JP7422085B2 - Joint structure between concrete-filled steel pipe column and reinforced concrete slab - Google Patents

Description

The present invention relates to a joint structure between a concrete-filled steel pipe column (hereinafter referred to as "CFT column") and a reinforced concrete slab (hereinafter referred to as "RC slab"). The present invention particularly relates to a joint structure in which a CFT column penetrates an RC slab that is a flat slab.

Flat slab structures have been used in buildings such as office buildings, residences, warehouses with many external walls, and basements, which offer advantages such as saving formwork and reducing floor height. Here, the flat slab structure is generally composed of reinforced concrete columns (RC columns) and RC slabs. However, in this case, it is necessary to install a structure called a capital section that transmits the vertical load applied to the RC slab to the columns, which causes problems such as lowering the ceiling height around the columns and worsening workability. Ta.

Therefore, various bonding structures between CFT columns and RC slabs have been proposed as structures in which the capital portion can be omitted. 9 and 10, Patent Document 1 discloses that four ribs 63 are welded to the steel pipe column 61 through slits provided in the steel pipe column 61, and each rib 63 is A joint structure is described in which a portion is located within the steel pipe column 61, the other portion is located within the RC slab 64, a horizontal supporting steel plate 62 is welded to the steel pipe column 61, and the RC slab 64 is placed on the supporting steel plate 62. has been done.

Referring to FIGS. 11 and 12, Patent Document 2 states that support steel plates 73 are attached to the CFT column 71 so as to surround the CFT column 71 at two locations, the bottom surface position of the RC slab 72 and the top surface position of the RC slab 72 in the CFT column 71. , 74 are bonded together, and is capable of withstanding horizontal loads.

Referring to FIGS. 13(A) and 13(B), Patent Document 3 states that on the outer circumferential surface of the steel pipe column 81 at a position between the upper end reinforcing bars 86 and the lower end reinforcing bars 87, which are slab reinforcements of the RC slab 84. A plurality of perforated dowels 82 whose main surfaces are vertical are fixed, and auxiliary reinforcing bars 83 other than the slab reinforcements 86 and 87 are passed through the holes 82a of the dowels to reduce the vertical load applied to the RC slab. A bonding structure that can withstand this is described.

Japanese Patent Application Publication No. 8-109695 Japanese Patent Application Publication No. 2000-160685 Japanese Patent Application Publication No. 2008-088639

However, all of the techniques disclosed in Patent Documents 1 to 3 have room for further improvement from the viewpoint of withstanding the vertical load applied to the RC slab.

Specifically, in the joining structure of Patent Document 1, the ribs interfere with the slab streaks, so the slab streaks cannot be sufficiently fixed at the joint. Furthermore, since the ribs only protrude slightly into the steel pipe column, the vertical load applied to the RC slab cannot be sufficiently transmitted to the filled concrete.

Since the joint structure of Patent Document 2 focuses on withstanding horizontal loads, the vertical loads applied to the RC slab cannot be sufficiently transmitted to the filled concrete.

In the joint structure of Patent Document 3, the vertical load applied to the RC slab is simply transmitted to the filled concrete inside the column by joining the steel pipe column and the filled concrete, so the vertical load applied to the RC slab is also reduced. It cannot be transferred sufficiently to the filled concrete. In addition, in the joint structure of Patent Document 3, when the vertical load applied to the RC slab is large and the steel pipe plate thickness is thin, local plasticization of the steel pipe column precedes and the steel pipe column breaks early. There are concerns.

In view of the above problems, an object of the present invention is to provide a joint structure between a CFT column and an RC slab that can withstand a larger vertical load applied to the RC slab.

The gist of the present invention is as follows.
(1) A joint structure between a steel pipe column filled with concrete and an RC slab,
A plurality of ribs are connected to the steel pipe column by passing through slits provided in the steel pipe column so that the main surfaces thereof are substantially vertical planes, and each rib has a portion inside the steel pipe column. The other part is located in the RC slab,
A support steel plate is connected to the outer circumferential surface of the steel pipe column and the lower ends of the plurality of ribs so that its main surface is a substantially horizontal plane,
The RC slab is placed on the support steel plate,
A joining structure characterized in that each of the ribs has a first through hole in the portion located within the steel pipe column.

(2) The joining structure according to (1) above, wherein each of the ribs has a plurality of first through holes along a substantially vertical direction.

(3) each of the ribs has a second through hole in the other portion located within the RC slab;
arranging auxiliary reinforcing bars passing through the second through hole in the RC slab;
The joint structure according to (1) or (2) above, wherein at least some of the slab reinforcements are U-shaped reinforcement bars in a vertical view, and the U-shaped portions of the reinforcement bars hook the auxiliary reinforcement bars.

(4) The joining structure according to (3) above, wherein each of the ribs has a plurality of second through holes along a substantially vertical direction.

(5) In the above (3) or (4), the auxiliary reinforcing bar is a ring-shaped reinforcing bar that passes through the second through hole of each of the ribs and extends so as to surround the steel pipe column in a horizontal view. The described joint structure.

(6) The joint structure according to (3) or (4) above, wherein the auxiliary reinforcing bars are at least four linear reinforcing bars arranged so as to surround the steel pipe column in a horizontal view.

(7) The connection between the plurality of ribs and the steel pipe column and/or the connection between the supporting steel plate and the outer peripheral surface of the steel pipe column and the lower end of the plurality of ribs is performed by fillet welding (1). ) to (6).

(8) In any one of (1) to (7) above, wherein the auxiliary steel plate is connected to the outer circumferential surface of the steel pipe column and the upper ends of the plurality of ribs such that the main surface thereof is a substantially horizontal plane. The described joint structure.

The joint structure between a CFT column and an RC slab according to the present invention can withstand a larger vertical load applied to the RC slab.

It is (A) a vertical sectional view and (B) a horizontal sectional view of the joint structure 100 according to the first embodiment of the present invention. 2 is a diagram illustrating the position of a slit 14 provided in a steel pipe column 10 in the joint structure 100 of FIG. 1. FIG. FIG. 3 is a diagram illustrating a fracture mode when a punching shear force is applied to the slab 20. FIG. 3 is a vertical cross-sectional view of a joining structure 200 according to a second embodiment of the present invention. FIG. 3 is a horizontal cross-sectional view of a joining structure 300 according to a third embodiment of the present invention. It is (A) a vertical sectional view and (B) a horizontal sectional view of a joining structure 400 according to a fourth embodiment of the present invention. It is (A) a vertical sectional view and (B) a horizontal sectional view of a joining structure 500 according to a fifth embodiment of the present invention. FIG. 6 is a horizontal cross-sectional view of a joining structure 600 according to a sixth embodiment of the present invention. FIG. 2 is a plan view showing a joining structure described in Patent Document 1. FIG. 9 is a sectional view taken along line AA in FIG. 9; FIG. 2 is a vertical cross-sectional view showing the joining structure described in Patent Document 2. FIG. 2 is a perspective view showing a joining structure described in Patent Document 2. (A) is a plan view showing the joining structure described in Patent Document 3, and (B) is a sectional view taken along line AA in (A).

Embodiments of the present invention will be described below with reference to the drawings. Note that corresponding members in each embodiment will be described using the same reference numerals in each embodiment.

(First embodiment)
A bonding structure 100 between a CFT column and an RC slab according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. In this embodiment, by penetrating the steel pipe column 10 through the RC slab 20, the welding load can be reduced and the cost and time required for construction can be reduced compared to when the steel pipe column is divided. As the RC slab, a prestressed concrete slab (PC slab) can be mentioned.

That is, referring to FIGS. 1 and 2, a plurality of (eight in this embodiment) slits 14 are provided in a steel pipe column 10 whose interior is filled with concrete 12. A rib 30, which will be described later, passes through each slit 14. Although the steel pipe column 10 shown in FIG. 1 is a circular steel pipe, the present invention is not limited thereto, and a square steel pipe may also be used.

Referring to FIG. 1, a plurality of (eight ribs in this embodiment) ribs 30 pass through a slit 14 provided in the steel pipe column 10 so that the main surfaces thereof are substantially vertical planes. A portion of each rib 30 is located within the steel pipe column 10 and the other portion is located within the RC slab 20. In addition, "the main surface of the rib is substantially vertical" refers to the case where the main surface of the rib coincides with the vertical surface, as well as the case where the main surface of the rib is inclined within a range of 5 degrees or less from the vertical surface. Also included. Since each rib 30 extends both inside and outside the steel pipe column 10, the out-of-plane bending that occurs in the skin plate of the steel pipe column 10 is reduced compared to when ribs are installed only on the outside of the steel pipe column 10. It is possible to prevent the skin plate from becoming plastic at an early stage.

Further, the support steel plate 40 is connected to the outer circumferential surface of the steel pipe column 10 and the lower ends of the plurality of ribs 30 so that its main surface becomes a substantially horizontal surface. Then, the RC slab 20 is placed on this supporting steel plate 40. In addition, "the main surface of the supporting steel plate is a substantially horizontal plane" refers to the case where the main surface of the supporting steel plate is inclined within a range of 5 degrees or less from the horizontal plane, in addition to the case where the main surface of the supporting steel plate coincides with a horizontal plane. Also included.

Here, in this embodiment, each rib 30 has a first through hole 32 in a portion located inside the steel pipe column 10 that penetrates the front and back surfaces thereof. As a result, the contact area between the rib 30 and the filling concrete 12 increases, and as a result, in addition to the adhesive force between the rib 30 and the filling concrete 12, the contact area between the first through hole 32 and the lower end of the rib 30 and the filling concrete 12 increases. The bearing force allows the vertical load transmitted from the RC slab 20 to be transmitted to the filled concrete 12 within the steel pipe column 10. Therefore, the joint structure 100 of this embodiment can withstand a larger load in the vertical direction applied to the RC slab 20.

In this embodiment, referring to FIG. 1(B), two ribs are arranged in each of four directions forming an angle of 90 degrees from the steel pipe column 10 when viewed horizontally, for a total of eight ribs. did. This makes it easy to avoid interference with the slab lines 22 in the RC slab 20. The number of ribs is not limited to eight, and for example, a total of four ribs, one in each of the four directions, may be arranged (instead of eight ribs).

The rib 30 is made of a steel plate. The thickness of the rib 30 is not particularly limited, but the lower limit can be, for example, 6 mm, and the upper limit can be 32 mm, considering the skin plate thickness (maximum 28 mm) in the case of a circular steel pipe column. can. When using a square steel pipe, it is not limited to this. Although the shape of the rib 30 is not particularly limited, it is preferable that the main surface has a rectangular shape as shown in FIG. 1(A). The vertical length L _v of the rib 30 is preferably set to 70 to 90% of the slab thickness in order to ensure the concrete covering thickness. Further, the horizontal length of the portion of the rib 30 located outside the steel pipe column 10 is preferably 50 to 200% of the slab thickness. Further, from the viewpoint of reliably transmitting the vertical load to the filling concrete 12, it is preferable that the horizontal length of the portion of the rib 30 located inside the steel pipe column 10 be 15 to 30% of the diameter of the steel pipe column 10. preferable.

The number, shape, and dimensions of the first through holes 32 that each rib 30 has are not particularly limited. However, from the viewpoint of smoothly filling the first through hole with concrete, the shape of the first through hole 32 is preferably circular. Furthermore, from the viewpoint of increasing the contact area between the ribs 30 and the filling concrete 12, it is preferable to provide a plurality of holes of appropriate dimensions rather than one large hole. Therefore, each rib 30 preferably has a plurality of first through holes 32 along the substantially vertical direction, and has three first through holes 32 in this embodiment. As a result, vertical loads can be reliably transmitted by the filled concrete 12. Here, "along the substantially vertical direction" means a state in which adjacent first through holes at least partially overlap in the vertical direction.

In this embodiment, the support steel plate 40 is a ring-shaped steel plate that extends so as to surround the steel pipe column 10, as shown in FIG. 1(B). In this case, it is preferable that the supporting steel plate 40 is divided into two equal parts and joined together by welding or the like. However, the shape of the support steel plate 40 is not particularly limited as long as the support steel plate 40 extends directly below all the ribs and has a size that can support the RC slab 20. The thickness of the supporting steel plate 40 is preferably about 10 to 20% of the slab thickness. Embodiments in which the shape of the support steel plate 40 is different will be described later.

Next, the arrangement of reinforcing bars within the RC slab 20 will be explained. As shown in FIG. 3, in the final state where the slab 20 is destroyed by the push-out shear force, a failure surface A forming part of the side surface of the cone is assumed to extend upward at 45 degrees from the top surface of the supporting steel plate 40. be done. In order to withstand such destruction, reinforcing bars of sufficient length must be continuous on both sides of the fracture surface A as a boundary. However, it is difficult to arrange a sufficient length of reinforcing bars between the fracture surface A and the steel pipe column 10 using the normal reinforcement arrangement method.

Therefore, in this embodiment, reinforcing bars are arranged within the RC slab 20 as shown in FIGS. 1(A) and 3. First, each rib 30 has three second through holes 34 extending vertically through its front and back surfaces in a portion located inside the RC slab 20. Then, three ring-shaped auxiliary reinforcing bars 28 are arranged in the RC slab 20, passing through second through holes located at the same height in each rib 30, and extending so as to surround the steel pipe column 10 in a horizontal view. do. Among the plurality of slab reinforcements 22 arranged in a lattice shape in a horizontal view, some of the slab reinforcements are U-shaped reinforcement bars 24 in a vertical view, and the U-shaped portion of this U-shaped reinforcement 24 is the auxiliary reinforcement 28. It is arranged so that it is hooked (knit together). Thereby, even if the fracture surface A is pulled, the U-shaped reinforcing bars 24 can resist, and the RC slab 20 can withstand a larger push-out shear force. In other words, it is possible to ensure the fixation of the slab lines 22 and to reinforce the RC slab around the joint.

Note that among the slab reinforcements 22, the reinforcing bars 26 that do not hook the auxiliary reinforcing bars 28 may be upper and lower reinforcing bars that are general slab reinforcements, or may be a pair of upper and lower reinforcing bars that overlap in the vertical direction. It may also be a U-shaped reinforcing bar with its tips connected to each other.

In addition, when each rib 30 has a plurality of second through holes 34, these are preferably arranged along the substantially vertical direction. Here, "along the substantially vertical direction" means a state in which adjacent second through holes at least partially overlap in the vertical direction.

Here, as shown in FIG. 1(A), if the lower surface of the supporting steel plate 40 is aligned with the lower surface of the RC slab 20, the formwork work can be facilitated and the finished appearance can be improved. In addition, the entire ceiling surface is flat, minimizing the area of supporting steel plates exposed to fire, which greatly simplifies fireproofing time and costs. Furthermore, since the supporting steel plates are embedded in a reinforced concrete slab, heat transfer to the supporting steel plates in the event of a fire is also minimized. On the other hand, if the upper surface of the supporting steel plate 40 is aligned with the lower surface of the RC slab 20, the effective depth of the RC slab becomes longer by the thickness of the supporting steel plate 40, and the RC slab can withstand a larger punching shear force.

Further, it is preferable that the connection between the plurality of ribs 30 and the steel pipe column 10 and/or the connection between the support steel plate 40 and the outer peripheral surface of the steel pipe column 10 and the lower end of the plurality of ribs 30 is performed by fillet welding. The cost and time required for construction can be reduced compared to when these connections are made by full penetration welding.

(Second embodiment)
With reference to FIG. 4, a bonding structure 200 between a CFT column and an RC slab according to a second embodiment of the present invention will be described. The joining structure 200 according to this embodiment is the same as the joining structure 100 according to the first embodiment except for the shape of the ribs 30 and the number of first through holes 32.

In this embodiment, the maximum vertical length of the portion of the rib 30 located within the steel pipe column 10 is longer than the vertical length of the portion of the rib 30 located within the RC slab 20. Therefore, a larger load in the vertical direction can be transmitted to the filled concrete 12 within the steel pipe column 10. Moreover, in the case of such a rib shape, as shown in FIG. 4, it becomes easy to increase the number of first through holes. In this embodiment, four first through holes 32 are provided along the vertical direction.

(Third embodiment)
Referring to FIG. 5, a bonding structure 300 between a CFT pillar and an RC slab according to a third embodiment of the present invention will be described. The joint structure 300 according to this embodiment is the same as the joint structure 100 according to the first embodiment except for the arrangement of the auxiliary reinforcing bars 28. Note that a vertical cross-sectional view of the joining structure 300 according to this embodiment is the same as FIG. 1(A), and therefore will be omitted.

In this embodiment, as shown in FIG. 5, three linear auxiliary reinforcing bars 28A, three linear auxiliary reinforcing bars 28B, three linear auxiliary reinforcing bars 28C, and three linear auxiliary reinforcing bars Reinforcing bars 28D are arranged to surround the steel pipe column 10 in a horizontal view. The three auxiliary reinforcing bars 28A each pass through the second through holes 34 located at the same height in the two ribs. The three auxiliary reinforcing bars 28B each pass through second through holes 34 located at the same height in two other ribs. The three auxiliary reinforcing bars 28C each pass through second through holes 34 located at the same height in two further ribs. The three auxiliary reinforcing bars 28D each pass through the second through holes 34 located at the same height in the remaining two ribs. The U-shaped reinforcing bars 24 are arranged so that the U-shaped portion thereof hooks (knits together) the auxiliary reinforcing bars 28A, 28B, 28C, and 28D.

(Fourth embodiment)
With reference to FIG. 6, a bonding structure 400 between a CFT column and an RC slab according to a fourth embodiment of the present invention will be described. The joining structure 400 according to this embodiment is the same as the joining structure 100 according to the first embodiment except that it includes the auxiliary steel plate 50.

By placing the RC slab 20 on the supporting steel plate 40, shear force and out-of-plane bending occur in the skin plate of the steel pipe column 10. Since the CFT column may use a steel pipe with a thin plate thickness, there is a concern that stress will be concentrated particularly on the skin plate at the upper part of the rib 30, and this portion will become plastic at an early stage. Therefore, in this embodiment, the ring-shaped auxiliary steel plate 50 is connected to the outer circumferential surface of the steel pipe column 10 and the upper end of the plurality of ribs 30 so that its main surface becomes a substantially horizontal surface. This eliminates the above concerns even when a thin steel pipe is used. Preferably, the connection is made by fillet welding.

(Fifth embodiment)
With reference to FIG. 7, a bonding structure 500 between a CFT column and an RC slab according to a fifth embodiment of the present invention will be described. The joining structure 500 according to this embodiment is the same as the joining structure 100 according to the first embodiment, except that the shape of the supporting steel plate 40 is different.

In this embodiment, a total of four supporting steel plates 40 are provided, each of which is disposed directly under two ribs 30. Making the supporting steel plate approximately rectangular improves the yield during material processing, and arranging the supporting steel plate only below the ribs reduces the amount of steel used.

(Sixth embodiment)
With reference to FIG. 8, a bonding structure 600 between a CFT column and an RC slab according to a sixth embodiment of the present invention will be described. The joint structure 600 according to the present embodiment is the same as that of the first embodiment, except that the arrangement of the auxiliary reinforcing bars 28 is as shown in the third embodiment, and the shape of the supporting steel plate 40 is as shown in the fifth embodiment. It is the same as the joining structure 100 according to.

(Other embodiments)
The first to sixth embodiments described above are merely examples of the joining structure according to the present invention, and the present invention is not limited to these embodiments. For example, a joining structure may be formed by appropriately combining at least one or more of the first to sixth embodiments.

100, 200, 300, 400, 500, 600 Joint structure 10 Steel pipe column 12 Filled concrete 14 Slit 20 Reinforced concrete slab (RC slab)
22 Slab reinforcement 24 U-shaped reinforcement 26 Other slab reinforcement 28 Auxiliary reinforcement 30 Rib 32 First through hole 34 Second through hole 40 Support steel plate 50 Auxiliary steel plate

Claims (9)

A joint structure between a steel pipe column filled with concrete and a reinforced concrete slab,
A plurality of ribs are connected to the steel pipe column by passing through slits provided in the steel pipe column so that the main surfaces thereof are substantially vertical planes, and each rib has a portion inside the steel pipe column. The other part is located in the reinforced concrete slab,
A support steel plate is connected to the outer circumferential surface of the steel pipe column and the lower ends of the plurality of ribs so that its main surface is a substantially horizontal plane,
The reinforced concrete slab is placed on the supporting steel plate,
Each of the ribs has a first through hole in the part located in the steel pipe column, and a second through hole in the other part located in the reinforced concrete slab,
A joint structure characterized in that an auxiliary reinforcing bar passing through the second through hole is arranged in the reinforced concrete slab. The joint structure according to claim 1 , wherein at least some of the slab reinforcements are U-shaped reinforcement bars when viewed vertically, and the U-shaped portions of the reinforcement bars hook the auxiliary reinforcement bars. The joining structure according to claim 1 or 2 , wherein each of the ribs has a plurality of the first through holes along a substantially vertical direction. The joint structure according to any one of claims 1 to 3 , wherein the auxiliary reinforcing bars pass through each of the second through holes in at least two of the ribs. 5. The joining structure according to claim 1 , wherein each of the ribs has a plurality of second through holes along a substantially vertical direction. According to any one of claims 1 to 5 , the auxiliary reinforcing bar is a ring-shaped reinforcing bar that passes through the second through hole of each of the ribs and extends so as to surround the steel pipe column in a horizontal view. The described joint structure. The joint structure according to any one of claims 1 to 5 , wherein the auxiliary reinforcing bars are at least four linear reinforcing bars arranged to surround the steel pipe column in a horizontal view. Claims 1 to 7 , wherein the connection between the plurality of ribs and the steel pipe column and/or the connection between the supporting steel plate and the outer peripheral surface of the steel pipe column and the lower end of the plurality of ribs is performed by fillet welding. The joining structure according to any one of the above. The joint structure according to any one of claims 1 to 8 , wherein the auxiliary steel plate is connected to the outer circumferential surface of the steel pipe column and the upper ends of the plurality of ribs so that its main surface is a substantially horizontal plane.

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