JPH07324338A - Fixed type exposed pedestal structure - Google Patents

Abstract

PURPOSE:To enhance the rigidity and bearing force of an exposed pedestal and facilitate the construction. CONSTITUTION:This fixed type exposed pedestal structure has an upper pedestal metallic material 2 arranged on the upper surface of a foundation beam 7, a column 1 fixed thereon, a lower pedestal metallic material 6 buried in the concrete 3 of the foundation beam 7, and an anchor bolt 4 buried in the concrete 3 with the upper part being left. The upper part and lower part of the anchor bolt 3 are fixed to the upper pedestal metallic material 2 and the lower pedestal metallic material 6, respectively. The concrete 3 of the foundation beam 7 is nipped and fixed by the upper pedestal metallic material 2 and the lower pedestal metallic material 6 connected by the anchor bolt 4. A prestress lower than 60-100% of the yield strength of the anchor bolt is imparted to the anchor bolt 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed exposed column base structure in a steel structure used in the fields of civil engineering and construction.

[0002]

2. Description of the Related Art Among the methods of constructing a fixed type column base portion of a steel frame structure, a method of constructing an exposed type column base is disclosed in JP-A-5-258.
No. 32 is disclosed (hereinafter referred to as "Prior Art 1"). The exposed type column base of the prior art 1 is, as shown in FIG. 4, a foundation beam 7 made of concrete 3 and reinforcing bars 5,
A column base metal fitting 2 arranged on the upper surface thereof, a column 1 fixed on the upper surface of the column base metalwork 2, an anchor bolt 4 embedded in a concrete 3 for fixing the column base metalwork 2 and its lower end. And a fixing plate (metal 41) fixed to the section. The anchor bolt 4 is inserted into a sheath pipe 43 made of a vinyl chloride pipe (hereinafter referred to as a “vinyl chloride pipe”). As described above, in the prior art 1, the vinyl chloride pipe is used as the sheath pipe 43 to cut off the adhesion between the anchor bolt 4 and the concrete 3 and secure the anchoring force of the anchor bolt 4. Conventionally, such a structure has been generally used in the exposed column base.

Further, Japanese Patent Application No. 5-114990 proposes an exposed type column base as shown in FIG. 5 (hereinafter referred to as "prior art 2"). Prior art 2 is shown in FIG.
As shown in FIG. 2, a steel tube is used as the sheath tube 11 without using the metal 41, and the inside of the sheath tube 11 is filled with the grout material 8. Therefore, unlike the prior art 1, the anchor bolt The edge between the side surface 4 and the concrete 3 of the foundation is not cut, so that even if a large pulling force acts on the anchor bolt 4, it can withstand to some extent. That is, the degree of fixing of the column base fixing portion of Prior Art 2 is larger than that of Prior Art 1.

As a conventional example of a column base structure in which a rectangular steel tube column is embedded in a foundation beam portion, an embedded column base as shown in FIG. 6 is already known (hereinafter referred to as "prior art 3"). Prior art 3 is an embedded column pedestal in which a column 1 is embedded in concrete 3, and has a feature that the degree of fixation is greater than in prior art 2.

[0005]

The prior arts 1 and 2 both have a problem that the rigidity of the column base fixing portion is low (fixing degree is low). Each of them will be described below.

In the prior art 1, the anchor bolt 4 is not directly embedded in the concrete 3,
A sheath pipe 43, which is a PVC pipe, is embedded in the concrete 3, and the anchor bolt 4 is inserted inside the sheath pipe (PVC pipe) 43.
The interior of 43 is not filled with crout material. So to speak
An edge is cut between the side surface of the anchor bolt 4 and the concrete 3, and the pulling force acting on the anchor bolt 4 is as shown in FIG.
It can only be held with 41 pieces of hardware. Therefore, the degree of fixing of the column base fixing portion becomes low.

The prior art 2 has a problem that the grout material 8 needs to be hit twice, but has the advantage that the degree of fixing is larger than that of the prior art 1 as described above. However,
Compared with the embedded column base of the prior art 3, the degree of fixation is still low, and there is room for improvement.

On the other hand, the prior art 3 is an embedded column base and has a high degree of fixation, as described above. However, it was not easy to construct because it was necessary to build the pillars before the concrete of the foundation was placed, but the scaffolding for building the pillars was not secured. That is, the prior art 3 has a problem that it is more difficult to construct than the prior arts 1 and 2.

Further, a method of increasing the degree of fixation of the column base by prestressing the anchor bolt has been conventionally considered. However, when this method is applied to the prior art 1, there is a limit to the amount of pre-stress that can be applied, as described above (metal item 41 in FIG. 4). That is, there is a problem in that the concrete around the metal 41 is destroyed when an excessive prestress is applied to the anchor bolt. On the other hand, in the prior arts 2 and 3, it is impossible to apply prestress due to its structure.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a fixed type exposed column base structure which has high rigidity and proof stress and is easy to construct.

[0011]

A fixed type exposed column base structure of the present invention comprises a foundation beam composed of reinforcing bars and concrete, and
An upper column base metal fitting placed on the upper surface of the foundation beam, a column fixed to the upper surface of the upper column base metalwork, a lower column base metalwork embedded inside the concrete of the foundation beam, and a concrete of the foundation beam An anchor bolt embedded inside leaving an upper part, the upper part of the anchor bolt is fixed to the upper column base and the lower part is fixed to the lower column base, and the upper part is connected by the anchor bolt. The concrete of the foundation beam is sandwiched and fixed by the column pedestal and the lower column pedestal.

Further, the above-mentioned fixed type exposed column base structure is characterized in that the anchor bolt is given a prestress of 60 to 100% or less of the yield strength of the anchor bolt.

[0013]

The lower column pedestal according to the present invention has the same size and rigidity as the upper column pedestal, and the upper column pedestal and the lower column pedestal are connected through the anchor bolts. The reinforced concrete portion sandwiched between the upper column base metal fixture and the lower column base metal fixture {column base base, (A shown in FIGS. 1 and 2)} receives pressure from above and below. Therefore, even when a large bending moment acts on the column, the reinforced concrete portion of the column base A is deformed so as to rotate as a rigid body, and has the same degree as that of the embedded column base (prior art 3 / FIG. 6). Rigidity can be expected (Fig. 3). FIG. 3 shows FIG.
FIG. 3 is a conceptual diagram showing a portion in which the foundation beam is rigidly deformed. A shaded portion B shown in FIG. 3 is a portion where the reinforced concrete is rigidly deformed.

Further, since the area of the plane perpendicular to the column axis of the lower column pedestal is sufficiently large, the concrete around the lower column pedestal will not be destroyed even if a large prestress is applied to the anchor bolt.

For example, when a tensile force is applied upward to the anchor bolt of Prior Art 1 (FIG. 4), the concrete around the metal 41 is broken because of the projected area of the metal and the compressive fracture strength of the concrete. It is known that the force is “10 × σc × S” which is 10 times the value multiplied by. Here, S: projected area of the metal object (area perpendicular to the column axis of the metal object 41), σc: compressive fracture strength of concrete. In the case of the present invention, S (projected area of the lower column pedestal 6) compared to the prior art 1
Is much larger (S is closer to ∝ in the present invention), so a much larger prestress can be applied as compared with the prior art 1. However, if the prestress applied to the anchor bolt exceeds 100% of the yield strength of the anchor bolt, a problem in strength of the anchor bolt occurs. Also,
If the prestress is less than 60%, the desired effect cannot be obtained for the effect of improving the degree of fixation of the column base. Therefore, the prestress applied to the anchor bolt is preferably in the range of 60 to 100% or less of the yield strength of the anchor bolt.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a sectional view showing Embodiment 1 of the exposed column base structure of the present invention. As shown in FIG. 1, on the upper surface of the foundation beam 7 made of concrete 3 and reinforcing bars 5,
A disc-shaped upper column base metal 2 is arranged, and a column 1 made of a circular steel pipe is fixedly erected on the upper surface of the upper column base metal 2. Inside the concrete 3 which constitutes the foundation beam 7, a disk-shaped lower column base metal 6 is embedded. Lower pillar leg hardware 6
Has an anchor muscle 9. Further, inside the concrete 3, anchor bolts 4 are embedded in the vertical direction except for the upper part. The shaft portion of the anchor bolt 4 has a shape having a projection like a deformed bar or a stud shape. The upper part of the anchor bolt 4 is the upper column base metal fitting 2
In addition, the lower parts thereof are fixed to the lower column base metal parts 6 by nuts 14, respectively. The concrete 3 forming the foundation beam 7 is sandwiched between the upper column base metal member 2 and the lower column base metal member 6 connected by the anchor bolts 4, and the upper column base metal member 2
Are fixed on the upper surface of the foundation beam 7, and thus the pillar 1 is fixed on the foundation beam 7.

The dimensions of the constituent elements in this embodiment are as follows. The pillar 1 has a diameter (outer diameter) of 150 mm and a tube thickness of 9
It consists of a circular steel pipe of mm. The diameter of the upper column base metal fitting 2 is 280 mm, and the thickness of the anchor bolt attachment portion 2a is 34 mm. The diameter of the anchor bolt 4 is 28
mm. The lower column base metal member 6 has a diameter of 280 mm and a thickness of 34 mm.

FIG. 1 shows a state after construction. The construction process of this example is as follows. (1) The lower part of the anchor bolt 4 is fixed to the lower column base metal fitting 6 with the nut 14 and is arranged at a predetermined position of the foundation beam. (2) After arranging the reinforcing bars 5, concrete 3 is placed to construct a foundation beam. In addition, concrete pouring is to provide a predetermined enclosure around the reinforcing bar and fill it with concrete.
It is a work to remove the enclosure after solidification. (3) A column 1 and an upper column base metal member 2 (the upper column base metal member 2 is previously fixed to the lower end of the column 1) are laid through a level mortar 10 and a grout material (grout mortar) 8 to form an upper column. The upper portion of the anchor bolt 4 is fixed to the leg piece 2 with a nut 14.

In this embodiment, as shown in FIG. 1, the column base structure having high rigidity is obtained by attaching the lower column base metal member 6. The degree of fixation of the column (defined by the reciprocal of the bending angle of the column) when a bending moment is applied to the column 1 without prestressing the anchor bolt is the prior art 1 (FIG. 4) in this example. It was confirmed that the column base structure of the present invention has a high degree of fixation, which is 1.3 times as large as that of Example 1 and 1.1 times as large as that of Prior Art 2 (FIG. 5).

Next, regarding the column base having the structure shown in FIG. 1, 80% of the yield strength of the anchor bolt is applied to the anchor bolt.
Prestressed. As a result, concrete 1
No damage occurred at 0, and the degree of fixation was also improved. The above-mentioned effect is that the prestress is 6
The desired effect was obtained within the range of 0 to 100%.

On the other hand, as a result of comparing the example of FIG. 4 of the prior art 1 (the size of the anchor bolt is the same (diameter 28 mm), the area of the metal 41 = 750 mm ² ) with this embodiment, the prestress is the yield of the anchor bolt. The limit was 60% of strength.

[Second Embodiment] FIG. 2 is a sectional view showing a second embodiment of the present invention. As shown in FIG. 2, the second embodiment is different from the first embodiment in that the anchor bolt 4 is inserted into the sheath tube 11. That is, the anchor bolt 4 is a steel pipe (hereinafter, referred to as a “sheath pipe”) having protrusions on the inner and outer surfaces which are vertically embedded in the concrete 3 and arranged.
11 has been inserted. The gap between the anchor bolt 4 and the sheath tube 11 is filled with grout material 8. The lower end of the sheath tube 11 is fixed to the lower column base metal member 6 by welding. The anchor bolt 4 has a nut 14 at the top.
The large washer 16 and the lower column pedestal 6 are fixed to the upper column pedestal 2 and the lower portion to the lower column pedestal 6 by nuts 14, respectively.

In this embodiment, the sheath tube 11 has an outer diameter of 50.
It consists of a steel pipe of mm × tube thickness 6 mm. The dimensions of the column 1, the upper column base metal 2, the anchor bolt 4, and the lower column base metal 6 are the same as those in the first embodiment.

FIG. 2 shows the state after construction. The construction process of this example is as follows. (1) The lower part of the anchor bolt 4 is fixed to the lower column base metal piece 6 with the nut 14, and the lower part of the sheath tube 11 is fixed by welding, and the anchor beam 4 is arranged at a predetermined position of the foundation beam. (2) After arranging the reinforcing bars 5, concrete 3 is placed to construct a foundation beam. (3) The column 1 and the upper column base metal 2 (the upper column base metal 2 is fixed to the lower end of the column 1 in advance) are built through the level mortar 10, and the anchor bolt 4 is attached to the upper column base metal 2. The upper part is fixed with the nut 14 and the large washer 16, and at the same time, the grout material 8 is filled in the gaps between the upper column base metal member 2 and the concrete 3 and between the anchor bolts 4 and the sheath pipe 11. The grout material 8 is a sheath tube 11
It is poured from the lower end of the concrete through a hole penetrating the concrete 3. Here, the air is discharged from the air vent 17 in the sheath tube to the outside air.

In the above (2), it is conceivable that the anchor bolt 4 and the sheath tube 11 fixed to the lower column base metal member 6 may be bent by the pressure of the concrete when pouring the concrete. However, in this embodiment, even if the sheath tube 11 bends, the anchor bolt 4 does not receive a force, so that it does not bend, and there is an advantage in that the pillar 1 is not hindered from being built. In any case, also in this embodiment, the anchor bolt 4 is attached to the lower column base metal member 6, and therefore the concrete 3 is sandwiched by the upper column base metal member 2 and the lower column base metal member 6. Example 1 (Fig. 1)
Is the same as. Therefore, the present embodiment shown in FIG. 2 brings about the same effect as that of the first embodiment shown in FIG.

Although Examples 1 and 2 are examples of steel pipes having a circular cross section, the present invention is not limited to steel pipes having a circular cross section, and square steel pipes, H-shaped steel pipes, etc. Also,
The effect of the present invention does not change.

[0028]

As described above, according to the present invention, the concrete of the foundation beam is sandwiched between the upper column base metal member and the lower column base metal member connected by the anchor bolts, so that the rigidity and the yield strength are higher than in the conventional case. Since the column pedestal can be constructed and the anchor bolt can be given more prestress than before, the anchor bolt construction accuracy is low, that is, the through hole for the anchor bolt of the column pedestal metal. Since it is not necessary to precisely design the dimensional accuracy of the anchor bolt and the anchor bolt, the construction becomes easy, and thus the industrially useful effect is brought about.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an exposed column base structure of the present invention.

FIG. 2 is a cross-sectional view showing a second embodiment of the exposed column base structure of the present invention.

FIG. 3 is a conceptual diagram showing a portion where the foundation beam is rigidly deformed in the exposed column base structure of the present invention.

FIG. 4 is a cross-sectional view showing an exposed column base structure of Prior Art 1.

FIG. 5 is a cross-sectional view showing an exposed column base structure of Prior Art 2.

FIG. 6 is a sectional view showing an embedded column base structure of Prior Art 3.

[Explanation of symbols]

 1 Column 2 Upper Column Base Metal 2a Anchor Bolt Attachment 3 Concrete 4 Anchor Bolt 5 Reinforcing Bar 5a Foundation Beam Upper Reinforcing Bar 5b Foundation Beam Lower Reinforcing Bar 6 Lower Column Base Metal 7 Foundation Beam 8 Grout Material 9 Anchor Bar 10 Level Mortar 11 Sheath Pipe 12 Shear connector 13 Anchoring stud 14 Nut 15 Level nut 16 Large washer 17 Air vent 41 Hardware 43 Sheath pipe A Column base B B Reinforced concrete deforms rigidly

Claims (2)

[Claims] 1. A foundation beam composed of reinforcing bars and concrete, an upper column base metal member arranged on an upper surface of the foundation beam, a column fixed to an upper surface of the upper column base metal member, and a concrete interior of the foundation beam. An embedded lower column pedestal and an anchor bolt embedded in the concrete of the foundation beam leaving an upper portion, and the upper part of the anchor bolt is the upper column pedestal and the lower part is the lower column pedestal. A fixed-type exposed column base structure, in which concrete of the foundation beam is sandwiched and fixed by the upper column base metal member and the lower column base metal member which are respectively fixed and connected by the anchor bolt. 2. The fixed-type exposed column base structure according to claim 1, wherein the anchor bolt is prestressed to 60% to 100% of the yield strength of the anchor bolt.