JP6681277B2 - Joint strength evaluation method of beam-column joint structure, method of designing beam-column joint structure, and beam-column joint structure - Google Patents

Description

  The present invention relates to a joint strength evaluation method for a beam-column joint structure, a method for designing a beam-column joint structure, and a beam-column joint structure.

  SRC (Steel Reinforced Concrete) columns having a cross steel core as a core material are often used as the counter-propelled columns used in the counter-structuring method for super high-rise buildings. In addition, in recent years, due to the cost increase of RC (Reinforced Concrete: reinforced concrete structure), a column-beam joint structure using a column SRC beam S structure in which the beam is made of pure steel (S) has come to be used. In the joint of the pillar SRC beam S structure, it is common to use a diaphragm type, but the number of parts involved in manufacturing the steel frame, such as cutting of the pillar and welding of the diaphragm, and the number of processing man-hours are large factors that increase costs. Is a problem. Another problem is that it is necessary to strictly control the accuracy of the diaphragm position when the steel column is built.

  On the other hand, if the diaphragm of the beam-column joint is omitted, the local yield of the web of the column and the local collapse of the joint due to the out-of-plane bending deformation of the flange of the column precede the member yield of the column or beam. For this reason, there is a concern that the seismic performance will deteriorate. Therefore, only when it is confirmed that the local collapse of the joint does not occur by using the local proof stress evaluation formula of the joint shown in Non-Patent Document 1 or the like, the joint without the diaphragm has been designed. Specifically, in Non-Patent Document 1, the range of the plate thickness of the flange of the column having the H-shaped cross section, the plate thickness of the web, the fillet radius of the column, and the cross-sectional area of the flange of the beam is required in order to avoid using the diaphragm. It is prescribed.

Architectural Institute of Japan, “Steel Reinforced Concrete Structural Calculation Standards / Commentary”, p. 154-164

  However, for the local proof stress based on the design method of Non-Patent Document 1, the diaphragm cannot be omitted unless the flange of the column and the plate thickness of the web are very large. Therefore, there is a problem that it is not possible to adopt a non-diaphragm type by using a general rolled H-section steel (JIS-H or H-section steel with a constant outer method).

  The present invention has been made in view of such problems, and appropriately considers the load bearing effect of concrete in the joint local load bearing of the column SRC beam S structure of the non-diaphragm type, so that the conventional structure can be obtained. To provide a joint strength evaluation method for a beam-column joint structure, a method for designing a beam-column joint structure, and a beam-column joint structure that can reduce the plate thickness of the flange of the column and the plate thickness of the web in comparison. To aim.

In order to solve the above problems, the present invention proposes the following means.
The joint portion proof evaluation method of the column-beam joint structure of the present invention is a non-diaphragm type column-beam joint comprising a steel frame reinforced concrete column, a steel frame beam, and a joint part in which the beam is joined to the column. A method for evaluating a joint strength of a structure, wherein the column comprises a column steel frame having a web and a flange, the beam has a web and a flange, and is joined to the flange of the column steel frame at the joint part. That is, for the joint portion, in the proof stress of the column steel frame, the flange on the compression side of the beam, for the force to push the flange of the column steel frame in the thickness direction of the flange of the column steel frame, Characterized in that the flange of the column steel frame is evaluated by adding a proof stress against bearing pressure failure of the concrete inside the thickness direction of the flange of the column steel frame when deformed inward in the thickness direction. To have.
Generally, the bearing capacity of concrete is higher than the crushing strength of cones. According to the present invention, the proof stress of the joint is more appropriately evaluated by adding the proof stress of the column steel frame to the proof stress against the bearing failure of the concrete.

Further, in the joint portion proof stress evaluation method of the beam-column joint structure, in the joint portion, in the proof stress of the column steel frame, the flange on the tensile side of the beam is the flange of the column steel frame and the flange of the column steel frame. The pull-out force in the thickness direction of the cone-shaped fracture that occurs in the cover concrete outside the thickness direction of the flange of the pillar steel frame when the flange of the pillar steel frame is deformed to the outside in the thickness direction You may evaluate by adding the proof stress.
According to this invention, the proof stress of the joint can be more appropriately evaluated by adding the proof stress of the column steel frame and the proof stress against the cone-shaped fracture that occurs in the concrete.

Further, the joint strength evaluation method of another beam-column joint structure of the present invention is a non-diaphragm type including a steel-reinforced concrete column, a steel beam, and a joint part in which the beam is joined to the column. A method for evaluating joint strength of a beam-column joint structure, wherein the column includes a column steel frame having a web and a flange, the beam having a web and a flange, and the column steel frame at the joint portion. It is bonded to the flange, for the joint, is characterized by determining at least one of the maximum bending moment _j M _u by the full plastic bending moment _{j M p,} and (2) according to equation (1).
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, t _bf : Thickness of the flange of the beam, H _b : Due to the beam, F _c : Strength of the concrete of the column, d: _Cover thickness of the concrete with respect to the flange of the column steel frame, λ: bearing _capacity effect coefficient of the concrete, σ _cwu : tensile strength of the web of the column.

Further, the method of designing a beam-column joint structure according to the present invention is a non-diaphragm beam-column joint structure including a steel-framed reinforced concrete column, a steel-framed beam, and a joint part in which the beam is joined to the column. In the design method, the column comprises a column steel frame having a web and a flange, the beam has a web and a flange, and is joined to the flange of the column steel frame at the joint portion, in the joints, it is characterized by setting so as to satisfy the expressions (3) and the local yield bend moment _j M _y of the joint obtained by the equation (4), (5) and (6) .
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, r: Fillet radius of the column steel, t _bf : Thickness of the flange of the beam, A _bf : _Cross- sectional area of the flange of the beam , H _b : Due to the beam, F _c : Strength of the concrete of the column, d: Cover thickness of the concrete to the flange of the column steel frame, λ: Bearing effect coefficient of the concrete, _b Z _p : The Plastic section modulus of the beam, σ _by : Yield strength of the beam.

The column-beam joint structure of the present invention is a non-diaphragm type column-beam joint structure including a steel-framed reinforced concrete column, a steel-framed beam, and a joint portion in which the beam is joined to the column. , The pillar comprises a pillar steel frame having a web and a flange, the beam has a web and a flange, is joined to the flange of the pillar steel frame at the joint, in the joint, ( local yield bend moment _j M _y of the joint which is determined by 7) and (8) have been characterized in that it satisfies the equation (9) from equation (11).
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, r: Fillet radius of the column steel, t _bf : Thickness of the flange of the beam, A _bf : _Cross- sectional area of the flange of the beam , H _b : Due to the beam, F _c : Strength of the concrete of the column, d: Cover thickness of the concrete to the flange of the column steel frame, λ: Bearing effect coefficient of the concrete, _b Z _p : The Plastic section modulus of the beam, σ _by : Yield strength of the beam.

  According to these inventions, by appropriately considering the load bearing effect of concrete on the joint local load bearing of the non-diaphragm type column SRC beam S structure, the plate thickness of the flange of the column and The web thickness can be made thinner.

Further, in the joint strength proof evaluation method of the above-mentioned beam-column joint structure, when the total plastic bending moment _j M _p of the joint is determined, the local yield bending moment _j M _{y of the} joint according to the equation (12) is calculated. May be asked.

Further, in the above-described beam-column joint structure, the column steel frame may be a rolled H-section steel in which the flanges are integrally formed at both ends in the width direction of the web.
Moreover, in the above-mentioned beam-column joint structure, the column steel frame is a welded assembly H-shaped cross-section member in which the flanges are respectively joined to both ends in the width direction of the web, and the welded assembly H-shaped cross-section member is the web. And the flange may have a welded portion joined by complete penetration welding.

  According to the joint strength evaluation method of the beam-column joint structure, the method of designing the beam-column joint structure, and the beam-column joint structure of the present invention, the load bearing effect of concrete on the joint local portion of the non-diaphragm type column SRC beam S structure The thickness of the flange of the column and the thickness of the web can be made thinner by properly considering the above.

It is the perspective view which penetrated a part of beam-column joining structure of a 1st embodiment of the present invention. It is a sectional view of a pillar of the same beam-column joint structure. It is a side sectional view explaining a collapse mechanism at the time of full plastic proof of the same beam-column joint structure. FIG. 4 is a view showing a cross-sectional view taken along a cutting line A1-A1 in FIG. 3 together with a side surface of cover concrete. It is a figure which shows the sectional view of the cutting line A1-A1 in FIG. 3 with a bearing-pressure destruction part. It is a figure explaining the actual stress-strain characteristic of steel. It is a figure explaining the modeled stress-strain characteristic of steel. It is a figure showing the relationship between the yield strength in the calculation result of an all plastic bending moment, and an experimental result. It is a figure showing the relationship between the yield strength in the calculation result of a local yield bending moment, and an experimental result. It is a figure showing the relation between the calculation result of the maximum bending moment, and the maximum proof stress in an experimental result. It is a figure which shows the range which can be made non-diaphragm with respect to the plate thickness of the web of a pillar steel frame, and the plate thickness of a flange when the length of one side of concrete is 1100 mm. It is a figure which shows the range which can be made non-diaphragm with respect to the plate thickness of the web of a pillar steel frame, and the plate thickness of a flange when the length of one side of concrete is 1300 mm. In the beam-column joint structure of the second embodiment of the present invention, when the width of the flange of the column steel frame is 450 mm, it is a diagram showing a range in which non-diaphragmization is possible with respect to the plate thickness of the web of the column steel frame and the plate thickness of the flange. is there. In the column-beam joint structure, when the width of the flange of the column steel frame is 250 mm, it is a diagram showing a range in which non-diaphragm can be made to the plate thickness of the web of the column steel frame and the plate thickness of the flange.

(First embodiment)
Hereinafter, a first embodiment of a beam-column joint structure, a method for evaluating a joint strength of a beam-column joint structure, and a method for designing a beam-column joint structure according to the present invention will be described with reference to FIGS. 1 to 12.
As shown in FIG. 1, a beam-column joint structure 1 of the present embodiment includes a column 11 made of a steel reinforced concrete (SRC) structure, a beam 21 made of a steel frame, and a joint portion 31 in which the beam 21 is joined to the column 11. Equipped with.
The pillar 11 includes a pillar steel frame 12 having a web 14 and a flange 13, a plurality of reinforcing bars 15 surrounding the pillar steel frame 12, and concrete 16.
The column-beam joint structure 1 is of a type that does not use a diaphragm (stiffener) when joining the beam 21 to the column 11, that is, a non-diaphragm type.

When viewed in the longitudinal direction of the pillar steel frame 12 shown in FIG. 2, the plurality of reinforcing bars 15 are arranged at equal intervals on a reference line that has the shape of a rectangular edge.
The concrete 16 has a square or rectangular cross section orthogonal to the longitudinal direction.
As shown in FIG. 1, the beam 21 has an H-shaped cross section, and has a web 24 and a pair of flanges 23 joined to both ends of the web 24. The beam 21 extends in the horizontal direction. The beam 21 is a steel frame and is made of a steel plate or the like.
The flange 23 of the beam 21 is welded to the flange 13 of the column steel frame 12 at the joint 31. The web 24 of the beam 21 is welded or high-strength bolted to the flange 13 of the column steel frame 12. The joint portion 31 (the welded portion and the pillar steel frame 12 and the beam 21 near the welded portion) where the flange 13 of the pillar steel frame 12 and the beam 21 are joined is surrounded by concrete 16.

  The pillar steel frame 12 may be a rolled H-section steel in which the flanges 13 are integrally formed at both ends of the web 14 in the width direction. Further, the pillar steel frame 12 may be a welded assembly H-shaped cross-section member in which the flanges 13 are joined to both ends of the web 14 in the width direction. In this case, the welded assembly H-shaped cross-section member may have a welded portion in which the web 14 and the flange 13 are joined by complete penetration welding.

[1. Disintegration mechanism proposed in the present invention]
As a collapse mechanism of the main beam-column joint structure 1, the mechanism shown in FIGS. 3 to 5 is assumed. 3 to 5 show a state after the beam-column joint structure 1 is deformed. It is assumed that the flange 13 of the pillar steel frame 12 has a plastic hinge 13 ₁ formed above and a plastic hinge 13 ₂ formed below. It is assumed that the plastic rotation angles θ ₁ and θ ₂ described below are deformed from a state of 0 (radian) to a positive state of the plastic rotation angles θ ₁ and θ ₂ shown in FIGS. 3 to 5.
For tensile force side of the flange 23 of the beam 21 (the upper flange 23 1 in this _example) pulls the flange 13 of the column steel 12 in out-of-plane, pillars steel 12 is steel, the out-of-plane deformation of the flange 13 And local yielding of the web 14 occurs. As a result, the local yield 14a is formed on the web 14 of the pillar steel frame 12. Further, the flange 13 of the column steel 12, plastic hinge 13 ₁ is formed.
When the flange 13 of the pillar steel frame 12 is deformed out of plane, the cover concrete 16a outside the flange 13 is crushed in a cone shape. The side surface 16a1 of the cover concrete 16a is shown by hatching in FIG.

As shown in FIG. 3, when the compression-side flange 23 (the lower flange 23 _{2 in} this example) of the beam 21 pushes the flange 13 of the column steel frame 12 out of the plane, the flange 13 is inwardly out-of-plane. It is assumed that the deformation causes local yielding of the web 14 and the concrete 16 inside the flange 13 bears and fails. A bearing pressure destruction portion 16b is formed in the concrete 16. The bearing breakdown section 16b is shown with hatching in FIG. Further, the flange 13 of the column steel 12, plastic hinge 13 ₂ is formed.
Since the bearing capacity of concrete is generally larger than the cone-shaped fracture strength, the neutral axis C1 that satisfies the balance condition in the cross section of the joint 31 is above and below the beam beam _Hb (beam beam (composition), mm). the center of the direction located on the flange 23 ₂ side of the compression side.

This collapse mechanism assumes that the joint 31 is rotated by an angle θ (radian) with respect to the bending moment of the end of the beam 21. However, the angle θ is a minute angle and can be approximated as tan θ = θ.
The variables used in this collapse mechanism are x, y, and z (mm) shown in the figure. The variable x is a coefficient that determines the position of the neutral axis C1 with respect to the bending moment of the end of the beam 21, and can take any value of 0 or more and 1 or less. The variables y and z can take any positive numbers (values larger than 0). Using these variables x, y, and z, the out-of-plane deformation amounts δ ₁ , δ ₂ (mm) at the intersection of the flange 13 of the pillar steel frame 12 and the flanges 23 ₁ , 23 ₂ are expressed by equations (13) and (14). ) Equation (15) and Equation (16). Here, the plate thickness of the flange 23 of the beam 21 is t _bf (mm), and the width of the rigid region assumed at the intersection of the flange 13 and the flange 23 is t ′ (mm).

The plastic rotation angles θ ₁ and θ ₂ (radian) generated on the yield hinge line of the flange 13 of the pillar steel frame 12 can be expressed by the equations (17) and (18).

[2. First collapse model)
The joint strength evaluation method of the beam-column joint structure in the first collapse model of the collapse mechanism of the beam-column joint structure 1 described above is as follows. In addition, it is an evaluation method for evaluation. Resistance to Bearing destruction of the concrete 16 as referred to herein, relative to the force flange 23 ₂ of the compression side of the beam 21 to push the flange 13 of the column steel 12 in the thickness direction D of the flange 13 (see FIG. 3), the post It is the proof stress against bearing pressure failure of the concrete 16 on the inner side D1 of the flange 13 of the column steel frame 12 in the thickness direction D when the flange 13 of the steel frame 12 is deformed to the inner side D1 of the thickness direction D.
Generally, the bearing capacity of concrete is higher than the crushing strength of cones. By evaluating the proof stress of the column steel frame 12 by adding the proof stress against the bearing failure of the concrete 16, the proof stress of the joint portion 31 is evaluated more appropriately. Therefore, the plate thickness of the flange 13 of the pillar steel frame 12 and the plate thickness of the web 14 can be made thinner by appropriately considering the load bearing effect of the concrete 16.

Further, in the joint strength proof evaluation method for the beam-column joint structure described above, the joint 31 may be evaluated by adding the proof stress of the column steel frame 12 to the crush resistance of the cover concrete 16a against the cone-shaped fracture. Resistance to cone breakage occurring concrete cover 16a here, the flange 23 ₁ of the tension side of the beam 21 against a force to pull out the flange 13 of the column steel 12 in the thickness direction D, the flange 13 of the column steel 12 It is the proof stress against the cone-shaped fracture that occurs in the cover concrete 16a on the outer side D2 of the flange 13 of the pillar steel frame 12 on the outer side D2 of the thickness direction D when deformed to the outer side D2 in the thickness direction D.
By evaluating the proof stress of the pillar steel frame 31 by adding the proof stress against the cone-shaped fracture that occurs in the concrete 16, the proof stress of the joint portion 31 can be evaluated more appropriately.

Further, in the beam-column joint structure 1, when the column steel frame 12 of the column 11 is not surrounded by the concrete 16 (steel bar 15 and concrete 16) in the steel frame reinforced concrete, a constant load acts on the beam 21. At least a part of the joint portion 31 yields. However, when the pillar steel frame 12 of the pillar 11 is surrounded by the concrete 16, the joint portion 31 may not be yielded even when this constant load is applied to the beam 12.
Even if a constant load that yields the joint 31 is applied to the pillar steel frame 12 alone, the joint part 31 can be prevented from yielding by surrounding the pillar steel frame 12 with reinforced concrete to form the pillar 11.

[3. Second collapse model)
[3.1. Collapse bending moment)
FIG. 6 shows actual stress-strain characteristics of steel materials such as the pillar steel frame 12 and the beam 21. The horizontal axis of FIG. 6 represents the strain of the steel material, and the vertical axis represents the stress acting on the steel material. The steel material has an elastic region R1 in which the stress increases proportionally as the strain increases from the state where the strain is zero. The range in which the strain is larger than the elastic region R1 is the inelastic region R2. In the inelastic region R2, the rate of increase in stress is lower than in the elastic region R1. The stress at the boundary between the elastic region R1 and the inelastic region R2 is the yield stress σ ₁ .
In the inelastic region R2, the stress has the maximum value at the maximum stress σ ₂ . When the strain becomes larger than the strain corresponding to the maximum stress σ ₂ , the stress becomes lower than the maximum stress σ ₂ . The steel material fractures at a strain ε ₁ .

In the second collapse model, in obtaining the theoretical solution by the limit analysis, the first model having a rigid-plastic relationship shown by a line L1 in FIG. 7 is assumed as the stress-strain characteristics of the column steel frame 12 and the beam 21. . The horizontal axis of FIG. 7 represents the strain of the steel material, and the vertical axis represents the stress acting on the steel material.
In the first model, the stress increases with the strain remaining zero. The steel material yields when the stress reaches the yield stress σ ₁ . After the steel material yields, the strain increases without changing the stress. The first model does not consider strain hardening.
In contrast, the second model takes into account strain hardening. The stress-strain characteristic of the second model changes as shown by the line L2, and the steel material breaks at the maximum stress σ ₃ at the strain ε ₁ .

Next, the details of the collapse bending moment will be described.
Yield moment M ⁰ (N) of the yield hinge line of the flange 13 of the column steel 12 per unit length, and the yield axial force N ⁰ _c (N of the discontinuous line generated in the web 14 of the column steel 12 per unit length. / Mm) is given by equation (19) and equation (20), respectively.
Here, the plate thickness of the flange 13 of the column steel frame 12 is t _cf (mm), the plate thickness of the web 14 of the column steel frame 12 is t _cw (mm), and the yield strength of the flange 13 of the column steel frame 12 is σ _cfy (N / Mm ² ), and the yield strength of the web 14 of the pillar steel frame 12 is σ _cwy (N / mm ² ).

The internal work W _cf due to the out-of-plane deformation of the flange 13 of the pillar steel frame 12 is given by the equation (21) as the sum of the work due to the plastic rotation of each yield hinge line. Further, the internal work W _cw due to the local yielding of the web 14 of the column steel frame 12 is given by the expression (22) as the sum of the work due to the plastic flow generated on each discontinuous line.
The internal work W _RC1 due to the cone-shaped fracture occurring in the cover concrete 16a around the flange 23 ₁ on the tension side of the beam 21 is given by the equation (23). Internal work _{W RC2} according Bearing destruction within the concrete 16 occurring in the compression side of the flange 23 ₂ around the beam 21 is given by equation (24).
Here, the width of the flange 13 of the pillar steel frame 12 is B _c (mm), the cover thickness of the concrete 16 with respect to the flange 13 of the pillar steel frame 12 is d (mm, see FIG. 2), the strength of the concrete 16 (design standard strength) Is F _c (N / mm ² ), and the bearing effect coefficient of the concrete 16 is λ (1.5 in this embodiment).

From the principle of virtual work, the collapse bending moment M (Nmm) about the joint 31 is given by the equation (25). The total plastic bending moment _j M _p (Nmm), which is the minimum value of the collapse bending moment M, is obtained by solving Eqs. (26) simultaneously, and is given by Eqs. (27) to (30).

This collapse load is equivalent to the full plastic strength of the joint 31, the local yield bend moment _j M _y of the joint 31 (Nmm) is evaluated by the formula (31).

Further, in the collapse mechanism of FIG. 3, the internal work W _RC1 due to the cone-like fracture that occurs in the cover concrete 16a is ignored, and the collapse load N ¹ _c (N / the mm) (32) with equation, the maximum bending moment _j M _u corresponding to the maximum strength that will be described later in the joint 31 (Nmm) is obtained by equation (36) from (33).
Here, the tensile strength of the web 14 of the pillar steel frame 12 is σ _cwu (N / mm ² ).
The internal work W _RC1 is ignored because it is considered that when the maximum bending moment _{j Mu} is generated, the cone-like fracture of the cover concrete 16a has already occurred, and the internal work by the cover concrete 16a does not occur. .

The above-mentioned total plastic bending moment _j M _p is a bending moment that acts on the joint 31 when the strain is 0 and the stress is the yield stress σ ₁ . On the other hand, the maximum bending moment _{j Mu} is a bending moment that acts on the joint 31 when the strain becomes ε ₁ and the stress reaches the maximum stress σ ₃ in consideration of strain hardening.

Further, in Non-Patent Document 1, the condition for not using the diaphragm is given by Expression (37).
Here, the fillet radius of the pillar steel frame 12 is r (see FIG. 2, mm), and the cross-sectional area of the flange 23 of the beam 21 is A _bf (mm ² ). The cross-sectional area A _{bf mentioned} here means the cross-sectional area of one of the pair of flanges 23 of the beam 21.

[3.2. Evaluation of experimental results by collapse bending moment)
The collapse bending moment M obtained in [3.1] is based on the known limit theorem, and gives the upper limit of the collapse load. Therefore, the results of previous experiments (Satoshi Kitaoka and 2 others, "Development of utilization technology for thick web H-section steel, 7. Beam-end bending experiment of non-stiffener type column SRC / beam S joints", Architectural Institute of Japan conference lecture Correspondence between the joint strength and the calculated value of the collapse bending moment M in the structural summary conducted for this study (Abstract Summary (Kyushu), August 2007, p.1143-1144) and this study was investigated.

The yield strength of the joint and the yield strength of the joint are defined as the proof stress at the time when the tangential rigidity decreases to 1/3 of the initial rigidity in the load-displacement relationship of the beam end bending experiment, and the proof strength at the time when the load reaches the maximum value. did. FIG. 8 shows the result of comparison between the calculation result of the total plastic bending moment _j M _p and the experimental result.

The horizontal axis of FIG. 8 represents the calculation result of the total plastic bending moment _j M _p , and the vertical axis represents the yield strength in the experimental result. A line L6 in the figure represents a case where the calculation result of the total plastic bending moment _j M _p and the experimental result match, and the calculation result can accurately predict the experimental result.
The symbol “column SRC beam S” in the legend represents the case where the column in which the experiment was conducted this time has an SRC structure and the beam is formed of only steel frames. The “pillar S, beam S” marked with □ shows the results of previous experiments, and represents the case where the column and beam are made of only steel frames. The “column SRC beam S” marked with “O” shows the result of the previous experiment, and represents the case where the column has the SRC structure and the beam is formed of only the steel frame.

Table 1 shows the specifications of the column steel frame 12 of the column 11 used in this experiment. Three types of tests were performed by changing the specifications of the pillar steel frame 12 to a cross steel frame.
For example, No. In the sample of B1, the pillar steel frame 12 was a cross steel frame formed of the material of SN490B. The strength of the concrete 16 was Fc 27 N / mm ² or more, and the length D of one side was 860 mm. The main bar was a reinforcing bar having a diameter of 16 mm and made of the SD345 material, and 12 bars were arranged in the cross section shown in FIG. The stirrups were made of SD295 material and had a diameter of 10 mm, and were arranged at a pitch of 160 mm.

As shown in FIG. 8, it was found that the calculation result of the total plastic bending moment _j M _p was about 20% higher than the yield strength in the experimental result.

From the result of FIG. 8, the calculation result of the total plastic bending moment _j M _p of the joint portion 31 corresponding to the total plastic proof stress of the joint portion of this example tends to overestimate the experimental result, so The yield strength in the experimental results is estimated by multiplying by the reduction coefficient. For example, the value of the reduction coefficient is determined so that the sum of squares of the difference between the experimental result for each experiment and the calculation result multiplied by the reduction coefficient is minimized.
FIG 9 shows a comparison of the yield strength in the calculated results and experimental results of the full plastic bending moment _{j M} p _(local yield bend moment _{j M y)} of the junction 31 when multiplied by the reduction factor 0.8. It was found that by multiplying the calculation result by the reduction coefficient 0.8, the experimental result can be predicted accurately and on the safe side. Therefore, we have decided to evaluate the local yield bend moment _j M _y of the joint portions 31 at (31) below.

Figure 10 shows the results of comparison between the maximum strength in the calculated results and experimental results of maximum bending moment _j M _u. The horizontal axis of FIG. 10 represents the calculation result of the maximum bending moment _{j Mu} , and the vertical axis of FIG. 10 represents the maximum proof stress in the experimental result. The maximum bending moment _{j Mu} shows a good correspondence with the experimental result without multiplying the calculation result by the reduction coefficient.

[3.3. Concept of energy absorption in columns and beams]
Generally, in the design criteria for columns and beams, when an earthquake etc. occurs, the total plastic bending moment of the columns, beams, and the joints of columns and beams among the joints of columns and beams is calculated as More than the plastic bending moment. Since the portion joined by welding cannot be deformed so much, the joint between the column and the beam cannot absorb much energy. Therefore, the beam that can absorb more energy is first collapsed (yield) to absorb the energy such as earthquake.
The total plastic bending moment _b M _p (Nmm) of the beam 21 is given by the equation (38). Here, the plastic sectional modulus of the beam 21 is _b Z _p , and the yield strength of the beam 21 is σ _by (N / mm ² ).
All plastic bending moment _b M _p or more, that the conditions of the local yield bend moment _j M _y about the junction 31 beam 21 is expressed by the equation (39).

[3.4. Non-diaphragmable range in this embodiment]
With respect to the specifications of the column 11 and the beam 21 shown in Table 2, the non-diaphragmable range (range without using the diaphragm) in the column-beam joint structure was examined. For example, the fault H _c of the pillar steel frame 12 is 600 mm, the width B _c of the flange 13 of the pillar steel frame 12 is 300 mm, and the length D of one side of the concrete 16 is 1100 mm. In this case, the cover thickness d of the concrete 16 shown in FIG. 2 is (1100-600) / 2 = 250 mm.

FIG. 11 shows the results of an examination of the non-diaphragmable range based on the equations (37) and (39) of Non-Patent Document 1 with respect to the specifications shown in Table 2. The area expressing the equation (37) is R6, and the area expressing the equation (39) is R7. In the present invention, since the synthesizing effect of the concrete 16 is taken into consideration in the proof stress of the joint portion, the plate thickness t _cw of the web 14 of the pillar steel frame 12 and the plate thickness t _{cf of the} flange 13 are larger than those in the conventional non-patent document 1. It was found that non-diaphragmization is possible even when the thickness is thin.
That is, the region R8, which is obtained by removing the region R6 from the region R7, is the scope of the present invention in which the non-diaphragm can be newly formed.

  The specifications shown in Table 3 are obtained by increasing the length D of one side of the concrete 16 from 1100 mm to 1300 mm with respect to the specifications shown in Table 2.

FIG. 12 shows the result of examining the non-diaphragmization with respect to the specifications shown in Table 3. In this case, in the collapse mechanism of the beam-column joint structure 1 shown in FIGS. 3 to 5, the contribution of the cover concrete to the proof stress increases. In FIG. 12, the region R6 is the same as that in FIG. 11, but the region R9 representing the equation (39) extends to a range in which the plate thickness t _cw and the plate thickness t _cf are smaller than the region R7. As a result, the region R10, which is a region other than the region R9 and in which the non-diaphragm can be formed, becomes wider than the region R8.

Thus, Beam bonding structure 1 of the present embodiment, the local yield bend moment _j M _y of the joint portions 31 meet the equation (39) satisfies the further (40) below.

Design method Beam junction structure 1 of the present embodiment evaluates seeking at least one of the full plastic bending moment _j M _p and a maximum bending moment _j M _u of the joint 31. The total plastic bending moment _j M _p is a bending moment corresponding to the yield stress σ ₁ , and the maximum bending moment _j M _u is a bending moment corresponding to the maximum stress σ ₃ considering strain hardening. Therefore, the bending moment of the joint portion 31 can be appropriately evaluated, including the proof stress of the concrete 16 against the bearing failure and the proof stress of the cone-like breakage that occurs in the cover concrete 16a.

If the calculated total plastic bending moment _j M _p junction 31 evaluates seeking local yield bend moment _j M _y of the joint 31. Design method Beam junction structure 1 of the present embodiment, the local yield bend moment _j M _y of the joint portions 31 of the beam-column joint structure 1 is set so as to satisfy the equation (39).
As shown in the present embodiment, the present invention can achieve a reasonably wide range of non-diaphragm of a beam-column joint, as compared with the conventional technique that does not consider the synthetic effect of concrete.
The beam-column joint structure 1 has a column SRC beam S structure with a column-through non-diaphragm joint. Such a configuration has the advantages that the number of parts and the number of steel frame processing steps are reduced, and the vertical dimensional tolerance of the beam mounting position is relaxed.

As described above, according to the beam-column joint structure 1, the joint strength evaluation method for the beam-column joint structure 1, and the method for designing the beam-column joint structure 1 according to the present embodiment, the non-diaphragm type column SRC beam S is used. The plate thickness t _cf of the flange 13 of the column steel frame 12 and the plate thickness t _{cw of the} web 14 can be made thinner by properly considering the load bearing effect of the concrete 16 on the local joint strength of the structure.
The joint strength proof evaluation method for a beam-column joint structure of the present embodiment can be suitably used for the beam-column joint structure 1 before manufacturing and for the beam-column joining structure 1 after manufacturing.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 13 and 14, but the same parts as those of the above-mentioned embodiment are designated by the same reference numerals and the description thereof will be omitted, and only different points will be described. explain.
Although the model of the collapse mechanism of the beam-column joint structure 1 described in the first embodiment is elaborate, the calculation required for design is complicated. In view of this, in the present embodiment, by providing certain specifications in the specifications of the beam-column joint structure 1, the local yield bending moment _j of the joint 31 can be relatively easily maintained while the estimation accuracy of the yield strength of the joint is maintained to some extent. it is that to be able to evaluate the M _y.

The certain specifications specified here are as shown in Tables 4 and 5, that is, the following conditions. The fixed specifications are specifications that are relatively often used in practice.
The strength of the pillar steel frame 12 and the strength of the beam 21 are equal.
-The strength of the concrete 16 is Fc27N / mm ² or more.
The cover thickness d of the concrete 16 is 200 mm or more.
The width B _c of the pillar steel frame 12 is not less than 0.35 times and not more than 0.65 times the H _b of the beam 21.
The width B _c of the pillar steel frame 12 is 1.0 times or more and 2.0 times or less the width of the flange 23 of the beam 21.
-The beam _{Hb of the} beam 21 is 0.5 times or more and 1.4 times or less of the beam of the column steel frame 12.

The variables are the values at a constant, the flange of the column steel 12 and beams 21, 325N / mm ² of the web of yield strength, 700 mm blame _{H c} pillar steel 12, the length D of one side of the concrete 16 1100 mm , The concrete strength F _c is 27 N / mm ² .
For example, if the strength F _{c of} concrete is 27 N / mm ² and the column-beam joint structure 1 does not collapse, then the column-beam joint structure 1 does not collapse when the strength F _{c of} concrete is larger than 27 N / mm ^2. Of course.
It is preferable similarly larger for yield strength, likewise longer may be desirable for one side length D of the H _c and concrete 16 due pillar steel 12.
The plate thickness t _cw and the plate thickness t _cf of the column steel frame 12 described as “variable” in Tables 4 and 5 mean that the values can continuously change.

As shown in Table 4 and Table 5, for example, when the beam _{Hb of the} beam 21 is 700 mm, the width B _b of the flange 23 of the beam 21 is 350 mm, 300 mm, 250 mm, 200 mm, and the plate thickness of the web 24 of the beam 21. When t _bw is changed to 16 mm, 12 mm, etc. and the above equation (31) is solved, a large number of groups G1 having thin solid lines shown in FIGS. 13 and 14 are obtained. 13 shows the case where the width B _c of the flange 13 of the pillar steel frame 12 is 450 mm, and FIG. 14 shows the case where the width B _c of the flange 13 of the pillar steel frame 12 is 250 mm.
The horizontal axis in FIGS. 13 and 14 represents the value of the plate thickness t _cw of the web 14 of the column steel frame 12 with respect to the cross-sectional area A _bf of the flange 23 of the beam 21, and the vertical axis represents the cross-sectional area A _bf of the flange 23 of the beam 21. The value of the plate thickness t _cf of the flange 13 of the pillar steel frame 12 is shown.

In the above-mentioned fixed specification, the criterion including the group G1 can be expressed by the equations (41) to (44), that is, a curve L8 shown in FIGS. 13 and 14.
Here, the variables a and b are variables based on the equations (41) and (42).

In the beam-column joint structure 1 of the present embodiment, the width B _c of the flange 13 of the column steel frame 12, the plate thickness t _cw of the web 14 of the column steel frame 12, the plate thickness t _{cf of the} flange 13, and the flange 23 of the beam 21 are broken. The area _Abf satisfies the equations (41) to (44). In the method of designing the beam-column joint structure 1 of the present embodiment, the width B _c , the plate thickness t _cw , the plate thickness t _cf , and the cross-sectional area A _bf are set so as to satisfy the formulas (41) to (44).
Variables other than the width B _c , the plate thickness t _cw , the plate thickness t _cf , and the cross-sectional area A _bf may not be limited.

  For example, in FIG. 14, if the curve representing the formula (31) in the group G1 with respect to a certain specification is the curve L10, the region that satisfies the formula (39) in this case includes the curve L10 and is further indicated by an arrow than the curve L10. The area includes the area on the F1 side. On the other hand, the area satisfying the expressions (41) to (44) includes the curve L8 and further includes the area on the arrow F2 side of the curve L8.

According to the equations (41) to (44), the width B _c of the flange 13 of the column steel frame 12, the plate thickness t _cw of the web 14 of the column steel frame 12, the plate thickness t _{cf of the} flange 13, and the flange 23 of the beam 21. The non-diaphragmization determination can be performed only by the relationship of the cross-sectional area A _bf .
Expressions (41) to (44) narrow the non-diaphragmable range to some extent as compared with Expression (39), but present a non-diaphragmable range that is sufficiently superior to the prior art. Is.

As described above, according to the beam-column joint structure 1 and the method for designing the beam-column joint structure 1 of the present embodiment, the plate thickness of the flange 13 of the column steel frame 12 is properly considered in consideration of the load bearing effect of the concrete 16. It is possible to make t _cf and the plate thickness t _{cw of the} web 14 thinner.
Furthermore, dimensions such as the plate thickness t _cf at which the beam-column joint structure 1 does not collapse can be more easily obtained.

As described above, the first embodiment and the second embodiment 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 deviate from the gist of the present invention. Change, combination, deletion, and the like. Further, it goes without saying that the configurations shown in the respective embodiments can be appropriately combined and used.
For example, in the first and second embodiments, the pillar steel frame is a cross steel frame, but it may be an H-section steel or the like. The beam 21 is not limited to the H-section steel, but may be a cross steel frame or the like.

1 Column-beam joint structure 11 Column 12 Column steel frame 13, 23 Flange 14, 24 Web 21 Beam 31 Joint part

Claims (5)

A steel reinforced concrete column, a steel beam, and a joint portion in which the beam is joined to the column, and a joint strength evaluation method of a non-diaphragm type column-beam joint structure,
The column comprises a column steel frame having a web and a flange,
The beam has a web and a flange, and is joined to the flange of the pillar steel frame at the joint portion,
For the joint,
With respect to the proof stress of the column steel frame, the flange on the compression side of the beam pushes the flange of the column steel frame in the thickness direction of the flange of the column steel frame, the flange of the column steel frame is the thickness. Joint strength evaluation method of a column-beam joint structure characterized by adding a proof stress against bearing pressure failure of the concrete on the inner side in the thickness direction of the flange of the column steel frame when deformed inward in the direction . For the joint,
With respect to the proof stress of the pillar steel frame, the flange on the tensile side of the beam is pulled out in the thickness direction of the flange of the pillar steel frame from the flange of the pillar steel frame, and the flange of the pillar steel frame is the thickness. The column-beam joint according to claim 1, wherein the column-beam joint is evaluated by adding a proof stress against a cone-like fracture occurring in the cover concrete outside the thickness direction of the flange of the column steel frame when deformed outward in the direction. Method for evaluating joint strength of structures. A steel reinforced concrete column, a steel beam, and a joint portion in which the beam is joined to the column, and a joint strength evaluation method of a non-diaphragm type column-beam joint structure,
The column comprises a column steel frame having a web and a flange,
The beam has a web and a flange, and is joined to the flange of the pillar steel frame at the joint portion,
For the joint, at least one of the total plastic bending moment _j M _p according to the formula (1) and the maximum bending moment _j M _u according to the formula (2) is determined, and the joint strength evaluation method for a beam-column joint structure is characterized. .
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, t _bf : Thickness of the flange of the beam, H _b : Due to the beam, F _c : Strength of the concrete of the column, d: _Cover thickness of the concrete with respect to the flange of the column steel frame, λ: bearing pressure effect coefficient of the concrete, σ _cwu : tensile strength of the web of the column steel frame.

A method of designing a non-diaphragm type column-beam joint structure comprising a steel-reinforced concrete column, a steel beam, and a joint part in which the beam is joined to the column,
The column comprises a column steel frame having a web and a flange,
The beam has a web and a flange, and is joined to the flange of the pillar steel frame at the joint portion,
In the joint, the local yield bend moment _j M _y of the joint obtained by the expressions (3) and (4), and sets so as to satisfy the equation (5) and (6) Design method of beam-column joint structure.
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, r: Fillet radius of the column steel, t _bf : Thickness of the flange of the beam, A _bf : _Cross- sectional area of the flange of the beam , H _b : Due to the beam, F _c : Strength of the concrete of the column, d: Cover thickness of the concrete to the flange of the column steel frame, λ: Bearing effect coefficient of the concrete, _b Z _p : The Plastic section modulus of the beam, σ _by : Yield strength of the beam.

A column-beam joint structure of a non-diaphragm type comprising a steel-framed reinforced concrete column, a steel-framed beam, and a joint part in which the beam is joined to the column,
The column comprises a column steel frame having a web and a flange,
The beam has a web and a flange, and is joined to the flange of the pillar steel frame at the joint portion,
In the joint (7) local yield bend moment _j M _y of the joint obtained by the formula and (8), characterized in that it satisfies the equation (11) from (9) Column Junction structure.
Here, B _c : width of the flange of the column steel frame, t _cf : plate thickness of the flange of the column steel frame, σ _cfy : yield strength of the flange of the column steel frame, t _cw : the web of the column steel frame Thickness, σ _cwy : Yield strength of the web of the column steel, r: Fillet radius of the column steel, t _bf : Thickness of the flange of the beam, A _bf : _Cross- sectional area of the flange of the beam , H _b : Due to the beam, F _c : Strength of the concrete of the column, d: Cover thickness of the concrete to the flange of the column steel frame, λ: Bearing effect coefficient of the concrete, _b Z _p : The Plastic section modulus of the beam, σ _by : Yield strength of the beam.

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