JPH0426378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a strand tensioning method and a jack air device in a PC construction method that can introduce a designed tension force into a strand such as a prestressed steel wire.

<Conventional technology> The PC construction method, which applies tension to multiple PC cables (strands) at the same time and fixes them, is used in many fields such as anchor construction and bridge construction.

An example of a conventional strand tensioning method is shown in FIG.

First, pass the strands A exposed in the holes into the holes of the anchor head B one by one, and insert the wedge C into the holes.
position.

Then, a center hole type tensioning jack D is set on the anchor head B, and the end of the strand A is grasped and tensioned.

When a predetermined tension is applied to strand A, a cuneiform C
Anchor head B pulls into the hole to fix the end of strand A.

<Problems to be Solved by the Present Invention> According to the above-described fixing technology for strand A, once the wedge C is driven in to fix the strand A,
Since it is difficult to remove the wedge C and re-tension the strand A, the following problem arises.

<B> If an unreasonable condition occurs in the middle of strand A where tension is occurring, the tension in strand A cannot be released.

Furthermore, if the strand A is already stretched to its limit, no further tension can be applied to the strand A, and the wedge C cannot be removed.

<B> Even if strand A is fixed by applying a tension exceeding the design tension, it is very difficult to release strand A and redo the tensioning work.

Therefore, it becomes difficult to adjust the tension to the designed tension in each cross section inside the strand A.

<Objective of the present invention> The present invention was made to solve the above-mentioned problems, and even if excessive tension force is introduced, the strand can be released and the tensioning work can be repeated, and the tension can be restored as designed. power can be introduced. The purpose of this invention is to provide a strand tensioning method and a tension air device in the PC construction method.

<Structure of the present invention> An embodiment of the present invention will be described below with reference to the drawings.

<B> Structure of the tensile part of the strand (Figure 1) 1 is a strand of PC steel strands, 11 is a bearing plate buried in the concrete structure, 12 is an anchor head with a cone-shaped hole, 13 is an anchor It is a split wedge inserted into the hole of the head 12.

<B> Tensioning device The tensioning device consists of a tensioning jack 2 and a jacking air device 3.

The tensioning jack 2 is a well-known center-hole type hydraulic jack, and for example, the jack has a structure in which the tensioning force of the strand 1 is adjusted by gripping the strand 1 with a pulling head having a wedge body located at the tail end of a built-in piston. It is.

<C> Jacket air device The jackpot air device 3 is interposed between the bearing pressure plate 11 and the tension jack 2 to avoid contact between the wedge body 13 and the strand 1 when adjusting the tension of the strand 1, and to prevent the wedge body 13 from coming into contact with the strand 1 when the strand 1 is fixed. This device is intended to make the strand 1 hold the strand 13.

Specifically, a configuration was adopted in which an insulating tube 5 made of a tube material as shown in FIG. 4 was slid over the strand 1 using fluid pressure.

The specific structure will be explained below.

[Insulating Tube] (FIG. 4) The insulating tube 5 has an inner diameter larger than the diameter of the strand 1, and is a tubular body with both ends open, with a large diameter flange 51 protruding from one end.

By inserting this insulating tube 5 into the hole of the wedge body 13, the wedge body 13 and the strand 1 can be insulated.

The sliding operation of the insulating tube 5 is performed by the double piston part 6.
Do it with

[Double Piston Section] The operation of insulating or contacting the wedge body 13 and the strand 1 is performed using two pistons operated by fluid pressure such as hydraulic pressure or air pressure, that is, a pushing piston 61 located on the wedge body 13 side and a tension jack 2 side. and an extraction piston 62 located at.

The insulating tube 5 is inserted into both pistons 61 and 62, and the flange 51 is locked to the extraction piston 62.

Both pistons 61 and 62 are operated by fluid pressure such as oil pressure or air pressure.

<D> Tension adjustment method (1) Preparation for tension Set the tension jack air device 3 and tension jack 2 on the free end of the strand 1.

The insulating tube 5 is wrapped around the strand 1 with the flat cylindrical portion 52 facing toward the anchor head 12.

Then, the flat cylindrical portion 52 of the insulating tube 5 is inserted into the wedge body 1.
3 into the hole 3 to insulate the wedge 13 and the strand 1.

In order to prevent the insulating tube 5 from easily falling off the wedge body 13, an O-ring 4 is provided on the wedge body 13 to temporarily secure it.

(2) Tension adjustment operation (Figure 2) Grip the end of strand 1 with tension jack 2 to apply tension to strand 1.

At this time, both pistons 6 of the jack air device 3
1 and 62 are moved back in the tension direction.

The strand 1 is formed into a wedge 1 by inserting the insulating tube 5.
It is insulated from 3.

Furthermore, a wedge body 13 integral with the insulating tube 5 has protruded from the hole wall of the anchor head 12.

Therefore, even if the strand 1 is pulled back under tension, the strand 1 will not be gripped by the wedge body 13 while the insulating tube 5 insulates both 1 and 13.

In this way, when the strand 1 exceeds the design tension or is insufficient, the strand 1 is tensioned and pulled back as many times as desired to correct the tension of the strand 1 to the design value.

(3) Fixing operation (Fig. 3) When the strand 1 reaches the designed tension, move the extracting piston 62 backward while holding the end of the strand 1 with the tension jack 2, and then immediately move the pushing piston 61 to the anchor head. Move it forward to the 12th side.

As a result, as the extraction piston 62 retreats, the insulating tube 5 comes out from the wedge body 13 and the wedge body 5 comes into contact with the strand 1.

Immediately after the wedge body 13 contacts the strand 1, it is pushed by the pushing piston 61 and jumps into the hole of the anchor head 12, gripping and fixing the strand 1.

<Effects of the Present Invention> Since the present invention is as explained above, the following effects can be obtained.

(a) According to the conventional method, once the wedge body was fixed to the anchor head, it was extremely difficult to redo the tensioning operation of the strand.

In contrast, in the present invention, the strand can be tensioned and pulled back as many times as desired during tensioning.

Therefore, it is possible to confirm that the designed tension has been introduced into the strand and fix it.

(b) During tensioning of the strand, the strand and the wedge are completely insulated by the insulating tube.
The wedges do not damage the strands.

(c) When the wedge body is finally fixed to the anchor head, it can be fixed mechanically by fluid pressure.

Therefore, the worker does not have to manually fix the wedge as in the conventional method, and the safety of the work can be ensured.

[Brief explanation of drawings]

Fig. 1: Explanatory diagram of the tensioning method according to the present invention, Fig. 2
Figure: An explanatory diagram when adjusting the tension force, Figure 3: An explanatory diagram when fixing, Figure 4: A perspective view of an insulating tube, and Figure 5: An explanatory diagram of the prior art.

Claims (1)

[Claims] 1. When introducing prestress into a strand such as a prestressed steel wire, an insulating tube is inserted between the circumferential surface of the strand and a wedge that is inserted into the hole of the anchor head to grip and fix the strand. Strand tensioning in the PC construction method, which is characterized in that it is slidably interposed, and when the strand is tensioned, an insulated tube is used to insulate between the wedge body and the strand, and when the strand is fixed, the insulated tube is removed from the wedge body. Method. 2 A chair that connects a strand of PC steel wire or the like to the tip of a tensioning jack, with an insulating pipe body that slides under fluid pressure between the circumferential surface of the strand and the wedge that grips and fixes the strand to the anchor head. A jack air device with a pipe that can move in and out.