JP6166519B2 - Concrete filled steel pipe column - Google Patents

Description

  The present invention relates to a concrete-filled steel pipe column.

  A concrete filled steel tube (CFT (Concrete Filled Steel Tube)) column in which concrete is filled in a steel tube column is known (see, for example, Patent Document 1). In the technique disclosed in Patent Document 1, concrete is reinforced by a steel flat bar spot welded to the inner wall surface of the steel pipe column, thereby suppressing the cracking of the concrete along with the extension of the steel pipe column during a fire. . Further, in the technique disclosed in Patent Document 1, the flat bar is spot-welded to the inner surface of the steel pipe column so that the flat bar does not follow the expansion and contraction of the steel pipe column at the time of a fire.

JP-A-10-204993

  By the way, in the CFT column, there is a possibility that local buckling may occur at the column head of the steel pipe column as the steel beam extends in the event of a fire. In the part where such local buckling occurs, the concrete restraining force by the steel pipe column cannot be obtained. As a result, if the concrete column head is crushed, the CFT column may not be able to maintain structural stability.

  As a countermeasure, it is conceivable to reinforce the concrete with a flat bar as in the technique disclosed in Patent Document 1.

  However, in the technique disclosed in Patent Document 1, since the flat bar contacts the inner surface of the steel pipe column, fire heat is transmitted to the flat bar via the steel pipe column. Therefore, there is a possibility that the flat bar is thermally deteriorated and the reinforcing effect on the concrete column head is lowered.

  In consideration of the above facts, the present invention is to obtain a concrete-filled steel pipe column capable of suppressing thermal deterioration of the reinforcing member while suppressing the follow-up of the reinforcing member with respect to the vertical expansion and contraction of the steel pipe column in a fire. Objective.

The concrete-filled steel pipe column according to the first aspect is a steel pipe column in which steel beams are respectively joined to the upper and lower joints, and an upper floor side diaphragm and a lower floor side diaphragm respectively provided in the upper and lower joint parts, The filled concrete filled in the steel pipe pillar, and embedded in the filled concrete in a state spaced from the inner wall surface of the steel pipe pillar, and a part thereof is disposed on the pillar head of the filled concrete, The upper floor side diaphragm and a reinforcing member capable of relative displacement in the vertical direction are provided against the upward deformation in the vertical direction.

According to the concrete-filled steel pipe column according to the first aspect , a part of the reinforcing member is disposed on the column head of the filled concrete. By reinforcing the column head of the filled concrete with this reinforcing member, the collapse of the column head of the filled concrete is suppressed. Therefore, even if local buckling occurs at the column head of the steel tube column, the structural stability of the concrete-filled steel tube column is maintained.

  The reinforcing member is embedded in the concrete column head in a state of being spaced from the inner wall surface of the steel pipe column. Thereby, since it is suppressed that a fire heat is directly transmitted to a reinforcement member via a steel pipe pillar, the thermal deterioration of a reinforcement member is suppressed. Therefore, the collapse of the column head of the filled concrete is suppressed.

  Furthermore, the reinforcing member can be displaced relative to the upper floor diaphragm in the vertical direction against the vertical deformation of the steel pipe column in the event of a fire. Thereby, even if the upper floor side diaphragm follows the vertical expansion and contraction of the steel pipe column, the vertical displacement of the reinforcing member with respect to the filled concrete is suppressed. Therefore, damage to the filled concrete due to forced deformation of the reinforcing member is suppressed, so that the fire resistance performance of the concrete-filled steel pipe column is further improved.

A concrete-filled steel pipe column according to a second aspect is the concrete-filled steel pipe column according to the first aspect , wherein the reinforcing member is placed on the lower floor side diaphragm in a state of being spaced from the upper floor side diaphragm. ing.

According to the concrete-filled steel pipe column according to the second aspect , the reinforcing member is placed on the lower floor side diaphragm in a state of being spaced from the upper floor side diaphragm. Thereby, even if the upper floor side diaphragm follows the vertical expansion and contraction of the steel pipe column, the vertical displacement of the reinforcing member with respect to the filled concrete is suppressed. Therefore, the damage which arises in filling concrete by forced deformation of a reinforcement member is suppressed.

  The reinforcing member is placed on the lower floor side diaphragm. That is, the reinforcing member is supported by the lower floor side diaphragm. This eliminates the need for a fixture or the like for positioning (holding the position) the reinforcing member in the vertical direction with respect to the steel pipe column when filling the steel pipe column with filled concrete. Therefore, the workability is improved and the construction cost can be reduced.

A concrete-filled steel pipe column according to a third aspect is the concrete-filled steel pipe column according to the first aspect , wherein the upper floor diaphragm is formed with a through-hole through which the reinforcing member penetrates in the vertical direction, and the reinforcement A support member that supports the member so as to be relatively displaceable in the vertical direction is provided.

According to the concrete-filled steel pipe column according to the third aspect , the reinforcing member is supported by the supporting member provided on the upper floor diaphragm so as to be relatively displaceable in the vertical direction. Thereby, even if the upper floor side diaphragm follows the vertical expansion and contraction of the steel pipe column, the vertical displacement of the reinforcing member with respect to the filled concrete is suppressed. Therefore, the damage which arises in the column head of filling concrete by forced deformation of a reinforcement member is suppressed.

  Moreover, compared with the case where the reinforcement member is mounted on the lower floor side diaphragm, the length of the reinforcement member in the vertical direction is shortened by supporting the reinforcement member on the upper floor side diaphragm near the column head of the filled concrete. be able to. Therefore, the material cost of the reinforcing member can be reduced.

The concrete-filled steel pipe column according to the fourth aspect is the concrete-filled steel pipe column according to any one of the first to third aspects , wherein the reinforcing member is provided between the column head and the column base of the filled concrete. A plurality of reinforcing bars that are embedded and spaced apart from each other, and end strips that are embedded in the column head and the column base of the filling concrete, respectively, and bind the plurality of reinforcing bars ,have.

According to the concrete-filled steel pipe column according to the fourth aspect , the reinforcing member has a plurality of reinforcing reinforcing bars that are embedded between the column head and the column base of the filled concrete and are spaced apart from each other. Yes. Here, in the event of a fire, local buckling tends to occur not only at the column head of the steel pipe column but also at the column base of the steel pipe column. On the other hand, in this embodiment , end strips for restraining a plurality of reinforcing bars are embedded in the column head and column base of the filled concrete. Thereby, the reinforcement effect with respect to the column head and column base part of filling concrete is heightened. Therefore, the crushing of the column head and column base of the filled concrete is suppressed.

  In addition, by placing end band bars on the column heads and column bases of steel pipe columns where local buckling is likely to occur, omitting the band bars in the axial direction of steel pipe columns where local buckling is unlikely to occur. In addition, the fire performance of the concrete-filled steel pipe column can be improved efficiently.

A concrete-filled steel pipe column according to a fifth aspect is the concrete-filled steel pipe column according to the fourth aspect , wherein the reinforcing member is embedded in an intermediate portion in the axial direction of the filled concrete, and a plurality of reinforcing bars are bundled. A plurality of end strips are embedded in each of the column heads and column bases of the filling concrete at a higher density than the plurality of intermediate strips. .

According to the concrete-filled steel pipe column according to the fifth aspect , each of the column head and the column base of the filled concrete has a higher density than the plurality of intermediate strips embedded in the middle portion of the filled concrete in the axial direction. By burying the end band reinforcement, the fire resistance performance of the concrete-filled steel pipe column can be efficiently improved while reinforcing the intermediate part of the filled concrete.

  As described above, according to the concrete-filled steel pipe column according to the present invention, it is possible to suppress thermal deterioration of the reinforcing member while suppressing the follow-up of the reinforcing member to the vertical expansion and contraction of the steel pipe column at the time of a fire.

It is a longitudinal section showing the concrete filling steel pipe pillar concerning a 1st embodiment of the present invention. (A) is the 2A-2A sectional view taken on the line of FIG. 1, (B) is the 2B-2B sectional view taken on the line of FIG. It is a longitudinal cross-sectional view which shows the stress state at the time of the fire of the concrete filling steel pipe column shown by FIG. It is an expanded sectional view of FIG. 3 which shows the generation | occurrence | production part of the local buckling in the column head of a steel pipe column. It is an elevation view which shows the frame comprised with the general concrete filling steel pipe pillar and beam, (A) shows the state before a fire, (B) has shown the state after a fire. It is a model figure which shows the experimental evaluation model used for the fireproof performance evaluation of a general concrete filling steel pipe column, (A) shows the state before loading horizontal force, and (B) is when horizontal force is loaded. The deformation state and stress state of the concrete-filled steel pipe column are shown, and (C) shows a state where local buckling has occurred in the steel pipe column constituting the concrete-filled steel pipe column. It is an expanded sectional view equivalent to FIG. 1 which shows the modification of the reinforcement member in 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows a part of concrete filling steel pipe column which concerns on 2nd Embodiment of this invention. FIG. 9 is a sectional view taken along line 9-9 in FIG. 8. It is an expanded sectional view of FIG. It is a longitudinal cross-sectional view which shows a part of concrete filling steel pipe to which the modification of the reinforcement member in 2nd Embodiment of this invention was applied. It is sectional drawing equivalent to FIG. 2 (A) which shows the modification of the steel pipe pillar in 1st Embodiment of this invention.

  Hereinafter, a concrete-filled steel pipe column according to an embodiment of the present invention will be described with reference to the drawings. In addition, the arrow Z suitably shown in each figure has shown the material-axis direction (column-axis direction, an up-down direction) of a steel pipe column.

  First, the first embodiment will be described.

(Construction of concrete filled steel pipe column)
FIG. 1 shows a concrete-filled steel pipe column 10 according to the first embodiment as an example. The concrete-filled steel pipe column 10 includes a steel pipe column 12 and filled concrete 14 filled in the steel pipe column 12. The steel pipe column 12 is formed of a round steel pipe, and the upper and lower joints 12U and 12L as upper and lower joints, and between these upper and lower joints 12U and 12L. It has the steel pipe main-body part 12B extended.

  Steel beams 16 as horizontal members are joined to both sides of the upper end portion 12U and the lower end portion 12L. Each steel beam 16 is formed of H-shaped steel, and includes a pair of upper and lower upper flange portions 16A and lower flange portion 16B, and a web portion 16C that connects the upper flange portion 16A and the lower flange portion 16B. Yes. The end of each steel beam 16 is abutted against the outer surface of the upper end portion 12U or the lower end portion 12L and joined by welding.

  The upper finisher 12U is provided with a pair of upper and lower upper diaphragms and a pair of upper and lower upper diaphragms 18 and 20 as lower floor diaphragms. The upper floor side inner diaphragm 18 and the lower floor side inner diaphragm 20 are formed in a disk shape from a steel plate, and are in the column axial direction (steel pipe) so as to be continuous with the upper flange portion 16A and the lower flange portion 16B of the steel beam 16, respectively. It is arrange | positioned facing the pillar 12's axial direction). The outer peripheries of the upper floor side inner diaphragm 18 and the lower floor side inner diaphragm 20 are joined to the inner side surface of the finishing port 12U by welding or the like. The upper floor inner diaphragm 18 and the lower floor inner diaphragm 20 are joined together. Thus, the finishing part 12U is reinforced.

  In addition, filling holes 18A and 20A are formed in the center of the upper floor side inner diaphragm 18 and the lower floor side inner diaphragm 20, respectively, and the filled concrete 14 is filled into the steel pipe column 12 through these filling holes 18A and 20A. It has come to be. Similarly to the upper end portion 12U, the lower end portion 12L includes a pair of upper and lower upper diaphragms and a pair of upper and lower upper inner diaphragms 18 and 20 as lower floor diaphragms. Is provided.

(Structure of reinforcing member)
A reinforcing member 30 that reinforces the filled concrete 14 is disposed inside the steel pipe main body 12B. In other words, the reinforcing member 30 is disposed between the lower floor inner diaphragm 20 of the upper finish portion 12U and the upper floor inner diaphragm 18 of the lower finish portion 12L. In the following description, the upper end portion in the axial direction of the steel pipe main body portion 12B will be described as the column head portion 12BU, and the lower end portion in the axial direction of the steel pipe main body portion 12B will be described as the column base portion 12BL. Furthermore, filling concrete 14 filled in the column head portion 12BU, the column base portion 12BL, and the axial intermediate portion 12BM of the steel pipe main body portion 12B is replaced with the column head portion 14U, the column base portion 14L, and the axial direction intermediate portion of the filling concrete 14, respectively. This will be described as the unit 14M.

  The reinforcing member 30 extends in the column axis direction and is placed on the upper floor side inner diaphragm 18 of the lower mouth portion 12L in a state of being spaced from the lower floor inner diaphragm 20 of the upper mouth portion 12U. ing. That is, the reinforcing member 30 is disposed inside the steel pipe body 12B so as to be relatively displaceable in the vertical direction (column axis direction) with the lower floor side inner diaphragm 20 of the finishing port 12U.

  The reinforcing member 30 is embedded across the column head 14U and the column base 14L of the filling concrete 14 in a state of being spaced from the inner wall surface 12S1 of the steel tube main body 12B of the steel tube column 12. Thereby, it is comprised so that a fire heat may not be directly transmitted to the reinforcement member 30 via the steel pipe pillar 12. FIG.

  Further, the upper end portion of the reinforcing member 30 is embedded in the column head portion 14U of the filling concrete 14, and the column head portion 14U of the filling concrete 14 is reinforced by the upper end portion of the reinforcing member 30. On the other hand, the lower end portion of the reinforcing member 30 is embedded in the column head portion 14U of the filling concrete 14, and the column base portion 14L of the filling concrete 14 is reinforced by the lower end portion of the reinforcing member 30.

  More specifically, the reinforcing member 30 has a plurality of reinforcing bars 32, a plurality of upper band bars 34 and a plurality of lower band bars 36 as end band bars. A plurality of (in this embodiment, four) reinforcing reinforcing bars 32 are arranged such that the column axis direction is the longitudinal direction and are spaced apart from each other. Each reinforcing bar 32 is placed on the upper floor side inner diaphragm 18 of the lower edge portion 12L in a state where the upper end portion 32U is spaced from the lower floor side inner diaphragm 20 of the upper edge portion 12U. In addition, the filling concrete 14 is embedded across the column head 14U and the column base 14L.

  The lower end portion 32L of each reinforcing bar 32 may be simply placed on the upper floor side diaphragm 18 of the lower finish portion 12L, or the upper end portion 12L of the lower finish portion 12L may be suppressed in order to suppress displacement. The floor side inner diaphragm 18 may be joined by welding or an adhesive.

  The upper ends 32U of the plurality of reinforcing reinforcing bars 32 are embedded in the column heads 14U of the filled concrete 14. The column heads 14U of the filled concrete 14 are reinforced by these upper end portions 32U. Further, the upper end portions 32U of the plurality of reinforcing reinforcing bars 32 are bound by a plurality (six in this embodiment) of upper band bars 34. The plurality of upper band bars 34 are arranged at intervals in the axial direction of the reinforcing reinforcing bars 32 and are embedded in the column heads 14U of the filling concrete 14. In the present embodiment, the plurality of upper band streaks 34 are arranged at equal intervals or substantially equal intervals.

  As shown in FIG. 2 (A), each upper rebar 34 is formed of an annular rebar (strand) and is arranged so as to surround a plurality of reinforcing rebars 32 embedded in the outer peripheral portion of the filling concrete 14. It is fixed to each reinforcing bar 32 with a binding wire or the like (not shown). Thereby, the reinforcement force with respect to the column head 14U of the filling concrete 14 is heightened.

  As shown in FIG. 1, lower end portions 32 </ b> L of the plurality of reinforcing reinforcing bars 32 are embedded in the column base portions 14 </ b> L of the filled concrete 14. The column base portion 14L of the filled concrete 14 is reinforced by the lower end portions 32L. Further, the lower end portions 32 </ b> L of the plurality of reinforcing reinforcing bars 32 are bound by a plurality of lower band bars 36. A plurality (six in this embodiment) of lower band bars 36 are arranged at intervals in the axial direction of the reinforcing reinforcing bars 32 and are embedded in the column base portions 14L of the filled concrete 14. In the present embodiment, the plurality of lower band muscles 36 are arranged at regular intervals or substantially regular intervals.

  Each lower band rebar 36 is formed of an annular reinforcing bar (strip) similar to the upper band rebar 34, and is disposed so as to surround a plurality of reinforcing bars 32 embedded in the outer peripheral portion of the filling concrete 14. It is fixed to each reinforcing bar 32 with a binding wire (not shown). Thereby, the reinforcement force with respect to the column base part 14L of the filling concrete 14 is heightened.

  On the other hand, as shown in FIG. 1 and FIG. 2 (B), the axial intermediate portions 32M of the plurality of reinforcing reinforcing bars 32 are not bound by the reinforcing bars, and the intermediate portions 14M of the filled concrete 14 have the reinforcing bars. Is not buried. That is, the reinforcing member 30 reinforces the filling concrete 14 so that the bending strength of the column head 14U and the column base 14L is larger than the bending strength of the intermediate portion 14M of the filling concrete 14.

  Further, each reinforcing bar 32, upper band bar 34, and lower band bar 36 are embedded in the filled concrete 14 in a state of being spaced from the inner wall surface 12S1 of the side wall 12S of the steel pipe main body 12B. Thereby, it is comprised so that a fire heat may not be directly transmitted to each reinforcement reinforcing bar 32, the upper band reinforcement 34, and the lower band reinforcement 36 via the steel pipe main-body part 12B.

  Next, the operation of the first embodiment will be described.

  As shown in FIG. 3, for example, when the steel beam 16 expands in the axial direction (horizontal direction) due to thermal expansion during a fire, a horizontal force F acts on the finished joint 12U, and a bending moment M acts on the steel pipe body 12B. Occurs. The bending moment M gradually increases from the intermediate portion 12BM of the steel pipe main body portion 12B toward the column head portion 12BU and the column base portion 12BL.

  On the other hand, the steel pipe column 12 extends in the axial direction (arrow Z direction) due to thermal expansion at the time of a fire, but the extension in the axial direction gradually decreases due to a decrease in rigidity accompanying a temperature rise. Stretch deformation in the direction stops and turns into contraction deformation. In this state, when a horizontal force F is applied from the steel beam 16 to the upper end portion 12U, the column head portion 12BU and the column base of the steel pipe main body portion 12B generate a bending moment M as compared with the intermediate portion 12BM as described above. Local buckling K tends to occur in the side wall portion 12S on the compression side (arrow C side) of the portion 12BL. In particular, when the column head portion 12BU and the column base portion 12BL are rigidly joined to the steel beam 16 via the finishing port 12U and the extension amount of the steel beam 16 in the axial direction is large, the column head portion 12BU and Deformation with a large curvature occurs in the column base 12BL. When a large degree of compressive stress is generated in the side wall portion 12S on the compression side (arrow C side) of the column head portion 12BU and the column base portion 12BL by this deformation, the side wall portion 12S displaces (protrudes) outward in the out-of-plane direction. Bending K occurs.

  When local buckling K occurs in the column head portion 12BU or the column base portion 12BL, the bending rigidity of the concrete-filled steel tube column 10 is significantly reduced. Moreover, in the generation | occurrence | production part of local buckling K, as FIG. 4 shows, the side wall part 12S of the steel pipe main-body part 12B which restrained the filling concrete 14 swells outside, and the side wall of the filling concrete 14 and the steel pipe main-body part 12B A gap W is formed between the portion 12S. As a result, in the part where the local buckling K is generated, the restraining force (restraining effect) of the side wall portion 12S of the steel pipe main body portion 12B with respect to the filling concrete 14 cannot be obtained, and the compression side edge (outer peripheral portion) 14S of the filling concrete 14 becomes It becomes easy to crush.

  When the compression side edge 14S of the filled concrete 14 is crushed, the displacement in the material axial direction of the concrete filled steel pipe column 10 increases rapidly, and the compression side edge 14S of the filled concrete 14 is crushed along with the sudden increase in displacement in the material axial direction. Further progress may occur and the concrete-filled steel pipe column 10 may not be able to maintain structural stability.

  Here, “the concrete-filled steel pipe column 10 cannot maintain the structural stability” means, for example, that the vertical displacement of the concrete-filled steel pipe column 10 is excessive or the vertical displacement is abrupt. It means a state where the long-term axial force cannot be maintained, for example, by increasing. Moreover, although description is abbreviate | omitted, it is the same also when local buckling K generate | occur | produces in the column base part 12BL of the concrete filling steel pipe column 10. FIG.

  On the other hand, in this embodiment, a part of the reinforcing member 30 is embedded in the column head 14U and the column base 14L of the filling concrete 14. By this reinforcing member 30, the bending strength of the column head portion 14U and the column base portion 14L of the filled concrete 14 is enhanced. Thereby, even if local buckling K generate | occur | produces in the column head part 12BU and the column base part 12BL of the steel pipe main-body part 12B, the collapse of the column head part 14U and the column base part 14L of the filling concrete 14 is suppressed. Therefore, after the local buckling K occurs in the column head portion 12BU and the column base portion 12BL of the steel pipe main body portion 12B, the filled concrete 14 can bear the bending moment M and the axial force (long-term axial force) V. The axial force V can be smoothly transmitted to the intermediate portion 14M of the filled concrete 14. That is, even after the occurrence of local buckling K, the concrete-filled steel pipe column 10 can maintain the structural stability. Therefore, the fireproof performance of the concrete-filled steel pipe column 10 is improved.

  In the present embodiment, the upper ends 32U of the plurality of reinforcing reinforcing bars 32 embedded in the column head 14U of the filling concrete 14 are bound by the plurality of upper band bars 34. Similarly, lower end portions 32 </ b> L of a plurality of reinforcing reinforcing bars 32 embedded in the column base portion 14 </ b> L of the filling concrete 14 are bound by a plurality of lower side strips 36. Thereby, the reinforcement effect with respect to the column head 14U and the column base part 14L of the filling concrete 14 is heightened. Therefore, the collapse of the column head 14U and the column base 14L of the filling concrete 14 at the time of a fire is further suppressed.

  Further, in the present embodiment, a plurality of upper band bars 34 and a plurality of lower band bars 36 are embedded only in each of the column head portion 12BU and the column base portion 12BL of the steel pipe main body portion 12B where local buckling K is likely to occur. . Therefore, as compared with the configuration in which the streaks are uniformly embedded in the intermediate portion 14M of the filled concrete 14, it is possible to improve the fire resistance performance of the concrete-filled steel pipe column 10 and improve the cost reduction and the workability.

  Furthermore, the reinforcing member 30 is embedded in the filled concrete 14 in a state of being spaced from the inner wall surface 12S1 of the steel pipe main body 12B. Therefore, fire heat is not directly transmitted to the reinforcing member 30 via the steel pipe main body 12B. Therefore, since the thermal deterioration of the reinforcing member 30 is suppressed, the collapse of the column head 14U and the column base 14L of the filled concrete 14 is further suppressed.

  Moreover, the reinforcing member 30 is arranged with a gap G (see FIG. 1) in the vertical direction from the lower floor side inner diaphragm 20 of the upper finish portion 12U, and the edge of the lower floor side inner diaphragm 20 is cut off. It has been. Thereby, even if the lower floor side inner diaphragm 20 is displaced upward as the steel pipe column 12 extends in the vertical direction, the reinforcing member 30 does not follow the displacement of the lower floor side inner diaphragm 20. Thereby, since the upward displacement of the reinforcing member 30 with respect to the filling concrete 14 is suppressed, damage to the filling concrete 14 due to the forced deformation of the reinforcing member 30 is suppressed. If the lower floor side inner diaphragm 20 and the reinforcing member 30 are joined by welding or the like, the reinforcing member 30 is also displaced upward following the upward displacement of the lower floor side inner diaphragm 20. For this reason, since the column head 14U of the filled concrete 14 is significantly damaged by the forced deformation stress of the upper band 34 and the reinforcing reinforcing bar 32, the concrete-filled steel pipe column 10 cannot maintain the structural stability.

  Moreover, not only the edge of the lower floor side inner diaphragm 20 and the reinforcing member 30 is cut off, but a gap G is formed between the lower floor inner diaphragm 20 and the upper end portion of the reinforcing member 30. ing. Thereby, even if the lower floor side inner diaphragm 20 is displaced downward as the steel pipe column 12 contracts downward, the upper end portion of the reinforcing member 30 is not directly pressed downward by the lower floor side inner diaphragm 20. Thereby, since the downward displacement of the reinforcing member 30 with respect to the filling concrete 14 is suppressed, damage to the filling concrete 14 due to the forced deformation of the reinforcing member 30 is suppressed. Furthermore, buckling of the plurality of reinforcing reinforcing bars 32 is also suppressed.

  Further, the reinforcing member 30 is placed on the lower floor side inner diaphragm 20. That is, the reinforcing member 30 is supported by the lower floor side inner diaphragm 20. Thereby, when filling the steel pipe column 12 with the filled concrete, a fixture or the like for positioning (holding the position) the reinforcing member 30 in the vertical direction with respect to the steel pipe column 12 becomes unnecessary. Therefore, the workability is improved and the construction cost can be reduced.

  Here, FIG. 5A shows an example of a frame composed of a column 100 made of a general concrete-filled steel pipe column and beams 102A and 102B. In this frame, for example, when a fire 104 occurs as shown in FIG. 5B, the beam 102A extends in the horizontal direction (arrow J direction), so that the pillar 100 is deformed as shown in FIG. .

  FIG. 6 (A) shows an experimental evaluation model used for fire resistance performance evaluation of a column 110 made of a general concrete-filled steel pipe column. Since this experimental evaluation model shows the deformation state and the stress state as shown in FIG. 6B during heating, the deformation state and the stress state of the column 100 shown in FIG. 5B are appropriately simulated. It is said that you can. Then, when the loading heating experiment was conducted using the experimental evaluation model shown in FIG. 6 (A), the following new knowledge was obtained.

  That is, when the horizontal displacement (horizontal force F) generated at the upper end portion of the heated column 110 is large or when the axial force V generated at the column 110 is large, the column 110 is configured as shown in FIG. It was confirmed that local buckling K occurred in the column head and column base of the steel pipe column. Further, even when the heating time is relatively short and the concrete filled in the column 110 remains sufficiently proof, the column 110 loses its load supporting ability due to the above-mentioned local buckling K of the column head and column base. It was confirmed that the structural stability could not be maintained.

  When concrete concrete steel pipe pillar 10 concerning this embodiment is explained concretely by an example, the following was confirmed about local buckling K. That is, when the column width (diameter) of the steel pipe column 12 is D (see FIG. 2 (A)), the local buckling K in the column head 12BU is the upper end of the column head 12BU (the upper end 12U and the steel pipe body). It is likely to occur in the region from 2D to the intermediate portion 12BM from the boundary portion with the portion 12B), and particularly easily in the region from 1D to 2D. Similarly, the local buckling K in the column base 12BL is within the region from the lower end of the column base 12BL (the boundary between the lower end 12L and the steel pipe body 12B) to 2D from the intermediate portion 12BM. It is easy to generate | occur | produce especially in the area | region from 1D to 2D.

  Accordingly, the reinforcing member 30 is preferably embedded in the filled concrete 14 so that the upper end portion thereof is located in the 2D region from the upper end of the column head portion 14U of the filled concrete 14 toward the intermediate portion 14M. It is more preferable to embed in the filled concrete 14 so as to be located in a region up to 2D. At this time, the plurality of upper strips 34 are preferably embedded in a 2D region from the upper end of the column head 14U of the filling concrete 14 toward the intermediate portion 14M, and preferably embedded in a region from 1D to 2D. More preferred. Thereby, generation | occurrence | production of the local buckling K of the column head part 14U of the filling concrete 14 can be suppressed efficiently, reducing the material cost of the upper side band 34. FIG. The same applies to the lower band muscle 36.

  Further, in the present embodiment, an example is shown in which the upper band reinforcement 34 is embedded in the column head 14U of the filling concrete 14 and the lower band reinforcement 36 is embedded in the column base portion 14L of the filling concrete 14, but the present invention is not limited thereto. . For example, a plurality of strips may be disposed over substantially the entire length of the steel pipe body 12B, and the reinforcing reinforcing bars 32 may be bound by these strips.

  Further, for example, as shown in FIG. 7, the column head portion 14 </ b> U of the filling concrete 14 has a higher density than the plurality of middle strips 38 embedded in the middle portion 14 </ b> M of the filled concrete 14. 34 may be embedded. Specifically, the interval (pitch) P1 between the adjacent upper strips 34 is made narrower than the interval (pitch) P2 between the adjacent intermediate strips 38. Thereby, crushing of the column head 14U of the filling concrete 14 can be efficiently suppressed while increasing the bending strength of the intermediate portion 14M of the filling concrete 14. In addition, it is possible to improve the workability and reduce the cost as compared with a configuration in which a plurality of streaks are embedded at equal intervals (equal pitch) from the column head 14U to the column base 14L of the filled concrete 14. .

  Note that a plurality of lower strips 36 may be embedded in the column base portion 14 </ b> L of the filled concrete 14 at a higher density than the plurality of intermediate strips 38, similarly to the upper strips 34.

  Further, either one of the upper band reinforcement 34 and the lower band reinforcement 36 may be omitted, or both the upper band reinforcement 34 and the lower band reinforcement 36 may be omitted, and the column head 14U of the filling concrete 14 only by the reinforcing reinforcing bars 32. Etc. may be reinforced.

  Next, a second embodiment will be described. In addition, the thing of the structure similar to 1st Embodiment attaches | subjects a same sign, and abbreviate | omits suitably and demonstrates.

  As shown in FIGS. 8 and 9, the concrete-filled steel pipe column 40 according to the second embodiment extends in the vertical direction (column axis direction) and is spaced from the inner wall surface 12S1 of the steel pipe main body 12B. A reinforcing member 50 embedded in the filled concrete 14 is provided. The reinforcing member 50 is disposed across the upper end portion 12U and the column head portion 12BU of the steel pipe main body portion 12B, and is supported on the lower floor side inner diaphragm 20 of the upper end portion 12U so as to be relatively displaceable in the vertical direction. ing.

  Specifically, the reinforcing member 50 has a plurality of reinforcing reinforcing bars 52 and a plurality of end band reinforcing bars 54. A plurality (four in this embodiment) of the reinforcing reinforcing bars 52 are disposed so as to be spaced apart from each other while the column axis direction is the longitudinal direction. As shown in FIG. 10, each reinforcing reinforcing bar 52 has an upper end 52 </ b> A penetrating in a column axial direction through a through hole 42 formed in the lower floor side inner diaphragm 20 of the upper finishing portion 12 </ b> U. It is arranged over the mouth portion 12U and the column head portion 12BU of the steel pipe main body portion 12B.

  A portion of the reinforcing reinforcing bar 52 extending downward from the lower floor side inner diaphragm 20 is a reinforcing portion 52 </ b> B that reinforces the column head 14 </ b> U of the filled concrete 14. Each reinforcing portion 52B is embedded in the column head portion 14U of the filling concrete 14 in a state of being spaced from the inner wall surface 12S1 of the steel pipe main body portion 12B.

  The plurality of reinforcing portions 52 </ b> B are bundled by a plurality of end band strips 54. A plurality of (in the present embodiment, five) end band bars 54 are arranged at intervals in the axial direction of the reinforcing reinforcing bars 52 and are embedded in the column heads 14U of the filled concrete 14. As shown in FIG. 9, each end band 54 is formed of an annular reinforcing bar (strip), and is disposed so as to surround a plurality of reinforcing bars 52 embedded in the outer peripheral portion of the filling concrete 14. These are fixed to the reinforcing reinforcing bars 52 with binding wires (not shown). These end band bars 54 enhance the reinforcing force of the filling concrete 14 against the column head 14U.

  As shown in FIG. 10, a reinforcing bar fixing material 44 is installed in each through hole 42 formed in the lower floor side inner diaphragm 20 of the finishing joint 12U in a state where the reinforcing reinforcing bars 52 are penetrated. .

  The reinforcing bar fixing member 44 as a support member supports the reinforcing reinforcing bar 52 before the filling concrete 14 is filled in the steel pipe column 12 and until the filling concrete 14 filled in the steel pipe column 12 is hardened. 50, and when the lower floor side diaphragm 20 is displaced in the vertical direction along with the vertical expansion and contraction of the steel pipe column 12 in the event of a fire, it is easily destroyed and the lower floor The strength and the like are set so that the edges of the side diaphragm 20 and the reinforcing reinforcing bars 52 are cut off. The reinforcing reinforcing bars 52 are supported by the lower floor side inner diaphragm 20 through the reinforcing bar fixing members 44 so as to be relatively displaceable in the vertical direction. As the reinforcing bar fixing material 44, for example, metal materials, cement materials such as mortar and grout, plastic materials, and the like can be used.

  Next, the operation of the second embodiment will be described.

  A part of the reinforcing member 50 is embedded in the column head 14U of the filling concrete 14. By this reinforcing member 50, the bending strength of the column head 14U of the filled concrete 14 is enhanced. Thereby, even if local buckling K (refer FIG. 3) generate | occur | produces in the column head 12BU of the steel pipe main-body part 12B, the collapse of the column head 14U of the filling concrete 14 is suppressed. Therefore, as in the first embodiment, the filled concrete 14 can bear the bending moment M and the axial force V after the local buckling K occurs in the column head 12BU of the steel pipe main body 12B, and the shaft The force V can be smoothly transmitted to the intermediate portion 14M of the filled concrete 14. That is, even after the occurrence of local buckling K, the concrete-filled steel pipe column 40 can maintain the structural stability. Therefore, the fire resistance performance of the concrete-filled steel pipe column 40 is improved.

  Further, the reinforcing portions 52 </ b> B of the plurality of reinforcing reinforcing bars 52 constituting the reinforcing member 50 are bundled by a plurality of end band bars 54 embedded in the column head 14 </ b> U of the filled concrete 14. Thereby, the reinforcement effect with respect to the column head 14U of the filling concrete 14 is heightened. Further, the reinforcing member 50 is embedded in the filling concrete 14 in a state of being spaced from the inner wall surface 12S1 of the steel pipe column 12, so that fire heat is not directly transmitted to the reinforcing member 50 through the steel pipe column 12. It is configured. Therefore, as in the first embodiment, the collapse of the column head 14U of the filled concrete 14 at the time of a fire is further suppressed.

  Further, the plurality of reinforcing reinforcing bars 52 are supported by the lower inner diaphragm 20 of the upper finishing portion 12U via the reinforcing bar fixing member 44 so as to be relatively displaceable in the vertical direction. As a result, when the lower floor side inner diaphragm 20 is displaced in the vertical direction as the steel pipe column 12 expands and contracts in the vertical direction, the reinforcing bar fixing member 44 is broken, and the edge between the lower floor side inner diaphragm 20 and the reinforcing reinforcing bar 52 is cut. It is done. As a result, the lower floor side inner diaphragm 20 is relatively displaced in the vertical direction with respect to the reinforcing reinforcing bars 52. Therefore, even if the lower floor side inner diaphragm 20 is displaced in the vertical direction as the steel pipe column 12 expands and contracts in the vertical direction, the reinforcing reinforcing bars 52 do not follow the displacement of the lower floor side inner diaphragm 20. Therefore, since the vertical displacement of the reinforcing member 50 with respect to the filled concrete 14 is suppressed, damage caused to the filled concrete 14 is suppressed.

  Moreover, the vertical length of the reinforcing member 50 can be shortened by supporting the reinforcing member 50 on the lower floor side inner diaphragm 20 of the upper finishing portion 12U close to the column head 14U of the filled concrete 14. Therefore, the material cost of the reinforcing member 50 can be reduced.

  In this embodiment, as an example of the reinforcing bar fixing material 44, a material that is easily destroyed when the lower floor side diaphragm 20 such as a metal material, a cement material, or a plastic material is displaced in the vertical direction is used. However, it is not limited to this. For example, a rubber elastic body such as rubber or silicon may be used as the reinforcing bar fixing member 44.

  In this case, even if the lower floor side inner diaphragm 20 is displaced in the vertical direction as the steel pipe column 12 expands and contracts in the vertical direction, the reinforcing bar fixing material 44 of the rubber elastic body is elastically deformed in the vertical direction, so The following of the reinforcing reinforcing bars 52 with respect to the displacement of the inner diaphragm 20 is suppressed. Therefore, since the vertical displacement of the reinforcing member 50 with respect to the filled concrete 14 is suppressed, damage caused to the filled concrete 14 is suppressed.

  Moreover, in this embodiment, although one part of the reinforcement member 50 was embed | buried only in the column head 14U of the filling concrete 14, it is not restricted to this. For example, the reinforcing member 50 may be extended downward and may be embedded over the column head 14U and the intermediate portion 14M of the filling concrete 14, or may be embedded over the column head 14U and the column base 14L of the filling concrete 14. May be.

  Further, for example, the reinforcing member 50 is extended upward from the upper floor side inner diaphragm 18 of the lower end portion 12L, and is supported on the upper floor side inner diaphragm 18 so as to be relatively displaceable in the vertical direction. A part (the reinforcing portion 52B of the reinforcing reinforcing bar 52) may be embedded in the column base portion 14L of the filling concrete 14.

  Further, for example, as in the reinforcing member 60 shown in FIG. 11, the reinforcing reinforcing bars 62 are vertically penetrated through the lower floor side inner diaphragm 20 and the upper floor side inner diaphragm 18 of the finishing joint 12U, so that the filling concrete 14 A reinforcing reinforcing bar 62 may be embedded between the column head 14U and the column base 14L of the filling concrete 14 on the upper floor. In this case, the reinforcing reinforcing bars 62 may be supported by at least one of the lower floor side inner diaphragm 20 and the upper floor side inner diaphragm 18 so as to be relatively displaceable in the vertical direction. Moreover, what is necessary is just to embed the edge part reinforcement | strut | stripe 64 which binds the some reinforcing bar 62 suitably in each of the column head part 14U of the filling concrete 14, and the column base part 14L of the filling concrete 14 in an upper floor.

In the present embodiment, the thickness of the reinforcing bar fixing material 44 is approximately the same as that of the lower floor side inner diaphragm 20 of the finishing part 12U, but it is not necessarily required to be approximately the same. The support strength of the reinforcing reinforcing bars 52 may be increased by increasing the thickness of the reinforcing bar fixing member 44 as compared with the lower floor side inner diaphragm 20 of the upper finishing portion 12U.

  Next, modified examples of the first and second embodiments will be described. In the following, various modified examples will be described by taking the first embodiment as an example, but these modified examples are also applicable to the second embodiment.

  In the first embodiment, the example in which the reinforcing member 30 is embedded from the column head portion 14U to the column base portion 14L of the filled concrete 14 is shown, but the present invention is not limited thereto. In the event of a fire, generally, the temperature of the column head 12BU is likely to rise early compared to the column base 12BL of the steel pipe main body 12B. Therefore, in the column head portion 12BU of the steel pipe main body portion 12B, local buckling K is likely to occur at an early stage as compared with the column base portion 12BL. Therefore, the reinforcement member should just be embed | buried under the column head 14U of the filling concrete 14 at least.

  Moreover, in the said 1st Embodiment, although the reinforcement member 30 comprised the some reinforcing bar 32, the some upper strip 34, and the some lower strip 36, it was not restricted to this. The number and arrangement of the reinforcing bars 32, the upper band bars 34, and the lower band bars 36 can be changed as appropriate. For example, the upper band bars 34 and the lower band bars 36 are omitted, and the reinforcing member 30 is composed of one or more reinforcing bars 32. May be configured. Further, for example, the reinforcing member may be made of a shape steel such as an H-shaped steel or an L-shaped steel, or a steel plate.

  In the first embodiment, the upper floor side diaphragm 18 and the lower floor side diaphragm 20 are described as examples of the upper floor side diaphragm and the lower floor side diaphragm, but the present invention is not limited thereto. As the upper floor side diaphragm and the lower floor side diaphragm, a through diaphragm or an outer diaphragm may be used.

  Moreover, although the said 1st Embodiment showed the example which formed the steel pipe pillar 12 with the circular steel pipe of circular cross section, it does not restrict to this. For example, as shown in FIG. 12, the steel pipe column 22 may be a square steel pipe having a substantially square cross section. In this case, the length of one side of the square steel pipe corresponds to the column width D of the steel pipe column 22. Further, as the steel pipe column, for example, a square steel pipe having a substantially rectangular cross section may be used. In this case, the length of the short side corresponds to the column width D of the steel pipe column.

  The steel pipe column 12 may be provided with a fireproof coating. Further, in the first embodiment, the steel beam 16 is described as an example of the horizontal member, but a slab (for example, an RC floor slab or a flat slab) may be used instead of the steel beam 16.

  The first and second embodiments of the present invention have been described above. However, the present invention is not limited to such embodiments, and the first and second embodiments and various modifications may be used in appropriate combination. It goes without saying that the present invention can be carried out in various modes without departing from the gist of the present invention.

10 Concrete Filled Steel Tubular Column 12 Steel Tubular Column 12S1 Inner Wall 12U Upper Portion (Upper Portion)
12L lower part (lower part)
14 Filled concrete 14U Column head 14M Intermediate part 14L Column base 16 Steel beam (horizontal member)
18 Upper floor side diaphragm (upper floor side diaphragm)
20 Lower floor side diaphragm (lower floor side diaphragm)
22 Steel pipe column 30 Reinforcement member 32 Reinforcement reinforcing bar 34 Upper band reinforcement (end band reinforcement)
36 Lower band muscle (end band)
38 Middle part reinforcement 40 Concrete filled steel pipe column 42 Through hole 44 Rebar fixing material (support member)
50 Reinforcing member 52 Reinforcing bar 54 End band 60 Reinforcing member 62 Reinforcing bar 64 End band

Claims (3)

Steel pipe columns to which horizontal members are respectively joined to the upper and lower joints;
An upper floor diaphragm and a lower floor diaphragm respectively provided in the upper and lower joints;
Filled concrete filled in the steel pipe columns;
The steel pipe column is embedded in the filled concrete in a state of being spaced from the inner wall surface of the steel pipe column, and a part thereof is disposed at the column head of the filled concrete, and is A reinforcing member capable of relative displacement in the vertical direction with the lower floor side diaphragm of the joint portion,
With
The reinforcing member is placed on the upper floor diaphragm of the lower joint portion in a state of being spaced from the lower floor diaphragm of the upper joint portion,
Concrete filled steel pipe column. The reinforcing member is
A plurality of reinforcing reinforcing bars that are embedded across the column head and column base of the filling concrete and are spaced apart from each other;
Embedded in the column head and the column base of the filled concrete, respectively, and end strips that bind the plurality of reinforcing bars;
Having
The concrete-filled steel pipe column according to claim 1. The reinforcing member is embedded in an intermediate portion in the axial direction of the filled concrete, and has a plurality of intermediate band bars that bind the plurality of reinforcing reinforcing bars,
In each of the column head and the column base of the filled concrete, a plurality of the end strips are embedded at a higher density than the plurality of intermediate strips,
The concrete-filled steel pipe column according to claim 2.