Method of designing beam floor structure and beam floor structure

Abstract

To provide a design method of a beam floor structure capable of bearing bending moment when shear buckling occurs in a compression area of a web.SOLUTION: This design method of the beam floor structure is a design method of the beam floor structure having a steel frame H-shaped cross-sectional member 10 having an upper flange 11, a lower flange 12 and a web 13, and a floor slab 20 integrated with the H-shaped cross-sectional member 10 via a connecting member 23 arranged in the upper flange 11, and is set so as to satisfy a mathematical expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a beam-floor structure design method and a beam-floor structure. [Background technology]

[0002] Previously, studies have focused on the change in performance of H-shaped cross-section members (H-shaped steel) due to their restraint by floor slabs. For example, Patent Documents 1 to 4 provide rolled H-section members and composite beams that are expected to have the effect of restraining the lateral movement of floor slabs, while ensuring structural performance (bending strength and bending rigidity) equivalent to or greater than that of JIS sections, and achieving weight reduction. Moreover, Patent Document 5 aims to optimize the ratio of torsional rigidity between the floor slab and the beam while suppressing lateral buckling of the beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-153125 [Patent Document 2] Japanese Patent Application Publication No. 2020-153126 [Patent Document 3] Japanese Patent Publication No. 2020-153127 [Patent Document 4] Japanese Patent Application Publication No. 2020-153128 [Patent Document 5] Japanese Patent Application Publication No. 2018-154996 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Documents 1 to 5 do not mention the buckling performance of H-shaped cross-section members, nor do they specify the conditions, such as dimensions, that floor slabs must meet. Even in the event of buckling in such an H-section member, it is desirable for the web to be able to withstand the bending moment.

[0005] The present invention has been made in consideration of these problems, and aims to provide a design method and beam-floor structure that can withstand bending moments when shear buckling occurs in the compression area of ​​the web. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention proposes the following means. (1) Aspect 1 of the present invention is a method for designing a beam-floor structure comprising a steel H-shaped cross-section member having an upper flange, a lower flange, and a web, and a floor slab integrated with the H-shaped cross-section member via a connecting member installed on the upper flange, the method being set to satisfy equation (1). However, t w is the thickness of the web, E is the Young's modulus of the H-section member, F is the design standard strength of the H-section member, d' is the height of the part of the web where the compressive force acts, and d is the inside height of the H-section member.

[0007]

number

[0008] In this invention, the upper flange of the H-section member is integrated with the floor slab by a connecting member, and furthermore, the height d' of the portion of the web where the compressive force acts, i.e., the compression area of ​​the web, is less than half the internal height d of the H-section member. Therefore, even if equation (1) is satisfied and the web is outside the width-thickness ratio specified in the steel structure allowable stress design standards, if shear buckling occurs in the compression area of ​​the web, the bending moment can be borne by the tension part of the H-section member, the upper flange, and the compression part of the floor slab.

[0009] (2) Aspect 2 of the present invention may be a method for designing a beam-floor structure according to (1), in which the formula (2) is satisfied. however, s d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, Bc is the effective width of the floor slab, t c is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t f are the thicknesses of the upper flange and the lower flange, respectively.

[0010]

number

[0011] In this invention, by satisfying formula (2), the neutral axis of the H-section member and floor slab as a whole moves toward the floor slab from the central axis of the H-section member, preventing shear buckling in the web. Therefore, for example, an H-section member with a relatively thin web can be effectively used in a beam-floor structure, reducing the mass of the H-section member while ensuring the required bending rigidity and bending strength of the beam-floor structure.

[0012] (3) A third aspect of the present invention may be a method for designing a beam-floor structure according to (1) or (2), which is set so as to satisfy formula (3). however, s d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B c is the effective width of the floor slab, t c is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t f are the thicknesses of the upper flange and the lower flange, respectively.

[0013]

number

[0014] In this invention, by satisfying formula (3), the neutral axis of the H-section member and floor slab as a whole moves toward the floor slab from the central axis of the H-section member, preventing shear buckling and local buckling due to compression in the web. Therefore, for example, H-section members with relatively thin webs can be effectively used in beam-floor structures, reducing the mass of the H-section member while ensuring the required bending rigidity and bending strength of the beam-floor structure.

[0015] (4) A fourth aspect of the present invention may be a method for designing a beam-floor structure according to any one of (1) to (3), which is set so as to satisfy formula (4). however, s d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B c is the effective width of the floor slab, t c is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t f are the thicknesses of the upper flange and the lower flange, respectively.

[0016]

number

[0017] In this invention, by setting the formula (4) to be satisfied, the neutral axis of the H-shaped cross-section member and the floor slab as a whole can be more effectively prevented from moving into the upper flange or the floor slab, which would cause shear buckling and local buckling due to compression in the web.

[0018] (5) Aspect 5 of the present invention is a beam-floor structure comprising a steel H-shaped cross-section member having an upper flange, a lower flange, and a web, and a floor slab integrated with the H-shaped cross-section member via a connecting member installed on the upper flange, and configured to satisfy equation (5). however, s d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B cis the effective width of the floor slab, t c is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t w is the thickness of the web, E is the Young's modulus of the H-section member, F is the design strength of the H-section member, t f are the thicknesses of the upper flange and the lower flange, respectively.

[0019]

number

[0020] In this invention, by satisfying formula (5), the neutral axis of the H-section member and floor slab as a whole moves toward the floor slab from the central axis of the H-section member, preventing shear buckling and local buckling due to compression in the web. Therefore, for example, H-section members with relatively thin webs can be effectively used in beam-floor structures, reducing the mass of the H-section member while ensuring the required bending rigidity and bending strength of the beam-floor structure. [Effects of the Invention]

[0021] The beam-floor structure design method and beam-floor structure of the present invention can withstand bending moments when shear buckling occurs in the compression region of the web. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1A is a cross-sectional view of a beam-floor structure according to a first embodiment of the present invention, and FIG. 1B is a diagram illustrating the distribution of acting stresses, etc.; [Figure 2] FIG. 10A is a cross-sectional view of a beam-floor structure according to a second embodiment of the present invention, and FIG. 10B is a diagram illustrating the distribution of acting stresses, etc.; [Figure 3] FIG. 10 is a diagram showing practically preferable ranges of cross-sectional area ratio and outer height. [Figure 4] FIG. 10 is a diagram showing the relationship between bending strength ratio and moment of inertia. DETAILED DESCRIPTION OF THE INVENTION

[0023] (First embodiment) A first embodiment of a beam-floor structure and a design method for a beam-floor structure according to the present invention (hereinafter simply referred to as a design method) will be described below with reference to FIG.

[0024] [1.1. Beam-floor structure configuration]

[0025] As shown in FIG. 1(A), the beam-floor structure 1 of this embodiment includes an H-shaped cross-section member 10 and a floor slab 20. The H-section member 10 is a steel beam. For example, the H-section member 10 extends along a horizontal plane. The H-section member 10 has an upper flange 11, a lower flange 12, and a web 13.

[0026] The upper flange 11, the lower flange 12, and the web 13 are each formed in a flat plate shape. The upper flange 11 and the lower flange 12 are arranged to face each other in the vertical direction. The upper flange 11 is arranged higher than the lower flange 12. The web 13 is disposed between the upper flange 11 and the lower flange 12. The web 13 is joined to the middle portion of the upper flange 11 in the width direction and the middle portion of the lower flange 12 in the width direction. The thickness of the upper flange 11 and the thickness of the lower flange 12 may be different from each other or may be the same as each other. The width of the upper flange 11 and the width of the lower flange 12 may be different from each other or may be the same as each other. The H-shaped section member 10 may be an H-shaped steel, etc. The H-shaped section member 10 may be a welded H-shaped steel or a rolled H-shaped steel.

[0027] For example, the floor slab 20 is a concrete slab. The floor slab 20 includes concrete 21 and reinforcing bars (not shown). The concrete 21 is formed in a flat plate shape and is arranged such that the thickness direction of the concrete 21 is along the vertical direction. The reinforcing bars include a plurality of first reinforcing bars and a plurality of second reinforcing bars. The plurality of first reinforcing bars are arranged along the upper surface of the concrete 21. The plurality of second reinforcing bars are arranged along the upper surface of the concrete 21 and perpendicular to the plurality of first reinforcing bars when viewed in the vertical direction. The floor slab 20 does not need to have reinforcing bars.

[0028] The floor slab 20 is integrated with the H-section member 10 via a connecting member 23 installed on the upper flange 11 of the H-section member 10. For example, a headed stud is used as the connecting member 23. Note that the connecting member is not limited to a headed stud. The H-shaped section member 10 supports the floor slab 20 from below the floor slab 20 . The floor slab may be a composite deck slab having a deck plate and concrete placed on the deck plate. The beam-floor structure 1 is used in buildings and the like.

[0029] Here, the specifications of the beam-floor structure 1 are defined as follows. Some of the following dimensions are not shown in the drawings. The thickness of the web 13 is t w The thickness of each of the upper flange 11 and the lower flange 12 is defined as t (mm). f The thickness of the floor slab 20 is defined as t (mm). c The inner height of the H-section member 10 is defined as d (mm). If the external height (beam depth) of the H-shaped cross-section member 10 is defined as H (mm), then (d=H-2×t f ) relationship is satisfied. The cross-sectional area of ​​the H-shaped section member 10 perpendicular to the material axis direction is defined as A (mm 2 The distance from the top surface of the floor slab 20 (concrete 21) to the center of gravity of the H-shaped cross-section member 10 is defined as: s It is specified as d (mm).

[0030] The Young's modulus of the H-shaped cross-section member 10 is E (N / mm 2) is defined as follows. The Young's modulus ratio between the H-shaped cross-sectional member 10 and the concrete 21 of the floor slab 20 is defined as n (-). Here, the Young's modulus ratio n is defined as (E / Young's modulus of the concrete 21). The design standard strength of the H-shaped cross-sectional member 10 is defined as F (N / mm 2 ) is defined as follows. The height of the portion where the compressive force acts on the web 13 is defined as d' (mm). The effective width of the floor slab 20 is defined as B c (mm). Here, the effective width B c is the value defined in Document 1 (see [1.5]).

[0031] For example, the length of the H-shaped cross-sectional member 10 is defined as L, and the distance between two adjacent H-shaped cross-sectional members 10 in the width direction of the H-shaped cross-sectional member 10 is defined as a. At this time, the effective width B c in Document 1 is obtained, for example, by Equation (7-1) or (7-2). (when a < L) B c = (width of the H-shaped cross-sectional member 10) + 2 × (0.5 - 0.3a / L)a ··(7-1) (when L ≤ a) B c = (width of the H-shaped cross-sectional member 10) + 2 × 0.2L ··(7-2)

[0032] Note that for the effective width B c , the effective width (b eff ) defined on page 30 of Document 2 may be used.

[0033] [[1.2. Conditions for the H-shaped cross-sectional member for which the effects of the present embodiment are显著发挥]] As conditions for the H-shaped cross-sectional member 10 for which the effects of the present embodiment are显著发挥, the following examinations were conducted. Due to the thinning of the web 13 and the like in the cross-section of the H-shaped cross-sectional member 10, there is a concern about the occurrence of local buckling. However, after the concrete 21 of the floor slab 20 has hardened, the beam-floor structure 1 can function as a composite beam. Here, local buckling means the buckling in which the plate elements constituting the member are deformed out of plane when a load acts on the member.

[0034] As shown in Figure 1(B), by designing the cross section so that the position of the neutral axis L1 of bending of the H-shaped cross-section member 10 and the floor slab 20 as a whole (L1 is the vertical position of the neutral axis, but for convenience it is shown as the neutral axis L1) is near the upper flange 11, after the concrete 21 hardens, tensile force acts on most of the web 13 and the lower flange 12, making local buckling less likely to occur. In particular, axial contraction is restricted in the web 13, so that shear buckling is less likely to occur. Here, shear buckling means local buckling due to shear. Due to the restraining effect of the floor slab 20, the upper flange 11 does not buckle locally, and lateral buckling does not occur either (see Reference 1). Here, lateral buckling refers to buckling in which the entire member is deformed outward from the structural plane when a load is applied to the member.

[0035] By using high-strength steel for the H-section member 10, the H-section member 10 can be made thinner than when ordinary steel is used for the H-section member 10. The high-strength steel material referred to here is generally steel material for construction that satisfies the formula (11). However, σ u is the tensile strength of the steel (N / mm 2 ) 550≦σ u ≦1000 (11) The ordinary steel referred to here is, for example, steel with a design strength F of 235 to 325 N / mm 2 This means steel materials that:

[0036] In this embodiment, local buckling is less likely to occur in the web 13, so there is no need to consider the ineffective cross section based on the width-thickness ratio restriction described in Reference 3. In other words, even if the H-shaped cross section member 10 has a thin cross section with a thin thickness such as the web 13, it can be designed with the entire cross section being effective. Therefore, the cross section (web width-thickness ratio) that provides an advantageous effect in this embodiment is in a range equal to or greater than the web width-thickness ratio specified in Document 3 as in equation (12).

[0037]

number

[0038] In this embodiment, even if the H-shaped section member 10 has a thin cross section, it can be designed so that the entire cross section is effective, and therefore, by using a high-strength steel material, it is possible to achieve further thinning. Furthermore, even if shear buckling occurs in the compression region of the web 13, the bending moment can be borne by the tension portion of the H-shaped cross-section member 10 and the compression portion of the upper flange 11 and floor slab 20. The tension portion of the H-section member 10 here refers to the region below the neutral axis L1 of the H-section member 10 in Figure 1. The compression portion of the upper flange 11 and the floor slab 20 refers to the entire upper flange 11 and the floor slab 20 in Figure 1.

[0039] The effect of this embodiment is exhibited when the H-section member 10 is subjected to positive bending (compression on the upper flange 11 side). Therefore, it is preferable to apply this to sub-beams, second beams, etc., where both ends of the H-section member 10 in the material axis direction are pin-jointed and positive bending acts over the entire length of the H-section member 10. On the other hand, high-strength steel may have a lower strength retention rate at high temperatures than ordinary steel, so when using high-strength steel, it is advisable to conduct separate studies on fire resistance.

[0040] [1.3. Study of conditions under which local buckling due to shear does not occur in the web of an H-shaped cross-section member] As shown in Figure 1(B), the condition under which at least shear buckling (local buckling due to shear) does not occur in the web 13 is when the width-to-thickness ratio of the width (height) of the web 13 on which the compressive force acts is equal to or less than the width-to-thickness ratio specified for the web plate of a beam based on Literature 3. Note that Figure 1(B) also shows the neutral axis L1 and the center of gravity L2 of the H-section member 10 (L2 is the vertical position of the center of gravity, but for convenience it is shown as the center of gravity L2). In this embodiment, the compression region of the web 13 is treated as a "plate supported at two edges and subjected to pure shear," and the conditions under which local buckling does not occur in this portion are organized. The range of width-thickness ratio of the web 13 in which local buckling does not occur in a plate supported on two edges under pure shear is given by equation (13).

[0041]

number

[0042] The range of height d' of the portion of web 13 where compressive force acts, where local buckling does not occur in the region of web 13 where compressive force acts, is given by equation (14) from equation (13).

[0043]

number

[0044] The range of height d' in [1.2] is given by equation (10) based on equation (14) etc.

[0045]

number

[0046] In the design method according to [1.2], the setting is made to satisfy equation (10).

[0047] As shown in FIG. 1, the distance from the top surface of the floor slab 20 to the neutral axis L1 is defined as x n Then, the distance x that satisfies equation (14) n The range is given by equation (15).

[0048]

number

[0049] According to the document 1, the condition for the dimensions of the H-shaped cross section member 10 and the floor slab 20 that satisfies the formula (15) is the formula (16).

[0050]

number

[0051] In the design method according to [1.3], the setting is made to satisfy equation (16).

[0052] [1.4. Verification of the weight reduction effect of H-shaped cross-section members] An example of a high-strength, thin-walled H-section member that is the subject of this embodiment will be shown below. Here, we take as an example a high-strength thin-walled H-section member with a second moment of area equal to or greater than that of a rolled H-section member (other than a general-purpose product, JIS section) specified in Reference 4, and examine whether local buckling of the web 13 occurs based on equation (16). The cross-sectional shape of the H-section member is given on pages 18 and 19 of Reference 4. The design strength F of high-strength thin-walled H-shaped cross-section members is 780N / mm 2 , Young's modulus is 205000N / mm 2 The Young's modulus ratio was set to 15, following Reference 1.

[0053] The specified width-thickness ratio for the beam web plate given in Reference 3 is 39, calculated from equation (12). In normal structural design, the portion exceeding this specified value is considered an ineffective cross section, taking into account the effects of local buckling. Therefore, the web width-thickness ratio of the high-strength, thin-walled H-shaped cross section member 10 considered in this study is approximately 2 to 4 times the specified value, making more than half of the cross section of the web 13 ineffective. On the other hand, when formula (16) is satisfied, local buckling does not occur, and therefore the entire cross section of the H-shaped section member 10 can be considered effective. Table 1 shows the results of the study when the thickness of the floor slab 20 is 100 mm, 150 mm, and 200 mm, and the effective width is 1500 mm. Table 1 shows the results of the study on shear buckling.

[0054] [Table 1]

[0055] For example, in sample No. 1, an H-shaped steel beam (referred to as the "JIS section to be replaced" in Table 1) with an outer height H of 248 mm, a flange width of 124 mm, a web thickness of 5 mm, and a flange thickness of 8 mm, which is not a general-purpose product as specified in Reference 4, was replaced with an H-shaped cross-section member 10 so that the second moment of area was approximately equal. In the replaced H-shaped cross-section member 10, the outer height (referred to as "cross-section height") H was 350 mm, the width of the flanges 11 and 12 (referred to as "flange width") was 100 mm, the thickness of the web 13 (referred to as "web thickness") was 3 mm, and the thickness of the flanges 11 and 12 (referred to as "flange thickness") was 4.5 mm.

[0056] In this case, the ratio of the second moment of area of ​​the replaced H-section member 10 to the second moment of area of ​​the JIS section was 1.07 (referred to as "ratio of second moment of area to JIS section" in the same document). The ratio of the cross-sectional area perpendicular to the material axis direction of the replaced H-section member 10 to the cross-sectional area perpendicular to the material axis direction of the JIS section was 0.60 (referred to as "cross-sectional area ratio to JIS section" in the same document).

[0057] In addition, in Sample No. 1, the thickness of the floor slab 20 (hereinafter referred to as "slab thickness") t c 100mm, effective width (referred to as "effective slab width") B c was set to 1500 mm. The design strength F of the H-shaped cross-section member 10 is 780N / mm 2 It was decided. The width-thickness ratio of the web 13 (referred to as "web width-thickness ratio") is ((H-2t f ) / t c ) is obtained by the formula:

[0058] For example, in sample No. 1, the position of the neutral axis L1 in the vertical direction (hereinafter referred to as the "neutral axis position") was inside the floor slab 20. The distance from the top surface of the floor slab 20 to the center of gravity of the H-shaped cross-section member 10 (hereinafter referred to as "the distance from the top surface of the slab to the center of gravity of the beam") s d was 275 mm. The value of the right side of (16) (denoted as the upper limit of sd at which buckling does not occur in the web) sd' was 1112 mm. In this case, ( s d≦ s d'), that is, equation (16) is satisfied ("OK" in the "Judgment" column), so it was found that shear buckling did not occur at least in web 13 in sample No. 1.

[0059] Table 1 can be read for Samples No. 2 to 30 in the same way as for Sample No. 1. Since all cross sections except for sample Nos. 28 and 29 shown in Table 1 satisfy equation (16), shear buckling does not occur at least in the web 13, and the entire cross section of the web 13 can be considered effective against shear. Note that if the neutral axis L1 is inside the floor slab 20, the entire cross section can be considered effective regardless of equation (16).

[0060] The high-strength, thin-walled H-section member 10 used in this study has a cross-sectional area that is approximately 30 to 50% smaller than the rolled H-section member specified in Reference 4 that it is intended to replace. Therefore, while maintaining the same moment of inertia, the weight of the H-section member 10 can be reduced by up to approximately 50% by reducing the thickness. In addition, it is possible to design the entire cross section of the web 13 to be effective, maximizing the benefits of high strength.

[0061] [1.5. Literature] Reference 1: Architectural Institute of Japan (General Incorporated Association), "Design Guidelines and Commentary for Various Composite Structures," Maruzen Publishing Co., Ltd., 2023 Document 2: “Eurocode 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings”, 2004, Authority: The European Union Per Regulation 305 / 2011, Directive 98 / 34 / EC, Directive 2004 / 18 / EC Reference 3: "Allowable Stress Design Criteria for Steel Structures," edited by the Architectural Institute of Japan, Maruzen Publishing Co., Ltd., 2019 Reference 4: Japanese Standards Association, "JIS G 3192, Shape, Dimensions, Mass and Tolerances of Hot-Rolled Steel Sections," 2021

[0062] 1.6. Effects of this embodiment As explained above, in the design method of this embodiment, the upper flange 11 of the H-section member 10 is integrated with the floor slab 20 by the connecting member 23, and furthermore, the height d' of the portion of the web 13 where the compressive force acts, i.e., the compression area of ​​the web 13, is less than half the inside height d of the H-section member 10. Therefore, even if the web 13 is outside the range of the width-thickness ratio specified in Document 3, if shear buckling occurs in the compression area of ​​the web 13, the bending moment can be borne by the tension part of the H-section member 10 and the compression parts of the upper flange 11 and floor slab 20.

[0063] Furthermore, in the design method of this embodiment, there are cases where the formula (16) is set to be satisfied. In this case, by setting the formula (16) to be satisfied, the neutral axis L1 of the H-section member 10 and the floor slab 20 as a whole moves toward the floor slab 20 from the central axis of the H-section member 10, thereby preventing shear buckling from occurring in the web 13. Therefore, for example, an H-section member 10 with a relatively thin web 13 can be effectively used in the beam-floor structure 1, and the mass of the H-section member 10 can be reduced while ensuring the beam-floor structure 1 has a predetermined bending rigidity and bending strength.

[0064] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. 2. The same components as those in the above embodiment are designated by the same reference numerals, and a description thereof will be omitted. Only the differences will be described.

[0065] [2.1. External force conditions to be considered] In this embodiment, a case where a compressive force acts on the web 13 of the H-shaped cross-section member 10 as shown in FIG. 2(A) will be considered.

[0066] [2.2. Study of conditions under which local buckling due to compression does not occur in the web of an H-shaped cross-section member] The condition under which local buckling does not occur in the web 13 (it can be designed so that the entire cross section is effective) is when the width-to-thickness ratio of the width (height) of the web 13 on which the compressive force acts is less than the specified width-to-thickness ratio value based on Reference 3. In this embodiment, the compression region of the web 13 is treated as a "plate supported at two edges and subjected to pure compression" as shown in FIG. 2(B), and the conditions under which local buckling does not occur in this portion are organized. Here, the shape of the stress distribution (stress block) in the compressed area of ​​the web 13 is triangular, but in this embodiment, a safe evaluation was made by replacing the shape of the stress distribution with a square as a condition for receiving uniform compressive force. The range of width-thickness ratio of the web 13 in which local buckling does not occur in a plate supported on two edges under pure compression is given by equation (26).

[0067]

number

[0068] In this case, the range of height d' of the portion of web 13 where compressive force acts, where local buckling does not occur in the region of web 13 where compressive force acts, is given by equation (27) from equation (26).

[0069]

number

[0070] The distance x that satisfies equation (27) n The range is given by equation (28).

[0071]

number

[0072] According to the document 1, the condition for the dimensions of the H-shaped cross-section member 10 and the floor slab 20 to satisfy the formula (28) is given by the formula (29).

[0073]

number

[0074] Furthermore, if equation (29) is satisfied, equation (16) (the condition for shear buckling not to occur) is also satisfied, so there is no need to consider shear buckling in addition to local compressive buckling. In the design method according to [2.2], the equation (29) is satisfied. The beam-floor structure according to [2.2] is configured to satisfy the equation (29).

[0075] [2.3. Verification of the weight reduction effect of H-shaped cross-section members] The same study as for [1.4] was conducted. The results are shown in Table 2. Table 2 shows the results of the study on local buckling due to compression.

[0076] [Table 2]

[0077] For example, in sample No. 1, as in Table 1, ( s d≦ s d'), i.e., equation (29) is satisfied ("OK" in the "Judgment" column), so it was found that no shear buckling or local buckling due to compression occurred in web 13 of sample No. 1. In Table 2, all samples except for sample Nos. 22, 28, and 29 satisfy equation (29), so shear buckling and local buckling due to compression do not occur in the web 13 of these samples, and the entire cross section of the web 13 can be considered effective. Note that when the neutral axis L1 is inside the floor slab 20, the entire cross section can be considered effective regardless of equation (29). The high-strength, thin-walled H-section member 10 used in this study has a cross-sectional area that is approximately 30 to 50% smaller than the rolled H-section member specified in Reference 4 that it replaces. Therefore, while maintaining the same moment of inertia, the weight of the H-section member 10 can be reduced by up to approximately 50% by reducing the thickness. In addition, it is possible to design the entire cross section of the web 13 to be effective, maximizing the benefits of high strength.

[0078] 2.4. Effects of this embodiment As explained above, in the design method and beam-floor structure 1 of this embodiment, by setting equation (29) to be satisfied, the neutral axis L1 moves toward the floor slab 20 from the central axis of the H-shaped section member 10, preventing shear buckling and local buckling due to compression in the web 13. Therefore, for example, an H-shaped section member 10 with a relatively thin web 13 can be effectively used in the beam-floor structure 1, and the mass of the H-shaped section member 10 can be reduced while ensuring the beam-floor structure 1 has the required bending rigidity and bending strength.

[0079] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. 2. The same components as those in the previous embodiment are designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

[0080] [3.1. External force conditions to be considered] In this embodiment, we consider the case where the entire cross section of the web 13 of the H-shaped section member 10 is in tension. An example of the state of stress acting on the beam-floor structure 1 at this time is shown by the two-dot chain line L5 in Figure 2(B).

[0081] [3.2. Consideration of the conditions under which the entire cross section of the web of an H-shaped section member is in tension] The condition under which local buckling does not occur in the web 13 (it can be designed as fully effective in the entire cross section) is when the web 13 is fully tensile. This is equivalent to the case where the neutral axis L1 is located inside the upper flange 11 or the floor slab 20. At this time, the distance x where the neutral axis L1 is located inside the upper flange 11 or inside the floor slab 20 n The range of is given by equation (40).

[0082]

number

[0083] According to the document 1, the condition for the dimensions of the H-shaped cross-section member 10 and the floor slab 20 that satisfies the formula (40) is given by the formula (41).

[0084]

number

[0085] If formula (41) is satisfied, then both formula (16) (condition for shear buckling not occurring in the web 13) and formula (29) (condition for compressive local buckling not occurring in the web 13) are satisfied. In the design method according to [3.2], the setting is made to satisfy equation (41).

[0086] [3.3. Verification of the weight reduction effect of H-shaped cross-section members] The same study was conducted as for [1.4] and [2.3]. The results of the study are shown in Table 3. Table 3 shows the results of the study when the neutral axis L1 is inside the upper flange 11 or the floor slab 20.

[0087] [Table 3]

[0088] For example, in sample No. 1, as in Table 1, ( s d≦ s d'), i.e., equation (41) is satisfied ("OK" in the "Judgment" column). Therefore, in sample No. 1, no shear buckling or local buckling due to compression occurs in web 13, and the entire cross section of web 13 can be considered effective. Table 3 can be read for Samples No. 2 to 30 in the same way as for Sample No. 1. In addition, in the range that satisfies formula (41), the neutral axis L1 is inside the floor slab 20 in all cross sections except for samples No. 4 and No. 11. In this study, the high-strength, thin-walled H-section member 10 that satisfies equation (41) has a cross-sectional area that is 30 to 45% smaller than the rolled H-section member specified in Reference 4 that it replaces. Therefore, while maintaining the same moment of inertia, the weight of the H-section member 10 can be reduced by up to 45% by reducing the thickness. In addition, it is possible to design the entire cross section of the web 13 to be effective, maximizing the benefits of high strength.

[0089] 3.4. Effects of this embodiment As explained above, in the design method of this embodiment, by setting equation (41) to be satisfied, the neutral axis L1 of the H-shaped cross-section member 10 and the floor slab 20 as a whole can be more effectively prevented from moving into the upper flange 11 or the floor slab 20, which would cause shear buckling and local buckling due to compression in the web 13.

[0090] (supplement) [4.1. Practical Preferred Range] Here, the practically preferable ranges for the beam-floor structure targeted by the present invention are shown. Regarding formula (16), the following study was carried out using the specifications of the H-shaped cross-section member 10 and floor slab 20 shown in Table 4 as an example.

[0091] [Table 4]

[0092] Here, the distance from the top surface of the floor slab 20 to the center of gravity of the H-shaped section member 10 is s d is the outer height H of the H-shaped section member 10 and the thickness t of the floor slab 20 c Using this, it can be expressed as equation (42).

[0093]

number

[0094] In addition, the cross-sectional area ratio of the H-shaped section member 10 to the floor slab 20 is α (= B c ×t c / A)(-). Then, equation (29) can be expressed as equation (43) from equation (42).

[0095]

number

[0096] On the other hand, the range of the exterior height H commonly used for H-shaped cross-section members for architecture is expressed by equation (44). 100≦H≦1200 (44)

[0097] Here, the lower limit of Equation (44) is the minimum dimension of the H-shaped cross-section member specified in Reference 4, and the upper limit of Equation (44) is the maximum dimension of the H-shaped cross-section member for architecture currently in practical use. As a practical range for the cross-sectional area ratio α, the lower limit can be set from equation (43). The upper limit in equation (44) was set from a thin-walled H-section member with a moment of inertia equivalent to the minimum cross section of an H-section member specified in Reference 4. The set results are shown in Table 5.

[0098] [Table 5]

[0099] Note that the fillet portion of the thin-walled H-shaped cross-section member 10 was ignored. The dimensions of the floor slab 20 shown in Table 4 were used to calculate the cross-sectional area ratio α.

[0100] From the above, the practically preferable range in this embodiment can be shown as in FIG. In addition, the thickness of the floor slab 20 is t c is 100mm, effective width B c was estimated at 1500mm. If the dimensions of the floor slab 20 are constant, the larger the cross-sectional area ratio α, the smaller the cross-sectional area of ​​the H-shaped section member 10 and the smaller the mass of the H-shaped section member 10. Therefore, in this embodiment, a more preferable range is a range in which the cross-sectional area ratio α is larger than that in Document 4. In other words, a range in which the mass of the H-section member 10 is smaller than that of the H-section steel specified by JIS is set. Regarding strength, the design standard strength F is 325,780N / mm 2 is illustrated as an example.

[0101] In Figure 3, the design strength F is 780N / mm 2 A preferable range in this case is shown by hatched area R1. Samples No. 4 and 22 shown in Table 2 are plotted in Figure 3. Sample No. 22 has a design strength F of 780 N / mm 2 This case is outside the scope of application of the present invention, but the design standard strength F is 325N / mm 2 If so, it falls within the scope of application. Although the preferred range of the present embodiment is smaller when the design strength F is high, it is advantageous in terms of strength calculation. This point will be described in detail in [4.2].

[0102] [4.2. Benefits of high strength] In this embodiment, the beam-floor structure 1 can be designed without considering the dead zone even for a thin-walled cross section, and therefore, by using high-strength steel, high bearing strength of the H-shaped cross section member 10 can be ensured. Here, we will examine bending strength using strength as a parameter using the samples shown in Tables 1 to 3. The results of the examination are shown in Table 6. Table 6 shows the examination results for bending strength.

[0103] [Table 6]

[0104] Samples Nos. 31 to 62 in Table 6 have approximately the same moment of inertia as the H-section steel specified in Reference 4, but their section modulus is approximately 5 to 31% smaller. On the other hand, by using high-strength steel, the bending strength can be ensured to be equal to or greater than that of Reference 4. Here, the bending strength is the value (Z × F) obtained by multiplying the section modulus by the design strength, and the design strength in Reference 4 is 235 N / mm 2 It was decided.

[0105] Figure 4 shows the bending strength ratio (M y / M y_JIS ) and the moment of inertia. Here, M y_JIS means the bending strength of H-shaped steel as specified in Reference 4. M y means the bending strength of the H-shaped section member 10 having a second moment of area equivalent to that of the H-shaped steel specified in Reference 4. For example, the four symbols (cross, circle, square, and triangle) arranged vertically with the legend "equivalent to JIS248×124" indicate the design strength F of the H-shaped cross-section member 10 as 235, 325, 440, and 780 N / mm 2 This shows the results of the bending strength ratio when the bending strength is changed.

[0106] From Figure 4, the design strength F is 325N / mm 2 If this is the case, the bending strength can be secured at the same level as in Reference 4. In addition, if the design strength F is 440N / mm 2 If this is the case, a higher bending strength than that in Reference 4 can be ensured. As described above, the effect of this embodiment is more pronounced when high-strength steel is used.

[0107] Although the first to third embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to these embodiments, and the present invention also includes modifications, combinations, deletions, etc. of the configurations within the scope of the gist of the present invention. Furthermore, it goes without saying that the configurations shown in each embodiment can be used in appropriate combinations. For example, in the first to third embodiments, the design method does not have to be set to satisfy equation (41), equation (29), or equation (16).

[0108] 1 Beam floor structure 10 H-shaped cross-section member 11 Upper flange 12 Lower flange 13. Web 20 Floor slab 21 Concrete 23 Connecting member

Claims

1. a steel H-shaped cross-section member having an upper flange, a lower flange, and a web; A method for designing a beam-floor structure comprising: a floor slab integrated with the H-shaped cross-section member via a connecting member installed on the upper flange, the method being set to satisfy equation (1). However, t ｗ is the thickness of the web, E is the Young's modulus of the H-section member, F is the design standard strength of the H-section member, d' is the height of the part of the web where the compressive force acts, and d is the inside height of the H-section member. [Equation 1]

2. The method for designing a beam-floor structure according to claim 1, wherein the beam-floor structure is set so as to satisfy equation (2). however, ｓ d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B ｃ is the effective width of the floor slab, t ｃ is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t ｆ are the thicknesses of the upper flange and the lower flange, respectively. [Equation 2]

3. The method for designing a beam-floor structure according to claim 1, wherein the beam-floor structure is set so as to satisfy equation (3). however, ｓ d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B ｃ is the effective width of the floor slab, t ｃ is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t ｆ are the thicknesses of the upper flange and the lower flange, respectively. [Equation 3]

4. The method for designing a beam-floor structure according to claim 1, wherein the beam-floor structure is set so as to satisfy equation (4). however, ｓ d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B ｃ is the effective width of the floor slab, t ｃ is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t ｆ are the thicknesses of the upper flange and the lower flange, respectively. [Equation 4]

5. a steel H-shaped cross-section member having an upper flange, a lower flange, and a web; a floor slab integrated with the H-shaped section member via a connecting member installed on the upper flange, A beam-floor structure configured to satisfy equation (5). however, ｓ d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B ｃ is the effective width of the floor slab, t ｃ is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t ｗ is the thickness of the web, E is the Young's modulus of the H-section member, F is the design strength of the H-section member, t ｆ are the thicknesses of the upper flange and the lower flange, respectively. [Equation 5]

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