JPH04241907A - Tensioning method for pc steel material and disengagement-preventing tool used therefor - Google Patents

Abstract

PURPOSE:To prevent a PC steel material from being projected outward even in the case where a coupler joint connected to the PC steel material comes off when the PC steel material for pretension type prestressed concrete is tensioned. CONSTITUTION:A disengagement-preventing tool 1 consists of a vertically split cylindrical wedge 3 holding a PC steel material 10, a sleeve 2 whose inner surface is tapered, and which clamps the wedge, and a means 7 for shifting the sleeve in an axial direction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tensioning method for prestressed prestressed concrete steel such as pretension girders, and a pull-out prevention tool used therein.

0002

2. Description of the Related Art Pretension-type prestressed concrete girders and the like are manufactured using tension tables called abutments. The tension table is equipped with a perforated support plate at both ends, a plurality of stranded PC steel wires are inserted into the holes of the perforated support plate, and the stranded PC steel wires are fixed with a wedge-type grip on the outside of both support plates. The support plate at the end is pulled outward with a hydraulic jack, and the PC steel strands are tensioned to generate extremely high tension in the PC steel strands. A formwork is installed around the PC steel strands, concrete is poured into the formwork, and after curing and hardening, the hydraulic jack is released to introduce prestress into the concrete by the PC steel strands.

[0003] The PC steel stranded wire stretched between the tensioning tables is usually composed of a plurality of stranded wires connected in the middle with a connecting fitting (coupler joint). Above P
During tensioning work that tensions the wire from the C steel, a large tension is applied to the wire from the PC steel, so the wire from the PC steel may come out of the coupler joint. It is a safety issue because it flies outward at high speed.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for tensioning a prestressed steel material that solves the above-mentioned problems, and a pull-out prevention device used in the method.

[0005]

[Means for Solving the Problems] In the present invention, when tensioning PC steel for prestressed concrete using a pre-tension method, the PC steel This is a method for tensioning a PC steel material, which is characterized in that after installing a pull-out prevention device that prevents the PC steel material from being pulled out outward from the support plate, tension is applied to the PC steel material by pulling a tension table.

[0006] A pull-out prevention tool for suitably carrying out this method includes: a cylindrical vertical wedge that grips the prestressing steel material; a sleeve having an axial inner taper into which the outer diameter of the cylindrical vertical wedge is fitted; This is a tool for preventing pull-out of a PC steel material, which is characterized by being equipped with a shift device that moves this vertical wedge forward and backward in the axial direction of the sleeve.

[0007]

[Function] By carrying out the method of the present invention, even if the PC steel material slips out of the coupler joint, the PC steel material will not fly out from the support plate of the tension table, eliminating any safety problems. In addition, the pull-out prevention tool of the present invention releases the gripping force of the cylindrical vertical wedge, and when inserting the PC steel material into the hole of the support plate of the tensioning table, it is fitted onto the PC steel material and the PC steel material is inserted into the tensioning table. When secured to the support plate, the wedge is urged to grip the PC steel by operating the shift device to move the wedge forward in the axial direction within the sleeve, thereby causing the wedge to grip the PC steel. Therefore, the method of the present invention can be easily carried out by using this pull-out prevention device.

[0008]

[Embodiment] Fig. 1 is an overall longitudinal cross-sectional view showing a state in which a pull-out prevention device according to an embodiment of the present invention is attached to a PC steel material, and Fig. 2 is a B-
3 is a perspective view of the wedge forward and backward shift device 7. FIG. 4 shows an overall plan view of a pre-tension type prestressed concrete manufacturing apparatus. This device is equipped with a tensioning device 30 of the PC steel material at one end, a fixing device 40 at the other end, and a PC steel material 1
Set 0. A formwork 41 surrounding this PC steel material 10 is arranged, and concrete is poured into the formwork 41 with the PC steel material 10 under tension, and when the tension of the PC steel material 41 is released after curing and hardening, the concrete product is prestressed. will be introduced. The PC steel material 10 has a coupler joint 42 as required.
connected by.

The fixed end of the PC steel material 10 is attached and fixed to the fixing plate 43 of the fixing device 40, and the tensioning end is attached to the support plate 11 of the tensioning device 30. As shown in FIG. 5, the support plate 11 is connected to a tension plate 31 via a tension rod 32, and the tension plate 31 is pushed to the right in FIG. It will be done. The tension jack 33 is driven by a hydraulic pump 35. Therefore, the PC steel material 10 is tensioned via the support plate 11.

The process of attaching the PC steel material 10 to the support plate 11 will be explained with reference to FIG. FIG. 1 is a cross-sectional view of a portion where a PC steel material 10 passes through a support plate 11. A formwork is placed on the right side in the figure, and the support plate 11 is pulled to the left in the figure by a tension jack. Before inserting the PC steel material 10 into the hole of the support plate 11 from the right side in FIG. It is inserted into the hole 13 of the support plate 11, and then the outer grip 12 is fitted onto the outside. Next, PC steel material 1
The outer grip 12 is fixed to the outer surface 14 of the support plate 11 by pulling it one by one to the left in FIG. The outer grip 12 contacts the outer surface 14 of the support plate 11 and
The tension force of the C steel material 10 is supported by the support plate 11. Next, insert the pull-out prevention device 1 onto the inner surface 1 of the support plate 11 as much as possible.
5 side, and operate the wedge shift device 7 to press and fix the wedge against the taper of the sleeve.

The pull-out prevention tool 1 includes a cylindrical vertical split wedge 3 that grips a PC steel material 10, a sleeve 2 into which the tapered outer diameter of the vertical split wedge 3 is fitted, and a sleeve 2 to which the split wedge 3 is inserted.
It consists of a spring 5 that presses the split wedge 3 inward, and a shift device 7 that moves the split wedge 3 back from the sleeve 2. In this embodiment, the vertical wedge 3 is divided into three parts as shown in FIG. 2, but it may be divided into two to four parts. The vertical wedge 3 is pressed into the sleeve 2 by a spring 5, and grips the PC steel material 10 by the wedging action of the taper. The longitudinal wedge 3 is connected to a split flange 6 on the outside of the sleeve. An end metal fitting 4 is provided which serves as a seat for a spring 5 and an outer end face seat. A shift device 7 is interposed between the end metal fitting 4 and the split flange 6.

The shift device 7 pulls the vertical wedge 3 against the biasing force of the spring 5 to release it from the taper of the sleeve 2, thereby releasing the gripping force of the vertical wedge 3 on the PC steel material. An example is shown in FIG. The shift device 7 is interposed between the end metal fitting 4 and the split flange 6, and consists of two abutting rings 8 and 9. The rings 8 and 9 are movable relative to each other in the circumferential direction, and have irregularities on their contact surfaces.

[0013] By changing the contact portion of this unevenness, the ring 8
, 9 change their total thickness. This uneven change in thickness changes the distance between the end metal fitting 4 and the split flange 6, so
The taper positions of the vertical wedge 3 and the sleeve 2 are changed. The shift device 7 has the function of applying the spring 5 in the direction of pushing the wedge into the sleeve, and the function of releasing this bias. As illustrated in a perspective view in FIG. 3, the shift mechanism of the shift device 7 includes an axially movable ring such as ratchet teeth 22 and 24 that abuts against each other with a height difference between two rings 8 and 9. , handles 21, 2 to operate this
3 has been added.

After installing the pull-out prevention device 1, the support plate 11 of the tension stand is pulled by the hydraulic jack 33 and the PC steel material 10 is tensioned, so that even if the coupler joint 42 is pulled out, the PC The steel material 10 does not jump out from the support plate 11.

[0015]

Effects of the Invention By using the tensioning method for prestressing steel material, the simple pull-out prevention device, and the use of the present invention, it is possible to completely prevent the prestressing steel material from jumping out from the support plate. The pull-out prevention device of the present invention can be easily attached to a PC steel material, contributing to improved safety.

[Brief explanation of the drawing]

FIG. 1 is an overall longitudinal cross-sectional view showing an attached state of an embodiment of a pull-out prevention device of the present invention.

FIG. 2 is a BB arrow view of the apparatus in FIG. 1;

FIG. 3 is a perspective view of an example of a shift device.

FIG. 4 is an overall plan view of a pretension-type prestressed concrete manufacturing apparatus.

FIG. 5 is an explanatory diagram of a support device for a tension table of a prestressed concrete production device.

[Explanation of symbols]

1 Pull-out prevention device 2 Sleeve 3 Wedge 5 Spring 7 Shift device 8, 9 ring 10 PC steel material 11 Support plate 12 Outside grip 13 holes 30 Tension device 40 Fixed plate 41 Formwork 42 Coupler joint

Claims (2)

[Claims] Claim 1: When tensioning prestressed concrete prestressed concrete using the pretension method, the prestressed steel is inserted into the support plate of the tension table, and the formwork side part of the prestressed steel is pulled outward from the support plate. A method for tensioning a prestressed steel material, which comprises: attaching a pull-out prevention tool to prevent the prestressing steel material from coming out, and then pulling the tension table to apply tension to the prestressed steel material. 2. A cylindrical vertical wedge for gripping a prestressing steel material, a sleeve having an axial inner taper into which the outer diameter of the vertical wedge is fitted, and a shift for moving the wedge back and forth in the axial direction of the sleeve. A PC characterized by being equipped with a device.
A device to prevent steel from being pulled out.