Concrete reinforcing bar and reinforcement structure for concrete member

Abstract

To provide a concrete reinforcing bar with improved elongation performance and a reinforcement structure for a concrete member using the concrete reinforcing bar.SOLUTION: The concrete reinforcing bar includes a bar material body, a fixing member provided at one end side of the bar material body, and a friction die provided at a middle portion in a longitudinal direction of the bar material body, and the friction die is installed on the bar material body by being fastened after passing through the bar material body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a concrete reinforcing bar for reinforcing a concrete structure, and a reinforcing structure for a concrete member. [Background technology]

[0002] For example, PC steel rods are sometimes used not only in prestressed concrete but also as shear reinforcement in reinforced concrete structures, as shown in Patent Document 1. In Patent Document 1, anchoring members are provided on PC steel rods to form shear reinforcement devices, which are then placed on the side walls of box culverts to provide earthquake-resistant reinforcement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-206810 Summary of the Invention [Problem to be solved by the invention]

[0004] High-strength steel, such as PC steel bars, is desirable for use as the main reinforcement in reinforced concrete structures. However, compared to the deformed steel bars (e.g., SD345) commonly used in reinforced concrete structures, these bars have inferior elongation properties, which may result in insufficient deformation performance in reinforced concrete structures during earthquakes. Furthermore, the commonly used deformed steel bars also easily break after repeated plastic deformation after only a few cycles.

[0005] The present invention has been made in consideration of such problems, and its main object is to provide a concrete reinforcing bar with improved elongation performance, and a reinforcing structure for a concrete member using the concrete reinforcing bar. [Means for solving the problem]

[0006] To achieve this objective, the concrete reinforcing bar of the present invention comprises a bar body, an anchoring member provided at one end of the bar body, and a friction die provided at the middle of the bar body in the longitudinal direction, and the friction die is installed by fastening it to the bar body.

[0007] The concrete reinforcing bar of the present invention is characterized in that the friction die comprises a die body and a clamping adjustment portion that adjusts the amount of clamping of the die body relative to the bar body.

[0008] The concrete reinforcing bar of the present invention is characterized in that the bar body has a movable fixing portion on the other end side, and the movable fixing portion has an enlarged diameter portion fixed to the bar body and a storage portion that stores the enlarged diameter portion so that it can be freely moved in the axial direction of the bar body.

[0009] The concrete reinforcing bar of the present invention is characterized in that the above-mentioned friction die is used as the fixing member.

[0010] The concrete reinforcing bar of the present invention is characterized in that the bar body is made of high-strength steel or a rod-shaped material having a tensile strength equivalent to that of high-strength steel.

[0011] The reinforcement structure for concrete members of the present invention is a reinforcement structure for concrete members using the concrete reinforcing bar of the present invention, characterized in that the concrete reinforcing bar is arranged across adjacent concrete members.

[0012] The reinforcement structure for a concrete member of the present invention is characterized in that the concrete reinforcing bars are used as main reinforcements constituting the concrete member.

[0013] The reinforcement structure for a concrete member of the present invention is characterized in that the adjacent concrete members are a column portion and a foundation portion of a bridge pier.

[0014] According to the concrete reinforcing bar of the present invention, when an external force in the tensile direction that exceeds the maximum friction force between the bar body and the friction die acts on the bar body, the bar body slips relative to the friction die. This causes the bar body to behave as if it has undergone plastic deformation. Therefore, when high-strength steel or a rod-shaped material with a tensile strength equivalent to that of high-strength steel is used for the bar body, the concrete reinforcing bar can be used as a high-performance reinforcing bar with improved elongation performance while maintaining a tensile strength equivalent to that of high-strength steel.

[0015] Furthermore, even if an external force in the tensile direction exceeding the maximum friction force is repeatedly applied, the bar body simply repeatedly slides against the friction die and does not actually undergo plastic deformation. This makes it possible for the bar to withstand repeated large elongations that cannot be achieved with conventional rebars such as deformed steel bars commonly used in reinforced concrete structures. Furthermore, unlike conventional rebars, they do not suffer from so-called low-cycle fatigue, which causes breakage when subjected to repeated plastic deformation.

[0016] Therefore, by using concrete reinforcing bars as the main reinforcement or axial reinforcement of concrete members, it is possible to rationalize reinforcement arrangement and improve productivity compared to using conventional reinforcing bars. It is also possible to ensure the necessary deformation performance for concrete members during earthquakes.

[0017] Furthermore, by providing a movable fixing portion on the other end side of the bar body, even if an external force in the tensile direction that exceeds expectations acts on the bar body and causes a large slippage against the friction die, it is possible to stop the behavior at the point when the enlarged diameter portion collides with the storage portion.

[0018] As a result, for example, if concrete reinforcing bars are used in the columns and foundations of piers on a road bridge, the rod body will slide against the friction dies during earthquake motions at the assumed design level, absorbing energy as if undergoing plastic deformation. Also, during earthquake motions that exceed the assumed design level, the movable anchorage can be set to operate to suppress excessive deformation that would cause the rod body to slip out, making it possible to realize a pier structure with multiple strength-bearing stories. [Effects of the Invention]

[0019] According to the present invention, by fastening a friction die to the longitudinal intermediate portion of the bar body, it is possible to improve the elongation performance of the concrete reinforcing bar. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an example in which concrete reinforcing bars are arranged in an RC structure according to the present embodiment (part 1). [Figure 2] FIG. 10 is a diagram showing an example in which concrete reinforcing bars are arranged in an RC structure according to the present embodiment (part 2). [Figure 3] 1 is a diagram showing a concrete reinforcing bar according to the present embodiment; [Figure 4] 10A and 10B are diagrams showing the behavior of concrete reinforcing bars in the present embodiment. [Figure 5] FIG. 1 is a diagram showing a friction die according to the present embodiment (part 1). [Figure 6] FIG. 2 is a diagram showing a friction die according to the present embodiment (part 2). [Figure 7] FIG. 10 is a diagram showing an example in which concrete reinforcing bars are used in the column and foundation portions of a bridge pier in this embodiment. [Figure 8] FIG. 10 is a diagram showing an example in which concrete reinforcing bars are used for the columns and beams in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The concrete reinforcing bar of the present invention and a reinforcement structure for a concrete member using the concrete reinforcing bar will be described in detail with reference to Figs.

[0022] <<Concrete reinforcing rods>> The concrete reinforcing bar 10 is used in a concrete structure 5, for example, as a main reinforcement 511 of a column 51 of a bridge pier or the like as shown in Fig. 1(a), or as a part of the main reinforcement 511 as shown in Fig. 1(b) and Fig. 2(a). Alternatively, the concrete reinforcing bar 10 is used as an axial reinforcing bar 513 arranged in parallel to the main reinforcement 511 as shown in Fig. 2(b).

[0023] As shown in Figures 3(a) and (b), the structure comprises a bar body 1, a fixing member 2, and a friction die 3. Alternatively, as shown in Figure 3(c), in addition to the above-mentioned components, it comprises a movable fixing part 4.

[0024] <Bar body> The bar body 1 is made of PC steel, which is generally used as a tendon, but is not limited to this. For example, high-strength steel or FRP (Fiber Reinforced Plastics) with equivalent tensile strength can also be used.

[0025] <Fixing member> The anchoring member 2 can be any of those commonly used to fasten reinforcing bars to concrete, such as a semicircular hook, a T-head, or an anchoring plate. Figure 3(a) shows an example in which an anchoring plate 21 is used as the anchoring member 2.

[0026] Alternatively, as shown in Fig. 3(b), a main reinforcement 511 connected via a coupling sleeve 22 can be used as the anchoring member 2. When used as a part of the main reinforcement 511, it can be connected to other main reinforcement 511 arranged coaxially, as shown in Fig. 1(b) and Fig. 2(a). Furthermore, the anchoring member 2 may employ a friction die 3, which will be described later, as shown in Fig. 3(c).

[0027] Friction Dies As shown in Figures 3(a) to 3(c), a plurality of friction dies 3 are provided at predetermined intervals in the longitudinal middle portion of the bar body 1. Alternatively, as shown in Figure 2(a), at least one friction die 3 may be provided on the bar body 1.

[0028] The friction die 3 is attached to the bar body 1 by fastening the bar body 1 that passes through it. Therefore, when the external force acting on the bar body 1 in the tensile direction is equal to or less than the maximum friction force between the bar body 1 and the friction die 3, the bar body 1 does not slip relative to the friction die 3. In this case, the concrete reinforcing bar 10 functions like a deformed reinforcing bar, with the friction die 3 regarded as a node, as shown in Figure 4(a).

[0029] On the other hand, when the external force acting on the bar body 1 in the tensile direction exceeds the maximum friction force, the bar body 1 begins to slip against the friction die 3, as shown in Figure 4(b). This causes the bar body 1 to behave as if it has undergone plastic deformation, and the concrete reinforcing bar 10 can be treated as a high-performance reinforcing bar with improved elongation performance while maintaining the same tensile strength as high-strength steel.

[0030] Furthermore, even if an external force in the tensile direction exceeding the maximum friction force is repeatedly applied, the bar body 1 simply repeatedly slides against the friction die 3, and does not actually undergo plastic deformation. This makes it possible for the bar body 1 to withstand repeated large elongations that conventional reinforcing bars, such as deformed steel bars widely used in reinforced concrete structures, cannot achieve. Furthermore, it does not suffer from so-called low-cycle fatigue, which causes breakage when plastic deformation is repeated, as occurs with conventional reinforcing bars.

[0031] Therefore, if the concrete reinforcing bars 10 are used as main reinforcements 511 or axial reinforcements 513 in the column sections 51 and base sections 52 as shown in Figures 1 and 2, it is possible to rationalize the arrangement of reinforcement and improve productivity compared to when conventional reinforcing bars are used. Also, it is possible to ensure the necessary deformation performance for the concrete structure 5 during an earthquake.

[0032] The shape of the friction die 3 is such that it is large enough to prevent the concrete in the column section 51 or base section 52 from collapsing under pressure when the external force in the tensile direction acting on the bar body 1 exceeds the maximum friction force, that is, when a sliding start load is applied, and it is anchored to the concrete. The maximum friction force between the bar body 1 and the friction die 3 is set so that the sliding start load is smaller than the yield load of the bar body 1 or the friction die 3.

[0033] Furthermore, when multiple friction dies 3 are provided for the bar body 1, the spacing between them is set taking into consideration the sliding allowance L. The friction dies 3 that operate on the bar body 1 in this way are composed of a die body and a clamping adjustment unit that adjusts the amount of clamping of the die body relative to the bar body 1.

[0034] As shown in Figure 5(a), the die body is composed of a pair of half bodies 31, 31 formed by splitting a ring in half, with the outer diameter being larger than the cross section of the bar body 1 and the inner diameter being smaller than the outer diameter of the bar body 1. The tightening adjustment tool connecting these bodies is made of a bolt 32 inserted through both of the pair of half bodies 31, 31.

[0035] As shown in Fig. 5(b), the friction die 3 having such a shape sandwiches the bar body 1 between a pair of half bodies 31, 31. Next, using the countersunk portion provided on one of the half bodies 31, a bolt 32 is inserted into and screwed into an embedded nut 311 provided on each of the pair of half bodies 31, 31.

[0036] This allows the bar body 1 to be firmly clamped by the pair of halves 31, and the friction die 3 can be installed in a clamped state on the bar body 1. At this time, by appropriately changing the amount of tightening of the bolts 32, the amount of tightening of the pair of halves 31 relative to the bar body 1 can be adjusted, and the maximum friction force between the bar body 1 and the friction die 3 can be appropriately set.

[0037] The shapes of the die body and the clamping adjustment tool that constitute such a friction die 3 are not limited to those shown in Fig. 5. Other examples are shown in Figs. 6(a) and (b).

[0038] In Figure 6(a), a pair of half bodies 31, 31 formed by splitting a truncated conical ring in half, the outer diameter of which is larger than the cross section of the bar material body 1 and the inner diameter of which is smaller than the outer diameter of the bar material body 1, is used as the die body. A ring member 33 is used as the tightening adjustment tool. The inner peripheral surface of the ring member 33 is tapered to match the outer peripheral surfaces of the pair of half bodies 31, 31. A male thread is formed on the outer peripheral surface of the pair of half bodies 31, 31 formed by splitting the truncated conical ring in half, and a female thread is formed on the inner peripheral surface of the ring member 33.

[0039] In the friction die 3 having such a shape, the bar material body 1 is sandwiched between the pair of half bodies 31, 31. Next, the ring member 33 is screwed and fitted to house these. This allows the bar material body 1 to be firmly clamped between the pair of half bodies 31, 31, and the friction die 3 can be installed on the bar material body 1 in a clamped state.

[0040] In Figure 6(b), the die body is made up of a pair of halves 31, 31 formed by splitting an abacus bead in half, with an outer diameter larger than the cross section of the bar body 1 and an inner diameter smaller than the outer diameter of the bar body 1. A male thread is formed on the outer periphery of each of the pair of halves 31, 31 formed by splitting an abacus bead. The abacus bead is shaped like two truncated cones, similar to the beads of an abacus.

[0041] The tightening adjustment tool employs a pair of ring members 33, 33. The inner peripheral surface of each of the pair of ring members 33, 33 is tapered to fit the outer peripheral surfaces (upper or lower halves of the abacus beads) of the pair of half bodies 31, 31. A female thread is also formed on the inner peripheral surface.

[0042] In the friction die 3 having such a shape, the bar material body 1 is sandwiched between a pair of half bodies 31, 31. Next, a pair of ring members 33, 33 are fitted into these from both above and below so as to house them. This allows the bar material body 1 to be firmly clamped by the pair of half bodies 31, 31, and the friction die 3 can be installed on the bar material body 1 in a clamped state.

[0043] In either of the friction dies 3 shown in Figures 6(a) and 6(b), by appropriately changing the amount of engagement of the ring members 33 fitted into the pair of half bodies 31, 31, it is possible to adjust the amount of tightening of the pair of half bodies 31, 31 relative to the bar body 1, and thereby appropriately set the maximum friction force between the bar body 1 and the friction die 3.

[0044] These maximum frictional forces can be set not only by the amount of clamping of the die body against the bar body 1, but also by adjusting the state of the contact surface between the die body and the bar body 1 to change the static friction coefficient. Note that the friction die 3 does not necessarily have to be composed of the die body and a clamping adjustment tool. For example, a ring-shaped friction die 3 that is slightly smaller than the bar body 1 can be prepared and clamped by press-fitting it into the bar body 1.

[0045] <Movable fixing part> As shown in FIG. 3(c), the movable fixing portion 4 includes an expanded diameter portion 41 fixed to the other end side of the bar body 1, a storage portion 42 for storing the expanded diameter portion 41, and a flexible material 43.

[0046] The expanded diameter portion 41 has an outer shape that is sufficiently larger than the cross-sectional diameter of the bar body 1, and is disposed in a storage portion 42 that passes through the bar body 1. The storage portion 42 has a height that is sufficiently larger than the expanded diameter portion 41, and is formed so as to be movable a predetermined amount in the axial direction of the bar body 1.

[0047] The flexible material 43 is arranged so as to fill the gap between the expanded diameter portion 41 and the storage portion 42. The material may be a sponge or spring material, or a fluid such as oil, as long as it does not hinder the movement of the expanded diameter portion 41.

[0048] 4(c), when the bar body 1 is slipping relative to the friction die 3, the movable fixing portion 4 configured as described above moves the enlarged diameter portion 141 appropriately within the storage portion 142 in the axial direction of the bar body 1. When an unexpectedly large external force acts on the bar body 1, causing the bar body 1 to slip significantly relative to the friction die 3, the enlarged diameter portion 41 collides with the storage portion 42, and its movement can be stopped.

[0049] <<<Examples of concrete reinforcing rods>>> The behavior of the concrete reinforcing bar 10 having the above-described configuration can be explained as follows, taking as an example the case where it is used in the column portion 51 and foundation portion 52 of a bridge pier supporting a superstructure S, as shown in Figure 7(a).

[0050] <<Preparation>> When the concrete reinforcing bar 10 is used for the column section 51 and the base section 52, the maximum friction force is set in advance between the bar body 1 and the friction die 3. Here, the maximum friction force is set so that the external force in the tensile direction acting on the bar body 1 when earthquake motion of the assumed design level occurs becomes the sliding start load.

[0051] The concrete reinforcing bar 10 with the maximum friction force set in this way is arranged across the column portion 51 and the foundation portion 52 to construct the column portion 51 and the foundation portion 52.

[0052] <Before the earthquake motion reaches the elastic limit level> In the case of earthquake motion that does not reach the elastic limit level, the bar body 1 only undergoes elastic deformation, as shown in area A in Figure 7(d), and the bar body 1 does not slip against the friction die 3.

[0053] <Before the earthquake motion reaches the assumed design level> In the case of earthquake motion that does not reach the assumed design level, as shown in FIG. 7(b), the external force acting in the tensile direction on the bar body 1 exceeds the maximum friction force and becomes the sliding start load.

[0054] As a result, as explained with reference to Fig. 4(b), the bar body 1 begins to slide against the friction die 3. As a result, the bar body 1 behaves as if it has undergone plastic deformation, as shown in region B in Fig. 7(d), and the base of the column part 51 is plasticized to an extent that it does not lose its horizontal resistance force, thereby absorbing energy and maintaining its load-bearing capacity.

[0055] At this time, the bar body 1 does not actually undergo plastic deformation, but merely exhibits a sliding behavior relative to the friction die 3. Therefore, even if an earthquake force equivalent to the assumed design level or an earthquake force close to or greater than this level is repeatedly exerted on the bar body 1, the bar body 1 will simply repeat the sliding behavior relative to the friction die 3 as long as it does not slip out of the friction die 3.

[0056] <<When earthquake motion exceeds the assumed design level>> In the case of earthquake motion exceeding the assumed design level, the superstructure S is displaced even more, and as shown in FIG. 7(c), the bar body 1 behaves in such a way that it appears to undergo a sudden elongation deformation.

[0057] However, as explained with reference to Figure 4(c), the movable fixing portion 4 is provided on the other end side of the bar body 1, so that the enlarged diameter portion 41 collides with the storage portion 42 and stops its movement. This prevents excessive deformation of the bar body 1, and suppresses deformation that could cause fatal damage such as the collapse of the superstructure S.

[0058] In this way, if concrete reinforcing bars 10 are used in the reinforcing structure of the columns 51 and foundations 52 of the piers of a road bridge, in earthquake motions up to the assumed design level, the bar body 1 will slide against the friction dies 3, and energy can be absorbed by a behavior similar to plastic deformation. Furthermore, in earthquake motions that exceed the assumed design level, the movable anchors 4 can be activated to suppress excessive deformation, making it possible to realize a structure in which the columns 51 and foundations 52 of the piers have multiple load-bearing stories.

[0059] The concrete reinforcing bar and the reinforcement structure of the concrete member of the present invention are not limited to the above-described embodiment, and it goes without saying that various modifications are possible within the scope of the spirit of the present invention.

[0060] For example, as shown in FIG. 1(a), the movable fixing part 4 may be provided at the end on the other end side of the bar body 1, or may be omitted.

[0061] 1(a) and 1(b), the friction dies 3 provided at the longitudinal intermediate portion of the bar body 1 are installed between each pair of hoops 512 of the reinforcing bar cage that constitutes the column portion 51. However, this is not limited to this, and as shown in FIG. 2(a), they may be installed at intervals greater than the intervals between the hoops 512, or may be installed in only one location.

[0062] In this embodiment, the bar body 1 is made of prestressing steel, high-strength steel, or a rod-shaped member having an equivalent tensile strength, but this is not limiting. Any material with an elastic limit exceeding the sliding start load can be used as a rod-shaped member.

[0063] Furthermore, when the concrete reinforcing bar 10 is used as part of the main reinforcement 511, it may be arranged only on the base side of the column part 51 where damage is likely to occur, as shown in FIG. 1(b).

[0064] In addition, in Figures 1 and 2(a), the fixing member 2 is provided on one end side of the bar body 1 and is provided on the column portion 51, but as shown in Figure 2(b), the arrangement position may be reversed and it may be provided on the base portion 52 side.

[0065] Furthermore, the reinforcement structure of a concrete member using concrete reinforcing bars 10 may be used not only for the column portion 51 and the foundation portion 52, but also for the columns 53 and beams 54 of a concrete structure 5, as shown in Figures 8(a) and (b).

[0066] Specifically, FIG. 8(a) illustrates an example in which concrete reinforcing bars 10 are used as part of beam main reinforcements 541 in a column 53 and a beam 54.

[0067] Also, Figure 8(b) illustrates a case where a pair of beams 54 are arranged on both sides of a column 53, and concrete reinforcing bars 10 are used as axial reinforcing bars arranged parallel to the main beam reinforcement 541, and are arranged so as to straddle the column 53 and the pair of beams 54.

[0068] If the length of the concrete reinforcing bar 10 is insufficient, multiple concrete reinforcing bars 10 can be arranged in series, and joint sleeves 22 can be used as anchoring members 2. Adjacent bar bodies 1 can be connected via these joint sleeves 22. [Explanation of symbols]

[0069] 10 Concrete reinforcing bars 1. Bar body 2 Fixing member 21 Fixing plate 22 Joint sleeve 3 Friction Dies 31 Half body (die body) 311 Embedded Nut 32 Bolt (tightening adjustment part) 33 Ring member (tightening adjustment part) 4 Movable fixing part 41 Expanded diameter part 42 Storage area 43 Flexible materials 5. Concrete structures 51 Column (pier) 511 Main reinforcement 512 Hoop Muscle 513 Axial Reinforcement 52 Foundation (pier) 53 pillars 54 Beam 541 Beam main reinforcement S superstructure

Claims

1. A bar body; a fixing member provided on one end side of the bar body; a friction die provided at a longitudinal intermediate portion of the bar body, A concrete reinforcing bar characterized in that the friction die is installed by fastening it to the bar body.

2. The concrete reinforcing bar according to claim 1, A concrete reinforcing bar characterized in that the friction die comprises a die body and a clamping adjustment portion that adjusts the amount of clamping of the die body relative to the bar body.

3. The concrete reinforcing bar according to claim 1, The bar body has a movable fixing portion on the other end side, The movable fixing portion is an expanded diameter portion fixed to the bar body; a housing portion that houses the enlarged diameter portion so as to be movable in the axial direction of the bar body; A concrete reinforcing bar comprising:

4. The concrete reinforcing bar according to claim 1, A concrete reinforcing bar characterized in that the friction die is used as the fixing member.

5. The concrete reinforcing bar according to claim 1, 1. A concrete reinforcing bar, wherein the bar body is made of high-strength steel or a rod-shaped material having a tensile strength equivalent to that of high-strength steel.

6. A reinforcement structure for a concrete member using the concrete reinforcing bar according to claim 1, A reinforcement structure for concrete members, characterized in that the concrete reinforcing bar is provided across adjacent concrete members.

7. 7. The reinforcement structure for a concrete member according to claim 6, A reinforcement structure for a concrete member, characterized in that the concrete reinforcing bars are used as main reinforcements constituting the concrete member.

8. 7. The reinforcement structure for a concrete member according to claim 6, A reinforced structure for concrete members, characterized in that the adjacent concrete members are the column and foundation parts of a bridge pier.

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