JP5751780B2 - Shear reinforcement method for existing concrete structure and concrete structure - Google Patents

Description

  The present invention relates to a method for shear reinforcement of an existing concrete structure capable of improving shear strength.

Conventionally, shear reinforcement of an existing concrete structure is performed by integrating a shear reinforcement material installed in a bottomed hole drilled from one side of an existing concrete structure and an existing concrete structure with a filler. Is known (see, for example, Patent Document 1).
The calculation formula of the shear strength Vu of the concrete structure is represented by Vu = Vc + Vp + Vs. Here, Vc: shear strength without shear reinforcement (shear strength due to concrete part), Vp: shear strength increased by prestress, Vs: shear strength borne by the shear reinforcement.
That is, conventionally, the shear strength (shear strength) of the concrete structure has been increased by using a shear reinforcement for the concrete structure or introducing prestress to increase Vs and Vp.

Japanese Patent No. 4157510

Conventionally, shear reinforcement is performed by using a shear reinforcing material or introducing pre-stress for the purpose of increasing the above-described Vs and Vp, and the above-described shear reinforcement is performed for the purpose of increasing Vc. Absent.
The present invention provides a method for shear reinforcement of an existing concrete structure in which shear reinforcement is performed by raising Vc described above.

According to the shear reinforcement method for an existing concrete structure according to the present invention, a hole extending continuously in the member axial direction from one end surface of the existing concrete structure in the member axial direction is formed in the existing concrete structure. Since the concrete having higher concrete strength than the concrete constituting the existing concrete structure was placed in the interior, the shear strength Vu = Vc + Vp + Vs of the concrete structure was increased. Without introducing pre-stress, a concrete structure with an increased Vc in the calculation formula of the shear strength Vu of the concrete structure can be obtained, and the shear strength of the existing concrete structure can be increased . Also, existing concrete structure be a reinforced concrete structure, so easily the hole forming operation to avoid the rebar.
However,
Vc: Shear strength without shear reinforcement (shear strength by concrete part),
Vp: shear strength increased by prestress,
Vs: Shear strength borne by the shear reinforcement.
Since the existing concrete structure is a reinforced concrete structure and the hole is formed avoiding the reinforcing bars in the reinforced concrete structure, the shear strength of the reinforced concrete structure can be increased without impairing the function of the reinforcing bars.
According to the concrete structure according to the present invention, the existing concrete structure is configured in a hole formed so as to extend continuously from one end surface in the member axial direction of the existing concrete structure in the member axial direction . Since concrete having a higher concrete strength than concrete was cast and formed , the shear strength Vu of the concrete structure Vu = Vc + Vp + Vs was raised, so without using a shear reinforcement or introducing prestress. A concrete structure with an increased Vc in the calculation formula for the shear strength Vu of the concrete structure can be obtained.

The figure which shows the shear reinforcement method of the existing concrete structure (Embodiment 1). (A) is sectional drawing along the member axial direction of a concrete structure, (b) is sectional drawing along the direction orthogonal to the member axial direction of a concrete structure (Embodiment 1).

Embodiment 1
As shown in FIG. 1, the shear reinforcement method for an existing concrete structure according to the first embodiment is applied to the existing concrete structure 1 </ b> A (see FIG. 1A) such as a box culvert, a retaining wall, a bridge pier, and an abutment. Existing concrete having a bottomed hole by forming a hole 3 in the existing concrete structure 1A so as to extend continuously from the one end surface 2 in the member axial direction X of the concrete structure 1A along the member axial direction X From the concrete which formed the structure 1B (refer FIG.1 (b)) and comprised the said existing concrete structure 1A in the said hole 3 from the one end surface 2 side of the member axial direction X of the said existing concrete structure 1B Also, high-strength concrete 4 having a high concrete strength is placed (see FIG. 1 (b)), and the high-strength concrete 4 is solidified so that the high-strength concrete 4 and the existing concrete are solidified. Forming a concrete structure 1 which has been integrated with preparative structure 1B (see FIG. 1 (c)).
That is, by forming the concrete structure 1 in which a part of the concrete of the existing concrete structure 1A is replaced with the high-strength concrete 4, the concrete structure 1 having the above-described calculation formula of the shear strength Vu is increased. Is.
That is, as shown in FIG. 2, the concrete structure 1 according to the first embodiment is continuous along the member axial direction X from the end surface 2 in the member axial direction X of the existing concrete structure 1 </ b> A (see FIG. 1A). Then, the existing concrete structure 1B having a bottomed hole 3 having a bottomed hole 3 perforated so as to extend, and the existing concrete structure 1B are integrated by being cast into the hole 3 and solidified. And made of high strength concrete 4.

  The hole 3 is, for example, one end surface 2 in the member axial direction X of the wall portion of the existing concrete structure 1A so as to continuously extend along the vertical direction that is the member axial direction X of the existing concrete structure 1A. It is formed so as to continuously extend downward from the end face.

  The hole 3 is a central portion in the thickness direction of the wall portion so as to avoid the reinforcing bars in the wall portion from the upper end surface of the wall portion of the existing concrete structure 1A by using a drilling machine or a high-pressure water jet (water jet) not shown. Formed.

As shown in FIG. 2 (b), the hole 3 may be configured to be intermittently formed along the lateral direction Y of the wall portion of the existing concrete structure 1A. The structure formed so that it may continue along the horizontal direction Y of a wall part may be sufficient.
Furthermore, as shown in FIG. 2B, the cross-sectional shape of the hole 3 (the cross-sectional shape of the hole when the hole is cut so as to be orthogonal to the member axial direction X) is any square, rectangular, circular, or the like. It may be a shape.

  According to the first embodiment, by replacing a part of the concrete of the existing concrete structure 1A with the high-strength concrete 4, the shear strength Vu of the concrete structure can be reduced without using a shear reinforcement or introducing prestress. A concrete structure 1 with an increased Vc in the calculation formula can be obtained, and the shear strength of the existing concrete structure 1A can be increased.

  Further, for example, when the existing concrete structure 1A is a box culvert, when the hole 3 is formed on the inner side surface (the surface along the member axial direction X) of the wall portion of the box culvert, The concrete placement machine must be carried in, and various piping and power cables are installed inside the box culvert. The work had to be done after the power supply was stopped. Further, for example, when the existing concrete structure 1A is a retaining wall, a hole 3 is formed on the side surface (a surface along the member axial direction X) of the retaining wall facing the road, and the high-strength concrete 4 is driven into the hole 3 The construction work had to be done while blocking the road. Thus, when forming the hole 3 in the surface along the member axial direction X of the existing concrete structure 1A, there are difficulties in terms of workability. On the other hand, according to the first embodiment, the hole 3 extending continuously in the member axial direction X from the one end surface 2 in the member axial direction X of the existing concrete structure 1A is formed, and the member axial direction X of the existing concrete structure 1A is formed. Since high-strength concrete is placed in the hole 3 from one end face 2 of the steel plate, the existing concrete structure 1A is sheared more than the hole 3 is formed in the surface along the member axial direction X of the existing concrete structure 1A. Reinforcing work can be easily performed.

  Moreover, when the existing concrete structure 1A is a reinforced concrete structure, the reinforcing bars are often arranged on the side close to the surface along the member axial direction X of the reinforced concrete structure. For this reason, when forming the hole 3 in the surface along the member axial direction X of the reinforced concrete structure as the existing concrete structure 1A, the position of the reinforcing bar in the existing concrete structure 1A is confirmed after the position of the reinforcing bar is present. Therefore, it is necessary to form the hole 3 so as to avoid this, and the hole forming operation avoiding the reinforcing bar is difficult. On the other hand, according to the first embodiment, since the hole 3 extending in the member axial direction X from the one end surface 2 in the member axial direction X of the existing concrete structure 1A is formed, the thickness of the reinforced concrete structure in which the reinforcing bars are not arranged. It becomes easy to form the hole 3 aiming at the central portion of the direction, and the hole forming work avoiding the reinforcing bars can be easily performed.

Embodiment 2
In the case of the first embodiment, for example, by introducing prestress into the high-strength concrete 4 by a pretension method, the shear strength Vu = Vc + Vp + Vs of the concrete structure (shear strength increased by prestress) can be increased. As a result, the shear reinforcement effect can be further improved.

  Note that the larger the difference between the concrete strength of the high-strength concrete 4 and the concrete strength of the concrete constituting the existing concrete structure 1A, the better. For example, when the concrete strength of the concrete constituting the existing concrete structure 1A is 24N, high-strength concrete 4 having a concrete strength of 30N or more may be used.

  A hole 3 extending continuously in the axial direction X of the top plate or floor slab of the existing concrete structure 1A is formed, and the concrete strength is higher than the concrete constituting the existing concrete structure 1A in the hole 3 Large high-strength concrete 4 may be placed.

  In addition, the member axial direction X means the up-down direction in the site | part and wall part extended up and down of the existing concrete structure 1A, and the direction orthogonal to a wall part in the top plate and floor slab of the existing concrete structure 1A. say.

  The existing concrete structure 1A may be an unreinforced concrete structure or a reinforced concrete structure.

1 Concrete structure, 1A Existing concrete structure, 3 holes,
4 High-strength concrete, X Member axial direction.

Claims (3)

The existing concrete structure is formed with a hole extending continuously from one end surface in the member axial direction of the existing concrete structure in the member axial direction, and the concrete is made more concrete than the concrete constituting the existing concrete structure in the hole. A method for reinforcing a shearing of an existing concrete structure, characterized by increasing Vc of the shear strength Vu = Vc + Vp + Vs of the concrete structure by placing concrete with high strength.
However,
Vc: Shear strength without shear reinforcement (shear strength by concrete part),
Vp: shear strength increased by prestress,
Vs: Shear strength borne by the shear reinforcement. 2. The method of reinforcing a shear of an existing concrete structure according to claim 1, wherein the existing concrete structure is a reinforced concrete structure, and the holes are formed avoiding the reinforcing bars in the reinforced concrete structure. Concrete having a higher concrete strength than the concrete constituting the existing concrete structure is placed in a hole formed so as to continuously extend in the member axial direction from one end surface of the existing concrete structure in the member axial direction. Thus , the concrete structure is characterized by increasing the shear strength Vu = Vc + Vp + Vs of the concrete structure.
However,
Vc: Shear strength without shear reinforcement (shear strength by concrete part),
Vp: shear strength increased by prestress,
Vs: Shear strength borne by the shear reinforcement.

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