JPS59217831A - Concurrent tension of tensing members of different lengths - Google Patents

Abstract

PURPOSE:To give uniform tension stress to tension members of different lengths by a method in which tension members are grouped into ones of different lengths, and each group is tensed by respectively separate jacks. CONSTITUTION:Plural tension members 1 each of which is covered with a sheath 11 are folded at their middle portions and inserted into an excavated pit 2 where plural guide shafts 4 are fixed. The bent portions 12 of the tension members 1 are hooked on the guide shafts 4, and cement mortar 5 is poured into the pit 2 and hardened for fixation. The tension members 1a and 1b coupled with the guide shafts 4a and 4b are held and tensed by means of different jacks A and B for the members of different lengths. Uniform tension stress can thus be given to all of the tension members to enable the tension members to be used effectively as designed.

Description

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

BACKGROUND ART Conventionally, when tension members of different lengths are simultaneously tensioned by a single jack to give the same tension force, there has been a problem in that the tension stress becomes non-uniform. For example, a method for tensioning tendons in a U-turn removable anchor as shown in FIG. 6 will be explained.

That is, in FIG. 3, a guide shaft p is positioned in a direction perpendicular to the drilling direction of the hole m during drilling m, and an unbonding tendon r having a sheath attached to the outer periphery is bent in the middle, and the bending is moored to the guide shaft, tension material r positioned outside the drilling hole m is fixed under tension, and when removing, both ends are unfixed and one end is pulled to pull out the tension material r. It is.

In such a construction method, when a large number of tension members r are moored and tensioned to one guide shaft p, the guide shaft cannot withstand the tension force of the many tension members r, and the mortar filled around the guide shaft cannot withstand the tension. Cracks may occur in grout such as. Therefore, a method has been adopted in which a plurality of guide shafts p are appropriately spaced and positioned in the drilling m, and a plurality of tension members r are moored to each guide shaft p, so that the total tension is distributed 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 an appropriate distance J in the direction of the medium hole in the drilling hole m, so that the tension material r moored to each guide shaft p is The total length varies depending on the tension member r moored to the guide shaft p. Therefore, when all the 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 hole m of the guide shaft p can be sufficiently tensioned. However, the tension material r moored to the guide shaft p located deeper than the guide shaft p is longer in length, and if tensioned at the same time by the same jack, elongation will occur due to the longer length. It is impossible to apply the same tension force as the shorter tendon r. 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 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 In the method for simultaneously tensioning tendons of different lengths according to the present invention, the tendons of different lengths constitute a group of tendons,
The above object is achieved by associating the same number of tensioning jacks as the number of tensioning material groups with each tensioning material group, and tensioning the tensioning material with separate jacks for each tendon material group.

EXAMPLES Hereinafter, the present invention will be explained in detail based on examples 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 PO steel wire, PC steel, or P wire for use in the unpond 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 nine ring bodies 31 and 31 as shown in FIG. The guide shaft 4 is folded back and placed inside the bent portion 12 of the tension 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, the length of the tendons 1 is the same. Even if there are a plurality of tension members, each guide shaft 4 constitutes a tendon group.

A plurality of guide shafts 4 are provided in the drilling hole 2 at appropriate intervals in the drilling direction.
is fixed. That is, the tension material 1 is inserted into the hole 2 with the tip of the bent portion 12 hung on the guide shaft 4, and each guide shaft 4 is positioned at an appropriate distance in the direction of the hole in the hole 2, and Mortar 5 is injected into 2 and hardened to be fixed. Both ends of the tendon 1 are positioned outside the drilled hole 2.

A bearing pressure plate 6 is positioned on the outer periphery of the ground surface of the drilled hole 2, and a tendon insertion hole 71 is provided on the bearing pressure plate 6.
Anchor head 7 in which a wedge 72 is positioned
is placed.

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

Jacket A has a sliding ram 8 whose pulling head 81 is cylindrical.
It is attached to the anchor head Z side of No.2. A plurality of tendon insertion holes 83 are formed in the pulling head 81 , and both ends of the tendon 1 inserted through the tendon insertion holes 71 of the anchor head 7 are passed through the tendon insertion holes 83 . . The tendon 1a, which is moored to the guide shaft 4a located at the shallowest position in the drilled hole 2 of the tendon 1, is attached to a wedge 84 positioned in the tendon insertion hole 83 through which the tendon 1a is inserted.
to hold it. The tendon material 1b moored to the guide shaft 4b located at the back of the guide shaft 4a and the drilled hole 2 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. The tension material 1b moored to this jack BJ guide shaft 4b is gripped. The jack B has a pulling head 92 attached to the rear end of a sliding ram 91, and a tension material insertion hole 93 is formed in the blinking head 92. Both the tension materials 1a and 1b moored to the guide shaft 4a and the guide shaft 4b are inserted through the tension material insertion hole 93, and only the tension material 1b moored to the guide shaft 4b is held by the wedge 94. The tension material 1a that was gripped by jack A is not gripped by jack B.

Tension material 1a moored to each guide shaft 4a, 4b as described above
- Grip 1b with different jacks A and B for different guide shafts 4a and 4b, and drive the jacks A and B to tension it.

Each tension member 1a, 1b moored to each guide shaft 4a, 4b
If the number of screws is the same, the sliding rams 82 of each jack A, B
・By changing the pressure-receiving area of 91, each tension member 1a・
It is possible to apply the same tension to 1b. In other words, when tensioning material 1a and 1b moored to two guide shafts 4a and 4b are tensioned by two jacks A and H, jack A tensions tension material 1a moored to guide shaft 4a located at the shallowest position. The pressure receiving area of the sliding ram 82 is made twice the pressure receiving area of the sliding ram 91 of the other jack B.

The above two jacks A and B are used as in the embodiment described above.
Jack B is fixed on the sliding ram 82 of jack A, and pressure oil of the same pressure is fed to both jacks A and B. The jack A moves the pulling head 81 along with the sliding of the sliding ram 82.
The tension material 1a gripped by the wedge 84 is tensioned, and the jack B fixed to the sliding ram 82 is moved. Jacket B has a wedge 94 on the pulling head 92.
Since the tension material 1b is gripped by
The sliding of the sliding ram 82 tensions both the tension members 1a and 1b.

On the other hand, jack B uses the wedge 94 to tighten the tension material 1b.
When only the tension members 1a and 1b are held, the jack B only has to tension half the number of tension members 1a and 1b that are tensioned by the jack A, so the output of the jack B only needs to be half that of the jack A. The pressure receiving area of the sliding ram 82 is twice that of the other sliding ram 91, which means that even if the pressure of the supplied pressure oil is the same, the jack A is twice as large as the jack B due to the supply of pressure oil. It becomes possible to generate output automatically.

Therefore, although the jack A tensions all the tension members 1a and 1b, the jack B, which tensions only half of the tension members 1b, absorbs the difference in elongation caused by the difference 1 between the lengths of the tension members 1a and 1b. The sliding ram 91 slides, making it possible to apply the same tension force to the tendon material 1b as that to the tendon material 1a.

Therefore, the stroke of the sliding ram 910 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 may be multiplied by a positive number in proportion to the number of tendons 1 tensioned by the jacks.

By changing the pressure-receiving area of the sliding ram mentioned above, it is possible to equally apply the designed tension force to all the tension members 1. Even if the pressure of the pressure oil sent to each jack is multiplied by a positive number in proportion to the number of tension members 10 tensioned in each jack, and the pressure oil is sent to each jack from multiple pumps P, tension force is equally applied to each tension member 1. It is possible to
The explanation has been given on the case where the same number of tension members 1 are moored to each guide shaft 4 and the same tension force is applied to each tension member 1 when the tension members 1 are fixed to each guide shaft 4. If the number of tension members 1 is different, pressure oil may be supplied to each jack at a pressure doubled in proportion to the number of tension members 1 tensioned by each jack.

Further, in the above embodiment, the case where the jack B is fixed to the sliding ram 82 of the jack A is explained, but instead of connecting the jack A and the jack B, for example, the jack B is mounted on a pedestal-like mount to receive the reaction force. The tension member 1 may be tensioned by placing the tension member 1 on the tension member 1 and driving the jacks A and B separately.

Effects of the Invention This invention has the above-mentioned structure, and since the tension is tensioned by separate jacks for each group of tension members having different lengths, it is possible to uniformly apply tension stress to all the tension members. , it can be effectively used as a tensile material for design.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an embodiment of the tensioning method for a removable anchor according to the present invention in a state of construction, Fig. 2 is a perspective view of the tensioning 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: Jacketing, 1: Tensile material, 2: Drilling, 3:
・Support ring, 4. Guide shaft, 5. Mortar, 6. Bearing plate, 7. Anchor head. 1st Prisoner 2vA Figure 3

Claims (1)

[Claims] When tensioning a plurality of tension members of different lengths at the same time, the tension members of different lengths constitute a tension member group, and the same number of tensioning jacks as the number of tension member groups are used. Corresponding to each tendon group 1. Simultaneous tensioning method for tendons of different lengths, characterized by tensioning the tendons by separate jacks for each tendon group