JP6261976B2 - Cross section beam - Google Patents

Description

  The present invention relates to a steel variable cross-section beam in which the beam formation at the beam end portion is larger than the beam formation at the beam center portion.

  In recent years, steel variable cross-section beams, in which the beam formation at the end of the beam is larger than the beam formation at the center of the beam, are used in buildings. For example, Patent Document 1 discloses a cross-section beam in which a prefabricated H-shaped steel with a large beam is joined to both ends of a prefabricated H-shaped steel with a small beam so that the upper surfaces of the upper flanges are flush with each other. ing.

  In the cross section beam of Patent Document 1, a reinforcing plate provided by extending the lower flange of the beam center is joined to the web of the beam end, so that the axial force of the lower flange of the beam center is applied to the web of the beam end. The beam is transmitted to the end of the beam by the shearing force of the beam, so that the beam cross section is sized according to the stress distribution, enabling rational design of the beam and minimizing the amount of steel frame.

  However, such a cross-section beam has a lower lateral buckling strength than a general steel beam because the lower flange of the beam center and the lower flange of the beam end are not continuously connected. Accordingly, when the lateral buckling restraining effect of the variable cross-section beam obtained by the floor slab supported by the variable cross-section beam is not sufficient, it is necessary to take measures to improve the lateral buckling strength of the lateral stiffener.

JP 2011-52462 A

  This invention considers the fact which concerns, and makes it a subject to improve the lateral buckling proof strength of a cross-section beam.

  The invention of the first aspect includes a steel beam center portion having a lower flange, a web and an upper flange, and a lower flange, a web and an upper flange, which are connected to the beam center portion, and the beam is formed more than the beam center portion. A steel beam end to which the upper flange and the upper flange of the beam central portion or the lower flange and the lower flange of the beam central portion are connected to the lower flange or the upper flange of the beam central portion. A lateral plate that suppresses lateral buckling that occurs in at least one of the beam center portion and the beam end portion provided on the beam end portion web around the reinforcement plate, and a reinforcing plate joined to the beam end web And a bending cross-section beam.

  In the invention of the first aspect, by providing a lateral buckling suppression portion on the web at the end of the beam located around the reinforcing plate, the lateral buckling that occurs in at least one of the beam center and the beam end is suppressed, and the cross section beam The lateral buckling strength of can be improved.

  According to a second aspect of the present invention, in the variable cross-section beam according to the first aspect, the lateral buckling suppression portion is provided between the lower flange of the beam end and the reinforcing plate, and between the reinforcing plate and the upper flange of the beam end. It is the rib provided in the up-down direction in at least one between.

  In the invention of the second aspect, the rib can suppress the deformation of the lower flange or the upper flange of at least one of the beam center portion and the beam end portion out of the plane and improve the lateral buckling strength of the cross section beam. it can.

  According to a third aspect of the invention, in the cross-section beam according to the first aspect, the lateral buckling suppression portion connects the column joint portion of the upper flange of the beam end and the end of the lower flange of the beam end, or It is an extending portion of the reinforcing plate provided so as to exceed a diagonal line connecting a column joint portion of the lower flange of the beam end portion and an end portion of the upper flange of the beam end portion.

  In the invention of the third aspect, the column joint of the upper flange of the beam end and the end of the lower flange of the beam end are connected, or the end of the column flange of the lower flange of the beam end and the upper flange of the beam end. By providing the reinforcing plate so that it crosses the diagonal line connecting the parts, the reinforcing plate is arranged so as to straddle the diagonal line. The lateral buckling strength of the beam can be improved.

  Since this invention set it as the said structure, the lateral buckling proof strength of a cross-section beam can be improved.

It is a front view which shows the cross section beam which concerns on 1st Embodiment of this invention. It is a front view which shows the variation of the cross section beam which concerns on 1st Embodiment of this invention. It is a front view which shows the variation of the cross section beam which concerns on 1st Embodiment of this invention. It is a front view which shows the variation of the cross section beam which concerns on 1st Embodiment of this invention. It is a front view which shows the variation of the cross section beam which concerns on 1st Embodiment of this invention. It is a front view which shows the cross section beam which concerns on 2nd Embodiment of this invention. It is a front view which shows the variable cross-section beam concerning 3rd Embodiment of this invention. It is AA sectional drawing of FIG. 7, and sectional drawing which shows the variation of the web reinforcement member which concerns on 3rd Embodiment of this invention. It is an elevational view showing a variable cross-section beam according to the first to third embodiments of the present invention. It is an elevation which shows the variation of the cross-section beam which concerns on 1st-3rd embodiment of this invention. It is an elevation which shows the variation of the cross-section beam which concerns on 1st-3rd embodiment of this invention. It is a front view which shows the variation of the cross section beam which concerns on 1st-3rd embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. First, the cross section beam according to the first embodiment of the present invention will be described.

  In the front view of FIG. 1, a variable cross-section beam 10 in which one beam end portion 16 is supported on a steel column 12 is shown. The cross section beam 10 is provided as a large beam. In FIG. 1, the left side portion of the cross section beam 10 is depicted, but the right side portion has the same configuration as the left side portion, and is a steel column (hereinafter referred to as “column”) disposed opposite the column 12. 14 ”), the other beam end of the variable cross-section beam 10 is supported. That is, the variable cross-section beam 10 is installed between the column 12 and the column 14.

  The cross section beam 10 includes a beam center portion 24 made of an H-shaped steel having a lower flange 18, a web 20 and an upper flange 22, and a beam end made of an H-shaped steel having a lower flange 26, a web 28 and an upper flange 30. It has the part 16, the reinforcement plate 32 which consists of a steel plate, and the lateral buckling suppression part 34, and is comprised.

  The beam center portion 24 and the beam end portion 16 include an upper flange 22 end surface of the beam center portion 24, an upper flange 30 end surface of the beam end portion 16, a web 20 end surface of the beam center portion 24, and a web 28 end surface of the beam end portion 16. They are connected together by welding. The beam center portion 24 and the beam end portion 16 may be joined by other joining methods such as bolt joining.

  The beam formation of the beam end portion 16 is larger than the beam formation of the beam center portion 24. The upper surface of the beam central portion 24 (upper flange 22) and the upper surface of the beam end portion 16 (upper flange 30) are flush with each other, and the width of the upper flange 22 is smaller than the width of the upper flange 30. . The upper flange 22 of the beam central portion 24 and the upper flange 30 of the beam end portion 16 may have different or equal widths as long as the upper surfaces are flush with each other. For example, the width of the upper flange 22 and the width of the upper flange 30 may be made equal so that the upper flange 22 end surface of the beam center portion 24 and the end surface of the upper flange 30 of the beam end portion 16 coincide with each other. If the upper flange 22 of the beam central portion 24 and the upper flange 30 of the beam end portion 16 are connected, the upper surfaces of the upper flange 22 and the upper flange 30 may not be flush with each other. Here, the connection between the upper flange 22 and the upper flange 30 means that the upper flange 22 and the upper flange 30 are in contact with each other. For example, the upper flange 22 and the upper flange 30 having different plate thicknesses may be connected with their lower surfaces being flush with each other, or may be connected such that the centers of the plate thicknesses are aligned.

  The reinforcing plate 32 is disposed on the extension line of the lower flange 18 of the beam center portion 24, and the rear end portion is joined to the end portion of the lower flange 18 of the beam center portion 24 by welding and connected to the lower flange 18. . Further, the reinforcing plate 32 is joined to the web 28 of the beam end portion 16 by welding at the side end portion.

  The reinforcing plate 32 is provided to transmit the axial force of the lower flange 18 of the beam central portion 24 to the beam end portion 16 by the shearing force of the web 28 of the beam end portion 16. The reinforcing plate 32 has a length such that the tip end portion 42 does not reach the side surface of the column 12 (the tip end portion 42 is located on the center side of the variable cross section beam 10 with respect to the end surface of the variable cross section beam 10). The reinforcing plate 32 is not provided to be joined to the end portion of the lower flange 18 of the beam center portion 24, and the lower flange 18 of the beam center portion 24 protrudes from the end surface of the beam center portion 24 (end surface of the web 20). The protruding portion may be the reinforcing plate 32.

  The lateral buckling suppressing portion 34 is made of a steel plate as a rib provided in the vertical direction between the lower flange 26 of the beam end portion 16 and the reinforcing plate 32 and between the reinforcing plate 32 and the upper flange 30 of the beam end portion 16. The vertical ribs 44 and 46 are configured to suppress lateral buckling occurring in at least one of the beam center portion 24 and the beam end portion 16. The vertical ribs 44 and the vertical ribs 46 are arranged on a straight line in the vertical direction. The vertical ribs 44 and the vertical ribs 46 may be arranged on a straight line obliquely with respect to the vertical direction.

  The lower end of the vertical rib 44 is on the upper surface of the lower flange 26, the side end of the vertical rib 44 is on the web 28, the upper end of the vertical rib 44 is on the lower surface of the reinforcing plate 32, and the lower end of the vertical rib 46 is on the reinforcing plate 32. The side ends of the vertical ribs 46 are joined to the web 28 and the upper ends of the vertical ribs 46 are joined to the lower surface of the upper flange 30 by welding. That is, the lateral buckling suppressing portion 34 is provided on the web 28 of the beam end portion 16 located around the reinforcing plate 32.

  The reinforcing plate 32 and the vertical ribs 44 and 46 are provided in the same arrangement on the front and back surfaces of the web 28 of the beam end portion 16.

  The beam end portion 28 is joined to diaphragms 38 and 40 provided in the joint portion 36 of the column 12 by welding the end portions of the lower flange 26 and the upper flange 30, respectively, so that the side surface of the column 12 (joint portion 36). In addition, the end portion of the web 28 is joined to the joint portion 36 of the column 12 by welding. In addition, you may join the side surface of the pillar 12 (joint part 36), and the edge part of the web 28 with other joining methods, such as bolt joining.

  A floor slab 48 made of reinforced concrete is formed on the variable cross-section beam 10 by placing concrete. The floor slab 48 is provided integrally with the variable cross-section beam 10 by a stud 50 provided on the upper surface of the upper slabs 22 and 30 of the variable cross-section beam 10 and embedded in the floor slab 48. The floor slab 48 may be a floor slab having another configuration such as a deck slab or a precast slab.

  Next, the action and effect of the cross section beam according to the first embodiment of the present invention will be described.

  In the variable cross-section beam 10 according to the first embodiment of the present invention, as shown in FIG. 1, at least one of the lower flanges 26 and 18 of the beam end portion 16 and the beam center portion 24 and the reinforcing plate by the longitudinal ribs 44 and 46. It can suppress that 32 deform | transforms out of a plane. That is, by providing the lateral buckling suppressing portion 34 on the web 28 of the beam end portion 16 located around the reinforcing plate 32, the lateral buckling occurring in at least one of the beam central portion 24 and the beam end portion 16 is suppressed, and the cross section is changed. The lateral buckling strength of the beam 10 can be improved. For example, the lateral buckling strength can be increased as compared with a conventional variable cross-section beam that is reinforced only by a reinforcing plate.

  Further, in the variable cross-section beam 10 of the first embodiment of the present invention, the reinforcing plate 32 is provided so that the front end portion 42 of the reinforcing plate 32 does not reach the side surface of the column 12. It is possible to prevent the portion 36 from having a complicated structure, and it is possible to reduce time and labor when joining the cross section beam 10 to the column 12. For example, a diaphragm for allowing the axial force acting on the reinforcing plate 32 to flow to the column 12 may not be provided in the joint portion 36. Further, for example, the troublesome work of joining both the end portion of the web 28 of the cross section beam 10 and the end portion of the reinforcing plate 32 to the side surface of the column 12 (joint portion 36) can be eliminated. . By these, the workability at the time of joining the cross section beam 10 to the column 12 can be improved.

  The first embodiment of the present invention has been described above.

  In the first embodiment of the present invention, as shown in FIG. 1, the lateral buckling suppressing portion 34 is provided between the lower flange 26 of the beam end portion 16 and the reinforcing plate 32 and between the reinforcing plate 32 and the beam end portion 16. Although the example which comprised the vertical ribs 44 and 46 provided in the up-down direction between the upper flanges 30 was shown, a lateral buckling suppression part is between the lower flange 26 and the reinforcement plate 32 of the beam end part 16, The ribs provided in the vertical direction may be provided on at least one of the reinforcing plate 32 and the upper flange 30 of the beam end portion 16. The vertical ribs 44, 46 only have to have at least one of the upper and lower ends joined to the upper flange 30, the lower flange 26, or the reinforcing plate 32.

  For example, the longitudinal ribs 44 and the longitudinal ribs 46 may be shifted in the lateral direction as in the cross-section beams 52 and 54 provided as large beams shown in the front views of FIGS. 4 and 5, like the cross-section beams 56 and 58 provided as large beams, between the lower flange 26 of the beam end 16 and the reinforcing plate 32, and between the reinforcing plate 32 and the beam end 16. The vertical ribs 44 and 46 may be provided only on one side between the upper flanges 30. In addition, for example, the lateral buckling suppressing portion is disposed on at least one between the lower flange 26 of the beam end portion 16 and the reinforcing plate 32 and between the reinforcing plate 32 and the upper flange 30 of the beam end portion 16 with respect to the vertical direction. You may comprise with the rib provided diagonally.

  Further, if the lateral buckling suppressing portion is provided on the web 28 of the beam end portion 16 located around the reinforcing plate 32, the upper and lower end portions are welded to the upper flange 30 and the lower flange 26 of the beam end portion 16, respectively. May be configured to have ribs that are joined together and arranged away from the tip portion 42 of the reinforcing plate 32.

  Moreover, in 1st Embodiment of this invention, although the reinforcement plate 32 and the vertical ribs 44 and 46 were provided in the front and back of the web 28 of the beam end part 16, the reinforcement plate 32 and the vertical rib 44 were shown. , 46 may be provided only on one of the front and back surfaces of the web 28 at the beam end 16.

  Next, a second embodiment of the present invention will be described. In the description of the second embodiment of the present invention, the same components as those in the first embodiment are denoted by the same reference numerals, and are appropriately omitted.

  First, a cross section beam according to a second embodiment of the present invention will be described. As shown in the front view of FIG. 6, in the cross section beam 60 of the second embodiment, the column joint portion 62 (left end portion) of the upper flange 30 of the beam end portion 16 and the end portion of the lower flange 26 of the beam end portion 16. An extended portion 68 of the reinforcing plate 32 provided so as to exceed the oblique line 66 connecting 64 (right end portion) is a lateral buckling suppressing portion 70. That is, the lateral buckling suppressing portion 70 is provided on the web 28 of the beam end portion 16 located around the reinforcing plate 32. The cross section beam 60 is provided as a large beam.

  The extending portion 68 may be configured by setting the length of the reinforcing plate 32 to a length exceeding the oblique line 66, or may be configured by joining a steel plate to the end of the reinforcing plate 32 by welding. Good.

  The reinforcing plate 32 has a distal end portion 42 (the distal end portion of the extending portion 68) that does not reach the side surface of the column 12 (the distal end portion 42 is located closer to the center of the variable cross section beam 60 than the end surface of the variable cross section beam 60). It has become.

  Next, the operation and effect of the cross section beam according to the second embodiment of the present invention will be described.

  In the cross section beam 60 according to the second embodiment of the present invention, as shown in FIG. 6, the reinforcing plate 32 is disposed so as to straddle the oblique line 66 by providing the reinforcing plate 32 so as to exceed the oblique line 66. Therefore, the fracture mode in which the vicinity of the oblique line 66 is a fracture line is suppressed by the reinforcing plate 32, and the lateral buckling strength of the variable cross-section beam 60 can be improved.

  Further, in the variable cross-section beam 60 of the second embodiment of the present invention, the reinforcing plate 32 is provided so that the tip portion 42 of the reinforcing plate 32 does not reach the side surface of the column 12. It is possible to prevent the portion 36 from having a complicated structure, and it is possible to reduce time and labor when joining the cross section beam 60 to the column 12.

  Next, a third embodiment of the present invention will be described. In the description of the third embodiment of the present invention, components having the same configurations as those of the first embodiment are denoted by the same reference numerals and are appropriately omitted.

  First, a cross section beam according to a third embodiment of the present invention will be described. As shown in FIG. 8A which is a front view of FIG. 7 and a cross-sectional view taken along line AA of FIG. 7, in the variable cross-section beam 72 of the third embodiment, the lower flange 26 and the reinforcing plate 32 of the beam end portion 16. A backing plate 74 made of a steel plate as a web reinforcing member attached to the web 28 between the two by fillet welding serves as a lateral buckling suppressing portion 76. The backing plate 74 is provided on the front and back surfaces of the web 28. That is, the lateral buckling suppressing portion 76 is provided on the web 28 of the beam end portion 16 located around the reinforcing plate 32. The cross section beam 72 is provided as a large beam.

  Next, the operation and effect of the cross section beam according to the third embodiment of the present invention will be described.

  In the cross section beam 72 according to the third embodiment of the present invention, as shown in FIG. 7, the member that bears the shearing force acting on the web 28 between the lower flange 26 of the beam end portion 16 and the reinforcing plate 32 is cut off. By increasing the area by the contact plate 74, shear deformation generated in the web 28 can be suppressed and the lateral buckling strength of the variable cross-section beam 72 can be improved.

  The third embodiment of the present invention has been described above.

  In the third embodiment of the present invention, an example in which the backing plate 74 is provided on the front and back surfaces of the web 28 has been described. However, the backing plate 74 may be provided only on one surface of the front and back surfaces of the web 28.

  Further, in the third embodiment of the present invention, an example in which the web reinforcement member is the backing plate 74 has been shown. However, as long as shear deformation generated in the web 28 can be suppressed, the web reinforcement member is a member having any shape. Also good. For example, as shown in the cross-sectional views of FIGS. 8B and 8C, a shape steel 78 having an L-shaped structural cross section or a shape steel 80 having a T-shaped structural cross section may be used as the web reinforcing member. Good.

  The first to third embodiments of the present invention have been described above.

  In the first to third embodiments, as shown in the elevation views of FIGS. 9A to 9C, the lateral buckling suppressing portions 34, 70, and 76 are formed on steel beams having the same left and right end shapes. However, different lateral buckling suppression portions 34, 70, and 76 may be provided at the left and right ends of the steel beam, respectively.

  Further, the lateral buckling suppression portions 34, 70, 76 may be provided at the ends having the vertical hunches by changing the shapes of the left and right ends of the steel beam. For example, as shown in the elevation views of FIGS. 10A to 10C, the other end portion 82 of the steel beam is not provided with a haunch, and the end portion 82 having the same beam formation as the beam central portion 24 is formed on the beam. It may be rigidly connected to the column. 10 (a) to 10 (d), there are variable cross-section beams 88, 90, 92 in which the end portion 82 of the steel beam is rigidly joined to a small beam 86 made of H-shaped steel by bolt joining using a splice plate 84. It is shown.

  Furthermore, in the first to third embodiments of the present invention, the upper surface of the beam center portion 24 and the upper surface of the beam end portion 16 are flush with each other, and the lower surface of the beam center portion 24 is higher than the lower surface of the beam end portion 16. Although the example in which the lateral buckling suppression portions 34, 70, 76 are provided on the beam to form the variable cross-section beams 10, 52, 54, 56, 58, 60, 72 has been shown, the lower surface of the beam central portion 24 and the beam end portion are shown. The lateral buckling suppression portions 34, 70, 76 may be provided on a steel beam in which the lower surface of the beam 16 is flush and the upper surface of the beam center portion 24 is lower than the upper surface of the beam end portion 16 to form a cross section beam. Good. In this case, as long as the lower flange 18 of the beam center portion 24 and the lower flange 26 of the beam end portion 16 are connected, the lower surfaces of the lower flange 18 and the lower flange 26 do not have to be flush with each other. Here, the connection between the lower flange 18 and the lower flange 26 means that the lower flange 18 and the lower flange 26 are in contact with each other. For example, the lower flange 18 and the lower flange 26 having different plate thicknesses may be connected such that the upper surfaces thereof are flush with each other, or the centers of the plate thicknesses may be connected to each other. In this case, the reinforcing plate 32 is connected to the upper flange 22 of the beam central portion 24 and joined to the web 28 of the beam end portion 16. For example, the cross-section beams 94, 96, and 98 shown in the elevation views of FIGS. Further, one end of the cross-section beam may be as shown in any of FIGS. 1, 6, and 7, and the other end may be as shown in any of FIGS. 11 (a) to (c).

  By connecting the lower flange 18 of the beam center portion 24 and the lower flange 26 of the beam end portion 16 to a steel beam in which the upper surface of the beam center portion 24 is lower than the upper surface of the beam end portion 16, the lateral buckling of the second embodiment is applied. In the case where the restraining portion 70 (see FIG. 6) is applied, the diagonal portion connecting the column joint portion of the lower flange 26 of the beam end portion 16 and the end portion of the upper flange 30 of the beam end portion 16 is exceeded. A reinforcing plate 32 is provided. This also makes it possible to improve the lateral buckling strength of the variable cross-section beam by suppressing the failure mode in which the vicinity of the oblique line is the failure line by the reinforcing plate 32.

  In the first to third embodiments of the present invention, the example in which the cross-section beams 10, 52, 54, 56, 58, 60, and 72 are large beams is shown. However, the first to third embodiments of the present invention are described. The variable cross-section beams 10, 52, 54, 56, 58, 60, and 72 can be applied to steel beams. For example, as shown in the front views of FIGS. 12A to 12C, the cross-section beams 100, 102, and 104 that constitute the small beam by providing the lateral buckling suppression portions 34, 70, and 76 on the steel beam are the large beams 106. You may provide so that it may be supported.

  Further, in the first to third embodiments of the present invention, the columns 12 and 14 are steel columns. However, the columns 12 and 14 are made of reinforced concrete, steel reinforced concrete, CFT (Concrete-Filled Steel). It may be a column having various structures such as a tube (filled steel tube concrete structure).

  The first to third embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and the first to third embodiments may be used in combination. Needless to say, the present invention can be implemented in various forms without departing from the gist of the invention.

10, 52, 54, 56, 58, 60, 72, 88, 90, 92, 94, 96, 98, 100, 102, 104 Cross section beam 16 Beam end 18, 26 Lower flange 20, 28 Web 22, 30 Upper flange 24 Beam center portion 32 Reinforcement plates 34, 70, 76 Lateral buckling suppression portions 44, 46 Vertical rib (rib)
62 Column junction 64 End 66 Diagonal line 68 Extension part

Claims (6)

A steel beam center with a lower flange, a web and an upper flange;
A steel beam end provided with a lower flange, a web and an upper flange, connected to the beam central portion, having a larger beam formation than the beam central portion, and a lower flange connected to the lower flange of the beam central portion; ,
A reinforcing plate connected to the upper flange of the beam central portion and joined to the web of the beam end;
A lateral buckling suppressing portion that is provided on a web of the beam end portion around the reinforcing plate and suppresses lateral buckling that occurs in at least one of the beam center portion and the beam end portion;
A variable cross-section beam.   The lateral buckling suppression portion is a rib provided in a vertical direction between at least one of a lower flange of the beam end and the reinforcing plate and between the reinforcing plate and the upper flange of the beam end. 2. The cross section beam according to 1. The Lateral restraint portion is a extended portion of the reinforcing plate provided so as to exceed the diagonal line connecting the ends of the flanges on the beam end and the pillar junction of the lower flange of the front Kihari end The variable cross-section beam according to claim 1. A steel beam center with a lower flange, a web and an upper flange;
A lower flange, a web, and an upper flange are connected to the beam central portion, the beam formation is larger than the beam central portion, the upper flange is the upper flange of the beam central portion, or the lower flange is below the beam central portion. A steel beam end connected to the flange;
A reinforcing plate connected to the lower flange or the upper flange of the beam central portion and joined to the web of the beam end;
A lateral buckling suppressing portion that is provided on a web of the beam end portion around the reinforcing plate and suppresses lateral buckling that occurs in at least one of the beam center portion and the beam end portion;
Have
The lateral buckling suppression portion is a cross section that is a rib provided in the vertical direction only between one of the lower flange of the beam end and the reinforcing plate and between the reinforcing plate and the upper flange of the beam end. Beams. A steel beam center with a lower flange, a web and an upper flange;
A lower flange, a web, and an upper flange are connected to the beam central portion, the beam formation is larger than the beam central portion, the upper flange is the upper flange of the beam central portion, or the lower flange is below the beam central portion. A steel beam end connected to the flange;
A reinforcing plate connected to the lower flange or the upper flange of the beam central portion and joined to the web of the beam end;
A lateral buckling suppressing portion that is provided on a web of the beam end portion around the reinforcing plate and suppresses lateral buckling that occurs in at least one of the beam center portion and the beam end portion;
Have
The lateral buckling suppression portion is provided in the vertical direction between the lower flange of the beam end and the reinforcing plate, and between the reinforcing plate and the upper flange of the beam end. A cross-section beam, which is a rib that is shifted from the length direction. A steel beam center with a lower flange, a web and an upper flange;
A lower flange, a web, and an upper flange are connected to the beam central portion, the beam formation is larger than the beam central portion, the upper flange is the upper flange of the beam central portion, or the lower flange is below the beam central portion. A steel beam end connected to the flange;
A reinforcing plate connected to the lower flange or the upper flange of the beam central portion and joined to the web of the beam end;
A lateral buckling suppressing portion that is provided on a web of the beam end portion around the reinforcing plate and suppresses lateral buckling that occurs in at least one of the beam center portion and the beam end portion;
Have
The lateral buckling suppression portion is formed on the beam end web between the lower flange of the beam end and the reinforcing plate, or on the beam end web between the reinforcing plate and the upper flange of the beam end. A variable cross-section beam that is a patch plate.

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