KR102254583B1 - High Performance Steel fiber - Google Patents

Abstract

A steel fiber according to embodiments is for reinforcing cement-based materials, comprising: a first arch portion having a convex shape in a first direction and having a first radius of curvature; a second arch portion having a convex shape in a second direction and having a second radius of curvature; and a connecting portion connecting the first arch portion and the second arch portion. In addition, the steel fiber according to embodiments may include a first member connected to one end of the first arch portion and a second member connected to one end of the second arch portion.

Description

High Performance Steel fiber

The present invention relates to a high-performance steel fiber for reinforcing building materials and/or civil engineering materials, and specifically relates to a structure that increases energy absorption efficiency for bending and/or tensile force acting on a cement-based composition by including an arch shape in the steel fiber. .

In general, a concrete member has excellent compressive strength, durability and rigidity, but has low tensile strength, flexural strength, impact strength, and energy absorption capacity. According to this characteristic, the concrete member has a limitation that it is highly likely to be destroyed when a tensile or dynamic load is applied.

In order to solve the above problem, a method of improving physical properties such as tensile strength, impact resistance, and peeling resistance by mixing steel fibers for reinforcing concrete in a concrete member has been widely used.

In general, steel fibers for reinforcing concrete have a material of steel processed into a fiber form. When steel fibers having a relatively short length are evenly dispersed in a concrete member, physical properties such as tensile strength, flexural strength, and shear strength of large concrete can be improved. In addition, it can be a means to increase the resistance to cracks as it has the characteristics of being resistant to impact.

In order for the steel fibers to bind to the concrete and exhibit the above properties, the steel fibers must be evenly dispersed in the concrete, and have high adhesion to the concrete and must be well adhered to the concrete composition. In addition, the steel fiber must have a material having high tensile strength against external stress.

Looking at the conventional steel fiber technology, there is a hooked ends type steel fiber in which both ends are bent in a straight steel fiber having a circular cross-section disclosed in Korean Patent Application Publication No. 2013-0129385. In addition, Korean Patent Publication No. 1,403,659 uses a ring-shaped steel fiber spaced at both ends.

In addition to the above examples, there are a number of examples of steel fibers for improving the flexural toughness by reducing the rebound rate during pouring after mixing into shotcrete and preventing pulling out after pouring.

Such conventional steel fibers for reinforcing concrete have been most often applied to shotcrete, which is a secondary support material during tunnel excavation. In addition, it is often used in places such as floor slabs where reinforcement is difficult due to its small cross section and crack control is required.

In the case of steel fibers applied to shotcrete, the size is 0.5~0.55mm in diameter and 30~35mm in length, whereas steel fibers reinforced in the floor slab mainly use sizes of 0.75~0.90mm in diameter and 50~60mm in length.

Conventional end-hook type steel fibers are generally formed in a hook shape by bending both ends of a straight body at a predetermined angle. In the case of using such a shape, when the steel fiber is pulled from the concrete due to the tensile force acting after the occurrence of the crack, the adhesion performance decreases in the straight part other than the hook part, and the pull-out resistance strength decreases sharply. For this reason, when using end-hook type steel fibers, there is a fatal limitation in improving the mechanical performance of concrete members.

In order to solve these limitations, technologies implementing their own characteristics from Korean Patent Publication No. 1,073,393 or Korean Utility Model Publication Nos. 361,900 and 406,191 to U.S. Patent No. 6,060,163 are disclosed.

However, steel fibers devised to improve adhesion performance as in the above patents have a problem in that they must have a relatively short length or high tensile strength in order to exhibit performance for achieving the purpose.

In particular, in the case of spaced ring-shaped steel fibers as in Korean Patent Publication No. 1,403,659, both ends of the ring-shaped spaced apart are located above the center, and have close contact portions that protrude obliquely downward in the inner side of the both ends, but in the case of a circular shape Since double joint welding treatment is required at both ends, there is a problem of deterioration in quality or productivity due to poor welding.

In the case of steel fibers having an arcuate shape as in Korean Patent No. 10-1596246, it discloses a feature of reducing the amount of steel fibers mixed in comparison with the degree of improvement in the performance of the member. However, this has a problem that the amount of energy absorption is insufficient for the tensile force acting on the concrete.

The present invention is conceived from the problems of the prior art as described above, and is characterized by including an arch structure in the shape of the steel fiber main body. By distributing the steel fibers having the above shape inside the cement-based material, it is possible to improve the mechanical performance of the cement-based member including the steel fibers.

Using the present invention, there may be an advantage that a cement-based member can have a desired property value by using relatively few materials.

In addition, when the existing steel fibers are mixed into the cement and hardened, there is a problem that the steel fibers are not uniformly dispersed throughout the member. When the steel fiber according to the present invention is used, the mechanical performance of the concrete member may have a better effect compared to the same input amount.

Steel fibers according to the embodiments may be used to reinforce members used in construction and/or civil works. In addition, it can be used for reinforcing interior and exterior materials for buildings.

The steel fiber has a convex shape toward a first direction, a first arch portion having a first radius of curvature, a second arch portion having a convex shape toward a second direction opposite to the first direction, and having a second radius of curvature , A connection part connecting one end of the first arch part and one end of the second arch part, a first member connected to the other end of the first arch part, and a second member connected to the other end of the second arch part.

The steel fiber according to the embodiments may include a first connecting arch portion having a convex shape toward a second direction in a portion where the first arch portion and the connecting member are connected. A second connection arch portion having a convex shape toward the first direction may be further included in a portion where the second arch portion and the connection portion are connected.

The steel fiber according to the embodiments may include a third connection arch portion having a convex shape toward a second direction at a portion where the first arch portion and the first member are connected. In addition, a portion at which the second arch portion and the second member are connected may include a fourth connection arch portion having a convex shape toward the first direction.

The steel fiber according to the embodiments may be a steel fiber in which at least one of the first radius of curvature and the second radius of curvature is greater than at least one of each of the first to fourth connecting portions.

The steel fiber has a convex shape toward a first direction, a first arch portion having a first radius of curvature, a second arch portion having a convex shape toward a second direction opposite to the first direction, and having a second radius of curvature , A connection part connecting one end of the first arch part and one end of the second arch part, a first member connected to the other end of the first arch part, and a second member connected to the other end of the second arch part. In addition, the connection portion may include a third arch portion having a third radius of curvature and connected to the first arch portion, and a fourth arch portion having a fourth radius of curvature and connected to the second arch portion.

In the steel fiber according to the embodiments, the third arch portion may have a convex shape toward the second direction, and the fourth arch portion may have a convex shape toward the first direction.

The steel fiber according to the embodiments is in the portion where the first arch portion and the third arch portion are connected, the first connecting arch portion having a convex shape toward the second direction, and the portion where the second arch portion and the fourth arch portion are connected. It may include a second connection arch portion having a convex shape toward the first direction.

The steel fiber according to the embodiments may be a steel oil in which the first connecting arch portion and the third arch portion are connected by a third member, and the second connecting arch portion and the fourth arch portion are connected by the fourth member.

The steel fiber according to the embodiments may be a steel fiber in which at least one of the first radius of curvature and the second radius of curvature has a value greater than at least one of the third radius of curvature and the fourth radius of curvature.

The steel fiber according to the embodiments may be a third connection arch portion having a convex shape toward a second direction at a portion where the first arch portion and the first member are connected, and a portion where the second arch portion and the second member are connected It may be a steel fiber including a fourth connection arch portion having a convex shape toward the first direction.

The steel fiber according to the embodiments may be a steel fiber in which at least one of the third radius of curvature and the fourth radius of curvature is greater than at least one of each of the first to fourth connecting arch portions.

The steel fiber according to the embodiments may be a steel fiber having a symmetrical shape based on a point that becomes the center of the connection part.

The steel fiber according to the embodiments may have a straight length (L) of 30 mm or more and 80 mm or less.

The steel fiber according to the embodiments may be a steel fiber having a cross-sectional diameter of 0.3 mm or more and 1.0 mm or less.

In the steel fiber according to the embodiments, the steel forming the material of the steel fiber may have a tensile strength of 500Mpa or more and 2800Mpa or less.

Steel fibers according to the embodiments may be used for the purpose of reinforcing interior and exterior materials for construction.

The steel fibers according to the embodiments may be used to reinforce a cement-based material.

The steel fiber according to the embodiments may be used to reinforce a synthetic resin-based material.

According to the steel fibers for reinforcing building materials and/or civil engineering materials according to the embodiments, by including a shape forming an arch structure symmetrical to each other, it is possible to have a higher pull-out resistance strength than the conventional one.

In addition, it is possible to obtain a technical effect of improving mechanical performance such as tensile strength, flexural strength, and/or energy absorption capacity of the cement composite including steel fibers according to the embodiments.

The characteristic of the conventional hook-type steel fiber is that the pull-out resistance strength decreases rapidly at the straight end after the hook portion. In contrast, the steel fiber according to the embodiments has a characteristic in that the entire length of the fiber resists the pull, thereby maintaining the pull-out resistance strength.

In addition, in the case of conventional semi-circular steel fibers, a problem of workability occurs due to agglomeration of fibers when blended into a cement composite, and a steep frictional cost in the cement matrix when drawing in the cement-based composite is caused. Therefore, the material of the conventional steel fiber for improving the drawing performance is required to have a higher level than the tensile strength of the generally used steel wire.

The steel fibers for reinforcing building materials and/or civil engineering materials according to the embodiments may have two pairs and/or a pair of symmetrical arch shapes in the longitudinal direction of the body. The arch shape included in the steel fiber may have an appropriate radius of curvature, and it may be easily drawn in the cement matrix, so that a separate high level of tensile strength may not be required, and workability may be excellent.

In addition, according to embodiments, it is possible to increase the energy absorption rate than a steel fiber member having a single arch shape by arranging a pair and/or two pairs of symmetrical arch shapes.

According to the arch-shaped steel fibers for reinforcing building materials and/or civil engineering materials according to the embodiments, there may be an effect of dramatically reducing the amount of steel fibers mixed in comparison to the performance compared to the conventional steel fibers for reinforcing building materials. In addition, there may be an effect of obtaining an economic advantage by reducing the amount and cost of consumable materials.

Building materials and/or civil engineering materials according to embodiments According to the arch-shaped steel fiber for material reinforcement, durability for extending the life of a cement composite building can be secured from the elasticity of the arch-shaped body, and manufacturing and productivity can be improved due to a simple technical configuration.

In the case of using the arch-shaped steel fiber for reinforcing construction and/or civil engineering materials according to the embodiments, since the initial curing crack resistance of the concrete increases, there may be an effect of reducing the cost of repairing defects due to cracks.

1 is a view showing the external shape and geometrical element values of steel fibers according to embodiments.
2 is a view showing the external shape and geometrical element values of steel fibers according to embodiments.
3 is a view for explaining the adhesion and resistance to deformation of the steel fiber when a force acts on the steel fiber according to the embodiments.
Figure 4 shows a pull-out test specimen for testing the effect of the steel fiber on the tensile performance of the specimen.
5 is an experimental result of a pull-out test for an end-hook type steel fiber, which is an existing type of steel fiber.
6 is an experimental result of a pull-out test for a single arch-shaped steel fiber, which is a steel fiber of an existing type.
7 is a test result of a pull-out test of a steel fiber according to the first embodiment.
8 is a test result of a pull-out test of a steel fiber according to a second embodiment.
9 is a test result of a pull-out test of a steel fiber according to a third embodiment.
10 is a test result of a pull-out test of a steel fiber according to a fourth embodiment.
11 is a test result of a pull-out test of a steel fiber according to a fifth embodiment.
12 is for explaining the method of the flexural performance test for testing the effect of the steel fiber on the flexural performance of the specimen.
13 is an experimental result of an end-hook type, a single arc type, and a flexural performance test for the steel fiber according to the first embodiment.
14 is an end-hook type, a single arc type, and experimental results of the flexural performance test for the steel fiber according to the first embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that the object of the present invention can be specifically understood and realized.

In this process, the size or shape of the components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, terms specifically defined in consideration of the configuration and operation of the present invention may vary according to the intention or custom of users and operators.

Meanwhile, in the present invention, terms such as'first','and/or''second' may be used to describe various elements, but the elements are not limited to the above terms. The above terms are only used for the purpose of distinguishing one component from other components. For example, within a range not departing from the scope of the rights according to the concept of the present invention, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

These terms should be defined and understood based on the contents throughout this specification.

Hereinafter, a method of improving the physical properties of a cement-based member by including the arcuate steel fiber 1 according to the embodiments in concrete will be described.

Cement-based members such as concrete can make a structure without being limited in size or shape, and have the characteristics of securing and transporting materials easily. Concrete is a material widely used in building construction because its compressive strength is greater than that of other materials and has the advantage of being able to freely obtain any required strength.

However, concrete has the properties of a brittle material, and has a disadvantage in that its tensile strength and flexural strength are smaller than that of compressive strength. In the process of transporting the member or due to the self-weight of the concrete, tension may be generated at both ends of the member. In order to prevent the member from being destroyed for the above reasons, it is possible to supplement physical properties by including a steel material inside the concrete member.

Unlike concrete, steel has the properties of a ductile material and has a strong characteristic of tensile strength. Steel having a thin shape like a fiber is called a steel fiber (1). The steel fiber (1) can be evenly distributed in the concrete during the construction process using the concrete member. This can play a role in adding the properties of the concrete, which is strong against compressive force, and the properties of steel, which are strong against tensile force and warpage. As a result, an ideal member having both the advantages of concrete and steel can be obtained.

The steel fiber 1 according to the embodiments may be used to reinforce a building material and/or a civil engineering material, and in particular, may be used to reinforce a cement-based material. In addition, the steel fibers 1 according to the embodiments may be used to reinforce interior and exterior materials for construction. By uniformly dispersing fibers having a steel material in concrete, it is possible to improve tensile strength, flexural strength, resistance to cracks, toughness, shear strength, and impact resistance. In addition, it has the effect that the installation work of the wire mesh or the reinforcing bar is not required, so that economic efficiency, workability and safety can be improved.

In order to improve the performance of the member through the steel fiber (1), each of the steel fibers (1) must be well adhered to the concrete inside the member, and as a result, the member made of two materials must be made to behave integrally. The property of the steel fiber (1) sticking to the concrete is called adhesion, and how well the adhesion is done can be expressed through a measure called adhesion strength. The stronger the steel fiber 1 is attached to the concrete, the better the properties of the reinforced concrete member mixed with the steel fiber 1 can also be improved.

The straight length (L) may mean the maximum value of the distance the steel fiber 1 has in the longitudinal direction. That is, the straight length L of the steel fiber 1 is the other end of the first member 21 and the second member 22 on the side where the first member 21 is not connected to the first arch portion 11. It may be a linear distance between the other end of the second member 22 that is not connected to the second arch portion 12.

The average resistance length Lt of the steel fiber 1 may mean the length of the steel fiber 1 when the steel fiber 1 is stretched in a straight line. That is, the average resistance length Lt may be a value obtained by dividing the volume of the steel fiber 1 by the cross-sectional area of the steel fiber 1.

Hereinafter, referring to FIG. 1, a shape of a steel fiber 1 for reinforcing a cement-based material having a pair of arches according to embodiments will be described.

1(a) shows the structure of a pair of steel fibers 1 having a symmetrical arch shape according to embodiments. 1(b) shows the linear length (L) and the average resistance length (Lt) of the steel fiber 1 according to the embodiments.

The steel fiber 1 according to the embodiments has a first arch portion 11 having a convex shape toward the first direction B1 and having a first radius of curvature R1, and a first arch portion 11 opposite to the first direction B1. A second arch portion 12 having a convex shape toward the second direction B2 and having a second radius of curvature R2 may be included. In addition, the steel fiber may include a connecting portion 20 connecting one end of the first arch portion 11 and one end of the second arch portion 12 to each other.

The steel fiber 1 according to the embodiments includes a first member 21 connected to the other end of the first arch part 11 and a second member 22 connected to the other end of the second arch part 12. I can.

The steel fiber 1 according to the embodiments includes a first connecting arch portion 31 having a convex shape toward the second direction B2 at a portion where the first arch portion 11 and the connecting portion 20 are connected. The second arch portion 12 and the connecting portion 20 may be connected to each other, and a second connecting arch portion 32 having a convex shape toward the first direction B1 may be included.

The steel fiber 1 according to the embodiments is a third connection arch portion 33 having a convex shape toward the second direction B2 at a portion where the first arch portion 11 and the first member 21 are connected. And a fourth connection arch portion 34 having a convex shape toward the first direction B1 at a portion where the second arch portion 12 and the second member 22 are connected. .

Specifically, the radius of curvature of the first connecting arch portion 31 is the first length (D1), the radius of curvature of the second connecting arch portion 32 is the second length (D2), and the third connecting arch portion 33 A radius of curvature of) may be a third length D3, and a radius of curvature of the fourth connection arch portion 34 may be a fourth length D4.

At this time, the first radius of curvature R1 and the second radius of curvature R2 are the first connecting arch portion 31, the second connecting arch portion 32, the third connecting arch portion 33, and the fourth connecting arch portion. (34) It may have a value greater than at least one of each radius of curvature. That is, the length of the arch of the first and second arch portions 11 and 12 is longer than at least one of the first to fourth connecting arch portions 31, 32, 33, 34, in other words, the straight length L and / Or it may be configured to have a long average resistance length (Lt).
The steel fiber 1 according to the embodiments may have a symmetrical shape based on a point that becomes the center of the connection part 20.

The steel fiber 1 according to the embodiments differs in a straight line length (L) representing the distance between one end of the steel fiber 1 and the other end and/or the average resistance length (Lt), which is the length of the entire body of the steel fiber 1 As a result, the degree of improvement in concrete properties may vary.

Hereinafter, referring to FIG. 2, a shape of a steel fiber 1 for reinforcing a cement-based material having two pairs of arches according to other embodiments will be described.

2(a) shows the structure of the steel fibers 1 having two pairs of symmetrical arches according to embodiments. 2(b) shows the linear length (L) and the average resistance length (Lt) of the steel fiber 1 according to the embodiments.

The steel fiber 1 according to the embodiments has a convex shape toward the first direction B1 and is convex toward the first arch portion 11 and the second direction B2 having a first radius of curvature R1. A second arch portion 12 having a shape and a second radius of curvature R2 may be included. In addition, it may include a connecting portion 20 connecting one end of the first arch portion 11 and one end of the second arch portion 12.

In addition, the steel fiber 1 according to the embodiments includes a first member 21 connected to the other end of the first arch part 11 and a second member 22 connected to the other end of the second arch part 12. Can include.

The connection part 20 according to the embodiments has a third radius of curvature R3, a third arch part 13 connected to the first arch part 11, and a fourth radius of curvature R4, and has a second radius of curvature. It may include a fourth arch portion 14 connected to the tooth portion 12.

In the steel fiber 1 according to the embodiments, the third arch portion 13 has a convex shape in the first direction B1, and the fourth arch portion 14 has a convex shape in the second direction B2. It may be a steel fiber (1) having. In addition, the steel fiber 1 includes a first connecting arch portion 31 having a convex shape toward the second direction B2 at a portion where the first arch portion 11 and the third arch portion 13 are connected. In addition, a second connection arch portion 32 having a convex shape toward the first direction B1 may be included at a portion where the second arch portion 12 and the fourth arch portion 14 are connected.

In addition, the first connecting arch portion 31 and the third arch portion 13 are connected by a third member 23, and the second connecting arch portion 32 and the fourth arch portion 14 are a fourth member. It can be connected by (24).

In the steel fiber 1 according to other embodiments, the third arch portion 13 has a convex shape in the second direction B2, and the fourth arch portion 14 is convex in the first direction B1. Can have.

In the steel fiber 1 according to the embodiments, at least one of the first radius of curvature R1 and the second radius of curvature R2 is greater than at least one of the third radius of curvature R3 and the fourth radius of curvature R4. Can be a value. That is, the length of the arch of the first and second arch portions 11 and 12 is longer than at least one of the third and fourth arch portions 13 and 14, that is, the straight length L and/or the average resistance length (Lt) can be configured to be long.

The steel fiber 1 according to the embodiments is a third connection arch portion 33 having a convex shape toward the second direction B2 at a portion where the first arch portion 11 and the first member 21 are connected. And a fourth connection arch portion 34 having a convex shape toward the first direction B1 at a portion where the second arch portion 12 and the second member 22 are connected. .

In the steel fiber 1 according to the embodiments, at least one of the third radius of curvature R3 and the fourth radius of curvature R4 is a first connection arch portion 31, a second connection arch portion 32, and a third Each of the connection arch portion 33 and the fourth connection arch portion 34 may have a value greater than at least one of a radius of curvature. That is, the length of the arch of the third and fourth arch portions 13 and 14 is longer than at least one of the first to fourth connecting arch portions 31, 32, 33, 34, in other words, the straight length L and / Or it may be configured to have a long average resistance length (Lt).

The steel fiber 1 according to the embodiments may have a symmetrical shape based on a point that becomes the center of the connection part 20.

In the steel fiber 1 according to other embodiments, the third arch portion 13 has a convex shape in the second direction B2, and the fourth arch portion 14 is in the first direction B1. It may be a steel fiber (1) having a convex shape.

The steel fiber 1 according to the embodiments may have different linear length (L) and average resistance length (Lt) values.

Hereinafter, with reference to FIG. 3, when a pulling force acts on the end of the steel fiber 1, the effect of the shape of the steel fiber 1 according to the embodiments on the cementitious material will be described.

3(a) shows the steel fibers 1 into the first region 1001 to the fourth region 1004 in order to explain a mechanism in which a force acts on the steel fiber 1 when one end of the steel fiber 1 is pulled. It is a separate drawing. 3(b) is a view showing the second area 1002 separately to explain the resistance of the steel fiber 1 to the applied force when a force acts on the second area 1002.

The steel fiber 1 according to the embodiments includes a first member 21 and a first region 1001 including a half of the first arch portion 11 toward the first member 21, and It includes a second region 1002 including a half of the connecting member on the side connected to the tooth 11 and a half of the first arch 11 on the side connected to the connecting member, and the side connected to the second arch 11 It includes a third region 1003 including half of the connecting member and a half of the second arch portion 12 on the side connected to the connecting member, and a second arch portion toward the second member 22 and the second member 22 ( A fourth area 1004 including half of 12) may be included.

According to embodiments, the first region 1001 may include the first member 21, the first resistance part 2001 and/or the second resistance part 2002. The second region 1002 may include a third resistor portion 2003, a fourth resistor portion 2004 and/or a fifth resistor portion 2005. The third region 1003 may include a sixth resistor portion 2006, a seventh resistor portion 2007 and/or an eighth resistor portion 2008. The fourth region 1004 may include the ninth resistance portion 2009, the tenth resistance portion 2010 and/or the second member 22.

Specifically, a pulling force may be applied to an end where the first member 21 is located in the first region 1001 and/or an end where the second member 22 is located in the second region 1002. In this case, the first region 1001, the second region 1002, the third region 1003 and/or the fourth region 1004 of the steel fiber 1 may absorb energy due to a pulling force.

When a tensile force acts on the concrete containing the steel fiber 1 and the deformation of the steel fiber 1 occurs by the tensile force, the maximum pulling load and/or energy absorption rate of the steel fiber 1 is the linear length of the steel fiber 1 (L ), the average resistance length (Lt) of the steel fiber 1 and/or the characteristic of the curved portion in the body of the steel fiber 1.

Since the steel fiber 1 is attached and hardened inside the concrete, when a force acts on the concrete and/or the steel fiber 1, a stress may occur between the surface of the steel fiber 1 and the concrete. Therefore, if the surface area of the steel fiber 1 is large, a greater adhesion force may be generated for the same stress. Even if the steel fibers 1 having the same straight length L, the steel fibers 1 having a longer average resistance length Lt may have a larger surface area. Steel fibers 1 having a larger surface area may have stronger adhesion to concrete.

In addition, when the steel fiber 1 is pulled in both directions, the steel fiber 1 receives a force that is straightened in a straight line. If the steel fiber 1 has a curved shape, a resistance force of the steel itself is generated against the tensile force that attempts to cut the steel in a straight line. The resistance to deformation can absorb energy due to the tensile force acting on the concrete.

With reference to FIG. 3(b), it looks at the aspect in which the adhesion force acts in the second region 1002 of the steel fiber 1 according to the embodiments.

When a pulling force (F) acts on one end of the second region 1002, the third resistance unit 2003, the fourth resistance unit 2004 and/or the fifth resistance unit 2005 absorbs energy. can do. In this case, due to the presence of each of the resistance units, the second region average resistance length Lt2 may be longer than the second region linear length L2.

Due to the above effect, the steel fiber 1 including the first region 1001 to the fourth region 1004 including the resistance unit according to the embodiments has an average resistance length Lt compared to a linear length L Can increase. As the average resistance length Lt increases, the adhesion of the steel fibers 1 increases, and thus the degree of energy absorption of the steel fibers 1 may increase.

Specifically, compared with the steel fiber 1 of the type having hooks on both sides of the straight body and/or the steel fiber 1 having only one arch, the steel fiber 1 having two symmetrical arch shapes has a straight length (L ), the average resistance length (Lt) may be longer. This can have the effect of increasing the surface area of the steel fiber (1). In addition, it is possible to have the characteristic of increasing the adhesive force acting between the steel fiber (1) and concrete.

Referring to Figure 3 (b), looks at the action of the resistance force against deformation in the second region 1002 of the steel fiber 1 according to the embodiments.

When the pulling force (F) acts on one end of the second region 1002, the third resistance unit 2003, the fourth resistance unit 2004, and the fifth resistance unit 2005 are all straightened. You will receive strength. In this case, each of the resistance units may have resistance to straightening.

At this time, the resistance of the second region 1002 against deformation is the first radius of curvature R1, which is the radius of curvature of the third resistance unit 2003, the radius of curvature of the fourth resistance unit 2004, and/or the fifth resistance. It may vary depending on the radius of curvature of the negative (2005).

That is, in the steel fiber 1 according to the embodiments, the first radius of curvature R1 and the eighth resistance portion 2008, which are the radius of curvature of the second resistance portion 2002 and/or the third resistance portion 2003, and /Or the second radius of curvature R2, which is the radius of curvature of the ninth resistor unit 2009, may be appropriately adjusted. In addition, the radius of curvature of the first resistor portion 2001, the fourth resistor portion 2004, the seventh resistor portion 2007, and/or the tenth resistor portion 2010 may be appropriately adjusted. In addition, the radius of curvature of the fifth resistor portion 2005 and/or the sixth resistor portion 2006 can be appropriately adjusted. According to this adjustment, it is possible to change the resistance of the steel fiber 1 to the force causing deformation.

Due to the above effect, the steel fiber 1 including the resistance part according to the embodiments may have an effect of increasing the degree of energy absorption compared to the steel fiber 1 having a linear shape.

That is, compared with the steel fiber 1 of the type having hooks on both sides of the straight body and/or the steel fiber 1 having only one arch, the steel fiber 1 having two symmetrical arch shapes has more resistance. I can. This may have an effect of increasing the resistance of the steel fiber (1). In addition, when the tensile force acting on the concrete tries to deform the steel fiber 1, the resistance of the steel fiber 1 can be increased.
In addition, the steel fiber 1 according to the embodiments has a point symmetrical structure based on a point that becomes the center of the connecting portion 20, thereby structurally improving the bending toughness ability in all directions.

Hereinafter, with reference to FIGS. 4 to 11, the experimental results of the maximum pull-out load and energy absorption amount according to the embodiment of the steel fibers 1 will be described.

4 is a diagram of a pull-out test specimen applied to a steel fiber according to embodiments. The material of the specimen is cement and its height is 76.2mm. The cross section of the specimen where the steel fiber is located is a square with a length of 25.4 mm on one side.

The experiment according to the embodiments was conducted in a pull-out test method, and was performed in a manner that a tensile force was applied to both directions of the concrete by including the steel fiber (1) inside the concrete specimen. Through this experiment, it is possible to measure the maximum tensile load acting on the concrete and/or the steel fibers 1 contained therein. In addition, through this experiment, the displacement of the members due to the tensile force acting on the concrete and/or the steel fibers 1 contained therein can be measured.

The load-displacement graph can be obtained by experiments according to the embodiments. The vertical axis represents the maximum pulling load acting on the steel fiber 1, and the horizontal axis represents the deformation of the steel fiber 1. The energy absorbed by the steel fiber 1 can be obtained through the area of the graph.

An energy-displacement graph can be obtained by experiments according to the embodiments. The vertical axis represents the energy absorbed by the steel fiber 1, and the horizontal axis represents the deformation of the steel fiber 1. The energy-displacement graph is the integral value of the load-displacement graph.

The examples of FIGS. 5 to 11 are the results of experiments conducted using different steel fibers 1 having a diameter of 0.75 mm. The tensile strength of the steel fiber 1 used in each of the embodiments is 1500 MPa.

5 is an experimental result of a pull-out test for an end-hook type steel fiber.

The experiment of FIG. 5 is a pull-out test for end-hook type steel fibers that have been widely used in the past. The end-hook type steel fiber according to the experiment of FIG. 5 has a linear length (LH) of 60 mm. Five specimens were used.

5(a) is a load-displacement graph, FIG. 5(b) is an energy-displacement graph, and FIG. 5(c) is a diagram showing the average maximum load of the specimens in a dotted line in the maximum pull-out load result table of the specimens, and FIG. 5 ( d) is a diagram showing the absorbed energy of the end-hook type steel fiber with a dotted line among the results of each of the examples.

5(e) is a view showing the shape of an end-hook type steel fiber that has been widely used in the past.

In the experiment for the end-hook type steel fiber, a maximum load of 240.82N and an average absorbed energy amount of 1971.02 N*mm were derived according to the average of five test specimens.

6 is an experimental result of a pull-out test for a single arcuate steel fiber.

In the experiment of FIG. 6, a pull-out test was performed on a single arc-shaped steel fiber having only one arc shape. The single arc-shaped steel fiber according to the experiment of FIG. 6 has a straight line length (LH) of 60 mm. Three specimens were used.

6(a) is a load-displacement graph, FIG. 6(b) is an energy-displacement graph, and FIG. 6(c) is a diagram showing the average maximum load of the specimens in a dotted line in the maximum pull-out load result table of the specimens, and FIG. 6 ( d) is a diagram showing the absorbed energy of a single arc-shaped steel fiber with a dotted line among the results of each of the examples.

In the experiment for the steel fiber containing only one arch structure, the maximum load of 249.79N and the average absorbed energy amount of 1740.04 N*mm were derived according to the average of three specimens.

7 is an experiment result of a pull-out test according to the first embodiment.

In the experiment of the first embodiment, the third radius of curvature (R3) and the fourth radius of curvature (R4) have an infinite value, and a pull-out test is conducted on a steel fiber (1) having a pair of symmetrical arches. I did it. The steel fiber 1 according to the first embodiment has a straight length L of 60 mm. Five specimens were used.

7(a) is a load-displacement graph, FIG. 7(b) is an energy-displacement graph, and FIG. 7(c) is a diagram showing the average maximum load of the specimens with a dotted line in the maximum pull-out load result table of the specimens, and FIG. 7 ( d) is a diagram showing the absorbed energy of the first embodiment with a dotted line among the results of each of the embodiments.

In the experiment according to the first embodiment, a maximum load of 422.09 N and an average absorbed energy amount of 4232.77 N*mm were derived according to the average of five specimens.

8 is an experiment result of the pull-out test according to the second embodiment.

In the experiment for the second embodiment, the third radius of curvature (R3) and the fourth radius of curvature (R4) had values other than infinity, so that a pull-out test was performed on steel fibers 1 having two pairs of symmetrical arches. It was in progress. The steel fiber 1 according to the second embodiment has a straight length L of 60 mm. Four specimens were used. In the experiment according to the second embodiment, the fracture occurred in the two specimens, and the two specimens in which the fracture occurred were included only in the maximum pullout strength analysis and excluded from the energy absorption performance analysis.

8(a) is a load-displacement graph, FIG.8(b) is an energy-displacement graph, and FIG.8(c) is a diagram showing the average maximum load of the specimens in a dotted line in the maximum pull-out load result table of the specimens, and FIG. d) is a diagram showing the absorbed energy of the second embodiment with a dotted line among the results of each of the embodiments.

In the experiment for Example 2, the maximum load of 350.62 N was obtained according to the average of the four specimens, and the average absorbed energy amount of 4006.62 N*mm was derived according to the average of the two specimens.

9 is an experiment result of a pull-out test according to the third embodiment.

In the experiment for the third embodiment, the third radius of curvature (R3) and the fourth radius of curvature (R4) have an infinite value, and a pull-out test is conducted on a steel fiber (1) having a pair of symmetrical arches. I did it. The steel fiber 1 according to the third embodiment has a linear length L of 55 mm. Five specimens were used, Fig. 9(a) is a load-displacement graph, Fig. 9(b) is an energy-displacement graph, and Fig. 9(c) shows the average maximum load of the specimens in a dotted line in the maximum pull-out load result table of the specimens. 9(d) is a diagram in which the absorbed energy of the third embodiment is indicated by dotted lines among the results of each of the embodiments.

In the experiment for Example 3, a maximum load of 372.05N and an average absorbed energy amount of 3377.92 N*mm were derived according to the average of five test specimens.

10 is an experiment result of a pull-out test according to the fourth embodiment.

In the experiment for the fourth embodiment, the third radius of curvature (R3) and the fourth radius of curvature (R4) had values other than infinity, so that a pull-out test was performed on steel fibers 1 having two pairs of symmetrical arches. It was in progress. The steel fiber 1 according to the fourth embodiment has a straight length L of 55 mm. Five specimens were used. In the experiment according to the fourth embodiment, since a fracture occurred in three specimens, the three specimens in which the fracture occurred were included only in the maximum pullout strength analysis and excluded from the energy absorption performance analysis.

10(a) is a load-displacement graph, FIG. 10(b) is an energy-displacement graph, and FIG. 10(c) is a diagram showing the average maximum load of the specimens with a dotted line in the maximum pull-out load result table of the specimens, and FIG. d) is a diagram showing the absorbed energy of the fourth embodiment with a dotted line among the results of each of the embodiments.

In the experiment for Example 4, a maximum load of 342.25 N was obtained according to the average of five specimens, and an average absorbed energy amount of 3580.16 N*mm was derived according to the average of two specimens.

11 is an experiment result of the pull-out test according to the fifth embodiment.

In the experiment for the fifth embodiment, the third radius of curvature (R3) and the fourth radius of curvature (R4) had values other than infinity, so that a pull-out test was performed on steel fibers 1 having two pairs of symmetrical arches. It was in progress. The steel fiber 1 according to the fifth embodiment has a linear length L of 42 mm. Five specimens were used.

FIG. 11(a) is a load-displacement graph, FIG. 11(b) is an energy-displacement graph, and FIG. 11(c) is a diagram showing the average maximum load of the specimens in a dotted line in the maximum pull-out load result table of the specimens, and FIG. 11 ( d) is a diagram showing the absorbed energy of the fifth embodiment with a dotted line among the results of each of the embodiments.

In the experiment for Example 5, a maximum load of 390.46 N and an average absorbed energy amount of 2976.51 N*mm were derived according to the average of five specimens.

Hereinafter, the results of the experiments according to Examples 1 to 5 are compared with the experimental results of the existing end-hook steel fibers.

In the first, second, and conventional end-hook steel fibers experiments, all three experiments used a specimen having a straight length (L) of 60 mm.

The energy absorption of the first embodiment having a pair of arches is 4232.77 N*mm, which is about 114% higher than that of the end-hook steel fiber. In addition, the maximum pull-out load was 422.09 N, which was about 75% higher than that of the end-hook steel fiber. Therefore, the first embodiment may have superior performance than the end-hook steel fiber.

The energy absorption of the second embodiment having two pairs of arches is 4006.62 N*mm, which is about 103% higher than that of the end-hook steel fiber. In addition, the maximum pull-out load was 350.62N, which was about 45% higher than that of the end-hook steel fiber. Therefore, the second embodiment may have better performance than the end-hook steel fiber.

In the third and fourth examples, a test specimen having a linear length (L) of 55 mm was used.

The energy absorption of the third embodiment having a pair of arches is 3377.82 N*mm, which is about 71% higher than that of the end-hook steel fiber. In addition, the maximum pull-out load was 372.05 N, which was about 54% higher than that of the end-hook steel fiber. Accordingly, the third embodiment may have superior performance than the end-hook steel fiber, although the straight length L is shorter than that of the end-hook steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

The energy absorption of the fourth embodiment having two pairs of arches is 3580.16 N*mm, which is about 81% higher than that of the end-hook steel fiber. In addition, the maximum pull-out load was 342.25N, which was about 42% higher than that of the end-hook steel fiber. Accordingly, the fourth embodiment may have superior performance than the end-hook steel fiber, even though the straight length L is shorter than that of the end-hook steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

In the fifth embodiment, a test specimen having a linear length (L) of 42 mm was used.

The energy absorption of the fifth embodiment having two pairs of arches is 2976.51 N*mm, which is about 51% higher than that of the end-hook steel fiber. In addition, the maximum pull-out load was 390.46N, which was about 62% higher than that of the end-hook steel fiber. Accordingly, the fifth embodiment may have superior performance than the end-hook steel fiber, although the straight length L is shorter than that of the end-hook steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

Hereinafter, the results of the experiments according to the first to fifth embodiments are compared with the experimental results of the existing single arc-shaped steel fibers.

In the first embodiment, the second embodiment, and the experiments on the single arc-shaped steel fibers used in the past, all three experiments used a test specimen having a straight length (L) of 60 mm.

The energy absorption of the first embodiment having a pair of arches is 4232.77 N*mm, which is about 143% higher than that of the single arched steel fiber. In addition, the maximum pull-out load was 422.09 N, which was about 69% higher than that of single arched steel fiber. Therefore, the first embodiment may have better performance than a single arcuate steel fiber.

The energy absorption of the second embodiment having two pairs of arches is 4006.62 N*mm, which is about 130% higher than that of the single arched steel fiber. In addition, the maximum pull-out load was 350.62N, which was about 40% higher than that of single arch steel fiber. Therefore, the second embodiment may have better performance than the single arc-shaped steel fiber.

In the third and fourth examples, a test specimen having a linear length (L) of 55 mm was used.

The energy absorption of the third embodiment having a pair of arches is 3377.82 N*mm, which is about 117% higher than that of the single arched steel fiber. In addition, the maximum pull-out load was 372.05 N, which was about 49% higher than that of single arched steel fiber. Accordingly, the third embodiment may have superior performance than the single arc-shaped steel fiber, although the straight length (L) is shorter than that of the single arc-shaped steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

The energy absorption of the fourth embodiment having two pairs of arches is 3580.16 N*mm, which is about 106% higher than that of the single arched steel fiber. In addition, the maximum pull-out load was 342.25N, which was about 37% higher than that of single arch steel fiber. Therefore, the fourth embodiment may have superior performance than the single arc-shaped steel fiber, although the straight length (L) is shorter than that of the single arc-shaped steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

In the fifth embodiment, a test specimen having a linear length (L) of 42 mm was used.

The energy absorption of the fifth embodiment having two pairs of arches was 2976.51 N*mm, which is about 71% higher than that of the single arched steel fiber. In addition, the maximum pull-out load was 390.46N, which was about 56% higher than that of single arch steel fiber. Therefore, the fifth embodiment can have superior performance than the single arched steel fiber, although the straight length L is shorter than that of the single arched steel fiber. This means that less material can be used and a better effect than existing steel fibers can be obtained.

Hereinafter, the results of the flexural performance test according to the first embodiment described above will be described with reference to FIGS. 12 to 14.

12 is a view to help explain the bending test applied to the steel fiber according to the embodiments.

12(a) is a diagram for explaining a method of applying a two-part loading test as a method for examining the flexural performance test. Fig. 12(b) is an enlarged view of a notch portion of a two-part loading test. 12(c) is a graph showing the result values according to the results of the flexural performance test.

As described above, the steel fiber 1 of the first embodiment is a steel fiber 1 having a pair of symmetrical arches since the third radius of curvature R3 and the fourth radius of curvature R4 have infinite values. For the bending performance test was conducted.

The material of the specimen is cement, and it is a square-shaped specimen of 150mm x 150mm x 550mm, made with a notch in the lower part of the center, and loaded at two equal points according to the test method of BS EN 14651 (Test method for metallic fibered concrete-Measuring the flexural tensile strength). Experimented by test.

Specifically, it is possible to obtain a CMOD-F graph by an experiment according to the embodiments. The vertical axis represents the residual flexural tensile strength of the specimen, and the horizontal axis represents the CMOD (Crack Mouth Opening Displacement), which is the displacement value after cracking in the notch.

13 and 14 are results of experiments using the above-described end-hook steel fiber, single arc steel fiber, and steel fiber 1 of the first embodiment. The experiment was conducted by placing steel fibers having a tensile strength of 1,500 Mpa, a diameter of 0.75 mm, and a length of 60 mm at a mixing amount of 30 kg/m^3.

Table 1 is the mixing ratio of concrete for checking the flexural performance.

Design standard compressive strength (MPa) Maximum dimension of coarse aggregate (mm) Air volume (%) S/a(%) W/C(%) Unit material quantity (kg/m ³ ) Water(W) Cement (C) Fine aggregate (S) Coarse aggregate (G) High performance AE water reducing agent (AD) 30 25 5 48.3 48.0 171 356 893 959 2.1

The flexural performance can be grasped through Fr1, Fr2, Fr3, Fr4 representing the residual flexural tensile strength and FL, which is the flexural strength. FL is the flexural strength when the initial cracking occurs. Fr1 to Fr4 are the residual flexural tensile strength. Fr1 is the strength of residual bending when the width of the notch in the specimen (A) is 0.5mm wide, Fr2 is the strength of the residual bending when the width (A) of the notch in the specimen is 1.5mm wide, and Fr3 is the notch in the specimen area. It is the strength of residual warpage when the width (A) of is 2.5mm wide, and Fr4 is the strength of the residual warpage when the width (A) of the notch in the specimen is 3.5mm wide.

The flexural test result can be confirmed through the graph of FIG. 13.

Figure 13 (a) is a graph showing the comparison of the flexural performance test results of the first embodiment and the end-hook type steel fiber. 13(b) is a graph showing a comparison of the flexural performance test results of the steel fiber 1 of the first embodiment and the single arc steel fiber.

Looking at the experimental results, in the case of the first embodiment, FL = 5.34 MPa, Fr1 = 4.06 MPa, Fr2 = 4.74 MPa, Fr3 = 4.39 MPa, Fr4 = 3.79 MPa.

In addition, in the case of concrete reinforced with conventional end-hook type steel fibers, FL = 4.0 MPa, Fr1 = 3.26 MPa, Fr2 = 3.58 MPa, Fr3 = 3.61 MPa, Fr4 = 3.51 MPa.

In addition, in the case of a single arc steel fiber, FL=4.67MPa, Fr1=3.14MPa, Fr2=3.49MPa, Fr3=3.74MPa, Fr4=3.51MPa.

With reference to FIG. 14, when a conventional end-hook type steel fiber is used and when the steel fiber 1 of the first embodiment is used, the bending performance is compared with each other.

In the first embodiment, compared with the conventional end-hook type steel fiber, FL (4.0 MPa/5.34 MPa) is 33.38%, Fr1 (3.26 MPa/4.06 MPa) is 24.57%, and Fr2 (3.58 MPa/4.74 MPa) is 32.37%. %, Fr3(3.61MPa/4.39MPa) increases by 21.66%, Fr4(3.51/3.79MPa) increases by 8.22%. Therefore, it can be seen that the steel fiber 1 of the first embodiment exhibits superior performance against warpage than the conventional end-hook type steel fiber.

With reference to FIG. 14, when a single arcuate steel fiber is used and when the steel fiber 1 of the first embodiment is used, the bending performance is compared with each other.

In the first embodiment, compared with single arc steel fiber, FL (4.67 MPa/5.34 MPa) is 14.31%, Fr1 (3.14 MPa/4.06 MPa) is 29.13%, Fr2 (3.49 MPa/4.74 MPa) is 35.92%, and Fr3 (Fr3) is 35.92%. 3.74 MPa/4.39 MPa) is 17.41%, Fr4 (3.61 MPa/3.79 MPa) is 5.0%. Increases by Therefore, it can be seen that the first embodiment exhibits superior performance against warpage than a single arcuate steel fiber.

The adhesion strength between the steel fiber 1 and concrete according to the first embodiment is superior to that of the conventionally invented steel fiber. Therefore, it can be seen that the bending performance of the concrete member including the steel fiber 1 of the first embodiment is also excellent.
As can be seen through the results of FIGS. 13 and 14, the conventional end-hook type steel fiber and the single arch type steel fiber have a line symmetrical structure, whereas the steel fiber 1 according to the embodiment of the present invention has a connection part 20 It can be seen that by having a point symmetrical structure based on the point that becomes the center of, structurally, there is an effect of improving the flexural toughness ability in all directions. In addition, there is a connection portion 20 between the first arch portion and the second arch portion constituting the double arched structure according to the embodiment of the present invention, and the length of the adhesive strength increases due to this connection portion, thereby further improving the flexural toughness capability. Therefore, compared to existing products, the mechanical friction strength is increased due to the presence of two arches and a connection portion interposed therebetween, thereby improving the flexural toughness performance.

Since conventional steel fibers have a nominal diameter of 0.30mm or more and 1.00mm or less and are generally used, the embodiments may also have a standard of 0.30mm or more and 1.00mm or less.

In addition, since the conventional steel fiber has a standard of 30mm or more and 80mm or less of a straight length (L) and is generally used, embodiments may also have a standard of 30mm or more and 80mm or less.

In addition, since the conventional steel fiber is generally used as a material having a tensile strength of 500 MPa or more and 2800 Mpa or less, the examples may also have a tensile strength of 500 MPa or more and 2800 Mpa or less.

Conventional steel fibers are generally used for reinforcing cement-based materials among materials used in construction and/or civil works. However, the steel fibers according to the embodiments may also be used for reinforcing synthetic resin-based materials. In addition, the steel fibers according to the embodiments may be used for reinforcing interior and exterior materials for buildings.

As described above, the present invention is not limited to the above-described embodiments. As can be seen from the appended claims, the present invention can be modified by a person skilled in the art to which the present invention belongs, and such modifications are within the scope of the present invention.

1: steel fiber
11: 1st arch part
12: second arch portion
13: 3rd arch part
14: fourth arch portion
20: connection
21: first member
22: second member
23: third member
24: fourth member
31: 1st connecting arch part
32: second connection arch portion
33: 3rd connecting arch part
34: 4th connecting arch part
R1: first radius of curvature
R2: second radius of curvature
R3: 3rd radius of curvature
R4: 4th radius of curvature
D1: first length
D2: second length
D3: third length
D4: fourth length
B1: first direction
B2: 2nd direction
L: straight length (L)
Lt: Average resistance length (Lt)
L2: 2nd area straight length (L)
Lt2: Average resistance length of the second region (Lt)
1001: first area
1002: second area
1003: third area
1004: fourth area
2001: 1st curved part
2002: 2nd curved part
2003: 3rd curved part
2004: 4th curved part
2005: 5th curved part
2006: 6th curved part
2007: 7th Curve
2008: 8th Curve
2009: 9th Curve
2010: The 10th Curve

Claims (19)

A first arch portion having a convex shape toward a first direction and having a first radius of curvature;
A second arch portion having a convex shape toward a second direction opposite to the first direction and having a second radius of curvature;
A connection portion connecting one end of the first arch portion and one end of the second arch portion;
A first member connected to the other end of the first arch portion; And
A second member connected to the other end of the second arch portion; In the high-performance steel fiber comprising a,
A third connection arch portion having a convex shape toward the second direction at a portion where the first arch portion and the first member are connected; And
A fourth connection arch portion having a convex shape toward the first direction at a portion where the second arch portion and the second member are connected; Including more,
At least one of the first radius of curvature and the second radius of curvature is a high-performance steel fiber having a value greater than at least one of a radius of curvature of each of the third connection arch portion and the fourth connection arch portion.
The method of claim 1
A first connecting arch portion having a convex shape toward the second direction at a portion where the first arch portion and the connecting portion are connected; And
A second connection arch portion having a convex shape toward the first direction at a portion where the second arch portion and the connection portion are connected; High-performance steel fiber further comprising a.
delete The method of claim 2
At least one of the first radius of curvature and the second radius of curvature has a value greater than at least one of each of the first to fourth connecting arch portions.
A first arch portion having a convex shape toward a first direction and having a first radius of curvature;
A second arch portion having a convex shape toward a second direction opposite to the first direction and having a second radius of curvature;
A connection portion connecting one end of the first arch portion and one end of the second arch portion;
A first member connected to the other end of the first arch portion; And
A second member connected to the other end of the second arch portion; Including
The connection part
A third arch portion having a third radius of curvature and connected to the first arch portion; And
A fourth arch portion having a fourth radius of curvature and connected to the second arch portion; In the high-performance steel fiber comprising a,
At least one of the first radius of curvature and the second radius of curvature has a value greater than at least one of the third radius of curvature and the fourth radius of curvature.
The method of claim 5
The third arch portion has a convex shape toward the first direction
The fourth arch portion is a high-performance steel fiber having a convex shape toward the second direction.
The method of claim 5
The third arch portion has a convex shape toward the second direction
The fourth arch portion is a high-performance steel fiber having a convex shape toward the first direction.
The method of claim 6
A first connecting arch portion having a convex shape in the second direction is included at a portion where the first arch portion and the third arch portion are connected, and
A high-performance steel fiber comprising a second connection arch portion having a convex shape toward the first direction at a portion where the second arch portion and the fourth arch portion are connected.
According to claim 8
The first connecting arch portion and the third arch portion are connected by a third member,
The high-performance steel fiber that the second connection arch portion and the fourth arch portion are connected by a fourth member.
delete The method of claim 5,
A third connection arch portion having a convex shape toward the second direction is included at a portion where the first arch portion and the first member are connected, and
A high-performance steel fiber comprising a fourth connection arch portion having a convex shape toward the first direction at a portion where the second arch portion and the second member are connected.
The method of claim 11
At least one of the third radius of curvature and the fourth radius of curvature has a value greater than at least one of each of the first to fourth connecting arch portions.
The method according to claim 1 or 5
The steel fiber is a high-performance steel fiber having a symmetrical shape based on a point that becomes the center of the connection part.
The method according to claim 1 or 5
High-performance steel fibers having a straight length of 30 mm or more and 80 mm or less.
The method according to claim 1 or 5
The diameter of the cross section of the steel fiber is 0.3mm or more and 1.0mm or less high-performance steel fiber.
The method according to claim 1 or 5
The steel forming the steel fiber is a high-performance steel fiber having a tensile strength of 500Mpa or more and 2800Mpa or less.
The method according to claim 1 or 5,
The steel fiber is a high-performance steel fiber used to reinforce a cement-based material.
The method according to claim 1 or 5
The steel fiber is a high-performance steel fiber used to reinforce a synthetic resin-based material.
The method according to claim 1 or 5
The steel fiber is a high-performance steel fiber used to reinforce interior and exterior materials for construction.

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