JPH04189974A - Prevention against corrosion for steel pc cable fixation part - Google Patents

Abstract

PURPOSE:To improve the corrosionproof effect by applying grease on a PC steel twisted wire at the inside part of an anchor plate and applying a plastic sheath at the coated part and pouring the secondary grout. CONSTITUTION:A hole 20 is formed at a fixation part 1, and a PC steel twisted wire 10 is inserted into the hole 20. Then, the primary grout 21 is poured into an anchor fixation part C, and hardened. Then, grease 27 is applied in a length range of each twisted wire 10 which correspond to the extension quantity in the case when the twisted wire 10 is tightened, and a plastic sheath 29 is applied. Further, the second grout 22 is poured into the gap part (d) of a free edge part (b), and after hardening, an anchor plate 23 is arranged, and the twisted wire 10 is fixed by the plate 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing rust of the anchoring portion of a PC cable used in rock anchors, earth anchors, or ordinary prestressed concrete structures.

[Conventional technology]

PC steel strands are constantly loaded with stress when used in combination, so when exposed to a corrosive environment, not only normal steel corrosion but also delayed fracture due to stress corrosion sideways occurs. This may result in the cable not being able to function as a cable.

For this reason, it is necessary to perform sufficient anti-corrosion treatment, and recently, when anchors are used as permanent anchors, reliable anti-corrosion treatment has come to be performed.

FIG. 5 shows a conventional example, in which 1 is a cable anchorage made of rock, ground, or concrete.

The fixing section 1 is provided with a hole 2 having a small diameter on the entrance side and a large diameter on the back side by means such as poling.

An unbonded PC steel stranded wire 10 constituting a PC cable is inserted into this hole 2.

The fixing device 11 is fixed to the end of the part of the PC steel stranded wire 10 corresponding to the back side of the hole 2, and the PC steel stranded wire 10
A predetermined length of plasti and grease 3 is covered from the inner end of the hole 2, and grout 4 is injected into the inside of the hole 2. After this grout 4 has hardened, regroud 5 is injected over the entire length of the hole 2.

Further, an anchor plate 6 having an opening with the same diameter as the entrance of the hole 2 is arranged, and a camp 7 is placed on the outside of this plate 6.
be fixed by means such as bolting.

In addition, a water stop plate 13 that is fixed to the outer ends of the anchor head 9 and the protection box 12 is fitted inside the cap 7, and an elastic water stop material 8 such as an O-ring is installed in the groove of the plate 130 insertion hole. It is.

The PC1Fil stranded wire 10 is fixed to the anchor with a wedge 14 or the like provided at the throat 9 through the cap 7, the anchor head 9, the plate 13, and the protective box 12.
The inside is filled with rust-preventing mortar or grease 15.

In this way, the anchor head a, the anchor free length part b, and the fixed anchor attachment body C are constructed.

FIG. 6 shows a conventional example of a temporary anchor, in which a hole 20 is formed in the fixing part 1 by poling, into which a stranded PC steel wire 10 is inserted.

Next, a primary grout 21 is injected into the portion of the anchor fixed attachment body C, and after this is hardened, a secondary grout 22 is injected into the free length of the anchor.

Then, cover the opening of the hole 200 Å with an anchor plate 23,
The PC steel stranded wire 10 passing through this plate 23 is fixed with a crimp 26 consisting of a sleeve 24 and a wedge 25.

[Problems to be Solved by the Invention] The anchor fixing method shown in FIG. 5 is suitable for long-term use and is highly effective in preventing the intrusion of water in a corrosive environment, but there is a problem in that it requires a lot of work.

In addition, the anchor fixed method shown in section 6 is secondary grout 2.
2 is often not completely filled to the rear of the anchor plate 23, and a gap d often exists as shown in FIG.

In such a situation, corrosive environmental water may enter from between the anchor plate 23 and the anchoring portion 1 such as rock or concrete I-, and accumulate in the gap d.

When water in a corrosive environment accumulates in this way, it not only comes into direct contact with the PC stranded wire 10, but also reaches the vicinity of the clip 26 that fixes the PCfil stranded wire 10, creating a gap between it and the surrounding materials. A complex chemical reaction occurs, and 11
Interaction with the high stress exerted on the 0 may lead to delayed fracture.

Therefore, it is important to protect the vicinity of the anchor plate even if the temporary anchor is used for a short period of time.

However, methods such as the permanently used anchor shown in FIG. 5, which are extremely complicated and costly to construct, are not desirable.

An object of the present invention is to solve the above-mentioned problems and provide a method for preventing corrosion of a PC cable fixing section, which has a large corrosion-preventing effect and is relatively easy to install.

[Means to solve the problem]

In order to solve the above problems, this invention has a PC steel stranded wire 1
In the anchoring section of a steel iIPC cable consisting of one or more strands, before placing the anchor plate for anchoring, tighten the inner part from the position where the anchor plate is placed for each PC steel strand that makes up the cable. Grease is applied to an area corresponding to the length that corresponds to the amount that the wire stretches under tension from the PC steel, and this applied area is covered with plastin grease, then secondary grout is injected, and then the anchor plate is placed. A method for preventing corrosion of a PC steel fixing part is provided, which is characterized by fixing a PC steel strand to the anchor plate.

〔Example〕

Figures 1 to 4 show an embodiment of the method of the present invention, in which a hole 20 is formed in the pin fixing part 1 by poling, and a stranded PC steel wire 10 is inserted therein, similar to the conventional example shown in Figure 6. do.

Next, the primary grout 21 is injected into the part of the anchor constant attachment body C, and after this hardens, the secondary grout 22 is press-fitted into the free length part b, and after it hardens, the anchor plate 23 is placed. Before injecting grease 22, apply 22 g of grease to each of the PC steel stranded wires 10 that make up the PC cable.
Apply 7.

The above-mentioned grease application part is about the same length as when the wire 10 is tensed from Pc steel, from the vicinity of the hole of the anchor plate 23 when the anchor plate 23 is placed, to the inner side of the anchor plate 23.

After applying the grease 27 as described above, the applied area is covered with a plastic sheath 29 such as polyethylene.

After that, secondary grease 22 is injected into the gap between the free lengths.

When the amount of elongation of the wire 10 is smaller than that of PC steel, a plastic sheath 23 with a length corresponding to the elongation may be used.
As shown in FIG.
The corrosive environmental water remains in the gap d above the sheath 2, and the corrosive environmental water flows from there
9 and may come into contact with the PC steel strand wire 10.

Therefore, the length of the plastic sheath 29 must be such that its end reaches the inside of the secondary grout 22 without fail.

In the above embodiment, when the PC steel stranded wire 10 is tensed, the part of the steel stranded wire 10 to which the grease 27 is attached stretches and becomes fixed, so that the grease 27 is filled up to the wedge 25. become a state.

Since it is necessary to prevent external corrosion of the clip and anchor head in such a fixed state, it is preferable to cover the outside of the clip 26 with a cap 30 as shown in FIG.

Although FIG. 3 shows the case where there is only one PCfJ stranded wire 10, when fixing a plurality of PC steel stranded wires 10 as shown in FIG. Cover.

Further, in the above case, a better anticorrosion effect can be obtained by filling the inside of the cap 30, 32 with grease.

Note that this corrosion prevention method can also be used for corrosion prevention of cable anchorage parts of ordinary prestressed concrete structures.

〔Effect of the invention〕

The anti-corrosion method of this invention involves applying grease to the PC strands on the inside of the anchor plate, covering this applied area with a plastic sheath, and then injecting secondary grout. Next, even if water from a corrosive environment accumulates in the voids above the grout, this water may come into direct contact with the PC stranded wire, or reach the clip section where the PCIiii stranded wire is anchored, causing damage to the PC @ stranded wire. This has the effect of eliminating the risk of causing

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing an embodiment of the method of the invention, Fig. 2 is a longitudinal sectional view showing the same effect as above, Figs. 3 and 4 are longitudinal sectional views showing other embodiments, and Fig. 5. 7 to 7 are vertical cross-sectional views showing conventional examples. 1... Fixing part, 20... Hole,
21...-Next grout, 22...Secondary grout, 23...Anchor plate, 26...Clip, 27...Grease, 29...Plastic sheath, a...
...Anchor head, b...Anchor free length part, C...Anchor fixed attachment body, d...Void part. Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] (1) At the anchorage part of a steel PC cable consisting of one or more PC steel strands, an anchor plate is placed in advance for each PC steel strand making up the cable before placing the anchor plate for anchoring. Grease is applied to an area corresponding to the length that corresponds to the amount that the prestressed steel strands expand under tension on the inside of the position, and after covering this applied area with a plastic sheath, secondary grout is injected, and then A steel P characterized in that an anchor plate is arranged and a PC steel stranded wire is fixed to this anchor plate.
C Corrosion prevention method for cable anchorage.