Reverse beam structure

Abstract

To provide a reverse-beam structure for efficiently suppressing lateral buckling.SOLUTION: A reverse beam-structured B1 (B2) includes slabs 11 (12) and steel beams 20 projecting upward from the slabs 11 (12), respectively. The slabs 11 (12) are respectively joined to studs 16 (17) extending in the vertical direction. A gusset plate 31 is joined to the bottom plate 24 of the lower part of the steel frame beam 20. Gusset plates 32,33 are joined to the lower end and the upper end of the second side plate 26, which is located above the bottom plate 24 of the steel frame girder 20. The gusset plate 31 is joined to the stud 15 (16), and the gusset plate 32,33 is joined to the stud 16 (17) above the gusset plate 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an inverted beam structure in which a beam protrudes upward from a slab. [Background technology]

[0002] In order to run large ducts or the like to the outside of a building at the top of a room, steel beams are sometimes used in an inverted beam structure. In an inverted beam structure for steel beams, as described in Patent Document 1, for example, a slab is formed on the bottom flange of the beam, and the beam protrudes above this slab. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-138120 Summary of the Invention [Problem to be solved by the invention]

[0004] In an inverted beam structure, it is possible to install lateral stiffeners on the beams to suppress lateral buckling. In this case, it takes time and effort to install the lateral stiffeners by welding them to the beams. Therefore, it is possible to select beam members with a large beam width according to the span between columns so that lateral stiffeners are not necessary. However, in this case, the cost of the beams increases, making it uneconomical. [Means for solving the problem]

[0005] The inverted beam structure that solves the above problem is an inverted beam structure comprising a slab and a beam protruding upward from the slab, wherein the slab is joined to a vertical member extending in the vertical direction, a first joint is joined to the lower part of the beam, a second joint is joined to a position on the beam above the first joint, and the first joint and two or more second joints on the beam above the first joint and spaced apart vertically are joined to the vertical member. [Effects of the Invention]

[0006] According to the present invention, lateral buckling in an inverted beam structure can be effectively suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a longitudinal sectional view schematically showing an inverted beam structure according to an embodiment of the present invention. [Figure 2] FIG. 10 is a vertical cross-sectional view showing a main part of an inverted beam structure in a first modified example of an embodiment of the present invention. [Figure 3] FIG. 10 is a vertical cross-sectional view showing a main part of an inverted beam structure in a second modified example of an embodiment of the present invention. [Figure 4] FIG. 10 is a vertical cross-sectional view showing a main part of an inverted beam structure in a third modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] (reverse beam structure) An inverted beam structure according to one embodiment of the present invention will be described below with reference to Fig. 1. Here, an inverted beam structure of a steel beam connected to a slab on the nth floor in a multi-story building is assumed.

[0009] As shown in Figure 1, on the nth floor of the building, inverted beam structures B1 and B2 having steel beams 20 that respectively constitute the floor and ceiling of the nth floor are arranged. The inverted beam structure B2 has the same configuration as the inverted beam structure B1. The inverted beam structure B1 (B2) includes a steel beam 20 made of H-shaped steel. The steel beam 20 includes a lower flange 21, an upper flange 23, and a web 22 connecting these. Reinforcing plates 21a and 23a extending toward the outside of the building are welded to the ends of the lower flange 21 and the upper flange 23 on the outside (outside) side of the building, respectively. The reinforcing plates 21a and 23a are made of steel plates.

[0010] Furthermore, the steel beam 20 is provided with a bottom plate 24, a first side plate 25, and a second side plate . Bottom plate 24 extends vertically and protrudes from bottom flange 21 to the outside of the room, and is disposed on the underside (bottom surface) of bottom flange 21 of steel beam 20. Bottom plate 24 is formed from a rectangular steel plate with one of the four corners cut out into a substantially triangular shape. A portion of bottom plate 24 on the steel beam 20 side is welded to the bottom surface of bottom flange 21 of steel beam 20 and the bottom surface of reinforcing plate 21a.

[0011] The first side plate 25 is a rectangular steel plate, and is welded to the surface 22a of the web 22 of the steel beam 20 on the inside (inside) of the building, the upper surface 21t of the lower flange 21, and the lower surface 23d of the upper flange 23.

[0012] The second side plate 26 is a steel plate with an isosceles trapezoidal notch 26a formed on one of the long sides of a rectangle. This second side plate 26 is composed of a vertically extending plate member, and its short side extends further toward the outside of the room than the lower flange 21 and the upper flange 23. The second side plate 26 is welded to the outside surface 22b of the web 22, the upper surface 21t of the lower flange 21, the upper surface 21at of the reinforcing plate 21a, the lower surface 23d of the upper flange 23, and the lower surface 23ad of the reinforcing plate 23a.

[0013] Slabs 11 and 12 having a predetermined thickness are formed on the bottom flanges 21 of the steel beams 20 of the inverted beam structures B1 and B2, respectively. Slab 11 forms the floor of the nth floor and the ceiling of the (n-1)th floor. Slab 12 forms the ceiling of the nth floor and the floor of the (n+1)th floor directly above. Slabs 11 and 12 have the same structure. Slab reinforcement (not shown) and stud bolts 13 and 14 are embedded in slab 11 (12). Stud bolts 13 and 14 are arranged extending horizontally so that their ends abut surfaces 22a and 22b of web 22.

[0014] Furthermore, the lower ends of vertically extending studs 16, 17 (vertical members) are embedded in the slabs 11, 12, respectively.

[0015] Directly below stud 16 is placed stud 15, which stands upright from the floor slab (not shown) of the (n-1)th floor. Directly above stud 16 is placed stud 17, which stands upright from the slab 12 of the (n+1)th floor. Stud 15 (16) is placed with a gap between it and stud 16 (17) directly above it, so that its outer surface is flush with stud 16 (17). Furthermore, studs 15, 16, and 17 are made by joining multiple H-shaped steel beams vertically.

[0016] The exterior side of the bottom plate 24 of the steel beam 20 of the inverted beam structure B1 (B2) is joined to the upper end of the stud 15 (16) via a gusset plate 31.

[0017] The lower end of the stud 16 (17) is joined via a gusset plate 32 to the lower end of the second side plate 26 of the steel beam 20 of the inverted beam structure B1 (B2). Furthermore, the lower ends of the studs 16 (17), the gusset plates 32, and the lower ends of the second side plates 26 are embedded in the slab 11 (12).

[0018] The upper end of the second side plate 26 of the steel beam 20 of the inverted beam structure B1 (B2) is joined to the stud 16 (17) at a predetermined height from the lower end via a gusset plate 33. Here, the predetermined height corresponds to the position where the upper end of the second side plate 26 of the steel beam 20 is provided.

[0019] In this embodiment, the gusset plate 31 joined to the bottom plate 24 of the steel beam 20 of the inverted beam structure B2 (B1) corresponds to the first joint. In each inverted beam structure B2 (B1), the two or more second joints located above the bottom plate 24 and spaced apart in the vertical direction on the steel beam 20 correspond to gusset plates 32, 33 joined to the upper and lower ends of the second side plate 26. In addition, in the inverted beam structure B2 (B1), the vertical members include the first stud 17 (16) and the second stud 16 (15) provided below the first stud 17 (16). Furthermore, the second side plate 26 corresponds to a plate joined to the vertical member side of the upper flange 23 and the vertical member side of the lower flange 21, and has a notch 26a formed in its center.

[0020] (Construction method for reverse beam structure) Next, a construction method for the above-mentioned reverse beam structures B1 and B2 will be described. In this construction method, first, the steel beam 20 is placed, with the bottom plate 24, first side plate 25, second side plate 26, and stud bolts 13, 14 arranged on it. Then, the lower ends of the partition posts (16, 17) are joined to the lower end of the second side plate 26 via a gusset plate 32. Next, the bottom plate 24 is joined to the upper ends of the partition posts (15, 16) via a gusset plate 31. The upper ends of the partition posts (16, 17) are joined to the second side plate 26 via a gusset plate 33. Next, concrete forms (not shown) and slab reinforcement (not shown) are placed, and concrete is poured. The concrete forms are then removed, and the slabs 11, 12 are constructed.

[0021] (Operation of the embodiment) The lower part of the bottom plate 24 of the steel beam 20 of the inverted beam structure B1 (B2) is joined to the stud 15 (16) via a gusset plate 31. In addition, the lower and upper ends of the second side plate 26 of the steel beam 20 of the inverted beam structure B1 (B2) are joined to the stud 16 (17) via gusset plates 32, 33, respectively. As a result, the steel beam 20 of the inverted beam structure B1 (B2) is joined to the stud 16 (17) at two or more different locations spaced apart vertically, and is also joined to the lower stud 15 (16), so the steel beam 20 is firmly joined.

[0022] According to this embodiment, the following effects can be obtained. (1) In this embodiment, the lower and upper ends of the second side plate 26 of the steel beam 20 of the inverted beam structure B1 (B2) are joined to the studs 16 (17) joined to the slab 11 (12) via gusset plates 32, 33, respectively. As a result, the steel beam 20 of the inverted beam structure B1 (B2) is firmly joined to the studs 16 (17) not only at the lower ends but also at the upper ends of the second side plate 26, so that lateral buckling of the steel beam 20 can be efficiently suppressed.

[0023] (2) In this embodiment, the inverted beam structure B1 (B2) joins the bottom plate 24 of the steel beam 20 protruding upward from the slab 11 (12) to the stud 15 (16) via the gusset plate 31. This allows the steel beam 20 of the inverted beam structure B1 (B2) to suppress lateral buckling and to be joined to the upper end of the stud 15 (16).

[0024] (3) In this embodiment, the second side plate 26 of the steel beam 20 is welded to the lower surface 23d of the upper flange 23 and the lower surface 23ad of the reinforcing plate 23a extending from the upper flange 23. As a result, the upper end of the second side plate 26 is joined to the stud 16 (17) via the upper flange 23 and the reinforcing plate 23a, which further suppresses lateral buckling of the steel beam 20.

[0025] (4) In this embodiment, the second side plate 26 of the steel beam 20 has a notch 26a formed in the center. This allows the second side plate 26 to have the notch 26a in the center portion that is not required for joining or strength, thereby reducing the amount of material that constitutes the steel beam 20. This allows for cost reduction.

[0026] (Example of change) This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. In the above embodiment, the second side plate 26 of the steel beam 20 of the inverted beam structure B1 (B2) has the above-mentioned shape, and the upper end of the second side plate 26 is joined to the stud 16 (17). The shape of the plate of the steel beam 20 of the inverted beam structure B1 (B2) is not limited to the shape shown in the above embodiment and can be changed as appropriate. Furthermore, the mounting positions of the first and second side plates 25, 26 are not limited to the positions shown in the embodiment and can be changed as appropriate. The reverse beam structures in the first to third modified examples of the above embodiment will be described below with reference to Figures 2 to 4. The reverse beam structures shown in each modified example differ in the portion above the slab 11. Here, in the reverse beam structures shown in each modified example, the same components as those in the above embodiment will be given the same reference numerals, and detailed description thereof will be omitted.

[0027] <First modification example> In the inverted beam structure B3 of the first modified example shown in Figure 2, instead of providing a reinforcing plate 23a (see Figure 1) on a steel beam 40, an upper plate 41 is welded onto the upper flange 23. The upper plate 41 has a rectangular plate shape and is welded to the upper surface of the upper flange 23. Furthermore, the upper plate 41 on the stud 16 side protrudes further toward the outside of the room than the upper flange 23.

[0028] In addition, the second side plate 42 of the steel beam 40 has a plate shape with a right-angled trapezoidal notch 42a formed in the long side of the rectangle. The lower end of the second side plate 42 is joined to the lower end of the stud 16 via the gusset plate 32 and is embedded in the slab 11.

[0029] Additionally, a gap corresponding to the thickness of the upper flange 23 is provided between the second side plate 42 and the top plate 41 located above it. The upper end of the steel beam 40 is joined to the stud 16 via a gusset plate 46 that spans the upper end of the second side plate 42 and the top plate 41. In this case, holes for passing joining bolts through the gusset plate 46 are provided so as to be on the same vertical plane as the centers of the bolts that join the top plate 41 to the stud 16. Here, the gusset plates 32, 46 correspond to the second joining portion.

[0030] In this inverted beam structure B3, the centers of the bolts on the top plate 41 and the second side plate 42 are located on the same vertical plane, so there is no mechanical eccentricity in the top plate 41 and the second side plate 42. This improves the effectiveness of efficiently suppressing lateral buckling compared to the configurations of the inverted beam structures B1 and B2 shown in FIG. 1. Furthermore, in this inverted beam structure B3, the presence of the cutout 42a reduces the volume of the plate, thereby reducing costs. Furthermore, because this cutout 42a is larger than the cutout 26a in FIG. 1, wiring and piping can be passed through the cutout 42a.

[0031] <Second modification example> In the second modified inverted beam structure B4 shown in FIG. 3, a steel beam 50 has a top plate 51 welded onto the top flange 23. This top plate 51 has a rectangular plate shape and is welded to the top surface of the top flange 23 so as to extend vertically. Furthermore, this top plate 51 protrudes from the top flange 23 toward the exterior and is joined to the stud 16 via a gusset plate 56. The second side plate 52 of the steel beam 50 has a shape consisting of a vertically long rectangular upper portion 52a, a horizontally rectangular lower portion 52c, and a trapezoidal central portion 52b connecting the upper and lower portions. The width of the upper portion 52a of the second side plate 52 is approximately the same as the width of the portion on the stud 16 side relative to the web 22 of the top flange 23. The lower portion of the second side plate 52 protrudes toward the stud 16 relative to the bottom flange 21 and is joined to the stud 16 via a gusset plate 32. Here, the gusset plates 32 and 56 correspond to the second joint portion.

[0032] In this inverted beam structure B4, the upper plate 51 located above the upper flange 23 is attached to the stud 16 via a gusset plate 56, so that the upper part of the steel beam 40 can be efficiently joined to the stud 16. Furthermore, the reinforcing plate 23a welded to the upper flange 23 can be omitted, which reduces costs and shortens the construction period.

[0033] <Third modification example> In the above embodiment, the upper end of the second side plate 26 of the steel beam 20 of the inverted beam structures B1 and B2 is joined to the stud 16 via a gusset plate 33, which is a plate member extending vertically. The gusset plate used to join the upper end of the steel beam to the stud (vertical member) is not limited to a configuration extending vertically, and a gusset plate extending horizontally may also be used.

[0034] Specifically, the steel beam 60 of the inverted beam structure B5 of the third modified example shown in Fig. 4 has a reinforcing plate 23b protruding from the upper flange 23 toward the outside of the room, and a second side plate 62. The second side plate 62, like the second side plate 26 of the steel beam 20, has a plate shape with a trapezoidal notch 62a in the center.

[0035] Similarly to the reinforcing plate 23a, the reinforcing plate 23b extends horizontally and is welded to the upper end of the second side plate 62. The reinforcing plate 23b has a hole through which a bolt 70 is inserted. Furthermore, the stud 16 is provided with a horizontal gusset plate 16a extending horizontally and attached between the flanges of the stud 16, and a horizontal gusset plate 16b attached to the outside of the stud 16. The horizontal gusset plate 16b is provided so as to be in a straight line (flush) with the horizontal gusset plate 16a. Then, with the hole in the reinforcing plate 23b aligned with the hole formed in the horizontal gusset plate 16b of the stud 16, the bolt 70 passes through and is joined using a nut (not shown) that screws onto the bolt 70. Here, the gusset plate 32 and the bolt 70 correspond to the second joint.

[0036] Even with this structure, the upper end of the steel beam 60 can be efficiently joined to the stud 16. Furthermore, space can be secured above the upper flange 23 of the steel beam 60. In addition, because the joining is performed with the penetrating bolt 70, the joining position of the horizontal gusset plate 16b and the joining position of the reinforcing plate 23b are positioned on the same axis, so no eccentricity occurs in the horizontal gusset plate 16b and the reinforcing plate 23b.

[0037] In the above embodiment, studs 16, 17 were used as vertical members connecting the upper ends of the steel beams 20 of the inverted beam structures B1, B2. The vertical members connecting the upper ends of the steel beams 20 of the inverted beam structures B1, B2 are not limited to studs, as long as they extend vertically and do not deform even when a force that would cause the steel beams 20 to lateral buckle is applied. For example, instead of studs, steel pipes, frame members, etc. may be used as vertical members. Furthermore, the length of the vertical members is not limited to members that extend from the floor to the ceiling on each floor, and may be members that constitute spandrel walls, etc., with a height of less than half the height of the floor.

[0038] Next, the technical ideas that can be understood from the above-described embodiment and modified examples will be additionally described below. (a) The inverted beam structure according to any one of claims 1 to 3, characterized in that the vertical members and the beams are joined via gusset plates extending horizontally or vertically. [Explanation of symbols]

[0039] B1, B2, B3, B4, B5... inverted beam structure, 11, 12... slab, 13, 14... stud bolt, 15, 16, 17... partition (vertical member), 16a, 16b... horizontal gusset plate, 20, 40, 50, 60... steel beam, 21... bottom flange, 21a, 23a... reinforcing plate, 22... web, 22a... first surface, 22b... second surface, 23... top flange, 24... bottom plate, 25... first side plate, 26, 42, 52, 62... second side plate, 26a, 42a, 62a... cutout, 31... gusset plate as first joint, 32, 33, 46, 56... gusset plate as second joint, 41, 51... top plate, 70... bolt as second joint.

Claims

1. A reverse beam structure comprising a slab and a beam protruding upward from the slab, The slab is joined to a vertically extending longitudinal member, A first joint is joined to the lower part of the beam, A second joint portion is joined to the beam at a position above the first joint portion, An inverted beam structure characterized in that the first joint and two or more second joints located above the first joint and spaced apart vertically on the beam are joined to the vertical member.

2. The vertical member includes a first stud and a second stud provided below the first stud, the beam is joined to the first stud; The inverted beam structure according to claim 1 , wherein the first joint is joined to the second stud.

3. The beam is an H-shaped steel beam, The inverted beam structure according to claim 1 or 2, characterized in that the beam is joined to the vertical member side of the upper flange and the vertical member side of the lower flange via a plate having a notch formed in the center.

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