JP4424112B2 - Multi-layer steel structure - Google Patents

Description

  The present invention relates to a multilayer steel structure having excellent earthquake resistance.

  The collapse mode when a seismic force larger than the design assumption is input to the multi-layer steel frame is the partial collapse mode (Fig. 6) in which the column yields at the beam-column joint 40 and the specific layer collapses. Are broadly divided into an overall collapse mode (FIG. 7) in which plastic hinges (plasticized portions) 30 are dispersed at the beam ends.

  The partial collapse mode, in which a column of a specific layer yields in advance and damage is concentrated, occurs when the beam-to-beam strength ratio is low in a frame structure, which is not preferable because the energy absorption capacity of the entire frame decreases.

  The whole collapse mode occurs when a frame structure with a constant beam-to-column strength ratio is used, damage is distributed to the beam ends of each layer, the energy absorption capacity as a frame is high, and the steel structure has excellent earthquake resistance. can get.

Therefore, in order to improve seismic performance in the design of building structures, the goal is often to ensure the overall collapse mode. For example, Non-Patent Document 1 recommends that the column beam strength ratio be 1.5 or more.
"Cold Forming Square Steel Pipe Design and Construction Manual" (Japan Architecture Center)

  However, even in the case of a multi-layered building with a frame structure in which the column beam strength ratio is set so that the overall collapse mode is formed, a large bending moment acts on the column due to a large earthquake, as schematically shown in FIG. As shown, the column base may be damaged, the first layer may collapse, or the upper and lower ends of the column may be damaged at the second layer or more.

  FIG. 8 is a diagram schematically showing the bending moment distribution of the column in the first layer of the multi-layered steel structure when an external force such as a seismic wave is applied. In the figure, 50 is a foundation (ground plane), 20 is a beam, 10 Is a column, 10a is a column base, 10b is a first layer column head, 10c is a second layer column lower end, 10d is a second layer column upper end, and C is a neutral point.

  The neutral point C of the bending moment distribution generated in the column 10 in the first layer is different in the degree of fixing at the junction between the beam 20 and the column head 10b and the junction between the foundation (horizontal plane) 50 and the column base 10a. It is located above or below half of the height.

  As shown in the figure, when the foundation (ground plane) 50 and the column base 10a are rigidly connected, the neutral point C comes to be located on the side of the column head from the half position of the floor height. There is a high risk that a large bending moment acts, the column base 10a is damaged, and the first layer collapses.

  The bending moment distribution of a column in a certain layer of the multi-layered steel structure is affected by the bending moment distribution immediately above and below the layer. For example, the column lower end 10c of the column 10 in the second layer is affected by the first layer. A bending moment larger than the upper end 10d is applied.

  The present invention is a multi-layered steel structure that guarantees a collapse mode that causes damage to the beam ends of each layer. When the seismic force is large, the first layer collapse or damage to a specific layer is prevented and excellent in earthquake resistance. The purpose is to provide things.

The object of the present invention can be achieved by the following means.
1. In a multi-layer steel structure with a frame structure with a beam-bearing strength ratio exceeding 1.2 , the yield stress of the column member is set higher than the yield stress of the beam member, and the joint between the column base and the foundation in the first layer is half In the case of rigid joining, the column member is made of high yield point steel, and the rotational rigidity of the column base in the semi-rigid joining is made substantially the same as the fixing degree of the column head of the first layer. Structure.
2. 2. The multi-layer steel structure according to claim 1, wherein the column base and the foundation are joined via a vibration control device.
3. In a multi-layered steel structure with a frame structure with a beam-bearing strength ratio exceeding 1.2 , the yield stress of the column member is set higher than the yield stress of the beam member, and the connection between the column and the foundation beam in the first layer is half In the case of rigid joining, the column member is made of high yield point steel, and the rotational rigidity of the column base in the semi-rigid joining is made substantially the same as the fixing degree of the column head of the first layer. Structure.
4). 4. The multi-layered steel structure according to 3, wherein the column and the foundation beam are joined through a vibration control device.

  According to the present invention, the collapse mode in which damage is dispersed at the beam ends of each layer is secured regardless of the yield ratio of the steel for the column member, and the collapse of the first layer and the specific layer due to the column damage is prevented. Therefore, it is possible to alleviate the low YR characteristic of the steel for column members required in the current allowable stress design, and the selectivity of the steel for column members is greatly expanded.

For example, in the conventional allowable stress design, the steel for a column member is required to have a low YR characteristic of YR <80%, but the steel for a column member is also required to have excellent high heat input weld toughness. mm Steel grades ^{2 and} higher that are applicable to column members have been limited. According to the present invention, since the requirement for low YR characteristics is relaxed, the steel types that can be applied to column members are expanded with steel materials of 570 N / mm grade ² or higher.

  The multilayer steel structure according to the present invention defines the column beam strength ratio, the connection state between the column base and the foundation, and the yield stress ratio between the column member steel and the beam member steel.

  In the multilayer steel structure according to the present invention, the column beam strength ratio exceeds 1.0, preferably 1.2 or more. When the beam-to-column strength ratio exceeds 1.0, the column is less likely to yield than the beam, damage is dispersed at the beam ends of each layer, and the seismic energy is less than that when the column-beam strength ratio is 1.0 or less. Absorption is good. The value of 1.2 or higher is preferable because of the variation in the yield point of materials and the influence of higher-order modes. This is because it becomes higher.

  The rotational rigidity of the column base of the first layer is determined so that an excessive bending moment is not applied to the column base and damage to the column base is prevented. Preferably, the neutral point in the distribution of the bending moment of the column is set to be approximately the center of the floor height. To do. Specifically, the column base and the foundation are semi-rigidly connected, and the rotational rigidity of the column base is set to be substantially the same as the degree of fixation of the column head of the first layer.

  Furthermore, in the multi-layer steel structure according to the present invention, the steel for the column member is a high yield point steel having a higher yield stress than the steel for the beam member, and the column beam rigidity ratio is lowered after ensuring a certain column beam strength ratio. Thus, the bending moment distribution of the column is leveled and a specific layer is prevented from collapsing in all the layers of the multi-layer steel structure.

  FIGS. 4 and 5 show the results of determining the degree of column damage by a simulation test with respect to the four-pattern frame structure based on the combination of the yield stress of the column member and the rotational rigidity of the column base. FIG. 4 shows the total column damage degree in two or more layers when the first layer has any one of four patterns of frame structures, and FIG. 5 shows the column base damage degree for the first layer.

  When the steel for the column member and the steel for the beam member are made of ordinary steel, the effect of the semi-rigid connection between the column base and the foundation is obtained in the first layer, and damage to the column base is reduced (FIG. 5). The degree of damage at two or more layers is rather increased, and the risk of a collapsed layer at the second and higher layers is increased (FIG. 4).

  On the other hand, when the steel material for column members is high yield point steel, the degree of damage in the first layer and the second layer or more is reduced as compared with the case of using ordinary steel. In particular, when the steel material for the column member is made of high yield point steel and the column base and the foundation are semi-rigidly joined, the risk that a collapse layer is generated in all layers including the first layer of the multi-layer steel structure is reduced.

  The simulation test was performed on a 10-layer, 3-span framework model (designed with a floor height of 4 m, span length of 8 m, structural characteristic coefficient Ds = 0.25, column beam yield ratio of 1.5), Yokohama SURFACE, EL CentroNS, HachinoheEW, KobeNS. , TaftEW waves were input as seismic waveforms adjusted to a maximum speed of 200 kine respectively, and the average damage state of the five waves was obtained.

In the test, the yield strength of the column material in the 10-layer 3-span frame model is 325 N / mm ² (ordinary steel) and 650 N / mm ² (high yield point steel), and the rotational rigidity of the column base is rigid and semi-rigid. The two types were as follows.

  The rotational stiffness of the column bases that are semi-rigidly connected is the same as that of the first layer column head node (excluding the effect of the first layer column), and the maximum velocity of the seismic waveform of 200 kine is It is about 4 times the level assumed in the next design.

  FIG. 1 schematically shows a first embodiment of the present invention. In a multi-layer steel structure in which a column 1 is made of high yield steel and a beam 2 is made of ordinary steel, the column base 1a and the foundation 4 are made semi-rigid. The case of joining is shown.

FIG. 2 is a diagram schematically showing the bending moment distribution of the column in the first layer of the multi-layered steel structure shown in FIG. 1. The column base 1a and the foundation 4 are semi-rigidly connected with the same degree of fixing of the column head of the first layer. By doing so, the neutral point b in the bending moment distribution is located at approximately half of the floor height, and an excessive bending moment is prevented from being applied to the column base 1a. (In the figure, the neutral point b of the bending moment is displayed above the center of the floor height to show a semi-rigid connection.)
FIG. 3 is a diagram showing a second embodiment of the present invention. In the first layer, the foundation beam 5 is used and the foundation beam 5 and the column 1 are semi-rigidly joined.

It is also possible to join the column base 1a and the column 1 to the foundation (the ground plane 4) and the foundation beam 5 through a vibration control device at the joint between the column base 1a and the foundation 4 and the column 1 and the foundation beam 5. In that case, damage to the column is further reduced. Hysteretic dampers that act on the bending moment are suitable for the vibration control device , the yield strength is lower than the bending yield strength of the column, and the initial rotational stiffness is the rotational stiffness of the first layer column head node (however, the first layer column It is desirable to be greater than
When designing the multi-layered steel structure according to the present invention, the bending moment distribution of the column is obtained by inputting the horizontal seismic force for design.

The figure which shows one Embodiment of this invention. The figure which shows the effect of this invention. The figure which shows 2nd embodiment of this invention. The figure which shows the influence of the yield stress of a column beam and the rotation rigidity of a column end which gives to the damage of the column of two or more layers. The figure which shows the influence of the yield stress of a column beam and the rotational rigidity of a column end which gives to the damage of the column of the 1st layer. The figure explaining partial collapse mode. The figure explaining the whole collapse mode. Bending moment distribution chart of a column. The figure which shows typically the case where a 1st layer turns into a collapsed layer in the collapse mode where damage disperse | distributes to the beam end of each layer.

Explanation of symbols

1 Column 1a Column base 2 Beam 3 Beam-column joint 4 Foundation (ground plane)
5 foundation beam 10 pillar (conventional example)
10a column base 10b column head 10c column bottom 10d column top 20 beam (conventional example)
30 Plastic hinge (conventional example)
40 Beam-column joint (conventional example)
50 foundation (ground plane) (conventional example)

Claims (4)

In a multi-layer steel structure with a frame structure with a beam-bearing strength ratio exceeding 1.2 , the yield stress of the column member is set higher than the yield stress of the beam member, and the joint between the column base and the foundation in the first layer is half In the case of rigid joining, the column member is made of high yield point steel, and the rotational rigidity of the column base in the semi-rigid joining is made substantially the same as the fixing degree of the column head of the first layer. Structure. The multilayer steel structure according to claim 1, wherein the column base and the foundation are joined via a vibration control device. In a multi-layered steel structure with a frame structure with a beam-bearing strength ratio exceeding 1.2 , the yield stress of the column member is set higher than the yield stress of the beam member, and the connection between the column and the foundation beam in the first layer is half In the case of rigid joining, the column member is made of high yield point steel, and the rotational rigidity of the column base in the semi-rigid joining is made substantially the same as the fixing degree of the column head of the first layer. Structure. The multilayer steel structure according to claim 3, wherein the column and the foundation beam are joined via a vibration control device.

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