Seismic foundation structure, and construction method of seismic foundation structure

Abstract

To provide a seismic foundation structure, and a construction method of the seismic foundation structure capable of realizing a rigid structure while reducing a construction period when constructing a precast concrete as a part of a lower side foundation in which a seismic device is installed.SOLUTION: A seismic foundation structure 1 in which a seismic device 5 is installed, includes: a concrete foundation part 3; a precast concrete seismic foundation part 4 which is installed at a position above the foundation part 3, and in which the seismic device 5 is provided on an upper surface 4t; and a post-installation foundation part 6 which is constructed through post-installation of concrete 61c between the foundation part 3 and the seismic foundation part 4, wherein the seismic foundation part 4 includes vertical steel bars 42 in which upper end parts 42a are buried, and in which lower end parts 42b of the vertical steel bars 42 project from a lower surface 4d of the seismic foundation part 4 to be buried in the post-installation foundation part 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a seismic isolation foundation structure in which a seismic isolation device is installed, and a method for constructing the seismic isolation foundation structure.

Background Art

[0002] When constructing a building structure, in order to suppress vibrations when an earthquake or the like occurs, it is widely practiced to construct a seismic isolation foundation structure by providing a seismic isolation device in the foundation. For example, Patent Document 1 describes a configuration including a lower foundation constructed on the ground, an upper foundation provided at an interval above the lower foundation, and a seismic isolation device provided between the lower foundation and the upper foundation. In this configuration, the lower foundation is formed of cast-in-place concrete. In order to construct such a seismic isolation foundation structure in a shorter construction period, the lower foundation where the seismic isolation device is provided may be partially made of precast concrete. Regarding this, Patent Document 2 describes a configuration including a lower seismic isolation foundation provided on an upper body, a seismic isolation device provided on the lower seismic isolation foundation, and an upper seismic isolation foundation provided on the seismic isolation device, and the lower seismic isolation foundation is made of precast concrete. In this configuration, after constructing the lower body on site, the lower seismic isolation foundation is installed on the lower body. In the configuration described in Patent Document 2, the lower seismic isolation foundation is only provided on the lower body with grout interposed therebetween, and the lower seismic isolation foundation and the lower body are not configured to be firmly joined. When the lower foundation where the seismic isolation device is provided is partially made of precast concrete, it is desirable to integrate the precast concrete part and the other part constructed by casting concrete on site to make the structure stronger.

[0003] Regarding this, Patent Document 3 describes a configuration in which some of a plurality of reinforcing bars arranged inside the foundation extend upward from the upper surface of the foundation and are inserted into a receiving portion that opens to the bottom surface of the foundation block. In this configuration, after placing a foundation provided with a plurality of reinforcing bars extending vertically from the upper surface of the foundation with concrete, the reinforcing bars are inserted into a receiving portion that opens to the bottom surface of the foundation block, and the foundation block is installed. In a configuration such as that of Patent Document 3, when installing the foundation block, since it is necessary to insert the reinforcing bars protruding from the upper surface of the foundation into each of the plurality of receiving portions, each of the reinforcing bars must be accurately arranged according to the position of the receiving portion. Therefore, a lot of time is required for construction. When partially making the lower foundation provided with the seismic isolation device a precast concrete structure, it is desired to realize a strong structure while reducing the construction period.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a seismic isolation foundation structure and a method for constructing a seismic isolation foundation structure that can realize a strong structure while reducing the construction period when partially making the lower foundation provided with the seismic isolation device a precast concrete structure.

Means for Solving the Problems

[0006] The inventors of the present invention, as a seismic isolation foundation structure for installing a seismic isolation device, install a receiving base on a concrete base portion with reinforcement bars in the base portion, and install a precast concrete seismic isolation base portion with the lower member ends of vertical reinforcing bars protruding thereon. Then, with the lower member ends of the vertical reinforcing bars protruding downward from the seismic isolation base portion, concrete is cast between the base portion and the seismic isolation base portion to construct a post-cast base portion. By this method, since the lower member ends of the vertical reinforcing bars are embedded in the post-cast base portion without using a reinforcing bar joint, the post-cast base portion and the seismic isolation base portion can be firmly joined. This is a feature of the present invention. In order to solve the above problems, the present invention adopts the following means. That is, the seismic isolation foundation structure of the present invention is a seismic isolation foundation structure in which a seismic isolation device is installed, and includes a concrete base portion, a precast concrete seismic isolation base portion installed at a position above the base portion and having the seismic isolation device provided on the upper surface, and a post-cast base portion constructed by post-casting concrete between the base portion and the seismic isolation base portion. The seismic isolation base portion includes a concrete portion and vertical reinforcing bars having upper ends embedded in the concrete portion. The lower ends of the vertical reinforcing bars protrude from the lower surface of the concrete portion and are embedded in the post-cast base portion. According to the configuration as described above, the seismic isolation foundation structure includes a base portion, a seismic isolation base portion installed at a position above the base portion and having the seismic isolation device provided on the upper surface, and a post-cast base portion. Since the post-cast base portion is constructed between the base portion and the seismic isolation base portion, it is located below the seismic isolation base portion. The space between the seismic isolation base portion and the base portion is integrated by vertical reinforcing bars provided such that each of the upper end portion and the lower end portion of the seismic isolation base portion is embedded in the concrete portion of the seismic isolation base portion and the post-cast base portion, respectively. Therefore, a strong structure can be realized. Here, the post-cast base part is constructed by post-casting concrete between the base part and the seismic isolation base part after providing the seismic isolation base part at a position above the base part. Therefore, immediately before constructing the post-cast base part by post-casting the concrete, the lower end part of the vertical reinforcing bar of the seismic isolation base part is provided so as to protrude from the lower surface of the concrete part. For this reason, by simply placing concrete so as to embed the vertical reinforcing bar between the base part and the seismic isolation base part to construct the post-cast base part, the lower end part of the vertical reinforcing bar is embedded in the post-cast base part, and the structure in which the seismic isolation base part and the post-cast base part are integrated by the vertical reinforcing bar as described above can be realized. That is, for example, when placing concrete on-site so that the lower end of the reinforcing bar is embedded in the concrete and the upper end protrudes from the concrete, and then placing a precast concrete member on it while inserting the upper end of the reinforcing bar into a receiving hole or the like, it is not necessary to provide the reinforcing bar in advance with excessive accuracy. In this way, since the seismic isolation base structure can be easily constructed, the construction period can be reduced. Therefore, when partially making the lower base where the seismic isolation device is provided into a precast concrete structure, it becomes possible to provide a seismic isolation base structure that can reduce the construction period and realize a strong structure.

[0007] In one aspect of the present invention, the base part includes a concave part formed to be recessed downward from the upper surface, the seismic isolation base part is provided at the position of the concave part such that the lower surface is located below the upper surface of the base part, and the concrete for forming the post-cast base part is placed up to a height above the lower surface of the seismic isolation base part in the concave part. According to such a configuration, a seismic isolation foundation part is provided at a position of a recess formed by being recessed downward from the upper surface of the base part, such that the lower surface of the seismic isolation foundation part is positioned below the upper surface of the base part, and concrete for forming the post-cast foundation part is placed up to a height above the lower surface of the seismic isolation foundation part of the recess. For this reason, in the seismic isolation foundation part, at least the entire lower surface thereof is positioned within the concrete for forming the post-cast foundation part and is in contact with the concrete. In this way, since the entire lower surface of the seismic isolation foundation part is surface-bonded to the post-cast foundation part, the integrality between the seismic isolation foundation part and the post-cast foundation part is enhanced. In addition, since the post-cast foundation part is formed inside the recess of the base part, the post-cast foundation part is laterally constrained by the base part. Further, by placing the concrete for forming the post-cast foundation part up to a height above the lower surface of the seismic isolation foundation part, at least the lower part of the side surface of the seismic isolation foundation part is laterally constrained by the concrete of the post-cast foundation part. In this way, it is possible to realize a seismic isolation foundation structure with higher integrality in which forces acting in the horizontal direction are efficiently transmitted among the base part, the post-cast foundation part, and the seismic isolation foundation part.

[0008] In one aspect of the present invention, a method for constructing a seismic isolation foundation structure of the present invention and the seismic isolation foundation structure is a method for constructing a seismic isolation foundation structure in which a seismic isolation device is installed, including a step of installing a precast concrete seismic isolation foundation part including a concrete part and a vertical reinforcing bar provided such that an upper end part thereof is embedded in the concrete part and a lower end part thereof protrudes from the lower surface of the concrete part, at a position above a concrete base part; a step of constructing a post-cast foundation part by post-casting concrete so as to embed the lower end part of the vertical reinforcing bar between the base part and the seismic isolation foundation part, and integrating the base part, the post-cast foundation part, and the seismic isolation foundation part; and a step of installing the seismic isolation device on the upper surface of the seismic isolation foundation part. According to the above configuration, the post-cast foundation part is constructed by post-casting concrete between the base part and the seismic isolation foundation part after providing the seismic isolation foundation part at a position above the base part. In such a configuration, vertical reinforcing bars are provided between the base part and the seismic isolation foundation part in such a way that the upper ends are embedded in the concrete part of the seismic isolation foundation part and the lower ends protrude from the lower surface of the concrete part. By simply placing the concrete, a strong structure in which the seismic isolation foundation part and the base part are integrated by the vertical reinforcing bars can be realized. As a result, a seismic isolation foundation structure having a strong structure can be easily constructed, so that the construction period can be reduced. Therefore, when the lower foundation where the seismic isolation device is provided is partially made of precast concrete, it is possible to provide a seismic isolation foundation structure capable of realizing a strong structure while reducing the construction period.

Effects of the Invention

[0009] According to the present invention, when the lower foundation where the seismic isolation device is provided is partially made of precast concrete, it is possible to provide a seismic isolation foundation structure and a method for constructing the seismic isolation foundation structure capable of realizing a strong structure while reducing the construction period.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 6

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Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0011] The present invention relates to a seismic isolation foundation structure in which a seismic isolation device is installed, and a method for constructing the seismic isolation foundation structure. The seismic isolation foundation structure includes a concrete base part, a precast concrete seismic isolation foundation part installed above the base part, and a cast-in-place concrete cast-in-place foundation part provided between the base part and the seismic isolation foundation part. Vertical reinforcing bars are embedded in the seismic isolation foundation part, the upper end part is embedded, the lower end part protrudes from the bottom surface of the seismic isolation foundation part, and the vertical reinforcing bars are embedded in the cast-in-place foundation part. Hereinafter, with reference to the accompanying drawings, a mode for carrying out the seismic isolation foundation structure and the method for constructing the seismic isolation foundation structure according to the present invention will be described based on the drawings. A longitudinal sectional view showing the configuration of the seismic isolation foundation structure according to an embodiment of the present invention is shown in FIG. 1. The seismic isolation foundation structure 1 supports a structure such as a building from below. As shown in FIG. 1, the seismic isolation foundation structure 1 includes a base part 3, a seismic isolation foundation part 4, a seismic isolation device 5, a cast-in-place foundation part 6, and an upper foundation part 7. The base portion 3 is constructed on the ground G. The base portion 3 is made of concrete. The base portion 3 is, for example, a mat slab. The base portion 3 includes a concrete portion 31 formed by in-situ concrete and base reinforcement bars (not shown) embedded in the concrete portion 31. A recess 35 is formed at a predetermined position of the base portion 3. The recess 35 is formed by being recessed downward from the upper surface 3t of the base portion 3. The recess 35 is formed in a rectangular shape (rectangular) when viewed from above. Inside the recess 35, a part of the base reinforcement bars (not shown) where the recess 35 is not provided protrudes vertically and horizontally into the recess 35 from the bottom surface 35d and the inner surface 35s of the recess 35, so that a part of the base reinforcement bars is exposed. The base reinforcement bars are arranged so as not to interfere with the receiving pedestal 90 and the seismic isolation base portion 4 (including the vertical reinforcement bars 42) described later.

[0012] At the position of the recess 35, a receiving pedestal 90 that supports the seismic isolation base portion 4 described later is provided. The lower end of the receiving pedestal 90 is supported by the ground G. The lower side of the receiving pedestal 90 is embedded in the base portion 3. The upper side of the receiving pedestal 90 is embedded in the post-cast base portion 6 described later. The receiving pedestal 90 is formed of, for example, steel frame, steel pipe, etc. The receiving pedestal 90 has a receiving frame 91, a plurality of support columns 92, and a connecting member 93. The plurality of support columns 92 are provided so as to extend in the vertical direction H. The lower end portion of each support column 92 is placed on the ground G. The lower end portion of each support column 92 may be embedded in the ground G. The lower side of each support column 92 is embedded in the base portion 3. The upper side of each support column 92 protrudes upward from the bottom surface 35d of the recess 35 of the base portion 3.

[0013] The connecting member 93 extends in the lateral direction and connects the plurality of support columns 92 to each other. The connecting member 93 is provided, for example, at the height of the lower end portion and the middle portion of the support column 92 and is embedded in the concrete portion 31 of the base portion 3. The receiving frame 91 extends horizontally at the positions of the upper ends of the plurality of columns 92 and connects the plurality of columns 92 to each other. Therefore, the receiving frame 91 is provided above the bottom surface 35d of the recess 35. The receiving frame 91 is formed, for example, in a rectangular shape in plan view. Thus, the receiving frame 91 is provided at the uppermost part of the receiving base 90 and abuts against the lower surface 4d of the seismic isolation base portion 4 (the concrete portion 41 thereof) when supporting the seismic isolation base portion 4. Note that the configuration of the receiving base 90 is not limited in any way as long as it can sufficiently support the load of the seismic isolation base portion 4, and can be changed to a configuration other than that exemplified above.

[0014] The seismic isolation base portion 4 is installed at a position spaced apart from the base portion 3, above the base portion 3, and more specifically, above the bottom surface 35d of the recess 35 formed in the base portion 3. The seismic isolation base portion 4 is supported from below by the receiving base 90 within the recess 35. FIG. 2 is a front view showing a state in which only the seismic isolation base portion, a seismic isolation device to be described later, and the upper base portion are assembled among the seismic isolation base structures according to the embodiment of the present invention. FIG. 3 is a side view of FIG. 2 and is a view when the state in which only the seismic isolation base portion, the seismic isolation device, and the upper base portion are assembled is viewed from a horizontal direction different from that of FIG. 2. The seismic isolation base portion 4 is made of precast concrete. The seismic isolation base portion 4 is formed in a predetermined shape in a factory in advance. The seismic isolation base portion 4 is formed in a rectangular parallelepiped shape. The seismic isolation base portion 4 includes a concrete portion 41, vertical reinforcing bars 42 embedded in the concrete portion 41, and a base plate 43.

[0015] When viewed in plan, the concrete portion 41 is formed such that one side extending in the first direction D1 in the horizontal plane is approximately twice as long as the other side extending in the second direction orthogonal to the first direction D1 in the horizontal plane. Inside the concrete portion 41, reinforcing bars (not shown) are formed and embedded in a cage shape so as to extend in the vertical direction H and the horizontal directions D1 and D2.

[0016] The base plate 43 is provided on the upper surface 4t of the concrete part 41. The base plate 43 is used to fix the seismic isolation device 5. As shown in FIG. 2, in the present embodiment, a plurality of, for example, two base plates 43 are provided at intervals in the first direction D1. Each of the base plates 43 has a predetermined thickness in the vertical direction H and is formed such that its upper surface has a predetermined levelness. In the present embodiment, a plurality of blind nuts 44 into which mounting bolts 55 for fixing the seismic isolation device 5 are inserted are embedded in the concrete part 41. Each blind nut 44 is joined and provided to the base plate 43 so that its upper end is exposed from the upper surface of the base plate 43. A fixing anchor (not shown) is connected to the lower end of the blind nut 44. The fixing anchor is embedded in the concrete part 41 together with the blind nut 44. In the concrete part 41, placing holes 45 are formed for use when placing the concrete 61c of the post-cast foundation part 6, which will be described later, under the seismic isolation foundation part 4. Two placing holes 45 are provided corresponding to each of the base plates 43. The placing holes 45 are provided at the central positions of each of the base plates 43. A hole (not shown) is opened at the central position of the base plate 43 so as to communicate with the placing holes 45. The placing holes 45 are formed to penetrate the concrete part 41 vertically.

[0017] The vertical reinforcing bars 42 are provided so as to extend in the vertical direction H. The upper end portion 42a of the vertical reinforcing bar 42 is embedded in the concrete part 41 of the seismic isolation foundation part 4. The lower end portion 42b of the vertical reinforcing bar 42 protrudes downward from the lower surface 4d of the concrete part 41 of the seismic isolation foundation part 4. An anchor nut 42c is joined to the lower end portion 42b.

[0018] As described above, the seismic isolation base portion 4 is installed above the base portion 3 at a position overlapping the recessed portion 35 when viewed from above, as shown in FIG. 1. The seismic isolation base portion 4 is supported by the support base 90 at a position spaced upward from the bottom surface 35d of the recessed portion 35 of the base portion 3. The seismic isolation base portion 4 is installed at a position spaced in the first direction D1 from the inner side surface 35s of the recessed portion 35. The seismic isolation base portion 4 is also installed at a position spaced from the inner side surface 35s of the recessed portion 35 in the second direction orthogonal to the first direction D1. In this way, in each of the first direction D1 and the second direction D2, the side surface 4s of the seismic isolation base portion 4 is provided spaced from the inner side surface 35s of the recessed portion 35. Further, the lower surface 4d of the seismic isolation base portion 4 is provided so as to be positioned below the upper surface 3t of the base portion 3 around the recessed portion 35. That is, the seismic isolation base portion 4 is provided such that a lower part thereof is accommodated in the recessed portion 35 at the position of the recessed portion 35. Also, the seismic isolation base portion 4 is provided such that an upper part thereof protrudes upward from the upper surface 3t around the recessed portion 35.

[0019] As shown in FIGS. 2 and 3, the seismic isolation device 5 includes flange plates 51 and 52 provided vertically, and a laminated rubber portion 53 provided between these flange plates 51 and 52. In the present embodiment, a plurality of seismic isolation devices 5 are fixed to one seismic isolation base portion 4. The seismic isolation devices 5 are provided at intervals in the first direction D1, as shown in FIGS. 1 and 2. In the present embodiment, two seismic isolation devices 5 are provided for one seismic isolation base portion 4 so as to have a two-in-one configuration. Each of the seismic isolation devices 5 is attached to the seismic isolation base portion 4 by a plurality of attachment bolts 55. More specifically, for each seismic isolation device 5, after the lower flange plate 51 is provided in contact with the base plate 43 of the seismic isolation base portion 4, the attachment bolts 55 penetrate the flange plate 51 and the base plate 43 from above and are inserted and fastened to the respective socket nuts 44 embedded in the seismic isolation base portion 4, thereby attaching the seismic isolation device 5 to the seismic isolation base portion 4. In this way, a plurality of seismic isolation devices 5 are provided on the upper surface 4t of the concrete portion 41 of the seismic isolation foundation portion 4 via the base plate 43 of the seismic isolation foundation portion 4.

[0020] As shown in FIG. 1, the post-cast foundation portion 6 is constructed by post-casting concrete 61c between the base portion 3 and the seismic isolation foundation portion 4. Specifically, the post-cast foundation portion 6 is formed by cast-in-place filling of concrete 61c in the gap between the bottom surface 35d and the inner surface 35s of the recess 35 and the lower surface 4d and the side surface 4s of the seismic isolation foundation portion 4 within the recess 35 of the base portion 3. The concrete 61c is cast to a height above the lower surface 4d of the seismic isolation foundation portion 4 within the recess 35. In this embodiment, the concrete 61c is cast to the same height as the upper surface 3t of the base portion 3 around the recess 35. The post-cast foundation portion 6 has a reinforced concrete structure including a base reinforcing bar (not shown) protruding into the recess 35 from the bottom surface 35d and the inner surface 35s of the recess 35 and a concrete portion 61 formed by the hardening of the post-cast concrete 61c. Due to such a post-cast foundation portion 6, the entire lower surface 4d of the seismic isolation foundation portion 4 is surface-bonded to the concrete portion 61 of the post-cast foundation portion 6. Also, below the seismic isolation foundation portion 4, the side surface 4s of the seismic isolation foundation portion 4 is surrounded by the concrete portion 61. As a result, at least the lower side of the side surface 4s of the seismic isolation foundation portion 4 is in a state of being laterally restrained by the concrete 61c of the post-cast foundation portion 6. The lower end portion 42b of the vertical reinforcing bar 42 provided to protrude downward from the lower surface 4d of the concrete portion 41 of the seismic isolation foundation portion 4 is embedded in the concrete portion 61 of the post-cast foundation portion 6.

[0021] The upper foundation portion 7 is of precast concrete construction. The upper foundation portion 7 is formed in a predetermined shape in a factory in advance. The upper foundation portion 7 includes a footing portion 71 provided on the seismic isolation device 5 and a column portion 72 extending vertically upward from the footing portion 71. The footing portion 71 is formed, for example, in a rectangular parallelepiped shape. The footing portion 71 is formed such that its shape in plan view is substantially the same as that of the concrete portion 41 of the seismic isolation foundation portion 4. That is, the footing portion 71 is formed such that, in plan view, one side extending in the first direction D1 is approximately twice as long as the other side extending in the second direction. In the footing portion 71, reinforcing bars (not shown) are provided and embedded in a cage shape so as to extend in the vertical direction H and the horizontal directions D1 and D2. Further, main reinforcing bars 75 connected to the main reinforcing bars 82 of the foundation beam 8 are embedded in the footing portion 71. Both ends of the main reinforcing bars 75 are provided so as to protrude laterally from the footing portion 71.

[0022] As shown in FIGS. 2 and 3, a base plate 73 for fixing the seismic isolation device 5 is provided on the lower surface of the footing portion 71. In the present embodiment, two base plates 73 are provided at intervals in the first direction D1. Each of the base plates 73 has a predetermined thickness in the vertical direction H and is formed such that its lower surface has a predetermined levelness. In the present embodiment, a plurality of blind nuts 74 and the like into which mounting bolts 56 for fixing the seismic isolation device 5 are inserted are embedded in the footing portion 71. Each blind nut 74 is joined to the base plate 73 such that its lower end is exposed from the lower surface of the base plate 73. A fixing anchor (not shown) is connected to the upper end portion of the blind nut 74. The fixing anchor is embedded in the footing portion 71 together with the blind nut 74.

[0023] The upper foundation portion 7 is provided such that each of the base plates 73 abuts on the upper flange plate 52 of each of the seismic isolation devices 5 provided in a two - unit configuration. The upper flange plate 52 of each of the seismic isolation devices 5 is fixed to the upper foundation part 7 by a plurality of mounting bolts 56. Each mounting bolt 56 penetrates the upper flange plate 52 and the base plate 73 of the seismic isolation device 5 from below and is inserted and fastened to each socket nut 74. In this way, each of the seismic isolation devices 5 and the upper foundation part 7 are joined via the base plate 73.

[0024] As shown in FIG. 1, the column part 72 extends upward from the footing part 71. The column part 72 is, for example, of precast concrete construction integrally formed with the footing part 71. On this column part 72, for example, columns of a structure are connected. The footing part 71 is connected to foundation beams 8 extending in the horizontal directions D1 and D2. That is, the column part 72 and the foundation beam 8 are joined to each other via the footing part 71. Thereby, the footing part 71 constitutes the column-beam joint part of the column part 72 and the foundation beam 8. Each foundation beam 8 is, for example, of reinforced concrete construction. The foundation beam 8 includes a concrete part 81, main reinforcement bars 82, and shear reinforcement bars 83. The main reinforcement bars 82 and the shear reinforcement bars 83 are embedded in the concrete part 81. The main reinforcement bars 82 are connected to the main reinforcement bars 75 protruding laterally from the footing part 71 via a connection joint (not shown). Note that the configurations of the upper foundation part 7 and the foundation beam 8 shown here are merely examples, and their configurations can be changed as appropriate.

[0025] Next, a method for constructing the seismic isolation foundation structure as described above will be explained. FIG. 4 is a diagram showing the flow of a method for constructing a seismic isolation foundation structure. As shown in FIG. 4, the method for constructing the seismic isolation foundation structure according to the present embodiment includes a step S1 of constructing a base part, a step S2 of installing a seismic isolation foundation part above the base part, a step S3 of constructing a post-cast foundation part and integrating the base part, the post-cast foundation part, and the seismic isolation foundation part, and a step S4 of installing a seismic isolation device.

[0026] FIG. 5 is a diagram showing a method for constructing a seismic isolation foundation structure, and is a longitudinal sectional view showing a state in which a base portion is constructed. First, in step S1 of constructing the base portion, as shown in FIG. 5, the base portion 3 constructed on the ground G is constructed. When constructing the base portion 3, first, on the ground G, a base reinforcing bar (not shown) to be embedded in the concrete portion 31 of the base portion 3 is installed. The base reinforcing bar is also arranged for the portion where the recess 35 is formed. Further, a receiving stand 90 is installed on the ground G. At this time, for the receiving stand 90, level adjustment is performed so that the receiving frame 91 located at the upper end has a predetermined height and a predetermined level. In the present embodiment, two receiving stands 90 are arranged side by side in one recess 35. The positions of the two receiving stands 90 are adjusted so that the heights of the receiving frames 91 located at the upper ends are the same and the upper surfaces of the receiving frames 91 are located in the same horizontal plane. Also, a formwork for forming the base portion 3 is assembled. At this time, a formwork for forming the recess 35 is assembled at a predetermined position. After the assembly of the formwork, concrete is placed in the formwork on-site to form the concrete portion 31. Thereby, the base portion 3 having the recess 35 is constructed.

[0027] After the construction of the base portion 3, step S2 of installing a seismic isolation base portion above the base portion is performed. Prior to this step S2, a precast concrete seismic isolation base portion 4 is transported to the construction site. The seismic isolation base portion 4 is manufactured in a predetermined shape in a factory or the like in advance. The seismic isolation base portion 4 is formed by arranging cage-shaped reinforcing bars and then placing concrete for forming the concrete portion 41 in a formwork (not shown) having a predetermined shape. At this time, a predetermined number of vertical reinforcing bars 42, sleeve nuts 44, etc. are set at predetermined positions in the formwork. When the concrete placed in the formwork hardens and the concrete portion 41 is formed, the precast concrete seismic isolation base portion 4 is manufactured. In the seismic isolation base portion 4, since the vertical reinforcing bars 42 protrude from the lower surface 4d, it is desirable to manufacture it in a posture such that the upper and lower are reversed and the upper surface 4t faces downward and the lower surface 4d faces upward.

[0028] FIG. 6 is a view showing the state in which the seismic isolation foundation part is carried into the construction site. The manufactured seismic isolation foundation part 4 is carried into the construction site by a transport vehicle such as a trailer. At this time, the seismic isolation foundation part 4 is mounted on the loading platform of the transport vehicle with the upper surface 4t facing downward and the vertical reinforcing bars 42 protruding from the lower surface 4d facing upward. As shown in FIG. 6, the seismic isolation foundation part 4 carried into the construction site is lowered from the loading platform of the transport vehicle by a hoisting machine such as a crane and temporarily placed in a temporary placement area or the like provided at the construction site. Also at this time, the seismic isolation foundation part 4 is temporarily placed on the ground Gf of the temporary placement area with the upper surface 4t facing downward and the vertical reinforcing bars 42 protruding from the lower surface 4d facing upward.

[0029] FIG. 7 is a view showing the state in which the seismic isolation foundation part is lifted and inclined. When installing the seismic isolation foundation part 4 from the temporary placement area above the base part 3, the wire W of a hoisting machine such as a crane is hung on the bracket 102 attached to one end 4a of the seismic isolation foundation part 4 in the second direction D2. Then, the hoisting machine lifts one end 4a of the seismic isolation foundation part 4 via the wire W. Then, as shown in FIG. 7, the seismic isolation foundation part 4 is inclined with the side where the bracket 102 is provided on the one end 4a side being lifted about the other end 4b located on the side opposite to the one end 4a in the second direction D2. FIG. 8 is a view showing the state in which the seismic isolation foundation part is erected. Furthermore, when the hoisting machine lifts one end 4a of the seismic isolation foundation part 4 via the wire W, as shown in FIG. 8, the seismic isolation foundation part 4 is in a state of being erected on the ground Gf of the temporary placement area with the side surface 4s on the other end 4b side facing downward. Subsequently, a bracket 103 is attached to the other end 4b side located on the lower side in FIG. 8. Then, the wire W of a hoisting machine such as a crane is hung not only on the bracket 102 on the one end 4a side of the seismic isolation foundation part 4 but also on the bracket 103 on the other end 4b side. FIG. 9 is a view showing the state following FIG. 8, and is a view showing the state in which the seismic isolation foundation part is lifted with the upper surface facing upward. After that, using a hoisting machine, the other end 4b side is lifted via the wire W. Then, as shown in FIG. 9, the seismic isolation base portion 4 rotates such that the upper surface 4t faces upward. With the hoisting machine, the orientation of the seismic isolation base portion 4 is changed until the upper surface 4t faces vertically upward.

[0030] FIG. 10 is a view showing a state following FIG. 9, and is a view showing a state in which the seismic isolation base portion is placed on the receiving stand within the recess. FIG. 11 is a longitudinal sectional view showing a state following FIG. 10, and is a state in which the wire and brackets are removed from the seismic isolation base portion. FIG. 10 is a view of the seismic isolation base portion as viewed from the first direction D1, and FIG. 11 is a view of the seismic isolation base portion as viewed from the second direction D2. Subsequently, the seismic isolation base portion 4 lifted by the hoisting machine is moved above the recess 35 of the concrete base portion 3. Then, as shown in FIGS. 10 and 11, using the hoisting machine, the seismic isolation base portion 4 is lowered and placed on the receiving stand 90 that protrudes upward from the bottom surface 35d of the recess 35. In the present embodiment, since two receiving stands 90 are provided in the recess 35 so as to be spaced apart in the first direction D1, the seismic isolation base portion 4 is placed so as to straddle each of these two receiving stands 90. After that, the wire W and the brackets 102, 103 are removed from the seismic isolation base portion 4. In this way, in the step S2 of installing the seismic isolation base portion above the base portion, a precast concrete seismic isolation base portion 4 is installed at a position above the concrete base portion 3 and spaced apart from the base portion 3. The seismic isolation base portion 4 is installed at a position above the bottom surface 35d of the recess 35 of the base portion 3 and spaced apart from the bottom surface 35d. In this state, the seismic isolation base portion 4 is installed at a position spaced apart in the horizontal directions D1 and D2 with respect to the inner surface 35s of the recess 35. Further, the seismic isolation base portion 4 is provided at the position of the recess 35 such that the lower surface 4d is positioned below the upper surface 3t of the base portion 3 around the recess 35.

[0031] FIG. 12 is a longitudinal sectional view showing a state in which the post-cast foundation portion is constructed and the base portion, the post-cast foundation portion, and the seismic isolation base portion are integrated. After installing the seismic isolation foundation part 4, a post-cast foundation part is constructed, and a process S3 of integrating the base part, the post-cast foundation part, and the seismic isolation foundation part is carried out. In this process S3, as shown in FIG. 12, concrete 61c is post-cast between the base part 3 and the seismic isolation foundation part 4. The concrete 61c is placed in the recess 35 up to a height above the lower surface 4d of the seismic isolation foundation part 4. As shown in FIG. 12, the concrete 61c is placed, for example, up to a height equivalent to the upper surface 3t of the base part 3 around the recess 35. The placing of the concrete 61c is carried out, for example, through a placing hole 45 formed in the central part of the concrete part 41 of the seismic isolation foundation part 4. Also, the concrete 61c can be carried out through the gap between the inner surface 35s of the recess 35 of the base part 3 and the side surface 4s of the seismic isolation foundation part 4. By the hardening of the placed concrete 61c, a post-cast foundation part 6 formed by post-casting the concrete 61c between the base part 3 and the seismic isolation foundation part 4 is constructed. The vertical reinforcing bars 42 protruding downward from the lower surface 4d of the seismic isolation foundation part 4 are embedded in the concrete part 61, so that the seismic isolation foundation part 4 and the post-cast foundation part 6 are firmly integrated. Also, the foundation reinforcing bars arranged to protrude into the recess 35 from the bottom surface 35d and the inner surface 35s of the recess 35 of the base part 3 are embedded in the concrete part 61, so that the base part 3 and the post-cast foundation part 6 are firmly integrated. In this way, the base part 3, the post-cast foundation part 6, and the seismic isolation foundation part 4 are integrated.

[0032] Thereafter, a process S4 of installing the seismic isolation device is carried out. In this process S4, as shown in FIG. 1, the seismic isolation device 5 is installed on the upper surface of the seismic isolation foundation part 4. The seismic isolation device 5 is manufactured in a factory as a unit in a state where a laminated rubber part 53 is provided between the upper and lower flange plates 51, 52. The seismic isolation device 5 fixes the lower flange plate 51 to the seismic isolation foundation part 4 by a plurality of mounting bolts 55. Each mounting bolt 55 penetrates the flange plate 51 and the base plate 43 and is inserted and fastened to each pocket nut 44 embedded in the seismic isolation foundation part 4. The seismic isolation device 5 is installed in a two-row configuration with respect to each of the two base plates 43 provided on the upper surface of the seismic isolation foundation part 4. Thereby, the seismic isolation foundation structure 1 in the present embodiment is constructed.

[0033] After the installation of the seismic isolation device 5, an upper foundation part 7 made of precast concrete is installed on the upper flange plate 52 of the seismic isolation device 5. The upper foundation part 7 is manufactured in a predetermined shape in advance at a factory or the like. The upper foundation part 7 places the base plates 73 provided on the lower surface of the footing part 71 on each of the upper flange plates 52 of the two arranged seismic isolation devices 5. The upper flange plate 52 is fixed to the lower surface of the footing part 71 by a plurality of mounting bolts 56. Each mounting bolt 56 penetrates the flange plate 52 and the base plate 73 and is fastened to a blind nut 74 embedded in the footing part 71. Thereby, the seismic isolation device 5 and the upper foundation part 7 are connected. After installing the upper foundation part 7 in this way, a foundation beam 8 extending in the horizontal directions D1 and D2 is connected to the footing part 71, and a column (not shown) extending upward is connected to the column part 72 provided on the upper foundation part 7, thereby constructing a structure.

[0034] The seismic isolation foundation structure 1 as described above is a seismic isolation foundation structure 1 where the seismic isolation device 5 is installed, and includes a concrete base part 3, a precast concrete seismic isolation foundation part 4 installed at a position above the base part 3 and having the seismic isolation device 5 provided on the upper surface 4t, and a cast-in-place foundation part 6 constructed by cast-in-place concrete 61c between the base part 3 and the seismic isolation foundation part 4. The seismic isolation foundation part 4 includes a concrete part 41 and a vertical reinforcing bar 42 with an upper end part 42a embedded in the concrete part 41. The lower end part 42b of the vertical reinforcing bar 42 protrudes from the lower surface 4d of the concrete part 41 and is embedded in the cast-in-place foundation part 6. According to the configuration as described above, the seismic isolation foundation structure 1 includes a base portion 3, a seismic isolation foundation portion 4 which is installed at a position above the base portion 3 and has a seismic isolation device 5 provided on the upper surface 4t, and a post-cast foundation portion 6. Since the post-cast foundation portion 6 is constructed between the base portion 3 and the seismic isolation foundation portion 4, it is located below the seismic isolation foundation portion 4. Between the seismic isolation foundation portion 4 and the base portion 3, the upper end portion 42a and the lower end portion 42b of the seismic isolation foundation portion 4 are integrated by vertical reinforcing bars 42 provided so as to be respectively embedded in the concrete portion 41 of the seismic isolation foundation portion 4 and the post-cast foundation portion 6. Therefore, a strong structure can be realized. Here, the post-cast foundation portion 6 is constructed by post-casting concrete 61c between the base portion 3 and the seismic isolation foundation portion 4 after the seismic isolation foundation portion 4 is provided at a position above the base portion 3. Therefore, in the stage immediately before constructing the post-cast foundation portion 6 by post-casting the concrete 61c, the lower end portion 42b of the vertical reinforcing bar 42 of the seismic isolation foundation portion 4 is provided in a state of protruding from the lower surface 4d of the concrete portion 41. For this reason, by simply placing the concrete 61c so as to embed the vertical reinforcing bar 42 between the base portion 3 and the seismic isolation foundation portion 4 to construct the post-cast foundation portion 6, the lower end portion 42b of the vertical reinforcing bar 42 is embedded in the post-cast foundation portion 6, and the structure in which the seismic isolation foundation portion 4 and the post-cast foundation portion 6 are integrated by the vertical reinforcing bar 42 as described above can be realized. That is, for example, when placing a precast concrete member on top of the concrete placed on-site after embedding the lower end of the reinforcing bar in the concrete and protruding the upper end from the concrete, it is not necessary to provide the reinforcing bar in advance with excessive accuracy. In this way, since the seismic isolation foundation structure 1 can be easily constructed, the construction period can be reduced. Therefore, when making the lower foundation where the seismic isolation device 5 is provided partially of precast concrete, it is possible to provide the seismic isolation foundation structure 1 capable of reducing the construction period while realizing a strong structure.

[0035] In particular, in the present embodiment, a plurality of seismic isolation devices 5 are provided for one seismic isolation foundation portion 4. For example, when constructing a seismic isolation foundation section where a seismic isolation device is provided by placing concrete on-site and then providing a plurality of seismic isolation devices on the seismic isolation foundation section, it is necessary to individually adjust the height and horizontal level of each of the seismic isolation devices for each seismic isolation device. On the other hand, in the above-described configuration, since the plurality of seismic isolation devices 5 are installed on one seismic isolation foundation section 4 manufactured as precast concrete, if the upper surface of the seismic isolation foundation section 4 is properly formed at the time of factory shipment, when installing the seismic isolation foundation section 4 at the construction site, by adjusting the height and horizontal level of the seismic isolation foundation section 4, the height and horizontal level of each seismic isolation device 5 provided on the seismic isolation foundation section 4 are basically automatically adjusted. That is, the necessity of individually adjusting the height and horizontal level for each of the plurality of seismic isolation devices 5 is reduced. Therefore, also from this perspective, the construction period when constructing the seismic isolation foundation structure 1 can be reduced.

[0036] Further, the base section 3 includes a recessed portion 35 formed to be recessed downward from the upper surface 3t, and the seismic isolation foundation section 4 is provided at the position of the recessed portion 35 such that the lower surface 4d is located below the upper surface 3t of the base section 3, and the concrete 61c for forming the post-cast foundation section 6 is placed up to a height above the lower surface 4d of the seismic isolation foundation section 4 in the recessed portion 35. According to such a configuration, the seismic isolation foundation section 4 is provided at the position of the recessed portion 35 formed to be recessed downward from the upper surface 3t of the base section 3 such that the lower surface 4d of the seismic isolation foundation section 4 is located below the upper surface 3t of the base section 3, and the concrete 61c for forming the post-cast foundation section 6 is placed up to a height above the lower surface 4d of the seismic isolation foundation section 4 in the recessed portion 35. For this reason, in the seismic isolation foundation section 4, at least the entire lower surface 4d is positioned in the concrete 61c for forming the post-cast foundation section 6 and is in contact with the concrete 61c. In this way, since the entire lower surface 4d of the seismic isolation foundation section 4 is surface-bonded to the post-cast foundation section 6, the integrality between the seismic isolation foundation section 4 and the post-cast foundation section 6 is enhanced. In addition, since the post-cast base portion 6 is formed inside the concave portion 35 of the base portion 3, the post-cast base portion 6 is laterally restrained by the base portion 3. Further, by placing the concrete 61c for forming the post-cast base portion 6 up to a height above the lower surface 4d of the seismic isolation base portion 4, at least the lower portion of the side surface 4s of the seismic isolation base portion 4 is laterally restrained by the concrete 61c of the post-cast base portion 6. In this way, a seismic isolation foundation structure with higher integrity can be realized in which forces acting in the horizontal directions D1 and D2 are efficiently transmitted among the base portion 3, the post-cast base portion 6, and the seismic isolation base portion 4.

[0037] Moreover, the construction method of the seismic isolation foundation structure 1 as described above is a construction method of the seismic isolation foundation structure 1 where the seismic isolation device 5 is installed. It includes a step S2 of installing a precast concrete seismic isolation base portion 4 provided with a concrete portion 41 and a vertical reinforcing bar 42 whose upper end portion 42a is embedded in the concrete portion 41 and whose lower end portion 42b protrudes from the lower surface 4d of the concrete portion 41 at a position above the concrete base portion 3; a step S3 of constructing a post-cast base portion 6 by post-casting concrete 61c so as to embed the lower end portion 42b of the vertical reinforcing bar 42 between the base portion 3 and the seismic isolation base portion 4 to integrate the base portion 3, the post-cast base portion 6, and the seismic isolation base portion 4; and a step S4 of installing the seismic isolation device 5 on the upper surface 4t of the seismic isolation base portion 4. According to the above configuration, the post-cast base portion 6 is constructed by post-casting the concrete 61c between the base portion 3 and the seismic isolation base portion 4 after providing the seismic isolation base portion 4 at a position above the base portion 3. In such a configuration, by simply placing the concrete 61c so as to embed the vertical reinforcing bar 42 whose upper end portion 42a is embedded in the concrete portion 41 of the seismic isolation base portion 4 and whose lower end portion 42b protrudes from the lower surface 4d of the concrete portion 41 between the base portion 3 and the seismic isolation base portion 4, a strong structure in which the seismic isolation base portion 4 and the base portion 3 are integrated by the vertical reinforcing bar 42 can be realized. Thereby, since the seismic isolation foundation structure 1 having a strong structure can be easily constructed, the construction period can be reduced. Therefore, when the lower foundation where the seismic isolation device 5 is provided is partially made of precast concrete, it is possible to provide the seismic isolation foundation structure 1 that can realize a strong structure while reducing the construction period.

[0038] (Modification of the embodiment) Note that the seismic isolation foundation structure of the present invention and the construction method of the seismic isolation foundation structure are not limited to the above-described embodiments described with reference to the drawings, and various modifications can be considered within the technical scope thereof. For example, in the above embodiment, the upper end portion 42a of the vertical reinforcing bar 42 is embedded in the concrete portion 41 of the seismic isolation foundation portion 4, and the socket nut 44 to which the mounting bolt 55 is fastened is embedded in the concrete portion 41, but the present invention is not limited thereto. FIG. 13 is a cross-sectional view showing a joint portion between a seismic isolation foundation portion and a seismic isolation device in a seismic isolation foundation structure according to a modification of the above embodiment. As shown in FIG. 13, in the seismic isolation foundation portion 4B of the seismic isolation foundation structure 1B in the present modification, the upper end portion 42a of the vertical reinforcing bar 42B embedded in the concrete portion 41 and the lower end portion of the mounting bolt 55 for fixing the lower flange plate 51 of the seismic isolation device 5 are joined via a connection joint 200 embedded in the concrete portion 41. Even in such a configuration, it is possible to provide the seismic isolation foundation structure 1B that can realize a strong structure while reducing the construction period, similar to the above embodiment.

[0039] (Other modifications) In addition, in the above embodiment, two seismic isolation devices 5 are joined to one seismic isolation foundation portion 4, but the number of seismic isolation devices 5 joined to one seismic isolation foundation portion 4 may be one or three or more. In addition, in the above embodiment, two receiving stands 90 are provided in the recess 35, and one seismic isolation foundation portion 4 is supported from below by these two receiving stands 90. For example, one receiving stand 90 may be provided in the recess 35, and one seismic isolation foundation portion 4 may be supported by one receiving stand 90. In addition, in the above-described embodiment, the seismic isolation foundation portion 4 is formed by a single-layer structure, but the seismic isolation foundation portion 4 may be formed by stacking a plurality of planar members made of precast concrete. Also, in the above-described embodiment, an anchor nut 42c is joined to the lower end portion 42b of the vertical reinforcing bar 42 provided in the seismic isolation foundation portion 4. However, a reinforcement form in which only the vertical reinforcing bar is used without providing an anchor nut, or a reinforcement form in which the lower end portion is bent into a hook shape may be employed. In addition, as long as the gist of the present invention is not deviated from, it is possible to select the configurations exemplified in the above-described embodiment, or to appropriately change them to other configurations.

Explanation of Reference Numerals

[0040] 1, 1B Seismic isolation foundation structure 6 Post-cast foundation portion 3 Base portion 35 Recess 3t Upper surface of the base portion 41 Concrete portion 4, 4B Seismic isolation foundation portion 42, 42B Vertical reinforcing bar 4t Upper surface of the seismic isolation foundation portion (concrete portion) 42a Upper end portion 4d Lower surface of the seismic isolation foundation portion (concrete portion) 42b Lower end portion 5 Seismic isolation device 61c Concrete

Claims

1. A seismic isolation foundation structure in which a seismic isolation device is installed, a base portion made of concrete, a precast concrete seismic isolation foundation portion installed above the base portion and having the seismic isolation device provided on its upper surface, a post-cast foundation portion constructed by post-casting concrete between the base portion and the seismic isolation foundation portion, comprising: the seismic isolation foundation portion includes a concrete portion and vertical reinforcing bars with upper ends embedded in the concrete portion, and lower ends of the vertical reinforcing bars protrude from the lower surface of the concrete portion and are embedded in the post-cast foundation portion A seismic isolation foundation structure characterized by the above.

2. The base portion includes a recess formed by being recessed downward from the upper surface, and the seismic isolation foundation portion is provided at the position of the recess such that its lower surface is located below the upper surface of the base portion, The concrete for forming the post-cast foundation portion is cast up to a height above the lower surface of the seismic isolation foundation portion in the recess The seismic isolation foundation structure according to Claim 1, characterized by the above.

3. A method for constructing a seismic isolation foundation structure in which a seismic isolation device is installed, a step of installing a precast concrete seismic isolation foundation portion including a concrete portion and vertical reinforcing bars with upper ends embedded in the concrete portion and lower ends provided to protrude from the lower surface of the concrete portion above a base portion made of concrete, a step of constructing a post-cast foundation portion by post-casting concrete between the base portion and the seismic isolation foundation portion so as to embed the lower ends of the vertical reinforcing bars, and integrating the base portion, the post-cast foundation portion, and the seismic isolation foundation portion, a step of installing the seismic isolation device on the upper surface of the seismic isolation foundation portion, A method for constructing a seismic isolation foundation structure characterized by including the above steps.

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