JP3198642B2 - Prestressed concrete board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed PS (prestressed) concrete plate.

[0002]

2. Description of the Related Art In recent years, in the construction field, labor shortages and the aging of workers have become problems. Next, prefabricated building members and mechanized construction (robotization) are performed. In addition, since a further effect of labor saving can be expected by reducing the weight of the members, in the case of exterior materials (curtain walls), by adding a reinforcing material such as carbon fiber to concrete, the bending strength is increased and the plate thickness is reduced. In addition, efforts have been made to reduce the weight.

[0003] The PC (precast) plate is one of the important technologies for achieving the above-mentioned object, and recently,
In order to compensate for the weakness of concrete against tensile force, a so-called PS (prestressed) concrete plate to which a compressive force is applied in advance with a tension material such as a steel wire has been used.

As a technique for introducing prestress into this PC board, conventionally, as shown in FIG. 4, a plurality of tendons 12 are arranged in a mold 11 in parallel with each other, and these tendons 12 are provided.
A pretensioning method in which concrete is poured into the formwork 11 while a tensile force (arrow P) is applied to the formwork 11;
There is known a post-tension system in which concrete is poured into the inside and a tension is applied to the tendon 12 after the concrete is hardened.

[0005]

However, in the conventional prestressing technique, a large number of tendons are required, so that the pretensioning method or the post-tensioning method requires a lot of labor for the tensioning work. And there was a problem in productivity. In addition, since the tendon members are arranged linearly in parallel with each other, there is a problem that the crossing direction of the tendon members is poor in resistance to out-of-plane bending and in-plane shear force.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a PS having excellent structural performance capable of improving productivity by reducing labor of tension work for introducing prestress.
It is to provide a concrete board.

[0007]

In order to solve the above-mentioned problems, a PS concrete plate according to a first aspect of the present invention provides a flexible tension member at a required position in a mold by forming a parallelogram substantially similar to the mold. It is arranged in advance, and its free end is extended to the outside of the form on two adjacent sides of the form, and after casting concrete, prestress is applied by applying tension to the tendon from the free end. It has the introduced configuration (claim 1).

Further, in the PS concrete plate according to the second invention, a flexible tendon is preliminarily arranged at a required position in the mold as a parallelogram substantially similar to the mold, and its free end is formed in the mold. On the two adjacent sides, extend outside the formwork,
Prestress is introduced by casting concrete while tension is applied to the tendon from the free end (claim 2).

[0009]

The first invention is a PS concrete plate to which prestress is introduced by a post-tension system, and the second invention is a pre-stress system. The number of flexible tendons used is basically one for the required area, and only one tensioning operation is required, so that the productivity is greatly improved as compared with the conventional tensioning method.

[0010] Specifically, the flexible tendon is preliminarily arranged at a required position in the mold as a parallelogram substantially similar to the mold, and its free end is formed on two adjacent sides of the mold. At a position extending outside the formwork. Therefore, when tension is applied to the tendon from the two free ends, a prestress force is introduced as an oblique compressive force from the corners (four corners) of the tendon as shown in FIG. 2, and its horizontal and vertical components are derived. I do. For this reason, the bending strength in two directions of the PS concrete plate is improved. Further, since the introduced force acts as an oblique compression force, it has not only out-of-plane bending but also resistance to in-plane shearing force (FIG. 3).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete PS plate according to the present invention will be described below based on an embodiment of a PC board shown in the drawings.

As shown in FIG. 1, a flexible tendon 2 is previously arranged at a predetermined position in a rectangular form 1 as a parallelogram loop substantially similar to the form. The required position here can be arbitrarily determined, but the relative relationship of the tendon 2 to the form 1 is such that the sides 3, 4, 5, 6 of the tendon 2 are substantially parallel to the sides of the form 1. To do. The tension member 2 draws the above loop in one stroke, crosses each other at one point 7 and forms one corner of a parallelogram there, and then connects the free ends 2a and 2b after the crossing point 7 to the form 1 Are extended to the outside of the mold at the two sides 1a and 1b adjacent to each other.

As the tension member 2, in addition to a conventional PC steel wire, a composite material made of flexible carbon fiber, aramid fiber, or the like can be used. The composite material includes a strand in which hundreds to tens of thousands of single fibers are made into a strand, and a bundle in which a bundle is bundled in a sheath. Since the latter, such as carbon fiber, does not rust, it can be applied to coastal structures, etc.
It can be used in harsh environments.

As a method of introducing prestress in the present PS concrete plate, any of a pretensioning method and a posttensioning method is possible, but the case of the posttensioning method will be described below. In the case of the post-tensioning method, the tendon 2 used is one in which grease or the like is applied to the surface of the tendon 2 or unbonded by covering with a sheath or the like in order to reduce the adhesion of concrete. Is preferred.

Next, in the form 1 in which the tendon 2 is disposed, the free ends 2a and 2b of the tendon 2 are left inside the form 1 while being left outside the form 1. Concrete 8 is cast. At this stage, the tension applied to the tension member 2 at this stage may be such that it is tight. In addition, the terminal portion of the composite material is bonded to fibers of the terminal portion with an adhesive such as epoxy resin.

When the concrete 8 has hardened, it is released,
The ends 2a and 2b of the tension members 7 are pulled in the direction in which the tension members 7 extend (the direction of the arrow P in FIG. 1).
(FIG. 3) is used to fix the tension member 7, thereby introducing a compressive force (prestress) to the concrete plate 10.

FIG. 2 shows the direction of the introduced prestress. The prestress is generated in a direction in which the loop of the tendon 2 is made to be generally circular. That is,
A prestress force C is introduced as an oblique compression force from the parallelogram corners (four corners) of the tendon 2 toward the center of the loop, and its horizontal component Ch and vertical component Cv are compressed in the short side and long side directions of the PC board. Acts as a force (prestress) and contributes to the improvement of out-of-plane bending strength in two directions, horizontal and vertical.

Further, since the introduction force acts as an oblique compression force, not only the above-mentioned out-of-plane bending strength is improved, but also FIG.
In addition, the resistance to in-plane shearing force as shown by arrows A and B can be improved. This is because even if a compressive force is generated in the directions of the arrows a and b due to the in-plane shearing force of the arrows A and B and a tensile force is generated in the directions of the arrows c and d, the prestress force opposes the tensile force. Because. Therefore, the present PC board is also suitable as a member for use receiving such in-plane shearing force, and can obtain desired structural performance.

In the PC board having the above-described structure, the number of the tension members 2 is one and only one tensioning operation is required, so that the productivity of the PC board can be greatly improved as compared with the conventional tensioning method. In addition, since the strength of the out-of-plane bending and the in-plane shearing force in two directions can be improved, a PC having a more excellent structural performance than the conventional PC board of FIG. You can get a board.

In the above embodiment, a prestress is introduced by the post-tension method to obtain the PS concrete plate. However, it is also possible to introduce the prestress by the pre-tension method. In this case, a flexible tensioning member 2 is formed in a mold 1 substantially similar to the mold 1 by using a support member such as a roller, a pulley, or a frame rotatably supported on a core material serving as a shaft. Are arranged as parallelograms. Then, the free ends 2a, 2b are extended to the outside of the mold at two adjacent sides 1a, 1b of the mold 1, and the free ends 2a, 2b are formed.
b, tension is applied to the tendon 2 to introduce prestress,
The concrete 8 is cast in that state.

Although the above description has been given of the precast product, the above configuration can be applied not only to the precast product but also to a cast-in-place slab and a beam.

[0022]

In summary, according to the present invention, the following excellent effects can be obtained.

1) In the PS concrete plate according to the first and second aspects, the number of flexible tendons used is basically one for a required area, and the tensioning operation can be performed only once. The productivity is greatly improved as compared with the conventional tensioning method.

2) Any PS according to claim 1 or 2
The corners of the tendon (four corners) for concrete boards
, A prestress force is introduced as an oblique compression force, and its horizontal and vertical components are derived. For this reason, the bending strength in two directions of the PS concrete plate is improved. The introduction power is
Since it acts as an oblique compression force, it has strength against not only out-of-plane bending but also in-plane shearing force. From this,
It can be said that the PS concrete plate according to the present invention is superior in structural performance as compared with the conventional case where tension is applied in one direction.

3) In short, it is possible to manufacture a PS concrete plate having higher productivity and structural performance than the conventional method. In addition, by using a composite material such as carbon fiber as the tendon, it becomes possible to produce a PS concrete plate having excellent durability.

[Brief description of the drawings]

FIG. 1 is a view showing an arrangement relationship between a mold of a PC board and a tension member in one embodiment of the present invention.

FIG. 2 is a sectional view showing the PC board obtained according to FIG. 1 together with a prestress direction.

FIG. 3 is a top view showing the PC board obtained in FIG. 1 in relation to an in-plane shearing force.

FIG. 4 is a diagram showing a positional relationship between a mold of a conventional PC board and a tension member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Form frame 1a, 1b Two adjacent sides of a form frame 2 Flexible tendon 2a, 2b Free end 3,4,5,6 Each side of tendon 7 Intersection point 8 Concrete 9 Fixing tool 10 Concrete plate A , B arrow C prestressing force Ch horizontal component Cv vertical component a, b, c, d arrows

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) E04C 2/00-2/54 E04G 21/12 104

Claims (2)

(57) [Claims] 1. A flexible tendon material is previously arranged at a required position in a mold as a parallelogram substantially similar to the mold, and its free end is extended to the outside of the mold at two adjacent sides of the mold. A prestressed concrete plate, wherein the prestress is introduced by applying tension to the tendon from the free end after the concrete is cast in an extended state. 2. A flexible tendon material is preliminarily arranged at a required position in the mold as a parallelogram substantially similar to the mold, and its free end is extended to the outside of the mold at two adjacent sides of the mold. A prestressed concrete plate wherein prestress is introduced by extending concrete and placing concrete while tension is applied to the tendon from the free end.