JP2013087520A - Fireproof reinforcement structure of concrete-filled steel pipe column - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fireproof reinforcement structure of a concrete-filled steel pipe column, capable of suppressing local buckling of the steel pipe column.SOLUTION: A concrete-filled steel pipe column 10 includes a steel pipe column 12, and infilled concrete 14 filled inside the steel pipe column 12. The steel pipe column 12 comprises a rectangular steel tube, and includes upper and lower steel pipe joint parts 12A to which a steel frame beam 16 as a horizontal member is joined, and a steel pipe body part 12B extending between the steel pipe joint parts 12A. A steel pipe upper end (column head) 12BU and a steel pipe lower end (column base) 12BL as axial direction ends in the steel pipe body part 12B are provided with cylindrical members 22U and 22L as buckling suppressing members, respectively.

Description

  The present invention relates to a fireproof reinforcing structure for a concrete-filled steel pipe column.

  A concrete filled steel tube (CFT) column in which concrete is filled in a steel tube column is known. In general, the CFT column is superior in fire resistance because the axial force that can be borne is larger than that of a hollow steel tube column and the heat capacity is increased by filling the concrete. 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.

  On the other hand, an earthquake-proof reinforcement structure for earthquake-proofing the column head and column base of a steel pipe column is known (for example, Patent Document 1). The seismic reinforcement structure disclosed in Patent Document 1 surrounds a column head of a steel pipe column by two divided reinforcing steel plates, and fills a gap between the column head and the divided reinforcing steel plate with mortar.

JP-A-10-204993

  By the way, in a concrete filling steel pipe column, local buckling becomes easy to generate | occur | produce in the column head part and column leg part of a steel pipe column with the temperature rise at the time of a fire. And when local buckling generate | occur | produces in the column head part or column base part of a steel pipe column, the axial direction displacement of a concrete filling steel pipe column will progress rapidly, and it may lead to collapse.

  However, the seismic reinforcement structure disclosed in Patent Document 1 increases the bending strength of the column head and column base of the steel column against seismic force, and the column head and column base of the steel column during a fire. The local buckling is not considered.

  In view of the above facts, an object of the present invention is to obtain a fireproof reinforcing structure for a concrete-filled steel pipe column that can suppress local buckling of the steel pipe column.

  The fireproof reinforcing structure for a concrete-filled steel pipe column according to claim 1, wherein the steel pipe column has 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, Filled concrete filled in the steel pipe column, and a buckling suppressing member provided on the side wall of the axial end portion of the steel pipe main body portion and suppressing displacement of the side wall in the out-of-plane direction.

  According to the fireproof reinforcement structure of a concrete-filled steel pipe column according to claim 1, by providing a buckling suppression member on the side wall of the axial end portion of the steel pipe main body, the displacement of the side wall in the out-of-plane direction is suppressed. Has been. Therefore, the local buckling of the axial direction edge part in a steel pipe main-body part is suppressed.

  The fireproof reinforcement structure for a concrete-filled steel pipe column according to claim 2 is the fireproof reinforcement structure for a concrete-filled steel pipe column according to claim 1, wherein the buckling suppression member is a side wall of an axial end portion of the steel pipe main body. Opposite with a gap.

  According to the fireproof reinforcing structure for a concrete-filled steel pipe column according to claim 2, when the side wall of the axial end portion of the steel pipe main body portion is displaced outwardly in the out-of-plane direction, the side wall comes into contact with the buckling suppression member. Displacement outward in the out-of-plane direction is limited. Therefore, local buckling of the side wall at the axial end of the steel pipe main body is suppressed.

  The fireproof reinforcing structure for a concrete-filled steel pipe column according to claim 3 is the fireproof reinforcing structure for a concrete-filled steel pipe column according to claim 1 or 2, wherein the buckling suppression member is an axial direction in the steel pipe main body. It is a cylindrical member surrounding the end.

  According to the fireproof reinforcement structure of a concrete-filled steel pipe column according to claim 3, the steel pipe body is confined by the confining effect (restraint effect) of the tubular member by surrounding the axial end of the steel pipe body with the buckling suppression member. Displacement of the side wall of the axial end portion in the portion to the outside in the out-of-plane direction is suppressed. Therefore, the local buckling suppression force with respect to the side wall at the axial end of the steel pipe column is improved.

  Since this invention was set as said structure, it can suppress the local buckling of a steel pipe column.

It is an elevation view which shows the concrete filling steel pipe column to which the fireproof reinforcement structure of the concrete filling steel pipe column which concerns on 1st Embodiment of this invention was applied. (A) is the sectional view on the 2A-2A line of FIG. 1, (B) is explanatory drawing explaining the attachment method of the cylindrical member in 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the stress state of the concrete filling steel pipe column in 1st 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-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 sectional drawing equivalent to FIG. 2 (A) which shows the modification of the cylindrical member in 1st Embodiment of this invention. (A)-(C) are sectional drawings equivalent to FIG. 2 (A) which shows the modification of the cylindrical member in 1st Embodiment of this invention. It is an elevation view which shows the modification of the cylindrical member in 1st Embodiment of this invention. (A) is an elevation view showing a concrete-filled steel pipe column to which a fireproof reinforcement structure for a concrete-filled steel pipe column according to a second embodiment of the present invention is applied, and (B) is 9B-9B in FIG. 9 (A). It is line sectional drawing. It is a top view which shows a building. It is a longitudinal cross-sectional view equivalent to FIG. 3 which shows the concrete filling steel pipe column to which the fireproof reinforcement structure of the concrete filling steel pipe column concerning 3rd Embodiment of this invention was applied. (A) is a sectional view taken along line 12A-12A in FIG. 11, and (B) corresponds to FIG. 12 (A) showing a modified example of the fireproof reinforcing structure for a concrete-filled steel pipe column according to the third embodiment of the present invention. It is sectional drawing. It is sectional drawing equivalent to FIG. 12 (A) which shows the modification of the fireproof reinforcement structure of the concrete filling steel pipe column which concerns on 3rd Embodiment of this invention.

  Hereinafter, a fireproof reinforcing structure for 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 steel pipe column in each embodiment.

  First, the first embodiment will be described.

  FIG. 1 shows, as an example, a concrete-filled steel pipe column 10 to which a concrete-filled steel pipe column fireproof reinforcement structure (hereinafter simply referred to as “fireproof reinforcement structure”) 20 according to the first embodiment is applied. The concrete-filled steel pipe column 10 includes a steel pipe column 12 and filled concrete 14 (see FIG. 2A) filled in the steel pipe column 12. The steel pipe column 12 is formed 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. doing. The fireproof reinforcing structure 20 according to the present embodiment is applied to a steel pipe upper end (column head) 12BU and a steel pipe lower end (column base) 12BL as axial ends in the steel pipe main body 12B.

  The steel beam 16 is composed of H-shaped steel, and has a pair of upper and lower upper flange portions 16A and lower flange portions 16A, and a web portion 16B that connects the upper flange portion 16A and the lower flange portion 16A. It is abutted against the outer surface of the steel pipe joint 12A and joined by welding. On the other hand, a pair of upper and lower inner diaphragms 18 is provided on the inner side surface of the steel pipe joint 12A. Each inner diaphragm 18 is provided so as to be continuous with the upper flange portion 16A or the lower flange portion 16A of the steel beam 16, and the steel pipe joint 12A is reinforced by the inner diaphragm 18. Further, a filling hole 18A (see FIG. 3) is formed at the center of each inner diaphragm 18, and the filled concrete 14 is filled into the steel pipe column 12 through these filling holes 18A.

  Here, cylindrical members 22U and 22L as buckling suppression members are provided around the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL on the steel pipe joint portion 12A side in the steel pipe main body portion 12B. Since these cylindrical members 22U and 22L have the same configuration, the cylindrical member 22U provided in the steel pipe upper end portion 12BU will be described in detail, and the description of the cylindrical member 22L provided in the steel pipe lower end portion 12BL will be omitted as appropriate. To do.

  As shown in FIGS. 2A and 2B, the cylindrical member 22U is formed in a cylindrical shape by connecting a pair of cover bodies 24 to each other. Each cover body 24 is formed of a steel plate, and includes a cover main body portion 24A having a substantially C-shaped cross section and a flange portion 24B extending outward from an opening side end portion of the cover main body portion 24A. These cover bodies 24 are arranged with their respective opening sides facing each other so as to surround the steel pipe upper end portion 12BU, and the flange portions 24B that are butted together are connected (joined) by bolts 26 and nuts 28. Thus, when the steel pipe upper end portion 12BU is displaced outward in the out-of-plane direction of the side wall 12S, the side wall 12S comes into contact with the inner surface of the cover main body portion 24A, and the outward displacement in the out-of-plane direction is limited (suppressed). It is like that.

  As shown in FIG. 1, drop prevention ribs 25 are arranged on the outer periphery of the steel pipe upper end portion 12BU along the column circumferential direction, and the cylindrical member 22U at the top of the column is installed on the drop prevention ribs 25. ing. The cylindrical member 22U at the top of the column and the fall prevention rib 25 may be joined by welding or the like, or the cylindrical member 22U at the top of the pillar may be simply placed on the fall prevention rib 25 without joining by welding or the like. . In the latter case, it is preferable to provide an appropriate allowance with the fall prevention rib 25 so that it does not fall when the position of the cylindrical member 22U at the top of the column is shifted due to an earthquake or the like. In addition, the fall prevention rib 25 may be installed in a ring shape over the entire outer periphery of the steel pipe upper end 12BU, or may be installed intermittently.

  As shown in FIG. 2A, a gap E is formed between the side wall 12S of the steel pipe upper end 12BU and the cover main body 24A in a state where the steel pipe upper end 12BU bears a long-term axial force. It has become. Thereby, in the normal time before a fire etc. generate | occur | produce, each side wall 12S of the steel pipe upper end part 12BU is not restrained by the cylindrical member 22U. Moreover, the clearance gap E is set to the value which can suppress the local buckling K (refer FIG. 3) of the side wall 12S of the steel pipe upper end part 12BU mentioned later.

  Furthermore, when the width (column column) of the steel pipe main body 12B is D, the reinforcing range (height of the cylindrical member 22U) H (see FIG. 1) of the tubular member 22U with respect to the steel pipe upper end 12BU is the upper end of the steel pipe. It is set to 1D or more from the upper end of the part 12BU toward the steel pipe intermediate part 12BM.

  In addition, as FIG. 1 shows, the cylindrical member 22L provided in the steel pipe lower end part 12BL is above the upper flange part 16A of the steel beam 16 to be joined immediately below the steel pipe main body part 12B or the upper flange part 16A. It is placed on the floor slab installed at the top. Moreover, cylindrical member 22U, 22L is not provided in steel pipe intermediate part 12BM between steel pipe upper end part 12BU and steel pipe lower end part 12BL.

  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 steel pipe joint 12A, and a bending moment M acts on the steel pipe main body 12B. Will occur. 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 steel pipe column 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, and when reaching a certain temperature, the axial direction The expansion deformation to ceases and turns into contraction deformation. In this state, when a horizontal force F acts from the steel beam 16 to the steel pipe joint 12A, as described above, the steel pipe upper end 12BU and the steel pipe lower end 12BL generate a bending moment M larger than that of the steel pipe intermediate part 12BM. Local buckling K tends to occur on the side wall 12S on the compression side (arrow C side). 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. When a large degree of compressive stress is generated on the compression side (arrow C side) side wall 12S of the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL by this deformation, the side wall 12S is displaced outwardly (out of the surface). K is generated.

  When local buckling K 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, cylindrical members 22U and 22L are provided on the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL in the steel pipe main body portion 12B. Thereby, for example, when the side wall 12S on the compression side of the upper end portion 12BU of the steel pipe is displaced outward in the out-of-plane direction, the side wall 12S comes into contact with the inner surface of the cylindrical member 22U, and the displacement outward in the out-of-plane direction is limited. Is done. By this cylindrical member 22U, the bending rigidity of the concrete-filled steel pipe column 10 is reduced by restricting the outward displacement of the side wall 12S on the compression side of the steel pipe upper end 12BU so that local buckling K does not occur. Is suppressed. Therefore, the fireproof performance of the concrete-filled steel pipe column 10 is improved. The same applies to the lower end 12BL of the steel pipe.

  Further, in the present embodiment, as shown in FIG. 2 (A), by surrounding the steel pipe upper end portion 12BU with the tubular member 22U, the side wall 12S of the steel pipe upper end portion 12BU is displaced outwardly in the out-of-plane direction. The cylindrical member 22U exhibits a confining effect that resists with its circumferential axial force. Therefore, the displacement of the side wall 12S of the steel pipe upper end portion 12BU to the outside in the out-of-plane direction can be efficiently suppressed.

  Furthermore, in this embodiment, the clearance gap E is formed between the side wall 12S of the steel pipe upper end part 12BU, and the cylindrical member 22U. Thereby, until the side wall 12S of the steel pipe upper end part 12BU contacts the cylindrical member 22U, the steel pipe upper end part 12BU is not restrained by the cylindrical member 22U. That is, in a normal time before a fire or the like occurs, bending rigidity is not given to each side wall 12S of the steel pipe upper end portion 12BU. Therefore, the bending rigidity does not change abruptly at the boundary part (near the fall prevention rib 25) between the part where the tubular member 22U is provided in the steel pipe body part 12B and the other part of the steel pipe body part 12B. Thus, local buckling K tends to occur in the steel pipe upper end portion 12BU where a large bending moment is generated as compared with the steel pipe intermediate portion 12BM.

  On the other hand, in the configuration in which the gap E is not formed between the side wall 12S of the steel pipe upper end portion 12BU and the cylindrical member 22U, and the steel pipe upper end portion 12BU is restrained by the cylindrical member 22U from the normal time, the steel pipe main body portion 12B. The bending rigidity abruptly changes between the part where the cylindrical member 22U is provided and the other part of the steel pipe body 12B. Therefore, when the bending moment M described above acts on the steel pipe main body 12B, the rotation about the boundary between the part where the tubular member 22U is provided in the steel pipe main part 12B and the other part of the steel pipe main body 12B. Deformation may occur in the steel pipe body 12B. When this rotational deformation occurs, stress concentrates at the boundary between the portion of the steel pipe body 12B where the cylindrical member 22U is provided and the other portion of the steel pipe body 12B, and local buckling K occurs at the boundary. It becomes easy to do.

  In contrast, in the present embodiment, as described above, the gap E is formed between the side wall 12S of the steel pipe upper end portion 12BU and the tubular member 22U, so that local buckling K is likely to occur in the steel pipe upper end portion 12BU. Become. That is, the part where the local buckling K occurs can be limited to the steel pipe upper end part 12BU. Therefore, local buckling K can be efficiently suppressed. Moreover, since the range which carries out a fireproof reinforcement can be limited to the steel pipe upper end part 12BU and the steel pipe lower end part 12BL in the steel pipe main-body part 12B, an improvement of workability | operativity, a work period shortening, and cost reduction can be aimed at.

  Furthermore, since this embodiment is the structure which provides the cylindrical members 22U and 22L in the steel pipe upper end part 12BU and the steel pipe lower end part 12BL, it can be easily applied also to the existing concrete filling steel pipe column 10. FIG. Therefore, versatility is improved.

  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 configured as shown in FIG. It was confirmed that local buckling K occurred at the upper end and the lower end of the steel pipe column. Moreover, even if the heating time is relatively short and the filled concrete of the column 110 remains sufficiently proof, the column 110 loses its load supporting ability due to the local buckling K of the steel pipe column and collapses. Was confirmed.

  When concrete concrete steel pipe pillar 10 in 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 12B is D (see FIG. 2A), the local buckling K at the steel pipe upper end 12BU is the upper end (the boundary between the steel pipe fitting 12A and the steel pipe main body 12B). Part) to 2D, particularly in the 1D region from the upper end. Similarly, local buckling K in the steel pipe lower end portion 12BL is likely to occur in the region from the lower end (boundary portion between the steel pipe fitting portion 12A and the steel pipe main body portion 12B) to 2D, and in particular, 1D from the lower end. It is easy to occur in the area.

  Accordingly, from the viewpoint of suppressing the occurrence of local buckling K, the reinforcing range H of the tubular member 22U with respect to the steel pipe upper end portion 12BU is preferably 1D or more from the upper end of the steel pipe upper end portion 12BU toward the steel pipe intermediate portion 12BM. The above is more preferable. Further, in consideration of workability and material cost, it is desirable that the reinforcing range H of the cylindrical member 22U is 1D ≦ H ≦ 2D from the upper end of the steel pipe upper end portion 12BU toward the steel pipe intermediate portion 12BM. Thereby, generation | occurrence | production of the local buckling K of steel pipe upper end part 12BU can be suppressed efficiently, reducing the material cost of the cylindrical member 22U. The same applies to the lower end 12BL of the steel pipe.

  Note that the above-described destruction due to local buckling K is a phenomenon that has not been confirmed in previous experiments. In the previous experiments, the cross section of the pillar 110 was implemented with a small cross section (for example, about 300 mm × 300 mm). However, in the experiment in which the local buckling K described above was confirmed, the cross section of the pillar 110 was large in area (600 mm). × 600 mm). When the curvature generated in the column head and the column base is the same, the compressive strain generated in the upper end portion and the lower end portion of the steel pipe column increases in proportion to the distance from the neutral axis position of the column 110 to the steel tube column. If the cross section becomes large, the compressive strain generated on the side wall of the steel pipe column also increases in proportion thereto. For this reason, when a large horizontal force is generated at the upper end portion of a large cross-sectional column (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-described experiment, it is considered that the compressive strain generated in the steel pipe column exceeded the allowable compressive strain for local buckling of the steel pipe column. This compressive strain includes a long-term compressive strain ε1 caused by a long-term axial force, a compressive strain ε2 caused by a forced deformation (horizontal force F) accompanying the extension of the beam, and a compression caused by an additional bending moment accompanying the extension of the beam. It can also be considered as the sum of strains ε3.

  In the configuration in which the steel beam 16 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 16 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 a configuration in which the steel beam 16 is joined only to one side of the steel pipe joint 12A as in a side column 10A or a corner column 10B (see FIG. 10) described later, 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 joint 12A becomes long (for example, about 10 m or more), the extension amount 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 the portion 12BL becomes large (for example, the column member angle is about 1/50 rad), the compressive strains ε2 and ε3 may be excessive. The present embodiment is suitable for fireproof reinforcement of the concrete-filled steel pipe column 10 (side column 10A or corner column 10B) in which the steel beam 16 is joined to one side of the steel pipe joint 12A.

  Next, a modification of the first embodiment will be described. In addition, 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.

  In the above embodiment, the pair of cover bodies 24 constituting the cylindrical member 22U are joined by the bolts 26 and the nuts 28, but these cover bodies 24 may be joined by welding or the like. In this case, as shown in FIG. 6, the flange portion 24B of the cover body 24 can be omitted as appropriate.

  Moreover, in the said embodiment, the clearance gap E is provided between the cover main-body part 24A which comprises the cylindrical member 22U, and the side wall 12S of the steel pipe upper end part 12BU so that the steel pipe upper end part 12BU is not restrained by the cylindrical member 22U at the normal time. Although formed, it is not restricted to this. The cylindrical member 22U only needs to be able to suppress the outward displacement of the side wall 12S of the steel pipe upper end portion 12BU in the out-of-plane direction. For example, the cylindrical member 22U may be integrated with the side wall of the steel pipe upper end portion 12BU.

  More specifically, the cylindrical member 32 shown in FIG. 7A is formed into a cylindrical shape by joining a pair of cover bodies 34 having a substantially C-shaped cross section by welding or the like, and has a steel pipe upper end 12BU. Is enclosed. A gap between the tubular member 32 and the side wall 12S of the steel pipe upper end portion 12BU is filled with a fireproof filler 36 having fireproof performance such as polymer cement mortar and fireproof adhesive (for example, isocyanate). With this refractory filler 36, the tubular member 32 is integrated with the upper end 12BU of the steel pipe.

  Moreover, the cylindrical member 42 shown by FIG. 7 (B) is comprised by joining a pair of cover bodies 44 with a cross-sectional arc shape by welding etc., and is surrounding the steel pipe upper end part 12BU. The gap between the tubular member 32 and the side wall 12S of the steel pipe upper end portion 12BU is filled with a refractory filler 36, and the tubular member 42 is integrated with the steel pipe upper end portion 12BU by the refractory filler 36. Yes.

  Furthermore, the cylindrical member 52 shown in FIG. 7C is formed into a cylindrical shape by joining four cover bodies 54 having an L-shaped cross section by welding or the like, and surrounds the steel pipe upper end portion 12BU. These cover bodies 54 are overlapped on the side wall 12S of the steel pipe upper end portion 12BU, and the outer peripheral portion thereof is joined to the side wall 12S of the steel pipe upper end portion 12BU by welding, an adhesive, or the like. Thereby, the cylindrical member 52 is integrated with the steel pipe upper end part 12BU.

  Thus, by integrating the cylindrical members 32, 42, 52 into the steel pipe upper end portion 12BU, the above-described compressive strain ε2 caused by the forced deformation accompanying the extension of the beam and the additional bending moment accompanying the extension of the beam are reduced. The resulting compressive strain ε3 can be reduced. Further, the long-term compressive strain ε1 due to the long-term axial force is reduced by joining the cylindrical members 32, 42, 52 and the steel pipe joint 12A (see FIG. 1) so that the long-term axial force can be transmitted. It is also possible. Therefore, local buckling of the side wall 12S of the steel pipe upper end portion 12BU is suppressed.

  As shown in FIGS. 7A and 7B, when using the refractory filler 36, the cover bodies 34, 44 and the side wall 12S of the steel pipe upper end portion 12BU are provided with holes and recesses as cotters. It may be formed to enhance the integrity of the steel pipe upper end portion 12BU and the cylindrical members 32, 42.

  Moreover, when long-term axial force is not transmitted between the cylindrical members 32, 42, 52 and the steel pipe joint 12A, that is, when it is not necessary to reduce the long-term compressive strain ε1, for example, as shown in FIG. As described above, a gap G may be formed between the tubular member 32 and the steel pipe joint 12A. Thereby, since the attachment of the cylindrical member 32 with respect to the steel pipe upper end part 12BU becomes easy, workability | operativity improves.

  Furthermore, you may wind a fiber reinforcement sheet around steel pipe upper end part 12BU as a buckling suppression member. Thereby, since the displacement to the out-of-plane direction outer side of each side wall 12S of the steel pipe upper end part 12BU is suppressed by the confinement effect of the fiber reinforced sheet, local buckling of the side wall 12S is suppressed. Furthermore, the compressive strains ε2 and ε3 can be reduced by causing the fiber reinforced sheet to bear the tensile stress on the upper end portion 12BU of the steel pipe and reducing the bending deformation of the upper end portion 12BU of the steel pipe. Therefore, local buckling of the side wall 12S of the steel pipe upper end portion 12BU can be further suppressed.

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

  9A and 9B show, as an example, a steel pipe upper end portion 12BU in a steel pipe main body portion 12B to which the fireproof reinforcing structure 60 according to the second embodiment is applied. The steel pipe upper end portion 12BU is provided with an annular stiffening rib 62 as a buckling suppressing member. The annular stiffening rib 62 is formed of a ring-shaped steel plate in plan view, and is disposed along the circumferential direction (column circumferential direction) of the steel pipe column 12 on the outer periphery of the steel pipe main body 12B. Surrounds 12BU. Further, the inner peripheral portion 62A of the annular stiffening rib 62 is joined to each side wall 12S of the steel pipe upper end portion 12BU by welding or the like. By this annular stiffening rib 62, out-of-plane rigidity is imparted to each side wall 12S of the steel pipe upper end portion 12BU.

  Further, when the width of the steel pipe main body portion 12B is D, the distance H from the upper end of the steel pipe upper end portion 12BU to the annular stiffening rib 62 is effective within 2D.

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

  As shown in FIGS. 9A and 9B, the steel pipe upper end portion 12BU is provided with an annular stiffening rib 62, and the annular stiffening rib 62 causes each side wall 12S of the steel pipe upper end portion 12BU to be attached to each side wall 12S. Out-of-plane rigidity is provided. Therefore, generation | occurrence | production of the local buckling K (refer FIG. 3) of the side wall 12S of the steel pipe upper end part 12BU is suppressed.

  Further, by enclosing the steel pipe upper end portion 12BU with the annular stiffening rib 62, the annular stiffening rib 62 resists the displacement of the side wall 12S of the steel pipe upper end portion 12BU outward in the out-of-plane direction by the circumferential axial force. Demonstrate the confining effect. Therefore, the suppression effect with respect to the displacement to the out-of-plane direction outer side of the side wall 12S of the steel pipe upper end part 12BU improves.

  Further, by stiffening the side wall 12S of the upper end 12BU of the steel pipe by the annular stiffening rib 62 arranged along the circumferential direction of the steel pipe column 12, the side wall 12S is not given bending rigidity or the bending rigidity is given. Out-of-plane rigidity can be imparted to the side wall 12S while keeping the amount small. Thereby, since bending rigidity does not change abruptly in the peripheral part of the annular stiffening rib 62 in the steel pipe upper end part 12BU, the aforementioned rotational deformation is suppressed. Therefore, local buckling of the side wall of the steel pipe upper end portion 12BU can be efficiently suppressed.

  The annular stiffening rib 62 may be formed by connecting a plurality of rod-shaped lateral stiffening ribs in a ring shape in plan view. A plurality of annular stiffening ribs 62 may be provided at intervals in the axial direction of the steel pipe upper end portion 12BU. In this case, as described above, the plurality of annular stiffening ribs 62 are preferably provided in a range within 2D from the upper end of the steel pipe upper end portion 12BU toward the steel pipe intermediate portion 12BM. The side wall 12S of the upper end portion 12BU of the steel pipe and the inner peripheral portion of the annular stiffening rib 62 are basically welded all around, but if sufficient stress can be transmitted, they may be joined by intermittent welding or spacers such as joint hardware The steel pipe upper end portion 12BU may be joined to the side wall 12S with a gap therebetween.

  Moreover, although this embodiment demonstrated the case where the fireproof reinforcement structure 60 was applied to the steel pipe upper end part 12BU as an example, the fireproof reinforcement structure 60 is applicable also to the steel pipe lower end part 12BL.

  Next, a third embodiment will be described. In addition, the thing of the structure similar to 1st, 2nd embodiment attaches | subjects the same code | symbol, and abbreviate | omits suitably and demonstrates.

  As shown in FIG. 10, the fireproof reinforcement structure 70 (see FIG. 11) according to the third embodiment is applied to the side pillar 10 </ b> A or the corner pillar 10 </ b> B arranged on the outer periphery of the building 11. Steel beams 16 are joined to these side columns 10A or corner columns 10B from one side in the horizontal direction (arrow X direction or arrow Y direction), whereas in the inner column 10C, the horizontal direction (arrow X direction, And the steel beam 16 is joined from both sides in the direction of arrow Y). Thus, the fireproof reinforcement structure 70 (refer FIG. 11) which concerns on this embodiment is applied to the side column 10A or the corner column 10B to which the steel beam 16 is joined from one side in the horizontal direction.

  FIG. 11 shows a concrete-filled steel pipe column 10 to which the fireproof reinforcing structure 70 is applied as an example. This concrete-filled steel pipe column 10 constitutes a corner column 10B (see FIG. 10), and a steel beam 16 is joined to the steel pipe joint 12A from one side (right side in FIG. 11) in the horizontal direction (arrow X). ing. Therefore, when a horizontal force F acts on the steel pipe joint 12A due to thermal expansion of the steel beam 16 at the time of a fire, a compressive force (arrow C) acts on the side wall 12S1 on the steel beam 16 side at the steel pipe upper end portion 12BU. Local buckling K is likely to occur in 12S1. On the other hand, in the steel pipe lower end portion 12BL, a compressive force (arrow C) acts on the side wall 12S2 opposite to the steel beam 16, and local buckling K is likely to occur on the side wall 12S2.

  Therefore, in the third embodiment, stiffening plates 72 are provided on the side wall 12S1 of the steel pipe upper end portion 12BU and the side wall 12S2 of the steel pipe lower end portion 12BL. Since these stiffening plates 72 have the same configuration, the stiffening plate 72 provided on the side wall 12S1 of the steel pipe upper end 12BU will be described in detail, and the stiffening plate 72 provided on the side wall 12S2 of the steel pipe lower end 12BL. Will be omitted as appropriate.

  As shown in FIG. 12 (A), the stiffening plate 72 is formed of a steel plate, and is overlaid on the side wall 12S1 of the steel pipe upper end portion 12BU, and the outer peripheral portion of the steel pipe upper end portion 12BU is welded, glued, or the like. It is joined to the side wall 12S1. The stiffening plate 72 gives out-of-plane rigidity to the side wall 12S1 of the upper end 12BU of the steel pipe.

  Further, as shown in FIG. 11, when the width of the steel pipe main body 12B is D (see FIG. 12A), the reinforcing range H of the stiffening plate 72 with respect to the steel pipe upper end 12BU is the steel pipe upper end 12BU. 1D or more from the upper end of the steel tube toward the steel pipe intermediate portion 12BM. Similarly, the reinforcing range H of the stiffening plate 72 with respect to the steel pipe lower end portion 12BL is set to 1D or more from the lower end of the steel pipe lower end portion 12BL toward the steel pipe intermediate portion 12BM.

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

  As shown in FIG. 11, stiffening plates 72 are provided on the side wall 12S1 of the steel pipe upper end portion 12BU on the steel beam 16 side and the side wall 12S2 of the steel pipe lower end portion 12BL on the side opposite to the steel beam 16 respectively. By these stiffening plates 72, out-of-plane rigidity is imparted to the side wall 12S1 of the steel pipe upper end portion 12BU and the side wall 12S2 of the steel pipe lower end portion 12BL. Therefore, since the displacement of the side wall 12S1 of the steel pipe upper end portion 12BU and the side wall 12S2 of the steel pipe lower end portion 12BL to the outside in the out-of-plane direction is suppressed, the local buckling K of these side walls 12S1 and 12S2 is suppressed.

  Further, by providing the stiffening plate 72 only on the side wall 12S1 of the steel pipe upper end portion 12BU and the side wall 12S2 of the steel pipe lower end portion 12BL, the stiffening plate 72 is provided on all four side walls 12S of the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL. Compared with the structure which provided, improvement of workability and cost reduction can be aimed at.

  Next, a modification of the third embodiment will be described.

  In the said 3rd Embodiment, although the outer peripheral part of the stiffening plate 72 was joined to the side wall 12S1 by the side of the steel beam 16 of steel pipe upper end part 12BU by welding etc., it is not restricted to this. For example, the stiffening plate 72 may be joined to the side wall 12S1 of the steel pipe upper end portion 12BU with an adhesive or the like, or may be joined using an anchor or the like.

  More specifically, in the modification shown in FIG. 12 (B), the stud bolt 78 is fixed by the chemical anchor 76 to the side wall 12S1 of the steel pipe upper end 12BU and the mounting hole 74 formed in the filled concrete 14. . On the other hand, a bolt hole 82 is formed in the stiffening plate 72, and the stiffening plate 72 is overlapped on the side wall 12S1 of the upper end portion 12BU of the steel pipe by a stud bolt 78 and a nut 79 penetrating the bolt hole 82. It is joined. Thereby, since the out-of-plane rigidity is imparted to the side wall 12S1 of the steel pipe upper end portion 12BU, the displacement of the side wall 12S1 to the outside in the out-of-plane direction is suppressed.

  As another modification, as shown in FIG. 13, the stiffening plate 72 may be opposed to the side wall 12S1 of the steel pipe upper end 12BU with a gap E between the side wall 12S1. Specifically, the stiffening plate 72 is opposed to the side wall 12S1 of the upper end 12BU of the steel pipe with the spacer 84 interposed therebetween, and is connected to the upper end 12BU of the steel pipe by the stud bolt 78 and the nut 79 that are penetrated through the bolt holes 82. It is attached. The spacer 84 forms a gap E between the side wall 12S1 of the upper end portion 12BU of the steel pipe and the stiffening plate 72. Thereby, until the side wall 12S1 of the steel pipe upper end part 12BU contacts the stiffening plate 72, bending rigidity is not provided to the side wall 12S1 of the steel pipe upper end part 12BU by the stiffening plate 72.

  Here, for example, when the side wall 12S1 on the compression side of the upper end portion 12BU of the steel pipe is displaced outward in the out-of-plane direction, the side wall 12S1 comes into contact with the inner surface of the stiffening plate 72 and the displacement outward in the out-of-plane direction is limited. Is done. Accordingly, the stiffening plate 72 restricts the displacement of the side wall 12S1 of the steel pipe upper end 12BU outward in the out-of-plane direction so that local buckling does not occur, thereby suppressing the decrease in the bending rigidity of the concrete-filled steel pipe column 10. The Therefore, the fireproof performance of the concrete-filled steel pipe column 10 is improved.

  Further, the stiffening plate 72 in the steel pipe main body 12B is provided in the same manner as in the first embodiment by opening the gap E between the side wall 12S1 of the upper end 12BU of the steel pipe and facing the stiffening plate 72. Rotational deformation around the boundary between the part and the other part in the steel pipe body 12B is suppressed. Thereby, local buckling becomes easy to generate | occur | produce in steel pipe upper end part 12BU. That is, the site where local buckling occurs can be limited to the steel pipe upper end portion 12BU. Therefore, local buckling of the steel pipe upper end portion 12BU can be efficiently suppressed.

  In the first to third embodiments, the cylindrical members 22U and 22L as buckling suppression members are provided on both the steel pipe upper end 12BU and the steel pipe lower end 12BL. However, the steel pipe upper end 12BU and the steel pipe lower end are provided. One of the cylindrical members 22U and 22L provided in 12BL may be omitted. That is, it is only necessary that the cylindrical members 22U, 22L and the like as buckling suppressing members are provided on at least one of the steel pipe upper end portion 12BU and the steel pipe lower end portion 12BL.

  Moreover, in the said 1st-3rd embodiment, although the concrete filling steel pipe pillar 10 of the inner diaphragm type using the inner diaphragm 18 was demonstrated to the example, the said embodiment is a concrete filling steel pipe of a through diaphragm type or an outer diaphragm type. It can also be applied to pillars.

  Furthermore, the steel pipe column 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. Moreover, the circumferential direction (column circumferential direction) of a steel pipe column means the direction along the width direction of each side wall 12S of the steel pipe column 12 in the case of the steel pipe column 12 provided with the some side wall 12S like a square steel pipe. In the case of a steel pipe column having a side wall with a circular cross section like a round steel pipe, it means a direction along the circumference (circumferential direction).

  The steel pipe column 12 may be provided with a fireproof coating. Furthermore, in the first to third embodiments, 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 to third embodiments of the present invention have been described above. However, the present invention is not limited to such embodiments, and the first to third 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 Pipe Column 12 Steel Pipe Column 12A Steel Pipe Joint 12B Steel Pipe Main Body 12BU Steel Pipe Upper End (Axial End)
12BL Lower end of steel pipe (Axial end)
14 Filled concrete 16 Steel beam (horizontal member)
20 Fireproof reinforcement structure for concrete-filled steel tubular columns 22U Tubular member (buckling suppression member)
22L cylindrical member (buckling suppression member)
32 Cylindrical member (buckling suppression member)
42 Cylindrical member (buckling suppression member)
52 Cylindrical member (buckling suppression member)
60 Fireproof reinforcement structure for concrete-filled steel tubular columns 62 Annular stiffening rib (buckling suppression member)
70 Fireproof reinforcement structure for concrete-filled steel tubular columns 72 Stiffening plate (buckling suppression member)

Claims (3)

A steel pipe column 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 steel pipe column;
A buckling suppression member provided on a side wall of the axial end of the steel pipe main body, and suppressing displacement of the side wall in the out-of-plane direction;
A fireproof reinforcement structure for concrete filled steel pipe columns.   2. The fireproof reinforcing structure for a concrete-filled steel pipe column according to claim 1, wherein the buckling suppression member is opposed to a side wall of an axial end portion of the steel pipe main body with a gap.   The fireproof reinforcement structure for a concrete-filled steel pipe column according to claim 1 or 2, wherein the buckling suppression member is a cylindrical member surrounding an axial end portion of the steel pipe main body.

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