JP6174984B2 - Steel beam - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a steel beam that forms a floor step on the upper surface of a floor slab that is installed and supported between columns.

  A steel beam having a haunch at the end can reduce the amount of steel while securing a predetermined resistance bending moment and resistance shearing force, and is used as one of the techniques for building a building at low cost. For example, Patent Document 1 discloses a steel beam with a step formed by connecting an H-shaped steel with a large beam to both ends of an H-shaped steel with a small beam.

  When using such steel beams to form floor steps on the floor surface of the floor slabs that make up the building, generally, steel beams with different beam structures are joined to the joints of the columns, respectively. The floor slabs are formed on these steel beams.

  However, for example, when steel beams with different beam formations are joined to steel joint members as joints embedded in reinforced concrete columns, the force can be reliably transmitted between the columns. In order to join steel beams, it is necessary to make the structure of the joint member complicated, or to provide an additional member such as a core material on the joint member. Furthermore, it is necessary to change the structure of the joint member according to the level difference of the floor level difference. As a result, a lot of labor is required to process the joint portion of the column, and the amount of members increases. This problem can also occur in the case of columns having other structures such as steel structures, steel reinforced concrete structures, and CFT (Concrete-Filled Steel Tube) structures.

JP 2011-52462 A

  This invention considers the fact which concerns, and makes it a subject to form a floor level | step difference by a steel beam, making the structure of the joint part of a pillar the same.

  In the first aspect of the invention, the first beam portion joined to the first joint portion of the first column, and a position higher than the first joint portion of the second column disposed facing the first column A second beam portion joined to the second joint portion, and both ends thereof are connected to the first beam portion and the second beam portion, and the lower surface is flush with the lower surface of the second beam portion. And a step portion is formed between the first beam portion and the lower surface of the first beam portion so that the upper surface is flush with the upper surface of the first beam portion and the upper surface of the second beam portion. A steel beam having a third beam portion that is lower than the second beam portion and forms a step portion with the second beam portion.

  In the invention of the first aspect, by forming a step difference between the third beam portion and the second beam portion by creating a height difference between the upper surface of the third beam portion and the upper surface of the second beam portion, A floor step can be formed by creating a height difference between the floor surface of the floor slab formed on the third beam portion and the floor surface of the floor slab formed on the second beam portion. Thereby, the structure of the joint part of a pillar can be made the same and a floor level difference can be formed with a steel beam. Moreover, by providing the haunch at both ends of the steel beam, the resistance bending moment and the resistance shearing force at both ends of the steel beam can be increased.

  The invention of the second aspect is joined to the first beam portion joined to the first joint portion of the first pillar and the second joint portion of the second pillar arranged to face the first pillar. The second beam portion and both end portions are connected to the first beam portion and the second beam portion, the lower surface is flush with the lower surfaces of the first beam portion and the second beam portion, and the upper surface is the first beam. A steel beam having a third beam portion that is lower than the upper surfaces of the beam portion and the second beam portion and forms a step portion between the first beam portion and the second beam portion.

  In the invention of the second aspect, a difference in height is created between the upper surface of the third beam portion and the upper surfaces of the first and second beam portions, so that the third beam portion is between the first beam portion and the second beam portion. By forming the stepped portion, a floor difference is created between the floor surface of the floor slab formed on the third beam portion and the floor surface of the floor slab formed on the first and second beam portions. A step can be formed. Thereby, the structure of the joint part of a pillar can be made the same and a floor level difference can be formed with a steel beam. Moreover, by providing the haunch at both ends of the steel beam, the resistance bending moment and the resistance shearing force at both ends of the steel beam can be increased.

  In the invention of the third aspect, the first beam portion joined to the first joint portion of the first pillar, and the position higher than the first joint portion of the second pillar disposed to face the first pillar A second beam part that is joined to the second joint part and has a top surface lower than the upper surface of the second joint part to form a stepped part between the second joint part, The first beam part is connected to the second beam part, the lower surface is flush with the lower surface of the second beam part, and is higher than the lower surface of the first beam part. Is a steel beam having a third beam portion having a stepped portion formed on the upper surface and flush with the upper surfaces of the first beam portion and the second beam portion.

  In the invention of the third aspect, a step is formed between the second joint portion and the second beam portion by creating a height difference between the upper surface of the second joint portion and the upper surface of the second beam portion. Thus, a floor step can be formed by creating a height difference between the floor surface of the floor slab formed on the second beam portion and the floor surface of the floor slab formed near the second column. Thereby, the structure of the joint part of a pillar can be made the same and a floor level difference can be formed with a steel beam. Moreover, a floor step can be formed near the second pillar.

  Since this invention set it as the said structure, the structure of the joint part of a pillar can be made the same and a floor level | step difference can be formed with a steel beam.

It is a front view which shows the steel beam which concerns on 1st Embodiment of this invention. It is a perspective view which shows the reinforcement plate which concerns on 1st Embodiment of this invention. It is a front view which shows the variation of the steel beam which concerns on 1st Embodiment of this invention. It is a front view which shows the steel beam which concerns on 2nd Embodiment of this invention. It is a front view which shows the variation of the steel beam which concerns on 2nd Embodiment of this invention.

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

  In the front view of FIG. 1, a steel beam 10 is installed between a reinforced concrete column 12 as a first column and a reinforced concrete column 14 as a second column arranged opposite to the column 12. It is shown. The joint part 16 as the first joint part of the pillar 12 is configured to have a joint member 18 embedded in the pillar 12, and the joint part 20 as the second joint part of the pillar 14 is It has a connection member 22 embedded in the column 14. Further, the joint portion 20 is located higher than the joint portion 16.

  The joint member 18 and the joint member 22 are the same member. That is, the joint part 16 and the joint part 20 have the same structure. The joint members 18 and 22 are members in which H-shaped steels are integrated so as to be orthogonal to each other so as to project in four directions in a plan view. End members 24 and 26 are joined to each other. The joint members 18 and 22 and the beam end members 24 and 26 are rigidly joined by joining the lower flange, the web, and the upper flange by welding. If the end of the joint member 18 and the beam end member 24 are the same beam, and the end of the joint member 22 and the beam end member 26 are the same beam, the joint member 18 and the joint member 22 are formed. May not be the same member.

  The steel beam 10 includes a first beam portion 28, a second beam portion 30, and a third beam portion 32. The first beam portion 28 includes a beam end member 24 and a beam end member 34 made of H-shaped steel and having the same beam structure as the beam end member 24. The beam end member 24 and the beam end member 34 are bolted to the lower flange, web, and upper flange of the beam end member 24 and to the lower flange, web, and upper flange of the beam end member 34. The lower flange, the web, and the upper flange of the beam end member 24 and the lower flange, the web, and the upper flange of the beam end member 34 are joined together via the splice plates 36, 38. The beam end member 24 and the beam end member 34 may be joined by a method other than the splice plate. For example, the beam end member 24 and the beam end member 34 may be joined by welding.

  The second beam portion 30 includes a beam end member 26 and a beam end member 40 made of H-shaped steel and having the same beam structure as the beam end member 26. The beam end member 26 and the beam end member 40 are bolted to the lower flange, web, and upper flange of the beam end member 26 and to the lower flange, web, and upper flange of the beam end member 40. The lower flange, the web, and the upper flange of the beam end member 26 and the lower flange, the web, and the upper flange of the beam end member 40 are joined together via the splice plates 36 and 38. The beam end member 26 and the beam end member 40 may be joined by a method other than the splice plate. For example, the beam end member 26 and the beam end member 40 may be joined by welding.

  The third beam portion 32 includes a beam center member 42 made of H-shaped steel. The beam center member 42 and the beam end members 34 and 40 constitute a beam member 44 in which the beam members 34 and 40 are joined to both ends of the beam center member 42 by welding, respectively, and are integrally connected. The end of the beam central member 42 on the column 12 side is integrally connected to the end of the beam end member 34 by joining the upper flange and the web together by welding, and the end of the beam central member 42 on the column 14 side is The lower flange and the web are joined together by welding and are integrally connected to the end of the beam end member 40.

  That is, the steel beam 10 includes a first beam portion 28 joined to the joint portion 16 of the column 12, a second beam portion 30 joined to the joint portion 20 of the column 14, and both ends of the first beam portion. 28 and a third beam portion 32 respectively connected to the second beam portion 30.

  The beam formation of the first beam portion 28 and the second beam portion 30 is equal, and the beam formation of the first beam portion 28 and the second beam portion 30 is larger than that of the third beam portion 32. The lower surface of the second beam portion 30 and the lower surface of the third beam portion 32 are flush with each other, and the lower surface of the third beam portion 32 is higher than the lower surface of the first beam portion 28. Thereby, a stepped portion 46 is formed between the first beam portion 28 and the third beam portion 32. The upper surface of the first beam portion 28 and the upper surface of the third beam portion 32 are flush with each other, and the upper surface of the third beam portion 32 is lower than the upper surface of the second beam portion 30. Thereby, a stepped portion 48 is formed between the second beam portion 30 and the third beam portion 32. The beam formation of the first beam portion 28 and the second beam portion 30 may not be equal.

  The beam end members 34 and 40 are provided with steel reinforcing plates 50 and 52, respectively. As shown in the perspective views of FIGS. 1 and 2, the reinforcing plate 50 is disposed on the extension line of the lower flange 54 of the beam center member 42, and the rear end portion is on the column 12 side of the lower flange 54 of the beam center member 42. The side end portions are joined to the web of the beam end member 34 by welding. The reinforcing plate 52 is disposed on the extension line of the upper flange 56 of the beam center member 42, the rear end portion is joined to the end portion of the upper flange 56 of the beam center member 42 on the column 14 side by welding, and the side end portion is the beam. The end member 40 is joined to the web by welding. The reinforcing plate 50 transmits the axial force of the lower flange 54 of the beam central member 42 to the first beam portion 28 by the shearing force of the web of the beam end member 34, and the reinforcing plate 52 is connected to the upper flange 56 of the beam central member 42. An axial force is provided to transmit the axial force to the second beam portion 30 by the shearing force of the web of the beam end member 40. The reinforcing plates 50 and 52 are not provided to be joined to the end portions of the lower flange 54 and the upper flange 56, and the lower flange 54 and the upper flange 56 are projected from the end surface (the end surface of the web) of the beam center member 42. The protruding portions may be formed as the reinforcing plates 50 and 52 in advance.

  A floor slab 58 made of reinforced concrete is formed on the steel beam 10 by concrete placement. That is, the steel beam 10 is placed on the upper surfaces of the first beam portion 28, the third beam portion 32, and the second beam portion 30, and a floor slab 58 is provided over these upper surfaces. It is a floor beam. The thicknesses of the floor slabs 58 formed on the first beam portion 28, the third beam portion 32, and the second beam portion 30 are substantially equal, and are between the second beam portion 30 and the third beam portion 32. By forming the stepped portion 48, there is a height difference between the floor surface of the floor slab 58 formed on the third beam portion 32 and the floor surface of the floor slab 58 formed on the second beam portion 30. A floor step 60 is formed.

  Next, the operation and effect of the steel beam according to the first embodiment of the present invention will be described.

  In the steel beam 10 according to the first embodiment of the present invention, as shown in FIG. 1, the thickness of the floor slab 58 formed on the third beam portion 32 and the second beam portion 30 is substantially equal, By forming a stepped portion 48 between the third beam portion 32 and the second beam portion 30 with a height difference between the upper surface of the beam portion 32 and the upper surface of the second beam portion 30, the third beam portion is formed. The floor step 60 can be formed by making a height difference between the floor surface of the floor slab 58 formed on the floor 32 and the floor surface of the floor slab 58 formed on the second beam portion 30.

  Therefore, the floor steps 60 can be formed by the steel beam 10 with the same structure of the joint portions 16 and 20 of the columns 12 and 14. That is, it is possible to standardize (standardize) the joints of the pillars. In addition, since the steel beam of different beam is not joined to the joint member to form a height difference between the upper surfaces of the steel beams in the joint part, the structure of the joint member becomes complicated, An increase in the amount of members constituting the joint member can be suppressed. By these, the construction cost for forming a floor level | step difference can be reduced.

  Moreover, in the steel beam 10 which concerns on 1st Embodiment of this invention, since the both ends of the steel beam 10 comprise a haunch, the resistance bending moment and resistance shear force of the both ends of the steel beam 10 can be made high.

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

  In the first embodiment of the present invention, an example in which the floor step 60 is formed on one end side of the steel beam 10 is shown, but one end of the steel beam 10 is shown as a steel beam 68 shown in the front view of FIG. The floor steps 60 and 62 may be formed on both the part side and the other end side. In FIG. 3, both end portions of the third beam portion 32 are connected to the first beam portion 64 and the second beam portion 30, and the beam formation of the first beam portion 64 and the second beam portion 30 is equal, and the third beam portion The beam formation of the first beam portion 64 and the second beam portion 30 is larger than the beam formation of 32. The lower surface of the third beam portion 32 is flush with the lower surfaces of the first beam portion 64 and the second beam portion 30, and the upper surface of the third beam portion 32 is from the upper surfaces of the first beam portion 64 and the second beam portion 30. By making the height lower, there is a difference in level between the upper surface of the third beam portion 32 and the upper surfaces of the first beam portion 64 and the second beam portion 30, thereby providing a step between the first beam portion 64 and the third beam portion 32. A portion 66 is formed, and a stepped portion 48 is formed between the second beam portion 30 and the third beam portion 32. The beam formation of the first beam portion 64 and the second beam portion 30 may not be equal.

  A floor slab 58 made of reinforced concrete is formed on the steel beam 68 by concrete placement. That is, the steel beam 68 is placed on the upper surfaces of the first beam portion 64, the third beam portion 32, and the second beam portion 30, and a floor slab 58 is provided over these upper surfaces. It is a floor beam. The thicknesses of the floor slabs 58 formed on the first beam portion 64, the third beam portion 32, and the second beam portion 30 are substantially equal.

  This creates a height difference between the floor surface of the floor slab 58 formed on the third beam portion 32 and the floor surface of the floor slab 58 formed on the first beam portion 64 and the second beam portion 30. Floor steps 62 and 60 are formed.

  Further, in the first embodiment of the present invention, an example in which the thickness of the floor slab 58 formed on the first beam portion 28, the third beam portion 32, and the second beam portion 30 is substantially equal is shown. The floor slab 58 formed on the first beam portion, the third beam portion, and the second beam portion may have different thicknesses as long as the required level difference in level can be formed. For example, in FIG. 1, there is a difference in height required between the floor surface of the floor slab 58 formed on the third beam portion 32 and the floor surface of the floor slab 58 formed on the second beam portion 30. If the floor level difference can be formed, the thickness of the floor slab 58 formed on the third beam portion 32 may be different from the thickness of the floor slab 58 formed on the second beam portion 30. Further, for example, in FIG. 3, the height required between the floor surface of the floor slab 58 formed on the third beam portion 32 and the floor surface of the floor slab 58 formed on the first beam portion 64. A difference in level difference between the floor surface of the floor slab 58 formed on the third beam portion 32 and the floor surface of the floor slab 58 formed on the second beam portion 30 can be formed. The floor slab 58 formed on the first beam portion 64, the third beam portion 32, and the second beam portion 30 may have different thicknesses as long as the floor level difference can be formed.

  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 steel beam according to a second embodiment of the present invention will be described. As shown in the front view of FIG. 4, in the steel beam 70 of the second embodiment, the beam end member 72 made of H-shaped steel whose beam formation is smaller than the beam formation at the end portion of the connection member 22 is the connection member. It is joined to the end of 22. The joint member 22 and the beam end member 72 are rigidly joined by joining the lower flange and the web together by welding.

  Further, a reinforcing plate 74 is provided on the web of the joint member 22. The reinforcing plate 74 is disposed on the extension line of the upper flange 76 of the beam end member 72, the rear end portion is joined to the end portion on the column 14 side of the upper flange 76 by welding, and the side end portion is the web of the joint member 22. Are joined by welding. The reinforcing plate 74 is provided to transmit the axial force of the upper flange 76 of the beam end member 72 to the joint member 22 by the shearing force of the web of the joint member 22. The reinforcing plate 74 is not provided by being joined to the end of the upper flange 76, but is formed by projecting the upper flange 76 from the end surface of the beam end member 72 (the end surface of the web). The reinforcing plate 74 may be used.

  The steel beam 70 has a first beam portion 28, a second beam portion 78, and a third beam portion 32. The second beam portion 78 has a beam end member 72 that is the same beam as the beam center member 42. The beam end member 72 and the beam center member 42 are bolted to the lower flange, web, and upper flange of the beam end member 72 and the lower flange, web, and upper flange of the beam center member 42. The lower flange, the web, and the upper flange of the beam end member 72 and the lower flange, the web, and the upper flange of the beam center member 42 are joined together via the splice plates 36, 38. The beam end member 72 and the beam center member 42 may be joined by a method other than the splice plate. For example, the beam end member 72 and the beam center member 42 may be joined by welding.

  The beam center member 42 and the beam end member 34 constitute a beam member 80 in which the beam end member 34 is joined to one end portion of the beam center member 42 by welding.

  That is, the steel beam 70 includes a first beam portion 28 joined to the joint portion 16 of the column 12, a second beam portion 78 joined to the joint portion 20 of the column 14, and both ends of the first beam portion. 28 and the third beam portion 32 respectively connected to the second beam portion 78.

  The beam formation of the second beam portion 78 and the third beam portion 32 is equal, and the beam formation of the first beam portion 28 is larger than that of the third beam portion 32. The lower surface of the third beam portion 32 and the lower surface of the second beam portion 78 are flush with each other, and the lower surface of the third beam portion 32 is higher than the lower surface of the first beam portion 28. Thereby, a stepped portion 46 is formed between the first beam portion 28 and the third beam portion 32.

  Further, the upper surface of the third beam portion 32 is flush with the upper surfaces of the first beam portion 28 and the second beam portion 78, and the upper surface of the second beam portion 78 is the joint portion 20 (the joint member 22). ) Lower than the top surface. As a result, a step portion 82 is formed between the joint portion 20 and the second beam portion 78.

  A steel beam (not shown, hereinafter referred to as “steel beams 96 and 98”) provided to project from the joint member 22 in two directions orthogonal to the beam length direction 94 of the steel beam 70 in plan view; A floor slab 59 is formed by placing concrete on the steel beam 100 provided to project from the mouth member 22 to the opposite side of the steel beam 70 in plan view. A floor slab 58 is formed on the steel beam 70 by concrete placement. That is, the steel beam 70 is placed on the upper surfaces of the first beam portion 28, the third beam portion 32, and the second beam portion 78, and the floor slab 58 is provided over these upper surfaces. The steel beams 96, 98, and 100 are floor beams that are placed on these upper surfaces, and are provided with a floor slab 59 over the upper surfaces. The thicknesses of the steel beams 70 (the first beam portion 28, the third beam portion 32, and the second beam portion 78) and the floor slabs 58, 59 formed on the steel beams 96, 98, 100 are substantially equal. Yes.

  Since the upper surfaces of the steel beams 96, 98, 100 and the upper surface of the joint member 22 are flush with each other, the stepped portion 82 is formed between the joint portion 20 and the second beam portion 78, so that the column 14 A difference in level is created between the floor surface of the floor slab 59 formed on the steel beams 96, 98, 100 in the vicinity and the floor surface of the floor slab 58 formed on the second beam portion 78, resulting in a floor step 84. Is formed.

  Next, operations and effects of the steel beam according to the second embodiment of the present invention will be described.

  In the steel beam 70 according to the second embodiment of the present invention, as shown in FIG. 4, the steel beam 70 (the first beam portion 28, the third beam portion 32, and the second beam portion 78), and the steel beam 96, The floor slabs 58 and 59 formed on 98 and 100 are substantially equal in thickness, and a height difference is created between the upper surface of the joint portion 20 (joint member 22) and the upper surface of the second beam portion 78. By forming a stepped portion 82 between the joint portion 20 and the second beam portion 78, the floor surface of the floor slab 59 formed on the steel beams 96, 98, 100 near the column 14 and the second beam portion The floor level difference 84 can be formed by making a height difference between the floor slab 58 formed on the floor 78 and the floor surface.

  Therefore, the floor steps 84 can be formed by the steel beams 70 with the same structure of the joints 16 and 20 of the columns 12 and 14. Further, a floor step 84 can be formed near the pillar 14.

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

  In the second embodiment of the present invention, an example in which the second beam portion 78 is rigidly joined to the joint member 22 has been shown. However, like the steel beam 86 shown in the front view of FIG. The web of the second beam portion 78 may be joined to the provided gusset plate 88 with a high tension bolt 90 or the like so that the upper and lower flanges of the second beam portion 78 and the joint member 22 are not joined.

  In the steel beam 86, the third beam portion 32 is integrally provided on the second beam portion 78, and the beam end member 34, the third beam portion 32, and the second beam portion 78 are integrally connected. A beam member 92 is formed.

  In the steel beam 86, the joining position (joining height) of the second beam portion 78 with respect to the column 14 is adjusted by joining the web of the second beam portion 78 to the joint member 22 using the gusset plate 88. In addition, since the axial force is not transmitted between the second beam portion 78 and the upper flange and the lower flange of the joint member 22, the structural cross section (beam formation) of the second beam portion 78 is reduced. be able to.

  Moreover, in 2nd Embodiment of this invention, the floor slab formed on the steel beam 70 (the 1st beam part 28, the 3rd beam part 32, and the 2nd beam part 78) and the steel beam 96,98,100. In the example, the thicknesses 58 and 59 are substantially equal to each other. However, the floor surface of the floor slab 59 formed on the steel beams 96, 98 and 100 near the column 14 and the floor formed on the second beam portion 78 are shown. If the required level difference can be created between the floor surface of the slab 58 and a floor step can be formed, the steel beam 70 (the first beam portion 28, the third beam portion 32, and the second beam portion 78). The floor slabs 58, 59 formed on the steel beams 96, 98, 100 may have different thicknesses.

  The first and second embodiments of the present invention have been described above.

  In the first and second embodiments of the present invention, an example in which the first and second columns are reinforced concrete columns 12 and 14 has been shown. However, the first and second columns are made of steel reinforced concrete, steel frame, and CFT. Columns with other structures such as (Concrete-Filled Steel Tube: filled steel tube concrete structure) may be used.

  In the steel beams 10, 68, 70, 86 shown in the first and second embodiments of the present invention, the step portions 48, 66, 82 are formed at the ends of the steel beams 10, 68, 70, 86. It has special technical features such as forming floor steps 60, 62, and 84, and should be used particularly effectively in buildings such as hospitals where there are many floor steps for the installation and wiring of inspection equipment. it can. The steel beams 10, 68, 70, 86 are steel beams with a haunch provided at the end, which can reduce the cost by reducing the amount of steel, and further form a floor step. Because it can reduce costs, it is a technology that can contribute to building construction at low cost.

  The first and second embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and the first and second 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, 68, 70, 86 Steel beam 12 columns (first column)
14 pillars (second pillar)
16 spout (first spout)
20 joint part (second joint part)
28, 64 First beam portion 30, 78 Second beam portion 32 Third beam portion 48, 66, 82 Stepped portion

Claims (3)

A first beam portion joined to the first joint portion of the first pillar;
A second beam part joined to a second joint part at a position higher than the first joint part of the second pillar disposed opposite to the first pillar;
Both end portions are connected to the first beam portion and the second beam portion, and the lower surface is flush with the lower surface of the second beam portion and is higher than the lower surface of the first beam portion. A step portion is formed between the second beam portion and the upper surface is flush with the upper surface of the first beam portion and the upper surface of the second beam portion is lower than the upper surface of the second beam portion. A third beam portion to be formed;
Steel beam with. A first beam portion joined to the first joint portion of the first pillar;
A second beam portion joined to the second joint portion of the second column disposed opposite to the first column;
Both end portions are connected to the first beam portion and the second beam portion, the lower surface is flush with the lower surfaces of the first beam portion and the second beam portion, and the upper surface is the first beam portion and the second beam portion. A third beam portion that forms a step portion between the first beam portion and the second beam portion lower than the upper surface of the beam portion;
Steel beam with. A first beam portion joined to the first joint portion of the first pillar;
It is joined to the second fitting part located at a position higher than the first fitting part of the second pillar arranged opposite to the first pillar, and the upper surface is made lower than the upper surface of the second fitting part, A second beam portion forming a step portion between the second joint portion;
Both end portions are connected to the first beam portion and the second beam portion, and the lower surface is flush with the lower surface of the second beam portion and is higher than the lower surface of the first beam portion. A third beam portion that forms a step portion between the upper surface and the upper surface of the first beam portion and the second beam portion;
Steel beam with.

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