JP4952049B2 - Shear reinforcement structure and method for reinforced concrete members - Google Patents

Description

  The present invention relates to a shear reinforcement structure and method for existing reinforced concrete members.

  When reinforcing a reinforced concrete member subjected to a shear load such as a wall of a structure or a beam, embed a new shear reinforcement bar in the concrete member so as to bear the tensile stress imposed by the concrete member. The method is widely used. At this time, in order to obtain a sufficient shear reinforcement effect, it is ensured that stress is transmitted between the shear reinforcement bar and the concrete member, and the shear reinforcement bar is surely applied to the concrete so that it can resist the tensile stress. It is necessary to fix in the member.

  As such a shear reinforcement structure having a fixing structure for reliably transmitting stress, for example, as shown in FIGS. 11 and 12, a drilling hole 21 is provided from the surface of the reinforced concrete member 10, and fixing materials 31 are provided at both ends. The shear structure 30 formed by arranging the shear reinforcing bar 32 provided and injecting the filler 33 into the excavation hole 21 may be used. According to such a configuration, the fixing material 31 provided at both ends of the shear reinforcing bar 32 improves the fixing strength, and the shear reinforcing bar 32 can resist the tensile stress, so that the shear strength of the concrete member 12 is improved.

Moreover, as a construction method similar to this, Patent Document 1 discloses a method in which a shear reinforcing member having cylindrical fixing members at both ends of a shear reinforcing bar is installed in a reinforced concrete member.
JP-A-2005-105808

  However, in the above-described shear reinforcement structure, in order to obtain a sufficient effect, it is necessary to arrange many shear reinforcement bars, and there is a problem that it takes time and effort for construction.

  Then, this invention is made | formed in view of said problem, The objective is that the number of installation of a reinforcement member can be reduced compared with the past, and the reinforced concrete member which can improve a shear strength is obtained. A shear reinforcement structure and a shear reinforcement method are provided.

In order to achieve the above-mentioned object, the shear reinforcement structure of a reinforced concrete member of the present invention is a shear reinforcement structure of an existing reinforced concrete member on which a shear load acts, and is reinforced concrete so as to intersect with an oblique crack surface caused by the shear load. An excavation hole provided in the member, a bar-shaped reinforcing material obtained by combining a plurality of strip-shaped plate members at right angles so that the cross section has a cross shape, and a support mechanism attached to at least two locations of the reinforcing material And a reinforcing member inserted into the excavation hole so that the orientation of the plate material is about 45 ° with respect to the main stress direction of the shear load acting on the reinforced concrete member, and the excavation hole is filled And a grout (first invention).

According to the reinforcing structure for a reinforced concrete member according to the present invention, since the reinforcing member acts like a tenon on the oblique crack surface, the shear strength can be improved. Therefore, since it is possible to reinforce with fewer reinforcing members than the number of shear reinforcing bars used in the conventional shear reinforcing structure, the number of excavation holes can be reduced and workability can be improved. It becomes possible.
In addition, according to the reinforcing structure for a reinforced concrete member according to the present invention, it is possible to securely fix and fix the reinforcing material in the reinforced concrete member by providing the supporting pressure mechanism at both ends of the reinforcing member.
Furthermore, the cross-sectional secondary moment of the reinforcing material is increased by combining a plurality of plate members so that the cross-section is radial. Therefore, since the role as a tenon can be sufficiently expected, the proof stress against the shear load acting on the reinforced concrete member is improved.
Further, it is possible to effectively obtain a tenon effect with a small number of plate materials by connecting the belt-like plate materials so as to be orthogonal to each other.
Furthermore, the plate is arranged so that the direction of the plate is about 45 ° with respect to the main stress direction of the shear load, and the direction of the main stress and the direction of the plate are made different, so that the plate works as a wedge when the shear load is applied. It is possible to prevent the splitting in the principal stress direction from being induced. Therefore, a board | plate material does not become a weak point of a reinforced concrete member.

According to a second invention, in the first invention, the reinforcing material has a shear strength larger than a shear load acting on the oblique crack surface.
According to the reinforcing structure for a reinforced concrete member according to the present invention, since the reinforcing material acts like a tenon on the oblique crack surface, the shear strength can be improved.

A third invention is characterized in that, in the first or second invention, the supporting pressure mechanism is a plate-like member attached to both ends of the reinforcing material.
According to the reinforcing structure of a reinforced concrete member according to the present invention, the reinforcing member has a radial cross section and is not attached so as to cover the entire plate member, but has a large gap between adjacent plate members. Therefore, the contact area between the plate-like member and the reinforced concrete member is widened, and the reinforcing member can be reliably supported and fixed in the reinforced concrete member.

According to a fourth invention, in any one of the first to third inventions, the reinforced concrete member is a culvert.
According to the reinforcing structure for a reinforced concrete member according to the present invention, an existing culvert can be reinforced.

According to a fifth invention, in any one of the first to fourth inventions, the excavation hole is provided only on one surface of the reinforced concrete member.
According to the reinforcing structure for a reinforced concrete member according to the present invention, an existing reinforced concrete member in the ground can be reinforced from the inside of the reinforced concrete member.

According to a sixth invention, in any one of the first to fifth inventions, the reinforcing material is made of a reinforced plastic such as a steel material or FRP.
According to the reinforcing structure of a reinforced concrete member according to the present invention, it is possible to face a tensile load acting on the reinforced concrete member by using a reinforcing material made of steel or reinforced plastic.

According to a seventh invention, in any one of the first to sixth inventions, the pressure supporting mechanism is made of a reinforced plastic such as a steel material or FRP.
According to the reinforcing structure of a reinforced concrete member according to the present invention, it is possible to face a tensile load acting on the reinforced concrete member by using a bearing mechanism made of steel or reinforced plastic.

According to an eighth aspect of the present invention, there is provided a method for shear reinforcement of a reinforced concrete member in an existing reinforced concrete member subjected to a shear load, wherein the excavation hole provided in the reinforced concrete member so as to intersect with an oblique crack surface caused by the shear load And inserting a reinforcing member composed of a rod-shaped reinforcing material formed by combining a plurality of strip-shaped plate members so that the cross section is radial and a pressure bearing mechanism attached to both ends of the reinforcing material into the excavation hole. The grooving hole is filled with grout, and shear reinforcement is performed by the Dowwell effect of the reinforcing member .

  ADVANTAGE OF THE INVENTION According to this invention, the shear strength of a reinforced concrete member improves, ensuring the bearing pressure fixing force of a reinforcement member.

  Hereinafter, an embodiment of the shear reinforcement structure of the present invention will be described with reference to the drawings. In addition, in this embodiment, although the application example to the wall surface of the existing BOX culvert is demonstrated, it cannot be overemphasized that this invention is not limited to the application to a BOX culvert, and can be applied also to an existing reinforced concrete member. Needless to say, the present invention is not limited to application to a wall surface, and can be applied to beams, columns, and the like.

  FIG. 1 is a cross-sectional view showing an underground BOX culvert 41 that is an object of installation of the shear reinforcement structure of the present embodiment. As shown in FIG. 1, earth and sand 42 exist outside the BOX culvert 41, and earth pressure Q of the earth and sand 42 acts on the outer wall 43 of the BOX culvert.

  FIG. 2 is an enlarged view of a reinforced concrete member in a portion surrounded by a broken line in the outer wall portion of the BOX culvert 41 in FIG. 1, and FIG. 3 is a cross-sectional view taken along line A-A ′ in FIG.

  As shown in FIGS. 2 and 3, the reinforced concrete member 10 that generally constitutes the BOX culvert 41 includes a concrete member 12, main reinforcing bars 11 arranged on the outside and inside of the concrete member 12, and orthogonal to the main reinforcing bars 11. It is provided with the arranged distribution muscle 13.

  The earth pressure Q acts on the reinforced concrete member 10 as the shear load P, and the reaction force P ′ acts on the support portion of the outer wall portion 43 in FIG. As will be described later, the shear load P and its reaction force P ′ generate an oblique crack surface (a surface on which cracks are likely to occur due to the shear load) as shown by a one-dot chain line in FIG.

  In the shear reinforcement structure 20 of the present embodiment, a drilling hole 21 is provided on one surface of such a reinforced concrete member 10 so as to intersect with the oblique crack surface at an appropriate interval, and the reinforcing member 22 is provided in the drilling hole 21. It is formed by inserting and filling the gap in the excavation hole 21 with the grout 27 and hardening the grout 27. That is, as shown in FIGS. 2 and 3, the shear reinforcement structure 20 includes an excavation hole 21 provided on the surface of the reinforced concrete member 10, a reinforcement member 22 inserted into the excavation hole 21, and an inside of the excavation hole 21. The structure includes a grout 27 filled in the gap.

  4 is a view showing the reinforcing member 22 according to the present embodiment, and FIG. 5 is a cross-sectional view taken along the line B-B ′ of FIG. 4. As shown in FIGS. 4 and 5, the reinforcing member 22 is composed of a rod-shaped reinforcing material 23 and supporting pressure mechanisms 24a and 24b attached to both ends of the reinforcing material 23. As shown in FIG. The axial direction is arranged substantially in parallel with the direction of action of the shear load.

The reinforcing member 23 is configured by connecting four strip-shaped plate members 25 at right angles to each other so that the cross-sectional shape is a cross.
The pressure bearing mechanism 24 includes a disk-shaped fixing plate 24 made of a steel material, and is firmly attached to both ends of the reinforcing material 23.
The reinforcing member 22 is disposed in the reinforced concrete member 10 so that the direction of the plate member 25 is about 45 ° with respect to the direction of the shear load.

  In the present embodiment, the method of making the cross-sectional shape of the reinforcing member 23 cross with four plate members 25 has been described, but the present invention is not limited to this, and three plate members 25 (FIG. 6) or The cross-sectional shape may be a cross shape by combining two angles 26 (FIG. 7), two plate members (not shown) having a slit in the center portion, and the like.

  Further, in the present embodiment, the method for making the support mechanism 24 the disk-shaped fixing plate 24 in the disk shape has been described. However, the present invention is not limited to this, and for example, a square or a cylindrical shape may be used. Good.

  Furthermore, in the present embodiment, the reinforcing material 23 and the support mechanism 24 are made of steel, but the material is not limited to this, and reinforced plastic such as FRP may be used.

  Moreover, in this embodiment, although the method to provide the bearing mechanism 24 in the both ends of the reinforcing material 23 was demonstrated, it is not limited to this, The bearing mechanism 24 is provided in any location of the reinforcing material 23. Also good.

  Next, the principle that the shear strength of the reinforced concrete member 10 is improved by the shear reinforcement structure 20 of the present invention is as follows. As an example, a simple beam of the reinforced concrete member 10 is used, and a shear load acts on any two symmetrical points with respect to the center of the beam. In other words, a case where a certain shear force is generated in the concrete member 12 between the action point and the fulcrum will be described. In the following description, since the load acting on the reinforced concrete member 10 is symmetric with respect to the center plane of the reinforced concrete member 10, an analysis model of one half of the reinforced concrete member 10 is considered.

FIG. 8 is a diagram illustrating stress transmission in the reinforced concrete member 10 in a state where a shear load is applied. As shown in FIG. 8, reinforced concrete member 10, in consideration of symmetry, the applied load P _1, the equilibrium by its fulcrum by reaction the reaction force P _{2 (=} P _1).

Concrete member 12 in the balanced state, the stress transfer mechanism for transmitting a compressive stress acting in the direction connecting the point P ₂ acting point and the fulcrum reaction force acting load P ₁ is formed. In addition, tensile stress acts on the stress transmission mechanism approximately perpendicular to the direction in which compressive stress acts according to the theory of the stress circle of the molding, and when the shear load acting on the reinforced concrete member 10 increases, This tensile stress also increases. If the tensile stress becomes excessive and the concrete member 12 cannot withstand this tensile stress, the concrete member 12 will be obliquely cracked along the stress transmission mechanism, causing shear failure. That is, the oblique crack surface is generated in the direction connecting the point where the load acts and the point where the fulcrum reaction force acts.

Next, the wedge effect of the fixing plate 24 will be described.
FIG. 9 is a cross-sectional view taken along the line CC ′ of FIG. 5 and shows the wedge effect in the fixing portion of the fixing plate 24. As shown in FIG. 9, when a tensile stress is applied to the reinforcing member 23, a wedge-shaped tensile member having a θ of about 20 ° with respect to the reinforcing member 23 is provided near the fixing plate 24 attached to the end of the reinforcing member 23. A compression region is formed by the stress and the reaction force. This compression region exerts a wedge effect (hereinafter referred to as a wedge effect), and the reinforcing member 22 is reliably supported and fixed against a tensile stress.

  Accordingly, as shown in FIGS. 2 to 5, the shear reinforcement structure 20 of the present invention is provided with fixing plates 24 a and 24 b at both ends of the reinforcing member 23, and the tensile stress acting on the concrete member 12 is obliquely cracked (see FIG. 1). It is to be borne by the reinforcing material 23 provided so as to cross. Further, the tensile stress acting on the reinforcing member 23 causes a wedge effect on the fixing plates 24a and 24b, and the reinforcing member 22 is firmly supported and fixed by the concrete member 12 due to the wedge effect, and the reinforcing member 23 is subjected to the tensile stress. It becomes possible to resist more effectively.

  Further, the reinforcing member 22 is provided so as to intersect with the oblique crack surface, and the effect that the reinforcing member 23 of the reinforcing member 22 acts as a tenon (so-called dowel effect) is used to prevent shear fracture. Is.

  Since the shear reinforcement bars 32 used in the conventional shear reinforcement structure (FIGS. 12 and 13) are provided for the purpose of bearing only the tensile stress, reinforcing bars having a small bending strength are used. Accordingly, since the shear reinforcement bars 32 are also deformed together with the concrete member 12, the function as a tenon is low, and the shear failure is allowed to proceed with an increase in the shear load, and finally the dowel effect is sufficiently generated. The reinforced concrete member 10 has been destroyed before, and the shear strength cannot be improved.

  On the other hand, the reinforcing member 22 used in the shear reinforcing structure 20 of the present embodiment has a larger sectional secondary moment than the shear reinforcing bar 32 and a large bending rigidity. For this reason, the function as a tenon is high, a sufficient dowel effect can be expected from the beginning of loading of the shear load, and the shear strength can be improved. In addition, when a reinforcing material having a shear strength equal to or greater than the shearing force generated on the oblique crack surface is used as the reinforcing material 23, the reinforcing material 23 can resist the force to be separated along the oblique crack surface. Can be improved.

  Further, when a steel pipe having a large bending rigidity is used as a reinforcing material in anticipation of the tenon effect, the fixing plate 24 must be made larger than the diameter of the steel pipe in order to obtain a predetermined wedge effect. The reinforcing member 22 is a concrete member necessary for obtaining a predetermined wedge effect even when the fixing plate 24 is made smaller by using a reinforcing member 23 composed of a plurality of plate members as compared with the case where a steel pipe is used. 12 and the contact area between the fixing plate 24 can be secured.

  As shown in FIGS. 2 and 3, the shear reinforcement structure 20 of the present embodiment has a reinforcement member 22 arranged in a direction orthogonal to the member axis. Normally, oblique cracks follow the stress transmission mechanism. In other words, the reinforcing member 22 intersects with the oblique crack because it occurs in an oblique direction with respect to the member axis. For this reason, even if the reinforcing member 22 is arranged in a direction orthogonal to the member axis as in the shear reinforcing structure 20 of the present embodiment, a shear reinforcing effect can be obtained.

  Moreover, the reinforcement member 22 can be arrange | positioned so that it may cross | intersect an oblique crack by inserting the reinforcement member 22 only in one surface of the reinforced concrete member 10 in a member orthogonal direction. For this reason, the shear reinforcement structure 20 of this embodiment can perform shear reinforcement from one surface of the reinforced concrete member 10.

  Thus, since the shear reinforcement can be performed from one surface of the reinforced concrete member 10, it is particularly effective when the outer wall portion of the BOX culvert that is an underground structure is to be sheared. As shown in FIG. 1, earth and sand 42 exist outside the outer wall 43 of the BOX culvert 41. According to the shear reinforcement structure 20 of the present embodiment, as described above, it is possible to perform construction from one side of the reinforced concrete member 10 and to perform shear reinforcement work on the outer wall portion 43 of the BOX culvert 41. However, it is not necessary to work from both sides of the outer wall portion 43, and therefore construction can be performed from the inside of the BOX culvert 41 without excavating the earth and sand 42.

  Furthermore, the plate material 25 is arranged so that the direction of the plate material 25 is about 45 ° with respect to the main stress direction of the shear load, and the direction of the main stress direction and the direction of the plate material 25 are different from each other. It acts as a wedge and can prevent the splitting in the principal stress direction. Therefore, a board | plate material does not become a weak point of a reinforced concrete member.

As described above, according to the shear reinforcement structure of the present embodiment, since the reinforcing member is sufficiently supported and fixed to the reinforced concrete member, the shear strength of the reinforced concrete member can be improved.
In addition, since the reinforcing member is provided so as to intersect with the crack surface caused by the shear load, efficient reinforcement is possible.

  By the effect of the above two points, compared to the shear reinforcement bars used in the conventional method, since the reinforcement member can perform the shear reinforcement with a small number, the number of excavation holes provided in the concrete member can be reduced, Workability is improved. Moreover, since it can construct from one side of a reinforced concrete member, even when there is earth and sand on the back of the outer wall on the other side such as a BOX culvert, construction can be performed from the inside without excavating the earth and sand.

  In the present embodiment, the strip-shaped plate member 25 is used in a cross-shaped cross section as the reinforcing member 23. However, the present invention is not limited to this. As long as the fixing plate 24 can obtain a predetermined wedge effect, the fixing plate 24 may be arranged. In such a case, it is desirable to arrange the reinforcing member 22 in the reinforced concrete member 10 so that the center of the angle formed by the adjacent plate members 25 of the reinforcing member 22 substantially coincides with the main stress direction of the shear load.

  In addition, in this embodiment, although the application example to the existing reinforced concrete member 10 was demonstrated, it cannot be overemphasized that this invention is not limited to the application to the reinforced concrete member 10, and can be applied also to a steel frame reinforced concrete member. Absent.

It is sectional drawing which shows the underground BOX culvert used as the installation object of a shear reinforcement structure. It is an enlarged view of the reinforced concrete member of the part enclosed with the broken line of the outer wall part of the BOX culvert 41 in FIG. It is A-A 'sectional drawing of FIG. It is a figure which shows the reinforcement member which concerns on this embodiment. FIG. 5 is a B-B ′ cross-sectional view of FIG. 4. The example of the reinforcing material comprised from three board | plate materials is shown, and it is a reinforcing material sectional drawing. An example of a reinforcing material composed of two angles is shown and is a cross-sectional view of the reinforcing material. It is a figure which shows the stress transmission in the reinforced concrete member in the state where the shear load is acting. FIG. 6 is a cross-sectional view taken along the line C-C ′ of FIG. 5, illustrating a wedge effect at a fixing portion of the fixing plate. An example of a reinforcing material having a cross-sectional rice shape is shown, and is a cross-sectional view of the reinforcing material. It is a cross-sectional view which shows the conventional shear reinforcement structure which has a fixing tool in the both ends of a shear reinforcement. It is D-D 'sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reinforced concrete member 11 Main rebar 12 Concrete member 13 Power distribution bar 20 Shear reinforcement structure 21 Excavation hole 22 Reinforcement member 23 Reinforcement material 24 Support mechanism (= fixing plate)
25 Plate material 26 Angle 27 Grout 30 Conventional shear reinforcement structure 31 Fixing material 32 Shear reinforcement bar 33 Filler 41 BOX culvert 42 Earth and sand 43 Outer wall

Claims (8)

A shear reinforcement structure for an existing reinforced concrete member on which a shear load acts,
Excavation holes provided in the reinforced concrete member so as to intersect the oblique crack surface caused by the shear load,
It is composed of a bar-shaped reinforcing material obtained by combining a plurality of strip-shaped plate members at right angles so that the cross section has a cross shape, and a support mechanism attached to at least two locations of the reinforcing material , A reinforcing member inserted so that the orientation of the plate material is about 45 ° with respect to the principal stress direction of the shear load acting on the reinforced concrete member ;
A shear reinforcement structure for a reinforced concrete member, comprising a grout filled in the excavation hole.   The shear reinforcement structure for a reinforced concrete member according to claim 1, wherein the reinforcing material has a shear strength greater than a shear load acting on the oblique crack surface. 3. The shear reinforcement structure for a reinforced concrete member according to claim 1, wherein the bearing mechanism is a plate-like member attached to both ends of the reinforcing material. The reinforced concrete member shear reinforcement structure according to any one of claims 1 to 3 , wherein the reinforced concrete member is a culvert. The shear reinforcement structure for a reinforced concrete member according to any one of claims 1 to 4 , wherein the excavation hole is provided only on one surface of the reinforced concrete member. The shear reinforcement structure for a reinforced concrete member according to any one of claims 1 to 5 , wherein the reinforcing material is made of a reinforced plastic such as a steel material or FRP. The shear reinforcement structure for a reinforced concrete member according to any one of claims 1 to 6 , wherein the bearing mechanism is made of a reinforced plastic such as steel or FRP. In the shear reinforcement method of the existing reinforced concrete member where the shear load acts,
Excavation holes provided in reinforced concrete members are provided so as to intersect with the oblique crack surface caused by the shear load,
Inserting a reinforcing member composed of a rod-shaped reinforcing material formed by combining a plurality of strip-shaped plate members so that the cross section is radial and a pressure bearing mechanism attached to both ends of the reinforcing material into the excavation hole,
Filling the borehole with grout ,
A shear reinforcement method for a reinforced concrete member, wherein shear reinforcement is performed by the Dowwell effect of the reinforcement member.

Images