JPS63103146A - Precast concrete panel - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to improving the strength of precast concrete plates.

[Prior Art] Precast concrete plates with truss reinforcements are usually used for the floors and walls of buildings, and one side has a smooth finished surface and functions as a formwork.

This precast concrete plate is desirably as lightweight as possible in consideration of ease of transportation and handling on site, and therefore a thin plate with parallel upper and lower surfaces is usually used.

However, as shown in Fig. 6, even if the reinforcing truss bars (1) are planted in the concrete (2), when the area of the precast concrete plate (3) becomes large, the concrete When transporting the board (3) or when constructing a frame using the concrete board (3) and pouring concrete, a support member (not shown) (so-called shoring) is required to support the concrete board (3). . This is because the strength of the concrete plate (3) is low, so that the concrete plate (3) tends to bend due to its own weight or external force. In this case, the larger the area of the concrete plate (3) or the thinner the plate thickness, the more the above-mentioned supporting members must be provided. FIG. 4 is a perspective view showing a state in which it is lifted by (4).

[Problems to be Solved by the Invention] With the conventional precast concrete plate whose upper and lower surfaces are parallel as described above, it was necessary to provide a support member to support the concrete plate, so the above-mentioned transportation and There was a problem in that the work when pouring concrete was complicated.

The present invention was made to solve this problem, and an object of the present invention is to obtain a precast concrete plate that can reduce or eliminate the need for supporting members that support the precast concrete plate.

Means for solving the problem It is molded to medium height.

[Function] In this invention, the central part of the upper surface of the precast concrete plate is formed to be gradually thicker than the peripheral part, so that the shape of this concrete plate is close to that of a so-called "beam of equal strength." This means that when using the same amount of concrete as before, the maximum stress in the concrete plate can be increased.

[Examples] The present invention will be described below based on illustrated examples. 81
The figure shows a precast concrete plate (3) according to this invention.
1 is a cross-sectional view showing a first example of
) is a truss reinforcement installed in concrete (2) for reinforcement, and the truss reinforcement (1) in this example is a plurality of continuous mountain-shaped parts as shown in FIGS. 2 and 3. A lower end truss (1b) is formed between each of the angled portions (la). This truss muscle (
1) is the same as that used for the conventional concrete plate (3) above.

As shown in Fig. 1, this concrete plate (3) has a substantially flat bottom surface (2a), and
On the other hand, the upper surface (2b) on which the truss reinforcement (1) is implanted has a central part that is gradually thicker than the peripheral part, and is formed into a medium-height shape.
This first embodiment shows the case where the central part is swollen in a drum shape1.The above figure 2 shows a concrete plate (3
Figure 3 above shows the cross section of the central part of concrete and plate (
3) shows a cross-section of the peripheral edge of each.

Therefore, in the precast concrete plate of the present invention configured as described above, for example, when the concrete plate (3) is placed or lifted using the left and right ends in FIG. When placed at the construction site as a formwork and concrete is poured into the frame, the force due to its own weight or external force is applied from the top to the bottom in the figure as a uniformly distributed load or a concentrated load. This force causes the flat bottom surface (2) of the concrete plate (3) to
A tensile force acts on a), while a compressive force acts on the upper surface (2b), which has a drum-like bulge in the center.

By the way, a conventional precast concrete plate can be thought of as a "beam with a uniform cross section" in terms of material mechanics, whereas the precast concrete board (3) according to the present invention is a "beam with uniform strength". It has a shape similar to a beam (a beam designed so that the tensile and compressive circumferential stresses of each cross section are constant in the axial direction). This is because one of the "beams of equal strength" like this example
This is because a double-end supported beam with a rectangular cross section has a middle-height shape in which the central part of the beam is gradually thicker than the peripheral part. In comparing this "beam with equal strength" and "beam with a uniform cross section", if the maximum stress of both beams is the same, the volume of the "beam with equal strength" will be significantly reduced. This is known mechanically. Therefore, in the concrete plate (3) according to the present invention when the same amount of concrete as the conventional one is used, the maximum allowable stress can be significantly increased.

Fig. 4 is a cross-sectional view of a precast concrete plate (3) corresponding to Fig. 1, showing a second embodiment of the present invention. A case is shown in which the upper surface (2b) is formed into a stepped shape. Since this shape has no curved surface, it is easy to manufacture.

FIG. 5 is a cross-sectional view of a precast concrete plate [3] corresponding to FIG. 1, showing a third embodiment of the present invention. The top surface of concrete (2) that composes (3)
2b) is formed into a step-like shape, and an inclined surface (2C) is provided at each corner of the step. With this shape, the corners of the steps do not form acute angles, so the strength is increased compared to the one shown in Figure 4 above, and cracks are less likely to occur at the corners, and it is easier to manufacture. .

Note that the lower surface (2a) of the concrete (2) of the concrete plate (3) in this invention only needs to be substantially flat, and may not be perfectly flat, but may be curved or have some irregularities, for example.

In addition, although the above explanation shows the case of a thin-walled precast concrete plate (3), even if the wall is somewhat thick, the concrete plate (3) with improved strength can be obtained by using the above structure. can.

By the way, in the above explanation, we explained the case where the strength of the concrete plate is increased using the same amount of concrete as before, but if the maximum stress is to be the same as before, it is necessary to use a much larger amount of concrete than before. This can reduce the weight of the concrete plate.

[Effects of the Invention] As explained above, this invention has a structure in which the central part of the upper surface of the concrete in which the truss reinforcements are planted is formed into a medium-height part that is gradually thicker than the peripheral part, thereby increasing the strength of the precast concrete plate. This results in an increase in the number of support members supporting the concrete plate, which has the effect that the number of support members supporting the concrete plate can be reduced compared to the conventional case, or can be completely eliminated.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a precast concrete plate showing the first embodiment of the present invention, and Fig. 2 shows a part of the cross section along the line ■-■ in Figs. 1, 4, and 5. An enlarged cross-sectional view showing
FIG. 3 is an enlarged sectional view showing a part of the cross section along the line m-■ in FIGS. 1, 4, and 5, and FIG.
The 1st r! ! FIG. 5 is a sectional view equivalent to FIG. 1 showing the third embodiment of the present invention, and FIG.
The figure is a perspective view showing a conventional precast concrete board. (1)...Truss muscle, (2a)...Lower surface, (
2b)...Top surface, (3)...Precast concrete plate. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 6

Claims (1)

[Claims] A precast concrete plate on which truss reinforcements are planted, the lower surface of which is shaped like a flat plate, and the center part of the upper surface where the truss reinforcements are installed is formed into a medium-height shape with a thickness that is gradually thicker than the peripheral edge.