Beam member

Abstract

To provide a beam member which facilitates manufacture using a robot for welding, and hardly causes stress concentration.SOLUTION: A beam member 1 includes: an H-shaped steel beam part 2 which has an upper flange 21, a lower flange 22 and a web 23; a joint plate 3 which is welded to respective edges of the upper flange 21 and the lower flange 22 on a side face side of the H-shaped steel beam part 2, and to which an end plate of another beam is coupled by tensile force of a bolt; and a rib 4 which is welded to a rear face of the joint plate 3. The rib 4 includes: a one vertical rib part 41 and an other vertical rib part 42 which face each other at an interval in an extension direction of the H-shaped steel beam part 2 and are welded to the web 23; an upper horizontal rib part 43 which is connected to an upper end side of the one vertical rib part 41 and the other vertical rib part 42; and a lower horizontal rib part 44 which is connected to a lower end side of the one vertical rib part 41 and the other vertical rib part 42.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a beam member having a beam joint structure for joining another beam to another beam. [Background technology]

[0002] As shown in FIG. 9 , a beam member 100 is known, which includes an H-shaped steel beam 101 having an upper flange 101a, a lower flange 101b, and a web 101c, a joining plate 102 welded to the edges of the upper flange 101a and the lower flange 101b on the side of the H-shaped steel beam 101 and to which an end plate of another beam is fastened with a beam-fixing bolt, and a vertical plate rib 103 welded to the back surface of the joining plate 102. In fabricating the beam member 100, the upper edge of the joining plate 102, to which the vertical plate rib 103 has been previously welded, is welded to the upper flange 101a, and the lower edge is welded to the lower flange 101b. The rear edge of the vertical plate rib 103 that contacts the web 101c is then welded to the web 101c. These welding operations can be performed by a welding robot.

[0003] Patent document 1 discloses a beam joining structure that includes a main girder having a web and a pair of flanges provided at both ends of the web, a secondary beam, and a gusset plate that joins the main girder and the secondary beam, and that can reduce the time and cost required for welding work. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2018-104960 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when manufacturing the beam member 100, it is necessary to weld the rear edge of the vertical plate rib 103 to the web 101c at a position directly behind the joining plate 102, and there was a problem that the joining plate 102 gets in the way during this welding work, making it difficult to use a welding robot.

[0006] 10, in the case of a beam member 200 using a joining plate 201 having a U-shaped cross section with vertical ribs 201a on both sides and welded to a web 101c, the vertical ribs 201a can be easily welded to the web 101c using a welding robot. However, in order to insert the column fixing bolts into the flanges 101a and 101b, it is necessary to provide notches at the top and bottom ends of the vertical ribs 201a of the joining plate 201, and the presence of such notches causes a problem of stress concentration at the recessed corner A in the figure.

[0007] An object of the present invention is to provide a beam member that can be easily manufactured using a welding robot and in which stress concentration is unlikely to occur. [Means for solving the problem]

[0008] The beam member of the present invention comprises a steel beam portion having an upper flange, a lower flange, and a web, a joining plate welded to the edges of the upper flange and the lower flange on the side of the steel beam portion and to which an end plate of another beam is fastened with a beam fixing bolt, and a rib welded to the back surface of the joining plate, The rib includes a first longitudinal rib portion and a second longitudinal rib portion that are opposed to each other and spaced apart in the extension direction of the steel beam portion and welded to the web, an upper horizontal rib portion connected to upper ends of the first vertical rib portion and the second vertical rib portion, and a lower horizontal rib portion connected to lower ends of the first vertical rib portion and the second vertical rib portion, The upper flange and the lower flange have vertically formed through-holes through which column fixing bolts are inserted, and the upper horizontal rib portion and the lower horizontal rib portion are located at a distance from the upper flange and the lower flange, respectively, that allows the column fixing bolts to be inserted through the through-holes.

[0009] With the above configuration, the first vertical rib portion and the second vertical rib portion are opposed to each other at a distance in the extension direction of the steel beam portion and can be positioned close to the edge of the joining plate, so that the first vertical rib portion and the second vertical rib portion can be easily welded to the web of the steel beam portion using a welding robot without being obstructed by the joining plate. Furthermore, the upper horizontal rib portion and the lower horizontal rib portion are positioned at a distance from the upper flange and the lower flange, respectively, that allows the column fixing bolt to be inserted into the insertion hole, and since the joining plate is not formed with a notch for the column fixing bolt, problems such as stress concentration that occur in structures that provide such notches can be avoided.

[0010] The rib may have a closed cross-sectional shape in which the one vertical rib portion, the other vertical rib portion, the upper horizontal rib portion, and the lower horizontal rib portion are connected to form a polygon, thereby increasing the reinforcing force of the joining plate provided by the rib.

[0011] The distance between the end of the upper horizontal rib in the extension direction and the upper flange may be wider than the distance between the center of the upper horizontal rib in the extension direction of the steel beam portion and the upper flange, and the distance between the end of the lower horizontal rib in the extension direction and the lower flange may be wider than the distance between the center of the lower horizontal rib in the extension direction and the lower flange. This makes it easier to insert the column fixing bolt into the insertion hole of the flange.

[0012] The upper horizontal rib may be located near the lower end of the uppermost bolt insertion hole of the joining plate, and the lower horizontal rib may be located near the upper end of the lowermost bolt insertion hole of the joining plate. This allows the tensile force of the beam fixing bolts inserted into the bolt insertion holes and fastened to the joining plate to be transmitted to the lower horizontal rib as close as possible to the beam fixing bolts. Furthermore, by making the vertical lengths of the first longitudinal rib and the second longitudinal rib and the welding length to the web as long as possible, the reinforcing force of the joining plate can be further increased.

[0013] The beam section may have an upper vertical plate welded to the center of the upper horizontal rib in the extension direction of the steel beam section, extending upward and welded to the joining plate, and a lower vertical plate welded to the center of the lower horizontal rib in the extension direction, extending downward and welded to the joining plate. This makes it possible to further increase the reinforcing force of the joining plate by the upper vertical plate and the lower vertical plate welded to the rib section and the joining plate.

[0014] Alternatively, the upper horizontal rib may be divided into an upper first section and an upper second section at the center in the extension direction of the steel beam section, with either the upper first section or the upper second section having an upper vertical plate section extending upward at the center and welded to the joining plate, and the lower horizontal rib may be divided into a lower first section and a lower second section at the center in the extension direction of the steel beam section, with either the lower first section or the lower second section having a lower vertical plate section extending downward at the center and welded to the joining plate. This allows the upper vertical plate section and the lower vertical plate section to further increase the reinforcing force of the joining plate.

[0015] The joining plate may be provided with a nut portion or a female screw into which the beam fixing bolt is screwed, which makes it possible to screw the beam fixing bolt also into the inner portion of the rib. [Effects of the Invention]

[0016] The present invention has the advantage that it can be easily manufactured using a welding robot and stress concentration is unlikely to occur. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic perspective view showing a beam joining structure in which another beam (sub-beam) is joined to the side surface of a beam member (main beam) of an embodiment. [Figure 2]Figure 1(A) is an explanatory diagram showing an intermediate product in which a rib is welded to the joining plate of Figure 1, and Figure 1(B) is an explanatory diagram showing the welding points of the upper vertical plate portion and the lower vertical plate portion to the rib. [Figure 3] 1A is a schematic perspective view showing an intermediate product in which a rib is welded to the joining plate of FIG. 1, and FIG. 1B is a schematic perspective view of the same product as seen from another direction. [Figure 4] FIG. 2 is a schematic perspective view showing a beam member according to the embodiment. [Figure 5] 1A is an explanatory diagram showing a modified example of the formation of upper and lower vertical plate portions for a rib, and FIG. 1B is an explanatory diagram showing the state of the divided rib before welding. [Figure 6] 10 is an explanatory diagram showing a modified example of the state of the divided rib before welding. FIG. [Figure 7] 10A and 10B are explanatory diagrams showing modified examples of the rib. [Figure 8] FIG. 10 is an explanatory diagram showing an example of an intermediate manufactured product in which a rib and a nut are welded to a joining plate. [Figure 9] FIG. 10 is a diagram showing a conventional example, and is an explanatory diagram showing an intermediate product in which a plate rib is welded to a joining plate. [Figure 10] 10 is an explanatory diagram showing locations where stress concentration occurs in an intermediate manufactured product using a joining plate with a U-shaped cross section having vertical ribs on both sides. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. 1 shows a beam connection structure 9 in which another beam (sub-beam) 8 is connected to the side of a beam member (main beam) 1 of the embodiment. The beam member 1 includes an H-shaped steel beam portion 2, a connecting plate 3, and a rib 4 welded to the back surface of the connecting plate 3.

[0019] The H-shaped steel beam 2 has an upper flange 21, a lower flange 22, and a web 23 connecting the upper flange 21 and the lower flange 22. The upper flange 21 and the lower flange 22 of the H-shaped steel beam 2 have a plurality of insertion holes 2a formed in the vertical direction, through which column fixing bolts (not shown) are inserted.

[0020] The joining plate 3 is disposed on the side of the H-shaped steel beam 2 at the location where the insertion hole 2a is formed, and is welded and fixed to the edges of the upper flange 21 and the lower flange 22. An end plate 81 of the other beam 8 is fixed to this joining plate 3 so as to face it. A bolt insertion hole 81a is formed in the horizontal direction in this end plate 81, and a beam fixing bolt (such as a regular bolt) 82 is passed through this bolt insertion hole 81a and fastened to a nut portion on the joining plate 3 side. As a result, the beam 8 is fixed to the H-shaped steel beam 2 by tension connection of the beam fixing bolt 82.

[0021] 2(A) shows an intermediate product in which a rib 4 is welded to a joining plate 3, and FIG. 2(B) shows the welding locations of an upper vertical plate portion 51 and a lower vertical plate portion 52 to the rib 4. The rib 4 has a rectangular closed cross-sectional shape consisting of one vertical rib portion 41 and the other vertical rib portion 42 that face each other and are spaced apart in the extension direction of the H-shaped steel beam 2, an upper horizontal rib portion 43 connected to the upper ends of the one vertical rib portion 41 and the other vertical rib portion 42, and a lower horizontal rib portion 44 connected to the lower ends of the one vertical rib portion 41 and the other vertical rib portion 42. The rib 4 has a plate width corresponding to the distance between the joining plate 3 and the web 23, and the end faces of the one vertical rib portion 41 and the other vertical rib portion 42 that face the H-shaped steel beam 2 are welded to the web 23, as described below.

[0022] Two bolt insertion holes 3a are formed horizontally in a position above the upper horizontal rib portion 43 and a position below the lower horizontal rib portion 44 of the joining plate 3. The upper horizontal rib portion 43 is close to the lower end of the upper bolt insertion hole 3a, and the lower horizontal rib portion 44 is close to the upper end of the lower bolt insertion hole 3a. Since nuts are attached to the beam fixing bolts 82 inserted into the bolt insertion holes 3a, the proximity is set to a range within which the nuts can be attached.

[0023] In this embodiment, an upper vertical plate 51 extending upward is fixed by welding to the center of the upper horizontal rib 43 in the extension direction of the H-shaped steel beam 2. Furthermore, a lower vertical plate 52 extending downward is fixed by welding to the center of the lower horizontal rib 44 in the extension direction of the H-shaped steel beam 2. The upper vertical plate 51 and the lower vertical plate 52 have a plate width equivalent to the distance between the joining plate 3 and the web 23. The upper vertical plate 51 and the lower vertical plate 52 are not essential.

[0024] 3(A) and 3(B), the entire outer periphery of the end face of the rib 4 that contacts the joining plate 3 is single-sided fillet welded to the joining plate 3. In addition, both side edges of the end faces of the upper vertical plate portion 51 and the lower vertical plate portion 52 that contact the joining plate 3 are also welded to the joining plate 3. Note that in FIG. 3(A) and other figures, the welded areas are shown in black, but in FIG. 3(B) and other figures, which show hidden lines, the hidden welded areas are shown with a dotted pattern.

[0025] As shown in Figure 4, in the production of the beam member 1, the intermediate product in which the rib 4 is welded to the joining plate 3 as described above is welded to the H-shaped steel beam section 2. In the production of this beam member 1, the upper edge of the joining plate 3 is welded to the upper flange 21 of the H-shaped steel beam section 2, and the lower edge of the joining plate 3 is welded to the lower flange 22 of the H-shaped steel beam section 2.

[0026] The one vertical rib portion 41 of the rib 4 is single-sided fillet welded to the web 23 of the H-shaped steel beam portion 2 on the outside of the end face that contacts the web 23, and the other vertical rib portion 42 is single-sided fillet welded to the web 23 on the outside of the end face that contacts the web 23. All or part of the upper horizontal rib portion 43 and the lower horizontal rib portion 44 may be welded to the web 23, but in this embodiment, they are not welded to the web 23 to make it suitable for use with a welding robot. The upper vertical plate portion 51 and the lower vertical plate portion 52 are not welded to the web 23 using a welding robot. Note that the welding work for producing the intermediate product is not performed in the position shown in FIG. 4, but in a position tilted 90 degrees from this position and with the intermediate product positioned on top.

[0027] The upper horizontal rib portion 43 and the lower horizontal rib portion 44 of the rib 4 are located at a distance from the upper flange 21 and the lower flange 22, respectively, that allows the column fixing bolt to be inserted into the insertion hole 2a.

[0028] In the beam joint structure 9 having the above-mentioned beam member 1, the force acting on the joint plate 3 due to the tensile force acting on the beam fixing bolt 82 is transmitted from the upper horizontal rib portion 43 and the lower horizontal rib portion 44 welded to the joint plate 3 through the one vertical rib portion 41 and the other vertical rib portion 42 to the web 23 of the H-shaped steel beam portion 2.

[0029] In the beam member 1, the first longitudinal rib portion 41 and the second longitudinal rib portion 42 are opposed to each other at a distance in the extension direction of the H-shaped steel beam portion 2 and can be positioned close to the edge of the joining plate 3. This allows the first longitudinal rib portion 41 and the second longitudinal rib portion 42 to be easily welded to the web 23 of the H-shaped steel beam portion 2 using a welding robot without being obstructed by the joining plate 3. This reduces welding defects that occur when using a welding robot, and also enables good inspection of welding quality using a camera. Note that it is preferable to position the first longitudinal rib portion 41 and the second longitudinal rib portion 42 as close as possible to the edge of the joining plate 3, because the joining plate 3 is less likely to interfere with welding the first longitudinal rib portion 41 and the second longitudinal rib portion 42 to the web 23 and the inspection.

[0030] Furthermore, the upper horizontal rib portion 43 and the lower horizontal rib portion 44 are located at a distance from the upper flange 21 and the lower flange 22, respectively, that allows the column fixing bolt to be inserted into the insertion hole 2a, and since the joining plate 3 does not have a notch formed therein for inserting the column fixing bolt, problems such as stress concentration that occur in structures that have such notches can be avoided.

[0031] When the rib 4 has a closed cross-sectional shape in which one vertical rib portion 41, the other vertical rib portion 42, the upper horizontal rib portion 43 and the lower horizontal rib portion 44 are connected to form a polygon, the reinforcing force of the joining plate 3 by the rib 4 can be increased.

[0032] When the upper horizontal rib portion 43 is close to the lower end of the uppermost bolt insertion hole 3a of the joining plate 3 and the lower horizontal rib portion 44 is close to the upper end of the lowermost bolt insertion hole 3a of the joining plate 3, in the beam joining structure 9 including the beam member 1, the tensile force generated in the beam fixing bolt 82 can be transmitted to the horizontal rib portions 43, 44 as close as possible to the beam fixing bolt 82. In addition, the vertical lengths of the one longitudinal rib portion 41 and the other vertical rib portion 42 and the welding length to the web 23 can be made as long as possible, thereby further increasing the reinforcing force of the joining plate 3.

[0033] The provision of an upper vertical plate 51 welded to the center of the upper horizontal rib 43 in the extension direction of the H-shaped steel beam 2 and extending upward, and a lower vertical plate 52 welded to the center of the lower horizontal rib 44 in the extension direction of the H-shaped steel beam 2 and extending downward, can further increase the reinforcing force of the joining plate 3. Of course, a structure without the upper vertical plate 51 and the lower vertical plate 52 is also possible.

[0034] The upper vertical plate portion 51 and the lower vertical plate portion 52 are not limited to being manufactured as separate members from the rib 4 as described above. For example, as shown in Figures 5(A) and 5(B), the upper horizontal rib portion 43 may be divided into an upper first portion 43a and an upper second portion 43b at the center in the extension direction of the H-shaped steel beam portion 2, and the upper vertical plate portion 51 may be formed by extending upward from the upper second portion 43b, which is either the upper first portion 43a or the upper second portion 43b, at the center and welded to the joining plate 3. Similarly, the lower horizontal rib portion 44 may be divided into a lower first portion 44a and a lower second portion 44b at the center in the extension direction of the H-shaped steel beam portion 2, and the lower vertical plate portion 52 may be formed by extending downward from the lower first portion 44a, which is either the lower first portion 44a or the lower second portion 44b, at the center and welded to the joining plate 3. That is, the one vertical rib portion 41, the upper first portion 43a, the lower first portion 44a and the lower vertical plate portion 52 may be formed by bending a single plate, and the upper vertical plate portion 51, the upper second portion 43b and the lower second portion 44b may be formed by bending a single plate.

[0035] These bent members are welded so that the divided upper first portion 43a and upper second portion 43b are connected to each other, and also so that the divided lower first portion 44a and lower second portion 44b are connected to each other. However, the structure may be left divided without such welding, although this weakens the reinforcing force of the joining plate 3. The insufficient reinforcing force can be compensated for by increasing the plate thickness of the joining plate 3 and the plate thickness of the rib 4.

[0036] 6, the upper horizontal rib 43 may be divided into an upper first portion 43a and an upper second portion 43b at the center in the extension direction of the H-shaped steel beam 2, and may have an upper vertical plate portion 51 extending upward from the upper first portion 43a, which is either the upper first portion 43a or the upper second portion 43b, at the center and welded to the joining plate 3. Alternatively, the lower horizontal rib 44 may be divided into a lower first portion 44a and a lower second portion 44b at the center in the extension direction of the H-shaped steel beam 2, and may have a lower vertical plate portion 52 extending downward from the lower first portion 44a, which is either the lower first portion 44a or the lower second portion 44b, at the center and welded to the joining plate 3. That is, the upper vertical plate portion 51, the upper first portion 43a, the one vertical rib portion 41, the lower first portion 44a and the lower vertical plate portion 52 may be formed by bending a single plate, and the upper second portion 43b, the other vertical rib portion 42 and the lower second portion 44b may be formed by bending a single plate.

[0037] These bent members are welded so that the divided upper first portion 43a and upper second portion 43b are connected to each other, and so that the divided lower first portion 44a and lower second portion 44b are connected to each other. However, although this weakens the reinforcing force of the joining plate 3, the divided structure may be left as is without such welding. Alternatively, the divided structure may be left as is without the upper vertical plate portion 51 and the lower vertical plate portion 52. That is, such a structure also has an upper horizontal rib portion 43 (the upper first portion 43a and the upper second portion 43b in the divided state (gap forming state)) connected to the upper ends of the one vertical rib portion 41 and the other vertical rib portion 42, and a lower horizontal rib portion 44 (the lower first portion 44a and the lower second portion 44b in the divided state (gap forming state)) connected to the lower ends of the one vertical rib portion 41 and the other vertical rib portion 42. Furthermore, in the rib 4 structures described above and below, the one vertical rib portion 41 and the other vertical rib portion 42 may be divided at the center in the vertical direction. Even in these structures, any insufficient reinforcing force can be compensated for by increasing the thickness of the joining plate 3 or the rib 4.

[0038] As shown in FIG. 7 , the distance between the end of the upper cross rib 43 in the extension direction of the H-shaped steel beam 2 and the upper flange 21 may be wider than the distance between the center of the upper cross rib 43 in the extension direction of the H-shaped steel beam 2 and the upper flange 21, and the distance between the end of the lower cross rib 44 in the extension direction and the lower flange 22 may be wider than the distance between the center of the lower cross rib 44 in the extension direction and the lower flange 22. This allows for easy insertion of column fixing bolts into the insertion holes 22a of the flanges 21 and 22, while also allowing the upper cross rib 43 and the lower cross rib 44 to be located close to the bolt insertion holes 3a. In the rib 4 shown in FIG. 7 , the center of the upper cross rib 43 has a mountain-like shape that protrudes upward, and the center of the lower cross rib 44 has a valley-like shape that protrudes downward. The rib 4 has a closed hexagonal cross section overall.

[0039] In the above example, nuts are individually fastened on-site to the beam-fixing bolts 82 passed through the bolt insertion holes 3a outside the enclosed area surrounded by the first vertical rib portion 41, the second vertical rib portion 42, the upper horizontal rib portion 43, and the lower horizontal rib portion 44. However, as shown in FIG. 8 , a structure may be adopted in which, inside the enclosed area, four bolt insertion holes 3a are formed, for example, in two rows and two columns, and nuts 35 onto which the beam-fixing bolts 82 passed through the bolt insertion holes 3a are threaded are welded or caulked to the joining plate 3, thereby integrally providing the nut portions on the joining plate 3. This allows another beam 8 to be joined to the beam member 1 using many beam-fixing bolts 82. Alternatively, a plate member having multiple female threads (tapped screw holes) aligned with the arrangement of the bolt insertion holes 3a may be welded to the joining plate 3. FIG. 8 also shows an example structure that does not have an upper vertical plate portion 51 or a lower vertical plate portion 52.

[0040] Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiments within the same scope as the present invention or within an equivalent scope. [Explanation of symbols]

[0041] 1: Beam member 2: H-shaped steel beam section 2a: Insertion hole 3: Joint plate 3a: Bolt insertion hole 4: Rib 8: Another beam 9: Beam joint structure 21: Upper flange 22: Lower flange 22a: Insertion hole 23: Web 35: Nut 41: One side vertical rib 42: Other longitudinal rib part 43: Upper horizontal rib 43a: Upper 1st part 43b: Upper 2nd part 44: Lower horizontal rib 44a:Lower 1st part 44b: Lower 2nd part 51: Upper vertical plate 52: Lower vertical plate part 81: End plate 81a: Bolt insertion hole 82: Bolt

Claims

1. The present invention comprises a steel beam portion having an upper flange, a lower flange, and a web, a joining plate welded to the edges of the upper flange and the lower flange on the side of the steel beam portion, and to which an end plate of another beam is fastened with a beam fixing bolt, and a rib welded to the back surface of the joining plate, The rib includes a first longitudinal rib portion and a second longitudinal rib portion that are opposed to each other and spaced apart in the extension direction of the steel beam portion and welded to the web, an upper horizontal rib portion connected to upper ends of the first vertical rib portion and the second vertical rib portion, and a lower horizontal rib portion connected to lower ends of the first vertical rib portion and the second vertical rib portion, A beam member characterized in that the upper flange and the lower flange have vertically formed through-holes through which column fixing bolts are inserted, and the upper horizontal rib portion and the lower horizontal rib portion are located at a distance from the upper flange and the lower flange, respectively, that allows the column fixing bolts to be inserted into the through-holes.

2. 2. The beam member according to claim 1, wherein the rib has a closed cross-sectional shape in which the one vertical rib portion, the other vertical rib portion, the upper horizontal rib portion and the lower horizontal rib portion are connected to form a polygon.

3. In a beam member as described in claim 1 or claim 2, the distance between the end side of the upper horizontal rib portion in the extension direction and the upper flange is wider than the distance between the center side of the upper horizontal rib portion in the extension direction of the steel beam portion and the upper flange, and the distance between the end side of the lower horizontal rib portion in the extension direction and the lower flange is wider than the distance between the center side of the lower horizontal rib portion in the extension direction and the lower flange.

4. A beam member as described in any one of claims 1 to 3, characterized in that the upper horizontal rib portion is close to the lower end side of the uppermost bolt insertion hole of the joining plate, and the lower horizontal rib portion is close to the upper end side of the lowermost bolt insertion hole of the joining plate.

5. A beam member as described in any one of claims 1 to 4, characterized in that it has an upper vertical plate portion welded to the center of the extension direction of the steel beam portion of the upper horizontal rib portion, extending upward and welded to the joining plate, and a lower vertical plate portion welded to the center of the extension direction of the lower horizontal rib portion, extending downward and welded to the joining plate.

6. A beam member according to any one of claims 1 to 4, characterized in that the upper horizontal rib portion is divided into an upper first portion and an upper second portion at the center side in the extension direction of the steel beam portion, and either the upper first portion or the upper second portion has an upper vertical plate portion extending upward at the center side and welded to the joining plate, and the lower horizontal rib portion is divided into a lower first portion and a lower second portion at the center side in the extension direction of the steel beam portion, and either the lower first portion or the lower second portion has a lower vertical plate portion extending downward at the center side and welded to the joining plate.

7. 7. The beam member according to claim 1, wherein the joining plate is provided with a nut portion or a female screw into which the beam fixing bolt is screwed.

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