JP2567435Y2 - Pillar hardware - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal used for a column base in a building having a steel structure or a steel reinforced concrete structure.

[0002]

2. Description of the Related Art Generally, a column base in a steel structure or a steel reinforced concrete structure is fixed to an underground beam or a foundation concrete through a metal called a column base metal. FIG. 6 shows an example of a typical fixing structure disclosed in Japanese Patent Application Laid-Open No. H2-256741, in which a column base metal 2 is welded to the lower end of a column 1 and an underground beam is attached by an anchor bolt 4. After the column is erected, a filling mortar 5 is cast over the entire lower surface of the column base fitting 2.

Although this structure is effective for fixing the column base, it cannot sufficiently cope with a recent design method assuming a limit state of a structure, that is, a so-called "limit state design method". In other words, various materials such as cold-rolled materials, welded materials, shaped steel, etc. are currently used as column members, all of which are the lower limit of allowable design stress referred to in the Building Standard Law,
Although it satisfies the so-called "F-value", there are considerable differences in the actual mechanical properties. For example, in the case of cold-rolled materials, there are some variations due to the degree of work. / mm ² may be higher.

[0004] When a column base is regarded as a pin in the limit state of a structure such as an extreme earthquake, if the strength level of the column material is too high, the deformation of the column material is within the elastic range. As a result, an excessive load is transmitted as it is to the column base where there is no margin in design, which may cause a separation between the column base and the foundation concrete, yielding of anchor bolts, crushing of concrete, and the like.

FIG. 3 shows a distribution diagram of moments acting on a steel column / beam structure. In a normal design, the maximum value of the moment applied to the column material occurs at the column base. As shown in FIG. 6, the thickness of the ordinary column base metal must be larger than the flange thickness of the column material, and the relationship between the bending moment acting on the column base and the rotation angle of the column base. Can obtain stable characteristics substantially in the elastic range as shown in FIG. However, assuming a case in which an excessive horizontal force such as a large earthquake acts on the structure and the column base yields in design, the total plastic moment of the column is composed of the column base hardware and the anchor bolt If the total plastic moment of the column base is exceeded, the yield phenomenon of either the column base hardware or the anchor bolt occurs prior to the column yielding. Regardless of whether the column base hardware or the anchor bolt yields, the relationship between the moment generated on the column base and the rotation angle is a slip type as shown in FIG. There is a problem that the performance as a product deteriorates.

As means for avoiding such drawbacks of the column base, according to Japanese Patent Application Laid-Open No. 1-97740, the position where the column acting moment due to the horizontal force is minimized, that is, approximately half of the height to the beam. It has been proposed to place the column pedestal at 1/3 the height. FIG. 7 is a conceptual diagram and a bending moment diagram of the whole building, and FIG. 8 is an enlarged view of a portion A in FIG. According to this idea, the structure of the pillar base itself becomes rational, but the pillar dimensions of the first floor part become large, and there is a drawback in aesthetics,
It is not practical because it is not easy to use as a building.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, and the position of the column base is set to the normal ground level, and any high-strength material can be used as the column. An object of the present invention is to provide a structure of a column base in which a moment larger than designed is not applied to an anchor bolt or a foundation concrete part of the column base.

The present invention is a column base metal having an upper portion welded to a column lower end and a bottom plate portion fixed by an anchor bolt protruding from a base portion, and having a shape corresponding to the column material upward from the bottom plate portion. A pillar base metal having a rising flange portion, forming a cross-section defect near the center in the height direction of the flange portion, and making the strength of the cross-section defect part equal to the design strength of the column material. The cross-section defect portion may be formed by providing one or more horizontal U-shaped grooves on the surface of the flange portion, or by providing a single hole or a plurality of holes arranged in the horizontal direction in the flange portion. The shape may be different for each flange surface.

According to the present invention, by forming a cross-section defect near the center in the height direction of the column base hardware flange portion, plastic deformation is caused in this portion where stable hysteresis characteristics including recovery can be expected. No matter what high-grade material is used for the column, the anchor bolts on the column base and the foundation concrete section are prevented from acting more moment than expected in the design.

[0010]

FIG. 1 shows an embodiment of the present invention. 1 is a pillar, 2
Is a column base metal, 3 is an underground beam on which these are erected, and 4 is an anchor bolt. Numeral 5 is a filling mortar to be filled in the middle between the column base metal and the underground beam. In an actual construction method, a level adjusting mortar or a leveling block is placed in this portion. Are also used, but these are not shown.

As is apparent from comparison with the conventional one as shown in FIG. 6, this pillar base metal has a shape corresponding to the pillar material in the middle of rising from the bottom plate 23 and connecting to the pillar material 1.
That is, if the column material is a rectangular steel pipe, it is characterized in that it has a flange portion 21 having substantially the same cross section as this and a horizontal groove portion 22 is formed near the center in the height direction. The groove 22 is an intentionally formed cross-sectional defect, and a position where plastic deformation first occurs in the column base metal when an excessive external force is applied is specified in this portion. In order to further assure the location of the occurrence, the upper and lower flange portions 21 which are thick sound portions are sandwiched between the groove portions 22, and the upper and lower column members 1 and the bottom plate portion 23 of the hardware are connected via this. Reference numeral 24 denotes a welded joint between the column base metal 2 and the column 1.

The shape of the groove 22 must not cause excessive stress concentration such that it is deformed by normal stress, and is preferably a U-shape having no sharp corners. And
In order to plastically deform the groove portion of the column base metal first in the entire column-base system, the effective cross-sectional area A _e of the column base metal in the groove portion needs to satisfy the following expression. F · A _c = σ _y · 1 / α · A _e (1) where F: F value that defines the material of the entire system, A _c : cross-sectional area of column portion, σ _y : column base The yield point stress of the metal, α: a stress concentration coefficient determined by the shape of the groove, where the left side of the equation (1) is the design strength of the column material, and the right side is the strength of the cross-sectional defect formed in the column base metal flange. .

Since the stress concentration coefficient α in the equation (1) is a value having a wide range based on experience, the calculation result of the effective cross-sectional area A _e of the column base metal in the groove portion is allowed to vary about ± 10%. However, if the effective area _Ae is set to be much larger than the value obtained by the equation (1), the probability of the first plastic deformation occurring at the cross-sectional defect decreases, and the purpose of forming the cross-sectional defect is purposely reduced. On the contrary, if the value is smaller than the value according to the equation (1), the possibility of plastic deformation due to the normal horizontal force increases, which is not preferable.

Since such a cross-section defect is provided in the flange portion of the column base metal, it is a metal-only portion, and is a portion where stable hysteresis characteristics including recovery can be expected. It is effective as a place to cause deformation. As a material of the column base metal, forged steel or cast steel is preferable because the variation in σ _y is small and the weldability is good.

To show a specific design example, the column material has one side D =
This is a square steel tube made of cold-rolled material with a thickness of 350 mm and a thickness of 12 mm. The design F-value is 33 kg / mm ² , and the column base metal is made of cast steel and σ _y = 30
-35 kg / mm ² , flange length H = 175 mm, wall thickness 16 mm, groove width 8 mm, depth 4 mm, U-shape produced plastic deformation in groove as expected in loading test with full-size test piece .

In the above formula (1), the shape of the cross-sectional defect is not limited to the U-shaped groove as long as the shape gives the same effective cross-sectional area. An appropriate number of small-diameter holes arranged in the horizontal direction may be provided. FIG. 2 shows an example in which holes are provided. Reference numeral 25 denotes a hole provided in the flange portion 21 as a cross-section defect portion. The shape of the hole may be any of a circle, an ellipse, and an ellipse.

In the case where the horizontal load condition varies depending on the position of the pillar in the building, such a groove or hole may not be uniform on each surface of the flange, but may have a different shape for each flange surface. Further, when a hole is provided, it is possible to fill the hole with a bolt, a pin, concrete, or the like from the viewpoint of securing buckling strength, and to provide a mechanism for transmitting only a compressive force.

When a normal steel pipe having a circular cross section or an H-shaped steel is used as a column in addition to a square steel pipe, if the flange portion of the column base metal is also formed in a shape corresponding to these, the relationship of the equation (1) is not at all. The same is true.

[0019]

According to the present invention, no matter what high-strength material is used for the column, no moment beyond the design expectation acts on the anchor bolts and concrete part of the column base, and the plastic deformation does not change. Since it occurs in a metal part having stable characteristics, a safe building structure can be realized even in the event of a large earthquake or the like.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of an embodiment of the present invention.

FIG. 2 is a side view showing a configuration of another embodiment of the present invention.

FIG. 3 is a moment distribution diagram of the structure according to the present invention.

FIG. 4 is a graph showing a relationship between a moment and a rotation angle in a column base.

FIG. 5 is a graph showing a relationship between a moment and a rotation angle at a column base.

FIG. 6 is a side view showing an outline of a conventional example.

FIG. 7 is a conceptual diagram and a bending moment diagram showing an outline of another conventional example.

FIG. 8 is an enlarged side view of a portion A in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 pillar 2 pillar base metal 21 flange 22 groove 23 bottom plate 24 welded joint 25 hole 3 underground beam 4 anchor bolt 5 filling mortar

Claims (3)

(57) [Scope of request for utility model registration] An upper part is welded to a lower end of a column material, and a bottom plate part is fixed by an anchor bolt projecting from a base part, wherein the flange rises upward from the bottom plate part in a shape corresponding to the column material. A column base metal member having a portion, a cross-section defect portion is formed near the center of the flange portion in the height direction, and the strength of the cross-section defect portion is equal to the design strength of the column material. 2. The cross-sectional defect portion is formed by providing one or a plurality of horizontal U-shaped grooves on the surface of the flange portion, or by providing a single hole or a plurality of holes arranged in the horizontal direction on the flange portion. The column base hardware described in. 3. The column base metal fitting according to claim 1, wherein the cross-section defective portion has a different shape for each flange surface.