JP2024045594A - Joint structure between columns and beams - Google Patents

Abstract

[Problem] To provide a joint structure between a column and a beam that can increase the rigidity of a frame. [Solution] A joint structure between a concrete-filled steel pipe column having a cylindrical steel pipe 21 extending vertically, main reinforcement arranged inside the steel pipe and extending vertically, and concrete filled inside the steel pipe, and an H-shaped steel beam, the joint structure includes an upper diaphragm 31 and a lower diaphragm 32 that are provided on the outer surface 21a of the steel pipe and have a circular outer shape in a plan view, and are joined to upper and lower flanges 11 and 12 of the beam 1, and stiffening parts 34, 35 provided on at least one of the upper and lower parts of the upper and lower diaphragms. [Selected Figure] Figure 2

Description

The present invention relates to a joint structure between columns and beams.

A joint structure between a concrete-filled steel pipe (CFT) column, in which reinforcing bars and concrete are filled inside the steel pipe, and a steel-framed (S) beam has been known.

Patent Document 1 discloses that a recess (notch) that is recessed inward from the side surface of a column is provided, and the end of the beam is inserted into the recess to reach the inside of the column, thereby joining the column and the beam. A beam penetration type has been proposed.

Patent document 2 proposes an external diaphragm type in which an external diaphragm is welded to the outer surface of the column, and then the external diaphragm is welded to the flange of the beam to join the column and beam.

By adopting a circular outer diaphragm that has a circular annular shape in plan view, it is possible to create a frame plan with less waste in fitting with external walls, etc. than with a rectangular outer diaphragm that has a rectangular ring shape in plan view, and it is possible to create a structure plan with less waste when fitting with external walls, etc., and to improve the connection details of diagonal beams. It can be simplified.

The upper and lower columns are joined by main reinforcement bars (connecting rebars) placed inside the steel pipes and filled with concrete, and the edges of the upper and lower steel pipes are cut.

JP 2016-142062 A Japanese Patent Application Publication No. 2017-160754

However, circular external diaphragms have problems in that they are more likely to deform inward and outward from the plate surface when resisting tensile forces from beams than rectangular external diaphragms, and columns can slip out of beam-column joints, where the stress state is complex, leading to a decrease in the rigidity of the frame.

The present invention has been made in view of the above-mentioned circumstances, and provides a column-to-beam joint structure that can increase structural rigidity.

In order to achieve the above object, the present invention employs the following means.
In other words, the column-to-beam joint structure according to the present invention includes a steel pipe extending in the vertical direction and formed in a cylindrical shape, a main reinforcement placed inside the steel pipe and extending in the vertical direction, and a main reinforcing bar placed inside the steel pipe and filled in the inside of the steel pipe. A joint structure of a concrete-filled steel pipe-built column and an H-beam beam, which has a concrete part, which is provided on the outer surface of the steel pipe, has a circular shape in plan view, and has a concrete part on the top and bottom of the beam. It is characterized by comprising an upper diaphragm and a lower diaphragm that are joined to a flange, and a stiffening section provided on at least one of the upper and lower parts of the upper diaphragm and the lower diaphragm.

In a column-beam joint structure configured in this way, the stiffening parts provided on at least one of the upper and lower parts of the upper and lower diaphragms reinforce the tensile rigidity in the beam tensile direction, thereby increasing the rigidity of the frame.

In addition, in the column-beam joint structure of the present invention, the stiffening portion may be arranged on a line connecting the center of the steel pipe and the extension direction of the beam.

In the column-to-beam joint structure configured in this way, the stiffening part is generally placed on a line connecting the center of the steel pipe and the direction of extension of the beam, so that when designing the upper and lower diaphragms, Damage to the upper diaphragm and lower diaphragm near the expected yield line (by a guideline, etc.) is suppressed.

According to the joint structure between a column and a beam according to the present invention, the rigidity of the frame can be increased.

1 shows a joint structure between a column and a beam according to a first embodiment of the present invention, and FIG. 3(a) is a horizontal cross-sectional view, and FIG. FIG. 7A shows a joint structure between a column and a beam according to a second embodiment of the present invention, and FIG. 3A is a horizontal sectional view, and FIG. In the column-beam joint structure according to the second embodiment of the present invention, analysis results for confirming the effect of the stiffening portion are shown.

(First embodiment)
A joint structure between a column and a beam according to a first embodiment of the present invention will be explained using the drawings.
FIG. 1 shows a joint structure between a column and a beam according to a first embodiment of the present invention, and (a) is a horizontal cross-sectional view, and (b) is a cross-sectional view taken along the line AA in (a).
As shown in FIG. 1, in the column-to-beam joint structure 100 of this embodiment, a steel-framed beam 1 is joined to a concrete-filled steel pipe-built column 2. In this embodiment, four beams 1 are arranged perpendicularly to the pillar 2 in plan view. Note that the number of beams 1 can be set as appropriate.

Each beam 1 is made of H-shaped steel. The beam 1 has an upper flange 11, a lower flange 12, and a web 13.

The upper flange 11 and the lower flange 12 are arranged apart from each other in the vertical direction. The upper flange 11 and the lower flange 12 are formed into plate shapes. The plate surfaces of the upper flange 11 and the lower flange 12 are arranged along a horizontal plane.

The web 13 connects the upper flange 11 and the lower flange 12. The web 13 is formed in a plate shape. The plate surface of the web 13 is arranged along a vertical plane.

The column 2 includes a steel pipe 21, a plurality of main reinforcements 22, and a concrete portion 23. The steel pipe 21 is formed into a cylindrical shape with the vertical direction as the axial direction. The steel pipe 21 has a steel pipe main body 21b arranged above and below the beam 1, and a cover plate 21c arranged at a height corresponding to the beam 1. Both the steel pipe main body 21b and the cover plate 21c are formed in a cylindrical shape with the vertical direction as the axial direction. The steel pipe main body 21b and the closing plate 21c are metal-touched without welding.

The main reinforcing bars 22 are arranged along the inside of the steel pipe 21. The main reinforcing bars 22 are arranged at intervals in the circumferential direction. The main reinforcing bars 22 extend in the vertical direction. In this embodiment, 24 main reinforcements 22 are arranged, but the number of main reinforcements 22 can be set as appropriate. The concrete portion 23 is filled inside the steel pipe 21. The main reinforcement 22 is fixed to the concrete part 23.

The column-beam joint structure 100 includes an upper diaphragm 31, a lower diaphragm 32, and a number of cotters 33.

The upper diaphragm 31 and the lower diaphragm 32 have a function of transmitting load from the beam 1 to the column 2. The upper diaphragm 31 and the lower diaphragm 32 are provided so as to protrude radially outward from the outer surface 21a of the steel pipe 21. The upper diaphragm 31 and the lower diaphragm 32 are joined to the steel pipe 21 by welding or the like. In this embodiment, the upper diaphragm 31 and the lower diaphragm 32 are joined between the steel pipe main body 21b and the closing plate 21c.

The upper diaphragm 31 is positioned at approximately the same height as the upper flange 11 of the beam 1. The thickness of the upper diaphragm 31 is slightly greater than the thickness of the upper flange 11. The upper diaphragm 31 is joined to the upper flange 11 by welding or the like.

The lower diaphragm 32 is arranged at approximately the same height as the lower flange 12 of the beam 1. The thickness of the lower diaphragm 32 is slightly thicker than the thickness of the lower flange 12. The lower diaphragm 32 is joined to the lower flange 12 by welding or the like.

The upper diaphragm 31 and the lower diaphragm 32 are formed in the shape of an annular plate having a predetermined thickness in the vertical direction. As shown in FIG. 1(a), the outer peripheral surfaces 30a of the upper diaphragm 31 and the lower diaphragm 32 are substantially circular. The portions 30b of the outer peripheral surfaces of the upper diaphragm 31 and the lower diaphragm 32 that are joined to the upper flange 11 and the lower flange 12 are linear in shape corresponding to the end faces of the upper flange 11 and the lower flange 12.

The cotter 33 is provided so as to protrude radially inward from the inner surface 21d of the closing plate 21c of the steel pipe 21. The cotter 33 is made of a metal material such as a piece of steel plate. The cotter 33 is joined to the inner surface 21d of the cover plate 21c by welding or the like.

In this embodiment, the cotters 33 are arranged at four locations on the inner surface 21d of the cover plate 21c at equal intervals in the circumferential direction, and in three vertical rows. The cotters 33 suppress the vertical displacement of the concrete portion 23. The number and arrangement of the cotters 33 can be set as appropriate.

A line connecting the center O of the steel pipe 21 and the extending direction of the beam 1 in plan view is defined as a first imaginary line L1. A second imaginary line L2 is a line that is perpendicular to the center O of the steel pipe 21 and extends to the middle (center) of two adjacent first imaginary lines L1 in plan view. The cotter 33 is placed on the second imaginary line L2.

As shown in FIG. 1(b), the cotter 33 is provided at the upper end 21u (at a height position directly below the upper diaphragm 31), the lower end 21w (at a height position directly above the lower diaphragm 32), and the center in the vertical direction of the blocking plate 21c. The cotter 33 may be disposed below the upper end 21u of the blocking plate 21c with a gap therebetween, or above the lower end 21w of the blocking plate 21c with a gap therebetween.

The cotter 33 has a rectangular shape in a vertical cross section passing through the center O of the steel pipe 21 and the cotter 33. As shown in FIG. 1(a), the cotter 33 has a substantially rectangular shape in a horizontal cross section, with the surface that is joined to the inner surface 21d of the cover plate 21c having a shape (curved surface) corresponding to the inner surface 21d of the cover plate 21c. Because the horizontal cross section of the cotter 33 is substantially rectangular, it is possible to obtain a slip prevention reaction force for the concrete portion 23 more efficiently than, for example, a cotter with a circular cross section. It is preferable that the cotter 33 is slightly tapered to avoid stress concentration.

In the column-beam joint structure 100 configured in this manner, multiple cotters 33 are provided that protrude inward from the inner surface 21d of the steel pipe 21. The cotters 33 are fixed to the concrete portion 23, improving the adhesion between the steel pipe 21 and the concrete portion 23, thereby increasing the rigidity of the frame.

The beam 1 is joined to the first imaginary line L1 of the steel pipe 21, and a cotter 33 is provided on the second imaginary line L2 between the orthogonal first imaginary lines L1. This improves the fixation of the steel pipe 21 to the concrete portion 23 near the second imaginary line L2 (the portion not joined to the beam 1), and reinforces the rigidity in the column axis direction.

(Second embodiment)
Next, a joint structure between a column and a beam according to a second embodiment will be explained using mainly FIGS. 2 and 3. Note that components having the same functions as those of the above-described embodiments are given the same reference numerals, and explanations thereof will be omitted.

FIG. 2 shows a joint structure between a column and a beam according to a second embodiment of the present invention, where (a) is a horizontal cross-sectional view and (b) is a cross-sectional view taken along line BB of (a).
As shown in FIG. 2, the column-beam joint structure 100A of this embodiment includes an upper diaphragm 31, a lower diaphragm 32, and a plurality of upper stiffening portions 34 and lower stiffening portions 35.

The upper stiffening part 34 is provided on the upper surface (upper part) of the upper diaphragm 31 and the lower diaphragm 32. The lower stiffening portion 35 is provided on the lower surface (lower portion) of the upper diaphragm 31 and the lower diaphragm 32. The upper stiffening section 34 and the lower stiffening section 35 are plate-shaped members having a predetermined thickness in the vertical direction. The upper stiffening section 34 and the lower stiffening section 35 are made of a metal material such as a steel plate.

The upper stiffening portion 34 and the lower stiffening portion 35 are provided at four locations spaced apart in the circumferential direction. In this embodiment, they are arranged on the first virtual line L1. The width of the upper stiffening portion 34 and the lower stiffening portion 35 is greater than the width of the upper flange 11 and the lower flange 12 of the beam 1.

Next, an analysis of the above-mentioned column-beam joint structure 100A will be described.
The effects of the upper stiffening portion 34 and the lower stiffening portion 35 were confirmed.
The upper flange 11 and the lower flange 12 have a width of 300 mm and a plate thickness of 28 mm. The upper diaphragm 31 and the lower diaphragm 32 have a plate thickness of 45 mm. Stiffening parts are provided on both the top and bottom of the upper diaphragm 31 and the lower diaphragm 32 or on either the top or bottom. In Example 1, the plate thickness of the stiffening parts is 3 mm (1.06 times), in Example 2, the plate thickness of the stiffening parts is 6 mm (1.13 times), in Example 3, the plate thickness of the stiffening parts is 9 mm (1.2 times), and in Example 4, the plate thickness of the stiffening parts is 45 mm (2 times). The steel pipe (covering plate) to which the diaphragm is attached is not taken into consideration. In addition, the plate thickness of the stiffening parts means the total thickness of the top and bottom when both the top and bottom are provided.

As shown in Figure 3, the thicker the stiffening part is, the higher the initial rigidity is, and the smaller the deformation at the yield strength level (2,750 kN) is.

In the column-beam joint structure 100A configured in this manner, the tensile rigidity in the beam tension direction is reinforced by the upper stiffening portion 34 and the lower stiffening portion 35 provided on the upper and lower parts of the upper diaphragm 31 and the lower diaphragm 32, respectively, thereby increasing the rigidity of the frame.

In addition, by arranging the upper stiffening portion 34 and the lower stiffening portion 35 on the first imaginary line L connecting the center O of the steel pipe 21 and the extension direction of the beam 1, damage to the upper diaphragm 31 and the lower diaphragm 32 near the yield line that is generally assumed (by guidelines, etc.) when designing the upper diaphragm 31 and the lower diaphragm 32 is suppressed.

Note that the assembly procedure shown in the above-described embodiments, the shapes and combinations of each component, etc. are merely examples, and various changes can be made based on design requirements and the like without departing from the gist of the present invention.

In the embodiment shown above, the upper stiffening portion 34 is provided on the upper portion of the upper diaphragm 31 and the lower diaphragm 32, and the lower stiffening portion 35 is provided on the lower portion of the upper diaphragm 31 and the lower diaphragm 32, but the present invention is not limited to this. It is sufficient that the stiffening portion is provided on at least one of the upper portion and the lower portion of the upper diaphragm 31 and the lower diaphragm 32.

1 Beam 2 Column 11 Upper flange 12 Lower flange 21 Steel pipe 21a External surface 21d Inner surface 22 Main reinforcement 23 Concrete section 31 Upper diaphragm 32 Lower diaphragm 33 Cotter 34 Upper stiffening section (stiffening section)
35 Lower stiffening section (stiffening section)
100 Column and beam joint structure L1 First imaginary line L2 Second imaginary line O Center

Claims (2)

A concrete-filled steel pipe-built column having a steel pipe extending in the vertical direction and formed into a cylindrical shape, a main reinforcement arranged inside the steel pipe and extending in the vertical direction, and a concrete part filled inside the steel pipe. A joint structure with an H-shaped steel beam,
an upper diaphragm and a lower diaphragm that are provided on the outer surface of the steel pipe, have a circular outer shape in plan view, and are joined to the upper and lower flanges of the beam;
A column-to-beam joint structure comprising: a stiffening section provided on at least one of the upper and lower portions of the upper diaphragm and the lower diaphragm. The column-to-beam joint structure according to claim 1, wherein the stiffening portion is arranged on a line connecting the center of the steel pipe and the extending direction of the beam.

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