JPH0749687B2 - PC slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a prestressed concrete (hereinafter referred to as PC) having a floor slab made of cast-in-place concrete constructed by prestressing an unbonded PC steel material throughout the entire area. ) Regarding slabs.

(Prior Art) Conventionally, PC slabs are also known as flat slabs
As shown in Fig. 9 and Fig. 9, the large beam part 1, beam part 2 and floor slab part 3 are integrally formed by cast-in-place concrete, and the PC steel materials 4, 4 are arranged vertically and horizontally over the entire floor slab part 3. It is embedded and tensioned to prestress it to form a thin and strong slab.

This conventional PC slab has a thin overall structure, and is made of PC steel 4,
Since it is necessary to generate a lift force in the central part of the floor slab by the tension of 4 ……, a so-called unbonded cable in which PC strands are inserted into a synthetic resin sheath and grease is filled in the spaces is used.

In addition, in general, when building a building with a prestressed concrete structure using unbonded PC steel such as unbonded cables, the
Since the tension caused by the steel material may be released, it was necessary to design the main structural portion, that is, at least the girder portion, to have sufficient bearing capacity even when there is no tension caused by the PC steel material.

(Problems to be solved by the invention) Therefore, in the above-mentioned flat slab, a large amount of reinforcing bars were arranged in the portion corresponding to the large beam between columns without taking PC steel material into the stress calculation. For this reason, there is a problem in that the structure has a high yield strength structure that is not normally required, resulting in high cost.

In view of the conventional problems as described above, the present invention aims to provide a PC slab that has sufficient strength even in the event of a disaster due to fewer bar arrangements, can be constructed economically, and is closer to the conventional flat slab. It is a thing.

(Means for constructing the problem) The characteristics of the PC slab of the present invention, which solves the above-mentioned conventional problems and achieves the intended purpose, are pre-stressed by integrally embedding a bond-type PC steel material. The given precast flat beam is laid horizontally between lower structures such as columns, and a floor slab made of cast-in-place concrete supported by the precast flat beam on the upper surface side and integrated with the precast flat beam is provided. This is because prestressing was applied over the entire area with a type of PC steel.

(Function) The PC slab of the present invention uses a flat beam made of precast and has a prestressed concrete structure in which a bond type PC steel material is embedded integrally.
As a steel material that can withstand a disaster, it can be the target of stress calculation during design. In addition, the floor slab made of cast-in-place concrete integrated with the precast flat beam is prestressed entirely by unbonded PC steel, and has a thin structure with good elasticity.

(Example) Next, the Example of this invention is described about drawing.

1 to 5 show a first embodiment of a PC slab according to the present invention. In this PC slab, precast flat beams 11,11 …… made of prestressed concrete are erected in a grid pattern between columns 10, 10 …… made of cast-in-place concrete or precast concrete, and the position of this flat beam 11 is the girder part. ing.

Each of these flat beams 11 is molded into a flat cross-sectional shape with a large width compared to the height, and inside it, bond type PC steel materials 12, 12 are embedded in the longitudinal direction in addition to the reinforcing bars, and the pretensioning method is used. Pre-stress is applied in the longitudinal direction. Further, on the upper surface of the flat beam 11, hoop reinforcements 13, 13 ... For being integrated with the cast-in-place concrete on the upper surface are projected, and the main reinforcement 14 is inserted into the top of the hoop reinforcement 13.

Flat beam 1 erected between pillars 10 and 10 in this way.
A slab 15 made of cast-in-place concrete is integrally formed on the upper surface of 1,11 .... The floor slab 15 is formed by supporting the support under the flat beam 11 as necessary, supporting the support on the lower surface of the floor slab to assemble a template, and providing the necessary reinforcements on top of it. The unbonded cables 16, 16 ..., which are PC steel materials of the type, are arranged vertically and horizontally except in the longitudinal direction on the flat beam 11, and the cast-in-place concrete is poured. After that, with the solidification of concrete, the unbonded cables 16, 16 ... are tensioned, and vertical and horizontal prestress is applied to the entire floor slab 15.

As shown in FIG. 3, each unbonded cable is arranged so that the position where it intersects with the flat beam 11 is high and that the central portion between the flat beams 11 is low.

Further, on each of the pillars 10, the end portions of the flat beams 11, 11 adjacent to each other in the longitudinal direction are straddled, both ends are opened to the upper surface of the floor slab 15, and a bond type PC steel sheath is embedded. After solidifying the cast-in-place concrete of the floor slab 15, the bond type secondary tension PC steel material 18 is inserted into the sheath and tensioned to partially prestress the girder including the flat beam 11. In addition to the integration of the parts in the longitudinal direction, the upward stress on the pillar 10 is reduced, and the concentration of stress at the end position of the precast flat beam 11 is relieved.

Although the floor slab 15 made of cast-in-place concrete is formed on the upper surface of the flat beam 11 in the above-mentioned embodiment, in addition to this, as in the second embodiment shown in FIG. 11a may be formed in a mountain shape, and the top 11a may be embedded in the floor slab 15 made of cast-in-place concrete.
As in the third embodiment shown in FIG. 7, the flat beam 11 may be entirely embedded in the floor slab 15 made of cast-in-place concrete so that the lower surface is completely flat.

In the second and third embodiments, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

(Effect of the invention) As described above, the PC slab of the present invention uses the precast flat beam that is prestressed with the bond type PC steel material in the large beam portion, so that the PC steel material embedded in the flat beam is Since the prestress is not removed even in the event of a disaster, the stress can be included in the design calculation, and compared with all conventional products that are prestressed with unbonded PC steel, the rebar in the girder is The number is small, and it is not necessary for a complicated large beam part when assembling the formwork of the floor slab, and the economical efficiency is remarkably improved.

[Brief description of drawings]

1 to 5 show a first embodiment of the present invention, FIG. 1 is a plan view of the entire slab showing the arrangement of each structural member, and FIG. 2 is a sectional view taken along the line AA of FIG. Fig. 3 is a sectional view taken along line BB in Fig. 4, Fig. 4 is a sectional view of a large beam portion, Fig. 5 is a sectional view of a pillar portion, and Fig. 6 is a sectional view of a large beam portion in the second embodiment. Figure,
FIG. 7 is a cross-sectional view of the girder portion of the third embodiment, FIG. 8 is a plan view showing the arrangement of structural members of a conventional flat slab, and FIG.
The drawing is a sectional view taken along the line CC in FIG. 10 …… Pillar, 11 …… Precast flat beam, 12 ……
PC steel, 13 …… Hoop, 14 …… Main bar, 15 …… Floor, 16
…… Unbonded cable, 18 …… Secondary tension PC steel.

Claims (1)

[Claims] 1. A precast flat beam in which a bond type PC steel material is integrally embedded and prestressed is laid horizontally between lower structures such as columns, and is supported on the precast flat beam and the upper surface side. A PC slab in which a floor slab made of integrated cast-in-place concrete is provided, and prestress is applied to the floor slab with unbonded PC steel material over the entire area.