JP2000248560A - Base isolation construction of pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a pile top from breaking down due to shearing force or bending moment at an earthquake, while effectively utilizing the shearing proof stress of a pile main body. SOLUTION: In this base isolation construction of a pile, by covering a pile top 3 with a pile top cap provided with a closed ended cylindrical pipe 1, the interior of the bottomed pipe 1 becomes a hollow space formed in the pile top 3. Reinforcements 4 as tesile resisting material are vertically arranged in the hollow space, the lower ends are fixed to the bottom part of the hollow space, i.e., the bottom plate 5 of the bottomed pipe 1 by nuts 6, and the upper parts of the reinforcements 4 are fixed to a base slab 7 as the base part of an upper structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile, particularly a seismic isolation structure at a pile head.

[0002]

2. Description of the Related Art There are two types of pile foundations: a support pile type and a friction pile type. In the former, when a good quality support layer is deep underground, an upper structure is constructed on a pile driven into the support layer. Accordingly, the structure is a type in which the weight of the structure is stably supported by the support layer, and the latter is a basic type in which the upper structure is supported by the frictional force with the surrounding ground when there is no high-quality support layer.

[0003] Naturally, these piles must be able to reliably support the weight of the superstructure, but in the event of an earthquake, a large shear force or bending moment acts on the pile head due to the horizontal force from the superstructure. Therefore, when designing and constructing, it is necessary to give due consideration to earthquake safety.

[0004]

Conventionally, as a method of joining a pile and a foundation slab, a pile head of a cast-in-place concrete pile is embedded in the foundation slab by about 10 cm, and a main bar of the pile previously set is fixed to the foundation slab. There was a method of making the pile head of the ready-made pile into the foundation slab by the pile diameter length, but in these joining methods, the degree of fixation α was 1.0, that is, almost rigid, and in the case of a huge earthquake, Excessive shearing force and bending moment act on the pile head, which may lead to unexpected situations such as breakage of the pile and collapse of the superstructure.

In addition, the pile head of a PC pile or a PHC pile is set to 10 cm.
PC steel wires and steel rods embedded in the foundation slab and left at the time of pile cutting are anchored to the foundation slab, and the joint reinforcement is welded to the pile head of a steel pipe pile or a ready-made concrete pile with an outer shell steel pipe. There have been methods of fixing to the slab or reinforcing the inside of the pile by filling the hollow part with reinforced concrete with a length of about twice the diameter of the pile. Experiments have shown that a significant bending moment is generated at the pile head under the action of the axial force, though it is smaller than that.

On the other hand, there has been proposed a structure in which a seismic isolation bearing using seismic isolation rubber is interposed between a pile head and a foundation slab. In such a joining method, a horizontal force from an upper structure is cut off. While it is possible to prevent the generation of a shearing force at the pile head, the shearing strength inherent in the pile body is not used at all, and there is a lack of economy.

The present invention has been made in view of the above-mentioned circumstances, and has a pile excavator capable of preventing a breakage at a pile head due to a shear force or a bending moment during an earthquake while effectively utilizing the shear strength of the pile body. The purpose is to provide a seismic structure.

[0008]

In order to achieve the above object, a seismic isolation structure for a pile according to the present invention is characterized in that a tensile resistance material is provided in a hollow space formed inside a pile head. It is arranged vertically and its lower end is fixed near the bottom of the hollow space, and the upper part of the tensile resistance material is fixed to the base of the upper structure.

Further, in the seismic isolation structure for a pile according to the present invention, a pile head cap having a bottomed tube is covered on the pile head to form the hollow space inside the bottomed tube, and a periphery of the bottomed tube is provided. Is filled with a solidifying material and integrated with the pile head.

In a seismic isolation structure for a pile according to the present invention, a foundation-side slide plate slidable on an upper surface of the pile head or the cap of the pile head is attached to a lower surface of the base.

Further, in the seismic isolation structure for a pile according to the present invention, a vertically extensible sliding member is interposed between the pile head or the pile head cap and the foundation side sliding plate.

[0012] In the seismic isolation structure for a pile according to the present invention, a predetermined outer pipe is projected from the base portion into the ground so as to surround the pile, and a skirt-like shape is provided on a peripheral edge of the foundation side slide plate. A tubular portion is provided so that the tubular portion is fitted into the outer tube.

[0013] In the seismic isolation structure for a pile according to the present invention, a reinforcing steel, a PC steel, and a PC are provided in a hollow space formed inside the pile head.
A steel rod, a tensile resistance material such as a bolt is arranged in the vertical direction and the lower end thereof is fixed near the bottom of the hollow space, and the upper part of the tensile resistance material is fixed to the base of the upper structure, for example, the base plate. is there.

Thus, the tensile resistance material is free from oblique deformation and elongation deformation in the hollow space from the surroundings, and is free for a predetermined length.
By the way, in the conventional joining method, the upper part of the reinforcing steel was constrained by the concrete of the foundation slab, and the lower part was also constrained by the concrete filled in the pile and welding to the pile head. When a horizontal relative displacement occurs between the plate and the pile head, the reinforcing bars cannot absorb the horizontal relative displacement, and in the event of a huge earthquake, a large shear force acts on the reinforcing bars, which often breaks. Was.

However, in the seismic isolation structure for a pile according to the present invention, even if a horizontal relative displacement occurs between the base of the upper structure and the pile head during an earthquake, the tensile resistance material has a predetermined length as described above. Since the tensile resistance material does not receive any restraint from the surroundings for a long time, the tensile resistance material absorbs the above-described horizontal relative displacement by its elongational deformation capability while being obliquely deformed, and there is no fear of breaking even under a huge earthquake. And in such a state,
A state in which the pile head and the base of the superstructure are joined only via the tensile resistance material, that is, a pin state, is maintained, and thus a bending moment is generated in the pile head by the horizontal force from the superstructure. Without transmitting the horizontal force to the pile, the shear strength can be used effectively.

The structure of the pile is not limited as long as a hollow space is formed inside the pile head. For example, not only PHC piles, PC piles, or steel pipe piles originally having a hollow structure, but also cast-in-place concrete piles formed by appropriately forming a form so as to form a hollow space inside the pile head are also included in the present invention. Included in the stake.

The hollow space may be formed in any manner, and a hollow portion such as a PHC pile may be used as it is. However, a pile head cap having a bottomed tube is attached to the pile head. When the inside of the bottomed tube is covered with the hollow space, and the solidified material is filled around the bottomed tube and integrated with the pile head, a tensile resistance material is pre-attached to the bottom of the bottomed tube. The workability can be improved.

In the seismic isolation structure for a pile described above, when an earthquake of a certain size or more is encountered, the pile head and the base of the superstructure are in an unfixed state due to, for example, crushing of concrete, and a relative horizontal displacement is generated between the two. Even if this occurs, the tensile resistance material that joins the pile head and the base of the superstructure does not break, and therefore, the state of the pin joint between them is maintained, and a bending moment is generated at the pile head. Although the shear strength of the pile main body can be effectively used without the above, if a foundation side sliding plate slidable on the upper surface of the pile head or the pile head cap is attached to the lower surface of the base, an earthquake When the horizontal force is small, the horizontal force from the upper structure acts as a shear force on the pile head due to the static friction between the upper surface of the pile head or the pile head cap and the foundation-side sliding plate, and the horizontal force during the earthquake is constant. On If that, because both are relatively slid, by an amount corresponding to the dynamic frictional force at that time, seismic horizontal force acts on the pile head as shear force.

Therefore, it is possible to clearly grasp the upper limit of the shearing force acting on the pile main body, and it is possible to perform a rational design in consideration of the shear strength of the pile main body. Even in such a case, the tensile resistance material absorbs the relative horizontal displacement between the pile head and the base of the superstructure without breaking, and a part of the horizontal force from the superstructure is applied to the pile head as a shearing force. While transmitting, the joint is maintained in the pin state, and no bending moment is generated at the pile head.

In the case where a vertically extensible sliding member is interposed between the pile head or the pile head cap and the foundation side sliding plate, the sliding member may be a pile due to horizontal force during an earthquake. Absorption of rotational deformation at the head prevents separation of the sliding surface. As a result, there is no concern that the pile head tilts and separates from the slide plate on the foundation side, and the vertical load and the horizontal force as designed are reliably transmitted, and stress concentration occurs at the pile head, leading to damage. It is also possible to avoid it.

It is sufficient that at least one of the upper and lower surfaces of the sliding member slides with the pile head, the pile head cap, or the base side sliding plate, and either one of them may be fixed. Conceivable. Considering the use of plastic composite materials such as Somalite and Teflon (trade name) that have little aging or chemical change as the sliding member that can expand and contract in the vertical direction, and a disc spring when the vertical supporting load is small. Can be

In addition, a predetermined outer tube is projected from the base into the ground so as to surround the pile, and a skirt-like tubular portion is provided on a peripheral edge of the base-side slide plate, and the tubular portion is attached to the outer side. If it is configured to fit into the pipe, the horizontal force from the upper structure during the earthquake will project to the pile and the lower surface of the upper structure in the case of a small or medium-sized earthquake where the horizontal force does not exceed the static frictional force. To the installed outer pipe according to their rigidity ratio. On the other hand, in the case of a large earthquake in which the horizontal force from the upper structure exceeds the static friction force described above,
Only the horizontal force corresponding to the dynamic friction force acts, and all the remaining horizontal force is distributed to the outer pipe except for the portion transmitted to the pile head via the tensile resistance material.

That is, in the case of a small or medium-sized earthquake, only the horizontal force corresponding to the rigidity ratio with the outer pipe is transmitted to the head of the pile supporting the vertical load of the upper structure in the case of a small-to-medium-sized earthquake. ,
In the case of a large earthquake, no horizontal force greater than the dynamic friction force acts except for the transmission via the tensile resistance material. Therefore, it is also possible to secure higher earthquake resistance in combination with the shear strength of the outer pipe while effectively utilizing the shear strength of the pile.

Since the skirt-like tubular portion provided on the periphery of the base-side slide plate is fitted into the outer tube, it is possible to absorb a construction error of the pile head top end height.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a seismic isolation structure for a pile according to the present invention will be described below with reference to the accompanying drawings.
It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof is omitted.

(First Embodiment)

FIG. 1 is a sectional view showing a seismic isolation structure for a pile according to this embodiment. As can be seen from the figure, the seismic isolation structure for a pile according to the present embodiment is such that a pile head cap 2 having a cylindrical bottomed pipe 1 is covered on a pile head 3 so that the inside of the bottomed pipe 1 is piled. 3, a reinforcing bar 4 as a tensile resistance material is vertically disposed in the hollow space, and the lower end thereof is formed at the bottom of the hollow space, that is, the bottom plate 5 of the bottomed tube 1.
And the upper part of the reinforcing bar 4 is fixed to a base plate 7 which is the base of the upper structure. The depth of the bottomed tube 1, that is, the length of the reinforcing bar 4 that does not receive any constraint from the surroundings, can be set to, for example, about 50 to 60 cm.

Here, four L-shaped locking portions 8 are provided on the upper edge of the bottomed tube 1, and the locking portions 8 are hooked to the top end of the pile head 3 to thereby form the bottomed tube 1. The pile head cap 2 can be put on the pile head 3 in a state where 1 is suspended in the pile head 3. Such a bottomed pipe 1 can be constituted by, for example, a steel pipe.

On the other hand, concrete 9 which is a solidifying material is filled around the bottomed tube 1 so that the bottomed tube 1 and thus the pile cap 2 and the pile head 3 can be integrated. I have.

In order to construct the seismic isolation structure of the pile according to the present embodiment, first, the reinforcing bar 4 is formed through the through hole 12 formed in the lid 11.
2 (see FIG. 2), their ends are fixed to the bottom 5 of the bottomed tube 1 with nuts 6, and the lid 11 is attached to the bottomed tube 1.
So that there is no gap between it and the upper opening.
Then, an annular bottom formwork 13 is attached to the lower periphery of the bottomed tube 1.

Next, the pile head cap 2 to which the reinforcing bar 4, the lid 11 and the bottom form 13 are attached is put on the pile head 3 of the pile body 10, and the bottomed tube 1 is suspended in the pile head 3. Keep in state.

Next, concrete 9 is filled between the bottomed tube 1 and the inner surface of the pile head 3, and while the concrete is prevented from flowing into the bottomed tube 1 by the lid 11, the base plate 7 is filled.
To build. The concrete filling around the bottomed tube 1 can be performed together with the concrete work for constructing the base plate 7.

In the seismic isolation structure for a pile according to the present embodiment, a reinforcing bar 4 is disposed vertically in a hollow space formed inside the pile head 3 and the lower end thereof is fixed near the bottom of the hollow space. The upper side of the reinforcing bar is fixed to the base plate 7.

For this reason, the reinforcing bar 4 is not subject to any constraint from the surroundings in the hollow space for oblique deformation and elongation deformation,
It is in a free state over a predetermined length. Therefore,
When a horizontal relative displacement occurs between the foundation plate 7 of the upper structure and the pile head 3 at the time of the earthquake, as shown in FIG. Absorbs relative displacement.

As described above, according to the seismic isolation structure of the pile according to the present embodiment, the reinforcing bar 4 can freely deform obliquely and elongate in the bottomed tube 1 without any constraint from the surroundings. To absorb the relative horizontal displacement between the foundation plate 7 of the upper structure and the pile head 3 during an earthquake.

Therefore, when an earthquake of a certain scale or more is encountered, concrete is crushed at the joint between the pile head 3 and the foundation plate 7 of the upper structure, and as a result, a relative horizontal displacement occurs between the two. However, the reinforcing bar 4 that joins the pile head 3 and the foundation plate 7 is not broken, so that the state of the pin connection between the two is maintained, and the pile main body is generated without generating a bending moment in the pile head 3. The shear strength of 10 can be effectively used.

Further, according to the seismic isolation structure for a pile according to the present embodiment, the pile head cap 2 having the bottomed tube 1 is put on the pile head 3 to form a hollow space inside the bottomed tube, Since the surroundings of the pipe 1 are filled with the concrete 9 and integrated with the pile head 3, it is possible to attach the reinforcing bar 4 or the like to the bottom of the bottomed pipe 1, thereby improving workability.

In the present embodiment, the pile head 3 is
The hollow space is newly formed in the inside, and the reinforcing bar 4 is arranged in the hollow space. However, if there is provided, for example, a bracket-shaped portion for fixing the reinforcing bar 4 in the hollow inside of the pile body 10. Alternatively, the lower end of the reinforcing bar 4 may be directly fixed to the portion. In this case, a pile cap is not required. Also in this configuration, an appropriate lid is attached to the pile head before the foundation slab is constructed so that the hollow space is secured around the reinforcing bar 4, and then the foundation slab is constructed.

(Second Embodiment)

Next, a second embodiment will be described. In addition, the same reference numerals are given to components and the like that are substantially the same as those in the above-described embodiment, and description thereof is omitted.

FIG. 4 is a sectional view showing the seismic isolation structure of the pile according to this embodiment. As can be seen from the figure, the seismic isolation structure of the pile according to the present embodiment is similar to the first embodiment in that
By covering the pile head 3 with the pile head cap 21 having the above, the inside of the bottomed tube 1 is made into a hollow space formed inside the pile head 3, and the reinforcing bar 4 is vertically arranged in the hollow space. The lower end is fixed to the bottom of the hollow space, that is, the bottom plate 5 of the bottomed tube 1 with a nut 6, and the upper part of the reinforcing bar 4 is fixed to a base plate 7 which is the base of the upper structure.

Here, in the present embodiment, unlike the first embodiment, a flange-shaped locking portion 23 is provided around the upper edge of the bottomed tube 1, and the locking portion 23 is attached to the top of the pile head 3. By hooking on the end, the pile head cap 21 can be put on the pile head 3 in a state where the bottomed tube 1 is suspended in the pile head 3.

On the lower surface of the base plate 7, a base side slide plate 22 slidable on the upper surface of the locking portion 23 of the pile head cap 21 is attached.

In order to construct the seismic isolation structure of the pile according to the present embodiment, first, the reinforcing bar 4 is inserted into the through hole 24 formed in the foundation side sliding plate 22 (see FIG. 5), and the ends thereof are provided. The bottom tube 1 is fixed to the bottom 5 with a nut 6, and an annular bottom form 13 is attached around the bottom of the bottomed tube 1.

Next, the pile head cap 21 to which the reinforcing bar 4 and the bottom form 13 are attached is put on the pile head 3. Then, the bottomed pipe 1 is held in a suspended state in the pile head 3, and in this state, concrete 9 is placed between the peripheral surface of the bottomed pipe 1 and the inner surface of the pile head 3.
Fill.

Next, the base side slide plate 22 is fixed by using a suitable support, and the base plate 7 is constructed and integrated in such a state.

In the seismic isolation structure for a pile according to this embodiment, when the horizontal force during an earthquake is small, the pile cap 21
The horizontal force from the upper structure acts on the pile head 3 as a shear force due to the static friction force between the upper surface of the base and the foundation side slide plate 22,
If the horizontal force at the time of the earthquake exceeds a certain scale, the two slide relatively to each other.
The horizontal force at the time of the earthquake acts on the pile head 3 as a shear force.

When a relative horizontal displacement occurs between the pile head 3 and the foundation plate 7 due to the sliding between the upper surface of the pile head cap 21 and the lower surface of the foundation side slide plate 22, the first embodiment Similar to the embodiment, the rebar 4 is free from oblique deformation and elongation deformation in the hollow space from the surroundings and is free for a predetermined length, so that the rebar 4 can be seen in FIG. The above-mentioned horizontal relative displacement is absorbed by their elongation deformability while obliquely deforming.

As described above, according to the seismic isolation structure of the pile according to this embodiment, when the horizontal force during an earthquake is small,
When the horizontal force from the upper structure acts on the pile head 3 as a shear force due to the static friction force between the upper surface of the pile head cap 21 and the lower surface of the foundation side sliding plate 22, and the horizontal force at the time of the earthquake exceeds a certain scale, Are relatively slid, the horizontal force at the time of the earthquake acts on the pile head 3 as a shear force by an amount corresponding to the dynamic friction force at that time.

Therefore, it is possible to clearly grasp the upper limit of the shearing force acting on the pile main body 10, and it is possible to make a rational design in consideration of the shearing strength of the pile. In addition,
In such a case, as in the first embodiment, the reinforcing bars 4
Absorbs the relative horizontal displacement between the pile head 3 and the foundation plate 7 of the superstructure without breaking, transmits a part of the horizontal force from the superstructure to the pile head 3 as a shearing force, and Is maintained in a pin state, so that a horizontal force can be transmitted to the pile main body 10 without generating a bending moment at the pile head 3 and the shear strength can be effectively used.

In addition, the pile head cap 21 has almost the same constructional operation and effect as the pile head cap 2 of the first embodiment, but the description is omitted here.

In the present embodiment, the pile head cap 21 and the foundation side slide plate 22 are configured to be slidable. However, as described in the first embodiment, the reinforcing bar 4 is directly fixed to the hollow interior of the pile body 10. If so, the pile cap 21 becomes unnecessary. Therefore, in such a case, the top end of the pile head 3 and the foundation side slide plate 22 may be configured to be slidable.

(Third Embodiment)

Next, a third embodiment will be described. In addition, the same reference numerals are given to components and the like that are substantially the same as those in the above-described embodiment, and description thereof is omitted.

FIG. 7 is a sectional view showing the seismic isolation structure of the pile according to this embodiment. As can be seen from the figure, the seismic isolation structure of the pile according to the present embodiment is similar to the first and second embodiments, in that the pile head cap 21 provided with the bottomed tube 1 is put on the pile head 3 so that the pile head 3 is covered. The inside of the bottom tube 1 is a hollow space formed inside the pile head 3, and a reinforcing bar 4 is vertically arranged in the hollow space, and the lower end thereof is formed at the bottom of the hollow space, that is, the bottom plate 5 of the bottomed tube 1. And the upper part of the reinforcing bar 4 is fixed to a base plate 7 which is the base of the upper structure.

Here, in this embodiment, similarly to the second embodiment, a flange-shaped locking portion 23 is provided around the upper edge of the bottomed tube 1, and the locking portion 23 is hooked on the top end of the pile head 3. With the bottomed pipe 1 suspended in the pile head 3, the pile cap 2
1 can be put on the pile head 3,
A sliding member 31 that is vertically expandable and contractible is disposed on the upper surface of the locking portion 23, and the upper surface of the sliding member slides on the base-side sliding plate 22 attached to the lower surface of the base plate 7. It has become.

That is, in the second embodiment, the upper surface of the locking portion 23 of the pile head cap 21 and the lower surface of the foundation-side slide plate 22 attached to the foundation plate 7 slide, whereas in this embodiment, A sliding member 31 is interposed between the two, and the upper surface of the sliding member and the lower surface of the base-side sliding plate 22 slide with each other.

For the sliding member 31, for example, a plastic composite material such as Somalite or Teflon (trade name) which is less likely to change over time or chemically can be used.

In order to construct the seismic isolation structure of the pile according to the present embodiment, first, the reinforcing bar 4 is inserted into the through hole 24 formed in the foundation side sliding plate 22 (see FIG. 8). Perform the same procedure as in the embodiment.

In the seismic isolation structure for a pile according to this embodiment, as in the second embodiment, when the horizontal force during an earthquake is small, the upper structure is formed by the static friction force between the upper surface of the sliding member 31 and the foundation side sliding plate 22. When the horizontal force from the object acts on the pile head 3 as a shear force, and the horizontal force during an earthquake exceeds a certain scale,
Since the two slide relatively, the horizontal force at the time of the earthquake is a shear force equivalent to the dynamic friction force at that time.
However, in the present embodiment, since the sliding member 31 is stretchable, the sliding member absorbs the rotational deformation of the pile head 3 due to the horizontal force during the earthquake, as shown in FIG.
Prevent separation of sliding surfaces.

In the case where the relative horizontal displacement at the time of the earthquake occurs between the pile head 3 and the foundation plate 7 due to the sliding between the upper surface of the sliding member 31 and the lower surface of the foundation-side sliding plate 22, each of the above-described operations is performed. Similar to the embodiment, the reinforcing bar 4 is free from oblique deformation and elongation in the hollow space and is free for a predetermined length in the hollow space. The above-mentioned horizontal relative displacement is absorbed by the deformability.

As described above, according to the pile seismic isolation structure of the present embodiment, the vertically extensible sliding member 31 is interposed between the pile head cap 21 and the foundation side sliding plate 22. Therefore, the sliding member absorbs the rotational deformation at the pile head 3 due to the horizontal force at the time of the earthquake and prevents the sliding surface from being separated. For this reason, there is no fear that the pile head 3 is inclined and separated from the foundation side slide plate 22, and the vertical load and the horizontal force as designed are reliably transmitted, and stress concentration occurs on the pile head 3, leading to breakage. Can be avoided beforehand.

In this embodiment, as in the second embodiment,
When the horizontal force at the time of the earthquake is small, the horizontal force from the upper structure acts on the pile head 3 as a shear force due to the static friction force between the upper surface of the sliding member 31 and the lower surface of the foundation side sliding plate 22, and the horizontal force at the time of the earthquake is reduced. If the scale exceeds a certain level, the two slide relatively to each other, so that the horizontal force at the time of the earthquake acts on the pile head 3 as a shear force corresponding to the dynamic friction force at that time. Therefore, the upper limit of the shearing force acting on the pile main body 10 can be clearly understood, and a rational design in consideration of the shearing strength of the pile can be performed.

Further, as in the above embodiments, the rebar 4 absorbs the relative horizontal displacement between the pile head 3 and the base plate 7 of the upper structure without breaking, and a part of the horizontal force from the upper structure. Is transmitted to the pile head 3 as a shear force, and the joining state is maintained in a pin state, so that a horizontal force is transmitted to the pile body 10 without generating a bending moment in the pile head 3 to effectively use the shear strength. It is possible to do.

In addition, the pile head cap 21 has substantially the same constructional operation and effect as the pile head cap 2 of the first embodiment, but the description thereof is omitted here.

In this embodiment, a plastic composite material is used as the sliding member, but a disc spring 41 may be used instead as shown in FIG. At the lower edge of the disc spring 41, horizontal movement is restrained by a stopper 42 erected on the periphery of the pile head cap 21a, but at the upper edge thereof, it is slidable with the lower surface of the base side slide plate 22. It is configured in.

The operation and effect according to the modification are substantially the same as those of the above-described embodiment, and the description thereof is omitted here.

(Fourth Embodiment)

Next, a fourth embodiment will be described. In addition, the same reference numerals are given to components and the like that are substantially the same as those in the above-described embodiment, and description thereof is omitted.

FIG. 11 is a sectional view showing the seismic isolation structure of a pile according to this embodiment. As can be seen from the figure, the seismic isolation structure of the pile according to the present embodiment is similar to each of the above-described embodiments, by covering the pile head 3 with the pile head cap 21 having the bottomed tube 1, thereby forming the bottomed tube. 1 is a hollow space formed inside the pile head 3, and a reinforcing bar 4 is vertically arranged in the hollow space, and a lower end of the reinforcing bar 4 is attached to a bottom of the hollow space, that is, a bottom plate 5 of the bottomed tube 1. 6 and the upper part of the reinforcing bar 4 is fixed to a base plate 7 which is the base of the upper structure. Further, similarly to the third embodiment, the locking portion 23 of the pile head cap 21 and the base-side sliding plate 22 attached to the base plate 7.
In this embodiment, the outer pipe 51 is projected from the base plate 7 into the ground so as to surround the pile main body 10, and the base-side slide plate 22a A skirt-like cylindrical portion 52 is provided on the periphery of the outer tube 51, and the cylindrical portion is fitted into the outer tube 51.

The seismic isolation structure of the pile according to the present embodiment may be constructed in substantially the same manner as in the third embodiment. However, prior to the construction of the foundation slab 7, the positioning of the foundation side sliding plate 22a is performed. It is only necessary to fit the skirt-shaped tubular portion 52 provided on the peripheral edge of the base side slide plate into the outer tube 51 and drop it. That is, the fitting error in the height direction of the pile main body 10 can be automatically absorbed by the fitting.

In the seismic isolation structure of the pile according to the present embodiment, the horizontal force from the upper structure during an earthquake is small in the case of a small or medium-sized earthquake where the horizontal force does not exceed the static frictional force.
It is distributed to the pile main body 10 and the outer pipe 51 protruding from the foundation plate 7 according to their rigidity ratio.

On the other hand, in the case of a large earthquake in which the horizontal force from the upper structure exceeds the above-mentioned static friction force, only the horizontal force corresponding to the dynamic friction force acts on the pile head 3, Reinforcing bar 4
All of the remaining horizontal force is distributed to the outer tube 51 except for the portion transmitted to the pile head 3 through the outer pipe 51.

The operation relating to the sliding member 31 and the operation relating to the rebar 4 are the same as those in the third embodiment, and therefore the description thereof is omitted here.

As described above, according to the seismic isolation structure for a pile according to the present embodiment, the outer pipe 51 is projected from the foundation slab 7 into the ground so as to surround the pile main body 10, and the foundation side slides. Since the skirt-shaped tubular portion 52 is provided on the peripheral edge of the plate 22a and the tubular portion is fitted into the outer tube 51,
In the case of a small-to-medium-sized earthquake, only the horizontal force corresponding to the rigidity ratio with the outer pipe 51 is transmitted to the pile head 3 up to the static friction force,
In the case of a large earthquake, except for the transmission via the rebar 4,
No horizontal force greater than the dynamic friction force acts.

Therefore, the pile main body 10 is not damaged, and in the worst case, only the outer pipe 51 is destroyed, and the basic function of the pile main body 10 to support the vertical load of the upper structure is maintained even under a large earthquake. It is possible to use the outer pipe 5 while effectively utilizing the shear strength of the pile body 10.
It is also possible to secure higher earthquake resistance in combination with the shear strength and the like of (1).

Further, according to the pile seismic isolation structure of the present embodiment, the skirt-like cylindrical portion 52 provided on the peripheral edge of the foundation-side slide plate 22a is fitted into the outer tube 51.
Construction errors at the height of the pile head 3 at the top end can be absorbed.

The effect of the sliding member 31 and the reinforcing bar 4
The effects and the like related to the third embodiment are the same as those of the third embodiment, and thus description thereof is omitted here.

[0079]

As described above, according to the seismic isolation structure of a pile according to the first aspect of the present invention, the tensile resistance material can be freely inclined and deformed in the hollow space without any constraint from the surroundings. It expands and deforms to absorb the relative horizontal displacement between the base of the superstructure and the pile head during an earthquake.

Therefore, even when a relative horizontal displacement occurs between the pile head and the base of the superstructure during the earthquake, the tensile resistance material joining the pile head and the base does not break, and The state of the pin connection is maintained between the two, and thus the shear strength of the pile main body can be effectively used without generating a bending moment at the pile head.

Further, according to the seismic isolation structure for a pile according to the second aspect of the present invention, since a tensile resistance material can be pre-attached to the bottom of the bottomed pipe, the effect of improving workability is also achieved. .

According to the seismic isolation structure for a pile according to the third aspect of the present invention, the upper limit of the shearing force acting on the pile main body can be clearly grasped, and a ratio considering the shear strength of the pile main body can be obtained. This also has the effect of enabling a realistic design.

Further, according to the seismic isolation structure for a pile according to the present invention, there is no concern that the pile head is tilted and separated from the foundation side slide plate, so that the vertical load and the horizontal force as designed are ensured. In addition to transmitting the stress to the pile head, it is possible to prevent the stress concentration at the pile head from occurring and to prevent the pile head from being damaged.

Further, according to the seismic isolation structure of a pile according to the present invention, it is possible to ensure higher seismic resistance in combination with the shear resistance of the outer tube while effectively utilizing the shear resistance of the pile. Also has the effect of becoming.

[0085]

[Brief description of the drawings]

FIG. 1 is a sectional view of a seismic isolation structure for a pile according to a first embodiment.

FIG. 2 is a perspective view of a pile head cap used in the pile seismic isolation structure according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating the operation of the seismic isolation structure of the pile according to the first embodiment.

FIG. 4 is a sectional view of a seismic isolation structure for a pile according to a second embodiment.

FIG. 5 is an exploded perspective view of a pile head cap and a foundation-side slide plate used in the seismic isolation structure of the pile according to the second embodiment.

FIG. 6 is a sectional view showing the operation of the seismic isolation structure for a pile according to the second embodiment.

FIG. 7 is a sectional view of a seismic isolation structure for a pile according to a third embodiment.

FIG. 8 is an exploded perspective view of a pile head cap and a foundation-side slide plate used in the pile seismic isolation structure according to the third embodiment.

FIG. 9 is a cross-sectional view showing the operation of the pile seismic isolation structure according to the third embodiment.

FIG. 10 is a sectional view of a seismic isolation structure for a pile according to a modification of the third embodiment.

FIG. 11 is a sectional view of a seismic isolation structure for a pile according to a fourth embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 bottomed pipe 2, 21 pile head cap 3 pile head 4 steel bar (tensile resistance material) 7 foundation plate of superstructure (base) 9 concrete (solidified material) 10 pile body (pile) 22, 22 a foundation side sliding plate 31 Sliding member 41 Belleville spring (sliding member) 51 Outer tube 52 Tube part

Claims (5)

[Claims] 1. A tensile resistance material is disposed vertically in a hollow space formed inside a pile head, and a lower end thereof is fixed near a bottom of the hollow space, and an upper structure is provided above the tensile resistance material. The seismic isolation structure of the pile, which is established at the base of the pile. 2. A pile head cap having a bottomed tube is covered on the pile head to form the hollow space in the bottomed tube, and a solidified material is filled around the bottomed tube to form the hollow space. The seismic isolation structure of a pile according to claim 1, which is integrated. 3. The seismic isolation structure for a pile according to claim 1, wherein a foundation-side slide plate slidable on an upper surface of the pile head or the pile head cap is attached to a lower surface of the base. 4. The seismic isolation structure for a pile according to claim 3, wherein a vertical sliding member is interposed between the pile head or the pile head cap and the foundation side sliding plate. 5. A predetermined outer tube is projected from the base portion into the ground so as to surround the pile, and a skirt-like tube portion is provided on a peripheral edge of the base-side slide plate, and the tube portion is attached to the outside. The seismic isolation structure for a pile according to claim 4, wherein the pile is configured to be fitted into a pipe.