JP7285043B2 - Joint structure of precast concrete slab - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for joining precast concrete slabs used for floor slabs of bridges or the like at the installation site.

BACKGROUND ART Many road bridges and the like employ steel girders or concrete girders between fulcrums and join a plurality of precast concrete slabs arranged thereon to form a concrete floor slab. For joining the precast concrete slabs, for example, as described in Patent Document 1, reinforcing bars are protruded in loops from both adjacent precast concrete slabs, and these reinforcing bars are embedded in the concrete at the joint. is used.

In such a joint structure, when a large tensile force or shear force acts on both of the joined precast concrete slabs, a large bearing force is generated between the loop-shaped reinforcing bars and the concrete at the joint that contacts them inside. works. This bearing force corresponds to the “abdominal pressure” described in Non-Patent Document 1, and it is necessary to suppress the degree of stress in the concrete due to this bearing force to the extent that crushing does not occur. That is, as shown in FIG. 10, the bending radius of the reinforcing bar 51 is increased to extend the range H in which the supporting force Pu acts in the vertical direction, or the diameter φ of the reinforcing bar 51 is increased so that the supporting force acts in the horizontal direction. By enlarging the range of compression, the bearing stress of the concrete is reduced.

On the other hand, Patent Literature 2 proposes placing a steel plate inside a hoop-shaped curved reinforcing bar in order to suppress the bearing stress from increasing. By arranging the steel plate inside the curved rebar, the tensile force of the rebar is distributed widely and transmitted to the concrete, thereby reducing the bearing stress.

JP 2009-264040 A JP-A-8-326197

F. Leonhardt, E. Mönnich, (Translated by Hideo Yokomichi), Bar Arrangement of Reinforced Concrete, P42-P46, published on April 30, 1985, Kajima Publishing Co., Ltd.

However, the conventional joint structure as described above has the following problem that needs to be solved.
In a joint structure in which joint concrete is placed between adjacent precast concrete slabs, rainwater or the like may enter the boundary between the joint concrete and the precast concrete slabs. In addition, joint concrete is more susceptible to microcracks than precast concrete, and rainwater may enter through such cracks. Reinforcing bars tend to rust due to rainwater infiltration, and the durability of concrete deteriorates.

In addition, loop-shaped reinforcing bars used in joints of precast concrete slabs may need to have a large bending radius in order to suppress the bearing pressure stress on the joint concrete. In addition, the bending radius may be limited to maintain the strength of the rebar. And the limited bending radius may require thicker precast concrete slabs. As the thickness of the precast concrete slab increases, the weight becomes excessively large, impairing applicability and economy.
On the other hand, when a steel plate is placed inside a loop-shaped reinforcing bar as described in Patent Document 2, the reinforcing bar is bent into a nearly rectangular shape, making it difficult to maintain a large bending radius.

The present invention has been made in view of the above circumstances, and its object is to improve the durability of joints of precast concrete slabs and to reduce the thickness of precast concrete slabs. To provide a joint structure for precast concrete slabs.

In order to solve the above problems, the invention according to claim 1 is characterized in that a plurality of reinforcing members protrude from both opposing joint end surfaces of two precast concrete slabs to be joined together, and between the opposing joint end surfaces, the Joint concrete is placed so as to embed the reinforcing member, the reinforcing member is an FRP material in which a large number of bundled continuous fibers are bound with a synthetic resin, and both ends are embedded in the precast concrete slab. The middle part protrudes from the upper and lower parts of the joint end surface and is curved and continuous in a loop shape, and a plurality of FRP materials protruding from one of the precast concrete slabs and formed into a loop shape are connected to the other precast It is inserted between a plurality of looped FRP materials projecting from the concrete slab, and at least part of the curved portion of the FRP material projecting from both precast concrete slabs has a cross-sectional shape along the axis of the FRP material. The FRP material has a flat shape expanded so as to protrude in a lateral direction with respect to the FRP material, and the FRP material is formed by arranging a plurality of string-like bodies in which continuous fibers are bundled and bundled in a belt shape. The material is curved so that both sides are inside and outside, and the string-like body is inserted through the inside of a tubular body made of a flexibly deformable sheet, filled inside the tubular body, and curved. Provided is a joint structure of precast concrete slabs in which the continuous fibers are bound by a synthetic resin that is hardened in a compacted state.

In this joining structure, since a plurality of string-like bodies are used, a large cross-sectional area is ensured even if the diameter of each string-like body is small, and a reinforcing member having sufficient strength can be obtained. Further, since the bearing force acts on the wide surfaces of the parallel strings, the degree of bearing stress of the concrete can be kept small when a large tensile force acts on the FRP material. In addition, since the diameter of each string-like body can be reduced, the difference in circumferential length between the inner side and the outer side of the curved portion can be kept small, and the difference in the degree of stress between the continuous fibers can be reduced.

In addition, in this joint structure, the synthetic resin that binds the continuous fibers is confined inside the tubular body. can be made When the cylindrical body is filled with uncured synthetic resin, it can be flexibly deformed, and can be molded into a curved shape after the cylindrical body is filled with uncured synthetic resin. . Therefore, the uncured impregnating resin can be impregnated between the continuous fibers in a state in which the continuous fibers are curved and a substantially equal tensile force is introduced to the respective continuous fibers.

The invention according to claim 2 is directed to the joint structure of precast concrete slabs according to claim 1, wherein the bundled continuous fibers constituting each of the string-like bodies are connected to the string-like body at a portion where the FRP material is curved. shall be twisted by 180° or more around the axis of

In this joint structure, it is possible to reduce the occurrence of a length difference in the curved portions caused by the twisting of the bundles of continuous fibers that constitute each string-like body. Therefore, it is possible to suppress the occurrence of a stress degree difference between the continuous fibers.

The invention according to claim 3 is the joint structure of precast concrete slabs according to claim 1 or claim 2, wherein the shape of the center axis of the curved portion of the reinforcing member is a semicircular shape. It is assumed that the cross section has a flat shape over the entire area of the portion.

In this joint structure, since the reinforcing member is curved in the shape of an arc, a substantially uniform bearing stress toward the center of the arc against the joint concrete contacting inside the curved portion when a tensile force is introduced. degree works. Since the width of the FRP material is expanded in the entire curved portion, the degree of bearing pressure acting on the joint concrete can be made almost uniform over a wide range, and the degree of bearing stress can be reduced. can be suppressed.

The invention according to claim 4 is the precast concrete slab joint structure according to any one of claims 1 to 3, wherein the reinforcing member is embedded in the joint concrete and reinforces the joint concrete. All rod-shaped or linear members are FRP materials using non-conductive continuous fibers.

In this joint structure, since the reinforcing member embedded in the joint concrete is non-conductive, it is possible to suppress the generation of minute electric current between the reinforcing bars and PC steel materials embedded in the precast concrete slab. can be done. As a result, occurrence of electrical corrosion in reinforcing bars and PC steel materials is reduced, and the durability of the floor slab is improved.

As described above, in the precast concrete slab joint structure of the present invention, the durability of the joint portion of the precast concrete slabs is improved, and the thickness of the precast concrete slabs can be reduced.

1 is a schematic cross-sectional view of a joint structure that functions in the same manner as the joint structure of precast concrete slabs according to the present invention, and a schematic plan view of the joint before placing concrete. FIG . FIG. 2 is a schematic perspective view showing a joint end of precast concrete slabs joined by the joint structure shown in FIG. 1 ; 3 is a schematic perspective view and a cross-sectional view showing an example of a reinforcing member that can be used in the joint structure of the precast concrete slabs shown in FIGS. 1 and 2. FIG. FIG. 4 is an exploded view showing an arrangement state of continuous fibers of the reinforcing member shown in FIG. 3; FIG. 4 is a schematic perspective view and cross-sectional view showing another example of a reinforcing member that can be used in a joint structure that functions similarly to the joint structure of precast concrete slabs according to the present invention. FIG. 6 is an exploded view showing an arrangement state of continuous fibers of the reinforcing member shown in FIG. 5; FIG. 4 is a schematic perspective view and cross-sectional view showing another example of a reinforcing member that can be used in a joint structure that functions similarly to the joint structure of precast concrete slabs according to the present invention. FIG. 8 is an exploded view showing an arrangement state of continuous fibers of the reinforcing member shown in FIG. 7; FIG. 2 is a schematic perspective view showing an example of a reinforcing member that can be used in the joint structure of precast concrete slabs according to the present invention, and an enlarged perspective view showing a state of a cross section thereof. FIG. 4 is a schematic diagram illustrating the bearing force acting between the loop-shaped reinforcing member arranged at the joint of the precast concrete slab and the concrete embedding the loop-shaped reinforcing member.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a joint structure that functions in the same manner as the joint structure of precast concrete slabs according to the present invention, and a plan view before placing joint concrete. Moreover, FIG. 2 is a schematic perspective view showing the joint end of the precast concrete slabs joined by the structure shown in FIG.
In this joint structure, two precast concrete slabs 1 to be joined to each other are arranged so that joint end faces 1a face each other, and a plurality of loop-shaped reinforcing members 2 protrude from both joint end faces 1a. A plurality of lateral reinforcing members 3 are arranged in a direction substantially perpendicular to the direction in which the reinforcing members 2 protrude, and a joint portion concrete 4 is placed so as to embed the reinforcing members 2 and the lateral reinforcing members 3. is.

The precast concrete slab 1 serves as a floor slab of a road bridge, and is supported on, for example, a plurality of steel girders (not shown). A plurality of joints are arranged in the axial direction of the steel girder, and the joint end face 1a is set substantially perpendicular to the axial line of the steel girder. These precast concrete slabs 1 are made of reinforced concrete or prestressed concrete, and reinforcing bars or reinforcing bars and PC steel material sufficient to support the load acting on the road surface are arranged in the concrete.

The reinforcing member 2 is an FRP material in which continuous fibers having high strength are bundled and bound with a synthetic resin. In addition, FRP materials in which continuous fibers are similarly bundled and bound with a synthetic resin are used for the lateral reinforcing members. Aramid fibers, mineral fibers, carbon fibers, steel fibers, etc. can be used as the continuous fibers, but those made of non-conductive materials are desirable.

As shown in FIGS. 1 and 2, each of the plurality of reinforcing members 2 is partially embedded in the precast concrete slab 1 and protrudes from the upper portion and lower portion of the joint end surface 1a, and is curved to form a loop. It is continuous in shape. The portion embedded in the precast concrete slab 1 has a length that can sufficiently resist even when a pull-out force acts on the portion protruding in a loop shape. Although it is desirable that the curved portion projecting from the joint end face 1a has a circular arc shape, it may be bent in another shape to form a continuous loop.
It should be noted that illustration of a part of the lateral reinforcing member is omitted in FIG. 2 .

As shown in FIG. 3, the reinforcing member 2 has a linear portion 11 embedded in the precast concrete slab 1 and has a substantially circular cross section or a shape with substantially the same vertical and horizontal dimensions. The curved portion 12 has a flat shape with an increased width in the lateral direction. The cross section deforms so as to gradually expand the width at the linear portion protruding from the precast concrete slab 1, and the entire curved portion 12 has a flat cross-sectional shape with a substantially equal width. The width of the portion having the flat cross-sectional shape is approximately 1.5 to 2.0 times the thickness of the portion embedded in the precast concrete slab 1 .

As shown in FIG. 4, the fibers forming the reinforcing member 2 are woven into a braided cord, and are formed by combining a plurality of string-like bodies 2a in which a plurality of continuous fibers are bundled. In the example shown in FIG. 4, a thick braid is formed by weaving 16 cord-like bodies, and this is impregnated with a synthetic resin to form a rod. In the curved portion 12, the interlaced string-like bodies 2a are spaced roughly and arranged in a flat shape to increase the width. Each cord-like body 2a is arranged spirally around the center line of a thick braid, and eight cord-like bodies 2a are slanted in opposite directions and woven together.

In such a joint structure, the reinforcing members 2 projecting from the precast concrete slab 1 and embedded in the joint concrete 4 are made of FRP material, and deterioration of the joint due to corrosion of these reinforcing members 2 is prevented. be. In general, joint concrete placed on site is more likely to develop fine cracks than precast concrete slabs manufactured at a factory or the like, and if reinforcing bars are embedded in the joint concrete 4, there is a risk of early corrosion. Moreover, corrosion may progress early due to the influence of snow melting agents and the like. Since the FRP material is used as the reinforcing member 2 in the joint structure, deterioration of the joint concrete 4 due to corrosion of the reinforcing member 2 is avoided. In particular, by using the FRP material also for the lateral reinforcing member 3, local batteries are prevented from occurring between the reinforcing bars and PC steel materials placed on the precast concrete slab 1, and electrical corrosion is promoted. can be suppressed.

In addition, since the reinforcing member 2 has a flat cross section at the curved portion 12, the contact area with the joint concrete 4 can be increased. As a result, it is possible to reduce the degree of bearing stress acting on the joint portion concrete 4 when a tensile force acts on the reinforcing member 2, and the bending is performed in a state in which the degree of bearing stress is suppressed to a predetermined value or less. The vertical area of the portion 12 can be reduced. That is, the radius of curvature of the curved portion 12 can be reduced to reduce the interval between the upper and lower positions protruding from the precast concrete slab 1, and the thickness of the precast concrete slab 1 can be reduced. Further, since the reinforcing member 2 bears the tensile force with a large number of fine continuous fibers, even if the radius of curvature is made small, the influence on the strength can be kept small.

In general, when a thick or thick member is bent, a difference in length in the axial direction occurs between the inner peripheral side and the outer peripheral side of the curved portion. This can lead to stress differentials when axial tensile forces are applied. In the case of a member in which a large number of continuous fibers are bundled together, if the continuous fibers are arranged in parallel and the member is bent, there is a possibility that a significant difference in the degree of stress may occur between the outer peripheral side and the inner peripheral side. However, in the reinforcing member 2 of the above-described embodiment, since the continuous fibers are used as the braid, the positions of the continuous fibers in the curved portion 12 continuously change within the cross section of the reinforcing member 2. , and the difference in the length of each continuous fiber can be kept small. Therefore, the stress difference between the continuous fibers is small, and a decrease in strength due to a large stress difference between the continuous fibers can be avoided.

FIG. 5 is a schematic perspective view and a schematic sectional view showing a reinforcing member that can be used in place of the reinforcing member 2 used in the joint structure of the precast concrete slabs shown in FIGS. 1 and 2. FIG. Moreover, FIG. 6 is a developed view showing an arrangement state of the continuous fibers of the reinforcing member shown in FIG.
This reinforcing member 5 is an FRP material in which continuous fibers are bundled and bound with a synthetic resin in the same manner as the reinforcing member 2 shown in FIGS. Similarly, both ends are embedded in the precast concrete slab 1, and the portion protruding from the joint end surface of the precast concrete slab 1 is loop-shaped. As shown in FIG. 5, the reinforcing member 5 has a flat cross-sectional shape even at the linear portion 21 embedded in the precast concrete slab, and the loop-shaped curved portion 22 has an increased width. be.

This reinforcing member 5 is also braided from a plurality of string-like bodies 5a each made by bundling a large number of continuous fibers, but the weaving method is different from that of the reinforcing member 2 shown in FIGS. This is a so-called flat braid. That is, as shown in FIG. 6, each cord-like body 5a is arranged in a direction inclined with respect to the axis of the reinforcing member within the flattened width, and repeatedly moved between both side edges to form a zigzag shape. It's becoming The cord-like bodies intersecting between the side edges are woven together. These cord-like bodies 5a are arranged such that the space between the cord-like bodies is made coarser at the curved portion 22 and the width thereof is increased.
Even if such a reinforcing member 5 is used in the joint structure of the precast concrete slab 1, the same effects as when the reinforcing member 2 shown in FIGS. 3 and 4 is used can be obtained.

FIG. 7 is a schematic perspective view and a schematic sectional view showing another example of a reinforcing member that can be used in place of the reinforcing member 2 used in the joint structure of the precast concrete slabs shown in FIGS. 1 and 2. FIG. Moreover, FIG. 8 is a developed view showing an arrangement state of continuous fibers of the reinforcing member shown in FIG.
This reinforcing member 6 is an FRP material in which bundled continuous fibers are bound with a synthetic resin. The shape of the cross section is almost circular. In the portion 32 that protrudes from the joint end surface of the precast concrete slab 1 and curves in a loop shape, the continuous fibers are arranged so as to expand in the width direction to form a flat cross-sectional shape.

The bundled continuous fibers move to a position rotated by 180° around the central axis between the start point and the end point of the range in which the width of the reinforcing member 6 is expanded. That is, the bundle of continuous fibers is twisted 180° within the range where the width increases. As shown in FIG. 8, each continuous fiber 6a forms a flat cross-sectional shape while gently drawing a curve within the expanded width. is impregnated between continuous fibers.

In the range where the width of the reinforcing member 6 is expanded and the cross section is flattened, the continuous fiber 6a draws a sinusoidal curve or a curve approximating this on the developed view, and the curved portion 32 is approximately half the wavelength. Become. The continuous fibers 6a are distributed with a substantially uniform cross-sectional shape in the axial direction by gradually shifting the phases of the curves drawn by the respective continuous fibers 6a on the developed view.
The continuous fibers 6a shown by curved lines in FIG. 8 represent a part of a large number of bundled continuous fibers. There are also many continuous fibers in between.

In such a reinforcing member 6, the continuous fibers that were on the outer peripheral side of the curved portion at one end 32a of the curved portion 32 become the inner peripheral side at the other end 32b, and the one end 32a becomes the inner peripheral side. The continuous fibers on the other side become the outer peripheral side at the other end 32b. Therefore, each of the continuous fibers has substantially the same length between the curved portions 32, and when a tensile force acts on the curved portion 32, it is possible to suppress the occurrence of a large difference in the degree of stress between the continuous fibers. can be done.
In addition, by using such an FRP material whose width is expanded at the curved portion 32 as a reinforcing member for the joint structure of precast concrete slabs, the same effect as when using the reinforcing member 2 shown in FIGS. 3 and 4 can be obtained. can be obtained.

FIG. 9 is a schematic perspective view showing another example of a reinforcing member that can be used in place of the reinforcing member 2 used in the joint structure of precast concrete slabs shown in FIGS. A joint structure of precast concrete slabs according to the present invention uses this reinforcing member.
In this reinforcing member 7, continuous fibers are divided into a plurality of bundles 7a, and these bundles 7a are arranged flat as shown in FIG. 9(b). These bundles 7a are restrained by weft threads 43 so as to maintain their flat shape, and are inserted inside a thin tubular body 44 that is flexibly deformable. Such a reinforcing member 7 is curved so that the flat surface forms a curved surface as shown in FIG. is impregnated into the continuous fiber bundle 7a.

The straight portions 41 on both sides of the curved portion 42 of the reinforcing member 7 are embedded in the precast concrete slab, and a part of the straight portion 42 and the curved portion 42 protrude from the joint surface of the precast concrete slab. It is arranged.
Each of the bundles 7a of continuous fibers may be arranged substantially parallel to each other, but has substantially the same length as the arc drawn by the axis of the curved portion 42, and rotates 180° around the axis. It is desirable to have a twist in the pitch. By introducing twist in this manner, the length difference between the continuous fibers in the curved portion 42 is kept small. This makes it possible to suppress the difference in the degree of stress between the continuous fibers.

In the joint structure of the precast concrete slabs using such a reinforcing member 7 as well, deterioration of the joint due to corrosion of the reinforcing member 7 is suppressed, and the curved portion 42 of the reinforcing member 7 has a flat cross-sectional shape. The bearing force acts over a wide width. Therefore, it is possible to reduce the thickness of the precast concrete slab by reducing the bearing force or by suppressing the bending range.

The joint structure of the precast concrete slabs described above is an embodiment of the present invention, and the present invention is not limited thereto. Therefore, the material, the shape of the members, the dimensions, etc. can be appropriately changed within the scope of the present invention.
For example, the facing joint surfaces of the two precast concrete slabs to be joined are not limited to vertical surfaces, but may be inclined so that the interval is reduced on the lower side, or the lower portions may protrude from both sides. It may function as a formwork when pouring concrete for the joint.

1: precast concrete slab, 1a: joint end surface of precast concrete slab,
2: Reinforcing member 2a: String-shaped body of continuous fibers bundled 3: Horizontal reinforcing member 4: Joint concrete 5: Reinforcement member 5a: String-shaped body of continuous fiber bundled 6: Reinforcing member
6a: continuous fiber 7: reinforcing member 7a: bundle of continuous fibers
11: Linear portion embedded in precast concrete slab of reinforcing member, 12: Curved portion of reinforcing member,
21: Straight portion of reinforcing member, 22: Curved portion of reinforcing member,
31: Straight portion of reinforcing member, 32: Curved portion of reinforcing member,
41: Straight portion of reinforcing member 42: Curved portion of reinforcing member 43: Weft thread 44: Cylindrical body
51: rebar

Claims (4)

A plurality of reinforcing members protrude from both opposing joint end surfaces of two precast concrete slabs to be joined together,
Joint concrete is placed between the opposing joint end faces so as to embed the reinforcing member,
The reinforcing member is
It is an FRP material in which a large number of bundled continuous fibers are bound with a synthetic resin,
Both ends are embedded in the precast concrete slab, and an intermediate portion protrudes from the upper and lower portions of the joint end face and curves to form a continuous loop,
A plurality of looped FRP materials projecting from one of the precast concrete slabs are inserted between a plurality of looped FRP materials projecting from the other precast concrete slab,
At least part of the curved portion of the FRP material protruding from both precast concrete slabs has a cross-sectional shape that is enlarged and flattened so as to protrude in the lateral direction with respect to the axis of the FRP material,
The FRP material is formed by arranging a plurality of string-like bodies in which continuous fibers are bundled and bundled in a band shape, and the both sides of the band-like FRP material are curved so that both sides are inside and outside,
The cord-like body is inserted through the inside of a tubular body made of a flexibly deformable sheet, the inside of the tubular body is filled, and the continuous fibers are bound by a synthetic resin that is hardened in a curved state. A joint structure of precast concrete slabs, characterized by: 2. The method according to claim 1, wherein the bundled continuous fibers constituting each of said string-like bodies are twisted by 180° or more around the axis of said string-like body at the portion where said FRP material is curved. Joint structure of precast concrete slabs. 3. The curved portion of the reinforcing member has a semicircular center axis, and the entire curved portion has a flat cross section. Joint structure of the described precast concrete slabs. 2. All of the rod-shaped or linear members embedded in the joint concrete and including the reinforcing member that reinforces the joint concrete are FRP materials using non-conductive continuous fibers. The joint structure of precast concrete slabs according to any one of claims 1 to 3.

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