Column-beam joint structure

Abstract

To facilitate a design where a base material part of a mounting member breaks prior to a welded part, in the case where the tabular mounting member such as a diaphragm is welded to a flange at an end part in the material axis direction of an H-shaped cross-section beam.SOLUTION: A column-beam joint structure which is formed between a column and an H-shaped cross section beam in which the direction crossing the column is a material axis direction includes a tabular mounting member which is joined to the column and which is joined to a flange of the H-shaped cross section beam by a welded part, at an end part in the material axis direction of the H-shaped cross section beam. The plate thickness of the mounting member is smaller than the plate thickness of the flange.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a column-beam joint structure. [Background technology]

[0002] In a column-beam joint structure in which an H-shaped cross-section beam is welded on-site to a diaphragm that is pre-joined to a column such as a square steel pipe, there is a concern that cracks that occur near the welded part during an earthquake may propagate and lead to fracture. It is sometimes difficult to perform on-site welding with stable quality, and welding defects or parts with low toughness may occur in the welded part. If a crack reaches such a part, it may transform into a brittle crack and lead to early fracture. On the other hand, the quality of the base material of the diaphragm and beam flange is more stable than the welded part, so if a steel material with high toughness is used, even if a crack occurs in the base material part during an earthquake, it is unlikely to transform into a brittle crack and cause fracture early.

[0003] From this viewpoint, it is desirable to design a column-beam joint structure so that the base material part, rather than the welded part, breaks first. For example, Patent Document 1 describes a design technique in which a protrusion of approximately the same width as the beam flange formed on the diaphragm is butt-welded to the beam flange so that the base material part of the diaphragm breaks before the welded part at the corners on both sides of the protrusion. Patent Document 2 also describes a design technique in which a reduced width part is formed near the end of the beam flange and an increased width part is formed at the end so that the base material part of the beam flange breaks before the welded part at the reduced width part. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-076521 A [Patent Document 2] Japanese Patent Application Publication No. 11-210158 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned beam-column joint structure, the thickness of the diaphragm is generally larger than that of the beam flange. The reason for this is to avoid a decrease in deformation capacity by absorbing positional deviations caused by dimensional tolerances with the beam flange, accumulated manufacturing errors of members, welding deformation, etc. The above-mentioned Patent Document 1 also assumes that the thickness of the diaphragm is larger than that of the beam flange. In this case, however, the bearing strength of the diaphragm side is likely to be larger than that of the beam flange and the welded part, so it is not easy to design the base material part of the diaphragm to break before the welded part.

[0006] On the other hand, the design in which the base material of the beam flange breaks before the welded part as in Patent Document 2 above is not affected by the thickness of the diaphragm being greater than that of the beam flange. However, compared to a diaphragm that is relatively small and easy to handle, it is not easy to process a narrowed portion or the like on a long beam member.

[0007] Therefore, the present invention aims to provide a column-beam joint structure that makes it easy to design a structure in which, when a plate-shaped mounting member such as a diaphragm is welded to a flange at the end of an H-shaped cross-section beam in the material axis direction, the base material portion of the mounting member breaks before the welded portion breaks. [Means for solving the problem]

[0008] [1] A column-beam joint structure formed between a column and an H-shaped cross-section beam whose material axis direction is a direction intersecting the column, comprising a plate-shaped mounting member joined to the column and joined to a flange of the H-shaped cross-section beam at an end of the H-shaped cross-section beam in the material axis direction by a weld, and the plate thickness of the mounting member is smaller than the plate thickness of the flange. [2] A column-beam joint structure as described in [1], wherein the inspection ratio calculated by dividing the bending moment acting on a cross section perpendicular to the material axis direction by the yield moment at the cross section is greater at at least one position of the mounting member than the inspection ratio of the flange. [3] A column-beam joint structure as described in [2], wherein the mounting member includes a portion formed to the same width as the flange. [4] A column-beam joint structure as described in [2], wherein the mounting member includes a portion formed with a width smaller than that of the flange. [5] A column-beam joint structure described in any one of [1] to [4], wherein the groove for the weld is formed by processing the end surface of the mounting member opposite the end surface of the flange. [6] A column-beam joint structure described in any one of [1] to [5], wherein the column is separated into a first part and a second part in the axial direction, and the mounting member is sandwiched between the respective ends of the first part and the second part and welded to the respective end faces of the first part and the second part. [7] A column-beam joint structure described in any one of [1] to [5], wherein the mounting member is welded to the side of the column. Effect of the Invention

[0009] According to the above configuration, the plate thickness of the plate-shaped mounting member is smaller than the plate thickness of the flange of the H-shaped cross-section beam, so that, for example, by appropriately setting the planar shape of the diaphragm, it is possible to easily design the mounting member so that the base material portion breaks before the welded portion. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of a column-beam joint structure according to one embodiment of the present invention; [Diagram 2] FIG. 2 is a view taken along the line AA in FIG. [Diagram 3] FIG. 2 is a diagram for explaining the difference between when the end face processing for forming a groove is performed on a flange and when the end face processing is performed on a diaphragm in the example of FIG. 1. [Figure 4] 3 is a first diagram showing another example of a planar shape of a diaphragm in the column-beam joint structure shown in FIG. 2. FIG. [Diagram 5] 2. FIG. 4 is a second diagram showing another example of the planar shape of the diaphragm of the column-beam joint structure shown in FIG. [Figure 6] 3 is a third diagram showing another example of the planar shape of the diaphragm of the column-beam joint structure shown in FIG. 2. FIG. [Figure 7] 13A to 13C are diagrams showing examples of planar shapes of diaphragms in modified examples of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0012] Fig. 1 is a diagram showing an example of a column-beam joint structure according to an embodiment of the present invention, and Fig. 2 is a view taken along line AA in Fig. 1. The column-beam joint structure 1 is formed between a column 2 and an H-shaped section beam 3 whose material axis direction is a direction (X direction in the figure) intersecting the axial direction of the column 2 (Z direction in the figure). The column 2 is, for example, a cold-formed rectangular steel pipe, and the H-shaped section beam 3 is, for example, a rolled H-shaped steel or a welded assembled H-shaped steel, but is not limited to these examples. The H-shaped section beam 3 has an upper flange 31, a lower flange 32, and a web 33.

[0013] Furthermore, the column-beam joint structure 1 includes diaphragms 41 and 42 as mounting members. The diaphragm 41 is joined to the column 2 and is joined to the upper flange 31 at the end of the H-shaped section beam 3 in the material axis direction by a welded portion 51. The diaphragm 42 is joined to the column 2 and is joined to the lower flange 32 at the end of the H-shaped section beam 3 in the material axis direction by a welded portion 52. Backing metals 53 and 54 are disposed at the welded portions 51 and 52, respectively. The diaphragms 41 and 42 are through diaphragms and are inserted in the middle of the column 2. More specifically, the diaphragm 41 is sandwiched between the portions 2A and 2B of the column 2 separated in the axial direction, and is welded to the end faces of the portions 2A and 2B. The diaphragm 42 is sandwiched between the portions 2B and 2C of the column 2 separated in the axial direction, and is welded to the end faces of the portions 2B and 2C.

[0014] On the other hand, at the end of the H-section beam 3 in the material axis direction, the web 33 is joined to the splice plate 43 welded to the side surface of the column 2 (part 2B) at a welded part 55. The web 33 may be bolted to the splice plate 43. The web 33 may also extend beyond the upper flange 31 and the lower flange 32 to the column 2 side, and be directly welded to the side surface of the column 2 (part 2B). In this case, the extended web 33 needs to be welded to the diaphragms 41, 42.

[0015] In this embodiment, the plate thickness of the diaphragm, which is a plate-shaped mounting member, is smaller than the plate thickness of the flange of the H-shaped cross-section beam 3 to which they are joined. In FIG. 1, it is illustrated that for the plate thickness td of the diaphragm 41 and the plate thickness tf of the upper flange 31, td < tf, but the relationship between the plate thickness of the diaphragm 42 and the plate thickness of the lower flange 32 is the same. Further, in this embodiment, the groove for the welded portion between the diaphragm and the flange is formed by machining the end face of the diaphragm facing the end face of the flange. More specifically, the groove for the welded portion 51 between the diaphragm 41 and the upper flange 31 is formed by machining the end face 41E (see FIG. 3(b)) of the diaphragm 41. Similarly, the groove for the welded portion 52 between the diaphragm 42 and the lower flange 32 is formed by machining the end face of the diaphragm 42. The machining of the end face for forming the groove is, for example, a cutting process for forming an oblique angle on the end face, but is not limited to this example.

[0016] According to the configuration of this embodiment as described above, since the plate thicknesses of the diaphragms 41 and 42 are smaller than the plate thickness of the flange of the H-shaped cross-section beam 3, by appropriately setting the planar shapes of the diaphragms 41 and 42 as described below, it is possible to design such that the base material portions of the diaphragms 41 and 42 are broken prior to the welded portions 51 and 52 with respect to loads such as during an earthquake. For example, as shown in FIG. 2, when the diaphragm 41 has a planar shape including a narrow-width portion 411 formed to the same width as the upper flange 31, a wide-width portion 413 that is wider than the narrow-width portion 411 and joined to the column 2, and a tapered portion 412 therebetween, the vicinity of the boundary between the narrow-width portion 411 and the tapered portion 412 becomes the most easily broken portion 41F. By ensuring a sufficient distance between this portion 41F and the welded portion 51, the base material portion of the diaphragm 41 is yielded prior to the occurrence of a crack in the welded portion 51 during an earthquake or the like, and the energy due to the load during an earthquake or the like can be absorbed by the yielding of the base material portion without the crack progressing in the welded metal portion or the heat-affected zone of the welded portion 51.

[0017] As a more specific design method, regarding the verification ratio α calculated for the cross-section (Y-Z cross-section in the figure) orthogonal to the material axis direction of the H-shaped cross-section beam 3 by the diaphragm 41 and the upper flange 31, the verification ratio d α at at least any position of the diaphragm 41 b is made larger than the verification ratio y α of the upper flange 31. Here, the verification ratio α is obtained by dividing the bending moment M acting on the cross-section orthogonal to the material axis direction of the H-shaped cross-section beam 3 by the yield moment M y of the same cross-section. In the column-beam joint structure 1, the bending moment M increases as it approaches the column 2 as schematically shown in the moment diagram of FIG. 1. On the other hand, the cross-section yield moment M y is calculated by multiplying the section modulus Z by the yield stress σ y of the steel material, and increases in proportion to the section modulus Z or the yield stress σ y of the steel material. Here, the F value, which is the design reference strength of the steel material, may be used as the yield stress σ

[0018] In the example shown in FIG. 2, in the narrow-width portion 411 of the diaphragm 41, the width of the member is the same as that of the upper flange 31, but the plate thickness is smaller than that of the upper flange 31 (td < tf), so the cross-sectional area of the member is smaller than that of the upper flange 31. Therefore, for example, if the H-shaped cross-section beam 3 and the diaphragm 41 are formed of materials of the same strength, the cross-section yield moment d M y of the narrow-width portion 411 is smaller than the yield moment b M y of the cross-section of the upper flange 31( d M y < b M y ). Also, since the diaphragm 41 is closer to the column 2, the moment d M at the narrow-width portion 411 is larger than the moment b M of the upper flange( d M > b M). Therefore, the verification ratio d α = d M / d M yis the inspection ratio of the upper flange 31 b α = b M / b M y will be greater than.

[0019] On the other hand, in the tapered portion 412 of the diaphragm 41 closer to the column 2 and in the wide portion 413 in the vicinity of the column 2, the width of the member is increased, so that the cross-sectional area is larger than that of the narrow portion 411. Therefore, the yield moment d M y Therefore, the moment is larger than that of the narrow portion 411 because it is closer to the pillar 2. b Even if M becomes larger, the calibration ratio in the tapered portion 412 and the wide portion 413 d α is smaller than the narrow portion 411, and the inspection ratio of the upper flange 31 b In this example, the narrow part 411 is closest to the pillar 2 and the moment d Because M is large, the test ratio d The angle α is the largest, and the boundary between narrow portion 411 and tapered portion 412, which is also the shape change point, becomes portion 41F most susceptible to destruction.

[0020] As long as the most fragile portion 41F is formed in the diaphragm 41 as described above, the test ratio is not necessarily the same as the entire narrow portion 411. d α is the inspection ratio of the upper flange 31 b It is not necessary for the test ratio to be larger than α. Therefore, for example, in the portion close to the welded portion 51 of the diaphragm 41, d α is the inspection ratio of the upper flange 31 b The width of the diaphragm 41 and the strength of the material may be selected so as to be less than α.

[0021] The diaphragm 41 may be made of a steel material with consideration given to toughness so that cracks generated during an earthquake do not quickly turn into brittle cracks. Since the diaphragm 41 is smaller in size than the H-section beam 3, even if a relatively expensive steel material is used, the increase in cost can be suppressed.

[0022] Although the above describes the diaphragm 41 and the upper flange 31, the same applies to the diaphragm 42 and the lower flange 32.

[0023] The condition for breaking the base material of the diaphragms 41, 42 before the welds 51, 52 does not necessarily have to be determined using the above-mentioned test ratio α. For example, a geometric notch may be intentionally formed in any of the diaphragms 41, 42 to obtain a ductile crack initiation index. d α cr is the ductile crack initiation index of the upper flange 31 or the lower flange 32. f α cr The ductile crack initiation index α may be designed to be less than cr is an index described in Yuichiro Inaba and Jin Kuwamura, "Effect of material properties on ductile crack initiation in steel joints in buildings," Abstracts of the Architectural Institute of Japan Annual Meeting (Tohoku), pp. 413-414, 2000. α cr = τ peak 2 ×e local / e u It is calculated as follows. τ peak is the peak value of the stress triaxiality, e u is the uniform elongation of the material, e local indicates the axial strain.

[0024] On the other hand, according to the configuration in this embodiment in which the groove is formed by processing the end face of the diaphragm, it is possible to absorb the positional deviation in the height direction between the diaphragm and the flange due to the accumulation of dimensional tolerances, manufacturing errors of the members, welding deformation, etc. As shown in FIG. 3(a), when the plate thickness td of the diaphragm 41X is equal to or greater than the plate thickness tf of the flange 31X, if the groove is formed by processing the end face of the diaphragm, two backing metals 53X and 53Y are required to absorb the positional deviation. In contrast, in this embodiment, as shown in FIG. 3(b), since the plate thickness td of the diaphragm is smaller than the plate thickness tf of the flange, even if the groove is formed by processing the end face 41E of the diaphragm 41, the positional deviation can be absorbed with one normal backing metal 53. The same is true for the diaphragm 42 and the lower flange 32. As already mentioned, the diaphragms 41 and 42 before attachment to the column 2 are smaller in size and easier to handle than the H-shaped cross-section beam 3, which is a long beam member, so that the end face processing for forming the groove is easier.

[0025] Fig. 4 is a first diagram showing another example of the planar shape of the diaphragm of the beam-column joint structure shown in Fig. 2. In the illustrated example, the diaphragm 41 includes a narrow portion 411 having the same width as the upper flange 31 of the H-shaped cross section beam 3, and a wide portion 413 that is wider than the narrow portion 411 and is joined to the column 2, and no tapered portion is formed as in the example of Fig. 2. In this case, the vicinity of the boundary between the narrow portion 411 and the wide portion 413 of the diaphragm 41 becomes the portion 41F that is most susceptible to destruction.

[0026] Fig. 5 is a second diagram showing another example of the planar shape of the diaphragm of the beam-column joint structure shown in Fig. 2. In the illustrated example, the diaphragm 41 includes an inverse tapered portion 414 formed following the welded portion 51 between the diaphragm 41 and the upper flange 31 of the H-shaped cross-section beam 3, and a wide portion 413 that is wider than the narrow portion 411 and is joined to the column 2. The inverse tapered portion 414 is formed so as to narrow toward the wide portion 413, and therefore includes a portion formed with a width smaller than that of the upper flange 31. In this case, the vicinity of the boundary between the inverse tapered portion 414 and the wide portion 413 of the diaphragm 41 becomes the portion 41F that is most likely to break.

[0027] Fig. 6 is a third diagram showing another example of the planar shape of the diaphragm of the beam-column joint structure shown in Fig. 2. In the illustrated example, the diaphragm 41 includes a narrow portion 411 having the same width as the upper flange 31 of the H-shaped cross-section beam 3, and a wide portion 413 that is wider than the narrow portion 411 and is joined to the column 2, and a notch 415 is formed on both sides of the narrow portion 411 in the width direction. At the notch 415, the width of the diaphragm 41 is smaller than that of the upper flange 31. In this case, the vicinity of the notch 415 in the diaphragm 41 becomes the portion 41F that is most likely to break.

[0028] Fig. 7 is a diagram showing an example of a planar shape of a diaphragm in a modified embodiment of the present invention. In the above embodiment, an example in which the diaphragm 41 is a through diaphragm inserted in the middle part of the column 2 has been described, but the diaphragm 41 may be an external diaphragm as shown in Fig. 7 and welded to the side surface of the column 2. In the case of an external diaphragm, the column 2 is not separated in the axial direction. As shown by the example of Fig. 7, the plate-shaped mounting member in the column-beam joint structure according to the embodiment of the present invention may be a through diaphragm or an external diaphragm, and may not necessarily be called a diaphragm as long as it is joined to the column and joined to the flange at the end of the H-shaped cross section beam in the material axial direction by a welded portion.

[0029] As already explained for the example of Fig. 2, in the examples of Fig. 4 to Fig. 7, by ensuring a sufficient distance between the most fragile part 41F and the welded part 51, it is possible to prevent cracks from progressing in the welded metal part or the welded heat-affected part, and to absorb energy due to loads during earthquakes and the like by the yielding of the base metal part. Note that, although the diaphragm 41 on the upper flange side has been explained in the examples of Fig. 4 to Fig. 7 above, the diaphragm 42 on the lower flange side can also have a similar shape. It is preferable that the diaphragms 41 and 42 have the same shape, but they may have different shapes. [Explanation of symbols]

[0030] 1...beam-column joint structure, 2...column, 3...H-section beam, 31...upper flange, 32...lower flange, 33...web, 41, 42...diaphragm, 41E...end face, 411...narrow portion, 412...tapered portion, 413...wide portion, 414...reverse taper portion, 415...notch portion, 43...splice plate, 51, 52, 55...welded portion, 53, 54...backing plate.

Claims

1. A column-beam joint structure formed between a column and an H-shaped cross section beam whose material axis direction is a direction intersecting the column, A plate-shaped mounting member is provided which is joined to the column and joined to the flange of the H-shaped cross section beam at an end portion in the material axis direction of the H-shaped cross section beam by a welded portion, A column-beam joint structure in which the plate thickness of the mounting member is smaller than the plate thickness of the flange.

2. 2. The column-beam joint structure according to claim 1, wherein an inspection ratio calculated by dividing a bending moment acting on a cross section perpendicular to the material axis direction by a yield moment in the cross section is greater at at least one position of the mounting member than the inspection ratio of the flange.

3. The column-beam joint structure according to claim 2 , wherein the mounting member includes a portion formed to have the same width as the flange.

4. The column-beam joint structure according to claim 2 , wherein the mounting member includes a portion formed to have a width smaller than that of the flange.

5. 2. The column-beam joint structure according to claim 1, wherein a groove for the weld is formed by machining an end surface of the mounting member that faces an end surface of the flange.

6. the pillar is axially separated into a first portion and a second portion; The column-beam joint structure according to any one of claims 1 to 5, wherein the mounting member is sandwiched between the respective ends of the first part and the second part and welded to the respective end faces of the first part and the second part.

7. The column-beam joint structure according to claim 1 , wherein the mounting member is welded to a side surface of the column.

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