JP6728742B2 - Steel beam - Google Patents

Description

The present invention relates to a steel beam.

In office buildings, logistics, commercial facilities, etc., a frame having a steel beam, such as a steel frame structure or a CFT (Concrete Filled Steel Tube) structure, is often used. Usually, as a design method of a steel frame beam, a design is made to ensure energy absorption capacity by bending and yielding the beam end in advance during an earthquake. By the way, it is considered effective to reduce the thickness of the web plate in order to reduce the cost of the steel beam, but there is a problem that the local buckling of the web plate easily occurs when the width-thickness ratio of the web plate becomes large. In this regard, there is known a technique of stiffening the web plate at the end of the steel beam with a stiffener (see, for example, Patent Document 1).

JP, 2005-105543, A

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of suppressing the local buckling of a steel beam and reducing the cost more than ever before.

The present invention adopts the following means in order to solve the above-mentioned problems. That is, the present invention is a steel frame beam that is laterally bridged between a pair of columns, and a pair of beam end members located at both ends of the steel frame beam and joined to the columns, and the beam end member. A beam central member having a bending yield hinge forming region that forms a bending yield hinge during an earthquake, and a stiffening member provided on the web material in the bending yield hinge forming region of the beam central member. It is characterized by being provided.

In the present invention, the member is selected so that the beam center member of the steel beam forms a bending yield hinge (plastic hinge) during an earthquake. For example, in the steel beam of the present invention, the beam center and the member thickness may be set such that the bending yield hinge forming region is formed in an end region of the beam center member. The beam center member of the steel beam is less affected by long-term stress than the beam end member. Therefore, if it is possible to resist the seismic force by setting the bending yield hinge in the beam center member, efficient member selection can be performed.

In the present invention, since the beam center member having the bending yield hinge forming region can reduce the bending stress as compared with the beam end member, the member thickness is relatively reduced within the range where local buckling does not occur. Is acceptable. Further, according to the present invention, among the beam central members, the stiffening member is provided in the web material in the bending yield hinge forming region that forms the bending yield hinge at the time of an earthquake to suppress local buckling. Therefore, it is possible to reduce the thickness of the web material while suppressing the local buckling of the bending yield hinge formation region in the beam center member, and it is possible to efficiently reduce the cost. Further, in the length (inter-column span dimension) of the steel beam, the beam center member occupies a larger proportion than the beam end member, and the beam center member occupies about 80% of the total length of the steel beam. There are many cases. INDUSTRIAL APPLICABILITY According to the present invention, the amount of steel material of the beam central member that occupies most of the entire length of the steel beam can be reduced while suppressing local buckling, so that the effect of cost reduction is very excellent.

Further, in the present invention, the stiffening member may be arranged to extend along the longitudinal direction of the beam center member in the bending yield hinge forming region of the beam center member. In other words, the stiffening member may be a horizontal stiffening plate horizontally joined to the web material in the bending yield hinge forming region of the beam central member. Accordingly, by arranging the stiffening member along the longitudinal direction of the beam central member, local buckling of the web material can be efficiently suppressed, and the deformability of the beam member can be improved.

According to the present invention, it is possible to provide a technique capable of reducing the cost as compared with the conventional technique while suppressing the local buckling of the steel beam.

FIG. 1 is a side view of a main part of a beam-column structure 1 according to an embodiment. FIG. 2 is a diagram illustrating the position of the horizontal stiffening plate joined to the web material in the steel beam according to the embodiment. FIG. 3 is a diagram illustrating a steel frame beam according to the first modification. FIG. 4 is a diagram illustrating a steel frame beam according to the second modification. FIG. 5 is a diagram illustrating a steel frame beam according to Modification Example 3. FIG. 6 is a diagram illustrating a steel frame beam according to Modification 4. FIG. 7 is a diagram illustrating a steel frame beam according to Modification Example 5.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment>
FIG. 1 is a side view of a main part of a beam-column structure 1 according to an embodiment. The column-beam frame structure 1 according to the embodiment is a steel frame structure and mainly includes a steel frame column 2 and a steel frame beam 3.

The steel column 2 is a rectangular steel tube column extending in the vertical direction of the building. On the other hand, the steel beam 3 is horizontally laid between a pair of opposing steel columns 2. In this embodiment, the steel beam 3 is configured as an H-shaped steel beam.

The steel beam 3 includes a pair of beam end members 31 and 31 located at both ends in the longitudinal direction (inter-column span direction) X of the steel beam 3, and a beam center member located inside the pair of beam end members 31 and 31. 32. The beam end member 31 has an upper flange plate 31a and a lower flange plate 31b extending in the width direction Z of the steel beam 3, and a web plate 31c extending in the vertical direction Y of the steel beam 3. An upper flange plate 31a is joined to the upper end of the web plate 31c by welding or the like, and a lower flange plate 31b is joined to the lower end of the web plate 31c by welding or the like. The upper flange plate 31a and the lower flange plate 31b are joined to the web plate 31c so as to be parallel to each other, and a predetermined plate is provided substantially at the center of the upper flange plate 31a and the lower flange plate 31b in the width direction Z of the steel beam 3. A web plate 31c having a thickness tw1 is installed.

Similarly to the beam end member 31, the beam center member 32 also has an upper flange plate 32a and a lower flange plate 32b extending in the width direction Z of the steel beam 3, and a web plate 32c extending in the vertical direction Y of the steel beam 3. An upper flange plate 32a is joined to the upper end of the web plate 32c by welding or the like, and a lower flange plate 32b is joined to the lower end of the web plate 32c by welding or the like. The upper flange plate 32a and the lower flange plate 32b are joined to the web plate 32c so as to be parallel to each other, and a predetermined plate is provided substantially at the center of the upper flange plate 32a and the lower flange plate 32b in the width direction Z of the steel beam 3. A web plate 32c having a thickness tw2 is installed.

The beam end member 31 of the steel beam 3 is joined to the steel column 2 by friction joining or welding using high-strength bolts. The beam end member 31 and the beam center member 32 of the steel beam 3 are joined by using a splice plate 33, a high-strength bolt 34, a nut 35, and the like. However, the method of joining the steel column 2 and the beam end member 31 of the steel beam 3 and the method of joining the beam end member 31 and the beam center member 32 of the steel beam 3 are not limited to the above examples, and various methods may be adopted. You can

A horizontal stiffening plate 5 as a stiffening member is provided on the web member 32c in an end region of the beam central member 32 in the longitudinal direction X. The horizontal stiffening plate 5 is a flat steel member also called a so-called horizontal stiffener, and is extended along the longitudinal direction X of the beam central member 32 (steel beam 3). The horizontal stiffening plate 5 is joined to the web member 32c by, for example, welding. FIG. 2 is a diagram illustrating the position of the horizontal stiffening plate 5 joined to the web member 32c in the steel frame beam 3 according to the embodiment. FIG. 2 shows a cross section of the steel beam 3 on one end side of the beam central member 32. The horizontal stiffening plates 5 are provided with two horizontal stiffening plates 5 on each side of the web member 32c, but the number of the horizontal stiffening plates 5 attached to the web member 32c is not particularly limited. Further, the other end side of the beam central member 32 in the steel frame beam 3 is also similar to the aspect on the one end side shown in FIG.

In the steel frame beam 3 of the present embodiment, a bending yield hinge forming region Ryh that forms a bending yield hinge during an earthquake is formed on the end side of the beam central member 32. In other words, the beam center member 32 of the steel beam 3 has its beam formation and member thickness set so that a bending yield hinge (plastic hinge) Hg is formed in the end region thereof at the time of an earthquake.

For example, in the steel frame beam 3, the plate thickness tw2 of the web plate 32c of the beam center member 32 is designed to be smaller than the plate thickness tw1 of the web plate 31c of the beam end member 31, which allows the beam end member to be released during an earthquake. The members are selected so that the bending yield hinge forming region Ryh is formed on the end side of the beam central member 32 without the bending yield of 31. In addition, in the steel beam 3 of the present embodiment, not only the thickness of the web plate but also the width (width) and the thickness of the flange plate are designed to be different in the beam center member 32 and the beam end member 31, As a result, the bending strength of the beam center member 32 can be made lower than the bending strength of the beam end member 31, and the beam center member 32 can be adjusted to yield during bending. For example, the width dimensions of the flange plates 32a and 32b in the beam center member 32 are set so that the beam center member 32 bends and yields while suppressing the beam end member 31 from bending and yielding during an earthquake. , 31b may be designed to be smaller than the width dimension thereof. Further, the thickness dimensions of the flange plates 32a and 32b of the beam center member 32 may be designed to be smaller than the thickness dimensions of the flange plates 31a and 31b of the beam end member 31. In the steel beam 3 of the present embodiment, the beam end members 31 and the beam center member 32 have the same beam formation, but the bending yield hinge forming region Ryh is formed on the end side of the beam center member 32. The beam formations of the beam end member 31 and the beam center member 32 may be set to different dimensions.

In the steel beam 3 of the present embodiment, the section in which the horizontal stiffening plate 5 is arranged from the end of the beam central member 32 toward the inner side of the span can be obtained by an appropriate calculation formula, for example, the bending yield hinge forming region. It can be determined by the range in which Ryh is formed.

Since the steel beam 3 configured as described above has the bending yield hinge forming region Ryh in the end region of the beam center member 32, the plate thickness tw2 of the web plate 32c in the beam center member 32 is set to the web in the beam end member 31. The size can be made smaller than the plate thickness tw1 of the plate 31c. As a result, the amount of steel used for the beam center member 32 can be reduced, and the cost can be reduced. Further, in the present embodiment, since the horizontal stiffening plate 5 is arranged in the bending yield hinge forming region Ryh of the beam central member 32, even if the web plate 32c is thinned, local buckling occurs in the web plate 32c. Can be suppressed.

Furthermore, in the steel beam 3, the ratio of the length of the beam central member 32 to the total length in the longitudinal direction X (inter-column span dimension) is significantly larger than the ratio of the length of the beam end member 31. For example, in the steel beam 3 of the present embodiment, the length of the beam central member 32 is about 80% of the total length, which accounts for most of the length. Therefore, by realizing the thinning of the web plate 32c in the beam central member 32 occupying most of the length of the steel beam 3 (while suppressing local buckling), the effect of cost reduction is more remarkable. It becomes possible to do it.

Further, the relationship between the deformation angle of the steel beam 3 and the holding strength in the present embodiment is such that the bending yield hinge is formed in the beam central member 32 during an earthquake. Compared with the above, the timing of forming the hinge is delayed, and as a result, it is possible to secure a large holding strength at the same deformation angle (for example, 1/100).

<Modification>
Next, another embodiment will be described. 3 to 6 are views for explaining the steel beam 3 according to the modification. Each drawing shows a side view of the bending yield hinge forming region Ryh on one end side of the beam central member 32 of the steel beam 3. In the modified example 1 shown in FIG. 3, one horizontal stiffening plate 5 is horizontally arranged on one side of the web plate 32c.

Moreover, in the modification 2 shown in FIG. 4, the vertical stiffening plate 6 is provided adjacent to the horizontal stiffening plate 5. The vertical stiffening plate 6 is a flat plate steel material that is extended and arranged along the vertical direction Y in the beam center member 32. In this modification, the horizontal stiffening plate 5 and the vertical stiffening plate 6 correspond to the stiffening member in the present invention, and the horizontal stiffening plate 5 and the vertical stiffening plate 6 suppress local buckling of the web plate 32c. .. Modification 4 shown in FIG. 5 is an example in which the arrangement pattern of the vertical stiffening plate 6 is different from that of Modification 1. As shown in FIGS. 4 and 5, by using the horizontal stiffening plate 5 and the vertical stiffening plate 6 together, the restraining effect of the web plate 32c is further increased, and the local buckling of the web plate 32c is more preferably suppressed. be able to. 4 and 5, the number of vertical stiffening plates 6 to be installed is not particularly limited.

In Modified Example 4 shown in FIG. 6, only the vertical stiffening plate 6 is provided in the bending yield hinge forming region Ryh of the beam central member 32 of the steel beam 3, and the horizontal stiffening plate 5 is not provided. 4 is different from the second modification shown in FIG. In Modification 3, the vertical stiffening plate 6 corresponds to the stiffening member in the present invention, and the vertical stiffening plate 6 suppresses local buckling of the web plate 32c. In addition, in the steel frame beam 3 according to the modified example 5 shown in FIG. 7, in addition to the bending yield hinge forming region Ryh of the beam center member 32, the horizontal stiffening plate 5 is also provided on the web plate 31c of the beam end member 31. 1 is different from the embodiment shown in FIG. In Modification 5, the vertical stiffening plate 6 may be joined to the web plate 31c instead of the horizontal stiffening plate 5 or in combination with the horizontal stiffening plate 5.

Although the embodiment and the modification of the present invention have been described above, the steel beam according to the present invention is not limited to these, and these can be combined as much as possible. Further, although the steel frame column 2 in the column beam frame structure 1 is described as an example of a square steel pipe column, it is not limited to this.

DESCRIPTION OF SYMBOLS 1... Column beam structure 2... Steel column 3... Steel beam 5... Horizontal stiffening plate 6... Vertical stiffening plate 31... Beam end member 32... Beam center member 31a , 32a... Upper flange plates 31b, 32b... Lower flange plates 31c, 32c... Web material Ryh... Bending yield hinge forming region

Claims (3)

A steel beam crossed between a pair of columns,
A pair of beam end members located at both ends of the steel beam and joined to the column,
The beam end member is joined to the beam end member and has a bending yield hinge forming region for forming a bending yield hinge at the time of an earthquake in the end region, and the thickness of the web material is designed to be smaller than the thickness of the web material in the beam end member. and the beam center member,
A stiffening member that is joined to the web material in the bending yield hinge forming region formed in the end region of the beam central member and suppresses local buckling of the web material in the bending yield hinge forming region ,
With steel beams. In the beam center member, the beam formation and member thickness are set so that the bending yield hinge forming region is formed in the end region of the beam center member,
The steel beam according to claim 1. The stiffening member is arranged to extend along the longitudinal direction of the beam center member in the bending yield hinge forming region of the beam center member.
The steel beam according to claim 1 or 2.

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