JPH0425847Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a tensioning and fixing device for prestressed concrete, which tensions and fixes tensioning materials mainly made of fiber reinforced materials such as FRP and FRM. be.

(Conventional technology) FRP, which uses high-strength fibers such as glass fiber, carbon fiber, and aramid fiber, has excellent corrosion resistance and is attracting attention as a tension material for prestressed concrete.

Even when FRP is used as a tendon, as in the case of conventional steel materials for prestressed concrete, the ends of the tendon must be tension-fixed using a tensioning and fixing device.

As shown in FIGS. 5 and 6, a conventional tendon tension material for prestressed concrete in which a tendon material 4 is placed in a hole 3 formed in concrete 1 through a sheath 2 and is fixed in a tensioned state. - The fixing device 5 includes a grip 7 provided concentrically at the entrance of the hole 3 of the concrete 1 via a bearing plate 6, and a tension member 4 penetrating inside this grip 7.
It is formed of a plurality of wedge pieces 8 which are press-fitted into the grip 7 and surround the grip 7.

In addition, in order to prevent the tendon 4 from coming off, as shown in FIGS. 7 to 9, a concave and convex portion 9 is provided on the inner surface of the wedge piece 8 that contacts the tendon 4, in which concave and convex portions are alternately present in the rod axis direction. is being established.

(Problems to be Solved by the Invention) However, when tensioning and fixing the FRP tensioning material 4 using such a conventional wedge-type tensioning and fixing device 5, there is a problem that the tensioning material 4 tends to break near the device 5. There is a point. This may be due to the fact that the tendon 4 is reinforced only in the tensile direction (axial direction), so there are minute defects on the surface of the tendon and that it is weak against shearing force. In particular, in the wedge anchoring method, the distribution of bearing stress generated between each wedge piece 8 and the tendon material 4 is as shown in FIG. 10, and the bearing stress is concentrated at the tip of each wedge piece 8. There is. Further, the distribution of the axial force P generated in the tendon 4 is as shown in FIG. 11, and the force is greatest at the tip of the wedge piece 8 in the contact area. Therefore, the wedge piece 8 is in a state where it is easily broken at its tip.

Further, when the uneven portion 9 is provided on the inner surface of the wedge piece 8, as shown in FIG. .

Therefore, the slippage within the tendon 4 due to the action of the above force develops sequentially from the tip of the wedge piece 8 backward, and eventually the entire rod surface layer is scraped off.
The tension material 4 will be pulled out.

The object of the present invention is to provide a tensioning and anchoring system for prestressed concrete that can alleviate the bearing stress generated at the tip of the wedge piece and prevent the rod from coming off.

(Means for solving the problem) The configuration of the present invention to achieve the above purpose is as follows:
A tendon tensioning and fixing device for prestressed concrete in which a tendon penetrating through a grip is tensioned and fixed by a plurality of wedge pieces press-fitted into the grip surrounding the tendon. The base side of the inner surface in contact with the tendon is provided with a concave and convex portion in which unevenness is alternately present in the axial direction of the tendon, and the other portion of the inner surface of each wedge piece in contact with the tendon is smooth when viewed in the axial direction of the tendon. The present invention relates to a tendon tensioning and fixing device for prestressed concrete, characterized in that the smooth portion is provided with a plurality of slits that are intermittent in the circumferential direction and continuous in the longitudinal direction.

(Function) According to such a device, when looking at the tip of the wedge piece where bearing stress tends to concentrate, the inner surface of the wedge piece is smooth when viewed in the rod axial direction, and the screw thread seen in the conventional structure is smooth. Shearing of the tendons due to piles is prevented. Furthermore, although the tendons are softer and more easily deformed than steel materials for prestressed concrete, since the smooth portions are provided with slits along the longitudinal direction, the restraint due to deformation of the tendons can be relaxed. Further, since the inner surface on the base side is provided with an uneven portion, the tension member 4 can be prevented from being pulled out by the crests of the uneven portion biting into each other. At this location, the bearing stress is small, so the negative impact of the mountain digging is not a problem.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3. Note that portions corresponding to those in FIGS. 5 to 9 described above are designated by the same reference numerals.

In the prestressed concrete tensioning and fixing device of this embodiment, the tensioning material 4 of each wedge piece 8 is
A screw-shaped uneven portion 9 in which unevenness is alternately present in the axial direction is provided on the base side of the inner surface that is in contact with. The other part of the inner surface of each wedge piece 8 that is in contact with the tension material 4 is a smooth part 10 when viewed in the axial direction, and this smooth part 10 has a plurality of slits that are intermittent in the circumferential direction and continuous in the longitudinal direction. 11 are provided.

2 and 3 using such a wedge piece 8.
As shown in the figure, when the tension material 4 is tensioned and fixed, at the tip of each wedge piece 8 where bearing stress tends to concentrate,
Since the inner surface is a smooth part 10, it is different from the conventional seventh part.
Shearing of the tendon material 4 due to the thread-like peaks seen in the structures shown in FIGS. 9 to 9 is prevented. In addition, tension material 4
is softer and more easily deformed than steel for prestressed concrete, so by providing the slits 11 along the longitudinal direction in the smooth portion 10, the restraint on the deformation of the tendon 4 can be made gentler. As a result, the bearing stress generated at the tip of the wedge piece 8 is alleviated, and the axial distribution of the bearing stress acting on the circumferential surface of the tendon 4 becomes as shown in Fig. 4, which is more averaged than before. be done.

However, if the inner surface of the wedge piece 8 is smooth as a whole, the frictional force between the wedge piece 8 and the tension material 4 will be insufficient, and the tension material 4 will be pulled out. This is prevented by providing a screw-like uneven portion 9 on the inner surface of the base.

At the tip of this threaded uneven portion 9, frictional force due to bearing stress acts between the tension material 4 and the wedge piece 8, so the rod axial direction force decreases between them, and the In the concavo-convex portion 9, an axial force sufficient to scrape off the rod surface due to the thread-like ridges is no longer generated.

In addition, the tensioning and fixing mechanism for prestressed concrete tendons according to the present invention is not limited to the above-mentioned FRP rod tendons;
A bundle of fiber materials fixed with molten metal called re-inforced metal, or
It can be applied in exactly the same way to multiple strands of FRP and FRM, and even to strands of high-strength fiber materials twisted together in a search pattern.

(Effect of the invention) As explained above, in the tensioning and fixing device for prestressed concrete tendons according to the invention, of the inner surface of each wedge piece that comes into contact with the tendon, the tip side excluding the base is smooth when viewed in the axial direction. Since it is a department,
Although this is a part where bearing stress tends to concentrate, the stress concentration can be alleviated and shearing of the tendon material can be prevented. In addition, tendons are softer and more easily deformed than steel materials for prestressed concrete, but since the smooth part has slits in the longitudinal direction, the restraint caused by deformation of the tendon can be alleviated, and the circumferential surface of the tendon can be easily deformed. The acting bearing stress can be averaged out. Further, since the proximal inner surface of each wedge piece is provided with concave and convex portions arranged alternately in the axial direction, the FRP rod can be prevented from being pulled out by the bite. Since the position where the threaded uneven portion is provided has the smallest bearing stress, there is no risk that the surface of the tendon material will be scraped off by the threaded ridge.

[Brief explanation of drawings]

Figures 1A to 1D show an example of a wedge piece used in the device of the present invention, with Figure A being a front view and Figure B
is an inside view, Figure C is a right end view of Figure B, Figure D is a right end view of Figure B.
2 and 3 are front views and longitudinal sectional views of the device of this embodiment, and FIG. 4 is an explanatory diagram of the axial force distribution of the tendon in the device of this embodiment. , FIG. 5 and FIG. 6 are a front view and a vertical cross-sectional view of a conventional device, FIG. 7 is a front view of a conventional wedge piece, FIG. 8 is an inside view thereof, and FIG. Enlarged view of the section,
Fig. 10 is an explanatory diagram showing the distribution of bearing stress acting on the tendon by a conventional wedge piece, Fig. 11 is an explanatory diagram of the distribution of axial force acting on the tendon in the case of the conventional device, and Fig. 12 FIG. 2 is a longitudinal cross-sectional view showing the state of contact between the tension member and the wedge piece. 1... Concrete, 3... Hole, 4... FRP
Rod, 5... Tension/fixing device, 7... Grip, 8... Wedge piece, 9... Screw-shaped uneven part, 10
...Smooth part, 11...Slit.

Claims (1)

[Scope of utility model registration request] A tendon tensioning and fixing device for prestressed concrete in which a tendon penetrating through a grip is tensioned and fixed by a plurality of wedge pieces press-fitted into the grip surrounding the tendon. The base side of the inner surface in contact with the tendon is provided with a concave and convex portion in which unevenness is alternately present in the axial direction of the tendon, and the other portion of the inner surface of each wedge piece in contact with the tendon is smooth when viewed in the axial direction of the tendon. Department,
A tendon tensioning and fixing device for prestressed concrete, characterized in that the smooth portion is provided with a plurality of slits that are intermittent in the circumferential direction and continuous in the longitudinal direction.