JPS6250619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing a concrete slab.

In general, when a concrete slab 2 is constructed on top of multiple beams 1 as shown in Figure 1, when the stress applied to the concrete slab 2 is measured, it is found that the stress applied to each beam is as shown in Figure 1B. The upward stress becomes maximum at , and the relationship between the maximum value a of the upward stress and the maximum value b of the downward stress is a>b.

For this reason, cracks often occur in the concrete slab 2 at a portion corresponding to the beam 1. In order to prevent this, the thickness of the concrete slab 2 has conventionally been increased, but such a solution has the drawback of significantly increasing costs.

An object of the present invention is to provide a method for constructing a concrete slab having a structure that suppresses increases in cost and prevents cracks.

A first invention to achieve the above object is that when constructing a concrete slab formed by being supported by a plurality of beams, before pouring concrete in the cast-in-place concrete layer, A tension member is provided in a direction perpendicular to each other, with both ends protruding longer than both the left and right edges of the beam, and the tension members are placed across both sides of the beam, and both ends of the tension members are straddled on both sides of each beam. Applying tension to each tension member by supporting it with a force jig, then pouring a cast-in-place concrete layer by embedding these tension members, and removing the reaction jig after the concrete hardens;
The second invention is characterized in that prestress is partially applied to a cast-in-place concrete layer, and the second invention is characterized in that when constructing a concrete slab formed by being supported by a plurality of beams, both ends are supported between the beams. A precast plate such as a precast concrete plate or a deck plate is erected, and tension members are placed on each of the beams in a direction perpendicular to the beam, and with both ends spanning the precast plates on both sides of the beam. With both ends of each of the tendons being supported by reaction jigs fixed to the precast plates on each side, tension is applied to each of the tendons, and these tendons are embedded in the precast plate. A cast-in-place concrete layer is placed on the board, and after the cast-in-place concrete layer has hardened, the tension members are separated from the reaction jig, and a prestress is partially applied to the cast-in-place concrete layer. It is characterized by:

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an example of a concrete slab 2 constructed according to the present invention. The concrete slab 2 of this embodiment is entirely composed of a cast-in-place concrete layer, and is placed on each beam 1 in the layer, with the direction perpendicular to the beam 1, and both ends connected to the beam. straddle the left and right sides of 1
A tension material 3 such as PC steel is built-in and reinforced in a tensioned state.

In this way, if the concrete slab 2 is reinforced with the tension material 3 at each beam 1 part to create a partially prestressed concrete structure, the upward stress acting on the concrete slab 2 at each beam 1 part can be alleviated, and the concrete slab It is possible to prevent cracks from forming in the connection portion between the beam 1 and the beam 1.

FIG. 3 shows an example of the first construction method of the concrete slab 2 according to the present invention. As shown in the figure, the floor formwork 4 and beam formwork 5 are supported by supports 6, slab reinforcement 7 is placed on the floor formwork 4, and the beam formwork 5 is
Place beam reinforcement 8 inside. Further, tension members 3 such as prestressing steel materials are arranged on each beam 1, and both ends of these tension members 3 are supported by reaction force jigs 9 and tensioned.

The reaction jig 9 may be of the type that applies tension to the tension material 3 by extending its entire length in the longitudinal direction, for example, in the relationship between a screw screw and a nut, or it may be of the type that does not change in length and may be a hydraulic jig. Or use a type that applies tension using screws. Further, tension members 3 are placed in grooves at both ends of the reaction jig 9, and are prevented from slipping out in the longitudinal direction by stopper members to apply tension. Furthermore, the gripping portions at both ends of the reaction jig 9 are covered with foam material or the like to prevent concrete from entering. In this state, concrete is poured on the floor formwork 4 and inside the beam formwork 5 to form the concrete slab 2 and the beam 1. After the concrete hardens, the reaction jig 9 is removed, and the recesses formed at both ends of the tendon 3 are filled with concrete to flatten the concrete slab 2. In addition, each formwork 4, 5
will also be removed.

FIG. 4 shows another example of the first construction method. In this embodiment, a reaction jig 9 is arranged below the formworks 4 and 5 to tension the tension material 3.

FIG. 5 shows still another example of the first construction method. In this embodiment, a precast plate 10 such as a precast concrete plate or a deck plate is erected with both ends supported by a beam 1 made of a steel frame, slab reinforcement 7 is provided on the precast plate 10, and each beam 1 is provided with slab reinforcement 7. A tension material 3 is disposed only in the corresponding portions so as to straddle the left and right precast plates 10, and is supported and tensioned by a reaction jig 9. In this state, concrete is cast in place using the precast board 10 as a formwork, and the slab reinforcement 7 and tension material 3 are embedded in this cast in place concrete layer 11.
As a result, a composite concrete slab 2 is formed by the precast board 10 and the cast-in-place concrete layer 11. After the cast-in-place concrete layer 11 hardens, the reaction force jig 9 is removed, and the recess after the removal is filled with concrete and flattened.

FIG. 6 shows an example of the second construction method of the concrete slab 2 according to the present invention.

In this embodiment, a precast board 10 made of a precast concrete board is erected with both ends supported by a beam 1 made of a steel frame. Tension members 3 are disposed on each beam 1 so that both ends thereof straddle the left and right precast plates 10, and both ends of these tendons 3 are fixed to the precast plates 10 on each side with bolts 12. A tension force is applied by supporting the reaction force jig 13. At this time, a variable-length reaction jig 14 such as a turnbuckle is interposed between the ends of adjacent precast plates 10 on the beam 1 to prevent the precast plates 10 on both sides from coming closer together due to the tension of the tension material 3. Let's prevent it.

The location of each reaction jig 13 is wrapped with concrete removal material such as foam material to prevent it from being buried in concrete.

In this state, concrete is cast in place using the precast board 10 as a formwork, and the tension material 3 and reaction jig 1 are placed in this cast in place concrete layer 11.
Embed 4. After the concrete has hardened, the concrete removing material and the reaction force jig 13 are removed, and the holes formed in their remains are filled with concrete 16 and flattened. The reaction jig 14 is buried in concrete.

FIG. 7 shows another example of the second method of constructing a concrete slab according to the present invention. In this embodiment, a metal fitting 17 is provided in advance to be embedded in the end of a precast plate 10 made of a precast concrete plate located on the beam 1, and this embedded metal fitting 17 is fixed with a welding part 18 to separate each precast plate 10. Fix it to beam 1. In addition, the tensioning material 3, which is disposed so as to straddle the left and right precast boards 10 only in the portion corresponding to each beam 1, is tensioned by a tension applying means such as a jack, and each precast board 10 is
A fixed type reaction jig 13 fixed with bolts 12 is used to fixedly support the device. The area around the reaction jig 13 is wrapped with a concrete removing material such as foam material to prevent it from being buried in concrete. In this state, concrete is cast in place using the precast board 10 as a formwork, and the tension material 3 is embedded in the cast in place concrete layer 11. After the concrete hardens, the concrete removal material 15 is removed, and the tension material 3 is attached to the reaction jig 1.
3 and fill the hole made there with concrete 16 to level it.

FIG. 8 shows another example of the second method of constructing a concrete slab according to the present invention. This embodiment is almost the same as the embodiment shown in FIG. 7, except that a deck plate is used as the precast board 10. Further, due to the use of a deck plate, the reaction jig 13 is fixed to the precast plate 10 by welding, and the precast plate 10 is directly fixed to the beam 1 at a welded portion 18.

As explained above, in the method for constructing a concrete slab according to the present invention, the parts corresponding to the beams are partially reinforced by applying prestress, so that the upward stress acting on the concrete slab at each beam part is alleviated. This will prevent cracks from forming in the concrete slab at each beam. Furthermore, in the present invention, the structure is not reinforced by increasing the thickness of the concrete slab, but is partially reinforced with tendons, so reinforcement measures to prevent cracks can be implemented without significantly increasing costs. be able to.

[Brief explanation of the drawing]

FIGS. 1A and 1B are cross-sectional views of a conventional concrete slab and diagrams showing the stress distribution thereof; FIG. 2 is a cross-sectional view of an embodiment of a concrete slab according to the present invention;
3, 4 and 5 are cross-sectional views showing three examples of the first method of manufacturing a concrete slab according to the present invention, and FIGS. 6, 7 and 8 are sectional views according to the present invention. It is sectional drawing which shows three types of examples of the 2nd manufacturing method of a concrete slab. 1... Beam, 2... Concrete slab, 3...
Tensile material, 4, 5...Formwork, 6...Support, 7...
...Slab reinforcement, 8...Beam reinforcement, 9...Reaction jig,
10... Slab lower plate, 11... Cast-in-place concrete layer, 12... Bolt, 13... Reaction jig, 14
... Reaction jig, 15 ... Concrete removal material, 1
6... Concrete, 17... Embedded hardware, 18
……welded part.

Claims (1)

[Claims] 1. When constructing a concrete slab supported by a plurality of beams, before pouring the cast-in-place concrete layer, a In addition, a reaction jig is used in which tension members are arranged so that both ends protrude longer than both the left and right edges of the beam, and are straddled on both sides, and both ends of the tension members are made to extend over both sides of each beam. After that, a cast-in-place concrete layer is poured by supporting and applying tension to each tendon, and then a cast-in-place concrete layer is poured by embedding these tendons, and after the concrete has hardened, the reaction jig is removed and the cast-in-place concrete layer is placed. A method of constructing a concrete slab characterized by partially applying prestress to the concrete slab. 2. When constructing a concrete slab supported by multiple beams, a precast plate such as a precast concrete plate or deck plate is erected with both ends supported between the beams, and the corresponding A reaction jig in which tension members are arranged in a direction perpendicular to the beam, with both ends spanning the precast plates on both sides of the beam, and both ends of each tension member are fixed to the precast plates on each side. A tension force is applied to each of the tendons in a state where they are supported by a cast-in-place concrete layer, and a cast-in-place concrete layer is placed on the precast board by embedding these tendons, and after the cast-in-place concrete layer has hardened, A method for constructing a concrete slab, comprising separating each tension member from the reaction jig and partially applying prestress to a cast-in-place concrete layer.