Bed structure

Abstract

To provide a floor structure that makes reinforcement around an open hole unnecessary while allowing weight saving of a steel beam by making a board thickness of a web of the steel beam thinner.SOLUTION: A floor structure 2 comprises a steel beam 25 in an H-shaped cross section having a web 26 and a pair of flanges 27, 28 arranged so as to interpose the web, and a floor slab 40 supported from downward by the steel beam, at least one open hole 26a is formed at the web, the floor slab has concrete 41 supported on the steel beam and a shear connector 42 connected to an upper flange 27 which is one of the pair of flanges and buried in the concrete, and satisfies a prescribed expression, at least one shear connector is arranged respectively at the part of the upper flange corresponding to a position where the open hole of the web is not formed in a material axis direction of the steel beam.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a floor structure. [Background technology]

[0002] Traditionally, concrete floor slabs have been widely used as floor slabs in buildings. In addition, H-shaped steel beams are widely used as members to support these floor slabs. The steel beams support vertical loads such as the weight of the floor slab and the live load of the floor slab, and transmit these loads to the main beam. Both ends of the steel beams are generally friction-jointed to the main beam with high-strength bolts, so-called pin joints, with only the webs of the steel beams being friction-jointed to the main beam. In addition, the top surface of the upper flange of the steel beams is generally fastened to the floor slab with shear connectors such as headed studs.

[0003] As mentioned above, because both ends of the steel beam are pin-jointed to the main girder, it does not resist horizontal loads such as earthquake forces, but only vertical loads. Therefore, as the weight of the steel beam increases, the horizontal force as inertia increases, and the main girder needs to have more strength to resist this increase in horizontal force, so there is currently a widespread demand for lighter steel beams. Furthermore, in the webs of steel beams, through holes are often provided for passing pipes and other equipment (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-142224 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when piping holes are provided in the webs of steel beams, there is a possibility that the area around the piping holes may be damaged early. To prevent this, it is common to reinforce the area around the through holes with steel plates or to thicken the webs of the steel beams. However, the processing for reinforcing the area around the through holes takes time and costs money. In addition, thickening the webs of the steel beams increases the weight of the steel beams.

[0006] The present invention has been made in consideration of such problems, and aims to provide a floor structure that reduces the weight of steel beams by reducing the thickness of the webs of the steel beams, while eliminating the need for reinforcement around the through holes. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention proposes the following means. The floor structure of the present invention comprises a steel beam with an H-shaped cross section having a web and a pair of flanges arranged on either side of the web, and a floor slab supported from below by the steel beam, wherein the web has at least one through hole formed therein, and the floor slab has concrete supported on the steel beam and a shear connector joined to an upper flange, which is one of the pair of flanges, and embedded in the concrete, satisfying equations (1) to (4), and wherein at least one shear connector is arranged in each of the portions of the upper flange corresponding to positions in the material axis direction of the steel beam where no through hole is formed in the web. Where, w: Design uniformly distributed load for the steel beam (N / mm 2 ), b c t: the effective width of the floor slab (mm). L: if one through hole is formed in the web, it is the diameter of the through hole (mm). If multiple through holes are formed in the web, it is the maximum value of the diameters of the multiple through holes (mm). B: the width of the steel beam (mm), t f : the thickness of each of the pair of flanges (mm), σ y : Yield strength of the steel beam (N / mm 2 ), dc : The thickness of the floor slab (mm). L w When one through hole is formed in the web, the through hole and the steel beam in the material axial direction are both ends Distance between The shorter of (mm), and when the plurality of through holes are formed in the web, the distance between adjacent through holes is Minimum (mm). w : thickness of the web (mm), d w : The height of the web (mm).

[0008]

number

[0009] Below is an explanation of equations (1) to (4). Equation (1) is the bending strength M of the composite section consisting of concrete and the upper flange. c It represents. Equation (2) is the bending strength M c Specifically, by satisfying formula (2), the concrete and the upper flange are prevented from bending and breaking due to the mass of the floor slab per effective width and the vertical load due to the uniformly distributed design load at the position where the through hole is formed in the web in the material axis direction.

[0010] Formula (3) expresses the condition for preventing early shear failure of the web between adjacent through holes or between a through hole and the end of a steel beam. Specifically, by satisfying formula (3), it is guaranteed that the bottom flange will yield before the web fails in shear due to the shear force generated by the vertical load at a position in the material axis direction where no through hole is formed. In other words, by satisfying formulas (2) and (3), it is possible to resist the bending moment and shear force caused by the vertical load without reinforcing the periphery of the through hole of the web. Furthermore, by satisfying equation (4), a steel beam with a large width-to-thickness ratio of the web, i.e., a steel beam with a thin web, can be made, and the cross-sectional performance against bending moment can be improved while reducing the weight of the steel beam. According to the above, even if a through hole is formed in the web of a steel beam having a reduced weight due to a thin web, the steel beam can be used without requiring reinforcement of the web.

[0011] However, in order to achieve the above-mentioned effect, the concrete of the floor slab and the upper flange of the steel beam must behave as a single unit in the positions where no web through holes are formed, and for this reason, at least one shear connector must be placed in each of the parts of the upper flange that correspond to the positions where no web through holes are formed in the material axis direction.

[0012] In the floor structure, the steel beams may be welded H-shaped steel beams. According to this invention, the thickness of the web can be made thin without depending on the thickness of the flange, and the weight of the steel beam can be reduced. Effect of the Invention

[0013] According to the floor structure of the present invention, the thickness of the webs of the steel beams can be reduced, thereby reducing the weight of the steel beams and eliminating the need for reinforcement around the through holes. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view of a building equipped with a floor structure according to one embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along line A1-A1 in FIG. [Diagram 3] FIG. 2 is a cross-sectional view perpendicular to the material axis direction of a steel beam in the floor structure. [Figure 4] FIG. 1 is a schematic diagram showing a cross section of a floor structure of an embodiment used in the study, as viewed from the side. [Diagram 5] FIG. [Figure 6]FIG. 13 is a schematic cross-sectional side view of a floor structure of a comparative example. [Figure 7] FIG. 2 is a perspective view of an analytical model of the floor structure of the embodiment. [Figure 8] FIG. 13 is a perspective view of an analytical model of a floor structure of a comparative example. [Figure 9] FIG. 13 is a diagram showing an example of an analysis result of a floor structure in an embodiment. [Figure 10] FIG. 13 is a diagram showing an example of an analysis result of a floor structure of a comparative example. [Figure 11] This figure shows the change in design uniformly distributed load relative to the deflection at the center of the steel beam's axial direction. [Figure 12] FIG. 10 is a diagram showing a cross section of a floor structure in a modified example of one embodiment of the present invention as viewed from the side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of a floor structure, a method for designing a floor structure, and a method for constructing a floor structure according to the present invention will be described with reference to Figs. 1 to 12. In the following, the design method of the floor structure will be simply referred to as the design method, and the construction method of the floor structure will be simply referred to as the construction method.

[0016] [1. Floor structure configuration] As shown in Fig. 1, a floor structure 2 is used in a building 1. In Fig. 1, a floor slab 40, which will be described later, is indicated by a two-dot chain line. As shown in FIGS. 1 and 2, the floor structure 2 includes a plurality of column members 10, a plurality of girders 15, a plurality of steel beams 25, piping 35, and a floor slab 40. It should be noted that the floor structure 2 does not necessarily have to include a plurality of column members 10, a plurality of girders 15, and piping 35.

[0017] The multiple column members 10 are made of steel, RC (Reinforced Concrete), SRC (Steel Reinforced Concrete), CFT (Concrete Filled Steel Tube), etc. For example, the multiple column members 10 extend in the vertical direction. The multiple column members 10 are arranged on the intersections of multiple straight lines that form a grid in a plan view (in a grid pattern). For example, the girder 15 is made of H-shaped steel. The girder 15 extends in a direction along a horizontal plane. The girder 15 has a first web 16, a first upper flange 17, and a first lower flange 18. The multiple girder 15 is installed on the multiple column members 10. The multiple girder 15 is arranged in a frame shape in a plan view, surrounding a predetermined area. A gusset plate 19 is joined to the first web 16 of the girder 15 by welding or the like (see FIG. 2).

[0018] The steel beam 25 extends in the material axis direction Z of the steel beam 25 along the horizontal plane. The steel beam 25 is made of H-shaped steel, and the cross section perpendicular to the material axis direction Z is H-shaped. The steel beam 25 is preferably a welded and assembled H-shaped steel (welded and assembled H-shaped cross section) manufactured by welding and joining a plurality of steel strips together. The steel beam 25 has a second web (web) 26, a second upper flange (flange, upper flange) 27, and a second lower flange (flange) 28. As shown in Fig. 2, the second web 26 is formed in a flat plate shape that has a rectangular shape when viewed in the thickness direction of the second web 26. The second web 26 is arranged so that the thickness direction of the second web 26 is along a horizontal plane. A plurality of through holes 26a are formed in the second web 26. The plurality of through holes 26a are arranged at intervals in the material axis direction Z. When viewed in the thickness direction of the second web 26, each through hole 26a has a circular shape. The shape of the through holes 26a when viewed in the thickness direction of the second web 26 is not limited to a circular shape, and may be a rectangular shape, etc. Although a plurality of through holes 26a are formed in the second web 26, the second web 26 is not reinforced with a known reinforcing material. In other words, a reinforcing material is not bonded to the periphery of the through holes 26a in the second web 26 to increase the strength of the periphery of the through holes 26a in the second web 26.

[0019] The flanges 27, 28 are formed in a flat plate shape and are respectively disposed so that the thickness direction of the flanges 27, 28 is along the up-down direction. The second lower flange 28 is disposed below the second upper flange 27. The flanges 27, 28 are disposed so as to sandwich the second web 26 in the up-down direction. The second web 26 connects the center of the width direction of the lower surface of the second upper flange 27 and the center of the width direction of the upper surface of the second lower flange 28.

[0020] Here, as shown in FIG. 3, dimensions and the like of a cross section perpendicular to the material axis direction Z of the steel beam 25 are defined. The thickness of the second web 26 is t w The width of the second web 26 (the height of the second web 26) is defined as d w The thickness of each of the flanges 27 and 28 is specified as t f The depth of the steel beam 25 is defined as H (mm). The width of the steel beam 25 is defined as B (mm). The width-thickness ratio of the second web 26 is greater than 80 and less than or equal to 160. The width-thickness ratio of the second web 26 is the thickness t w Width d of second web 26 relative to w The ratio (d w / t w ). The thickness t of the second web 26 w The thickness t of each of the flanges 27 and 28 is preferably 3.2 mm or more and 6 mm or less. f It is preferable that the width-thickness ratio of the second web 26 satisfies the formula (10).

[0021]

number

[0022] As shown in FIG. 2, the maximum hole diameter of the plurality of through holes 26a (the maximum value of the diameters of the plurality of through holes 26a) is defined as L (mm). Minimum , L w It stipulates that: The yield strength of the steel beam 25 is σ y (N / mm 2 )

[0023] In the material axis direction Z, a position in the second web 26 where the through holes 26a are not formed is referred to as a non-formed web position P1. In Fig. 2, the non-formed web position P1 is indicated by hatching. A portion of the second upper flange 27 corresponding to the non-formed web position P1 in the material axis direction Z is referred to as the non-formed upper flange portion P2. The non-formed upper flange portion P2 refers to a portion of the second upper flange 27 that is at the same position in the material axis direction Z as the non-formed web position P1. In Figure 2, the non-formed upper flange portion P2 is shown with hatching.

[0024] 1 and 2, the plurality of steel frame girders 25 are provided inside the area surrounded by the plurality of girders 15 (within the area surrounded by the plurality of girders 15). The plurality of steel frame girders 25 are arranged side by side with intervals between each other. Both ends of the steel beams 25 are supported by the girders 15. The steel beams 25 are pin-jointed to the girders 15. Specifically, as shown in FIG. 2, the second web 26 of the steel beam 25 and the gusset plate 19 are joined to each other by fastening members 29 including high-strength bolts or the like. In the vertical direction, the second upper flange 27 and the first upper flange 17 of the girder 15 are disposed at the same positions. The second lower flange 28 is disposed above the first lower flange 18 of the girder 15. That is, the beam depth H of the steel beam 25 is smaller than the beam depth of the girder 15. However, in this embodiment, in order to improve the cross-sectional performance of the steel beam 25, the beam depth H of the steel beam 25 is close to the beam depth of the girder 15. The flanges 27, 28 are not joined to the flanges 17, 18 of the girder 15, respectively.

[0025] For example, the piping 35 is made of a steel pipe. As shown in Fig. 1 and Fig. 2, the outer diameter of the piping 35 and the diameter of the through hole 26a of the steel beam 25 are equal to each other. The piping 35 is disposed in the through hole 26a of the steel beam 25.

[0026] As shown in Fig. 2, the floor slab 40 is provided above the multiple girders 15 and the multiple steel girders 25. The floor slab 40 is supported from below by first upper flanges 17 of the multiple girders 15 and second upper flanges 27 of the multiple steel girders 25. In this embodiment, the floor slab 40 is a concrete floor slab. The floor slab 40 includes concrete 41 and a shear connector 42. The concrete 41 is formed into a flat plate shape with its thickness direction aligned with the up-down direction. The concrete 41 is supported on the first upper flange 17 of the main girder 15 and the second upper flange 27 of the steel sub-girder 25 from below the concrete 41 by the first upper flange 17 and the second upper flange 27, respectively.

[0027] For example, the shear connector 42 is a headed stud. The floor slab 40 has a plurality of shear connectors 42. The lower ends of the plurality of shear connectors 42 are joined to the upper surfaces of the first upper flange 17 of the main girder 15 and the second upper flange 27 of the steel sub-girder 25 at intervals from each other. The shear connectors 42 are embedded in the concrete 41. At least one of the multiple shear connectors 42 is disposed on each of the non-formed upper flange portions P2. Here, "at least one shear connector 42 is disposed on the non-formed upper flange portion P2" means that the entire lower end of at least one shear connector 42 is joined to the non-formed upper flange portion P2. In this embodiment, the shear connector 42 is also arranged in a portion P3 other than the non-formed upper flange portion P2 of the second upper flange 27. However, in the floor structure 2, it is not essential that the shear connector 42 is arranged in the portion P3.

[0028] Here, the thickness of the floor slab 40 is d c The effective width of the floor slab 40 is defined as b c The uniformly distributed load for design of the steel beam 25 is defined as w (N / mm 2 ) When multiple steel beams 25 are arranged inside a space surrounded by multiple girders 15, the effective width b c is the pitch of the multiple steel beams 25. When one steel beam 25 is placed inside a space surrounded by multiple girders 15, the effective width b c is half the distance between a pair of opposing girders arranged parallel to the steel beam 25. For example, the design uniform load w is c The load is the sum of the weight of the floor slab 40 per unit area, the weight of the steel beams 25, and the live load determined based on the Building Standards Act according to the type of room in which the floor structure 2 is used. The type of room is, for example, an office. In this case, the live load is 2900 N / m 2 It is.

[0029] [2. Study on reinforcement of second web of sub-beam in floor structure] Below, the results of examining the specifications of the floor structure 2 in which reinforcement of the second web 26 is not required even if the second web 26 has the through-holes 26a formed therein will be described.

[0030] When a downward load acts on the floor slab 40, a bending moment and a shear force act on the floor structure 2. Even if the second web 26 has the through-hole 26a formed therein, the specifications of the floor structure 2 that can withstand these bending moments and shear forces without reinforcing the second web 26 were examined. The configuration of the floor structure 2 of the embodiment used in the study is shown in Figures 4 and 5. Both ends of the steel beam 25 in the material axis direction Z are supported so as to be rotatable around an axis along the width direction of the steel beam 25 and to be movable in the material axis direction Z. 4 shows a portion of an unformed web position P1 and an unformed upper flange portion P2 in the floor structure 2. The plurality of shear connectors 42 are disposed one each in the unformed upper flange portion P2.

[0031] 6 is a schematic side cross-sectional view of a floor structure 2A of a comparative example. The floor structure 2A differs from the floor structure 2 only in the position where the shear connector 42 is disposed. In the floor structure 2A, the shear connector 42 is disposed in a portion of the second upper flange 27 located above the center of the through hole 26a.

[0032] [2.1. Consideration of cases where bending moment acts on floor structure] If the through hole 26a is formed in the second web 26, when a bending moment acts on the floor structure 2, it cannot be expected that the second web 26 will be able to withstand the bending moment. For this reason, we investigated the conditions under which the concrete 41 and the second upper flange 27, which are connected by the shear connector 42 and behave as a single unit, can withstand this bending moment. Here, the bending strength M of the concrete 41 and the second upper flange 27 according to the formula (11) is c (Nmm) is specified.

[0033]

number

[0034] In addition, the bending strength M c The formula (11) for determining the above is derived as an approximation from the condition that the second upper flange 27 of the steel beam 25 is in tensile yield. Bending strength M c By satisfying formula (12), the concrete 41 and the second upper flange 27 are prevented from bending and breaking in the portion where the through hole 26a is formed in the material axis direction Z.

[0035]

number

[0036] In addition, equation (12) is derived from the condition that the composite section consisting of the concrete 41 and the second upper flange 27 does not yield in bending due to a vertical uniformly distributed load (e.g., the design uniformly distributed load w) acting on the position where the through hole 26a is formed in the second web 26.

[0037] [2.2. Consideration of the case where shear force acts on floor structure] Even when the through hole 26a is formed in the second web 26, in the floor structure 2 of the embodiment, the shear connector 42 joins the non-formed upper flange portion P2 to the concrete 41. Therefore, by satisfying formula (13), the second lower flange 28 yields due to this shear force before the non-formed web position P1 shear yields.

[0038]

number

[0039] Incidentally, formula (13) is derived as a condition for the shear yield strength of the second web 26 at the non-formed web position P1 to exceed the tensile yield strength of the upper and lower flanges 27, .

[0040] [3. Verification by Simulation] In the floor structure 2 of the embodiment and the floor structure 2A of the comparative example, the necessity of reinforcement in the second web 26 of the steel beam 25 was verified by simulation. An analytical model of the floor structure 2 is shown in Fig. 7, and an analytical model of the floor structure 2A is shown in Fig. 8. Note that concrete 41 is not shown in Figs. 7 and 8. As shown in FIG. 5, the length of the floor structure 2, 2A in the material axis direction Z is 6800 mm. The width of the floor structure 2, 2A (effective width b c ) is 3000 mm. The diameter of the through hole 26a is 600 mm. The pitch L of the through hole 26a is 800 mm. The pitch of the shear connector 42 is 800 mm. The beam depth H of the steel beam 25 is 700 mm. The thickness d of the floor slab 40 is 100 mm. b The cross-sectional shape of the steel beam 25 is BH-700x175x4.5x9. The equivalent stress and displacement of the floor structures 2 and 2A were obtained by FEM (Finite Element Method) analysis. An example of the analysis result is shown in Figures 9 and 10. It was found that the equivalent stress and displacement of the floor structure 2 of the example were smaller than those of the floor structure 2A of the comparative example.

[0041] 11 shows the change in the design uniformly distributed load w with respect to the deflection at the center of the material axis direction Z of the steel beam 25. The solid line L1 represents the results for the floor structure 2. The dotted line L2 represents the results for the floor structure 2A. It was found that for a certain design uniformly distributed load w, the deflection at the center of the steel beam 25 in the material axis direction Z is smaller in floor structure 2 than in floor structure 2A.

[0042] In the floor structure 2B of the modified example shown in FIG. 12, one through hole 26a is formed in the second web 26. In this case, the diameter of the through hole 26a is defined as L (mm). In the material axis direction Z, the shorter of the distances between the through hole 26a and the end of the material axis direction Z of the second web 26 (steel beam 25) is defined as L. w It is specified in mm.

[0043] As described above, according to the floor structure 2, 2B of this embodiment, the formula (11) is the bending strength M of the composite section consisting of the concrete 41 and the second upper flange 27. c Equation (12) represents the bending strength M c Specifically, by satisfying formula (12), the concrete 41 and the second upper flange 27 are prevented from bending and breaking at the non-formed web position P1 due to the mass of the floor slab 40 per effective width and the vertical load due to the design uniformly distributed load w.

[0044] Formula (13) expresses a condition for preventing early shear failure of the second web 26 between the adjacent through holes 26a. Specifically, by satisfying formula (13), it is ensured that the second lower flange 28 yields at the non-forming web position P1 before the second web 26 shears and fails due to the shear force generated by the vertical load. That is, by satisfying formulas (12) and (13), it is possible to resist the bending moment and shear force caused by the vertical load without reinforcing the periphery of the through hole 26a of the second web 26. Furthermore, by satisfying equation (10), a steel beam with a large width-to-thickness ratio of the second web 26, i.e., a steel beam with a thin web, can be made, and the cross-sectional performance against bending moment can be improved while reducing the weight of the steel beam 25. As described above, even if a through hole 26a is formed in the second web 26 of a steel beam 25 which has been made lighter by the thin-walled second web 26, the steel beam 25 can be used without requiring reinforcement of the second web 26.

[0045] The second web 26 of the steel beam 25 is not reinforced by a reinforcing material. Therefore, when the through hole 26a is formed in the second web 26, the steel beam 25 can be used without necessarily reinforcing the second web 26 with a reinforcing material. The steel beam 25 is a welded H-shaped steel beam. Therefore, the plate thickness of the second web 26 can be made thin without depending on the plate thickness of the flanges 27, 28, and the steel beam 25 can be made lighter.

[0046] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0047] 2,2B floor structure 25 Steel Beam 26 Second Web (Web) 26a Through hole 27 Second upper flange (flange, upper flange) 28 Second lower flange (flange) 40 Floor slab 41 Concrete 42 Shear Connector

Claims

1. A steel beam having an H-shaped cross section and a pair of flanges arranged to sandwich the web; A floor slab supported from below by the steel beams; Equipped with The web has at least one through hole formed therein; The floor slab is Concrete supported on the steel beams; A shear connector joined to an upper flange, which is one of the pair of flanges, and embedded in the concrete; having Formulas (1) to (4) are satisfied, A floor structure in which at least one shear connector is arranged in each of the portions of the upper flange corresponding to positions in the material axis direction of the steel beam where the through holes of the web are not formed. Where w: Design uniformly distributed load of the steel beam (N / mm ２ ), b ｃ t: Effective width of the floor slab (mm). L: Diameter of the through hole (mm) when one through hole is formed in the web, and maximum diameter of the through holes (mm) when multiple through holes are formed in the web. B: Width of the steel beam (mm), t ｆ : thickness of each of the pair of flanges (mm), σ ｙ : Yield strength of the steel beam (N / mm ２ ), d c : Thickness of the floor slab (mm). L ｗ t: When one through hole is formed in the web, it is the shorter of the distances (mm) between the through hole and both ends of the steel beam in the material axis direction, and when multiple through holes are formed in the web, it is the minimum distance (mm) between adjacent through holes. ｗ : thickness of the web (mm), d ｗ : the height of the web (mm). [0010]

2. 2. The floor structure of claim 1, wherein the web is not reinforced with a stiffener.

3. 3. The floor structure according to claim 1, wherein the steel beams are welded H-shaped steel beams.

Images