JP7335924B2 - Concrete reinforcing bars with unevenness - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reinforcing bar embedded in a concrete structure to reinforce the concrete structure.

In Patent Document 1, wound fibers (fiber bundle A) are wound around a fiber core impregnated with resin, secondary reinforcing fibers are arranged in the longitudinal direction, and further wound fibers (fiber bundle B) are wound from above. Disclosed is a structural rod wound with a The bonding strength between the fiber core and the wound fiber is enhanced, and the fiber core is prevented from falling out of the structural rod. In addition, since the surface of the structural rod is uneven, the bonding strength with the concrete is enhanced.

JP-A-3-103561

The greater the unevenness of the surface of the structural rod (the higher the height of the protrusions), the greater the bonding strength (adhesive stress) with concrete. The unevenness of the surface of the structural rod can be increased by applying a strong twist to the fiber bundle wound around the fiber core. Lost). If the structural rods embedded in the concrete structure cannot follow the deflection of the concrete structure, cracks and gaps will occur around the structural rods in the concrete structure, and the strength of the concrete structure will decrease.

SUMMARY OF THE INVENTION An object of the present invention is to provide a concrete reinforcing bar having irregularities with well-balanced adhesion stress and flexibility (modulus of elasticity) between concrete structures.

The concrete reinforcing bar having unevenness according to the present invention comprises a resin-impregnated fiber bundle obtained by impregnating a plurality of high-strength fiber bundles with a resin, and a coating material wound around the outer peripheral surface of the resin-impregnated fiber bundle. The material has a twisted wire structure in which multiple threads are twisted, and is loosely twisted so that it deforms into a semi-elliptical cross section when wrapped around the outer peripheral surface of the resin-impregnated fiber bundle. Characterized by

High-strength fibers include carbon fibers, glass fibers, boron fibers, aramid fibers, polyethylene fibers, PBO (polyp-phenylenebenzobisoxazole) fibers, basalt fibers, and other fibers. These fibers are very thin and can be impregnated with resin by bundling a large number of high-strength fibers. Since it becomes possible to do so, the characteristics of high-strength fibers can be maximized.

The resin with which the high strength fibers are impregnated may be a thermosetting resin or a thermoplastic resin. Thermosetting resins include, for example, epoxy, unsaturated polyester, vinyl ester, phenol, cyanate ester, and polyimide. Polyamide, polycarbonate, polyphenylene sulfide, polyetheretherketone and the like are used as the thermoplastic resin.

The covering material has a stranded wire structure in which multiple threads are twisted. As the yarn constituting the covering material, the above-mentioned high-strength fibers (for example, carbon fibers) can be used in a twisted manner, but the covering material is wound around the outer peripheral surface of the resin-impregnated fiber bundle, so it is expensive. Tensile strength is not required, so it is preferable to use a material different from the high-strength fiber, for example, a material that is relatively inexpensive and relatively heat resistant.

A polyester thread such as a polyethylene terephthalate (PET) thread can be used as the thread constituting the covering material. Aramid threads (polyparaphenylene terephthalamide threads, polymetaphenylene isophthalamide threads, etc.) and vinylon threads (vinylon threads obtained by acetalizing polyvinyl alcohol, etc.) may also be used.

In one embodiment, the modulus of elasticity of the yarn is lower than that of the high strength fibers. The increase in rigidity is suppressed, and a supple concrete reinforcing bar can be obtained.

The coating material wound around the outer peripheral surface of the resin-impregnated fiber bundle forms irregularities on the outer peripheral surface (surface) of the concrete reinforcing bar. As described above, since the covering material has a stranded wire structure in which multiple threads are twisted, it is easy to form convex portions on the outer peripheral surface of the resin-impregnated fiber bundle by winding it around the outer peripheral surface of the resin-impregnated fiber bundle. . Concrete reinforcing bars having unevenness on the outer peripheral surface are well fixed in the concrete structure.

According to this invention, the covering material having a twisted structure is characterized by loosely twisting a plurality of threads so that they are deformed into a semi-elliptical cross section by being wound around the outer peripheral surface of the resin-impregnated fiber bundle. and That is, the covering material has a stranded structure in which a plurality of yarns are twisted, but the degree of twisting is not tight. The loosely twisted covering material is easy to deform, and it conforms to the surface shape of the resin-impregnated fiber bundle in the range where it contacts the resin-impregnated fiber bundle by being wound around the outer peripheral surface of the resin-impregnated fiber bundle, and in the range where it does not contact the covering material. It exhibits a cross-sectional shape (semi-elliptical cross-section) that smoothly rises in the direction away from the resin-impregnated fiber bundle. As a result, while ensuring the elastic modulus of the concrete reinforcement made up of the resin-impregnated fiber bundle and the covering material, the surface unevenness reduces the maximum bond stress of the concrete reinforcement to the concrete structure (concrete structure and concrete reinforcement). fixation force between muscles) can be improved.

If the threads forming the covering material are strongly twisted, the covering material tends to bite into the resin-impregnated fiber bundle when the covering material is wound around the resin-impregnated fiber bundle. The encroachment of the covering material disturbs the fiber orientation (linearity) of the resin-impregnated fiber bundles and lowers the elastic modulus of the concrete reinforcement. Loosely twisting the threads also helps to prevent the elastic modulus of the concrete reinforcing bars from decreasing.

Specifically, the appropriate twist angle of the yarn is in the range of 1.0 to 4.5°, more preferably in the range of 1.5 to 4.0°. It is possible to improve the maximum bond stress without significantly lowering the elastic modulus of concrete reinforcing bars.

In one embodiment, the resin impregnated in the resin-impregnated fiber bundle is also impregnated in the covering material. If the coating material is wound around the resin-impregnated fiber bundle before the resin impregnated in the resin-impregnated fiber bundle is cured, the resin impregnated in the resin-impregnated fiber bundle is also impregnated (permeated) into the coating material. Curing (typically heating) the resin after wrapping the coating material around the resin-impregnated fiber bundle allows the coating material to be firmly adhered to the surface of the resin-impregnated fiber bundle.

Preferably, a gap is formed (secured) between the covering materials wound around the outer peripheral surface of the resin-impregnated fiber bundle. It is possible to ensure the maximum size of unevenness (height of the protrusion) formed on the outer peripheral surface of the concrete reinforcing bar.

The present invention also provides a concrete reinforcing cable prepared by preparing a plurality of concrete reinforcing bars as described above and twisting the plurality of concrete reinforcing bars together. On the surface of the concrete reinforcement cable, in addition to the irregularities formed on the outer peripheral surface of the concrete reinforcing bars, there are also irregularities due to the grooves formed by twisting multiple concrete reinforcing bars together. Fixing efficiency can be further improved. Of course, it goes without saying that the tensile strength of double-tracked concrete reinforcing cables is higher than that of single-tracked concrete reinforcing bars.

1 is a front view of a concrete reinforcing cable; FIG. FIG. 2 is a cross-sectional view of a concrete reinforcing cable along line II-II of FIG. 1; It is a perspective view which shows the mode of manufacture of a concrete reinforcing bar. It is a longitudinal cross-sectional view of a concrete reinforcing bar. (A) shows a cross-sectional view of the covering material before being wound around the resin-impregnated fiber bundle, and (B) shows a cross-sectional view of the covering material after being wound around the resin-impregnated fiber bundle. It is an enlarged front view of a covering material. 4 is a graph showing the relationship between the twist angle of the coating material and the elastic modulus and maximum bond stress of concrete reinforcing bars.

FIG. 1 shows a front view of a concrete reinforcing cable embedded in a concrete structure, and FIG. 2 shows a sectional view of the concrete reinforcing cable along line II--II in FIG.

The concrete reinforcing cable 1 is composed of seven concrete reinforcing bars 10 . The concrete reinforcing cable 1 shown in FIGS. 1 and 2 is constructed by placing one concrete reinforcing bar 10 in the center and six concrete reinforcing bars 10 twisted around it. When viewed in cross section, the concrete reinforcing cable 1 and the seven concrete reinforcing bars 10 all have substantially circular external shapes.

The concrete reinforcing cable 1 is typically embedded in a concrete structure to increase the strength of the concrete structure, especially the tensile strength. The length and diameter of the concrete reinforcing cable 1 as well as the structure (number, placement, etc. of concrete reinforcing bars 10) depend on the dimensions of the concrete structure and the required strength. For example, a plurality of concrete reinforcement cables 1 having a diameter of about 10 to 30 mm are embedded in a concrete structure at predetermined intervals. A concrete structure in which the concrete reinforcing cable 1 is embedded is strong against not only compressive force but also tensile force.

Each of the seven concrete reinforcing bars 10 constituting the concrete reinforcing cable 1 has a cross section of a large number of long continuous carbon fibers 21 impregnated with thermosetting resin or thermoplastic resin (hereinafter referred to as resin 22). It is composed of a resin-impregnated fiber bundle (hereinafter referred to as a wire rod) 20 made of carbon fiber reinforced plastic bundled in a circular shape and a coating material 30 spirally wound around the wire rod 20 .

The carbon fibers 21 forming the wire 20 are composed of very thin filaments with a diameter of, for example, 5-7 μm. A large number of carbon fibers 21 impregnated with resin 22 are bundled to have a circular cross section as described above, and are aligned in the longitudinal direction while being twisted at a constant angle.

The covering material 30 wound around the wire 20 is made by twisting a plurality of yarns, for example, about 20 PET yarns obtained by twisting a large number of PET fibers. By winding the coating material 30 around the outer peripheral surface of the wire 20, the outer peripheral surface of the wire 20 is covered with the coating 30, and the wire 20 is protected. In addition, as shown in FIG. 1, the outer peripheral surface of the concrete reinforcing bar 10 is uneven due to the coating material 30 wound around the wire rod 20 . As described above, concrete reinforcing cables 1 (concrete reinforcing bars 10) are typically embedded in concrete structures and used to increase the strength of concrete structures. The attachment of the concrete reinforcing cable 1 to the concrete structure is facilitated by the irregularities on the outer peripheral surface of each of the concrete reinforcing bars 10 and the spiral grooves formed on the surface by twisting the plurality of concrete reinforcing bars 10 together. The degree of stress is increased, and the concrete reinforcing cable 1 becomes difficult to come off from the concrete structure.

Fig. 3 shows how the concrete reinforcing bar 10 is manufactured, Fig. 4 shows a longitudinal section of the concrete reinforcing bar 10, Fig. 5(A) shows an enlarged cross section of the coating material 30 before wrapping, and Fig. 5(B) shows a Enlarged cross-sections of subsequent cladding 30 are shown, respectively.

Referring to FIG. 3, two covering materials 30 and one wire 20 are paid out from a lapping machine (not shown) (in FIGS. 3 and 4, the two covering materials 30 are denoted by reference numerals 30A and 30B, respectively). ). Both of the two coating materials 30A and 30B are spirally wound around the outer peripheral surface of the wire 20 with a predetermined interval, and the two coating materials 30A and 30B are alternately wound around the outer peripheral surface of the wire 20 in the longitudinal direction. be done.

3 and 5(A), the covering material 30 is made by twisting a plurality of PET yarns 31, for example 19 to 20, each of which contains a large number of PET fibers 32. be As will be described later, the PET yarns 31 forming the covering material 30 are not strongly twisted, but rather loosely twisted. Therefore, when the covering material 30 is wrapped around the outer peripheral surface of the wire 20 by a wrapping machine, the covering material 30 (twisted wire of multiple PET yarns 31) is deformed as shown in FIGS. , has a substantially semi-elliptical shape convex outward (in the direction away from the wire rod 20) when viewed from the cross section.

The covering material 30 is wrapped around the outer peripheral surface of the wire 20 when the resin 22 impregnated in the wire 20 is not cured (wrapping). For this reason, when the covering material 30 is wound around the wire 20, the resin 22 impregnated in the wire 20 impregnates the multiple PET yarns 31 (the multiple PET fibers 32 constituting the PET yarns 31) constituting the covering material 30. permeates (compare FIG. 5(A) and FIG. 5(B)). The coating material 30 is firmly fixed to the outer peripheral surface of the wire rod 20 by curing the resin 22 . Seven concrete reinforcing bars 10 are prepared by winding a covering material 30 around the outer peripheral surface of a wire 20, and six reinforcing bars are twisted around one of them (closing). A concrete reinforcing cable 1 is thus formed. For one of the seven concrete reinforcing bars 10 arranged in the center, a plurality of untwisted PET yarns 31 (for example, a flat type in which a plurality of PET yarns 31 are arranged parallel to each other) ) wound around the outer peripheral surface of the wire rod 20 may be used. In this case, unevenness is not formed on the surface of one concrete reinforcing bar 10 arranged in the center.

Referring to FIG. 4, by adjusting the delivery speed of the wire 20 in the wrapping machine, the distance D between the two longitudinally adjacent covering materials 30A and 30B wound around the outer peripheral surface of the wire 20 can be changed. can be done. By adjusting the interval D, the coating materials 30A and 30B are placed on the outer peripheral surface of the wire rod 20 without overlapping the side portions of the coating materials 30A and 30B adjacent in the longitudinal direction or keeping the overlapping range to a small extent. It is possible to wind the coating material 30A and 30B, and it is possible to secure the maximum size of the unevenness (height of the convex portion) formed by the coating materials 30A and 30B.

As described above, the covering material 30 is constructed by twisting about 19 to 20 PET yarns 31 together. The covering material 30, which is made by strongly twisting the PET yarn 31, tends to maintain its shape when wound around the outer peripheral surface of the wire rod 20, and the size of the unevenness (height of the convex portion) formed on the surface of the concrete reinforcing bar 10. ) can be made larger. However, at the same time, if the shape of the covering material 30 wound around the wire 20 is maintained as it is by twisting the PET yarn 31 strongly, the covering material 30 will not adhere to the surface of the wire 20 when the covering material 30 is wound around the wire 20. The straightness of the carbon fibers 21 forming the wire rod 20 is disturbed. If the linearity of the many carbon fibers 21 in the longitudinal direction is hindered, the elastic modulus of the concrete reinforcing bar 10 (concrete reinforcing cable 1) is lowered.

FIG. 6 is an enlarged front view schematically showing the covering material 30. As shown in FIG. Fig. 7 shows the twist angle of the PET yarn 31 constituting the covering material 30 (referred to as the "covering material twist angle") (horizontal axis) and the elastic modulus and maximum bond stress of the concrete reinforcing bar 10 (both vertical axis). It is a graph showing the relationship. A plurality of triangular plots in the graph of FIG. 7 indicate the measured values of the modulus of elasticity, and the circle plots indicate the measured values of the maximum bond stress. The solid line in the graph of FIG. 7 indicates an approximation curve representing the relationship between the coating material twist angle α and the elastic modulus of the concrete reinforcing bar 10 based on the elastic modulus measurement results (triangular plots). The dashed line in the graph of FIG. 7 indicates an approximate curve representing the relationship between the coating material twist angle α and the maximum bond stress of the concrete reinforcing bar 10 based on the measurement results of the maximum bond stress (circle plot). The elastic modulus was measured according to JIS A1192:2005 (tensile test method for continuous fiber reinforcing material for concrete) (unit: GPa). The maximum bond stress was measured according to JSCE-E539 (test method for bond strength between continuous fiber reinforcing material and concrete by pull-out test) defined by the Japan Society of Civil Engineers (unit: N/mm ² ).

Referring to FIG. 6, the covering material twist angle α is the angle between the longitudinal direction of the covering material 30 and the twisted PET yarn 31 . For example, if 20 PET yarns 31 with a diameter of 0.375 mm are twisted 27 times per meter, the 20 PET yarns 31 are twisted at a twist angle of about 1.9°. In Fig. 7, using the covering material twist angle α as a variable, multiple types of concrete reinforcing bars 10 were created with different covering material twist angles α in the range of 0° to 5.4°. Measurement results for elastic modulus and maximum bond stress are shown.

Referring to FIG. 7, covering material twist angle α=0.0° means that a plurality of PET yarns 31 are wound around the outer peripheral surface of wire 20 without being twisted at all. The elastic modulus of the concrete reinforcing bar 10 in which a plurality of PET threads 31 are wound around the wire rod 20 without being twisted at all is relatively large (approximately 170 Gpa). On the other hand, the concrete reinforcing bar 10 with the covering material twist angle α=0.0 has a small maximum bond stress (approximately 4.5 N/mm ² ). This is because when a plurality of untwisted PET yarns 31 are wound around the wire rod 20, the PET yarns 31 cover the outer peripheral surface of the wire rod 20 with a substantially uniform thickness, and the surface is hardly uneven. It is from.

Referring to FIG. 7, the larger the coating material twist angle α, that is, the stronger the twist of the plurality of PET yarns 31, the lower the elastic modulus (solid line). (dashed line) increases. As is clear from FIG. 7, the elastic modulus and the maximum bond stress have a relationship in which one increases and the other decreases. By adopting a coating material twist angle α of 1.0 to 4.5°, preferably 1.5 to 4.0°, the elastic modulus is not significantly reduced and the maximum bond stress degree is improved, that is, the elastic modulus It is possible to provide the concrete reinforcing bar 10 having an excellent balance between the strength and the maximum bond stress.

1 Concrete reinforcement cable
10 Concrete reinforcement
20 wire (resin-impregnated fiber bundle)
21 carbon fiber
22 Resin
30, 30A, 30B Coating material
31 PET thread
32 PET fiber

Claims (7)

A resin-impregnated fiber bundle obtained by impregnating a plurality of high-strength fiber bundles with a resin, and a coating material wound around the outer peripheral surface of the resin-impregnated fiber bundle,
The covering material is
It has a twisted wire structure in which a plurality of yarns are twisted, and is loosely twisted so that it deforms into an outwardly convex semi-elliptical shape when viewed from the cross section by being wound around the outer peripheral surface of the resin-impregnated fiber bundle. characterized by
Concrete reinforcing bars with unevenness. The yarn is made by twisting multiple fibers of a material different from the high-strength fiber,
A concrete reinforcing bar having unevenness according to claim 1 . The elastic modulus of the yarn is lower than the elastic modulus of the high-strength fiber,
A concrete reinforcing bar having unevenness according to claim 2 . Characterized in that the twist angle of the yarn is in the range of 1.0 to 4.5 °,
A concrete reinforcing bar having unevenness according to any one of claims 1 to 3. Characterized in that the twist angle of the yarn is in the range of 1.5 to 4.0 °,
A concrete reinforcing bar having unevenness according to any one of claims 1 to 3. The resin impregnated in the resin-impregnated fiber bundle is also impregnated in the coating material,
A concrete reinforcing bar having unevenness according to any one of claims 1 to 5. A plurality of concrete reinforcing bars having unevenness according to any one of claims 1 to 6 are twisted together,
Concrete reinforcement cable.

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