranded wire 21 is 15.2 mm. In addition, the resin coating layer 23 is made of two types, an epoxy resin and a polyethylene resin, both of which have solid particles buried in the surface in order to increase the adhesive force with cement grout. The thickness of the resin coating layer 23 is 0.6 mm, and the outer diameter of the anticorrosion strand 21b coated with the resin coating layer 23 is 16.4 mm.
Becomes The polyethylene sheath 25 has a thickness of 1.25 mm
A difference of 1.0 mm, 2.0 mm, and 4.0 mm was provided between the inner diameter of the polyethylene sheath 25 and the outer diameter of the resin coating layer 23 of the anticorrosion strand 21b. The outer diameter of the polyethylene sheath 25 of the obtained cable is 19.9 mm, 20.9 mm, and 22.9 mm.

Table 1 can be obtained from the results shown in FIG.

[0033]

[Table 1]

Next, the cable having the structure shown in FIG.
Epoxy resin is applied to each strand 22 before being stranded.
by coating and bonding with a thickness of 2 mm
3 and an outer diameter of 17.6 m created from the strand 22.
1.0mm, 2.0m around the outer circumference of the anticorrosion stranded wire 21b
A cable having an outer diameter of 21.1 mm, 22.1 mm and 24.1 mm was prepared by covering a polyethylene sheath 25 having an inner diameter of 4.0 mm and an inner diameter of 4.0 mm and a thickness of 1.25 mm, and the same friction measurement test as above. Was done.

The result is as shown in FIG.

The results shown in FIG. 6 indicate that the resin coating layer 23
Since the surface is not roughened, the frictional force is slightly smaller than that shown in FIG.

Similarly, Table 2 can be obtained from the results shown in FIG.

[0038]

[Table 2]

From the above test results, it is considered that the difference between the outer diameter of the resin coating layer and the inner diameter of the polyethylene sheath is preferably 0.6 mm or more in consideration of the practical length of the free length portion of the anchor. It could be confirmed.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which a cable having the structure shown in FIG. 2 is prepared as follows and applied to an anchor is shown in FIG.
Shown in

First, an epoxy resin is applied by powder coating to a bare PC steel strand 21a having an outer diameter of 15.2 mm, and the strand 21
Coat with a film thickness of 0.6 mm so that the eyes of a appear.

Further, the strands 22 forming the strand 21a
Filled with epoxy resin also in the gaps, and by burying solid particles on the surface of the epoxy resin coating, rich in anticorrosion, and enhanced adhesion to cement grout,
The anticorrosion strand 21b having the resin coating layer 23 on the surface is formed.

Next, the anticorrosion stranded wire 21b having the resin coating layer 23 is supplied to a continuous extruder for polyethylene, and the outer diameter of the anticorrosion stranded wire 21b is set at 2.
A polyethylene sheath 25 having an inner diameter larger by 0 mm was formed. The thickness of the polyethylene sheath 25 is 1.25 mm
And the outer diameter was 20.9 mm.

Before the cable formed as described above is put into the hole C of the boring slope, it is cut to a length of 21 m, the polyethylene sheath 25 at the tip of 4 m is peeled off, and the fixing length of 4 m is removed. A was formed.

The boundary between the fixing long portion A from which the polyethylene sheath 25 has been peeled off and the free long portion B covered by the polyethylene sheath 25 is stopped with a resin 26 and then inserted into the hole C on the slope. The cement grout 6 was injected and filled into the gap between the cable and the hole C.

A support plate 9 and a fixing device 10 are provided on the upper surface of the hole C on the slope, and an anticorrosion material filling case 12 for filling an anticorrosion material is provided on the back surface of the support plate 9. The bottom surface of the anticorrosion material-filled case 12 is formed by an eye panel 13 having a plurality of cable insertion holes.

After the cement grout 6 has solidified,
The anticorrosion stranded wire 21b is tensioned from above and the wedge 11 fixes the anticorrosion stranded wire 21b to the fixing device 10, whereby the anchor installation work is completed.

[0048]

As described above, the cable according to the present invention has an excellent anticorrosion property of the PC stranded wire itself, and forms a fixing portion having a high adhesive force to cement grout simply by peeling off the polyethylene sheath. Therefore, it is possible to obtain an effect that free elongation can be secured in the free length portion covered with the polyethylene sheath.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an installation example of a cable according to the present invention.

FIG. 2 is a sectional view showing an example of a cable according to the present invention.

FIG. 3 is a sectional view showing another example of the above.

FIG. 4 is a sectional view of a reference example.

FIG. 5 is a graph showing the results of an effect confirmation test.

FIG. 6 is a graph showing the results of an effect confirmation test.

FIG. 7 is a sectional view showing a conventional example.

FIG. 8 is a sectional view showing a conventional example.

FIG. 9 is a sectional view showing a conventional example.

FIG. 10 is a sectional view showing a conventional installation example.

FIG. 11 is a sectional view showing a conventional installation example.

[Explanation of symbols]

 21a stranded wire 21b anticorrosive stranded wire 22 strand 23 resin coating layer 25 polyethylene sheath

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Etsuji Ishibashi 1-1-1, Koyokita, Itami-shi In Itami Works, Sumitomo Electric Industries, Ltd. (72) Inventor Yoshihiko Higashita 1-1-1, Koyokita, Itami-shi Sumitomo (58) Investigated field (Int. Cl. ⁶ , DB name) E04C 5/08 B32B 15/08 D07B 1/16

Claims (4)

(57) [Claims] 1. A resin coating layer in which an epoxy resin or a polyethylene resin is adhered to a surface of a stranded wire, is formed to a thickness of at least 0.4 mm or more so as to leave an eye on the stranded wire. An unbonded anticorrosive PC steel stranded wire, wherein a polyethylene sheath having an inner diameter of 0.6 mm to 6 mm larger than the outer diameter of the resin coating layer of the stranded wire is provided on the outer periphery of the stranded wire on which the layer is formed. 2. The unbonded anticorrosion PC steel stranded wire according to claim 1, wherein solid particles are embedded or roughened in said resin coating layer. 3. An epoxy resin or a polyethylene resin is filled in a gap between the strands forming the stranded wire.
Or the unbonded anticorrosion PC steel stranded wire according to 2. 4. A resin coating layer in which an epoxy resin or a polyethylene resin having a thickness of 0.4 mm or more is adhered to the surface of each strand forming the strand, and a resin layer of the strand is formed on the outer periphery of the strand. An unbonded anticorrosive PC steel strand, comprising a polyethylene sheath having an inner diameter of 0.6 mm to 6 mm larger than the outer diameter of the coating layer.