KR102043306B1 - Steel fiber for reinforcing concrete - Google Patents

Abstract

The present invention relates to a steel fiber for reinforcing concrete, which comprises: a first circular arc body consisting of steel fibers of a circular arc shape; a second circular arc body extending from an end of the first circular arc body and consisting of arc-shaped steel fibers having phase opposite to that of the first circular arc body; and a third circular arc body extending from an end of the second circular arc body and consisting of arc-shaped steel fibers having phase opposite to that of the second circular arc body, thereby being dispersed inside the concrete to improve the strength of the concrete.

Description

Steel fiber for reinforcing concrete}

The present invention relates to a steel fiber for concrete reinforcement. More particularly, the present invention relates to a steel fiber for concrete reinforcement, in which steel fibers buried in concrete at the cracked surface of the steel fiber reinforced concrete are pulled out and wave dissipated.

Steel fiber (steel fiber) is distributed in concrete to overcome the brittleness that can be called the greatest vulnerability of concrete to increase the toughness, bending strength, crack resistance, shear strength, ductility, impact resistance.

Steel fiber-reinforced concrete is concrete that is made by randomly introducing and distributing steel fibers with short cross sections and short lengths. Steel fiber-reinforced concrete is used in construction and civil engineering structures, and by adding steel fiber to concrete, the tensile strength, flexural tensile strength and flexural toughness of concrete are increased, thereby improving the mechanical properties of the concrete itself. Therefore, by using the improved mechanical properties can be applied to the floor slab instead of welded wire mesh or reinforcing bar can be improved construction and economical design.

1 is a view showing a wave steel fiber according to the prior art, Figure 2 is a view for explaining the fracture mechanism of the wave steel fiber embedded in concrete. As shown in FIG. 1, the wave-type steel fiber is formed with a plurality of waves 102 repeatedly with respect to the length of the steel fiber 100, thereby improving resistance when pulled.

Referring to FIG. 2, when the tensile force is applied to the concrete 104, a crack occurs in the concrete 104. In the case of the wave-shaped steel fiber 100 positioned across the crack 106, the bending of the wave 102 is Because of the small number of steel fibers 104 at the cracks 106 of the concrete 104 immediately when a large number of waves 102 are buried in the concrete 104 on both sides of the cracks 106 and the tensile force is continuously applied. Breakage will occur. That is, as the wave 102 buried in the concrete 104 is unfolded, fracture occurs immediately in the crack 106 without dissipation of plastic energy.

Accordingly, in order to reinforce the concrete 104 more effectively through the steel fiber 100, the steel fiber 100 buried in the concrete 104 is pulled out and the wave 102 is unfolded so as to dissipate plastic energy. It is necessary.

The present invention has been made to solve the above-mentioned conventional problems, the object of the present invention is as follows.

The present invention is to provide a steel fiber for concrete reinforcement that can be dissipated plastic energy as the steel fiber is pulled and the wave is stretched in the crack surface in the steel fiber reinforced concrete.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention provides a circular arc-shaped steel fiber, a circular arc-shaped steel fiber extending from the end of the first circular arc body and having a phase opposite to the first circular arc body A second circular arc body comprising a third circular arc body made of an arc-shaped steel fiber extending to an end of the second circular arc body and having an opposite phase to the second circular arc body, and being dispersed inside the concrete; To improve the steel fiber to provide concrete reinforcement.

When the radius of the first arc body is R and the length of the straight line connecting the outer end of the first arc body and the outer end of the third arc body is L, the following [Formula] can be satisfied.

[expression]

Here, the length L of the straight line connecting the outer end of the first arc body and the outer end of the third arc body may be formed to 50 to 70mm.

The hook may further include hooks extending from an outer end of the first arc body and an outer end of the third arc body, respectively, to increase pulling resistance.

Here, the hook may be bent from the first arc body and the third arc body to the convex portions of the first arc body and the third arc body.

The cross section of the steel fiber may be formed in a square or a circle.

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Referring to the effects of the present invention configured as described above are as follows.

Steel fiber for concrete reinforcement according to an embodiment of the present invention, in the steel fiber reinforced concrete, the tensile strength and flexural tension, and bending, so that the steel fibers buried in the concrete from the crack surface can be pulled out and the dissipation of the plastic energy as the wave unfolds Toughness resistance can be improved.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

The above summary as well as the detailed description of the preferred embodiments of the present application described below will be better understood when read in connection with the accompanying drawings. Preferred embodiments are shown in the drawings for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown.
1 shows a wave-like steel fiber according to the prior art;
2 is a view for explaining the failure mechanism of the wave-like steel fibers embedded in concrete;
3 is a view showing a steel fiber for concrete reinforcement according to an embodiment of the present invention;
Figure 4 is a view for explaining the shape ratio of the steel fiber for concrete reinforcement according to an embodiment of the present invention;
5 is a view for explaining the destruction mechanism of the steel fiber for concrete reinforcement according to an embodiment of the present invention;
6 to 11 is a view for explaining the resistance mechanism of the steel fiber for concrete reinforcement according to an embodiment of the present invention;
12 is a view showing a steel fiber for concrete reinforcement according to another embodiment of the present invention; And
13 is a view showing the interfacial friction force in the concrete crack state of the steel fiber for concrete reinforcement according to another embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the accompanying drawings are only described in order to more easily disclose the contents of the present invention, but the scope of the present invention is not limited to the scope of the accompanying drawings that will be readily available to those of ordinary skill in the art. You will know.

In describing the embodiments of the present invention, the same components and the same reference numerals are used for the components having the same functions, and are not completely identical to the components of the prior art.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

3 is a view showing a steel fiber for concrete reinforcement according to an embodiment of the present invention, Figure 4 is a view for explaining the shape ratio of the steel fiber for concrete reinforcement according to an embodiment of the present invention. And, Figure 5 is a view for explaining the destruction mechanism of the steel fiber for concrete reinforcement according to an embodiment of the present invention, Figures 6 to 11 illustrate the resistance mechanism of the steel fiber for concrete reinforcement according to an embodiment of the present invention. It is a figure for following.

3 to 11, steel fiber 10 for concrete reinforcement, the first arc body 12, the second arc body 13, the third arc body 14, the hook 16, the concrete 18, a straight line The part 20, the crack 22, and the crack surface 24 are shown.

The steel fiber 10 for concrete reinforcement according to the present embodiment is a steel fiber 10 for reinforcement which is dispersed in the concrete 18 and improves the strength of the concrete 18, and has a circular arc shape having a radius R. FIG. A first circular arc body 12 made of steel fibers and a second circular arc body made of steel fibers having an arc shape extending from an end of the first circular arc body 12 and having a phase opposite to that of the first circular arc body 12 ( 13) and a third circular arc body 14 extending from an end of the second circular arc body and made of arc-shaped steel fibers having a phase opposite to that of the second circular arc body 13, wherein the first circular arc body When the length of the straight line connecting the outer end of (12) and the outer end of the third circular arc body 14 is L, the following Equation 1 is satisfied.

The steel fiber 10 for concrete reinforcement according to the present embodiment extends from an end portion of the first arc body 12 and the first arc body 12 having a circular arc shape and is opposite to the first arc body 12. A second circular arc body 13 having an arc shape in a direction, and a third circular arc body 15 extending from an end of the second circular arc body 13 and formed in a direction opposite to the second circular arc body 13. do. In addition to the conventional pull resistance mechanism, by placing a small arc of curvature in the longitudinal direction of the steel fiber 10 for concrete reinforcement and a large radius of curvature, the bending occurs when the steel fiber 10 is pulled out of the concrete 18. It is to improve the pull resistance by causing the plastic energy dissipation.

3 and 4, the steel fiber 10 for concrete reinforcement according to the present embodiment extends from an end portion of an arc-shaped first arc body 12 having a radius R and a first arc body 12. A second circular arc body 13 made of an arc-shaped steel fiber 10 having a radius R having a phase opposite to that of the first circular arc body 12, and a second circular arc body extending from an end of the second circular arc body 13. 13 and a third circular arc body 15 formed in the opposite direction. The radii of the first arc body 12, the second arc body 13, and the third arc body 14 may be substantially the same.

Steel fiber 10 for concrete reinforcement according to the present embodiment is composed of three arc-shaped waveforms. In this case, the above Equation 1 is manufactured to have a small curvature waveform compared to the length of the steel fiber 10.

Hereinafter, with reference to Figure 5 will be described the destruction mechanism of the steel fiber 10 for concrete reinforcement according to this embodiment. When the tensile force is applied to the concrete 18 in the state in which the steel fiber 10 is distributed in the concrete 18, the concrete 18 will be cracked.

In the cracks 22, steel fibers 10 for concrete reinforcement may be disposed across the cracks 22, and as the tensile force increases in the concrete 18, the cracks of the concrete 18 open and thus the crack surface 24. ), Straightening proceeds as the steel fiber 10 is pulled out, thereby forming a straight portion 20 (see FIG. 5). 6 illustrates a free body diagram of the steel fiber 10 for concrete reinforcement at this time. Referring to FIG. 6, the steel fiber 10 includes: i) interfacial adhesion force Pb between the concrete 18 and the surface of the steel fiber 10, ii) interfacial friction force Pf generated along the curved portion of the steel fiber 10, iii) The plastic energy dissipation is generated due to the unfolding of the arc-shaped steel fiber 10 embedded in the concrete 18, resulting in an additional resistive force (Pp). As the additional resistance force Pp is generated, the flexural tensile resistance and the flexural toughness resistance of the steel fiber reinforced concrete are improved.

That is, in the related art, many bends having a small curvature having a large curvature are embedded in the concrete, so that the steel fiber is not pulled out of the concrete and fracture occurs at the cracked portion. By applying a large arc-shaped arc body of a radius of curvature, the steel fiber 10 is straightened in the process of being pulled out more easily in the concrete 18, so that plastic energy dissipation occurs.

The resistance (P) of the steel fiber 10 distributed in the concrete 18 is as shown in [Equation 2].

7 illustrates the interfacial adhesion force Pb in the concrete 18 cracked state of the concrete reinforcing steel fiber 10 according to the present embodiment, the interfacial adhesion force Pb can be determined by the following [Equation 3] have.

And, Figure 8 shows the interfacial friction force (Pf) in the concrete 18 cracked state of the concrete reinforcing steel fiber 10 according to this embodiment, the interfacial friction force can be determined by the following [Equation 4] .

On the other hand, Figure 9 shows that the concrete reinforcing steel fiber 10 is pulled out of the concrete 18 in the cracking state of the concrete 18 of the concrete reinforcing steel fiber 10 according to the present embodiment is causing the plastic energy dissipation. . As the tensile force is applied to the concrete 18, the crack 22 is further opened and the steel fiber 10 having a small curvature is straightened while being easily pulled out of the crack surface 24 of the concrete 18, thereby producing a plastic energy. Dissipation occurs.

FIG. 10 illustrates a plastic stress state of the concrete reinforcing steel fiber 10 having a circular cross section, and assumes that the concrete reinforcing steel fiber 10 has a circular cross section. FIG. 10 shows the strain and plastic stress in the circular cross section of the steel fiber 10 as the steel fiber 10 unfolds with a small curvature. 11 shows a free body diagram when the concrete reinforcing steel fiber 10 is pulled out of the concrete 18.

Referring to FIG. 10, the strain ε1 and the stress σ1 may be calculated by the following Equations 5 and 6 below.

here,

e = distance from the center of the steel fiber cross section to the neutral axis;

X2 = distance away from the center of the steel fiber cross section;

ρ = radius of curvature of the steel fiber;

σ Y = steel fiber yield strength;

Then, the pull tensile force (T) of the steel fiber 10 according to the spreading is calculated as shown in Equation 7 below.

By modifying [Equation 7], the following [Equation 8] can be obtained.

Looking at [Equation 5], the greater the degree of bending of the steel fiber 10 for concrete reinforcement (that is, the p value in Figure 11), the greater the strain can be generated to secure a greater pull resistance. However, when the radius of curvature ρ becomes more than a certain degree, due to the excessively large curvature radius, the steel fibers 10 themselves may be aggregated in the concrete 18, thereby degrading the uniformity of steel fiber uniformity. This, in turn, affects the strength of the concrete and degrades the concrete quality.

In addition, when the steel fiber is produced with a steel wire having a tensile strength of 1,100 MPa or more, the steel fiber 10 is unfolded due to the repulsive force due to the elasticity of the steel wire itself. It takes Therefore, in order to avoid the above problems and to apply practically, the shape ratio of the steel fiber 10 for concrete reinforcement according to the present embodiment as follows.

3 and 4, the steel fiber 10 for concrete reinforcement according to the present embodiment extends from the end of the arc-shaped first arc body 12 and the first arc body 12 of radius R. And a second arc body 13 made of an arc-shaped steel fiber 10 having a radius R having a phase opposite to that of the first arc body 12, and extending from an end portion of the second arc body 13 and having a second arc. A third arc body 14 made of arc-shaped steel fibers 10 of radius R having a phase opposite to that of the body 13, wherein the height h of the arc body is defined by the string (AB or BC) of the arc. The height h of the first circular arc body 12, the second circular arc body 13, and the third circular arc body 14 is defined by the following equation when defined as the length of a straight line extending vertically from the center to the circular arc. do.

In other words,

Is established and summarized as in [Equation 9].

In [Equation 9]

Is applied, it is transformed into the following Equation 10,

Substituting Equation 10 above into Equation 8 results in Equation 11 below.

In Equation 11 above, the height h of the first arc body 12, the second arc body 13, and the third arc body 14 below is limited to 0.1R <h <R. You can get Equation 12,

Summarizing [Equation 12],

As, the steel fiber 10 for concrete reinforcement according to the present embodiment is determined to satisfy the above [Equation 1].

The present embodiment proposes a steel fiber 10 for reinforcing concrete having a length L of 50 to 70 mm of a straight line connecting the outer end of the first arc body 12 and the outer end of the third arc body 14. In consideration of the dispersion in the unconsolidated concrete 18 and the convenience of factory fabrication, the length L of the straight line connecting the outer end of the first arc body 12 and the outer end of the third arc body 14 is 50 to 70 mm. desirable. When L is smaller than 50 mm, the dispersion effect is not reduced in the concrete 18 that is not hardened, and when 70 mm or more, dispersion may not be performed well due to entanglement between the steel fibers 10.

The steel fiber 10 for concrete reinforcement according to the present embodiment further includes hooks 16 extending from the other end of the first arc body 12 and the other end of the third arc body 14, respectively, to increase pull resistance. can do. The hook 16 may be bent from the first arc body 12 and the third arc body 14 toward the convex portion of each of the first arc body 12 and the third arc body 14. Referring to FIG. 3, a hook 16 extending linearly in a line segment direction connecting the other end of the first arc body 12 and the other end of the third arc body 14 is formed. This hook 16 is exerted a tensile force on the concrete 18 to increase the pull resistance in the concrete 18 when the steel fiber 10 is pulled out. In the present embodiment, the hook 16 is configured in a straight line, but has a stepped portion in a line segment direction connecting the other end of the first arc body 12 and the other end of the third arc body 14 to increase the pull resistance as necessary. It is also possible to form the hook 16.

The cross section of the steel fiber 10 for concrete reinforcement may be circular or square. In this embodiment, the steel fiber 10 having a circular cross section is provided, but the steel fiber 10 may be configured in a rectangular cross section.

The steel fiber for concrete reinforcement according to the embodiment of the present invention has been described above.

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Hereinafter, with reference to the drawings will be described for the steel fiber for concrete reinforcement according to another embodiment of the present invention.

12 is a view showing a steel fiber for concrete reinforcement according to another embodiment of the present invention, Figure 13 is a view showing the interfacial friction force in the concrete crack state of the steel fiber for concrete reinforcement according to another embodiment of the present invention.

Steel fiber 10 for concrete reinforcement of this embodiment includes a first circular arc body 12, the second circular arc body 13, the third circular arc body 14 and the hook 16, as in the embodiment of the present invention do.

Here, the first circular arc body 12, the second circular arc body 13, the second circular arc body 14 is the same as the embodiment of the present invention, the description of the same components will be omitted.

However, the hook 16 of the present embodiment extends from the other end of the first circular arc body 12 and the other end of the third circular arc body 14, respectively, to increase the pull resistance of the first circular arc body 12 and the third. The arc body 14 may be bent toward the convex portion of each of the first arc body 12 and the third arc body 14, but may be bent at a larger angle than the hook of the embodiment of the present invention.

In other words, if the hook 16 of one embodiment of the present invention is located entirely on the line connecting the other end of the first arc body 12 and the other end of the third arc body 14, the hook 16 of the present embodiment As shown in FIG. 12, the bent portion of the first circular arc body 12 and the third circular arc body 14 is a line segment connecting the other end of the first circular arc body 12 and the other end of the third circular arc body 14. The first circular arc body 12 and the third circular arc body 14 are positioned above, but the ends of the hooks 16 are connected to the other end of the first circular arc body 12 and the other end of the third circular arc body 14. Each side of the convex portion can be further bent to achieve an angle with the line segment between the hook 16 connecting the other end of the first arc body 12 and the other end of the third arc body 14.

As a result, as shown in FIG. 13, the interfacial friction force may be increased to further improve the pull resistance of the steel fiber 10 for concrete reinforcement.

As described above, the preferred embodiments of the present invention have been described, and the fact that the present invention can be embodied in other specific forms in addition to the above-described embodiments without departing from the spirit or scope thereof has ordinary skill in the art. It is obvious to them. Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive, and thus, the present invention is not limited to the above description and may be modified within the scope of the appended claims and their equivalents.

10: steel fiber for concrete reinforcement 12: first arc body
13: second arc body 14: third arc body
16: hook 18: concrete
20: straight portion 22: crack portion
24: crack surface

Claims (7)

A first circular arc body made of steel fibers having a circular arc shape;
A second circular arc body extending from an end of the first circular arc body and formed of arc-shaped steel fibers having a phase opposite to that of the first circular arc body;
A third circular arc body extending at an end of the second circular arc body and made of steel fibers having an arc shape having a phase opposite to that of the second circular arc body; And
Extending from the outer end of the first arc body and the outer end of the third arc body, respectively, to increase the pull resistance and from the first arc body and the third arc body of the first arc body and the third arc body; A hook bent to the side of the convex portion;
Steel fiber for concrete reinforcement, including being dispersed inside the concrete to improve the strength of the concrete. The method of claim 1,
When the radius of the first arc body is R and the length of the straight line connecting the outer end of the first arc body and the outer end of the third arc body is L, the steel fiber for concrete reinforcement satisfying the following formula .
[expression]

The method of claim 2,
The length L of the straight line connecting the outer end of the first arc body and the outer end of the third arc body is 50 to 70mm, characterized in that the steel fiber for concrete reinforcement. delete delete The method of claim 1,
Cross section of the steel fiber is a steel fiber for concrete reinforcement, characterized in that the rectangular or circular.

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