JP5758207B2 - Concrete filled steel pipe column - Google Patents

Concrete filled steel pipe column Download PDF

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JP5758207B2
JP5758207B2 JP2011128513A JP2011128513A JP5758207B2 JP 5758207 B2 JP5758207 B2 JP 5758207B2 JP 2011128513 A JP2011128513 A JP 2011128513A JP 2011128513 A JP2011128513 A JP 2011128513A JP 5758207 B2 JP5758207 B2 JP 5758207B2
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steel pipe
concrete
filled
column
reinforcing
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JP2012255283A (en
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俊彦 西村
俊彦 西村
智仁 岡▲崎▼
智仁 岡▲崎▼
長岡 勉
勉 長岡
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株式会社竹中工務店
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Description

  The present invention relates to a concrete-filled steel pipe column.
  A concrete filled steel tube (CFT) column in which concrete is filled in a steel pipe is known. In general, the CFT column has a large axial force (burden axial force) that can be borne compared to a hollow steel tube column, and since the heat capacity increases as the concrete is filled, the CFT column is excellent in fire resistance. Therefore, depending on the design conditions (for example, when the load axial force of the column is relatively small and the fire duration time is short), it is possible to omit the fireproof coating of the CFT column.
  Here, in the technique disclosed in Patent Document 1, a rib (flat bar) extending in the axial direction of the steel pipe is attached to the inner peripheral surface of the steel pipe by spot welding. In the event of a fire, the ribs are resisted against the axial tensile force generated in the concrete due to the difference in thermal expansion between the steel pipe and the concrete, thereby suppressing cracks in the concrete.
JP-A-10-204993
  However, in the technique disclosed in Patent Document 1, although the fire resistance (fire resistance time) is improved, when local buckling occurs in the steel pipe, the proof stress of the CFT column is drastically reduced and the deformation becomes excessive.
  In view of the above facts, an object of the present invention is to obtain a concrete-filled steel pipe column in which a sudden decrease in yield strength during a fire is suppressed.
The concrete-filled steel pipe column according to claim 1 is a column steel pipe having upper and lower steel pipe joints to which a horizontal member is joined, and a steel pipe main body part extending between the steel pipe joints, and in the column steel pipe Filled concrete, and the bending strength of the filled concrete in the axial end portion of the steel pipe main body portion are embedded in the filled concrete, and the bending strength of the filled concrete in the axial middle portion of the steel pipe main body portion is And reinforcing means for reinforcing the filled concrete so as to be large and suppressing collapse of the filled concrete in the axial end portion due to local buckling of the axial end portion during a fire .
According to the concrete-filled steel pipe column according to claim 1, the filling in the axial end portion in the steel pipe main body portion with respect to the bending strength of the filled concrete in the axial middle portion in the steel pipe main body portion by the reinforcing means embedded in the filled concrete. Filled concrete is reinforced to increase the bending strength of the concrete. As a result, even if local buckling occurs at the axial end of the steel pipe body during a fire , the filled concrete in the axial end bears a bending moment and resists the compressive force generated by local buckling. Thus, the crushing of the filled concrete can be prevented. As a result, the axial end of the steel pipe main body can bear an axial force even after local buckling, and the axial force can be smoothly transmitted to the axial center of the steel pipe. . Therefore, a sudden decrease in proof stress (collapse) after local buckling of the concrete-filled steel pipe column during a fire is suppressed.
Furthermore, compared with the structure which reinforces filling concrete with the same bending strength over the full length of a steel pipe main-body part, improvement of workability and cost reduction can be aimed at.
The concrete-filled steel pipe column according to claim 2 is a column steel pipe having upper and lower steel pipe joint portions to which a horizontal member is joined, and a steel pipe main body portion extending between the steel pipe joint portions, and the steel pipe joint portion. A diaphragm provided in the column, filled concrete filled in the column steel pipe, and an end portion joined to the diaphragm, extending from the diaphragm only to one of the upper and lower sides, and in the axial end of the steel pipe main body Reinforcement that is embedded in the filled concrete and reinforces the filled concrete so that the bending strength of the filled concrete in the axial end portion is larger than the bending strength of the filled concrete in the axial middle portion of the steel pipe main body. Means.
The concrete-filled steel pipe column according to claim 3 is the concrete-filled steel pipe column according to claim 1 or 2 , wherein the reinforcing means is embedded in the filled concrete in an axial end portion of the steel pipe main body portion, It has an end reinforcement member that transmits a bending moment with the filled concrete in the steel pipe joint, and the length of the end reinforcement member along the axial direction of the steel pipe body is the steel pipe body It is said to be more than the width of.
According to the concrete-filled steel pipe column according to claim 3 , the length along the axial direction of the steel pipe main body part of the end reinforcing member is equal to or greater than the width of the steel pipe main body part, thereby reducing the material cost and reducing the material cost. It is possible to suppress the occurrence of local buckling at the axial end of the portion. This is because local buckling is likely to occur at the axial end of the steel pipe main body within the region of the length of the end reinforcing member described above.
The concrete-filled steel pipe column according to claim 4 is the concrete-filled steel pipe column according to claim 3 , wherein the end reinforcing member has a bending strength of the filled concrete in an axial end portion of the steel pipe main body portion. It is embed | buried in this filling concrete so that it may become small as it goes to the axial direction intermediate part of the said steel pipe main-body part from a joint part.
According to the concrete-filled steel pipe column according to claim 4 , the bending strength of the filling concrete in the axial end portion of the steel pipe main body portion is directed from the steel pipe joint portion to the axial intermediate portion of the steel pipe main body portion by the end reinforcing member. Reinforced to become smaller according to Thereby, by performing optimal reinforcement according to the stress state, excessive reinforcement can be eliminated, and workability can be improved and cost can be reduced.
  As used herein, “so that the bending strength of the filled concrete decreases from the steel pipe joint to the axial middle part of the steel pipe body” means that the bending strength of the filled concrete is reduced from the steel pipe joint to the steel pipe body. It is a concept that includes a configuration that gradually decreases toward an intermediate portion in the axial direction and a configuration that gradually decreases.
  Since this invention was set as said structure, it can suppress the rapid fall of yield strength at the time of a fire.
It is a longitudinal section showing a concrete filling steel pipe pillar concerning one embodiment of the present invention. (A) is the elements on larger scale of FIG. 1, (B) is the 2B-2B sectional view taken on the line of FIG. 2 (A). It is a longitudinal cross-sectional view equivalent to FIG. 1 which shows the stress state of the concrete filling steel pipe column which concerns on one Embodiment of this invention. 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 steel pipe column are shown, and (C) shows a state where local buckling has occurred in the steel pipe constituting the concrete steel pipe column. (A) And (B) is an enlarged view equivalent to Drawing 2 (B) showing the modification of the end part reinforcement member in one embodiment of the present invention. (A) is an enlarged view equivalent to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 7B-7B sectional view taken on the line of FIG. 7 (A). It is. (A) is an enlarged view equivalent to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 8B-8B sectional view taken on the line of FIG. 8 (A). It is. (A) is an enlarged view corresponding to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 9B-9B sectional view taken on the line of FIG. 9 (A). It is. (A) is an enlarged view corresponding to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 10B-10B sectional view taken on the line of FIG. 10 (A). It is. (A) is an enlarged view corresponding to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 11B-11B sectional view taken on the line of FIG. 11 (A). It is. (A) is an enlarged view equivalent to FIG. 2 (A) which shows the modification of the edge part reinforcement member in one Embodiment of this invention, (B) is the 12B-12B sectional view taken on the line of FIG. 12 (A). It is. (A) And (B) is an enlarged view equivalent to the partially expanded view of FIG. 1 which shows the modification of the edge part reinforcement member in one 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 axial direction (up-down direction) of the column steel pipe in this embodiment.
  FIG. 1 shows a concrete-filled steel pipe column 10 according to an embodiment. The concrete-filled steel pipe column 10 includes a column steel pipe 12, a filling concrete 14 filled in the column steel pipe 12, and a reinforcing steel bar 20 as a reinforcing means. The column steel pipe 12 is composed of a square steel pipe, and has an upper and lower steel pipe joint portion 12A to which a steel beam 16 as a horizontal member is joined, and a steel pipe main body portion 12B extending between these steel pipe joint portions 12A. Yes.
  The steel beam 16 is made of H-shaped steel and has a pair of upper and lower flange portions 16A and a web portion 16B that connects the flange portion 16A, and the end thereof is abutted against and welded to the outer surface of the steel pipe joint portion 12A. Yes. On the other hand, a pair of upper and lower inner diaphragms 18 is provided on the inner wall surface of the steel pipe joint 12A. Each inner diaphragm 18 is provided so as to be continuous with the flange portion 16 </ b> A of the steel beam 16, and the steel pipe joint 12 </ b> A is reinforced by the inner diaphragm 18. Further, a filling hole 18A is formed at the center of each inner diaphragm 18, and the filled concrete 14 is filled into the column steel pipe 12 through these filling holes 18A.
  Here, the filled concrete 14 filled in the steel pipe body 12B between the upper and lower steel beams 16 is filled in the steel pipe middle 12BM as an axially middle portion in the steel pipe body 12B by a plurality of reinforcing bars 20. The bending strength of the concrete 14 is reinforced so that the bending strength of the filled concrete 14 in the steel pipe upper end 12BU and the steel pipe lower end 12BL as axial ends is increased.
  Specifically, as shown in FIGS. 2A and 2B, the filling concrete 14 in the upper end portion (column head) 12BU of the steel pipe in the steel pipe main body portion 12B has a plurality of end reinforcing members. In the present embodiment, four reinforcing reinforcing bars 20 are embedded. The reinforcing bars 20 are arranged with a predetermined interval in the circumferential direction of the column steel pipe 12 with the axial direction being the axial direction of the column steel pipe 12 (arrow Z direction), and each upper end is welded to the inner diaphragm 18. Etc. are joined. Further, when the width (column column) of the steel pipe body 12B is D, the length L of each reinforcing bar 20 (the length along the axial direction of the steel pipe body 12B) is the width D of the steel pipe body 12B. 1.0 times or more. These reinforcing reinforcing bars 20 reinforce the filling concrete 14 in the steel pipe upper end portion 12BU, and the filling concrete 14 in the steel pipe joint 12A and the filling concrete in the steel pipe upper end portion 12BU through the inner diaphragm 18 and the reinforcing reinforcing bars 20. The bending moment is transmitted to the 14. Similarly, as shown in FIG. 1, the filled concrete 14 in the lower end portion (column base portion) 12BL of the steel pipe is reinforced by a plurality of reinforcing bars 20.
  On the other hand, the filling concrete 14 in the steel pipe intermediate part 12BM in the steel pipe main body part 12B is not reinforced by the reinforcing reinforcing bars 20. Thereby, the bending proof stress of the filling concrete 14 in the steel pipe upper end part 12BU and the steel pipe lower end part 12BL is large with respect to the bending proof stress of the filling concrete 14 in the steel pipe intermediate part 12BM.
  Next, the operation of this 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 steel pipe joint 12A, and a bending moment M acts on the steel pipe main body 12B. Occurs. The bending moment M gradually increases from the steel pipe intermediate part 12BM toward the steel pipe upper end part 12BU and the steel pipe lower end part 12BL. On the other hand, the column steel pipe 12 expands in the axial direction (arrow Z direction) due to thermal expansion in the event of a fire, but the expansion in the axial direction gradually decreases due to a decrease in rigidity accompanying a temperature rise. The expansion deformation to ceases and turns into contraction deformation. In this state, when a horizontal force F is applied from the steel beam 16 to the steel pipe connection part 12A, the compression of the steel pipe upper end part 12BU and the steel pipe lower end part 12BL which generate a large bending moment as compared with the steel pipe intermediate part 12BM as described above. Local buckling K tends to occur on the side (arrow C side) side surface. In particular, when the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL are rigidly joined to the steel beam 16 via the steel pipe connection portion 12A, and the steel beam 16 has a large extension in the axial direction, the steel pipe upper end portion A deformation | transformation with a big curvature arises in 12BU and steel pipe lower end part 12BL. Due to this deformation, a large degree of compressive stress is generated on the compression side (arrow C side) side surfaces of the steel pipe upper end 12BU and the steel pipe lower end 12BL, and local buckling K occurs in the steel pipe upper end 12BU and the steel pipe lower end 12BL.
  When local buckling occurs in the steel pipe upper end part 12BU and the steel pipe lower end part 12BL, the bending rigidity of the concrete-filled steel pipe column 10 is significantly reduced. When the axial force (vertical load) V acting on the concrete-filled steel pipe column 10 is large, after the occurrence of local buckling K, the deformation due to the bending moment M rapidly progresses and collapses to the filling concrete 14 on the local buckling K side. Produce. As a result, the concrete-filled steel pipe column 10 loses its load supporting ability and may collapse brittlely.
  As a countermeasure, in this embodiment, the reinforcing steel bar 20 is filled so that the bending strength of the filling concrete 14 in the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL becomes larger than the bending strength of the filling concrete 14 in the steel pipe intermediate portion 12BM. The concrete 14 is reinforced. Thereby, even if local buckling K occurs in the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL, the filling concrete 14 in the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL bears the bending moment M and the local buckling K. By resisting the compressive force generated by, the collapse of the filled concrete 14 is suppressed. As a result, the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL can bear the axial force V even after the occurrence of local buckling K, and the axial force V is smoothly applied to the steel pipe intermediate portion 12BM of the column steel pipe 12. It is possible to communicate. Therefore, a sudden decrease in proof stress (collapse) after the occurrence of local buckling K of the concrete-filled steel pipe column 10 during a fire is suppressed. The shearing force is transmitted by the residual shear strength of the column steel pipe 12 and the filled concrete 14 and the dowel effect of the reinforcing reinforcing bars 20.
  Moreover, in the concrete filling steel pipe column 10 which concerns on this embodiment, compared with the structure which reinforces the filling concrete 14 with the same bending proof stress over the full length of the steel pipe main-body part 12B, improvement of workability, construction period reduction, and cost reduction. Can be achieved. Furthermore, by limiting the range in which the reinforcing bar 20 is provided to the steel pipe upper end 12BU and the steel pipe lower end 12BL, the reinforcing bar 20 can be bonded in advance to the inner diaphragm 18 at a factory or the like, so that the on-site joining work is omitted. can do.
  Here, FIG. 4A 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, as shown in FIG. 4B, when a fire 104 occurs, the beam 102A extends in the horizontal direction (arrow J direction), so that the pillar 100 is deformed as shown in FIG. .
  FIG. 5 (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 a deformed state and a stress state as shown in FIG. 5B during heating, the deformed state and the stress state of the column 100 shown in FIG. 4B 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. 5 (A), the following new knowledge was obtained.
  That is, when the horizontal displacement (horizontal force F) generated at the upper end of the heated column 110 is large, or when the axial force V generated at the column 110 is large, the column 110 is moved as shown in FIG. It was confirmed that local buckling K was generated at the upper end and lower end of the column steel pipe to be formed. Further, even when the heating time is relatively short and the concrete filled in the column 110 still has sufficient proof stress, the column 110 loses its load supporting ability due to the local buckling K of the column steel pipe and collapses. Was confirmed.
  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 width of the steel pipe main body portion 12B is D (see FIG. 2B), the local buckling K in the steel pipe upper end portion 12BU is likely to occur in the region from the upper end to 2D. To D in the region. Similarly, the local buckling K in the steel pipe lower end portion 12BL is likely to occur in the region from the lower end to 2D, and is particularly likely to occur in the region from the lower end to D.
  Therefore, from the viewpoint of suppressing the occurrence of local buckling K, the length L of the reinforcing reinforcing bar 20 is preferably D or more, and more preferably 2D or more. Furthermore, in consideration of workability and material cost, it is desirable that the length L of the reinforcing steel bar 20 satisfies D ≦ L ≦ 2D. Thereby, generation | occurrence | production of the local buckling K of the steel pipe upper end part 12BU and the steel pipe lower end part 12BL can be suppressed, reducing the material cost of the reinforcement reinforcing bar 20.
  Note that the above-described destruction due to local buckling K is a phenomenon that has not been confirmed by experiments. Until now, the cross section of the pillar 110 has been implemented with a small cross section (for example, about 300 mm × 300 mm). We are carrying out. The compressive strain generated at the upper and lower ends of the column steel pipe increases in proportion to the distance from the neutral axis position of the column 110 to the column steel pipe. If the cross section becomes large, the compressive strain generated in the column steel pipe also increases in proportion to this. For this reason, when a large horizontal force is generated at the upper end portion of a column having a large cross section (for example, 600 mm × 600 mm or more) due to a fire, a large compressive strain is generated at the upper end portion and the lower end portion of the column. In the above experiment, it is considered that the compressive strain generated in the column steel pipe exceeded the allowable compressive strain for local buckling of the column steel pipe. This compressive strain includes a long-term compressive strain ε1 resulting from a long-term axial force, a compressive strain ε2 resulting from forced deformation (horizontal force F) due to the extension of the beam, and a compressive strain ε3 resulting from an additional bending moment due to the extension of the beam. It is also possible to think of it as the sum of
  In the configuration in which the steel beam 12 is joined to both sides of the steel pipe joint 12A as in the present embodiment, the opposite horizontal force acts on both sides of the steel pipe joint 12A as each steel beam 12 extends. Therefore, these horizontal forces cancel each other. Therefore, the above-described compression strains ε2, ε3 tend to be small. On the other hand, in the configuration in which the steel beam 16 is joined only to one side of the steel pipe joint 12A as in the outer peripheral column, the compressive strains ε2 and ε3 are likely to increase. In particular, when the beam span of the steel beam 16 joined to one side of the steel pipe connection part 12A becomes long (for example, 10 mm or more), the amount of extension of the steel beam 16 at the time of fire increases, and the steel pipe upper end 12BU and the steel pipe lower end Since the horizontal displacement (forced deformation) of 12BL becomes large (for example, 1/50 rad or more), the compression strains ε2 and ε3 may be excessive. The present embodiment is thus suitable for reinforcing a concrete-filled steel pipe column in which the steel beam 16 is joined to one side of the steel pipe joint 12A or the steel pipe joint 12A from three directions.
  Note that the number and arrangement (pitch) of the reinforcing reinforcing bars 20 can be appropriately changed. For example, as shown in FIG. 6 (A), the reinforcing reinforcing bars 20 may be arranged in a circular shape in plan view, or as shown in FIG. 6 (B), the reinforcing reinforcing bars 20 may be arranged in plan view. It may be arranged in a square shape.
  Next, a modification of the end reinforcing member will be described. In addition, in the modified example demonstrated below, illustration of the filling concrete 14 (refer FIG. 1) with which the column steel pipe 12 is filled is abbreviate | omitted suitably. Moreover, below, although the case where various modifications are applied to the steel pipe upper end part 12BU is demonstrated to an example, these modifications are applicable also to the steel pipe lower end part 12BL.
First, in the modification shown in FIGS. 7A and 7B, two types of reinforcing reinforcing bars 22 and 24 having different lengths are used as the end portion reinforcing members. Specifically, the reinforcing reinforcing bar 22 has a length L 1 that is substantially half the length L 2 of the reinforcing reinforcing bar 24. These reinforcing bars 22 and 24 are arranged in an axial direction (arrow Z direction) of the column steel pipe 12 and alternately arranged at predetermined intervals in the circumferential direction of the column steel pipe 12, and the upper ends of the reinforcing bars 22 and 24 are arranged. It is joined to the inner diaphragm 18 by welding or the like. Thereby, the bending strength of the filling concrete 14 in the steel pipe upper end part 12BU is gradually reduced from the steel pipe joint part 12A toward the steel pipe intermediate part 12BM.
  In this way, the lengths of the reinforcing reinforcing bars 22 and 24 are changed, and the bending strength of the filled concrete 14 in the steel pipe upper end portion 12BU is changed according to the bending moment M (see FIG. 3) acting on the steel pipe upper end portion 12BU. Therefore, excessive reinforcement can be eliminated by decreasing in steps toward the steel pipe intermediate portion 12BM. Therefore, the material cost of the reinforcing reinforcing bars 22 and 24 can be reduced.
  Further, in the above-described embodiment (see FIG. 1) in which the lengths L of all the reinforcing bars 20 are substantially the same, the bending rigidity of the steel pipe upper end portion 12BU is larger than the bending rigidity of the steel pipe intermediate portion 12BM. Rotational deformation (bending deformation with a large curvature) around the boundary surface between the portion 12BU and the steel pipe intermediate portion 12BM (near the tip of the reinforcing steel bar 20) occurs, and stress concentrates on the steel pipe intermediate portion 12BM near the boundary surface. . When the steel beam 16 extends in the axial direction (horizontal direction) and the load axial force of the concrete-filled steel pipe column 10 is large, local buckling may occur in the steel pipe intermediate part 12BM near the boundary surface.
  On the other hand, in the present modification, the bending strength of the filled concrete 14 in the steel pipe upper end portion 12BU is gradually reduced from the steel pipe joint portion 12A toward the steel pipe intermediate portion 12BM, so that the steel pipe upper end portion 12BU and the steel pipe intermediate portion are reduced. Stress concentration of the steel pipe intermediate part 12BM near the boundary surface with the part 12BM (near the tip of the reinforcing steel bar 24) is reduced. Therefore, the occurrence of local buckling of the column steel pipe 12 near the boundary surface is suppressed.
  In this modification, the bending strength of the filled concrete 14 in the steel pipe upper end portion 12BU is changed from the steel pipe joint portion 12A to the steel pipe intermediate portion 12BM in accordance with the bending moment M (see FIG. 3) acting on the steel pipe upper end portion 12BU. For example, by using three or more types of reinforcing bars having different lengths, the bending strength of the filling concrete 14 is gradually reduced from the steel pipe joint 12A toward the steel pipe intermediate part 12BM. May be. In this modification, the lengths of the reinforcing reinforcing bars 22 and 24 are changed. However, the reinforcing bar diameters and the material strengths of the reinforcing reinforcing bars 22 and 24 may be changed, or the reinforcing reinforcing bars having different lengths, reinforcing bar diameters, and material strengths. May be used in appropriate combination.
Next, in the modification shown in FIGS. 8A and 8B, the reinforcing reinforcing bars 20 are bound by a plurality of ring-shaped hoop bars 26 arranged at intervals in the axial direction of the column steel pipe 12. Has been. Thereby, a larger bending moment can be transmitted between the filling concrete 14 in the steel pipe joint 12A and the filling concrete 14 in the steel pipe upper end portion 12BU. Therefore, even when the axial force acting on the steel pipe upper end portion 12BU is large or when the steel beam 16 extends excessively in the axial direction (horizontal direction), the axial force is smoothly transmitted to the steel pipe intermediate portion 12BM. The Therefore, a higher axial force can be borne compared to the above embodiment (see FIG. 1).
The diameter and arrangement (pitch) of the hoop muscle 26 can be changed as appropriate. Further, the hoop line 26 may be arranged in a spiral shape instead of a ring shape.
Next, in the modification shown in FIGS. 9A and 9B, a mechanical fixing 34 as a fixing member is provided at the tip of the reinforcing reinforcing bar 20. By providing the mechanical fixing 34 at the tip of the reinforcing reinforcing bar 20 in this way, the bending moment is more smoothly transmitted between the filling concrete 14 in the steel pipe joint 12A and the filling concrete 14 in the steel pipe upper end 12BU. Is done. Therefore, a higher axial force can be borne compared to the above embodiment (see FIG. 1).
As the fixing member, for example, a fixing plate, a plate nut, or the like can be used instead of the mechanical fixing 34.
  Next, in the modified example shown in FIGS. 10A and 10B, a plurality of L-shaped steels 28 are used as end reinforcing members. Each L-shaped steel 28 is disposed at each corner of the steel pipe upper end portion 12BU with the opening side facing inward while the axial direction is the axial direction of the column steel pipe 12 (arrow Z direction). Is joined to the inner diaphragm 18 by welding or the like. In addition, the length L of each L-shaped steel 28 is 1.0 times or more the width D of the steel pipe body 12B.
  Thus, by making the end reinforcement member L-shaped steel 28, the contact area with the filled concrete 14 (see FIG. 1) is increased. Thereby, since the dowel effect of the L-shaped steel 28 is improved, a larger bending moment and shear force are transmitted between the filled concrete 14 in the steel pipe joint 12A and the filled concrete 14 in the steel pipe upper end 12BU. Can do.
  Even if the surface of the L-shaped steel 28 is provided with studs or irregularities, or through holes are formed in the L-shaped steel 28, the integrity (adhesive force) between the L-shaped steel 28 and the filled concrete 14 is increased. good. Further, as shown in FIGS. 11A and 11B, these L-shaped steels 28 may be connected by a horizontal plate 30 passed to the adjacent L-shaped steels 28. As a result, a larger bending moment and shearing force can be transmitted between the filled concrete 14 in the steel pipe joint 12A and the filled concrete 14 in the steel pipe upper end 12BU.
  Next, in the modification shown in FIGS. 12A and 12B, a hook-shaped reinforcing bar 32 configured in a hook shape is used as the end reinforcing member. The saddle-shaped reinforcing bar 32 is configured by connecting a plurality of vertical bars 32A and a plurality of horizontal bars 32B in a lattice shape. Moreover, the length L of the hook-shaped reinforcing bar 32 is 1.0 times or more the width D of the steel pipe main body 12B. By connecting the vertical bars 32A and the horizontal bars 32B in a lattice shape in this way, the integrity of the bar-shaped reinforcing bars 32 and the filled concrete 14 (see FIG. 1) is increased, so the filled concrete 14 in the steel pipe joint 12A. And a larger bending moment and shearing force can be transmitted between the steel pipe upper end portion 12BU and the filled concrete 14.
  In the above-described embodiment and various modifications, the reinforcing reinforcing bar 20 and the like are joined to the inner diaphragm 18 by welding. For example, a screw portion is provided at one end of the reinforcing reinforcing rod 20 and the screw portion is formed in the inner diaphragm 18. The mounting holes may be screwed or fixed with nuts. Further, instead of the inner diaphragm 18, the reinforcing reinforcing bars 20 and the like may be joined to the through diaphragm.
  Furthermore, the inner diaphragm 18 can be omitted. For example, in the modification shown in FIG. 13A, the steel pipe joint 12A and the steel beam 16 are joined via the outer diaphragm 36. Specifically, a pair of upper and lower outer diaphragms 36 is provided on the outer peripheral surface of the steel pipe joint 12 </ b> A, and a gusset plate 38 is provided between the pair of outer diaphragms 36. The flange portions 16A of the steel beam 16 are welded to the outer diaphragms 36, respectively. Further, the web portion 16 </ b> B of the steel beam 16 is joined to the gusset plate 38 with a high-strength bolt 40.
  In such a configuration in which the inner diaphragm 18 (see FIG. 1) does not exist, the reinforcing reinforcing bars 20 may be embedded across the filling concrete 14 in the steel pipe joint portion 12A and the filling concrete in the steel pipe upper end portion 12BU. Thereby, even if local buckling occurs in the steel pipe joint 12A, a bending moment is transmitted between the filled concrete 14 in the steel pipe joint 12A and the filled concrete 14 in the steel pipe upper end 12BU. Moreover, since the filling concrete 14 in the steel pipe upper end part 12BU can resist the compressive force generated by local buckling, the crushing of the filling concrete 14 is suppressed.
  Note that the fixing length of the reinforcing reinforcing bars 20 with respect to the filled concrete 14 in the steel pipe joint 12A may be adjusted as appropriate according to the bending moment acting on the steel pipe upper end 12BU. Further, as shown in FIG. 13 (B), a reinforcing steel bar 42 may be embedded across the filled concrete 14 in the steel pipe lower end portion 12BL, the steel pipe fitting portion 12A, and the steel pipe upper end portion 12BU. Thereby, while workability improves, a bigger bending moment can be transmitted between the filling concrete 14 in 12 A of steel pipe connection parts, and the filling concrete 14 in steel pipe upper end part 12BU. In addition, what is necessary is just to fill the filling concrete 14 in the column steel pipe 12 in the state which attached the reinforcing steel 42 to the column steel pipe 12 with the holding metal fitting etc. which are not illustrated at the time of construction.
  Furthermore, in the said embodiment, although only the filling concrete 14 in the steel pipe upper end part 12BU and the steel pipe lower end part 12BL was reinforced by edge part reinforcement members, such as the reinforcing steel bar 20, it is not restricted to this. The filled concrete 14 in the column steel pipe 12 is reinforced so that the bending strength of the filled concrete 14 in the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL is larger than the bending strength of the filled concrete 14 in the steel pipe intermediate portion 12BM. For example, in addition to the reinforcing reinforcing bars 20 as the reinforcing means, reinforcing bars as reinforcing means over the entire length of the column steel pipe 12 may be embedded in the filling concrete 14. In this case, the bending strength of the filling concrete 14 in the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL is larger than the bending strength of the filling concrete 14 in the steel pipe intermediate portion 12BM by the amount of the reinforcing reinforcing bar 20 as the end portion reinforcing member. Become.
  Furthermore, the column steel pipe 12 is not limited to a square steel pipe having a substantially square cross section, and may be a square steel pipe or a round steel pipe having a rectangular cross section. In addition, in the rectangular steel pipe having a rectangular cross section, the length of the short side corresponds to the width D of the steel pipe main body, and in the case of a round steel pipe, the diameter corresponds to the width D of the steel pipe main body. The column steel pipe 12 may be provided with a fireproof coating. Furthermore, in the above embodiment, the steel beam 16 has been 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.
  Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and may be used in combination with one embodiment and various modifications, and departs from the gist of the present invention. Needless to say, the present invention can be carried out in various modes within a range not to be performed.
10 Concrete Filled Steel Pipe Column 12 Column Steel Pipe 12A Steel Pipe Joint 12B Steel Pipe Main Body 12BU Steel Pipe Upper End (Axial End)
12BM Steel pipe intermediate part 12BL Steel pipe lower end part (Axial direction end part)
14 Filled concrete 16 Steel beam (horizontal member)
20 Reinforcing bars (reinforcing means, end reinforcing members)
24 Reinforcing bars (reinforcing means, end reinforcement members)
28 L-shape steel (reinforcement means, end reinforcement member)
32 Barbed rebar (reinforcement means, end reinforcement member)
42 Reinforcing bars (reinforcing means, end reinforcement members)

Claims (4)

  1. Column steel pipes having upper and lower steel pipe joints to which horizontal members are joined, and a steel pipe body extending between the steel pipe joints,
    Filled concrete filled in the column steel pipe;
    The filled concrete is embedded in the filled concrete so that the bending strength of the filled concrete in the end portion in the axial direction of the steel pipe main body portion is larger than the bending strength of the filled concrete in the axial middle portion of the steel pipe main body portion. Reinforcing means for suppressing collapse of the filled concrete in the axial end portion accompanying local buckling of the axial end portion in the event of a fire ,
    Concrete-filled steel pipe column with.
  2. Column steel pipes having upper and lower steel pipe joints to which horizontal members are joined, and a steel pipe body extending between the steel pipe joints,
    A diaphragm provided in the steel pipe joint,
    Filled concrete filled in the column steel pipe;
    An end portion is joined to the diaphragm, extends only from the diaphragm to one of the upper and lower sides, is embedded in the filling concrete in the axial end portion of the steel pipe main body portion, and the filling in the axial intermediate portion of the steel pipe main body portion Reinforcing means for reinforcing the filled concrete so that the bending strength of the filled concrete in the axial end portion is larger than the bending strength of the concrete;
    Concrete-filled steel pipe column with.
  3. The reinforcing means has an end reinforcing member that is embedded in the filled concrete in the axial end portion of the steel pipe main body and transmits a bending moment with the filled concrete in the steel pipe joint,
    The concrete-filled steel pipe column according to claim 1 or 2, wherein a length along the axial direction of the steel pipe main body part of the end reinforcing member is equal to or greater than a width of the steel pipe main body part.
  4. The end reinforcing member is formed on the filled concrete such that the bending strength of the filled concrete in the axial end portion of the steel pipe main body portion decreases from the steel pipe joint portion toward the axial middle portion of the steel pipe main body portion. The concrete-filled steel pipe column according to claim 3, which is buried.
JP2011128513A 2011-06-08 2011-06-08 Concrete filled steel pipe column Active JP5758207B2 (en)

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CN103216014A (en) * 2013-04-25 2013-07-24 沈阳建筑大学 Assembling type frame structure joint
CN103216006A (en) * 2013-04-25 2013-07-24 沈阳建筑大学 Fabricated type frame structure for concrete filled steel tubes
CN105888080B (en) * 2016-04-11 2018-01-19 青岛理工大学 Assembled steel tube casing reinforced concrete combined joint and installation method

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