JPH10292487A - Exposure type pedestal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent anchor bolts from being extracted in a severe earthquake and, at the same time, maintain the flexibility of columns by providing a spring washer between a tightening nut and a base plate and also providing a resin layer containing fluorine between the tightening nut and the spring washer. SOLUTION: A spring washer 7 provided between a tightening nut 6 and a base plate 4A is formed into the shape of the side surface of a truncated cone, the overall of which is spring-deformed, and a spring force is transmitted to the nut 6 and the plate 4A through the overall periphery of both end edges of the shape. In an earthquake, the entire washer 7 is telescoped in the axial direction of the anchor bolts 2 due to a variation in compressive energizing force, and the upper and lower end edges 7A and 7B of the washer 7 slide the coated layer of a fluorine-containing resin coated steel plate 8 so as to expand or contract the washer 7 in the radial direction. By this, the washer 7 on the extraction side is extended against an action to cause the rotation of a pedestal 4 so as to relieve an extraction force against the bolts 2, and the flexibility of the entire pedestal 4 can be maintained by the extension of the pulling side washer 7 and retraction of the compression side washer 7.

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 of a building such as a building or a structure, and more particularly to an improvement of the earthquake resistance of an exposed column base structure in which a steel column is not wrapped around a foundation concrete.

[0002]

2. Description of the Related Art Generally, in an exposed column base structure, as shown in FIG. 1, a base plate 4A of a column base 4 is fixed to an anchor bolt 2 having one end embedded in a foundation 1, usually through a mortar 3. , The flat washer 5 and the nut 6 are fitted in order,
The column base 4 is fixed to the foundation 1 by being tightened with the nut 6.

When calculating the seismic resistance of an exposed column base, if the column base is assumed to be a pin that freely rotates with respect to the foundation, no bending moment acts on the foundation in the calculation, and the foundation and the pile are compared. It can be slight. However, actually, in order to prevent the column pedestal from being pulled out from the foundation even during a large earthquake, the anchor bolt is tightened with a nut via a flat washer as described above, which restricts the rotation of the column. Since the bending moment according to the degree of fixation is transmitted to the foundation and the pile, there is a possibility that the foundation or the pile may be destroyed under the seismic force below the design. To cope with this, various methods have been conventionally proposed.

Japanese Unexamined Patent Publication No. Hei 7-224434 discloses that a high-strength steel is used for pulling during a large earthquake by using anchor bolts of different materials such as extremely low yield point steel and high-strength steel in combination with one column base. At the same time, a structure has been proposed which prevents the falling-off and at the same time ensures flexibility by elongation of the extremely low yield point steel. However, in this structure, special steels such as extremely low yield point steel and high tensile steel are used for the anchor bolts, so that they have to be very expensive. In addition, since it is necessary to replace ordinary anchor bolts made of ordinary steel with anchor bolts made of these different materials in order to apply it to existing buildings, it is suitable as a method for improving the earthquake resistance of existing buildings. Absent.

Japanese Patent Application Laid-Open No. 1-62523 discloses a method in which a predetermined axial force is applied to an anchor bolt by tightening a nut by using a spring washer having a contact surface with a nut and a lower end of an outer downward projecting portion rounded. A structure has been proposed in which a tension is applied to improve the accuracy of tension management. Using this structure, if you tighten and fix it within the spring deformation limit of the spring washer,
Since the spring washer is deformed in accordance with the rotation of the column, it can be expected that the transmission of the bending moment directly to the foundation can be reduced.

However, in reality, since the friction coefficient between steel and steel is extremely large, even if the steel is rounded, the spring between the base plate and the spring washer due to slippage between the base plate and the spring washer when the anchor bolt is pulled out. The washer is rarely deformed, and the rounded effect is hardly exhibited. Further, since both the spring washer and the base plate rust within a few years, the coefficient of friction between them increases more and more.
Therefore, although it is useful for temporarily improving the tension management in the initial construction, it is not suitable as a method for permanently securing flexibility during an earthquake.

As a means for reducing the coefficient of friction between the spring washer and the base plate, a method of immersion in oil or the like is conceivable. However, the frequency of maintenance increases, so that it is not suitable for practical use. As a means for ensuring flexibility without slippage between steel members, it is conceivable to use a spring washer in the form of a spiral spring. At both ends of the spring washer, a part of the circumference of the washer is attached to the base plate or the nut. Due to the contact, an uneven force is applied to the base plate or the nut, and the nut or the anchor bolt may be locally broken during an earthquake.

[0008]

SUMMARY OF THE INVENTION The basic object of the present invention is to provide an exposed column base structure which simultaneously satisfies the conflicting requirements of preventing anchor bolts from being pulled out during a large earthquake and ensuring column flexibility. It is to be. Another object of the present invention is to provide an exposed column base structure that can be easily applied to an existing building as well as a new one without using a large cost by using ordinary steel for the anchor bolt.

It is still another object of the present invention to provide an exposed column base structure which can maintain maintenance-free flexibility for a long period of time with respect to friction of a binding portion.

[0010]

In order to achieve the above object, an exposed column base structure according to the first aspect of the present invention has a fastening structure in which one end is fitted from the other end of an anchor bolt embedded and fixed in a foundation. In an exposed column base structure in which a base plate of a column base is fastened to the base with a nut, a spring washer interposed between the tightening nut and the base plate has a truncated conical side shape in which the whole is spring-deformed. A spring force is transmitted to the tightening nut and the base plate over the entire periphery of both end edges, and at least one layer of a fluorine-containing resin is provided between the tightening nut and at least one of the base plate and the spring washer. It is characterized by intervening.

In order to achieve the above object, an exposed column base structure according to a second aspect of the present invention comprises a base plate of a column base with a fastening nut fitted at one end from the other end of an anchor bolt embedded and fixed in a foundation. In the exposed column base structure fastened to the foundation, a spring washer interposed between the fastening nut and the base plate applies a spring force to the fastening nut and the base plate without substantially deforming the spring. It is characterized in that both end faces for transmitting and a spring deformed portion between the both end faces and projecting outward with respect to the anchor bolt are integrally formed.

[0012]

In the first aspect of the present invention, the spring washer is held in a state of being compressed and biased between the tightening nut and the base plate. The spring washer having the shape of the side of the truncated cone is spring-deformed as a whole. This spring deformation is a deformation in which the spring washer expands and contracts in the axial direction of the anchor bolt, and accordingly both ends of the spring washer expand and contract radially around the anchor bolt (that is, in the radial direction of the spring washer). is there. During this spring deformation, the frictional force between the spring washer (the edge thereof) and the tightening nut and / or the base plate is caused by the fluorine-containing resin layer interposed between the spring washer and at least one of the tightening nut and the base plate. The spring washer is extremely small and the sliding property is ensured, so the spring washer can be spring deformed with a high degree of freedom, and the spring washer on the tension side expands when the column base rotates, so the pulling force against the anchor bolt is eased. At the same time, the spring washer on the compression side shrinks, thereby ensuring the flexibility of the column base as a whole.

The fluorine-containing resin layer may be a coating layer of a fluorine-containing resin-coated steel plate, or a fluorine-containing resin coating formed on at least one of a tightening nut, a base plate and a spring washer. It may be a layer. In the second invention, the spring washer is deformed by a spring deforming portion extending between both end faces, and both end faces for transmitting the spring force to the tightening nut and the base plate are not substantially spring deformed. The friction force between the spring nut and the base plate does not substantially cause a problem, and the spring washer can be spring-deformed with a high degree of freedom. When the washer extends and the spring washer on the compression side contracts, it is possible to simultaneously prevent the anchor bolt from being pulled out and the flexibility of the entire column base.

[0014] Of the two end faces of the spring washer, one end face is formed of three or more portions that substantially equally divide the entire circumference of the washer, and the other end face is formed of a single portion extending over the entire circumference of the washer. The spring washer of the second invention can be easily manufactured by punching and bending. Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

[0015]

【Example】

Embodiment 1 FIG. 2 shows an example of an exposed column base structure according to the first invention. FIG. 2B is an enlarged view of a part of FIG. With the fastening nut 6 fitted at one end from the other end of the anchor bolt 2 having one end embedded and fixed in the foundation 1,
The base plate 4A of the column base 4 is fastened to the foundation 1.

The spring washer 7 interposed between the tightening nut 6 and the base plate 4A has the shape of a frusto-conical side surface which is entirely spring-deformed, and the tightening nut 6 and the base plate 4A are respectively provided on the entire periphery of both end edges thereof. The spring force is transmitted to the spring. Between the fastening nut 6 and the spring washer 7 and between the base plate 4A and the spring washer 7, a disc-shaped fluorine-containing resin-coated steel plate 8 having a bolt hole in the center is interposed.

As the fluorine-containing resin, it is desirable to use a tetrafluoroethylene resin having an extremely small friction coefficient and excellent sliding properties. Tetrafluoroethylene resin is generally known by a trade name such as “Teflon”. The nut 6 includes a spring washer 7 and the nut 6 and the base plate 4A.
It is tightened to the extent that it is not completely flattened. As a result, the spring washer 7 is in a state of being compressed and urged by the axial force of the anchor bolt 2, and during the earthquake, the spring washer 7 as a whole is changed by the fluctuation of the compression and urging force.
And the upper edge 7 of the spring washer 7
A and the lower edge 7B slide on the coating layer of the fluorine-containing resin-coated steel sheet 8 to expand and contract in the radial direction of the washer.

Accordingly, the spring washer 7 on the pull-out side (tensile side) expands and the spring washer 7 on the compression side contracts against the action of the column base 4 trying to rotate, so that the rotation restraining force is reduced. Therefore, the degree of freedom (flexibility) of rotation of the column base 4 is increased, and the bending moment with respect to the foundation 1 is reduced. That is, the extension of the spring washer 7 on the tension side reduces the pulling force with respect to the anchor bolt, and the extension of the tension-side washer and the contraction of the compression-side spring washer ensure the flexibility of the column base as a whole.

Since the fluorine-containing resin-coated steel sheet 8 is hardly rusted and has a small coefficient of friction, the upper edge of the spring washer 7 and the nut 6
And the sliding property between the lower edge of the spring washer 7 and the base plate 4A can be ensured over a long period of time. The inner diameter of the fluorine-containing resin-coated steel sheet 8 (the diameter of the bolt hole at the center) is calculated by taking the workability into consideration and calculating the diameter of the anchor bolt 2 +2.
mm, the outer diameter is large enough to prevent the spring washer 8 on the compression side from protruding even when the column base 4 rotates, and the plate thickness is a friction force generated slightly between the spring washer 8 and the spring washer. With a thickness that ensures strength that cannot be torn. The material of the steel plate serving as the base material of the fluorine-containing resin-coated steel plate 8 may be ordinary steel. [Embodiment 2] FIG. 3 shows an example of an exposed column base structure according to the second invention. FIG. 3 (2) is an enlarged view of a part of FIG. 3 (1), and FIG. 3 (3) is an enlarged view of only a spring washer.

A base plate 4A of the column base 4 is fastened to the foundation 1 by a fastening nut 6 fitted at one end from the other end of the anchor bolt 2 having one end embedded and fixed in the foundation 1. Spring washers 9 interposed between the tightening nut 6 and the base plate 4A transmit spring force to the tightening nut 6 and the base plate 4A without substantially deforming the spring.
1, 9A2 and spring deformed portions 9 between both end surfaces 9A1 and 9A2, which protrude outward with respect to the anchor bolt 2.
And B are integrally formed. The spring washer 9 is shown in FIG.
Has a U-shaped cross section, both end faces 9A1 and 9A2 are substantially flat, and the spring deforming portion 9B is substantially arc-shaped.

The nut 6 is tightened so that the spring washer 9 is not completely flattened between the nut 6 and the base plate 4A. Thereby, the spring washer 9 is attached to the anchor bolt 2.
Is in a state of being compressed and biased by the axial force of
At the time of the earthquake, the spring washer 9 is deformed by the deformation of the biasing force of the spring, and the spring bolt 9B is bent by the bending deformation of the spring deforming portion (extending portion) 9B.
However, both end faces 9A1 and 9A1 are not substantially deformed.

Accordingly, the spring washer 9 on the pulling-out side (tensile side) expands and deforms against the action of the column base 4 trying to rotate, thereby alleviating the rotation restraining force. (Flexibility) is increased, and the bending moment with respect to the foundation 1 is reduced. That is, the extension of the spring washer 7 on the tension side reduces the pulling force with respect to the anchor bolt, and the extension of the tension-side washer and the contraction of the compression-side spring washer ensure the flexibility of the column base as a whole.

At this time, since both end faces 9A1 and 9A2 for transmitting the spring force to the tightening nut 6 and the base plate 4A are not substantially deformed, both end faces 9A1 and 9A of the spring washer 9 are formed.
The frictional force between 2 and the nut 6 and the base plate AA does not matter. Since there is no need to consider frictional force, even if rust occurs, it is not affected and maintenance-free effects of the spring washer can be maintained for a long time.

FIGS. 4 and 5 show an example of manufacturing the spring washer 9 having a U-shaped cross section. In the example shown in FIG. 4, an annealed spring steel plate is formed into a cruciform blank 10 having an anchor bolt hole 10A at the center as shown in FIG. 4A by punching or the like, and then a cruciform arm 10B is formed. After being formed into the final shape of the spring washer 9 as shown in FIG. 4 (2) by bending, heat treatment is performed to impart predetermined spring characteristics to complete the spring washer.

In this example, the lower end surface 9A2 of the spring washer 9 is integrally continuous over the entire circumference of the washer, whereas the upper end surface 9A1 of the spring washer 9 is formed of four portions that divide the entire circumference into approximately four equal parts. Although some gaps remain between the corners of each part, the spring force can be transmitted to the tightening nut or the base plate over substantially the entire circumference. In the example shown in FIG. 5, as shown in FIG.
5 (2) and 5 (3) by punching and forming into a shape having a chamfered corner C of each arm 10B.
Is formed so that the arms 10B are in line contact with each other at the corner C as shown in FIG. Further, the line contact portion C can be joined by welding or the like. However, even without joining, the four upper end surfaces 9A1 of the spring washer 9 can constitute a substantially continuous spring force transmitting surface.

As a material of the spring washers 7 and 9 used in the first and second embodiments, a spring steel plate is generally suitable.
Those having a thickness of about 2.3 mm to 20 mm can be easily obtained as commercial materials.

[0027]

As described above, according to the present invention,
An exposed column base structure that satisfies the conflicting requirements of preventing anchor bolts from being pulled out during a large earthquake and ensuring column flexibility is provided. The exposed column base structure of the present invention does not require much expense by using ordinary steel for the anchor bolts, and can be easily applied to existing buildings as well as new ones. Furthermore, maintenance-free flexibility can be ensured for a long period without being affected by the friction of the binding portion.

[Brief description of the drawings]

1 (1) and (2) are (1) a sectional view of a conventional exposed column base structure and (2) a partially enlarged sectional view thereof.

FIGS. 2 (1), (2) and (3) are (1) a sectional view showing an example of an exposed column base structure according to the first invention of the present application;
(2) An enlarged sectional view of a part thereof, and (3) an enlarged sectional view of only a spring washer.

FIGS. 3 (1), (2) and (3) are (1) a sectional view showing an example of an exposed column base structure according to the second invention of the present application,
(2) An enlarged sectional view of a part thereof, and (3) an enlarged sectional view of only a spring washer.

FIGS. 4 (1) and (2) are perspective views showing steps of manufacturing a spring washer used for the exposed column base structure of the second invention.

FIGS. 5 (1), (2) and (3) show steps (1) in plan view, (2) in plan view and (2) in a step of producing a spring washer used for the exposed column base structure of the second invention. 3) It is a perspective view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Foundation 2 ... Anchor bolt 3 ... Mortar 4 ... Column base 4A ... Base plate 5 ... Flat washer 6 ... Tightening nut 7 ... Spring washer 7A ... Upper end surface of spring washer 7 7B ... Lower end surface of spring washer 7 8 ... Fluorine content Resin-coated steel plate 9 Spring washer 9A1 Upper end surface of spring washer 9 9A2 Lower end surface of spring washer 9 9B Spring deformed portion of spring washer 9 Cross-shaped blank 10A Anchor bolt hole of cross-shaped blank 10 10B Arm of character-shaped blank 10

Claims (5)

[Claims] 1. An exposed column base structure in which a base plate of a column base is fastened to said base by a fastening nut fitted from the other end of an anchor bolt having one end embedded and fixed in the foundation. A spring washer interposed between the base plate and the base plate has a truncated conical side shape which is entirely spring-deformed, and transmits spring force to the tightening nut and the base plate over the entire periphery of both end edges thereof, respectively. An exposed column base structure, wherein at least one layer of a fluorine-containing resin is interposed between at least one of the attachment nut and the base plate and the spring washer. 2. The exposed column base structure according to claim 1, wherein said fluorine-containing resin layer is made of a steel sheet coated with a fluorine-containing resin. 3. A fluorine-containing resin coating layer formed on a surface of at least one of the fastening nut, the base plate and the spring washer. Item 2. An exposed column base structure according to Item 1. 4. An exposed column base structure in which a base plate of a column base is fastened to said base by a fastening nut fitted at one end from the other end of an anchor bolt having one end embedded and fixed in the foundation. A spring washer interposed between the base plate and both ends of the clamping nut and the base plate for transmitting a spring force without substantially deforming the spring is provided between the both end surfaces and the outer surface of the anchor bolt. An exposed column base structure characterized by being integrally formed with a spring deforming portion projecting in a direction. 5. An exposed column, wherein one end face of the both end faces is composed of three or more portions substantially equally dividing the entire circumference of the washer, and the other end face is formed of a single portion extending over the entire circumference of the washer. Leg structure.