JP7228398B2 - Joint structure of CFT column and RC column - Google Patents

Description

TECHNICAL FIELD The present invention relates to a joint structure of a CFT column and an RC column.

For example, in a multi-story logistics facility, a floor having a floor height exceeding 10 m is provided on the lower floor, and a multi-story and complicated material handling frame is provided in the floor to constitute warehouse equipment, which has been proposed and put into practical use.

On the other hand, it is practically difficult to plan high-floor RC pillars with a floor height exceeding 10 m due to technical difficulties such as the concrete casting method and the weight of PC. In addition, it is also difficult to apply due to technical difficulties such as the complicated steel frame connection for the material handling frame, the advance of the material handling period, and the request for a short construction period for high floors due to securing the process.

On the other hand, the above problem is solved by constructing the lower floors with high floor heights with CFT columns and joining the CFT columns (concrete-filled steel pipe columns) of the lower floors and the RC columns (reinforced concrete columns) of the upper floors. can be done.

Moreover, as a structure/construction method for joining an RC column and a CFT column, there is a method in which switching from a CFT column to an RC column is performed layer by layer (see, for example, Patent Document 1).

In this structure/construction method, a boundary layer is formed between the lower part with the CFT column and the upper part with the RC column, and the boundary layer, which is the joint between the CFT column and the RC column, extends across the upper and lower beams. A steel pipe is installed. Then, the steel pipe is filled with concrete, and the column main reinforcement extending from the RC column in the upper layer is inserted. A stud is protruded from the inner peripheral surface of the steel pipe in the portion below the column head of the boundary layer column.

As another structure/construction method for joining a CFT column to an RC column, a base plate is provided at the lower end of the steel pipe of the CFT column, the base plate is placed on the upper end surface of the concrete part of the RC column, and the CFT column is erected, and the RC column is Some fix the base plate to the concrete part via anchor bolts anchored in the concrete part.

Japanese Unexamined Patent Application Publication No. 2009-2006

However, in the above-mentioned conventional structure/construction method in which steel pipes are installed in the boundary layer, the entire boundary layer column, that is, the CFT column is switched to the RC column for each layer, so the amount of steel used is said to be extremely large. There's a problem.

In addition, in the structure/construction method in which the conventional base plate is placed on the upper end surface of the concrete part of the RC column and the CFT column is erected, anchor bolts are placed in place before the concrete part of the RC column is placed. Also, it is necessary to fasten the base plate and the anchor bolt with a nut or the like.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a joint structure between a CFT column and an RC column that can reduce the amount of steel material used and reduce the on-site work.

In order to achieve the above objects, the present invention provides the following means.

The joint structure of a CFT column and an RC column of the present invention is a structure for joining a lower CFT column and an upper RC column, and has a shape in which a steel pipe extends upward from the upper end of the CFT column. is provided, the main reinforcement of the RC column is inserted into the neck wrapping steel pipe portion, and the interior of the neck wrapping steel pipe portion is filled with concrete. and

In the joint structure of the CFT column and the RC column of the present invention, it is possible to reduce the amount of steel materials used and reduce the on-site work compared to the conventional structure, and the workability and economic efficiency of joining the CFT column and the RC column. can be significantly improved.

1 is a diagram showing a multi-story logistics facility having a joint structure of CFT columns and RC columns according to an embodiment of the present invention; FIG. It is a figure which shows the junction structure of the CFT column and RC column which concern on one Embodiment of this invention. It is a figure which shows the junction structure of the CFT column and RC column which concern on one Embodiment of this invention. It is a figure which shows the moment sharing of the joint structure (joint part) of a CFT column and an RC column which concerns on one Embodiment of this invention, and the stress for design. It is a figure which shows the construction method using the joint structure (joint part) of the CFT column and RC column which concerns on one Embodiment of this invention. It is a figure which shows the junction structure of the CFT column and RC column which concerns on the modification of one Embodiment of this invention. Specimen No. used in the structural performance confirmation experiment. 1 (a) is an elevational view, (b) is a sectional view taken along the line AA' of FIG. 7(a), and (c) is a sectional view taken along the line BB' of FIG. 7(a). be. It is a figure which shows the load cycle performed by the structure performance confirmation experiment. Specimen no. 1 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown). Specimen no. 2 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown). Specimen no. 3 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown). Specimen no. 4 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown). Specimen no. 5 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown) of No. 5. FIG. Specimen no. 6 is a diagram showing the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown) of No. 6. FIG. Specimen no. 1, (a) at R=+1.0% and (b) at +5.0% (final break).

A joint structure of a CFT column and an RC column according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG.

First, in this embodiment, as shown in FIG. 1, for example, the joint structure A of CFT columns and RC columns of the present invention will be described as being applied to the framework of a warehouse 1 of a multi-story distribution facility.
In addition, the warehouse 1 is constructed by providing a floor having a floor height of more than 10 m on the lower floor, and equipping the floor with a multi-layered and complicated material handling frame. Furthermore, the high-floor lower part 1a has a CFT structure with CFT columns 2, and the upper part 1b has an RCSS structure with a hybrid frame combining RC columns 3 and steel beams 4.

In addition, the joint structure A of the CFT column and the RC column of the present invention can be applied not only to the multi-story logistics facility (1), but also to the lower layer part (lower layer part 1a) of the CFT structure, for example, to offices, commercial facilities, RCSS structures, etc. The upper part of the RC structure (upper part 1b) may be adopted in a complex facility having a house and a hotel. , there is no particular need to limit its application.

On the other hand, in the joint structure A of the CFT column and the RC column of this embodiment, as shown in FIGS. about 1.5 m), inserting the main reinforcement 7 of the RC column 3 of the upper layer 1b into the neck wrapping steel pipe portion 6, which is the extending portion of the steel pipe 5, and pouring and filling the concrete 8. It is configured to be fixed by

In addition, on the side of the top portion 6a of the neck wrapping steel pipe portion 6, an annular rib plate is provided as a stiffening portion 9 that protrudes inward from the inner surface of the neck wrapping steel pipe portion 6 and extends and connects in the circumferential direction. The portion 6 is stiffened to suppress out-of-plane deformation. Furthermore, as shown in FIG. 3 , a fixing plate 10 is attached to the lower end portion 7d of the main reinforcement 7 of the RC column 3 at the portion to be inserted into the neck wrapping steel pipe portion 6 . As a result, since the main reinforcement 7 and the concrete 8 inside the neck wrapping steel pipe portion 6 are integrated, the main reinforcement 7 is prevented from slipping out of the concrete 8 inside the neck wrapping steel pipe portion 6 due to the gradual increase in deformation, and the neck wrapping steel pipe The shear strength of the concrete 8 inside the portion 6 is reliably ensured.

Furthermore, the joint structure A of the CFT column and the RC column of this embodiment is configured to satisfy the following stress transmission conditions.

First, as shown in FIGS. 3 and 4, the bending moment sharing elements are the RC column portion from the height of the inflection point of the RC column 3 to the switching height of the top portion 6a of the neck wrapping steel pipe portion 6, and the switching height to the upper end of the beam 4 directly below connected to the CFT column 2, and the second lever portion from the stiffening portion 9 by the rib plate to the bottom portion 6b of the neck wrapping steel pipe portion 6.

Then, as shown in FIG. 4 and Table 1, the design stress of each element is set. In addition, the axial force is transmitted only to the reinforced concrete portion, and the steel pipe 6 of the lever portion does not bear the axial force.

Also, the bending stress and the additional shearing force of the lever portion are set as shown in FIG. 4 and formulas (1) to (5).

Here, a is the distance from the switching height to the height of the inflection point, M1 is the bending moment at the height of the bottom 6b of the neck wrapping steel pipe portion 6, Q is the shear force at the height of the inflection point, and h1 is the switching height. distance from the bottom to the stiffening part 9, he is the distance from the bottom of the neck wrapping steel pipe part 6 to the switching height, h2 is the upper end of the beam 4 directly below the bottom part 6b of the neck wrapping steel pipe part 6 connected to the CFT column 2 h0 is the distance from the upper end of the beam 4 directly below connected to the CFT column 2 to the stiffening part 9, R1 is the shear force at the height position of the stiffening part, R2 is directly below connected to the CFT column 2 is the shear force at the height position of the upper end of the beam 4.

In addition, it is desirable that the applicable range of the joint structure A between the CFT column and the RC column of the present embodiment be set as shown in Table 2 in a) to g) below.
a) Applies to buildings with a height of 60m or less.
b) Not applicable to columns that generate pull-out force during an earthquake.
c) Use square section members for RC and CFT columns.
d) RC and CFT columns shall be aligned and no eccentricity allowed.
e) No braces shall be attached directly to the joint post.
f) Table 1 shall be used as a basis for the applicable range of material specifications, shapes, dimensions, plate thicknesses, etc. of materials to be joined and materials to be joined.
g) Yield hinges are not permitted at main joints and joint legs.

Next, an example of a method of joining the CFT column 2 of the lower layer portion 1a and the RC column 3 of the upper layer portion 1b using the joining structure A of the CFT column and the RC column of the present embodiment will be described.

First, as shown in FIG. 5(a), the steel pipe 5 of the CFT column 2, which is integrally provided by welding the rib plate (stiffening portion 9) and the neck wrapping steel pipe portion 6 to the top portion 2a, is erected at a predetermined position. enter.

As shown in FIGS. 5(b) and 5(c), the ends of the steel pipes 5 of the CFT columns 2 are bolted to erect the steel beams 4, and the deck plates 11 are laid while being supported by the steel beams 4. , slab reinforcement 12 are arranged.

Next, as shown in FIGS. 5(d) and 5(e), concrete 8 is cast and filled inside the steel pipe 5 of the CFT column 2 except for the neck wrapping steel pipe portion 6, and slab concrete 13 is cast. do.

As shown in FIG. 5(f), the reinforcing bar unit 16 of the RC column 3 with the donut spacers 14 attached to the upper and lower predetermined positions and the guide angles 15 attached to the four corners is lifted by a lifting machine, and the lower end side of the neck wrapping steel pipe portion 6 is lifted. The reinforcing bar unit 16 is erected by inserting it inside. Further, as shown in FIG. 5(g), the formwork 17 of the RC column 3 is installed above the neck-wrapped steel pipe portion 6 while being supported by shoring.

Next, as shown in FIG. 5(h), the concrete 8 for the RC column 3 is placed and the concrete 8 is placed inside the neck wrapping steel pipe portion 6. Next, as shown in FIG. By removing the formwork 17 when the concrete 8 develops a predetermined strength, the CFT column 2 and the RC column 3 are integrally connected by the joint structure A of the CFT column and the RC column of this embodiment.

Therefore, in the joint structure A of the CFT column and the RC column of this embodiment having the above configuration, the amount of steel used can be reduced and the on-site work can be reduced compared to the conventional one. It becomes possible to greatly improve the workability and economic efficiency of joining the pillars 3 .

In the joint structure A of the CFT column and the RC column of this embodiment, by being configured so as to satisfy the conditions of the above formulas (1) to (5), in addition to workability and economic efficiency, reliability can realize a joint with a high

Furthermore, in this embodiment, it is possible to reduce the building frame cost (the number of steel frames) by the area where the RCSS construction method is used. Furthermore, since only the high-floor floors of the CFT structure can be erected first, the material handling work period for the lower floor area can be secured.

In addition, since the fixing plate 10 is attached to the lower end portion 7d of the main reinforcement 7 of the RC column 3, it prevents the main reinforcement 7 from slipping out of the concrete 8 inside the neck wrap steel pipe portion 6 due to the gradual increase in deformation. The shear strength of the concrete 8 inside the steel pipe portion 6 is reliably ensured.

(Modification)
Next, a modification of the above-described embodiment will be described mainly with reference to FIG.
In the following modified examples, the same reference numerals are given to the same members as those used in the above-described embodiment, and the description thereof will be omitted.
As shown in FIG. 6, in this modified example, reinforcing bars (main bars different from the main bars 7) 18 are provided. The reinforcing bars 18 extend vertically. The reinforcing bar 18 is arranged across the boundary portion P between the neck-wrapped steel pipe portion 6 and the RC column 3 .

A lower portion of the reinforcing bar 18 is arranged inside the neck-wrapped steel pipe portion 6 . A lower end 18 d of the reinforcing bar 18 is arranged above a lower end 7 d of the main bar 7 . A fixing plate 19 is attached to the lower end portion 18 d of the reinforcing bar 18 . The fixing plate 19 integrates the main reinforcement 7 and the concrete 8 . In addition, the fixing position of the reinforcing bar 18 may be up to the height position of the lower end portion 7d of the main bar 7 .

The upper part of the reinforcing bar 18 is arranged inside the RC column 3 . The upper ends 18u of the reinforcing bars 18 are arranged below the upper ends (not shown) of the main bars 7 .

The length from the boundary P to the lower end 18d of the reinforcing bar 18 and the length from the boundary P to the upper end 18u of the reinforcing bar 18 are set according to the strength of the concrete and the strength of the reinforcing bar. It is about 50 times.

In this modification, the rib plate (stiffening portion 9) shown in the above embodiment is not provided.

In the joint structure A1 of the CFT column and the RC column shown above, the amount of steel used can be reduced and the on-site work can be reduced compared to the conventional method. It is possible to greatly improve the efficiency and economic efficiency.

Next, the results of a structural performance confirmation experiment of the joint structure A of the CFT column and the RC column of the embodiment shown above will be described.
In this experiment, the pillars of the lower floors with high floor heights are made of CFT, and the CFT pillars-RC pillars that are switched to RC pillars in the middle of the upper floors are tested to confirm the structural performance, and the validity of the assumed load bearing formula is verified. This is to verify.

Specimens of the specimen are shown in Table 3, and a diagram of the specimen (only specimen No. 1 as a representative example) is shown in FIG.

By controlling the horizontal displacement of the force application point, the force application method is to perform positive and negative alternating cyclic shearing under a constant axial force (axial force ratio η = 0, +0.15, +0.4) according to the force cycle shown in FIG. give force.

9 to 14 show the CFT column base bending moment-member deformation angle relationship (shear force-member deformation angle relationship is also shown) for each specimen. Also, as a representative example, the specimen No. FIG. 15 shows the state of destruction when R=+1.0% and 5.0% (final destruction) in 1.

In FIG. 15, as a representative example, test specimen No. 1 shows the state of destruction of the other test specimen No. 1. 2 to 6, the specimen No. 1, the outermost main reinforcement 7 near the boundary P between the neck-wrapped steel pipe 6 and the RC column 3 yielded, and the concrete above the boundary P (RC column 3) fell off. The joint structure A of the CFT column and the RC column is configured to satisfy the conditions of the above formulas (1) to (5), so that the concrete 8 inside the neck wrapping steel pipe part 6 does not shear fracture. It was confirmed. Even with a configuration in which shear reinforcing bars are not provided inside the CFT column 2 including the neck-wound steel pipe portion 6, as in Test Specimen No. 6, the concrete 8 inside the neck-wound steel pipe portion 6 is susceptible to shear failure. I didn't get it.

As shown in FIG. 13, test specimen No. 5 has no axial force, so the hysteresis loop area is small and the energy absorption capacity is low.

Although one embodiment of the joint structure of the CFT column and the RC column according to the present invention has been described above, the present invention is not limited to the above-described one embodiment, and can be changed as appropriate without departing from the scope of the present invention. be.

1 Multi-layer logistics facility (warehouse)
1a Lower layer 1b Upper layer 2 CFT column 2a Top 3 RC column 4 Steel beam 5 Steel pipe 6 Neck winding steel pipe 6a Top 6b Bottom 7 Main bar 8 Concrete 9 Stiffener 10 Fixing plate 11 Deck plate 12 Slab bar 13 Slab concrete 14 Donut Spacer 15 Guide angle 16 Reinforcement unit 17 Formwork A Joint structure of CFT column and RC column

Claims (3)

A structure for joining a lower CFT column and an upper RC column, comprising:
A neck-wrapped steel pipe portion formed by extending a steel pipe upward is provided at the upper end of the CFT column,
The main reinforcement of the RC column is inserted into the neck wrapping steel pipe portion, and concrete is placed and filled inside the neck wrapping steel pipe portion ,
The neck-wrapped steel pipe portion has a stiffening portion projecting inward from the inner surface,
As a condition for stress transmission,
The bending moment sharing elements are the RC column part from the height of the reflexion point of the RC column to the switching height of the top of the neck winding steel pipe part, and the beam directly below connected to the CFT column from the switching height. Divided into a first lever portion extending to the upper end and a second lever portion extending from the stiffening portion to the bottom portion of the neck wrapping steel pipe portion,
Joint of CFT column and RC column characterized in that the bending stress and additional shear force of the first lever portion and the second lever portion are installed so as to satisfy the following formulas (1) to (5) structure.

Here, a is the distance from the switching height to the height of the inflection point, M1 is the bending moment at the bottom height of the neck wrapping steel pipe, Q is the shear force at the height of the inflection point, and h1 is from the switching height. Distance to the stiffening part, he is the distance from the bottom of the neck-wrapped steel pipe part to the switching height, h2 is the distance from the bottom of the neck-wrapped steel pipe part to the upper end of the beam directly below connected to the CFT column, h0 is the CFT column R1 is the shear force at the height of the stiffener, and R2 is the shear force at the height of the top of the beam directly below connected to the CFT column. . The joint structure of the CFT column and the RC column according to claim 1 , wherein a fixing plate is provided at the lower end of the main reinforcement of the RC column for fixing the main reinforcement to the concrete inside the neck-wrapped steel pipe portion. 3. The joint structure of a CFT column and an RC column according to claim 1 , further comprising reinforcing bars extending in the vertical direction and arranged across the boundary between the neck-wrapped steel pipe portion and the RC column.

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