JPH11286945A - Pedestal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric pedestal structure capable using, on eccentric side, an anchor bolt having the same diameter as an anchor bolt used on non- eccentric side, and resistant to a bending moment of the same degree as a non-eccentric pedestal structure. SOLUTION: This pedestal structure comprises a pedestal hardware 20 having a bottom plate 22, a protruding part 21 provided on the bottom plate 22 so as to be fitted to the cross sectional form of a column 110, and a bolt base part 24, 25 provided on the upper surface of the bottom plate 22, and it is fastened to a concrete foundation 11 by an anchor bolt 12 extending through the bottom plate 22. The pedestal-hardware 20 is formed in such a manner that the protruding part 21 in the horizontal plane is off-centered from the bottom plate 22, and the yielding point of the anchor bolt 12 used on the eccentric side is set larger than the yielding point of the anchor bolt 12 used on the non-eccentric side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a column base structure having column base metal fittings used for erecting a steel column of a civil engineering building structure on a concrete foundation, and particularly to a side column or a corner column. It relates to the column base structure to be used.

[0002]

2. Description of the Related Art As a column base structure used to build a steel column on a concrete foundation, a column base metal manufactured by casting or forging as shown in FIGS. 10 and 11 is used. FIG. 10 is a plan view of the column base hardware, and FIG. 11 is a cross-sectional view (part 11-11 of FIG. 10) of a main portion showing a column base structure in which a steel column is constructed on a concrete foundation using the column base metal. is there. In the figure, a column base metal fitting 100 is welded to the lower end of a steel column 110 via a projection 101 provided on the upper surface thereof. Next, it is placed via a partial mortar on the concrete foundation 111 cast in advance. Since an anchor bolt 112 is provided in the concrete foundation 111 in advance, positioning is performed by a bolt hole 103 provided in a bottom plate 102 constituting the column base metal fitting 100. After this positioning, for example, a wooden frame 113 is arranged and the mortar 11 is placed between the bottom plate 102 of the pillar base 100 and the concrete foundation 111.
Fill 4 After the mortar 114 has solidified, the wooden frame 11
3 is removed and the nut 115 is fastened to fix the column base metal 100 to the concrete foundation 111.

[0003] As shown in the figure, a pillar base 100 is a steel column 1.
In the case of using the one that is symmetrical with the center of 10 or the protruding part 101, the one that is intended for the side pillar used for the side part of the building and the corner pillar used for the corner of the building is: Since the side surface of the concrete foundation 111 protrudes outward from the building from the center of the pillar 110, work on site is extremely difficult, and the area of the building is reduced, so that the site area cannot be effectively used. Therefore, at the side pillars and corner pillars, pillar base hardware as shown in Figs. 7 to 9 in which the dimension from the center of the pillar to the outer surface of the concrete foundation is significantly smaller than that of the center pillar is shown in Figs. It is proposed in, for example, Japanese Patent Publication No. 3074. 7 is a plan view of the column base metal, FIG. 8 is a side sectional view of the column base structure showing the column base metal of FIG. 7 in a section 8-8 in FIG. 7, and FIG. 9 is 9-9 of the column base metal of FIG. It is sectional drawing.
The column base metal fittings 70 in this figure are also made by casting or die forging in the same manner as in FIGS.
The center of the horizontal section of the protrusion 71 for welding and fixing 10 and the center of the bottom plate 72 are formed eccentric.
Reference numerals 74 and 75 denote bolt pedestals extending from the protruding portion 71, and a surface substantially parallel to the bottom surface of the bottom plate 72 is formed on the upper surface of a corner of the bottom plate 72. In addition, between the bolt pedestals 74 and 75 of the bottom plate 72, the ribs 76 are inclined so as to be inclined from near the protruding portion 71 toward the peripheral edge.
Are formed.

[0004]

In the column base metal fitting 70 and the column base structure shown in FIGS. 7 to 9, the center of the projecting portion 71 and the bottom plate 7 are provided.
By eccentrically deviating from the center of the column 2, when used as a column base metal for a side column or a corner column of a building, the dimension from the center of the column 110 to the outer surface of the column base metal 70 is reduced.
The eccentric side (FIGS. 7 to 9) of this column base metal fitting 70 is compared with the distance 1 from the axial force center of the steel column 110 to the bolt hole in the bolt pedestal 74 on the non-eccentric side (left side in FIGS. 7 to 9). On the right)
The distance to the bolt hole in the bolt pedestal 75 is naturally short. The difference is the so-called eccentricity e. The bending moment acting on the steel column mounted on the column base works equally in both the left and right directions. However, since the force acting on the anchor bolt increases in accordance with the magnitude of the eccentric amount, the anchor bolt 81 used on the eccentric side is larger than the anchor bolt 82 used on the non-eccentric side. Usually, the embedding depth of the anchor bolt is required to be at least 20 times as large as the diameter of the anchor bolt. Therefore, when a thick anchor bolt is used, the embedding depth needs to be deeper than that of a thinner bolt.

The use of the eccentric column base metal fitting 70 is intended for a side column or a corner column used for a corner of a building, and the side of the concrete foundation extends from the center of the column to the outside of the building. In this way, the use of the thick anchor bolt 81 requires the concrete foundation 83 to be thick, though it is intended to prevent the concrete foundation 83 from protruding in the direction. As a result, the side of the concrete foundation sometimes protruded outside the building.

Therefore, in the present invention, an eccentric column base structure is used.
Provides a column base structure that can make the diameter of the anchor bolt used on the eccentric side the same as the diameter of the anchor bolt used on the non-eccentric side, and that can withstand the same bending moment as a column base structure without eccentricity. It is intended to be.

[0007]

A column base structure according to the present invention comprises a bottom plate, a protrusion provided on the bottom plate so as to conform to the cross-sectional shape of the column, and a bolt pedestal provided on the upper surface of the bottom plate. And a column base metal having a bottom portion, which is fastened to a concrete foundation with an anchor bolt penetrating the bottom plate, wherein the column base metal decenters the center of the protrusion in the horizontal plane and the center of the bottom plate. The yield point of the anchor bolt used on the eccentric side is made larger than the yield point of the anchor bolt used on the non-eccentric side.

In the present invention, it is preferable that the anchor bolts on the eccentric side and the non-eccentric side have the same thickness. In the present invention, the yield point F ′ of the eccentric side anchor bolt
Is the yield point of the non-eccentric anchor bolt as F, the distance from the axial force center of the non-eccentric steel column to the bolt center of the bolt pedestal as l, and the eccentric amount as e,

[0009]

(Equation 1) It is preferable that the following relationship is satisfied. Where F '

[0010]

(Equation 2) , The allowable bending moment on the eccentric side becomes the same as the allowable bending moment on the non-eccentric side even if the thickness of the anchor bolts on the eccentric side and the non-eccentric side are the same, so that the effect of the eccentricity is eliminated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view (1-1 sectional view of FIG. 2) of an embodiment of a column base structure of the present invention, and FIG. 2 is a plan view of the column base metal. In these figures, the same parts as those in FIGS. FIG. 3 is a graph showing the relationship between the axial force N and the allowable bending moment M of the column base structure.

Reference numeral 22 denotes a bottom plate of the column base hardware 20, which is mounted on the concrete foundation 11. Bottom plate 2
2, a projection 21 is provided above the projection 2 so that the projection 21 is fixed to the end of the steel column 110 by welding, for example, so as to conform to the cross-sectional shape of the steel column 110 such as a square or a round. Has become. Bolt pedestals 24 and 25 are provided extending from the protruding portion 21 toward the upper surface of the corners of the bottom plate, and bolt holes 23 are formed at the corners of the bolt pedestals 24 and 25 at the corners of the bottom plate. And the anchor bolt 12 is penetrated. Further, a rib 26 is formed between the bolt pedestals 24 and 25 of the bottom plate 22 in the form of a slope inclined from the vicinity of the protrusion 21 toward the periphery.
The projection 21 of the pillar base 20 can be used as the pillar base 20 of the side pillar or the corner pillar of the structure by the center of the horizontal plane being eccentric from the center of the bottom plate 22. ing.

Here, the bolt holes 2 in the bolt pedestal portion 24 on the non-eccentric side from the axial force center (column center line) of the steel column 110
Assuming that the distance to 3 (corresponding to the center of the bolt 12) is 1 and the amount of eccentricity is e, the axial force center of the steel column 110 (column center line)
The distance from the eccentric side to the bolt hole 23 (corresponding to the center of the bolt) in the bolt base 25 on the eccentric side is le. The anchor bolt 12 used has the same thickness on the non-eccentric side and the eccentric side, and the yield point F 'of the anchor bolt on the eccentric side is changed to the yield point F of the anchor bolt used on the non-eccentric side. Larger than.

Assuming that the axial force acting on the steel column 110 built on the column base structure is N and the bending moment M that the column base structure can withstand is a graph (a) shown in FIG.
There is such a relationship. The bending moment acts on the steel column 110 equally in both the left and right directions. Now, when a force from the left side acts on the steel column 110 in FIG. 1, the bending moment due to the force acts on the non-eccentric side (left side) anchor bolt, and the proof stress of the non-eccentric side anchor bolt is set to Ta. And the allowable bending moment M is as follows. In addition,
Here, l is the distance from the center of the column to the center of the anchor bolt.

[0015]

(Equation 3) However, when a force from the right side acts on the steel column, the eccentric side anchor bolt is pulled, and the distance from the center of the column to the anchor bolt is le. Therefore, the resistance of the eccentric side anchor bolt is set to Ta '. And the allowable bending moment M 'is as follows.

[0016]

(Equation 4) When the strength of the anchor bolts on the non-eccentric side and the eccentric side is the same, the bending moment that the anchor bolt on the eccentric side can withstand is small, and the graph shown in FIG. 3B is obtained.

On the other hand, the strength Ta of the anchor bolt is expressed by the following equation.

[0018]

(Equation 5) Here, α is a coefficient, n is the number of anchor bolts on the pulling side, A is the shaft cross-sectional area of the anchor bolt, and F is the yield point of the anchor bolt (unit: ton / cm ² ).

As is apparent from equations (1) to (3),

[0020]

(Equation 6) It is.

In order to increase the allowable bending moment M 'on the eccentric side, the yield point F' of the anchor bolt on the eccentric side needs to be larger than the yield point F of the anchor bolt on the non-eccentric side. As F · l / (le) approaches, FIG.
(B) becomes a graph (a) of the allowable bending moment of the column base structure without eccentricity, so that the following relationship is preferably satisfied.

[0022]

(Equation 7)

[0023]

EXAMPLE Regarding a column base structure for a 300 mm × 300 mm prism, there is no eccentricity, and a case where the same anchor bolt is used as when there is no eccentricity when the eccentricity is 50 mm (comparative example). A comparison was made between the cases where the present invention was applied.

The column base metal used for the column base structure without eccentricity has a structure as shown in FIGS. 10 and 11, the size of the bottom plate is 550 mm × 550 mm, and there are bolt holes at four corners. The distance between the bolt holes is 430 mm each. The anchor bolt used here has the diameter of M42,
The material is SS490 and its yield point is 2.8t / c
m ² . FIG. 4 shows the relationship between the axial force and the bending moment in this case, and the maximum allowable bending moment was 42 tons.

FIG. 5 shows the relationship between the axial force and the bending moment when the eccentricity is 50 mm, and the relationship between the axial force and the bending moment is the same as that for the case without eccentricity. The maximum allowable bending moment is reduced to 35 tonm. did.

However, in the case of the present invention in which ^two eccentric anchor bolts are made of SN490 material (yield point: 3.3 ton / cm ² ) using a column base metal eccentric by 50 mm,
The relationship between the axial force and the bending moment is as shown in FIG. 6, and the maximum allowable bending moment was improved to 42 tons.

This shows that the yield point of the anchor bolt used on the eccentric side is preferably 1 / (le) times the yield point of the anchor bolt used on the non-eccentric side.

[0028]

As described above, by using the present invention, the diameter of the anchor bolt used on the eccentric side can be made the same as the diameter of the anchor bolt used on the non-eccentric side in the eccentric column base structure. Moreover, it is possible to endure the same bending moment as the column base structure without eccentricity.

[Brief description of the drawings]

1 is a side sectional view of an embodiment of a column base structure of the present invention (FIG. 2);
1-1 section).

FIG. 2 is a plan view of an example of a column base metal used in the column base structure of the present invention.

FIG. 3 is a graph showing a relationship between an axial force and a bending moment of a column base structure.

FIG. 4 is a graph showing a relationship between an axial force and a bending moment of the column base structure when there is no eccentricity described in the embodiment.

FIG. 5 is a graph showing a relationship between an axial force and a bending moment of a column base structure of a comparative example in the case of eccentricity described in the example.

FIG. 6 is a graph showing the relationship between the axial force and the bending moment of the column base structure of the present invention described in the examples.

FIG. 7 is a plan view of an eccentric column base hardware.

8 is a side sectional view showing a section taken along line 8-8 in FIG. 7 of the column base structure;

FIG. 9 is a 9-9 sectional view of the eccentric column base hardware of FIG. 7;

FIG. 10 is a plan view of a normal column base hardware.

11 is a side sectional view showing a section 11-11 of FIG. 10 of the column base structure;

[Explanation of symbols]

 11, 83, 111 Concrete foundation 12, 81, 82, 112 Anchor bolts 20, 70, 100 Pillar metal fittings 21, 71, 101 Projecting parts 22, 72, 102 Bottom plate 23, 103 Bolt holes 24, 25, 74, 75 bolts Base 26, 76 Rib 110 Steel column 113 Wooden frame 114 Mortar 115 Nut

Claims (1)

[Claims] 1. A pillar base having a bottom plate, a projection provided on the bottom plate so as to conform to the cross-sectional shape of the column, and a bolt pedestal provided on an upper surface of the bottom plate. In a column base structure fastened to a concrete foundation by an anchor bolt penetrating the bottom plate, the column base metal is formed by eccentricizing the center of the protruding portion on the horizontal plane and the center of the bottom plate, and on the eccentric side. Column base structure characterized in that the yield point of the used anchor bolt is larger than the yield point of the anchor bolt used on the non-eccentric side.