JPS6338510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete slab reinforced on both side edges of a beam.

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.

In addition, conventional reinforcing methods (Special Publications No. 57 -
10261), but this method is for reinforcing the slab of a building that has already been constructed.
The load will be concentrated on the slab at the location of the fasteners, making it impossible to obtain sufficient reinforcement.In addition, the cost will be high because the work to attach the steel plate will be done after the slab is constructed, and the steel plate will be exposed on the surface of the slab. There were problems such as the floor surface being uneven.

The purpose of the present invention is to provide a concrete slab with a structure that suppresses cost increases, prevents cracks, and has a uniform surface finish, and is characterized by being supported by multiple beams. In a concrete slab formed by a cast-in-place concrete layer constituting the concrete slab, a cast-in-place concrete layer is provided on each of the beams, in a direction perpendicular to the beams, and with both ends of each beam in the center. Tensile members that protrude longer than both edges and span the left and right sides are installed in a tensioned state, and a partial prestress is applied to the upper part of the beam in the cast-in-place concrete layer at a position with the beam in the center. Concrete slabs are characterized by:

Next, embodiments of the present invention will be described with reference to the drawings from FIG. 2 onwards.

FIG. 2 shows an embodiment of a concrete slab 2 according to the present invention. The concrete slab 2 of this embodiment has a cast-in-place concrete layer as a whole, 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 it outward from both the left and right edges of 1.
A tension material 3 such as PC steel is built-in in a tensioned state for reinforcement.

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. Correspondingly, a tension material 3 is disposed only on the left and right precast plates 10 of the portion, and is supported and tensioned with 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 plate 10 made of a precast concrete plate is erected with both ends supported by a beam 1 made of a steel frame. A tension member 3 is disposed on each beam 1 so as to straddle the left and right precast plates 10, and both ends of these tension members 3 are fixed to the precast plates 10 on each side with fixed type tension members 12 fixed to the precast plates 10 on each side. It is supported by a force jig 13 to apply tension. At this time, a variable-length reaction force 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, an embedded metal fitting 17 is provided in advance at the end of the 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, so that each precast plate 10 is attached to the beam 1. Fixed to 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.

FIG. 9 shows an example of a third method for constructing a concrete slab according to the present invention. In this embodiment, the tension member 3 provided with the sheath 19 is disposed only on the upper part of the beam 1 and on both sides of the beam 1 so as to span both sides of the beam 1, and the fixing plate 20 is attached to one end of the tension member 3, and the tension member 3 is attached to the other end. Concrete removal material such as foam material 15
to prevent it from being buried in concrete.
Concrete is cast in this state, and the sheath 19 and tendons 3 are embedded to form a concrete slab 2. After the concrete has hardened, the concrete removal material 15 is removed, the other end of the tension material 3 protruding into the recess is tensioned with jacks, etc., and in this state, the other end of the tension material 3 is tightened with the grip chuck 21 and the fixing plate 22. The concrete slab 2 is gripped and held in place, and then the recesses of the concrete slab 2 are filled with concrete 16 and flattened.

FIG. 11 shows another example of the third method of constructing a concrete slab according to the present invention. This example differs from the embodiment shown in FIG. 9 only in that the concrete slab 2 is formed of a precast plate 10 and a cast-in-place concrete layer 11, and that the beam 1 is a steel frame.

FIG. 12 shows still another example of the third method of constructing a concrete slab according to the present invention. This embodiment shows an example in which one end of the tendon 3 is fixed by protruding from the sheath 19 and attaching it to concrete without using the fixing plate 20. Other points are similar to the embodiment shown in FIG.

As explained above, in the 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 can be alleviated in each beam part, and each This will prevent cracks from forming in the concrete slab at the beams. In addition, in the present invention, the concrete slab is not reinforced by increasing its thickness, but is partially reinforced with tendons, so there is no significant cost increase, and the prestress is applied to the beams and Since it is applied uniformly to both sides, there is no stress concentration and a stable crack prevention effect can be obtained.

[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. 9, 11, and 12 are cross-sectional views showing three examples of the second method for manufacturing a concrete slab, and FIGS. 12 and 12 are cross-sectional views showing three examples of the third method for manufacturing a concrete slab according to the present invention. 10 are cross-sectional views showing an example of the structure for fixing the other end of the tendon material in the third method. 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 force jig, 14... Reaction force jig, 15... Concrete removal material, 16... Concrete, 17...
Embedded hardware, 18... Welding part, 19... Sheath, 20
... Fixing plate, 21 ... Grip chuck, 22
...Fixer plate.

Claims (1)

[Claims] 1. In a concrete slab formed by being supported by a plurality of beams, in the cast-in-place concrete layer constituting the concrete slab, there is a layer of cast-in-place concrete on each of the beams, in a direction perpendicular to the beams, and at both ends of each beam. With each beam in the center, tension members are built in in a tensioned state, protruding longer than both sides of the beam, and spanning both sides. A concrete slab characterized by being prestressed.