JP2010216115A - Steel frame structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease moment generated in a column base during an earthquake, so as to have the column base restricted within an elastic deformation zone, and eventually to let it act so that the whole of the steel frame structure is fallen within the elastic deformation zone. <P>SOLUTION: This steel frame structure 1, which includes a steel pipe column 2 and a beam material 3 rigidly joined to a column-beam joint 22 of the steel pipe column 2, is characterized as follows: a column-beam strength ratio of the column-beam joint 22 is 1.5 or more; and the strength<SB>c</SB>σ<SB>y</SB>of the lowermost story of the steel pipe column 2 satisfies the inequality (1). In the inequality (1): cZp represents a plastic section modules of the steel pipe column; h represents a ratio of the height of the inflection point of the moment of the steel pipe column to the floor height of the lowermost story; n represents an axial force ratio of the steel pipe column; τ represents a strength rise ratio (=1.3) up to the maximum strength of the beam material; and bMPL and bMPR each represents a plastic section modules of the beam material. A yield ratio of the steel pipe column is set at 99% or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steel structure constructed by rigidly connecting a beam to a beam-to-column joint in a steel tube column, and particularly prevents the steel tube column from being easily plastically deformed when a load is applied due to an earthquake or the like. It is related with the steel structure suitable for doing.

  2. Description of the Related Art Conventionally, a steel structure including a steel frame frame including a steel pipe column and a beam member rigidly connected to a column beam joint in the steel pipe column has been constructed. In general, this steel frame frame is designed in such a way that the beam material is designed to yield before the steel tube column at the time of large stress such as a large earthquake at the beam-column joint between the steel tube column and the beam material. It is. This is because if a column is damaged during the action of a large stress, the risk of building collapse increases, and it is difficult to repair the building, so it is necessary to rebuild the entire area. In addition, even when stress due to small and medium earthquakes is applied, the design is such that the deformation of the steel pipe columns and beam materials is suppressed to the extent of elastic deformation as much as possible.

  FIG. 8 schematically shows the structure and moment of this steel frame frame. In the steel structure 7 constructed by rigidly joining the beam material 72 to the beam-column joint 73 in the steel pipe column 71, the steel pipe column 71 and the beam material 72 are rigidly joined to each other. When applied to the structure 7, moment stress is generated in the vicinity of the beam-column joint 73 corresponding to the member contact. In addition, when a moment is generated in the column beam joint 73, a moment stress is also generated in the column base 71a located at the lower end of the lowermost steel pipe column 71.

  Further, in the lowermost steel pipe column 71, an inflection point P at which this moment becomes 0 appears from the upper end to the column base 71a. In general, the lowermost column is rigidly fixed to the concrete foundation, and the height at which the inflection point P appears in the steel pipe column 71 due to the difference in the fixing degree between the column head and the column base is as shown in FIG. Above the center K. As a result, the moment generated in the column base 71a of the lowermost steel pipe column 71 becomes larger. And if the moment which generate | occur | produces in the column base part 71a of this steel pipe column 71 becomes larger by the load by an earthquake rather than the stress which arises in each structure part, the said column base part 71a will be plastically deformed.

  For this reason, conventionally, the thickness of the steel pipe column 71 is maintained at the same thickness as before, and the steel material constituting the steel pipe column 71 is simply made of high-strength steel, thereby suppressing this in the elastic deformation range. Was adopted.

  However, in the method of increasing the strength of only the material while simply maintaining the plate thickness of the steel pipe column 71, the material cost becomes high after all, and a large barrier is generated in terms of practical use. For this reason, in addition to simply making the steel pipe column 71 high-strength steel, it is necessary to promote cost reduction by reducing the weight and thickness of the steel pipe constituting the steel pipe column 71.

  Incidentally, in the prior art, for example, techniques disclosed in Patent Documents 1 and 2 have been disclosed for the purpose of improving the seismic performance of a steel structure including a steel frame frame. The disclosed technique of Patent Document 1 is a method in which a joining panel is provided at a beam-to-column joint where a steel pipe column and a beam material are joined, and the bending strength of the joining panel is less than the sum of the bending strength of the columns above and below. is there.

  However, in the technology disclosed in Patent Document 1, no particular mention or examination is made on the column base portion of the steel pipe column, and the degree of freedom in setting the yield ratio cannot be improved for the entire steel tube column shaft.

  The disclosed technique of Patent Document 2 is a multi-layer steel structure having a frame structure with a column beam bearing strength ratio exceeding 1.0, and a neutral point (anti-reverse) of the bending moment distribution of the first layer column so that the column base is not damaged. A technique is disclosed in which a music point is set at a predetermined position in the floor height direction. Specifically, by using high-yield point steel for the first layer column member and lowering the beam-to-beam rigidity ratio, the neutral point (inflection point) of the bending moment distribution of the first layer column member is further increased. Shifted in the high direction.

  However, the disclosed technique of Patent Document 2 does not specifically mention specific condition setting for keeping the column base portion in the elastic deformation region. In addition, there is no disclosure about the point of reducing the cost while maintaining the column base portion in the elastic region.

JP 2006-291698 A JP 2004-45820 A

  Therefore, the present invention has been devised in view of the above-described problems, and its object is to elastically deform the column base by reducing the moment generated in the column base during an earthquake. By controlling the steel pipe column in the entire steel structure so that it can be accommodated in the elastic deformation region, it is possible to improve the earthquake resistance, and also to realize these at a good low cost Is to provide an excellent steel structure.

・・・・・（１） In order to solve the above-mentioned problem, a steel structure according to claim 1 of the present application is a steel structure including a steel pipe column and a beam member rigidly joined to a column beam joint in the steel pipe column. The joint portion has a column beam yield ratio of 1.5 or more, and the strength _c σ _y in the lowermost layer of the steel pipe column satisfies the following formula (1).

(1)

Here, _{c Z p:} plastic section modulus of the steel pipe column, h: height ratio of the inflection point of moment in the steel pipe column for the lowermost floor height, n: steel column axial force ratio, tau: maximum beam members strength increase rate up to yield strength _{(= 1.3), b M PL} , b M PR: plastic section modulus of the beam material

  The steel structure according to claim 2 is characterized in that, in the invention according to claim 1, the steel pipe column has a yield ratio of 99% or less.

According to the present invention having the above-described configuration, the beam-column joint portion excluding the column leg portion at least in the lowermost steel tube column by setting the column beam strength ratio between the steel tube column and the beam material to 1.5 or more. In the place where the moment stress is generated, the material of the steel pipe column is selected so that the relationship of the formula (1) is established in the lowermost layer of the steel pipe column, or the section modulus is set. Optimize various parameters such as the first. As a result, even when a load due to a large earthquake is applied, the entire steel structure can be suppressed to the elastic region, and as a result, the seismic performance of the entire steel structure can be improved. In the past, while the steel tube column thickness was the same, only the steel material was high strength steel, but in the present invention, the range of the formula (1) is satisfied and the proof stress ratio is constant. The plate thickness of the steel pipe column can be reduced while making the steel material high strength steel. As a result, the weight can be reduced, and the material cost and the construction cost can be reduced.

It is a perspective view of the steel structure to which the present invention is applied. It is a sectional side view of the steel structure to which the present invention is applied. It is the figure which showed typically the moment loaded on the steel structure to which this invention is applied. It is a figure which shows the result of having calculated | required the relationship of the plate | board thickness of a steel pipe column, and the yield strength of a steel pipe column by simulation. It is a figure for demonstrating the taking-out position of a partial frame. It is another figure which shows the result of having calculated | required the relationship between the plate | board thickness of a steel pipe column, and the yield strength of a steel pipe column by simulation. It is another figure which shows the result of having calculated | required the relationship of the plate | board thickness of a steel pipe column, and the yield strength of a steel pipe column by simulation. It is the figure which showed typically the structure of the steel frame frame, and its moment.

Hereinafter, as an embodiment of the present invention, a steel structure excellent in earthquake resistance will be described in detail.

  FIG. 1 is a perspective view of a steel structure 1 to which the present invention is applied, and FIG. 2 is a side view thereof. The steel structure 1 includes a steel pipe column 2 and a beam member 3 joined to the steel pipe column 2.

  The steel pipe column 2 includes a steel pipe 21 having a predetermined plate thickness having a square cross section and a column beam joint 22. The column beam joint 22 has a lower plate 51 and an upper plate 52, and a steel pipe in which a lower plate 51 is attached to a lower end via a joining plate 53, and an upper plate 52 is attached to an upper end via welding to the joining plate 53. 53. The steel pipe 53 and the steel pipe 21 have substantially the same thickness.

  Incidentally, the steel pipe 21 and the column beam joint portion 22 constituting the steel pipe column 2 are both formed by cold forming.

  The steel pipe column 2 plays a role of preventing the collapse and collapse of the steel structure 1 while supporting the weight of the steel structure 1 itself even in a large shake caused by a large earthquake. From the viewpoint of preventing the yielding of the steel pipe column 2 at the beginning even when a large stress such as a large earthquake is applied, the steel pipe column 2 is designed to fit within the elastic deformation region, as will be described later. .

  The beam member 3 is formed of a so-called H-shaped steel including a web portion 31 and a pair of flange portions 32 a and 32 b provided at both ends of the web portion 31. This beam material 3 is manufactured by rolling, for example. In addition, this beam material 3 is not limited to when comprised as what is called a H-section steel, You may be comprised by shapes other than this.

The beam member 3 having such a structure is welded in a state where the end surface 3a of the web 31 is in contact with the surface of the steel pipe 53, and the flanges 32a and 32b are connected to the upper plate 52 and the lower plate through the through diaphragm 56. By being welded to the plate 51, it is integrated with the column beam joint 22. As a result, the beam member 3 is rigidly joined to the column beam joint 22 to form a steel frame ramen structure.

  Further, the steel pipe 21 in the steel pipe column 2 is arranged in a stacked manner on the column beam joint portion 22 as indicated by an imaginary line in FIG. In this way, the steel pipe column 2 is configured continuously from the uppermost layer to the lowermost layer by alternately stacking the steel pipes 21 and the beam-column joints 22 and joining them up and down. It will be built. Incidentally, in the lowest layer in the steel structure 1, the steel pipe column 2 is fixed on the ground.

  Next, specific structural mechanical characteristics of the steel pipe column 2 and the beam member 3 in the steel structure 1 to which the present invention is applied will be described.

  FIG. 3 schematically shows the moment applied to the steel structure 1 to which the present invention is applied. Since the steel structure 1 is constructed by rigidly joining the beam 3 to the beam-column joint portion 22 in the steel pipe column 2, if a stress due to an earthquake is applied to the steel structure 1, the column corresponding to the member contact Moment stress is generated in the vicinity of the beam joint portion 22. Further, when a moment is generated in the column beam joint 22, a moment stress is also generated in the column base 2 a located at the lower end of the lowermost steel pipe column 2. Since the weight of the steel structure 1 and the seismic load increase toward the lower layer, the magnitude of the moment at the column base 2a increases accordingly. Further, in the lowermost steel pipe column 2, an inflection point S at which this moment becomes 0 appears from the upper end to the column base 2 a. The height of the inflection point S is assumed to be h.

  In the present invention, the structural mechanical properties of the column beam joint 22 are defined as follows. That is, in the beam-column joint portion 22, the proof strength of the steel pipe column 2 is set sufficiently larger than the proof strength of the beam material 3, and the steel tube column 2 (more specifically, the steel pipe 21 excluding the column beam joint portion 22) and the beam The column beam strength ratio with the material 3 (= the strength of the steel pipe column 2 / the strength of the beam material 3) is 1.5 or more.

  For example, as described in P46 of the cold-formed square steel pipe design and construction manual (Nippon Bunka Center, 2003), the column collapses in advance and collapses, and the beam collapses in advance. In order to cause beam collapse preferentially, it is mentioned that the column beam strength ratio is 1.5 or more. On the basis of this, the present invention provides a column beam excluding the column leg portion 2a in at least the lowermost steel tube column 2 by setting the column beam yield strength ratio between the steel tube column 2 and the beam material 3 to 1.5 or more. It is possible to keep this in the elastic deformation region at the place where the moment stress is generated in the joint portion 22.

・・・・・（１） In the present invention, the strength _c σ _y in the lowermost layer of the steel pipe column 2 satisfies the following formula (1).

(1)

Here, _{c Z p:} plastic section modulus of the steel pipe column 2, h: height ratio of the inflection point S of moment in the steel column 2 for the lowermost floor height, n: axial force ratio of the steel pipe column 2, tau: strength increase rate of up to strength of the beam member _{3 (= 1.3), b M} PL, b M PR: exhibits plastic section modulus of the beam member 3. By the way, the value of the yield rate of increase 1.3 here is based on “The Architectural Institute of Japan, Structural Engineering Vol.51B, (2005), p381”.

Among these parameters, h, _b M _PL , and _b M _PR are the values of the steel structure 1 itself, such as the cross-sectional characteristics of the steel pipe column 2 and the beam material 3 and the height of the inflection point S in the steel structure 1. This means that the material is selected so that the strength _c σ _y of the lowermost layer in the steel pipe column 2 is larger than the right side of the equation (1) obtained by substituting parameters depending on the configuration. Actually, the strength _c σ _y of the lowermost layer in the steel pipe column 2 means the strength focused on the column base 2a having the largest moment.

  Hereinafter, the derivation process of the equation (1) will be described.

・・・・・（２） In the partial frame model shown in FIG. 3, the balance formula at the column beam joint 22 is expressed by the following formula (2).

(2)

In equation _(2), b _{M L,} b _{M R} represents a moment in the beam member 3 in the right and left sides of the beam-column joints 22. Further, _c M _1U and _c M _2D represent moments in the steel pipe columns 2 located above and below the column beam joint portion 22. Q represents the shear force generated in the lowermost steel pipe column.

  In FIG. 3, the height of the inflection point of the second layer column is 1 / 2H. However, it may be modified as appropriate according to the cross section of the second and third layer columns / beams.

・・・・・（３）
（２）、（３）式より、下記の（４）式を導くことができる。

・・・・・（４） On the other hand, the bending moment generated in the column base 2a is expressed by the following equation (3).

(3)
From the equations (2) and (3), the following equation (4) can be derived.

(4)

・・・・・（５） In order to prevent the column base 2a from being in a completely plastic state while plastic deformation occurs in the beam 3 and the yield strength increases, it is necessary to satisfy the following formula (5).

(5)

_{Here, b M L = τ × b} M PL, b M R = τ × b M PR, also _c M _P represents a full plastic stress in columnar leg portion 2a.

・・・・・（１） Then, when the above expression (5) is expressed as the condition of the column strength, it can be arranged as shown in (1).

(1)

  Of the variables defined in the equation (1), only the height h of the inflection point S can be obtained by the following calculation.

・・・・・（６） In the partial frame model shown in FIG. 3, the balance formula at the column beam joint 22 can be expressed by the following formula (6).

(6)

・・・・・（７） When it is assumed that the member deformation angles generated in the left and right beam members 3 are equal, it can be defined by the following equation (7).

(7)

・・・・・（８） From the equations (6) and (7), the following equations (8) and (9) can be derived.

(8)

・・・・・（９）

(9)

・・・・・（１０） When the bending angle of the steel pipe column 2 at the inflection point S is equal to the deformation matching condition, the following equation (10) can be derived from the equations (8) and (9).

(10)

  By solving the equation (10), the inflection point height h can be obtained.

_Here, h _{Q L,} h _{Q R} is the shear stress in the beam members 3 in the right and left sides of the beam-column joints _{22, L R, L L} is the beam member 3 in the right and left sides of the beam-column joints 22 member length in, E _b is the Young's modulus in the beam member 3 in the right and left sides of the beam-column joints 22, in the _b I _{L, b} I _R Liang material 3 on the left and right sides of the beam-column joints 22 Represents the moment of inertia of the cross section.

In determining the strength _c σ _y in the lowermost layer of the steel pipe column 2 specifically, when obtaining the right side of the equation (1), h is obtained by solving the equation (10), and the remaining Regarding the parameters, various parameters based on the design of the cross-sectional characteristics of the steel pipe column 2 and the beam material 3 in the actual steel structure 1 are substituted.

  As described above, according to the present invention, the column beam strength ratio between the steel pipe column 2 and the beam material 3 is 1.5 or more, so that at least the column leg portion 2a in the lowermost steel pipe column 2 is excluded. The material of the steel pipe column 1 is selected so that the moment stress is generated in the beam joint portion 22 and is maintained in the elastic deformation region, and the relationship of the formula (1) is established in the lowermost layer of the steel pipe column 2. Alternatively, optimization of various parameters such as the section modulus is attempted. As a result, even when a load due to a large earthquake is applied, the entire steel structure 1 can be suppressed to the elastic region, and as a result, the seismic performance of the entire steel structure 1 can be improved.

In the present invention employing the above-described configuration, the steel pipe column 2 may have a yield ratio of more than 80%. Alternatively, any material may be applied as long as the yield ratio of the steel material constituting the steel pipe column 2 is 99% or less. In order to ensure the deformation performance, the steel frame member has a rule that the yield ratio is 80% or less. However, by setting the steel pipe column 2 within the elastic range according to the present invention, the steel material yield ratio can be freely set. The degree can be improved. Moreover, since the yield ratio is the ratio between the yield strength and the tensile strength, the yield strength is relatively increased by relaxing the yield ratio of the steel material, and the steel pipe column is kept within the elastic range (Equation (1 It is possible to expect a synergistic effect that it is easy to satisfy

  Hereinafter, Example 1 of the steel structure 1 to which the present invention is applied will be described.

  The results of the simulation of the relationship between the thickness of the steel pipe column 2 and the yield strength of the steel pipe column 2 in the steel beam column 2 and the beam specifications of the beam material 3 as shown in Table 1 in the steel structure 1 are as follows. 4 (a) and 4 (b).

  By the way, in this Table 1, as shown in FIG. 5 (a), the extraction position of the partial frame is a region indicated by diagonal lines in which the beam 3 is extracted symmetrically with the steel pipe column 2 as the center. “Beam length left” is the beam material 3 on the left side of the steel pipe column 2 shown in FIG. 5A, and “Beam length right” is the beam material 3 on the right side of the steel tube column 2 shown in FIG. Is shown.

A curve corresponding to the above equation (1) is shown in FIG. On the upper side of the equation (1), it means that the strength _c σ _y in the lowermost layer of the steel pipe column 2 can be an elastic deformation region. In the relationship between the column yield ratio and the column yield strength, the region satisfying the equation (1) can be indicated by a solid line in FIG.

That is, it means that the column plate thickness and the column yield strength must be in the region above the curve of the formula (1). Further, in the figure, a constant yield strength curve of the steel pipe column 2 having a width of 600 mm is shown. In the conventional structure, the thickness of the column plate is set to 36 mm, but the thickness of the column plate is decreased along the constant yield strength curve and the column yield strength is improved. As a result, in the constant yield strength curve, when the column yield strength is 400 N / mm ² , the steel tube column 2 can be made completely elastic when the column yield strength is 500 N / mm ^2. It becomes possible. Conventionally,
While only the steel material was made high strength steel while making the plate thickness of the steel pipe column 2 the same, in the present invention, by reducing the yield ratio of the steel material, only the yield strength was increased while the tensile strength was the same, The difference is that the thickness of the steel pipe column 2 is reduced. In this example, the column yield strength satisfying the formula (1) can be obtained by setting the yield ratio to 85% or more of the conventional steel. More preferably, the intention of the present invention can be reliably realized by setting the yield ratio to 90% or more. As a result, the weight can be reduced, and the material cost and the construction cost can be reduced.

  Hereinafter, Example 2 of the steel structure 1 to which the present invention is applied will be described.

  In the steel pipe column 2 and the beam material 3 of the beam material 3 as shown in Table 2 in the steel structure 1, the result of actually obtaining the relationship between the plate thickness of the steel tube column 2 and the yield strength of the steel tube column 2 by simulation is shown. It shows to Fig.6 (a), (b).

  By the way, in this Table 1, as shown in FIG. 5 (b), the position where the partial frame is taken out is an area indicated by oblique lines extracted from the steel pipe column 2 so that the left beam 3 is longer. The “beam length left” in the frame is the beam material 3 on the left side of the steel pipe column 2 shown in FIG. 5 (a), and the “beam length right” is on the right side of the steel tube column 2 shown in FIG. 5 (a). A certain beam member 3 is shown.

A curve corresponding to the above equation (1) is shown in FIG. Further, in the figure, a constant yield strength curve of the steel pipe column 2 having a width of 700 mm is shown. In the conventional structure, the thickness of the column plate is set to 36 mm, but the thickness of the column plate is decreased along the constant yield strength curve and the column yield strength is improved. As a result, it is possible to make the steel pipe column 2 completely elastic when the column yield strength is 400 N / mm ² and when the column yield strength is 500 N / mm ^2. It becomes possible. In the relationship between the column yield ratio and the column yield strength, a region satisfying the equation (1) can be indicated by a solid line in FIG. Conventionally, only the steel material was made high strength steel while keeping the plate thickness of the steel pipe column 2 the same. However, in the present invention, by reducing the yield ratio of the steel material, only the yield strength is maintained with the same tensile strength. In that the thickness of the steel pipe column 2 is reduced. As a result, the weight can be reduced, and the material cost and the construction cost can be reduced. In this example, the column yield strength satisfying the formula (1) can be obtained by setting the yield ratio to 80% or more of the conventional steel. More desirably, the intention of the present invention can be reliably realized by setting the yield ratio to 90% or more.

  Hereinafter, Example 3 of the steel structure 1 to which the present invention is applied will be described.

  Fig. 3 shows the results obtained by the simulation of the relationship between the thickness of the steel pipe column 2 and the yield strength of the steel pipe column 2 in the steel pipe column 2 and the column specifications of the beam 3 as shown in Table 3 in the steel structure 1 7 (a) and (b).

A curve corresponding to the above equation (1) is shown in FIG. In the relationship between the column yield ratio and the column yield strength, the region satisfying the equation (1) can be indicated by a solid line in FIG. Further, in the figure, a constant yield strength curve of the steel pipe column 2 having a width of 950 mm is shown. In the conventional structure, the thickness of the column plate is 40 mm. However, the thickness of the column plate is lowered along this constant yield strength curve, and the column yield strength is improved. As a result, when the column yield strength is 500 N / mm ² in the constant yield strength curve, the elastic range can be obtained. In this example, by setting the yield ratio to 95% or higher compared to the conventional steel, or by setting the yield ratio to 80% or higher in the tensile strength class 590N / mm grade ² steel, Satisfactory column yield strength can be obtained. More desirably, the intention of the present invention can be reliably realized by setting the yield ratio to 90% or more.

DESCRIPTION OF SYMBOLS 1 Steel structure 2 Steel pipe pillar 3 Beam material 21 Steel pipe 22 Column beam joint 31 Web part 32 Flange part

Claims (2)

In a steel structure comprising a steel pipe column and a beam member rigidly joined to a column beam joint in the steel pipe column,
The beam-column joint has a beam-column strength ratio of 1.5 or more,
The steel structure is characterized in that the strength _c σ _y in the lowermost layer of the steel pipe column satisfies the following formula (1).

(1)
Here, _{c Z p:} plastic section modulus of the steel pipe column, h: height ratio of the inflection point of moment in the steel pipe column for the lowermost floor height, n: steel column axial force ratio, tau: maximum beam members strength increase rate up to yield strength _{(= 1.3), b M PL} , b M PR: plastic section modulus of the beam material The steel structure according to claim 1, wherein the steel pipe column has a yield ratio of 99% or less.

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