Evaluation method for steel beam with concrete floor and steel beam with concrete floor

Abstract

To provide an evaluation method for a steel beam with a concrete floor that can evaluate the lateral buckling of the steel beam with a concrete floor.SOLUTION: In a steel beam with a concrete floor, a bending moment Md generated in a stud 18 is calculated based on a stress Fh in the width direction generated at the joint between a bottom flange 15 and a web 13 due to lateral buckling, and a distance D between a top flange 14 and a bottom flange 15 at the web 13. In addition, a bending strength Mc generated in the stud is calculated using a tensile strength Pa2 per stud 18 determined by the cone-shaped fracture of a concrete floor 12, and distances j1 and j2 from one end of the top flange 14 to the stud in the width direction. The lateral buckling of the steel beam with a concrete floor is then evaluated based on the magnitude relation between the bending moment Md and the bending strength Mc.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating a steel beam with a concrete floor, in which the steel beam is joined to a concrete floor via a stud, and to a steel beam with a concrete floor. [Background technology]

[0002] Conventionally, steel beams with concrete floors have been known, as disclosed in Patent Document 1, for example. The steel beams with concrete floors have a steel beam and a concrete floor. The steel beams are made of H-shaped steel beams with a web, an upper flange, and a lower flange. A plurality of studs are joined to the upper flange of the steel beam. The concrete floor is formed by hardening concrete that is poured so that it is supported by the upper flange and the studs are fixed in place. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-023440 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of steel beams with concrete slabs, even if the steel beams are made stronger and larger in cross section, there are few cases where the concrete slabs are made stronger or thicker. In such cases, the rigidity and strength of the concrete slabs and studs are reduced relative to the steel beams. Therefore, a method for evaluating steel beams with concrete slabs was needed. [Means for solving the problem]

[0005] A method for evaluating a steel beam with a concrete slab that solves the above-mentioned problem involves evaluating a steel beam with a concrete slab, which includes a left column, a right column, a steel beam of a predetermined length joined to the left column and the right column, and a concrete floor installed on the steel beam. The steel beam has an upper flange that joins the concrete floor, a lower flange connected to the upper flange by a web, and headed studs erected on the upper flange and anchored to the concrete floor. The method calculates a bending moment Md in the stud based on a widthwise stress Fh that occurs at the joint between the lower flange and the web due to lateral buckling and the distance D between the upper flange and the lower flange at the web. The method also calculates a bending strength Mc in the stud based on a tensile strength Pa2 per stud determined by cone-shaped fracture of the concrete floor and the distance j1 from one end of the upper flange to the stud in the width direction. The lateral buckling of the steel beam with a concrete slab is evaluated based on the magnitude relationship between the bending moment Md and the bending strength Mc.

[0006] A steel beam with a concrete floor that solves the above problem includes a left column, a right column, a steel beam of a predetermined length joined to the left column and the right column, and a concrete floor installed on the steel beam. The steel beam has an upper flange that joins the concrete floor, a lower flange that connects the upper flange to the web, and headed studs that are erected on the upper flange and anchored to the concrete floor. In the steel beam with a concrete floor, a bending moment Md that occurs in the stud is calculated using a widthwise stress Fh that occurs at the joint between the lower flange and the web due to lateral buckling and the distance D between the upper flange and the lower flange at the web. Furthermore, a bending strength Mc that occurs in the stud is calculated using a tensile strength Pa2 per stud determined by cone-shaped fracture of the concrete floor and the widthwise distance j1 of the stud from one end of the upper flange. The magnitude relationship between the bending moment Md and the bending strength Mc is Mc≧Md.

[0007] With the above configuration, the lateral buckling of a steel beam with a concrete slab can be evaluated based on the magnitude relationship between the bending moment Md and the bending strength Mc. Based on the evaluation results, the stud length can be determined so that the bending strength Mc is greater than the bending moment Md, for example.

[0008] In the above configuration, the stud is a first stud, the upper flange has a headed second stud aligned in the width direction with the first stud, and the bending strength Mc may be calculated further using the distance j2 from one end of the upper flange in the width direction to the second stud.

[0009] According to the above configuration, even if second studs are arranged in a line in the width direction of the steel beam, the lateral buckling of the steel beam with concrete floor can be evaluated based on the magnitude relationship between the bending moment Md and the bending strength Mc.

[0010] In the above configuration, the bending moment Md is obtained by multiplying the flange shaft strength by a coefficient α, and the coefficient α at which the bending moment Md is equal to the bending strength Mc is the stud pull-out strength coefficient αs. Based on the results of an experiment conducted on the steel beam with concrete floor, a relationship between the stud pull-out strength coefficient αs, the lateral buckling slenderness ratio of the steel beam, and the plastic deformation magnification of the steel beam with concrete floor can be derived, and the stud amount can be determined based on said relationship so that the bending strength Mc is equal to or greater than the bending moment Md calculated using the stud pull-out strength coefficient αs that obtains a plastic deformation magnification equal to or greater than a standard value.

[0011] According to the above configuration, the number of studs can be determined so as to obtain a desired plastic deformation ratio for the steel beam with concrete floor. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a steel beam with a concrete floor. [Figure 2]FIG. 2 is a diagram illustrating the resistance mechanism of a stud against lateral buckling. [Figure 3] FIG. 3 is a front view showing a schematic configuration of an example of an experimental device used in the method for evaluating a steel beam with a concrete floor. [Figure 4] FIG. 4 is a top view showing a schematic configuration of an example of an experimental device. [Figure 5] FIG. 5 is a side view showing a schematic configuration of an example of an experimental device. [Figure 6] Figure 6 is a graph showing the relationship between the story drift angle and horizontal force in each test beam. [Figure 7] FIG. 7 is a graph showing the relationship between the beam member angle and the beam end moment for each test beam. [Figure 8] FIG. 8 is a graph showing an example of the relationship between the stud pull-out resistance coefficient and the plastic deformation magnification. [Figure 9] FIG. 9 is a graph showing an example of the relationship between the lateral buckling slenderness ratio and the stud pull-out resistance coefficient. [Figure 10] FIG. 10 is a diagram for explaining how to determine the average positive and negative values ​​of the plasticity ratio θ / θp when the full plastic yield strength decreases. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of a method for evaluating a steel beam with a concrete floor and a steel beam with a concrete floor will be described with reference to FIGS. As shown in FIG. 1, a steel beam 10 with a concrete floor has a steel beam 11 and a concrete floor 12. The steel beam 11 is composed of an H-shaped steel beam having a web 13, an upper flange 14, and a lower flange 15. The steel beam 11 is joined to a left column 16 and a right column 17, and is thereby erected between the left column 16 and the right column 17. A plurality of studs 18 are joined to the upper flange 14 of the steel beam 11 so as to extend upward. Each stud 18 is a headed stud and is fixed to the concrete floor 12. The plurality of studs 18 are arranged at a predetermined stud pitch p in the extension direction of the steel beam 11. The concrete floor 12 is formed by hardening concrete that is poured so as to be supported by the upper flange 14 and to embed the studs 18.

[0014] The inventors conducted a structural experiment on such a steel beam 10 with a concrete slab to investigate the relationship between the number of studs (such as the stud pitch p) when the concrete slab 12 fails in a cone shape and the plastic deformation capacity of the steel beam 11. From the results of the experiment, they discovered a method for evaluating a steel beam with a concrete slab, a method for determining a reasonable number of studs to ensure a desired plastic deformation capacity.

[0015] (Stud resistance mechanism) The resistance mechanism of the studs when a steel beam buckles laterally will be described with reference to Figure 2. Note that here, the resistance mechanism will be described using the case where two studs are arranged in the width direction of the steel beam so as to sandwich the central axis of the steel beam 11 when viewed from above (double).

[0016] As shown in Figure 2, when a steel beam 11 is subjected to a load in its extension direction and undergoes lateral buckling, the stress Fh in the bottom flange 15 in the width direction due to the lateral buckling can be expressed as a coefficient α times the flange axial strength Af·σyf, as follows: Fh=α·Af·σyf It becomes like this. And the bending moment Md generated in the stud 18 based on this stress Fh is Fh×D. Here, Af is the flange cross-sectional area, σyf is the flange yield stress, and D is the beam depth of the steel frame beam 11, which is the distance between the upper flange 14 and the lower flange 15 in the web 13.

[0017] On the other hand, assuming that the stud 18 within the range of 45° from the top of the lateral buckling resists the lateral buckling, the effective range of the stud 18 is 2D. Let Pa2 be the tensile strength per stud determined by the conical failure of the concrete floor 12, j1 and j2 (<j1) be the distances from the right end of the upper flange 14 of each stud 18, and p be the stud pitch. Then, the bending strength Mc of the stud 18 that resists the lateral buckling is Mc=(Pa2×j1+Pa2×j2^2 / j1)×2D / p It becomes like this. j1 is the distance corresponding to the first stud, and j2 is the distance corresponding to the second stud. Pa2 is a value calculated based on "5. Tensile Force Application Case" in "Chapter 5 Prefixed Anchor · Type A Design" of "Japan Society of Civil Engineers Various Composite Structure Design Guidelines · Explanation of the Same 2023.8". More specifically, the tensile strength Pa2 is the allowable tensile force per headed stud when determined by the conical failure of the fixed concrete. In this embodiment, the reduction coefficient used in the calculation of this allowable tensile force is set to 1.

[0018] The coefficient α when Md = Mc is the lateral buckling stress coefficient at the boundary where the concrete floor 12 undergoes conical failure. When this coefficient α is defined as the stud pull-out strength coefficient αs, when the coefficient α is greater than or equal to the stud pull-out strength coefficient αs, Mc≧Md, so the conical failure of the concrete floor 12 is prevented.

[0019] Here, the case where the studs 18 are arranged side by side in the width direction (double) has been described for the resistance mechanism. In the case where the studs 18 are arranged in a single row along the central axis of the steel frame beam 11 in the top view (single), the bending strength Mc can be calculated with j2 = 0.

[0020] (Experimental equipment and methods) The experimental device and method used in the method for evaluating the concrete-floor-equipped steel beam 10 will be described with reference to FIGS.

[0021] As shown in FIG. 3, the experimental apparatus 30 includes a frame 31 and a loading device 32 . The frame 31 is assumed to be a quarter-scale of the actual size, and includes a steel beam 10 with a concrete floor, which is the subject of the experiment, as well as a left column 16 and a right column 17 extending in the vertical direction. Square steel pipes (□-200mm x 16mm) were used for the left column 16 and right column 17. The column span L between the left column 16 and the right column 17 was 6000mm. The column height H of the left column 16 and the right column 17 was 1500mm. The lower end of the left column 16 is connected to the floor 5 via a left column lower end connector 33 (pin). The lower end of the right column 17 is connected to the floor 5 via a right column lower end connector 34 (pin).

[0022] Each column 16, 17 is provided with an upper diaphragm 35, 37 and a lower diaphragm 36, 38. In each column 16, 17, the web 13 of the steel beam 11 is welded to the portion between the upper diaphragm 35, 37 and the lower diaphragm 36, 38. The upper flange 14 of the steel beam 11 is welded to the upper diaphragms 35, 37. The bottom flange 15 of the steel beam 11 is welded to the lower diaphragms 36, 38. The beam interior length Lb was set to 5800 mm.

[0023] The upper end of the left column 16 is connected to the force beam 45 via a left column upper end connector 41 (pin). The upper end of the right column 17 is connected to the force beam 45 via a right column upper end connector 42 (pin). The force beam 45 extends in the extension direction of the steel beam 11. An H-shaped steel (H-beam length 400 mm × flange width 400 mm × web thickness 13 mm × flange thickness 21 mm) was used for the force beam 45. During the experiment, a horizontal load P was applied to the force beam 45 by the loading device 32 along the extension direction of the steel beam 11. Specifically, the loading device 32 repeatedly applied a positive load to the right in FIG. 3 and a load to the left in FIG. 3 to the force beam 45.

[0024] The experimental device 30 is equipped with displacement measuring devices that measure horizontal displacement at various points. The displacement measuring device 51 measures the horizontal displacement D1 of the left column upper end connector 41 at a position 750 mm above the central axis of the steel beam 11 as the horizontal displacement of the left column head. The displacement measuring device 52 measures the horizontal displacement D2 of the left column lower end connector 33 at a position 750 mm below the central axis of the steel beam 11 as the horizontal displacement of the left column base. The displacement measuring device 53 measures the horizontal displacement D3 of the right column upper end connector 42 at a position 750 mm above the central axis of the steel beam 11 as the horizontal displacement of the right column head. The displacement measuring device 54 measures the horizontal displacement D4 of the right column lower end connector 34 at a position 750 mm below the central axis of the steel beam 11 as the horizontal displacement of the right column base.

[0025] Displacement measuring device 55 measures horizontal displacement D5 of the upper diaphragm 35 on the left column 16. Displacement measuring device 56 measures horizontal displacement D6 of the lower diaphragm 36 on the left column 16. Displacement measuring device 57 measures horizontal displacement D7 of the upper diaphragm 37 on the right column 17. Displacement measuring device 58 measures horizontal displacement D8 of the lower diaphragm 38 on the right column 17.

[0026] As shown in FIG. 4 , orthogonal beams 61 are joined to both sides of each column 16, 17 in a horizontal direction perpendicular to the extension direction of the steel beams 11. The orthogonal beams 61 are made of SM490A H-shaped steel (H-350 mm × 110 mm × 9 mm × 12 mm). The orthogonal beams 61 are joined to the joints of the steel beams 11 at each column 16, 17. The concrete floor 12 is installed to cover a rectangular area with the left orthogonal beam 61 and the right orthogonal beam 61 as a pair of opposite sides. The width W of the concrete floor 12 is 1800 mm. The thickness of the concrete floor 12 is 35 mm. Studs 18 (φ6 mm × height 25 mm) joined to the upper flanges of the steel beams 11 and the orthogonal beams 61 are fixed to the concrete floor 12. In the orthogonal beams 61, the studs 18 are installed along the central axis of the orthogonal beams 61 when viewed from above. In addition, a single welded wire mesh 47 (@3.2 mm, 50 mm x 50 mm) is buried in the concrete floor 12.

[0027] As shown in Figure 5, a support column 62 is joined to the tip of each orthogonal beam 61. The support column span in the horizontal orthogonal direction was set to 1600 mm. The support columns 62 were made of STKR400 square steel pipes (□-100 mm x 9 mm). The support columns 62 were fixed to the floor 5 via support column connectors 63.

[0028] The experimental method using the above-mentioned experimental apparatus 30 will now be described. In this experimental method, various test beams were installed as steel beams 11 in the experimental apparatus 30, and then a gradually increasing positive and negative cyclic loading was applied, with the same amplitude repeated twice in the order of R = ±0.005, ±0.010, ±0.015, ±0.020, ±0.030, ±0.040, ±0.050, ..., based on the story deformation angle R of the frame 31. Then, the horizontal load P and the horizontal displacements D1 to D8 of the column head, column base, and diaphragm were measured.

[0029] (Test beam and experimental results) Table 1 shows details of each test beam and an example of the experimental results.

[0030] [Table 1]

[0031] In Table 1, for the cross section of each test beam, D indicates the beam thickness (mm), B indicates the flange width (mm), tw indicates the web thickness (mm), and tf indicates the flange thickness (mm). The notation in [ ] defines the cross-sectional shape of each test beam.

[0032] Test beams Nos. 1, 2, and 3 were made of TMCP385B material with cross section A. Test beam No. 4 was made of SM490A material with cross section B. Test beams Nos. 5 and 6 were made of TMCP385B material with cross section C. Test beams Nos. 7 and 8 were made of TMCP385B material with cross section D.

[0033] The flange generalized width-thickness ratio is a value calculated by B / (2·tf)·√(F / E). The web generalized width-thickness ratio is a value calculated by (D-2·tf) / tw·√(F / E). F is the standard strength of each steel type, and E is the Young's modulus of each steel type. The notation in [] indicates the rank of the beam component type. The beam component type refers to the beam component type shown in the Building Standards Act-related notification "Building Notification No. 1792 of 1980."

[0034] λ is the slenderness ratio calculated using the beam's internal length Lb. λb is the lateral buckling slenderness ratio (=√(Mp / Me)) calculated based on "5.1 Lateral buckling strength of beams" in the "Architectural Institute of Japan, Guidelines for Plastic Design of Steel Structures 2017.2" using the reference strength F, with the buckling length being the beam length. Mp is the full plastic moment, and Me is the elastic lateral buckling moment.

[0035] In terms of stud arrangement, "single" indicates that the studs 18 are arranged in one row along the central axis of the steel beam 11 when viewed from above. "double" indicates that the studs 18 are arranged in two rows on either side of the central axis of the steel beam 11 when viewed from above. "@" indicates the stud pitch p.

[0036] The stud composite ratio is the ratio of the required amount of studs for a fully composite beam, calculated based on the "Architectural Institute of Japan, Various Composite Structure Design Guidelines and Commentary 2023.8." Stiffener stiffening indicates whether the beam end is reinforced by horizontal stiffeners and intermediate edge stiffeners. The stiffeners are made of 3.5mm thick SS400 material.

[0037] The yield point σy of the steel material is shown in the order of flange / web. The compressive strength of concrete σc indicates the compressive strength of the concrete floor 12. In terms of failure characteristics, B indicates lateral buckling of the beam, L indicates local buckling of the beam, C indicates cone-shaped failure of the concrete floor, and S indicates fracture of the stud.

[0038] The maximum strength Mmax is the average positive and negative value of the maximum beam end moment M. Also, the value in [ ] indicates the ratio to the average positive and negative value cMp of the total plastic strength of composite beams calculated based on the "Architectural Institute of Japan Composite Structure Design Guidelines and Commentary 2023.8."

[0039] The plastic deformation magnification ηp was calculated by subtracting 1 from the average positive and negative values ​​of the ductility ratio θ / θp at the time of full plastic yield strength reduction, which was obtained based on the experimental results. The average positive and negative values ​​of the ductility ratio θ / θp at the time of full plastic yield strength reduction were obtained using the method shown in Figure 10.

[0040] Figure 6 shows the relationship between the story drift angle R and the horizontal force (horizontal load) P for each test beam obtained through the experiment. The story drift angle R is calculated based on the horizontal displacements D1 to D4 and the column height H as follows: R = (D1 + D3 - D2 - D4) / (2 H).

[0041] Figure 7 shows the relationship between the beam member angle θ and the beam-end moment M for each test beam obtained through the experiment. The beam member angle θ is calculated as θ = (D5 + D7 - D6 - D8) / (2·D) based on the horizontal displacements D5 to D8 mentioned above and the distance D indicating the beam length. The beam-end moment M can be calculated as M = P·H·Lb / (2·L), where P is the horizontal force (horizontal load), H is the column height, Lb is the beam clearance length, and L is the column span. Figure 8 also shows the relationship between the stud pull-out strength coefficient αs and the plastic deformation magnification ηp, based on these experimental results.

[0042] As shown in Figure 8, the above-mentioned experiment revealed that the larger the stud pull-out strength coefficient αs, the higher the plastic deformation ratio ηp. In other words, the larger the stud pull-out strength coefficient αs, the higher the plastic deformation capacity. Furthermore, when ensuring the same plastic deformation ratio ηp, sections B and D, which have a large lateral buckling slenderness ratio λb, require a larger stud pull-out strength coefficient αs than sections A and C, which have a small lateral buckling slenderness ratio λb.

[0043] The inventors set ηp=4 as the lower limit of the plastic deformation magnification ηp at which the flange member type is FA rank and the stud 18 will not break. Fig. 9 shows the value of the stud pull-out resistance coefficient αs at which the plastic deformation magnification ηp=4 can be ensured.

[0044] As shown in Fig. 9, when the lateral buckling slenderness ratio λb≦1.4, it was found that the stud 18 only needs to have a pull-out strength equivalent to 1.1% of the flange axial strength (=Af·σyf) (stud pull-out strength coefficient αs ≒ 0.011). On the other hand, when the lateral buckling slenderness ratio λb is in the range of >1.4, it was found that a pull-out strength of approximately 3.5% of the flange axial strength (=Af·σyf) (stud pull-out strength coefficient αs = 0.023 to 0.035) is required.

[0045] (Operation of the embodiment) The inventors set a threshold value for the stud pullout strength coefficient αs for each lateral buckling slenderness ratio λb in the graph of Figure 9, using a plastic deformation magnification ηp = 4 as the reference value. More specifically, the stud pullout strength coefficient αs for which a plastic deformation magnification ηp ≥ 4 is obtained is specified as αs ≥ 0.011 when the lateral buckling slenderness ratio λb ≤ 1.4. Furthermore, the stud pullout strength coefficient αs for which a plastic deformation magnification ηp ≥ 4 is obtained is specified as αs ≥ 0.1λb - 0.129 when the lateral buckling slenderness ratio λb is 1.4 < 1.65. The bending moment Md is then calculated using a stud pullout strength coefficient αs equal to or greater than the threshold value corresponding to the lateral buckling slenderness ratio λb, and the stud quantity (such as the stud pitch p and distances j1 and j2) is set so that the bending moment Md ≤ bending strength Mc is satisfied.

[0046] The effects of this embodiment will be described. (1) According to the evaluation method for steel beams with concrete slabs, the bending moment Md and bending strength Mc are calculated using various parameters based on the design details at the time. Then, by comparing these bending moments Md and bending strength Mc, it is possible to rationally evaluate factors related to the lateral buckling of the steel beams with concrete slabs 10, such as the number of studs.

[0047] (2) According to the evaluation method for steel beams with concrete slabs, it is possible to select a stud pull-out strength coefficient αs that will provide a plastic deformation magnification ηp equal to or greater than the reference value based on the lateral buckling slenderness ratio λb of the steel beam 11. Then, based on the selected stud pull-out strength coefficient αs, it is possible to set the amount of studs that will provide the desired plastic deformation magnification ηp. In addition, since the installation of excessive studs 18 is prevented, costs related to the studs 18 can be reduced.

[0048] (3) The bending strength Mc of the studs 18 is calculated according to the arrangement of the studs 18 provided on the steel beam 11. This increases the degree of freedom of the steel beam 10 with concrete floor to be evaluated.

[0049] (4) The reduction coefficient used to calculate the tensile strength Pa2 determined by the cone-shaped fracture was set to 1. This allows for a more rational evaluation of the stud quantity. As a result, it is possible to suppress the performance degradation of the steel beam 10 with concrete slab due to the stud quantity.

[0050] This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. The studs 18 may be joined to the upper flange 14 so that three or more studs are lined up in the width direction.

[0051] In the evaluation method for steel beams with concrete slabs, the steel beams with concrete slabs can be evaluated by comparing the bending moment Md and bending strength Mc based on the design details at the time. Therefore, evaluation is not limited to the number of studs, and the material of the steel beams 11, for example, can also be evaluated. [Explanation of symbols]

[0052] 5...Floor, 10...Steel beam with concrete floor, 11...Steel beam, 12...Concrete floor, 13...Web, 14...Upper flange, 15...Lower flange, 16...Left column, 17...Right column, 18...Stud, 30...Experimental equipment, 31...Frame, 32...Loading device, 33...Left column lower end connection part (pin), 34...Right column lower end connection part (pin), 35...Upper diaphragm, 36...Lower diaphragm, 37...Upper diaphragm, 38...Lower diaphragm, 41...Left column upper end connection part (pin), 42...Right column upper end connection part (pin), 45...Load beam, 47...Welded wire mesh, 51, 52, 53, 54, 55, 56, 57, 58...Displacement measuring device, 61...Orthogonal beam, 62...Support column, 63...Support column connection part.

Claims

1. A method for evaluating a steel beam with a concrete floor, the steel beam having a predetermined length joined to a left column, a right column, the left column, and the right column, and a concrete floor installed on the steel beam, The steel beam is an upper flange that joins the concrete floor; a lower flange connected to the upper flange by a web; a headed stud that is erected on the upper flange and fixed to the concrete floor; and The bending moment Md generated in the stud is calculated based on the stress Fh in the width direction generated at the joint between the lower flange and the web due to lateral buckling and the distance D between the upper flange and the lower flange in the web, and The bending strength Mc generated in the stud is calculated using the tensile strength Pa2 per stud determined by the cone-shaped fracture of the concrete floor and the distance j1 from one end of the upper flange to the stud in the width direction. The lateral buckling of the steel beam with concrete floor is evaluated based on the magnitude relationship between the bending moment Md and the bending strength Mc. Evaluation method for steel beams with concrete slabs.

2. the stud is a first stud; The upper flange is a headed second stud aligned with the first stud in the width direction; The bending strength Mc is calculated by further using the distance j2 from one end of the upper flange to the second stud in the width direction. The method for evaluating a steel beam with a concrete floor according to claim 1.

3. The bending moment Md is obtained by multiplying the flange shaft strength by a coefficient α, The coefficient α at which the bending moment Md and the bending strength Mc are equal is the stud pull-out strength coefficient αs, Based on the results of an experiment conducted on the steel beam with a concrete slab, the relationship between the stud pull-out strength coefficient αs, the lateral buckling slenderness ratio of the steel beam, and the plastic deformation magnification of the steel beam with a concrete slab is derived, Based on the above relationship, the stud quantity is determined so that the bending strength Mc is equal to or greater than the bending moment Md calculated using the stud pullout strength coefficient αs that provides a plastic deformation ratio equal to or greater than the reference value. A method for evaluating a steel beam with a concrete floor according to claim 1 or 2.

4. A steel beam with a concrete floor, the steel beam having a left column, a right column, a steel beam of a predetermined length joined to the left column and the right column, and a concrete floor installed on the steel beam, The steel beam is an upper flange that joins the concrete floor; a lower flange connected to the upper flange by a web; a headed stud that is erected on the upper flange and fixed to the concrete floor; and The bending moment Md generated in the stud is calculated using the stress Fh in the width direction generated at the joint between the lower flange and the web due to lateral buckling and the distance D between the upper flange and the lower flange in the web. The tensile strength Pa2 per stud is determined by the cone-shaped fracture of the concrete floor, and the bending strength Mc of the stud is calculated using the distance j1 of the stud in the width direction from one end of the upper flange in the width direction. The magnitude relationship between the bending moment Md and the bending strength Mc is Mc≧Md. Steel beams with concrete floor.

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