JP2681082B2 - Frame structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a frame structure that constitutes a middle-high-rise structure, and in particular, an energy absorbing mechanism utilizing plastic deformation is formed in the lowermost layer and the uppermost layer. It is related to the frame structure. [Prior Art] In order to protect a building structure from external forces such as an earthquake, it is necessary to make the frame structure that constitutes the structure a seismic structure. However, by increasing the rigidity of the conventional structure, seismic resistance is improved. In the case of being able to exert the effect, there is a problem that an increase in design stress or the like causes an increase in member cross section and an increase in member weight, which causes increase in material cost and imbalance in structural balance. By the way, in recent years, with respect to the external force of the scale such as the largest earthquake that is expected to occur within the service life of the building structure, to the extent that the building structure is not collapsed The idea of allowing plastic deformation to absorb the energy of the external force has been accepted, and a design method called the ultimate design method aiming at so-called plasticization is actually being applied. The applicant has previously proposed and applied for a frame structure using this ultimate design method (Japanese Patent Application No.
61-231689 (JP-A-63-89743) "Brace type flexible rigid structure having seismic energy absorption function" and the like). The frame 1 as a whole is shown in FIG. The frame 1 is of a middle and high layer composed of columns 2 and beams 3, and an energy absorbing mechanism 5 is formed in the lowermost layer L thereof. The energy absorbing mechanism 5 is, for example, as shown in FIG. 4, and rigid members (plasticizing members) 6 are provided in a region surrounded by the columns 2 and the beams 3. This rigid member 6 is located on the ground G so that it is located between the columns 2 and 2.
The rigid members 6 are connected to each other by a connecting member 7 made of, for example, H-shaped steel. A brace 8 is extended from the rigid member 6 toward a joint portion C of the pillar 2 and the beam 3 via a mounting plate 9. The brace 8 is connected to the beam 3 at the joint portion C by a gusset plate 10. Is attached to. Here, the members constituting the frame 1, that is, the columns 2, the beams 3, the braces 8 and the like are
The material and cross-sectional shape of the frame 1 are selected so that the stress generated by an external force of an earthquake scale that is expected to occur several times during the service life of the frame 1 is within the allowable stress level. The rigid member 6 provided in the lowermost layer L of the frame 1
The material and cross-sectional shape are selected so that they will yield to an external force of the largest earthquake scale expected to occur during the service life of frame 1. When an external force of an earthquake scale that is expected to occur several times during the service life of frame 1 is applied to frame 1 provided with energy absorbing mechanism 5 as described above, each member is within the elastic range in the restoring force characteristics. It will behave. Further, when an external force of the largest earthquake magnitude that is expected to occur during the service life of the frame 1 is applied, the energy of the external force is transmitted to the rigid member 6 via the brace 8 so that the rigid member 6 Yields (bend yields). As a result, most of the energy of the external force is converted into plastic strain energy in this lowermost layer L, and the energy transmitted to the layers above this is reduced, so that the seismic (isolation) effect on the entire frame is improved. Is what you can get. [Problems to be Solved by the Invention] By the way, according to the above-mentioned frame 1, unlike the conventional earthquake-resistant frame, which increases the proof stress of each structural member to obtain an earthquake-proof effect, the rigid member 6 has a plastic deformation capability. Since the energy of the external force is absorbed, it is possible to realize a frame structure that can obtain the seismic energy absorption effect without increasing the proof stress of the members that form the frame structure 1. As a result, the member cross section increases as described above. In addition, it has an excellent effect that problems such as an increase in material cost due to an increase in member weight and an imbalance of structural balance can be solved. However, in the frame 1, since the energy absorbing mechanism 5 for alleviating the influence of external force is configured only in the lowermost layer L of the frame 1, the energy configured in the lowermost layer L is reduced. While the rigid member 6 of the absorbing mechanism 5 needs to use one having a large plastic deformation ability, the pillar 2 has a large deformation ability and can retain the restoring ability even during a large deformation ( For example, high-strength steel must be used, which results in a large limitation in selecting members, a high height, and a large amount of deformation of the lowermost layer L. There was a point to be improved in that special construction had to be performed in consideration of a large amount of deformation. The present invention has been made in view of the above circumstances, and an object thereof is to provide a frame structure capable of eliminating the above problems while obtaining an excellent seismic isolation effect by the frame 1. [Means for Solving Problems] In the frame structure according to the present invention, when a large external force due to an earthquake or the like is applied to a middle-high-rise structure, most of the energy of the external force is the lowest layer of the structure. The distribution of the yield shear force coefficient of each floor is set to disperse and concentrate in the upper layer, and the energy absorbing mechanism that absorbs energy by plastic deformation of the members is arranged in the lowermost layer and the uppermost layer, respectively, and the energy absorption The mechanism absorbs the energy to be dispersed and concentrated in the lowermost layer and the uppermost layer. The above energy absorption mechanism is
It is preferable that the elastic member includes a flexible member that allows elastic deformation and a rigid member that allows plastic deformation. [Operation] When an external force is applied to the frame according to the present invention due to an earthquake or the like, the energy due to the external force is dispersed and absorbed in the energy absorption mechanism formed in the lowermost layer and the energy absorption mechanism formed in the uppermost layer. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and the reference numeral 15 as a whole is the frame according to the present invention. The frame 15 is a middle- and high-rise building composed of steel-framed pillars 16 and beams 17, and in this embodiment, it is assumed to constitute a 10-story building. An energy absorbing mechanism 5 is formed on the lowermost layer L and the uppermost layer H of the frame 15, that is, the first floor and the tenth floor in the embodiment. In this case, the energy absorbing mechanism 5 is similar to that shown in FIG. That is, rigid members (plasticizing members) 18 and 18 are erected so as to be positioned between the columns 16 and 16 in a region surrounded by the pillars 16 and the beams 17, and the upper ends of these rigid members 18 are, for example, H They are connected by a connecting member 7 made of shaped steel. From the rigid member 18,
The brace 8 extends toward the joint portion C between the pillar 16 and the beam 17, and is attached to the beam 17 at the joint portion C. However, the rigid member 18, which is a constituent element of the energy absorbing mechanism 5 configured in the lowermost layer L (first floor) of the frame 15, is erected on the foundation ground G, but is configured in the uppermost layer H (10th floor). The rigid member 18, which is a constituent element of the energy absorbing mechanism 5, is supported and fixed at its base end to the beam 17 that constitutes the ceiling of the ninth floor (the beam that constitutes the floor of the tenth floor). In addition, each member constituting the frame 15, that is, the pillar 16, the beam 17, the brace 8 and the like is made of a flexible member (elastic member) made of ordinary steel or the like.
The material and cross-sectional shape of the material are selected so that the stress generated by an external force of earthquake magnitude, which is expected to occur several times during the service life of 15, is within the allowable stress level. And frame
The rigid members provided on the lowermost layer L and the uppermost layer H of 15.
The material and cross-sectional shape of 18 are selected so that they will yield to an external force of the largest earthquake magnitude expected to occur during the service life of frame 15. Here, an optimal combination of the physical property values of the flexible member pillar 16 and the rigid member 6 will be described. The combination of these physical property values changes depending on the level setting of the floor height of the suspension 15 and the maximum earthquake that can be endured by the strain energy absorption capacity of the rigid member 18 and the earthquake that remains elastic. According to the results of examinations such as the above, the combination as given by the following equation is most preferable. sQy / hQy ≧ 1/3 sδy / hδy ≧ 3.0 h / h ≧ 0.35 hQy: Sum of yield shear forces of rigid members of the layer sQy: Sum of yield shear forces of flexible members of the layer hδy: Yield deformation of rigid members Amount sδy: Yield deformation amount of flexible member h: Average value of apparent plastic deformation ratio h: Average value of cumulative plastic deformation ratio In the frame that constitutes the building, damage to each layer due to external force such as earthquake is almost There is a uniform "optimal yield shear force coefficient distribution" (hereinafter abbreviated as "optimal distribution"). On the other hand, if the structural strength of a certain layer is made lower than this optimum distribution (a strength gap is provided), damage will be concentrated on that layer. The present invention correctly utilizes this action, and the energy absorption mechanism 5 formed in the lowermost layer and the uppermost layer is deformed by an external force to prevent damage to other layers.
In Fig. 2, the horizontal axis is the yield shear force coefficient and the vertical axis is the hierarchy of frame 15, and the input energy is all the same (V _E ≈150 cm / se
In the present invention, the optimum distribution (line (a)) is shown for the case c), and in the present invention, the optimum distribution (a) is divided into the first floor (bottom layer) and the tenth floor (top layer), respectively. Intensity gaps are added as shown in diagrams (b) and (c). That is, the distribution of the yield shear force coefficient of each floor is set so that most of the external force such as an earthquake is dispersed and concentrated in the lowermost layer and the uppermost layer of this structure. The energy concentration rate to each floor at this time is shown in the following table according to the result of the simulation. From the above table, 1 compared to the case where the energy absorption mechanism 5 is provided only on the first floor (lowermost layer) or 10th floor (uppermost layer).
It can be seen that energy is distributed to the 10th and 10th floors, and the amount of energy absorbed in each is almost halved. In other words, this means that there is plenty of energy absorption capacity,
In other words, when the energy absorption mechanism 5 is composed of the lowermost layer L and the uppermost layer H, the energy absorption ability required for each energy absorption mechanism becomes low, and the restrictions on design and member selection are greatly eased. Will be done. In other words, the flexible member such as the pillar 16 that constitutes the energy absorbing mechanism 5 of the frame 15 has the same physical properties as the flexible member constituting the energy absorbing mechanism 5 of the conventional frame 1, that is, the elastic deformation ability and the restoring retention. It is no longer necessary to expect the capacity, and the rigid member 18 is not required to have a plastic deformation capacity as large as that of the rigid member 6 that constitutes the energy absorbing mechanism 5 of the conventional frame 1 described above. It becomes possible to use ordinary steel instead of the high-strength steel. Further, the concentration of energy on the energy absorbing mechanism 5 is also reduced as compared with the conventional frame 1 in which the energy absorbing mechanism 5 is formed only on the first layer, so that the amount of deformation of the layers constituting the energy absorbing mechanism 5 is reduced and the member surface is reduced. In addition to the cost reduction in the design, it is possible to reduce the design cost. Moreover, since the amount of deformation of the energy absorbing mechanism 5 is small, that is, the amount of deformation of the layers forming the energy absorbing mechanism 5 is small, it is not necessary to give special consideration to the arrangement of equipment and the mounting of exterior materials. . Furthermore, as is clear from the above table, most of the energy of the external force (99.57% in the case of the above table) is concentrated in the uppermost layer and the lowermost layer, so almost no energy is concentrated in the middle floor (upper layer). In the case of the table, only 0.43% on the 8th floor), these middle floors can be a simple elastic design. [Effects of the Invention] As described above, the present invention allows the frame structure that constitutes a middle-high-rise structure to receive most of the energy from the external force when the large external force such as an earthquake is applied to the lowermost layer of the structure. The distribution of the yield shear force coefficient of each floor is set to disperse and concentrate in the upper layer, and then the energy absorption mechanism that absorbs the energy by the external force by the plastic deformation of the member is formed in the lowermost layer and the uppermost layer. Therefore, when an external force is applied to the frame due to an earthquake or the like, the energy of the external force is dispersed and absorbed by the energy absorbing mechanism formed in the lowermost layer and the uppermost layer. As a result, the frame is not isolated from the external force, but the energy concentration rate to each energy absorbing mechanism is greatly reduced compared to the conventional frame in which the energy absorbing mechanism is configured only in the lowermost layer, and these energy absorbing mechanisms are configured. The selection range and design conditions of the members or members forming the layers having the energy absorbing mechanism are relaxed, and the cost can be reduced in terms of both design and construction. Also, since the amount of deformation due to external force is reduced due to the reduction of the energy concentration rate in the energy absorption mechanism, a large deformation occurs when arranging equipment and mounting exterior materials like the conventional frame structure in which the energy absorption mechanism is configured only in the bottom layer. No need to consider. Furthermore, most of the energy of the external force is concentrated only in the lowermost layer and the uppermost layer, so the middle layers other than these can have a simple elastic design, and it is possible to expect further cost reduction and other excellent effects. is there.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 is an overall elevation view of the frame structure, and FIG. 2 is an optimum yield shear force coefficient distribution, and 1 of the frame structure according to the embodiment. FIG. 3 is a view showing a strength gap between the first floor and the tenth floor, FIG. 3 is an overall elevation view showing a conventional frame structure, and FIG. 4 is an elevation view showing an example of an energy absorbing mechanism. L: bottom layer, H ... top layer, 5 ... energy absorption mechanism, 8 ... brace, 16 ... pillar, 17 ... beam, 18 ... rigid member. (The above symbols 8, 16, and 17 are flexible members.)

Claims (1)

(57) [Claims] It is a frame structure that constitutes a middle-high-rise structure, and when a large external force is applied due to an earthquake or the like, most of the energy from the external force is dispersed to the bottom layer and the top layer of the structure and concentrated so that it is concentrated on each floor. The distribution of the yield shear force coefficient is set, and the energy absorption mechanism that absorbs energy by the plastic deformation of the members is arranged in the lowermost layer and the uppermost layer, respectively, and these energy absorption mechanisms disperse the energy in the lowermost layer and the uppermost layer. A frame structure characterized by absorbing the energy to be concentrated. 2. The frame structure according to claim 1, wherein the energy absorbing mechanism includes a flexible member that allows elastic deformation and a rigid member that allows plastic deformation.