Joining structure for precast floor slab

Abstract

To provide a joining structure for a precast floor slab capable of improving load withstanding performance, reducing the thickness of the precast floor slab and improving construction efficiency.SOLUTION: A reinforcing steel bar projecting part 54 includes: a base part 57 located on a joining end surface side; and a diameter expansion part 6 located on a tip side in a direction projecting from the joining end surface, coaxially connected to the base part 57 and having an outer diameter larger than that of the base part 57. A base part side end surface 611 of the diameter expansion part 6 is a flat surface orthogonal to an axis of the reinforcing steel bar projecting part 54 or a first tapered surface leading radially outwardly from an axis of the diameter expansion part 6 toward the tip side gradually. An outer peripheral surface at least on the tip side of the diameter expansion part 6 (outer peripheral surface 63a of a second tapered part 63) is a second tapered surface of which outer diameter gradually becomes smaller from the base part 57 side toward the tip side.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a joint structure for a precast deck and a method for manufacturing reinforcing bars for a precast deck. [Background technology]

[0002] A known joint structure for joining precast decks together involves providing loop-shaped loop joints at the ends of the precast decks that protrude from the concrete part, arranging the loop joints of each of the precast decks being joined alternately at the joints between the precast decks, inserting reinforcing bars into these loop joints, and filling them with concrete (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5337122 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when loop joints are provided at the joints of precast decks, the deck thickness is determined by the constraints of the inner bending radius of the semicircular hooks of the loop joints, and it may be difficult to make the precast decks thinner. In addition, when inserting reinforcing bars inside the loop joints, the internal reinforcing bars of the loop joints are inserted from the ends of the arranged loop joints in the arrangement direction, so it is necessary to secure construction space, which causes a problem of poor workability. In addition, even when precast decks are joined by providing joints between them, high load-bearing performance after the yielding of the reinforcing bars is desired, similar to the case of constructing the precast decks as a single unit without joints.

[0005] Therefore, an object of the present invention is to provide a precast deck slab joint structure and a method for manufacturing reinforcing bars for a precast deck slab joint structure that can improve load-bearing performance while also enabling the precast deck slab to be made thinner and easier to work with. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a joint structure for precast floor slabs, in which precast floor slabs are joined together via joints, the precast floor slabs having a concrete portion and a reinforcing bar that extends linearly in the direction in which the precast floor slabs are joined together, is embedded in the concrete portion and protrudes from a joint end face of the concrete portion on the other precast floor slab side, the joints being located between the joint end faces of the precast floor slabs that are joined together, and the joint end face of the reinforcing bar of each of the precast floor slabs that are joined together protrudes from the joint end face of the reinforcing bar of each of the precast floor slabs that are joined together to the other precast floor slab. a reinforcing bar protrusion protruding toward the joint end face and having a joint concrete in which the reinforcing bar protrusion is embedded, the reinforcing bar protrusion having a base located on the joint end face side and an enlarged diameter portion located on the tip side in the direction protruding from the joint end face, connected coaxially to the base and having an outer diameter larger than that of the base, the end face on the base side of the enlarged diameter portion being a plane perpendicular to the axis of the reinforcing bar protrusion, or a first tapered surface gradually extending radially outward from the axis of the enlarged diameter portion toward the tip side, and the outer peripheral surface at least on the tip side of the enlarged diameter portion being a second tapered surface whose outer diameter gradually decreases from the base side toward the tip side.

[0007] In the present invention, the bearing resistance of the end face on the base side of the enlarged portion acts mainly in the axial direction of the rebar, similar to the adhesion resistance of the rebar, and is less likely to act in the radial direction toward the periphery of the enlarged portion. This makes it possible to suppress destruction of the concrete around the rebar protrusion, and even if the rebar yields, high load-bearing performance can be maintained. Compared to conventional loop rebars, the rebar protrusions do not restrict the thickness of the precast deck due to the bending radius, so the precast deck can be made thinner. Because the rebar protrusions extend in a straight line, the arrangement of reinforcing bars is easier than when conventional loop rebars are provided, improving workability.

[0008] In the precast deck joint structure of the present invention, the inclination angle of the first tapered surface relative to a plane perpendicular to the axis of the reinforcing bar protrusion may be 60° or less, and the taper angle of the second tapered surface may be 1° or more and 15° or less.

[0009] In the precast deck joint structure of the present invention, the outer diameter of the expanded portion may be 1.5 to 1.7 times the outer diameter of the base, and the axial length dimension of the expanded portion may be 1.5 to 2.5 times the outer diameter of the base.

[0010] With this configuration, destruction of the concrete around the protruding reinforcing bar can be further suppressed, and even if the reinforcing bar yields, higher load-bearing capacity can be maintained.

[0011] In the precast deck joint structure of the present invention, the expansion portion may have a first tapered portion in which the first tapered surface is formed, a cylindrical cylindrical portion coaxially connected to the tip side of the first tapered portion, and a second tapered portion coaxially connected to the tip side of the cylindrical portion and in which the second tapered surface is formed.

[0012] With this configuration, resistance is reduced during the step of drawing the expanded diameter portion from the die when the expanded diameter portion is integrally formed with the base portion by high-frequency induction heating, and the processing can be easily performed.

[0013] In order to achieve the above-mentioned object, the method for manufacturing rebars for a joint structure of a precast deck slab of the present invention is a method for manufacturing rebars for a precast deck slab in which the rebars for the joint structure of the above-mentioned deck slab are manufactured, in which the expanded portion is integrally formed with the base portion by high-frequency induction heating.

[0014] In the present invention, the enlarged diameter portion is integrally formed with the base portion by high-frequency induction heating, thereby increasing the fatigue durability of the reinforcing bar projection. Effect of the Invention

[0015] According to the present invention, it is possible to reduce the thickness of precast deck slabs and improve workability. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a vertical cross-sectional view showing a joint structure of a precast deck according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing a joint structure of a precast deck according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing the shape of an expanded diameter portion. [Figure 4] 13A and 13B are diagrams showing other shapes of the enlarged diameter portion. [Diagram 5] FIG. 2 is a vertical cross-sectional view of a test specimen. [Figure 6] FIG. 2 is a horizontal cross-sectional view of the test specimen. [Figure 7] 1 is a graph showing the relationship between load and displacement at the center of the span. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a joint structure for a precast floor slab and a method for manufacturing reinforcing bars for a precast floor slab according to an embodiment of the present invention will be described with reference to Figs. 1 to 7. As shown in Figures 1 and 2, the precast deck joint structure 1 according to this embodiment is provided on a bridge and is a joint structure for adjacent precast decks 2, 3 in the bridge axis direction. The adjacent precast decks 2, 3 in the bridge axis direction are joined via a joint 4 provided between them. In the following, the precast deck 2 located on one side of the bridge axis direction may be referred to as the first precast deck 2, and the precast deck 3 located on the other side of the bridge axis direction may be referred to as the second precast deck 3.

[0018] The precast decks 2, 3 have a concrete portion 51, bridge axis direction reinforcing bars 52 extending in the bridge axis direction, and bridge axis perpendicular direction reinforcing bars 53 extending in a direction perpendicular to the bridge axis. The concrete portion 51 is formed in a plate shape. The concrete portion 51 of the first precast floor slab 2 and the concrete portion 51 of the second precast floor slab 3 are arranged with a gap in the bridge axis direction. A joint portion 4 is provided between the concrete portion 51 of the first precast floor slab 2 and the concrete portion 51 of the second precast floor slab 3. An end surface 511 of the concrete portion 51 in the bridge axis direction is formed into a surface that gradually slopes from the lower side to the upper side toward the joint 4. The end surface 511 of the concrete portion 51 in the bridge axis direction is referred to as a joint end surface 511.

[0019] A plurality of bridge axis direction reinforcing bars 52 are provided at intervals in the direction perpendicular to the bridge axis on both the upper and lower sides of the concrete portion 51. The bridge axis direction reinforcing bars 52 are longer than the length dimension of the concrete portion 51 in the bridge axis direction, and protrude in the bridge axis direction from the joint end surface 511 of the concrete portion 51. The part of the bridge axis direction reinforcing bars 52 protruding from the concrete portion 51 is referred to as a reinforcing bar protruding part 54. The bridge axis direction reinforcing bars 52 correspond to reinforcing bars in the claims.

[0020] Multiple reinforcing bars 53 orthogonal to the bridge axis are provided at intervals in the bridge axis direction on both the upper and lower sides of concrete section 51. Reinforcing bars 53 orthogonal to the bridge axis provided on the upper side of concrete section 51 are provided below bridge axis direction reinforcing bars 52 provided on the upper side of concrete section 51. Reinforcing bars 53 orthogonal to the bridge axis provided on the lower side of concrete section 51 are provided above bridge axis direction reinforcing bars 52 provided on the lower side of concrete section 51. Reinforcing bars 53 orthogonal to the bridge axis are reinforcing bars.

[0021] As shown in FIG. 3, an expanded diameter portion 6 having a larger outer diameter than the base end side is formed at the tip of the rebar protruding portion 54. The base end side (right side in FIG. 3), i.e., the portion on the concrete portion 51 side, of the rebar protruding portion 54 is referred to as a base portion 57. That is, the expanded diameter portion 6 has a larger outer diameter than the base portion 57. The base portion 57 has the same outer diameter as the portion of the bridge axis direction rebar 52 that is embedded in the concrete portion 51. The expanded diameter portion 6 and the base portion 57 are arranged coaxially. The axes of the expanded diameter portion 6 and the base portion 57 extend in the bridge axis direction. The expanded diameter portion 6 is formed integrally with the base portion 57 by processing the tip portion of the bridge axis direction rebar 52 by high-frequency induction heating to increase the diameter. The bridge axis direction rebar 52 is manufactured by forming the expanded diameter portion 6 integrally with the base portion 57 by high-frequency induction heating.

[0022] The expanded diameter portion 6 has a first tapered portion 61, a cylindrical portion 62, and a second tapered portion 63. The first tapered portion 61 is continuous with the tip side of the base portion 57. The cylindrical portion 62 is continuous with the tip side of the first tapered portion 61. The second tapered portion 63 is continuous with the tip side of the cylindrical portion 62. The first tapered portion 61, the cylindrical portion 62, and the second tapered portion 63 are arranged coaxially in this order.

[0023] The first tapered portion 61 is shaped like a truncated cone. The outer diameter of the first tapered portion 61 gradually increases from the base portion 57 side toward the cylindrical portion 62 side. The outer diameter of the end of the first tapered portion 61 on the base portion 57 side is the same as the outer diameter of the base portion 57. The outer peripheral surface 61a of the first tapered portion 61 is continuous with the outer peripheral surface of the base portion 57. The outer peripheral surface 61a of the first tapered portion 61 corresponds to the first tapered surface. The cylindrical portion 62 is cylindrical. The outer diameter of the cylindrical portion 62 is constant throughout the axial direction. The outer diameter of the cylindrical portion 62 is the same as the outer diameter of the end of the first tapered portion 61 on the cylindrical portion 62 side. An outer peripheral surface 62a of the cylindrical portion 62 is continuous with an outer peripheral surface 61a of the first tapered portion 61. The second tapered portion 63 is frustum-shaped. The outer diameter of the second tapered portion 63 gradually decreases from the cylindrical portion 62 side toward the tip side. The tip surface 63b of the second tapered portion 63 is a flat surface perpendicular to the axis. The outer diameter of the second tapered portion 63 on the cylindrical portion 62 side is the same as the outer diameter of the cylindrical portion 62. The outer peripheral surface 63a of the second tapered portion 63 is continuous with the outer peripheral surface of the cylindrical portion 62. The outer peripheral surface 63a of the second tapered portion 63 corresponds to the second tapered surface.

[0024] The outer diameter of the expanded portion 6, i.e., the outer diameter of the cylindrical portion 62, is 1.5 to 1.7 times the outer diameter of the base portion 57. If the outer diameter of the expanded portion 6 is H and the outer diameter of the base portion 57 is D, then it is expressed by the following formula (1). 1.5D≦H≦1.7D …(1)

[0025] The axial length of the expanded diameter portion 6 is 1.5 to 2.5 times the outer diameter of the base portion 57. The axial length of the expanded diameter portion 6 is L, as shown in the following formula (2). 1.5D≦L≦2.5D …(2)

[0026] The outer peripheral surface 61a of the first tapered portion 61 corresponds to the end face on the base 57 side of the expanded diameter portion 6. The end face on the base 57 side of the expanded diameter portion 6 is referred to as the base side end face 611. The base side end face 611 is inclined with respect to a plane perpendicular to the axis. The angle R1 at which the base side end face 611 is inclined with respect to the plane perpendicular to the axis is 60° or less.

[0027] 4, the expanded diameter portion 6 may not be provided with the first tapered portion 61, and may instead be composed of a cylindrical portion 62 and a second tapered portion 63. In such a case, the cylindrical portion 62 is coaxially connected to the base portion 57. In this case, the base-side end face 611 corresponds to the end face 62b of the cylindrical portion 62 on the base portion 57 side. The angle R1 at which the base-side end face 611 is inclined with respect to a plane perpendicular to the axis is 0°.

[0028] In both the case where the first taper portion 61 is provided in the expanded diameter portion 6 and the case where it is not provided, the angle R1 at which the base side end face 611 is inclined with respect to a plane perpendicular to the axis is set to be greater than or equal to 0° and less than or equal to 60°, as shown in the following formula (3). 0°≦R1≦60° …(3) Angle R2 at which outer circumferential surface 63a of second tapered portion 63 is inclined with respect to the axis, ie, the taper angle of second tapered portion 63, is equal to or greater than 1° and equal to or less than 15°, as shown in the following formula (4). 1°≦R2≦15° …(4)

[0029] Next, the action and effect of the joint structure of the precast floor slab according to this embodiment will be described. In the joint structure of the precast deck according to this embodiment, the bearing resistance of the enlarged portion 611 acts mainly in the axial direction of the bridge axis direction reinforcing bar 52, similar to the adhesion resistance of the bridge axis direction reinforcing bar 52, and is less likely to act in the radial direction toward the periphery of the enlarged portion 6. Therefore, destruction of the concrete around the reinforcing bar protrusion 54 can be suppressed, and high load-bearing performance can be maintained even if the bridge axis direction reinforcing bar 52 yields. Since the reinforcing bar protrusion 54 is not restricted in thickness of the precast deck 2, 3 by the bending radius compared to the conventional loop reinforcing bar, the precast deck 2, 3 can be made thinner. Since the reinforcing bar protrusion 54 extends linearly, the arrangement of the reinforcing bar (reinforcing bar orthogonal to the bridge axis direction 53) is easier than when the conventional loop reinforcing bar is provided, and the workability can be improved.

[0030] In the joint structure of the precast floor slab according to this embodiment, the outer diameter H of the enlarged diameter portion 6 is 1.5 to 1.7 times the outer diameter D of the base portion 57, and the length dimension L in the axial direction of the enlarged diameter portion 6 is 1.5 to 2.5 times the outer diameter D of the base portion 57. The angle R1 at which the base side end face 611 is inclined with respect to a plane perpendicular to the axis is set to 0° to 60°, and the angle R2 at which the outer peripheral surface 63a of the second tapered portion 63 is inclined with respect to the axis is 1° to 15°. With this configuration, destruction of the concrete around the reinforcing bar protruding portion 54 can be further suppressed, and even if the reinforcing bar yields, a higher load-bearing performance can be maintained.

[0031] In the joint structure of the precast deck according to this embodiment, the expansion section 6 has a first tapered section 61 on which a first tapered surface is formed, a cylindrical columnar section 62 coaxially connected to the tip side of the first tapered section 61, and a second tapered section 63 on which a second tapered surface is formed and coaxially connected to the tip side of the cylindrical section 62. With this configuration, there is little resistance in the pull-out process from the mold when the expansion section 6 and the base section 57 are integrally molded by high-frequency induction heating, and processing can be easily performed.

[0032] In the method for manufacturing reinforcing bars for a joint structure of a precast deck according to this embodiment, the enlarged diameter portion 6 is integrally formed with the base portion 57 by high-frequency induction heating. In this manner, the fatigue durability of the reinforcing bar protruding portion 54 can be increased.

[0033] A load test was conducted using a specimen for the joint structure of the precast floor slab according to this embodiment. The specimen for the joint structure of the precast floor slab according to this embodiment has three combinations (R1, R2) of the angle R1 at which the base end surface 611 is inclined relative to a plane perpendicular to the axis and the angle R2 at which the outer peripheral surface 63a of the second taper portion 63 is inclined relative to the axis: (60, 15), (60, 1), and (0, 1). D19 was used for the reinforcing bars. The outer diameter H of the enlarged portion 6 is about 1.7 times (1.7D) the outer diameter D of the base 57, and the length L of the enlarged portion 6 in the axial direction is about twice (2D) the outer diameter D of the base 57. For comparison, a load test was also conducted on a specimen of a precast floor slab that was cast in one piece without a joint. The shapes of the RC floor slab specimens are shown in Figures 5 and 6. The relationship between the load and the displacement at the center of the span as a result of the loading test is shown in Figure 7. It can be seen from Figure 7 that the test specimens of the precast deck joint structure according to this embodiment retain their load-bearing capacity even after the yielding of the reinforcing bars (bridge axis direction reinforcing bars 52 on the tension side), just like the test specimens of the precast deck that are cast in one piece without any joints.

[0034] The above describes an embodiment of the joint structure of a precast deck according to the present invention, but the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the precast decks 2, 3 are provided on a bridge, but they may be provided on something other than a bridge. In the above embodiment, the expanded diameter section 6 is provided with the first taper section 61, the cylindrical section 62, and the second taper section 63 arranged side by side from the base end side to the tip end side. The expanded diameter section 6 may be provided with the second taper section 63 on the tip side of the first taper section 61 without the cylindrical section 62. As described above, the expanded diameter section 6 may be provided with the cylindrical section 62 and the second taper section 63 without the first taper section 61. In this case, the cylindrical section 62 is connected to the base section 57, and the end face of the cylindrical section 62 on the base section 57 side corresponds to the end face of the expanded diameter section 6 on the base section 57 side.

[0035] In the above embodiment, the outer diameter H of the expanded diameter portion 6 is 1.5 to 1.7 times the outer diameter D of the base portion 57, and the length dimension L in the axial direction of the expanded diameter portion 6 is 1.5 to 2.5 times the outer diameter D of the base portion 57. The angle R1 at which the base end face 611 is inclined with respect to a plane perpendicular to the axis is set to be 0° or more and 60° or less, and the angle R2 at which the outer peripheral surface 63a of the second tapered portion 63 is inclined with respect to the axis is 1° or more and 15° or less. The outer diameter H of the expanded diameter portion 6, the length dimension L in the axial direction, the angle R1 at which the base end face 611 is inclined with respect to a plane perpendicular to the axis, and the angle R2 at which the outer peripheral surface 63a of the second tapered portion 63 is inclined with respect to the axis may be values ​​other than those described above. [Explanation of symbols]

[0036] 1 Joint structure 2,3 Precast deck 4 Joint 6 Expanded diameter part 51 Concrete Section 52 Bridge Axial Reinforcement (Reinforcement) 54 Reinforcement bar protrusion 57 Base 61 First taper section 61a Outer circumferential surface (end surface on the base side, first tapered surface) 62 Cylinder section 62b End face (base end face) 63 Second taper section 63a Outer periphery (second tapered surface) 511 Joint end face 611 Base end face H Outer diameter of enlarged part D Outside diameter of base R1 angle R2 angle

Claims

1. The precast deck slabs are joined together via joints, The precast deck is Concrete section, a reinforcing bar extending linearly in the direction in which the precast floor slabs are joined, embedded in the concrete portion, and protruding from a joint end surface of the other precast floor slab side in the concrete portion; The joint is Located between the joint end faces of the precast floor slabs that are joined to each other, A reinforcing bar protrusion protruding from the joint end surface of each of the reinforcing bars of the precast floor slabs to be joined to each other toward the other precast floor slab is arranged, The joint concrete in which the reinforcing bar protrusion is embedded is provided, The reinforcing bar protruding portion is A base portion located on the joining end surface side; an expanded diameter portion located on a tip side in a direction protruding from the joint end surface, coaxially connected to the base portion, and having an outer diameter larger than that of the base portion; The end surface on the base side of the enlarged diameter portion is a plane perpendicular to the axis of the reinforcing bar protruding portion, or a first tapered surface that gradually moves from the axis of the enlarged diameter portion toward the radially outer side toward the tip side, A joint structure for precast decks, in which the outer peripheral surface at least at the tip side of the expanded diameter portion is a second tapered surface whose outer diameter gradually decreases from the base side toward the tip side.

2. The inclination angle of the first tapered surface with respect to a plane perpendicular to the axis of the reinforcing bar protrusion is 60° or less, The precast deck joint structure according to claim 1 , wherein the taper angle of the second taper surface is greater than or equal to 1° and less than or equal to 15°.

3. The outer diameter of the expanded portion is 1.5 to 1.7 times the outer diameter of the base portion, 3. A precast deck joint structure as described in claim 1 or 2, wherein the axial length dimension of the expanded portion is 1.5 to 2.5 times the outer diameter of the base portion.

4. The enlarged diameter portion is a first tapered portion in which the first tapered surface is formed; A cylindrical portion coaxially connected to a tip side of the first tapered portion; A precast deck joint structure as described in claim 1 or 2, further comprising: a second tapered portion coaxially connected to the tip side of the cylindrical portion and forming the second tapered surface.

5. In the method for manufacturing reinforcing bars for a joint structure of a precast slab according to claim 1 or 2, A method for manufacturing reinforcing bars for precast decks, in which the expanded portion is integrally formed with the base portion by high-frequency induction heating.

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