JP2023068285A - Fastening structure of exposed column base - Google Patents

Abstract

To provide a fastening structure of an exposed column base that is effective when applied to a steel column that serves as a corner column or a side column of a steel construction.SOLUTION: In a fastening structure of an exposed column base, filling mortar 6 solidified in a flat plate shape is interposed between a lower surface of a base plate 2 fixed to a lower end of a steel column 1 and an upper surface of a foundation concrete 3 and a plurality of anchor bolts 7 penetrating the base plate 2 are tightened with nuts 9. A horizontal anchor material 5 having a male screw portion 5a at its end is screwed into a screw hole 2a formed in an outer peripheral surface of the base plate 2, and then, covering concrete 4 is laminated on the upper surface of the foundation concrete 3 to a height sufficient for the horizontal anchor material 5 to be fastened to the covering concrete. When a shear force directed towards the outside of a building acts, the horizontal anchor material 5 provided in a direction opposite to the shear force resists the shear force. Together with shear resistance by a bearing pressure of the covering concrete, a structure can resist the shear force acting on each column.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exposed column base installed in a steel-framed building, and more particularly, to a fixing structure for an exposed column base that is effective when applied to a steel frame column that serves as a corner pillar or side pillar of a building. be.

A column base of a steel-framed building (building) is tightly joined to a foundation structure (foundation concrete) by a plurality of anchor bolts. Such pedestals are broadly classified into exposed pedestals, embedded pedestals, and root-wrapped pedestals. With regard to the embedded type column base and the root wrap type column base, the shear force is transmitted to the concrete around the column base without any special measures. Is required.

In exposed-type column bases, shear forces generated by earthquakes, etc. are generally processed (transmitted) by the following mechanisms (a) to (c) corresponding to FIGS. 7 (a) to (c), respectively. .
(a) Friction on the bottom surface of the base plate Friction on the bottom surface of the base plate (the contact surface between the base plate 2 and the filling mortar 6) is the basis of the shear force transmission mechanism in the exposed type column base. If this frictional force Qf can resist the shearing force Q, there is no problem, but depending on the stress state, the frictional force may be insufficient.
(b) Shear strength of anchor bolt The shear strength Qa of the anchor bolt 7 is ensured as an essential structural member for the column base. Since the gap around the anchor bolt becomes large due to construction accuracy, measures for shear force transmission are required separately.
(c) Bearing Pressure by Concrete Around Column Base The bearing pressure by concrete is the shear strength due to the bearing pressure resistance of the base plate 2 embedded in the covering concrete and the side surface of the steel frame column 1 . In general construction, in order to hide the anchor bolts 7, they are often completely buried in a concrete layer 4 such as slab concrete (hereinafter referred to as "coating concrete"), and the bearing force is used as shear strength. It is something to do. It is important that the covering concrete 4 laminated on the base concrete 3 has a structure capable of resisting the shearing force Q.

FIG. 7 is an explanatory diagram showing the state of resistance to the shearing force Q in each of the above transmission mechanisms (a) to (c). (a) Friction of the bottom surface of the base plate and (b) Shear strength of the anchor bolts are both typical measures for the exposed type column base. Although not often pointed out, the following problems are assumed respectively.

That is, there is an interpretation that the filling mortar 6 used in the mechanism (a) cannot be used in structurally important locations because it is not a designated building material under the Building Standards Law. Further, in the mechanism (b), a bending moment is generated due to bending deformation in the clearance between the anchor bolt 7 and the bolt insertion hole of the base plate 2, and the bending moment causes a decrease in shear resistance. In addition, in the structural design of buildings, it is rare for wire rods such as anchor bolts and reinforcing bars to bear the shear force.

On the other hand, the mechanism (c) directly receives the shearing force Q with the bearing force Qp of the concrete, so it is suitable for the design concept of reinforced concrete construction. From the viewpoint of design, it is common practice to cover the anchor bolts 7 with covering concrete 4 that also serves as slab concrete. In this case, the covering concrete 4 has a detent function of the nut 9 screwed on the upper part of the anchor bolt 7, and there is an advantage that a single nut can be used instead of a double nut. However, in the support pressure mechanism using the coated concrete 4, when a shear force Q acts in the outward direction of the building at the column base corresponding to the corner pillar A and the side pillar B of the building shown in the upside down view of FIG. As shown in 7(c), there is no covering concrete 4 outside the building, so there is a problem that the shear force Q cannot be resisted. In addition, such a problem is not limited to the corner pillar A and the side pillar B of the building as described above. A similar problem arises from the absence of an extension of the covering concrete 4 on the left side).

Related to the transmission mechanism (c) above, Patent Documents 1 and 2 disclose conventional techniques for reinforcing the entire column base by covering the upper portion of the exposed column base with coated concrete. In the steel frame column base described in Patent Document 1, a reinforced concrete set larger than the outer dimensions of the reinforced concrete of the foundation column is provided so as to surround the lower end of the steel frame column, the base plate, and the projecting portion of the anchor bolt, and is below the reinforced concrete. By embedding the base of the column in the foundation concrete (reinforced concrete of the underground beam), the shear strength to resist the shear force acting on the building was enhanced. However, as is clear from the drawing, the reinforced concrete surrounding the lower ends of the steel columns protrudes greatly outward from the side of the foundation concrete (reinforced concrete of the underground beams), so the steel column bases are not suitable for the outer wall of the building. However, it is not suitable for application to corner posts and side posts installed near steel columns.

The pedestal structure described in Patent Document 2 is an exposed type pedestal in which the projection length of the anchor bolts from the upper surface of the base plate is set longer than usual, and all the anchor bolts are surrounded by the projected excess length. Attach the rebar (horizontal force bearing member) bent in a substantially rectangular shape, and further cover concrete (second concrete) to the height where the protruding part of the anchor bolt and the rebar (horizontal force bearing member) are buried. 1st concrete). According to this configuration, the shear strength can be increased without protruding the covering concrete in the side direction of the column base. There is room for improvement in terms of material costs and work costs, such as the need for mounting work.

Japanese Patent No. 2710737 (see FIGS. 6 to 10, paragraph numbers 0011 to 0014) Japanese Patent No. 5464689 (see FIGS. 1 to 5, paragraph numbers 0017 to 0036)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing structure for an exposed column base that is effective when applied to a steel frame column that serves as a corner column or a side column of a steel frame building. do.

In order to solve the above problems, in the invention according to claim 1 of the present application, a plurality of anchor bolts whose lower portions are embedded in the foundation concrete that supports the building are provided with insertion holes for the anchor bolts in the peripheral portion. The base plate, which is fixed to the lower end of the steel frame column, is placed on the upper surface of the foundation concrete with a gap between them, and the upper surface of the foundation concrete and the lower surface of the base plate are fixed by tightening the nuts screwed on the upper part of the anchor bolts. After injecting mortar material into the gap and fixing the steel frame column to the foundation concrete via the solidified filling mortar layer, the cover concrete is laminated on the upper surface of the foundation concrete so that at least the base plate is buried. In the structure, the horizontal expansion of the cladding concrete is not formed in at least one direction. It is characterized by adopting a configuration in which horizontal anchor members are joined in opposite directions and embedded in the covering concrete. In addition, the horizontal anchor material in the present invention is an anchor material arranged in a horizontal direction, and for example, a deformed reinforcing bar having a male threaded portion at its end, a threaded joint reinforcing bar, or the like is preferably used. Also, the horizontal anchor material must be at a height that ensures sufficient adhesion in the covering concrete.

According to the above configuration, the covering concrete spreads in at least one direction, such as a corner post of a building in which the covering concrete does not extend in two directions, or a side pillar in which the covering concrete does not extend in one direction. Anchor material is horizontally connected to the base plate at the bottom of the steel frame column located in the installation place where it is not installed, in the direction opposite to the outside of the building. When a shear force directed toward the outside of the building due to an earthquake or the like acts on the legs, the shear force is resisted by the fixing force of the anchor members extending in the opposite direction. As a result, shear resistance can be obtained even when the covering concrete on the top of the pedestal does not extend outward from the building.

In the present invention, in the above configuration, the horizontal anchor member has a male screw portion at its end, and is screwed into a screw hole drilled in the outer peripheral surface of the base plate via the male screw portion (claim 2). Alternatively, in place of the screw holes, it is screwed into a screw hole metal fitting joined to the base plate (claim 3), or further to a structure in which a nut is screwed through a plate with a hole joined to the base plate (claim 4). Alternatively, by using various members and means, the horizontal anchor member can be horizontally joined to a specific portion of the base plate.

In the present invention, the following effects are obtained by adopting the above configuration.
(1) When a shear force acts on the column base of a building due to an earthquake, etc., the horizontal anchor material that is joined to the base plate at the bottom of the steel frame column resists the shear force in the direction opposite to the shear force. Shear resistance can also be obtained from the covering concrete for building corner posts, side posts, etc. where the covering concrete does not extend outward.
(2) When using a deformed reinforcing bar or threaded reinforcing bar with a male screw at the end as a horizontal anchor material and screwing it to the screw provided on the base plate side, the horizontal anchor at the construction site Anchor materials can be easily attached, and compared to other methods such as welding reinforcing bars to the base plate, this greatly contributes to the reduction of member costs and work costs.
(3) When the horizontal anchor material is screwed in at the construction site, the horizontal anchor material does not interfere with the transportation work when the steel frame column with the base plate fixed to the lower end is transported to the construction site. Also, since the horizontal anchor material is attached after erecting the steel frame column, the erection work of the steel frame column is also not hindered.

FIG. 4 is a cross-sectional view showing the fixing structure of the exposed-type column base according to the present invention; FIG. 4 is a perspective view showing a state of bonding of horizontal anchor members at a stage before layering covering concrete; FIG. 6 is a cross-sectional view showing the fixing structure of the exposed type column base according to the second embodiment of the present invention; FIG. 11 is a cross-sectional view showing a fixing structure of an exposed-type column base according to a third embodiment of the present invention; FIG. 11 is a cross-sectional view showing a fixing structure of an exposed-type column base according to a fourth embodiment of the present invention; FIG. 11 is a cross-sectional view showing a fixing structure of an exposed-type column base according to a fifth embodiment of the present invention; (a) to (c) are explanatory diagrams showing a shear force transmission mechanism in the fixing structure of the exposed type column base. FIG. 4 is an explanatory diagram showing directions in which shear force cannot be applied to corner posts, side posts, and the like, where covering concrete does not spread toward the outside of the building.

Hereinafter, embodiments of the present invention will be described in detail with reference to drawings related to the embodiments. Targeted. It should be noted that the present invention is not limited to the outer pillars of buildings as described above, but can also be applied to central pillars under installation conditions in which coating concrete is not formed in at least one direction.

FIG. 1 is a first embodiment relating to the fixing structure of the exposed type column base, and is a cross-sectional view showing the main part thereof. The anchoring structure of the exposed type column base according to the present invention is a coating concrete 4 that surrounds the lower end of the steel column 1 on the upper surface of the foundation concrete 3 in which the steel column 1 is fixed via the base plate 2. A horizontal anchor member 5 made of a deformed reinforcing bar is embedded inside the coated concrete 4 in the opposite direction to the outside of the building (the right side of the steel column 1 in FIG. 1) while being joined to the base plate 2. It is a configuration that The horizontal anchor member 5 is formed by forming a male threaded portion 5a at the end of a deformed reinforcing bar. It is installed in a horizontal state so as to be parallel to the base concrete 3 and the covering concrete 4 . It is also possible to use a threaded joint reinforcing bar or a fully threaded bolt instead of a deformed reinforcing bar having a male threaded portion at its end.

Furthermore, in the fixing structure, a filling mortar 6 (non-shrinkage mortar) solidified into a flat plate is provided between the lower surface of the base plate 2 fixed to the lower end of the steel frame column 1 and the upper surface of the foundation concrete 3, and the base plate 2 Washers 8 are inserted through the upper ends of a plurality of anchor bolts 7 passing through through holes (oversized holes) 2b formed in the periphery of the anchor bolts 7, and these are tightened with two nuts 9, 9 (single nuts may be used). ing. The covering concrete 4 is provided with a height (thickness) slightly exceeding the upper end positions of the anchor bolts 7 .

According to the above configuration, when a shearing force Q acts on the building due to an earthquake or the like, the horizontal anchor member 5 provided on the base plate 2 at the lower end of the steel frame column 1 resists the shearing force Q with its adhesive force T. Sufficient shear resistance can be obtained even in a state where the covering concrete 4 on the upper part of the column base does not spread toward the outside of the building. As in other embodiments described later, a male thread is formed at the opposite end of the horizontal anchor member 5, and a separate fixing plate is provided to increase the fixing force of the horizontal anchor member 5. is also possible.

FIG. 2 shows that after erection of the steel column 1 is completed and flat plate-like filling mortar 6 is formed on the lower surface of the base plate 2, the male threaded portion 5a of the horizontal anchor member 5 is screwed into the screw hole 2a of the base plate 2. It is a perspective view which shows the state joined to the outer peripheral surface (side surface) by doing. That is, it shows the state before the covering concrete 4 is laminated. This embodiment 1 is applied to a steel frame column 1 positioned at an outer corner of a building. While joining 5A, two horizontal anchor members 5B, 5B are similarly joined in the opposite direction across the steel column 1 to the other surface that is in a positional relationship perpendicular to the one surface. . After that, the cover concrete 4 is placed on the upper surface of the foundation concrete 3 by an appropriate method to a height exceeding the upper ends of the anchor bolts 7, and the horizontal anchor members 5A, 5A, 5B, 5B, the base plate 2 and the anchor bolts 7 are buried.

As for the height (thickness) of the covering concrete 4, if the base plate 2 is buried even a little, the shear resistance due to the bearing pressure can be obtained in calculation. Since pressure is required, even if the top of the anchor bolt 7 is not completely buried as in the embodiment, it is preferable to stack the layers to a height close to that. Moreover, a necessary condition for the covering concrete 4 to the horizontal anchors 5A, 5A, 5B, 5B is that they can be fixed, and it is sufficient that the same cover thickness as the covering concrete 4 can be secured.

FIGS. 3 to 6 show examples of anchoring structures for exposed-type column bases according to the present invention, in which the joining forms of the horizontal anchor members are different. Parts that overlap with the first embodiment are indicated by the same reference numerals, and descriptions thereof are omitted. In the second embodiment shown in FIG. 3, a long nut 20 (screw hole metal fitting) is welded to the outer peripheral surface of the base plate 2 at its end surface, and the horizontal anchor member 5 is connected to the screw hole (not shown) of the long nut 20 and the male screw. They are joined by screwing the threaded portion 5a. The long nut 20 is welded to the upper surface of the base plate 2 in the third embodiment shown in FIG. 4, and the long nut 20 is welded to the lower surface of the base plate 2 in the fourth embodiment shown in FIG. In the fifth embodiment shown in FIG. 6, a plate 21 with a hole is welded to the outer peripheral surface of the base plate 2 in an upright state, a horizontal anchor member 5 is inserted through the through hole 21a of the plate 21 with a hole, and a nut on the opposite side is attached. It is fixed at 9,9. These second to fifth embodiments have the advantage over the first embodiment that there is no cross-sectional loss of the base plate 2 due to the drilling of the screw holes.

The present invention is not limited to the above embodiments, and various modifications can be made within the technical concept of the present invention, such as the type and number of horizontal anchor members used, and the column base structure.

The fixing structure of the exposed type column base according to the present invention exhibits its superiority in terms of economy when used for the column base of a steel structure, especially for a steel frame column positioned as a corner pillar or a side pillar of a building. , further development is expected.

DESCRIPTION OF SYMBOLS 1... Steel column, 2... Base plate, 2a... Screw hole, 2b... Insertion hole, 2c... Pouring hole, 3... Foundation concrete, 4... Coating concrete, 5, 5A, 5B... Horizontal anchor material, 6... Filling mortar, 7 Anchor bolt 8 Washer 8a Air release groove 9 Nut 10 Template 11 Level mortar 12 Form material 13 Grout filling funnel 20 Screw hole fitting (long nut) 21 … perforated plate

Claims (4)

For a plurality of anchor bolts whose lower parts are embedded in the foundation concrete, a base plate which is fixed to the lower end of the steel frame column and which is provided with insertion holes for the anchor bolts in the peripheral part is spaced from the upper surface of the foundation concrete. mortar material is injected between the upper surface of the base concrete and the lower surface of the base plate in a state of being fixed by tightening a nut that is screwed onto the upper part of the anchor bolt, and the solidified filling mortar is interposed between the upper surface of the base concrete and the lower surface of the base plate. An exposed type column base anchoring structure in which, after fixing a steel frame column to the base concrete, a cover concrete is layered so that at least the base plate is buried on the upper surface of the base concrete, and the cover concrete spreads in the horizontal direction. is not formed in at least one direction to the base plate fixed to the lower end of the steel frame column located at the installation location, the horizontal anchor is directed in the direction opposite to the direction in which the horizontal extension of the covering concrete is not formed. An anchoring structure for an exposed column base characterized by joining materials and embedding them in the covering concrete. 2. The fixing structure of the exposed type column base according to claim 1, wherein the horizontal anchor member has a male threaded portion at its end and is screwed into a screw hole drilled in the outer peripheral surface of the base plate. 2. The fixing structure of the exposed type column base according to claim 1, wherein the horizontal anchor member has a male screw at its end and is screwed into a screw hole metal fitting joined to the base plate. 2. The fixing structure of the exposed type column base according to claim 1, wherein the horizontal anchor member has a male screw at an end portion and is screwed with a nut through a holed plate joined to the base plate.

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