JP2005320720A - Column base structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simply constituted column base by dispensing with a conventional base plate, a conventional anchor bolt, a conventional sleeve, etc.; to save labor for shop fabrication by reducing a material for use in the column base; to enhance workability on a factory job site by easing accuracy management; and to reduce costs. <P>SOLUTION: A steel pipe column 1 such as a closed-cross-section square or circular steel pipe is used as a steel frame column; a cylindrical rising cage 3, which is composed of a main reinforcement 4 and a hoop reinforcement 5, as deformed bars, is used for a concrete foundation 2; the rising cage 3 is protruded from a top surface of the concrete foundation 2 by a predetermined length; an upper protruded part 3B of the rising cage 3 is inserted into the lower part of the steel pipe column 1; concrete 6 is infilled into the lower part of the steel pipe column 1 in such a manner that at least the protruded part 3B is embedded therein; and a protrusion 7, which is protruded inward, is provided on the inner surface of the lower end of the steel pipe column 1, so that a force, which is applied to the column, can be effectively transferred to the foundation 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a column base structure for joining a column having a closed cross section such as a steel pipe and a foundation of a reinforced concrete structure.

  As shown in FIG. 6, in the conventional column base, a base plate 60 is attached to the lower end of the steel column 50 by welding or the like, and the tip of the anchor bolt 61 embedded and fixed in the concrete foundation 51 is formed in a hole previously drilled in the base plate 60. Generally, a method of fixing the steel column 50 to the concrete foundation 51 by inserting, tightening and fastening the nut 62 (for example, Patent Document 1, Patent Document 2, etc.). Further, on the outer periphery of the anchor bolt 61, a rising bar arrangement 63 composed of a birdcage-shaped main bar and a hoop line surrounding the anchor bolt is installed.

Further, in Japanese Patent Application No. 2004-1021, as shown in FIG. 7, a plurality of cast steel sleeves 70 are fixed to the inside of the lower part of the steel column 50 at intervals in the circumferential direction, instead of the base plate, and the concrete foundation 51 The anchor bolt 71 embedded and fixed in the sleeve is inserted into the sleeve 70, high strength mortar or the like is injected into the sleeve and solidified, and the steel column 50 is fixed to the concrete foundation 51.
JP 2003-193559 A Japanese Patent No. 2003-184180

  The conventional column base as described above has the following problems.

  (1) In FIG. 6, it is necessary to fix the base plate to the lower end of the column, and in FIG. 7, it is necessary to fix the sleeve to the inside of the column.

  (2) Since the tip of the anchor bolt is inserted into the bolt hole of the base plate in FIG. 6 and the hole of the sleeve in FIG. 7, advanced technology is required to ensure the installation accuracy of the anchor bolt.

  (3) In FIG. 6, a nut is required to fix the anchor bolt and the base plate. In FIG. 7, in order to fix the sleeve and the deformed steel bar, an operation of filling high strength mortar is required.

  (4) In FIG. 6, since the base plate is larger than the column cross section, the foundation (dimension a of the foundation rising portion in FIG. 6) that receives this is increased. Furthermore, a birdcage-shaped bar arrangement composed of a main bar and a hoop is required on the outer periphery of the anchor bolt. Therefore, the foundation is larger for the pillar.

  The present invention has been made to solve the above-mentioned problems, focusing on the stress transmission function of the column base, changing the way of thinking, and the conventional column base configuration of the base plate, anchor bolt, sleeve, etc. By providing a column base with a simple configuration without using requirements, and reducing the materials used for the column base, labor saving in factory processing, ease of accuracy control and ease of work on the factory floor, cost It aims at reducing.

  The invention of claim 1 of the present invention is a column base structure for fixing a lower portion of a column on a concrete foundation, and includes a closed section column (a steel column with a closed section such as a square steel tube or a circular steel tube), concrete, A protruding main bar made of a deformed steel bar embedded in the foundation, wherein the deformed steel bar protrudes upward from the upper surface of the concrete foundation by a predetermined length upward. Inserted inside, the closed section column is filled with concrete so that at least the deformed steel bar in the column is buried, and a projection projecting inward is provided on the inner surface of the lower end of the closed section column It is a column base structure characterized by being.

  That is, according to the present invention, a column base structure is formed by using a closed cross-section column, a deformed steel bar of a concrete foundation rising main bar, and filled concrete, and a conventional base plate, anchor bolt, sleeve and the like are unnecessary. Further, it is only necessary to provide a simple protrusion on the inner surface of the closed cross-section column that transmits the force to the internal concrete by the supporting pressure when the column is subjected to a tensile force or bending. The rising main bar of the deformed steel bar is provided with a hoop bar, and, for example, 15 times or more of the main bar diameter is embedded in the concrete in both the upper and lower portions of the rising bar bar composed of the main bar and the hoop bar. The inner concrete may be filled so that the deformed steel bar in the closed section column is completely buried, or may be filled up to the upper part of the closed section column.

  According to a second aspect of the present invention, in the column base structure according to the first aspect of the present invention, there is provided a column base structure characterized in that additional cast concrete is placed around the lower part of the closed section column. That is, when the stress of the closed section column is transmitted to the concrete foundation and the concentrated direct pressure and shear force at the boundary surface are relieved, the stress is applied to the concrete foundation around the closed section column as necessary. Placing additional cast concrete. This is because it is known that the concentrated strength at the deep part of the concrete is larger than the concentrated strength at the concrete surface. This reinforced concrete can also be used as a floor.

  According to a third aspect of the present invention, in the column base structure according to the first or second aspect, a protrusion projecting inward is provided on the inner surface of the intermediate portion filled with the concrete of the closed section column. It is a column base structure characterized by that. That is, if necessary, in addition to the protrusion at the lower end of the closed cross-section column, a protrusion is also provided on the inner surface of the intermediate section of the closed cross-section column to increase the bearing pressure on the internal concrete.

  According to a fourth aspect of the present invention, in the column base structure according to any one of the first to third aspects, a chevron is provided at the lower end of the closed section column, and two sides of the chevron are provided. A column is characterized in that a projection is constituted by a vertical side located inside the column, and a positioning member for positioning the closed section column on the concrete foundation is constituted by a horizontal side protruding outside the column. It is a leg structure.

  That is, the projections at the lower end and middle of the closed cross-section column can be formed by fixing square steel, angle steel, flat steel, striped steel plate, etc. on the inner surface of the column by welding, etc. Using a chevron such as chevron steel and chevron steel, place one vertical side along the inner surface of the column and fix it with welding or bolts, use this vertical side as a protrusion, and the other side outside the column It is preferable to make it project horizontally and use this horizontal side as a positioning plate when building a pillar.

  According to a fifth aspect of the present invention, in the column base structure according to any one of the first to third aspects, a chevron is provided on the outer side of the lower portion of the closed cross-section column. The vertical side of the two sides is attached to the outer surface of the column, and the horizontal side that protrudes outward constitutes a positioning member that positions the closed section column on the concrete foundation, and is attached to the lower inner surface of the closed section column. The column base structure is characterized in that a projection is formed by the provided plate material.

  That is, in the case of using angle-shaped hardware, it can be arranged on the outer periphery of the lower part of the closed cross-section column. In this case, a plate material such as flat steel is attached to the lower inner surface of the closed cross-section column. The angle metal and the plate material may be fixed by welding or the like, but it is preferable that the vertical side of the angle metal and the plate material such as flat steel are bolted together with the column side plate interposed therebetween. In this way, when the angle-shaped hardware is arranged outside the column, the stability at the time of installation of the closed section column is good, and the supporting pressure on the concrete foundation can be reduced when the compression force of the column is large.

  According to a sixth aspect of the present invention, in the column base structure according to any one of the first to fifth aspects, the length of the deformed steel bar inserted into the inside of the closed section column is the diameter of the steel bar. It is a column base structure characterized by being 15 times or more. That is, the adhesion between the deformed steel bar in the closed section column and the internal concrete is secured, and when the column is pulled or bent, the force can be sufficiently transmitted to the concrete foundation.

  According to a seventh aspect of the present invention, in the column base structure according to any one of the first to sixth aspects, the deformed bar is provided with a hoop, and the deformed bar and the hoop Is a column base structure characterized by being bound by a binding wire (wire or the like), and a metal adhesive (epoxy resin-based metal adhesive or the like) is impregnated and solidified in the binding portion.

  That is, in order to increase the degree of fixation with respect to the bending stress applied to the column, the main bar and the hoop bar made of deformed steel bars are bound with a wire or the like, and the intersection is fixed with a metal adhesive. When the main bar is subjected to tensile or compressive force, the hoop bar fixed in the direction perpendicular to the axial direction of the main bar is fixed to the concrete, so the main bar will not adhere and become difficult to extend. Since the rotational deformation is restricted, the degree of fixation increases. It is not necessary to fix all the hoops with a metal adhesive, and it is effective to simply fix a plurality of hoops with a metal adhesive.

  In general, in order to fix a column to the foundation, the force of the column base must be transmitted to the foundation via an anchor material. Therefore, in the past, it was necessary to fix anchor materials such as anchor bolts on the basis and fix them to the pillars. Therefore, a base plate is used or a cylindrical sleeve fixed to a column is used.

  On the other hand, in the present invention, instead of the anchor bolt, the rising main bar embedded in the concrete foundation is extended and inserted into a closed section column (hereinafter referred to as a tubular body), and concrete is placed inside the tubular body. To fix the pillar and concrete foundation. When a tensile force acts on such a column base, the tensile force is transmitted from the protrusions on the inner surface of the tube to the internal concrete, and is also transmitted to the internal concrete by the adhesion and frictional force between the wall of the tube and the concrete. And the tensile force is transmitted to the concrete foundation as the tensile force of the main bars by the adhesion force and friction force of concrete. Shear force is transmitted to the concrete foundation through a columnar reinforced concrete section at the boundary between the column and foundation. When compressive force acts, it is transmitted to the internal concrete by the adhesion and frictional force between the inner wall of the tube and the concrete, and this compressive force is transmitted as it is to the concrete foundation. The compressive force applied to the tube directly supports the concrete foundation. The shear force is constrained by the cast-in-place concrete, but even in the case of a fully exposed column base, there is a frictional force of 40% of the support pressure on the outer periphery of the tube in addition to the columnar reinforced concrete section at the boundary between the column and the foundation. Communicated to the foundation.

  In addition, against the bending stress of the column base due to the bending moment, a bearing reaction force is applied to the internal concrete in the horizontal direction. Therefore, in the main reinforcement on the tension side, in addition to the adhesive force and frictional force between the pipe wall and the concrete, The supporting pressure of the protrusion is transmitted to the internal concrete, and a tensile force is generated in the main bar due to the adhesion and frictional force between the main bar and the concrete, and is transmitted to the concrete foundation. On the compression side, the support pressure part at the lower end of the tube gives compressive force to the concrete foundation, so that the bending moment applied to the column is transmitted to the concrete foundation. Against the shearing force, the exposed column base is also resisted by the shearing strength of the reinforced concrete section and the sliding strength of the bearing part at the lower end of the pipe (generally 40% of the bearing part).

  Since the column base structure of the present invention is configured as described above, it has the following effects.

  (1) Instead of anchor bolts, it is a structure in which the rising main reinforcement embedded in the concrete foundation is extended and inserted into the pipe of a closed section column, and concrete is placed inside this pipe, so The degree of processing is extremely small.

  (2) A simple column base structure with deformed steel bars and internal concrete can reliably transmit the axial force, bending moment and shear force acting on the column base to the concrete foundation. With respect to the bending stress of the column base, a horizontal reaction force is applied to the internal concrete, so a vertical friction force is generated, and the column tube and the internal concrete are integrated. Therefore, advanced technology is not necessary because the purpose can be achieved by filling concrete.

  (3) Since the outer width of the riser bar inserted into the closed cross-section column is 5 cm or more smaller than the inner diameter of the column, the installation accuracy of the rebar bar may be the construction accuracy of a normal reinforced concrete structure. If a reinforcing bar is set up from the foundation bottom, there is no need for a support structure to support the anchor as in the conventional method, and it can be implemented with universal technology.

  (4) The tensile force applied to the column or the stress borne by the tube of the column is provided on the inner surface of the tube so that the protrusion can be easily transferred to the internal reinforced concrete by bearing pressure against the inner concrete and friction between the inner wall of the tube and the concrete. However, this is a light device and is simpler than conventional fixing of a base plate or a sleeve.

  (5) By attaching the vertical side of the angled hardware to the inside of the column as a protrusion on the lower end, or attaching the angled hardware to the outside and fixing the inner flat steel etc. as a protruding hardware by bolting etc., the horizontal side of the angled metal Can be positioned with a temporary dowel or mechanical anchor as a positioning plate, and the column tube can be easily installed on the foundation surface. Further, since the ground contact surface of the angle-shaped hardware has an area with respect to the compressive force, there is an effect of reducing the local support pressure of the ground contact surface to the foundation. Further, since the inserted reinforcing bar bears the tensile force generated by the bending of the column base, the anchor bolt is not required unlike the conventional base plate type, and therefore no out-of-plane bending stress due to the reaction force of the anchor bolt is generated.

  (6) Summarizing the above, according to the present invention, a column base structure with the least amount of material, the clearest force transmission mechanism, and no need for advanced technology can be obtained. In comparison, the cost can be reduced by 30 to 50%.

  Hereinafter, the present invention will be described based on the illustrated embodiments. FIG. 1 is a horizontal sectional view, a front view, and a vertical sectional view showing a basic configuration of a column base structure of the present invention. In the present invention, a steel pipe column 1 such as a square steel pipe or a circular steel pipe having a closed cross section is used as a steel column. As the concrete foundation 2, a cylindrical or square tubular rising reinforcing bar 3 composed of a deformed steel bar main bar 4 and a hoop bar 5 is used, and the rising reinforcing bar 3 is set to a predetermined length from the upper surface of the concrete foundation 2. The upper protruding portion 3B of the rising reinforcing bar 3 is inserted into the lower part of the steel pipe column 1, and the concrete is filled in the lower part of the steel pipe column 1, and the conventional base plate, anchor bolt, sleeve Etc. are unnecessary. Moreover, the protrusion 7 which protrudes toward an inside is provided in the inner surface of the lower end part of the steel pipe column 1, and stress can be effectively transmitted to the internal concrete 6 by the supporting pressure as will be described in detail later.

  The concrete 6 is filled so that at least the upper protruding portion 3B of the rising reinforcing bar 3 is completely buried. Concrete 6 may be filled up to the top of the steel pipe column 1. The concrete 6 may be filled from an inlet provided on the side surface of the steel pipe column 1 or may be filled from the upper part of the steel pipe column 1. The length of the main reinforcement (deformed bar) 4 embedded in the concrete 6 is at least 15 times the diameter of the bar, ensuring adhesion between the deformed bar 4 in the steel pipe and the internal concrete 6, and the column is tensioned or bent. When received, the force can be sufficiently transmitted to the concrete foundation 2. In addition, the outer diameter of the rising reinforcing bar 3 is determined so that a gap of 5 cm or more is formed between the inner surface of the steel pipe column 1 and the main reinforcing bar 4, and the installation accuracy of the rising reinforcing bar 3 is set to a normal reinforced concrete construction. Let accuracy.

  Further, a fixing metal 8 as a bearing plate is attached to the main reinforcing bar (deformed bar) 4 of the lower embedded part 3A of the rising reinforcing bar 3 embedded in the concrete foundation 2 so as to increase the fixing degree. The fixing metal 8 is formed by combining, for example, a cylinder and a disk, is inserted through the main reinforcement 4, and is fixed at a predetermined position with a mortar grout, an adhesive, or the like. The position of the fixing metal 8 is about 15 times the diameter of the reinforcing bar from the top surface of the concrete foundation 2 and is used as a fixing fixing point with respect to the tensile force of the main reinforcing bar 4 so that the effect of increasing the rotational rigidity against the bending stress of the column base can be obtained. To.

  Further, in order to increase rotational rigidity, the intersection of the main bar (deformed bar) 4 and the hoop bar 5 is bound with a wire or the like, and an epoxy-based metal adhesive is impregnated and solidified in the bound part, so that the main bar 4 and the hoop bar The intersection of 5 is fixed firmly. Since such an intersection is fixed equivalent to welding, the hoop bar 5 orthogonal to the axial extension of the main bar 4 is restrained by the concrete, and the fixing effect of the rising reinforcing bar 3 on the concrete is fixed. The rotational rigidity can be improved. This bonding method can be applied not only to the concrete foundation but also to the steel pipe column. Further, if the main reinforcement 4 and the hoop reinforcement 5 are fixed firmly with an adhesive, the rising reinforcing bar 3 itself becomes a rigid body, and when the concrete is placed after the rising reinforcing bar 3 is installed, the impact after the concrete is placed Because the deformation is small, it is easy to maintain the installation accuracy.

  FIG. 2 shows the arrangement and various forms of protrusions. As shown in FIG. 2 (b), in addition to the protrusion 7 at the lower end, there is an upper protruding portion 3B or concrete 6 as necessary. You may provide the protrusion 9 in the inner surface in the intermediate part of the steel pipe pillar 1 to perform. In addition, you may make it reinforce by providing the hoop 10 made from a steel plate in the upper end part of the upper protrusion part 3B of the rising reinforcement bar 3, or the boundary part of 3 A of lower embedding parts, and the upper protrusion part 3B.

  FIGS. 2 (c) and 2 (d) are examples in which a chevron cross section steel material 11 or an angle steel 11 'is used for the projection 7 at the lower end, and one side is arranged along the inner surface of the lower end of the steel pipe column 1, and welding is performed. Twelve bolts and nuts 13 are joined. In the case of welding, a positioning temporary bolt hole 14 for welding is provided, and welding is performed by attaching a bolt. The bolt may be removed after welding. In the case of bolt joining, a filler 15 may be interposed. A protrusion 7 is formed at a vertical side 11 a located inside the steel pipe column 1.

  The other horizontal side 11b protrudes to the outside of the steel pipe column 1 and can be used as a positioning plate for the steel pipe column 1. In addition, this horizontal side 11b also has the effect of reducing the bearing pressure of the ground contact surface to the concrete foundation 2 of the steel pipe column 1. As shown in FIGS. 2 (a) and 2 (b), a positioning hole 16 is formed in the horizontal side 11b, and a dowel (round steel is embedded with a resin adhesive and fixed from the upper surface of the concrete foundation 2 and fixed. The steel pipe column 1 is positioned by inserting a mechanical anchor into the positioning hole 16. After positioning, dowels etc. are removed. As shown in FIG. 2 (a), an unnecessary portion (shaded portion) of the horizontal side 11b can be deleted.

  FIGS. 2 (e) and 2 (f) are examples in which an angle metal 11 such as an angle steel is attached to the outside of the steel pipe column 1. In this case, the vertical side 11a of the angled hardware 11 is attached to the lower outer surface of the steel pipe column 1, a plate material 19 such as flat steel is attached to the lower inner surface of the steel pipe column 1, and the vertical side 11a and the plate material 19 are connected to the steel pipe column 1. Are joined with bolts and nuts 13. Bolt joining is preferable, but welding or the like may be used. The horizontal side 11b of the angle-shaped metal object 11 is used as a positioning plate with its lower surface aligned with the lower end surface of the steel pipe column 1. The plate material 19 is used as the protrusion 7. When the angle hardware 11 is arranged outside in this way, as shown in FIG. 2 (e), the angle hardware 11 can be installed in a square shape in a plan view, and when the steel pipe column 1 is installed, When it is stable and the axial compression force of the column is large, it contributes to the reduction of the bearing pressure on the concrete foundation 2.

  FIG. 2 (g) is an example in which square steel is used for the projection 7 at the lower end, and this square steel is joined to the inner surface of the steel pipe column 1 by upper and lower welds 12. The lower weld 12 finishes its lower surface smoothly. This square steel can also be used for the projection 9 in the middle part.

  FIG. 2 (h) shows an example in which angle steel is used for the projection 9 at the middle part, and the upper and lower flange tips are joined to the inner surface of the steel pipe column 1 by the upper and lower welds 12, and the corners are projected inward.

  FIG. 2 (i) is an example in which a striped steel plate 17 is used for the projection 9 in the middle part, and the steel pipe column 1 is formed by the striped steel plate 17, or the striped steel plate 17 is partially attached to the inner surface of the steel pipe column 1. Then, it is fixed by slot welding 18. The protrusion 7 at the lower end is formed as a protrusion protruding inward and outward by horizontally welding a steel plate to the lower end surface of the steel pipe column.

  When the structure receives a horizontal force such as an earthquake or wind pressure, a column erected on the reinforced concrete generates a reaction force that balances the stress applied to the column base in order to stabilize the structure. FIG. 3 (a) shows a part of the frame structure. The column 1 is deformed as indicated by a dotted line, and the bending moment applied to the column is distributed as indicated by a number of horizontal lines. The stress applied to the column base at this time is a bending moment, a shearing force, and an axial compressive force acting on the column. FIG. 3 (b) shows a part of the construction surface in which a streak is provided on the pillar 1. When a horizontal force such as an arrow is applied to the upper frame, a tensile force is generated on the left column, and a tensile force is also generated on the staggered difference. Accordingly, the reaction force from the foundation generates a tensile reaction force and a shear reaction force in which vertical and horizontal components of different tensile forces are added as shown in the figure. For the right column in the figure, a reaction force is generated according to the law of action and reaction according to the stress of the left column. In short, since an axial force, a bending moment, and a shearing force act on the column base, a mechanism for transmitting these stresses to the foundation is necessary.

  The stress transmission mechanism of the column base structure according to the present invention is as shown in FIG. 4 (in the case of a column with a straight frame in FIG. 3B). That is, as shown in FIG. 4 (a), when a tensile force acts on the steel pipe column 1, the tensile force is transmitted from the lower end projection 7 (intermediate projection 9) to the internal concrete 6. It is transmitted to the inner concrete 6 by the adhesion and friction force between the inner wall and the concrete, and the tensile force is transmitted to the concrete foundation 2 as the tensile force of the main reinforcement (deformed bar) 4 due to the adhesion and friction force of the deformed steel bar 4 and concrete 6 Is done. The shearing force is transmitted to the concrete foundation 2 through a columnar reinforced concrete section at level A at the boundary between the steel pipe column 1 and the concrete foundation 2.

  As shown in FIG. 4 (b), when a compressive force is applied to the steel pipe column 1, it is transmitted to the inner concrete 6 by the adhesion and frictional force between the inner wall of the steel pipe column 1 and the concrete, and the compression transmitted to the inner concrete 6. The force is transmitted to the concrete foundation 2 as it is. The compressive force applied to the steel pipe column 1 directly supports the concrete foundation 2. Regarding the shear force, in addition to the column-shaped reinforced concrete section at level A, 40% of the support pressure on the outer periphery of the steel pipe column 1 is generally evaluated as the shear strength.

  In addition, when receiving bending moment, axial force, and shear force, the stress transmission mechanism is as shown in FIG. 5 (in the case of the rigid frame column in FIG. 3A). As shown in FIG. 5A, when a horizontal force of Q is applied to the inflection point 0, the bending moment of the column base becomes DA (M). Since the steel pipe column 1 tends to be turned to the right by Q, the internal reinforced concrete 6 is resisted by a force Qo as shown in FIG. 5 (b). The magnitude of this Qo is a bending moment distribution of the steel pipe column as shown in FIG. 5 (b) since there is almost no bending resistance at the lower boundary of the steel pipe column 1 itself. Moreover, in order for a bending moment to transfer to internal reinforced concrete, it transmits by the compressive force and frictional force which the supporting pressure of the projection part 7 and the column inner wall give to the internal concrete 6. The transmitted force becomes the tensile force of the main muscle 4. On the other hand, a compression field is formed toward the bearing portion in FIG. Therefore, at the boundary portion, when the bending moment M is borne by the tension rebar 4 and the bearing portion receiving the compressive force, the shearing force is resisted by the friction of the bearing portion, and when the additional cast concrete 20 is placed, Restrain the shear force in the region above the part. That is, when the stress shown in FIG. 5 (a) occurs, the stress burden as shown in FIG. 5 (b) and FIG. 5 (c) occurs.

  In the column base structure of the present invention, it can be said that the tubular body is fitted with a reinforced concrete column shape protruding from the concrete foundation above the boundary. At the boundary, the boundary between the steel pipe column 1 and the concrete foundation 2 is a distribution of reaction force when subjected to bending as shown in FIG. 5 (d). In the main tension bar 4, in addition to the adhesion force between the inner wall of the steel pipe column 1 and the concrete, the supporting pressure of the projection 7 at the lower end (protrusion 9 at the middle part) is transmitted to the internal concrete 6 and is pulled by the adhesion force between the main bar and the concrete. A force is generated in the main muscle 4. Further, as shown in FIG. 5 (c), a compression field is generated, and the bearing section at the lower end of the steel pipe column 1 on the opposite side gives a compressive force to the concrete foundation 4, so that the bending moment applied to the steel pipe column 1 is the concrete foundation. 2 is transmitted. The axial compressive force applied to the steel pipe column 1 acts to reduce the tensile force of the tensile main reinforcement 4 and increase the compressive force No of the bearing portion.

  The shear force is resisted by the shear strength of the reinforced concrete shown in FIG. 5 (d) and the slip strength of 40% of the bearing section. When this resistance is smaller than the acting shear strength, the cast concrete 20 may be laid up from the boundary level. This reinforced concrete 20 can be used as a floor.

  Needless to say, the present invention is not limited to the illustrated examples.

BRIEF DESCRIPTION OF THE DRAWINGS It is embodiment which shows the fundamental structure of the column base structure of this invention, (a) is a horizontal sectional view, (b) is a front view side view, (c) is a vertical sectional view. The arrangement and various forms of protrusions used in the present invention are shown, (a) is a horizontal sectional view of the column base part, (b) is a vertical sectional view of the column base part, (c) and (d) are (E) and (f) are horizontal cross-sectional views when the angled hardware is placed outside the column, vertical cross-sectional views when angled hardware is used for the protrusion, and (g) uses square steel for the protrusion. (H) is a vertical cross-sectional view when angle steel is used for the protrusion, and (i) is a vertical cross-sectional view when striped steel plate is used for the protrusion. It is a front view which shows the stress state when a horizontal force acts on a column beam frame, (a) is a case of a rigid frame frame, and (b) is a case of a staggered frame. It is a vertical sectional view showing a stress transmission mechanism (when receiving an axial force / shearing force) in the present invention, (a) is a tensile force, and (b) is a compressive force. The stress transmission mechanism in the present invention (when receiving bending moment, axial force and shearing force) is shown, (a) is a front view showing the stress applied to the column base, and (b) is the bending moment applied to the tube. (C) is a vertical cross-sectional view showing the stress applied to the filled concrete, and (d) is a horizontal cross-sectional view showing the cross-section and the stress sharing portion at the boundary surface. The column base using the conventional base plate is shown, (a) is a vertical sectional view, (b) is a horizontal sectional view. FIG. 2 shows a column base using a conventional sleeve, where (a) is a front view, (b) is a horizontal sectional view, and (c) and (d) are vertical sectional views before joining.

Explanation of symbols

1. Steel pipe column (closed section column)
2 …… Concrete foundation 3 …… Standing reinforcing bar 3A… Lower embedded part of rising reinforcing bar 3B… Upper protruding part of rising reinforcing bar 4 …… Main bar of deformed steel bar 5 …… Hoop bar 6 …… Inner concrete 7 …… Protrusion (Lower end)
8 …… Fixing hardware 9 …… Protrusions (intermediate part)
DESCRIPTION OF SYMBOLS 10 ... Steel plate hoop 11 ... Angle section steel 11 '... Angle steel 11a ... Vertical side 11b ... Horizontal side 12 ... Welding 13 ... Bolt and nut 14 ... Positioning temporary bolt hole 15 ... Filler 16 ... Positioning hole 17 ... Striped steel plate 18 ... Slot welding 19 ... Plate material 20 ... Reinforced concrete

Claims (7)

It is a column base structure for fixing the lower part of the column on the concrete foundation,
A deformed steel bar projecting portion, which is composed of a closed cross-section column and a rising main bar made of a deformed steel bar embedded in a concrete foundation, protrudes upward from the upper surface of the concrete foundation by a predetermined length, It is inserted into the inside of the lower part of the closed section column, and the inside of the closed section column is filled with concrete so that at least the deformed steel bar in the column is buried, and the inner surface of the lower end part of this closed section column is internally inserted. A pedestal structure characterized in that a protrusion protruding in the direction is provided.   2. The column base structure according to claim 1, wherein additional cast-in concrete is placed around a lower portion of the closed section column.   The column base structure according to claim 1 or 2, wherein a protrusion projecting inward is provided on an inner surface of an intermediate portion filled with concrete of a closed-type cross-section column. .   In the column base structure according to any one of claims 1 to 3, a mountain-shaped hardware is provided at a lower end of the closed-section cross-section column, and a vertical position located inside a column of two sides of the mountain-shaped hardware. A column base structure characterized in that a protrusion is constituted by the side and a positioning member for positioning the closed section column on the concrete foundation is constituted by a horizontal side protruding outside the column.   In the column base structure according to any one of claims 1 to 3, a chevron is provided outside the lower part of the closed cross-sectional column, and a vertical side of the two sides of the chevron is a column. A positioning member that positions the closed section column on the concrete foundation is formed by a horizontal side that is attached to the outer surface and protrudes to the outside of the column, and a protrusion is formed by a plate material that is attached to the inner surface of the lower part of the closed section column Column base structure characterized by being made.   The column base structure according to any one of claims 1 to 5, wherein the length of the deformed steel bar inserted into the closed cross-section column is 15 times or more the diameter of the steel bar. Column base structure. The column base structure according to any one of claims 1 to 6, wherein the deformed steel bar is provided with a strip, the deformed steel bar and the strip are bound by a binding wire, and the bonded portion is metal-bonded. Column base structure characterized in that the material is impregnated and solidified.

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