Back-to-back beam mounting structure

Abstract

To suppress deformation of a pair of back-laminated beams during an earthquake while attaching a mounting member to the pair of back-laminated beams.SOLUTION: A back-laminated beam attachment structure comprises: a pair of back-laminated beams 20 facing each other in a beam width direction across a column 12; a connecting member 60 with a square cylindrical portion 62 that is fitted between web portions 26 of the pair of back-laminated beams 20 and connects the pair of back-laminated beams 20; and reinforcing studs 30 and reinforcing braces 52 that are attached to the connecting member 60.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a back-to-back beam mounting structure. [Background technology]

[0002] A truss beam is known that includes a pair of upper string beams, a pair of lower string beams, and multiple shear resisting braces (see, for example, Patent Document 1). The pair of upper string beams are arranged facing each other in the beam width direction, sandwiching a column. Similarly, the pair of lower string beams are arranged facing each other in the beam width direction, sandwiching a column. The shear resisting brace connects the upper string beam and the lower string beam that face each other in the vertical direction.

[0003] Also, a pair of back-to-back beams (double beams) is known that are arranged opposite each other in the beam width direction on both sides of a pillar (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-503942 A [Patent Document 2] Japanese Utility Model Application Publication No. 4-134303 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, it is conceivable to attach mounting members such as braces, dampers, and studs to a pair of back-to-back beams.

[0006] However, for example, if a mounting member such as a brace is attached to one of a pair of back-to-back beams, stress may be concentrated in one of the back-to-back beams during an earthquake, causing the back-to-back beam to deform.

[0007] In consideration of the above, an object of the present invention is to suppress deformation of a pair of back-to-back beams during an earthquake while attaching mounting members to the pair of back-to-back beams. [Means for solving the problem]

[0008] According to the first aspect The back-to-back beam mounting structure comprises a pair of back-to-back beams facing each other in the beam width direction across a column, a connecting member having a square tubular portion that is fitted between the web portions of the pair of back-to-back beams and connects the pair of back-to-back beams, and a mounting member that is attached to the connecting member.

[0009] First aspect According to the back-to-back beam mounting structure, a pair of back-to-back beams face each other in the beam width direction with a column in between. A square tube-shaped portion of a connecting member is fitted between the web portions of the pair of back-to-back beams. The pair of back-to-back beams is connected by the square tube-shaped portion. In addition, a mounting member is attached to the connecting member.

[0010] Here, in the present invention, as described above, the pair of back-to-back beams are reinforced by connecting the pair of back-to-back beams with the square tubular portion, and thus deformation of the pair of back-to-back beams is suppressed when stress is concentrated on the pair of back-to-back beams from the mounting member during an earthquake.

[0011] According to the second aspect The back-to-back beam mounting structure is According to the first aspect In the back-to-back beam mounting structure, the connecting member is provided on the square tube portion and has a gusset plate portion that is arranged along the beam core of the pair of back-to-back beams in a planar view, and the mounting member is attached to the gusset plate portion.

[0012] Second aspect According to the back-to-back beam mounting structure, the connecting member has a gusset plate portion. The gusset plate portion is provided on the rectangular tube portion of the connecting member and is disposed along the beam center of the pair of back-to-back beams in a plan view. The mounting member is attached to the gusset plate portion.

[0013] As a result, during an earthquake, the load is input from the mounting member through the gusset plate toward the beam core of the pair of back-to-back beams. As a result, eccentric bending that occurs in the pair of back-to-back beams during an earthquake is reduced. Therefore, deformation of the pair of back-to-back beams during an earthquake is further suppressed.

[0014] According to the third aspect The back-to-back beam mounting structure is According to the first aspect In the back-to-back beam mounting structure, the connecting member has a horizontal flange portion extending laterally of the back-to-back beam from the lower end or upper end of the square tube portion, and the mounting member is attached to the horizontal flange portion.

[0015] Third aspect According to the back-to-back beam mounting structure, the connecting member has a horizontal flange portion. The horizontal flange portion extends from the lower end or the upper end of the rectangular tube portion to the side of the back-to-back beam. The mounting member is attached to the horizontal flange portion.

[0016] By providing the connecting member with horizontal flange portions in this manner, it is possible to easily attach horizontal braces or the like to the sides of the pair of back-to-back beams while suppressing deformation of the pair of back-to-back beams during an earthquake. Effect of the Invention

[0017] As described above, according to the back-to-back beam mounting structure of the present invention, it is possible to mount mounting members to a pair of back-to-back beams while suppressing deformation of the pair of back-to-back beams during an earthquake. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an elevation view showing a frame to which a back-to-back beam mounting structure according to a first embodiment is applied. [Diagram 2] FIG. 2 is a perspective view showing the connecting member shown in FIG. [Diagram 3] 3 is a side view of the connecting member shown in FIG. 2 as viewed from the beam width direction of the back-to-back beams. [Figure 4] 4 is a cross-sectional view taken along line 4-4 of FIG. 3. [Diagram 5] 5 is a cross-sectional view taken along line 5-5 of FIG. [Figure 6] FIG. 11 is a plan view showing a frame to which a back-to-back beam mounting structure according to a second embodiment is applied. [Figure 7] 7 is a partially enlarged plan view of FIG. 6 showing the connecting member shown in FIG. 6. [Figure 8] 8 is a cross-sectional view taken along line 8-8 in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] First embodiment First, the first embodiment will be described.

[0020] (Existing frame) FIG 1 shows an existing structure 10 including a pair of back-to-back beams 20 to which the back-to-back beam mounting structure according to this embodiment is applied. The existing structure 10 is made of steel. The existing structure 10 includes a pair of columns 12 and a pair of back-to-back beams 20 erected on the pair of columns 12. The existing structure 10 is an example of a structure.

[0021] The pair of columns (steel columns) 12 are formed, for example, from square steel pipes. The bases of the pair of columns 12 are supported by a foundation 14. The foundation 14 is, for example, a footing, and is buried in the ground G. A concrete floor 16 is laid on the ground G.

[0022] 2, the pair of back-to-back beams 20 are formed of C-shaped steel. Each back-to-back beam 20 has an upper flange portion 22 and a lower flange portion 24 that face each other in the vertical direction, and a web portion 26 that connects the upper flange portion 22 and the lower flange portion 24.

[0023] The pair of back-to-back beams 20 are disposed facing each other in the beam width direction (arrow W direction) with the column 12 (see FIG. 1) in between. The pair of back-to-back beams 20 are disposed with their respective web portions 26 facing inward (toward the column 12) and with the openings of the C-shaped steel facing outward. The pair of back-to-back beams 20 are joined to the column 12 by joining means such as welding or bolts (not shown) with the column 12 sandwiched between the respective web portions 26.

[0024] (Reinforcement structure for existing structure) 1, an existing frame 10 is reinforced by a reinforcing stud 30 and a pair of reinforcing braces 50, 52. The reinforcing stud 30 and the reinforcing brace 52 are examples of mounting members.

[0025] (Reinforced studs) 2 and 3, the reinforcing stud 30 is formed of a C-shaped steel. This reinforcing stud 30 has a pair of flange portions 32 and a web portion 34 that connects the pair of flange portions 32. Note that the reinforcing stud 30 is not limited to a C-shaped steel, and may be formed of, for example, an H-shaped steel or a steel pipe.

[0026] 1, the reinforcing stud 30 is disposed between a pair of columns 12, and its column base is supported by a foundation 36. The foundation 36 is, for example, a footing, and is buried in the ground G. The column heads of the reinforcing stud 30 are attached to a pair of back-to-back beams 20 via connecting members 60, which will be described later.

[0027] (Reinforcement brace) The pair of reinforcing braces 50, 52 are provided on the structural surface of the frame 40 formed by one of the columns 12 (the column 12 on the left side in FIG. 1), the reinforcing stud 30, and the pair of back-to-back beams 20. The pair of reinforcing braces 50, 52 are, for example, X-shaped turnbuckle braces, and are arranged along diagonal corners of the frame 40.

[0028] One reinforcing brace 50 has its lower end joined to the base portion of the reinforcing stud 30, and its upper end joined to the column capital portion of one of the columns 12. The other reinforcing brace 52 has its lower end joined to the base portion of one of the columns 12, and its upper end joined to the pair of back-to-back beams 20 via connecting members 60 described below.

[0029] An opening 44 such as a passageway is formed in the frame 42 surrounded by the other pillar 12 (the pillar 12 on the right side in FIG. 1), the reinforcing stud 30, and the pair of back-to-back beams 20.

[0030] (Connecting parts) 2 and 4, the connecting member 60 has a square tube portion 62, a horizontal flange portion 64, and a gusset plate portion 66. The square tube portion 62 is formed, for example, from a square steel pipe. The square tube portion 62 is fitted between the web portions 26 of the pair of back-to-back beams 20 with its axial direction being the beam formation direction (vertical direction) of the back-to-back beams 20.

[0031] 4, the height (axial length) of the square tube portion 62 is the same as the beam configuration of the pair of back-to-back beams 20. The upper end portion of the square tube portion 62 is disposed at the same height as the upper flange portion 22 of the pair of back-to-back beams 20. The lower end portion of the square tube portion 62 is disposed at the same height as the lower flange portion 24 of the pair of back-to-back beams 20.

[0032] It should be noted that the shape and size of the rectangular tube portion 62 can be appropriately changed. Therefore, for example, the upper end portion of the rectangular tube portion 62 may protrude upward beyond the upper flange portions 22 of the pair of back-to-back beams 20.

[0033] 5, the cross-sectional shape of the rectangular tube portion 62 is a rectangle with the longitudinal direction being the material axis direction of the back-to-back beams 20. The rectangular tube portion 62 has a pair of side wall portions 62A facing each other in the beam width direction of the back-to-back beams 20, and a pair of side wall portions 62B facing each other in the material axis direction of the back-to-back beams 20. The outer surfaces of the pair of side wall portions 62A are in contact (surface contact) with the inner surfaces of the web portions 26 of the pair of back-to-back beams 20, respectively.

[0034] A plurality of through holes 62H penetrating the side wall portions 62A in the thickness direction are formed in the pair of side wall portions 62A of the rectangular tube portion 62. Also, a plurality of through holes 26H penetrating the web portions 26 in the thickness direction are formed in the web portions 26 of the pair of back-to-back beams 20.

[0035] The multiple through holes 26H are respectively connected to multiple through holes 62H formed in a pair of side wall portions 62A of the rectangular cylindrical portion 62. The web portions 26 and the rectangular cylindrical portion 62 of the pair of back-to-back beams 20 are integrally connected by bolts 70 and nuts 72 inserted into these through holes 26H, 62H.

[0036] 4, a horizontal flange portion 64 is provided at the lower end of the rectangular tube portion 62. The horizontal flange portion 64 is formed of a steel plate or the like having a rectangular shape in a plan view, and is joined to the lower end of the rectangular tube portion 62 by welding or the like.

[0037] The horizontal flange portions 64 extend laterally from the lower ends of the square tube portions 62, and are overlapped on the lower surfaces of the lower flange portions 24 of the pair of back-to-back beams 20. The horizontal flange portions 64 are joined to the lower flange portions 24 of the pair of back-to-back beams 20 by welding (fillet welding) or the like. The pair of back-to-back beams 20 is reinforced by the horizontal flange portions 64.

[0038] As shown in Fig. 3, a gusset plate portion 66 is provided on the lower surface of the horizontal flange portion 64. The gusset plate portion 66 is formed of a rectangular steel plate or the like when viewed from the beam width direction of the back-to-back beams 20. Also, as shown in Fig. 5, the gusset plate portion 66 is disposed with its thickness direction being the beam width direction of the back-to-back beams 20. The gusset plate portion 66 is disposed along the beam core 20C of the pair of back-to-back beams 20 in a plan view.

[0039] As shown in Fig. 4, a plurality of through holes 66H are formed in the gusset plate portion 66. The plurality of through holes 66H penetrate the gusset plate portion 66 in the thickness direction. The plurality of through holes 66H are also arranged at intervals in the vertical direction. The web portion 34 of the column head portion of the reinforcing stud 30 is overlapped on the gusset plate portion 66.

[0040] A plurality of through holes 34H are formed in the web portion 34 of the column head of the reinforcing stud 30. The plurality of through holes 34H penetrate the web portion 34 in the thickness direction. The plurality of through holes 34H also communicate with a plurality of through holes 66H formed in the gusset plate portion 66. The gusset plate portion 66 and the column head of the reinforcing stud 30 are joined together by bolts 38 and nuts 39 inserted into these through holes 34H, 66H.

[0041] As shown in Fig. 2, the bracket 54 provided on the upper end of the reinforcing brace 52 is placed on the gusset plate portion 66. Through holes (not shown) are formed in the bracket 54 and the gusset plate portion 66. The bracket 54 and the gusset plate portion 66 are joined together by the bolts 56 and nuts 58 inserted into the through holes. The bracket 54 may be, for example, a shuttlecock plate.

[0042] (action) Next, the operation of the first embodiment will be described.

[0043] 2, according to the back-to-back beam mounting structure of this embodiment, a square tube portion 62 of a connecting member 60 is fitted between the web portions 26 of a pair of back-to-back beams 20. This square tube portion 62 and the web portions 26 of the pair of back-to-back beams 20 are integrally connected by a plurality of bolts 70 and nuts 72.

[0044] In this way, by connecting the web portions 26 of the pair of back-to-back beams 20 via the square tube portions 62, the joints (attachment portions) of the pair of back-to-back beams 20 with the reinforcing studs 30 and the reinforcing braces 52 are reinforced. As a result, when stress is concentrated on the pair of back-to-back beams 20 from the reinforcing studs 30 and the reinforcing braces 52 during an earthquake, deformation of the pair of back-to-back beams 20 is suppressed.

[0045] Additionally, the reinforcing studs 30 and the reinforcing braces 52 are joined to gusset plate portions 66 of the connecting members 60. The gusset plate portions 66 are disposed along the beam cores 20C (see FIG. 5) of the pair of back-to-back beams 20 in a plan view.

[0046] As a result, during an earthquake, the load of the reinforcing studs 30 and the reinforcing braces 52 is input toward the beam cores 20C of the pair of back-to-back beams 20 via the gusset plate portions 66. As a result, eccentric bending occurring in the pair of back-to-back beams 20 during an earthquake is reduced. Therefore, deformation of the pair of back-to-back beams 20 during an earthquake is further suppressed.

[0047] 4, the connecting member 60 is provided with a horizontal flange portion 64. This horizontal flange portion 64 is disposed along the lower surfaces of the lower flange portions 24 of the pair of back-to-back beams 20, and is joined to these lower flange portions 24 by welding or the like. This horizontal flange portion 64 reinforces the joints between the reinforcing studs 30 and the reinforcing braces 52 in the pair of back-to-back beams 20, thereby further suppressing deformation of the pair of back-to-back beams 20 during an earthquake.

[0048] Also, as shown in FIG. 1, in this embodiment, by providing a reinforcing stud 30 in the existing frame 10, the existing frame 10 can be reinforced by a pair of reinforcing braces 50, 52 while an opening 44 for a passage or the like can be secured on one side of the reinforcing stud 30.

[0049] Second Embodiment Next, a second embodiment will be described. In the second embodiment, the same reference numerals will be used to designate the same members as in the first embodiment, and the description thereof will be omitted as appropriate.

[0050] (Existing frame) 6 shows an existing frame 80 having a pair of back-to-back beams 20 to which the back-to-back beam mounting structure according to the second embodiment is applied. The existing frame 80 is a flat frame made of steel. The existing frame 80 has two pairs of back-to-back beams 20 and two pairs of back-to-back beams 82.

[0051] A column 12 is disposed at each corner of the existing frame 80. As shown in Fig. 7, a pair of back-to-back beams 20 and a pair of back-to-back beams 82 are disposed around each column 12 in a grid pattern (lattice pattern) in plan view. These back-to-back beams 20 are joined to the column 12 by joining means such as welding or bolts (not shown).

[0052] (Reinforcement structure for existing structure) 6, the existing frame 80 is reinforced by a pair of reinforcing horizontal braces 90. The pair of reinforcing horizontal braces 90 is, for example, an X-shaped turnbuckle brace, and is arranged along diagonal corners of the existing frame 80.

[0053] 7, one end of each reinforcing horizontal brace 90 is attached to one end of the pair of back-to-back beams 20 via a connecting member 100, and the other end is attached to the other end of the pair of back-to-back beams 20 via a connecting member 100. The reinforcing horizontal brace 90 is an example of an attachment member.

[0054] (Connecting parts) 8, the connecting member 100 has a rectangular tube portion 102 and a horizontal flange portion 104. The rectangular tube portion 102 is formed, for example, from a rectangular steel pipe. The rectangular tube portion 102 is fitted between the web portions 26 of the pair of back-to-back beams 20 with its axial direction being the material axis direction of the back-to-back beams 20.

[0055] The rectangular cylindrical portion 102 has a pair of side wall portions 102A facing each other in the beam width direction of the back-to-back beams 20, and a pair of side wall portions 102B facing each other in the beam configuration direction (up-down direction) of the back-to-back beams 20. The outer surfaces of the pair of side wall portions 102A are in contact (surface contact) with the inner surfaces of the web portions 26 of the pair of back-to-back beams 20, respectively.

[0056] A plurality of through holes 102H are formed in the pair of side walls 102A of the rectangular tube portion 102, penetrating the side walls 102A in the thickness direction. The plurality of through holes 102H are respectively connected to a plurality of through holes 26H formed in the web portions 26 of the pair of back-to-back beams 20. The web portions 26 of the pair of back-to-back beams 20 and the rectangular tube portion 102 are integrally connected by bolts 110 and nuts 112 inserted into the through holes 26H, 102H.

[0057] The horizontal flange portion 104 is provided at the lower end of the rectangular tube portion 102. The horizontal flange portion 104 is formed from a steel plate or the like that is rectangular in plan view, and is joined to the lower end of the rectangular tube portion 102 by welding or the like.

[0058] The horizontal flange portions 104 extend laterally from the lower ends of the rectangular tubular portions 102, and are overlapped on the lower surfaces of the lower flange portions 24 of the pair of back-to-back beams 20. The horizontal flange portions 104 are joined to the lower flange portions 24 of the pair of back-to-back beams 20 by welding (fillet welding) or the like. The pair of back-to-back beams 20 is reinforced by the horizontal flange portions 104.

[0059] The horizontal flange portion 104 passes under one of the back-to-back beams 20 and extends to the side of the back-to-back beams 20. A bracket 92 provided at one end of the reinforcing horizontal brace 90 is overlapped on this horizontal flange portion 104. Furthermore, the horizontal flange portion 104 and the bracket 92 each have a through hole (not shown). One end of the reinforcing horizontal brace 90 is attached to the pair of back-to-back beams 20 by a bolt 94 and a nut 96 inserted into these through holes.

[0060] 7, the reinforcing horizontal brace 90 is arranged so that an extension line of its brace core 90C passes through a target point P set on the column 12 in a plan view. This allows the stress of the reinforcing horizontal brace 90 to be efficiently transmitted to the column 12 via the connecting member 100 and the pair of back-to-back beams 20 during an earthquake.

[0061] In this embodiment, the target point P is set on the side surface of the pillar 12. However, the location of the target point P can be changed as appropriate, and for example, the target point P may be set at the center (material axis) of the pillar 12 in a plan view.

[0062] (action) Next, the operation of the second embodiment will be described.

[0063] 8, in the back-to-back beam mounting structure according to this embodiment, the connecting member 100 has a horizontal flange portion 104. The horizontal flange portion 104 passes from the lower end of the square tube portion 102 to the underside of the back-to-back beams 20 on both sides and extends out to the sides of these back-to-back beams 20. One end of the reinforcing horizontal brace 90 is attached to the extending portion of the horizontal flange portion 104.

[0064] By providing the horizontal flange portion 104 in this manner to the connecting member 100, the reinforcing horizontal brace 90 can be easily attached to the side of the pair of back-to-back beams 20 while suppressing deformation of the pair of back-to-back beams 20 during an earthquake.

[0065] 7, by changing the shape and size of the horizontal flange portion 104, the attachment angle of the reinforcing horizontal brace 90 to the pair of back-to-back beams 20 can be easily adjusted. This allows the reinforcing horizontal brace 90 to be attached to the pair of back-to-back beams 20 so that the brace core 90C of the reinforcing horizontal brace 90 passes through the target point P of the column 12 in a plan view.

[0066] In this embodiment, the horizontal flange portion 104 is provided at the lower end portion of the rectangular tubular portion 102. However, the horizontal flange portion 104 may be provided at the upper end portion of the rectangular tubular portion 102.

[0067] (Modification) Next, modified examples of the first and second embodiments will be described. Note that, although various modified examples will be described below using the first embodiment as an example, these modified examples can also be appropriately applied to the second embodiment.

[0068] In the first embodiment, the gusset plate portion 66 of the connecting member 60 is disposed along the beam core 20C of the pair of back-to-back beams 20 in a plan view. However, the gusset plate portion 66 may be disposed at a position deviated from the beam core 20C of the pair of back-to-back beams 20 in a plan view, for example.

[0069] In the first embodiment, the reinforcing stud 30 and the reinforcing brace 52 are attached to the gusset plate portion 66 of the connecting member 60. However, the reinforcing stud 30 and the reinforcing brace 52 are not limited to being attached to the gusset plate portion 66, and may be attached to, for example, a steel frame member or the like provided at the lower end of the square tube portion 62, or may be attached to the horizontal flange portion 64. Furthermore, for example, the horizontal flange portion 64 and the gusset plate portion 66 may be omitted from the connecting member 60, and the reinforcing stud 30 and the reinforcing brace 52 may be attached to the square tube portion 62.

[0070] In the first embodiment, the reinforcing brace 52 serving as the mounting member is a turnbuckle brace. However, the reinforcing brace serving as the mounting member is not limited to the turnbuckle brace and may be, for example, a steel brace.

[0071] In the first embodiment, the mounting members are the reinforcing studs 30 and the reinforcing braces 52. However, the mounting members are not limited to the reinforcing studs 30 and the reinforcing braces 52, and may be, for example, dampers or the like.

[0072] In the first embodiment, the square tube portion 62 of the connecting member 60 is disposed so that its axial direction coincides with the beam height (vertical direction) of the back-to-back beams 20. However, the installation direction of the square tube portion 62 of the connecting member 60 can be changed as appropriate depending on the situation. For example, if the beam height of the back-to-back beams 20 is low, the square tube portion 62 may be disposed so that its axial direction coincides with the material axis direction of the back-to-back beams 20.

[0073] In the first embodiment, the pair of back-to-back beams 20 are formed of C-shaped steel. However, the pair of back-to-back beams 20 is not limited to C-shaped steel, and may be formed of, for example, square steel pipes. The pair of back-to-back beams 20 is not limited to steel construction (steel beams), and may be, for example, wood construction (wood beams).

[0074] In the first embodiment, the existing frame 10 is provided on the first floor of the structure and supported by the foundation 14. However, the existing frame 10 may be provided on the second or higher floor of the structure.

[0075] Furthermore, in the above-mentioned first embodiment, the pair of back-to-back beams 20 is existing, but the pair of back-to-back beams 20 may be newly installed. Also, in the above-mentioned first embodiment, the frame is the existing frame 10, but the frame may be a newly installed frame.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the embodiments and various modified examples may be used in appropriate combinations, and it goes without saying that the present invention can be embodied in various forms without departing from the gist of the present invention. [Explanation of symbols]

[0077] 12 Pillars 20 Pair of back-to-back beams 20C Beam center (beam center of a pair of back-to-back beams) 26 Web section (web section of back-to-back beam) 30 Reinforcement stud (mounting member) 52 Reinforcement brace (mounting member) 60 Connecting member 62 Square tubular portion (square tubular portion of connecting member) 66 Gusset plate part 90 Reinforcement horizontal brace (mounting member) 100 Connecting member 102 Square tubular portion (square tubular portion of connecting member) 104 Horizontal flange portion (horizontal flange portion of connecting member) W: Beam width direction of a pair of back-to-back beams

Claims

1. A pair of back-to-back beams facing each other in the beam width direction with a column in between; A connecting member having a square tubular portion that is fitted between the web portions of the pair of back-to-back beams and is bolted to the web portions to connect the pair of back-to-back beams; An attachment member attached to the connecting member; A back-to-back beam mounting structure.

2. A pair of back-to-back beams facing each other in the beam width direction with a column in between; A connecting member having a square tube-shaped portion that is fitted between the web portions of the pair of back-to-back beams and connects the pair of back-to-back beams; An attachment member attached to the connecting member; Equipped with The connecting member is provided on the square tube portion and has a gusset plate portion arranged along the beam core of the pair of back-to-back beams in a plan view, The mounting member is attached to the gusset plate portion. Back-to-back beam mounting structure.

3. A pair of back-to-back beams facing each other in the beam width direction with a column in between; A connecting member having a square tube-shaped portion that is fitted between the web portions of the pair of back-to-back beams and connects the pair of back-to-back beams; An attachment member attached to the connecting member; Equipped with The connecting member has a horizontal flange portion extending from a lower end or an upper end of the square tube portion to a side of the back-to-back beam, The mounting member is attached to the lateral flange portion. Back-to-back beam mounting structure.

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