JP2005256424A - Steel frame exposed column base structure - Google Patents

Abstract

[PROBLEMS] To improve the seismic performance of a column base in a steel-exposed type column base structure, simplify the construction, and reduce the construction period and cost.
In the fixing structure of the present invention, a foundation beam lower reinforcement 2, a foundation beam upper reinforcement 3, and a rib reinforcement 4 are embedded in a foundation concrete 1, and a U-shaped hoop reinforcement binding reinforcement in a column-shaped portion 5. 6, the hoop bar 7 and the anchor bolt 8 are arranged, the upper end of the anchor bolt 8 is inserted into the insertion hole 11 of the base plate 10 connected to the column member 9, and the nuts 12 and 13 are attached to the upper part of the anchor bolt 8. The initial tension is introduced into the anchor bolt 8 by tightening the nuts 12 and 13, thereby fixing the base plate 10 to the foundation concrete 1. A non-shrinkable grout material 14 is filled between the base plate 10 and the foundation concrete 1.
[Selection] Figure 1

Description

  The present invention relates to a steel frame exposed column base structure.

  The Great Hanshin Earthquake caused damage to many steel structures such as collapses and wrecking, some of which were due to damage to the exposed steel column bases. These damages have been reported to be due to anchor bolt products such as breakage of anchor bolts in steel-frame exposed column bases, slipping out of foundation concrete, and related design and construction defects. In response to this damage, the Ministry of Land, Infrastructure, Transport and Tourism (former Ministry of Construction) issued a notification in December 1995 regarding the design of column bases for steel structures (see Non-Patent Document 1). It is described in “2001 edition of structural technical standards for buildings” published by the Japan Architecture Center. Against this background, basic research has been conducted on the stress transferability and strength of steel-exposed column base structures.

  As shown in FIG. 3, in the conventional steel frame exposed column base structure, the upper surface corner of the base plate 30 is connected to the upper end of the anchor bolt 32 by tightening the nut 31. A plate-shaped fixing plate 33 is sandwiched between two nuts 34 and 35 and fixed to the lower end portion of the anchor bolt 32.

  As shown in FIG. 4, external force such as bending stress M, axial compression force N of the column, and shear force Q is applied to the column member 36. The shearing force Q is transmitted to the foundation concrete 37 by frictional resistance between the lower surface of the base plate 30 and the top end surface of the foundation concrete 37.

  When bending stress M is applied to the column member 36, the lower surface on one side of the base plate 30 becomes a compression region, and a compression reaction force QP acts from the basic concrete 37 toward the base plate 30. A tensile reaction force QF that resists the pulling force QR to be pulled out acts on the anchor bolt connected to the opposite end of the base plate, and a bending stress is generated by the compression reaction force QP and the tensile reaction force QF opposite to each other. M is transmitted to the foundation concrete 37.

  The tensile reaction force QF acting on the anchor bolt 32 varies depending on the magnitude of the axial compression force N of the column member 36. A large bending stress M is applied to the column member 36 due to the horizontal force of the entire building structure, such as during an earthquake or storm, and a large tensile reaction force QF acts on the anchor bolt 32 on the tension side.

  Therefore, since anchor bolts are an important factor that affects the plastic deformation capacity of the column base, SS400, SS490, etc. of general structural rolled steel materials having plastic deformation capacity are used. Furthermore, after installing the anchor bolt 32, a reinforcing bar having a cross-sectional area and a strength equal to the product of the cross-sectional area of the anchor bolt and the strength thereof is arranged as a main reinforcing bar 38 to form a reinforced concrete column cross section.

  Further, when the tensile force QR of the anchor bolt 32 increases and becomes too large, a force is generated that the fixing plate 33 tries to peel a part of the foundation concrete 37 upward, and as shown by a dotted line in FIG. 37 may cause a cone-like peeling failure.

  In order to suppress this cone-like fracture, it is necessary to improve the bearing strength of the foundation concrete 37 against the fixing plate 33, that is, the strength of the tensile force reaction force QF of the anchor bolt 32.

Therefore, the anchor bolt 32 is lengthened, and the fixing length at which the fixing plate 33 is installed is set to be 20 times or more the anchor bolt diameter (see Non-Patent Document 2).
1456 Article 1456 related to the Building Standards Act Explanation of steel pipe structure design and construction guidelines, Architectural Institute of Japan

  However, in the case where both anchor bolts and column reinforcements are conventionally arranged, it is difficult to arrange underground beams because a large amount of thick reinforcing bars are arranged in the vertical column reinforcement. There was a problem that it took time for construction.

  Also, if the anchor bolt is too long, when the tension force acts on the column and the force to pull out the anchor bolt is applied, the anchor bolt will be stretched and the tightening nut will loosen. There was a problem that the degree of fixation was low.

  Therefore, the present invention has been made in view of the above problems, and in the steel frame exposed column base structure, the seismic performance of the column base is improved, the construction is simplified, the construction period is shortened, and the cost is reduced. Provide a fusing structure.

  The steel-exposed-type column base structure of the present invention that solves the above problems includes an anchor bolt that is embedded in the foundation concrete of the column mold portion that serves as the foundation of the column, and an upper portion of the anchor bolt projects from the top surface of the foundation concrete, and the anchor bolt A base plate which is inserted on the foundation concrete and is integrated with a pillar of the building on the top, a nut for fastening and fixing the base plate between the foundation concrete and a horizontal plate in the foundation concrete A steel exposed column base structure for fixing a pillar of the building on the foundation concrete via the base plate, and serving as a support body for bundling the hoop bars. A bundling laying bar is arranged outside and parallel to the anchor bolt, and the hoop barb is placed in front so as to surround the hoop barbing laying barb. And wherein placing the outer peripheral end portion of the pillar-shaped portion (the first invention).

  The exposed steel column base structure according to a second aspect of the present invention is characterized in that, in the first aspect, the hoop muscle bundling laying bar is arranged at an outer peripheral end of the column type part.

  The steel frame exposed column base structure according to a third aspect of the present invention is characterized in that, in the first or second aspect of the invention, a U-shaped bar is used for the hoop muscle binding erection.

ADVANTAGE OF THE INVENTION According to this invention, in a steel frame exposed type column base structure, it becomes possible to improve the earthquake resistance performance of a column base, to simplify construction, and to reduce a construction period and cost.
In the present invention, since the anchoring strength of the anchor bolt is increased by arranging the hoop reinforcement at the outer peripheral end of the columnar section, it is not necessary to arrange the column main reinforcement. Therefore, there is no complicated bar reinforcement of the column main bar which has been done in the conventional column base, labor saving work can be done, the amount of reinforcing bars to be used can be reduced, the construction time can be shortened, and the concrete filling ability can be reduced. It becomes easy and the quality can be increased.

In addition, since the hoop reinforcement bundling bars use thin objects, it is easy to place underground beams, shortening the work period and reducing costs.
And it becomes possible by using the U-shaped hoop reinforcement bundling reinforcement to improve the anchoring force of the anchor bolt to the columnar part concrete.
In addition, the U-shaped hoop tying tie bar is economical because it is easily available and cheap, and has the advantage of being easy to manage because it does not mix with other materials.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall side view of a fixing structure of an exposed fixed column base according to an embodiment of the present invention. As shown in FIG. 1, the fixing structure of this embodiment has a foundation beam 1 with a bottom beam 2, a foundation beam 3, and a stirrup 4 embedded therein, and a column-shaped portion 5 for binding a U-shaped hoop. The laying bar 6, the hoop bar 7, and the anchor bolt 8 are arranged, the upper end of the anchor bolt 8 is inserted into the insertion hole 11 of the base plate 10 connected to the column member 9, and the nut 12 13 is attached and the nuts 12 and 13 are tightened to introduce an initial tension to the anchor bolt 8, thereby fixing the base plate 10 to the foundation concrete 1. A non-shrinkable grout material 14 is filled between the base plate 10 and the foundation concrete 1.

  The construction method is shown below. First, the fixing plate 15 is screwed to the anchor bolt 8 to prevent the cone-like destruction, and the lower surface level of the fixing plate 15 is moved from the top end level of the foundation concrete 1 to a predetermined fixing length.

In the present embodiment, for example, a screw joint of material SD490 is used as the anchor bolt. According to the 2001 "Structure Related Technical Standards for Building Structures", the anchor bolts have the ability to extend as long as the effective cross-sectional area of the screw is equal to or greater than that of the shaft. It can be said that it is an anchor bolt (hereinafter abbreviated). Therefore, the screw joint reinforcing bar has an elongation capability because the cross-sectional areas of the screw portion and the shaft portion are substantially equal, and is effective as an anchor bolt.
In this embodiment, as the fixing plate, for example, a plate nut (trade name of Tokyo Steel Co., Ltd., a general rating of Nippon Building Center has been acquired) is used.

Then, as shown in FIG. 1, the lower end of the threaded reinforcing bar 8 as an anchor bolt is screwed and fixed to a nut 17 welded and fixed to the end of the lower positioning guide 16. The upper end side is inserted into an insertion hole of an upper positioning guide (not shown) and temporarily fixed with a washer and a nut, and the verticality and horizontality of the threaded bar 8 are confirmed and adjusted.
Then, the screw joint reinforcing bar 8 is set at the column installation position on the foundation bottom (discard) concrete, and the lower positioning guide 16 is fixed to the foundation bottom (discard) concrete with bolts 18 and nuts 19.
The U-shaped hoop muscle bundling reinforcement 6 is such that both ends of the U-shape are directed upward, and each vertical line portion of the U-shape is a corner of the column-shaped section of the column-shaped portion 5. Arrangement is made so that the U-shaped hoop reinforcement bundling reinforcement 6 is located on the outer peripheral side of the threaded reinforcing bar and is opposed to the reinforcement.
Then, a predetermined number of hoops 7 are arranged so as to surround the U-shaped hoop reinforcement bundling reinforcement 6 at the four corners of the columnar part 5.

  After fixing the screw joints 8 and hoops 7 on the foundation bottom (discard) concrete, confirm that the lower surface level of the plate nut 15 is at a predetermined fixing length from the top edge level of the foundation concrete 1 and The plate nut 15 is fixed by filling a non-shrinkable grout material between the nut 15 and the screw joint reinforcing bar 8.

Thereafter, the concrete is cast to a predetermined level to form the foundation concrete 1, and when the concrete is hardened, the upper positioning guide is removed and a horizontal level is obtained with a mortar (commonly known as a wharf). After the mortar (commonly known as the wharf) has hardened, the pillars are built.
The column material 9 to which the base plate 10 is connected is carried in, and the insertion hole 11 of the base plate 10 is inserted into the screw joint reinforcing bar 8 to stand.
The column material is, for example, a square steel pipe, a round steel pipe, an H-shaped steel, and the like, and the base plate 10 is made of cast steel, forged steel, steel plate, or the like.
After the column material 9 is erected, the non-shrinkable grout material 14 is filled between the base plate 10 and the foundation concrete 1. Further, a non-shrinkable grout material 14 is filled in the gap between the screw joint reinforcing bar 8 and the insertion hole of the base plate 10 and the gap between the base plate and the nut.

  Then, the base plate 10 is tightened by the nuts 12 and 13, and the non-shrinkable grout material 14 overflows from the gap between the base plate 10 and the nut 12. After confirming that the gap between the insertion hole of the base plate 10 and the gap between the base plate 10 and the nut 12 is sufficiently filled, initial tension is introduced to the screw joint 8 to fix the base plate 10 to the foundation concrete 1.

  Therefore, according to the structure of the embodiment of the present invention, it is not necessary to have the sophistication that a specialized column base construction company raises the U-shaped hoop muscle bundling muscle and the hoop muscle. In addition, there is no need to meet and rework by a specialized column base construction company to ensure accuracy when laying the foundation and placing concrete. This eliminates the need for technicians for each type of work and simplifies process management.

  FIG. 2 shows an arrangement method of the U-shaped hoop muscle bundling laying bars according to the embodiment of the present invention, and is an arrangement example of (a) an H-shaped column and (b) a rectangular column.

  As shown in FIG. 2, the U-shaped hoop reinforcement bundling reinforcement 6 can resist the U-shaped bottom plate portion in the direction in which the force acts in consideration of the axial direction applied to the opposite axis of the screw joint reinforcing bar 8. Such an arrangement is possible.

  As shown in FIG. 2 (a), in the case of using an H-shaped column, a plurality of U-shaped hoop muscle binding laying muscles are connected to the direction of the flange of the H-shaped column and both ends of the hoop muscle tying building muscle. By installing so that the straight line connecting the parts is vertical, the adhesion between the foundation concrete and the column base can be improved.

  In addition, as shown in FIG. 2B, in the case of using a square column, two U-shaped hoop muscle binding tie bars are installed so as to cross the diagonal extension of the square column, It is possible to improve the adhesion between the foundation concrete and the column base by setting the installation angle so as to surround the square column with the U-shaped hoop muscle binding laying bar.

  In this embodiment, only three examples of U-shaped hoop muscle bundling laying bars are shown in FIGS. 2 (a) and 2 (b), but they are arranged depending on the shape of the columns and the required strength of the structure. The number of muscles and the location of reinforcement can be changed.

It is a whole side view of the fixation structure of the exposure type fixed column base which concerns on the Example of this invention. The arrangement | positioning method of the U-shaped hoop muscle bundling construction reinforcement which concerns on the Example of this invention is shown, (a) In the case of an H-type column, (b) It is an example of arrangement in the case of a square column. It is a conventional steel frame exposed column base structure diagram. It is a figure which shows the external force and reaction force which act on a column base.

Explanation of symbols

1 and 37 Foundation concrete 2 Bottom beam 3 of the foundation beam Top bar 4 Stirrup 5 Columnar part 6 U-shaped hoop reinforcement tying bar 7 Hoop reinforcement 8 Anchor bolt (= screw joint reinforcement)
9, 36 Column material 10, 30 Base plate 14 Non-shrink grout material 15 Fixing plate (= plate nut)
32 Anchor bolt 33 Fixing plate 38 Main bar

Claims (3)

An anchor bolt that is buried in the foundation concrete of the pillar mold part that becomes the foundation of the pillar, and the upper part protrudes from the top surface of the foundation concrete, and the anchor bolt is inserted on the foundation concrete and placed on the foundation concrete. A base plate integrated with a pillar, a nut for fastening and fixing the base plate between the foundation concrete, and a hoop bar arranged horizontally in the foundation concrete, on the foundation concrete A steel-exposed-type column base structure for fixing the building pillar via the base plate,
A hoop muscle bundling laying muscle serving as a support for bundling the hoop muscles is arranged in parallel to the outer side of the anchor bolt, and the hoop muscle is surrounded by the column shape so as to surround the hoop muscle bundling laying muscle. The steel-frame-exposed-type column base structure characterized by being arranged at the outer peripheral end of the part.   2. The exposed steel column base structure according to claim 1, wherein the hoop muscle bundling laying bar is disposed at an outer peripheral end portion of the column mold portion. The steel-exposed column base structure according to claim 1 or 2, wherein a U-shaped muscle is used for the hoop muscle binding erection muscle.

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