JP2021161793A - Composite slab - Google Patents

Abstract

To provide a composite slab wherein, if the thickness of the mountain-top concrete is made higher than the current 100 mm, the performance of the composite slab can be enhanced by the increased height.SOLUTION: There is provided a composite slab with an inverted end closed deck plate, in which the mountain-top concrete thickness H mm satisfies the following equations (1) and (2) when the cross-sectional area per 1000 mm width of the deck plate is S mm2. (1) H=S/(α,r)-d, (2) 2≤α≤2×1.1, provided that r=the ratio of the tensile reinforcement of the part that receives the maximum bending moment under long-term load of the reinforced concrete beam, d=average concrete thickness (mm) in the deck plate height region. This structure can enhance the cross-sectional performance as the composite slab and will reduce cracking as well as increase the live load bearing ability.SELECTED DRAWING: Figure 3

Description

The present invention relates to a synthetic slab in which a deck plate and concrete are integrated, and in particular, an end in which a beam mounting portion of an end closure is formed at a mountain surface height position by crushing the end portion in the length direction of the deck plate. It relates to a closed deck plate (hereinafter, "end closed deck plate" is abbreviated as "encro deck plate"), that is, a synthetic slab constructed by using a reverse encro deck plate.

The deck plate has a trapezoidal corrugated cross-sectional shape in which the peaks and valleys are continuous on the slope and has flat portions at the height of the valleys on both sides in the width direction. It is widely used when constructing.

When a load is applied to a floor slab (concrete floor slab) made of a deck plate that is not embossed or specially bent, the deck plate and concrete are bent. The concrete in the part where the tensile force acts due to bending (the part below the neutral line) cracks, and a force is generated in which the deck plate and the concrete are displaced from each other in the longitudinal direction. In addition, peeling also occurs along with the deviation.

On the other hand, in the synthetic slab using the deck plate for the synthetic slab in which the deck plate is embossed or specially bent (for example, the deck plate 1 in FIG. 1 (however, the emboss is not applied in the figure)), the deviation is suppressed. As a result, the combined effect of the two can be exhibited, and a floor with high performance can be constructed.
In FIG. 1, reference numeral 2 is a mountain portion (or mountain surface), 3 is a valley portion (or valley surface), 4 is a slope portion, and 7 and 8 are flat portions at valley surface height positions on both sides in the width direction.

When a load is applied to the synthetic slab, cracks begin to occur in the concrete on the tension side, but in the range where the cracks are small, the load is held by the effective equivalent cross section consisting of the concrete on the compression side from the neutral axis and the deck plate on the tension side. Will be done. While maintaining this state, no decrease in yield strength is observed, and the floor load can be supported in a stable state.

However, as the concrete thickness increases, the distance from the neutral shaft to the tensile edge (lower edge of the floor slab) increases, so that a large tensile force is generated in the tension-side concrete, and cracks tend to increase. That is, a gap is likely to occur between the deck plate and the concrete, and the theoretical cross-sectional performance cannot be maintained.
Therefore, according to the "Deck Plate Floor Structure Design and Construction Standards 2018" (Japanese Society of Steel Construction), the effective deck plate mountaintop concrete thickness as a synthetic slab is 50 mm or more and 100 mm or less. This is a numerical value whose performance is directly confirmed from the past experimental results, as described in the standard.

JP-A-2007-118020

When a synthetic slab is used, the cross-sectional performance of the synthetic slab is improved by setting the thickness of the concrete on the deck plate mountain top to 100 mm or more, and a larger load load support and a crack reduction effect can be expected.
However, assuming that the deck plate mountain top concrete thickness is 100 mm or more, the current synthetic slab design system is to design the deck plate mountain top concrete thickness with performance up to 100 mm as described above, and the concrete thickness is 100 mm. Even if a cross section exceeding the above was used, the performance could not be increased by that amount, and conversely, the allowable load was reduced by the increase in the weight of the floor slab.
As shown in FIGS. 2 (a) and 2 (b), for example, as a case of a deck plate having a height of 75 mm, even if the thickness of the mountain concrete is increased by 20 mm from 100 mm to 120 mm, for example, the performance is correspondingly increased. Since the moment of inertia of area and the moment of inertia of area are treated as the same without stacking, the permissible load is reduced by the amount of increase in own weight (concrete weight equivalent to a thickness of 20 mm). That is, even if the thickness of the mountain concrete is 120 mm, it is regarded as the cross-sectional performance of the synthetic slab having the thickness of 100 mm of the mountain concrete.

In the above-mentioned "Deck plate floor structure design / construction standard 2018", the thickness of the deck plate mountaintop concrete was set to 100 mm or less as shown in FIGS. 3 (a) and 3 (b). Is assumed to be at the height of the valley surface.
That is, in the case of the general deck plate 1A in which the end is not closed in FIG. 3 (a), and in the case where the beam mounting portion 5B in which the end is closed is formed at the valley surface height position in FIG. 3 (b). It is assumed that the end closed deck plate 1B of the above is used.

The deck plate of FIG. 3 (c) was not assumed under the same standard.

The present invention has been made based on the above background, and an object of the present invention is to obtain a synthetic slab capable of increasing the performance of the increased performance when the thickness of the mountain concrete is increased from the current 100 mm.

The synthetic slab of the invention of claim 1 that solves the above problems is a deck plate in which a mountain portion and a valley portion continuously form a trapezoidal corrugated cross-sectional shape on a slope and have flat portions at the height of the valley surface on both sides in the width direction. A composite of deck plate and concrete, which was constructed using a reverse-end closed deck plate in which the end in the length direction was crushed to form a beam mounting part with an end closure at the height of the mountain surface. It ’s a slab,
When the cross-sectional area per meter width of the deck plate is Smm ² .
The mountain top concrete thickness H is a value satisfying the following equations (1) and (2).
H = S / (α · r) −d ・ ・ ・ (1)
2 ≦ α ≦ 2 × 1.1 ・ ・ ・ (2)
However,
r = Tension rebar ratio of the part that receives the maximum bending moment under long-term load of the reinforced concrete beam d = Average concrete thickness in the deck plate height region

A second aspect of the present invention is characterized in that the tensile reinforcing bar ratio r in the synthetic slab of the first aspect is 0.004.

The deck plate in the synthetic slab of the present invention is an encrodeck plate in which an end portion in the length direction is crushed to form a beam mounting portion with an end obstruction at a mountain surface height position, that is, as shown in FIG. 3 (c). It is a reverse enclosure deck plate 1C. The beam mounting portion is indicated by reference numeral 5C.
When a load is applied to the floor slab by the deck plate, the deck plate and the concrete are bent, and the concrete in the part where the tensile force acts due to the bending (the part below the neutral line) is cracked.
When the concrete at the bottom cracks, the bending force is the force that causes the concrete to shift with respect to the deck plate.
In the case of a normal end-closed deck plate 1B in which a beam mounting portion with an end blockage is formed at a valley surface height position in FIG. 3 (b), the concrete 6 is displaced as shown in FIG. 4 (b). In addition, peeling also occurs along with the deviation.
However, in the case of the reverse concrete deck plate 1C in which the beam mounting portion 5C with the end blockage is formed at the mountain surface height position in FIG. 3 (c), the reverse concrete deck plate is formed as shown in FIG. 4 (a). That is, since the beam mounting portion 5C is located at the height of the mountain surface, the end closing portion of the deck plate effectively acts as a slip stopper for the concrete 6 in the valley portion of the synthetic slab. Therefore, the deck plate 5C and the concrete 6 are prevented from being displaced from each other and peeled off due to the mutual displacement, resulting in an effectively integrated synthetic slab.

In the present invention, since the deck plate is a reverse-encrodeck plate, the deck plate and the concrete are prevented from being displaced from each other as described above, and a synthetic slab that is effectively integrated can be obtained. Under the condition that satisfies (2), it was found that when the thickness of the concrete on the mountain is made higher than the current 100 mm, it is possible to obtain a synthetic slab that can increase the performance by the increased amount. Is.

In equation (1), r is "the ratio of the tensile reinforcing bar of the part that receives the maximum bending moment under long-term load of the reinforced concrete beam (the ratio of the reinforcing bar cross-sectional area to the beam cross-sectional area)". In "The cross-sectional area of the tensile reinforcing bar of the part that receives the maximum positive and negative bending moments under long-term load is
"0.004 x beam width x beam effectiveness" (that is, the tensile rebar ratio r is 0.004), or 4/3 times the amount required by the existing stress, whichever is smaller or greater. "
It is said that.

In the present invention, the tensile reinforcing bar ratio R in the synthetic slab is regarded as α times the tensile reinforcing bar ratio r of the reinforced concrete beam, but basically it is "α = 2" (that is, twice the tensile reinforcing bar ratio r of the reinforced concrete beam). grasp. The reason is that the entire peripheral surface of the reinforcing bar in the reinforced concrete beam is the surface that adheres to the concrete, and the concrete and the reinforcing bar are integrated, whereas the deck plate in the synthetic slab has a synthetic effect due to the adhesion of one side. In the case of a reinforced concrete beam, it is basically twice the tensile reinforcing bar ratio r. α is a numerical value adopted as a coefficient with respect to the tensile reinforcing bar ratio r, and in the present invention, a numerical value such that the range of α is larger than 2 and smaller than 2.1 is adopted.

Although the present invention relates to a floor (floor slab), the "tensile reinforcing bar ratio of a beam (reinforced concrete beam)" is used because the synthetic slab is a unidirectional slab.
That is, in the synthetic slab, the cross section of the deck plate is a tensile reinforcing bar, but unlike the reinforced concrete floor slab, which is a bidirectional slab in which the reinforcing bars are arranged in two directions at right angles, the synthetic slab has a deck plate that fulfills the reinforcing bar function in one direction. This is because it can be treated as an arrangement of unidirectional beams similar to "reinforced concrete beams" as a structure.

The effect of the synthetic slab of the present invention, that is, when the thickness of the mountain concrete is made higher than the current 100 mm, it is possible to increase the performance by the increased amount, which is described in the "mode for carrying out the invention" described later. In the embodiment of the above, an inverted encrodeck plate having specific shape and dimensions will be described as an example in accordance with the concept described in the above-mentioned "Reinforced concrete structure / calculation standard / explanation".

It is a figure which shows the shape / dimension of the deck plate adopted in the synthetic slab of the Example of this invention. In the case of a synthetic slab using a general deck plate in which the valley surface is placed on the beam (including the case of a normal end-blocking deck plate in which a beam mounting portion of the end-blocking is formed at the height of the valley surface). The figure shows a comparison between the case where the deck plate mountain top concrete thickness is 100 mm (a) and the case where the deck plate mountain top concrete thickness exceeds that (b). It is a figure explaining that the performance of the above cannot be added up. The end-closed deck plate is described. (A) is a general deck plate 1A having a beam mounting portion that is not end-closed, and (b) is a beam-mounted end-closed deck at a valley surface height position. The normal end closure deck plate 1B on which the placement portion 5B is formed, (c) is the reverse enclosure deck plate 1C in which the beam mounting portion 5C of the end closure is formed at the height of the mountain surface, which is the object of the present invention. show. (A) shows a synthetic slab constructed using the reverse encrodeck plate 1C, (b) indicates a synthetic slab constructed using the normal encrodeck plate 1B, and in the case of a synthetic slab using the reverse encrodeck plate 1C, It is a figure explaining that concrete is hard to shift with respect to a deck plate. The synthetic slab constructed on the deck plate of FIG. 1 is schematically shown, and is a diagram for explaining the effect of the synthetic slab of the present invention as a numerical example.

Hereinafter, embodiments for carrying out the synthetic slab of the present invention will be described with reference to the drawings.

The effect of the synthetic slab of the present invention, that is, when the thickness of the mountain concrete is made higher than the current 100 mm, it is possible to increase the performance by the increased amount, that is, the deck having the cross-sectional shape and dimensions shown in FIG. The plate will be taken up and explained.
In the present invention, the synthetic slab is treated as a reinforced concrete beam, but as an example, the synthetic slab is regarded as a reinforced concrete beam having a width of 1000 mm and a width of H mm.
h = Yamagami concrete thickness mm
d = average concrete thickness mm in the deck plate height area
S = Deck plate cross-sectional area mm ²
Then
The beam cross-sectional area corresponds to 1000 x H (= 1000 x (h + d)),
The deck plate cross-sectional area S corresponds to the reinforcing bar cross-sectional area,
Is.
Therefore, the tensile rebar ratio R in the synthetic slab is
R = S / 1000 (h + d) ・ ・ ・ Equation (3)
Is.

A specific numerical example will be described below.
As shown in FIG. 1, the cross-sectional shape and dimensions of one deck plate are 1.0 mm in thickness, 75 mm in height and 600 mm in width, and the cross-sectional area is 880 mm ² (cross-sectional area S = 1480 mm per 1 meter (1000 mm)). Calculate in the case of ^2).
More specifically, the "average concrete thickness d in the deck plate height region" in the formula (1) is "the width dimension of the deck plate x d = the total cross-sectional area of the valley space and the valley equivalent space". It is a numerical value d such that, and is also called a groove conversion slab thickness.
Here, the valley equivalent space refers to the connecting portion area space when the deck plates are connected to each other in the width direction. Normally, the valley space and the connecting area space are the same size.
The "average concrete thickness d in the deck plate height region" of the illustrated deck plate is 36 mm (d = 36 mm).

The specific calculation is as follows.
Here, the tensile reinforcing bar ratio r of the reinforced concrete beam is set to "r = 0.004" in accordance with the concept described in the above-mentioned "Reinforced concrete structure / calculation standard / explanation".
Further, as described in [0018], in the present invention, since the numerical value of the coefficient α is basically grasped as 2, it is set to “α = 2.0”.

As described above, assuming that r = 0.004 and α = 2.0,
The tensile rebar ratio of the synthetic slab is R = α × r = 0.008.
^{Since the cross-sectional area S = 1480 mm 2} and d = 36 mm per meter of the above cross-sectional shape and dimensions,
Substituting into equation (3)
0.008 = 1480/1000 (h + 36)
therefore,
h = 1480 / (2 x 0.004) x 1000-36
= 149 mm (≈150 mm)
Will be.
That is, since the reverse enclosure deck plate is used to prevent the deck plate and the concrete from being displaced from each other, even if the thickness h of the mountaintop concrete of the synthetic slab exceeds 100 mm, it is synthesized as long as it is up to about 150 mm. It was found that it is possible to exert the effect effectively. (Because the tensile reinforcing bar ratio R of the synthetic slab of the present invention satisfies the requirement of the tensile reinforcing bar ratio in the "reinforced concrete structure / calculation standard" when calculated as a reinforced concrete beam).

As described above, by making it possible to make the mountaintop concrete thickness h of the synthetic slab using the reverse encrodeck plate thicker than before, the permissible load is reduced by the increase in its own weight without increasing the cross-sectional performance. It is possible to solve the problem of becoming. That is, the cross-sectional performance of the synthetic slab is higher than that of the conventional synthetic slab of 100 mm or less, and in addition to the increase in the load load, the effect of reducing cracks can be expected.

1 (1A, 1B, 1C) Deck plate 2 Mountain part (or mountain surface)
3 Tanibe (or valley surface)
4 Slope 5 (5B, 5C) Beam mounting part 6 Concrete 7, 8 Flat part at valley height on both sides in the width direction of the deck plate 10 Beam

Claims (2)

The mountain surface height is formed by crushing the lengthwise end of the deck plate which has a trapezoidal corrugated cross-sectional shape in which the peaks and valleys are continuous on the slope and has flat portions at the valley height on both sides in the width direction. It is a synthetic slab in which the deck plate and concrete are integrated, which was constructed using a reverse-end closed deck plate with a beam mounting part with an end closure formed at the position.
When the cross-sectional area of the deck plate per 1000 mm width is S mm ² ,
A synthetic slab characterized in that the thickness Hmm of the mountain concrete is a value satisfying the following equations (1) and (2).
H = S / (α · r) −d ・ ・ ・ ・ (1)
2 ≦ α ≦ 2 × 1.1 ・ ・ ・ (2)
However,
r = Tension rebar ratio of the part that receives the maximum bending moment under long-term load of the reinforced concrete beam d = Average concrete thickness (mm) in the deck plate height region The synthetic slab according to claim 1, wherein the tensile reinforcing bar ratio r is 0.004.

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