Seismic isolation structure

Abstract

To provide a base isolation structure capable of reducing additional bending moment generated at a pile head due to horizontal deformation of a base isolation device.SOLUTION: A base isolation structure has a plurality of pile bodies 2, a first upper footing 311 (upper foundation) of an upper structure capable of being relatively displaced to the pile body 2 in a horizontal direction, a first steel girder 71 that extends in a first horizontal direction and is installed on the first upper footings 311 adjacent in the first horizontal direction, a second steel girder 72 that extends in a second horizontal direction and is installed on the first upper footings 311 adjacent in the second horizontal direction, and a sliding bearing 4 disposed between the plurality of pile bodies 2 and the first upper footings 311. The first upper footing 311 is disposed at an intersection between the first steel girder 71 and the second steel girder 72 and has a steel angle brace 8 (load support beam), which is disposed to surround the intersection, connected to the first steel girder 71 and the second steel girder 72, and reinforces the first upper footing 311, and concrete 313 to embed the intersection and the steel angle brace 8.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a seismic isolation structure.

Background Art

[0002] Generally, seismic isolation structures are widespread. Patent Document 1 discloses a seismic isolation structure in which a slab-shaped underground foundation that connects the pile heads of a large number of piles buried in the ground and a building foundation arranged on the underground foundation are provided with a seismic isolation device therebetween. Further, a seismic isolation structure is also known in which a connecting beam that connects the pile heads of adjacent piles is provided instead of the underground foundation, and a seismic isolation device is provided between the pile head and the building foundation. In recent years, there has been an increasing need for seismic isolation structures that can shorten the construction period and have high cost performance. A pile head seismic isolation structure in which a seismic isolation device is provided between the pile head and the building foundation without providing an underground foundation or a connecting beam that connects the pile heads of a large number of piles is also becoming widespread. Hereinafter, an underground foundation or a connecting beam that connects the pile heads of a large number of piles is referred to as "connecting beam etc.". Such a pile head seismic isolation structure can shorten the construction period and reduce costs by not providing a connecting beam etc., and is sometimes adopted in buildings having a relatively low-rise and large floor area, such as large-scale logistics warehouses (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the pile cap base isolation structure, by omitting the connecting beam or the like, rotational deformation may occur at the pile cap during an earthquake, causing the performance of the base isolation device to fluctuate and affecting the base isolation performance and seismic performance. Therefore, it is necessary to consider time history response analysis, and for example, advanced judgments such as ministerial certification and review at the optional standard level are required. The allowable value of the rotational deformation occurring at the pile cap during an earthquake is very small, such as 1 / 100 radian or less, and is limited to the range that can be confirmed by experiments. Therefore, when trying to keep the amount of rotational deformation occurring at the pile cap during an earthquake below the allowable value, the design may become complicated. During an earthquake, the base isolation device undergoes horizontal deformation, and the additional bending moment generated during this horizontal deformation, so-called P-δ, becomes very large. Therefore, in the pile cap base isolation structure where the connecting beam or the like is omitted, the pile needs to handle the additional bending moment. Therefore, it is desired to reduce the additional bending moment generated at the pile cap due to the horizontal deformation of the base isolation device.

[0005] An object of the present invention is to provide a base isolation structure capable of reducing the additional bending moment generated at the pile cap due to the horizontal deformation of the base isolation device.

Means for Solving the Problem

[0006] To achieve the above object, the seismic isolation structure according to the present invention includes a plurality of pile bodies buried in the ground and arranged in a first horizontal direction and a second horizontal direction intersecting the first horizontal direction, an upper foundation of a superstructure provided above each of the pile heads of the plurality of pile bodies and capable of relative displacement in the horizontal direction with respect to the pile bodies, a first steel girder extending in the first horizontal direction and installed on the upper foundation adjacent to the first horizontal direction, a second steel girder extending in the second horizontal direction and installed on the upper foundation adjacent to the second horizontal direction, and a sliding bearing provided between each of the pile heads of the plurality of pile bodies and the upper foundation. The sliding bearing includes a sliding plate fixed to the lower surface of the upper foundation and a sliding material fixed on the pile head of the pile body and slidable along the lower surface of the sliding plate. The upper foundation is disposed at the intersection of the first steel girder and the second steel girder, and includes a load support beam disposed so as to surround the intersection and joined to the first steel girder and the second steel girder to reinforce the upper foundation, and concrete for embedding the intersection and the load support beam.

[0007] Since the additional bending moment generated in the sliding bearing acts on the sliding plate side rather than the sliding material side, in the seismic isolation structure according to the present invention, by fixing the sliding plate to the upper foundation of the superstructure instead of the pile body, the additional bending moment acting on the pile body can be significantly reduced.

[0008] Further, in the seismic isolation structure according to the present invention, the upper foundation is disposed at the intersection of the first steel girder and the second steel girder, and includes a load support beam disposed so as to surround the intersection and joined to the first steel girder and the second steel girder to reinforce the upper foundation, and concrete for embedding the intersection and the load support beam.

[0009] With such a configuration, the additional bending moment acts on the upper foundation on the sliding plate side. However, since the upper foundation is reinforced by providing the load support beam, the acting additional bending moment can be handled.

[0010] In the seismic isolation structure according to the present invention, a shear connector may be joined to the load support beam.

[0011] By adopting such a configuration, the upper foundation can be made into a stronger structure.

Effects of the Invention

[0012] According to the present invention, it is possible to reduce the additional bending moment generated at the pile head due to the horizontal deformation of the seismic isolation device.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] Hereinafter, the seismic isolation structure according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6. As shown in FIGS. 1 and 2, the seismic isolation structure 1 according to the present embodiment is adopted in a structure 11 having a plurality of pile bodies 2 buried in the ground and an upper structure body 3 provided on the plurality of pile bodies 2. As shown in FIG. 2, the seismic isolation structure 1 has a plurality of pile bodies 2, an upper structure body 3, a sliding bearing 4 and a laminated rubber bearing 5 provided between the pile bodies 2 and the upper structure body 3. The pile bodies 2 and the upper structure body 3 are relatively displaceable in the horizontal direction. The structure 11 is, for example, a relatively low-rise building with a large floor area such as a large-scale logistics warehouse.

[0015] The pile bodies 2 are arranged at intervals in the first horizontal direction and the second horizontal direction orthogonal to the first horizontal direction. In the drawings, the first horizontal direction is indicated by arrow X, and the second horizontal direction is indicated by arrow Y. Among the regions where a plurality of pile bodies 2 are provided, the plurality of pile bodies provided in the inner first region 21 in plan view are denoted as first pile bodies 22, and the plurality of pile bodies provided in the outer second region 23 are denoted as second pile bodies 24. In the present embodiment, the second region 23 is arranged so as to surround the outer periphery of the first region 21. The first region 21 corresponds to the region of the outer peripheral portion of the structure 11 in plan view. The second region 23 corresponds to the region inside the structure 11 in plan view.

[0016] As shown in FIGS. 2 and 3, a first pile head footing 221 is provided on the pile head of the first pile body 22. As shown in FIG. 1, the planar shape of the first pile head footing 221 is a square, and each side of the square is arranged in a direction obliquely extending at 45° with respect to the first horizontal direction and the second horizontal direction. As shown in FIGS. 2 and 4, a second pile head footing 241 is provided on the pile head of the second pile body 24. As shown in FIG. 1, the planar shape of the second pile head footing 241 is a square or a rectangle, and each side of the square is arranged in a direction extending in the first horizontal direction and the second horizontal direction. In the present embodiment, a circular portion 231 having a substantially circular planar shape is present in a part of the second region 23. The second pile head footing 241 provided in this circular portion 231 is arranged in a direction along the circumferential direction of the circle.

[0017] As shown in FIGS. 1, 2, and 4, the second pile head footings 241 adjacent to each other in the horizontal direction are connected by a connecting beam 6. In the present embodiment, the second pile head footing 241 is connected by a connecting beam 6 to at least one of the second pile head footings 241 adjacent to it in the first horizontal direction and the second pile head footings 241 adjacent to it in the second horizontal direction. The first pile head footings 221 adjacent to each other in the horizontal direction are not connected.

[0018] The first pile body 22 and the first pile head footing 221 are rigidly joined. Although the first pile body 22 and the first pile head footing 221 are rigidly joined, since the first pile head footing 221 has no degree of fixity, it behaves as a pinned joint and is treated as a pinned joint in structural calculations. Either rigid joining or semi-rigid joining can be adopted for the second pile body 24 and the second pile head footing 241. For the structural calculation of the pile body 2, a design stress is calculated using a calculation program that can simultaneously calculate pile bodies 2 with different degrees of fixity, namely pinned joints and semi-rigid joints, at the pile head, and appropriately evaluate the ratio of the shear force borne by the seismic force.

[0019] The foundation 32 of the superstructure 3 is an independent foundation. The foundation 32 has a plurality of concrete upper footings 31 arranged on the first pile head footing 221 and the second pile head footing 241 respectively. As shown in FIGS. 2 - 4, the superstructure 3 is provided with a first steel girder 71 extending in the first horizontal direction and erected on the upper footing 31 adjacent in the first horizontal direction, and a second steel girder 72 extending in the second horizontal direction and erected on the upper footing 31 adjacent in the second horizontal direction. The upper footing 31 is arranged at the intersection of the first steel girder 71 and the second steel girder 72. The intersection of the first steel girder 71 and the second steel girder 72 is embedded in the concrete 313 of the upper footing 31. Shear connectors such as headed studs for fixing to the concrete 313 may be provided on the first steel girder 71 and the second steel girder 72. The upper footings 31 adjacent in the first horizontal direction are joined by the first steel girder 71. The upper footings 31 adjacent in the second horizontal direction are joined by the second steel girder 72. Columns 9 and a floor (not shown) are provided on the upper footing 31.

[0020] Among the plurality of upper footings 31, the upper footing 31 disposed on the first pile cap footing 221 is denoted as the first upper footing 311, and the upper footing 31 disposed on the second pile cap footing 241 is denoted as the second upper footing 312. The first upper footing 311 corresponds to the upper foundation in the claims. The planar shape of the first upper footing 311 is square, and each side of the square is arranged in a direction extending obliquely at 45° with respect to the first horizontal direction and the second horizontal direction. The planar shape of the second upper footing 312 is square or rectangular, and each side of the square is arranged in a direction extending along the first horizontal direction and the second horizontal direction. The second upper footing 312 provided in a substantially circular portion 231 where a part of the planar shape of the second region 23 is provided is arranged in a direction along the tangent direction of the circle.

[0021] As shown in FIG. 3, the sliding bearing 4 is provided between the first pile cap footing 221 and the first upper footing 311. The sliding bearing 4 has a sliding plate 41 and a sliding material 42 slidable along the sliding plate 41. The sliding plate 41 is fixed to the lower surface of the first upper footing 311. The sliding material 42 is fixed on the first pile cap footing 221. The sliding material 42 slides along the lower surface of the sliding plate 41. The sliding bearing 4 may be selected from elastic sliding bearings and rigid sliding bearings, etc., or a plurality of these may be used in combination.

[0022] As shown in FIG. 4, the laminated rubber bearing 5 is provided between the second pile cap footing 241 and the second upper footing 312. The laminated rubber bearing 5 may be selected from, for example, high-damping rubber-based laminated rubber bearings, natural rubber-based laminated rubber bearings, laminated rubber bearings with lead plugs, laminated rubber bearings with tin plugs, etc., or a plurality of these may be used in combination.

[0023] As shown in FIG. 5, a steel frame impact beam 8 is provided on the first upper footing 311 so as to surround the intersection 73 of the first steel frame girder 71 and the second steel frame girder 72 and is joined to the first steel frame girder 71 and the second steel frame girder 72. The steel frame impact beam 8 is embedded in the concrete 313 of the first upper footing 311. The steel frame impact beam 8 corresponds to the load support beam in the claims.

[0024] The steel frame impact beam 8 extends in a direction that is 45° oblique to the first horizontal direction and the second horizontal direction. Four steel frame impact beams 8 are provided on one first upper footing 311 so as to surround the intersection 73 of the first steel frame girder 71 and the second steel frame girder 72. As shown in FIGS. 5 and 6, shear connectors 81 such as headed studs for fixing to the concrete 313 of the first upper footing 311 may be provided on the steel frame impact beam 8. Reinforcing bars may be provided on the first upper footing 311 in addition to the shear connectors 81 for the purpose of shear transmission for the integration of the first steel frame girder 71, the second steel frame girder 72, the steel frame impact beam 8, and the concrete 313. For example, when the column 9 provided on the upper footing 31 is an RC column, as shown in FIG. 3, U-shaped reinforcing bars 82 may be provided inside the first upper footing 311. The joining method of the steel frame impact beam 8 to the first steel frame girder 71 and the second steel frame girder 72 may be any joining method capable of stress transmission. For example, welding joints, HTB joints, pin joints, rigid joints, etc., and these may be combined.

[0025] Next, the operation and effects of the seismic isolation structure according to the present embodiment will be described. Since the additional bending moment generated in the sliding bearing 4 acts on the sliding plate 41 side rather than the sliding material 42 side, in the seismic isolation structure 1 according to the present embodiment, by fixing the sliding plate 41 to the first upper footing 311 of the superstructure 3 instead of the first pile body 22, the additional bending moment acting on the first pile body 22 can be significantly reduced. Generally, in pile head seismic isolation, since there is no beam at the pile head and the fixing degree of the pile head part cannot be expected, when an additional bending moment acts on the pile body side when the seismic isolation device undergoes horizontal deformation during an earthquake, the pile body itself needs to bear it. The additional bending moment of the seismic isolation device, namely the so-called P-δ bending, is very large, so in many cases, the pile bearing capacity and rigidity are insufficient and the pile head seismic isolation structure cannot be adopted. As described above, in the seismic isolation structure of this embodiment, since the additional bending moment acting on the first pile body 22 can be reduced, it becomes easy to adopt the pile head seismic isolation structure.

[0026] In the seismic isolation structure of this embodiment, the additional bending moment will act on the first upper footing 311 of the superstructure 3 on the sliding plate 41 side. On the contrary, in the seismic isolation structure of this embodiment, since the steel frame impact beam 8 is provided to reinforce the first upper footing 311, the acting additional bending moment can be processed, and the weight of the superstructure 3 can be reliably borne even during the horizontal deformation of the sliding bearing 4 during an earthquake. In addition, since the sliding plate 41 is fixed to the first upper footing 311, the first upper footing 311 becomes larger in plan view. For this reason, during an earthquake, it may move outside the column 9 above the first upper footing 311 in plan view, and it becomes necessary to bear the weight of the superstructure 3 at the overhanging part outside the column 9 of the first upper footing 311. On the contrary, in the seismic isolation structure of this embodiment, since the steel frame impact beam 8 is provided to reinforce the first upper footing 311, even when it moves outside the column 9 above the first upper footing 311 in plan view during an earthquake, the weight of the superstructure 3 can be borne.

[0027] In the seismic isolation structure 1 according to this embodiment, a shear connector 81 is joined to the steel frame impact beam 8. By adopting such a configuration, the first upper footing 311 can be made into a stronger structure.

[0028] In the seismic isolation structure 1 according to the present embodiment, the steel frame impact beam 8 extends in a direction inclined at 45° with respect to the first horizontal direction and the second horizontal direction. The planar shape of the outer contour of the first upper footing 311 of the superstructure 3 as viewed from the vertical direction is a square in which each side extends in a direction inclined at 45° with respect to the first horizontal direction and the second horizontal direction. The planar shape of the first pile head footing 221 of the pile head of the first pile body 22 as viewed from the vertical direction is also a square in which each side extends in a direction inclined at 45° with respect to the first horizontal direction and the second horizontal direction. By adopting such a configuration, since the planar shapes of the first pile head footing 221 of the first pile body 22 and the first upper footing 311 of the superstructure 3 correspond to each other, the installation of the sliding bearing 4 becomes easy.

[0029] In the seismic isolation structure 1 according to the present embodiment, during an earthquake, the seismic isolation device undergoes horizontal deformation due to the rotational deformation of the pile head, and the additional bending moment generated at the pile head due to this horizontal deformation of the seismic isolation device can be made smaller in the case of the sliding bearing than in the case of the laminated rubber bearing. In the seismic isolation structure 1 according to the present embodiment, the first pile body 22 provided with the sliding bearing 4 does not connect the adjacent first pile bodies 22 and the pile heads to each other, and the second pile body 24 provided with the laminated rubber bearing 5 at the pile head connects the adjacent second pile bodies 24 and the pile heads to each other with a connecting beam 6. Thereby, in the seismic isolation structure 1 according to the present embodiment, the relatively small additional bending generated at the pile head of the first pile body 22 where the sliding bearing 4 is installed is processed by the first pile body 22, and the relatively large additional bending moment generated at the pile head of the second pile body 24 where the laminated rubber bearing 5 is installed can be processed by the second pile body 24 and the connecting beam 6. By doing so, compared with the case where all the pile heads of the pile bodies are connected by the connecting beam 6, only the pile heads of the second pile bodies 24 where the laminated rubber bearings 5 are installed need to be connected by the connecting beam 6, so that the construction period can be shortened and the cost can be reduced. Also, compared with the case where all the pile heads of the pile bodies are connected by the connecting beam 6, the building weight can be reduced, and the number of pile bodies, the pile diameter, etc. can be reduced. The first pile body 22 provided with the sliding bearing 4 does not connect the pile heads, and the second pile body 24 provided with the laminated rubber bearing 5 may be designed to connect the pile heads with the connecting beam 6, so that the structural plan and the like can be easily designed.

[0030] The embodiments of the seismic isolation structure according to the present invention have been described above. However, the present invention is not limited to the above embodiments and can be appropriately modified without departing from the gist thereof. For example, in the above embodiment, the first horizontal direction and the second horizontal direction are orthogonal, but they do not have to be orthogonal.

[0031] In the above embodiment, the first upper footing 311 is disposed at the intersection 73 of the first steel girder 71 and the second steel girder 72, and a steel frame impact beam 8 is provided so as to surround the intersection 73 and joined to the first steel girder 71 and the second steel girder 72. The intersection 73 and the steel frame impact beam 8 are embedded in the concrete 313. On the other hand, the first upper footing 311 may not be provided with the steel frame impact beam 8.

[0032] The shear connector 81 may or may not be joined to the steel frame impact beam 8. When the shear connector 81 is joined to the steel frame impact beam 8, the type of the shear connector 81 may be appropriately set.

[0033] In the seismic isolation structure 1 according to the above embodiment, the steel frame impact beam 8 extends in a direction inclined at 45° with respect to the first horizontal direction and the second horizontal direction. The plan view shapes of the first footing footing 221 of the pile head of the first pile body 22 and the first upper footing 311 of the superstructure 3 are squares that are diagonal at 45° with respect to the first horizontal direction and the second horizontal direction. The direction in which the steel frame impact beam 8 extends and the plan view shapes of the first footing footing 221 and the first upper footing 311 may be appropriately set. The plan view shapes of the second footing footing 241 and the second upper footing 312 may also be appropriately set.

[0034] In the seismic isolation structure 1 according to the above-described embodiment, the sliding bearing 4 and the laminated rubber bearing 5 are provided, but only the sliding bearing 4 may be provided. In this case, all the pile bodies 2 correspond to the first pile bodies 22, the first upper footing 311 is provided at the pile head, and the first upper footing 311 of the superstructure 3 is disposed above it. In the seismic isolation structure 1 according to the above-described embodiment, the second pile head footings 241 adjacent in the horizontal direction are connected by the connecting beam 6, but they may not be connected. The second pile head footings 241 adjacent in the horizontal direction may be connected by a connecting member such as a mat slab instead of the connecting beam 6.

Explanation of Reference Numerals

[0035] 1 Seismic isolation structure 2 Pile body 3 Superstructure 4 Sliding bearing 5 Laminated rubber bearing 6 Connecting beam (connecting member) 8 Steel frame impact beam (load supporting beam) 9 Column 11 Structure 21 First region 22 First pile body 23 Second region 24 Second pile body 31 Upper footing 32 Foundation 41 Sliding plate 42 Sliding material 71 First steel frame girder 72 Second steel frame girder 73 Intersection 81 Shear connector 82 U-shaped reinforcing bar 221 First pile head footing (pile head, footing) 231 Circular part 241 Second pile head footing (pile head) 311 First upper footing (upper foundation) 312 Second upper footing 313 Concrete

Claims

1. A plurality of piles buried in the ground and arranged in a first horizontal direction and a second horizontal direction intersecting the first horizontal direction; An upper foundation of a superstructure provided above each of the pile heads of the plurality of piles and horizontally displaceable relative to the piles; A first steel girder extending in the first horizontal direction and installed on the upper foundation adjacent to the first horizontal direction; A second steel girder extending in the second horizontal direction and installed on the upper foundation adjacent to the second horizontal direction; A sliding bearing provided between each pile head of the plurality of piles and the upper foundation, and having: The sliding bearing includes: A sliding plate fixed to the lower surface of the upper foundation; A sliding material fixed on the pile head of the pile and slidable along the lower surface of the sliding plate; The upper foundation is disposed at the intersection of the first steel girder and the second steel girder; A load support beam made of steel, disposed so as to surround the intersection and obliquely spanned with respect to the first steel girder and the second steel girder, with both ends joined to the first steel girder and the second steel girder respectively to reinforce the upper foundation; Concrete for embedding the intersection and the load support beam; The upper foundation reinforced by the load support beam is a seismic isolation structure configured to be resistant to an additional bending moment acting on the upper foundation.

2. The seismic isolation structure according to claim 1, wherein a shear connector is joined to the load support beam.

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