JP2024055864A - Seismic isolation structure - Google Patents

Abstract

A seismic isolation structure capable of reducing the additional bending moment generated at the pile head due to horizontal deformation of a seismic isolation device is provided. [Solution] The present invention includes a plurality of pile bodies 2, a first upper footing 311 (upper foundation) of an upper structure that can be displaced horizontally relative to the pile bodies 2, a first steel frame girder 71 extending in a first horizontal direction and erected on the first upper footing 311 adjacent to the first horizontal direction, a second steel frame girder 72 extending in a second horizontal direction and erected on the first upper footing 311 adjacent to the second horizontal direction, and a sliding support 4 provided between the plurality of pile bodies 2 and the first upper footing 311. The first upper footing 311 is disposed at the intersection of the first steel frame girder 71 and the second steel frame girder 72, and includes a steel frame brace beam 8 (load support beam) that is disposed so as to surround the intersection and is joined to the first steel frame girder 71 and the second steel frame girder 72 to reinforce the first upper footing 311, and concrete 313 in which the intersection and the steel frame brace beam 8 are embedded. [Selected Figure] Figure 3

Description

The present invention relates to a seismic isolation structure.

In general, seismic isolation structures are widespread. Patent Document 1 discloses a seismic isolation structure in which a seismic isolation device is provided between a slab-shaped underground foundation that is installed on top of a number of piles buried in the ground and connects the pile heads of the many piles, and a building foundation that is placed on the underground foundation. Also known is a seismic isolation structure in which a tie beam is provided to connect the pile heads of adjacent piles instead of the underground foundation, and a seismic isolation device is provided between the pile heads and the building foundation.
In recent years, there has been an increasing need for seismic isolation structures that can shorten construction time and are cost-effective, and pile-top seismic isolation structures in which a seismic isolation device is provided between the pile head and the foundation of a building without providing underground foundations or tie beams that connect the pile heads of many pile bodies are becoming more widespread. In the following, underground foundations and tie beams that connect the pile heads of many pile bodies are referred to as "tie beams, etc.". By not providing tie beams, such pile-top seismic isolation structures can shorten construction time and reduce costs, and are sometimes adopted in buildings with relatively low floors and large floor areas, such as large-scale logistics warehouses (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 11-13068

However, in a pile-top seismic isolation structure, by omitting tie beams, rotational deformation occurs at the pile head during an earthquake, which may cause fluctuations in the performance of the seismic isolation device and affect the seismic isolation and earthquake resistance performance. For this reason, consideration must be given to time history response analysis, and advanced judgment is required, such as ministerial certification and arbitrary orientation level review.
The allowable value of rotational deformation that occurs at the head of a pile during an earthquake is very small, for example, 1/100 radian or less, and is limited to the range that can be confirmed by experiments. Therefore, if you try to keep the amount of rotational deformation that occurs at the head of a pile during an earthquake below the allowable value, the design can become complicated.
During an earthquake, the seismic isolation device undergoes horizontal deformation, and the additional bending moment, known as P-δ, that occurs during this horizontal deformation becomes very large. Therefore, in a pile-top seismic isolation structure that omits tie beams, etc., the piles must be able to handle the additional bending moment.
For this reason, it is desirable to reduce the additional bending moment that occurs at the pile head due to the horizontal deformation of the seismic isolation device.

The present invention aims to provide a seismic isolation structure that can reduce the additional bending moment that occurs at the pile head due to horizontal deformation of the seismic isolation device.

In order to achieve the above-mentioned object, the seismic isolation structure of the present invention comprises 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 that is provided above each of the pile heads of the plurality of pile bodies and is capable of moving horizontally relative to the pile bodies, a first steel frame girder that extends in the first horizontal direction and is erected on the upper foundation adjacent to the first horizontal direction, a second steel frame girder that extends in the second horizontal direction and is erected on the upper foundation adjacent to the second horizontal direction, and the pile heads of each of the plurality of pile bodies. and a sliding support provided between the upper foundation, the sliding support having a sliding plate fixed to the underside of the upper foundation and a sliding material fixed to the top of the pile head of the pile body and capable of sliding along the underside of the sliding plate, the upper foundation having a load-bearing beam disposed at the intersection of the first steel girder and the second steel girder, surrounding the intersection and connected to the first steel girder and the second steel girder to reinforce the upper foundation, and concrete in which the intersection and the load-bearing beam are embedded.

The additional bending moment that occurs in the sliding support acts on the sliding plate side, not on the sliding material side, so in the seismic isolation structure of the present invention, the sliding plate is fixed to the upper foundation of the superstructure, rather than to the pile body, making it possible to significantly reduce the additional bending moment acting on the pile body.

In addition, in the seismic isolation structure of the present invention, the upper foundation has a load-bearing beam that is located at the intersection of the first steel girder and the second steel girder, is arranged to surround the intersection, is joined to the first steel girder and the second steel girder, and reinforces the upper foundation, and has concrete in which the intersection and the load-bearing beam are embedded.

With this type of configuration, the additional bending moment acts on the upper foundation on the sliding plate side, but the upper foundation is reinforced by providing a load-supporting beam, so it can handle the additional bending moment that acts.

In addition, in the seismic isolation structure according to the present invention, a shear connector may be joined to the load-supporting beam.

This structure makes the upper foundation stronger.

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

FIG. 2 is a pile-laying diagram of a seismic isolation structure according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is an enlarged view of part B in FIG. 2 . FIG. 3 is an enlarged view of part C in FIG. 2 . 4 is a cross-sectional view taken along line D-D of FIG. 3. 6 is a cross-sectional view taken along line E-E of FIG. 5.

Hereinafter, a seismic isolation structure according to an embodiment of the present invention will be described with reference to FIGS.
As shown in Figures 1 and 2, a seismic isolation structure 1 according to this embodiment is adopted in a structure 11 having a plurality of pile bodies 2 buried in the ground and a superstructure 3 provided on the plurality of pile bodies 2. As shown in Figure 2, the seismic isolation structure 1 has a plurality of pile bodies 2, the superstructure 3, and a sliding bearing 4 and a laminated rubber bearing 5 provided between the pile bodies 2 and the superstructure 3. The pile bodies 2 and the superstructure 3 are capable of relative displacement 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.

The pile bodies 2 are arranged at intervals in a first horizontal direction and a second horizontal direction perpendicular to the first horizontal direction. In the drawings, the first horizontal direction is indicated by an arrow X, and the second horizontal direction is indicated by an arrow Y.
Of the regions in which the multiple pile bodies 2 are provided, the multiple pile bodies provided in the first region 21 on the inside in a plan view are referred to as first pile bodies 22, and the multiple pile bodies provided in the second region 23 on the outside are referred to as second pile bodies 24. In this embodiment, the second region 23 is disposed so as to surround the outer periphery of the first region 21. The first region 21 corresponds to the region on the outer periphery of the structure 11 in a plan view. The second region 23 corresponds to the region on the inside of the structure 11 in a plan view.

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 first pile head footing 221 has a square shape in a plan view, and each side of the square is disposed in a direction extending obliquely at 45° with respect to the first horizontal direction and the second horizontal direction.
As shown in Figures 2 and 4, a second pile head footing 241 is provided on the pile head of the second pile body 24. As shown in Figure 1, the shape of the second pile head footing 241 in a plan view is a square or rectangle, and each side of the square is arranged in a direction extending in the first horizontal direction and the second horizontal direction. In this embodiment, a circular portion 231 having a substantially circular shape in a plan view is provided in a part of the second region 23. The second pile head footing 241 provided on this circular portion 231 is arranged in a direction along the circumferential direction of the circle.

1, 2 and 4, the second pile head footings 241 adjacent to each other in the horizontal direction are connected to each other by a tie beam 6. In this embodiment, the second pile head footing 241 is connected to at least one of the second pile head footings 241 adjacent to each other in the first horizontal direction and the second pile head footings 241 adjacent to each other in the second horizontal direction by the tie beam 6.
The first pile head footings 221 adjacent to each other in the horizontal direction are not connected to each other.

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 fixation, they behave as a pin joint and are also treated as a pin joint in structural calculations.
The second pile body 24 and the second pile head footing 241 can be connected in either a rigid or semi-rigid manner.
The structural calculations for the pile body 2 involve simultaneously calculating the pile body 2 with different degrees of fixation at the pile head, namely pin joints and semi-rigid joints, and calculating the design stress using a calculation program that can appropriately evaluate the proportion of shear force borne by the earthquake force.

The foundation 32 of the upper structure 3 is an independent foundation. The foundation 32 has a plurality of upper footings 31 made of concrete disposed on the first pile head footing 221 and the second pile head footing 241, respectively.
As shown in Figures 2 to 4, the upper structure 3 is provided with a first steel girder 71 extending in the first horizontal direction and erected on an upper footing 31 adjacent in the first horizontal direction, and a second steel girder 72 extending in the second horizontal direction and erected on an upper footing 31 adjacent in the second horizontal direction.
The upper footing 31 is disposed 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. The first steel girder 71 and the second steel girder 72 may be provided with shear connectors such as headed studs for fastening to the concrete 313.
The upper footings 31 adjacent to each other in the first horizontal direction are joined by a first steel girder 71. The upper footings 31 adjacent to each other in the second horizontal direction are joined by a second steel girder 72.
Above the upper footing 31 are columns 9 and a floor (not shown).

Of the multiple upper footings 31, the upper footing 31 disposed on the first pile head footing 221 is referred to as a first upper footing 311, and the upper footing 31 disposed on the second pile head footing 241 is referred to as a second upper footing 312. The first upper footing 311 corresponds to the upper foundation in the claims.
The first upper footing 311 has a square shape in a plan view, and each side of the square is disposed so as to extend obliquely at 45° with respect to the first horizontal direction and the second horizontal direction.
The second upper footing 312 has a square or rectangular shape in plan view, and is arranged so that each side of the square extends in the first horizontal direction and the second horizontal direction. The second upper footing 312 provided on the portion 231 of the second region 23 that has a substantially circular shape in plan view is arranged so as to be oriented along the tangent direction of the circle.

As shown in FIG. 3, the sliding bearing 4 is provided between the first pile head footing 221 and the first upper footing 311. The sliding bearing 4 has a sliding plate 41 and a sliding member 42 that can slide along the sliding plate 41. The sliding plate 41 is fixed to the lower surface of the first upper footing 311. The sliding member 42 is fixed on the top of the first pile head footing 221. The sliding member 42 slides along the lower surface of the sliding plate 41. The sliding bearing 4 may be selected from an elastic sliding bearing, a rigid sliding bearing, or the like, or a combination of these may be used.

As shown in FIG. 4, the laminated rubber bearing 5 is provided between the second pile head footing 241 and the second upper footing 312. The laminated rubber bearing 5 may be selected from, for example, a high damping rubber laminated rubber bearing, a natural rubber laminated rubber bearing, a lead plug laminated rubber bearing, a tin plug laminated rubber bearing, or the like, or a combination of two or more of these may be used.

As shown in FIG. 5, the first upper footing 311 is provided with a steel frame fire beam 8 that is arranged to surround the intersection 73 between the first steel girder 71 and the second steel girder 72 and is joined to the first steel girder 71 and the second steel girder 72. The steel frame fire beam 8 is embedded in the concrete 313 of the first upper footing 311. The steel frame fire beam 8 corresponds to the load-supporting beam in the claims.

The steel frame fire beams 8 extend in a direction that is inclined at 45° with respect to the first horizontal direction and the second horizontal direction. Four steel frame fire beams 8 are provided in one first upper footing 311 so as to surround an intersection 73 between the first steel frame girder 71 and the second steel frame girder 72. As shown in Figs. 5 and 6, the steel frame fire beams 8 may be provided with shear connectors 81 such as headed studs for fastening to the concrete 313 of the first upper footing 311.
The first upper footing 311 may be provided with reinforcing bars in addition to shear connectors 81 for shear transfer for the purpose of integrating the first steel girder 71, the second steel girder 72, and the steel bracing beam 8 with the concrete 313.
For example, in the case where the column 9 provided on the upper footing 31 is a reinforced concrete column, a U-shaped reinforcing bar 82 may be provided inside the first upper footing 311 as shown in FIG.
The method of joining the steel frame fire beam 8 to the first steel frame girder 71 and the second steel frame girder 72 may be any joining method that allows stress transmission. For example, the joining methods include welding, HTB, pin, and rigid joining, and combinations of these may also be used.

Next, the action and effect of the seismic isolation structure according to this embodiment will be described.
Since the additional bending moment generated in the sliding support 4 acts on the sliding plate 41 side rather than the sliding material 42 side, in the seismic isolation structure 1 of this embodiment, the sliding plate 41 is fixed to the first upper footing 311 of the upper structure 3 rather than the first pile body 22, thereby significantly reducing the additional bending moment acting on the first pile body 22.
Generally, in pile-top seismic isolation, since there is no beam at the pile head, the degree of fixation of the pile head cannot be expected, if the additional bending moment acting on the pile body when the seismic isolation device is horizontally deformed during an earthquake is applied to the pile body, the pile body itself must bear it. Since the additional bending moment of the seismic isolation device, the so-called P-δ bending, is very large, the pile strength and rigidity are insufficient, and the pile-top seismic isolation structure cannot be adopted in many cases. As described above, in the seismic isolation structure of this embodiment, the additional bending moment acting on the first pile body 22 can be reduced, making it easier to adopt the pile-top seismic isolation structure.

In the seismic isolation structure of this embodiment, the additional bending moment acts on the first upper footing 311 of the superstructure 3 on the sliding plate 41 side. In contrast, in the seismic isolation structure of this embodiment, the first upper footing 311 is reinforced by providing the steel frame fret beams 8, so that the acting additional bending moment can be handled and the weight of the superstructure 3 can be reliably supported even when the sliding bearing 4 is horizontally deformed during an earthquake.
In addition, the first upper footing 311 is made larger in plan view by fixing the sliding plate 41 to the first upper footing 311. Therefore, in an earthquake, the first upper footing 311 may move outward from the upper column 9 in a plan view, and the weight of the upper structure 3 must be borne by the protruding portion of the first upper footing 311 that is outward from the column 9. In contrast, in the seismic isolation structure of this embodiment, the first upper footing 311 is reinforced by providing the steel frame fire beam 8, so that the weight of the upper structure 3 can be borne even if the first upper footing 311 moves outward from the upper column 9 in a plan view during an earthquake.

In the seismic isolation structure 1 according to this embodiment, a shear connector 81 is joined to the steel frame fire beam 8. This configuration allows the first upper footing 311 to have a stronger structure.

In the seismic isolation structure 1 according to this embodiment, the steel frame fire 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 shape of the first upper footing 311 of the upper structure 3 when viewed from the vertical direction is a square with each side extending 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 when viewed from the vertical direction is also a square with each side extending in a direction inclined at 45° with respect to the first horizontal direction and the second horizontal direction. With this configuration, the planar shapes of the first pile head footing 221 of the first pile body 22 and the first upper footing 311 of the upper structure 3 correspond to each other, making it easier to install the sliding bearing 4.

In the seismic isolation structure 1 according to this embodiment, the seismic isolation device is horizontally deformed due to the rotational deformation of the pile head during an earthquake, and the additional bending moment generated at the pile head due to the horizontal deformation of the seismic isolation device can be made smaller when the seismic isolation device is a sliding bearing than when the seismic isolation device is a laminated rubber bearing. In the seismic isolation structure 1 according to this embodiment, the first pile body 22 on which the sliding bearing 4 is provided does not connect the pile head to the adjacent first pile body 22, and the second pile body 24 on which the laminated rubber bearing 5 is provided at the pile head is connected to the adjacent second pile body 24 by the tie beam 6. As a result, in the seismic isolation structure 1 according to this embodiment, a relatively small additional bending generated at the pile head of the first pile body 22 on which the sliding bearing 4 is provided is handled by the first pile body 22, and a relatively large additional bending moment generated at the pile head of the second pile body 24 on which the laminated rubber bearing 5 is provided is handled by the second pile body 24 and the tie beam 6. By doing this, construction time can be shortened and costs can be reduced, since it is only necessary to connect the pile heads of the second pile bodies 24, on which the laminated rubber bearings 5 are installed, with the tie beams 6, compared to when the pile heads of all the pile bodies are connected with the tie beams 6. Also, compared to when the pile heads of all the pile bodies are connected with the tie beams 6, the building weight can be reduced and the number of pile bodies and pile diameter, etc. can be reduced.
The first pile body 22, on which the sliding bearing 4 is provided, does not have its pile head connected, while the second pile body 24, on which the laminated rubber bearing 5 is provided, can be designed so that its pile heads are connected by connecting beams 6, making it easy to design the structural plan, etc.

Although the embodiment of the seismic isolation structure according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit of the present invention.
For example, in the above embodiment, the first horizontal direction and the second horizontal direction are perpendicular to each other, but they do not have to be perpendicular to each other.

In the above embodiment, the first upper footing 311 is disposed at the intersection 73 between the first steel girder 71 and the second steel girder 72, and a steel fire beam 8 is disposed to surround the intersection 73 and joined to the first steel girder 71 and the second steel girder 72, and the intersection 73 and the steel fire beam 8 are embedded in the concrete 313. In contrast, the first upper footing 311 does not necessarily need to be provided with a steel fire beam 8.

A shear connector 81 is joined to the steel frame fire beam 8, but it does not have to be joined.
When a shear connector 81 is joined to a steel frame brace beam 8, the type of the shear connector 81 may be set appropriately.

In the seismic isolation structure 1 according to the above embodiment, the steel frame fire 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 first pile head footing 221 of the pile head of the first pile body 22 and the first upper footing 311 of the upper structure 3 is a square inclined at 45° with respect to the first horizontal direction and the second horizontal direction. The extension direction of the steel frame fire beam 8 and the planar shape of the first pile head footing 221 and the first upper footing 311 may be set appropriately.
The planar shapes of the second pile head footing 241 and the second upper footing 312 may also be set appropriately.

In the seismic isolation structure 1 according to the above 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, and a first upper footing 311 is provided at the pile head, and the first upper footing 311 of the superstructure 3 is disposed above that.
In the seismic isolation structure 1 according to the above embodiment, the horizontally adjacent second pile head footings 241 are connected by the tie beams 6, but they do not have to be connected. The horizontally adjacent second pile head footings 241 may be connected by a connecting material such as a mat slab instead of the tie beams 6.

1 Seismic isolation structure 2 Pile body 3 Superstructure 4 Sliding bearing 5 Laminated rubber bearing 6 Tie beam (connecting material)
8. Steel frame fire beam (load-bearing 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 beam 72 Second steel beam 73 Intersection 81 Shear connector 82 U-shaped reinforcement bar 221 First pile head footing (pile head, footing)
231 Circular portion 241 Second pile head footing (pile head)
311 First upper footing (upper foundation)
312 Second upper footing 313 Concrete

Claims (2)

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 an upper structure provided above each of the pile heads of the plurality of pile bodies and capable of being displaced horizontally relative 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;
A sliding bearing is provided between the pile head of each of the plurality of pile bodies and the upper foundation,
The sliding bearing is
A sliding plate fixed to the lower surface of the upper foundation;
A sliding member fixed on the top of the pile head of the pile body and capable of sliding along the lower surface of the sliding plate;
The upper foundation is disposed at an intersection between the first steel girder and the second steel girder,
a load-bearing beam that is arranged to surround the intersection and is connected to the first steel girder and the second steel girder to reinforce the upper foundation;
and concrete in which the intersection and the load-supporting beam are embedded. The seismic isolation structure of claim 1, in which a shear connector is joined to the load-bearing beam.

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