JP7299944B2 - Prestressed concrete manufacturing method and manufacturing apparatus - Google Patents

Description

The present invention relates to a prestressed concrete manufacturing method and manufacturing apparatus characterized by a method of introducing tension to prestressed concrete tendons when a fiber rope is used as a tendon to apply prestress to the prestressed concrete. .

In prestressed concrete (hereinafter also simply referred to as "PC"), PC steel is generally used as a tendon for introducing tension.
On the other hand, a technique using a nonmetallic rope-like member as a tendon has also been developed.
For example, Patent Literature 1 below discloses a technique in which a tendon made of a rope-like member is wound around a pulley or the like outside a concrete formwork and arranged while being folded back inside the formwork.

JP 2015-168091 A

However, the invention described in Patent Document 1 has at least one of the following problems.
(1) The tendon may be damaged by the contact of the aggregate contained in the placed concrete with the tendon, and the tendon may be cut when the tension force is applied.
(2) When trying to fix the tendon by tying it, a large load is locally applied to the knot of the tendon, and the tendon may be cut with a small load.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a means capable of more preferably introducing a tension force when a non-metallic rope is applied as a tendon used in prestressed concrete.

The present invention, which has been made to solve the above-mentioned problems, arranges a plurality of rows of tendons in the form by stretching the tendon made of a non-metallic rope while folding it with a folding tool provided outside the form. A method for producing prestressed concrete comprising: (A) a step of fixing the end of the tendon to a tension introducing tool; ( C ) applying tension to the tendon while measuring the tension generated at the ends of the tendon; and a step of providing a protective surface for preventing damage.
In the present invention, in ( C ) above, the protective surface can be provided by applying a liquid agent to the tendon.
In addition, the present invention can also be configured such that the protective surface contains particulate matter.
Further, in the present invention, in the above (A), a loop may be formed by winding the ends of the tendons around the tension introduction tool in a figure 8 shape.
Further, in the present invention, in (A) above, the ends of the tendon can be knitted into the tendon to be integrated.
In addition, the present invention is a prestressed concrete manufacturing apparatus using a tendon made of a non-metallic rope, which is arranged in a formwork and outside the formwork, and by folding back the tendon, A folding tool capable of arranging a plurality of rows of tendons in the formwork, a tension introduction tool capable of pulling the tendons while fixing the ends of the tendons outside the formwork, and the plurality of rows of tendons It is characterized by comprising at least one load cell capable of measuring the tension generated in the entire tendon and the other load cell capable of measuring the tension generated at the end of the tendon.

According to the present invention, at least one of the effects described below can be obtained.
(1) By stretching the tendon while folding it back, it is possible to suppress a large load from being locally applied to the tendon and reduce the risk of the tendon breaking with a small load.
(2) By providing a protective surface on the tendon surface, it is possible to prevent damage due to contact with aggregates in the placed concrete.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the overall configuration of a PC specimen manufacturing apparatus for carrying out the method of introducing tension according to the present invention; Schematic which shows the fixing example of a tendon. The table|surface which shows the tensile test result of each experimental example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1> Overall configuration (Fig. 1)
FIG. 1 shows an example of a PC test piece manufacturing apparatus that implements the method of introducing tension according to the present invention.
In the manufacturing apparatus shown in FIG. 1, a tendon 10 is placed in a concrete formwork (hereinafter also simply referred to as "formwork A"), and the tendon 10 is folded back outside the formwork A and placed in the formwork A again. It has at least a folding tool 20 for pulling it in and a tension introducing tool 30 capable of pulling the fixed tendon 10 while fixing the end of the tendon 10 outside the formwork A. .
Details of each element will be described below.

<2> Tendon (Fig. 1)
The tendon 10 is a member for introducing prestress to concrete after hardening.
In the present invention, a non-metallic rope material is used for the tendon 10 .
In the present invention, non-metal includes at least aramid, vinylon, polyethylene and polyester.
Further, in the present invention, the rope material is a cord-like member having flexibility to the extent that it can be folded back with a folding tool 20 described later.
In this embodiment, a continuous fiber rope made of aramid fiber is used as the tendon 10 .

<3> Formation of a protective surface on tendon The tendon 10 may be damaged due to wire breakage or the like caused by contact with aggregates contained in the placing concrete.
In that case, it is desirable to form a protective surface on the tendon 10 and prevent the aggregate from directly contacting the tendon 10 with the protective surface.
As a method for forming the protective surface, a method of applying a liquid agent such as a resin, paint, or adhesive that can be expected to have a protective effect on the surface of the tendon 10, a method of attaching particulate matter to the surface via an adhesive or the like, or Any combination of these, and so on.
It should be noted that the work of forming the protective surface does not matter before or after the introduction of the tension force, and the optimum execution time may be appropriately selected by experiment or the like.

An adhesion improving agent that improves the adhesion of concrete to the prestressing tendon 10 can also be used as the liquid used for forming the protective surface.
Inorganic materials such as silica sand and alumina powder can be used as the particulate material used to form the protective surface, and the particulate material may be pre-mixed with the liquid agent to be applied.

<4> Folding Tool (Fig. 1)
The folding tool 20 is a member for folding back the tendon 10 outside the formwork A and deploying the tendon 10 inside the formwork A again.
As the folding tool 20, a single pipe, a pulley, or the like around which the tendon 10 can be wound can be used.
In FIG. 1, the tendons 10 are arranged in a five-row configuration in the form A by providing two folding tools 20 at each end outside the form and folding the tendons 10 alternately.
Further, when the folding tool 20 itself is configured to be rotatable, the tension of the tendon 10 before and after folding can be adjusted as if the tension of a stringed instrument is adjusted by this rotating operation.

<5> Tension introduction tool (Fig. 1, Fig. 2)
The tension introducing tool 30 is a jig for introducing tension to the tendon 10 .
In this embodiment, the tension force introducer 30 is provided on one end side of the formwork A (right side of the paper surface in FIG. 1), a jack 31, a reaction force body 32a provided at one end of the jack 31, and a movement provided at the other end of the jack 31 The body 33a, the fixture 34a provided on the moving body 33a, the displacement holder 35 provided between the reaction body 32a and the moving body 33a, and the other end side of the formwork A (left side of the paper in FIG. 1) It is composed of a reaction force body 32b, a moving body 33b, a fixture 34b, and two load cells 36 (36a, 36b) provided.
The reaction force body 32a (32b) and the moving body 33a (33b) are made of steel having a hole through which the tendon 10 can be inserted.
The displacement holder 35 uses a jack base that can be expanded and contracted by screwing.

<6> Load cell (Fig. 1)
Of the two load cells 36 provided on the other end side of the formwork A, the load cell 36a provided between the reaction force body 32b and the moving body 33b measures the tension of the five rows of tendons 10 as a whole, A load cell 36b provided between the fixing 34b measures the tension generated at the end of the tendon 10. As shown in FIG.
With this configuration, when the value obtained by multiplying the tension measured by the load cell 36b by the number of tensions is different from the tension measured by the load cell 36a, each folding tool 20 is rotated to adjust them so that they are the same. By doing so, the tension can be made uniform.

<7> Fixer (Fig. 2)
The anchor 34 is a member for anchoring the tendon 10 .
An example of a method of fixing the tendon 10 by the fixing device 34 will be described below.

<7.1> Fixing Method 1: Loop Knot [Fig. 2(a)]
In this method, the ends of the tendons 10 are tied to the fixture 34 so as to form a loop.
With this configuration, the friction of the tendon 10 is increased by reciprocating the tensile loads acting on the tendon 10, the tendon 10 is prevented from slipping, and the ends of the tendon 10 can be firmly fixed. .
In FIG. 2(a), the fixture 34 is composed of two steel pipes spaced apart from each other, and at least one loop B is formed by winding the tendon 10 around the two steel pipes in a substantially figure-of-eight shape. The end of the prestressing tendon 10 after forming the loop B is wound around a separate steel bar and fixed by a method such as tying.

In addition, the present invention is not limited to the configuration shown in FIG.
Further, although the fixing effect can be expected to be improved as the number of loops B increases, in the present invention, at least one loop B may be provided.

<7.2> Fixing Method 2: Weaving [Fig. 2(b)]
In this method, the ends of the tendon 10 are folded back and woven into the tendon 10 to be fixed.
In FIG. 2(b), the fixture 34 is made of a single steel pipe, and after the tendon 10 is wound around this steel pipe, the end of the tendon 10 and the tendon 10 at the tip of the folded back are woven together, A braided portion C of a predetermined length is formed.
With this configuration, the end portion of the tendon 10 can be firmly fixed.

Ice splicing or the like can be used to form the braided portion C. FIG.
When the tendon 10 is woven, the tendon 10 may be woven in a form conforming to the twist of the rope constituting the tendon 10, or may be woven in a form in which a further twist is added to the twist of the rope.

<8> Experimental example (comparison of fixing methods) (Fig. 3)
Tensile tests were performed on the same tendon 10 using various fixing methods.
In the tensile test, the tendon 10 is passed through the center holes of the jack 31 and the load cell 36, and fixed to a steel bar that receives a reaction force at the tip by various fixing methods. A force was applied, and the maximum load was measured until it slipped, slipped out, and broke.
・Experimental example 1: A tendon is fixed to a steel pipe with a double knot.
・Experimental example 2: A tendon is fixed to a steel pipe with two knots.
・Experimental example 3: A tendon is wound around two steel pipes in a substantially figure 8 shape and fixed.
・Experimental example 4: The end of the tendon wound around the steel pipe is woven and fixed according to the twist of the tendon.
・Experimental example 5: The end of the tendon wound around the steel pipe is woven and fixed so as to add a twist to the twist of the tendon.
・Experimental example 6: The end of the tendon wound around the steel pipe is fixed with a wire grip.
・Experimental example 7: The end of the tendon was fixed with a single-strand grip coated with epoxy resin.
FIG. 3 shows the results of the tensile test.

As shown in FIG. 3, in Experimental Examples 1 and 2, which were fixed by double knots and double knots, and in Experimental Example 6, in which the end of the tendon wound around the steel pipe was fixed by wire flipping, the maximum load remained low, Good results were obtained in that Experimental Examples 3, 4, and 5 were able to obtain a maximum load superior to Experimental Examples 1 and 2.
In addition, Experimental Examples 3 and 5 were able to obtain even better results assuming that no slippage occurred and even fracture occurred.
Therefore, in the present invention, even in the mode in which the tendon 10 is fixed by tying or knitting without using mechanical fixing as in Experimental Example 7 (especially Experimental Examples 3 to 5), the tension is good. It was found that it can be introduced into
In carrying out the method according to the present invention, it is needless to say that any method can be selected from the above-described Experimental Examples 1 to 7 and other fixing methods at sites where high tension setting is not required. neither.

<9> Other configuration examples (1)
The present invention is not only applicable to configurations in which tendons 10 are arranged in only one direction, as shown in FIG.
That is, the method of forming a protective surface on a tendon and fixing the tendon according to the present invention is capable of introducing prestress in the vertical and horizontal directions of concrete by arranging the tendon 10 so as to fold back in the vertical and horizontal directions. Configuration can also be applied.

<10> Other configuration examples (2)
As shown in FIG. 1, the present invention only has a configuration in which a single tendon 10 is stretched while being folded back outside the formwork A, so that a plurality of rows of tendons 10 are arranged inside the formwork A. Not applicable.
That is, the method of forming a protective surface on a tendon and fixing the tendon according to the present invention can also be applied to the case where a plurality of tendons 10 made of non-metallic ropes are individually arranged and a tension force is introduced to each. can do.

10 Tension material 20 Folding tool 30 Tension force introduction tool 31 Jack 32 Reaction force body 33 Moving body 34 Fixing tool 35 Displacement holding tool 36 Load cell A Formwork B Loop C Weaving part

Claims (6)

A method for producing prestressed concrete in which a plurality of rows of tendons are arranged in the formwork by stretching the tendons made of non-metallic ropes while folding them back with a folding tool provided outside the formwork,
(A) fixing the end of the tendon to a tension introduction tool;
(B) introducing tension to the tendon while measuring the tension generated in the entire tendon of the multi-row structure and the tension generated at the end of the tendon;
( C ) providing a protective surface for preventing damage on the surface of the tendon, regardless of whether the tension force is applied to the tendon;
characterized by having at least
A method for producing prestressed concrete. In the above ( C ), the protective surface is provided by applying a liquid agent to the tendon,
The method for producing prestressed concrete according to claim 1. characterized in that the protective surface contains particulate matter,
The method for producing prestressed concrete according to claim 1 or 2. In the above (A), a loop is formed by winding the end of the tendon around the tension introduction tool in a figure 8 shape,
The method for producing prestressed concrete according to any one of claims 1 to 3. In the above (A), the end of the tendon is woven into the tendon to integrate it,
The method for producing prestressed concrete according to any one of claims 1 to 4. An apparatus for manufacturing prestressed concrete using tendons made of non-metallic ropes,
a formwork;
A folding tool that can be arranged outside the formwork and folds the tendon so that a plurality of rows of tendons can be arranged in the formwork;
a tension introducing device capable of pulling the tendon while fixing the ends of the tendon outside the formwork;
one load cell capable of measuring the tension force generated in the entire tendon of the multi-row configuration;
the other load cell capable of measuring the tension generated at the end of the tendon;
characterized by comprising at least
Equipment for manufacturing prestressed concrete.

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