JP2001164580A - Pile foundation construction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To definitely support a horizontal force acting to a pile head portion during a great earthquake by maintaining a coupling state between the pile head portions of foundation piles and a foundation framing body almost to a pin connection (bending resistance is zero) regardless of an extent of the axial force. SOLUTION: A coupling hole 3 is formed on the bottom surface of the foundation framing body 1, and the pile head portion 4 of the foundation pile 2 is inserted to the inside of a coupling hole 3. Between the upper end wall 4a of the pile head portion of the foundation piles and the bottom wall 3a inside the upper end hole mutually facing each other, an elastic body 5 is interposed which is combined only with one wall 4a of the walls 4a, 3a opposite to each other and not combined with other wall 3a. Between the facing surfaces of the elastic body 5 at the non-combined side and the wall 3a, a slip plate 6 is interposed which permits the relative slide in the horizontal direction of the facing surfaces. Between the outer peripheral wall 4b of the pile head portion of the foundation pile and the inner peripheral wall 3b of the coupling hole, an elastic body 8 or a viscous body 9 is interposed which is coupled only to one of the peripheral wall 4b among the facing peripheral walls 4b, 3b and is not coupled to the other peripheral wall 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile foundation structure formed by connecting a foundation frame and a foundation pile.

[0002]

2. Description of the Related Art A connection structure of a pile head of a foundation pile of a structure in a building or civil engineering has been planned mainly on rigid connection. Therefore, in most buildings, a pile foundation structure in which a pile head is rigidly connected to a foundation frame has been used. Some parts were not completely rigid, but seemed to be semi-rigid, but by design they were treated as rigid.

[0003] When the pile head of the foundation pile is rigidly connected, a large bending moment is generated at the pile head during a large earthquake, so that the pile head is likely to be damaged. Many have been reported. Of course, if the strength of the pile and the foundation is high, it is possible to prevent the pile head from being damaged in any earthquake, but it is not realistic in terms of cost and efficiency.

In order to avoid damage to the pile head,
In recent years, examples have been proposed in which the pile head of the foundation skeleton and the foundation pile is connected with pins. With the pin connection, the bending moment at the pile head can be reduced to zero, so that damage to the pile head can be prevented.

[0005]

However, it is technically very difficult to completely connect the head of the pile to the foundation frame with a pin. For example, even if a structural pin connection could be made in the state before the earthquake, if a large axial force (vertical force) acts on the foundation pile during the earthquake, the strong axial force will significantly increase the bending resistance. As a result, the function as the pin connection cannot be performed substantially.

In addition, a large horizontal force acts on the pile head in addition to bending stress during an earthquake.
There was also a possibility that it might not be able to completely resist the powerful horizontal force during an earthquake.

The present invention has been made in view of the above circumstances, and maintains the connection state between a pile head and a foundation frame close to perfect pin connection (no bending resistance) regardless of the magnitude of the axial force. And can reliably resist horizontal force acting on the pile head during a large earthquake, and as a result, it is possible to reliably prevent damage to the pile head during a large earthquake It is another object of the present invention to provide a pile foundation structure that can reduce costs by reducing the specifications of piles and the number of piles in some cases.

[0008]

According to a first aspect of the present invention, in a pile foundation structure in which a foundation frame and a foundation pile are coupled, a coupling hole having an upper end closed by an inner bottom wall is formed on a lower surface of the foundation frame. Is formed, and the pile head of the foundation pile is inserted into the connection hole, and opposing walls are provided between the pile head upper end wall of the foundation pile and the upper end inner bottom wall of the connection hole facing each other. An elastic body coupled to only one of the walls and uncoupled to the other wall is interposed, and between the opposing surfaces of the elastic body on the non-coupled side and the wall, a horizontal A sliding plate that allows relative sliding in the direction is interposed, and furthermore, between the outer peripheral wall of the pile head of the foundation pile and the inner peripheral wall of the coupling hole, only one of the peripheral walls facing each other is coupled. A non-coupled elastic body is interposed on the other peripheral wall.

According to a second aspect of the present invention, in a pile foundation structure in which a foundation frame and a foundation pile are coupled, a coupling hole whose upper end is closed by an inner bottom wall is formed in a lower surface of the foundation frame. One of the opposing walls is inserted between the pile head upper end wall of the foundation pile opposing each other and the upper end inner bottom wall of the coupling hole by inserting the pile head of the foundation pile inside the coupling hole. And a non-coupled elastic body is interposed on the other wall, and a horizontal relative slip between the opposed surfaces between the non-coupled side elastic body and the wall. Further, between the outer peripheral wall of the pile head of the foundation pile and the inner peripheral wall of the coupling hole, only one of the opposing peripheral walls is connected and not connected to the other peripheral wall. Characterized in that a viscous body is interposed.

The operation of the above configuration will be described. When the pile head of the foundation pile is completely pin-connected to the foundation frame, the pile head rotation angle at the time of a large earthquake (level 2 earthquake) is about 0.5 ° at the maximum. This is because the ground resists further rotation and restrains the rotation. Therefore, 0.
If a pile head connection structure with zero rotation resistance can be realized within the range of the pile head rotation angle of about 5 °, it can be considered that the pile head is connected to the foundation body in a completely pinned state in practical use.

In the present invention, an elastic body (or viscous body) is interposed between the inner peripheral wall of the connection hole of the foundation frame and the outer peripheral wall of the pile head of the foundation pile. This elastic body has an extremely small elastic modulus compared to iron, which is the material of the foundation pile, so it has enough deformation to make the pile head completely pin-coupled against the rotation of the foundation pile during an earthquake. Occurs.

Also, during an earthquake, a horizontal force is transmitted from the foundation to the pile head. At this time, the elastic body (or viscous body) interposed between the outer peripheral wall of the pile head and the inner peripheral wall of the connection hole of the foundation frame is deformed by horizontal force.
Since the pile head is inserted inside the connection hole, it supports the horizontal force reliably.

Here, the following example is given to supplement the horizontal resistance in the case of a viscous body. That is, water does not resist static loads, but when jumping over high cliffs,
Water resistance is great. Similarly, when a viscous material is used, it does not resist static load because it will creep, but it will not creep for dynamic loads such as earthquakes. To support the force that has been applied.

In addition, a vertical force (axial force) acts on the pile head during an earthquake in addition to the bending moment. However, the elastic body (viscous body) arranged on the peripheral wall of the pile head is connected only to the foundation pile or only to the foundation frame, and not to both, so the vertical force from the foundation frame is Is hardly transmitted to the elastic body (viscous body) in the peripheral wall portion, and hardly affects the action and effect of the elastic body (viscous body).

Even if a slight force is transmitted, the effect is canceled for the following reasons. That is, the elastic body (viscous body) has a very small elastic modulus and is highly deformable compared with iron or the like, which is a material of the pile body, and has a contact area of the peripheral wall portion (the peripheral wall on the non-bonding side with the elastic body or viscous body). Is smaller than the upper end face of the pile head, the vertical force from the foundation body is supported only on the upper end face of the pile head, and is not supported on the peripheral wall.

Further, when an earthquake occurs, a large or small axial force acts on the pile head of the foundation pile. Even in this case, the gap between the upper inner bottom wall of the coupling hole of the foundation frame and the upper wall of the pile head is large. An elastic body is interposed in the pile, and the elastic body has an extremely low elastic modulus compared to iron, which is the material of the pile. Sufficient deformation occurs to bring it into a connected state. However, when this elastic body is connected to both the foundation and the pile head, the rotation of the pile head causes a displacement between the upper and lower parts of the elastic body, resulting in horizontal resistance that contributes to bending resistance. However, in the present invention, this elastic body is connected to only one of the foundation frame and the pile head, and a slip plate is interposed on the side not connected,
This sliding plate prevents the occurrence of horizontal resistance that contributes to bending resistance due to slippage.

Further, when a viscous material is interposed in the peripheral wall portion of the pile head, the following operation is also generated in addition to the above operation.

First, a vibration equation of a structure during an earthquake is given by the following equation. [M] {X} ″ + [K] {X} = {P} − [C] {X} ′ where {X}: displacement vector {X} ′: velocity vector {X} ″: acceleration vector {P }: External force vector [M]: Mass matrix [K]: Stiffness matrix [C]: Damping matrix

{P} is the seismic load transmitted from the pile head to the structure. As is clear from the structure of the equation, {P}-[C] {X} ′ is substantially transmitted to the system. Can be regarded as the input load. [C] {X} ′ always acts in the direction of decreasing {P}, so if [C] is increased, {P} − [C] {X} ′
Can be reduced. That is, when [C] is increased, the same effect as when the seismic load is reduced can be obtained.

Since the viscous material is a material having an extremely large damping constant, if the viscous material is installed on the peripheral wall of the pile head, {P}
-The value of [C] {X} 'can be reduced, and the same effect (seismic isolation effect) as when the seismic load is reduced can be obtained.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. 1 is an elevational sectional view showing an embodiment of a pile foundation structure according to the present invention, and FIG. 2 is a sectional view taken along the line II-II of FIG. The pile foundation structure of this embodiment is formed by connecting a foundation frame 1 and a foundation pile 2. A circular coupling hole 3 whose upper end is closed by an inner bottom wall 3a is formed on the lower surface of the foundation frame 1, and a pile head 4 of the circular foundation pile 2 is inserted into the circular coupling hole 3. ing.

At the center between the opposing upper wall 4a of the pile head of the foundation pile 2 and the inner bottom wall 3a of the upper end of the coupling hole 3, the diameter of the upper end wall 4a of the pile head of the foundation pile 2 is made smaller. The formed disk-shaped elastic body 5 is interposed. In this case, the elastic body 5 is connected to the pile head upper end wall 4a of the foundation pile 2,
The upper end inner bottom wall 3a of the coupling hole 3 is not coupled. The elastic body 5 and the upper end inner bottom wall 3 of the coupling hole 3 which are not coupled to each other.
A sliding plate 6 is interposed between the facing surfaces of the sliding surfaces a to allow the relative sliding of the facing surfaces in the horizontal direction. Sliding plate 6
Is a steel plate coated with a material having a low coefficient of friction, such as Teflon or synthetic resin, and is joined to the upper inner bottom wall 3a of the joining hole 3. Also, on the upper surface of the elastic body 5,
A steel plate 7 for smoothing sliding with the sliding plate 6 is attached.

A cylindrical elastic member 8 (or viscous member 9) is interposed between the outer peripheral wall 4b of the pile head of the foundation pile 2 and the inner peripheral wall 3b of the coupling hole 3. This elastic body 8 (or viscous body 9) is attached to the pile head outer peripheral wall 4b,
The inner peripheral wall 3b of the coupling hole 3 is not coupled.
The elastic members 5 and 8 are made of, for example, a rubber plate,
Is made of, for example, a viscoelastic rubber having both viscosity and elasticity used in a normal seismic isolation device.

Next, the operation will be described. In the above-mentioned pile foundation structure, the elastic body 8 (or viscous body 9) is interposed between the inner peripheral wall 3b of the coupling hole 3 of the foundation frame 1 and the outer peripheral wall 4b of the pile head 4 of the foundation pile 2. Since the elastic body 8 (or viscous body 9) has an extremely small elastic coefficient compared to iron or the like, which is a material of the foundation pile 2, the pile head 4 is completely fixed with respect to the rotation of the foundation pile 2 during an earthquake. Sufficient deformation occurs to bring it into a pinned state. Also, in the event of an earthquake, large and small axial forces act on the pile head 4.
An elastic body 5 is interposed between the base pile a and the upper end wall 4a of the pile head 4. Since the elastic body 5 has an extremely small elastic coefficient compared with iron or the like, which is a material of the foundation pile 2, Due to the rotation of the foundation pile 2 at a time, sufficient deformation occurs to bring the pile head 4 into a completely pinned state. Therefore, the pile head 4
And the presence of the elastic body 8 (or viscous body 9) on the outer peripheral wall 4b of the pile head 4 irrespective of the magnitude of the acting axial force. The connection state of the base frame 1 can be maintained in a state close to perfect pin connection (bending resistance is zero).

In addition, the elastic member 5 on the upper end wall 4a of the pile head 4
Is connected to both the foundation frame 1 and the pile head 4, the rotation of the pile head 4 causes a displacement between the upper and lower portions of the elastic body 5, and a horizontal resistance that contributes to bending resistance occurs. ,
In the present embodiment, the elastic body 5 is connected only to the pile head 4 side, and the sliding plate 6 is intentionally interposed on the non-bonded side. Generation of horizontal resistance that contributes to resistance can be prevented as much as possible.

The elastic body 8 (or viscous body 9) disposed on the outer peripheral wall 4b of the pile head 4 is connected only to the pile head 4 and is not connected to the foundation frame 1 side. The vertical force (axial force) from the foundation body 1 is hardly transmitted to the elastic body 8 (or the viscous body 9), and almost no upper end wall 4 of the pile head is provided.
a, and hardly affects the function and effect of the elastic body 8 (or the viscous body 9).

The horizontal force at the time of the earthquake can be reliably reduced from the foundation frame 1 to the pile head 4 because the pile head 4 is inserted into the coupling hole 3 via the elastic body 8 (or viscous body 9). Part 4
And the horizontal force acting on the pile head 4 during a large earthquake can be reliably resisted.

When the viscous body 9 is used for the outer peripheral wall 4b of the pile head 4 instead of the elastic body 8, in addition to the above-mentioned effects, in particular, the viscous body attenuates the energy. It can also show a seismic isolation effect.

In the above embodiment, the pile head outer peripheral wall 4
The elastic body 8 (or viscous body 9) disposed on the pile b is attached to the entire surface of the pile outer peripheral wall 4b in a cylindrical shape. Is also good.

In the above embodiment, the elastic body 5 and the elastic body 8 (or the viscous body 9) are connected to the pile head 4 side. You may couple | bond only with the base frame 1 side. In any case, it is not necessary to connect to both the opposing surface and the wall.

[0031]

As described above, according to the present invention,
Regardless of the magnitude of the axial force during the earthquake, the connection between the pile head and the foundation can be maintained in a state close to perfect pin connection (no bending resistance). Therefore, breakage of the foundation pile during an earthquake can be reliably prevented, and as a result, costs can be reduced by reducing the specifications and the number of foundation piles. Further, since the pile head is inserted into the connection hole of the foundation frame through an elastic body or a viscous body, the pile head can sufficiently resist horizontal force during a large earthquake. In addition, when a viscous body is used for the outer peripheral wall of the pile head, in addition to the above effects, it is possible to exhibit a seismic isolation effect (as if the seismic load was reduced). The prevention of breakage of the foundation pile and the cost reduction effect can be made more reliable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 foundation frame 2 foundation pile 3 connection hole 3a upper inner bottom wall 3b inner peripheral wall 4 pile head 4a pile head upper wall 4b pile head outer peripheral wall 5 elastic body 6 sliding plate 8 elastic body 9 viscous body

Claims (2)

[Claims] 1. A pile foundation structure in which a foundation frame and a foundation pile are coupled to each other, wherein a coupling hole whose upper end is closed by an inner bottom wall is formed on a lower surface of the foundation frame. The pile head of the foundation pile is inserted, and between the upper end wall of the pile head and the upper inner bottom wall of the coupling hole facing each other, only one of the opposing walls is connected to the other. A sliding plate that interposes a non-coupled elastic body on the wall and allows horizontal relative sliding between the facing surfaces between the facing non-coupled elastic body and the wall. Further, an elastic body which is connected to only one of the opposing peripheral walls and not connected to the other peripheral wall between the pile head outer peripheral wall of the foundation pile and the inner peripheral wall of the coupling hole. Pile foundation structure characterized by intervening. 2. A pile foundation structure in which a foundation frame and a foundation pile are coupled to each other, wherein a coupling hole whose upper end is closed by an inner bottom wall is formed on a lower surface of the foundation frame. The pile head of the foundation pile is inserted, and between the upper end wall of the pile head and the upper inner bottom wall of the coupling hole facing each other, only one of the opposing walls is connected to the other. A sliding plate that interposes a non-coupled elastic body on the wall and allows horizontal relative sliding between the facing surfaces between the facing non-coupled elastic body and the wall. Further, a viscous body that is connected to only one of the opposing peripheral walls and not connected to the other peripheral wall between the pile head outer peripheral wall of the foundation pile and the inner peripheral wall of the coupling hole. Pile foundation structure characterized by intervening.