JP2004211487A - Anchorage structure of tendon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anchorage structure for a tendon which does not concentrate local compressive stress due to bearing pressure at an anchoring portion in a concrete structure. <P>SOLUTION: The anchorage structure anchores a tendon 3 for introducing a tensile force to a concrete structure 4, and the end of the tendon is fixed to an anchoring cylinder 1 fixed to the concrete structure and tensile reaction is transmitted to the concrete structure through skin friction resistance between the anchoring cylinder 1 and the concrete structure. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tension member fixing structure for fixing a tension member used for constructing a prestressed concrete (PC) structure, manufacturing a precast member, or connecting the precast member.
[0002]
[Prior art]
The method of constructing the prestressed concrete structure can be classified into a pretensioning method and a post-tensioning method depending on whether the tension member is tensioned before constructing the concrete structure e or the tension member is tensioned after constructing the concrete structure e.
In the post-tension method, concrete is first poured into a mold in which a sheath tube f is arranged to construct a concrete structure e. Then, after the concrete has hardened, the PC steel wire d is inserted into the sheath tube f. The PC steel wire d is a tension member, and after being tensioned by the jack, the PC steel wire d is fixed to the end face of the concrete structure e. For fixing, a perforated rectangular plate material called a supporting plate a is arranged on an end face of the concrete structure e, and a fixing head b having a hole for inserting an end of the PC steel wire d is installed on the supporting plate a, A wedge c is bitten between the hole of the fixing head b and the PC steel wire d to fix the end of the PC steel wire d to the fixing head b.
[0003]
Here, a large compressive stress is generated in the concrete structure e on the back side of the supporting plate a to which the PC steel wire d is fixed by the supporting pressure. For this reason, the concrete structure e around the anchoring portion has a larger thickness than the intermediate portion where the PC steel wire d is only inserted because the thickness of the concrete structure e is increased for reinforcement and the reinforcing steel bars are arranged. Tend to increase. Also, in order to prevent the fixing portion from protruding from the outer surface of the concrete structure e, a recess for accommodating the fixing head b and the like is formed in advance, and fixing is often performed therein, which also increases the structure of the fixing portion. And cause complications.
[0004]
[Problems to be solved by the invention]
The above-described conventional tension member fixing structure has the following problems.
<B> When a tension reaction force acting as an anchoring load is applied to the end face of the concrete structure, a large amount of compressive stress is concentrated on the concrete structure around the anchoring portion. For this reason, it is necessary to increase the size of the structure around the fixing portion or to reinforce the structure.
<B> In many cases, the purpose of adopting a prestressed concrete structure is to reduce the thickness of the member and reduce the weight. For this reason, it is not desirable that the fixing section becomes large.
<C> When the fixing device used for fixing the tension member protrudes greatly from the end face of the concrete structure, it is often necessary to provide a depression in the end surface of the concrete structure so that the fixing device does not protrude.
[0005]
[Object of the invention]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a tension member fixing structure in which local compressive stress due to bearing pressure is not concentrated on a concrete structure of a fixing portion. And
It is another object of the present invention to provide a tension member fixing structure capable of making the shape of the concrete structure of the fixing portion as small as possible and having a simple structure.
Further, it is another object of the present invention to provide a tensioning material anchoring structure that hardly requires reinforcement of a concrete structure around the anchoring portion.
The present invention achieves at least one of these objects.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a tensioning material fixing structure of the present invention is a tensioning material fixing structure for fixing a tensioning material for introducing a tension into a concrete structure, wherein the concrete structure Fixing the end of the tension member to the fixing cylinder fixed to the fixing structure, and transmitting a tension reaction force to the concrete structure via a peripheral frictional resistance between the fixing cylinder and the concrete structure. It is a structure characterized by the following. Here, a wedge is used to fix the tension member to the fixing cylinder, and the wedge is a low elastic wedge made of a material having a smaller elastic coefficient than the tension member, and is provided at a plurality of positions in the axial direction. The tendon can be fixed. A wedge may be used to fix the tension member to the fixing cylinder, and a tooth-shaped wedge having a plurality of protrusions may be used as the wedge.
[0007]
Also, a tensioning material fixing structure for fixing a tensioning material for introducing a tension to a concrete structure, wherein an end portion of the tensioning material is attached to an exposed end surface of a fixing cylinder fixed to the concrete structure. The fixing device is mounted thereon, and the tension reaction force is transmitted to the concrete structure through frictional friction between the fixing cylinder and the concrete structure.
[0008]
Further, in the above-described tension member fixing structure, a convex portion or a concave portion may be provided on the outer peripheral surface of the fixing cylinder. Further, a low elastic layer made of a material having a smaller elastic coefficient than the fixing cylinder may be interposed between the outer peripheral surface of the fixing cylinder and the concrete structure. Further, a flexible protruding piece may be provided on the outer peripheral surface of the fixing cylinder.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
<A> Scope of application The fixing structure of the tension member 3 of the present invention can be applied in various situations in which the tension member 3 that has been pulled and tensioned is fixed.
The most suitable is a case where the concrete structure 4 is used for fixing when the concrete structure 4 is made into a prestressed concrete structure. Also in this case, an inner cable system in which the tendon 3 is arranged inside the concrete structure 4 or a fixing stand provided with the tendon 3 arranged outside the concrete structure 4 and protruded from the concrete structure 4 It can be applied to both of the external cable type in which the tension member 3 is fixed to the outside. Here, the prestressed concrete structure includes a structure constructed on site, a precast member manufactured in a factory or the like.
Further, also in the case where a plurality of precast blocks are tightly joined by the tendon 3, the tendon fixing structure of the present invention can be adopted.
[0011]
<B> Tensioning material Tensioning material 3 is a material that is tensioned by being pulled by a jack or the like.
Known materials such as a PC steel wire, a PC steel stranded wire, a PC steel rod, and a fiber reinforced plastic wire such as aramid fiber can be used for the tension member 3.
The tendon material 3 is placed inside the concrete structure 4 or the like by inserting it into a sheath tube 5 that has been placed in advance. The sheath tube 5 is a known member arranged for the purpose of forming a hole into which the tendon 3 is inserted, and may be any material having a strength enough to hold the hole in the concrete structure 4.
[0012]
<C> Fixing cylinder The fixing cylinder 1 is a member that transmits the tension reaction force of the tension member 3 to the concrete structure 4. The fixing cylinder 1 is disposed inside the concrete structure 4 and is fixed by the binding force of the concrete. For this reason, the stress generated in the fixing cylinder 1 is transmitted to the concrete structure 4 via the peripheral frictional resistance with the surrounding concrete. For this reason, since the stress concentration is reduced when the outer peripheral area of the fixing cylinder 1 is large, it is preferable to use a long fixing cylinder 1. As long as the fixing cylinder 1 has the same outer shape as the sheath tube 5, it is not necessary to particularly increase the shape of the concrete structure of the fixing section as in the related art.
The fixing cylinder 1 has only to be a hollow structure through which the tension member 3 can be inserted, and a cylindrical, frusto-conical, or square cylinder can be used. The fixing cylinder 1 is formed of a material that is not broken or easily deformed by a tension reaction force acting in the axial direction. For example, castings, steel materials, ceramics, and the like can be used as materials.
Protrusions 11 are provided on the outer periphery of the fixing cylinder 1 at predetermined intervals in the axial direction, for example. With such a structure, the adhesive force with the concrete structure 4 can be increased.
[0013]
Further, a low elastic layer 12 made of a material having a smaller elastic coefficient than the fixing cylinder 1 can be provided on the outer periphery of the fixing cylinder 1. When a material is loaded on a rigid material having a large elastic coefficient, stress may be concentrated near the loading portion. In the fixing cylinder 1 of the present invention, it is preferable to disperse the stress in the entire region and minimize the concentration of stress on the concrete structure 4 as much as possible. For this reason, for example, by providing the low elasticity layer 12, the fixing load is dispersed over the entire area of the fixing cylinder 1. The operation of the low elastic layer 12 will be described later.
There is also a method of providing a flexible protruding piece 13 on the outer periphery of the fixing cylinder 1 and deforming the protruding piece 13 to avoid stress concentration. This method will also be described in detail in an embodiment described later.
Further, the concrete structure 4 can be reinforced by arranging a spiral reinforcing bar around the fixing cylinder 1 as necessary.
[0014]
Embodiment 1
A fixing structure of a tension member using a fixing cylinder 1a provided with convex portions 11 at predetermined intervals in the axial direction on the outer peripheral surface will be described (see FIG. 1).
After disposing the fixing cylinder 1a near the end face of the concrete structure 4, concrete is cast to integrate the fixing cylinder 1a with the concrete structure 4.
Then, the tension member 3 is passed through the sheath tube 5 and the fixing cylinder 1a, and both ends or unfixed ends of the tension member 3 are tensioned by jacks. A wedge 2a is driven into the mouth of the fixing cylinder 1a whose inside is formed in a mortar shape, and the tensioned material 3 is fixed to the fixing cylinder 1a.
In a configuration in which the concrete structure 4 is not directly supported as shown in FIG. The power is transmitted to the concrete structure 4 by the frictional resistance of the peripheral surface with the concrete. Therefore, the fixing load of the tension member 3 is dispersed and transmitted to the periphery of the fixing cylinder 1a, and receives compressive force intensively as in the case where the conventional supporting plate a is disposed on the end face of the concrete structure 4. Nothing. If no stress concentration occurs in the concrete structure 4, reinforcement of the concrete structure 4 around the fixing portion can be reduced or eliminated.
[0015]
Embodiment 2
In a second embodiment, an example will be described in which the ends of the tendon members 3 are not fixed locally but are dispersed and fixed (see FIG. 2). The structure of the outer peripheral surfaces of the fixing cylinders 1b and 1c can adopt the structure adopted in other embodiments.
In the second embodiment, in order to fix the end of the tendon 3 in a section having a width, a plurality of wedges is used, or a long wedge corresponding to the length of the fixed section is used.
For example, a plurality of low elastic wedges 2b made of a material having a smaller elastic coefficient than the tendon material 3 are arranged in the fixed section of the fixing cylinder 1b (see FIG. 2A). If the tension member 3 is fixed at a plurality of locations, the tension reaction force is transmitted for each of the fixed locations, so that the fixing force can be dispersed. Further, if the low elastic wedge 2b is used, the load can be divided into the low elastic wedges 2b arranged before and after the wedge is deformed. That is, even if a plurality of wedges are arranged, if one wedge is too effective, the tension member 3 is fixed only by the wedge, but by weakening the effect of each wedge, it is widely fixed. The load can be distributed. Here, when setting the wedge, a plurality of low-elastic wedges 2b can be connected by a steel rod or the like so that only the low-elastic wedge 2b arranged on the head is not pushed by the jack.
[0016]
Further, by using the long wedge 2, the same effect as the dispersion effect described above can be obtained. Since the long wedge 2 has a large contact area with the fixing cylinder 1c, the long wedge 2 can be dispersed and the load can be transmitted to the fixing cylinder 1c.
A plurality of projections are provided on the outer periphery of the long wedge 2 to form a tooth-shaped wedge 2c (see FIG. 2B). By forming the wedge surface in an irregular shape in this manner, only the protrusion comes into contact with the inner surface of the fixing cylinder 1c, and the load is transmitted from the contact portion, so that the fixing load can be dispersed.
[0017]
Embodiment 3
In a third embodiment, a tension member fixing structure in which the tension member 3 is fixed using a known fixing device 6 will be described (FIG. 3).
Conventionally, a wedge-type fixing device 6a in which a fixing head b provided with a through hole through which the tension member 3 is inserted and a wedge c is used (see FIG. 3A). The tension member 3 is fixed by the wedge fixing device 6a, and a tension reaction force is transmitted to the concrete structure 4 via the fixing cylinder 1d.
First, the concrete structure 4 is constructed so that the end surface of the fixing cylinder 1d is exposed from the end surface of the concrete structure 4. Then, a wedge-type fixing device 6a is installed on the exposed annular end surface of the fixing cylinder 1d. The tension member 3 is fixed to the wedge fixing device 6a, and a fixing load is transmitted from the contact surface between the wedge fixing device 6a and the fixing cylinder 1d to the inside of the fixing cylinder 1d.
This fixing structure is also applicable to the case where a known nut-type fixing device 6b is used, in which a bolt-type cover 31 having a thread groove at the end of the tendon material 3 is attached and a nut is fitted to perform fixing. 3 (b)).
[0018]
Embodiment 4
In a fourth embodiment, a structure for dispersing the tension reaction force transmitted to the fixing cylinder 1e over a wider range will be described. This structure can be applied to other embodiments.
FIG. 4 shows a fixing structure of the tendon material fixed on the end surface of the fixing cylinder 1e by fixing the tendon material 3 with the wedge fixing device 6a. A low elastic layer 12 coated with an epoxy resin or the like is provided on the outer periphery of the fixing cylinder 1e. When the method of transmitting the load in order from the end of the fixing cylinder 1e is employed as described above, stress is relatively likely to be collected on the outer periphery near the mouth of the fixing cylinder 1e. Therefore, if the low elastic layer 12 is provided on the outer periphery of the fixing cylinder 1e near the mouth, the tension reaction force is easily transmitted to the rear of the fixing cylinder 1e by deforming the low elastic layer 12. Since the low elastic layer 12 has a function of deforming and postponing the load, the low elastic layer 12 can be provided in an arbitrary range such as near the mouth of the fixing cylinder 1e, the upper half or the entire area.
FIG. 4 shows an embodiment in which the wedge-type fixing device 6a is used for fixing the tension member 3, but the fixing method is not limited to this, and the low elastic layer may be used in other embodiments. 12 can be provided.
[0019]
Embodiment 5
Similarly to the fourth embodiment, the fifth embodiment is a description of a structure for dispersing the tension reaction force transmitted to the fixing cylinder 1f in a wider range. This structure can also be applied in other embodiments.
For example, a plurality of flange-shaped projecting pieces 13 are provided on the outer periphery of the fixing cylinder 1f at intervals in the axial direction (see FIG. 5). The protruding piece 13 is preferably a plate-shaped one that easily bends when a load acts thereon, but may be provided with a protruding material made of a material having a small elastic coefficient and easily deformable, such as rubber. Further, it is preferable that the outer peripheral surface of the fixing cylinder 1f located between the projecting pieces 13 is made to have a configuration in which frictional resistance does not occur much by making the outer circumferential surface smooth or the like.
The force transmitted from the wedge fixing device 6a to which the tension member 3 is fixed in the axial direction of the fixing cylinder 1f is mainly supported by the protruding pieces 13. If the protruding piece 13 is a member having high rigidity, stress will be concentrated near the mouth of the fixing cylinder 1f. However, when the projecting piece 13 is deformed by the transmitted force, the force is also sequentially transmitted to the rear projecting piece 13.
Note that, as in the fourth embodiment, the fixing type of the tension member 3 is not limited to the wedge fixing device 6a.
[0020]
【The invention's effect】
Since the tensioning member fixing structure of the present invention is as described above, the following effects can be obtained.
<B> The tension reaction force is transmitted to the concrete structure through the frictional resistance of the peripheral surface of the fixing cylinder. For this reason, local compressive stress due to bearing pressure does not concentrate on the concrete structure.
<B> By arranging a fixing cylinder having the same outer shape as that of the sheath tube, the tension member can be fixed. For this reason, the shape of the concrete structure of the fixing portion can be made as small as possible, and the structure can be made simple.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of a tension member fixing structure according to the present invention.
FIG. 2A is a sectional view of an embodiment of a tension member fixing structure in which a plurality of low elastic wedges are arranged. (B) Sectional drawing of the Example of the fixing | fixing structure of the tension material which arrange | positioned the tooth type wedge.
FIG. 3A is a cross-sectional view of an embodiment of a tension member fixing structure in which a tension member is fixed by a wedge fixing device. (B) Sectional drawing of the Example of the tension material fixing structure which fixed the tension material with the nut type fixing tool.
FIG. 4 is a sectional view of an embodiment of a tension member fixing structure in which a low elastic layer is provided on the outer periphery of a fixing cylinder.
FIG. 5 is a sectional view of an embodiment of a tension member fixing structure in which a projecting piece is provided on the outer periphery of a fixing cylinder.
FIG. 6 is a sectional view of an embodiment of a conventional tension member fixing structure using a wedge fixing device and a support plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fixing cylinder 2 ... Wedge 3 ... Tendon 4 ... Concrete structure 5 ... Sheath tube

Claims (7)

A tensioning material anchoring structure for anchoring a tensioning material for introducing tension into a concrete structure,
An end of the tension member is fixed to a fixing cylinder fixed to the concrete structure, and a tension reaction force is applied to the concrete structure through a peripheral frictional resistance between the fixing cylinder and the concrete structure. Characterized by communicating to
Tensioning material anchoring structure. A wedge is used to fix the tension member to the fixing cylinder, and the wedge is a low elastic wedge made of a material having a smaller elastic coefficient than the tension member, and the tension member is provided at a plurality of positions in the axial direction. Characterized by fixing,
The fixing structure for a tendon according to claim 1. A wedge is used to fix the tension member to the fixing cylinder, and the wedge is a tooth-shaped wedge having a plurality of protrusions.
The fixing structure for a tension member according to claim 1. A tensioning material anchoring structure for anchoring a tensioning material for introducing tension into a concrete structure,
On the exposed end surface of the fixing cylinder fixed to the concrete structure, a fixing tool having an end of the tension member fixed thereto is placed, and a peripheral friction resistance between the fixing cylinder and the concrete structure is set. Transmitting a tension reaction force to the concrete structure through
Tensioning material anchoring structure. A convex portion or a concave portion is provided on an outer peripheral surface of the fixing cylinder.
The fixing structure for a tendon according to any one of claims 1 to 4. A low elastic layer made of a material having a smaller elastic coefficient than the fixing cylinder is interposed between the outer peripheral surface of the fixing cylinder and the concrete structure,
A fixing member for a tendon according to any one of claims 1 to 5. A flexible protrusion is provided on an outer peripheral surface of the fixing cylinder.
A fixing structure for a tendon according to any one of claims 1 to 6.

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