JP2004300681A - Frame structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frame structure having a megastructure excellent in aseismatic prperty. <P>SOLUTION: In a frame structure 10 provided with a pair of columns 16, 16 and a truss frame structure 18 laterally surported between these columns, an axial yielding part 30 having a smaller sectional area than other parts of the lower chord member 22 between the column 16 and a strut member 26A nearest to the column is formed and it is constituted to bring an axial yielding state prior to the bending hinge of the column 16 when a specified earthquake force occurs. In this way, a form close to a beam yield prior shape can be taken and its collapse mechanism forms the whole collapse configuration and hence the aseismatic property can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a frame structure such as a skyscraper having a large atrium in the lowermost part.
[0002]
[Prior art]
In a frame structure such as a skyscraper, as a method for forming a large atrium in the lowermost part, as shown in FIG. 4, a pair of columns 1, 1 and a horizontal space between the columns 1, 1 are used. There is known a so-called megastructure 3 composed of a truss frame 2 that is bridged (see Patent Document 1).
[0003]
In the conventional megastructure 3, the assumed seismic force is set to be large, and the strength of the column 1 is increased so that bending hinges (bending yield) are not simultaneously generated in both the column head and the column base of the column 1.
[0004]
[Patent Document 1]
JP-A-8-270081 [0005]
[Problems to be solved by the invention]
However, in the megastructure 3 of the skyscraper, since the truss frame 2 is stronger than the column 1, if an earthquake larger than expected occurs, as shown by reference numerals 4 and 5 in FIG. There is a high possibility that bending hinges will occur on both the base and the column base. In this case, plastic energy can be absorbed only in the lowest layer of the building, which may lead to story collapse.
[0006]
Therefore, an object of the present invention is to provide a frame structure having a megastructure with more excellent earthquake resistance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pair of pillars and a truss frame suspended between them (lower chord, upper chord, and between the lower chord and upper chord). A frame comprising a plurality of bundles and diagonal members), the lower chord between the column and the bundle closest to the column has a lower cross-sectional area than other portions of the lower chord. Is formed so that when a predetermined seismic force is generated, the shaft yielding occurs prior to the bending hinge of the column.
[0008]
Such a configuration takes a form close to a so-called beam yielding precedent type, and its collapse mechanism is a total collapse type, and the earthquake resistance is improved.
[0009]
Further, the shaft yielding portion is characterized in that it has a length which does not cause buckling, although it yields when a predetermined axial force (stress along the longitudinal direction of the lower chord material) is applied to the lower chord material. Thereby, collapse of the truss frame itself can be prevented.
[0010]
Further, it is effective that a sliding member is slidably attached to the shaft yielding portion, and the floor slab is fixed to the sliding member so as to be movable with respect to the lower chord material. Thereby, the force from the floor slab is not transmitted to the lower chord material, and the stress generated in the slab frame or column can be reduced.
[0011]
From a similar viewpoint, it is also preferable to arrange a cushion material between the floor slab and the pillar.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
1 (a) and 1 (b) are conceptual diagrams showing the structure and collapse mechanism of a skyscraper as a frame structure according to the present invention, and FIG. 2 is a detailed view of a part II in FIG. 1 (a). . FIG. 3 is a sectional view taken along line III-III in FIG. As shown in FIG. 1, the skyscraper 10 according to the present embodiment has a large atrium space 12 formed in the lowermost portion, and this portion is constituted by a so-called megastructure 14. That is, at least one wall portion of the skyscraper 10 is composed of a pair of pillars 16, 16 and a truss frame 18 laid between the pillars 16, 16 at a predetermined height from the ground, The space surrounded by the columns 16, 16 and the truss frame 18 is defined as the atrium space 12. In the present embodiment, each of a pair of wall portions facing each other has the megastructure 14. In addition, the upper floor portion 20 above the megastructure 14 is constructed with a general ramen structure or the like.
[0014]
The pillars 16 in the megastructure 14 are mainly made of, for example, reinforced concrete, and are built on a foundation or an underground floor structure in the ground (not shown) and extend vertically upward.
[0015]
As shown in FIG. 2, the truss frame 18 includes a lower chord member 22 and an upper chord member 24 arranged in parallel at a predetermined distance from each other, and a bundle member disposed between the lower chord member 22 and the upper chord member 24. (Vertical member) 26 and diagonal member 28. H-shaped steel is preferably used for the lower chord member 22, the upper chord member 24, the bundle member 26 and the diagonal member 28. Each end of the lower chord material 22 and the upper chord material 24 is joined to the adjacent column 16. Regarding the diagonal member 28 installed between each column 16 and the bundle member 26 (subscript A in FIG. 2) closest to the column 16, the upper end of the diagonal member 28 is The lower end is joined to the corner between the bundle material 26 and the lower chord material 22 at the corner between them. A pair of diagonal members 28, 28 are arranged between the adjacent bundle members 26, 26 in an inverted V-shape.
[0016]
In the lower chord member 22 of the truss frame 18, an axial yielding portion 30 is formed in a portion between each column 16 and a bundle member 26A closest to the column 16. The shaft yielding portion 30 is configured so that, when an axial force higher than expected due to the occurrence of an earthquake occurs in the lower chord material 22, the axial yield occurs prior to other portions of the lower chord material 22. In addition, when a force corresponding to the axial force causing the axial yielding portion 30 to cause axial yielding acts on the joint portion 32 between the column 16 and the lower chord material 22 in the horizontal direction, a bending hinge is generated in the column 16. Not set.
[0017]
The size or shape of the shaft yielding portion 30 is determined as follows. First, the cross-sectional area of the shaft yielding portion 30 is determined so that axial yielding occurs due to the axial force generated in the lower chord material 22 by the assumed seismic force. The magnitude of the axial force is set to a value that does not cause a bending hinge on the column 16 even when a force equivalent to the axial force is applied horizontally to the joint 32 of the column 16 with the lower chord material 22. Once the cross-sectional area of the shaft yielding portion 30 is determined, the slenderness ratio at which the axial yielding portion 30 does not buckle even when the axial force is generated in the lower chord material 22 is determined based on the cross-sectional area determined in advance. Determine. Then, the length corresponding to the slenderness ratio is defined as the length L of the axial yielding portion 30 (see FIG. 3). Of course, portions other than the shaft yielding portion 30 in the lower chord material 22 have a larger sectional area than the shaft yielding portion 30 so that axial yielding and buckling do not occur due to the axial force.
[0018]
Further, in the present embodiment, the floor slab 34 is installed on the lower chord 22 of the truss frame 18. For this purpose, as can be seen from FIG. 3, between the lower chords 22 of a pair of truss frames 18 (only one of which is shown in FIG. 3) facing each other, small beams 36 for supporting the floor slab 34 are provided. A plurality of them are suspended. In portions other than the shaft yielding portion 30, the ends of the small beams 36 are directly joined to the lower chord material 22 by welding or the like. On the other hand, in the shaft yielding section 30, the steel pipe (sliding member) 38 surrounds the shaft yielding section 30, and the end of the beam 36 is joined to the steel pipe 38. The steel pipe 38 is a rectangular steel pipe having a rectangular cross section, and is slidably mounted on the shaft yielding portion 30. The floor slab 34 is placed on the small beam 36 and the lower chord 22 provided in this manner, and is fixed to the steel pipe 38 in the shaft yielding portion 30 using a stud (not shown) or the like. Is done. Further, a cushion material 40, for example, a styrofoam having a thickness of about 30 mm is interposed between the floor slab 34 and the pillar 16.
[0019]
In the above-described configuration, when an earthquake force larger than the above-mentioned assumption is generated, the axial yielding portion 30 of the lower chord material 22 in the truss frame 18 causes axial yielding before the other, and the column supporting the truss frame 18 The bending moment of the column 16 is not generated more than expected, and the simultaneous bending hinge of the column head and the column base of the column 16 is prevented. In other words, as shown in FIG. 1B, a beam yielding advance type in which axial yielding occurs at the axial yielding portion 30 of the lower chord material 22 prior to the occurrence of the bending hinge in the column 16. It takes a close form. Further, even if a bending hinge is formed on the column, the position of the bending hinge becomes a column base as shown by reference numeral 42 in FIG. As a result, a partial collapse at the lowermost portion of the skyscraper 10 is avoided, and a so-called total collapse type is obtained. In the total collapse type, plastic energy is absorbed in all layers of the skyscraper 10, so seismic resistance is significantly improved compared to the case where plastic energy can only be absorbed locally, such as partial collapse. Will be done.
[0020]
The dimension and shape of the shaft yielding portion 30 are set so that shaft yielding occurs but buckling does not occur. This also prevents the truss frame 18 itself from collapsing. In particular, in the present embodiment, since the periphery of the shaft yielding portion 30 is surrounded by the square steel pipe 38, the effect of further suppressing the occurrence of buckling can be obtained.
[0021]
Further, the floor slab 34 is attached to the lower chord member 22 of the truss frame 18, but the floor slab 34 is not directly fixed to the lower chord member 22, but is fixed to the slidable square steel pipe 38. The amount of seismic force transmitted to the lower chord material 22 via the slab 34 is greatly reduced. In addition, since the cushion material 40 is arranged between the floor slab 34 and the column 16, the force from the floor slab 34 to the column 16 is also reduced. Since the floor slab 34 is in a floating state (floating state) with respect to the column 16 and the truss frame 18, the occurrence of the bending hinge on the column 16 is further suppressed.
[0022]
In the present invention, the rigidity of a part of the lower chord member 22 in the truss frame 18 is actively reduced, but the part is limited between the column 16 and the bundle member 26A adjacent to the column 16. Therefore, it is possible to sufficiently support the vertical force that always acts. This means that in the truss frame 18, even if the rigidity of the portion is lower than that of the other portions, the vertical force hardly changes compared to the case where the entire lower chord member 22 has the same rigidity. This is based on the findings of the present inventors.
[0023]
As described above, the preferred embodiments of the present invention have been described in detail, but it goes without saying that the present invention is not limited to the above embodiments.
[0024]
For example, in the above embodiment, the shaft yielding portion 30 is surrounded by the square steel pipe 38. However, from the viewpoint of floating the floor slab 34, a sliding member of another form, for example, an inverted U-shaped shaped steel is slid. The floor slab 34 may be fixed to the shaft yielding portion 30 so as to be movable. The present invention is also applicable to other frame structures other than the skyscraper.
[0025]
【The invention's effect】
As described above, by adopting the configuration according to the present invention, the earthquake resistance of the frame structure having the megastructure is improved. In particular, in a skyscraper building in which it is necessary to increase the strength of the truss frame, the configuration of the present invention capable of avoiding story collapse is extremely effective.
[Brief description of the drawings]
1 (a) and 1 (b) are explanatory views schematically showing a structure and a collapse mechanism of a skyscraper which is a frame structure according to the present invention.
FIG. 2 is a detailed view of a portion II in FIG. 1;
FIG. 3 is a sectional view taken along line III-III in FIG. 2;
FIG. 4 is an explanatory view schematically showing a collapse mechanism of a conventional frame structure.
[Explanation of symbols]
10 ... skyscraper (frame structure), 12 ... atrium space, 14 ... megastructure, 16 ... pillar, 18 ... truss frame, 22 ... lower chord material, 24 ... upper chord material, 26 ... bundle material, 28 ... diagonal material, Reference numeral 30 denotes a shaft yielding part, 34 denotes a floor slab, 36 denotes a beam, 38 denotes a steel pipe (sliding member), and 40 denotes a cushion material.

Claims (4)

A pair of pillars,
A lower truss material, an upper chord material, and a truss frame that includes a plurality of bundles and diagonal members disposed between the lower chord material and the upper chord material, and is laterally suspended between the pair of pillars. In the frame structure,
A portion of the lower chord between the column and the bundle closest to the column is formed with an axial yielding portion having a smaller cross-sectional area than other portions of the lower chord,
The frame structure, wherein the shaft yielding portion is configured to generate an axial yielding prior to a bending hinge of the column when a predetermined seismic force is generated. 2. The frame structure according to claim 1, wherein the shaft yielding portion has a length such that the shaft yields when a predetermined axial force is generated in the lower chord member, but does not cause buckling. 3. A sliding member slidably attached to the shaft yielding portion,
The frame structure according to claim 1, further comprising: a floor slab fixed to the sliding member and movable with respect to the lower chord member. The frame structure according to claim 3, further comprising a cushion material disposed between the floor slab and the column.

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