JP6919672B2 - H-shaped steel beam - Google Patents

Description

The present invention relates to an H-shaped steel beam having an H-shaped cross section orthogonal to the longitudinal direction and having the beam end portion stiffened by a stiffening member.

In recent years, steel-framed H-section steel beams tend to have a large beam length and a large beam length in order to prevent the beam from bending due to the increase in size and space of the building. In order to reduce the amount of steel material in terms of both cost and manufacturability, the thickness of the web, which has a small contribution to rigidity, tends to be thin, and as a result, the number of H-shaped steel beams having a large cross section and a thin web tends to increase.

In such an H-shaped steel beam having a large cross-section thin-walled web, there is a risk that a large bending moment acts on the end portion during a large earthquake and local buckling occurs.
For example, when the beam length of the H-shaped steel beam 21 is long, as shown in FIG. 9, the bending moment at the end is predominant, so that on one web surface when the beam cross section is bisected by the neutral axis, Bending buckling occurs as shown by the thick gray ellipse.
On the other hand, when the beam length of the H-shaped steel beam 21 is short, as shown in FIG. 10, the shearing force is superior to the bending moment at the end, so that the shear buckling as shown by the thin gray ellipse Occurs.

As a structure for preventing local buckling and improving deformation performance, a technique of providing a stiffening member on a web is known.
For example, as proposed in Patent Document 1, a method of installing a horizontal stiffener 25 orthogonal to the beam web 23 of the H-shaped steel beam 21 (see FIG. 11), or a beam web 23 proposed in Patent Document 2. There is a method of installing a plurality of vertical stiffeners 27 orthogonal to the above (see FIG. 12), or a method of installing a combination of the vertical stiffener 27 and the horizontal stiffener 25 proposed in Patent Document 3 (see FIG. 13).
In all of these methods, stiffeners (horizontal stiffener 25, vertical stiffener 27) are joined to the beam web 23 by welding, thereby controlling the width-thickness ratio or boundary conditions of the beam web 23 to perform buckling. The purpose is to make it less likely to occur.

Japanese Unexamined Patent Publication No. 2016-23417 Japanese Unexamined Patent Publication No. 2011-208434 Japanese Unexamined Patent Publication No. 2014-51822

FIG. 14 schematically shows a state in which a load is applied to the conventional stiffening structure shown in FIG. In the case of such a stiffening structure, as shown in FIG. 14, in addition to the upper and lower flanges 28 and 29, the web 23 is constrained vertically and horizontally by the pillar 9 and the vertical stiffener 27, or when adjacent to each other, the vertical stiffener 27. It becomes a shape and is divided into a rectangular plate shape with a small width-thickness ratio in the beam material axial direction.
Therefore, the web 23 causes out-of-plane deformation in a narrow divided range, and the amount of deformation becomes large.

Further, since the entire vertical stiffener 27 is warped or twisted and deformed due to the local buckling of the web 23, the proof stress of the vertical stiffener 27 is reduced at an early stage, and the effect of restraining the lower flange 29, for example, cannot be maintained. Therefore, as shown in FIG. 15, the lower flange 29 buckles locally at an early stage after the maximum yield strength of the beam, and the yield strength of the beam drops sharply.

As described above, the conventional stiffening method mainly aims to stiffen the shear buckling of the web, and the effect of stiffening the local buckling of the flange, which affects the deformation performance after the maximum yield strength, cannot be expected. There is a problem.
In particular, Patent Document 2 is based on the premise that a horizontal haunch is provided on the beam flange at the joint between the beam and the column, and the vertical stiffener 27 provided on the web 23 is expected to stiffen the local buckling of the flange at the beam end. It's not a thing.
Further, when a stiffening member having a length equivalent to that of the beam is provided as in the conventional stiffening method, there is a problem that the steel weight is large and the maneuverability at the time of manufacturing is poor.

The present invention has been made to solve such a problem, and is made of H-section steel which can be expected to have a local buckling and stiffening effect of a flange in addition to stiffening of a web and has excellent deformation performance after the maximum yield strength. The purpose is to provide beams.

(1) The H-shaped steel beam according to the present invention has a web connecting the upper flange, the lower flange, and the upper and lower flanges, has an H-shaped cross section orthogonal to the longitudinal direction, and the beam end is stiffened by a stiffening member. H-shaped steel beam
The stiffening member is arranged orthogonally to the beam longitudinal direction, and is joined to the upper flange and the web.
It is provided with a lower stiffening member that is provided on a virtual straight line continuous with the upper stiffening member at a predetermined distance from the upper stiffening member and is joined to the web and the lower flange. It is characterized by.

(2) Further, in the above-mentioned item (1), the beam dimension is h, the beam width is B, and the web thickness is t.
The total length Ls of the upper stiffening member and the lower stiffening member is h / 2 ≦ Ls ≦ 3h / 4.
The width Hs of the stiffening member is (Bt) / 4 ≦ Hs ≦ (Bt) / 2.

(3) The H-shaped steel beam according to the present invention has a web connecting the upper flange, the lower flange, and the upper and lower flanges, has an H-shaped cross section orthogonal to the longitudinal direction, and the beam end is stiffened by a stiffening member. An H-beam beam whose upper flange is stiffened by a floor slab or the like.
The stiffening member is arranged orthogonally to the longitudinal direction of the beam, has a length of h / 2 to 3 h / 4 with the beam dimension as h, and is joined to the lower flange and the web. It is characterized by being provided with a member.

(4) Further, in the above-described (3), the stiffening member is provided on a virtual straight line continuous with the lower stiffening member at a predetermined distance from the lower stiffening member. The web is provided with an upper stiffening member that is shorter than the lower stiffening member joined to the upper flange.

(5) Further, in the above-mentioned (3) or (4), the beam width is B and the web thickness is t.
The width Hs of the stiffening member is (Bt) / 4 ≦ Hs ≦ (Bt) / 2.

(6) Further, in any one of the above (1) to (5), the stiffening member is provided at the beam end in two or more rows continuously in the longitudinal direction. be.

In the present invention, the stiffening member provided at the beam end is arranged orthogonally to the beam longitudinal direction, and the upper stiffening member joined to the upper flange and the web, and the upper stiffening member and a predetermined distance from each other. In addition to the stiffening of the web, the maximum is provided by providing the web and the lower stiffening member joined to the lower flange, which are provided on a virtual straight line continuous with the upper stiffening member. The local buckling and stiffening effect of the flange after the proof stress can be expected, and the deformation performance after the maximum proof stress is excellent.
Further, since the stiffening member is divided into an upper stiffening member and a lower stiffening member, one stiffening member has a smaller size than the conventional one, so that the maneuverability is good and the manufacturability is excellent.

It is explanatory drawing of the H-section steel beam of one Embodiment of this invention, the side view (FIG. 1 (a)), the arrow view AA sectional view of FIG. 1 (a) (FIG. 1 (b)). It is a top view (FIG. 1 (c)). It is a figure explaining the action effect of the H-section steel beam of one Embodiment of this invention (the 1). It is a figure explaining the action effect of the H-section steel beam of one Embodiment of this invention (the 2). It is explanatory drawing of another aspect of the H-section steel beam of one Embodiment of this invention, and is the side view (FIG. 4A) and FIG. b)) (No. 1). It is explanatory drawing of another aspect of the H-section steel beam of one Embodiment of this invention (the 2). It is explanatory drawing of another aspect of the H-section steel beam of one Embodiment of this invention (the 3). It is explanatory drawing of the H-section steel beam of another embodiment of this invention. It is explanatory drawing of the H-section steel beam of another aspect of another embodiment of this invention. It is explanatory drawing of the local buckling of the conventional H-section steel beam which did not stiffen (the 1). It is explanatory drawing of the local buckling of the conventional H-section steel beam which did not stiffen (the 2). It is explanatory drawing of the H-section steel beam of the conventional example, and is the side view (FIG. 11 (a)) and the cross-sectional view taken along the arrow CC (FIG. 11 (b)) of FIG. 11 (a) (No. 1). .. It is explanatory drawing of the H-section steel beam of the conventional example, and is the side view (FIG. 12 (a)) and the cross-sectional view taken along the arrow HH (FIG. 12 (b)) of FIG. 12 (a) (part 2). .. It is explanatory drawing of the H-section steel beam of the conventional example, and is the side view (FIG. 13 (a)) and the cross-sectional view of EE of FIG. 13 (a) (FIG. 13 (b)) (part 3). .. It is explanatory drawing which explains the problem of the prior art (the 1). It is explanatory drawing which explains the problem of the prior art (the 2). It is explanatory drawing of the analysis result which confirms the effect of one Embodiment of this invention.

[Embodiment 1]
As shown in FIG. 1, the H-shaped steel beam 1 according to the embodiment of the present invention has a web 7 connecting the upper flange 3, the lower flange 5, and the upper and lower flanges 3, 5 and is orthogonal to the longitudinal direction. The cross section is H-shaped, one end is joined to the column 9, and the beam end is stiffened by the stiffening member 11.
Then, the stiffening member 11 is arranged orthogonally to the beam longitudinal direction, and the upper stiffening member 11a joined to the upper flange 3 and the web 7 and the upper stiffening member 11a are separated from each other by a predetermined distance and are upper. It is provided on a virtual straight line L continuous with the stiffening member 11a, and includes a web 7 and a lower stiffening member 11b joined to the lower flange 5.

As shown in FIG. 1, the upper stiffening member 11a and the lower stiffening member 11b of the present embodiment are formed of a rectangular plate-like body, and are provided on both sides of the web 7 with the web 7 interposed therebetween. The upper stiffening member 11a and the lower stiffening member 11b provided on both sides of the web 7 are preferably arranged so as to have a symmetrical positional relationship.

The lumber axial spacing p between the stiffening members 11 (see FIG. 1) or the lumber axial spacing p from the skin plate of the column 9 to the stiffening member 11 (see FIG. 1) is preferably a beam width B or less. ..
When the lumber axial spacing p between the stiffening members 11 or the lumber axial spacing p from the skin plate to the stiffening member 11 is the beam width B or more, between the skin plate and the stiffening member 11 or the stiffening member 11 Local buckling of the flange may occur first, and sufficient plastic deformation performance may not be obtained.
Further, the material axial distance from the skin plate of the column 9 to the stiffening member 11 farthest from the skin plate of the column 9 is preferably 0.5H or more (H: beam beam). When the lumber axial distance is 0.5 H or less, the stiffening range is insufficient with respect to the plasticized region at the beam end, and sufficient plastic deformation performance may not be obtained.

The total length of the upper stiffening member 11a and the lower stiffening member 11b, that is, the upper part of the set arranged on the upper and lower virtual straight lines L, where the beam dimension is h, the beam width is B, and the web thickness is t. The length Ls (see FIG. 1) obtained by adding the length Lsa of the stiffening member 11a and the length Lsb of the lower stiffening member 11b is set to h / 2 ≦ Ls ≦ 3h / 4.
The reason why Ls is set to h / 2 or more is that it is preferable to do so in order to obtain the stiffening effect of the web 7.
Further, by setting Ls to 3h / 4 or less, a gap can be formed between the upper stiffening member 11a and the lower stiffening member 11b, and the upper stiffening member 11a and the lower stiffening member 11b are conventional examples. As described above, the upper and lower flanges 3 and 5 are not restrained, and the structure is such that it is difficult to buckle.
Further, by dividing the stiffening member 11 into an upper stiffening member 11a and a lower stiffening member 11b, each member becomes smaller, and it is easy to handle and manufacture.

The width Hs of the stiffening member 11 (the width of one side of the stiffening member 11 provided on both sides of the web 7) is set to (Bt) / 4≤Hs≤ (Bt) / 2. ing.
The width Hs is set to (Bt) / 4 or more because it is preferable to increase the rigidity of the stiffening member 11 itself in the out-of-plane direction.
Further, by setting the width Hs to (Bt) / 2 or less, it does not protrude more than the upper and lower flanges 3 and 5.

The upper flange 3 and the web 7 of the upper stiffening member 11a are generally joined by welding, and the lower flange 5 and the web 7 of the lower stiffening member 11b are joined by welding, but the joining is limited to this. is not it. For example, bolt joints via end plates are also possible.
Further, it is preferable that the upper stiffening member 11a and the lower stiffening member 11b are joined in advance at a factory.

Next, the operation of the H-shaped steel beam 1 of the present embodiment will be described with reference to FIGS. 2 and 3.
FIG. 2 shows the stiffening members 11 installed at the same intervals as those in FIGS. 12 and 14 showing the conventional example. In this case, since the upper stiffening member 11a and the lower stiffening member 11b are not connected, the local buckling deformation of the web 7 is allowed to some extent in the portion of the web 7 where there is no stiffening member 11 (gray in the figure). The part shown is the part that is locally buckled). Therefore, the stress acting on the stiffening member 11 is suppressed, the proof stress of the stiffening member 11 itself is prevented from decreasing, and the flange restraining effect can be maintained even after the maximum proof stress of the beam.
Moreover, although local buckling occurs in the portion where the stiffening member 11 is not provided, the amount of out-of-plane deformation can be suppressed to be small because the range is wider than in the case of FIG.

FIG. 3 schematically shows the web local buckling when the installation interval of the stiffening member 11 is narrower than that in the case of FIG.
As shown in FIG. 3, when the installation interval of the stiffening member 11 is narrowed, the local buckling of the web 7 occurs in the central portion of the web 7 without the stiffening member 11. Since this is an out-of-plane deformation of the stiffening member 11 with respect to the strong axis direction, the proof stress of the stiffening member 11 does not decrease. Therefore, as in the case of FIG. 2, the stiffening member 11 can maintain the restraining effect of the upper and lower flanges 3 and 5 even after the maximum yield strength of the beam.

As described above, in the H-shaped steel beam 1 of the present embodiment, the stiffening member 11 is divided into upper and lower flanges 3 and 5 without being continuous with the upper and lower flanges 3 and 5, and is joined to the upper and lower flanges 3 and 5, respectively. Therefore, in addition to the local buckling / stiffening effect of the web 7, it is possible to suppress a decrease in the strength of the stiffening member 11 itself due to the local buckling / stiffening effect, and the local buckling / stiffening effect of the upper and lower flanges 3 and 5 can be suppressed. Can be expected. Then, by suppressing the local buckling of the upper and lower flanges 3 and 5, the deformation performance after the maximum proof stress is improved.
Further, since the stiffening member 11 is divided into an upper stiffening member 11a and a lower stiffening member 11b, the size of one stiffening member 11 is smaller than that of the conventional one, so that the maneuverability is good and the work at the time of manufacturing is performed. Excellent in sex.
Further, the lengths of the upper stiffening member 11a and the lower stiffening member 11b can be set shorter than those of the conventional example, the welding amount can be reduced, the man-hours and the cost can be reduced, and welding can be performed. It is possible to prevent the web 7 from warping due to the influence of heat.

The stiffening member 11 shown in FIG. 1 was a rectangular plate-like body, but may be a triangle as shown in FIG. 4, for example. Further, the stiffening member 11 may have a shape to be joined to the upper and lower flanges 3, 5 and the web 7, and may have various shapes, not limited to a rectangle or a triangle.

Further, in the stiffening member 11 shown in FIG. 1, a plurality of stiffening members 11 are arranged at equal intervals in the beam longitudinal direction, but as shown in FIG. 5, the installation interval is set at the beam end portion where the bending moment is predominant. It may be narrowed and the installation interval may be widened toward the center of the beam.

Further, as shown in FIG. 6, the plurality of upper stiffening members 11a and lower stiffening members 11b may be provided with horizontal stiffeners 13 connected in the longitudinal direction of the beam. By providing the lateral stiffener 13, the rigidity of the upper stiffening member 11a and the lower stiffening member 11b can be increased to prevent buckling and maintain the proof stress. The rigidity effect can be surely obtained.

[Embodiment 2]
As shown in FIG. 7, the H-shaped steel beam 15 of the present embodiment is a case of a composite beam or the like in which the upper flange 3 is stiffened by, for example, a reinforced concrete floor slab 17. In FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals.
When the upper flange 3 is stiffened by the floor slab 17, the stiffening of the upper flange 3 becomes unnecessary and the neutral axis is above the center line, so that the upper part of the web 7 does not need to be stiffened. In some cases, this embodiment is effective in such cases.

However, it is not excluded that the upper stiffening member 11a is provided, and as shown in FIG. 8, the upper stiffening member 11a may be provided. In this case, the upper stiffening member 11a may have a shorter length than the lower stiffening member 11b.

In the present embodiment, the upper stiffening member 11a can be made unnecessary or short, so that an efficient stiffening structure is obtained.

FEM analysis was performed to verify the performance improvement effect of this embodiment. The target beam has a cross section of H-1000 × 300 × 12 × 25 (SN490) and a cantilever length L of L = 5000 mm.
The stiffening members were installed in three rows above and below, with the material axial direction interval p being p = 200 mm. The analysis was carried out by completely fixing one beam end and loading the other beam end in the vertical direction with displacement control.
The analysis result is shown in FIG. In FIG. 16, the results for the beam without the stiffening member are also shown by broken lines. In a beam without a stiffener, the yield strength decreases early after reaching the total plastic yield strength. On the other hand, in a beam having a stiffening member, it is possible to maintain the proof stress even after reaching the total plastic proof stress, and it can be confirmed that the plastic deformation performance is improved.
From this analysis result, it was demonstrated that according to the present invention, it is possible to suppress a sudden decrease in proof stress after reaching the total plastic proof stress and improve the plastic deformation performance.

L Virtual straight line 1 H-section steel beam (Embodiment 1)
3 Upper flange 5 Lower flange 7 Web 9 Pillar 11 Stiffening member 11a Upper stiffening member 11b Lower stiffening member 13 Horizontal stiffener 15 H-shaped steel beam (Embodiment 2)
17 Floor slab <Conventional example>
21 H-section steel beam 23 Beam web 25 Horizontal stiffener 27 Vertical stiffener 28 Upper flange 29 Lower flange

Claims (6)

It is an H-shaped steel beam that has a web that connects the upper and lower flanges and these upper and lower flanges, has an H-shaped cross section perpendicular to the longitudinal direction, and the beam ends joined to the columns are stiffened by stiffeners. hand,
The stiffening member is arranged orthogonally to the beam longitudinal direction, and is joined to the upper flange and the web.
A lower stiffening member provided at a predetermined distance from the upper stiffening member and on a virtual straight line continuous with the upper stiffening member, and joined to the web and the lower flange.
The distance in the lumber axis direction to the upper stiffener and the lower stiffener closest to the column is less than or equal to the beam width, and the lumber axial distance to the upper stiffener and the lower stiffener farthest from the column. An H-shaped steel beam characterized by having more than half of the beam length. Let h be the beam dimension, B be the beam width, and t be the web thickness.
The total length Ls of the upper stiffening member and the lower stiffening member is h / 2 ≦ Ls ≦ 3h / 4.
The H-section steel beam according to claim 1, wherein the width Hs of the stiffening member is (Bt) / 4≤Hs≤ (Bt) / 2. Has a web connecting the upper flange and the lower flange and upper and lower flanges in the longitudinal direction orthogonal cross-section H-shaped, beam end is stiffened by the stiffening member, and the upper flange Thus is stiffened on the floor slab H-shaped steel beam
The stiffening member is arranged orthogonally to the longitudinal direction of the beam, has a length of h / 2 to 3 h / 4 with the beam dimension as h, and is joined to the lower flange and the web. An H-shaped steel beam characterized by being provided with members. The lower stiffening member is provided on a virtual straight line continuous with the lower stiffening member at a predetermined distance from the lower stiffening member, and is joined to the web and the upper flange. The H-section steel beam according to claim 3, further comprising an upper stiffening member that is shorter than the member. Let B be the beam width and t be the web thickness.
The H-section steel beam according to claim 3 or 4, wherein the width Hs of the stiffening member is (Bt) / 4≤Hs≤ (Bt) / 2. The H-section steel beam according to any one of claims 1 to 5, wherein the stiffening members are provided at the beam ends in two or more rows continuously in the longitudinal direction.

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