Joint structure and reinforced concrete member

Abstract

To provide a joint structure and a reinforced concrete member that are difficult to crack at both ends and can be joined with simple construction.SOLUTION: A joint structure that joins two PCa slabs 20 with embedded steel bars 21 at a joint surface 20f joins the PCa slabs 20 having a reinforcing section 26 made of fiber-reinforced concrete formed at an end of the joint surface 20f. The PCa slab 20 fixes the end of the steel bar 21 in a state where it is buried in the reinforcing section 26. The joint surfaces 20f of the PCa slabs 20 are joined together using an adhesive 30 that has a tensile strength greater than that of a fiber-reinforced concrete material that makes up the reinforcing section 26.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a joint structure used in the connecting portions of precast concrete decks of road bridges, and a reinforced concrete member used therein. [Background technology]

[0002] Conventionally, when constructing decks for road bridges and the like using multiple precast concrete (PCa) panels, adjacent PCa decks are joined together to form a single unit. Here, technology is being studied to make hardened concrete bodies such as deck slabs durable and strong (see, for example, Patent Document 1). This document describes a joint structure between the end of a hardened concrete body and joint concrete that is poured into this end. The end of this hardened concrete body is formed with a plurality of wedge-shaped protrusions that protrude in the connection axis direction when viewed from above and have a gradually tapering shape.

[0003] When joining PCa deck slabs, which are reinforced concrete members, it is necessary to resist the tensile force acting on the joint surface. For example, as shown in Fig. 10, PCa slabs 80 may be bonded together by placing a highly adhesive material such as an adhesive 88 on the joint surfaces of the PCa slabs 80. In this case, a tensile force acts on the joint surfaces, and the concrete 85 between the reinforcing bar 81 and the joint surfaces may crack, for example, as shown by crack R1.

[0004] Therefore, in order to resist the tensile forces acting on the joint surfaces, the reinforcing bars embedded in adjacent PCa decks are sometimes connected to each other. For example, as shown in FIG. 11, a PCa deck 90 in which a steel plate 96 placed on the joint surface and a reinforcing bar 91 embedded in concrete 95 are welded together may be bonded with an adhesive 88. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2021-143486 A Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, when connecting rebars embedded in adjacent PCa decks, it was necessary to provide mechanical joints, for example, in the PCa decks when manufacturing the PCa decks. Furthermore, in this case, it was necessary to inject grout into the mechanical joints when joining, which was time-consuming. Furthermore, in the case of the PCa deck 90 in FIG. 11, during manufacturing, it is necessary to weld the steel plate 96 placed at the joint surface to the reinforcing bar 91 embedded in the concrete, which is time-consuming. [Means for solving the problem]

[0007] The joining structure that solves the above-mentioned problems is a joining structure that joins concrete members having reinforcing bars embedded therein at their joint surfaces, wherein the ends of the concrete members on the joint surface side are made of fiber-reinforced concrete material, the ends of the reinforcing bars are fixed in a state embedded in the ends on the joint surface side, and the joint surfaces are joined by a joining material having a tensile strength equal to or greater than that of the fiber-reinforced concrete material.

[0008] In addition, a reinforced concrete member for solving the above problems is a reinforced concrete member made of precast concrete with reinforcing bars embedded therein, which is joined to the joint surfaces of adjacent concrete members via joint material, and in which the end on the joint surface side is made of fiber-reinforced concrete material, and the end of the reinforcing bar is embedded and fixed in the end on the joint surface side. Effect of the Invention

[0009] According to the present invention, the ends of reinforced concrete members are less likely to crack and can be joined with simple construction. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a precast concrete (PCa) floor slab to which the joint structure in the first embodiment is applied. [Diagram 2] FIG. 2 is a top view of a main part of a PCa deck having a joint structure in the first embodiment. [Diagram 3] FIG. 2 is a front cross-sectional view of a main part of a PCa deck having a joint structure in the first embodiment. [Figure 4] 4 is a table showing various strengths according to materials of adhesive joints used in the joint structure in the first embodiment. [Diagram 5] FIG. 11 is a top view of a main part of a PCa deck having a joint structure in the second embodiment. [Figure 6] A front cross-sectional view of a main part of a PCa deck having a joint structure in the second embodiment. [Figure 7] FIG. 11 is a top view of a main part of a PCa deck having a joint structure in a third embodiment. [Figure 8] A front cross-sectional view of a main part of a PCa deck having a joint structure in a third embodiment. [Figure 9] This is a top view of the main parts of a PCa deck having a joint structure in a modified example. [Figure 10] FIG. 13 is a front cross-sectional view of a main part of a PCa deck having a joint structure in a conventional example. [Figure 11] FIG. 13 is a front cross-sectional view of a main part of a PCa deck having a joint structure in a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) A first embodiment of a joint structure will be described below with reference to Figures 1 to 4. In this embodiment, a joint structure for precast concrete (PCa) deck slabs used in road bridges and the like will be described.

[0012] As shown in Fig. 1, the road bridge 10 has multiple girders 15 and multiple PCa decks 20 as reinforced concrete members. The multiple girders 15 extend in the same direction. The multiple PCa decks 20 have a rectangular parallelepiped shape and are arranged in a direction perpendicular to the extension direction of the girders 15.

[0013] Fig. 2 is an enlarged top view of the joint portion of two PCa decks 20, and Fig. 3 is a front cross-sectional view of Fig. 2. In the top views of Fig. 2 and other figures, the reinforcing bars are embedded, but are shown by solid lines for ease of viewing. As shown in Fig. 2, each PCa slab 20 includes a plurality of reinforcing bars 21 and concrete 25 in which the reinforcing bars 21 are embedded. Furthermore, a reinforcing portion 26 is formed at the end of the PCa slab 20 in a direction perpendicular to the extension direction of the reinforcing bars 21 (the end on the joint surface 20f side). The reinforcing portion 26 has a compressive strength of 150 N / mm 2 The section is made of ultra-high strength fiber reinforced concrete (UFC). This UFC is a fiber reinforced concrete material in which concrete is reinforced by mixing steel fibers, and is stronger than normal concrete. For example, Slimcrete (registered trademark) can be used as this UFC.

[0014] In the reinforcing portion 26 of this embodiment, the reinforcing bar surrounding portion 26a in which the reinforcing bar 21 is embedded has a horizontal shape that is fixed to the UFC in a state in which the reinforcing bar 21 is embedded. Specifically, the reinforcing bar surrounding portion 26a has a length L1 in the longitudinal direction of the reinforcing bar 21 that is equal to or longer than the fixing length between the reinforcing bar 21 and the UFC. The connecting portion 26b between the reinforcing bars 21 of the reinforcing portion 26 and connected to the reinforcing bar surrounding portion 26a is shorter in the extending direction of the reinforcing bar 21 than the reinforcing bar surrounding portion 26a, and has an arc shape that smoothly connects to the reinforcing bar surrounding portion 26a in the horizontal plane. Furthermore, the portion between the outermost reinforcing bar 21 and the end face (exposed face) parallel to the reinforcing bar 21 is configured with an end face portion 26c that is longer than the reinforcing bar surrounding portion 26a. The joint surface 20f of the PCa floor slab 20 (reinforcing portion 26) is formed as a flat plane.

[0015] Furthermore, the pair (two pieces) of PCa deck slabs 20 to be joined are joined with adhesive 30 as a joining material. This adhesive 30 has a crack strength of UFC (8.0 N / mm 2 ) The adhesive 30 may be, for example, an epoxy resin material.

[0016] FIG. 4 shows the bond strength and cracking strength with deformed reinforcing bars. In this figure, the compressive strength, bond strength, and cracking strength of normal concrete (concrete 25) and UFC, which are usually used for PCa deck 20, are shown. In this case, if eight D19 reinforcing bars 21 are used at 125 mm pitch as the reinforcing bars 21 embedded in the PCa deck 20, the strength is about 790,740 N. Also, if the size of the UFC on the horizontal plane is 100 mm x 1 m, the strength is about 800,000 N. Therefore, since the cracking load of the UFC is larger than the yield load of the reinforcing bars 21 of this PCa deck 20, the structure is designed so that cracks do not occur at the end of the PCa deck 20 before the reinforcing bars 21 yield and fail.

[0017] (Manufacturing method and joining method for PCa floor slab 20) Next, a manufacturing method and a joining method for the two PCa decks 20 described above will be described. First, a formwork corresponding to the rectangular parallelepiped shape of the PCa deck 20 is placed in a factory. Then, after placing multiple reinforcing bars 21 in parallel in this formwork, a partition plate having a shape corresponding to the shape of the boundary is placed at the boundary between the concrete 25 and the reinforcing portion 26 composed of the UFC. Here, the reinforcing bars 21 are placed so that the ends of the reinforcing bars 21 are embedded in the UFC without being exposed from the joint surface 20f. The shape of the boundary is the shape of the side opposite the joint surface 20f of the reinforcing portion 26. Next, concrete is poured. When the poured concrete hardens to a predetermined hardness, the partition plate is removed. Next, UFC is filled and then hardened, so that the reinforcing portion 26 made of UFC is integrated with the concrete 25 in which the reinforcing bars 21 are embedded, and the above-mentioned PCa deck 20 is formed.

[0018] After that, the PCa decks 20 are arranged on the girder 15. Then, the spaces between the PCa decks 20 to be joined are enclosed to prevent the adhesive 30 from leaking, and the adhesive 30 is inserted between the adjacent joint surfaces 20f. The PCa decks 20 are joined by the adhesive 30.

[0019] (action) At the ends of the PCa deck 20, reinforcing parts 26 made of UFC with a higher tensile strength than the buried reinforcing bars 21 are formed. The PCa decks 20 are then joined together using an adhesive 30 with a higher tensile strength than the reinforcing parts 26. Therefore, adjacent PCa decks 20 are joined by the reinforcing parts 26 with a higher tensile strength than the reinforcing bars 21 and the adhesive 30 with a higher tensile strength than the reinforcing parts 26, so that the tensile force applied to the reinforcing bars 21 is transmitted to the reinforcing bars 21 of the adjacent PCa deck 20.

[0020] According to this embodiment, the following effects can be obtained. (1-1) In this embodiment, a reinforcing portion 26 made of UFC, which has high tensile strength, is formed at the end of the PCa deck 20. This makes it difficult for the concrete portion at the end to crack even when a tensile force acts on the end of the PCa deck 20. Furthermore, when manufacturing the PCa deck 20, there is no need to provide mechanical joints that connect the reinforcing bars together, or steel plates to be welded to the reinforcing bars, or to join the reinforcing bars to the mechanical joints, so the labor required for joining can be reduced.

[0021] (1-2) Reinforcement portion 26 of PCa deck 20 of this embodiment has reinforcing bar surrounding portion 26a having length L1 equal to or longer than the anchoring length with reinforcing bar 21, and connection portion 26b shorter than reinforcing bar surrounding portion 26a. This allows reinforcing bar 21 to be anchored to reinforcing portion 26 made of UFC using a small amount of UFC, so that stress applied to reinforcing bar 21 can be transmitted to reinforcing portion 26 formed at the end of PCa deck 20.

[0022] (1-3) The PCa deck 20 of this embodiment is bonded with the adhesive 30, which has a higher tensile strength than the reinforcing bars 21 and the reinforcing portions 26. For this reason, cracks in the adhesive 30 can be suppressed.

[0023] Second embodiment Next, a second embodiment of the joining structure will be described with reference to Figures 5 and 6. In this embodiment, a PCa deck 40 is used in which a plurality of wedge-shaped protrusions are provided in a sawtooth pattern on the joining end when viewed from above. Furthermore, in this embodiment, two PCa decks 40 are joined together with a cast-in-place UFC member 50 instead of the adhesive 30 in the first embodiment. In the following embodiment, parts similar to those in the above embodiment are given the same reference numerals, and detailed description will be omitted.

[0024] Each PCa deck 40 shown in Figures 5 and 6 has a rectangular parallelepiped shape, similar to the PCa deck 20 of the first embodiment, and includes a plurality of reinforcing bars 21, concrete 45 in which the reinforcing bars 21 are embedded, and a reinforcing portion 46 made of UFC. Similar to the reinforcing portion 26, the reinforcing portion 46 has a reinforcing bar surrounding portion 46a to which the embedded reinforcing bars 21 are fixed, connection portions 46b between the reinforcing bars 21, and an end surface portion 46c.

[0025] Furthermore, in this embodiment, unlike the reinforcing portion 26 of the PCa deck 20, an uneven shape having a plurality of continuous wedge-shaped protrusions 47 is formed on the joint surface of the reinforcing portion 46. A plurality of the wedge-shaped protrusions 47 are formed for each interval of the reinforcing bars 21.

[0026] In this embodiment, the pair (two pieces) of PCa deck slabs 40 to be joined are joined by a cast-in-place UFC member 50. That is, the cast-in-place UFC member 50 functions as a joining material.

[0027] When manufacturing the PCa deck 40 of this embodiment, first, a formwork corresponding to a substantially rectangular parallelepiped shape is arranged, similar to the PCa deck 20. In this case, the portion of the formwork that forms the joint surface has a shape corresponding to the formation of a plurality of continuous wedge-shaped protrusions 47.

[0028] Then, similar to the PCa deck 20, multiple reinforcing bars 21 are arranged in parallel, and a partition plate is placed at the boundary between the concrete 45 and the reinforcement portion 46, and then concrete is poured. Next, when the poured concrete has hardened to a predetermined hardness, the partition plate is removed. Then, UFC is filled into the space on the joint surface side, and then it is hardened, forming the above-mentioned PCa deck 40.

[0029] After that, the PCa deck 40 is arranged on the girder 15. Then, the joint is surrounded by a formwork, and UFC is filled into this formwork. The two PCa decks 40 are integrated together by the cast-in-place UFC member 50 formed by the hardening of the filled UFC.

[0030] According to this embodiment, in addition to the effects similar to those of (1-1) and (1-2) above, the following effects can be obtained. (2-1) In this embodiment, multiple wedge-shaped protrusions 47 are formed on the joint side end of the PCa deck 40. As a result, the cast-in-place UFC penetrates and integrates with the multiple wedge-shaped protrusions 47 on the joint surface of the PCa deck 40, making it possible to form a stronger joint surface.

[0031] Third embodiment Next, a third embodiment of the joint structure will be described with reference to Figures 7 and 8. In this embodiment, a PCa deck 60 is used, in which the end of the joint side is configured with a plurality of continuous uneven shapes. Then, these two PCa decks 60 are joined by a cast-in-place UFC member 70.

[0032] As shown in Figs. 7 and 8, the PCa deck 60 of this embodiment has a rectangular parallelepiped shape and includes a plurality of reinforcing bars 61, concrete 65 in which the reinforcing bars 61 are embedded, and a reinforcing portion 66 made of UFC. The PCa deck 60 has a series of convex portions 67 with a rectangular horizontal cross section protruding therefrom. The convex portions 67 are made of UFC. Furthermore, the ends of the reinforcing bars 61 are located within the convex portions 67 in a state in which the reinforcing bars 61 are embedded and fixed in the UFC. The intervals between the convex portions 67 are formed to a size that allows the cast-in-place UFC member 70 to be formed between the convex portions 67 in a state in which the convex portions 67 formed on the joint surfaces of other PCa decks 60 are inserted. Moreover, the surface of the reinforcing portion 66 opposite the joint surface is formed in a linear (flat) planar shape.

[0033] In this embodiment, a pair (two pieces) of PCa decks 60 to be joined are assembled so that the tips of the protruding parts 67 are aligned and overlapped, and are joined by a cast-in-place UFC member 70 arranged between these protruding parts 67. The cast-in-place UFC member 70 is arranged in a rectangular wave shape so as to be arranged around the protruding parts 67, with the protruding parts 67 of adjacent PCa decks 60 arranged alternately.

[0034] In manufacturing the PCa deck 60 of this embodiment, a formwork corresponding to a substantially rectangular parallelepiped shape is arranged, similar to the PCa deck 40. In this case, the portion of the formwork that forms the joint surface has a shape corresponding to the formation of the multiple protrusions 67.

[0035] In manufacturing the PCa deck 60 of this embodiment, a flat, planar partition plate is placed at the boundary between the concrete 65 and the reinforcing portion 66, and multiple reinforcing bars 61 are placed in parallel, similar to the PCa deck 40. In this case, the reinforcing bars 61 are placed so that their ends pass through the partition plate and are positioned on the central axis of the protruding portion 67 and are not exposed. Next, after pouring concrete, when the poured concrete hardens to a predetermined hardness, the partition plate is removed. Then, UFC is filled into the space on the joint surface side and then hardened. This forms the PCa deck 60 described above.

[0036] After that, the PCa decks 60 are lined up on the girder 15. In this case, the ends of the protruding parts 67 of the adjacent PCa decks 60 are arranged so as to be lined up alternately. The joints are then surrounded by a formwork, and UFC is filled into this formwork and allowed to harden to form a rectangular wave-shaped cast-in-place UFC member 70. The PCa decks 60 are joined by this cast-in-place UFC member 70.

[0037] According to this embodiment, in addition to the effects (1-1) to (1-3) above, the following effects can be obtained. (3-1) In this embodiment, rebar 61 is fixed to protruding portion 67 made of UFC of PCa deck 60. Then, with the protruding portions 67 of adjacent PCa deck 60 arranged alternately, cast-in-place UFC member 70 is formed to surround the protruding portions 67. As a result, the protruding portions 67 and the cast-in-place UFC member 70 are bonded with a wide bonding area, bonding the PCa deck slabs 60 together. Therefore, a stronger bonding surface can be formed.

[0038] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction. In the reinforcing portions (26, 46) of the first and second embodiments, in order to ensure an anchoring length with the reinforcing bars 21, the reinforcing bar surrounding portions 26a, 46a around the reinforcing bars 21 are shaped to be longer than the connection portions 26b, 46b located between the reinforcing bars 21. Alternatively, the portions between the reinforcing bars 21 may be shaped to be the same length as the portions around the reinforcing bars 21. For example, as shown in Fig. 9, two PCa slabs 31 joined with adhesive 30 are constructed by embedding reinforcing bars 21 in concrete 35. Furthermore, at each end of the PCa slabs 31, a reinforcing part 36 is formed in a linear (flat) planar shape parallel to the joint surface 31f. This reinforcing part 36 is constructed of UFC, and has a size that allows the end of the reinforcing bar 21 to be embedded at a length equal to or greater than the fixing length at which it is fixed to the UFC. In this configuration, the amount of UFC used increases, but the shape of the partition plate that is the boundary between the concrete 35 and the reinforcing part 36 can be simplified. Moreover, the reinforcing portion 46 of the PCa deck 40 of the second embodiment may be configured in a linear shape, similar to the reinforcing portion 36 of the PCa deck 31.

[0039] In the first embodiment, the two PCa decks 20 are joined with an adhesive 30. In the second and third embodiments, the two PCa decks 40, 60 are joined with cast-in-place UFC members 50, 70. The material for joining the two PCa decks at their joint surfaces is not limited to an adhesive or cast-in-place UFC members, and may be, for example, grout.

[0040] In the above embodiments, the PCa deck slabs 20, 40, 60 are described as having a generally rectangular parallelepiped shape as a whole. The shape of the two reinforced concrete members to be joined is not limited to this, and may be, for example, a shape in which the upper surface has a parallelogram shape. Furthermore, the two reinforced concrete members (PCa slabs 20) to be joined are not limited to being made of ordinary concrete (concrete 25) as shown in Fig. 4 except for the reinforcement at the ends. For example, the present invention can be applied to a PCa slab (reinforced concrete member) in which the rest of the members except for the reinforcement at the ends is made of prestressed concrete. In each of the above embodiments, the ends of the PCa slabs 20, 40, 60 are made of ultra-high strength fiber reinforced concrete material (UFC). The ends of the PCa slabs (reinforced concrete members) to be joined are not limited to UFC, and may be made of any fiber reinforced concrete material that has a crack load (crack strength) greater than the yield load of the reinforcing bars embedded in the concrete. For example, UHPFRC (ultra high performance fiber reinforced concrete) may be used, or a material with a compressive strength of 150 N / mm 2 It may also be a fiber reinforced concrete material having a strength lower than

[0041] In each of the above embodiments, concrete is poured into the formwork in which the reinforcing bars 21, 61 and the partition plate are arranged, and then the partition plate is removed. Then, UFC is filled to manufacture the PCa deck 20, 40, 60. The order in which the concrete and UFC are poured is not limited to this. For example, the UFC may be poured before the concrete, or they may be poured at the same time. When pouring at the same time, the partition plate is removed immediately after the concrete and UFC are filled. Then, after removing the partition plate, the concrete and UFC are allowed to harden.

[0042] In the above embodiments, the joint member has been described as a joint member for joining PCa decks 20, 40, 60 used in road bridges, etc. The joint structure for adjacent concrete members can be applied to not only road bridges, but also railroad facilities, port facilities, decks installed in tunnels, joint structures for PCa decks in buildings, and joint structures between PCa concrete members with embedded reinforcing bars as various structural materials.

[0043] Next, the technical ideas that can be understood from the above embodiment and other examples will be described below. 3. The joint structure according to claim 1, wherein (a) an end portion of the joint surface has a shape in which projections and recesses are continuously arranged.

[0044] (b) A joint structure as described in claim 1, 2 or (a), characterized in that an end of the reinforcing bar is placed in a convex portion formed at the end of the joint surface, and the joint is formed in such a way that the concave portion of the concrete member adjacent to the joint surface fits into the convex portion, and the joint material joins the concrete members together in a rectangular wave shape. [Explanation of symbols]

[0045] 10...highway, 15...girder, 20,31,40,60...PCa deck as reinforced concrete member, 20f,31f...joint surface, 21,61...reinforcement bar, 25,35,45,65...concrete, 26,36,46,66...reinforcement part, 26a,46a...surrounding part of reinforcing bar, 26b,46b...connection part, 26c,46c...end surface part, 30...adhesive as joint material, 47,67...convex part, 50,70...cast-in-place UFC member as joint material.

Claims

1. A joint structure for joining concrete members having reinforcing bars embedded therein at a joint surface, The end of the concrete member on the joint surface side is made of a fiber-reinforced concrete material, The end of the reinforcing bar is embedded in the end of the joint surface side and fixed in place, A joint structure characterized in that the joint surfaces are joined by a joint material having a tensile strength equal to or greater than that of the fiber-reinforced concrete material.

2. The joint structure described in claim 1, characterized in that the end portion on the joint surface side, which is made of the fiber-reinforced concrete material, has a portion surrounding the reinforcing bar where the reinforcing bar is fixed to the fiber-reinforced concrete material, and a connection portion between the reinforcing bars, which is an area shorter than the portion surrounding the reinforcing bar.

3. A reinforced concrete member made of precast concrete with reinforcing bars embedded therein, which is joined to the joint surfaces of adjacent concrete members via joint materials, The end portion on the joint surface side is made of a fiber-reinforced concrete material, A reinforced concrete member, characterized in that the end of the reinforcing bar is embedded and fixed in the end of the joint surface side.

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