JP2016216977A - Steel floorboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel floorboard having slits (long holes) at equal pitches in the steel floorboard, particularly, a plane part suitably used as a safety passage, a work floor, a corridor, stairs, the other floorboard or a building material.SOLUTION: In a dimension specification of respective parts of a steel floorboard of forming slits 1b at equal pitches in the same shape and the same size in an upper surface, assuming the upper opening ratio as P, a longitudinal width of the slit as a, a breadth of the slit as d and a longitudinal width of a cross rail 1c between the adjacent slits as b, a steel floorboard satisfies conditions of the following expressions (A)-(C). P≥0.426...................(A)(a/d)≤0.145.............(B) (a/d)<0.077×(a/b)+0.017...(C)SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a steel floorboard that is also suitably used as a safety passage, work floor, walkway, staircase and other floorboards or building materials, and in particular, a technical field of steel floorboards having slits (long holes) at an equal pitch in a plane portion. Belonging to.

  As shown in FIG. 1, the steel floor board is a processed product of a highly corrosion-resistant plated steel sheet having a thickness of about 1.6 to 2.0 mm, and the width dimension B (see FIG. 2) on the left and right is 200 to 250 mm. On both sides, both edges have a height of about 40 to 60 mm and an inwardly U-shaped leg portion 1a (FIGS. 1 and 6B), and a vertical width a of the slit (FIG. 2) on the upper surface (planar portion). ) Is approximately 15 mm to 20 mm, and the length (width dimension) in the left and right direction is 150 to 210 mm. It is formed in a row. Such a steel floor board 1 is mainly used as a floor material on a floor of a factory or a warehouse, as a passage plate on a building roof, as a floor material mounted on a beam 2 as illustrated in FIG. 1, or as a wall board or a fence board. In addition, it is already well known that it is preferably used.

Japanese Patent Laid-Open No. 8-21025

  The floorboard structure disclosed in Patent Document 1 has a U-shaped leg portion with an inward cross section so that the steel floorboard can be installed with a simple connection operation in the width direction and the longitudinal direction of the floorboard. Further, the present invention is characterized in that a joint member receiving portion having an L-shaped section is provided.

Since the steel floor board 1 is provided with the slits 1c in a regular arrangement as illustrated in FIG. 1, when this is used as a flooring, the weight that can be transported manually (for example, 6.5 kg per one) Since it is manufactured to a length (for example, about 1.5 m) and is easy to install, it is widely used not only on the floor but also in various areas such as wall boards, fence boards, and passage boards.
On the other hand, in order to clearly show the appearance of the steel floor board, design study of the upper surface opening ratio (slit opening ratio) of the steel floor board has not been performed.

For this reason, it is required to reduce the worker load by reducing the number of installed steel floorboards per total area, and while being wider than the width B of the conventional product, the weight is equal to or less than that of the conventional product. Some steel floorboards are required.
Moreover, when the width dimension B of the steel floor board is widened, it is a natural idea to keep the vertical width a of the slit wide according to the enlargement ratio in order to maintain the design aesthetics (the appearance is clean). However, for those who walk on the floors and walkways constructed with this steel floorboard, the lower the through the slit, the higher the installation height of the steel floorboard, the more often you feel fear when looking down. Get higher.

Therefore, the subject of this invention is the conditions which make the width dimension B of a steel floor board larger than a conventional product, and comprise the upper surface opening ratio P larger than a conventional product, and improve the design aesthetics (the cleanliness of an external appearance). An object of the present invention is to provide a steel floor board that is lighter than conventional products while maintaining the above.
Moreover, in addition to said subject, it is providing the steel floor board which does not hold fear when it looks down on the person who walks on a passage.

As means for achieving the above object, the steel floor board 1 according to the invention described in claim 1 relates to the dimensional specifications of each part of the steel floor board in which slits 1b having the same shape and the same size and the same pitch are formed on the upper surface. When the upper surface opening ratio is P, the vertical width of the slit is a, the horizontal width of the slit is d, and the vertical width of the horizontal rail 1c between adjacent slits is b, the conditions of the following equations (A) to (C) It is the structure which satisfy | filled.
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.017 (C)

The steel floor board 1 according to the invention described in claim 2 relates to the dimensional specification of each part of the steel floor board in which slits 1b having the same shape and the same size are formed on the upper surface. When the width is a, the horizontal width of the slit is d, and the vertical width of the horizontal rail 1c between adjacent slits is b, the following conditions (a), (b) and (d) are satisfied. It is characterized by.
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.001 (D)

  The steel floor board 1 according to the invention described in claim 3 is the steel floor board 1 according to the invention described in claim 1 or 2, wherein the left-right width dimension B is 300 mm or more and the plate thickness t is 1.4 mm. It is characterized by the following configuration.

The effects of the present invention will be described as follows based on the above-mentioned formulas (i) to (c) and (d), which are constituent elements of each invention.
“Explanation of P ≧ 0.426 in Formula (A)”
The meaning specified by the formula of P ≧ 0.426 defined for the upper surface opening ratio P in the above equation (A) is based on the premise that the upper limit of the upper surface opening ratio P of the conventional steel floorboard is 0.411. This is because the invention is based on the idea of realizing a configuration with an aperture ratio P that is larger than the numerical value, and the design aesthetics (the cleanliness of the appearance) increase as the upper surface aperture ratio P of the steel floor plate increases.
Therefore, the above formula (A) is a measure of the effect of improving the design aesthetics (clean appearance) of the steel floor board.

“Explanation of (a / d) ≦ 0.145 in the above equation (b)”
The above expression (b) defines the ratio between the vertical width a of the slit 1b (see FIG. 3) of the steel floor board and the horizontal width d in the left-right direction, and (a / d) is larger than 0.145. If the vertical width a of the slit becomes too large and exceeds the outer diameter (thickness) of the grip of the tool such as a screwdriver used during construction, and if the tool such as a screwdriver is accidentally dropped, the steel floor board There is a risk of falling through the slits.
For this reason, the outer diameter dimension (thickness) of the grip of a tool such as a screwdriver is set in consideration of a dimension that prevents the tool from falling. Furthermore, if the vertical width a of the slit becomes too large, the pedestrian feels fear when looking down.

“Explanation of (a / d) <0.077 × (a / b) +0.017” in Equation (c) above
The ratio (a / b) between the vertical width a of the slit and the vertical width b (see FIG. 2) of the horizontal rail 1c (see FIG. 3) between adjacent slits, and the slit 1b (FIG. 1). The meaning of the formula (c) defined with respect to the ratio a / d of the vertical width a of the reference) and the horizontal width d of the slit is (a / d) and (a / b) of the steel floor board. The ratio b / d represents the ratio between the width and the length of the horizontal beam 1c, so that the smaller this ratio (that is, the larger the right side of the formula (C)), the more the horizontal beam 1c is compared with the slit shape. It becomes elongate and it turns out that the design aesthetics (cleanness of an external appearance) of the steel floor board 1 increase. Incidentally, if it is outside the condition of the formula (c), as illustrated in the conventional examples No. 1 to No. 3 shown in FIG. Therefore, it can be recognized that the design aesthetics (the cleanliness of the appearance) of the conventional steel floorboard is this level.

On the other hand, in the range satisfying the conditions specified as described above, as illustrated in Nos. 2, 9, and 10 of the embodiment of the present invention shown in FIG. 3A, the cross beam 1c is considerably elongated as compared with the slit shape. It can be seen that the design aesthetics (the cleanliness of the appearance) of the steel floorboard is increasing.
Therefore, the above formula (C) is a condition for improving the design aesthetics (the cleanliness of the appearance) of the steel floor board.

[Explanation of Significance of (a / d) <0.077 × (a / b) +0.001 in Formula (d) above]
In the above formula (d), the ratio of the vertical width a of the slit to the vertical width b of the horizontal rail 1c between adjacent slits, and the ratio of the vertical width a of the slit to the horizontal length d of the slit 1b The meaning specified by the formula of the defined (a / d) <0.077 × (a / b) +0.001 is a more preferable condition of the formula (c).
That is, since b / d, which is the ratio of (a / d) to (a / b) of the steel floor plate, represents the ratio of the width b of the cross rail 1c and the horizontal width d of the slit 1b, this ratio is small. As described above (that is, as the right side of the formula (D) becomes larger), the crosspiece 1c becomes elongated as compared with the refreshing shape, and the design aesthetics (the cleanliness of the appearance) of the steel floor board 1 increases. As described in the above. In the range satisfying the condition specified by the above formula (D), as shown in Example Nos. 2, 5, and 7 of the present invention shown in FIG. 3A, the cross beam 1c between the slit shape and the adjacent slits. It can be seen that the balance of the vertical width b of the steel plate is good, and the design aesthetic appearance (cleanness of the overview) of the steel floor board 1 is further increased.
Therefore, the above formula (d) is a condition for improving the design aesthetics (the cleanliness of the appearance) of the steel floor board 1.

Moreover, the weight of the steel floor slab configured to satisfy the conditions of the above formulas (A), (B) and (C) can be reduced more than the weight of the conventional steel slab.
Furthermore, the weight of the steel floor slab configured to satisfy the conditions of the above formulas (A), (B), and (D) can be reduced more than the weight of the subordinate steel slab.

  In addition, the meaning of specifying the width dimension B at 300 mm or more is a configuration that can reduce the number of installed steel floor boards than before, and the meaning of specifying the sheet thickness t at 1.4 mm or less is the weight of the steel floor boards. This is a configuration that can be reduced compared to the prior art.

It is the perspective view which showed a part of usage example of a steel floor board. It is the top view which illustrated the dimension specification of the steel floor boards. Group A shows a part of each plan view of Examples No. 2, No. 5, No. 7, No. 9, and No. 10 of the present invention shown in the table of FIG. A part of plan views of conventional examples No. 1 to No. 3 of steel floorboards in the table shown in FIG. It is the table | surface which showed each dimension and the result of calculation of steel floor boards No.1-No.3 of a prior art example, and steel floor boards No.1-No.10 which are the Examples of this invention. FIG. 5 is a diagram for explaining the conditions of FEM analysis of a steel floor plate in which the shoulder displacement amount δ shown in FIG. 4 is calculated, in which FIG. A is a schematic explanatory diagram of the analysis conditions, and FIG. B is a symmetrical portion indicated by a dotted line in FIG. An analysis model diagram in which a quarter part of the whole is modeled using conditions, and FIG. C is an explanatory diagram of a calculation position of a shoulder displacement amount δ. Fig. A is a plan view showing the dimensions of each part of the steel floorboard, Fig. B is a sectional view taken along the line bb indicated in Fig. A, Fig. C is a sectional view taken along the line cc, and Fig. D is d. -D line arrow sectional drawing is shown. The conventional examples No. 1 to No. 1 shown in FIG. 4 are shown with the aspect ratio a / d of the slit of the steel floor board as the vertical axis and the ratio a / b of the vertical width of the slit to the vertical width of the horizontal rail as the horizontal axis. 3 is a chart showing analysis results for No. 3 and Examples No. 1 to No. 10 of the present invention. It is a graph which shows the analysis result which made the vertical axis | shaft the shoulder part displacement amount (delta) of the center part cross section shown to FIG. It is a top view explaining the calculation method of the upper surface opening ratio P of a steel floor board. It is the graph which showed the analysis result by making the ratio of shoulder part displacement amount (delta) of the center part cross section of steel floor boards, and the upper surface opening ratio P into a vertical axis | shaft, and making weight ratio W / W0 with comparative example No. 1 into a horizontal axis. .

The steel floor board 1 according to the first aspect of the present invention relates to the dimensional specifications of each part of the steel floor board in which slits 1b having the same shape and the same size are formed on the upper surface. When the width is a, the horizontal width of the slit is d, and the vertical width of the horizontal rail 1c between adjacent slits is b, the configuration satisfies the following formulas (A) to (C). To do.
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.017 (C)

The steel floor board 1 according to the invention described in claim 2 relates to the dimensional specification of each part of the steel floor board in which slits 1b having the same shape and the same size are formed on the upper surface. When the width is a, the horizontal width of the slit is d, and the vertical width of the horizontal rail 1c between adjacent slits is b, the following conditions (a), (b) and (d) are satisfied. It is characterized by.
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.001 (D)

  The invention described in claim 3 is the steel floor board 1 according to the invention described in claim 1 or 2, wherein the upper surface width dimension B is 300 mm or more and the plate thickness t is 1.4 mm or less. It is characterized by that.

Examples of the present invention will be described below.
In FIG. 1 and FIG. 5A, slits 1b having the same shape and the same pitch are formed alternately with the horizontal beam 1c, and a vertical beam (shoulder) 1a having an inward U-shape is formed on both sides. The Example of the steel floorboard 1 is shown.
The example of the dimension of each part of this steel floor board 1 was shown in FIG. 2 and FIG. That is, the vertical width of the slit 1b is a, the vertical width b of the horizontal beam 1c between adjacent slits, the horizontal width of the vertical beam 1a is c (see FIG. 2), the horizontal length of the slit is d (see FIG. 2), and the vertical beam 1a. 5H (see FIG. 6B), steel sheet thickness t, width dimension as B (see FIG. 2), and length as L (FIG. 5). Table 4 shows the values obtained by FEM analysis of the shoulder displacement δ of the cross section at the center of the steel floor board 1 generated when the vertical load F (981N) is loaded.

As shown in FIG. 5 for the analysis conditions of the FEM analysis, the length L is 1400 mm, the bottom width e (FIG. 6C) of the leg portion (vertical beam) 1a is 25 mm, and the height H of the same is 40 mm (FIG. 6B). The other specifications are the steel floor plate set under the conditions shown in the table of FIG. 4, supporting both ends in the longitudinal direction as shown in FIG. 5A, and the vertical load F = 981N applied to the center of the steel floor plate. It is assumed that it will be loaded.
Since this shape is symmetrical in both the length and width directions, as shown in FIG. 5B, a quarter of the assumed shape is modeled with a shell element using a symmetrical boundary condition, and the vertical load The vertical load is 245.25N, which is 1/4 of F = 981N.
In this analysis model, elastic analysis was performed with a Young's modulus of 205000 N / mm 2 and a Poisson's ratio of 0.3.
The width of the conventional example is 200 mm or 250 mm, and the plate thickness is 1.6 mm. On the other hand, the width dimension of the Example of this invention is 300 mm, and plate | board thickness is 1.4 mm.

  FIG. 7 shows the calculation results on the coordinates where the vertical / horizontal ratio of the slit of the steel floor board is the vertical axis and the ratio of the vertical width of the slit to the vertical width of the horizontal rail is the horizontal axis. The circles shown in FIG. 7 indicate examples of the steel floor board according to the present invention, and the numbers added to the circles are the numbers of the examples of the present invention described in the table of FIG. The same X mark shown in FIG. 7 indicates a comparative example, and the number added to the X mark indicates the number of the comparative example described in the table of FIG.

  According to the chart of FIG. 7, the straight line (broken line) connecting the ◯ mark 9 and the ◯ mark 10 which are steel floor boards according to the present invention is a / d = 0.077 × (a / b) +0. In the case of a region (condition) satisfying (a / d)> 0.077 × (a / b) +0.017, a slit shape such as x mark 1 to x mark 3 (in FIG. 3B) Comparative Example No. 1 to No. 3), and the horizontal beam 1c is not so narrow as compared with the slit shape (the vertical width of the slit and the vertical width of the horizontal beam are the same). It is judged that the design aesthetics (the cleanliness of the appearance) of is not improved.

  On the other hand, in the case of a region satisfying the expression of a / d ≦ 0.077 × (a / b) +0.017, the slit shapes shown in the circles 2, 9 and 10 in FIG. In the case of Example No.2, No.9, No.10), the crosspiece 1c is elongated in comparison with the slit shape, and the design aesthetics (cleanness of appearance) of the steel floorboard is improved. Will be understood.

  Further, in FIG. 7, the straight line connecting the circles 5 and 7 which are the products of the present invention is represented by the equation a / d = 0.077 × (a / b) +0.001, and a / In the case of a region satisfying the expression d ≦ 0.077 × (a / b) +0.001, the slit shapes shown in the circles 2, 5, and 7 in FIG. 7 (Example No. 3 in FIG. 3A). 2, No. 5 and No. 7), the crosspiece 1c is elongated compared to the shape of the slit 1b, and the design aesthetics (the cleanliness of the appearance) of the steel floor board is further improved. Will be understood.

  Moreover, although the area | region (condition) which satisfy | fills a / d <= 0.145 is made into the indispensable structural requirement of this invention, this is because the slit of a steel floor board appears large, so that the a / d value is large, and it looks There is an effect to feel openness. On the other hand, when the a / d value is larger than 0.145, the vertical width a of the slit becomes too large, and is wider than the outer diameter (thickness) of the grip of a tool such as a screwdriver during construction. Therefore, if the tool is dropped carelessly, it will pass through the slits in the steel floor board, which may cause an accident. Therefore, in order to prevent the accident of dropping of tools such as a screwdriver, an upper limit is set in consideration of a narrow slit width rather than the outer diameter of the grip portion of a tool such as a screwdriver. Furthermore, if the width of the slit becomes too large, when the pedestrian looks down, he / she feels fear, so the upper limit is set in consideration of the limit.

  For example, the vertical width a = 35 mm of the slit is set to be smaller than the outer diameter (thickness) of the grip of a tool such as a driver at the time of construction so as to prevent the tool from dropping. In addition, if the vertical width a of the slit is larger than 35 mm, the pedestrian feels a sense of fear when looking down. Therefore, considering the limitation, 240 mm (the minimum value of the horizontal width d of the slit of the present invention) In the case of FIG. 4), a / d ≦ 0.145 is set as the technical scope of the present invention in order to set the vertical width d of the slit to 35 mm or less.

  Next, in FIG. 8, the vertical axis is the shoulder displacement amount δ (see FIG. 5C) of the central portion in the longitudinal direction when the vertical load 981N is loaded on the central portion of the steel floor board, and the upper surface opening ratio P is set as follows. The calculation results on the horizontal axis are shown. The circles described in FIG. 8 are the numbers of the examples of the steel floor board according to the present invention. Similarly, the x mark shown in FIG. 8 indicates a comparative example, and the numbers appended to the x mark are the numbers of the comparative examples described in the table of FIG.

  In addition, as shown in FIG. 9, calculation of the upper surface opening ratio P of a steel floor board is defined as the area of the opening in one module (Aw) / 1 horizontal projection area product of one module (Aa). The area (Aw) of the opening in one module is obtained as (d−a) × a + (a × 0.5) 2 × π using the symbols shown in FIG. The horizontal projection area (Aa) of one module is defined as B × (a + b).

According to FIG. 8, the upper surface opening ratio P of ○ mark 1 showing the steel floor board of the embodiment of the present invention is 0.426. On the other hand, the upper surface opening ratio P of x mark 1 which shows the conventional steel floor board is 0.411.
In the present invention, the upper surface opening ratio P is configured to be as large as possible, so that the appearance of the steel floor board is refreshed and the design aesthetics (the cleanliness of the external appearance) of the steel floor board is improved.
Therefore, the above formula (A): P ≧ 0.426 is an essential matter of the present invention.

FIG. 8 shows that the limit value of the shoulder displacement amount δ at the center portion in the longitudinal direction of the steel floor plate generated in the loaded state shown in FIG. 5A is δ <4.67 mm.
When this is constructed with a steel floorboard, if the amount of deflection of the steel floorboard when walking on the floor (the amount corresponding to the shoulder displacement amount δ in the present application) exceeds the limit value, the passerby feels a sense of fear. Means that. For example, according to “Chapter 10 Deflection” of the Steel Structure Design Standard (3rd edition of 2002), in order not to let a passerby feel fear, the steel floorboard span L should be kept at 1/300 or less. Appropriate. For this reason, the design criteria for the amount of deflection caused by the weight of the person or object on the floor board are examined.

  For the purpose of improving the design aesthetics of the floor (cleanness of the appearance) and reducing the weight of the steel floorboard with a steel floorboard, the amount of deflection of the floorboard during walking is reduced if the upper surface area ratio P is designed as large as possible. It means that it becomes a problem. Therefore, if the upper surface opening ratio P is designed and constructed as small as possible for the purpose of limiting the amount of bending of the floor board during walking, there arises a problem that the design aesthetics (the cleanliness of the appearance) of the steel floor board is impaired. Therefore, it is not appropriate to adopt an easy solution that simply considers only the condition of the upper surface opening ratio P.

  Therefore, it is confirmed whether the steel floor board according to the present invention satisfies the limit value for setting the shoulder displacement amount δ at the center part in the longitudinal direction of the steel floor board generated in the loaded state shown in FIG. 5 to L / 300 or less. . Therefore, a more preferable implementation condition of the present invention may satisfy the limit value of the shoulder displacement amount δ, but is not particularly limited thereto.

Next, FIG. 10 shows the ratio of the shoulder displacement amount δ (see FIG. 5) at the center of the span of the steel floor board to the upper surface opening ratio P on the vertical axis, and the weight ratio W / with the comparative example No. 1 The calculation results with W0 on the horizontal axis are shown.
The circles shown in FIG. 10 indicate examples of the steel floor board according to the present invention, and the numbers added to the circles are the numbers of the examples of the present invention described in the table of FIG. The X mark shown in FIG. 10 indicates a comparative example, and the numbers added to the X mark are the numbers of the comparative examples described in the table of FIG. In FIG. 10, the x mark 1 is a comparison object as an example of a conventional steel floor board, and the symbol W 0 indicates the weight of the x mark 1.

  Note that the unit weight of the x mark 2 is heavier than that of the x mark 1. Moreover, the cross mark 3 has an extremely narrow width B compared to the product of the present invention. Therefore, in order to compare whether the weight can be reduced as compared with the conventional steel floorboard, the x mark 1 is judged to be appropriate, and the weight ratio W / W0 is adopted as an indicator of weight reduction.

According to FIG. 10, the value of the weight ratio W / W0 is less than 1 for all the circles that are steel floor boards according to the present invention. This means that it is lighter than conventional steel floorboards.
Therefore, in the steel floor board that satisfies the conditions specified by the above formulas (i), (b), (c), or the conditions specified by the above formulas (a), (b), (d), the horizontal beam 1c is elongated compared to the slit shape. The design aesthetics (cleanness of appearance) of the steel floor board are improved from the conventional products, and the weight of the steel floor board is lighter than the conventional steel floor board weight.

In addition, according to the table of FIG. 4, the width dimension B of the steel floor board is made larger than that of the conventional product, and the upper surface opening ratio P is made larger than that of the conventional product, while maintaining the design aesthetics (the clean appearance). In order to provide a steel floor plate that is lighter than conventional products, it is apparent that the width B is preferably 300 mm to 350 mm and the plate thickness t is 1.4 mm to 1.2 mm.
In addition, the applicable range of the steel floorboard according to the present invention is such that the width B of the steel floorboard is 150 mm to 350 mm, and the length L is 1000 mm to 4000 mm. Conceivable.

  Although the present invention has been described above based on the embodiments, the technical idea of the present invention is not limited to the above. I would like to remind you that it extends to the range of design changes and application modifications that are made by those skilled in the art as needed.

1 Steel floor board 1b Slit P Opening ratio d Horizontal width of slit 1c Horizontal beam a Vertical length of slit b Vertical width of horizontal beam

Claims (3)

Regarding the dimensional specification of each part of the steel floor plate with slits of the same size and the same pitch on the upper surface, the opening ratio of the upper surface is P, the vertical width of the slit is a, the horizontal length of the slit is d, the adjacent slit A steel floor board characterized by having a configuration satisfying the following formulas (A) to (C) when the vertical width of the horizontal rail is b:
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.017 (C) Regarding the dimensional specification of each part of the steel floor plate with slits of the same size and the same pitch on the upper surface, the opening ratio of the upper surface is P, the vertical width of the slit is a, the horizontal length of the slit is d, the adjacent slit A steel floor board characterized by having a configuration that satisfies the following formulas (A), (B), and (D) when the vertical width of the horizontal rail is b:
P ≧ 0.426 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (I)
(A / d) ≤ 0.145 (b)
(A / d) <0.077 × (a / b) +0.001 (D)   3. The steel floor board according to claim 1, wherein the steel floor board is configured to satisfy a width dimension B of 300 mm or more and a thickness t of 1.4 mm or less on the upper surface of the steel floor board.

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