JPS6231140B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing prestressed steel that is embedded in prestressed concrete and exerts tension thereon.

Concrete usually has extremely high compression strength, but low tensile strength. Therefore, tensioned prestressing steel (usually
Prestressed concrete, which combines the excellent compressive strength of concrete and the strong tensile strength of prestressed steel, has been put into practical use. If this is used for the outer walls of a nuclear reactor, etc., the PC steel material will deteriorate and it will be necessary to periodically replace it. As mentioned above, this PC steel material is under tension with a strong force, so when it is unfixed, it is instantly drawn into the sheath, which not only damages the surrounding area but is also extremely dangerous.

The present invention eliminates these drawbacks and provides a method for removing prestressed steel material for safe replacement of the prestressed steel material. A hollow cylindrical extension member with the same threads cut on the outer periphery as the anchor head is brought into contact with the head in a continuous arrangement with the threads of both aligned, and a rod-shaped tensioning member is attached to the extension member. The extension member is fixed to the anchor head by screwing its tip into the anchor head, and a jack with the ram pulled is set on the extension member, and the anchor nut is loosened by one stroke of the jack and moved. Then, return the jack ram, unset the jack, pull the ram again, set the extension member, and repeat the above steps in sequence.
The present invention resides in a method for removing a prestressed steel material, which is characterized by releasing the tension in the prestressed steel material and then pulling out the prestressed steel material. Embodiments will be described in detail below according to embodiments shown in the drawings.

FIG. 1 is a partial sectional view for explaining one embodiment of the present invention. In the figure, 1 is concrete, in which a sheath 11 is embedded, and a PC strand 12 is inserted into this sheath 11. Reference numeral 2 denotes an anchor that supports the tension applied to the PC strand 12, and the anchor plate 21 attached to the tip of the sheath 11 and the clipper 23 inserted into the cone hole 22 are used to tighten the PC strand.
An anchor head 24 for holding the strand 12 and an anchor nut 25 for supporting the anchor head 24 on the anchor plate 21.
It is composed of: That is, the tension applied to the PC strand 12 is transmitted to the anchor head 24 via the clipper 23, supported by the anchor plate 21 by the anchor nut 25, and transmitted to the concrete 1. This allows the concrete 1 to have sufficient strength not only in compression but also in tension.

Reference numeral 3 denotes an extension member composed of an extension pipe 31, a tightening plate 32, a tightening member 33, and the like. This extension pipe 31 has the same thread as that on the outer circumference of the anchor head 24 over its entire outer circumference, and its length L corresponds to the length of the PC strand 12 extended by tension. It is determined. The tightening plate 32 is a circular plate having a diameter slightly smaller than the outer diameter and larger than the inner diameter of the extension pipe 31, which has a through hole corresponding to the cone hole 22 of the anchor head 24, and the tightening member 33 is attached to this tightening plate 32. It is inserted into the drilled hole.

The tightening member 33 is provided with a flange 34 at one end B thereof, which is engaged with the through hole of the tightening plate 32, and the other end is provided with a screw cut into the cone hole 22 of the anchor head 24 on its outer periphery. A screw 35 is cut to be screwed into the PC strand 26, and a blind hole 36 into which the end of the PC strand 12 is inserted is opened from the end surface. 4 is an auxiliary nut for aligning the threads of the extension pipe 31 of the extension member 3 and the anchor head 24.

The removal of the PC strand 12 will be explained step by step below.

FIG. 2 shows the process of one embodiment of the present invention. First, the auxiliary nut 4 is screwed onto the head of the anchor head 24. FIG. 2 1 shows this state. At this time, the auxiliary nut 4 is not completely screwed together, leaving some margin, and the extension pipe 31 is screwed into this. When this screw is completely screwed in, the anchor head 24 and extension pipe 31
The threads of the screws are aligned. FIG. 2 shows this state. Next, the tightening member 33 is attached to the tightening plate 32.
, insert it into the extension pipe 31 , screw the screw 35 at the tip into the screw 26 of the cone hole 22 and tighten, and then attach the extension pipe 31 to the anchor head 24 .
sticks to. FIG. 2 shows this state.
Once the extension member 3 has been secured to the anchor head 24, the auxiliary nut 4 is removed. FIG. 24 shows this state.

In this way, the extension member 3 is attached to the anchor head 24.
Once it is fixed, the jack 5 is set on the extension member 3. FIG. 2 5 shows this state, with reference numeral 51 the jack body, 52 the jack air, and 53 the ram. The setting of the jack 5 on the extension member 3 is carried out with the ram 53 being pulled as shown. Next, the ram 53 is further pulled to remove the force applied to the anchor nut 25, and the anchor nut 25 is rotated and moved in accordance with the stroke of the jack 5. FIG. 26 shows this state. Here, ram 53 of Jacki 5
When the anchor head 24 and the distal end of the extension member 3 are returned, the anchor head 24 and the distal end of the extension member 3 are drawn into the sheath 11 until the anchor nut 25 contacts the anchor plate. FIG. 27 shows this state. Here, the setting of the jack 5 is temporarily released, the ram 53 is pulled, and in this state, the jack 5 is set again. FIG. 28 shows this state. Thereafter, the tension in the PC strand 12 is completely released by repeating the process described in FIG. 3 and subsequent figures. The tensioned PC strand 12 is pulled out by removing the anchor nut 25.

As described above, according to the prestressing steel material removal method of the present invention, since the tension in the prestressing steel material is gradually released using a jack, the prestressing steel material is instantly drawn into the sheath and the surrounding area is damaged. PC steel material can be removed extremely safely without any problems. moreover,
According to the construction method of the present invention, the extension member is connected to the PC.
Since the tension in the steel material is loosened, the tension can be released without leaving the prestressed steel material that has elongated during tension, so the anchoring part of the prestressed steel material can be made smaller and there are no obstructive protrusions. Not only is this advantageous from a safety standpoint, but the cap and other components can be made from inexpensive materials.

Although the embodiments shown in the drawings have been described in detail above, it goes without saying that the present invention is not limited thereto. For example, as long as the outer diameter of the extension pipe is the same as the outer diameter of the anchor head, and the mutual threads are the same, we are not limited to just pipes; we can also use various types of extension pipes, such as steel rods with holes drilled through them for tension members. Variations are possible.

In addition, various variations are conceivable for the tightening member, such as one in which the tightening member is threaded and tightened with a nut instead of a flange, and one in which the tightening member is directly connected to the PC steel bar with a nut. Furthermore, if the height of the anchor nut can be formed higher than the anchor head,
Auxiliary nuts are not required. Even with these various variations, effects equivalent to those of the above embodiment can be expected.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an embodiment of the present invention;
FIG. 2 is a diagram for explaining the process. 1... Concrete, 11... Sheath, 12...
... PC strand, 2 ... anchor, 21 ... anchor plate, 22 ... cone hole, 23 ... clipper, 24 ... anchor head, 25 ... anchor nut, 26 ... screw, 3 ... extension member,
31...Extension pipe, 32...Tightening plate, 3
3...Tightening member, 34...Flange, 35...Screw, 36...Blind hole, 4...Auxiliary nut, 5...
... Jyatsuki, 51... Jyatsuki main body, 52... Jyatsuki Chi Air, 53... Ram.

Claims (1)

[Claims] 1. In a method for removing prestressed concrete from prestressed concrete, tensed PC
A hollow cylindrical extension member, which has the same threads cut on the outer periphery as the anchor head, is brought into contact with the anchor head holding the steel material in a continuous arrangement with the threads of both parts aligned, and a rod-shaped tension member is attached. A fixed member is passed through the extension member and its tip is screwed into the anchor head to fix the extension member to the anchor head. A jack at the upper end with a ram is set on the extension member, and the anchor nut is tightened. Loosen the jack by one stroke and move it, then return the jack ram, unset the jack, pull the ram again, set the extension member, and repeat the above steps in order to release the tension in the PC steel. , a method for removing prestressed steel material, which is characterized by pulling out the prestressed steel material. 2. When fixing the extension member to the anchor head, an auxiliary nut is screwed onto the anchor head in advance, and the extension member is screwed in from the opposite side of the auxiliary nut to align the threads of both. A method for removing prestressing steel materials as described in Scope 1.