Seismic isolation foundation structure and construction method of seismic isolation foundation structure

Abstract

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

Description

[Technical Field]

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

[0002] 2. Description of the Related Art When constructing a building structure, it is common to provide a seismic isolation device in the foundation 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 installed along the ground. In this configuration, the foundation base is formed together with the foundation slab from cast-in-place concrete. The seismic isolation device is fixed to this foundation base with multiple anchor bolts. In such a configuration, the area where the seismic isolation device is installed needs to be provided with a large number of rebars, anchor bars, etc. at a high density in order to adequately support the load acting from above through the seismic isolation device and to resist the pull-out force acting on the seismic isolation device during an earthquake. Therefore, if the lower foundation on which the seismic isolation device is installed is formed by pouring concrete in place, as in the configuration of Patent Document 1, it will take a long time to construct the lower foundation on site, which could prolong the construction period.

[0003] In contrast, the part where the seismic isolation device is installed (hereinafter referred to as the seismic isolation foundation) 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 cap nut for fixing a seismic isolation device is placed on a foundation slab, the seismic isolation device is placed on the precast concrete plate, and anchor bolts are fastened to the cap nut to fix the seismic isolation device on the precast concrete plate. Furthermore, Patent Document 3 describes a configuration in which a lower base plate with a female thread is provided on the upper surface of a precast concrete lower seismic isolation foundation, and a seismic isolation device is fixed to the lower base plate. In this configuration, an anchor bolt that is fixed to the lower seismic isolation foundation is screwed into the lower end of the female thread. The lower flange of the seismic isolation device is fixed to the lower base plate of the lower seismic isolation foundation by inserting a bolt into a bolt insertion hole in the lower flange of the seismic isolation device and screwing it into the female thread. As in Patent Documents 2 and 3, the seismic isolation foundation (precast concrete panel in Patent Document 2, lower seismic isolation foundation in Patent Document 3) is made of precast concrete, thereby shortening the construction period.

[0004] In the configuration of Patent Document 2, the seismic isolation device is fixed to the precast concrete panel by fastening anchor bolts to a cap nut embedded in the precast concrete panel, sandwiching the lower flange of the seismic isolation device between the cap nut and the precast concrete panel. The cap nut is completely embedded inside the precast concrete panel. Therefore, when a pull-out force acts on the seismic isolation device, the pull-out force is resisted between the seismic isolation device and the precast concrete panel by the anchoring force of the cap nut with the concrete that makes up the precast concrete panel. 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 thread embedded in the lower seismic isolation foundation, sandwiching the lower flange of the seismic isolation device between the female thread and the lower end of the female thread. The female thread and the anchor bolt screwed into the lower end of the female thread are completely embedded inside the lower seismic isolation foundation. Therefore, when a pull-out force acts on the seismic isolation device, the pull-out force is resisted between the seismic isolation device and the lower seismic isolation foundation by the anchoring force of the anchor bolt and the concrete that makes up the lower seismic isolation foundation.

[0005] As described above, in Patent Documents 2 and 3, the cap nuts, female threads, and anchor bolts are all configured to be completely embedded in the precast concrete panel and lower seismic isolation foundation, which serve as the seismic isolation foundation. Therefore, even if attempts are made to increase the embedded length of these cap nuts and anchor bolts in order to more efficiently resist pull-out forces, they cannot be made longer than the height of the seismic isolation foundation. Therefore, in Patent Documents 2 and 3, there is a limit to how efficiently one can resist pull-out forces between the seismic isolation device and the seismic isolation foundation. When the base isolation structure for installing the seismic isolation device is made of precast concrete, it is desirable to efficiently prevent the device from lifting up during an earthquake. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-106236 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-32759 [Patent Document 3] Japanese Patent Application Publication No. 2020-51111 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that the present invention aims to solve is to provide a seismic isolation foundation structure and a method for constructing a seismic isolation foundation structure that can efficiently suppress the uplift of seismic isolation devices in the event of an earthquake when the seismic isolation foundation part for installing the seismic isolation devices is made of precast concrete. [Means for solving the problem]

[0008] In a seismic isolation foundation structure, between the PCa seismic isolation foundation on which the seismic isolation device is installed and the concrete base, connecting rebars with male threads are screwed into connecting members with female threads embedded in the seismic isolation foundation, while the rebar bodies of the connecting rebars are joined to rebar joints embedded in the base. This eliminates the need to pour concrete at the construction site to build the seismic isolation foundation, shortening the work period and enabling the seismic isolation foundation structure to be constructed efficiently, which is what led to the present invention. In order 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, and comprises a base portion made of reinforced concrete, a seismic isolation foundation portion made of precast concrete provided above the base portion, and the seismic isolation device installed above the seismic isolation foundation portion, wherein a joining member having a female thread portion formed on the inside and a connecting reinforcing bar having a male thread portion formed at one end are embedded in the seismic isolation foundation portion, a mounting bolt provided to pass through a through hole formed in the lower flange of the seismic isolation device from above is screwed into the female thread portion from above, the male thread portion of the connecting reinforcing bar is screwed into the female thread portion from below, the other end of the connecting reinforcing bar protrudes downward from the underside of the seismic isolation foundation portion, a reinforcing bar joint portion and an anchor bar are embedded in the base portion, the other end of the connecting reinforcing bar is joined to the reinforcing bar joint portion from above, and the upper end of the anchor bar is joined to the reinforcing bar joint portion from below. According to the above-described configuration, a precast concrete seismic isolation foundation is provided above a reinforced concrete foundation. A connecting member having a female thread formed on the inside and a connecting rebar having a male thread formed at one end are embedded in the seismic isolation foundation. A mounting bolt is inserted from above through a through-hole formed in the lower flange of the seismic isolation device. The female thread is threaded from above, and the male thread of the connecting rebar is threaded from below into the female thread. The other end of the connecting rebar protrudes downward from the underside of the seismic isolation foundation and is joined from above to a rebar joint embedded in the foundation. An anchor, also embedded in the foundation, is joined to the rebar joint from below. In this way, the connecting member, the connecting rebar, the rebar joint, and the anchor are joined to the seismic isolation device in this order via the mounting bolt. These connecting members, connecting rebars, rebar joints, and anchor bars as a whole span the seismic isolation base section and the base section, and are fixed to the concrete that makes up these sections. In this configuration, if an earthquake occurs and the building tilts, causing a pull-out force to act on the seismic isolation device, the pull-out force is resisted by the anchoring force of the joint members, connecting rebars, rebar joints, and anchors to the concrete constituting the base and seismic isolation base. Here, as described above, the joint members, connecting rebars, rebar joints, and anchors are all arranged to extend not only into the base but also into the base. Therefore, the overall embedded length of the pull-out force-resistant members can be made longer than if the pull-out force-resistant members were embedded only within the precast concrete base. Therefore, the pull-out force can be resisted more efficiently than if the pull-out force-resistant members were embedded only within the precast concrete base. In this way, if the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, it is possible to efficiently prevent the seismic isolation device from floating up in the event of an earthquake.

[0009] In addition, the seismic isolation foundation structure of the present invention is a seismic isolation foundation structure on which a seismic isolation device is installed, and comprises a base portion made of reinforced concrete, a seismic isolation foundation portion made of precast concrete provided above the base portion, and the seismic isolation device installed above the seismic isolation foundation portion, wherein a joining member having a female thread portion formed on the inside and a connecting reinforcing bar having a male thread portion formed at one end are embedded in the seismic isolation foundation portion, a mounting bolt provided to pass from above through a through hole formed in the lower flange of the seismic isolation device is screwed into the female thread portion from above, the male thread portion of the connecting reinforcing bar is screwed into the female thread portion from below, the other end of the connecting reinforcing bar protrudes downward from the underside of the seismic isolation foundation portion, a connection hole is formed on the upper surface of the base portion, the other end of the connecting reinforcing bar is inserted into the connection hole, and grout material is filled between the inner wall of the connection hole and the connecting reinforcing bar. According to the above-described configuration, a precast concrete seismic isolation foundation is provided above a reinforced concrete base. A connecting member having a female thread formed on the inside and a connecting rebar having a male thread formed at one end are embedded in the seismic isolation foundation. A mounting bolt is inserted from above through a through-hole formed in the lower flange of the seismic isolation device and is threaded into the female thread from above, and the male thread of the connecting rebar is threaded into the female thread from below. The other end of the connecting rebar protrudes downward from the underside of the seismic isolation foundation and is inserted into a connecting hole formed in the upper surface of the base. Grout is filled between the inner wall of the connecting hole and the connecting rebar. In this way, the connecting member and the connecting rebar are sequentially connected to the seismic isolation device via the mounting bolt. The connecting member and the connecting rebar are collectively fixed to the concrete that constitutes the seismic isolation foundation and the base. In this configuration, if an earthquake occurs and the building tilts, causing a pull-out force to act on the seismic isolation device, the pull-out force is resisted by the anchoring force of the joint members and the connecting rebars as a whole to the concrete that makes up the base and seismic isolation foundation. Here, as described above, the joint members and the connecting rebars as a whole are arranged to extend not only into the base but also into the base, so the overall embedded length can be longer than if the pull-out force-resistant members were embedded only inside the precast concrete seismic isolation foundation. Therefore, the pull-out force can be resisted more efficiently than if the pull-out force-resistant members were embedded only inside the precast concrete seismic isolation foundation. In this way, if the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, it is possible to efficiently prevent the seismic isolation device from floating up in the event of an earthquake. Furthermore, with this configuration, there is no need to pour concrete at the construction site to construct the seismic isolation foundation, which shortens the work period and enables the seismic isolation foundation structure to be constructed efficiently.

[0010] Furthermore, the seismic isolation foundation structure and the method for constructing a seismic isolation foundation structure of the present invention are a method for constructing a seismic isolation foundation structure on which a seismic isolation device is to be installed, and include the steps of: constructing a base portion made of reinforced concrete in which anchor bars and reinforcing bar joints to which the anchor bars are joined from below are embedded; lowering a precast concrete seismic isolation foundation portion, in which a joining member having a female thread portion formed on the inside and a connecting reinforcing bar having a male thread portion formed on one end and threadedly engaged with the female thread portion from below, from above the base portion; inserting and joining the other end of the connecting reinforcing bar that protrudes downward from the underside of the seismic isolation foundation into the reinforcing bar joint portion of the base portion from above and installing the seismic isolation foundation portion on the base portion; and installing the seismic isolation device above the seismic isolation foundation portion, and inserting a mounting bolt from above through a through hole formed in a lower flange of the seismic isolation device and screwing it into the female thread portion of the joining member, thereby fixing the seismic isolation device to the seismic isolation foundation portion. According to this configuration, a concrete base section is constructed in which anchor bars and rebar joints are embedded, a precast concrete seismic isolation foundation in which connecting members with female threads and connecting rebars are embedded is lowered from above the base section, the other ends of the connecting rebars are joined to the rebar joints, the seismic isolation foundation is installed on the base section, a seismic isolation device is installed above the seismic isolation foundation, and a mounting bolt is inserted from above through a through-hole formed in the lower flange of the seismic isolation device and threaded into the female thread of the connecting member to secure the seismic isolation device to the seismic isolation foundation. In this way, when the seismic isolation foundation for installing the seismic isolation device is made of precast concrete, a seismic isolation foundation structure can be constructed that can efficiently prevent the seismic isolation device from lifting up during an earthquake. [Effects of the Invention]

[0011] According to the present invention, when the seismic isolation base for installing the seismic isolation device is made of precast concrete, it is possible to efficiently prevent the seismic isolation device from floating up in the event of an earthquake. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a seismic isolation foundation structure according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the seismic isolation base part of the seismic isolation foundation structure of FIG. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a main part of the seismic isolation foundation structure of FIG. 1. [Figure 4] 2 is an enlarged cross-sectional view showing the joint members, connecting reinforcing bars, mounting bolts, reinforcing bar joints, and anchor bars provided in the seismic isolation foundation structure of FIG. 1. FIG. [Figure 5] 3 is a cross-sectional view showing the state after the base part has been constructed in the method for constructing a seismic isolation foundation structure according to the first embodiment. FIG. [Figure 6] 3 is a cross-sectional view showing the state in which a seismic isolation foundation part is installed on a base part in the method for constructing a seismic isolation foundation structure according to the first embodiment. FIG. [Figure 7] 3 is a cross-sectional view showing the state in which a seismic isolation device is installed on a seismic isolation foundation part in the method for constructing a seismic isolated foundation structure according to the first embodiment. FIG. [Figure 8] 2 is a cross-sectional view showing the state in which an upper seismic isolation foundation part is installed on a seismic isolation device in the method for constructing a seismic isolated foundation structure according to the first embodiment. FIG. [Figure 9] FIG. 3 is a cross-sectional view showing a base isolation foundation structure according to a modified example of the first embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a seismic isolation foundation structure according to another modified example of the first embodiment of the present invention. [Figure 11] FIG. 4 is a cross-sectional view showing a seismic isolation foundation structure according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is a seismic isolation foundation structure on which a seismic isolation device is installed, and is composed of a reinforced concrete base portion, a precast concrete PCa seismic isolation foundation portion installed on the base portion, and a seismic isolation device installed on the seismic isolation foundation portion. Its unique feature is that a connecting member with a female thread is embedded in the PCa seismic isolation foundation, and a connecting rebar with a male thread is joined to the female thread from below. In addition, reinforcing bar joints and anchor bars are embedded in the base, and connecting reinforcing bars protruding from the underside of the seismic isolation foundation are joined to the upper side of the reinforcing bar joints, and anchor bars are joined to the lower side of the reinforcing bar joints. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given of an embodiment of a seismic isolation foundation structure and a method for constructing a seismic isolation foundation structure according to the present invention with reference to the accompanying drawings. (First embodiment) Fig. 1 shows a cross-sectional view of a seismic isolation foundation structure according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view showing a seismic isolation base 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 portion 2A, a seismic isolation base portion 3, a seismic isolation device 4, and an upper seismic isolation base portion 5. The base 2A is made of reinforced concrete. The base 2A includes concrete 2c formed by hardening cast-in-place concrete and reinforcing bars (not shown) embedded in the concrete 2c. The base 2A is supported on foundation piles (not shown) built into the ground.

[0014] The seismic isolation base 3 is provided above the basement 2A. The seismic isolation base 3 is made of precast concrete and has, for example, a rectangular or circular shape when viewed from the top to bottom, and has a predetermined height in the vertical direction. As shown in FIG. 2, the seismic isolation base 3 includes concrete 3c formed into a predetermined shape and reinforcing bars 3s embedded in the concrete 3c. Some of the reinforcing bars 3s protrude downward from the bottom surface 3b of the concrete 3c as connecting reinforcing bars 3j to ensure integration with the basement 2A. The seismic isolation foundation 3 further includes connecting members 71 and connecting rebars 72, which will be described later. The upper portion of the connecting rebars 72 is embedded in the concrete 3c, and the lower portion, like the connecting rebars 3j, protrudes downward from the bottom surface 3b of the concrete 3c. In this way, the seismic isolation foundation 3 is configured such that the connecting rebars 3j and connecting rebars 72 protrude from the bottom 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 turned upside down and placed so that the top surface 3t is positioned downward and abuts against the floor or the like.

[0015] A cylindrical anchoring sleeve joint 77 is embedded in the concrete 2c of the base portion 2A so that its upper end is located slightly below the upper surface 2t of the base portion 2A but is not buried in the concrete 2c (see Figure 4). A connecting rebar 3j is inserted into this anchoring sleeve joint 77 from above. A grout material G such as mortar is filled between the connecting rebar 3j and the inner wall of the anchoring sleeve joint 77. In this way, the rebar 3s of the seismic isolation foundation 3 is joined to the anchoring sleeve joint 77, thereby joining the seismic isolation foundation 3 to the base portion 2A.

[0016] As shown in FIG. 1, the upper seismic isolation base 5 is provided above the seismic isolation device 4. The upper seismic isolation base 5 is made of precast concrete and has, for example, a rectangular or circular shape when viewed from the top and bottom, and has a predetermined height in the vertical direction. The upper seismic isolation base 5 includes concrete 5c formed into a predetermined shape and reinforcing bars 5s embedded in the concrete 5c. Some of the reinforcing bars 5s protrude upward from the top surface of the concrete 5c as connecting reinforcing bars 5j to ensure integration with the upper structure 6, which will be described later. The connecting reinforcing bars 5j are embedded in the concrete 6c of the upper structure 6. The upper seismic isolation base portion 5 further includes an upper connecting member 81 and upper anchor bolts 82, which will be described later.

[0017] An upper structure 6 is provided above the upper seismic isolation foundation 5. The upper structure 6 is the main body of the building equipped with the seismic isolation foundation structure 1A. The upper structure 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 a column 63 that constitutes the upper structure 6. The upper footing 62 has, for example, a rectangular or circular shape when viewed from the top-bottom direction, and is formed so as to protrude downward from the slab 61. The upper footing 62 includes concrete 6c formed by hardening cast-in-place concrete, and reinforcing bars (not shown) embedded in the concrete 6c.

[0018] The seismic isolation device 4 is installed above the seismic isolation base part 3. The seismic isolation device 4 is provided between the upper seismic isolation base part 5 and the seismic isolation base part 3. Multiple seismic isolation devices 4 are provided at intervals in the horizontal direction. As shown in Fig. 3, the seismic isolation device 4 has a plate-shaped lower flange 41, a plate-shaped upper flange 42 arranged 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 stacking metal plates 43m and plate-shaped rubber portions 43r in the vertical direction. The lower flange 41 and the upper flange 42 of the seismic isolation device 4 each have a plurality of through holes 41h, 42h formed at intervals in the circumferential direction on the radial outside of the laminated rubber portion 43. Each of the plurality of through holes 41h, 42h penetrates the lower flange 41 and the upper flange 42 in the vertical direction.

[0019] FIG. 4 is an enlarged cross-sectional view showing the joint members, connecting reinforcing bars, mounting bolts, reinforcing bar joints, and anchor bars provided in the seismic isolation foundation structure of FIG. 3 and 4, the lower flange 41 of the seismic isolation device 4, the seismic isolation base 3, and the base plate 2A are connected to one another via connecting members 71, connecting reinforcing bars 72, mounting bolts 73, reinforcing bar joints 74, and anchors 75. The connecting members 71, connecting reinforcing bars 72, mounting bolts 73, reinforcing bar joints 74, and anchors 75 are provided at positions that overlap with the multiple through holes 41h, respectively, when viewed from the top-bottom direction.

[0020] The connecting member 71 is buried in the upper part of the concrete 3c of the seismic isolation foundation 3. The connecting member 71 is, for example, a high nut, and is tubular extending in the vertical direction with a female thread portion 71s formed on the inside. The connecting member 71 is buried in the concrete 3c that forms the seismic isolation foundation 3 so that its upper end is exposed on the upper surface 3t of the seismic isolation foundation 3, and is fixed to the concrete 3c. The connecting rebar 72 extends vertically. One end (upper end) 72e of the connecting rebar 72 is formed with a male thread portion 72s. The connecting rebar 72 is formed by axially joining and integrating a shank-shaped fully threaded bolt 72a, which forms the male thread portion 72s, and a rebar 72b. The fully threaded bolt 72a and the rebar 72b may be joined by welding, but joining by friction welding is preferred because it achieves higher joint strength. From the perspective of strength, the connecting rebar 72 is preferably a steel material in which a JIS-standard screw is used for the male thread portion 72s and a JIS-standard rebar is used for the rebar 72b, and the two are joined by friction welding. The male thread portion 72s of such connecting rebar 72 is screwed into the female thread portion 71s of the joining member 71 from below. The other end (lower end) 72f of the connecting rebar 72 protrudes downward from the lower surface 3b of the seismic isolation base 3. The portion of the connecting reinforcing bar 72 that is embedded in the concrete 3c is fixed to the concrete 3c. The mounting bolt 73 is provided so as 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 a female thread portion 71s of a connecting member 71 embedded in the seismic isolation base 3.

[0021] The reinforcing bar joint portion 74 and the anchor bar 75 are embedded in the concrete 2c of the base portion 2A and fixed to the concrete 2c. The reinforcing bar joint 74 is a cylindrical joint extending in the vertical direction, known as a reinforcing bar sleeve joint. The reinforcing bar joint 74 is embedded in the concrete 2c forming the base portion 2A so that its upper end is positioned slightly below the upper surface 2t of the base portion 2A but is not buried in the concrete 2c (see FIG. 4). The other end 72f of the connecting reinforcing bar 72 protruding downward from the lower surface 3b of the seismic isolation base 3 is inserted into the reinforcing bar joint 74 from above. The anchor bars 75 extend vertically within the base portion 2A. The upper ends of the anchor bars 75 are inserted from below into the reinforcing bar joint portions 74. The lower ends of the anchor bars 75 are provided with mechanical fixing devices 76 or the like that expand in diameter from the outer peripheral surface of the anchor bars 75 radially outward. A grout material G such as mortar is filled between the other end 72f of the connecting rebar 72, the upper end of the anchor rebar 75, and the inner wall of the rebar joint part 74. In this way, the connecting rebar 72 is joined to the anchor rebar 75 via the rebar joint part 74.

[0022] 3, the upper flange 42 of the seismic isolation device 4, the upper seismic isolation base portion 5, and the upper footing 62 of the upper structure portion 6 are connected to one another via upper connecting members 81, upper anchor bolts 82, and upper mounting bolts 83. The upper connecting members 81, upper anchor bolts 82, and upper mounting bolts 83 are each provided at a position overlapping with each of the multiple through holes 42h when viewed from the top-bottom direction.

[0023] The upper connecting member 81 is buried under the upper seismic isolation foundation 5. The upper connecting member 81 is, for example, a high nut, and is cylindrical and extends in the vertical direction, with a female thread portion 81s formed on the inside. The upper connecting member 81 is buried in the concrete 5c that forms the upper seismic isolation foundation 5 so that its lower end is exposed on the underside of the upper seismic isolation foundation 5, and is fixed to the concrete 5c. 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 thread 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 base portion 5 and is embedded in the upper footing 62. The upper anchor bolt 82 is fixed to the concrete 5c of the upper seismic isolation base portion 5 and the concrete 6c of the upper footing 62. A mechanical fastener 86 or the like is provided at the upper end of the upper anchor bolt 82, the diameter of which expands radially outward from the outer circumferential surface of the upper anchor bolt 82. The upper mounting bolt 83 is provided so as to be inserted from below into 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 a female thread portion 81s of an upper joining member 81 embedded in the upper seismic isolation base portion 5.

[0024] In such a seismic isolation foundation structure 1A, a connecting member 71, a connecting rebar 72, a rebar joint 74, and an anchor 75 are joined in this order to the seismic isolation device 4 via mounting bolts 73. These connecting member 71, connecting rebar 72, rebar joint 74, and anchor 75 as a whole straddle the seismic isolation base 3 and base 2A, which are joined to each other by connecting rebar 3j, and are fixed to the concrete 3c, 2c that constitute these. Similarly, an upper connecting member 81 and an upper anchor bolt 82 are joined in this order to the seismic isolation device 4 via an upper mounting bolt 83. These upper connecting member 81 and upper anchor bolt 82 as a whole straddle the upper seismic isolation base 5 and the upper footing 62, which are joined to each other by connecting reinforcing bars 5j, and are fixed to the concrete 5c, 6c that make up these.

[0025] Next, a method for constructing the seismic isolation foundation structure 1A as described above will be described. FIG. 5 is a cross-sectional view showing a state in which a base portion has been constructed in the method for constructing a seismic isolated foundation structure according to the first embodiment. To construct the seismic isolation foundation structure 1A, first, the base portion 2A is constructed as shown in Fig. 5. To do this, reinforcing bars (not shown) and anchor bars 75 of the base portion 2A are arranged, and the upper ends of the anchor bars 75 are joined to the reinforcing bar joints 74 from below. After that, a formwork (not shown) is assembled, and concrete 2c is poured into the formwork. Once the concrete 2c hardens and develops a predetermined strength, the base portion 2A made of reinforced concrete is constructed, with the anchor bars 75 and reinforcing bar joints 74 embedded in it.

[0026] Next, the seismic isolation foundation 3 is installed on the base 2A. For this purpose, the seismic isolation foundation 3 is fabricated in advance from a factory or the like using precast concrete. The seismic isolation foundation 3 is composed of reinforcing bars 3s, connecting reinforcing bars 72, and a joint member 71, which is formed by threading the male thread portion 72s of one end 72e of the connecting reinforcing bar 72 into the female thread portion 71s from below, and these are embedded in concrete 3c. Because 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 position the bottom surface 3b facing upward when transporting the seismic isolation foundation 3. The seismic isolation foundation 3 is then turned upside down from the state it was in when transported and positioned above the base 2A with the bottom surface 3b facing downward. Additionally, the reinforcing bar joint portion 74 and the anchoring sleeve joint 77 are filled with grout material G.

[0027] FIG. 6 is a cross-sectional view showing a state in which a seismic isolation foundation part is installed on a base part in the method for constructing a seismic isolation foundation structure according to the first embodiment. Then, the seismic isolation base 3 is lowered from above the base 2A, and the other ends 72f of the connecting rebars 72 protruding downward from the underside 3b and the connecting rebars 3j are inserted from above into the rebar joint parts 74 and anchoring sleeve joints 77 of the base 2A, as shown in Figure 6. More specifically, the other ends 72f of the connecting rebars 72 and the connecting rebars 3j are buried inside the grout material G filled in the rebar joint parts 74 and anchoring sleeve joints 77. The seismic isolation base 3 is lowered to a height that leaves a gap of, for example, 25 to 35 mm between the underside 3b of the concrete 3c of the seismic isolation base 3 and the upper surface 2t of the basement 2A. Then, grout G, such as mortar, is filled between the underside 3b of the concrete 3c of the seismic isolation base 3 and the upper surface 2t of the basement 2A, joining the underside 3b of the seismic isolation base 3 and the upper surface 2t of the basement 2A. When filling the gap between the underside 3b of the seismic isolation base 3 and the upper surface 2t of the basement 2A with grout G, it is desirable to provide a through-hole 3h (shown only in Figure 6 ) in the center of the seismic isolation base 3 that penetrates the basement 3 in the vertical direction, and fill the grout G from above the basement 3 through this through-hole 3h. This allows the grout G to be injected and filled evenly from the center of the basement 3 to near the periphery. In this way, the seismic isolation base part 3 is installed on the base part 2A and joined.

[0028] FIG. 7 is a cross-sectional view showing a state in which a seismic isolation device is installed on a seismic isolation foundation portion in the method for constructing a seismic isolated 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. To do this, the seismic isolation device 4 is installed above the seismic isolation foundation 3, and then lowered and placed on the upper surface 3t of the seismic isolation foundation 3. Then, the mounting bolt 73 is inserted from above into the through hole 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female thread portion 71s of the connecting member 71.

[0029] FIG. 8 is a cross-sectional view showing a state in which an upper seismic isolation foundation part is installed on a seismic isolation device in the method for constructing a seismic isolated foundation structure according to the first embodiment. Then, as shown in FIG. 8 , a precast concrete upper seismic isolation foundation 5 is installed on the seismic isolation foundation 3. Like the seismic isolation foundation 3, the upper seismic isolation foundation 5 is fabricated in advance in a factory or the like. The upper seismic isolation foundation 5 is composed of reinforcing bars 5s, upper anchor bolts 82 (the lower portions thereof), and upper connecting members 81, each of which has the upper anchor bolt 82 screwed into a female thread 81s from above, embedded in 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, an upper mounting bolt 83 is inserted from below through a through hole 42h formed in the upper flange 42 of the seismic isolation device 4 and screwed into the female thread 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. After that, the upper structure portion 6 is constructed in sequence on the upper seismic isolation foundation portion 5.

[0030] The seismic isolation foundation structure 1A as described above is a seismic isolation structure 1A on which a seismic isolation device 4 is installed, and comprises a base portion 2A made of reinforced concrete, a seismic isolation foundation portion 3 made of precast concrete provided above the base portion 2A, and the seismic isolation device 4 installed above the seismic isolation foundation portion 3, and a connecting member 71 having a female screw portion 71s formed on the inside and a connecting reinforcing bar 72 having a male screw portion 72s formed at one end 72e are embedded in the seismic isolation foundation portion 3, and a through hole formed in the lower flange 41 of the seismic isolation device 4 is provided. An attachment bolt 73, which is arranged to pass through hole 41h from above, is screwed into the female threaded portion 71s from above, the male threaded portion 72s of the connecting rebar 72 is screwed into the female threaded portion 71s from below, the other end 72f of the connecting rebar 72 protrudes downward from the underside 3b of the seismic isolation foundation portion 3, a rebar joint portion 74 and an anchor bar 75 are embedded in the base portion 2A, the other end 72f of the connecting rebar 72 is joined to the rebar joint portion 74 from above, and the upper end of the anchor bar 75 is joined to the rebar joint portion 74 from below. According to the above-described configuration, a precast concrete base isolation foundation 3 is provided above a reinforced concrete base 2A. A connecting member 71 having a female thread 71s formed on the inside and a connecting rebar 72 having a male thread 72s formed on one end 72e are embedded in the base isolation foundation 3. A mounting bolt 73 is inserted from above through a through hole 41h formed in the lower flange 41 of the base isolation device 4 and threadedly engages the female thread 71s from above. The male thread 72s of the connecting rebar 72 is threadedly engaged with the female thread 71s from below. The other end 72f of the connecting rebar 72 protrudes downward from the lower surface 3b of the base isolation foundation 3 and is joined from above to a rebar joint 74 embedded in the base 2A. An anchor 75, similarly embedded in the base 2A, is joined to the rebar joint 74 from below. In this way, the connecting members 71, connecting rebars 72, rebar joints 74, and anchors 75 are joined in this order to the seismic isolation device 4 via mounting bolts 73. These connecting members 71, connecting rebars 72, rebar joints 74, and anchors 75 as a whole straddle the seismic isolation base 3 and base 2A, and are fixed to the concrete 3c, 2c that constitute these. In this configuration, if an earthquake occurs and the building tilts, causing a pull-out force to act on the seismic isolation device 4, the pull-out force is resisted by the anchoring force of the joint members 71, connecting rebars 72, rebar joints 74, and anchor bars 75, which together anchor the concrete 3c, 2c that make up the base 2A and the seismic isolation foundation 3. Because the joint members 71, connecting rebars 72, rebar joints 74, and anchor bars 75 are all configured to extend not only into the seismic isolation foundation 3 but also into the base 2A, as described above, the overall embedded length H1 (see FIG. 1 ) can be made longer than the upper limit of the embedded length when the pull-out force-resistant members are embedded solely within the precast concrete seismic isolation foundation 3, i.e., the height H2 of the seismic isolation foundation 3. Therefore, the pull-out force can be resisted more efficiently than when the pull-out force-resistant members are embedded solely within the precast concrete seismic isolation foundation 3. In this way, if the seismic isolation base 3 for installing the seismic isolation device 4 is made of precast concrete, it is possible to efficiently prevent the seismic isolation device 4 from floating up in the event of an earthquake.

[0031] In particular, in the above-described configuration, the seismic isolation foundation portion 3 is made of precast concrete, so there is no need to pour concrete at the construction site to construct the seismic isolation foundation portion 3, which shortens the work period and enables the seismic isolation foundation structure 1A to be constructed efficiently.

[0032] In addition, the seismic isolation base portion 3 further includes a connecting rebar 3j that protrudes downward from the lower surface 3b, and the seismic isolation base portion 3 and the base portion 2A are joined to each other by the connecting rebar 3j. According to the above-described configuration, the seismic isolation base portion 3 and the base portion 2A are joined to each other by the connecting rebar 3j, which makes it possible to efficiently prevent the seismic isolation device 4 from floating up when an earthquake occurs.

[0033] The method for constructing the seismic isolation foundation structure 1A as described above is a method for constructing the seismic isolation foundation structure 1A on which the seismic isolation device 4 is installed, and includes the steps of constructing a base portion 2A made of reinforced concrete in which anchor bars 75 and reinforcing bar joint portions 74 to which the anchor bars 75 are joined from below are buried, and constructing a precast concrete seismic isolation foundation in which a joining member 71 having a female screw portion 71s formed on the inside and a connecting reinforcing bar 72 provided such that a male screw portion 72s formed on one end 72e is screwed into the female screw portion 71s from below are buried. The method includes the steps of: lowering the base 3 from above the base portion 2A, inserting the other end 72f of the connecting rebar 72 protruding downward from the underside 3b of the base 3 into the rebar joint portion 74 of the base portion 2A from above and joining them, thereby installing the base 3 on the base portion 2A; and providing a seismic isolation device 4 above the base 3, inserting a mounting bolt 73 from above through a through hole 41h formed in the lower flange 41 of the seismic isolation device 4 and screwing it into the female thread portion 71s of the joint member 71, thereby fixing the seismic isolation device 4 to the base 3. According to this configuration, a concrete base 2A is constructed in which anchor bars 75 and reinforcing bar joints 74 are embedded, a precast concrete base isolation foundation 3 in which connecting members 71 with female threads 71s and connecting reinforcing bars 72 are embedded is lowered from above the base 2A, the other ends 72f of the connecting reinforcing bars 72 are joined to the reinforcing bar joints 74, the base isolation foundation 3 is installed on the base 2A, a base isolation device 4 is installed above the base 3, and a mounting bolt 73 is inserted from above through a through hole 41h formed in the lower flange 41 of the base isolation device 4 and screwed into the female threads 71s of the connecting members 71. In this way, when the base isolation foundation 3 for installing the base isolation device 4 is made of precast concrete, a base isolation foundation structure 1A can be constructed that can efficiently prevent the base isolation device 4 from lifting up during an earthquake.

[0034] (Modification of the first embodiment) In the first embodiment, after the base portion 2A is constructed, the seismic isolation base portion 3, the seismic isolation device 4, and the upper seismic isolation base portion 5 are sequentially installed on the base portion 2A, but this is not limited to this. FIG. 9 is a cross-sectional view showing a base-isolated foundation structure according to a modified example of the first embodiment of the present invention. For example, as shown in Figure 9, a precast concrete seismic isolation base 3, a seismic isolation device 4, and a precast concrete upper seismic isolation base 5 may be joined together in advance as an integrated unit. After constructing the base 2A, the entire assembly of the seismic isolation base 3, seismic isolation device 4, and upper seismic isolation base 5, which have been previously assembled as an integrated unit, may be lowered from above the base 2A, and the other end 72f of the connecting rebar 72 protruding downward from the underside 3b of the seismic isolation base 3 may be inserted from above into the rebar joint 74 of the base 2A and joined. This allows for more efficient construction of the seismic isolation foundation structure 1A.

[0035] (Another modification of the first embodiment) Furthermore, in the above first embodiment, the lower flange 41 of the seismic isolation device 4 is placed directly on the upper surface 3t of the concrete 3c that constitutes the seismic isolation foundation 3, and the concrete 5c that constitutes the upper seismic isolation foundation 5 is placed directly on the upper flange 42, but this is not limited to this. FIG. 10 is a cross-sectional view showing a seismic isolation foundation structure according to another modified example of the first embodiment of the present invention. 10, the seismic isolation base 3 may be configured to include a lower base plate 35 on the upper surface 3t of the concrete 3c, and a lower flange 41 of the seismic isolation device 4 may be provided on the lower base plate 35. Alternatively, the upper seismic isolation base 5 may be configured to include an upper base plate 55 on the lower surface of the concrete 5c, and the upper base plate 55 may be 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 plates. A plurality of anchor studs 37 are joined to the lower base plate 35 so as to protrude downward from the lower surface of the lower base plate 35. The plurality of anchor studs 37 are embedded in the concrete 3c of the seismic isolation base 3. A plurality of anchor studs 57 are joined to the upper base plate 55 so as to protrude upward from the upper surface of the upper base plate 55. The plurality of anchor studs 57 are embedded in the concrete 5c of the upper seismic isolation foundation 5.

[0036] (Another modification of the first embodiment) Furthermore, in the above embodiment, before the seismic isolation foundation 3 is lowered from above the base portion 2A, the reinforcing bar joint portion 74 and the fixing sleeve joint 77 are filled with grout material G, and then the other end 72f of the connecting reinforcing bar 72 and the connecting reinforcing bar 3j are lowered from above the base portion 2A so as to bury them from above into the grout material G filled in the reinforcing bar joint portion 74 and the fixing sleeve joint 77 of the base portion 2A, and the grout material G is filled in the gap between the underside 3b of the concrete 3c of the seismic isolation foundation 3 and the upper side 2t of the base portion 2A, but this is not limited to this. For example, the seismic isolation base 3 may be lowered from above the base 2A without filling the reinforcing bar joints 74 and the anchoring sleeve joints 77 with grout G. In this case, when filling the space between the lower surface 3b of the concrete 3c of the seismic isolation base 3 and the upper surface 2t of the base 2A with grout G, the grout G flows into the reinforcing bar joints 74 and the anchoring sleeve joints 77, so that the grout G is filled into the reinforcing bar joints 74 and the anchoring sleeve joints 77. In addition, to fill the grout material G between the underside 3b of the concrete 3c of the seismic isolation foundation 3 and the upper side 2t of the base portion 2A, a hose may be inserted close to the center of the seismic isolation foundation 3 when viewed in a plane, and the grout material G may be injected from the hose.

[0037] (Second embodiment) Next, a second embodiment of the seismic isolation foundation structure and the method for constructing a seismic isolation foundation structure according to the present invention will be described. The second embodiment of the seismic isolation foundation structure and the method for constructing a seismic isolation foundation structure described below differs from the seismic isolation foundation structure and the method for constructing a seismic isolation foundation structure described in the first embodiment 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 will be assigned the same reference numerals and their description will be omitted. FIG. 11 is a cross-sectional view showing a seismic isolation foundation structure according to a second embodiment of the present invention. As shown in FIG. 11, the seismic isolation foundation structure 1B includes a base portion 2B, a seismic isolation base portion 3, a seismic isolation device 4, and an upper seismic isolation base portion 5. In this embodiment, a connection hole 79 is formed in the upper surface 2t of the base portion 2B. The connection hole 79 extends downward from the upper surface 2t of the base portion 2B. The connection 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 connection rebar 72 protruding downward from the lower surface 3b of the concrete 3c of the seismic isolation base 3 is inserted into the connection hole 79. A grout material G such as mortar is filled between the inner wall of the connection hole 79 and the connection rebar 72, and the other end 72f of the connection rebar 72 is joined to the concrete 2c of the base portion 2B via the grout material G. The connection rebar 72 in the base portion 2B is embedded to a length greater than the required anchorage length so that the connection rebar 72 will not slip out of the base portion 2B even when a tensile force is applied to the connection rebar 72.

[0038] To construct such a seismic isolation foundation structure 1B, a reinforced concrete base portion 2B is constructed so that connection holes 79 are formed in the top surface 2t. To do this, rebar (not shown) for the base portion 2B is arranged, and sleeve joints or the like are set so that connection holes 79 are formed in predetermined positions. After that, formwork (not shown) is assembled, and concrete 2c is poured into the formwork. Once the concrete 2c hardens and develops a predetermined strength, the reinforced concrete base portion 2B with connection holes 79 is constructed.

[0039] Next, the seismic isolation foundation 3 is installed on the basement 2B. For this, the seismic isolation foundation 3 is fabricated in advance in a factory or the like using precast concrete. The connection holes 79 are also filled with grout G. Then, the seismic isolation foundation 3 is lowered from above the basement 2B with its underside 3b facing downward, and the other end 72f of the connecting rebar 72 protruding downward from the underside 3b of the seismic isolation foundation 3 is inserted from above into the connection hole 79 filled with grout G. The seismic isolation foundation 3 is lowered to a height that leaves a gap of, for example, about 25 mm to 35 mm between the bottom surface 3b of the concrete 3c of the seismic isolation foundation 3 and the top surface 2t of the basement 2B. Then, grout material G such as mortar is filled between the bottom surface 3b of the concrete 3c of the seismic isolation foundation 3 and the top surface 2t of the basement 2B to join the bottom surface 3b of the seismic isolation foundation 3 and the top surface 2t of the basement 2B. In this way, the seismic isolation base part 3 is installed on and joined to the base part 2B.

[0040] Next, the seismic isolation device 4 is fixed to the seismic isolation foundation 3. To do this, the seismic isolation device 4 is installed above the seismic isolation foundation 3, and then lowered and placed on the upper surface 3t of the seismic isolation foundation 3. Then, a mounting bolt 73 is inserted from above into the through-hole 41h formed in the lower flange 41 of the seismic isolation device 4 and screwed into the female thread 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 precast concrete upper seismic isolation foundation 5 is installed on the seismic isolation foundation 3, and the superstructure 6 is constructed sequentially on top of the upper seismic isolation foundation 5.

[0041] The seismic isolation foundation structure 1B as described above is a seismic isolation structure 1B on which a seismic isolation device 4 is installed, and includes a base portion 2B made of reinforced concrete, a seismic isolation foundation portion 3 made of precast concrete provided above the base portion 2B, and a seismic isolation device 4 installed above the seismic isolation foundation portion 3, and a connecting member 71 having a female screw portion 71s formed on the inside and a connecting reinforcing bar 72 having a male screw portion 72s formed at one end 72e are embedded in the seismic isolation foundation portion 3, and a lower flange 41 of the seismic isolation device 4 is formed. An attachment bolt 73 is provided to be inserted through the through hole 41h from above and is screwed into the female threaded portion 71s from above, the male threaded portion 72s of the connecting rebar 72 is screwed into the female threaded portion 71s from below, the other end 72f of the connecting rebar 72 protrudes downward from the lower surface 3b of the seismic isolation foundation portion 3, a connection hole 79 is formed on the upper surface 2t of the base portion 2B, the other end 72f of the connecting rebar 72 is inserted into the connection hole 79, and grout material G is filled between the inner wall of the connection hole 79 and the connecting rebar 72. According to the above-described configuration, a precast concrete base isolation foundation 3 is provided above a reinforced concrete base 2B. A joint member 71 having a female thread 71s formed on the inside and a connecting reinforcing bar 72 having a male thread 72s formed on one end 72e are embedded in the base isolation foundation 3. A mounting bolt 73 is inserted from above through a through hole 41h formed in the lower flange 41 of the base isolation device 4 and threadedly engages the female thread 71s from above. The male thread 72s of the connecting reinforcing bar 72 is threadedly engages 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 base isolation foundation 3 and is inserted into a connecting hole 79 formed in the upper surface 2t of the base 2B. Grout G is filled between the inner wall of the connecting hole 79 and the connecting reinforcing bar 72. In this way, the connecting members 71 and the connecting rebars 72 are joined in this order to the seismic isolation device 4 via the mounting bolts 73. These connecting members 71 and connecting rebars 72 as a whole straddle the seismic isolation base 3 and the basement 2B, and are fixed to the concrete 3c, 2c that constitute these. In this configuration, if an earthquake occurs and the building tilts, causing a pull-out force to act on the seismic isolation device 4, the pull-out force is resisted by the anchoring force of the joint members 71 and the connecting rebars 72 as a whole to the concrete 3c, 2c that make up the base 2B and the seismic isolation foundation 3. Here, as described above, the joint members 71 and the connecting rebars 72 as a whole are arranged to extend not only into the seismic isolation foundation 3 but also into the base 2B. Therefore, the overall embedded length H1 can be made longer than the upper limit of the embedded length when the pull-out force-resisting members are embedded only inside the precast concrete seismic isolation foundation 3, i.e., the height H2 of the seismic isolation foundation 3. Therefore, the pull-out force can be resisted more efficiently than when the pull-out force-resisting members are embedded only inside the precast concrete seismic isolation foundation 3. In this way, if the seismic isolation base 3 for installing the seismic isolation device 4 is made of precast concrete, it is possible to efficiently prevent the seismic isolation device 4 from floating up in the event of an earthquake.

[0042] In particular, in the above-described configuration, the seismic isolation foundation portion 3 is made of precast concrete, so there is no need to construct the seismic isolation foundation portion 3 by pouring concrete at the construction site, which shortens the work period and enables the seismic isolation foundation structure 1B to be constructed efficiently.

[0043] The construction method of the seismic isolation foundation structure 1B as described above is a construction method of the seismic isolation foundation structure 1B on which the seismic isolation device 4 is installed, and includes the steps of constructing a base part 2B made of reinforced concrete so that a connection hole 79 is provided on the top surface 2t, and installing a precast concrete seismic isolation foundation part 3 having embedded therein a joining member 71 having a female screw part 71s formed on the inside and a connecting rebar 72 having a male screw part 72s formed on one end 72e and screwed into the female screw part 71s from below, to the base part 2B. and a step of lowering the connecting rebar 72 from above, inserting the other end 72f of the connecting rebar 72 protruding downward from the underside 3b of the seismic isolation foundation 3 into the connection hole 79 filled with grout material G from above, thereby installing the seismic isolation foundation 3 on the base portion 2B, and a step of providing the seismic isolation device 4 above the seismic isolation foundation 3, 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 thread portion 71s of the connecting member 71, thereby fixing the seismic isolation device 4 to the seismic isolation foundation 3. According to this configuration, a reinforced concrete base 2B is constructed so that a connection hole 79 is provided on the top surface 2t, and a precast concrete base isolation foundation 3, in which a connecting member 71 with a female thread 71s and a connecting rebar 72 are embedded, is lowered from above the base 2B, and the other end 72f of the connecting rebar 72 is inserted from above into the connection hole 79 filled with grout G to install the base isolation foundation 3 on the base 2B. The base isolation device 4 is installed above the base isolation foundation 3, and a mounting bolt 73 is inserted from above through the through hole 41h formed in the lower flange 41 of the base isolation device 4 and screwed into the female thread 71s of the connecting member 71. In this way, when the base isolation foundation 3 for installing the base isolation device 4 is made of precast concrete, a base isolation foundation structure 1B can be constructed that can efficiently prevent the base isolation device 4 from lifting up during an earthquake.

[0044] The method for constructing the seismic foundation structure and seismic isolation foundation structure of the present invention is not limited to the above-mentioned embodiments and modified examples described with reference to the drawings, and various other modified examples are possible within the technical scope. For example, in the second embodiment, modifications similar to the modifications explained in relation to the first embodiment may be considered. For example, as explained with reference to Figure 9 in relation to the first embodiment, in the second embodiment too, the precast concrete seismic isolation base portion 3, the seismic isolation device 4, and the precast concrete upper seismic isolation base portion 5 may be joined together in advance as an integrated unit, and then joined to the base portion 2B. Alternatively, as explained with reference to Figure 10 in relation to the first embodiment, in the second embodiment too, the seismic isolation base portion 3 and the upper seismic isolation base portion 5 may be provided with a lower base plate 35 and an upper base plate 55, respectively.

[0045] Furthermore, in the second embodiment, before the seismic isolation foundation 3 is lowered from above the base portion 2B, the connection holes 79 are filled with grout material G, and then the other end 72f of the connecting rebar 72 is lowered from above the base portion 2B so as to be buried from above into the grout material G filled in the connection holes 79, and the grout material G is 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 this is not limited to this. For example, the seismic isolation base 3 may be lowered from above the base 2B without filling the connection holes 79 with grout G. In this case, when filling the gap between the lower surface 3b of the concrete 3c of the seismic isolation base 3 and the upper surface 2t of the base 2B with grout G, the grout flows into the connection holes 79, thereby filling the connection holes 79 with grout G. Furthermore, in the second embodiment, similarly 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 basement 2B with grout material G, a through-hole for filling the grout material G that passes through the seismic isolation foundation 3 in the vertical direction may be provided in the center of the seismic isolation foundation 3, and the grout material G may be filled through this through-hole from above the seismic isolation foundation 3. 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 basement 2A up to near the center of the seismic isolation foundation 3, and the grout material G may be injected from the hose.

[0046] In addition, the configurations given in the above embodiments can be selected or changed as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0047] 1A, 1B Seismic isolation foundation structure 72 Connecting rebar 2A, 2B Base part 72e One end 2t top surface 72f other end 3 Seismic isolation base part 72s Male thread part 3b Bottom 73 Mounting bolt 4 Seismic isolation device 74 Reinforcement bar joint 41 Lower flange 75 Anchor bar 41h Through hole 79 Connection hole 71 Joint material G Grout material 71s female thread

Claims

1. A seismic isolation foundation structure on which a seismic isolation device is installed, The reinforced concrete base and a precast concrete seismic isolation base provided above the base; The seismic isolation device is installed above the seismic isolation base portion; Equipped with A joining member having a female thread formed on the inside and a connecting reinforcing bar having a male thread formed on one end are embedded in the seismic isolation foundation, and an attachment bolt is inserted from above through a through hole formed in the lower flange of the seismic isolation device and is screwed into the female thread from above, the male thread of the connecting reinforcing bar is screwed into the female thread from below, and the other end of the connecting reinforcing bar protrudes downward from the underside of the seismic isolation foundation, A reinforcing bar joint and an anchor are embedded in the base portion, the other end of the connecting reinforcing bar is joined to the reinforcing bar joint from above, and the upper end of the anchor is joined to the reinforcing bar joint from below. A seismic isolation foundation structure characterized by:

2. A seismic isolation foundation structure on which a seismic isolation device is installed, The reinforced concrete base and a precast concrete seismic isolation base provided above the base; The seismic isolation device is installed above the seismic isolation base portion; Equipped with A joining member having a female thread formed on the inside and a connecting reinforcing bar having a male thread formed on one end are embedded in the seismic isolation foundation, and an attachment bolt is inserted from above through a through hole formed in the lower flange of the seismic isolation device and is screwed into the female thread from above, the male thread of the connecting reinforcing bar is screwed into the female thread from below, and the other end of the connecting reinforcing bar protrudes downward from the underside of the seismic isolation foundation, A connection hole is formed on the upper surface of the base portion, the other end of the connection rebar is inserted into the connection hole, and grout material is filled between the inner wall of the connection hole and the connection rebar. A seismic isolation foundation structure characterized by:

3. A method for constructing a seismic isolation foundation structure on which a seismic isolation device is installed, comprising: A step of constructing a reinforced concrete base portion in which anchor reinforcements and reinforcing bar joint portions to which the anchor reinforcements are joined from below are buried; a process of lowering a precast concrete seismic isolation foundation having embedded therein a joining member with a female thread portion formed on the inside and a connecting rebar with a male thread portion formed on one end that is screwed into the female thread portion from below, from above the base portion, and inserting the other end of the connecting rebar that protrudes downward from the underside of the seismic isolation foundation into the rebar joint portion of the base portion from above, joining them, and installing the seismic isolation foundation on the base portion; a step of providing the seismic isolation device above the seismic isolation base, inserting a mounting bolt from above through a through-hole formed in a lower flange of the seismic isolation device and screwing it into the female thread portion of the connecting member to fix the seismic isolation device to the seismic isolation base; A method for constructing a seismic isolation foundation structure, comprising:

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