Static structures (e.g. – buildings) – Means compensating earth-transmitted force
Reexamination Certificate
2002-06-05
2004-05-25
Chapman, Jeanette (Department: 3635)
Static structures (e.g., buildings)
Means compensating earth-transmitted force
C052S289000, C403S403000
Reexamination Certificate
active
06739099
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a column-and-beam join structure having a vibration-mitigating property in a steel frame when a steel structure building is constructed and, more specifically, to a column-and-beam join structure capable of absorbing the energy of an earthquake by split tees yielding before the column and the beam in a column-and-beam join structure which is made of a steel column and a steel beam using split tees.
In a column-and-beam join structure according to the present invention, the steel column includes not only an H-shaped steel column or a square steel tube column but also a column of any cross-sectional shape which may be connected using split tees, and the steel beam includes not only an H-shaped steel beam but also a section beam of an L-shape, a T-shape, or another shape in cross section, which may be connected using split tees.
BACKGROUND ART
When a steel column and a steel beam are connected in a steel structure building, there are cases where split tees of, for example, a T-shape (or an L-shape) are used. In such a column-and-beam join structure, in order to form a final collapse system at the time of a large earthquake or the like, when a square steel tube column is used as a steel column, the column-and-beam join structure is generally designed so as to cause the column to yield by applying a bending deformation, such as bulging or concaving a side wall of the column to which split tees are connected in accordance with a tension or a compression imposed thereon from the portion to which the beam is connected. However, since the flexural strength of the flanges of the split tees is critical in design, the thickness and width of the flanges must be increased in order to sufficiently secure the rigidity and proof stress of the flanges, and therefore it is not economical.
Further, in Japanese Unexamined Patent Publication No. H11-229493 or H7-102635, as shown in
FIGS. 19 and 20
, a column-and-beam join structure is proposed wherein: an H-shaped steel column
1
a
(
1
) is used as a steel column
1
; the flanges
5
of a pair of upper and lower split tees
4
are connected to a flange
2
of the H-shaped steel column
1
a
(
1
) using bolts
3
; the end portions
8
a
of both the upper and lower flanges
8
of an H-shaped steel beam
7
used as a steel beam are assembled between the webs
6
of both the upper and lower split tees
4
and are connected to the webs
6
using bolts
9
. In such a column-and-beam join structure, as shown in
FIG. 21
, if a tension F, which is imposed from the join portion of a flange
8
of the H-shaped steel beam
7
, is applied to the flange
5
of a split tee
4
: the flange
5
undergoes bending deformation while bulging so as to separate from the face of a flange
2
of the H-shaped steel column
1
a
(
1
); with the bending deformation of the flange
5
, the bolts
3
used for connecting the flange
5
to the flange
2
of the H-shaped steel column
1
a
(
1
) undergo a bending tension as shown in
FIG. 21
; the bolts
3
are prized, twisted and cut by the prying action; and thus the tension rupture of the bolts
3
constitutes a final collapse system. In such a case of the tension rupture of bolts as stated above, the column is sometimes damaged by the tension.
On the other hand, in the case of designing a final collapse system for a large earthquake or the like, it is not desirable to make the join portions of a steel column and split tees rupture, and therefore it is an original technique to design the system so as to impose all cross-sectional proof stress on a steel beam so that the rupture may occur in the steel beam itself. However, the yield stress itself of a steel material used for a beam is controlled with only the lower limit of the yield stress. Therefore, even though a system is designed so as to impose all cross-sectional proof stress on a beam, since there are cases where the proof stress of the beam is excessively large, the rupture may occur in bolts, split tees or the portion to which a column is connected, which have no allowance in proof stress, as a result.
Considering the absorption of earthquake energy by a column-and-beam join portion based on the above discussion, in the case where a rupture occurs by the bending deformation of the flange of a split tee, even though the flange bulges for example, the flange sticks closely to the join face of a column finally and therefore the tension and the compression do not become symmetrical and, in the case where a rupture occurs by the tension rupture of bolts, a gap is gradually generated between the face of a column and the face of the flange of the split tee where they are connected by bolts and therefore both loops of tension and compression cannot be obtained when the bolts are plasticized, and, in either of the cases, the deformation develops in one direction and therefore the present situation is that, though the present technique can cope with the design on the proof stress of the split tee, the design of the split tee is not a design capable of coping with the absorption of earthquake energy.
Japanese Unexamined Patent Publication No. 2001-32369 discloses a technology wherein the flange of a split tee is used as an energy absorbing member by making the bending yield of the flange of the split tee precede the tension yield of bolts. However, in the case where the web of a split tee undergoes tension, this technology is effective, but, in the case where the web undergoes compression, energy absorption cannot be expected and, therefore, there is a room for further improvement.
Further, there presently is a column-and-beam join structure constructed by directly welding the ends of both the upper and lower flanges of an H-shaped steel beam to a steel column. However, such conventional method has a drawback of generating a rupture caused by the welding portion of a steel column and an H-shaped steel beam becoming a critical portion.
Thus, at present, in order to prevent a rupture at a weld portion of a steel column and an H-shaped steel beam, as disclosed in Japanese Unexamined Patent Publication No. H8-4112 for example, notches are formed on both sides adjacent to the edges of both the upper and lower flanges of an H-shaped steel beam which is directly welded to a steel column and, by so doing, the portions having the function of absorbing earthquake energy are provided, so that the portions of the H-shaped steel beam except the portions which are welded to the steel column can yield positively. However, when the portions having the function of absorbing earthquake energy are ruptured by a large earthquake or the like and the portions cannot be reused, as the portions having the function of absorbing earthquake energy are welded to the steel column and it is basically impossible to replace the portions having the function of absorbing earthquake energy after the rapture. Therefore, in reality, the steel structure building has to be reconstructed even though the H-shaped steel beam is not ruptured.
In the meantime, disclosed in Japanese Unexamined Patent Publication No. 2000-192547 is a column-and-beam join structure which is provided with an energy absorbing function by reinforcing the end of the lower flange of an H-shaped steel beam which is welded to a steel column via a diaphragm with a beam supporting reinforcing member which is composed of extra mild steel and welded to the steel column, and disclosed in Japanese Unexamined Patent Publication No. H8-151686 is a column-and-beam join structure which is provided with an energy absorbing function by welding ribs composed of a metal material having a lower yield stress than that of a material used for a column or a beam to both the upper and lower flanges of an H-shaped steel beam and by rigidly connecting the steel column to the H-shaped steel beam via the upper and lower ribs. However, when a beam supporting reinforcing member or a portion having an energy absorbing function is ruptured by a large earthquake or the like and becomes hardly reusable, it is impossible to replace
Maeda Yasushi
Okada Ken
Suzuki Kazuaki
Takeuchi Toru
Wada Akira
Chapman Jeanette
Nippon Steel Corporation
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