US20190085560A1

US20190085560A1 - Reinforcement steel

Info

Publication number: US20190085560A1
Application number: US15/880,608
Authority: US
Inventors: Akihiko Takahashi; Yuichi YASHIRO
Original assignee: Ono Kogyosyo Co Ltd
Current assignee: Ono Kogyosyo Co Ltd
Priority date: 2017-09-19
Filing date: 2018-01-26
Publication date: 2019-03-21
Also published as: JP6792775B2; CN109518882A; JP2019052516A

Abstract

A reinforcement steel bar includes a shaft part and a head part formed by forging an end portion of the shaft part. A front end surface with its normal direction aligned with an axial direction of the shaft part is formed at a front end portion of the head part. A base end portion of the head part projects from the shaft part in a radial direction of the shaft part. A plate-shaped flange portion is formed at an outer peripheral part of the base end portion of the head part.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to reinforcement steel.

2. Description of the Related Art

A coupling structure for coupling decks laid on a bridge superstructure is configured such that a reinforcement steel bar of one of the decks and a reinforcement steel bar of the other deck are caused to project to a space between the decks, and concrete is placed in the space.
There is an example of reinforcement steel used in a ferroconcrete structure such as the aforementioned deck coupling structure, in which a diameter of a head part of the reinforcement steel is expanded more than a diameter of a shaft part thereof (see Japanese Patent Application Publication No. 2017-071925, for example).

SUMMARY OF THE INVENTION

The head part of the conventional reinforcement steel mentioned above is formed into a truncated conical shape with its diameter gradually expanded from a front end portion to a base end portion thereof. The above-described shape of the head part has a problem of a low anchoring force to the concrete because of low resistance of the head part when a pressure originating from the concrete is applied from the front end side to the base end side of the reinforcement steel.
An object of the present invention is to solve the aforementioned problem by providing reinforcement steel which is capable of increasing an anchoring force to concrete.
To solve the problem, the present invention provides a reinforcement steel which includes a shaft part and a head part formed by forging an end portion of the shaft part. A front end surface with its normal direction aligned with an axial direction of the shaft part is formed at a front end portion of the head part. A base end portion of the head part projects from the shaft part in a radial direction of the shaft part. A plate-shaped flange portion is formed at an outer peripheral part of the base end portion of the head part.
According to the reinforcement steel of the present invention, when a pressure originating from concrete is applied from a front end side of the reinforcement steel to a base end side thereof, the front end surface and the flange portion of the head part can receive the pressure. Meanwhile, when the pressure originating from the concrete is applied from the base end side of the reinforcement steel to the front end side thereof, the base end portion and the flange portion of the head part can receive the pressure.
In this way, according to the reinforcement steel of the present invention, it is possible to increase resistance of the head part against the pressure from the concrete. Therefore, the reinforcement steel of the present invention can reliably bring the head portion into engagement with the concrete, thereby increasing an anchoring force of the reinforcement steel to the concrete.
As mentioned above, in the reinforcement steel of the present invention, the anchoring force to the concrete is increased by providing the head part with the flange portion. Thus, a volume of the head part can be reduced more than that in a configuration of not providing the head part with the flange portion. This makes it possible to reduce an amount of deformation of an end portion of the shaft part so as not to cut off metallic fibers (fiber flows) of the head part when the head part is formed by forging the end portion of the shaft part.
In the above-described reinforcement steel, it is preferable to locate the front end surface at a concentric position with the shaft part, and to locate an outer edge portion of the front end surface outside, in the radial direction of the shaft part, of a corner portion between a base end surface of the head part and an outer peripheral surface of the shaft part.
In this configuration, a thickness from the front end surface to the corner portion between the base end surface of the head part and the outer peripheral surface of the shaft part is equal to a maximum value of a thickness of the head part in the axial direction of the shaft part. Thus, it is possible to increase shear strength of the head part when a tensile force is applied from the concrete to the reinforcement steel.
In the above-described reinforcement steel, if the corner portion is formed into a curved surface or if a recess is formed along the corner portion, a stress is less likely to be concentrated on the corner portion between the flange portion and the outer peripheral surface of the shaft part when the pressure originating from the concrete is applied from the base end side of the reinforcement steel to the front end side thereof. Thus, it is possible to increase fatigue resistance at a junction between the head part and the shaft part.
In the above-described reinforcement steel, it is preferable to provide the head part with a flat surface which is parallel to the axial direction of the shaft part. Moreover, a distance from a shaft center of the shaft part to the flat surface is set preferably in a range from 0.5 to 0.7 times as large as a diameter of the shaft part.
When the above-described reinforcement steel is laid in a ferroconcrete structure, if the flat surface of the head part is directed to an outer surface of the structure, a covering depth of the flat surface of the head part is subject to the regulation of the covering depth. Moreover, the covering depth of the flat surface of the head part becomes substantially the same as a covering depth of the shaft part.
In this way, it is possible to reduce the covering depth of the entire reinforcement steel and thus to reduce the weight of the structure. When the reinforcement steel of the present invention is applied to a deck, it is possible to increase strength of the deck while reducing its weight as low as that of the existing deck. Furthermore, the thickness of the deck can be kept at a minimum deck thickness as defined in design standards (the Specifications for Highway Bridges).
In the above-described reinforcement steel, it is possible to increase a surface area of the head part when a protrusion that extends linearly on an outer surface of the head part is caused to project therefrom. Thus, the anchoring force of the reinforcement steel to the concrete can be increased.
When the above-described reinforcement steel is deformed reinforcement steel provided with a rib on an outer peripheral surface of the shaft part, it is possible to further increase the anchoring force of the reinforcement steel to the concrete.
According to the reinforcement steel of the present invention, since the head part is provided with the front end surface and the flange portion, it is possible to increase the anchoring force to the concrete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing reinforcement steel according to a first embodiment of the present invention.

FIG. 2A is a plan view, FIG. 2B is a front view, and FIG. 2C is a rear view showing the reinforcement steel according to the first embodiment of the present invention.

FIG. 3 is a transverse sectional view showing a coupling structure using the reinforcement steel according to the first embodiment of the present invention.

FIG. 4A is a perspective view and FIG. 4B is a side view showing reinforcement steel according to a second embodiment of the present invention.

FIG. 5 is a transverse sectional view showing a coupling structure using the reinforcement steel according to the second embodiment of the present invention.

FIG. 6A is a perspective view, FIG. 6B is a side view, and FIG. 6C is a front view showing reinforcement steel according to a third embodiment of the present invention.

FIG. 7A is a perspective view and FIG. 7B is a transverse sectional view showing reinforcement steel according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
Note that in the description of the embodiments, the same constituents are denoted by the same reference numerals and overlapping explanations thereof will be omitted.

First Embodiment

As shown in FIG. 1, a reinforcement steel bar 1A of a first embodiment is deformed reinforcement steel made of steel. The reinforcement steel bar 1A includes a shaft part 10 and a head part 20 formed at a front end portion of the shaft part 10.
The shaft part 10 is formed by providing grid ribs 11 on an outer peripheral surface of a rod-shaped member having a circular cross section. Accordingly, the ribs 11 form asperities on the outer peripheral surface of the shaft part 10.
As shown in FIG. 2A, the head part 20 is formed at the front end portion of the shaft part 10. The head part 20 is a forged region of the front end portion of the shaft part 10. In other words, the shaft part 10 and the head part 20 constitute an integrated member.
The head part 20 has a larger diameter than that of the shaft part 10. In the first embodiment, the entire head part 20 projects from the shaft part 10 in a radial direction of the shaft part 10.
The head part 20 of the first embodiment is formed into a truncated conical shape with its diameter gradually expanded from a front end side to a base end side (see FIG. 1). An opening angle of an outer peripheral surface of the head part 20 is set preferably in a range from about 50 degrees to 60 degrees.
A thickness L1 of the head part 20 in an axial direction of the shaft part 10 is set preferably in a range from 1.0 to 1.2 times as large as a diameter D1 of the shaft part 10.
As shown in FIG. 2B, a front end surface 21 of the head part 20 is a flat surface of a circular shape with its normal direction aligned with the axial direction of the shaft part 10. The front end surface 21 is located at a concentric position with the shaft part 10.
A diameter D2 of the front end surface 21 is set preferably in a range from 1.0 to 1.3 times as large as the diameter D1 of the shaft part 10. In the first embodiment, an outer edge portion of the front end surface 21 is located outside, in the radial direction of the shaft part 10, of the outer peripheral surface of the shaft part 10.
As shown in FIGS. 2A and 2C, a base end surface 22 of the head part 20 is a flat surface of a circular shape with its normal direction aligned with the axial direction. The shaft part 10 is connected to a central part of the base end surface 22. As shown in FIG. 2C, in the first embodiment, a diameter D3 of the base end surface 22 is set preferably in a range from 1.6 to 2.0 times as large as the diameter D1 of the shaft part 10. An outer edge portion of the base end surface 22 is located outside, in the radial direction of the shaft part 10, of the outer peripheral surface of the shaft part 10.
As shown in FIG. 2A, the outer peripheral edge portion of the front end surface 21 is located outside of a corner portion 23 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10.
The corner portion 23 is formed into a curved surface. Moreover, the corner portion 23 is preferably formed into the curved surface having a radius in a range from 1.0 mm to 3.0 mm.
As shown in FIG. 1, a plate-shaped flange portion 24 that projects in the radial direction of the shaft part 10 is formed at an outer peripheral part of a base end portion of the head part 20.
The flange portion 24 is a ring-shaped region formed on the entire outer periphery of the base end portion of the head part 20. As shown in FIG. 2A, each of a front end surface and a base end surface of the flange portion 24 is a flat surface with its normal direction aligned with the axial direction of the shaft part 10.
As shown in FIG. 2B, an outside diameter D4 of the flange portion 24 is set preferably in a range from 2.1 to 2.5 times as large as the diameter D1 of the shaft part 10. A width of the flange portion 24 (an amount of projection of the flange portion 24) in the radial direction of the shaft part 10 is set preferably in a range from 0.2 to 0.4 times as large as the diameter D1 of the shaft part 10.
Meanwhile, as shown in FIG. 2A, a thickness L2 of the flange portion 24 in the axial direction of the shaft part 10 is set preferably in a range from 0.2 to 0.6 times as large as the diameter D1 of the shaft part 10.
A protrusion 25 that extends linearly from the front end portion to the base end portion of the head part 20 projects from an outer surface of the head part 20 of the first embodiment. The protrusion 25 is an elongated region with its axial cross section formed into a rectangular shape.
As shown in FIG. 2B, the protrusion 25 extends straight in the radial direction while passing through the center point of the front end surface 21. In addition, the protrusion 25 extends from the outer peripheral edge portion of the front end surface 21 to both sides of the head part 20. As shown in FIG. 2A, the protrusion 25 is formed across the outer peripheral surface of the head part 20 and the front end surface of the flange portion 24. An amount of projection of the protrusion 25 is set preferably in a range from 0.5 mm to 2.0 mm.
Next, a coupling structure for decks 110 by using the reinforcement steel bar 1A of the first embodiment will be described.
As shown in FIG. 3, the first embodiment will describe a coupling structure for coupling the decks 110 laid on a bridge superstructure 100 that includes RC decks.
The decks 110 that are adjacent to each other are placed on bridge beams with an interval in between. Thus, a space 200 is defined between the adjacent decks 110.
Each deck 110 is a precast member made of ferroconcrete. The reinforcement steel bar 1A of the first embodiment is laid inside the deck 110. Moreover, a region on the front end side of the reinforcement steel bar 1A projects in a horizontal direction from an end surface of the deck 110.
Meanwhile, other reinforcement steel bars 2 are disposed above the reinforcement steel bar 1A projecting from one of the decks 110, and still other reinforcement steel bars 2 are disposed below the reinforcement steel bar 1A projecting from the other deck 110.
After the reinforcement steel bars 1A are laid in the space 200 as described above, concrete C is placed in the space 200 to bury the reinforcement steel bars 1A in the concrete C.
Then, the reinforcement steel bars 1A in the decks 110 are anchored to the concrete C, whereby the adjacent decks 110 are coupled to each other through the intermediary of the concrete C.
According to the reinforcement steel bar 1A of the above-described first embodiment, when a pressure originating from the concrete C is applied from the front end side of the reinforcement steel bar 1A to the base end side thereof, the front end surface 21 and the flange portion 24 of the head part 20 can receive the pressure as shown in FIG. 3.
Moreover, in the reinforcement steel bar 1A of the first embodiment, when the pressure originating from the concrete C is applied from the base end side of the reinforcement steel bar 1A to the front end side thereof, the base end surface 22 and the flange portion 24 of the head part 20 can receive the pressure.
Furthermore, in the reinforcement steel bar 1A of the first embodiment, the ribs 11 formed on the outer peripheral surface of the shaft part 10 engage with the concrete C.
Thus, the reinforcement steel bar 1A of the first embodiment can increase resistance of the head part 20 against the pressure from the concrete C. Accordingly, it is possible to bring the reinforcement steel bar 1A of the first embodiment reliably into engagement with the concrete C and thus to increase an anchoring force to the concrete C.
In the reinforcement steel bar 1A of the first embodiment, the head part 20 projects toward the other reinforcement steel bars 2. Accordingly, even if the reinforcement steel bar 1A moves inside the concrete C, it is possible to suppress a displacement of the reinforcement steel bar 1A by allowing the head part 20 to get stuck with the other reinforcement steel bars 2.
In the reinforcement steel bar 1A of the first embodiment, the thickness from the front end surface 21 to the corner portion 23 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10 is equal to a maximum value of the thickness of the head part 20 in the axial direction of the shaft part 10. This makes it possible to increase shear strength of the head part 20 when a tensile force is applied from the concrete C to the reinforcement steel bar 1A.
In the reinforcement steel bar 1A of the first embodiment, the corner portion 23 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10 is formed into the curved surface. For this reason, when the pressure originating from the concrete C is applied from the base end side to the front end side of the reinforcement steel bar 1A, a stress is less likely to be concentrated on the corner portion 23 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10. This makes it possible to increase fatigue resistance at a junction between the head part 20 and the shaft part 10.
In the reinforcement steel bar 1A of the first embodiment, a surface area of the head part 20 can be increased by using the protrusion 25 formed on the outer surface of the head part 20. Thus, it is possible to increase the anchoring force to the concrete C.
In the reinforcement steel bar 1A of the first embodiment, the anchoring force to the concrete C is increased by providing the head part 20 with the flange portion 24. Thus, a volume of the head part 20 can be reduced more than that in a configuration of not providing the head part 20 with the flange portion 24. This makes it possible to reduce an amount of deformation of the end portion of the shaft part 10 so as not to cut off metallic fibers (fiber flows) of the head part 20 when the head part 20 is formed by forging the end portion of the shaft part 10.
Although the first embodiment of the present invention has been described above, the present invention is not limited to the above-described first embodiment but can be changed as appropriate within a range not departing from the scope thereof.
In the first embodiment, the flange portion 24 is formed entirely around the head part 20 as shown in FIG. 1. Instead, the flange portion 24 may be formed on part of an outer peripheral portion of the head part 20. Alternatively, multiple flange portions 24 may be formed on the outer peripheral portion of the head part 20.
In the first embodiment, the protrusion 25 is formed on the front end surface 21 and the outer peripheral surface of the head part 20 as well as on the front end surface of the flange portion 24. However, the region to form the protrusion 25 on the outer surface of the head part 20 is not limited to the foregoing. For example, the protrusion 25 may be formed only on the front end surface 21 of the head part 20. Alternatively, the protrusion 25 need not be formed on the outer surface of the head part 20.
In the first embodiment, the ribs 11 are formed on the outer peripheral surface of the shaft part 10 as shown in FIG. 1. However, the ribs 11 need not be formed on the outer peripheral surface of the shaft part 10. That is to say, the shaft part 10 may be formed of a round rod.
While the first embodiment has described the structure for coupling the decks 110 to each other as shown in FIG. 3, the structure that can apply the reinforcement steel of the present invention is not limited thereto, and the present invention is applicable to various ferroconcrete structures.
In the first embodiment, the reinforcement steel bars 1A are laid in a direction of extension of the superstructure 100. Instead, the reinforcement steel bars 1A may be laid in a width direction of the superstructure 100 so as to connect decks that are juxtaposed in the width direction of the superstructure 100. Moreover, the layout structure of the reinforcement steel bars 1A including orientations, positions, and the like thereof are not limited. For example, the reinforcement steel bars 1A may be disposed above the other reinforcement steel bars 2.

Second Embodiment

Next, a reinforcement steel bar 1B of a second embodiment will be described.
As shown in FIG. 4A, the reinforcement steel bar 1B of the second embodiment has substantially the same configuration as that of the reinforcement steel bar 1A of the above-described first embodiment (see FIG. 1), except that the shapes of the head parts 20 are different from each other.
In the reinforcement steel bar 1B of the second embodiment, a flat surface 27 is formed on the head part 20. As shown in FIG. 4B, a direction orthogonal to the axial direction of the shaft part 10 is defined as a normal direction of the flat surface 27.
In the reinforcement steel bar 1B, a distance L3 (a distance in the radial direction of the shaft part 10) from the shaft center (the axis) of the shaft part 10 to the flat surface 27 is substantially equal to the radius of the shaft part 10.
Note that the distance L3 in the radial direction of the shaft part 10 from the shaft center of the shaft part 10 to the flat surface 27 is set preferably in a range from 0.5 to 0.7 times as large as the diameter D1 of the shaft part 10. This makes it possible to hold the distance L3 within a range of a manufacturing error when forging the head part 20.
Meanwhile, by setting the distance L3 from the shaft center of the shaft part 10 to the flat surface 27 equal to or more than 0.5 times of the diameter D1 of the shaft part 10, it is possible to sufficiently secure the anchoring force of the head part 20 and to prevent the head part 20 from deterioration in strength.
In the meantime, by setting the distance L3 from the shaft center of the shaft part 10 to the flat surface 27 equal to or less than 0.7 times of the diameter D1 of the shaft part 10, it is possible to prevent the flat surface 27 from being located largely outside of the outer peripheral surface of the shaft part 10.
As shown in FIG. 5, in the structure for coupling the decks 110 using the reinforcement steel bars 1B of the second embodiment, the flat surface 27 of the head part 20 of the reinforcement steel bar 1B is directed to an upper surface or a lower surface of the concrete C.
Meanwhile, other reinforcement steel bars 2 are disposed between the reinforcement steel bar 1B projecting from one of the decks 110 and the reinforcement steel bar 1B projecting from the other deck 110.
In this way, a covering depth T1 of the flat surface 27 of the head part 20 is subject to the regulation of a covering depth of the reinforcement steel bar 1B as a whole.
Moreover, the covering depth of the flat surface 27 of the head part 20 becomes substantially equal to a covering depth T2 of the shaft part 10. As a consequence, it is possible to reduce the covering depth of the entire reinforcement steel bar 1B and thus to reduce the weight of the superstructure 100.
Although the second embodiment of the present invention has been described above, the present invention is not limited to the above-described second embodiment but can be changed as appropriate within the range not departing from the scope thereof as has been mentioned in regard to the first embodiment.

Third Embodiment

Next, a reinforcement steel bar 1C of a third embodiment will be described.
As shown in FIG. 6A, the reinforcement steel bar 1C of the third embodiment has substantially the same configuration as that of the reinforcement steel bar 1B of the above-described second embodiment (see FIG. 4A), except that the shapes of the head parts 20 are different from each other. In the reinforcement steel bar 1C of the third embodiment, two flat surfaces 27 are formed on the head part 20.
In the third embodiment, the two flat surfaces 27 formed on the head part 20 are formed substantially parallel to each other while interposing the center of the head part 20 in between as shown in FIG. 6B.
Meanwhile, in the third embodiment, the front end surface 21 is formed into a rectangle in front view as shown in FIG. 6C. When the front end surface 21 is formed into the rectangle as described above, it is possible to increase an axial cross-sectional area of the head part 20 and thus to increase the shear strength thereof.
Although the third embodiment of the present invention has been described above, the present invention is not limited to the above-described third embodiment but can be changed as appropriate within the range not departing from the scope thereof as has been mentioned in regard to the second embodiment.

Fourth Embodiment

Next, a reinforcement steel bar 1D of a fourth embodiment will be described.
As shown in FIG. 7A, the reinforcement steel bar 1D of the fourth embodiment has substantially the same configuration as that of the reinforcement steel bar 1A of the above-described first embodiment (see FIG. 1), except that the shapes of the head parts 20 are different from each other. In the reinforcement steel bar 1D of the fourth embodiment, a recess 28 is formed at the junction between the head part 20 and the shaft part 10.
In the fourth embodiment, the recess 28 is formed along the corner portion 23 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10.
As shown in FIG. 7B, the recess 28 is a region of the base end surface 22 recessed along an outer peripheral edge portion of the shaft part 10. A bottom surface of the recess 28 is formed into a curved surface.
In the fourth embodiment, the recess 28 is formed in the base end surface 22 at the time of forging the front end portion of the shaft part 10 to the head part 20.
Note that the method of forming the recess 28 in the base end surface 22 is not limited to a particular method. However, when the recess 28 is formed at the timing of forging, it is possible to retain the strength of the head part 20 because the metallic fibers (the fiber flows) of the head part 20 are not cut off in this case.
Although the fourth embodiment of the present invention has been described above, the present invention is not limited to the above-described fourth embodiment but can be changed as appropriate within the range not departing from the scope thereof as has been mentioned in regard to the first embodiment.
In the fourth embodiment, the recess 28 is formed continuously into a circular shape along the outer peripheral surface of the shaft part 10 as shown in FIG. 7A. However, the width and depth of the recess 28 are not limited to particular values. Meanwhile, the recess 28 may be formed discontinuously instead.
In the meantime, the bottom surface of the recess 28 of the fourth embodiment is formed into the curved surface as shown in FIG. 7B. However, the shape of the recess 28 is not limited to a particular shape, and its cross section may be rectangular or triangular. Alternatively, the bottom surface of the recess 28 may have a curved surface formed by continuously providing multiple curved surfaces with different curvatures.

Claims

1. A reinforcement steel comprising:

a shaft part; and

a forged head part provided at an end portion of the shaft part, wherein

a front end surface with a normal direction aligned with an axial direction of the shaft part is formed at a front end portion of the head part,

a base end portion of the head part projects from the shaft part in a radial direction of the shaft part,

a plate-shaped flange portion is provided at an outer peripheral part of the base end portion of the head part, and

grid ribs are provided on an outer peripheral surface of the shaft part.

2. The reinforcement steel according to claim 1, wherein

the front end surface is located at a concentric position with the shaft part, and

an outer edge portion of the front end surface is located outside, in a radial direction of the shaft part, of a corner portion between a base end surface of the base end portion and an outer peripheral surface of the shaft part.

3. The reinforcement steel according to claim 2, wherein the corner portion has a curved surface.

4. The reinforcement steel according to claim 2, wherein a recess is formed along the corner portion.

5. The reinforcement steel according to claim 1, wherein a flat surface is provided on the front end and base end portions of the head part, and the flat surface is parallel to the axial direction of the shaft part.

6. The reinforcement steel according to claim 5, wherein a distance from a shaft center of the shaft part to the flat surface is in a range from 0.5 to 0.7 times as large as a diameter of the shaft part.

7. The reinforcement steel according to claim 1, wherein a linearly extending protrusion is provided along an outer surface of the head part.

8. (canceled)