JP5023245B1 - Pile head seismic isolation structure - Google Patents

Abstract

An object of the present invention is to provide a pile head seismic isolation structure in which the entire pile foundation is displaced integrally during an earthquake, and the construction labor can be reduced, the work period can be shortened, and the cost can be reduced.
A base-isolated structure in which an upper structure 4 is supported on the heads of a plurality of foundation piles 2 via a base isolation device 3, and the outer piles arranged on the outer periphery of the foundation pile 2 A connecting member 15 composed of the earth wall 13 and the horizontal connecting member 14 is formed between the heads, and the connecting member 15 is installed so as to surround the inner pile 2b disposed on the inner side. By utilizing the earth pressure of the ground surrounded by the member 15, the entire foundation pile 2 behaves as a group pile in the event of an earthquake and moves together in the same direction without being disjointed, greatly reducing foundation work. As a result, it is possible to obtain a pile head seismic isolation structure that can shorten the construction period and reduce costs.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a pile head seismic isolation structure in which the structure of a foundation pile head that is a foundation structure is improved to a base isolation structure in a base isolation structure constructed via a base isolation device on a foundation pile. Is.

  A plurality of techniques have been proposed and publicly known for the seismic isolation structure in which the seismic isolation device is installed on the head of the foundation pile to construct the upper structure. As a first prior art according to the public knowledge, it is a base structure of a base-isolated structure in which an upper structure is supported on a foundation via a laminated rubber, and a foundation beam is provided at the bottom of the upper structure. In addition, the foundation is formed only from an independent pile or an independent direct foundation, and the foundation beam between the piles or the direct foundation is omitted, and the ground of the pile head of the independent pile used as the foundation This is a base structure of a seismic isolation structure that allows the rotation without restricting rotation (see Patent Document 1).

  According to the foundation structure of this seismic isolation structure, the foundation in the base isolation structure is composed only of independent piles or independent direct foundations, and the foundation beam connecting them is omitted. It can be simplified and can greatly contribute to the reduction of construction cost and the construction period. In particular, when a pile is employed, by adopting a structure that allows rotation of the pile head relative to the ground, there is an advantage that the pile head moment is eliminated and the maximum moment generated in the pile is reduced.

  Further, as a second related art that is publicly known, a building body, a building foundation that transmits and supports the load of the building body to the ground, and a seismic isolation device that is fixed to the building foundation and supports the building body, The building foundation includes a plurality of steel pipe piles penetrating into the ground and a connecting member (foundation slab) that connects the pile heads of the plurality of steel pipe piles. The seismic isolation building is configured such that the seismic isolation device is fixed on the pile head of the steel pipe pile, and the large beam on the lowest floor of the building body is directly fixed on the seismic isolation device (Patent Document 2). reference).

  According to this base-isolated building, the pile heads of steel pipe piles are connected by connecting members (foundation slabs), so that even when subjected to horizontal force due to an earthquake, multiple steel pipe piles can be displaced horizontally. Since they are displaced in the same direction, the plurality of steel pipe piles can resist horizontal force and seismic resistance can be ensured.

  Further, as a third conventional technique that is publicly known, a pile head seismic isolation structure that seismically supports the upper structure with a seismic isolation device installed on a pile head, as a base for installing the seismic isolation device A flat pile head capital is integrated with the pile head, and the pile head bending moment accompanying the occurrence of pile head rotation can be transmitted from the pile head to the pile head capital, and between adjacent pile head capital To suppress the pile head rotation of each pile by bending back the pile head bending moment transmitted from each pile head to each pile head capital by interconnecting the pile head capitals This is a pile head seismic isolation structure provided with flat connecting beams (see Patent Document 3).

  According to this pile head seismic isolation structure, a flat pile head capital is provided on the pile head, a flat connecting beam is provided between the pile head capitals, and the pile head rotation is controlled by the flat connecting beam. Compared to the previous seismic isolation structure that unconditionally restrains the pile head rotation with a large cross-section and rigid foundation, the foundation as the lower structure can be greatly simplified, and the seismic isolation pit can also be made sufficiently shallow, The construction cost can be greatly reduced including the reduction of the amount of root cutting.

JP-A-9-273162 JP 2006-104883 A JP 2007-120232 A

  In the first prior art, the foundation beam connecting the piles is omitted, but a bottom plate is provided over the entire bottom surface of the pit, and a convex portion is formed on the bottom plate at a position directly above the pile. The head and the convex part of the bottom are connected by dowels, and the rotation of the pile head with respect to the ground is not restricted. However, there is a problem in that it takes a lot of construction work to form such a bottom board over the entire surface, and the cost of the foundation work becomes high. In addition, when the ground is good, it is possible to omit the bottom and leave it alone, but in such a case, the pile is displaced horizontally under the influence of the phase difference due to earthquake motion, The problem arises that it is not possible to ensure that the entire pile resists horizontal force.

  Moreover, in the said 2nd prior art, since several steel pipe piles are displaced in the same direction, without horizontally displacing, the heads of a steel pipe pile are connected with the foundation slab which is a connection member. As in the first prior art, in order to form the basic slab as the connecting member on the entire surface, not only a large amount of materials are required, but also the construction work is expensive and expensive. Have.

  Furthermore, in the third prior art, a flat pile head capital is provided integrally on all pile heads, and a flat connecting beam for connecting the pile head capitals to each other is provided. The formation of the head capital and the flat connecting beam has the problem that it takes a lot of work and the cost cannot be avoided.

  Therefore, in the prior art, the connecting beam and the foundation slab, which is a connecting member, are eliminated between the pile heads, and the entire pile is ensured to be displaced in the same direction without being displaced in the event of an earthquake. There is a problem to be solved in order to reduce the construction period and to reduce the cost.

  The present invention is a seismic isolation structure in which an upper structure is supported via a seismic isolation device on the heads of a plurality of foundation piles arranged as specific means for solving the problems of the above-described conventional example, In the foundation pile, a connecting member composed of earth wall and horizontal connecting material is formed between the outer pile heads arranged on the outer periphery, and the connecting member is installed so as to surround the inner pile arranged inside. The pile head isolation structure characterized by this is provided.

  In the present invention, the earth pressure wall includes an outer earth pressure wall and an inner earth pressure wall, and is formed integrally through the horizontal binder; the horizontal binder is a beam or a slab. And forming the earth pressure wall to a depth of at least 3 m from the ground surface as an additional requirement.

  According to the pile head seismic isolation structure according to the present invention, a connecting member composed of a earth wall and a horizontal connecting material is formed between the outer outer pile heads, and the connecting member surrounds the inner inner pile. By being installed, the whole pile behaves as a group pile at the time of an earthquake using the earth pressure of the ground surrounded by the connecting member, and it is displaced together in the same direction without being displaced separately, The connecting members such as the connecting beams that connect all the pile heads as in the example and the foundation slab formed on the entire surface can be eliminated, and the foundation work can be greatly reduced, the construction period can be shortened and the cost can be reduced. It has a seismic isolation effect.

BRIEF DESCRIPTION OF THE DRAWINGS It is a pile head seismic isolation structure which concerns on embodiment of this invention, Comprising: It is the side view shown schematically including a part of upper structure. It is the side view which showed the principal part of the outer periphery outer pile in the pile head seismic isolation structure which concerns on the same embodiment. It is the side view which showed the principal part of the inner inner pile in the pile head seismic isolation structure which concerns on the same embodiment. It is the pile head seismic isolation structure which concerns on the same embodiment, Comprising: It is the top view which abbreviate | omitted and showed one part in the state which set many foundation piles which are foundation structures. It is explanatory drawing which shows the earth pressure resistance concept by the earth pressure wall at the time of the earthquake in the pile head seismic isolation structure which concerns on the embodiment.

  The present invention will be described in detail based on the illustrated embodiment. First, in FIG. 1 to FIG. 4, a large number of foundation piles 2, which are foundation structures, are formed and arranged by a ground drill method or the like at a set interval with respect to the ground 1. The upper structure 4 is constructed through 3. In this case, a mounting member 5 such as a footing is provided on each seismic isolation device 3, and the PC pillar 6 and the lowermost PC beam 7 are tension-fixed to the mounting member 5 by a plurality of appropriate tension members 8. A prestressed concrete pile head seismic isolation structure installed with prestressing, a large span space structure with enhanced axial pressure effect of the seismic isolation structure and a rigid upper part with high elastic restoring force It becomes a structure.

  In attaching the seismic isolation device 3 to the foundation pile 2, the reinforcing steel pipe 9 is provided at the pile head, the concrete 10 is placed, and the anchor bolts 11 for connection are buried and formed integrally with the foundation pile 2. The seismic isolation device 3 is fixed via the connecting anchor bolt 11. The seismic isolation device 3 and the upper footing are connected by the connecting anchor bolt 12.

  As shown in FIGS. 2 and 4, in the foundation pile 2 of the foundation structure, the pile head portion of the outer pile 2 a arranged on the outer periphery has a connecting member composed of the earth pressure wall 13 and the horizontal connecting material 14. 15 are connected in series. The earth pressure wall 13 in this case is composed of an outer earth pressure wall 13a and an inner earth pressure wall 13b, and the outer earth pressure wall 13a and the inner earth pressure wall 13b are integrally connected by a horizontal connecting member 14 to form a connecting member 15. The space between the outer earth pressure wall 13 a and the inner earth pressure wall 13 b and the upper surface of the horizontal connecting material 14 is a pit 16.

  And as shown in FIG. 2, the depth or height H of the earth pressure wall 13 is formed to a height from the surface of the ground 1 to a depth of at least 3 m or more in the depth direction, or at least It is formed as a connecting member 15 in a state where the horizontal connecting member 14 is integrally engaged with or fitted to the pile head of the outer outer pile 2a. 4, the earth pressure wall 13 as the connecting member 15 is formed so as to surround the entire periphery in a closed shape or an enclosure shape, and thus the earth pressure formed in the closed shape or the enclosure shape is formed. The wall 13 is formed in the ground 1 so as to receive earth pressure from the outside and inside of the enclosure.

  Moreover, as shown in FIG. 3, each foundation pile 2 arrange | positioned inside surrounded by the earth pressure wall 13 formed in the shape of a closed shape or enclosure, ie, each inner pile 2b, is the inner pile 2b. The seismic isolation device 3 is attached to the upper surface of the base, and a mounting member 5 such as a footing is provided on the seismic isolation device 3, and the PC pillar 6 and the lower PC beam 7 of the upper structure 4 are attached via the mounting member 5 It is the same as the foundation pile arranged on the outer periphery in that About each inner pile 2b arrange | positioned inside, the soil around a pile head is excluded and the space part as the pit 16 is established, The space part periphery is formed as the gentle embankment 17, and the established pit The seismic isolation device 3 is positioned so as to face 16. In addition, it cannot be overemphasized that the entrance and exit for inspecting the seismic isolation apparatus 3 can be suitably provided in the floor slab of a building.

  Further, the connecting member 15 composed of the earth pressure wall 13 and the horizontal connecting member 14 is a huge structure in which the length L of one side of the structure 4 constructed in a rectangle exceeds, for example, 100 m. For example, a connecting member 15 having the same structure can be provided in the inner base pile 2 in a partition shape near the middle of the length. The soil 1 and the mortar or concrete are sprayed on the surface of the ground 1 and the embankment 17 to form the earth retaining portion 18 having the required thickness, and the slab having the required thickness is provided on the lowermost floor of the upper structure 4. 19 and PC beam 7 are formed.

  Thus, the connecting member 15 formed on the outer peripheral outer pile 2a is surrounded by surrounding the outer peripheral portion as a foundation in the ground 1 with the earth wall 13 over the required depth of at least 3 m or more. The soil pressure of the ground 1 is used so that the whole pile does not fall apart when an earthquake occurs. That is, the earth pressure of the enclosed ground 1 acts equally on the pile heads of the inner piles 2b installed on the inner side, and as shown in FIG. When the earth pressure due to the action is applied to the ground 1 in the direction of the arrow a, the earth pressure is received entirely by the earth pressure wall 13 of the connecting member 15 even if the earth pressure is partially strong or weak. Therefore, even the outer outer pile 2a and the inner inner pile 2b are subjected to the same earth pressure in the same direction, and the foundation pile 2 (outer pile 2a, inner pile 2b) even if there are repeated rocking due to the earthquake The whole is not disjointed, but is subjected to earth pressure in the same direction under the same conditions.

  Further, as shown in FIG. 5, regarding the horizontal force and earth pressure caused by repeated swinging during an earthquake, the horizontal force B caused by the earthquake on the earth pressure wall 13 of the connecting member 15 (the arrow from the right to the left in the figure). When this occurs, a reaction earth pressure b (left to right arrow in the figure) acts on the earth pressure wall 13, and a horizontal force C (left to right arrow in the figure) is generated by shaking back. In this case, a reaction earth pressure c (arrow from the right to the left in the figure) acts on the earth pressure wall 13, and in any case, the outer pile 2 a The heads of the foundation pile group 2 consisting of the inner piles 2b are not separated, but the same earth pressure is applied in the same direction. As a result, all the pile heads are connected. To tie beams and consolidated slab or the like can be eliminated for not only the foundation work can be greatly reduced, shortening the construction period and cost reduction can be achieved. In addition, the earth pressure wall ensures that all pile heads are integrated as a pile group during an earthquake, and the entire seismic isolation device installed on the pile heads is not separated and receives the horizontal force in the same direction at the same time. Because it is displaced, there is no partial damage.

Moreover, as an application condition of the pin seismic isolation structure of the seismic isolation device 3 attached to the pile head, in order to minimize the influence of the pile head displacement and the rotation allowable deformation of the seismic isolation device 3, the horizontal displacement of the pile head at the time of the earthquake is Restrictions are as follows.
(1) When the horizontal displacement of the pile head is less than the cross-sectional nucleus of the pile (the cross-sectional nucleus = φ / 4, φ: pile diameter)
The height (depth) of the earth wall is at least 3 m from the surface of the ground 1.
(2) When the horizontal displacement of the pile head is greater than or equal to the cross-sectional nucleus of the pile a. Same as (1).
b. The pile head is widened so that the displacement is within the cross-section nucleus, and the cross-section nucleus of the pile head is enlarged.
c. In the entire plane of the installed foundation pile, in addition to the outer pile, connecting members are provided on the inner piles arranged in rows at appropriate intervals so that the whole pile is subjected to earth pressure evenly so that it does not fall apart.

  The pile head seismic isolation structure according to the present invention is a connecting member 15 including a earth wall 13 and a horizontal connecting material 14 between the heads of the foundation pile 2 arranged on the outer periphery of the plurality of arranged foundation piles 2. , And the connecting member 15 is installed so as to surround the inner foundation pile 2, so that the heads of the foundation pile group 2 do not swing apart with respect to the horizontal force due to the earthquake. Since the head secures the integrated behavior as a pile group, it can suppress the shaking caused by the earthquake and can fully exert the function of the seismic isolation device 3, so in the low-rise structure and the high-rise structure It can be widely used as a pile head seismic isolation structure.

DESCRIPTION OF SYMBOLS 1 Ground 2 Foundation pile 2a Outer pile 2b Inner pile 3 Seismic isolation device 4 Upper structure 5 Mounting member (footing)
6 PC pillar 7 PC beam 8 Tensile material 9 Reinforced steel pipe 10 Concrete 11, 12 Anchor bolt for connection 13 Earth pressure wall 13a Outer earth pressure wall 13b Inner earth pressure wall 14 Horizontal connecting material 15 Connection member 16 Pit 17 Embankment 18 Earth retaining part
19 Slab

Claims (4)

It is a seismic isolation structure in which the upper structure is supported via a seismic isolation device on the heads of the multiple foundation piles,
In the foundation pile, a connecting member composed of a earth wall and a horizontal connecting material is formed between the outer pile heads arranged on the outer periphery,
A pile head seismic isolation structure characterized in that the connecting member is installed so as to surround an inner pile arranged inside. The earth wall is
The pile head seismic isolation structure according to claim 1, comprising an outer earth pressure wall and an inner earth pressure wall, and is formed integrally with the horizontal connecting material. The horizontal binder is
The pile head seismic isolation structure according to claim 1 or 2, wherein the structure is a beam or a slab. The earth wall is
It forms to the depth of at least 3 m or more from a ground surface. The pile head seismic isolation structure of Claim 1 thru | or 3 characterized by the above-mentioned.

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