JPS6215368Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a PC formwork for floors that makes it possible to construct reinforced concrete floor slabs without using temporary materials such as formwork or scaffolding.

When constructing reinforced concrete floors for buildings using cast-in-place concrete, steel deck plates are often used as waste formwork. When the deck plate is used as a waste formwork, the bottom surface of the deck plate becomes the ceiling surface. Therefore, in the lower floors where the lower surface of the deck plate is the ceiling surface, a separate ceiling finish is applied to hide the lower surface of the deck plate for aesthetic reasons. As a result, the floor height of the building increases by the amount of ceiling finish, which requires extra materials and labor, which is uneconomical. In particular, in high-rise apartment buildings, etc., it is necessary to keep the floor height to a minimum in order to pursue economic efficiency, so the ceiling is not finished in this way, and the bottom surface of the floor slab on the upper floor is directly connected to the ceiling surface on the lower floor (commonly known as ``jima''). (or ceiling). The ceiling will be finished with paint or cloth, so the surface needs to be smooth. In order to obtain this smooth surface, precast concrete (PC) disposable formwork for floors has recently come into use. for this floor
As shown in Figure 1, the PC formwork consists of placing reinforcing bars 2 and C-shaped steel 1 on top of precast concrete 3', forming precast concrete 3'' on top of reinforcing bars 2, and forming the precast concrete 3'' on top of the reinforcing bars 2. It consists of a structure in which a part of C-shaped steel 1 is embedded in precast concrete 3.This PC floor formwork is manufactured at a factory to a predetermined size due to the beam spacing. The above was carried out without using any hypothetical materials at the site.
PC formwork is laid on the floor, top reinforcements are arranged in some areas, and concrete 4 is poured on site as shown in Figure 4 to complete the construction work.

However, when the PC formwork for floors having the above structure is used, shrinkage cracks are likely to occur in the concrete portion of the lower surface of the C-shaped steel 1 along the length direction. this is,
As is clear from Figure 1, the web part of the C-shaped steel 1 divides the precast concrete 3 into two, so the precast concrete 3 at this position
The cross-sectional area of the concrete is halved, and as a result, the internal tensile force generated as the concrete shrinks during drying increases, and it is assumed that this exceeds the tensile strength of the concrete, causing cracks.

The present invention solves the above-mentioned conventional drawbacks, and C
A floor in which the section steel is not embedded in the precast concrete but is connected to the reinforcing bars in the precast concrete using connectors to prevent shrinkage cracks from occurring along the length of the lower concrete part of the C section. The purpose is to provide PC formwork for

The gist of the present invention is a PC formwork for floors, which is made by arranging reinforcing bars inside precast concrete and connecting the reinforcing bars and shaped steel placed on the precast concrete with connectors.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

3 is a plate-shaped precast concrete, and inside the precast concrete 3, mesh-shaped reinforcing bars 2 are arranged along the plate surface.
In this example, the thickness of the precast concrete 3 is approximately 50 to 70 mm. Reference numeral 1 denotes a C-shaped steel, which is placed on precast concrete 3 and connected to the reinforcing bars 2 by connectors 5 made of corrugated reinforcing bars. In this example, the interval between the C-section steels 1 is about 500 mm. In addition, when the beam spacing is wide, as shown in FIG. 11, two C-section steels 1 may be arranged back to back, and the connector 5 may be sandwiched between them and fixed by welding. In addition, as shown in FIG.
A T-shaped steel 6 can also be used instead of the shaped steel 1.

Next, the case of using the formwork of the present invention will be explained. First, the PC formwork for the floor is laid on the floor surface with the C-shaped steel 1 facing upward, and then concrete 4 is poured over it. Precast concrete 3 due to drying shrinkage of concrete 4
Although tensile force is applied inside the conventional floor PC
Unlike formwork, the cross section is not divided, so cracks as described above do not occur.

As explained above, thin-walled concrete is prone to shrinkage cracks, but the present invention has the effect of preventing the occurrence of cracks because a uniform cross section is ensured. In addition, when cast-in-place concrete is placed, a bending moment (stress in the direction perpendicular to the axis of the C-shaped steel) is generated in the PC part, and C
The maximum value is at the bottom of the section steel, but since it can be manufactured in advance at a factory, it is effective in arranging reinforcement that matches the stress. At the same time, the maximum bending moment occurs at the center of the span in the axial direction of the C-section steel, but this is also effective because the position of the reinforcing bars on the tension side is shifted downward. Furthermore, conventionally the C-shaped steel and reinforcing bars are fixed by welding, but the C-shaped steel and reinforcing bars are fixed at points, making it difficult to obtain a highly reliable product. Since the fixing part is long and linear, it has the effect of providing a highly reliable product.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional PC formwork for floors, Fig. 2 is a view taken along arrow a-a in Fig. 1, and Fig. 3 is a -b-b in Fig. 1.
Fig. 4 is a cross-sectional view of concrete poured into the floor PC formwork shown in Fig. 1, and Fig. 5 is a cross-sectional view of
Fig. 6 is a cross-sectional view of the PC formwork for the floor which is an embodiment of the present invention, and Fig. 7 is a sectional view taken from d in Fig. 6.
-d arrow view, Figure 8 is an e-e arrow view in Figure 6, Figure 9 is a sectional view of concrete poured into the PC formwork for the floor of the present invention in Figure 6, and Figure 10 is The f-f arrow view in Fig. 9, Figs.
Figure 2 is a view from the gg arrow in Figure 11, and Figure 14 is a view from the 1st
FIG. 3 is a view taken along the line hh in FIG. 3; 1...C-shaped steel, 2...Reinforcement, 3...Precast concrete, 4...Cast-in-place concrete, 5...Connector.

Claims (1)

[Scope of utility model registration request] For floors made by placing reinforcing bars inside precast concrete and connecting the reinforcing bars with shaped steel placed on the precast concrete using connectors.
PC formwork.