JP7266470B2 - Column base joint structure - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for joining the legs of columns used in buildings, structures, etc., to foundations made of concrete.

A structure that uses a plurality of anchor bolts embedded in the concrete of the foundation is widely adopted as a structure that joins the legs of a column to a concrete foundation. In such a joint structure, the upper ends of a plurality of anchor bolts protrude from the upper surface of the foundation and are inserted through the through holes of the base plate fixed to the lower end of the column. Then, by twisting and tightening the nuts on the anchor bolts, the base plate is joined so as to be pressed against the foundation.

When the lower end of the column is joined using anchor bolts in this way, a bending moment is generated at the lower end of the column when a horizontal force acts on the column. In the event of an earthquake or the like, the horizontal force acts repeatedly while reversing its direction, 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 manner, a pull-out force acts on the anchor bolt on the pulling side, causing the anchor bolt to elongate. 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 bending moment as described above, the plastic deformation that occurs in the bolts that fix the column base may remain after the action of the horizontal force is released. It is desirable to replace the bolt with a residual deformation with a new one to restore the state before the large horizontal force was applied.

Patent Literature 2 discloses a column base joint structure that allows rotational deformation of the lower end of a column due to a bending moment, and that is configured to be flexibly deformable.
This joint structure allows elongation to occur in a bolt connected to an anchor member embedded in the foundation concrete, and when the bending moment increases, the stress level of this bolt exceeds the yield point and plastic deformation occurs. When the plastic deformation remains, the bolt can be separated from the anchor member and replaced.

JP-A-4-80428 JP 2019-44401 A

However, the conventional technology has the following problems that need to be solved.
When a horizontal force acting on the column causes a bending moment at the lower end of the column and elongation occurs in the bolts that connect the lower end of the column to the foundation, the base plate is displaced so as to be lifted and separated 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. Such actions are repeated during an earthquake, and there is a risk that the mortar or concrete of the foundation will 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 deteriorates.

On the other hand, when a large bending moment acts and plastic deformation occurs in the bolt that joins the lower end of the column to the foundation and remains after unloading, it is desirable to replace the bolt with a new one. However, if the joint structure of the column base becomes complicated in order to allow replacement of the bolts, the workability deteriorates and the construction cost increases. For this reason, a structure that allows such bolts to be replaced easily and reliably is desired for joining column bases.

The present invention has been made in view of the circumstances as described above, and its object is to enable flexible deformation when a bending moment is applied, and to maintain good performance even if large deformation occurs repeatedly. To provide a column base joint structure that maintains a restoring function.

In order to solve the above-mentioned problems, the invention according to Claim 1 comprises: a foundation having a main portion formed of concrete; a bearing pressure plate fixed to the upper surface of the foundation; and the bearing pressure plate fixed to the foundation. a column erected on the foundation; a base plate fixed to a lower end of the column; and a joining bolt for superimposing and joining the base plate on the bearing plate; A bolt passes through a hole formed in the base plate and is screwed into a bolt hole formed in the bearing plate or the anchor bolt so that the joint is formed between the upper surface of the base plate and the head of the joint bolt. A bolt receiving member having a predetermined length in the axial direction of the bolt is inserted and tightened. The bolt receiving member is a cylindrical member in which the joint bolt is inserted through a central hole, and the lower end of the bolt receiving member is the base plate. and the head of the joint bolt is fixed to the upper end so as to restrain the joint bolt from coming out upward. means that the contact bolt is in contact with a gap narrow enough to prevent buckling of the joint bolt, or in a state in which the joint bolt and the inner peripheral surface of the center hole are allowed to move relative to each other in the vertical direction, Provided is a column base joint structure that is opposed to each other and allows deformation of the column by an amount of elongation of the joint bolt to which a tensile force acts when a bending moment acts on the lower end of the column. .

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 from the foundation on the tensile side. A base plate is fixed to the lower end of the column, and is superimposed on a bearing plate fixed to the upper surface of the foundation. That is, there is a relative displacement between the two plates. Therefore, even if a large horizontal force repeatedly reverses its direction, such as during an earthquake, irreversible deformation or displacement is less likely to occur in the lower end of the column and the bearing plate fixed to the foundation. . In particular, deformation or displacement is effectively reduced in a structure in which the pillars are made of wooden material and a structure in which the foundation is made of concrete. As a result, the structure maintains a good restoring force even if a load that is repeatedly reversed, such as during an earthquake, is applied.

Also, the joining bolts that join the bearing plate and the base plate are tightened through the bolt receiving members, so that the length can be appropriately set. Thereby, it is possible to set the extension amount of the joint bolt to be large on the tension side when the horizontal force acts on the column. Therefore, it is possible to allow the displacement of the lower end of the pillar in the rotational direction and to provide a structure that can be flexibly deformed. This joint bolt can be easily removed from above the foundation and replaced. As a result, even when plastic deformation remains in the joint bolt, it is possible to easily restore the state before the deformation.

In this column base connection structure, when the amount of elongation of the connection bolt increases 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, tensile strain and compressive strain are repeated, and the stress-strain history becomes loop-shaped. As a result, vibration energy can be effectively absorbed, and a damping structure with good damping performance can be obtained.

In addition, in this column base joint structure, the bolt receiving member prevents the joint bolt from buckling when compressive force is applied after the joint bolt undergoes plastic deformation on the tension side, and energy is released due to the stress-strain history. Absorption performance is effectively maintained.

The invention according to claim 2 is the column base joint structure according to claim 1 , wherein the joint bolt has a flange-shaped overhang, and the overhang is in contact with the upper surface of the bolt receiving member, It shall be fixed to the bolt receiving member by a fixing bolt.

The invention according to claim 3 is the column base joint structure according to claim 2, wherein the fixing bolt penetrates the brim-shaped overhang and the bolt receiving member in the axial direction of the joint bolt, Assume that it is screwed into a bolt hole provided in the base plate and tightened.

The invention according to claim 4 is the column base joint structure according to claim 1 or claim 2 , wherein the bolt receiving member is fixed to the base plate so as to be removable by an operation from above the base plate. shall be

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

The invention according to claim 5 is the column base joint structure according to any one of claims 1 to 4, wherein the tension of the tendon whose lower end is fixed to the foundation and whose upper end is fixed to the column is acting on the contact surface between the bearing pressure plate and the base plate.

In this column base joint structure, when the lower end of the column is displaced in the rotational direction, the tensile force of the tendons imparts a restoring force. Therefore, the structure has good restoring force.

As described above, in the column base joint structure of the present invention, it is possible to flexibly deform when a bending moment acts on the lower end of the column, and it has a good restoring function even when a large deformation occurs repeatedly. is maintained.

It is the front view and side view which show the column base joint structure which is one Embodiment of this invention. It is a plane sectional view and an elevation sectional view which show the column base joint structure shown in FIG. 1. It is the side view and sectional drawing which show the joint part of the base plate and 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 bearing plate of the column base joint structure which is other embodiment of this invention. It is sectional drawing which shows the joint part of the base plate and bearing plate of the column base joint structure which is other embodiment of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a front view and a side view showing a column base joint structure according to one embodiment of the present invention. 2 is a cross-sectional view taken along line AA and line BB in FIG.
This column base joint structure joins the lower end of a column 1 made of wooden material to a concrete base 2 . The pillar 1 is made of laminated lumber in which small cross-sections of wood are glued together, and a base plate 3 made of steel is attached to the lower end surface thereof in contact therewith. A bearing pressure plate 4 made of steel is fixed to the upper surface of the concrete foundation 2 , and the base plate 3 is superimposed on the bearing pressure plate 4 so as to be in close contact with them, and they are joined by joint bolts 5 .

The pillar 1 has a rectangular cross-sectional shape, and is a flat rectangular cross-section with one side longer than the other adjacent side. The lower end is joined to the base 2 so as to have resistance to the bending moment acting in the long side direction.
The column 1 has an axial hole in its center through which a tendon 6 is inserted. The lower end of this tendon 6 is embedded in the concrete of the foundation 2 and fixed. Then, a tension force is introduced at the upper portion (not shown) of the column 1, prestress is introduced to the column 1, and the column 1 is pressed toward the foundation 2 by force in the axial direction.

The base plate 3 is a rectangular plate-like member having a dimension larger than the cross section of the column 1, and has a portion that protrudes from the side surface of the column 1 when it is brought into contact with the lower end surface of the column 1. The base plate 3 is fixed to the column 1 by a plurality of embedded bolts 7 axially embedded from the lower end surface of the column 1 as shown in FIG. 2(b). One end of the embedded bolt 7 is screwed into a 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 of the column 1 . The part embedded in the post 1 is inserted into a preformed hole and bonded with an adhesive.

Attachment of the base plate 3 to the pillar 1 can be performed, for example, as follows.
An insertion hole for an embedded bolt 7 is previously formed in the column 1 upward from the lower end surface. One end of the embedded bolt 7 is twisted into the bolt hole of the base plate 3 , the projecting portion is inserted into the insertion hole formed in the column 1 and the base plate 3 is brought into contact with the lower end surface of the column 1 . Then, the base plate 3 can be attached to the lower end of the column 1 by injecting an adhesive into the hole into which the embedded bolt 7 is inserted and hardening it. An epoxy resin, for example, can be used as the adhesive.

The bearing pressure plate 4 is fixed to the foundation 2 with a plurality of anchor bolts 8 . Anchor bolts 8 have their lower ends embedded in the concrete of foundation 2 and their upper ends twisted into bolt holes of bearing plate 4 installed along the upper surface of foundation 2 .
The bearing pressure plate 4 can be fixed to the concrete of the foundation 2 by the following steps, for example.
When placing the concrete of the foundation 2, a cylindrical formwork is installed at a position where the anchor bolt 8 is embedded, and a hole is formed downward from the upper surface. Then, the anchor bolts 8 are fixed to the bearing pressure plate 4 in advance, the anchor bolts 8 are inserted into the holes, and the bearing pressure plate 4 is accurately installed at a predetermined position. The holes and the underside of the support plate 4 are filled with mortar, and the support plate 4 is fixed at a predetermined position on the foundation 2 by hardening the mortar.

Moreover, as another method, the following method can also be adopted.
Before pouring the concrete forming the foundation, the bearing plate 4 and the anchor bolts 8 fixed thereto are supported in a precise position by a temporary support frame. Then, the anchor bolts 8 are embedded together with the temporary support frame, and the concrete of the foundation 2 is poured to a position where it comes into close contact with the bearing pressure plate 4 . The bearing plate 4 is fixed on the foundation 2 by hardening of the concrete.

The base plate 3 is joined to the bearing plate 4 by joint bolts 5 as shown in FIG.
The joint bolt 5 is inserted through a central hole 9 a of a thick cylindrical bolt receiving member 9 , and the base plate 3 is fastened to the bearing plate 4 via the bolt receiving member 9 . The joint bolt 5 has a flange-like projecting portion 5b below a hexagonal head portion 5a with which a tool is engaged. The projecting portion 5 b abuts on the upper surface of the bolt receiving member 9 , and the bolt receiving member 9 is sandwiched between the projecting portion 5 b and the base plate 3 . The joint bolt 5 is inserted through a through hole provided in the base plate 3 and screwed into a bolt hole formed in the bearing plate 4 at its tip end. By strongly screwing the joint bolt 5 into the bolt hole of the bearing pressure plate 4 , the bolt receiving member 9 is pressed against the base plate 3 and the base plate 3 is pressed against the bearing pressure plate 4 .
The joint bolts 5 transmit the tensile force acting from the column 1 to the bearing plate 4 and the anchor bolts 8 , and the cross-sectional area or the number of the joint bolts 5 are set so that the anchor bolts 8 expand more than the anchor bolts 8 .

The projecting portion 5b of the joint bolt 5 is fixed to the upper surface of the bolt receiving member 9 by an upper fixing bolt 10 so as not to separate from the bolt receiving member 9. As shown in FIG. Also, the bolt receiving member 9 is fixed to the base plate 3 with a lower fixing bolt 11 . The lower fixing bolt 11 passes through the base plate 3 from below, is screwed into a bolt hole formed in 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 accommodated in a recess 3 a formed in the lower surface of the base plate 3 so as not to prevent the base plate 3 from coming into close contact with the pressure bearing plate 4 .

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

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 force acts between the base plate 3 and the bearing plate 4 on the compression side, causing tension. On the side, a tensile force acts on the joint bolt 5 that joins the base plate 3 and the bearing plate 4 . As a result, the joint bolt 5 is elongated, and the base plate 3 is displaced so as to be lifted from the bearing plate 4 . When the horizontal force repeatedly reverses its direction as in the case of an earthquake, the compression side reverses to the tension side and the tension side reverses to the compression side, and the legs of the column 1 are repeatedly displaced. When the extension of the joint bolt 5 is within the elastic range with respect to such displacement, the column 1 has a restoring force due to the elastic force of the joint bolt 5 . When the elongation of the joint bolt 5 reaches the plastic region, the tension force of the tendon 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 and the bearing plate 4 made of steel, and large deformation occurs after the large horizontal force during an earthquake acts. Residual is avoided.

Moreover, the length of the joint bolt 5 is set large by tightening it through the bolt receiving member 9 . As a result, the amount of elongation increases when a tensile force acts, and the structure including the column 1 can be flexibly deformed. Then, when the tensile stress reaches the plastic region, the head of the joint bolt 5 is fixed to the bolt receiving member 9, so that a compressive force acts on the joint bolt 5 after being elongated and deformed. Therefore, the amount of energy absorbed by the stress-strain hysteresis increases, making it possible to effectively attenuate seismic motion.

Furthermore, when a large horizontal force such as an earthquake acts and deformation remains in 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 plastic deformation remains, the state before deformation can be easily restored.

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

The bolt receiving member 23 has a central hole through which the joint bolt 22 is inserted, and a plurality of bolt insertion holes 24 extending through the bolt receiving member 23 in the axial direction. A plurality of bolt holes are formed in the base plate 20 around the through holes through which the joint bolts 22 are inserted, and female threads are cut on the inner peripheral surface of the base plate 20, and fixing bolts 25 for fixing the bolt receiving member 23 are screwed therein. It is possible.

The joint bolt 22 has the bolt receiving member 23 sandwiched between the overhanging portion 22b and the base plate 20, and the tip portion thereof is screwed into the bolt hole of the bearing pressure plate 21 and tightened. The base plate 20 is thereby coupled to the bearing plate. A fixing bolt 25 is inserted from a hole formed in the overhanging portion 22b of the joint bolt 22 into a bolt insertion hole 24 provided at a corresponding position, and the tip thereof is screwed into a 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 22a of the joining bolt is fixed to the bolt receiving member 23. As shown in FIG.

This column base joint structure functions in the same manner as the structure shown in FIGS. work becomes possible.

In the column base joint structure shown in FIG. 4(b), the bolt receiving member 33 has a flange 33a at its lower end. The bolt receiving member 33 is fixed to the base plate 30 by a lower fixing bolt 35 inserted through a hole formed in the flange 33a.
A projecting portion 32b and a head portion 32a of the joint bolt 32 can be fixed to the upper portion of the bolt receiving member 33 by an upper fixing bolt 34, similarly to the structure shown in FIG.
Even with this structure, the base plate 30 is connected to the bearing plate 31 by the joint bolts 32, and the joint bolts 32 and the bolt receiving members 33 are removed when the joint bolts 32 are replaced.

In the column base joint structure shown in FIG. 5, a bolt receiving member 43 is inserted between the head 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 tightened by screwing it into the bolt hole.
In this structure, respective positions are set so that the central axis of the joint bolt 42 and the central axis of the anchor bolt 12 are aligned. A bolt hole is formed in the axial direction from the upper end surface of the anchor bolt 12, and the tip portion of the joint bolt 42 is screwed into the bolt hole and tightened. By tightening the joint bolts 42 in this manner, the bolt receiving member 43 can be pressed against the base plate 40 and the base plate can be pressed against the bearing pressure plate 41 for coupling. The bolt receiving member 43 is fixed to the base plate 40 by a fixing bolt 44 in the same manner as the structure shown in FIG. A male screw is formed on the outer peripheral surface of the upper portion of the anchor bolt 12, and it can be screwed into a bolt hole formed in the bearing pressure plate 41 and connected thereto, similar to the structure shown in FIG.
With 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, deformation of the bearing pressure 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 to these, and can be implemented by appropriately changing the form 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 and cross-sectional area of the joint bolt, the fixing structure of the head, etc. can be appropriately designed.
In the above-described embodiment, the means for fixing the head of the joint bolt to the bolt receiving member is to fix the projecting portion provided at the top of the joint bolt to the bolt receiving member with a bolt. means are not limited to 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: Column 2: Foundation 3: Base plate 3a: Recess provided on the lower surface of the base plate 4: Bearing plate 5: Joint bolt 5a: Head of joint bolt 5b: Overhang of joint bolt 6: Tendon 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: Bearing plate, 22: Joining bolt, 22a: Head of joining bolt, 22b: Overhanging portion of joining bolt, 23: Bolt receiving member, 24: Bot insertion hole, 25: Fixing bolt,
30: base plate, 31: bearing plate, 32: joint bolt, 32a: head of joint bolt, 32b: projecting portion of joint bolt, 33: bolt receiving member, 33a: flange of bolt receiving member, 34: upper fixing bolt , 35: lower fixing bolt,
40: Base plate, 41: Bearing plate, 42: Joining bolt, 42a: Head of joining bolt, 42b: Overhanging portion of joining bolt, 43: Bolt receiving member, 44: Fixing bolt

Claims (5)

a foundation whose main part is formed of concrete;
a bearing plate fixed to the upper surface of the foundation;
anchor bolts for fixing the bearing plate to the foundation;
a pillar erected on the foundation;
a base plate fixed to the lower end of the pillar;
a joining bolt that overlaps and joins the base plate onto the bearing pressure plate;
The joint bolt is
penetrates a hole formed in the base plate and is screwed into a bolt hole formed in the bearing plate or the anchor bolt;
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;
The bolt receiving member is
a cylindrical member having a center hole through which the joint bolt is inserted;
The lower end is fixed to the base plate, and the head of the joint bolt is fixed to the upper end so as to restrain the joint bolt from coming out upward,
The inner peripheral surface of the center hole and the outer peripheral surface of the joint bolt are separated from each other by a gap narrow enough to prevent buckling of the joint bolt, or in the vertical direction between the joint bolt and the inner peripheral surface of the center hole. are in contact and face each other in a state in which the relative displacement of
A column base joint structure, wherein when a bending moment acts on the lower end of the column, deformation of the column is allowed by an elongation amount of the joint bolt to which a tensile force acts. 2. The joint bolt according to claim 1, wherein the joint bolt has a brim-shaped projecting portion, the projecting portion is in contact with the upper surface of the bolt receiving member, and is fixed to the bolt receiving member by a fixing bolt. The described column base joint structure. 3. The fixing bolt passes through the brim-shaped projecting portion and the bolt receiving member in the axial direction of the joining bolt, and is screwed into a bolt hole provided in the base plate and tightened. 2. The column base joint structure according to 2. The column base joint structure according to claim 1 or 2, wherein the bolt receiving member is fixed to the base plate so as to be removable by an operation from above the base plate. 2. A pressure contact force due to a tension force of a tendon whose lower end is fixed to said foundation and whose upper end is fixed to said column acts on the contact surface between said bearing plate and said base plate. The column base joint structure according to any one of claims 1 to 4.

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