Seismic isolation foundation structure

Abstract

When the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, the upward movement of the seismic isolation device during an earthquake is effectively suppressed. [Solution] The seismic isolation foundation structure 1A comprises a base section 2A made of reinforced concrete, a seismic isolation foundation section 3 made of precast concrete provided above the base section 2A, and a seismic isolation device 4 installed above the seismic isolation foundation section 3. A connecting member 71 with a female threaded portion formed on the inside and a connecting reinforcing bar 72 with a male threaded portion formed at one end are embedded in the seismic isolation foundation section 3. An attachment bolt 73 inserted through the lower flange 41 of the seismic isolation device 4 is screwed into the female threaded portion from above, the male threaded portion of the connecting reinforcing bar 72 is screwed into the female threaded portion from below, the other end of the connecting reinforcing bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation section 3, the other end of the connecting reinforcing bar 72 is joined from above to a reinforcing bar joint section 74 embedded in the base section 2A, and the upper end of the anchor reinforcing bar 75 is joined to the reinforcing bar joint section 74 from below.

Description

Technical Field

[0001] The present invention relates to a seismic isolation foundation structure in which a seismic isolation device is installed.

Background Art

[0002] When constructing a building structure, it is widely practiced to provide a seismic isolation device at the foundation part to construct a seismic isolation foundation structure. For example, Patent Document 1 describes a configuration in which a seismic isolation device is installed on a foundation base that protrudes upward from a foundation slab provided along the ground. In this configuration, the foundation base is formed of cast-in-place concrete together with the foundation slab. The seismic isolation device is fixed to such a foundation base by a plurality of anchor bolts. In such a configuration, in the portion where the seismic isolation device is installed, in order to sufficiently support the load acting from above through the seismic isolation device and to resist the pulling force acting on the seismic isolation device during an earthquake, many reinforcing bars, anchor bars, etc. need to be provided at a high density. Therefore, if the lower foundation where the seismic isolation device is installed is to be formed by casting concrete in place as in the configuration of Patent Document 1, a lot of time is required for the construction of the lower foundation at the site, and the construction period may be prolonged.

[0003] On the other hand, the portion where the seismic isolation device is installed (hereinafter referred to as the seismic isolation foundation part) may be made of precast concrete PCa. For example, Patent Document 2 discloses a configuration in which a precast concrete plate formed by embedding a bag nut for fixing a seismic isolation device is installed on a foundation slab, the seismic isolation device is placed on the precast concrete plate, and the seismic isolation device is fixed on the precast concrete plate by fastening an anchor bolt to the bag nut. Furthermore, Patent Document 3 describes a configuration in which a lower base plate with a female threaded portion is provided on the upper surface of a lower seismic isolation foundation made of precast concrete, and a seismic isolation device is fixed to the lower base plate. In this configuration, an anchor bolt, which is fixed to the lower seismic isolation foundation, is screwed into the lower end of the female threaded portion. The seismic isolation device is fixed to the lower base plate of the lower seismic isolation foundation by inserting the bolt through the bolt insertion hole in the lower flange of the seismic isolation device and screwing it into the female threaded portion. As shown in Patent Documents 2 and 3, the construction period can be shortened by using precast concrete for the seismic isolation foundation (precast concrete slab in Patent Document 2, lower seismic isolation foundation in Patent Document 3).

[0004] In the configuration described in Patent Document 2, the seismic isolation device is fixed to the precast concrete slab by fastening anchor bolts to cap nuts embedded in the precast concrete slab, sandwiching the lower flange of the seismic isolation device. The cap nuts are completely embedded inside the precast concrete slab. Therefore, when an uplift force is applied to the seismic isolation device, the uplift force is resisted between the seismic isolation device and the precast concrete slab by the anchoring force of the cap nuts between the precast concrete slab and the concrete constituting the precast concrete slab. Furthermore, in the configuration of Patent Document 3, the seismic isolation device is fixed to the lower seismic isolation foundation by screwing a bolt into a female threaded portion embedded in the lower seismic isolation foundation, sandwiching the lower flange of the seismic isolation device. The female threaded portion and the anchor bolt screwed into the lower end of the female threaded portion are completely embedded inside the lower seismic isolation foundation. Therefore, when an uplift force is applied to the seismic isolation device, the uplift force is resisted between the seismic isolation device and the lower seismic isolation foundation by the anchoring force of the anchor bolt between the anchor bolt and the concrete constituting the lower seismic isolation foundation.

[0005] Thus, in Patent Documents 2 and 3, the cap nuts, female threaded portions, and anchor bolts are all completely embedded in the precast concrete slab and the lower seismic isolation foundation, respectively, which constitute the seismic isolation foundation. Therefore, even if one tries to increase the embedded length of these cap nuts and anchor bolts to more efficiently resist uplift forces, it is not possible to extend them beyond the height of the seismic isolation foundation. Consequently, in Patent Documents 2 and 3, there are limitations to how efficiently one can resist uplift forces between the seismic isolation device and the seismic isolation foundation. When the seismic isolation foundation for installing seismic isolation devices is made of precast concrete, it is desirable to efficiently suppress the uplift of the seismic isolation devices during an earthquake. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-106236 [Patent Document 2] Japanese Patent Publication No. 2011-32759 [Patent Document 3] Japanese Patent Publication No. 2020-51111 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a seismic isolation foundation structure that can efficiently suppress the uplift of the seismic isolation device during an earthquake, when the seismic isolation foundation for installing the seismic isolation device is made of precast concrete. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following means. In other words, the seismic isolation foundation structure of the present invention is a seismic isolation foundation structure on which a seismic isolation device is installed, comprising a base made of reinforced concrete, a seismic isolation foundation made of precast concrete provided above the base, and the seismic isolation device installed above the seismic isolation foundation, wherein a connecting member having a female threaded portion is embedded in the seismic isolation foundation, a connecting reinforcing bar having a male threaded portion is screwed into the female threaded portion from below, a mounting bolt for the seismic isolation device is screwed into it from above, and the other end of the connecting reinforcing bar is embedded in the base. According to the above configuration, a precast concrete seismic isolation foundation is provided above the reinforced concrete base. A connecting member having a female thread is embedded in this seismic isolation foundation. The mounting bolts for the seismic isolation device are screwed into the female thread from above, and a connecting reinforcing bar having a male thread is screwed into the female thread from below. The other end of this connecting reinforcing bar is embedded in the base. In this configuration, when an earthquake occurs and the building tilts, causing an uplift force to act on the seismic isolation device, the entire connecting member and connecting reinforcing bar provides anchoring force to the concrete constituting the base and seismic isolation foundation, resisting the uplift force. Here, as described above, the entire connecting member and connecting reinforcing bar is provided to be embedded not only in the seismic isolation foundation but also in the base, so the total embedding length can be made longer than when the member that resists the uplift force is embedded only inside the precast concrete seismic isolation foundation. Therefore, it is possible to resist the uplift force more efficiently than when the member that resists the uplift force is embedded only inside the precast concrete seismic isolation foundation. In this way, when the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, it becomes possible to efficiently suppress the lifting of the seismic isolation device during an earthquake.

[0009] In one embodiment of the present invention, the other end of the connecting reinforcing bar is joined from above to a reinforcing bar joint embedded in the base portion, and the anchor reinforcing bar is joined from below to the reinforcing bar joint portion. With the above configuration, if the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, it becomes possible to efficiently suppress the lifting of the seismic isolation device during an earthquake. [Effects of the Invention]

[0010] According to the present invention, when the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, it becomes possible to efficiently suppress the uplift of the seismic isolation device during an earthquake. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing a seismic isolation foundation structure according to the first embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view showing the base isolation foundation of the base isolation foundation structure. [Figure 3] Figure 1 is an enlarged cross-sectional view of the main part of the seismic isolation foundation structure. [Figure 4] Figure 1 is an enlarged cross-sectional view showing the connecting members, connecting reinforcing bars, mounting bolts, reinforcing bar joints, and anchor bars provided in the seismic isolation foundation structure. [Figure 5] This is a cross-sectional view showing the state in which the base portion has been constructed in the method for constructing a seismic isolation foundation structure according to the first embodiment. [Figure 6] This is a cross-sectional view showing the state in which the seismic isolation foundation is installed on the base portion in the method for constructing a seismic isolation foundation structure according to the first embodiment. [Figure 7] This is a cross-sectional view showing the state in which a seismic isolation device is installed on the seismic isolation foundation in the method for constructing a seismic isolation foundation structure according to the first embodiment. [Figure 8] This is a cross-sectional view showing the state in which the upper seismic isolation foundation is installed on the seismic isolation device in the method for constructing a seismic isolation foundation structure according to the first embodiment. [Figure 9] This is a cross-sectional view showing a seismic isolation foundation structure according to a modified example of the first embodiment of the present invention. [Figure 10] This is a cross-sectional view showing a seismic isolation foundation structure according to another modification of the first embodiment of the present invention. [Figure 11]It is a cross-sectional view showing a seismic isolation foundation structure according to a second embodiment of the present invention.

Mode for Carrying Out the Invention

[0012] The present invention is a seismic isolation foundation structure in which a seismic isolation device is installed, and is composed of a base part made of reinforced concrete, a seismic isolation foundation part made of precast concrete PCa provided on the base part, and a seismic isolation device installed on the seismic isolation foundation part. The feature is that a joining member having a female screw part is embedded in the seismic isolation foundation part made of PCa, and a connecting reinforcing bar having a male screw part screwed from below is joined to the female screw part. Further, a reinforcing bar joint part and anchor bars are embedded in the base part, a connecting reinforcing bar protruding from the lower surface of the seismic isolation foundation part is joined to the upper side of the reinforcing bar joint part, and anchor bars are joined to the lower side of the reinforcing bar joint part. Hereinafter, with reference to the accompanying drawings, a mode for implementing the seismic isolation foundation structure and the construction method of the seismic isolation foundation structure according to the present invention will be described based on the drawings. (First Embodiment) FIG. 1 shows a cross-sectional view showing a seismic isolation foundation structure according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the seismic isolation foundation part of the seismic isolation foundation structure of FIG. 1. FIG. 3 is an enlarged cross-sectional view of a main part of the seismic isolation foundation structure of FIG. 1. As shown in FIG. 1, the seismic isolation foundation structure 1A includes a base part 2A, a seismic isolation foundation part 3, a seismic isolation device 4, and an upper seismic isolation foundation part 5. The base part 2A is made of reinforced concrete. The base part 2A includes concrete 2c formed by the hardening of in-situ concrete and reinforcing bars (not shown) embedded in the concrete 2c. The base part 2A is supported on a foundation pile (not shown) constructed in the ground.

[0013] The seismic isolation foundation 3 is located above the base section 2A. The seismic isolation foundation 3 is made of precast concrete and, when viewed from above, has a rectangular or circular shape, for example, and has a predetermined height in the vertical direction. As shown in Figure 2, the seismic isolation foundation 3 comprises concrete 3c formed into a predetermined shape and reinforcing bars 3s embedded in the concrete 3c. A portion of the reinforcing bars 3s protrudes downward from the lower surface 3b of the concrete 3c as connecting reinforcing bars 3j to ensure integration with the base section 2A. The seismic isolation foundation 3 is further equipped with a connecting member 71 and a connecting reinforcing bar 72, which will be described later. The upper part of the connecting reinforcing bar 72 is embedded in the concrete 3c, and the lower part protrudes downward from the lower surface 3b of the concrete 3c, similar to the connecting reinforcing bar 3j. Thus, the seismic isolation foundation 3 has a configuration in which the connecting reinforcing bar 3j and the connecting reinforcing bar 72 protrude from the lower surface 3b. For this reason, when the seismic isolation foundation 3 is manufactured as a precast concrete structure in a factory or the like and transported to the site, it is placed upside down so that the upper surface 3t is on the bottom and in contact with the floor or the like.

[0014] A cylindrical anchoring sleeve joint 77 is embedded in the concrete 2c of the base section 2A such that its upper end is positioned slightly below the upper surface 2t of the base section 2A but is not embedded in the concrete 2c (see Figure 4). The connecting reinforcing bar 3j is inserted into this anchoring sleeve joint 77 from above. A grout material G, such as mortar, is filled between the connecting reinforcing bar 3j and the inner wall of the anchoring sleeve joint 77. In this way, the reinforcing bar 3s of the seismic isolation foundation section 3 is joined to the base section 2A by joining it to the anchoring sleeve joint 77.

[0015] As shown in Figure 1, the upper seismic isolation foundation 5 is located above the seismic isolation device 4. The upper seismic isolation foundation 5 is made of precast concrete and, when viewed from above, has a rectangular or circular shape, for example, and has a predetermined height in the vertical direction. The upper seismic isolation foundation 5 comprises concrete 5c formed into a predetermined shape and reinforcing bars 5s embedded in the concrete 5c. A portion of the reinforcing bars 5s protrudes upward from the top surface of the concrete 5c as connecting reinforcing bars 5j to ensure integration with the superstructure 6 described later. The connecting reinforcing bars 5j are embedded in the concrete 6c of the superstructure 6. The upper seismic isolation foundation section 5 is further equipped with an upper connecting member 81 and an upper anchor bolt 82, which will be described later.

[0016] Above the upper seismic isolation foundation 5, the superstructure 6 is provided. The superstructure 6 is the building body of the building equipped with the seismic isolation foundation structure 1A. The superstructure 6 includes, for example, an upper footing 62 below its lowest slab 61. The upper footing 62 is made of reinforced concrete and is provided on the upper seismic isolation foundation 5. The upper footing 62 is formed at the lower end of the columns 63 that constitute the superstructure 6. When viewed from above or below, the upper footing 62 is, for example, rectangular or circular in shape and is formed to protrude downward from the slab 61. The upper footing 62 comprises concrete 6c formed by the hardening of cast-in-place concrete and reinforcing bars (not shown) embedded in the concrete 6c.

[0017] The seismic isolation device 4 is installed above the seismic isolation foundation 3. The seismic isolation device 4 is located between the upper seismic isolation foundation 5 and the seismic isolation foundation 3. Multiple seismic isolation devices 4 are installed at intervals in the horizontal direction. As shown in Figure 3, the seismic isolation device 4 has a plate-shaped lower flange 41, a plate-shaped upper flange 42 positioned above the lower flange 41 at a distance, and a laminated rubber portion 43 provided between the lower flange 41 and the upper flange 42. The laminated rubber portion 43 is formed by alternately laminating metal plates 43m and plate-shaped rubber portions 43r in the vertical direction. The lower flange 41 and upper flange 42 of the seismic isolation device 4 have multiple through holes 41h and 42h formed radially outward from the laminated rubber portion 43, respectively, at circumferential intervals. Each of the multiple through holes 41h and 42h penetrates the lower flange 41 and upper flange 42 in the vertical direction.

[0018] Figure 4 is an enlarged cross-sectional view showing the connecting members, connecting reinforcing bars, mounting bolts, reinforcing bar joints, and anchor bars provided in the seismic isolation foundation structure of Figure 1. As shown in Figures 3 and 4, the lower flange 41 of the seismic isolation device 4, the seismic isolation foundation 3, and the base 2A are connected to each other via a connecting member 71, a connecting reinforcing bar 72, a mounting bolt 73, a reinforcing bar joint 74, and an anchor reinforcing bar 75. The connecting member 71, the connecting reinforcing bar 72, the mounting bolt 73, the reinforcing bar joint 74, and the anchor reinforcing bar 75 are each provided in a position that overlaps with each of the multiple through holes 41h when viewed from above.

[0019] The connecting member 71 is embedded in the upper part of the concrete 3c of the seismic isolation foundation 3. The connecting member 71 is, for example, a tall nut, and is cylindrical in shape extending in the vertical direction, with a female threaded portion 71s formed on its inside. The connecting member 71 is embedded in the concrete 3c forming the seismic isolation foundation 3 and is fixed to the concrete 3c such that its upper end is exposed on the upper surface 3t of the seismic isolation foundation 3. The connecting reinforcement bar 72 extends in the vertical direction. A male threaded portion 72s is formed at one end (upper end) 72e of the connecting reinforcement bar 72. The connecting reinforcement bar 72 is formed by joining an axially oriented threaded bolt 72a, which forms the male threaded portion 72s, and a reinforcement bar 72b in the axial direction. The threaded bolt 72a and the reinforcement bar 72b may be joined by welding, but joining by friction pressure welding is preferable as it provides higher joint strength. Furthermore, from a strength standpoint, it is preferable that the connecting reinforcement bar 72 is made of steel in which a JIS standard thread is used for the male threaded portion 72s and a JIS standard reinforcement bar is used for the reinforcement bar 72b, and both are joined by friction pressure welding. The male threaded portion 72s of such a connecting reinforcement bar 72 is screwed into the female threaded portion 71s of the connecting member 71 from below. The other end (lower end) 72f of the connecting reinforcement bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation 3. The portion of the connecting reinforcing bar 72 embedded in concrete 3c is anchored to concrete 3c. The mounting bolt 73 is provided to be inserted from above through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4. The mounting bolt 73 is screwed from above into the female threaded portion 71s of the connecting member 71 embedded in the seismic isolation foundation 3.

[0020] The reinforcing bar joint 74 and the anchor bars 75 are embedded in the concrete 2c of the base 2A and are anchored to the concrete 2c. The rebar joint 74 is a cylindrical, so-called rebar sleeve joint that extends vertically. The rebar joint 74 is embedded in the concrete 2c forming the base portion 2A such that its upper end is located slightly below the upper surface 2t of the base portion 2A but is not embedded in the concrete 2c (see Figure 4). The other end 72f of the connecting reinforcing bar 72 that protrudes downward from the lower surface 3b of the seismic isolation foundation portion 3 is inserted into the rebar joint 74 from above. The anchor bars 75 extend vertically within the base portion 2A. The upper end of the anchor bars 75 is inserted into the reinforcement bar joint portion 74 from below. The lower end of the anchor bars 75 is provided with a mechanical anchoring device 76 or the like, which expands in diameter radially outward from the outer surface of the anchor bars 75. A grout material G, such as mortar, is filled between the other end 72f of the connecting reinforcing bar 72 and the upper end of the anchor reinforcing bar 75, and the inner wall of the reinforcing bar joint 74. In this way, the connecting reinforcing bar 72 is joined to the anchor reinforcing bar 75 via the reinforcing bar joint 74.

[0021] As shown in Figure 3, the upper flange 42 of the seismic isolation device 4, the upper seismic isolation foundation 5, and the upper footing 62 of the superstructure 6 are connected to each other via the upper connecting member 81, the upper anchor bolt 82, and the upper mounting bolt 83. The upper connecting member 81, the upper anchor bolt 82, and the upper mounting bolt 83 are each provided in a position that overlaps with each of the multiple through holes 42h when viewed from above.

[0022] The upper connecting member 81 is embedded in the lower part of the upper seismic isolation foundation 5. The upper connecting member 81 is, for example, a tall nut, and is cylindrical in shape extending in the vertical direction, with a female threaded portion 81s formed on its inside. The upper connecting member 81 is embedded in the concrete 5c forming the upper seismic isolation foundation 5 and is fixed to the concrete 5c such that its lower end is exposed on the lower surface of the upper seismic isolation foundation 5. The upper anchor bolt 82 extends in the vertical direction. The lower end of the upper anchor bolt 82 is screwed from above into the female threaded portion 81s of the upper connecting member 81. The upper end of the upper anchor bolt 82 protrudes upward from the upper surface of the upper seismic isolation foundation 5 and is embedded in the upper footing 62. The upper anchor bolt 82 is anchored to the concrete 5c of the upper seismic isolation foundation 5 and the concrete 6c of the upper footing 62. A mechanical anchoring device 86 or the like is provided at the upper end of the upper anchor bolt 82, which expands in diameter radially outward from the outer circumferential surface of the upper anchor bolt 82. The upper mounting bolt 83 is provided to be inserted from below through a through hole 42h formed in the upper flange 42 of the seismic isolation device 4. The upper mounting bolt 83 is screwed from below into the female threaded portion 81s of the upper connecting member 81 which is embedded in the upper seismic isolation foundation 5.

[0023] In this seismic isolation foundation structure 1A, the seismic isolation device 4 is sequentially joined to the connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchoring bars 75 via mounting bolts 73. These connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchoring bars 75 are, as a whole, anchored in the concrete 3c and 2c that constitute the seismic isolation foundation 3 and the base 2A, which are joined to each other by connecting reinforcing bars 3j, and are located between them. Similarly, the upper connecting member 81 and the upper anchor bolt 82 are sequentially connected to the seismic isolation device 4 via the upper mounting bolt 83. These upper connecting member 81 and upper anchor bolt 82 as a whole are anchored to the concrete 5c and 6c that constitute the upper seismic isolation foundation 5 and the upper footing 62, which are joined to each other by connecting reinforcing bars 5j.

[0024] Next, we will explain the construction method for the seismic isolation foundation structure 1A described above. Figure 5 is a cross-sectional view showing the state in which the base portion has been constructed in the seismic isolation foundation structure construction method according to the first embodiment. To construct the seismic isolation foundation structure 1A, first, the base section 2A is constructed as shown in Figure 5. This involves placing reinforcing bars (not shown) and anchor bars 75 in the base section 2A, and joining the upper ends of the anchor bars 75 to the reinforcing bar joints 74 from below. After that, the formwork (not shown) is assembled, and concrete 2c is poured into the formwork. Once the concrete 2c hardens and reaches the required strength, the reinforced concrete base section 2A with the anchor bars 75 and reinforcing bar joints 74 embedded is constructed.

[0025] Next, the seismic isolation foundation 3 is installed on the base section 2A. For this, the seismic isolation foundation 3 is manufactured in advance at a factory or the like using precast concrete. The seismic isolation foundation 3 has reinforcing bars 3s, connecting reinforcing bars 72, and a connecting member 71 which is provided by screwing the male threaded portion 72s of one end 72e of the connecting reinforcing bar 72 into the female threaded portion 71s from below, all embedded in the concrete 3c. Since the other end 72f of the connecting reinforcing bar 72 and the connecting reinforcing bar 3j protrude from the bottom surface 3b of the seismic isolation foundation 3, it is preferable to have the bottom surface 3b facing upwards when transporting the seismic isolation foundation 3. When transporting such a seismic isolation foundation 3, it is inverted upside down and positioned above the base section 2A with the bottom surface 3b facing downwards. Furthermore, grout material G is filled into the rebar joint 74 and the anchoring sleeve joint 77.

[0026] Figure 6 is a cross-sectional view showing the state in which the seismic isolation foundation is installed on the base in the method for constructing a seismic isolation foundation structure according to the first embodiment. Then, the seismic isolation foundation 3 is lowered from above the base section 2A, and as shown in Figure 6, the other end 72f of the connecting reinforcement 72, which protrudes downward from the lower surface 3b, and the connecting reinforcement 3j are inserted from above into the reinforcement joint section 74 and the anchoring sleeve joint 77 of the base section 2A. More specifically, the other end 72f of the connecting reinforcement 72 and the connecting reinforcement 3j are embedded inside the grout material G filled into the reinforcement joint section 74 and the anchoring sleeve joint 77. The seismic isolation foundation 3 is lowered to a height such that there is a gap of, for example, 25 mm to 35 mm between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base section 2A. Then, grout material G such as mortar is filled between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base section 2A, joining the lower surface 3b of the seismic isolation foundation 3 and the upper surface 2t of the base section 2A. When filling the gap between the lower surface 3b of the seismic isolation foundation 3 and the upper surface 2t of the base section 2A with grout material G, it is desirable to provide a through-hole 3h (shown only in Figure 6) in the center of the seismic isolation foundation 3 that penetrates the seismic isolation foundation 3 vertically, and to fill the grout material G from above the seismic isolation foundation 3 through this through-hole 3h. In this way, the grout material G can be evenly injected and filled from the center of the seismic isolation foundation 3 to near the outer periphery. In this way, the seismic isolation foundation 3 is installed and joined on the base 2A.

[0027] Figure 7 is a cross-sectional view showing the state in which a seismic isolation device is installed on the seismic isolation foundation in the method for constructing a seismic isolation foundation structure according to the first embodiment. Next, as shown in Figure 7, the seismic isolation device 4 is fixed to the seismic isolation foundation 3. This involves installing the seismic isolation device 4 above the seismic isolation foundation 3, lowering the seismic isolation device 4, and placing it on the upper surface 3t of the seismic isolation foundation 3. Then, the mounting bolts 73 are inserted from above through the through holes 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female threaded portion 71s of the joining member 71.

[0028] Figure 8 is a cross-sectional view showing the state in which the upper seismic isolation foundation is installed on the seismic isolation device in the construction method of the seismic isolation foundation structure according to the first embodiment. Subsequently, as shown in Figure 8, the upper seismic isolation foundation 5, made of precast concrete, is installed on the seismic isolation foundation 3. The upper seismic isolation foundation 5, like the seismic isolation foundation 3, is manufactured in advance at a factory or similar facility. The upper seismic isolation foundation 5 has reinforcing bars 5s, the lower part of the upper anchor bolts 82, and an upper connecting member 81, which is provided by screwing the upper anchor bolts 82 into the female threaded portion 81s from above, embedded in the concrete 5c. The upper seismic isolation foundation 5 is lowered from above the seismic isolation device 4 and placed on the upper flange 42. Next, the upper mounting bolts 83 are inserted from below through the through holes 42h formed in the upper flange 42 of the seismic isolation device 4 and screwed into the female threaded portion 81s of the upper connecting member 81. This fixes the upper seismic isolation foundation 5 to the seismic isolation device 4. In this way, the seismic isolation foundation structure 1A is constructed. Subsequently, the superstructure 6 is constructed sequentially on the upper seismic isolation foundation 5.

[0029] The seismic isolation foundation structure 1A described above is a seismic isolation foundation structure 1A on which a seismic isolation device 4 is installed, comprising a base section 2A made of reinforced concrete, a seismic isolation foundation section 3 made of precast concrete provided above the base section 2A, and a seismic isolation device 4 installed above the seismic isolation foundation section 3, wherein a connecting member 71 with an internally formed female screw portion 71s and a connecting reinforcing bar 72 with an externally formed male screw portion 72s at one end 72e are embedded in the seismic isolation foundation section 3, and a through-hole is formed in the lower flange 41 of the seismic isolation device 4. A mounting bolt 73, which is provided to be inserted through the hole 41h from above, is screwed into the female threaded portion 71s from above, the male threaded portion 72s of the connecting reinforcing bar 72 is screwed into the female threaded portion 71s from below, the other end 72f of the connecting reinforcing bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation 3, a reinforcing bar joint portion 74 and an anchor reinforcing bar 75 are embedded in the base portion 2A, the other end 72f of the connecting reinforcing bar 72 is joined to the reinforcing bar joint portion 74 from above, and the upper end of the anchor reinforcing bar 75 is joined to the reinforcing bar joint portion 74 from below. According to the above configuration, a precast concrete seismic isolation foundation 3 is provided above the reinforced concrete base 2A. A connecting member 71 with an internally formed female thread 71s and a connecting reinforcing bar 72 with a male thread 72s formed at one end 72e are embedded in this seismic isolation foundation 3. A mounting bolt 73, provided to be inserted from above through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4, is screwed into the female thread 71s from above, and the male thread 72s of the connecting reinforcing bar 72 is screwed into the female thread 71s from below. The other end 72f of this connecting reinforcing bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation 3 and is joined from above to a reinforcing bar joint 74 embedded in the base 2A. An anchor reinforcing bar 75, similarly embedded in the base 2A, is joined to this reinforcing bar joint 74 from below. In this manner, the seismic isolation device 4 is sequentially joined to the connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchor bars 75 via mounting bolts 73. These connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchor bars 75 as a whole span between the seismic isolation foundation 3 and the base 2A, and are anchored to the concrete 3c and 2c that constitute them. In this configuration, when an earthquake occurs and the building tilts, causing an uplift force to act on the seismic isolation device 4, the entirety of the connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchor bars 75 provides anchoring force to the base section 2A and the concrete 3c and 2c constituting the seismic isolation foundation 3, resisting the uplift force. Here, as described above, the entirety of the connecting member 71, connecting reinforcing bars 72, reinforcing bar joints 74, and anchor bars 75 is provided to extend not only into the seismic isolation foundation 3 but also into the interior of the base section 2A. Therefore, the total buried length H1 (see Figure 1) can be made longer than the upper limit of the buried length when the member resisting the uplift force is buried only inside the precast concrete seismic isolation foundation 3, i.e., the height H2 of the seismic isolation foundation 3. Consequently, it is possible to resist the uplift force more efficiently than when the member resisting the uplift force is buried only inside the precast concrete seismic isolation foundation 3. In this way, when the seismic isolation foundation 3 for installing the seismic isolation device 4 is made of precast concrete, it becomes possible to efficiently suppress the uplift of the seismic isolation device 4 during an earthquake.

[0030] In particular, with the above configuration, since the seismic isolation foundation 3 is made of precast concrete, there is no need to pour concrete at the construction site to build the seismic isolation foundation 3, which shortens the work period and allows for the efficient construction of the seismic isolation foundation structure 1A.

[0031] Furthermore, the seismic isolation foundation 3 is further equipped with connecting reinforcing bars 3j that protrude downward from the lower surface 3b, and the seismic isolation foundation 3 and the base 2A are joined to each other by the connecting reinforcing bars 3j. With the above configuration, the seismic isolation foundation 3 and the base 2A are joined to each other by connecting reinforcing bars 3j, making it possible to efficiently suppress the lifting of the seismic isolation device 4 during an earthquake.

[0032] Furthermore, the above-described method for constructing the seismic isolation foundation structure 1A is a method for constructing the seismic isolation foundation structure 1A on which the seismic isolation device 4 is installed, and comprises the steps of constructing a reinforced concrete base section 2A in which anchor bars 75 and reinforcement joint sections 74 to which the anchor bars 75 are joined from below are embedded, and a precast concrete seismic isolation foundation in which a connecting member 71 with a female threaded portion 71s formed on the inside and a connecting reinforcing bar 72 in which a male threaded portion 72s formed on one end 72e is screwed into the female threaded portion 71s from below. The process includes the steps of: lowering part 3 from above the base part 2A, inserting the other end 72f of the connecting reinforcing bar 72 that protrudes downward from the lower surface 3b of the seismic isolation foundation part 3 into the reinforcing bar joint part 74 of the base part 2A from above and joining them to install the seismic isolation foundation part 3 on the base part 2A; and installing a seismic isolation device 4 above the seismic isolation foundation part 3, inserting a mounting bolt 73 through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4 from above and screwing it into the female threaded part 71s of the joining member 71 to fix the seismic isolation device 4 to the seismic isolation foundation part 3. With this configuration, a concrete base section 2A is constructed in which anchor bars 75 and rebar joints 74 are embedded. A precast concrete seismic isolation foundation section 3, in which a connecting member 71 with a female threaded portion 71s and connecting bars 72 are embedded, is lowered from above the base section 2A. The other end 72f of the connecting bars 72 is joined to the rebar joint 74 to install the seismic isolation foundation section 3 on the base section 2A. The seismic isolation device 4 is installed above the seismic isolation foundation section 3, and the mounting bolts 73 are inserted from above through the through holes 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female threaded portion 71s of the connecting member 71. This makes it possible to construct a seismic isolation foundation structure 1A that can efficiently suppress the uplift of the seismic isolation device 4 during an earthquake, even when the seismic isolation foundation section 3 for installing the seismic isolation device 4 is made of precast concrete.

[0033] (Modification of the first embodiment) In the first embodiment described above, after constructing the base section 2A, the seismic isolation foundation section 3, seismic isolation device 4, and upper seismic isolation foundation section 5 were sequentially installed on the base section 2A, but the embodiment is not limited to this. Figure 9 is a cross-sectional view showing a modified seismic isolation foundation structure according to the first embodiment of the present invention. For example, as shown in Figure 9, the precast concrete seismic isolation foundation 3, the seismic isolation device 4, and the precast concrete upper seismic isolation foundation 5 may be pre-assembled and joined together as a single unit. Then, after constructing the base section 2A, the entire pre-assembled unit of the seismic isolation foundation 3, seismic isolation device 4, and upper seismic isolation foundation 5 may be lowered from above the base section 2A, and the other end 72f of the connecting reinforcing bar 72 protruding downward from the lower surface 3b of the seismic isolation foundation 3 may be inserted from above into the reinforcing bar joint 74 of the base section 2A and joined together. This allows for more efficient construction of the seismic isolation foundation structure 1A.

[0034] (Other variations of the first embodiment) Furthermore, in the first embodiment described above, the lower flange 41 of the seismic isolation device 4 is placed directly on the upper surface 3t of the concrete 3c constituting the seismic isolation foundation 3, and the concrete 5c constituting the upper seismic isolation foundation 5 is placed directly on the upper flange 42, but the embodiment is not limited to this. Figure 10 is a cross-sectional view showing a seismic isolation foundation structure according to another modification of the first embodiment of the present invention. As shown in Figure 10, the seismic isolation foundation 3 may be configured such that a lower base plate 35 is provided on the upper surface 3t of the concrete 3c, and the lower flange 41 of the seismic isolation device 4 is provided on the lower base plate 35. Alternatively, the upper seismic isolation foundation 5 may be configured such that an upper base plate 55 is provided on the lower surface of the concrete 5c, and the upper base plate 55 is provided on the upper flange 42 of the seismic isolation device 4. The lower base plate 35 and the upper base plate 55 are made of steel plate. Multiple anchor studs 37 are attached to the lower base plate 35 so as to protrude downward from the lower surface of the lower base plate 35. The multiple anchor studs 37 are embedded in the concrete 3c of the seismic isolation foundation 3. Multiple anchor studs 57 are attached to the upper base plate 55 so as to protrude upward from the upper surface of the upper base plate 55. The multiple anchor studs 57 are embedded in the concrete 5c of the upper seismic isolation foundation 5.

[0035] (Other variations of the first embodiment) Furthermore, in the above embodiment, prior to lowering the seismic isolation foundation 3 from above the base section 2A, grout material G was filled into the reinforcing bar joints 74 and the anchoring sleeve joints 77. Then, the other end 72f of the connecting reinforcing bar 72 and the connecting reinforcing bar 3j were buried from above into the grout material G filled into the reinforcing bar joints 74 and anchoring sleeve joints 77 of the base section 2A. The grout material G was then filled into the gap between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base section 2A. However, the embodiment is not limited to this. For example, the seismic isolation foundation 3 may be lowered from above the base 2A without filling the rebar joint 74 and the anchoring sleeve joint 77 with grout material G. In this case, when filling the space between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base 2A with grout material G, the grout material G flows into the interior of the rebar joint 74 and the anchoring sleeve joint 77, thereby filling the rebar joint 74 and the anchoring sleeve joint 77 with grout material G. Furthermore, in order to fill the space between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base 2A with grout material G, a hose may be inserted to near the center of the seismic isolation foundation 3 when viewed from above, and the grout material G may be injected through the hose.

[0036] (Second Embodiment) Next, a second embodiment of the seismic isolation foundation structure and method for constructing the seismic isolation foundation structure according to the present invention will be described. The second embodiment of the seismic isolation foundation structure and method for constructing the seismic isolation foundation structure described below differs from the seismic isolation foundation structure and method for constructing the seismic isolation foundation structure described in the first embodiment above only in the configuration of the joint between the base portion 2A and the seismic isolation foundation portion 3. Therefore, in the following description, components common to the first embodiment above will be denoted by the same reference numerals and their descriptions will be omitted. Figure 11 shows a cross-sectional view illustrating a seismic isolation foundation structure according to a second embodiment of the present invention. As shown in Figure 11, the seismic isolation foundation structure 1B comprises a base section 2B, a seismic isolation foundation section 3, a seismic isolation device 4, and an upper seismic isolation foundation section 5. In this embodiment, a connecting hole 79 is formed in the upper surface 2t of the base portion 2B. The connecting hole 79 extends downward from the upper surface 2t of the base portion 2B. The connecting hole 79 can be realized, for example, by embedding a cylindrical sleeve joint or the like in the concrete 2c. The other end 72f of the connecting reinforcing bar 72, which protrudes downward from the lower surface 3b of the concrete 3c of the seismic isolation foundation 3, is inserted into the connecting hole 79. A grout material G, such as mortar, is filled between the inner wall of the connecting hole 79 and the connecting reinforcing bar 72, and the other end 72f of the connecting reinforcing bar 72 is joined to the concrete 2c of the base portion 2B via the grout material G. The connecting reinforcing bar 72 in the base portion 2B is embedded to a length greater than the necessary anchorage length so that the connecting reinforcing bar 72 does not come out of the base portion 2B even when a tensile force is applied to the connecting reinforcing bar 72.

[0037] To construct such a seismic isolation foundation structure 1B, a reinforced concrete base section 2B is constructed so that connection holes 79 are provided on the upper surface 2t. This involves placing reinforcing bars (not shown) for the base section 2B and setting sleeve joints, etc., to form the connection holes 79 at the predetermined locations. Then, formwork (not shown) is assembled and concrete 2c is poured into the formwork. Once the concrete 2c hardens and reaches the predetermined strength, a reinforced concrete base section 2B with connection holes 79 is constructed.

[0038] Next, the seismic isolation foundation 3 is installed on the base section 2B. For this, the seismic isolation foundation 3 is manufactured in advance at a factory or the like using precast concrete. Also, the connection holes 79 are filled with grout material G. Then, with the bottom surface 3b facing downwards, the seismic isolation foundation 3 is lowered from above the base section 2B, and the other end 72f of the connecting reinforcing bar 72 that protrudes downwards from the bottom surface 3b of the seismic isolation foundation 3 is inserted from above into the connection holes 79 filled with grout material G. The seismic isolation foundation 3 is lowered to a height such that there is a gap of, for example, 25 mm to 35 mm between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base section 2B. Then, grout material G such as mortar is filled between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base section 2B, thereby joining the lower surface 3b of the seismic isolation foundation 3 and the upper surface 2t of the base section 2B. In this way, the seismic isolation foundation 3 is installed and joined on the base 2B.

[0039] Next, the seismic isolation device 4 is fixed to the seismic isolation foundation 3. This involves installing the seismic isolation device 4 above the seismic isolation foundation 3, lowering the seismic isolation device 4, and placing it on the upper surface 3t of the seismic isolation foundation 3. Then, the mounting bolts 73 are inserted from above through the through holes 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female threaded portion 71s of the connecting member 71. In this way, the seismic isolation device 4 is fixed to the seismic isolation foundation 3, and the seismic isolation foundation structure 1B is constructed. After that, the upper seismic isolation foundation 5 made of precast concrete is installed on the seismic isolation foundation 3, and the superstructure 6 is sequentially constructed on the upper seismic isolation foundation 5.

[0040] The seismic isolation foundation structure 1B described above is a seismic isolation foundation structure 1B on which a seismic isolation device 4 is installed, comprising a base section 2B made of reinforced concrete, a seismic isolation foundation section 3 made of precast concrete provided above the base section 2B, and a seismic isolation device 4 installed above the seismic isolation foundation section 3, wherein a connecting member 71 with an internally formed female screw portion 71s and a connecting reinforcing bar 72 with an externally formed male screw portion 72s at one end 72e are embedded in the seismic isolation foundation section 3, and are formed on the lower flange 41 of the seismic isolation device 4 A mounting bolt 73, which is provided to be inserted through the through hole 41h from above, is screwed into the female threaded portion 71s from above, the male threaded portion 72s of the connecting reinforcement bar 72 is screwed into the female threaded portion 71s from below, the other end 72f of the connecting reinforcement bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation 3, a connecting hole 79 is formed in the upper surface 2t of the base portion 2B, the other end 72f of the connecting reinforcement bar 72 is inserted into the connecting hole 79, and grout material G is filled between the inner wall of the connecting hole 79 and the connecting reinforcement bar 72. According to the above configuration, a precast concrete seismic isolation foundation 3 is provided above the reinforced concrete base 2B. A connecting member 71 with an internally formed female thread 71s and a connecting reinforcing bar 72 with a male thread 72s formed at one end 72e are embedded in this seismic isolation foundation 3. A mounting bolt 73, provided to be inserted from above through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4, is screwed into the female thread 71s from above, and the male thread 72s of the connecting reinforcing bar 72 is screwed into the female thread 71s from below. The other end 72f of the connecting reinforcing bar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation 3 and is inserted into a connecting hole 79 formed in the upper surface 2t of the base 2B. Grout material G is filled between the inner wall of the connecting hole 79 and the connecting reinforcing bar 72. In this way, the seismic isolation device 4 is sequentially joined to the connecting member 71 and the connecting reinforcing bar 72 via mounting bolts 73. These connecting member 71 and the connecting reinforcing bar 72 as a whole span between the seismic isolation foundation 3 and the base 2B, and are anchored to the concrete 3c and 2c that constitute them. In this configuration, when an earthquake occurs and the building tilts, causing an uplift force to act on the seismic isolation device 4, the entire connecting member 71 and connecting reinforcing bars 72 resist the uplift force through anchoring force to the base section 2B and the concrete 3c and 2c constituting the seismic isolation foundation section 3. Here, as described above, the entire connecting member 71 and connecting reinforcing bars 72 are provided to extend not only into the seismic isolation foundation section 3 but also into the interior of the base section 2B. Therefore, the total buried length H1 can be made longer than the upper limit of the buried length when the member that resists the uplift force is buried only inside the precast concrete seismic isolation foundation section 3, i.e., the height H2 of the seismic isolation foundation section 3. Consequently, it is possible to resist the uplift force more efficiently than when the member that resists the uplift force is buried only inside the precast concrete seismic isolation foundation section 3. In this way, when the seismic isolation foundation 3 for installing the seismic isolation device 4 is made of precast concrete, it becomes possible to efficiently suppress the uplift of the seismic isolation device 4 during an earthquake.

[0041] In particular, with the above configuration, since the seismic isolation foundation 3 is made of precast concrete, there is no need to pour concrete at the construction site to build the seismic isolation foundation 3, which shortens the work period and allows for the efficient construction of the seismic isolation foundation structure 1B.

[0042] Furthermore, the above-described method for constructing the seismic isolation foundation structure 1B is a method for constructing the seismic isolation foundation structure 1B on which the seismic isolation device 4 is installed, and comprises the steps of constructing a reinforced concrete base section 2B such that a connecting hole 79 is provided on the upper surface 2t, and constructing a precast concrete seismic isolation foundation section 3, in which a connecting member 71 with an internal female screw portion 71s and a connecting reinforcing bar 72, which is provided by screwing a male screw portion 72s formed at one end 72e into the female screw portion 71s from below, are embedded in the base section 2B. The process includes the steps of lowering the connecting reinforcing bar 72 from above and inserting the other end 72f of the connecting reinforcing bar 72 that protrudes downward from the lower surface 3b of the seismic isolation foundation 3 into the connecting hole 79 filled with grout material G from above to install the seismic isolation foundation 3 on the base portion 2B, and fixing the seismic isolation device 4 to the seismic isolation foundation 3 by inserting the mounting bolt 73 from above through the through hole 41h formed in the lower flange 41 of the seismic isolation device 4 and screwing it into the female threaded portion 71s of the joining member 71. With this configuration, a reinforced concrete base section 2B is constructed so that a connecting hole 79 is provided on the upper surface 2t. A precast concrete seismic isolation foundation section 3, in which a connecting member 71 with a female threaded portion 71s and a connecting reinforcing bar 72 are embedded, is lowered from above the base section 2B. The other end 72f of the connecting reinforcing bar 72 is inserted from above into the connecting hole 79 filled with grout material G to install the seismic isolation foundation section 3 on the base section 2B. The seismic isolation device 4 is installed above the seismic isolation foundation section 3, and the mounting bolt 73 is inserted from above through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female threaded portion 71s of the connecting member 71. This makes it possible to construct a seismic isolation foundation structure 1B that can efficiently suppress the uplift of the seismic isolation device 4 during an earthquake, even when the seismic isolation foundation section 3 for installing the seismic isolation device 4 is made of precast concrete.

[0043] It should be noted that the seismic isolation foundation structure and the method for constructing the seismic isolation foundation structure of the present invention are not limited to the embodiments and modifications described above with reference to the drawings, and various other modifications are conceivable within the technical scope. For example, in the second embodiment, similar modifications as those described with respect to the first embodiment can be considered. For example, as explained with reference to Figure 9 with respect to the first embodiment, in the second embodiment as well, the precast concrete seismic isolation foundation 3, the seismic isolation device 4, and the precast concrete upper seismic isolation foundation 5 may be joined together in advance as an integrated unit and then joined to the base 2B. Alternatively, as described with reference to Figure 10 with respect to the first embodiment, in the second embodiment as well, the seismic isolation foundation 3 and the upper seismic isolation foundation 5 may each be equipped with a lower base plate 35 and an upper base plate 55, respectively.

[0044] Furthermore, in the second embodiment, prior to lowering the seismic isolation foundation 3 from above the base portion 2B, grout material G was filled into the connection holes 79, and then the other end 72f of the connecting reinforcing bar 72 was buried from above into the grout material G filled in the connection holes 79, so that the grout material G was filled into the gap between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base portion 2B, but the embodiment is not limited to this. For example, the seismic isolation foundation 3 may be lowered from above the base 2B without filling the connection hole 79 with grout material G. In this case, when filling the space between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base 2B with grout material G, the grout material flows into the interior of the connection hole 79, thereby filling the connection hole 79 with grout material G. Furthermore, in the second embodiment, similar to the first embodiment, in order to fill the space between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base portion 2B with grout material G, a through-hole for filling with grout material G may be provided in the center of the seismic isolation foundation 3, penetrating the seismic isolation foundation 3 vertically, and the grout material G may be filled from above the seismic isolation foundation 3 through this through-hole. Alternatively, a hose may be inserted between the lower surface 3b of the concrete 3c of the seismic isolation foundation 3 and the upper surface 2t of the base portion 2B to near the center of the seismic isolation foundation 3, and the grout material G may be injected through the hose.

[0045] In addition to the above, it is possible to select or replace the configurations listed in the above embodiments, or to change them to other configurations as appropriate, as long as it does not deviate from the spirit of the present invention. [Explanation of Symbols]

[0046] 1A, 1B Seismic isolation foundation structure 72 connecting reinforcing bars 2A, 2B Base part 72e One end 2t Top surface 72f Other end 3. Seismic isolation foundation section 72s Male screw section 3b Bottom surface 73 Mounting bolts 4 Seismic isolation device 74 Reinforcement bar joint 41 Lower flange 75 Anchor reinforcement 41h Through hole 79 Connection hole 71 Joining member G Grout material 71s Female thread section

Claims

1. A seismic isolation foundation structure on which seismic isolation devices are installed, The base is made of reinforced concrete, A precast concrete seismic isolation foundation is provided above the aforementioned base section, The seismic isolation device installed above the seismic isolation foundation, Equipped with, A connecting member having a female screw portion is embedded in the seismic isolation foundation. A connecting reinforcing bar having a male threaded portion is screwed into the female threaded portion from below, and the mounting bolt of the seismic isolation device is screwed into it from above. The other end of the connecting reinforcing bar is embedded in the base portion. A seismic isolation foundation structure characterized by the following features.

2. The other end of the connecting reinforcing bar is joined from above to a reinforcing bar joint embedded in the base, and the anchor reinforcing bar is joined from below to the reinforcing bar joint. The seismic isolation foundation structure according to feature 1.

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