REINFORCEMENT STEEL
A reinforcement steel bar includes a shaft part extending in a front-back direction, and a head part formed by forging an end portion of the shaft part. A width in a right-left direction of an upper end portion of the head part is formed wider than a diameter of the shaft part. The width in the right-left direction of a lower end portion of the head part is formed narrower than the diameter of the shaft part. An upper end surface extending parallel to an axial direction of the shaft part is formed at the upper end portion of the head part. A left side surface and a right side surface of the head part are inclined such that the width in the right-left direction of the head part is gradually reduced from the upper end portion to the lower end portion of the head part.
The present invention relates to reinforcement steel.
2. Description of the Related ArtA 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 reinforcement steel is made larger than that of a shaft part thereof to increase an anchoring force to concrete.
A ferroconcrete structure is subject to the regulation of a covering depth of concrete from reinforcement steel to an outer surface of the structure. Regarding the reinforcement steel with the head part having the larger diameter than that of the shaft part as mentioned above, if the covering depth of the head part is adjusted to a regulated value, then the covering depth of the shaft part becomes larger than the regulated value. Hence, this results in an increase in weight of the structure.
In this regard, there is another example of the conventional reinforcement steel in which a head part is formed into a semicircular shape by forming a flat surface on the head part (see Japanese Utility Model Registration No. 3191370, for example). In this configuration, if the flat surface of the head part is directed to an outer surface of the structure, the covering depth of the flat surface of the head part is subject to the regulation of the covering depth. As a consequence, it is possible to control the covering depth of the entire reinforcement steel.
SUMMARY OF THE INVENTIONWhen the head part has the semicircular shape as described above regarding the conventional reinforcement steel, an amount of deformation of an end portion of the shaft part is increased when the head part is formed by forging the end portion of the shaft part. This leads to a difficulty in forming the head part.
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, controlling a covering depth of the concrete, and also facilitating formation of a head part.
To solve the problem, the present invention provides a reinforcement steel which includes a shaft part extending in a front-back direction, and a head part formed by forging an end portion of the shaft part. A width in a right-left direction of an upper end portion of the head part is formed wider than a diameter of the shaft part, while the width in the right-left direction of a lower end portion of the head part is formed narrower than the diameter of the shaft part. An end surface extending parallel to an axial direction of the shaft part is formed at the upper end portion of the head part. A left side surface and a right side surface of the head part are inclined such that the width in the right-left direction of the head part is gradually reduced from the upper end portion to the lower end portion of the head part.
Note that in the present invention, the expressions up and down, back and front, and right and left are defined for the convenience of clarifying a configuration of reinforcement steel, and are not intended to limit the structure and a mode of use of the reinforcement steel of the present invention. For instance, the upper end portion of the head part may be placed downward or sideways.
According to the present invention, when a stress attributable to a bending tensile force and to a punching shear force is applied to the reinforcement steel buried in concrete, the head part engages with the concrete. Thus, it is possible to increase an anchoring force to the concrete.
Here, the anchoring force to the concrete can further be increased when the above-described reinforcement steel is deformed reinforcement steel provided with ribs on an outer peripheral surface of the shaft part.
Meanwhile, when the reinforcement steel of the present invention is laid in a ferroconcrete structure, if the end surface of the head part is directed to an outer surface of the structure, then a covering depth of the end surface of the head part is subject to the regulation. Moreover, the covering depth of the end surface of the head part becomes substantially the same as a covering depth of the shaft part. As a consequence, it is possible to control the covering depth of the entire reinforcement steel.
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).
Meanwhile, in the reinforcement steel of the present invention, the head part is provided with the left side surface and the right side surface. Hence, the head part is formed into a substantially triangular shape. In this way, a volume of the head part can be reduced more than that in a configuration of forming the head part into a semicircular shape. This makes it possible to reduce an amount of deformation of the 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. As a consequence, according to the reinforcement steel of the present invention, the head part can be formed easily.
In the above-described reinforcement steel, it is preferable to form each of the left side surface and the right surface into a flat surface so as to facilitate the formation of the head part.
In the above-described reinforcement steel, when a plate-shaped flange portion is formed at an outer peripheral part of a base end portion of the head part, it is possible to surely bring the head part into engagement with the concrete, and thus to increase the anchoring force of the reinforcement steel to the concrete.
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.
In the above-described reinforcement steel, it is preferable to incline the end surface downward from a central portion in the right-left direction to a side edge portion.
In this configuration, if the end surface of the head part is slightly tilted about the axis of the shaft part when the reinforcement steel is laid in the ferroconcrete structure, it is still possible to control the covering depth of the end surface of the head part.
In the above-described reinforcement steel, it is preferable to provide a front end portion of the head part with a front end surface with its normal direction aligned with the axial direction of the shaft part, and to locate an outer edge portion of the front end surface outside, in a 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, the 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 base end surface of the head part and the outer peripheral surface of the shaft part when a 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.
The reinforcement steel of the present invention is capable of increasing the anchoring force to the concrete and controlling the covering depth of the concrete. In addition, according to the reinforcement steel of the present invention, it is possible to reduce the amount of deformation of the end portion of the shaft part when the head part is formed. Thus, the head part can be formed easily.
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.
Moreover, in the following description, the expressions up and down, back and front, and right and left are defined for the convenience of clarifying a configuration of reinforcement steel of each of the embodiments, and are not intended to limit the structure and a mode of use of the reinforcement steel of the present invention.
First EmbodimentAs shown in
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.
The head part 20 is formed at the front end portion of the shaft part 10. The head part 20 is a region of the front end portion of the shaft part 10 shaped by forging. In other words, the shaft part 10 and the head part 20 constitute an integrated member.
The head part 20 projects from the shaft part 10 in a radial direction thereof. As shown in
As shown in
As shown in
The width L1 in the right-left direction of the upper end portion of the head part 20 is set preferably in a range from 1.9 to 2.5 times as large as the diameter D of the shaft part 10.
The upper end surface 23 extending parallel to an axial direction of the shaft part 10 is formed at the upper end portion of the head part 20. The upper end surface 23 is slightly inclined downward from a central portion in the right-left direction to two side edge portions. In other words, the upper end surface 23 is a convex surface in which the center point in the right-left direction is the highest while the surface gradually declines from the central portion toward the right and left side edge portions. The upper end surface 23 is inclined preferably at an angle equal to or below 8 degrees with respect to a horizontal direction.
A distance L2 from the shaft center (the axis) of the shaft part 10 to the central portion in the right-left direction of the upper end surface 23 is set preferably in a range from 0.5 to 0.7 times as large as the diameter of the shaft part 10. This makes it possible to hold the distance L2 within a range of a manufacturing error when forging the head part 20.
The left side surface 24 and the right side surface 25 are flat surfaces that extend downward from the left and right edge parts of the upper end surface 23.
The left side surface 24 and the right side surface 25 are inclined such that the width in the right-left direction of the head part 20 is gradually reduced from the upper end portion to the lower end portion thereof. That is to say, an interval in the right-left direction between the left side surface 24 and the right side surface 25 is gradually reduced downward, and a lower edge part of the left side surface 24 comes into contact with a lower edge part of the right side surface 25.
An opening angle R between the left side surface 24 and the right side surface 25 is set preferably in a range from about 55 degrees to 65 degrees.
The front end surface 21 of the head part 20 is a substantially triangular surface in front view, and is segmented into an upper front end surface 21a and a lower front end surface 21b.
As shown in
An outer edge portion of the upper front end surface 21a is located outside, in the radial direction of the shaft part 10, of a corner portion 26 between the base end surface 22 (see
As shown in
As shown in
A thickness L3 between the upper front end surface 21a and the base end surface 22 is set preferably in a range from 1.0 to 1.2 times as large as the diameter D of the shaft part 10. Meanwhile, a thickness L4 between a lower edge portion of the lower front end surface 21b and the base end surface 22 is set preferably in a range from 0.4 to 0.7 times as large as the diameter D of the shaft part 10.
As shown in
Next, a coupling structure for decks 110 by using the reinforcement steel bar 1A of the first embodiment will be described.
As shown in
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 between the reinforcement steel bar 1A projecting from one of the decks 110 and the reinforcement steel bar 1A projecting from the other deck 110.
Regarding the reinforcement steel bar 1A on the upper side in
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 first embodiment described above, when a stress attributable to a bending tensile force and to a punching shear force is applied to the reinforcement steel bar 1A buried in the concrete C, the head part 20 as well as the ribs 11 on the shaft part 10 engage with the concrete C.
Meanwhile, in the reinforcement steel bar 1A of the first embodiment, a surface area of the head part 20 is increased by the protrusion 27 provided on the front end surface 21 of the head part 20.
As a consequence, the reinforcement steel bar 1A of the first embodiment can 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.
As shown in
In the reinforcement steel bar 1A of the first embodiment, the corner portion 26 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 (see
When the reinforcement steel bar 1A of the first embodiment is laid in the concrete C, if the upper end surface 23 of the head part 20 is directed to the lower surface of the concrete C, a covering depth of the upper end surface 23 of the head part 20 is subject to regulation.
Moreover, a covering depth T1 of the upper end surface 23 of the head part 20 becomes substantially the same as a covering depth T2 of the shaft part 10. Thus, it is possible to control the covering depth of the entire reinforcement steel bar 1A.
In this way, it is possible to reduce the weight of the superstructure 100 by controlling the covering depth of the entire reinforcement steel bar 1A. As described above, when the reinforcement steel bar 1A of the first embodiment is applied to the deck 110, it is possible to increase strength of the deck 110 while reducing its weight as low as that of the existing deck. Furthermore, the thickness of the deck 110 applying the reinforcement steel bar 1A can be kept at a minimum deck thickness as defined in design standards (the Specifications for Highway Bridges).
As shown in
As shown in
Moreover, in the reinforcement steel bar 1A of the first embodiment, each of the left side surface 24 and the right side surface 25 of the head part 20 is formed into the flat surface.
Accordingly, in the reinforcement steel bar 1A of the first embodiment, the head part 20 can be easily formed at the end portion of the shaft part 10 by forging.
Although the first embodiment of the present invention has been described above, the present invention is not limited to the first embodiment but can be changed as appropriate within a range not departing from the scope thereof.
In the first embodiment, the upper end surface 23 of the head part 20 is inclined as shown in
In the first embodiment, each of the left side surface 24 and the right side surface 25 of the head part 20 is formed into the flat surface as shown in
In the first embodiment, the protrusion 27 is formed on the front end surface 21 of the head part 20 as shown in
In the first embodiment, the ribs 11 are formed on the outer peripheral surface of the shaft part 10 as shown in
While the first embodiment has described the structure for coupling the decks 110 to each other as shown in
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.
Second EmbodimentNext, a reinforcement steel bar 1B of a second embodiment will be described.
As shown in
In the reinforcement steel bar 1B of the second embodiment, the plate-shaped flange portion 28 is formed at an outer peripheral part of abase end portion of the head part 20. The flange portion 28 projects outward from the left side surface 24 and the right side surface 25 of the head part 20. As shown in
A width of the flange portion 28 in a direction of projection is set preferably in a range from 0.1 to 0.5 times as large as the diameter of the shaft part 10. In the meantime, as shown in
Here, the flange portion 28 is formed on the left side surface 24 and the right side surface 25 of the head part 20 in the second embodiment. Instead, the flange portion 28 may be formed entirely around the head part 20.
Meanwhile, in the second embodiment, the protrusion 27 is formed on the front end surface 21, the left side surface 24, and the right side surface 25 of the head part 20, as well as on a front end surface of the flange portion 28 thereof as shown in
As shown in
Meanwhile, in the reinforcement steel bar 1B of the second embodiment, its anchoring force to the concrete is increased by providing the head part 20 with the flange portion 28. Thus, the 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 28. This makes it possible to reduce an amount of deformation of the end portion of the shaft part 10 when the head part 20 is formed by forging the end portion of the shaft part 10.
Although the second embodiment of the present invention has been described above, the present invention is not limited to the 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.
For example, the upper end surface 23 of the head part 20 may be formed into a flat surface as shown in
Meanwhile, in the second embodiment, the region on the outer surface of the head part 20 to be provided with the protrusion 27 is not limited to a particular region. For example, the protrusion 27 may be formed only on the front end surface 21 of the head part 20. Alternatively, the protrusion 27 need not be formed on the outer surface of the head part 20.
Third EmbodimentNext, a reinforcement steel bar 1C of a third embodiment will be described.
As shown in
In the third embodiment, the recess 29 is formed along the corner portion 26 between the base end surface 22 of the head part 20 and the outer peripheral surface of the shaft part 10.
The recess 29 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 29 is formed into a curved surface.
In the third embodiment, the recess 29 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 29 in the base end surface 22 is not limited to a particular method. However, when the recess 29 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 third embodiment of the present invention has been described above, the present invention is not limited to the 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 first embodiment.
In the third embodiment, the recess 29 is formed continuously into a circular shape along the outer peripheral surface of the shaft part 10 as shown in
In the meantime, the bottom surface of the recess 29 of the third embodiment is formed into the curved surface. However, the shape of the recess 29 is not limited to a particular shape, and its cross section may be rectangular or triangular. Alternatively, the bottom surface of the recess 29 may have a curved surface formed by continuously providing multiple curved surfaces with different curvatures.
Claims
1. A reinforcement steel comprising:
- a shaft part extending in a front-back direction; and
- a forged head part provided at an end portion of the shaft part, wherein
- a width in a right-left direction of an upper end portion of the head part is formed wider than a diameter of the shaft part,
- the width in the right-left direction of a lower end portion of the head part is formed narrower than the diameter of the shaft part,
- an end surface extending parallel to an axial direction of the shaft part is formed at the upper end portion of the head part, and
- a left side surface and a right side surface of the head part are inclined such that the width in the right-left direction of the head part is gradually reduced from the upper end portion to the lower end portion of the head part, and
- the reinforcement steel is provided with grid ribs on an outer peripheral surface of the shaft part.
2. The reinforcement steel according to claim 1, wherein each of the left side surface and the right side surface is a flat surface.
3. The reinforcement steel according claim 1, wherein a plate-shaped flange portion is formed at an outer peripheral part of a base end portion of the head part.
4. The reinforcement steel according claim 1, wherein a linearly extending protrusion projects from an outer surface of the head part.
5. The reinforcement steel according claim 1, wherein the end surface is inclined downward from a central portion in the right-left direction to a side edge portion.
6. The reinforcement steel according claim 1, wherein
- a front end surface is formed at a front end portion of the head part, and a normal line of the front end surface is parallel to the axial direction of the shaft part, and
- an outer edge portion of the front end surface is outer than a corner portion in a radial direction of the shaft part, the corner portion is provided between a base end surface of the head part and an outer peripheral surface of the shaft part.
7. The reinforcement steel according claim 6, wherein the corner portion is formed into a curved surface.
8. The reinforcement steel according claim 6, wherein a recess is formed along the corner portion.
9. (canceled)
Type: Application
Filed: Jan 26, 2018
Publication Date: Mar 21, 2019
Inventors: Akihiko TAKAHASHI (Fukushima), Yuichi YASHIRO (Ibaraki)
Application Number: 15/880,609