JP2019196698A - Structural steelwork and design method of structural steelwork - Google Patents

Abstract

To provide a structural steelwork having an improved earthquake performance compared to a case in which a steel column is formed using steel material with a low yield ratio even if the steel column is formed using the steel material with a high yield ratio at least partially.SOLUTION: A structural steelwork 1 is provided that comprises a steel beam and a steel column 21 formed by steel material having a yield ratio greater than 80% and less than 90% and is configured in a steel frame structure having a plurality of layers 11 in a vertical direction and a column - beam yield strength ratio is greater than or equal to 1.5 or (1) formula is satisfied and a design strength of a column base part 22 used in the layer arranged in most downward in a plurality of layers among the steel material is less than or equal to 0.815 times of a yield strength the steel material. (number 1)SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel structure and a method for designing a steel structure.

In recent years, the scale of structures tends to increase, and the span of beams constituting the structure tends to become longer. For this reason, the cross section of a pillar becomes large and the thickness of the pillar tends to increase. As the column becomes thicker, the mass of the column increases and the cost required to weld the column increases. For this reason, it is effective to form the column with high-strength steel and reduce the thickness of the column or reduce the weight of the column.
However, when the tensile strength of the steel material is increased, the manufacturing cost of the steel material increases and the labor required for column welding increases.

Against this background, steel materials with high yield strength have been developed by relaxing (increasing) the yield ratio of steel materials. The yield ratio is defined as a value obtained by dividing the yield strength by the tensile strength.
When steel material with high yield strength is used for the column, the column is designed to avoid plasticizing. Even in special structural forms such as super-high-rise structures and seismic isolation structures, it is possible to perform design in which column deformation remains within the elastic range even during earthquakes by conducting structural analysis. However, this type of design is complicated and applicable structures are limited.

  For example, even in a steel structure having a steel frame ramen structure which is generally widely used as shown in Patent Document 1, the steel beam precedes the steel column by setting the column beam strength ratio to exceed a predetermined threshold. It is possible to form a framework collapse mechanism that yields. If the framework collapse mechanism is formed in the steel structure, the deformation of the steel column can be kept within the elastic range.

Japanese Patent No. 4424112

However, in the steel column, in the column base part used for the layer arranged at the lowest position among the plurality of layers constituting the steel structure, there is no structural element yielding ahead of the column base part. For this reason, when a load exceeding the yield strength acts on the column base, the column base is subject to plasticization. In order to cope with this, the column base portion of the conventional steel structure is made of a steel material having a low yield ratio and a relatively small yield ratio.
Compared to the conventional steel with a low yield ratio, a steel material with a relatively high yield ratio and a high yield ratio has a small strain hardening. Therefore, when the yield strength of the steel column is the same, the increase in yield strength after plasticization is small. For this reason, there is a concern that the structural performance of the steel column, the steel beam, and the like is deteriorated as compared with the conventional frame structure using the steel column.
On the other hand, when the tensile strength of the steel column is the same and the yield ratio increases, the load resistance until the steel material yields increases. However, if a large load acts temporarily, such as during an earthquake, there is no room for a load that can withstand the yield strength.

  The present invention has been made in view of such problems, and even when a steel column is formed using at least a portion of a steel material having a high yield ratio, the steel column is formed using a steel material having a low yield ratio. An object of the present invention is to provide a steel structure having improved seismic performance as compared with the case where it is formed. Another object of the present invention is to set a steel column to be formed using a low yield ratio steel material, even if the steel column is formed using at least a portion of a steel material having a high yield ratio. It is to provide a method for designing a steel structure with improved seismic performance as compared with the case where it is made.

In order to solve the above problems, the present invention proposes the following means.
A steel structure according to the present invention includes a steel beam and a steel column formed of a steel material with a yield ratio of more than 80% and 90% or less, and a steel structure having a steel frame ramen structure having a plurality of levels in the vertical direction. The column beam strength ratio is 1.5 or more, or satisfies the formula (1), and the column used for the layer disposed at the lowest position among the plurality of layers among the steel columns. The design strength of the leg portion is characterized by being 0.815 times or less the yield strength of the steel material.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. Moment, and _p M _p is the total plastic moment of the joint.

According to the present invention, the column beam strength ratio is 1.5 or more, or the steel beam is plasticized before the steel column in order to satisfy the formula (1), and the portion other than the column base portion of the steel column The seismic performance is equivalent to the case where a steel column is formed using a steel material with a yield ratio of 80% or less.
Further, the column base is formed using a steel material having a high yield ratio of more than 80% and 90% or less, and the design strength of the column base is 0.815 times or less of the yield strength of the steel. For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Therefore, more energy can be absorbed as compared with the case where the column base is formed of a steel material having a low yield ratio.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio.

In the steel structure design method of the present invention, the yield ratio of the steel material forming the steel column included in the steel structure having a steel frame structure having a plurality of levels in the vertical direction is more than 80% and not more than 90%. The column beam strength ratio is set to 1.5 or more, or set so as to satisfy the formula (2), and among the steel columns, the layer arranged at the lowest position among the plurality of layers The design strength of the column base used in the above is set to a value that is lower than the yield strength of the steel material.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. And _p M _p is the total plastic moment of the joint.

According to this invention, in order to set the column beam bearing strength ratio to 1.5 or more, or to satisfy the formula (2), the steel beam is plasticized before the steel column, and the column base of the steel column The seismic performance of the part other than the part is equivalent to the case where the steel column is formed using a steel material having a yield ratio of 80% or less.
In addition, the column base is formed using a steel material with a high yield ratio in which the yield ratio exceeds 80% and is less than 90%, and the design strength of the column base is set to a value that is lower than the yield strength of the steel. ing. For this reason, compared to the case where the design strength of the column base is set to be equivalent to the yield strength of the steel material, the true stress for the same true strain and the bending moment for the same rotation angle are increased, and the column base is more. Can absorb the energy.
Therefore, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

  Further, another steel structure of the present invention is a steel structure having a steel frame structure including a steel column formed of steel and having a plurality of levels in the vertical direction. The column base part used for the said hierarchy arrange | positioned lowest in the hierarchy is formed with the said steel material of the high yield ratio whose yield ratio exceeds 80% and is 90% or less, and the design strength of the said column base part is The yield strength of the steel material having the high yield ratio is 0.815 times or less, and the steel columns other than the column base are formed of the steel material having a yield ratio of 80% or less. It is said.

According to the present invention, the joint portion between the steel column other than the column base and the steel beam is formed of a steel material having a low yield ratio with a yield ratio of 80% or less. It becomes equivalent to the part.
Moreover, the column base part of a steel column is formed using the steel material of high yield ratio, and the design strength of a column base part is 0.815 times or less of the yield strength of steel materials. For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Thereby, more energy can be absorbed compared with the case where a column base part is formed with the steel material of a low yield ratio.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio.

  Further, another steel structure design method of the present invention is a steel column provided in a steel structure having a steel frame ramen structure having a plurality of levels in the vertical direction, and is arranged at the lowest position in the plurality of levels. The yield ratio of the steel material that forms the column base used in the hierarchy is set in the range of more than 80% and 90% or less, and the design strength of the column base is in the range of the yield ratio exceeding 80% and 90% or less. The yield ratio of the steel column other than the column base is set to a value of 80% or less.

According to this invention, the joint portion between the steel column and the portion other than the column base portion and the steel beam is set to be formed of a steel material having a low yield ratio of a yield ratio of 80% or less. Is equivalent to the conventional joint.
In addition, the steel column base is set to form a steel column base using a high yield ratio steel material with a yield ratio exceeding 80% and 90% or less, and the design strength of the column base is higher than the yield strength of the steel material. A reduced value is set. For this reason, even if a steel material with a high yield ratio is used, the true stress for the same true strain and the bending moment for the same rotation angle are higher than when the design strength of the column base is set equal to the yield strength of the steel material. Each becomes larger, and the column base can absorb more energy.
Therefore, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

Another steel structure of the present invention is a steel structure having a steel frame structure including a steel column formed of a steel material having a yield ratio of more than 80% and 90% or less, and the design of the steel column The strength is not more than 0.815 times the yield strength of the steel material.
According to the present invention, the entire steel column is formed using a steel material having a yield ratio of more than 80% and 90% or less, and the design strength of the steel column is 0.815 times or less of the yield strength of the steel material. . For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Thereby, for example, more energy can be absorbed in each part of the steel column than when the steel column is formed of a steel material having a low yield ratio of 80% or less.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio.

In another steel structure design method of the present invention, the yield ratio of the steel material forming the steel column provided in the steel structure with the steel frame ramen structure having a plurality of levels in the vertical direction exceeds 80% and is 90% or less. And the design strength of the steel column is set to a value that is lower than the yield strength of the steel material.
According to the present invention, the entire steel column is formed using the steel material having a high yield ratio of a yield ratio higher than the range of 80% or less and a yield ratio exceeding 80% and 90% or less. The design strength is set to a value that is lower than the yield strength of steel. For this reason, even if a steel material with a high yield ratio is used, the true stress for the same true strain and the bending moment for the same rotation angle are higher than when the design strength of the column base is set equal to the yield strength of the steel material. Each becomes larger, and more energy can be absorbed in each part of the steel column.
Therefore, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

Another steel structure of the present invention is a steel frame structure including a steel beam and a steel column formed of a steel material having a yield ratio of more than 80% and 90% or less, and having a plurality of levels in the vertical direction. The steel beam structure having a column beam strength ratio of 1.5 or more, or satisfying the formula (3), and among the steel columns, the layer arranged at the lowest position among the plurality of layers The column base used in the above is formed in a rectangular tube shape, and the design strength of the column base is a reduction factor α ₁ or less according to the expression (4) of the yield strength of the steel material.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. _P M _p is the total plastic moment of the joint, D ₁ is the length of one side outside w in the cross section of the column base, and t ₁ is the thickness of the column base is there.

According to the present invention, the column beam strength ratio is 1.5 or more, or the steel beam is plasticized before the steel column in order to satisfy the expression (3), and the portion other than the column base portion of the steel column The seismic performance is equivalent to the case where a steel column is formed using a steel material with a yield ratio of 80% or less.
In addition, the column base is formed in a square tube shape using steel with a high yield ratio of more than 80% and less than 90%, and the design strength of the column base is reduced by equation (4) of the yield strength of the steel. The coefficient α is ₁ or less. For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Therefore, more energy can be absorbed as compared with the case where the column base is formed of a steel material having a low yield ratio.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio. And compared with the case where the design strength of a steel column is 0.815 times or less of the yield strength of steel materials, a column base part can be comprised with an equivalent or less material, and a column base part can be reduced in weight.

Further, another steel structure of the present invention is a steel structure having a steel frame structure including a steel column formed of steel and having a plurality of levels in the vertical direction. The column base used for the level arranged at the lowest level in the level is formed in a rectangular tube shape, and the column base has a high yield ratio of more than 80% and not more than 90%. The column base is made of steel, and the design strength of the column base is not more than a reduction factor α ₁ times of the yield strength of the steel with the high yield ratio according to the formula (5), and other than the column base of the steel columns Is characterized by being formed of the steel material with a yield ratio of 80% or less.
However, D ₁ is the length of the outer side in the cross section of the column base, t ₁ is the thickness of the columnar leg portion.

According to the present invention, the joint portion between the steel column other than the column base and the steel beam is formed of a steel material having a low yield ratio with a yield ratio of 80% or less. It becomes equivalent to the part.
Moreover, the column base part of the steel column is formed in a rectangular tube shape using a steel material with a high yield ratio, and the design strength of the column base part is less than a reduction factor α ₁ times according to the formula (5) of the yield strength of the steel material. For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Thereby, more energy can be absorbed compared with the case where a column base part is formed with the steel material of a low yield ratio.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio. And compared with the case where the design strength of a steel column is 0.815 times or less of the yield strength of steel materials, a column base part can be comprised with an equivalent or less material, and a column base part can be reduced in weight.

Another steel structure of the present invention is a steel structure having a steel frame structure having a steel column formed in a square tube shape with a steel material having a yield ratio of more than 80% and 90% or less, The design strength of the steel column is characterized in that the yield coefficient of the steel material is a reduction factor α of ₂ times or less according to the equation (6).

According to the present invention, the steel column is entirely formed into a rectangular tube shape using a steel material with a yield ratio of more than 80% and 90% or less, and the design strength of the steel column is (6) the yield strength of the steel material. The reduction coefficient α according to the equation is ₂ times or less. For this reason, in a steel material with a high yield ratio, the true stress for the same true strain is higher than that of a steel material with a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material with a low yield ratio. Thereby, for example, more energy can be absorbed in each part of the steel column than when the steel column is formed of a steel material having a low yield ratio of 80% or less.
Accordingly, the seismic performance of the entire steel column can be improved as compared with the case where the entire steel column is formed of a material having a low yield ratio. And compared with the case where the design strength of a steel column is 0.815 times or less of the yield strength of steel materials, a column base part can be comprised with an equivalent or less material, and a column base part can be reduced in weight.

In the steel structure, the steel material having a yield ratio of more than 80% and 90% or less may have a yield strength of 400 MPa to 550 MPa and a tensile strength of 490 MPa to 640 MPa.
According to this invention, even when a steel column is formed using a steel material with higher yield strength and tensile strength, the seismic resistance of the entire steel column is greater than when the entire steel column is formed of a material with a low yield ratio. Performance can be improved.

In the steel structure, the steel material having a yield ratio of more than 80% and 90% or less may have a yield strength of 500 MPa to 650 MPa and a tensile strength of 590 MPa to 740 MPa.
According to this invention, even when a steel column is formed using a steel material with higher yield strength and tensile strength, the seismic resistance of the entire steel column is greater than when the entire steel column is formed of a material with a low yield ratio. Performance can be improved.

In the steel structure design method described above, the value reduced from the yield strength of the steel material may be 0.815 times or less the yield strength of the steel material.
According to the present invention, in a steel material having a yield ratio in the range of more than 80% and 90% or less, the true stress for the same true strain is set to be equal to or greater than the true stress of the steel material having a yield ratio of 80% or less, and the same rotation angle The bending moment with respect to can be made equal to or higher than the bending moment of steel having a yield ratio of 80% or less.

Further, in another method for designing a steel structure of the present invention, the shape of the column base is set to a rectangular tube shape, and the value obtained by reducing the yield strength of the steel material is the yield strength of the steel material ( 7) The reduction coefficient α according to the equation may be ₁ or less.

  According to this invention, compared with the case where the design strength of the column base is 0.815 times or less the yield strength of the steel material, the column base can be configured with the same or less material, and the column base is reduced in weight. be able to.

Further, in another method for designing a steel structure according to the present invention, the shape of the steel column is set to a rectangular tube shape, and a value obtained by reducing the yield strength of the steel material is (8 of the yield strength of the steel material). ) The reduction coefficient α may be ₂ times or less.

  According to this invention, compared with the case where the design strength of the steel column is 0.815 times or less the yield strength of the steel material, the steel column can be configured with the same or less material, and the steel column can be reduced in weight. .

  According to the steel structure of the present invention, even if the steel column is formed using at least a portion of the steel material having a high yield ratio, the seismic performance is improved as compared with the case where the steel column is formed using a steel material having a low yield ratio. Can be improved. Further, according to the method for designing a steel structure of the present invention, even if it is set to form a steel column using at least a part of a steel material having a high yield ratio, the steel column is formed using a steel material having a low yield ratio. The seismic performance can be improved as compared to the case where it is set to form.

It is a front view which shows typically the steel structure of 1st Embodiment of this invention. It is a figure which shows an example which modeled the true stress-true strain diagram of steel materials. (A) is sectional drawing of cutting line A1-A1 in FIG. 1, (B) is sectional drawing of cutting line A2-A2 in FIG. It is a front view which shows typically the frame collapse mechanism in which the steel beam yields ahead of a steel column in the steel structure. It is an enlarged view of the A6 part in FIG. It is a perspective view explaining the analysis model and analysis conditions used for the simulation of the column base part of the steel structure. It is a figure which shows the relationship of the rotation angle of a column base part with respect to the bending moment of the column base part obtained by simulation. It is a flowchart which shows the design method of the steel structure of 1st Embodiment of this invention. It is a figure which shows the outline | summary of a structure of the design apparatus of a steel structure. (A) is sectional drawing of the cutting line A1-A1 in FIG. 1 of the steel structure of 2nd Embodiment of this invention, (B) is the cutting line A2-A2 of FIG. 1 of the steel structure. It is sectional drawing. It is a flowchart which shows the design method of the steel structure of 2nd Embodiment of this invention. (A) is sectional drawing of the cutting line A1-A1 in FIG. 1 of the steel structure of 3rd Embodiment of this invention, (B) is the cutting line A2-A2 of FIG. 1 of the steel structure. It is sectional drawing. It is a flowchart which shows the design method of the steel structure of 3rd Embodiment of this invention. It is a figure which shows the analysis result of the largest interlayer deformation angle in each hierarchy. It is a figure explaining the maximum interlayer deformation angle in each hierarchy. It is a cross-sectional view of the steel column of the steel structure of the fourth embodiment of the present invention. It is a figure which shows the relationship of the rotation angle with respect to the bending moment of a column base, when the width-thickness ratio of the column base of the same steel column is 19. It is a figure which shows the relationship of the rotation angle with respect to the bending moment of a column base, when the width-thickness ratio of the same column base is 24. It is a figure which shows the relationship of the rotation angle with respect to the bending moment of a column base, when the width-thickness ratio of the same column base is 27. It is a figure which shows the relationship of the rotation angle with respect to the bending moment of a column base, when the width-thickness ratio of the same column base is 38. It is the figure which added the area | region corresponding to a true strain to the example which modeled the true stress-true strain diagram of steel materials. It is a figure which shows the relationship of the rotation angle of a column base part with respect to the bending moment of the column base part obtained by simulation. It is a figure which shows the analysis result of the largest interlayer deformation angle in each hierarchy. It is a figure showing the relationship of the reduction coefficient with respect to the width-thickness ratio obtained by simulation. It is a figure which shows the analysis result of the largest interlayer deformation angle in each hierarchy in case width-thickness ratio is 20. FIG. It is a figure which shows the analysis result of the largest interlayer deformation angle in each hierarchy in case width-thickness ratio is 26. It is a figure which shows the analysis result of the largest interlayer deformation angle in each hierarchy in case width-thickness ratio is 32.

(First embodiment)
Hereinafter, a first embodiment of a steel structure according to the present invention will be described with reference to FIGS. 1 to 9.
As shown in FIG. 1, the steel structure 1 of this embodiment is comprised by the steel frame ramen structure, and has the some hierarchy (floor) 11 in the up-down direction, for example. In the steel structure 1, a plurality of layers 11 are stacked in the vertical direction. The steel structure 1 includes a plurality of steel columns 21 and a plurality of steel beams 26.
The steel column 21 extends along the vertical direction. The plurality of steel columns 21 are arranged at intervals from each other along a horizontal plane. The steel column 21 (a column base 22 and a column main body 23 described later) is formed of a steel material having a yield ratio of more than 80% and 90% or less. Hereinafter, a steel material having a yield ratio of more than 80% and 90% or less is also referred to as a steel material having a high yield ratio.

FIG. 2 shows an example of modeling a true stress-true strain diagram of a steel material. The horizontal axis in FIG. 2 represents true strain, and the vertical axis represents true stress (MPa (megapascal)). A solid line L1 is a true stress-true strain diagram in a steel material having a yield ratio of 80% or less (hereinafter also referred to as a steel material having a low yield ratio). In a conventional steel frame structure having a steel frame ramen structure, a steel column formed of a steel material having a low yield ratio is used.
In the line L1, in the section from the state where the true stress is 0 to the yield strength σ1, the true stress increases while maintaining a proportional relation to the true strain. In the line L1, when the true stress exceeds the yield strength σ1, the amount of increase of the true stress with respect to the increase of the true strain gradually decreases as the true strain increases. In FIG. 2, the case where the yield ratio is 74% is indicated by a line L1. In steel materials with a low yield ratio, strain hardening is relatively large.

  A steel material with a high yield ratio (hereinafter referred to as a high yield ratio-low yield strength steel material, which is not changed in the longitudinal elastic modulus and yield strength σ1 of the steel material). The true stress-true strain diagram of the proof steel is a part of the high yield ratio steel material is indicated by a dotted line L2. In this case, the increase amount of the true stress with respect to the increase of the true strain after the true stress exceeds the yield strength σ1 is smaller than the increase amount of the steel material having a low yield ratio, and the line L2 is along the horizontal axis rather than the line L1. It becomes like this. In FIG. 2, the case where the yield ratio is 87% is indicated by a line L2. The same applies to the line L3 described later.

On the other hand, the true stress-true strain diagram of the steel material on which the steel column 21 is formed is indicated by a line L3 by a one-dot chain line. The steel material on which the steel column 21 is formed is a steel material in which the yield strength is increased to σ2 without changing the longitudinal elastic modulus and yield ratio of the steel material indicated by the line L2. That is, the steel material indicated by the line L3 (hereinafter referred to as a steel material having a high yield ratio-high yield strength. The steel material having a high yield ratio-high yield strength is a part of a steel material having a high yield ratio) has a high yield ratio. It is a steel material. In steel materials with a high yield ratio-high yield strength, strain hardening is relatively small.
In a steel material with a high yield ratio-high yield strength, the true stress for the same true strain is equal to or greater than the true stress of the steel material with a low yield ratio indicated by line L1. In other words, line L3 envelops line L1.

  In addition, you may comprise so that the line L3 may envelope the line L1 only in the range of the true strain produced when steel materials are actually used.

As shown in FIG. 1, the steel column 21 includes a column base 22 disposed at the lower end of the steel column 21 and a column main body 23 disposed above the column base 22.
Columnar leg portion 22 of the steel columns 21, are used in the lower end of the hierarchy 11 ₁ is most disposed below hierarchy among the plurality of layers 11 (e.g., the first floor). In this example, columnar leg portion 22 is disposed on the lower end of the hierarchy 11 _1. Although the columnar leg portion 22 is used for the lower end of the hierarchy 11 _1, columnar leg portion 22 of the steel columns 21, or may be used in a portion corresponding to the entire hierarchy 11 ₁ .
The column main body 23 is a portion other than the column base portion 22 of the steel column 21. In this example, the pillar body 23, an upper end of the hierarchy 11 _1, are used in a hierarchy 11 disposed above the hierarchy 11 _1.
Below, the column main body 23 is demonstrated first.

As shown in FIGS. 1 and 3A, the column main body 23 is formed of, for example, a square steel pipe having a rectangular cross section. In the cross section shown in FIG. 3A, the outer shape of the column main body 23 is, for example, a length L6 in both the vertical and horizontal directions, and the thickness of the column main body 23 is the length L7 at any position.
The column main body 23 is set to have an outer shape and a thickness assuming that the design strength of the column main body 23 is equivalent to the yield strength of a steel material having a high yield ratio-high yield strength.

As shown in FIGS. 1 and 3B, the column base portion 22 is formed of, for example, a square steel pipe having a rectangular cross section. In the cross section shown in FIG. 3B, the outer shape of the column base 22 is, for example, a length L6 in both the vertical and horizontal directions, and the thickness of the column base 22 is a length L8 at any position. The length L8 of the column base 22 is longer than the length L7 of the column main body 23.
That is, the column base 22 and the column main body 23 have the same outer shape, but the column base 22 is thicker. For this reason, the cross-sectional area by the cross section of the column base part 22 is wider than the cross-sectional area by the cross section of the column main body 23.

The design strength of the column base 22 is not more than a predetermined coefficient multiple (0.815 times) of the yield strength σ2 of the steel material having a high yield ratio-high yield strength. This predetermined coefficient is a value smaller than 1. In other words, the design strength of the column base 22 is reduced more than the yield strength of the steel material having a high yield ratio-high yield strength. The design strength mentioned here means strength for determining an allowable stress used for structural calculation of a steel structure.
Note that as the predetermined coefficient is reduced, the amount of material used for the column base portion 22 increases. For this reason, it is preferable that the lower limit value is 0.7 or more, and more preferably 0.75 even if it is less than or equal to a predetermined coefficient multiple from the economical rationality.

The reason why the predetermined coefficient is set to 0.815 is as follows. That is, in FIG. 2, among the conditions satisfying the condition that the line L3 envelops the line L1, the condition for making the yield strength σ2 as small as possible was obtained by simulation described later. At this time, the value of (σ1 / σ2) is 0.815.
If the design strength of the column base 22 is 0.815 times or less of the yield strength σ2 of the steel with a high yield ratio-high yield strength, the design strength of the column base 22 is the yield of the steel with a high yield ratio-high yield strength. Compared with the case where it is equivalent to the proof stress, the cross-sectional area by the cross section of the column base part 22 becomes large.

More specifically, for example, when the stress acting on the column base 22 is made constant, the design strength of the column base 22 is equivalent to the yield strength of a steel material having a high yield ratio-high yield strength. In comparison, when the design strength of the column base portion 22 is 0.815 times or less of the yield strength σ2 of the steel material having a high yield ratio-high yield strength, the cross-sectional area of the column base portion 22 is (1 /0.815) times or more.
The same applies to the case where the moment acting on the column base is made constant, although the ratio of the cross-sectional area may be different.

  The upper end portion of the column base portion 22 is joined to the lower end portion of the column main body 23 by welding or the like. As shown in FIG. 1, the lower end portion of the column base portion 22 is joined to the foundation B.

The steel beam 26 is formed of, for example, a steel material having an H-shaped cross section and extends along a horizontal plane. The plurality of steel beams 26 are arranged at intervals from each other along the vertical direction. The material forming the steel beam 26 is not particularly limited, and may be a steel material having a low yield ratio or a steel material having a high yield ratio-high yield strength.
The column main body 23 and the steel beam 26 of the steel column 21 are joined by a joint portion (panel) 31. For example, the joint portion 31 is configured by a part of the column main body 23, a welded portion that fixes the steel beam 26 to a part of the column main body 23, and the like.

In the steel structure 1 configured as described above, as shown in FIG. 4, a known framework collapse mechanism in which the steel beam 26 yields ahead of the steel column 21 is used. In FIG. 4, a joint portion 27 described later is highlighted.
That is, the strength of the joint portion 27 or the joint portion 31 joined to the joint portion 31 in the steel beam 26 is weaker than that of the steel beam 26 other than the joint portion 27 and the steel column 21. Therefore, when an earthquake occurs and the shaking of the earthquake is transmitted to the steel structure 1 via the foundation B, the steel beam is preceded by the part other than the joint part 27 in the steel beam 26 and the steel column 21. 26 junctions 27 or junctions 31 yield.

In order to realize the framework collapse mechanism, the steel structure 1 is configured such that the column beam bearing strength ratio is 1.5 or more, or the expression (11) is satisfied.
The column beam strength ratio here is defined as a value obtained by dividing the yield strength of the steel column (column) by the yield strength of the steel beam (beam).

However, in _(11), c _{M p} refers to the full plastic moment of the portion to be joined to the joint portion 31 of the steel columns 21. _b M _p means the total plastic moment of the portion of the steel beam 26 joined to the joint 31. _p M _p means the total plastic moment of the joint 31. The total plastic moments _c M _p , _b M _p , and _p M _p can be obtained from known equations.
The expression of Σ _c M _p means the sum of the total plastic moments of the portions joined to the joint 31 among all the steel columns 21 joined to the joint 31 of interest. For example, the description will be made assuming that the joint 31A among the plurality of joints 31 shown in FIG.
As shown in FIG. 5, it is assumed that the column main body 23A, the column main body 23B, the steel beam 26A, and the steel beam 26B of the steel column 21 are bonded to the joint 31A. In this case, the value of Σ _c M _{p is} the sum of the total plastic moment of the portion of the column body 23A joined to the joint 31A and the total plastic moment of the portion of the column body 23B joined to the joint 31A. become.

The expression of Σmin {1.5 _b M _p , 1.3 _p M _p } represents the total plastic moment of the portion joined to the joint 31 among all the steel beams 26 joined to the joint 31 of interest. It means the smallest value among the value of 1.5 times the sum and the value of 1.3 times the total plastic moment of the joint 31 of interest.
For example, in the example shown in FIG. 5, Σmin {1.5 _b M _p , 1.3 _p M _p } is expressed by the total plastic moment of the portion of the steel beam 26A joined to the joint 31A and the steel beam 26B. Of these, the smallest value is 1.5 times the sum of the total plastic moments of the portions joined to the joint portion 31A and 1.3 times the total plastic moments of the joint portion 31A.

  The fact that the beam-to-column strength ratio is 1.5 or more and that the equation (11) is satisfied is the result of the collapse of the framework described in the “2008 Cold Forming Square Steel Pipe Design and Construction Manual”, edited by the same editorial board. This is a condition for realizing the mechanism. However, the frame collapse mechanism in which the steel beam 26 yields before the steel column 21 is not limited to this.

Here, the result of having performed the simulation by a finite element method, changing the material of steel materials in order to form a column base part is explained. FIG. 6 shows the analysis model used in the simulation and the analysis conditions.
It is assumed that the column base portion 22 ′ is formed of a square steel pipe that is cold-press formed. The column base portion 22 ′ is modeled by a shell element, and has a steel pipe diameter of 600 mm and a plate thickness of 22 mm (□ 600 × 22). The width-thickness ratio of the rectangular steel pipe is 27, which corresponds to the vicinity of the FA rank limit value in the width-thickness ratio rank of the press column BCP325. The length L11 of the column base portion 22 ′ was 2700 mm, and the shear span ratio was 4.5. The column base portion 22 ′ was given the true stress-true strain relationship shown in FIG.
This analysis model is an idealized boundary condition by taking out from the column base 22 'of the steel frame frame structure subjected to horizontal force to the moment inflection point.

  As shown in FIG. 6, the column base portion 22 ′ is supported in a cantilever column shape by fixing the lower end portion of the column base portion 22 ′ to the support member B ′. That is, the lower end of the column base 22 'is a fixed end, and the upper end of the column base 22 is a free end. The upper end of the column base 22 'is the loading point. A monotonous load F2 was applied to the upper end of the column base portion 22 in the horizontal direction after applying a constant compression axial force F1 having an axial force ratio (acting axial force / (design strength × cross-sectional area)) of 0.3.

FIG. 7 shows the relationship of the rotation angle of the column base 22 ′ to the bending moment of the column base 22 ′ obtained by simulation. The horizontal axis in FIG. 7 represents the rotation angle (rad (radian)) of the column base 22 ′, and the vertical axis represents the bending moment (kNm (kilonewton meter)) acting on the column base 22 ′.
A solid line L16 is a simulation result of a steel material having a low yield ratio. A dotted line L17 is a simulation result with a steel material having a high yield ratio-low yield strength, and a dashed line L18 is a simulation result with a steel material having a high yield ratio-high yield strength.

  In any of the simulation results, the yield strength deteriorates due to local buckling occurring in the column base portion 22 ', and the column base portion 22' reaches the end. In the case of a steel material having a high yield ratio-low yield strength shown by line L17, the same behavior as that of the steel material having a low yield ratio shown by line L16 is shown up to the yield strength. However, the yield strength increase is small after yielding, and the maximum yield strength due to local buckling and the yield strength retained after yield strength degradation are smaller than in the case of steel materials with a low yield ratio. That is, when a steel material having a high yield ratio-low yield strength is used under such conditions, the energy that can be absorbed by the column base 22 'that causes plasticization is reduced, and the earthquake resistance as a framework is also reduced. There is a fear.

For example, assuming that the yield strength σ1 is 325 MPa and the yield strength σ2 is 400 MPa, a simulation was performed to obtain the true stress-true strain relationship of the steel material. In this case, the predetermined coefficient is 0.815 (= 325/400). At this time, as shown in FIG. 2, the yield strength σ2 is the smallest among the conditions that satisfy the condition that the line L3 envelops the line L1.
As shown in FIG. 7, in the steel material having the high yield ratio-high yield strength shown by the line L18, the bending moment with respect to the same rotation angle is higher than that of the steel material having the low yield ratio shown by the line L16. In addition, when the bending moment of the steel material with the low yield ratio shown by the point P1 is the largest, the steel material with the low yield ratio is locally buckled. When the bending moment of the steel with high yield ratio-high yield strength shown by point P2 is the largest, the steel with high yield ratio-high yield strength is locally buckled.

For example, when the steel material having a low yield ratio indicated by the line L16 increases from the rotation angle ₀ rad to θ _{0, the} area T1 formed by the line L16 and the horizontal axis is rotated, and the column base portion 22 ′ rotates from the rotation angle ₀ rad to θ _0. This is equivalent to the energy absorbed. When a steel material with a high yield ratio-high yield strength is used, the bending moment for the same rotation angle is larger than when a steel material with a low yield ratio is used, and the column base 22 'has more energy. It can be absorbed.

Generally, in order to lower the yield ratio of steel materials, it is necessary to add an alloy to the steel materials, and the cost required to manufacture the steel materials increases. Further, when the yield ratio of the steel material is lowered, the weldability of the steel material is deteriorated, for example, it is necessary to weld the steel material after the steel material is preheated.
By using a steel material with a high yield ratio, the manufacturing cost of the steel material can be reduced and the weldability of the steel material can be improved.

Next, the design method of the steel structure 1 of this embodiment for designing the steel structure 1 configured as described above will be described. FIG. 8 is a flowchart showing a steel structure design method S10 in the first embodiment of the present invention. The load acting on the column base portion 22 of the steel structure 1 is estimated in advance.
First, in the yield ratio selection step (step S11 shown in FIG. 8), the yield ratio of the steel material forming the steel column 21 included in the steel structure 1 exceeds 80%, which is higher than the normally used range of 80% or less. Set to a range of 90% or less. Specifically, the steel column 21 is set to be formed of a steel material having a high yield ratio-high yield strength. In the yield ratio selection step S11, the type (steel type) of the steel material used for the steel column 21 is set.
When the yield ratio selection step S11 ends, the process proceeds to step S13.

Next, in the collapse mechanism selection step (step S13), the column beam yield strength ratio is set to 1.5 or more, or is set so as to satisfy the expression (11). In this example, it is assumed that the column beam yield strength ratio is set to 1.5 or more, for example. When the collapse mechanism selection step S13 ends, the process proceeds to step S15.
Next, in the column base design strength setting step (step S15), the design strength of the column base 22 is set to a value not more than 0.815 times the yield strength of the steel material on which the column base 22 is formed. The design strength of the column main body 23 is set to be equivalent to the yield strength of a steel material having a high yield ratio-high yield strength. For this reason, even if the column base 22 and the column main body 23 are formed of the same high yield ratio-high yield strength steel material, the column base 22 is thicker than the column main body 23. In the column base design strength setting step S15, the cross-sectional shapes of the column base 22 and the column main body 23 are determined.
When the column base design strength setting step S15 is finished, all the steps of the steel structure design method S10 are finished, and the steel structure 1 is designed.

  The order of performing the yield ratio selection step S11, the collapse mechanism selection step S13, and the column base design strength setting step S15 is not particularly limited.

  The steel structure design apparatus may be configured by a computer by performing each step of the steel structure design method S10. As shown in FIG. 9, a steel structure design device 41 includes a CPU (Central Processing Unit) 42, a storage device 43, a recording / reproducing device 44, an input device 45, a display device 46, and an input / output interface. 47.

The CPU 42 includes a yield ratio selecting unit 42a that performs the above-described yield ratio selecting step S11, a collapse mechanism selecting unit 42b that performs the collapse mechanism selecting step S13, and a column base design strength setting unit that performs the column base design strength setting step S15. 42c.
The storage device 43 is a hard disk or the like, and stores various data, programs, and the like. The program includes a steel structure design program for causing the computer to function as the steel structure design device 41.

The recording / reproducing device 44 records and reproduces data with respect to a storage medium 44a such as a CD or a DVD. The storage medium 44a stores a steel structure design program and the like. When the storage medium 44a is inserted into the recording / reproducing device 44, the recording / reproducing device 44 reproduces the steel structure design program recorded on the storage medium 44a, and the reproduced steel structure design program, etc. Send to CPU42. The CPU 42 executes a design program or the like of the sent steel structure.
The input device 45 includes a keyboard, a mouse, and the like. The display device 46 is, for example, a liquid crystal display.

As described above, according to the steel structure 1 of the present embodiment, the beam strength ratio is 1.5 or more, or in order to satisfy the expression (11), the steel beam 26 is ahead of the steel column 21. Thus, the seismic performance of the column main body 23 of the steel column 21 is equivalent to the case where the steel column 21 is formed using a steel material having a low yield ratio of a yield ratio of 80% or less.
Further, the column base 22 is formed using a steel material having a high yield ratio of more than 80% and 90% or less, and the yield strength of the column base 22 is 0.815 times the yield strength of the steel. It is as follows. For this reason, in a steel material having a high yield ratio-high yield strength, the true stress for the same true strain is higher than that of a steel material having a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material having a low yield ratio. Thereby, more energy can be absorbed compared with the case where a column base part is formed with the steel material of a low yield ratio.
Therefore, the seismic performance of the steel column 21 as a whole can be improved as compared with the case where the entire steel column 21 is formed of a material having a low yield ratio.

Furthermore, about the steel column 21, the steel material of a high yield ratio is used to an upper hierarchy, and intensity | strength reduction is not carried out. Therefore, in a building where the column beam strength ratio is secured, the cross section can be minimized by using high yield strength, which is very economical.
This effect is the same also about steel structure design method S10 mentioned later.

In addition, according to the steel structure design method S10 of the present embodiment, the column beam strength ratio is set to 1.5 or more, or set so as to satisfy the expression (11). The steel beam 26 is plasticized, and the seismic performance of the column main body 23 of the steel column 21 is equivalent to the case where the steel column 21 is formed by using a steel material having a low yield ratio, for example, a normally used yield ratio is 80% or less. Become.
Moreover, the column base 22 is formed using a steel material having a high yield ratio-high yield strength in which the yield ratio exceeds 80% and is 90% or less, and the design strength of the column base 22 is increased to a high yield ratio-high yield strength. Is set to be 0.815 times or less of the yield strength of steel. For this reason, the true stress for the same true strain is equal to or greater than the true stress of the steel material having a low yield ratio, the bending moment for the same rotation angle is equal to or greater than the bending moment of the steel material having a low yield ratio, and the column base portion 22 is more. Can absorb the energy.
Therefore, the seismic performance of the steel column 21 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

The steel material with a high yield ratio may have a yield strength of 400 MPa to 550 MPa and a tensile strength of 490 MPa to 640 MPa. The yield strength and tensile strength of the steel material can be adjusted by additives and the like. By constituting the steel material in this way, even when the steel column 21 is formed using a steel material with higher yield strength and tensile strength, compared to the case where the entire steel column 21 is formed of a material with a low yield ratio, The seismic performance of the steel column 21 as a whole can be improved.
The steel material with a high yield ratio may have a yield strength of 500 MPa to 650 MPa and a tensile strength of 590 MPa to 740 MPa. By constituting the steel material in this way, even when the steel column 21 is formed using a steel material with higher yield strength and tensile strength, the steel frame is compared with a case where the entire steel column is formed of a material with a low yield ratio. The seismic performance of the column 21 as a whole can be improved.

In the column base design strength setting step S15, the design strength of the column base 22 is set to a value lower than the yield strength of the high yield ratio-high yield strength steel material on which the column base 22 is formed. May be. The design strength of the column base 22 is set to be equal to the yield strength of the steel material having a high yield ratio-high yield strength, and the true stress for the same true strain is compared with the case of using the steel material having a high yield ratio-low yield strength. The bending moment for the same rotation angle increases. As a result, the column base 22 can absorb more energy.
Therefore, the seismic performance of the steel column 21 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. 1, FIG. 10 and FIG. Only the point will be described.
As shown in FIG.1 and FIG.10, the steel structure 2 of this embodiment is provided with the steel column 51 instead of the steel column 21 of the steel structure 1 of 1st Embodiment. The steel column 51 includes a column main body 53 instead of the column main body 23 of the steel column 21.
The column main body 53 is formed of a steel material having a low yield ratio. The column body 53 is formed of, for example, a rectangular steel pipe having a rectangular cross section. In the cross section shown in FIG. 10A, the outer shape of the column main body 53 is, for example, a length L6 both vertically and horizontally, and the thickness of the column main body 53 is a length L8 at any position.

As shown in FIG. 10B, the same member as that of the first embodiment is used for the column base portion 22. The column base portion 22 is formed of a steel material having a high yield ratio-high yield strength. The column base part 22 has a design strength of the column base part 22 that is 0.815 times or less (or may be 0.815 times) the yield strength of a steel material having a high yield ratio-high yield strength.
In the present embodiment and the third embodiment to be described later, the same examination as in the first embodiment may be performed with a value of 0.815 as a predetermined coefficient.

Next, the design method of the steel structure 2 of this embodiment for designing the steel structure 2 configured as described above will be described. FIG. 11 is a flowchart showing a steel structure design method S20 in the second embodiment of the present invention.
First, in the column base part yield ratio selection step (step S21 shown in FIG. 11), the yield ratio of the steel material forming the column base part 22 of the steel column 51 is set in a range of more than 80% and 90% or less. Specifically, the steel column 51 is set to be formed of a steel material having a high yield ratio-high yield strength.
When the column base yield ratio selection step S21 is completed, the process proceeds to step S23.

Next, in the column base design strength setting step (step S23), the design strength of the column base 22 is set to a value not more than 0.815 times the yield strength of the steel material having a high yield ratio-high yield strength. When the column base design strength setting step S23 ends, the process proceeds to step S25.
Next, in the column body yield ratio selection step (step S25), the yield ratio of the column body 53 of the steel column 51 is set to a range of 80% or less. Specifically, the column main body 53 is set to be formed of a steel material with a low yield ratio.
When the column main body yield ratio selection step S25 is completed, all the steps of the steel structure design method S20 are completed, and the steel structure 2 is designed.

  In addition, the order which performs column base part yield ratio selection process S21, column base part design strength setting process S23, and column main body yield ratio selection process S25 is not specifically limited.

As described above, according to the steel structure 2 of the present embodiment, the joint portion between the column main body 53 of the steel column 51 and the steel beam 26 is constituted by a part of the column main body 53 and the like. For this reason, it is formed with a steel material having a low yield ratio of 80% or less that is usually used, and the seismic performance is equivalent to that of a conventional joint.
Further, the column base portion 22 of the steel column 51 is formed using a steel material having a high yield ratio-high yield strength, and the design strength of the column base portion 22 is 0.815 of the yield strength of the steel material having a high yield ratio-high yield strength. Is less than double. For this reason, in a steel material having a high yield ratio-high yield strength, the true stress for the same true strain is higher than that of a steel material having a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material having a low yield ratio. Thereby, more energy can be absorbed compared with the case where the column base part 22 is formed with the steel material of a low yield ratio.
Therefore, the seismic performance of the steel column 51 as a whole can be improved as compared with the case where the entire steel column 51 is formed of a material having a low yield ratio.

Furthermore, since the steel column 51 is composed of a steel material with a low yield ratio other than the column base 22 (that is, the column main body 53), consideration is given to the restrictions when using a steel material with a high yield ratio in the design of the upper frame. The design is relatively simple. Further, in the case of the configuration of the second embodiment, the degree of freedom in design can be increased because the column beam strength ratio is not necessarily ensured as in the first embodiment.
This effect is the same for the steel structure design method S20 described later.

Further, according to the steel structure design method S20 of the present embodiment, the joint portion 31 between the column main body 53 and the steel beam 26 in the steel column 51 has a low yield ratio of 80% or less. Since it is set to be formed of a steel material with a yield ratio, the seismic performance is equivalent to that of a conventional joint.
In addition, the column base 22 of the steel column 51 is set to be formed using a steel material having a high yield ratio-high yield strength in which the yield ratio is in the range of more than 80% and 90% or less. Is set to 0.815 times or less the yield strength of a steel material having a high yield ratio-high yield strength. For this reason, the true stress for the same true strain is equal to or greater than the true stress of the steel material having a low yield ratio, the bending moment for the same rotation angle is equal to or greater than the bending moment of the steel material having a low yield ratio, and the column base portion 22 is more. Can absorb the energy.
Therefore, the seismic performance of the steel column 51 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

In the column base design strength setting step S23, the design strength of the column base 22 is set to a value lower than the yield strength of the high yield ratio-high yield strength steel material on which the column base 22 is formed. May be.
If the design method of the steel structure is performed in this way, the design strength of the column base portion 22 is equal to the yield strength of the steel material having a high yield ratio-high yield strength even if a steel material having a high yield ratio-high yield strength is used. Compared with the case of setting, the true stress with respect to the same true strain and the bending moment with respect to the same rotation angle are increased, so that the column base 22 can absorb more energy.
Therefore, the seismic performance of the steel column 51 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. 1, 12, and 13. Only the point will be described.
As shown in FIG.1 and FIG.12, the steel structure 3 of this embodiment is provided with the steel column 61 instead of the steel column 21 of the steel structure 1 of 1st Embodiment.

As illustrated in FIG. 12A, the steel column 61 includes a column main body 63 instead of the column main body 23 of the steel column 21. The design strength of the column main body 63 is 0.815 times or less the yield strength of a steel material having a high yield ratio-high yield strength.
As shown in FIG. 12B, the same member as that of the first embodiment is used for the column base portion 22. The column base portion 22 is formed of a steel material having a high yield ratio-high yield strength.
That is, in this embodiment, the design strength of the steel column 61 is 0.815 times or less the yield strength of a steel material having a high yield ratio-high yield strength.

Next, the design method of the steel structure 3 of this embodiment for designing the steel structure 3 configured as described above will be described. FIG. 13 is a flowchart showing a steel structure design method S30 in the third embodiment of the present invention.
First, the above-described yield ratio selection step S11 is performed.
Next, in the steel column design strength setting step (step S31 shown in FIG. 13), the design strength in each part of the steel column 61 is a value not more than 0.815 times the yield strength of the steel material having a high yield ratio-high yield strength. Set to.
When the steel column design strength setting step S31 is completed, all the steps of the steel structure design method S30 are completed, and the steel structure 3 is designed.

  In addition, the order which performs yield ratio selection process S11 and steel frame design strength setting process S31 is not specifically limited.

As described above, according to the steel structure 3 of the present embodiment, the entire steel column 61 is formed using a steel material having a high yield ratio-high yield strength of which yield ratio exceeds 80% and is equal to or less than 90%. The design strength of the column 61 is 0.815 times or less the yield strength of a steel material having a high yield ratio-high yield strength. For this reason, in a steel material having a high yield ratio-high yield strength, the true stress for the same true strain is higher than that of a steel material having a low yield ratio, and the bending moment for the same rotation angle is higher than that of a steel material having a low yield ratio. Thereby, more energy can be absorbed compared with the case where the column base part 22 is formed with the steel material of a low yield ratio.
Therefore, the seismic performance of the steel column 61 as a whole can be improved as compared with the case where the entire steel column is made of a material having a low yield ratio.

Further, with respect to the steel column 61, the column main body 63 and the column base portion 22, that is, the entire steel column 61 is made of a steel material with a high yield ratio, and the strength is also reduced. Therefore, the column as in the configuration of the first embodiment is used. There is no need to consider the constraints on the beam strength ratio, and the degree of freedom in design increases. In addition, since the steel column 61 is entirely composed of the same steel material (steel material with a high yield ratio), it is not necessary to switch the steel material with a low yield ratio / high yield ratio as in the second embodiment, Easy to simplify production.
This effect is the same also about steel structure design method S30 mentioned below.

In addition, according to the steel structure design method S30 of the present embodiment, the entire steel column 61 is formed using a steel material having a high yield ratio-high yield strength in which the yield ratio exceeds 80% and is 90% or less. The design strength of the entire steel column 61 is set to a value obtained by reducing the yield strength of the steel material. For this reason, the true stress for the same true strain is equal to or greater than the true stress of the steel material having a low yield ratio, the bending moment for the same rotation angle is equal to or greater than the bending moment of the steel material having a low yield ratio, and the column base portion 22 is more. Can absorb the energy.
Therefore, the seismic performance of the steel column 61 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

In the steel column design strength setting step S31, the design strength in each part of the steel column 61 may be set to a value that is lower than the yield strength of the steel material having a high yield ratio-high yield strength.
If the design method of the steel structure is performed in this way, the design strength of the column base portion 22 is equal to the yield strength of the steel material having a high yield ratio-high yield strength even if a steel material having a high yield ratio-high yield strength is used. Compared with the case of setting, the true stress with respect to the same true strain and the bending moment with respect to the same rotation angle are increased, and more energy can be absorbed in each part of the steel column 61.
Therefore, the seismic performance of the steel column 61 as a whole can be improved as compared with the case where the entire steel column is set to be formed of a material having a low yield ratio.

(Analysis result 1)
In the steel structure 1 shown in FIG. 1, Steel Frame Structure has framework analysis of the case of the 8 levels 4 spans from the first layer 11 ₁ to the eighth hierarchy 11 ₈ (time history analysis) was performed. The height of the layer 11 ₁ is 4 m, and the height of the layers 11 other than the layer 11 ₁ is 3.75 m. The pitch of the steel column 21 was 6 m.
Tables 1 and 2 show the specifications of the cross section of the steel column and the steel beam of the steel structure.

As shown in Table 1, the cross-sectional dimension of the steel beam is H700 mm (height) × 250 mm (width) × 12 mm (thickness in the height direction) × 22 mm (width direction), for example, in the lower steel beam of the second layer. Thickness). As for the cross-sectional dimension of the steel beam, the height, the width, the height, and the thickness in the width direction gradually become smaller toward the upper level. It is a steel beam of RF (ceiling) and is H450 mm × 200 mm × 9 mm × 14 mm. The yield strength of all steel beams was 325 MPa.
As shown in Table 2, the cross-sectional dimensions of the steel column were 500 mm square and 19 mm thick in the first to sixth layers. In the seventh and eighth layers, the thickness was 500 mm square and the thickness was 16 mm.

Steel columns were set to the conditions of Case 1 to Case 5 shown in Table 2.
Table 2 shows the yield strength, design strength, and yield ratio of the steel column from the first layer to the eighth layer in each case. In the first hierarchy, the column base and the portion other than the column base may be shown separately.
Case 1 models a case where a steel column is formed of a steel material having a low yield ratio with a yield strength of 325 MPa and a yield ratio of 80% at all levels. Yield strength and design strength are equal to each other.
Case 2 is a case where the yield ratio of all layers is 90% in Case 1. Case 1 and case 2 are conventional steel structures.

In case 2, the yield strength of the column base is 400 MPa in case 2, and the design strength of the column base is 325 MPa, which is 0.815 times the yield strength. Case 3 satisfies the above-described expression (11) and corresponds to the first embodiment.
Case 4 was the same as Case 1, except that the yield strength of the column base was 400 MPa, the yield ratio was 90%, and the design strength of the column base was 325 MPa, 0.815 times the yield strength. Case 4 corresponds to the second embodiment.
In case 2, the yield strength of steel columns at all levels was 400 MPa in case 2, and the design strength of steel columns at all levels was 325 MPa, 0.815 times the yield strength. Case 5 corresponds to the third embodiment.

The above five cases were analyzed using the relationship of the rotation angle with respect to the bending moment in the low yield ratio steel material and the high yield ratio-high yield strength steel material shown in FIG.
For the ground motion, the NS component on the ground in JR West Takatori Station in the 1995 Hanshin Earthquake was used. A product obtained by amplifying the seismic wave so that the acceleration response spectrum Sa (T1) at the natural period 1.07 seconds of the analysis model is 1.5 g is input to the analysis model.

FIG. 14 shows the maximum interlayer deformation angle in each layer of the steel structure 1 as the analysis result of the time history response. The horizontal axis in FIG. 14 represents the maximum interlayer deformation angle (rad), and the vertical axis represents the layer number.
As shown in FIG. 15, the maximum interlayer deformation angle φ is defined as an angle formed by the steel column 21 of each layer 11 with the vertical direction. The maximum story drift with respect to the first hierarchy 11 ₁ phi _1, the maximum story drift with respect to the second hierarchy 11 ₂ phi _2, is as ‥ like.

A solid line L21 shown in FIG. A dotted line L22 is a simulation result of Case 2. A line L23 by a one-dot chain line is a simulation result of Case 3. A line L24 by a two-dot chain line is a simulation result of Case 4. A thick line L25 is a simulation result of Case 5.
In Case 1 and Case 2, the maximum interlayer deformation angle of the first layer is larger than the maximum interlayer deformation angle of the other layers, and damage is concentrated on the first layer. In case 2, steel material having a higher yield ratio than case 1 is used, so that the energy absorption performance of the column base portion is lowered as in the case of steel material having a high yield ratio-low yield strength shown in FIG. Damage is concentrated in the hierarchy.

On the other hand, in all of cases 3 to 5, the maximum interlayer deformation angle in the first layer is suppressed, and damage is dispersed in the upper layer. This is because, as shown by the line L3 in FIG. 2, the yield strength and tensile strength of the column base are improved, so that the deformation of the column base which is a plasticized part is suppressed, and the deformation is dispersed throughout the entire frame. It means that it was done.
As described above, it was confirmed that by using a steel material having a high yield ratio-high yield strength appropriately with a reduced design strength, the earthquake resistance can be improved more than when a steel material having a low yield ratio is used.

  Note that the steel material with a high yield ratio shows the same behavior even when the yield strength is 400 MPa or more and 550 MPa or less, or when the yield strength is 500 MPa or more and 650 MPa or less.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. 16 to 27. However, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted. explain.
As shown in FIG. 16, in the present embodiment, when the steel column 71 is a square steel pipe formed in a square tube shape, a detailed study on the predetermined coefficient was performed. In the present embodiment, the cross section of the steel column 71 is a square tube having a square outer shape. The length of the outer side in the cross section of the steel columns 71 and (steel pipe diameter), and the length of the other side of the outer adjacent to the one side, to one another in length D _2. The thickness of the steel column 71 in this cross section is a constant thickness t ₂ at any position around the steel column 71. In this case, the cross-sectional shape of the steel column 71 is constant regardless of the vertical position of the steel column 71.
In the steel column 71, the case where the length of one side, thickness, etc. change with the column base part 72 and the column main body is also considered. Even in this case, the column base 72 is formed in a rectangular tube shape. The lateral cross section of the column base 72 is a square tube having a square outer shape. The length of the outer side in the cross section of the column base 72, the length of the other side of the outer adjacent to the one side, to one another in length D _1. The thickness of the column base 72 in this cross section is a constant thickness t ₁ at any position around the column base 72.
Note that the description given below for the steel column 71 is similarly applied to the column base 72. The description of the column base 72 is similarly applied to the steel column 71.

Here, the steel columns 71, the ratio of the length _{D 2} relative to the thickness _{t 2,} the width-thickness ratio _{R 2.} In column base 72, the ratio of the length _{D 1} to the thickness _{t 1,} and the width-thickness ratio _{R 1.}
As an analysis model shown in FIG. 6, a steel column 71 (column base 72) having a steel pipe diameter (length D ₂ , D ₁ ) of 600 mm and thicknesses t ₂ , t _{1 changed} to 32 mm, 25 mm, 22 mm, and 16 mm. ) Was used. In this case, the width-to-thickness ratios R ₂ and R ₁ are 19, 24, 27, and 38, respectively.
The simulation was performed assuming the steel material having the low yield ratio and the steel material having the high yield ratio-high yield strength as the steel materials. The yield strength of the low yield ratio steel was 325 MPa, and the yield strength of the high yield ratio-high yield strength steel was 400 MPa. When 400 MPa, which is the yield strength of a steel material having a high yield ratio-high yield strength, is multiplied by 0.815, it is equivalent to 325 MPa, which is the yield strength of a steel material having a low yield ratio. Other analysis conditions are the same as in the first embodiment.

Respectively the relationship between the rotation angle of the columnar leg portion width-thickness ratio _{R 2} is for the bending moment of the column base in a case of 19,24,27,38 in FIG. 17 to FIG. A simulation result with a steel material having a low yield ratio is indicated by a solid line L31, and a simulation result with a steel material having a high yield ratio-high yield strength is indicated by a dashed line L32.
For the case width-thickness ratio R ₂ of all 19,24,27,38, for a given rotation angle, low yield ratio steel bending high yield ratio than the moment of - the bending of the steel material of the high yield strength The moment is never reduced.

In FIGS. 17 to 20, consider the change of the maximum strength of the columnar leg portion by width-thickness ratio R _2. The width thickness ratio R _2, considered tend follows. That is, in accordance with increase width-thickness ratio R _2, with respect to ultimate strength M1 steel low yield ratio, high yield ratio high yield point steel - Maximum Strength M2 high yield strength increases. The reason why such a tendency occurs will be described with reference to FIG. FIG. 21 is added to the true stress-true strain diagram of the low yield ratio steel material indicated by line L1 and the high yield ratio-high yield strength steel material indicated by line L3 in FIG.

For example, the length D ₂ of one side of the steel columns 71 will be described for the case of constant. When the thickness t ₂ of the steel column 71 increases and the width-thickness ratio R ₂ decreases, the steel column 71 becomes difficult to buckle even after exceeding the yield strength, and the region R in which the true strain ε _{1 in} FIG. ₆ , the steel column 71 buckles. At this time, the difference between the true stress of the steel material having a low yield ratio and the true stress of the steel material having a high yield ratio-high yield strength is small.
On the other hand, when the thickness t ₂ of the steel column 71 is decreased and the width-thickness ratio R ₂ is increased, the steel column 71 is likely to buckle after exceeding the yield strength, and the true strain ε _{2 in} FIG. steel column 71 buckles in a small region _{R 7.} At this time, the difference between the true stress of the steel material having a low yield ratio and the true stress of the steel material having a high yield ratio-high yield strength is large.
Therefore, steel and high yield ratio of low yield ratio in the width-thickness ratio R ₂ is small - the maximum strength in the steel of high yield strength is not much, low yield when large width-thickness ratio R ₂ The difference in maximum proof stress between the steel with a high ratio and the steel with a high yield ratio-high yield strength becomes large.

In Case 5 Case 3 shown in FIG. 14, the maximum story drift phi ₁ to the first hierarchy 11 ₁ than Case 1 using the steel columns formed from steel of a low yield ratio are greatly reduced. For this reason, the reduction factor (predetermined factor) in the case of using a steel material having a high yield ratio-high yield strength in order to obtain a framework performance (maximum interlayer deformation angle φ ₁ ) equivalent to that of case 1 is more rational (larger ) There is room for setting.

FIG. 22 shows a simulation result of the steel material having a low yield ratio indicated by the line L16 in FIG. 7, a simulation result of the steel material having a high yield ratio-low yield strength indicated by the line L17, and a high yield ratio indicated by the line L18. -In addition to the simulation result by the steel material of high yield strength, the simulation result shown by the line L34 by a dashed-two dotted line is added. FIG. 22 shows the result when the width-thickness ratio is 27, and includes the lines L31 and L32 of FIG. 19 as lines L16 and L18.
In the simulation result indicated by the line L34, the yield strength of the steel column was adjusted to 351 MPa and the reduction factor was adjusted to 0.926 in the steel material having a high yield ratio-high yield strength. The design strength of the steel column is 325 MPa, 0.926 times the yield strength 351 MPa. In this case, the maximum yield strength of the case in which the reduction factor is adjusted and the maximum yield strength of the simulation result by the steel material having a low yield ratio indicated by the line L16 are equal to each other. On the other hand, the maximum yield strength of the simulation result by the steel material having the high yield ratio-high yield strength shown by the line L18 is larger than the maximum yield strength of the case in which the reduction factor is adjusted.

On the other hand, the maximum yield strength of the simulation result by the steel material having the high yield ratio-low yield strength indicated by the line L17 is smaller than the maximum yield strength of the simulation result by the steel material having the low yield ratio indicated by the line L16.
These maximum proof stresses are the resistance force of column members, such as a steel column, with respect to a horizontal load (seismic force). When the yield strength deterioration due to local buckling occurs in the column member, damage concentrates on the strength degradation portion in the frame, leading to collapse. Therefore, if the maximum yield strength of the column member is the same between the steel material having a high yield ratio and the steel material having a low yield ratio, it is considered that the responsiveness as a framework is also equivalent.
Furthermore, using the steel column with the reduced coefficient adjusted, the time history response analysis of the eight-layer steel frame structure was performed in the same manner as the analysis result 1. Table 3 shows the specifications of the cross section of the steel column in Case 6 to Case 8 where the analysis was performed. In case 6 to case 8, the width-thickness ratio was 27, and the reduction factor of the column base or steel column was adjusted to 0.926. The analysis conditions other than those in Table 3 are the same as the analysis conditions in analysis result 1.

A difference between the specifications of the cross section of the steel column of the case 6 and the specifications of the cross section of the steel column of the case 3 corresponding to the first embodiment shown in Table 2 is that the yield strength of the column base is 351 MPa. This is a point in which a steel material having a high yield ratio-high yield strength is used, the reduction factor is adjusted to 0.926, and the design strength is set to 325 MPa.
A difference between the specifications of the cross section of the steel column of the case 7 and the specifications of the cross section of the steel column of the case 4 corresponding to the second embodiment shown in Table 2 is that the yield strength of the column base is 351 MPa. This is a point in which a steel material having a high yield ratio-high yield strength is used, the reduction factor is adjusted to 0.926, and the design strength is set to 325 MPa.
The cross section specifications of the steel column of the case 8 differ from the cross section specifications of the steel column of the case 5 corresponding to the third embodiment shown in Table 2 in that the steel column has a high yield strength of 351 MPa. This is a point in which a steel material having a yield ratio-high yield strength is used, the reduction factor is adjusted to 0.926, and the design strength is set to 325 MPa.

The analysis results of case 6 to case 8 are shown in FIG. 23 corresponding to FIG.
In FIG. 23, the simulation result of case 1 is shown by line L21. A dotted line L36 is a simulation result of Case 6. A line L37 by a one-dot chain line is a simulation result of case 7. A line L38 by a two-dot chain line is a simulation result of Case 8.
Maximum story drift with respect to the first hierarchy 11 ₁ from the case 6 8 is controlled to equal to or less than the maximum story drift with respect to the first hierarchy 11 ₁ of the case 1 using the steel low yield ratio. From this result, in steel columns using steel materials with high yield ratio-high yield strength at least in part, the conventional structure (low yield ratio) is given by giving the restoring force characteristics that the maximum yield strength is equivalent to steel materials with low yield ratio. It was found that the response at the time of earthquake can be controlled to the same extent as that of steel frames.

In order to generalize this knowledge to steel columns with various width-thickness ratios, finite element analysis was performed when the column cross-section of the steel column was changed variously, and the maximum yield strength and high yield of steel materials with low yield ratio were implemented. Ratio-The reduction factor of the design strength of the steel column was calculated so that the maximum yield strength of the steel with high yield strength would be equivalent. Of one side of the steel column the length _{D 2,} it was 600mm. The thickness _{t 2} of the steel columns, and 36mm, 32mm, 25mm, 22mm, 19mm, and 16mm. The axial force ratio was set to 0, 0.15, 0.3, 0.5.
These analysis results are shown in FIG. The horizontal axis in FIG. 24 represents the width-thickness ratio, and the vertical axis represents the reduction factor. The range below the reduction factor corresponding to the plot of each analysis result in FIG. 24 is an earthquake resistance equal to or higher than that of a conventional steel structure using a steel material having a low yield ratio even if a steel material having a high yield ratio-high yield strength is used. It is the range of the reduction factor that becomes the performance.

In Figure 24, the width-thickness ratio is less area R _11, high yield ratio - to design strength of the steel material of the high yield strength becomes equal to the design strength of steel low yield ratio reduction factor of about 0.815 is required. That is, in this region R _11, if the reduction coefficient axial force ratio and the like is also variously changed is not more than about 0.815, a high yield ratio - High Yield Strength design strength of steel is low yield ratio steel It will be equal to or better than the design strength.
In the width-thickness ratio greater area R _12, high yield ratio - to design strength of the steel material of the high yield strength becomes equal to the design strength of steel low yield ratio reduction factor to about 0.915 relaxation (larger )it can. This is consistent with the result that when the width-to-thickness ratio is large, as shown in FIGS. 17 to 21, local buckling occurs relatively early after the steel material exceeds the yield strength and the maximum strength is reached. ing.
In the region R ₁₃ between the region R ₁₁ and the region R _12, high yield ratio - reduction factor for the design strength of the steel material becomes equal to the design strength of steel with low yield ratio of high yield strength, the width-thickness ratio As the value increases, it gradually increases.
From this result, the reduction factor of the design strength of the steel material having a high yield ratio-high yield strength, the reduction factor α ₂ by the equation (12) for the steel column, and the reduction factor α ₁ by the equation (13) for the column base To do. Expressions (12) and (13) are expressions obtained by evaluating steel columns and column bases having various width-thickness ratios on the safe side.

(12) High yield ratio based on formula - reduction factor of design strength of steel to steel columns using high yield strength is in the region R ₁₂ and region R ₁₃ of the width-thickness ratio R _2, third from the first embodiment The reduction factor of 0.815 in the embodiment can be relaxed. In other words, giving a higher design strength to the yield strength of steel with a high yield ratio-high yield strength while giving structural performance equivalent to or less than that of a conventional steel frame with a low yield ratio steel. And a predetermined structural strength can be obtained with a smaller cross section.
In addition, the design method of the steel structure in the present embodiment is a value that is lower than the yield strength of the steel material having a high yield ratio-high yield strength in the design method of the steel structure in the first to third embodiments. the high yield ratio - equivalent to the reduction factor alpha ₁ below by a high yield strength of the yield strength of the steel (12) reduction coefficient alpha ₂ below or by formula (13).

As explained above, according to the steel structure of the present embodiment, in addition to the effects produced by the steel structures 1 to 3 of the first to third embodiments, the steel structure 1 to the steel structure The column base or the steel column can be configured with a material equivalent to or less than that of the object 3, and the column base or the steel column can be reduced in weight.
Moreover, according to the design method of the steel structure of this embodiment, in addition to the effect which the design method of the steel structure of 1st Embodiment to 3rd Embodiment show | plays, it is equivalent to the steel structure 1 to the steel structure 3 Alternatively, the column base or the steel column can be configured with less material, and the column base or the steel column can be reduced in weight.
Moreover, according to the steel structure of this embodiment and the design method of a steel structure, a steel structure can be constructed while suppressing the manufacturing cost of the steel column.

(Analysis result 2)
In order to verify the validity of the reduction factor of the design strength of the equations (12) and (13), the case A1 to the case C5 in Tables 4 to 6 are based on the eight-layer steel frame framework used in the analysis result 1. In this way, analysis was performed by changing the specifications of the cross section of the steel column.

Note that Case A1 to Case A5 shown in Table 4 are cases where the width-thickness ratio is 20, and the steel frames in the first to fifth layers with respect to the cross-sectional dimensions of the steel column shown in Table 2 in the analysis result 1 The cross-sectional dimension of the column was 500 mm square and the thickness was 25 mm.
Case B1 to Case B5 shown in Table 5 have a width-thickness ratio of 26, and are the same as the cross-sectional dimensions of the steel column shown in Table 2 in Analysis result 1.
Case C1 to Case C5 shown in Table 6 are cases in which the width-thickness ratio is 32, and the steel column in the first to fifth layers is compared with the cross-sectional dimension of the steel column shown in Table 2 in Analysis Result 1. The cross-sectional dimensions were 600 mm square and the thickness was 19 mm.

Cases A1, B1, and C1 are cases in which steel materials with a low yield ratio are used for all steel columns, and assume the structure of a conventional steel structure. The yield strength, design strength, and yield ratio at each level in cases A1, B1, and C1 are the same as the yield strength, design strength, and yield ratio at each level in case 1.
Cases A2, B2, and C2 are the cases where steel materials with high yield ratio-high yield strength are used without applying the design strength reduction factor to all steel columns, assuming the structure of a conventional steel structure. is there. The yield strength, design strength, and yield ratio at each level in cases A2, B2, and C2 are the same as the yield strength, design strength, and yield ratio at each level in case 2.

Case A3, B3, C3, when a predetermined coefficient in the steel structure of the first embodiment reduces the coefficient alpha ₁ and by equation (13) for column base, and the design of the steel structure of the first embodiment it is a case of a value with reduced reduction factor alpha ₁ or less than the yield strength of the steel in the process.
The yield strength, design strength, and yield ratio at each level other than the column base in cases A3, B3, and C3 are the same as the yield strength, design strength, and yield ratio at each level in case 3. The design strength and yield ratio at the column base in cases A3, B3, and C3 are the same as the design strength and yield ratio at the column base in case 3, respectively. However, the yield strength of the steel at the column base of the case A3, B3, C3 is a value obtained by multiplying the reduction factor alpha ₁ in accordance with the width-thickness ratio was adjusted to 325 MPa. For example, the width-thickness ratio is the reduction factor alpha ₁ according to (13) in the case of 20 is 0.834, the yield strength of the steel at the column base, and 389MPa from the equation (325 / 0.834) did.

Case A4, B4, C4, when a predetermined coefficient in the steel structure of the second embodiment and reduce the coefficient alpha ₁ according to (13) for column base, and the design of the steel structure of the second embodiment it is a case of a value with reduced reduction factor alpha ₁ or less than the yield strength of the steel in the process.
The yield strength, design strength, and yield ratio at each level other than the column base in cases A4, B4, and C4 are the same as the yield strength, design strength, and yield ratio at each level in case 4. The design strength and yield ratio at the column base in cases A4, B4, and C4 are the same as the design strength and yield ratio at the column base in case 4, respectively. However, the yield strength of the steel at the column base of the case A4, B4, C4 is a value obtained by multiplying the reduction factor alpha ₁ in accordance with the width-thickness ratio was adjusted to 325 MPa. For example, the width-thickness ratio is the reduction factor alpha ₁ according to (13) in the case of 20 is 0.834, the yield strength of the steel at the column base, and 389MPa from the equation (325 / 0.834) did.

Case A5, B5, C5, when a predetermined coefficient in the steel structure of the third embodiment has a reduction factor alpha ₂ by the equation (12) for steel columns, and a method of designing a steel structure of the third embodiment it is a case of a value with reduced reduction coefficient alpha ₂ or less than the yield strength of the steel at.
The design strength and yield ratio at each level in cases A5, B5, and C5 are the same as the design strength and yield ratio at each level in case 5. Case A5, yield strength of the steel in each hierarchy in B5, C5 is a value obtained by multiplying the reduction factor alpha ₂ in accordance with the width-thickness ratio was adjusted to 325 MPa. For example, the width-thickness ratio is the reduction factor alpha ₂ by (12) in the case of 20 is 0.834, the yield strength of the steel in each layer, was 389MPa from the equation (325 / 0.834) .
Other analysis conditions are the same as those of analysis result 1.

FIG. 25 shows the analysis result of the maximum interlayer deformation angle in each layer in case A1 to case A5 where the width-thickness ratio is 20. In FIG. 25, a solid line L41 is a simulation result of case A1. A dotted line L42 is a simulation result of case A2. A line L43 by a one-dot chain line is a simulation result of case A3. A line L44 by a two-dot chain line is a simulation result of case A4. A thick line L45 is a simulation result of case A5.
FIG. 26 shows the analysis result of the maximum interlayer deformation angle in each layer in case B1 to case B5 where the width-thickness ratio is 26. A solid line L46 is a simulation result of case B1. A dotted line L47 is a simulation result of case B2. A line L48 by a one-dot chain line is a simulation result of case B3. A line L49 by a two-dot chain line is a simulation result of case B4. A thick line L50 is a simulation result of case B5.

  FIG. 27 shows the analysis result of the maximum interlayer deformation angle in each layer in case C1 to case C5 where the width-thickness ratio is 32. A solid line L51 is a simulation result of case C1. A dotted line L52 is a simulation result of case C2. A line L53 by a one-dot chain line is a simulation result of case C3. A line L54 by a two-dot chain line is a simulation result of case C4. A thick solid line L55 is a simulation result of case C5.

In any width-thickness ratio, the case A2, which uses a steel material having a high yield ratio-high yield strength without applying a design strength reduction factor to the cases A1, B1, C1 which are the structures of conventional steel structures. in B2, C2, maximum story drift phi ₁ to the first hierarchy 11 ₁ is increased, damage concentration on the first layer 11 ₁ is the lowest layer is in progress.
On the other hand, in the cases A3 to A5, B3 to B5, and C3 to C5 using the reduction factors α ₂ and α _{1 according} to the equations (12) and (13), the conventional steel structure using a steel material with a low yield ratio. The response is controlled to a maximum interlayer deformation angle φ ₁ equal to or less than the structure of the object. From these results, it is considered that the reduction coefficients α ₂ and α ₁ according to the equations (12) and (13) are appropriate.

  The first to fourth embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the configuration does not depart from the gist of the present invention. Changes, combinations, deletions, etc. are also included. Furthermore, it goes without saying that the configurations shown in the embodiments can be used in appropriate combinations.

1, 2, 3 Steel structure 11 level 21, 51, 61, 71 Steel column 22, 72 Column base 26 Steel beam 31 Joint S10, S20, S30 Design method of steel structure

Claims (14)

A steel structure comprising a steel beam and a steel column formed of a steel material having a yield ratio of more than 80% and 90% or less, and having a plurality of layers in the vertical direction,
The beam-to-column strength ratio is 1.5 or more, or the formula (1) is satisfied,
The steel structure in which the design strength of the column base part used for the said hierarchy arrange | positioned most lower among the said steel columns among the said steel columns is 0.815 times or less of the yield strength of the said steel materials.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. Moment, and _p M _p is the total plastic moment of the joint.

A steel structure having a steel frame made of steel and having a plurality of layers in the vertical direction and having a plurality of layers,
Of the steel columns, the column base used in the lowermost layer among the plurality of layers is formed of the steel material having a high yield ratio with a yield ratio of more than 80% and 90% or less. ,
The design strength of the column base is 0.815 times or less the yield strength of the steel material with the high yield ratio,
A steel structure formed of the steel material having a yield ratio of 80% or less except for the column base portion of the steel column. A steel structure having a steel frame structure comprising a steel column formed of a steel material having a yield ratio of more than 80% and 90% or less,
A steel structure in which the design strength of the steel column is 0.815 times or less the yield strength of the steel material. A steel structure comprising a steel beam and a steel column formed of a steel material having a yield ratio of more than 80% and 90% or less, and having a plurality of layers in the vertical direction,
The column beam strength ratio is 1.5 or more, or the formula (2) is satisfied,
Of the steel pillars, the column base used for the layer disposed at the lowest position in the plurality of layers is formed in a rectangular tube shape,
A steel structure in which the design strength of the column base is less than or equal to a reduction factor α of ₁ by the expression (3) of the yield strength of the steel material.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. _P M _p is the total plastic moment of the joint, D ₁ is the length of the outer side in the cross section of the column base, and t ₁ is the thickness of the column base .

A steel structure having a steel frame made of steel and having a plurality of layers in the vertical direction and having a plurality of layers,
Of the steel pillars, the column base used for the layer disposed at the lowest position in the plurality of layers is formed in a rectangular tube shape,
The column base portion is formed of the steel material having a high yield ratio in which the yield ratio exceeds 80% and is 90% or less.
The design strength of the column base is a reduction factor α of ₁ or less according to the formula (4) of the yield strength of the steel material with the high yield ratio,
A steel structure formed of the steel material having a yield ratio of 80% or less except for the column base portion of the steel column.
However, D ₁ is the length of the outer side in the cross section of the column base, t ₁ is the thickness of the columnar leg portion.

A steel structure with a steel frame structure comprising a steel column formed in a rectangular tube shape with a steel material having a yield ratio of more than 80% and not more than 90%,
A steel structure in which the design strength of the steel column is less than or equal to ₂ times the reduction coefficient α according to the expression (5) of the yield strength of the steel material.
However, D ₂ is the length of the outer side in the cross section of the steel column, t ₂ is the thickness of the steel columns.

  The steel material according to any one of claims 1 to 6, wherein the steel material having a yield ratio exceeding 80% and not more than 90% has a yield strength of 400 MPa to 550 MPa and a tensile strength of 490 MPa to 640 MPa. Structure.   The steel material according to any one of claims 1 to 6, wherein the steel material having a yield ratio exceeding 80% and not more than 90% has a yield strength of 500 MPa to 650 MPa and a tensile strength of 590 MPa to 740 MPa. Structure. The yield ratio of the steel material forming the steel column provided in the steel structure by the steel frame structure having a plurality of layers in the vertical direction is set in a range of more than 80% and 90% or less,
The column beam strength ratio is set to 1.5 or more, or set to satisfy the formula (6),
Of the steel column, the design strength of the column base used in the lowermost layer among the plurality of levels is set to a value that is set to a value that is lower than the yield strength of the steel material. Design method.
Where _c M _p is the total plastic moment of the portion of the steel column that is joined to the joint with the steel beam, and _b M _p is the total plastic moment of the portion of the steel beam that is joined to the joint. And _p M _p is the total plastic moment of the joint.

In the steel column provided in the steel structure by the steel frame ramen structure having a plurality of layers in the vertical direction,
The yield ratio of the steel material forming the column base used in the lowermost layer among the plurality of layers is set in a range of more than 80% and 90% or less,
The design strength of the column base is set to a value obtained by reducing the yield strength of the steel material in a range where the yield ratio exceeds 80% and is 90% or less,
A method for designing a steel structure, wherein a yield ratio of the steel columns other than the column base is set to a range of 80% or less. The yield ratio of the steel material forming the steel column provided in the steel structure by the steel frame structure having a plurality of layers in the vertical direction is set in a range of more than 80% and 90% or less,
The design method of the steel structure which sets the design strength of the said steel column to the value reduced rather than the yield strength of the said steel materials.   The method for designing a steel structure according to any one of claims 9 to 11, wherein the value reduced from the yield strength of the steel material is a value not more than 0.815 times the yield strength of the steel material. The shape of the column base is set to a rectangular tube shape,
The method for designing a steel structure according to claim 9 or 10, wherein a value reduced from the yield strength of the steel material is not more than a reduction factor α ₁ times according to the expression (7) of the yield strength of the steel material.
However, D ₁ is the length of the outer side in the cross section of the column base, t ₁ is the thickness of the columnar leg portion.

The shape of the steel column is set to a rectangular tube shape,
The method for designing a steel structure according to claim 11, wherein a value reduced from the yield strength of the steel material is a reduction factor α ₂ times or less according to the equation (8) of the yield strength of the steel material.
However, D ₂ is the length of the outer side in the cross section of the steel column, t ₂ is the thickness of the steel columns.

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