JP2021085295A - Exposed column base foundation structure - Google Patents

Abstract

To provide an exposed column base foundation structure that a shear force acting on a column base can smoothly transmit to a concrete foundation.SOLUTION: An exposed column base foundation structure 80 has a grout layer 20 on a concrete foundation 10, and a base plate 30 on the grout layer 20. In the exposed column base foundation structure, a steel column 40 is fixed on an upper surface 31 of the base plate 30, anchor bolts 50 fixed into the base plate 30 are embedded in the concrete foundation 10, an endless shear key 60 or a shear key 60A with one or more clearances G provided in the middle of the endless shape is fixed on a lower surface 32 of the base plate 30, shear hardware 70 is embedded in the concrete foundation 10, and a part of the shear hardware 70 is protruded upward from the concrete foundation 10 and disposed inside the shear key 60 in the plan view, and the shear hardware 70 and the shear key 60 are overlapped in the vertical direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exposed column base structure.

As the foundation structure of the steel-framed pedestal, the base plate fixed by the anchor bolt embedded in the concrete foundation is exposed to the outside, and the exposed pedestal foundation structure and the base plate are embedded in the root-wrapping concrete foundation. There is a root-wound pedestal foundation structure, and an embedded pedestal foundation structure in which a base plate is embedded in a concrete foundation. Among them, the exposed column base structure is generally designed as a semi-fixed column base, and the rigidity can be varied from the pin column base to the fixed column base at the time of design, and compared with other column base foundation structures. It has the advantage of being easy to install.

In the exposed column base structure, it is necessary to transmit the shear force acting on the column base (shear force acting on the interface between the base plate and the concrete foundation) from the base plate to which the steel column is fixed to the concrete foundation. In the conventional design, the transmission means by the frictional force on the back surface of the base plate, the transmission means by the anchor bolts embedded in the concrete foundation from the base plate, and the transmission means by the shear key provided on the lower surface of the base plate are used. Shear force is transmitted.

Among these transmission means, the compression axial force of the steel column is required for the transmission means by frictional force, and therefore, it is not expected to expect a transmission means by sufficient frictional force when the tensile axial force acts on the column. Can not. In addition, regarding the transmission means by anchor bolts, both the shear strength of the anchor bolt and the shear strength of the edge of the concrete foundation are important. For example, in the case of a small and compact concrete foundation, a sufficient edge size is secured. It is difficult, and therefore it is difficult to expect the effect of this means of communication.

By the way, a grout layer for absorbing construction errors is generally formed between the base plate and the concrete foundation. In a normal design, the lower surface of the base plate having a smooth material surface becomes a sliding surface, but when the grout layer is cracked, a sufficient anti-slip effect by shear key cannot be expected.

Here, an exposed column base structure has been proposed that can secure the cone breaking resistance without increasing the amount of reinforcing bars. Specifically, anchor bolts having a base plate, anchor bolts, fixing portions, lower reinforcing bars, etc., and inserted into through holes near the four corners of the base plate whose columns are fixed on the upper surface are fixed via nuts. A fixing portion is provided near the lower end of the anchor bolt. Then, a lower reinforcing bar extending in the vertical direction is fixed to the lower part of the fixing portion (see, for example, Patent Document 1).

JP-A-2018-104945

According to the column base structure described in Patent Document 1, the lower reinforcing bar extending in the vertical direction is fixed to the lower part of the fixing portion provided near the lower end of the anchor bolt, so that the amount of reinforcing bar is not increased. It is possible to secure the cone breaking resistance. However, as described above, it is unclear whether or not the shearing force acting on the column base can be smoothly transmitted to the concrete foundation in a compact concrete foundation where it is difficult to secure a sufficient edge size, for example.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an exposed column base structure capable of smoothly transmitting a shearing force acting on a column base to a concrete foundation.

In order to achieve the above object, one aspect of the exposed column base structure according to the present invention is
There is a grout layer on the concrete foundation, a base plate on the grout layer, a steel column fixed on the upper surface of the base plate, and anchor bolts fixed to the base plate are embedded in the concrete foundation. It is an exposed type column base structure,
An endless shear key or a shear key having one or more gaps in the middle of the endless shear key is fixed to the lower surface of the base plate.
Shear metal fittings are embedded in the concrete foundation, and a part of the shear metal fittings protrudes above the concrete foundation and is arranged inside the shear key in a plan view.
It is characterized in that the shear metal and the shear key wrap in the vertical direction.

According to this aspect, the shear key fixed to the lower surface of the base plate and the shear metal piece protruding upward from the concrete foundation and arranged inside the shear key are vertically wrapped to form a column of the steel frame column. The shearing force acting on the legs can be smoothly transmitted from the base plate to the concrete foundation via the shear key and from the shear key via the shear hardware. That is, when the tensile axial force acts on the anchor bolt and sufficient frictional force cannot be expected, or when it is difficult to secure the edge size required to expect sufficient shear strength for the anchor bolt, compact concrete. Even for foundations, since a transmission route for transmitting shear force from shear key to concrete foundation via shear hardware is secured, smooth transmission of shear force is possible. As an example of the compact concrete foundation, a concrete foundation having a plane dimension of about 400 mm × 400 mm can be mentioned as an example.

Here, the shear key has an endless shape or a shape having one or more gaps in the middle of the endless shape. The endless shape includes a rectangular frame shape, a polygonal frame shape other than a rectangle, an annular shape, and the like. For example, the shear metal that protrudes upward from the concrete foundation is placed inside the rectangular frame-shaped shear key, and the shear force and the shear metal wrap in the vertical direction, so that the shear force from either direction is surely applied to the shear metal. It can be transmitted and the shear force can be transmitted to the concrete foundation via the shear hardware. A rectangular shear key in a plan view can be formed, for example, by a square steel pipe, or by welding the abutting ends of two channel steels or by welding the abutting ends of four flat steels. ..

Further, even if the shear key is not completely endless and has a shape having one or more gaps in the middle of the endless shape, the effect of reliably transmitting the shearing force from any direction to the shear metal is effective. There is no change in being played. For example, by arranging four angle steels in a substantially rectangular shape in a plan view with a gap between adjacent angle steels, or by arranging two channel steels with a gap between them. By arranging in a viewing rectangle, this form of shear key is formed. Instead of angle steel or channel steel, two or three flat steels joined by welding may be applied.

Further, regarding the configuration in which the shear metal and the shear key are wrapped in the vertical direction, the lap length is preferably set to a length at which the shearing force can be sufficiently transmitted, and can be set to, for example, about 5 mm to 20 mm. The lap length can also change due to construction errors in the grout layer.

Further, in another aspect of the exposed column base foundation structure according to the present invention, the shear metal fitting is
The sheer hardware is
With the central plate
A tubular member fixed to the upper and lower wide surfaces of the central plate, and
The central plate and the lower tubular member are embedded in the concrete foundation.
The upper tubular member and the shear key are vertically wrapped.

According to this aspect, since the shear metal has a central plate, when the shear metal is arranged in the concrete foundation and the fresh concrete for the concrete foundation is placed on the central plate, the shear is formed in the fresh concrete. It is possible to prevent the hardware from sinking. In addition, the tubular members are fixed to the top and bottom of the central plate, and the upper tubular member wraps vertically with the shear key, so that the shearing force acting on the column base is transmitted from the shear key to the upper tubular member. be able to. Further, by embedding the lower tubular member in the concrete foundation, the shearing force acting on the shear metal can be transmitted to the concrete foundation via the lower tubular member.

Here, the upper and lower tubular members are polygonal square tubular and cylindrical tubular members other than rectangular and rectangular in plan view, and like the shear key, square steel pipes and circular pipes, and a plurality of channel steels and chevrons. It can be formed of steel or a plurality of flat steels.

Further, in another aspect of the exposed column base foundation structure according to the present invention, the shear metal has a bolt, and the first bolt hole formed inside the tubular member of the central plate. The bolts are screwed together and project above and below the central plate.
A second bolt hole is opened in the base plate,
The head of the bolt is screwed into the second bolt hole, and the first nut screwed into the bolt supports the base plate from below.

According to this aspect, the base plate can be installed at a predetermined height level from the concrete foundation by screwing the head of a bolt that is screwed into the base plate and projects upward into the second bolt hole of the base plate. it can. At this time, since the first nut screwed into the bolt supports the base plate from below, the base plate is stably supported by the bolt. The second bolt hole provided in the base plate may be a through hole, or may be a counterbore groove formed from the lower surface of the base plate to a position in the middle of the thickness thereof. Further, since the bolt to be applied is screwed into the first bolt hole of the central plate and the head thereof is screwed into the second bolt hole of the base plate, it is preferable to apply a full screw bolt. ..

Further, in another aspect of the exposed column base structure according to the present invention, a second nut is further screwed into the bolt.
The second nut supports the central plate from below.

According to this aspect, the position of the bolt whose protrusion length is adjusted upward, for example, with respect to the central plate can be fixed by the second nut. That is, the second nut maintains the protruding length of the bolt from the central plate and fixes the height of the base plate screwed into the head of the bolt.

As can be understood from the above description, according to the exposed column base structure of the present invention, the shearing force acting on the column base can be smoothly transmitted to the concrete foundation.

It is a vertical cross-sectional view of an example of the exposed type column base foundation structure which concerns on embodiment. It is a perspective view of an example of the base plate constituting the exposed column base foundation structure and the shear key fixed to the lower surface thereof, viewed from diagonally below. It is a perspective view which looked at an example of the shear metal which constitutes the exposed column base foundation structure from diagonally above. Both (a) and (b) are plan views of a modified example of the shear key.

Hereinafter, an example of the exposed column base foundation structure according to the embodiment will be described with reference to the attached drawings. In the present specification and the drawings, substantially the same components may be designated by the same reference numerals to omit duplicate explanations.

[Exposure type column base foundation structure according to the embodiment]
An example of the exposed column base foundation structure according to the embodiment will be described with reference to FIGS. 1 to 3. Here, FIG. 1 is a vertical cross-sectional view of an example of the exposed column base foundation structure according to the embodiment. Further, FIG. 2 is a perspective view of an example of a base plate constituting the exposed column base foundation structure and a shear key fixed to the lower surface thereof as viewed from diagonally below. Further, FIG. 3 is a perspective view of an example of the shear hardware constituting the exposed column base foundation structure viewed from diagonally above.

The exposed column base foundation structure 80 includes a grout layer 20 on a concrete foundation 10 made of reinforced concrete, a base plate 30 on the grout layer 20, a steel column 40 fixed to an upper surface 31 of the base plate 30, and a base plate 30. It has a plurality of anchor bolts 50 (four in the illustrated example) fixed to the concrete foundation 10 and embedded in the concrete foundation 10.

The steel frame column 40 is formed of a shaped steel material such as H-shaped steel, but may be formed of a square steel pipe or the like. The steel column 40 is joined to the upper surface 31 of the base plate 30 by welding.

Anchor bolt holes 33 are provided at the four corners of the base plate 30, and for example, an anchor bolt 50 of a full screw type is screwed into each anchor bolt hole 33, and the head of the anchor bolt 50 is a nut 52 via a washer 51. It is fixed to the base plate 30 by being tightened by.

The rising portion of the concrete foundation 10 in the illustrated example has a square shape in a plan view, and is a compact concrete foundation having a plane dimension of about 400 mm × 400 mm. Therefore, the edge dimension t2 from the core of the anchor bolt 50 to the end surface 11 of the concrete foundation 10 is as small as about 40 mm to 70 mm. It should be noted that the form in which the size of the concrete foundation is large is not excluded, and the exposed column base foundation structure 80 in the illustrated example may have a form having a large concrete foundation.

As shown in FIG. 1, a shear force Q acts on the column base of the steel frame column 40 at the time of an earthquake or a strong wind. Further, one side fixed to the base plate 30 at the lower end of the steel frame column 40 by the overturning moment M (or the bending moment in the illustrated example, which is a counterclockwise bending moment in the illustrated example) acts on the steel frame column 40 (FIG. 1). A tensile axial force T acts on the anchor bolt 50 on the right side (right side), and a compressive axial force C acts on the anchor bolt 50 on the other side (left side in FIG. 1).

As described above, when the overturning moment M acts on the steel column 40, the lifting occurs in the vicinity of the anchor bolt 50 on which the tensile axial force T acts, and in such a lifting region, the friction on the back surface of the base plate 30 occurs. It cannot be expected that the shear force Q acting on the column base of the steel frame column 40 is transmitted to the concrete foundation 10 by the force. Further, regarding the transmission of the shear force Q to the concrete foundation 10 by the anchor bolt 50, both the shear strength of the anchor bolt 50 and the shear strength of the edge of the concrete foundation 10 are important, but they are small as shown in the illustrated example. In the case of a large-scale and compact concrete foundation 10, since the edge dimension t2 is small, it is difficult to expect transmission by these shear strengths.

Therefore, in the exposed column base foundation structure 80, an endless shear key 60 is fixed to the lower surface 32 of the base plate 30, a shear metal 70 is embedded in the concrete foundation 10, and a part of the shear metal 70 protrudes above the concrete foundation 10. In a plan view, the shear metal 70 is arranged inside the endless shear key 60, and the shear metal 70 and the shear key 60 are wrapped in the vertical direction with a lap length of t1.

Here, the lap length t1 is preferably set to a length capable of sufficiently transmitting the shear force Q from the shear key 60 to the shear metal 70, and can be set to, for example, about 5 mm to 20 mm. The lap length t1 may also change due to a construction error of the grout layer 20.

As is clearly shown in FIG. 2, the shear key 60 can be manufactured by joining four steel plates in a rectangular frame shape (square in the illustrated example) by welding, or by applying a square steel pipe. The shear key 60 is joined to the lower surface 32 of the base plate 30 by welding. A second bolt hole 34 is formed in or near the center of the base plate 30, and a shear key 60 is arranged around the second bolt hole 34. Further, four anchor bolts 50 are arranged on the outside of the shear key 60.

On the other hand, as clearly shown in FIG. 3, the shear metal fitting 70 includes the steel central plate 71, the tubular members 72 and 73 fixed to the upper and lower wide surfaces of the central plate 71, and the central plate 71. It has a bolt 74 that is screwed into a first bolt hole 71a formed inside the tubular members 72 and 73 and projects vertically above and below the central plate 71. The tubular members 72 and 73 can also be manufactured by joining four steel plates in a rectangular frame shape (square in the illustrated example) by welding or by applying a square steel pipe.

A second nut 76 is screwed onto the bolt 74, and the second nut 76 supports the central plate 71 from below. A first nut 75 is screwed above the bolt 74.

As shown in FIG. 1, in the concrete foundation 10, a central plate 71, a lower tubular member 73, and a part of bolts 74 are embedded in the shear metal 70.

After adjusting the protruding length of the bolt 74 from the central plate 71, the bolt 74 is fixed to the central plate 71 by turning the second nut 76 to bring it into contact with the lower surface of the central plate 71, and from the central plate 71. The upward protrusion length and the downward protrusion length of the bolt 74 of the bolt 74 are specified. This upward protrusion length leads to the adjustment of the height level of the base plate 30, and the downward protrusion length affects the degree of fixation of the shear metal 70 to the concrete foundation 10.

Further, the head of the bolt 74 is screwed into the second bolt hole 34 of the base plate 30, and by screwing while adjusting the buried length of the bolt 74 with respect to the base plate 30, the concrete foundation is screwed through the shear metal fitting 70. The base plate 30 can be installed at a predetermined height level from 10. Further, the first nut 75 screwed into the bolt 74 supports the base plate 30 from below, whereby the base plate 30 can be stably supported with respect to the bolt 74.

Since the shear metal fitting 70 has the central plate 71, when the shear metal fitting 70 is arranged on the concrete foundation 10 on the central plate 71 and the fresh concrete for the concrete foundation 10 is placed, the shear metal fitting 70 is contained in the fresh concrete. It is possible to prevent the 70 from sinking.

Further, the tubular members 72 and 73 are fixed to the upper and lower sides of the central plate 71, respectively, and the lower tubular member 73 is embedded in the concrete foundation 10 to obtain a shearing force Q acting on the column base of the steel frame column 40. , Can be transmitted to the concrete foundation 10 via the shear key 60 and the shear hardware 70.

Specifically, since the upper tubular member 72 wraps vertically with the shear key 60, the shearing force Q acting on the column base of the steel frame column 40 is upward from the shear key 60 as shown in FIG. It is transmitted to the tubular member 72 in the X1 direction. As described above, the lap length t1 is set from the viewpoint of this shear force transmissibility. Since the tubular member 72 and the shear key 60 are wrapped, it is possible to expect the bearing pressure strength in the wrapped region of the side surface of the tubular member 72.

Next, the shearing force Q transmitted to the tubular member 72 is transmitted to the concrete foundation 10 in the X2 direction via the central plate 71 and the lower tubular member 73. Therefore, the height of the lower tubular member 73 (the height buried in the concrete foundation 10) is also set from the viewpoint of shear force transmission.

For example, in a compact form in which the plane dimension of the concrete foundation 10 is about 400 mm × 400 mm as described above, a base plate 30 having a thickness of 36 mm and a plane dimension of about 300 mm × 300 mm can be applied.

In this embodiment, the shear key 60 fixed to the lower surface 32 of the base plate 30 has a thickness of about 9 mm, a height of about 25 mm, and a plane dimension of about 150 mm × 150 mm. The rectangular frame-shaped shear key 60 can be manufactured, for example, by joining four steel plates (SS400 or the like) by welding.

Further, in this embodiment, the shear hardware 70 has a central plate 71 having a thickness of about 3.2 mm and a plane dimension of about 100 mm × 100 mm, and a height of about 3.2 mm and a height of about 25 mm. It can be manufactured by the upper and lower tubular members 72 and 73 having a height of about 80 mm × 80 mm and the bolt 74 having a length of about 100 mm with M20. The tubular members 72 and 73 can also be manufactured by, for example, joining four steel plates (SS400 or the like) by welding.

Further, both FIGS. 4 (a) and 4 (b) are plan views of a modified example of the shear key. The shear key 60A shown in FIG. 4A has a shape having one or more (four in the illustrated example) gaps G in the middle of the endless shape (square in the illustrated example). Four angle steels 61 are arranged at each corner of the square, and each angle steel 61 is joined to the lower surface 32 of the base plate 30 by welding in a manner in which a gap G is provided between the adjacent angle steels 61. Instead of angle steel, two flat steel pieces may be used to manufacture an L-shaped piece in a plan view as shown in the illustrated example.

Even in the form of the shear key 60A having one or more gaps G in the middle of the endless shape, the shearing force transmitted from any direction can be effectively transmitted to the shear metal 70 arranged inside the shear key 60A.

On the other hand, the shear key 60B shown in FIG. 4B is formed of an annular steel pipe in a plan view. Not only the rectangular frame-shaped shear key 60, but also the shear key 60B having a circular shape (including an elliptical shape) in a plan view, the shearing force transmitted from any direction is applied to the shear key 70 arranged inside the shear key 60. Can be effectively communicated.

It should be noted that the configuration or the like described in the above embodiment may be another embodiment in which other components are combined, and the present invention is not limited to the configuration shown here. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form thereof.

10: Concrete foundation 11: End face 20: Grout layer 30: Base plate 31: Top surface 32: Bottom surface 33: Anchor bolt hole 34: Second bolt hole 40: Steel pillar 50: Anchor bolt 51: Washer 52: Nut 60, 60A, 60B : Sheer key 61: Angle steel 70: Shear hardware 71: Central plate 71a: First bolt hole 72: Upper tubular member 73: Lower tubular member 74: Bolt 75: First nut 76: Second nut 80: Exposed pillar Leg foundation structure

Claims (4)

There is a grout layer on the concrete foundation, a base plate on the grout layer, a steel column fixed on the upper surface of the base plate, and anchor bolts fixed to the base plate are embedded in the concrete foundation. It is an exposed type column base structure,
An endless shear key or a shear key having one or more gaps in the middle of the endless shear key is fixed to the lower surface of the base plate.
Shear metal fittings are embedded in the concrete foundation, and a part of the shear metal fittings protrudes above the concrete foundation and is arranged inside the shear key in a plan view.
An exposed column base foundation structure, characterized in that the shear metal and the shear key wrap in a vertical direction. The sheer hardware is
With the central plate
A tubular member fixed to the upper and lower wide surfaces of the central plate, and
The central plate and the lower tubular member are embedded in the concrete foundation.
The exposed column base foundation structure according to claim 1, wherein the upper tubular member and the shear key are vertically wrapped. The shear metal has a bolt, and the bolt is screwed into a first bolt hole formed inside the tubular member of the central plate, and the bolt protrudes above and below the central plate.
A second bolt hole is opened in the base plate,
The first or second claim, wherein the head of the bolt is screwed into the second bolt hole, and the first nut screwed into the bolt supports the base plate from below. Exposed type column base foundation structure. A second nut is further screwed into the bolt.
The exposed column base foundation structure according to any one of claims 1 to 3, wherein the second nut supports the central plate from below.

Images