JP2021001456A - Column base part joining structure - Google Patents

Abstract

To provide a column base part joining structure capable of flexibly deforming when a bending moment is applied, and maintaining a restoring function in a good state for a long time when large deformation is repeatedly generated.SOLUTION: A bearing plate 4 is fixed on a concrete foundation 2 by an anchor bolt 8, and a base plate 3 is fixed on the lower end of a column 1 erected on the foundation. The base plate 3 is superimposed on the bearing plate 4 and these are connected by joint bolts 5. The joint bolt 5 is inserted into a through hole formed in the base plate and screwed into a bolt hole formed in the bearing plate 4 or the anchor bolt 8. A bolt receiving member 9 having a predetermined length in the axial direction of the joint bolt is inserted and fastened between the upper surface of the base plate 3 and the head of the joint bolt 5.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structure in which the legs of columns used in buildings, structures, etc. are joined to a foundation made of concrete.

As a structure for joining the legs of columns to a concrete foundation, a structure using a plurality of anchor bolts embedded in the concrete of the foundation is widely adopted, and is described in, for example, Patent Document 1. In such a joint structure, the upper ends of the plurality of anchor bolts are projected from the upper surface of the foundation and inserted into the through holes of the base plate fixed to the lower ends of the columns. Then, the nut is twisted and tightened to the anchor bolt to join the base plate so as to press it against the foundation.

When the lower ends of the columns are joined using anchor bolts in this way, a bending moment is generated at the lower ends of the columns when a horizontal force is applied to the columns. Then, in the event of an earthquake or the like, the horizontal force reverses its direction and acts repeatedly, and along with this, the bending moment also reverses its direction and acts repeatedly.
When a bending moment acts on the lower end of the column in this way, a pulling force acts on the anchor bolt on the tension side, causing the anchor bolt to stretch. Then, when the tensile stress of the anchor bolt exceeds the yield point, plastic deformation occurs. On the compression side, on the other hand, the base plate is pressed against the foundation.

In the joint structure that resists the bending moment as described above, the plastic deformation that occurs in the bolt that fixes the column base may remain after the action of the horizontal force is released. It is desirable to replace the bolt with residual deformation with a new one and restore it to the state before the large horizontal force was applied.

Patent Document 2 discloses a column base joint structure that allows rotational deformation of the lower end of a column due to a bending moment and allows flexible deformation.
This joint structure allows the bolt connected to the anchor member embedded in the concrete of the foundation to stretch, and when the bending moment increases, the stress level of this bolt exceeds the yield point and is plastically deformed. Occurs. Then, when the plastic deformation remains, this bolt can be separated from the anchor member and replaced.

Japanese Unexamined Patent Publication No. 4-80428 JP-A-2019-444401

However, the conventional technology has problems for which the following solutions are desired.
When the horizontal force acting on the column creates a bending moment at the bottom of the column and the bolts that join the bottom of the column to the foundation stretch, the base plate is displaced to lift and separate from the mortar or concrete of the foundation. Then, when the direction of the bending moment is reversed, the base plate is strongly pressed against the mortar or concrete of the foundation. In the event of an earthquake, such an operation will be repeated, and the mortar or concrete of the foundation may deteriorate or deform at the contact portion with the base plate. When such deterioration or deformation occurs, the function of restoring the displacement of the lower end of the column is reduced.

On the other hand, when a large bending moment acts on the bolt that joins the lower end of the column to the foundation due to plastic deformation and remains even after unloading, it is desirable to replace the bolt with a new one. However, if the joint structure of the column base is complicated in order to enable the replacement of bolts, the workability is deteriorated and the construction cost is increased. Therefore, for joining the column bases, a structure capable of easily and surely replacing such bolts is desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is that it can be flexibly deformed when a bending moment is applied, and it is good even if a large deformation occurs repeatedly. It is to provide a column base joint structure in which the restoration function is maintained.

In order to solve the above problems, the invention according to claim 1 has a foundation in which a main portion is formed of concrete, a bearing plate fixed to the upper surface of the foundation, and the bearing plate fixed to the foundation. It has an anchor bolt, a pillar erected on the foundation, a base plate fixed to the lower end of the pillar, and a joining bolt for superimposing and joining the base plate on the bearing plate. The bolt penetrates the hole formed in the base plate and is screwed into the bolt hole formed in the bearing plate or the anchor bolt, and the joint is formed between the upper surface of the base plate and the head of the joint bolt. Provided is a column base joint structure in which bolt receiving members having a predetermined length in the axial direction of bolts are inserted and fastened.

In this column base joint structure, when a horizontal force acts on the column, the column is tilted and the lower end of the column is displaced so as to rise from the foundation on the tension side. A base plate is fixed to the lower end of the column and is overlapped with a bearing plate fixed to the upper surface of the foundation, and the base plate is displaced so as to be lifted from the bearing plate. That is, a relative displacement occurs between the two plates. Therefore, even if a large horizontal force repeatedly reverses the direction as in an earthquake, the lower end of the column and the bearing plate fixed to the foundation are less likely to undergo unrecoverable deformation or displacement. .. In particular, deformation or displacement is effectively reduced in a structure in which the pillars are made of wood and a structure in which the foundation is made of concrete. As a result, even if a load that repeatedly reverses is applied as in an earthquake, a good restoring force is maintained.

Further, the joining bolts that join the bearing plate and the base plate are tightened via the bolt receiving members, and the length can be appropriately set. As a result, it is possible to set the amount of elongation of the joining bolt to be large on the tension side when a horizontal force is applied to the column. Therefore, the structure can be flexibly deformed by allowing the lower end of the column to be displaced in the rotational direction. The joining bolt can then be easily removed and replaced from above the foundation. As a result, even when the plastic deformation remains on the joint bolt, it can be easily restored to the state before the deformation.

In the invention according to claim 2, in the column base joint structure according to claim 1, the lower end of the bolt receiving member is fixed to the base plate, and the joint bolt is pulled out upward at the upper end. It is assumed that the head of the joint bolt is fixed so as to restrain the joint bolt.

In this column base joint structure, when the elongation amount of the joint bolt becomes large and plastic deformation occurs, and then the tension side is reversed to the compression side, the head is fixed to the base plate via the bolt receiving member. A compressive force acts on the joint bolt. As a result, when the horizontal force is repeatedly reversed, the tensile strain and the compressive strain are repeated, and the stress-strain history becomes a loop. As a result, vibration energy is effectively absorbed, and it is possible to form a vibration control structure with good damping performance.

According to the third aspect of the present invention, in the column base joint structure according to the second aspect, the bolt receiving member is detachably fixed to the base plate by an operation from the upper side of the base plate. To do.

In this column base joint structure, the joint bolt and the bolt receiving member can be removed and easily replaced. Therefore, when the plastic deformation remains in the joining bolt, the joining bolt can be reliably replaced and restored to the initial state.

The invention according to claim 4 is the column base joint structure according to claim 2 or 3, wherein the bolt receiving member is a cylindrical member, and the joint bolt is inserted into a central hole. There is a narrow gap between the inner peripheral surface of the center hole and the outer peripheral surface of the joint bolt so as to prevent buckling of the joint bolt, or in the vertical direction between the joint bolt and the inner peripheral surface of the hollow hole. They shall be in contact and opposed to each other in a state where relative displacement is allowed.

In this column base joint structure, buckling of the joint bolt is prevented by the bolt receiving member when a compressive force is applied after the joint bolt undergoes plastic deformation on the tension side, and the energy absorption performance based on the stress-strain history. Is kept valid.

The invention according to claim 5 is the tensioning force of a tensioning material in which the lower end is fixed to the foundation and the upper end is fixed to the pillar in the column base joint structure according to any one of claims 1 to 4. It is assumed that the pressure contact force by the above acts on the contact surface between the bearing plate and the base plate.

In this column base joint structure, a restoring force is applied by the tension force of the tension member when the lower end portion of the column is displaced in the rotational direction. Therefore, the structure has a good restoring force.

As described above, the column base joint structure of the present invention can be flexibly deformed when a bending moment is applied to the lower end of the column, and also has a good restoration function even when a large deformation occurs repeatedly. Is maintained.

It is a front view and the side view which shows the column base joint structure which is one Embodiment of this invention. It is a plan sectional view and the vertical sectional view which show the column base joint structure shown in FIG. It is a side view and the cross-sectional view which shows the joint part of the base plate and the bearing plate in the column base joint structure shown in FIG. It is sectional drawing which shows the joint part of the base plate and the bearing plate of the column base joint structure which is another embodiment of this invention. It is sectional drawing which shows the joint part of the base plate and the bearing plate of the column base joint structure which is another embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view and a side view showing a column base joint structure according to an embodiment of the present invention. Further, FIG. 2 is a cross-sectional view taken along the line AA and BB in FIG.
In this column base joining structure, the lower end of the column 1 made of wood is joined to the concrete foundation 2. The pillar 1 is made of laminated wood having a small cross section of wood bonded to each other, and a base plate 3 made of steel is attached to the pillar 1 in contact with the lower end surface. Further, a bearing plate 4 made of steel is fixed to the upper surface of the concrete foundation 2, and the base plate 3 is superposed so as to be in close contact with the bearing plate 4, and these are connected by a joining bolt 5.

The pillar 1 has a rectangular cross-sectional shape, and the length of one side of the cross-section is a flat rectangle longer than the other adjacent sides. Then, it is joined to the foundation 2 so as to have a resistance force against a bending moment acting in the long side direction at the lower end portion.
A hole in the axial direction is formed in the central portion of the pillar 1, and the tension member 6 is inserted therethrough. The lower end of the tension member 6 is embedded in the concrete of the foundation 2 and fixed. Then, a tension force is introduced at the upper part (not shown) of the column 1, prestress is introduced into the column 1, and the column 1 is pressed toward the foundation 2 by a force in the axial direction.

The base plate 3 is a rectangular plate-shaped member, has a size larger than the cross section of the pillar 1, and has a portion protruding from the side surface of the pillar 1 when it comes into contact with the lower end surface of the pillar 1. As shown in FIG. 2B, the base plate 3 is fixed to the pillar 1 by a plurality of embedded bolts 7 embedded in the axial direction from the lower end surface of the pillar 1. One end of the embedded bolt 7 is screwed into the bolt hole of the base plate 3 to be connected, and a portion protruding upward from the upper surface of the base plate 3 is embedded in the lower end portion of the pillar 1. The portion embedded in the pillar 1 is inserted into a preformed hole and bonded with an adhesive.

The base plate 3 can be attached to the pillar 1 as follows, for example.
An insertion hole for the embedding bolt 7 is formed in advance in the pillar 1 from the lower end surface upward. One end of the embedded bolt 7 is twisted into the bolt hole of the base plate 3, the protruding portion is inserted into the insertion hole formed in the pillar 1, and the base plate 3 is brought into contact with the lower end surface of the pillar 1. Then, the base plate 3 can be attached to the lower end of the pillar 1 by injecting an adhesive into the hole into which the embedding bolt 7 is inserted and curing the adhesive. As the adhesive, for example, an epoxy resin can be used.

The bearing plate 4 is fixed to the foundation 2 by a plurality of anchor bolts 8. The lower part of the anchor bolt 8 is embedded in the concrete of the foundation 2, and the upper end is twisted into the bolt hole of the bearing plate 4 installed along the upper surface of the foundation 2.
The bearing plate 4 can be fixed to the concrete of the foundation 2 in the following steps, for example.
When placing the concrete of the foundation 2, a tubular formwork is installed at a position where the anchor bolt 8 is embedded, and a hole is formed from the upper surface to the lower side. Then, the anchor bolt 8 is fixed to the bearing plate 4 in advance, the anchor bolt 8 is inserted into the hole, and the bearing plate 4 is accurately installed at a predetermined position. A mortar is filled in the hole and the lower side of the bearing plate 4, and the bearing plate 4 is fixed at a predetermined position on the foundation 2 by hardening the mortar.

In addition, as another method, the following method can also be adopted.
Before placing the concrete forming the foundation, the bearing plate 4 and the anchor bolts 8 fixed to the bearing plate 4 are supported in the correct position by the temporary support frame. Then, the anchor bolt 8 is embedded together with the temporary support frame, and the concrete of the foundation 2 is placed to a position where it is in close contact with the bearing plate 4. As the concrete hardens, the bearing plate 4 is fixed on the foundation 2.

The base plate 3 is connected to the bearing plate 4 by a joining bolt 5 as shown in FIG.
The joining bolt 5 is inserted into a central hole 9a of a thick cylindrical bolt receiving member 9, and the base plate 3 is tightened to the bearing plate 4 via the bolt receiving member 9. The joining bolt 5 is provided with a brim-shaped overhang 5b under the hexagonal head 5a to which the tool is engaged. The overhanging portion 5b is in contact with the upper surface of the bolt receiving member 9, and the bolt receiving member 9 is sandwiched between the overhanging portion 5b and the base plate 3. Then, the joining bolt 5 is inserted into a through hole provided in the base plate 3, and the tip portion is screwed into the bolt hole formed in the bearing plate 4. By strongly screwing the joining bolt 5 into the bolt hole of the bearing plate 4, the bolt receiving member 9 is pressed against the base plate 3, and the base plate 3 is pressed against the bearing plate 4.
The joint bolt 5 transmits the tensile force acting from the column 1 to the bearing plate 4 and the anchor bolt 8, but the cross-sectional area or the number of the joint bolt 5 is set so as to cause greater elongation than the anchor bolt 8.

The overhanging portion 5b of the joining bolt 5 is fixed to the upper surface of the bolt receiving member 9 by the upper fixing bolt 10 so as not to be separated from the bolt receiving member 9. Further, the bolt receiving member 9 is fixed to the base plate 3 by the lower fixing bolt 11. The lower fixing bolt 11 penetrates the base plate from the lower side of the base plate 3, is screwed into a bolt hole formed on the lower end surface of the bolt receiving member 9, and is tightened to fix the bolt receiving member 9 to the base plate 3. The head of the lower fixing bolt 11 is housed in a recess 3a formed on the lower surface of the base plate 3 so as not to prevent the base plate 3 from coming into close contact with the bearing plate 4.

The central hole of the bolt receiving member 9 has an inner diameter slightly larger than the outer diameter of the joint bolt 5 through which the joint bolt 5 is inserted, and restrains the joint bolt 5 from being displaced in the lateral direction to prevent buckling of the joint bolt 5. Can be done.

In such a column base joint structure, when a horizontal force acts on the column 1 and a bending moment is generated at the lower end, a bearing pressure acts between the base plate 3 and the bearing plate 4 on the compression side, and tension is applied. On the side, a tensile force acts on the joint bolt 5 that connects the base plate 3 and the bearing plate 4. As a result, the joint bolt 5 is stretched and the base plate 3 is displaced so as to be lifted from the bearing plate 4. Then, when the horizontal force repeatedly reverses the direction and acts as in the case of an earthquake, the compression side is reversed to the tension side and the tension side is reversed to the compression side, and the legs of the column 1 are repeatedly displaced. When the elongation of the joining bolt 5 is within the elastic range with respect to such a displacement, the column 1 has a restoring force due to the elastic force of the joining bolt 5. When the elongation of the joining bolt 5 reaches the plastic region, the tension force of the tension member 6 arranged in the axial direction of the column 1 acts as a restoring force. At this time, the relative displacement between the column 1 and the foundation 2 occurs between the base plate 3 made of steel and the bearing plate 4, and after a large horizontal force during an earthquake is applied, a large deformation or the like occurs. It is avoided to remain.

Further, the length of the joining bolt 5 is set large by tightening the joint bolt 5 via the bolt receiving member 9. As a result, the amount of elongation when a tensile force acts is increased, and the structure including the column 1 can be flexibly deformed. Then, when the degree of tensile stress reaches the plastic region, a compressive force acts on the joint bolt 5 after the elongation deformation occurs because the head of the joint bolt 5 is fixed to the bolt receiving member 9. Therefore, the amount of energy absorbed by the stress-strain history becomes large, and it becomes possible to effectively attenuate the seismic motion.

Further, when a large horizontal force acts such as during an earthquake and deformation remains on the joint bolt 5, the joint bolt 5 can be easily replaced by removing the upper fixing bolt 10 that fixes the head of the joint bolt 5. It has become. Therefore, even if the plastic deformation remains, it can be easily restored to the state before the deformation occurs.

FIG. 4A is a cross-sectional view showing a joint portion between the base plate and the bearing plate of the column base joint structure according to another embodiment of the present invention.
In this column base joint structure, the base plate 20 fixed to the lower end of the column 1 and the bearing plate 21 fixed on the foundation 2 are superposed and joined by the joining bolt 22 as in the embodiment shown in FIG. However, the mode for fixing the bolt receiving member 23 is different.

The bolt receiving member 23 includes a plurality of bolt insertion holes 24 penetrating in the axial direction of the bolt receiving member 23, in addition to the central hole through which the joining bolt 22 is inserted. Then, a plurality of bolt holes are formed in the base plate 20 around the through holes through which the joining bolts 22 are inserted, and female threads are cut on the inner peripheral surface to screw in the fixing bolts 25 for fixing the bolt receiving members 23. It has become something that can be done.

The joint bolt 22 is tightened by sandwiching the bolt receiving member 23 between the overhanging portion 22b and the base plate 20, and screwing the tip portion into the bolt hole of the bearing plate 21. As a result, the base plate 20 is coupled to the bearing plate. Then, the fixing bolt 25 is inserted into the bolt insertion hole 24 provided at the corresponding position from the hole formed in the overhanging portion 22b of the joining bolt 22, and the tip portion is screwed into the bolt hole of the base plate 20 and tightened. .. Therefore, the bolt receiving member 23 is fixed to the base plate 20 by the fixing bolt 25, and the head portion 22a of the joining bolt is fixed to the bolt receiving member 23.

Even in such a column base joint structure, it functions in the same manner as the structures shown in FIGS. 1 to 3, and when the joint bolt 22 is replaced, not only the joint bolt 22 but also the bolt receiving member 23 can be removed, which is reliable. Work becomes possible.

In the column base joint structure shown in FIG. 4B, the bolt receiving member 33 has a flange 33a at the lower end. The bolt receiving member 33 is fixed to the base plate 30 by the lower fixing bolt 35 inserted into the hole formed in the flange 33a.
Similar to the structure shown in FIG. 3, the overhanging portion 32b and the head portion 32a of the joining bolt 32 can be fixed to the upper portion of the bolt receiving member 33 by the upper fixing bolt 34.
Even with such a structure, the base plate 30 is connected to the bearing plate 31 by the joining bolt 32, and the joining bolt 32 and the bolt receiving member 33 are removed when the joining bolt 32 is replaced, so that reliable work can be performed.

In the column base joint structure shown in FIG. 5, a bolt receiving member 43 is inserted between the head portion 42a of the joint bolt and the base plate 40, and the joint bolt 42 inserted through the through hole of the base plate 40 is formed in the anchor bolt 12. It is screwed into the bolt hole and tightened.
In this structure, the respective positions are set so that the central axis of the joint bolt 42 and the central axis of the anchor bolt 12 coincide with each other. Then, a bolt hole is formed in the axial direction from the upper end surface of the anchor bolt 12, and the tip end portion of the joint bolt 42 is screwed into the bolt hole and tightened. By tightening the joining bolt 42 in this way, the bolt receiving member 43 can be pressed against the base plate 40, and the base plate can be further pressed and joined to the bearing plate 41. The bolt receiving member 43 is fixed to the base plate 40 by the fixing bolt 44 in the same manner as the structure shown in FIG. 4A, and the head portion 42a and the overhanging portion 42b of the joining bolt are fixed to the upper portion. A male screw is formed on the outer peripheral surface of the upper portion of the anchor bolt 12, and the anchor bolt 12 can be screwed into a bolt hole formed in the bearing plate 41 to be connected in the same manner as the structure shown in FIG.
In such a structure, the tensile force acting on the joint bolt 42 is directly transmitted to the anchor bolt 12 and supported by the foundation 2. Therefore, the deformation of the bearing plate 41 can be suppressed.

The column base joint structure described above is an embodiment of the present invention, and the present invention is not limited thereto, and the form can be appropriately changed within the scope of the present invention. ..
For example, the cross-sectional shape and dimensions of the column, the shape and dimensions of the base plate and the bearing plate, the length of the joining bolt, the cross-sectional area, the fixing structure of the head, and the like can be appropriately designed.
Further, in the above-described embodiment, the means for fixing the head of the joining bolt to the bolt receiving member is such that the overhanging portion provided on the upper part of the joining bolt is fixed to the bolt receiving member with a bolt. It is not limited to any means. For example, an additional member capable of pressing the head of the joining bolt may be fixed to the bolt receiving member or the base plate.

1: Pillar, 2: Foundation, 3: Base plate, 3a: Recessed portion provided on the lower surface of the base plate, 4: Supporting plate, 5: Joint bolt, 5a: Head of joint bolt, 5b: Overhanging part of joint bolt, 6: Tension material, 7: Embedded bolt, 8: Anchor bolt, 9: Bolt receiving member, 9a: Center hole of bolt receiving member, 10: Upper fixing bolt, 11: Lower fixing bolt, 12: Anchor bolt,
20: Base plate, 21: Supporting plate, 22: Joining bolt, 22a: Joining bolt head, 22b: Joining bolt overhang, 23: Bolt receiving member, 24: Bolt insertion hole, 25: Fixing bolt,
30: Base plate, 31: Supporting plate, 32: Joining bolt, 32a: Joining bolt head, 32b: Joining bolt overhang, 33: Bolt receiving member, 33a: Bolt receiving member flange, 34: Upper fixing bolt , 35: Lower fixing bolt,
40: Base plate, 41: Supporting plate, 42: Joining bolt, 42a: Joining bolt head, 42b: Joining bolt overhang, 43: Bolt receiving member, 44: Fixing bolt

Claims (5)

The foundation, the main part of which is made of concrete,
A bearing plate fixed to the upper surface of the foundation and
Anchor bolts that fix the bearing plate to the foundation,
The pillars erected on the foundation and
A base plate fixed to the lower end of the pillar and
It has a joining bolt that superimposes and joins the base plate on the bearing plate.
The joining bolt is
It penetrates the hole formed in the base plate and is screwed into the bolt hole formed in the bearing plate or the anchor bolt.
A column base joint characterized in that a bolt receiving member having a predetermined length in the axial direction of the joint bolt is inserted and tightened between the upper surface of the base plate and the head of the joint bolt. Construction. The bolt receiving member is characterized in that a lower end thereof is fixed to the base plate and a head portion of the joint bolt is fixed to the upper end portion so as to restrain the joint bolt from coming out upward. The column base joint structure according to claim 1. The column base joint structure according to claim 2, wherein the bolt receiving member is detachably fixed to the base plate by an operation from the upper side of the base plate. The bolt receiving member is a cylindrical member, and the joining bolt is inserted into the center hole.
There is a narrow gap between the inner peripheral surface of the central hole and the outer peripheral surface of the joint bolt so that buckling of the joint bolt can be suppressed, or in the vertical direction between the joint bolt and the inner peripheral surface of the hollow hole. The column base joint structure according to claim 2 or 3, wherein the bolts are in contact with each other in a state in which the relative displacement of the bolts is allowed to face each other. Claim 1 is characterized in that the pressure contact force due to the tension force of the tension material whose lower end is fixed to the foundation and whose upper end is fixed to the pillar acts on the contact surface between the bearing plate and the base plate. The column base joint structure according to any one of claims 4 to 4.

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