JP2020166503A - Buckling load calculation method - Google Patents

Abstract

To provide a buckling load calculation method capable of accurately calculating a buckling load while reducing analysis time including model creation time as much as possible and eliminating complicated modeling.SOLUTION: The buckling load calculation method for creating a frame model of a building structure and calculating a buckling load in a computer, comprises the steps of: replacing a frame model formed by a long column, an A-frame including a lateral general column lateral to the long column, and a beam connecting the long column with the A-frame with a replacement frame model including a storey replacement frame containing a long column formed by a long column, a beam, a long lateral general column and a first brace having a layer stiffness of an A-frame; and performing a buckling eigenvalue analysis on the replacement frame model to calculate the buckling load.SELECTED DRAWING: Figure 6

Description

The present invention relates to a buckling load calculation method.

In a building formed of a steel structure, it is important to prevent a buckling phenomenon in which columns formed of shaped steel such as square steel pipes and H-shaped steel become unstable due to compressive force. Pillars include pillars that are longer than ordinary pillars due to their high floor height, pillars that are longer because they straddle multiple floors by forming a stairwell space, and pillars and beams with pins. There are columns that cannot be expected to have a stiffening effect due to the beams, and these columns are called "long columns".

Conventionally, as a design method for steel columns including long columns, a design method based on Non-Patent Document 1 and a design based on buckling eigenvalue analysis using a buckling deflection angle method (for reference, Non-Patent Document 2). The method has been applied. The design method based on Non-Patent Document 1 (Steel Structure Buckling Design Guideline) models the bending rigidity (rigidity) of a beam or column attached to a long column as a variable, and the horizontal movement of the long column is restricted. There are two cases, one is the case and the other is not restrained, and the case where the horizontal movement is not restrained is selected in the normal ramen frame. However, in this case, the effect of other members supporting the instability of the long column is completely ignored, resulting in a very disadvantageous calculation result for the long column.

As a relatively simple design method while solving the above-mentioned problems that occur in the case of the design method based on Non-Patent Document 1, there is a design method based on buckling eigenvalue analysis using the buckling deflection angle method. In this design method, an exact solution can be obtained by faithfully modeling the columns and beams that make up the building, but on the other hand, the amount of calculation increases dramatically as the number of members increases. Therefore, a design method based on as simple a modeling as possible is required. "Buckling eigenvalue analysis" is a model of a long column and columns attached to the top and bottom of the long column by the deflection angle method that can consider geometrical non-linearity, and models other members with ordinary beam elements. It is an analysis method to be converted. When a column is modeled by the deflection angle method of buckling, the resistance to horizontal force decreases as the axial force on the column increases, and it becomes easy to become unstable. When the axial force applied to the long columns and the columns above and below the long columns is gradually increased and the determinant of the overall rigidity matrix of the building becomes zero, that is, when the entire building loses resistance to external forces and becomes unstable. This is an analysis method in which the axial force is the buckling resistance of a long column.

The above-mentioned design method based on the simplest possible modeling is a design method based on the modeling of only one long pillar based on Non-Patent Document 3. The long pillars are often planned on the middle floor or the bottom floor of the building, for example, as shown in FIGS. 1 and 2. Therefore, as shown in FIG. 3, a simple model in which the influence of the peripheral members of the long column is integrated into the spring can be applied. In FIG. 3, the spring 1 represents the rotation restraint effect of the beam, the column, etc. attached to the stigma of the long column, and the spring 2 represents the rotation restraint effect of the base plate, the beam, the column, etc. attached to the column base of the long column. , The spring 3 expresses the effect of restraining the horizontal movement of the long column.

In the model shown in FIG. 3, it can be evaluated as the rigidity of the spring 3 = the layer rigidity. On the other hand, modeling as shown in FIG. 3 has its own problems. For example, the spring 1 and the spring 2 include the influence of the columns attached to the top and bottom of the long column, and the rigidity of these columns is also affected by the axial force. Therefore, the rigidity of the spring 1 and the spring 2 is also the axial force. Decreases as the value rises. However, it is extremely difficult to model a spring whose rigidity changes with the axial force as a variable (first problem). Further, in FIG. 3, the buckling mode cannot be obtained unless the long column is given an initial irregularity. Further, the obtained buckling mode lacks accuracy as described in detail below, and there is a problem that the deformation state of the long column at the time of buckling cannot be grasped (second problem).

In order to deal with the first problem, as shown in FIG. 4, a model including columns attached to the top and bottom of the long columns is proposed based on Non-Patent Documents 4, 5 and 6. In FIG. 4, of the three pillars, the central pillar is a long pillar, and ordinary pillars (long pillar upper and lower general pillars) are attached above and below the long pillar. The rotation restraint spring in FIG. 4 represents the influence of a beam attached to a column (including a long column).

In the model shown in Fig. 3, the rigidity of the horizontal spring can be regarded as the layer rigidity. On the other hand, in the model for a plurality of layers as shown in FIG. 4, the rigidity of the horizontal spring is not the layer rigidity. Therefore, in order to obtain the rigidity of the horizontal spring, it is necessary to divide the horizontal external force in the layer by the absolute displacement. The differences between the two are shown in FIG. 5 and Table 1.

In Table 1, P1, P2, and P3 are horizontal external forces acting on each floor, and δ1, δ2, and δ3 show inter-story deformation of each floor, respectively. It is easy to output the layer rigidity with general structural calculation software, but separate work using spreadsheet software is required to obtain horizontal external force and absolute displacement, which is complicated when the long columns are on a high floor. It can be a difficult task. In addition, depending on the model, the horizontal spring rigidity may be negative. Furthermore, even in the model shown in FIG. 4, the buckling mode cannot be obtained unless some initial irregularity is given to the long column, as in the model shown in FIG.

Steel Structure Buckling Design Guideline 4th Edition 2018 Architectural Institute of Japan Minoru Wakabayashi Detailed explanation of steel structure Maruzen 1985 Akinobu Takada, Motohide Tada, Shizuji Mukai "Consideration of buckling length of columns in a steel structural rigid frame frame that receives column axial force due to horizontal load" Architectural Institute of Japan Structural Papers Vol. 78, No. 693 pp .. 1969-1978, 2013.11. Mamoru Kimura, Yoshiro Suzuki, Toshiyuki Ogawa, Norio Igarashi, Hidehiko Ota "Effect of horizontal rigidity of skeleton on buckling length of inner column material of skeleton" Architectural Institute of Japan Academic Lecture Abstracts pp. 253-254, 1995.8. Norio Igarashi, Keiichi Sato "Buckling analysis of internal column members of the framework considering horizontal stiffening rigidity" Architectural Institute of Japan Structural Papers Vol. 73, No. 633 pp. 200-2017, 2008.11. "Toward CFT Structural Calculation Standardization-Criteria Considering Long Period Ground Motion-" Architectural Institute of Japan Conference (Kyushu) Structural Division Panel Discussion Material pp. 59-62, 2016.8. Architectural Institute of Japan

As described above, the calculation time can be enormous in the method of modeling all the members based on Non-Patent Document 1. On the other hand, as shown in FIG. 3, it is difficult to consider the influence of the pillars attached to the long pillars in the single long pillar model. Further, in the multi-floor model as shown in FIG. 4, it becomes complicated to replace the layer rigidity with the horizontal spring rigidity. Further, the simple model (simplified model) shown in FIGS. 3 and 4 has a problem that an initial irregularity must be given to the long column in order to obtain the buckling mode.

The present invention has been made in view of the above problems, and the buckling load can be calculated accurately while shortening the analysis time including the model creation time as much as possible and eliminating complicated modeling. The purpose is to provide a buckling load calculation method.

In order to achieve the above object, one aspect of the buckling load calculation method according to the present invention is
A buckling load calculation method that creates a frame model of a building frame and calculates a buckling load in a computer.
A frame model formed by a long pillar, an A frame including a long pillar side general pillar on the side of the long pillar, and a beam connecting the long pillar and the A frame is formed by the long pillar and the beam. A step of replacing the beam with a replacement frame model including a long column-containing floor replacement frame formed by the beam, the long column side general column, and the first brace having the layer rigidity of the A frame.
It is characterized by having a step of performing a buckling eigenvalue analysis on the substitution frame model and calculating a buckling load.

According to this aspect, the horizontal rigidity of the frame around the long column is replaced with a brace instead of a horizontal spring to create a replacement frame model, and the buckling eigenvalue analysis is performed on the replacement frame model. The analysis time including the model creation time can be shortened as much as possible compared to the settlement model that faithfully reproduces the building. Further, by replacing the layer rigidity with a brace instead of the horizontal spring rigidity, complicated modeling can be eliminated. Furthermore, by performing buckling eigenvalue analysis on the substitution frame model in which the layer rigidity is replaced with braces, it is possible to obtain analysis results close to the analysis results by the settlement model, and the buckling load can be calculated accurately. it can.

An actual building for which a replacement frame model including a long column-containing floor replacement frame formed by a long column, a beam, a general column on the side of the long column, and a first brace having layer rigidity of the A frame is modeled. For example, a one-story building including a long pillar can be mentioned. In addition to calculating the buckling load, the buckling mode can also be specified. It should be noted that "being on the side of the long pillar" includes not only being on the side of the long pillar and being at a distant position, but also being located adjacent to the long pillar.

Here, the method of obtaining the rigidity of the first brace from the layer rigidity of the A frame can be performed by using a manual calculation based on a general micro-deformation theory or a commercially available structural calculation software. However, when calculating the buckling load after constructing the replacement frame, the calculation method based on the minute deformation theory does not consider the geometrical rigidity, and it is difficult to cope with the large deformation of the frame model. Therefore, after the member is deformed. It is preferable to apply the buckling deflection angle method, which defines the relationship between stress and deformation based on the balance of forces.

Further, in another aspect of the buckling load calculation method according to the present invention, the frame model includes a plurality of vertical columns above and below the column, and a beam, and has a column. In the case of further equipped with no B frame
In the step of replacing with the replacement frame model,
The long column-free floor replacement frame formed by the long column upper and lower general columns, the beam, and the second brace having the layer rigidity of the B frame is combined with the long column-containing floor replacement frame. It is characterized by creating a replacement frame model.

According to this aspect, it is a building having multiple floors by modeling a multi-story building in which a long column-containing floor replacement frame and a long column-free floor replacement frame are joined to each other and performing buckling eigenvalue analysis. Therefore, it is possible to model the entire building having long columns on any floor and calculate the buckling load accurately. The method of obtaining the rigidity of the second brace from the layer rigidity of the B frame is the same as the method of obtaining the rigidity of the first brace from the layer rigidity of the A frame, and is a manual calculation based on a general micro-deformation theory or a commercially available structural calculation. It can be done by a method using software.

Further, in another aspect of the buckling load calculation method according to the present invention, when the member in the frame model is plasticized when the set interlayer deformation angle is reached, the plasticized member is included. It is characterized in that the replacement frame model is created by the first brace or the second brace having the rigidity of the A frame or the B frame.

According to this aspect, when one or more members are plasticized in the frame model, they are replaced by the rigid first brace or the second brace of the A frame or the B frame including the plasticized members. By creating a frame model, the buckling load of a long column during a large earthquake can be calculated more accurately.

As can be understood from the above description, according to the buckling load calculation method of the present invention, the analysis time including the model creation time is shortened as much as possible, and the buckling load is accurately eliminated while eliminating complicated modeling. Can be calculated.

It is a figure which shows a part of the frame model which a long pillar exists in the middle layer of a building. It is a figure which shows a part of the frame model which a long pillar exists in the bottom floor of a building. It is a figure which shows the simple frame model which concentrated the influence of the peripheral member of a long column into a spring. It is a figure which shows the frame model which made the long column and the upper and lower columns a frame model, and made the influence of the peripheral member of a column a rotation restraint spring and a horizontal spring. It is a figure explaining each calculation method of a horizontal spring rigidity and a layer rigidity. It is a flowchart of an example of the buckling load calculation method which concerns on embodiment. It is a figure which shows the settlement model which is a conventional frame model. It is a figure which shows an example of the substitution frame model created in the buckling load calculation method which concerns on embodiment. It is a figure explaining the method of creating the replacement frame model shown in FIG. It is a figure which shows the frame model in the buckling eigenvalue analysis example 1, (a) is the figure which shows the settlement model which concerns on Comparative Example 1, and (b) is the figure which shows the substitution frame model which concerns on Example 1. (C) is a diagram showing a horizontal spring model according to Comparative Example 2. It is a buckling mode diagram in the buckling eigenvalue analysis example 1, (a) is a buckling mode diagram of Comparative Example 1, (b) is a buckling mode diagram of Example 1, and (c). Is a buckling mode diagram of Comparative Example 2. It is a figure which shows the frame model in the buckling eigenvalue analysis example 2, (a) is the figure which shows the settlement model which concerns on Comparative Example 3, and (b) is the figure which shows the substitution frame model which concerns on Example 2. (C) is a diagram showing a horizontal spring model according to Comparative Example 4. It is a buckling mode diagram in the buckling eigenvalue analysis example 2, (a) is a buckling mode diagram of Comparative Example 3, (b) is a buckling mode diagram of Example 2, and (c). Is a buckling mode diagram of Comparative Example 4.

Hereinafter, the buckling load calculation method according to each embodiment will be described with reference to the attached drawings. In the present specification and the drawings, substantially the same components may be designated by the same reference numerals to omit duplicate explanations.

[Buckling load calculation method according to the embodiment]
First, an example of the buckling load calculation method according to the embodiment will be described with reference to FIGS. 6 to 9. Here, FIG. 6 is a flowchart of an example of the buckling load calculation method according to the embodiment. Further, FIG. 7 is a diagram showing a settlement model which is a conventional frame model, and FIG. 8 is a diagram showing an example of a replacement frame model created in the buckling load calculation method according to the embodiment. Further, FIG. 9 is a diagram illustrating a method of creating the replacement frame model shown in FIG.

The building to be analyzed by the buckling load calculation method according to the embodiment is a four-story building as shown in detail in the settlement model of FIG. 7, and the left end of the building has two to four floors. There are long pillars that are continuous up to, and on the side of the long pillar, there are three sets of three long pillar side general pillars with spans L1, L2, and L3, and there are multiple on the top and bottom of the long pillar. There are first-floor frames and fourth-floor frames formed by general columns and beams above and below the long columns.

In the buckling load calculation method according to the first embodiment, first, as shown in FIG. 6, a commercially available structural calculation software installed in the computer is used to model the settlement model shown in FIG. 7, for example. The initial cross-sectional rigidity (cross-sectional area, Young's modulus, etc.) of the constituent members is input, and the frame stress analysis is performed. Here, as the structural calculation software, product name: BUS-6 (manufactured by Structural System Co., Ltd.), product name: SuperBuild / SS7 (manufactured by Union System Co., Ltd.), etc. can be applied, and various types are applied to each floor of the frame model. The amount of deformation of each floor when the load (horizontal force at the time of an earthquake, wind load, etc.) is loaded is calculated, and the preparatory calculation for specifying the layer rigidity of each floor (including one-story building) is performed (step S1). ..

The frame model created in the computer in the frame stress analysis is the settlement model shown in FIG. 7. In this settlement model, the frame formed by the long pillar side general pillars and beams on the side of the long pillars on the second and third floors, which includes the long pillars extending from the second floor to the fourth floor, is called "A frame". To do. In addition, on the first and fourth floors that do not include the long pillars, on the side of the long pillar upper and lower general pillars located directly above and below the long pillars, the frame formed by the long pillar upper and lower general pillars and the beams is referred to as "B. "Frame". In the frame model shown in FIG. 7, a long pillar exists between the upper and lower general pillars, an A frame exists on the side of the long pillar, and a B frame exists on the side of the upper and lower general pillars. , Each is connected by a beam to form a settlement model.

Here, the "long pillar side general pillar" is a pillar (about 3 m) having a general length without having a length like a long pillar, and is located on the side of the long pillar. It means a general pillar to do. Further, the above-mentioned "long pillar upper and lower general pillars" are pillars of general length (about 3 m) that do not have a length like long pillars, and are above or below the long pillars. It means a general pillar that exists on the floor.

After performing the frame stress analysis to identify the relationship between the load to be loaded and the amount of deformation of each floor, the A frame is replaced with the first brace (step S2).

The first brace has the layer rigidity of the A frame surrounded by the alternate long and short dash line in FIG. 7, and the layer rigidity is the same as the layer shear force borne by the A frame by performing the frame stress analysis as shown in Table 1. , A frame can be easily calculated from the relationship with the amount of deformation of the floor including the frame. Then, as shown in FIG. 8, by representing the first brace as a one-sided flow brace having the layer rigidity of the A frame, the long column and the A frame including the long column side general column on the side of the long column and the A frame. A frame model (settlement model) formed by a beam connecting a long column and an A frame is formed by a long column, a beam, a general column on the side of the long column, and a first brace having a layer rigidity of the A frame. It is replaced with the formed long column-containing floor replacement frame (step S3).

Here, the method of obtaining the rigidity of the first brace from the layer rigidity of the A frame and the method of obtaining the rigidity of the second brace from the layer rigidity of the B frame are both manually calculated based on the general micro-deformation theory or commercially available. It can be obtained using structural calculation software.

The layer rigidity k2 of the first brace (the layer rigidity of the A frame), together with the layer rigidity k1 and k3 of the other second brace (the layer rigidity of the B frame described below), has the following formula as shown in FIG. It can be represented by (1).

In order to incorporate the one-way first brace into the model, members such as columns and beams to which the brace attaches are required. For the columns and beams to which the first brace is attached, the positions actually arranged and the actual members are adopted. The beam to which the first brace is attached acts as a spring that restrains the rotation of the stigma and pedestal of the long column. A rigid, semi-rigid, or pin joint structure can be applied to both ends of the beam according to the actual situation. For general columns on the side of long columns to which the first brace is attached, it is preferable to reduce the horizontal rigidity of the column itself by using the column base as a pin and reduce the horizontal rigidity other than the first brace as much as possible.

Next, the B frame is replaced with the second brace based on the relationship between the load and the amount of deformation of each floor in the frame stress analysis performed in step S1 (step S4).

The second brace has the layer rigidity of the B frame surrounded by the alternate long and short dash line in FIG. 7, and as shown in Table 1, the layer rigidity is the relationship between the load loaded by performing the frame stress analysis and the amount of deformation of each floor. It can be easily calculated from. Then, as shown in FIG. 8, by representing the second brace as a one-sided flow brace having the layer rigidity of the B frame, a plurality of long column upper and lower general columns above or below the long column and a beam are included. A B-frame frame model (settlement model) that does not have long columns is replaced by upper and lower long column-free floor replacements formed by the upper and lower general columns of long columns, beams, and a second brace that has the layer rigidity of the B frame. Replace with a frame (step S5).

The layer rigidity k1 and k3 (layer rigidity of the upper and lower B frames) of the second brace can be expressed by the equation (1) as shown in FIG. Further, when incorporating the second brace into the model, the points to be noted when incorporating the first brace into the model are followed as described above.

A replacement frame model is created by combining the long column-containing floor replacement frame already created in step S3 and the long column-free floor replacement frame created in step S5 (step S6).

The buckling load is calculated and the buckling mode is specified by performing the buckling eigenvalue analysis on the replacement frame model created in the computer (step S7).

According to the buckling load calculation method according to the embodiment, the horizontal rigidity of the frame around the long column is replaced with a brace instead of a horizontal spring to create a replacement frame model, and buckling with respect to the replacement frame model. By performing the eigenvalue analysis, the analysis time including the model creation time can be shortened as much as possible as compared with the settlement model that faithfully reproduces the building.

Further, by replacing the layer rigidity with a brace instead of the horizontal spring rigidity, complicated modeling can be eliminated.

Further, as described in detail in the following buckling eigenvalue analysis examples 1 and 2, the buckling eigenvalue analysis is performed on the substitution frame model in which the layer rigidity is replaced with the brace, and the analysis result close to the analysis result by the settlement model. Can be obtained, and the buckling load can be calculated accurately.

The building to be analyzed by the buckling load calculation method shown in FIG. 6 is a four-story building with long pillars on the middle floor, but it is a one-story building with long pillars. Is to be analyzed, in the flowchart of FIG. 6, the replacement frame model is created in step S3, and then the buckling eigenvalue analysis in step S7 is performed.

Further, in the frame stress analysis in step S1, when the interlayer deformation angle (1/100, 1/50, etc.) corresponding to the seismic level is generated and the member in the frame model is plasticized, the member is plasticized. In step S2, it was replaced with the first brace having the rigidity of the A frame including the plasticized member, and similarly, in step S4, it was replaced with the second brace having the rigidity of the B frame including the plasticized member. Later, in step S6, a replacement frame model is created. If the end of the beam is plasticized and a hinge is formed, the joining condition of the end is pin joining according to the actual condition.

According to this method, when one or more members are plasticized in the frame model, the frame is replaced by the first or second brace having the rigidity of the A frame or the B frame including the plasticized members. Since the model has been created, the buckling load of the long column during a large earthquake can be calculated more accurately.

[Example of buckling eigenvalue analysis]
<Buckling eigenvalue analysis example 1>
Next, a buckling eigenvalue analysis example 1 carried out by the present inventors will be described with reference to FIGS. 10 and 11. Here, FIG. 10 is a diagram showing a frame model in the buckling eigenvalue analysis example 1, and FIG. 10A is a diagram showing a settlement model according to the comparative example 1, and the specifications of each member are shown together. 10 (b) is a diagram showing a replacement frame model according to the first embodiment, and FIG. 10 (c) is a diagram showing both the cross-sectional areas of the first brace and the second brace, and FIG. 10 (c) is a comparison. It is a figure which shows the horizontal spring model which concerns on Example 2, and is the figure which showed the spring constant of each spring together. Further, FIG. 11 is a buckling mode diagram in the buckling eigenvalue analysis example 1, and FIGS. 11 (a), 11 (b), and 11 (c) are Comparative Example 1, Example 1, and Comparison, respectively. It is a buckling mode diagram of Example 2.

As is clear from FIG. 10A, the model to be analyzed is a four-story building with a long pillar at the left end of the middle floor.

From the buckling mode diagram of Comparative Example 1 shown in FIG. 11, when the long column buckles, the long column and the upper and lower general columns of the long column are compressed in the vertical direction. When the long column is compressed, the beam attached to the long column also follows the deformation. On the other hand, since the two general columns on the right side of the long column are not compressed so much, the beam attached to the long column (the member surrounded by the ellipse of the alternate long and short dash line in FIG. 11A) is tilted and the axis. Force is generated. Further, a horizontal force is generated to tilt the A frame and the B frame shown in FIG. 10A from right to left. As a result, as shown in FIG. 11A, the buckling mode is swayed to the left.

On the other hand, also in the model of FIG. 10B, when the long column is compressed, the beam attached to the long column follows and an axial force is generated on the beam. As a result, a horizontal force acts on the first brace and the second brace from right to left, resulting in a buckling mode swaying to the left as shown in FIG. 11B. It can be seen that the buckling mode of Example 1 shown in FIG. 11 (b) indicates a mode similar to the buckling mode of Comparative Example 1 of the settlement model shown in FIG. 11 (a).

Further, in drawing FIG. 11 (c) showing the buckling mode of the horizontal spring model of FIG. 10 (c), a minute initial irregularity is given to the column. Since the surrounding columns and beams are not modeled in the horizontal spring model, it can be seen that the buckling mode is significantly different from that of the settlement model, as shown in FIG. 11 (c).

As described above, the brace replacement model according to the first embodiment does not require the conversion work from the layer rigidity to the horizontal spring rigidity, and by incorporating the peripheral members into the brace model, a buckling mode close to that of the settlement model can be obtained. Has advantages.

Next, Table 2 shows the buckling load Pcr of the long column obtained by the buckling eigenvalue analysis of Comparative Examples 1 and 2 and Example 1.

From Table 2, the buckling load of Example 1 is a value close to the buckling load of Comparative Example 1 which is a settlement model (error is about 8%), demonstrating that high analysis accuracy can be obtained. There is. On the other hand, the buckling load of Comparative Example 2 has a large error of about half of the buckling load of Comparative Example 1, demonstrating that the design is extremely safe.

<Buckling eigenvalue analysis example 2>
Next, a buckling eigenvalue analysis example 2 carried out by the present inventors will be described with reference to FIGS. 12 and 13. Here, FIG. 12 is a diagram showing a frame model in the buckling eigenvalue analysis example 2, and FIG. 12A is a diagram showing a settlement model according to the comparative example 3, and the specifications of each member are shown together. 12 (b) is a diagram showing a replacement frame model according to the second embodiment, and FIG. 12 (c) is a diagram showing both the cross-sectional areas of the first brace and the second brace, and FIG. 12 (c) is a comparison. It is a figure which shows the horizontal spring model which concerns on Example 4, and is the figure which showed the spring constant of each spring together. Further, FIG. 13 is a buckling mode diagram in the buckling eigenvalue analysis example 2, and FIGS. 13 (a), 13 (b), and 13 (c) are comparative examples 3, 2, and comparison, respectively. It is a buckling mode diagram of Example 4.

As is clear from FIG. 12 (a), the model to be analyzed is a four-story building with a long pillar in the center of the middle floor, and the cross-sectional area and the moment of inertia of area of the right member are. It is higher than the member on the left side (C3> C2, G2> G1), and is an analysis model with a more complicated structure than the analysis model of Analysis Example 1.

From FIGS. 13 (a) and 13 (b), it can be seen that the buckling modes of Comparative Example 3 and Example 2 are both approximate modes. On the other hand, FIG. 13C shows that the buckling mode is significantly different from that of the settlement model, which is the same conclusion as in Analysis Example 1.

Next, Table 3 shows the buckling load Pcr of the long column obtained by the buckling eigenvalue analysis of Comparative Examples 3 and 4 and Example 2.

From Table 3, the buckling load of Example 2 is a value close to the buckling load of Comparative Example 3 which is a settlement model (error is about 1%), and it is demonstrated that high analysis accuracy can be obtained. There is. On the other hand, the buckling load of Comparative Example 4 has a large error of about 70% of the buckling load of Comparative Example 3, demonstrating that the design is extremely safe.

It should be noted that the configuration or the like described in the above embodiment may be another embodiment in which other components are combined, and the present invention is not limited to the configuration shown here. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form thereof.

Claims (3)

A buckling load calculation method that creates a frame model of a building frame and calculates a buckling load in a computer.
A frame model formed by a long pillar, an A frame including a long pillar side general pillar on the side of the long pillar, and a beam connecting the long pillar and the A frame is formed by the long pillar and the beam. A step of replacing the beam with a replacement frame model including a long column-containing floor replacement frame formed by the beam, the long column side general column, and the first brace having the layer rigidity of the A frame.
A method for calculating a buckling load, which comprises a step of performing a buckling eigenvalue analysis on the replacement frame model and calculating a buckling load. In the case where the frame model further includes a B frame having no long pillar, including a plurality of upper and lower general pillars of the long pillar above or below the long pillar, and a beam.
In the step of replacing with the replacement frame model,
The long column-free floor replacement frame formed by the long column upper and lower general columns, the beam, and the second brace having the layer rigidity of the B frame is combined with the long column-containing floor replacement frame. The buckling load calculation method according to claim 1, wherein a replacement frame model is created. When the member in the frame model is plasticized when the set interlayer deformation angle is reached, the first brace having the rigidity of the A frame including the plasticized member or the B frame or the said The buckling load calculation method according to claim 2, wherein the replacement frame model is created by the second brace.

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