JPH0329926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for simultaneously tensioning tendons of different lengths.

Prior Art Conventionally, when tensioning members of different lengths are simultaneously tensioned by a single jack to give the same tensioning force, there has been a problem in that the tensioning stress becomes uneven. For example, a method of tensioning tendons in a U-turn removable anchor as shown in FIG. 3 will be explained.

That is, in FIG. 3, the guide shaft p is positioned in the direction perpendicular to the drilling direction of the hole m during the drilling m,
Tensile material r for unbonding with a sheath on the outer periphery
is bent in the middle, the bent part is anchored to the guide shaft, and the tension material r positioned outside the drilling m is tautly fixed, and when removing it, the fixation of both ends is released and one end is fixed. The tension material r is pulled out by pulling.

In this construction method, when a large number of tendons r are moored and tensioned to one guide shaft p, the guide shaft cannot withstand the tension of the many tendons r, and the mortar filled around it Cracks may occur in grout such as. For this reason, it has been adopted to position a plurality of guide shafts p at appropriate distances during drilling m, and to moor a plurality of tension members r to each guide shaft p to distribute the total tension force to each guide shaft p. There is.

The problem with the above-mentioned anchor construction method is that the tendons r moored to each guide shaft p are positioned at appropriate intervals l in the direction of the hole being drilled. The total length differs for each tendon r moored to the shaft p. Therefore, when all tension members r are tensioned at the same time with the same jack, the shortest tension member r moored to the guide shaft p located at the shallowest position in the drilling hole m can be sufficiently tensioned. However, the tension material r moored to the guide shaft p located deeper than the guide shaft p becomes longer in length, and when tensioned at the same time by the same jack, the elongation due to the longer length becomes longer. Therefore, it is impossible to apply the same tension force as a tension member r having a short length. In other words, a situation arises in which the entire tension material r cannot be used as an effective anchor by applying the designed tension force.

Purpose of the Invention This invention was made to improve the above-mentioned drawbacks, and it is possible to apply tension stress uniformly to tendons of different lengths, and it is possible to effectively use them as designed tendons. The purpose of the present invention is to provide a method for simultaneously tensioning tendons of different lengths.

Structure of the Invention The method for simultaneously tensioning tendons of different lengths according to the present invention comprises forming tendon groups for each tendon material having different lengths, and applying tensioning jacks to each tendon material in the same number as the number of tendon groups. The above object is achieved by arranging the tension members into groups and tensioning the tension members by separate jacks for each group of tension members.

Embodiments Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In this embodiment, the present invention is implemented in a U-turn removable anchor.

In the figure, reference numeral 1 denotes a tendon material such as a PC steel wire or a PC steel stranded wire for use in the unbonded construction method, which has a sheath 11 on its outer periphery. A plurality of tension members 1 are folded back in the middle and inserted into holes 2 drilled in the ground. That is, a pair of rings 3 as shown in FIG.
1 and 31 are connected by a connecting plate 32, and a guide shaft 4 is fixed in the diametrical direction of one ring body 31.
The guide shaft 4 is inserted inside the tension member 1, and is folded back in the middle so that the guide shaft 4 is positioned inside the bent portion 12 of the tendon member 1. The number of tendons 1 moored to one guide shaft 4 can be selected as appropriate.

When there are multiple tendons 1 moored to one guide shaft 4, the lengths of these tendons 1 are the same, and even if there is a single tendon 1 moored to each guide shaft 4, Even if there are a plurality of tension members, a tendon group is constructed for each guide shaft 4.

A plurality of guide shafts 4 are fixed in the hole 2 at appropriate intervals in the drilling direction. In other words, while hanging on the guide shaft 4, drill the hole 2 with the bent part 12 side as the tip.
Tensile members 1 are inserted into the holes 2, and the guide shafts 4 are positioned at appropriate intervals in the drilling direction of the holes 2, and mortar 5 is injected into the holes 2 and hardened and fixed. Both ends of the tendon 1 are positioned outside the drilled hole 2.

A bearing plate 6 is positioned on the outer periphery of the ground surface of the borehole 2, and the anchor head 7 has a tendon insertion hole 71 on the bearing pressure plate 6, and a wedge 72 is positioned in the tendon insertion hole 71. It is placed there.

A number of jacks A and B corresponding to the number of guide shafts 4 fixed in the drilled hole 2 are stacked on the anchor head 7. In the embodiment, center hole jacks are used as the jacks A and B, but other known jacks such as a body jack can be used.

The jack A has a pulling head 81 attached to a cylindrical sliding ram 82 on the anchor head 7 side. A plurality of tendon insertion holes 83 are formed in the pulling head 81, and both ends of the tendon 1, which has been inserted through the tendon insertion holes 71 of the anchor head 7, are passed through the tendon insertion holes 83. . The tension material 1a moored to the guide shaft 4a located at the shallowest position in the drilled hole 2 of the tension material 1 is gripped by a wedge 84 positioned in the tension material insertion hole 83 inserted therethrough. The tendon 1b, which is anchored to the guide shaft 4b located deeper in the drilled hole 2 than the guide shaft 4a, is inserted through the tendon insertion hole 83 of the pulling head 81, but is not gripped by the wedge.

A jack B is fixed and stacked on the sliding ram 82 of the jack A. This jack B is made to grip the tension material 1b moored to the guide shaft 4b. The jack B has a pulling head 92 attached to the rear end of a sliding ram 91, and a tendon insertion hole 93 is formed in the pulling head 92.
The guide shaft 4a and the guide shaft 4 are inserted into this tension material insertion hole 93.
Both the tension members 1a and 1b moored to the guide shaft 4b are inserted through the tension member 1b, and only the tension member 1b moored to the guide shaft 4b is gripped by the wedge 74. The tension material 1a that was gripped by jack A is not gripped by jack B.

The tension members 1a, 1b moored to the respective guide shafts 4a, 4b as described above are gripped by different jacks A, B for different guide shafts 4a, 4b, and the jacks A, B are driven to tension them.

Each tension member 1 moored to each guide shaft 4a, 4b
If the numbers of a and 1b are the same, each jack A and B
By changing the pressure receiving areas of the sliding rams 82 and 91, it is possible to apply the same tension force to each tension member 1a and 1b by sending pressure oil of the same pressure with the same pump P. In other words, when tensioning members 1a and 1b moored to two guide shafts 4a and 4b are tensioned by two jacks A and B, tensioning material 1a moored to guide shaft 4a located at the shallowest position is tensioned. The pressure receiving area of the sliding ram 82 of jack A is made twice the pressure receiving area of the sliding ram 91 of the other jack B.

As in the above-mentioned embodiment, the two jacks A and B are fixed with jack B fixed on the sliding ram 82 of jack A, and pressure oil of the same pressure is fed to both jacks A and B. As the sliding ram 82 slides, the jack A tensions the tension material 1a held by the wedge 84 on the pulling head 81, and moves the jack B fixed to the sliding ram 82.
Since the tension member 1b is held in the pulling head 92 by the wedge 94 in the jack, the jack A pulls the tension member 1a,
This will make both sides nervous.

On the other hand, in the case of the jack B, only the tension material 1b is held by the wedge 94, and the tension material 1b is only tensioned by the tension material 1a and 1b by the jack A, so that the tension material 1b is only tensioned by the tension material 1b.
The output of jack A should be half that of jack A. The fact that the pressure receiving area of the sliding ram 82 is twice that of the other sliding ram 91 means that even if the pressure of the supplied pressure oil is the same, the jack A is twice the jack B due to the supply of pressure oil. It becomes possible to automatically generate twice the output.

Therefore, by the jack A, all the tension members 1a, 1b
tension material, half of which is tension material 1b
Jacket B, which tensions only tension materials 1a and 1b
The sliding ram 91 slides by absorbing the difference in elongation caused by the difference in length l, and the tension material 1a is attached to the tension material 1b.
It is possible to apply the same tension force as Therefore, the stroke of the sliding ram 91 of the jack B may be extremely small.

When the number of guide shafts 4 is three or more, that is, when three or more jacks are used, the pressure-receiving area of the sliding ram can be multiplied by a positive number in proportion to the number of tension members 1 tensioned by the jacks. good.

By increasing the pressure-receiving area of the pulling head as described above, it is possible to apply the designed tension force evenly to all the tension members 1, but it is also possible to make the pressure-receiving area of the sliding ram of each jack the same, and each Even if the pressure of the pressure oil sent to the jacks is multiplied by a positive number in proportion to the number of tension members 1 tensioned on the jack, and pressure oil is sent to each jack from a plurality of pumps P, the tension force is applied equally to each tension member 1 in the same way. Is possible.

The above is a case where the jack 9 is fixed to the sliding ram 82 of the jack 8 at the lowest stage, and when the same number of tension members 1 are moored to each guide shaft, the same tension force is applied to each tension member 1. As explained above, if the number of tension members 1 moored to each guide shaft 4 is different, even if pressure oil with a pressure doubled to each jack is sent to each jack in proportion to the number of tension members 1 tensioned by each jack. good.

In addition, the above-mentioned embodiment is the sliding ram 8 of the jack A.
2, the case where jack B is fixed is explained, but instead of jack A and jack B being connected, for example, jack B is placed on a pedestal-like pedestal to receive the reaction force, and each jack A and B are placed separately. The tensioning material 1 may be tensioned by driving the tensioning member 1.

Effects of the Invention This invention has the above-described configuration, and since the tendons are tensioned by separate jacks for each group of tendons having different lengths, it is possible to apply tension stress uniformly to all the tendons. Therefore, it can be effectively used as a tension material as designed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the tensioning method for a removable anchor according to the present invention, FIG. 2 is a perspective view of the tension member and support ring, and FIG. 3 is a tensioning method for a conventional removable anchor. It is a longitudinal cross-sectional view of the state. A, B... Jacket, 1... Tension material, 2... Drilling, 3... Support ring, 4... Guide shaft, 5... Mortar, 6... Bearing plate, 7... Anchor head.

Claims (1)

[Scope of Claims] 1. When tensioning a plurality of tendons of different lengths at the same time, each tension member of different length constitutes a group of tendons, and the same number of tensioning jacks as the number of groups of tendons are used. corresponds to each tension material group, and the tension materials are tensioned by separate jacks for each tension material group.