JPH0559228B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a repair/reinforcement method for existing slabs, and more specifically, an existing reinforced concrete slab that is reinforced with prestressing steel material that has cracked or bent existing reinforced concrete slabs. Regarding repair and reinforcement methods.

[Prior art] Conventionally, as a method for reinforcing an existing reinforced concrete slab using prestressing steel, there is
The one described in the publication No. 1 is known.

[Problems to be Solved by the Invention] JP-A No. 62-41869 discloses that a spacing member is provided as a fulcrum near the bottom surface of a slab, and a PC steel material is attached to the support members at both ends of the bottom surface of the slab via the fulcrum. A technique is disclosed in which the slab is fixed and reinforced by applying an upward force to the slab.

However, with this technology, due to the presence of the spacing member, the space within the ceiling is far away from the bottom surface of the slab.
Because the prestressing steel material protrudes, it has the disadvantage of making it difficult to place equipment piping within the ceiling.

In addition, although prestressing steel has strong tensile strength, it is weak in local bending strength, so if the spacing member is made of round steel, there will be point contact, and local bending force will act on the prestressing steel. There is a disadvantage that the steel can break, and if a member other than round steel is used, the sheath of the unbonded PC steel material will break, causing problems such as corrosion.

Furthermore, since the location where the fixing force acts, that is, the position of the fixing plate, is far from the core radius of the slab cross section, a large torsional moment f acts on the support member 52 as shown in FIG. Further, in order to prevent the cracks 51, a member 53 for reinforcing the support member 52 must be provided as shown in FIG. 8. In addition, in FIGS. 7 and 8, 54 is a fixing plate, and 55 is a PC steel wire.

Furthermore, since the work is carried out on the underside of the slab, all the work is directed upwards, making the work difficult and complicated.

[Object of the invention] Therefore, the object of the present invention is to reduce the amount of exposure inside the ceiling, prevent the occurrence of bending of the prestressing steel material,
Another object of the present invention is to provide a method for repairing and reinforcing existing slabs that does not generate new cracks in the slab during repair and is easy to construct.

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies and have arrived at the present invention.

That is, the existing slab repair/reinforcement method of the present invention involves drilling a slit hole that extends to the lower surface of the slab by cutting a certain length of the opposing beam edges of an existing reinforced concrete slab that has cracked or deflected. Insert the unbonded PC steel wire from above this slit hole toward the bottom surface of the slab, stretch it so that it is in direct contact with the bottom surface of the slab, and then pull it out from the opposing slit hole to the top of the beam. Unbonded PC placed in
The end of the steel wire is tension-fixed between tension fittings placed above the beam, and the slit hole is filled with concrete or the like.

[Example] Examples of the construction method of the present invention will be described below.

First, a case where the method is applied to an existing square slab (including one that approximates a square) will be explained.

First, in the square slab 1 shown in Fig. 1, a slit hole 3 of a certain width and length is made from the beam edge 2A at the center of the span of each beam 2 on the four peripheries toward the center of the slab. Hang the concrete of the four beams 2, which are the fixed ends of the extended slab, at a constant width up to the top reinforcement 5 (see Figure 2).

At the beam 2 position, the unbonded PC steel material 4 is placed on top of the upper reinforcement 5 as shown in Fig. 2, and this PC steel material 4 is sent to the bottom of the slab using the slit hole 3. Pull up the steel material 4 and place it on the other beam top reinforcement. If there are adjacent slabs, do the same for those slabs.
Extend the PC steel material and wire it to the upper end of the beam 5 of the building exterior 6 as shown in Figure 3.

The concrete of this part is removed so that the fixed end and the tension fitting 7 of the fixed end of the beam upper end 5 of the building exterior structure 6 are accommodated, and these are installed. Then, the PC steel material is passed through these metal fittings 7.

Next, ordinary concrete is poured into the slit holes 3 using a floating form (not shown), and non-shrinkage concrete is poured into the openings around the anchor plate and pocket former. In addition, before placing concrete, check to see if the slab reinforcement and beam reinforcement are damaged, and if they have been cut, repair them by welding them together using splints or the like.

Next, after confirming that the concrete compressive strength is 200Kg/cm2 ^or higher, a prestressing jack (not shown) is installed at the tension end to apply tension T to the PC steel material.
It is fixed with a predetermined load.

By applying tension to the prestressing steel material, an upward force F is applied to the prestressing steel material, lifting the slab and reducing cracks and deflection (see Figure 4). In FIG. 4, P indicates the position (length) of the slit hole.

When changing the suspension force between consecutive slabs, it is easy to do so simply by changing the rise h of the prestressing steel material (see Figure 4), changing the tension of the prestressing steel material, or changing the length of P. The pull-up force can be changed.

In this embodiment, unbonded PC steel strands are normally used as the unbonded PC steel material. In the above example, two wires are used in each of the X direction and the Y direction, but this is not a limitation.

Note that it is also preferable to interpose a rubber member at the intersection of the PC steel materials that protrude in close contact with the ceiling in order to avoid contact between the PC steel materials.

As mentioned above, in the case of a square slab, the slab load flows approximately equally to the beams on all four sides, so it is preferable to provide two wires each from unbonded PC steel in the X and Y directions, but You may add one or two at a time.

Next, when applying to an existing rectangular slab,
As shown in FIG. 5, two PC steel members 4 may be provided in the longitudinal direction (X direction).

In addition, PC steel material 4 is placed at one location in the X direction (about 3 pieces)
It may be.

In addition to the above examples, there are cases where the load of the slab cannot be transferred to the beam using prestressed steel (for example, when the beam is severely damaged and requires repair, or when the load after reinforcement due to a change in use is If the slab is large and requires reinforcement of the beam), the load of the slab can be directly applied to the pillars 10 by placing the prestressing steel members 4 so as to pass through the diagonal pillars 10 as shown in Figure 6. Can be transmitted, beam repair and
Reinforcement becomes unnecessary.

In this example, the prestress force is approximately 20 kg/cm ² per concrete cross section, so concrete with high compressive strength (approximately 300 kg/cm ² or more) is not required, and a design strength of approximately 180 kg/cm ² or more is sufficient; There is no problem in repairing and reinforcing the RC slab.

[Effect of the invention] According to the present invention, the following effects are achieved.

(1) A portion of the PC steel material is exposed on the underside of the slab, that is, inside the ceiling, but as it is in close contact with the underside of the slab, it does not affect the installation of equipment piping, etc. inside the ceiling.

(2) There are no local bends in the prestressing steel, so
The PC steel material will not be damaged, and the sheath will not break in the case of unbonded PC stranded wire, so there will be no corrosion problem.

(3) Since the fixed end position of the prestressing steel is within the core radius of the slab cross section, no torsion moment is generated.
Reinforcement against the torsional moment is not required.

(4) Workability is extremely high as most of the construction work is downward work on the top surface of the slab, and there is little upward work on the bottom surface of the slab.

(5) Since only new prestressing steel materials and fixed end members are added to the slab, there is almost no increase in fixed load.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the main part showing an example of the repair/reinforcement method of the present invention, Figs. 2 and 3 are schematic sectional views showing the state during chiseling in the method of the present invention, and Fig. 4 is a plan view of the main part showing an example of the repair/reinforcement method of the present invention. A schematic side view showing the direction of tension force and suspension force in the construction method, Figures 5 and 6 are plan views of main parts showing other examples of the construction method of the present invention, and Figures 7 and 8 are diagrams showing the conventional construction method. FIG. 1... Slab, 2... Beam, 2A... Beam edge, 3...
...Slit hole, 4...PC steel material, 5...Top reinforcement,
6...Building exterior, 7...Tension fittings.

Claims (1)

[Claims] 1. A slit hole is drilled through a certain length of the opposing beam edges of an existing reinforced concrete slab that has cracked or bent, and extends to the bottom surface of the slab. Insert the PC steel wire, stretch it with the unbonded PC steel wire in direct contact with the bottom surface of the slab, and then pull it out from the opposing slit hole to the top of the beam.
A method for repairing and reinforcing existing slabs, which is characterized by fixing the ends of steel wires under tension between tension fittings placed above the beams, and filling the slit holes with concrete, etc.