JP2601596Y2 - Tendon for prestressed concrete - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tendon for prestressed concrete which introduces compressive stress into concrete.

[0002]

2. Description of the Related Art In recent years, FRP reinforced in one direction by glass fiber, carbon fiber, aramid fiber and the like having high strength.
Prestressed tendons utilizing rods have been attracting attention as tendons for prestressed concrete because they have superior corrosion resistance.

There are two ways to introduce compressive stress (prestress) into concrete: a post-tension system and a pre-tension system.

[0004] In the former method, conventionally, only the sheath tube is buried when concrete is cast, and after a concrete is solidified, a tension material such as a PC steel material is passed through the sheath tube to introduce a predetermined tensile stress, and both ends of the concrete tube are concreted. It is to be fixed to the end of the member.

On the other hand, in the latter method, concrete is poured in a state where tensile material is applied to the tendon material, and after solidification, both ends of the tendon material are released. For many years, it has been necessary to ensure that the tendon and concrete are in close contact.

[0006]

However, since such a tendon is embedded in concrete or cement mortar for many years, it has a chemical resistance to a general alkaline environment (greater than pH = 12). It is necessary that the property is sufficient and that it is in close contact with concrete.

[0007] As a tendon for solving these problems, Japanese Patent Publication No. 4-50267 (Arapri patent) discloses a strip-shaped FRP. This is a unidirectional reinforced continuous filament (aromatic polyamide) / thermosetting resin matrix (epoxy, bismaleimide), and its cross-sectional shape is substantially rectangular (thickness / width = 1: 8 to 1:20).
It is intended to improve adhesion to concrete by shaping the surface into irregularities.

However, since the FRP rod according to the invention described in this publication is reinforced only in one direction, the FRP rod is tension-fixed by using a fixing device that utilizes a generally used compression friction principle. Then, a compressive stress in the thickness direction is generated at the same time as the tensile stress, and the shear stress is concentrated on a specific portion of the rod due to the compressive stress. As a result, the FRP rod may break inside or near the fixing device, that is, the chuck may break. There was.

The present invention solves the above problems, and an object of the present invention is to use an FRP rod as a tendon for prestressed concrete and improve alkali resistance and adhesion to concrete members. At the same time, it is intended to provide a tension material for prestressed concrete in which the chuck is less likely to break when the terminal is tensioned and fixed.

[0010]

According to the present invention, there is provided a tendon for prestressed concrete for introducing a compressive stress to concrete, the tendon being impregnated with a thermosetting resin. Core of a strip-shaped continuous fiber reinforced plastic using a long fiber-shaped reinforcing fiber as a unidirectional reinforcing material, and an alkali-resistant thermoplastic firmly adhered to the core and having a thickness of 0.5 to 2 mm And a coating layer made of resin, and the surface of the coating layer is formed with irregularities.

FIGS. 1A and 1B show an FRP according to the present invention.
The tension member A is made of a strip-shaped continuous fiber reinforced plastic (hereinafter, referred to as FRP) using a long fiber reinforcement fiber as a unidirectional reinforcement material, and the core portion 1 and the tension member A. A thermoplastic resin coating layer 2 firmly adhered to the portion 1;
The surface of the coating layer 2 has irregularities 3 formed thereon.

As the reinforcing fibers of the FRP constituting the core portion 1, glass fibers, carbon fibers, and long fibers of aramid fibers (polyparaphenylene terephthalamide fibers, aromatic polyetheramide fibers, etc.) are arranged in one direction. also of it is raised. Examples of the matrix thermosetting resin include unsaturated polyester resins, epoxy resins, and vinyl ester resins (epoxy acrylate resins and the like).

The volume content (Vf) of the fibers in the band-shaped core 1 is preferably 30 to 70% by volume. Further, the cross section perpendicular to the length direction of the core portion 1 is substantially rectangular, and the ratio of thickness to width is smaller than 1: 2, and preferably a flat plate having a ratio of 1: 5 to 1:20. It is formed into a cross section.

When the ratio is larger than 1: 5, the effect of reducing the thickness of the concrete member is not much different from that in the case of a circular cross section. When the ratio is smaller than 1:20, the fixing force at the terminal portion is reduced. Becomes smaller. Therefore, it is desirable that the thickness to width ratio be in the range of 1: 5 to 1:20.

The adhesive shear strength between the core portion 1 and the resin coating layer 2 requires a 50~100Kg f / cm ^2, also resin coating layer 2
The elastic modulus rather then preferable in the range of 17,000~28,000Kg / cm ^2, it is necessary to use a further alkali resistance resin.

As described above, the resin coating layer 2 used in the present invention may be any thermoplastic resin having alkali resistance, such as ABS (acrylonitrile-butadiene-styrene copolymer) and AAS (acrylonitrile-butadiene-styrene copolymer). Acrylonitrile-acrylic rubber-styrene copolymer), AE
Examples thereof include S (acrylonitrile-EPDM rubber-styrene copolymer) and modified PPE (polyphenylene ether modified with polystyrene).

If the thickness of the resin coating layer 2 is less than 0.5 mm, the effect of preventing fixing breakage is not sufficient, and if it exceeds 2 mm, the resin layer is broken when a compressive stress acts in the thickness direction during fixing. As a result, the strength of the FRP cannot be sufficiently utilized, so that it is limited to the range of 0.5 to 2 mm.

As a method for forming the resin coating layer 2 on the outer periphery of the core portion 1, for example, when the core portion 1 is formed into a strip shape by a pultrusion method or the like, the resin coating layer 2 is coated on the surface. Some are molded.

Further, the irregularities 3 are formed by rolling the surface of the formed tendon material A by heating and pressing, and the inner side thereof is orthogonal to the tensile direction as shown in FIG. Is formed in a sawtooth wave cross-sectional shape or a grid-like unevenness.

The manufacturing procedure of the prestressed concrete using the tendon A having the above structure will be described with reference to FIG.

First, as shown in FIG. 2A, the tendon material A is arranged in the mold 5. At this time, the terminal A1 on both sides of the tension member A is chucked with the fixing device 6 protruding outside the mold by an amount corresponding to the chuck margin for the fixing device 6, and in this state, one of the fixing devices A tensile force F is applied to 6 at a predetermined tension. Therefore, since the resin coating layer 2 receives the chucking force of the fixing device 6, the fixing is prevented from being cut off.

In this state, concrete C is poured into the form 5 as shown in FIG. 2B and solidified.

If the fixing device 6 is removed after the concrete C is solidified and the mold is removed, the prestressed concrete is completed as shown in FIG. 2 (c).

As shown in an enlarged view in a part of the figure, the irregularities 3 of the resin coating layer 2 are cut into the concrete C, and when the fixing device 6 is removed, the tensile force applied to the tendon material A is removed. Since F acts as a compressive force F on the concrete C, prestress can be applied.

In the above description, an example in which the present invention introduces prestress into concrete C by a pretension method has been described. However, it is needless to say that the present invention is not limited to the pretension method and can be applied to a post tension method. Absent.

[0026]

In the above construction, the resin coating layer covering the periphery of the FRP serving as the core can prevent breakage when the terminal is chucked to the fixing tool, and furthermore, the unevenness of the surface of the resin coating layer can reduce the chucking force with the fixing tool. Adhesion with concrete can be ensured. Irregularities of imparting the surface can be easily performed by heat deformation because it is heat-friendly plastic resin layer. In addition, since the surface is covered with an alkali-resistant thermoplastic resin, damage can be suppressed even if external force is applied, and even if the concrete is in close contact with highly alkaline concrete, it can be protected from this.

[0027]

EXAMPLES [Tensioning material] 61 Kevlar K49 (2840de) as reinforcing fiber bundles were aligned as a unidirectional reinforcing material, impregnated with a vinyl ester resin as a thermosetting resin, and passed through a throttle nozzle to a cross-sectional width of 19 mm. An FRP component having a size of 0.5 mm and a thickness of 1.25 mm was obtained. The reinforcing fiber content of the FRP component was 54 Vol%.

The FRP component is coated with an AAS resin as a resin coating layer and then heated to cure the FRP component.
A tensile material having a cross-sectional dimension of 20.5 mm × 2.5 mm in which the 6 mm resin coating layer layer and the FRP portion were firmly bonded was obtained.

Next, the tendon material surface is pressed by a heated metal roll having surface irregularities, so that the tendon material A
Surface irregularities having a predetermined groove depth were formed on the AS resin coating layer. The appearance shape of this tendon is as shown in FIG.

[Terminal Fixing Performance] A tensile test was performed by fixing the terminal of the tendon material using a commercially available wedge fixing type chuck (CH-5T-1 manufactured by Minebea). The surface depth of the chuck surface is 0.5 mm and the pulling speed is 5 mm.
mm / min and the distance between the chucks was 170 mm. The tensile breaking load was 3,100 kg.

On the other hand, a tensile test was similarly performed on the FRP portion excluding the coating, and as a result, the tensile breaking load was 23
00Kg, and the breaking position was the chuck portion.

The FRP part except for the coating is attached to
As a result of performing a tensile test using a dumbbell-shaped test piece according to SK7054, the tensile breaking strength was 130 kg /
It was mm ^2.

Thus, the theoretical tensile breaking load of the FRP portion of the tendon is calculated by the following equation.

130 kg / mm 2 × 19.5 mm × 1.25 mm = 3,170 kg Therefore, the fixing efficiency by the wedge fixing type chuck is as follows.

Tendon with coating: 3100 kg / 3170 kg = 98% FRP without coating: 2300 kg / 3170 kg = 73% [Adhesive strength of concrete] Portland cement containing aggregate (Toyo Instant Cement (trade name): 1 kg of cement and 150 kg of water
cc and kneaded sufficiently) using a PP container (3
After the concrete was poured into 30 × 230 × 120 mm), the test piece of the tendon obtained above was pierced vertically (embedment length 50 mm) and cured at room temperature for 90 hours.

After the concrete was cured, a test specimen was subjected to a pull-out test, and the value obtained by dividing the maximum pull-out resistance at this time by the contact area with the concrete was defined as the adhesive strength (Kg / cm ² ). The results obtained are shown in the table.

[0037]

[Table 1]

[0038]

As described in detail in the above embodiments, in the tendon for prestressed concrete according to the present invention, a long fiber-like supplement impregnated with a thermosetting resin is used.
The core made of FRP with strong fiber as a unidirectional reinforcing material is
Covering with a coating layer made of potash thermoplastic resin
Thereby, when the terminal is chucked to the fixing device, it is possible to prevent the shear stress from being concentrated on a specific portion of the rod and to prevent breakage in or near the fixing device, and furthermore, the unevenness of the resin coating layer with the fixing device can prevent the breaking. In addition to securing the chucking force and adhesion to concrete, the surface is covered with an alkali-resistant thermoplastic resin, so damage is suppressed even when subjected to external force, and it adheres to concrete with high alkalinity. Therefore, it is suitable as a tension member for prestressed concrete for introducing a compressive stress to a concrete member.

[Brief description of the drawings]

1 (a) and 1 (b) are three views of a tendon for prestressed concrete according to the present invention.

FIGS. 2 (a) to 2 (c) are cross-sectional views illustrating a procedure for producing a prestressed concrete using the same tendon.

[Explanation of symbols]

 A Tensioning material 1 FRP core 2 Resin coating layer 3 Unevenness C Concrete 6 Fixing tool

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Fukuhara 2-1-1 Yabuta Nishi, Gifu City, Gifu Prefecture Ube Nitto Kasei Co., Ltd. Gifu Research Institute (56) References JP-A-2-158321 (JP, A JP-A-62-176950 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E04C 5/00-5/10

Claims (1)

(57) [Scope of request for utility model registration] 1. A tension member for prestressed concrete for introducing compressive stress into concrete, wherein the tension member is a band in which a long fiber reinforcing fiber impregnated with a thermosetting resin is used as a unidirectional reinforcing material. A core made of a plate-shaped continuous fiber-reinforced plastic , a coating layer made of an alkali-resistant thermoplastic resin firmly adhered to the core and having a thickness of 0.5 to 2 mm, and a surface of the coating layer; Is a tensioning material for prestressed concrete, characterized by having irregularities formed on it.