JP3660994B2 - Reinforced concrete member joint structure, attachment used for the joint structure, and replacement rebar - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joining structure of a reinforced concrete member such as a column or a beam and a fixing part in a reinforced concrete structure, such as a joining structure in which a reinforced concrete column in a building structure is erected on a foundation. It relates to the attachments and replacement bars used.
[0002]
[Prior art]
In recent years, the spread of building structures such as condominiums has been remarkable, but at the same time, rebuilding life due to aging, effective measures against earthquakes, etc. have become problems, and are being studied from various viewpoints. In terms of strength of building structures, in addition to material and strength issues such as pillars and beams, it is essential to study material level joining, member level joining, structure level joining, etc. Often dominates the performance of building structures.
[0003]
Among these, joining at the structure level includes connection between structural members such as columns and beams, or joining between a structural member and a fixing portion. In the present specification, the fixing portion refers to a base portion, a ground, or the like. Fig.7 (a) has shown an example of the joining structure which joins the column of the conventional reinforced concrete to a fixing | fixed part. This reinforced concrete column 35 is reinforced with a reinforcing bar composed of a plurality of main bars (column main bars) 36 extending in the vertical direction and band bars (strips wound in a horizontal plane) 37. In such a conventional reinforced concrete column 35, the main reinforcement 36 extends from the column 35 to the fixing portion 38 and is embedded in the concrete 39 placed in the fixing portion 38.
[0004]
[Problems to be solved by the invention]
By the way, reinforced concrete members such as columns and beams in a reinforced concrete structure are composite members of concrete and reinforcing bars. However, reinforcing bars mainly exhibit toughness against tensile force, and concrete supports compressive force.
[0005]
However, for example, in a pillar 35 or the like of a building structure that stands on the fixing portion 38, when a horizontal force is applied due to an earthquake or other various causes, as shown in FIG. A bending moment and a shearing force are applied to 40 in a concentrated manner, and damage is likely to occur.
[0006]
Conventionally, if this part is damaged, it will have a considerable impact on the reduction of the strength and rigidity of the entire building structure, and a large-scale repair work on this part or, in some cases, rebuilding must be made.
[0007]
The object of the present invention is to solve such conventional problems, and with the aging of reinforced concrete structures, repeated bending moments and shearing forces are applied to the joints or concentrated due to earthquakes, etc. Therefore, it is an object of the present invention to provide a reinforced concrete joint structure that can be easily maintained and repaired even if a member end is damaged as a result of a bending moment or shear force acting on it. Note that the “joining part” between the reinforced concrete member and the fixing part such as the foundation part is a boundary part between the reinforced concrete member and the fixing part, but the joining part of the present invention is a part of the joining structure of the reinforced concrete member described later. Say it.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a reinforced concrete member joining structure in which a reinforced concrete member is joined to a fixing portion, and is connected between the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion. Provided is a joining structure for a reinforced concrete member, characterized in that a replacement reinforcing bar is detachably provided.
[0009]
A structure in which attachments are fixed to opposite ends of the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion, and both ends of the replacement reinforcement are detachably attached to the attachment. It is good.
[0010]
The replacement reinforcing bar is provided in a groove formed on the outer surface of the reinforced concrete member, and a cover plate is attached to an outer surface of a portion of the reinforced concrete member to which the replacement reinforcing bar is attached. Or it is good also as a structure fixed with concrete.
[0011]
In order to solve the above problems, the present invention provides an attachment for connecting a main reinforcing bar in the reinforced concrete member and a main reinforcing bar in the fixing unit in a reinforced concrete member bonding structure for bonding a reinforced concrete member to a fixing unit, and a replacement reinforcing bar, The attachment is fixed to each end of the main reinforcing bar in the reinforced concrete member and the main reinforcing bar in the fixing portion facing each other, and the replacement reinforcing bar is attached to the attachment at both ends. Provide attachments and replacement reinforcing bars.
[0012]
The attachment has a box shape in which one side is open and a U-shaped hole is formed at the bottom. The replacement rebar is composed of a rebar main body and upper and lower heads, and the rebar main body is the U-shaped hole. And the head is inserted into the attachment.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
EMBODIMENT OF THE INVENTION Embodiment regarding the joining structure of the reinforced concrete member which concerns on this invention, the attachment used for this joining structure, and a replacement reinforcing bar is described below with reference to drawings based on an Example.
[0014]
FIG. 1 is a diagram for explaining an outline of a joint structure of reinforced concrete members according to the present invention, using a reinforced concrete column 1 as an example of a reinforced concrete member and joining the joints 3 so as to stand up to a fixing portion 2. This reinforced concrete column 1 is reinforced with reinforcing bars such as a main reinforcing bar 4 and a reinforcing bar (not shown) in the same manner as a normal reinforced concrete column.
[0015]
In this reinforced concrete member joining structure 3, an attachment 6 is fixed to the lower end of a main reinforcement (referred to as “upper main reinforcement”) 4 embedded in a reinforced concrete column 1, and a main reinforcement embedded in a fixing portion 3 (referred to as “ An attachment 7 is fixed to the upper end of 5). A replacement reinforcing bar 8 is detachably mounted between the two attachments 6 and 7.
[0016]
Various structures can be considered for the attachments 6 and 7 and the replacement rebar 8. In the example of FIG. 1, the attachments 6 and 7 are substantially box-shaped, while the heads 9 are placed above and below the replacement rebar 8. Provided is a structure in which the head 9 is inserted into the attachments 6 and 7 from the side and attached, and is removable.
[0017]
According to the joint structure 3 of the reinforced concrete member having such a structure, the replacement rebar 8 is fatigued due to repeated bending moment and shearing force acting on the joint structure 3 in which the column 1 is joined to the fixing portion 2, If the replacement rebar 8 is damaged, it can be replaced with another new replacement rebar 8 relatively easily. Therefore, even if the joint structure 3 of a reinforced concrete member is used for many years, predetermined joint strength can be hold | maintained and continuous use of a building structure is enabled.
[0018]
(Example)
FIGS. 2-6 is a figure which shows the structure of the Example based on this invention, FIG. 2 shows the structure of the attachments 6 and 7 used for the joining structure 3 of the reinforced concrete member based on this invention, and the replacement | exchange rebar 8. FIG. It is a figure explaining. Fig.2 (a) has shown the replacement reinforcing bar 8 and its AA sectional drawing. The replacement reinforcing bar 8 is formed of a reinforcing bar main body 10 and upper and lower heads 9.
[0019]
The reinforcing bar main body 10 may have the same cross-sectional structure, thickness and material as the main reinforcing bars 4 and 5 used for the reinforced concrete pillar 1 and the fixing portion 2 of the building structure, or may have a different cross-sectional structure, thickness or material. . The upper and lower heads 9 are formed in a rectangular piece shape having a larger cross-sectional area than the reinforcing bar main body 10 and are formed integrally with the reinforcing bar main body 10.
[0020]
Although not shown, the rebar main body 10 may be configured by welding the rebar main body 10 and the upper and lower heads 9 as separate bodies, or by forming male screws on the upper and lower sides of the rebar main body 10 to form the upper and lower heads. It is good also as a structure which forms an internal thread in 9 and screws an upper and lower head to the reinforcing bar main body 10. In this case as well, the screwed portion should be welded to prevent loosening.
[0021]
When used for an actual replacement rebar 8, the rebar main body 10 of the replacement rebar 8 is covered with a protective cover (or protection cylinder) 11 as shown in FIG. . The protective cover 11 is made of a corrosion-resistant plastic or metal material. Alternatively, a flat plate formed of these materials may be wound around the rebar main body 10 and the ends thereof are heat-bonded to each other to be formed into a cylindrical shape and attached. When the reinforcing bar body 10 and the upper and lower heads 9 are separate bodies, the head 9 may be attached after the reinforcing bar body 10 is inserted into the protective cover 11.
[0022]
One of the features of the replacement rebar 8 according to the present invention is that it is protected by the protective cover 11 and does not adhere to surrounding concrete (such as pre-cast concrete 24 or mortar to be filled, which will be described later). Since it is possible to expand and contract independently, it is particularly difficult for the concrete of the concrete member (concrete column 1 in the embodiment) to be damaged.
[0023]
2C is a perspective view of the attachment 6, and FIG. 2D is a view showing the front, side, and bottom of the attachment 6, respectively. The attachment 6 has a substantially box shape with a space inside, and has left and right side walls 12, a back wall 13, a top wall 14 and a bottom wall 15, and an opening 16 is formed in the front.
[0024]
The attachment 7 has exactly the same structure as the attachment 6, and the attachment 6 is fixed to the lower end of the upper main muscle 4. Therefore, the attachment 7 is fixed to the upper end of the lower main muscle 5, as shown in FIG. Therefore, the vertical direction is opposite to that in FIG. 2C (see FIG. 3A), and the top wall 14 is located below and the bottom wall 15 is located above.
[0025]
A female screw hole 17 is formed in the top wall 14 so that it can be screwed to a male screw 18 formed at the lower end of the upper main reinforcement 4 and the upper end of the lower main reinforcement 5. Although not shown, as a structure for fixing the upper main bar 4 or the lower main bar 5 to the top surface wall 14, the upper main bar 4 and the attachment 6 may be welded directly to the top wall 14 or the lower main bar. 4 and the attachment 7 may be formed as an integral structure.
[0026]
The bottom wall 15 of the attachment 6 is formed with a substantially U-shaped hole 19 that opens to the front side and has a width slightly larger than the reinforcing bar body 10 of the replacement reinforcing bar 8. A guide edge 20 projecting downward is formed on the lower surface of the U-shaped hole 19.
[0027]
FIG. 3 shows a structure for fixing the upper and lower main bars 4, 5 and the attachments 6, 7 during use, and also shows a structure when the replacement reinforcing bar 8 covered with the protective cover 11 is set between the attachments 6, 7. FIG. FIG. 3A is a perspective view showing a state in which the upper and lower attachments 6 and 7 are screwed and fixed to the upper and lower main muscles 4 and 5.
[0028]
FIG. 3B is a perspective view showing a state in which the replacement reinforcing bar 8 is mounted between the upper and lower attachments 6 and 7 fixed to the upper and lower main reinforcing bars 4 and 5, and FIG. FIG. FIG.3 (d) shows AA sectional drawing of FIG.3 (c). The upper and lower heads 9 of the replacement rebar 8 are inserted into the upper and lower attachments 6 and 7 from the front opening 16, and the rebar main body 10 of the replacement rebar 8 is guided by the guide edge 20 and is inserted into the U-shaped hole 19. The replacement rebar 8 is detachably mounted by being inserted through the.
[0029]
FIGS. 4-6 is an Example of the joining structure of the reinforced concrete member based on this invention using the attachment 6 and replacement | exchange rebar 8 which were demonstrated above, and fixes the pillar 1 of the reinforced concrete of a building structure (base part etc.). It is a figure explaining the joining structure of the reinforced concrete member for standing up and fixing to 2. FIG. FIG. 4 shows a cross-sectional view of a reinforced concrete member joining structure 21 in which a reinforced concrete column 1 stands on a fixing portion 2. FIG. 5 (a) shows the AA cross section of FIG. 4 and FIG. Shown in 5 (b). FIG. 6 is an enlarged view of a main part of FIG.
[0030]
As shown in FIG. 4, the upper main bar 4 and the lower main bar 5 are attached to the corner portion 22 of the column 1 and the midpoint portion 23 of the side of the column 1 with the attachments 6 and 7 screwed to the lower and upper ends thereof. It is arranged and embedded in the precast concrete 24 and the fixing part 2. The state in which the upper main reinforcement 4 is embedded in the precast concrete 24 is clearly shown in FIG. In this embodiment, the positions where the upper main bars 4 and the lower main bars 5 are arranged are the positions of the corner portion 22 of the column 1 and the midpoint portion 23 of the side of the column 1. Even if not, other positions may be used as long as they are around the pillar 1 (reinforced concrete member).
[0031]
As shown in FIGS. 5A and 5B, the replacement reinforcing bar 8 includes an upper main reinforcing bar 4 and a lower main reinforcing bar 5 arranged at the corner portion 22 of the column 1 and the midpoint portion 23 of the side of the column 1. The upper main reinforcing bar 4 and the lower main reinforcing bar 5 are connected at these arrangement positions.
[0032]
As described above, a plurality of band bars 25 are arranged at regular intervals in the vertical direction so as to surround the plurality of upper main bars 4 arranged at the corner part 22 and the middle point part 23 of the side of the pillar 1, It is embedded in the precast concrete 24. In addition to the upper main reinforcing bar 4 and the band reinforcing bar 25, various reinforcing bars such as a shear reinforcing reinforcing bar and a core reinforcing bar are usually incorporated in the reinforced concrete column 1, but illustration of these reinforcing bars is omitted.
[0033]
In this embodiment, as shown in FIG. 4, in the vicinity of the replacement reinforcing bar 8, apart from the replacement reinforcing bar 8, a plurality of adhesion assisting reinforcing bars 41 are vertically arranged in the concrete column 1. Are attached and embedded in the pre-cast concrete 24. The adhesion assisting bar 41 has an upper end attached to and embedded in the precast concrete 24 slightly above the replacement reinforcing bar 8, and a lower end is close to the lower end of the concrete column member 21. It does not extend to the inside of the part 2 but is arranged so as to extend a little near the surface of the fixing part 2.
[0034]
Since the adhesion assisting muscle 41 that does not extend to the inside of the fixing unit 2 is arranged as described above, when a force such as a bending moment or a shearing force is applied from the outside due to an earthquake or the like, the deformation due to the force is caused by the adhesion assisting muscle. It is possible to prevent the portion of the reinforced concrete column 1 above the joint structure 3 of the reinforced concrete member from being damaged by being concentrated near the lower end portion of the joint structure 3 of the reinforced concrete column 1 near the lower end of 41.
[0035]
In the vertical region where the replacement reinforcing bar 8 is mounted, the cross section (eg, the AA cross section in FIG. 4) is the cross section of the precast concrete 24 (eg, the CC cross section in FIG. In particular, the area is slightly smaller, and the outer surface is recessed inward by a thickness substantially corresponding to the thickness of a cover plate 26 described later.
[0036]
As shown in FIGS. 5 and 6, a concave groove 27 is formed in the vertical direction on the outer surface of the precast concrete 24 at the corner portion 22 of the column 1 to which the replacement reinforcing bar 8 is mounted and the midpoint portion 23 of the side. . The cross-sectional area of the concave groove 27 is slightly larger than the area of the horizontal cross section of the attachment 6. In the concave groove 27, the attachments 6 and 7 screwed to the upper main bar 4 and the lower main bar 5 are exposed with their openings 16 facing outward.
[0037]
In this way, the replacement reinforcing bar 8 is mounted on the concrete column 1 in which the upper main bar 4 and the lower main bar 5 are embedded in the precast concrete 24. The replacement reinforcing bar 8 is mounted by inserting the upper and lower heads 9 of the replacement reinforcing bar 8 into the upper and lower attachments 6 and 8 from the respective openings 16, and the reinforcing bar main body 10 of the replacement reinforcing bar 8 is attached to the guide edge 20. It is guided and inserted into the U-shaped hole 19 and the concave groove 27.
[0038]
And the band 25 is assembled | attached so that the circumference | surroundings of the some replacement | exchange rebar 8 and the precast concrete 24 may be surrounded. Further, from the outside, the pair of left and right cover plates 26 are mounted so as to be fitted into the recessed portions of the pillar 1 having a small cross-sectional area so as to sandwich the pillar 1 from the left and right. The cover plate 26 has a concave horizontal cross-sectional shape, and is previously formed of a material such as reinforced concrete or steel.
[0039]
An inclined surface 28 is formed at the inner end of the cover plate 26. When the pair of cover plates 26 are attached, the cover plate 26 expands outwardly as shown in FIGS. 5 (a) and 5 (b). An opening groove 29 is formed. Note that an inclined surface 30 is formed on the edge of the precast concrete corresponding to the expanded opening groove 29 as shown in FIG. 6 (a). Easy to do.
[0040]
FIG. 6A shows a state where a pair of cover plates 26 is mounted, and FIG. 6B shows a cross section taken along the line AA. In the state where the pair of cover plates 26 are mounted, a space 31 is formed between the pre-cast concrete 24 and the cover plate 26 as shown in FIGS. A mortar (which may be concrete) 33 is filled into the space 31, the concave groove 27, and the wide open groove 29 from the wide open groove 29 and the opening 32 with the inclined surface 30 thereabove. Set up.
[0041]
The state after placement of the mortar 33 is shown in FIG. 6C and FIG. The cover plate 26 is fixed to the column 1 by the mortar 33 by placing the mortar 33 in the expanded opening groove 29. In this case, since the expanded opening groove 29 is expanded in a tapered shape, the contact area with the mortar 33 is increased by the expanded inclined surface 30, and the pair of cover plates 26 is more powerful. Is fixed to the pillar 1.
[0042]
The reinforcing fiber material 34 is further wound from the outer periphery of the mortar 33 placing surface of the pair of cover plates 26 thus fixed and the opened opening groove 29 that has been placed. The fiber reinforcing material 34 protects the pillar 1 such as waterproofing and moisture proofing, and may be adhered while applying an adhesive to the outer surface of the cover plate 26 or the like from the outside and winding the fiber reinforcing material 34 in advance. An adhesive may be applied to the inner surface of 34. In this manner, a reinforced concrete member joining structure 21 between the reinforced concrete column 1 and the fixing portion 2 is formed as shown in FIGS.
[0043]
According to the joint structure 21 of the reinforced concrete column 1 according to the present invention having the above-described configuration, the replacement rebar 8 is fatigued due to repeated bending moments and shearing forces acting on the joint structure 21 or is greatly caused by an earthquake. Even if the replacement rebar 8 is damaged due to bending moment or shearing force, it can be replaced with a new replacement rebar 8 to maintain the predetermined joint strength even if used for many years. Allows continuous use.
[0044]
When the replacement work of the replacement reinforcing bar 8 is performed, first, the reinforcing fiber material 34 is peeled off, the mortar 33 filled in the expanded opening groove 29 and the like is destroyed and removed, and the pair of cover plates 26 are removed. Further, the mortar 33 filled in the space 31 or the like is destroyed and removed. Then, the damaged or fatigued replacement reinforcing bar 8 is removed from the attachments 6, 7 to the concave groove 27 and replaced with a new replacement reinforcing bar 8.
[0045]
As mentioned above, although the embodiment of the connection structure of the reinforced concrete member concerning the present invention, the attachment used for the connection structure, and the replacement steel bar was explained based on the example, the present invention is limited to such an example. Needless to say, there are various embodiments within the scope of the technical matters described in the claims.
[0046]
For example, attachments and replacement rebars have a structure in which reinforced concrete structural members (columns, beams, etc.) and fixing members, or different reinforced concrete structural members are joined to each other so that the opposite ends of the main bars are detachably connected. The attachment and the replacement reinforcing bar may not be the structure of the above embodiment. For example, it is good also as a structure which can be joined with an attachment and a replacement reinforcing bar using fixing means, such as a clamp, a clip, and a screw.
[0047]
In addition, the placement of replacement reinforcing bars in reinforced concrete structural members (columns, beams, etc.) is not limited to the corners and the midpoints of the sides as in the embodiment, but concentrated on the side that receives a large bending moment and shearing force. The arrangement may be selected appropriately as required, such as arrangement. Moreover, it is good also as a structure which places and covers mortar and concrete directly, without providing a protective cover.
[0048]
【The invention's effect】
According to the joining structure of the reinforced concrete member according to the present invention having the configuration described above, and the attachment and replacement reinforcing bars used in the joining structure, the following effects are produced.
[0049]
(1) As a result of aging of reinforced concrete structures, repeated shearing force acts on the joints, or bending moments or shearing forces act intensively due to earthquakes, etc. By attaching a new replacement rebar to the attachment, maintenance and repair work can be done easily, so the life of the building structure in terms of structural strength can be extended, and damage due to earthquakes can be reduced easily. Can be recovered.
[0050]
(2) Since the replacement reinforcing bar according to the present invention does not adhere to surrounding concrete or the like and can be extended separately from the concrete or the like, it is possible to suppress damage to the concrete.
[0051]
(3) In the joint structure of reinforced concrete members according to the present invention, an attachment auxiliary bar is arranged along the replacement reinforcing bar separately from the replacement reinforcing bar, and one end side of the adhesion auxiliary reinforcing bar is placed in the precast concrete of the concrete member. It is attached and the other end does not extend to the inside of the fixing part, but it is provided to extend to the surface of the fixing part (in the case of a concrete column member, the lower end of the joint structure). When the force is applied, the deformation due to the force is concentrated at the lower end of the reinforced concrete member and at the lower part of the replaceable joint structure, and the main body side of the reinforced concrete member can be prevented from being damaged.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram for explaining an outline of a joining structure of reinforced concrete members according to the present invention.
FIG. 2 is a diagram showing a configuration of an embodiment according to the present invention, and is a diagram for explaining a structure of an attachment and a replacement reinforcing bar used for a joining structure of a reinforced concrete member according to the present invention.
FIG. 3 is a view showing a structure when a main reinforcing bar and an attachment are fixed in use and a replacement reinforcing bar covered with a protective cover is set on the attachment.
FIG. 4 is a cross-sectional view of a reinforced concrete member joining structure according to the present invention using attachments and replacement reinforcing bars, with a column standing on the foundation.
5 shows a cross-sectional view of FIG. 4, FIG. 5 (a) shows an AA cross section, and FIG. 5 (b) shows a BB cross section.
6 is an enlarged view of a main part of FIG.
FIG. 7 is a diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,35 Reinforced concrete pillar 2 Fixation part 3 Joining structure 4 Upper main reinforcement 5 Lower main reinforcement 6, 7 Attachment 8 Replacement reinforcement 9 Head 10 Replacement reinforcement reinforcing bar main body 11 Protective cover 12 Left and right side wall 13 Back wall 14 Top wall 15 Bottom wall 16 Opening 17 Female screw hole 18 Male screw 19 U-shaped hole 20 Guide edge 21 Reinforced concrete member joint structure 22 Column corner 23 Column side midpoint 24 Precast concrete 25, 37 Band 26 Cover plate 27 concave groove 28 inclined surface 29 at the inner end of the cover plate widened opening groove 30 inclined surface 31 space 32 opening 33 mortar 34 fiber reinforcing material 36 main reinforcement 39, 40 concrete 41 adhesion auxiliary reinforcement

Claims (4)

A reinforced concrete member joining structure for joining a reinforced concrete member to a fixing portion, wherein a reinforced concrete member is provided with a replacement reinforcing rod detachably provided between the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion. In the junction structure,
The replacement reinforcing bar is provided in a groove formed on the outer surface of the reinforced concrete member, and a cover plate is attached to an outer surface of a portion of the reinforced concrete member to which the replacement reinforcing bar is attached. Or the joining structure of the reinforced concrete member characterized by being fixed with concrete . A reinforced concrete member joining structure for joining a reinforced concrete member to a fixing portion, wherein a reinforced concrete member is provided with a replacement reinforcing rod detachably provided between the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion. In the junction structure,
Attachments are fixed to the opposite ends of the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion, and both ends of the replacement reinforcement are detachably attached to the attachment .
The replacement reinforcing bar is provided in a groove formed on the outer surface of the reinforced concrete member, and a cover plate is attached to an outer surface of a portion of the reinforced concrete member to which the replacement reinforcing bar is attached. Or the joining structure of the reinforced concrete member characterized by being fixed with concrete . The joining structure of reinforced concrete members according to claim 1 , wherein an adhesion assisting bar is disposed along the replacement reinforcing bar . In the joining structure of the reinforced concrete member for joining the reinforced concrete member to the fixing part, an attachment for connecting the main reinforcing bar in the reinforced concrete member and the main reinforcing bar in the fixing part, and a replacement reinforcing bar,
The attachment is fixed to each end portion of the main reinforcement in the reinforced concrete member and the main reinforcement in the fixing portion facing each other,
The replacement rebar is attached to the attachment at both ends thereof ,
The attachment has a box shape in which one side is open and a U-shaped hole is formed at the bottom. The replacement rebar is composed of a rebar main body and upper and lower heads, and the rebar main body is the U-shaped hole. An attachment and a replacement reinforcing bar, wherein the head is inserted into the attachment.

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