JP3575733B2 - Seismic isolation structure of pile - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pile, particularly a seismic isolation structure at a pile head.
[0002]
[Prior art]
There are two types of pile foundations: a support pile type and a friction pile type.The former is based on the fact that when a high-quality support layer is deep underground, the superstructure is built on a pile driven into the support layer. This is a type in which the weight is stably supported by the support layer, and the latter is a basic type in which the upper structure is supported by a frictional force with the surrounding ground when there is no good support layer.
[0003]
These piles tend to have relatively weak points against horizontal force due to their structural characteristics, and 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 upper structure. Therefore, when designing piles, sufficient consideration is given to seismic loads.
[0004]
[Problems to be solved by the invention]
However, when the superstructure encounters an extremely large earthquake, an excessive shear force or bending moment acts on the pile head, which may cause an unexpected situation such as breakage of the pile and eventually collapse of the superstructure.
[0005]
The present invention has been made in consideration of the above-described circumstances, and provides a pile seismic isolation structure capable of preventing a pile from being broken by a horizontal force from an upper structure, particularly a pile head. With the goal.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a seismic isolation structure for a pile according to the present invention supports an upper structure with a predetermined pile and projects a horizontal force resistance member on a lower surface of the upper structure, as described in claim 1. And burying it in the ground, the horizontal force from the upper structure during an earthquake is distributed to the pile and the horizontal force resistance member according to their rigidity ratio, and the horizontal force resistance member is It is constituted by a pipe body, and the pipe body is arranged so that the pile penetrates the inside of the pipe body.
[0007]
Further, in the seismic isolation structure for a pile according to the present invention, an elastic material is interposed in a gap between the pipe and the pile.
[0008]
Further, in the seismic isolation structure for a pile according to the present invention, as described in claim 3, the upper structure is supported by a predetermined pile, and a horizontal force resistance member is protrudingly provided on the lower surface of the upper structure. And a seismic isolation bearing is interposed between the pile and the upper structure so that almost all horizontal forces from the upper structure at the time of the earthquake flow to the horizontal force resistance member.
[0009]
In the seismic isolation structure for a pile according to the present invention, the horizontal force resistance member is formed of a pipe, and the pipe is disposed so that the pile penetrates the pipe.
[0010]
Further, in the seismic isolation structure for a pile according to the present invention, the horizontal force resistance member is configured to be capable of absorbing energy.
[0011]
In the seismic isolation structure for a pile according to the present invention, the vertical load from the upper structure is supported by the predetermined pile, but the horizontal force from the upper structure during the earthquake is the predetermined pile and the lower surface of the upper structure. To the horizontal force resistance member protruding from the horizontal force resistance member according to their rigidity ratio, and the horizontal force distributed to the horizontal force resistance member is transmitted to the surrounding ground.
[0012]
Therefore, only a part of the horizontal force from the upper structure is transmitted to the head of the pile that supports the vertical load of the upper structure, causing damage to the pile head and eventually damage to the upper structure. Is prevented beforehand.
[0013]
How to configure the horizontal force resistance member is optional, but if the horizontal force resistance member is configured to be able to absorb energy, the vibration energy of the upper structure is absorbed and the shaking due to the earthquake is rapidly attenuated. be able to. In order to make energy absorption possible, a method of forming a horizontal force resistance member using hysteretic damping material such as extremely mild steel, and providing a large number of slits in ordinary steel to make it easy to absorb energy are considered. Can be
[0014]
In addition, since the horizontal force resistance member is formed of a pipe and the pipe is arranged so that the pile penetrates the inside of the pipe, the construction site of the pile and the horizontal force resistance member is common. Thus, it is possible to reduce the construction cost.
[0015]
Here, when a gap is formed between the pipe and the pile, the gap may be left as it is, but if an elastic material is interposed in the gap, the horizontal force transmitted to the pile is Can be released to the surrounding pipe and further to the ground through the elastic material, so that the burden on the horizontal force of the pile can be reduced. As the elastic material and its use form, it is conceivable to arrange a plurality of coil springs radially in the above-described gap, sandwich an air cushion or a rubber sheet, or fill a rubber body or a sponge body.
[0016]
The rate at which the horizontal force from the superstructure is transmitted to the piles and the horizontal force-resisting material depends on their rigidity ratio to the horizontal deformation. With this, almost all the horizontal force from the upper structure can flow to the horizontal force resistance member, so that the piles can share the roles of supporting vertical loads, and the horizontal force resistance members can bear the horizontal load. Become. The seismic isolation bearing may be any type of bearing that does not substantially transmit the horizontal force from the upper structure to the pile, and specific examples include a laminated rubber bearing, a sliding bearing, and a bearing.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a seismic isolation structure for a pile according to the present invention will be described with reference to the accompanying drawings. In addition, the same reference numerals are given to components and the like that are substantially the same as those in the related art, and description thereof is omitted.
[0018]
FIG. 1 is an overall side view showing a seismic isolation structure for a pile according to the present embodiment. As can be seen from the figure, in the seismic isolation structure of a pile according to the present embodiment, the upper structure 1 is supported by the pile 2, and at the same time, the pile 2 penetrates through the pipe 3 as a horizontal force resistance member. Thus, it protrudes from the lower surface of the upper structure 1 and is buried in the ground 4.
[0019]
When deformed by receiving a horizontal force from the upper structure 1 during an earthquake, the pipe body 3 is preferably formed of a hysteretic damping type material, for example, ultra mild steel, so as to absorb vibration energy of the upper structure. Good. The tube 3 is made thicker to increase the rigidity of the tube itself so that the horizontal force from the upper structure 1 at the time of an earthquake flows through the tube as much as possible. For example, a horizontal rigidity sufficiently larger than the horizontal rigidity of the pile 2 is ensured by, for example, increasing the passive resistance from the ground.
[0020]
The gap between the pipe 3 and the pile 2 is filled with a rubber body 5 as an elastic material, as can be clearly understood from FIG.
[0021]
In order to construct the seismic isolation structure for a pile according to the present embodiment, first, the pipe 3 is driven into the ground 4, and then the earth and sand in the pipe is excavated and discharged. Next, the pile 2 is driven into the pipe 3 so as to penetrate the pipe 3. When the driving of the pile 2 is completed, a rubber body 5 is filled between the pile 2 and the pipe 3.
[0022]
In the seismic isolation structure of the pile according to the present embodiment, the vertical load from the upper structure 1 is supported by the pile 2 in a normal state or during an earthquake, but the horizontal force P from the upper structure 1 during the earthquake is used. As shown in FIG. 2, the pile 2 and the pipe 3 projecting from the lower surface of the upper structure are respectively distributed to P ₂ and P ₁ according to their rigidity ratio, and distributed to the pipe 3. The horizontal force P ₁ is transmitted to the surrounding ground 4.
[0023]
The horizontal force P ₂ distributed on the head of the pile 2, for the surrounded portion in the rubber body 5, [Delta] P by the tube 3 through the rubber member, further is transmitted to the ground 4. Then, a horizontal force of P ₂ −ΔP acts on the lower edge of the tubular body 3 and the rubber body 5.
[0024]
As described above, according to the pile seismic isolation structure of the present embodiment, the pipe 3 as a horizontal resistance member protrudes from the lower surface of the upper structure separately from the pile 2 supporting the upper structure 1. In this case, a part of the horizontal force from the upper structure 1 can be released to the pipe 3 in the event of an earthquake.
[0025]
Therefore, if the horizontal rigidity of the pipe 3 is increased to some extent with respect to the pile 2, the horizontal force acting on the pile 2 from the upper structure 1 can be greatly reduced, and thus the pile head is damaged. Therefore, it is possible to prevent a situation such as damage to the upper structure 1 beforehand. Further, in the case where the cross section of the pile 2 is determined by the horizontal load at the time of the earthquake, the cross-sectional dimension of the pile 2 can be reduced as much as the horizontal load is reduced.
[0026]
Further, according to the present embodiment, since the tubular body 3 as the horizontal force resistance member is configured to be able to absorb energy, it is possible to absorb vibration energy of the upper structure 1 and quickly attenuate shaking due to an earthquake.
[0027]
Further, according to the present embodiment, since the pipe 3 which is a horizontal force resistance member is arranged around the pile 2, the construction place of the pile 2 and the pipe 3 is common, and the construction cost can be reduced. It becomes.
[0028]
Further, according to the present embodiment, the gap formed between the pipe 3 and the pile 2 is filled with the rubber body 5 which is an elastic material, so that the horizontal force transmitted to the pile 2 is It is possible to escape to the surrounding pipe 3 and further to the ground 4 through the body, and it is possible to reduce the burden of the pile 2 on the horizontal force.
[0029]
In the present embodiment, the tube 3 is made of a hysteresis damping material. However, even if the steel 3 is made of ordinary steel which does not take such hysteresis attenuation, the tube 21 having the slit 22 as shown in FIG. In this case, the vibration energy of the upper structure 1 is absorbed by the deformation of the slit 22, and the vibration of the upper structure can be rapidly attenuated.
[0030]
Further, in the present embodiment, the pipe 3 which is a horizontal force resistance member is arranged such that the pile 2 penetrates the inside thereof, but the pipe 3 is necessarily disposed such that the pile 2 penetrates. It is not necessary, and the pile 2 and the pipe 3 may be installed at different places as shown in FIG. This configuration is also substantially the same as described above in that a part of the horizontal force from the upper structure 1 can flow to the pipe 3 to prevent the head of the pile 2 from being damaged.
[0031]
Further, the horizontal resistance member of the present invention is not necessarily required to be formed in a tubular shape, but in short, may be configured to transmit the horizontal force during an earthquake to the ground 4. FIG. 5 shows such a modification. The horizontal resistance member 31 shown in FIG. 5 is constructed by assembling steel plates by welding or the like so as to have a cross-section.
[0032]
In the present embodiment, the gap formed between the pipe 3 and the pile 2 is filled with a rubber body that is an elastic material. Instead of such a rubber body, a plurality of coil springs are radially inserted into the gap. A method of arranging or sandwiching an air cushion may be adopted, or such a gap may be left as it is as shown in FIG.
[0033]
Further, in the present embodiment, a gap is provided between the pipe 3 and the pile 2. However, even if no gap is provided, the upper structure 1 may be provided depending on the rigidity ratio between the pipe 3 and the pile 2. The point that the horizontal force is distributed to both is the same as described above, and there is no change in that the breakage of the pile head can be prevented beforehand.
[0034]
As described above, the ratio at which the horizontal force from the upper structure 1 is transmitted to the pile 2 and the pipe 3 that is a horizontal force resisting material depends on their horizontal rigidity ratio. However, if a laminated rubber bearing 41 as a seismic isolation bearing is interposed between the pile 2 and the upper structure 1 as shown in FIG. 7, almost all the horizontal force from the upper structure 1 is reduced. Since the flow can flow through the pipe 3 which is a horizontal force resistance member, the role of the pile 2 for supporting a vertical load and the role of the pipe 3 for bearing a horizontal load can be shared, and the pile 2 can be almost reliably broken at the pile head. Can be prevented.
[0035]
【The invention's effect】
As described above, according to the seismic isolation structure for piles of the present invention according to claim 1, a part of the horizontal force from the upper structure can be released to the horizontal force resistance member during an earthquake. In addition to reducing the horizontal force acting on the pile from the superstructure, it is possible to prevent damage at the pile head and eventually damage to the superstructure beforehand, and to construct the pile with the horizontal force resistance member Is common, and the effect that the construction cost can be reduced is also exerted.
[0036]
Further, according to the seismic isolation structure for a pile of the present invention according to claim 3, almost all horizontal forces during an earthquake from the upper structure can flow to the horizontal force resistance member, and damage at the pile head can be substantially ensured. This has a remarkable operational effect that it can be prevented.
[0040]
[Brief description of the drawings]
FIG. 1 is a diagram of a seismic isolation structure for a pile according to an embodiment, (a) is a side view, and (b) is a horizontal detailed sectional view along the line AA.
FIG. 2 is a detailed side view showing an operation of the seismic isolation structure of the pile according to the embodiment.
FIG. 3 is a detailed side view showing a seismic isolation structure of a pile according to a modified example, and a part of the structure is displayed in cross section.
4A and 4B are diagrams of a seismic isolation structure of a pile according to another modification, wherein FIG. 4A is an overall side view, and FIG. 4B is a horizontal cross-sectional view along line BB.
5A and 5B are diagrams of a seismic isolation structure of a pile according to still another modification, wherein FIG. 5A is an overall side view, and FIG. 5B is a horizontal cross-sectional view along line CC.
FIG. 6 is a detailed side view of a seismic isolation structure for a pile according to still another modification.
FIG. 7 is a detailed side view of a seismic isolation structure for a pile according to still another modification.
[Explanation of symbols]
Reference Signs List 1 superstructure 2 pile 3 pipe (horizontal force resistance member)
4 Ground 5 Rubber body (elastic material)
21 tubular body 31 horizontal force resistance member 41 seismic isolation bearing

Claims (5)

By supporting the upper structure with a predetermined pile and projecting a horizontal force resistance member on the lower surface of the upper structure and burying it in the ground, the horizontal force from the upper structure at the time of an earthquake is transmitted to the pile. The horizontal force resistance member is distributed to the horizontal force resistance member according to their rigidity ratio, and the horizontal force resistance member is formed of a tube, and the tube is arranged so that the pile penetrates the tube inside. A seismic isolation structure for piles. The seismic isolation structure for a pile according to claim 1, wherein an elastic material is interposed in a gap between the pipe and the pile. The upper structure is supported by a predetermined pile, and a horizontal force resisting member is protruded from the lower surface of the upper structure to be buried in the ground. A seismic isolation structure for a pile, wherein a seismic isolation bearing is interposed between the pile and the upper structure so that the pile flows. The seismic isolation structure for a pile according to claim 3, wherein the horizontal force resistance member is formed of a tube, and the tube is disposed so that the pile penetrates the tube. The seismic isolation structure of a pile according to any one of claims 1 to 4, wherein the horizontal force resistance member is configured to be capable of absorbing energy.

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