JP7537982B2 - Pile head seismic isolation structure and construction method thereof - Google Patents

Description

The present invention relates to a pile-top seismic isolation structure and a method for constructing the same, and more specifically, to a pile-top seismic isolation structure and a method for constructing the same that can more effectively suppress rigid body rotation of the solidified member relative to the prefabricated pile by improving the integrity between the solidified member to which the seismic isolation device is fixed and the prefabricated pile.

Various pile-top seismic isolation structures have been proposed that use a seismic isolation device placed and fixed on the top surface of the pile head of a pile driven into the ground to support an upper structure (for example, Patent Document 1). The pile-top seismic isolation structure described in Patent Document 1 uses a prefabricated pile with the upper end of a steel pipe protruding in the pile longitudinal direction beyond the top end surface of the outer shell concrete, and fills the hollow part of the pile head with a solidification material, into which multiple anchor bolts are embedded. Then, a seismic isolation device placed on the top surface of the solidification material of the flattened pile head is fixed to the prefabricated pile via multiple anchor bolts.

During an earthquake, horizontal forces are transmitted from the seismic isolation device to the solidification member via the anchor bolts, and stress acts on the solidification member to cause it to rotate rigidly relative to the prefabricated pile. In this pile-head seismic isolation structure, the prefabricated pile and the solidification member are integrated by adhesion at the contact surface between the steel pipe and the solidification member, and at the contact surface between the outer shell concrete and the solidification member. In a structure that relies on adhesion in this way, there is a limit to how much integration between the prefabricated pile and the solidification member can be improved. Therefore, there is room for improvement in suppressing the rigid rotation of the solidification member relative to the prefabricated pile.

JP 2019-100088 A

The object of the present invention is to provide a pile-top seismic isolation structure and a method for constructing the same that can more effectively suppress rigid body rotation of the solidification member relative to the prefabricated pile by improving the integrity between the solidification member to which the seismic isolation device is fixed and the prefabricated pile.

In order to achieve the above object, the method for constructing a pile head seismic isolation structure of the present invention includes, in a manufacturing process for a prefabricated pile, solidifying ready mixed concrete placed inside a steel pipe into a cylindrical shape to manufacture a prefabricated pile having a cylindrical outer shell concrete with the steel pipe integrated on its outer periphery and an upper end of the steel pipe protruding in the longitudinal direction of the pile beyond the upper end surface of the outer shell concrete, and in a construction process at a construction site, after driving the prefabricated pile into the ground, filling the inner portion of the pile head with a solidifying member to flatten the upper surface of the pile head, and embedding a plurality of fixing devices in the solidifying member at intervals in the circumferential direction of the pile, and then placing a seismic isolation device on the upper surface and attaching the seismic isolation device to the prefabricated pile via the plurality of fixing devices. In the method for constructing a pile head seismic isolation structure in which a plurality of reinforcing anchor bolts are embedded in the fresh concrete placed inside the steel pipe in the manufacturing process, the fresh concrete is solidified into a cylindrical shape to manufacture a prefabricated pile in which a plurality of the reinforcing anchor bolts are embedded at intervals around the pile in the upper end of the outer shell concrete, and in the construction process, the prefabricated pile is driven into the ground, and a vertical reinforcing bar extending in the longitudinal direction of the pile , separate from the fixing device, is connected to the upper end of each of the reinforcing anchor bolts, and the hollow portion is filled with the solidification member, thereby resulting in a state in which the plurality of vertical reinforcing bars are embedded in the solidification member.

The pile-top seismic isolation structure of the present invention uses, as a prefabricated pile, a cylindrical outer shell concrete having a steel pipe integrated on its outer peripheral surface, with the upper end of the steel pipe protruding in the longitudinal direction of the pile beyond the upper end surface of the outer shell concrete, the inner portion of the pile head is filled with a solidifying member to make the upper surface of the pile head flat, and a plurality of fixing devices are embedded in the solidifying member at intervals in the circumferential direction of the pile above the upper end surface of the outer shell concrete, and a seismic isolation device is fixed to the prefabricated pile via the plurality of fixing devices. In this pile-top seismic isolation structure, the prefabricated pile is used in which a plurality of reinforcing anchor bolts are embedded in the upper end of the outer shell concrete at intervals in the circumferential direction of the pile, and vertical reinforcing bars extending in the longitudinal direction of the pile connected to the upper ends of each of the reinforcing anchor bolts are embedded in the solidifying member separately from the fixing devices .

In the present invention, multiple reinforcing anchor bolts are embedded in the upper end of the outer shell concrete of a prefabricated pile, and multiple vertical reinforcing bars extending in the longitudinal direction of the pile connected to the upper end of each reinforcing anchor bolt are embedded in the solidification member. Therefore, the multiple reinforcing anchor bolts and vertical reinforcing bars can further increase the integrity of the solidification member to which the seismic isolation device is fixed and the prefabricated pile, and can more effectively suppress rigid body rotation of the solidification member relative to the prefabricated pile.

FIG. 2 is an explanatory diagram illustrating the pile head seismic isolation structure of the present invention in a vertical cross-sectional view. FIG. 2 is an explanatory diagram illustrating the precast pile of FIG. 1 in cross section. FIG. 2 is an explanatory diagram illustrating a vertical cross-sectional view of the precast pile of FIG. 1 driven into the ground. 4 is an explanatory diagram illustrating a vertical cross-sectional view of the pile head of FIG. 3 with the inner space therein filled with a solidification material; FIG. 1 is an explanatory diagram illustrating a cross-sectional view of another embodiment of the pile head seismic isolation structure of the present invention. FIG. 13 is an explanatory diagram illustrating yet another embodiment of the pile head seismic isolation structure of the present invention in a vertical cross-sectional view. FIG. 13 is an explanatory diagram illustrating yet another embodiment of the pile head seismic isolation structure of the present invention in a vertical cross-sectional view. FIG. This is an explanatory diagram showing, in a vertical cross-sectional view, another construction method of the pile head seismic isolation structure of the present invention, illustrating the state before the pre-solidified concrete member used as the solidification member is fitted into the precast pile. 9 is an explanatory diagram illustrating the state in which the concrete member of FIG. 8 is fitted onto a prefabricated pile and a seismic isolation device is installed on the top surface of the pile head. This is an explanatory diagram showing, in a vertical cross-sectional view, yet another construction method of the pile head seismic isolation structure of the present invention, illustrating the state before the pre-solidified concrete member used as the solidification member is fitted into the precast pile. 11 is an explanatory diagram illustrating the state in which the concrete member of FIG. 10 is fitted onto a prefabricated pile and a seismic isolation device is installed on the top surface of the pile head.

Below, the pile-top seismic isolation structure of the present invention and its construction method will be explained based on the embodiment shown in the figure.

The pile-top seismic isolation structure 1 of the present invention, as illustrated in Figures 1 and 2, supports an upper structure 18 in a seismic isolation manner using a seismic isolation device 13 placed and fixed on the top of the pile head of a prefabricated pile 2 driven into the ground G. This pile-top seismic isolation structure 1 can be used, for example, as a seismic isolation structure for the upper structure 18 of a building, condominium, etc.

In this invention, instead of using conventional SC piles (steel pipe composite piles) as they are, a special innovation is made in the pile manufacturing process. Then, the prefabricated piles 2 with the specially constructed pile heads are driven into the ground G to construct the pile head seismic isolation structure 1.

The seismic isolation device 13 is a general seismic isolation device. The seismic isolation device 13 includes a laminated rubber 14 in which multiple steel plates are embedded at intervals in the vertical direction, a lower flange 16 joined to the lower end of the laminated rubber 14, and an upper flange 15 joined to the upper end of the laminated rubber 14. The specifications and size of the seismic isolation device 13 are appropriately determined according to the required allowable axial force, etc. At a position on the outer periphery side of the laminated rubber 14 in the lower flange 16, multiple through holes are formed at intervals in the circumferential direction through which fixing bolts 17 for fixing the seismic isolation device 13 to the prefabricated pile 2 are inserted. The seismic isolation device 13 (laminated rubber 14, steel plate, upper and lower flanges 15, 16) in this embodiment is circular in plan view, but can also be polygonal, such as a square, in plan view. A seismic isolation device 13 equipped with a sliding barrier can also be used instead of the laminated rubber 14.

In the pile-head seismic isolation structure 1 of the present invention, a prefabricated pile 2 is used, which has a cylindrical outer shell concrete 4 with a steel pipe 3 integrated on its outer periphery, and the upper end of the steel pipe 3 protrudes in the pile longitudinal direction (upward) beyond the upper end surface of the outer shell concrete 4. A major feature of this prefabricated pile 2 is that multiple reinforcing anchor bolts 5 are already embedded in the upper end of the outer shell concrete 4.

The steel pipe 3 covers the outer surface of the outer concrete shell 4 over its entire length and is integrated with the outer concrete shell 4. The outer concrete shell 4 is made of high-strength concrete. The diameter of the prefabricated pile 2 is set to be approximately the same as the outer diameter of the seismic isolation device 13 (lower flange 16) or larger than the outer diameter of the seismic isolation device 13.

As shown in FIG. 1, in this embodiment, an enlarged head pile 19 (a PHC pile or a PRC pile with an enlarged cross section) is driven into the ground G at a deeper position, and a prefabricated pile 2 is driven on top of the enlarged head pile 19. The upper end of the enlarged head pile 19 and the lower end of the prefabricated pile 2 are connected by a joint metal fitting. The upper end of the pile head of the driven prefabricated pile 2 protrudes above the ground surface of the ground G. Instead of the enlarged head pile 19, a PHC pile or a PRC pile can be connected to the lower end of the prefabricated pile 2, or no other pile can be connected. The hollow portion below the head of the prefabricated pile 2 and the hollow portion of the enlarged head pile 19 are filled with cement milk or the like as a filler material 10.

In this embodiment, annular protrusions 3a that are continuous in the circumferential direction of the pile are arranged at intervals in the longitudinal direction (up-down direction) of the pile on the inner peripheral surface of the upper end of the steel pipe 3 that constitutes the prefabricated pile 2. The shape and arrangement of the protrusions 3a are not particularly limited as long as they increase the surface area of the inner peripheral surface of the steel pipe 3, and they can be provided intermittently or scattered in the circumferential direction of the pile. The protrusions 3a can be provided arbitrarily as necessary.

The multiple reinforcing anchor bolts 5 are arranged at intervals in the circumferential direction of the outer shell concrete 4, extend in the longitudinal direction of the precast pile 2, and are embedded in the upper end of the outer shell concrete 4. The thickness of the outer shell concrete 4 in the radial direction of the pile is set to, for example, 50 mm or more and 300 mm or less. The embedded length of the reinforcing anchor bolts 5 in the outer shell concrete 4 is set to, for example, 15 times or more and 40 times or less the outer diameter (thickness) of the reinforcing anchor bolts 5. The outer diameter (thickness) of the reinforcing anchor bolts 5 is set to, for example, 10 mm or more and 38 mm or less. The height position of the upper end of the reinforcing anchor bolt 5 (connection part 5a) is set to approximately the same level (height position) as the upper end surface of the outer shell concrete 4, and is set to a position lower than the upper end of the steel pipe 3.

A vertical reinforcing bar 6 extending in the longitudinal direction of the pile is connected to the upper end (connection part 5a) of each reinforcing anchor bolt 5. In this embodiment, the lower end of the vertical reinforcing bar 6, which has a threaded portion, is connected in a screwed state to the connection part 5a provided at the upper end of the reinforcing anchor bolt 5. The vertical reinforcing bar 6 is composed of a metal rod-shaped member such as round steel or threaded reinforcing bar. The outer diameter (thickness) of the vertical reinforcing bar 6 is set to, for example, 10 mm or more and 38 mm or less. The connection part 5a is composed of a metal joint fitting such as a joint nut.

The method of connecting the upper end of the reinforcing anchor bolt 5 and the lower end of the vertical reinforcement 6 is not particularly limited as long as the method results in the vertical reinforcement 6 being horizontally constrained relative to the reinforcing anchor bolt 5. For example, the upper end of the reinforcing anchor bolt 5 and the lower end of the vertical reinforcement 6 can be joined by welding or adhesive. Also, for example, the lower end of the vertical reinforcement 6 can be fitted into a fitting hole extending in the pile longitudinal direction provided in the connection part 5a of the reinforcing anchor bolt 5 to connect them.

In this embodiment, straight vertical reinforcement bars 6 are used, and an expansion fitting is provided at the upper end 6a of the vertical reinforcement bars 6. For example, a cap nut or the like is used as the expansion fitting. As an alternative to the expansion fitting, a configuration having a bent portion (hook) formed by bending the upper end 6a of the vertical reinforcement bars 6, or a configuration having a plate-shaped member (plate) joined to the upper end 6a of the vertical reinforcement bars 6 can also be used.

As shown in FIG. 2, in this embodiment, 12 reinforcing anchor bolts 5 and vertical reinforcement bars 6 are arranged at equal intervals around the pile periphery on the same circle centered on the pile core of the prefabricated pile 2 in a cross-sectional view. The specifications (shape, thickness, length, etc.) of the reinforcing anchor bolts 5 and vertical reinforcement bars 6, the number of reinforcing anchor bolts 5, their arrangement in the outer shell concrete 4, and their buried depth are determined appropriately according to the allowable axial force required for the pile head seismic isolation structure 1 and the specifications of the seismic isolation device 13.

In this embodiment, furthermore, horizontal reinforcement bars 7 that extend in the circumferential direction of the pile and connect adjacent vertical reinforcement bars 6 are embedded in the solidification member 9. The horizontal reinforcement bars 7 are, for example, made of reinforcing bars with a diameter of about 10 mm. The horizontal reinforcement bars 7 are arranged at multiple locations at intervals in the longitudinal direction of the pile of the vertical reinforcement bars 6. The horizontal reinforcement bars 7 can be installed arbitrarily as necessary.

As shown in FIG. 1, the hollow portion 2a of the pile head of the precast pile 2 is filled with the solidification member 9, and the top surface of the pile head is flat. In this embodiment, the upper end of the steel pipe 3 and the upper surface of the solidification member 9 are set at the same level. The solidification member 9 is made of concrete 9a. In this embodiment, the upper end of the filling material 10 is located lower than the upper end of the outer shell concrete 4, and the shell concrete 4 and the solidification member 9 overlap in the longitudinal direction of the pile (vertical direction). That is, the solidification member 9 is formed in a columnar shape having a large diameter portion with a relatively large outer diameter and a small diameter portion with a relatively small outer diameter located below it. The hollow portion 2a inside the outer shell concrete 4 at the pile head is filled with the small diameter portion, and the hollow portion 2a inside the steel pipe 3 above the outer shell concrete 4 is filled with the large diameter portion. For example, the upper end of the outer shell concrete 4 and the upper end of the filling material 10 can be set at the same height, so that there is no area where the outer shell concrete 4 and the solidification member 9 overlap in the longitudinal direction of the pile.

On the top of the solidification member 9, a plurality of fasteners 8 for fixing the seismic isolation device 13 to the prefabricated pile 2 are arranged at intervals around the pile. The fasteners 8 extend in the longitudinal direction of the pile and are embedded in the solidification member 9. For the fasteners 8, an anchor bolt having a connecting portion 8a (e.g., a socket, etc.) at the upper end to which the fixing bolt 17 can be connected, or a cap nut extending in the longitudinal direction of the pile to which the fixing bolt 17 can be connected is used. The embedding length of the fasteners 8 in the solidification member 9 is set to, for example, 15 to 40 times the outer diameter (thickness) of the fasteners 8. The level of the upper end of the fasteners 8 (connecting portion 8a) is set to the same level as the upper surface of the solidification member 9.

Each of the fixing devices 8 is disposed at a position corresponding to a through hole formed in the lower flange 16 of the seismic isolation device 13. As illustrated in FIG. 2, in this embodiment, twelve fixing devices 8 are disposed at equal intervals around the pile. Each fixing device 8 is disposed inside (toward the pile core) the upper end surface of the outer shell concrete 4. In addition, the vertical reinforcement 6 and the fixing devices 8 are disposed so that they are positioned on the same straight line that crosses the pile core of the prefabricated pile 2 in a cross-sectional view. The specifications, number, and arrangement of the fixing devices 8 embedded in the solidification member 9 are appropriately determined according to the allowable axial force required for the pile head seismic isolation structure 1 and the specifications of the seismic isolation device 13.

Although not shown in the drawings, the solidification member 9 further contains embedded therein multiple main reinforcements that extend in the longitudinal direction of the pile and are spaced apart around the periphery of the pile, as well as annular tie bars (hoop bars) that extend around the periphery of the pile and surround the main reinforcements. The main reinforcements and tie bars are arranged from near the bottom end of the small diameter section of the solidification member 9 to near the top end of the large diameter section of the solidification member 9. The main reinforcements and tie bars can be installed as needed.

That is, vertical reinforcement bars 6, horizontal reinforcement bars 7, fasteners 8, main reinforcement bars and ties are embedded in the solidification member 9 (concrete 9a) that fills the hollow portion 2a of the pile head of the prefabricated pile 2, forming a reinforced concrete structure. The prefabricated pile 2 and the solidification member 9 are firmly integrated by connecting multiple reinforcing anchor bolts 5 embedded in the outer concrete 4 of the prefabricated pile 2 to multiple vertical reinforcement bars 6 embedded in the solidification member 9.

The seismic isolation device 13 is placed on the top surface of the pile head and is fixed to the prefabricated pile 2 via multiple fixing devices 8. In this embodiment, the fixing bolt 17 is inserted from above into the through hole of the lower flange 16 and screwed into the connecting portion 8a provided at the upper end of the fixing device 8, thereby fixing the seismic isolation device 13 to the prefabricated pile 2 (solidification member 9). The upper flange 15 is fixed to the upper structure 18 by fixing members such as bolts.

On the underside of the upper structure 18, a plurality of pile-head seismic isolation structures 1, each of which is composed of a prefabricated pile 2 (including a solidification member 9) and a seismic isolation device 13, are arranged at intervals in the horizontal direction. Adjacent pile heads are connected to each other by tie beams 12 formed on the ground G. The tie beams 12 are formed, for example, of a reinforced concrete structure. In this embodiment, tie beams 12 are provided on all four sides of the pile head: left and right, front and back. Stud bolts 11 are joined to the outer periphery of the steel pipes 3 constituting the prefabricated pile 2 so as to protrude outward in the radial direction of the pile, and the stud bolts 11 are embedded in the tie beams 12. Tie beams 12 may be provided as necessary, and the pile-head seismic isolation structure 1 may also be configured without tie beams 12.

Next, the procedure for constructing the pile-top seismic isolation structure 1 will be explained.

In the manufacturing process of the prefabricated pile 2, the prefabricated pile 2 illustrated in FIG. 3 is manufactured in advance. In the manufacturing process, a plurality of reinforcing anchor bolts 5 are arranged at intervals in the circumferential direction of the pile inside the upper part of the steel pipe 3, and a partition plate forming the inner peripheral surface of the outer shell concrete 4 is installed inside the plurality of reinforcing anchor bolts 5 (pile core side). Next, fresh concrete is poured between the partition plate and the steel pipe 3. Then, with a retaining lid forming the upper end surface of the outer shell concrete 4 placed on the upper end of the reinforcing anchor bolt 5 (connection part 5a), the steel pipe 3 is rotated around the pipe axis center, and the fresh concrete is centrifugal compacted and solidified into a cylindrical shape. As a result, a prefabricated pile 2 is manufactured, which has a cylindrical outer shell concrete 4 with the steel pipe 3 integrated on the outer peripheral surface, the upper end of the steel pipe 3 protrudes in the pile longitudinal direction beyond the upper end surface of the outer shell concrete 4, and a plurality of reinforcing anchor bolts 5 are embedded at intervals in the circumferential direction of the pile at the upper end of the outer shell concrete 4. The manufactured prefabricated piles 2 are transported to the construction site where the pile head seismic isolation structure 1 will be constructed.

In the construction process at the construction site, a vertical hole for driving the prefabricated pile 2 is excavated to a specified depth using an excavator such as an earth auger into the ground G on which the pile-head seismic isolation structure 1 is to be constructed. Then, a base reinforcement material is injected into the bottom of the vertical hole, and the middle of the vertical hole is filled with a fixing liquid around the pile, and construction is carried out in the same manner as in the conventional method.

Next, as shown in FIG. 3, the prefabricated pile 2 is inserted into the excavated vertical hole and driven in. In this embodiment, the lower end of the prefabricated pile 2 and the upper end of the enlarged head pile 19 are connected with a joint fitting, and the prefabricated pile 2 and the enlarged head pile 19 are inserted into the vertical hole and driven in. The upper end of the pile head of the driven prefabricated pile 2 is made to protrude above the ground surface of the ground G. Although the method of driving the prefabricated pile 2 by the pre-boring method has been exemplified, the prefabricated pile 2 can also be driven in by the trench pile method or the vibrohammer method.

The hollow portion below the head of the prefabricated pile 2 and the hollow portion of the enlarged head pile 19 are filled with filler material 10. The hollow portion 2a of the head of the pile is left hollow. Stud bolts 11 are joined to the outer surface of the steel pipe 3 by welding.

Next, as shown in FIG. 4, vertical reinforcement bars 6 are connected to the upper ends (connection parts 5a) of each reinforcing anchor bolt 5 embedded in the outer shell concrete 4. Next, the vertical reinforcement bars 6 are connected together with horizontal reinforcement bars 7. Then, multiple fixing devices 8 are placed at intervals around the pile in the upper part of the hollow part 2a of the pile head, extending in the longitudinal direction of the pile, and main reinforcement bars and tie bars are arranged in the hollow part 2a.

Next, the hollow portion 2a of the pile head is filled with ready-mixed concrete, and the hollow portion 2a of the pile head is filled with the solidification member 9 (concrete 9a). The top surface of the pile head is then flattened, and the vertical reinforcement bars 6, horizontal reinforcement bars 7, fasteners 8, main reinforcement bars, and tie bars are filled in the solidification member 9. When the ready-mixed concrete is filled in the hollow portion 2a, the steel pipes 3 function as a formwork. The ready-mixed concrete is then solidified to form the solidification member 9, and the solidification member 9 and the prefabricated pile 2 are integrated together.

Then, the seismic isolation device 13 (lower flange 16) is placed on the top surface of the flattened pile head, and the seismic isolation device 13 is fixed to the prefabricated pile 2 via multiple fixing devices 8. In this embodiment, fixing bolts 17 are inserted into each through hole of the lower flange 16 from above, and screwed into the connecting portion 8a of the fixing device 8, thereby fixing the seismic isolation device 13 to the prefabricated pile 2 (fixing member 9). After the seismic isolation device 13 is installed, an upper structure 18 is constructed on top of the seismic isolation device 13, and the upper structure 18 is fixed to the upper flange 15 of the seismic isolation device 13.

When installing tie beams 12, reinforcing bars 12a that make up the tie beams 12 are placed between adjacent pile heads, and the outside of the reinforcing bars 12a are surrounded by formwork. Ready-mixed concrete is then poured inside the formwork and allowed to harden, after which the formwork is removed. This completes the construction of the pile head seismic isolation structure 1 with tie beams 12.

The procedure for constructing the pile-head seismic isolation structure 1 is not limited to the procedure shown above, and the work order can be changed as appropriate. For example, the stud bolts 11 can be joined to the prefabricated piles 2 in advance during the manufacturing process of the prefabricated piles 2. Also, for example, the main reinforcement and tie bars can be arranged before connecting the vertical reinforcement bars 6 to the upper ends of the reinforcing anchor bolts 5. Also, for example, the tie beams 12 can be constructed before installing the seismic isolation device 13 at the pile head.

In this way, in the manufacturing process of the prefabricated pile 2, a prefabricated pile 2 is manufactured in which multiple reinforcing anchor bolts 5 are embedded in the upper end of the outer shell concrete 4 at intervals in the circumferential direction of the pile. Then, in the construction process, vertical reinforcement bars 6 are connected to the upper end of each reinforcing anchor bolt 5, and multiple vertical reinforcement bars 6 are embedded in the solidification member 9. This results in a structure in which multiple reinforcing anchor bolts 5 embedded in the outer shell concrete 4 of the prefabricated pile 2 are connected to multiple vertical reinforcement bars 6 embedded in the solidification member 9. Therefore, the integrity of the solidification member 9 and the prefabricated pile 2 can be further improved, and rigid body rotation of the solidification member 9 relative to the prefabricated pile 2 can be more effectively suppressed.

In other words, in this pile-top seismic isolation structure 1, the horizontal stress acting on the solidification member 9 from the seismic isolation device 13 via the fixing device 8 during an earthquake is transmitted to the prefabricated pile 2 (shell concrete 4 and steel pipe 3) via the vertical reinforcement 6 and reinforcing anchor bolts 5, so that the stress is dispersed over a wider area. Therefore, the stress that causes the solidification member 9 to rotate rigidly relative to the prefabricated pile 2 can be effectively attenuated. Furthermore, in this pile-top seismic isolation structure 1, the stress is transmitted to the vertical reinforcement 6 and reinforcing anchor bolts 5, and the expansion of the shell concrete 4 and solidification member 9 is restrained and suppressed by the steel pipe 3, so that the pile-top seismic isolation structure 1 has excellent durability. Furthermore, by using a prefabricated pile 2 that is an improved version of the SC pile, the construction period required to construct the pile-top seismic isolation structure 1 can be significantly shortened compared to forming a cast-in-place pile at the construction site.

In this embodiment, when the construction process involves solidifying the ready-mix concrete at the construction site to form the solidified member 9, the position of the through hole formed in the lower flange 16 of the seismic isolation device 13 can be adjusted to match the position of the fixing device 8 (connecting portion 8a) at the construction site, making it easy to construct the pile-top seismic isolation structure 1. Since the upper end of the steel pipe 3 functions as a formwork, there is no need for tedious formwork installation work, and the pile-top seismic isolation structure 1 can be constructed efficiently with little labor effort.

When the vertical reinforcement bars 6 are connected to each other by the horizontal reinforcement bars 7 and the horizontal reinforcement bars 7 are embedded in the solidification member 9, the horizontal reinforcement bars 7 increase the integrity of the prefabricated pile 2 and the solidification member 9, and the solidification member 9 also has a higher resistance to shear force. Furthermore, the provision of the horizontal reinforcement bars 7 can further strengthen the resistance to the lever reaction force (horizontal force due to the lever action generated at the contact point between the steel pipe 3 and the solidification member 9) generated between the steel pipe 3 and the solidification member 9. In addition, the vertical reinforcement bars 6 are mutually constrained by the horizontal reinforcement bars 7, which is more advantageous in suppressing buckling of the vertical reinforcement bars 6 and makes the solidification member 9 less susceptible to deformation or damage. Therefore, it is even more advantageous in increasing the durability of the pile head seismic isolation structure 1.

Providing a head expansion fitting at the upper end 6a of the vertical reinforcement bar 6 increases the bonding surface between the vertical reinforcement bar 6 and the solidification member 9, thereby improving the integrity of the solidification member 9 and the prefabricated pile 2. The same effect can be obtained when a bent portion is provided at the upper end 6a of the vertical reinforcement bar 6 or when a plate-shaped member is joined to the upper end 6a of the vertical reinforcement bar 6.

As shown in FIG. 1, when the vertical reinforcement 6 is configured to extend above the bottom end of the fixing device 8, the horizontal stress transmitted from the seismic isolation device 13 to the fixing device 8 during an earthquake is more easily transmitted to the vertical reinforcement 6, and the stress transmitted to the vertical reinforcement 6 is more easily dispersed over a wide area of the prefabricated pile 2 via the reinforcing anchor bolts 5. This is therefore more advantageous in attenuating the stress that causes the solidification member 9 to rigidly rotate relative to the prefabricated pile 2.

In this embodiment, the reinforcing anchor bolt 5 is embedded in the shell concrete 4 to a position deeper than the lower end surface (upper end surface filled with the filler material 10) of the solidification member 9 with the inner hollow portion 2a filled. With this configuration, the horizontal stress transmitted from the seismic isolation device 13 to the reinforcing anchor bolt 5 via the fixing device 8 and the vertical reinforcement bar 6 during an earthquake is easily transmitted to a deeper range than the range of the shell concrete 4 facing the solidification member 9. This effectively distributes the stress generated during an earthquake over a wider range of the prefabricated pile 2, which is advantageous in avoiding stress concentration at the upper end of the shell concrete 4 facing the solidification member 9, making the upper part of the shell concrete 4 less likely to be damaged.

In addition, if the vertical reinforcement bars 6 are configured to extend above the ground surface of the ground G, the horizontal stress transmitted from the seismic isolation device 13 via the fixing device 8 to the upper part of the steel pipes 3 and solidification member 9 that are not buried in the ground G during an earthquake is more easily transmitted to the reinforcing anchor bolts 5 via the vertical reinforcement bars 6. Therefore, compared to when the upper ends of the vertical reinforcement bars 6 are located below the ground surface, this is advantageous in avoiding stress concentration at the upper ends of the steel pipes 3 and solidification member 9 exposed above ground, making the steel pipes 3 and solidification member 9 less susceptible to deformation or damage.

When the fixing device 8 is configured to extend below the ground surface of the ground G, the horizontal stress transmitted from the seismic isolation device 13 to the fixing device 8 during an earthquake is more easily transmitted to the portion of the prefabricated pile 2 that is buried in the ground G. Therefore, compared to when the lower end of the fixing device 8 is located above the ground surface, this is advantageous in avoiding stress concentration at the upper ends of the steel pipe 3 and solidification member 9 located above ground, making the steel pipe 3 and solidification member 9 less susceptible to deformation or damage.

By screwing the lower end of the vertical reinforcement bar 6, which has a threaded portion, into the connection portion 5a provided at the upper end of the reinforcing anchor bolt 5, the reinforcing anchor bolt 5 and the vertical reinforcement bar 6 can be connected easily and quickly. Since the connection can be made with fewer man-hours, it is also advantageous in shortening the construction period.

When the top surface of the steel pipe 3 and the top surface of the solidification member 9 are set at the same level, the entire area of the solidification member 9 in the pile longitudinal direction is covered by the steel pipe 3, making the solidification member 9 less susceptible to damage and greatly increasing the durability of the pile head seismic isolation structure 1. In addition, since there is no need to install formwork to mold the solidification member 9, the solidification member 9 can be efficiently molded with a small number of work steps.

In the pile-top seismic isolation structure 1 installed in a building or condominium, it is assumed that the direction of the stress transmitted from the seismic isolation device 13 to the solidification member 9 via the fixing device 8 is roughly uniform in all directions. In such a case, it is preferable to arrange the multiple reinforcing anchor bolts 5 and vertical reinforcing bars 6, and the multiple fixing devices 8 at equal intervals around the pile. On the other hand, for example, as in the pile-top seismic isolation structure 1 installed in a bridge, it may be assumed that the direction of the force transmitted from the seismic isolation device 13 to the solidification member 9 via the fixing device 8 is biased in a certain direction. In such a case, it is also possible to arrange the multiple reinforcing anchor bolts 5 and vertical reinforcing bars 6, and the multiple fixing devices 8 in a biased direction in which the force transmitted to the solidification member 9 is expected to be biased.

The alternative embodiment of the pile-top seismic isolation structure 1 illustrated in Figure 5 differs from the embodiment illustrated in Figures 1 to 4 in the arrangement of the fixing device 8. The other configurations are substantially the same.

In this pile-head seismic isolation structure 1, multiple fixing devices 8 are arranged at intervals in the circumferential direction of the pile above the upper end surface of the outer shell concrete 4. The fixing devices 8 are also arranged in the circumferential direction of the pile between adjacent vertical reinforcing bars 6. By arranging the fixing devices 8 above the upper end surface of the outer shell concrete 4 in this way, the fixing devices 8 can be arranged in a position close to the outer periphery of the prefabricated pile 2, so that the area of the top surface of the pile head can be used more efficiently and a seismic isolation device 13 with an outer diameter size approximately the same as the pile diameter of the prefabricated pile 2 can be fixed to the pile head.

This reduces the difference between the allowable axial force of the prefabricated pile 2 and the allowable axial force of the seismic isolation device 13 that can be fixed to the prefabricated pile 2, and therefore makes it possible to make the pile diameter of the prefabricated pile 2 smaller, which is extremely advantageous in reducing construction costs. Note that when using a seismic isolation device 13 that is polygonal in plan view, the outer diameter size of the seismic isolation device 13 means the diameter size of the circumscribed circle around the seismic isolation device 13.

Another embodiment of the pile-top seismic isolation structure 1 illustrated in Figure 6 differs from the embodiment illustrated in Figures 1 to 4 in the configuration of the steel pipes 3 and the vertical reinforcement bars 6. The rest of the configuration is substantially the same.

In this pile-top seismic isolation structure 1, horizontally penetrating holes 3b are formed at the positions where the steel pipes 3 form the tie beams 12. The horizontally extending reinforcing bars 12a that make up the tie beams 12 are inserted through the through holes 3b and the solidification member 9 and arranged. In other words, the reinforcing bars 12a that make up the tie beams 12 are embedded in the solidification member 9.

The upper end 6a of the vertical reinforcement 6 is bent in the longitudinal direction of the pile to provide a bent portion at the upper end 6a of the vertical reinforcement 6. In this embodiment, the upper end 6a of each vertical reinforcement 6 is bent inward (toward the pile core) at a substantially right angle to the longitudinal direction of the pile, but the bending direction and the bending angle relative to the longitudinal direction of the pile can be determined as appropriate. In this embodiment, the upper end of the outer shell concrete 4 and the upper end of the infill material 10 are set at the same height, and there is no overlapping area between the outer shell concrete 4 and the solidification member 9 in the longitudinal direction of the pile.

The procedure for constructing this pile-top seismic isolation structure 1 is generally the same as the procedure described in the embodiment illustrated in Figures 1 to 4. The through-holes 3b can be formed in advance during the manufacturing process of the prefabricated piles 2, or can be formed during the construction process. When placing the reinforcing bars 12a that make up the tie beams 12, the reinforcing bars 12a are inserted through the through-holes 3b. Then, the outside of the reinforcing bars 12a that make up the tie beams 12 are surrounded by formwork, and ready-mixed concrete is poured into the formwork to form the tie beams 12.

In this way, by providing through holes 3b at the positions where the steel pipes 3 connect the tie beams 12, the pile heads and the tie beams 12 can be integrally formed without any seams in the concrete 9a. This allows the pile heads and the tie beams 12 to be joined more firmly, improving the unity of the two. In this embodiment, the outer periphery of the steel pipes 3 has multiple small through holes 3b through which the reinforcing bars 12a can be inserted. However, for example, the outer periphery of the steel pipes 3 can also have through holes 3b of about the same size as the cross section of the tie beams 12.

Another embodiment of the pile-top seismic isolation structure 1 illustrated in Figure 7 differs from the embodiment illustrated in Figures 1 to 4 in the configuration of the pile head and the vertical reinforcement bars 6. The other configurations are substantially the same.

In this pile-top seismic isolation structure 1, the solidification member 9 of the reinforced concrete structure is arranged to protrude above the upper end of the steel pipe 3. That is, the lower part of the solidification member 9 is embedded in the steel pipe 3, and the upper part of the solidification member 9 protrudes above the steel pipe 3. Each fixing device 8 is arranged to straddle the upper end surface of the steel pipe 3 from top to bottom. The upper end of the steel pipe 3 of the prefabricated pile 2 driven into the ground G is set at the same level as the ground surface of the ground G. The height position of the upper end of the fixing device 8 (connecting part 8a) is set at a level higher than the ground surface of the ground G. A plate-shaped member extending horizontally is joined to the upper end 6a of the vertical reinforcement 6.

In this embodiment, the top of the pile head made of the solidification member 9 is cylindrical, and its outer diameter is set to approximately the same dimension as the pile diameter of the prefabricated pile 2. The height position of the upper end of the fixing device 8 (connecting portion 8a) is set to the same level as the upper surface of the solidification member 9. Each vertical reinforcement bar 6 protrudes above the steel pipe 3. Furthermore, multiple reinforcing bars 12a extending horizontally that constitute the tie beam 12 are inserted through the solidification member 9 and arranged. In other words, the reinforcing bars 12a that constitute the tie beam 12 are embedded in the upper part of the solidification member 9 located above the steel pipe 3.

The procedure for constructing this pile-head seismic isolation structure 1 is generally the same as that described in the embodiment illustrated in Figures 1 to 4. However, in this embodiment, when the prefabricated pile 2 is driven into the ground G, the upper end of the steel pipe 3 is set at the same level as the ground surface of the ground G. Then, the vertical reinforcement bars 6, the fixing devices 8, the main reinforcement bars, the tie bars, and the reinforcing bars 12a are respectively arranged in the hollow portion 2a of the pile head and above it, and the outside of the vertical reinforcement bars 6, the fixing devices 8, the main reinforcement bars, the tie bars, and the reinforcing bars 12a that protrude above the steel pipe 3 are surrounded by a formwork.

Next, fresh concrete is poured into the hollow portion 2a of the pile head and into the inside of the formwork, filling it up to the top end of the fixing device 8 (connecting portion 8a), filling the hollow portion 2a and the inside of the formwork and flattening the top surface of the pile head. The fresh concrete filled in the hollow portion 2a of the pile head and inside the formwork is then solidified to form the solidification member 9. Fresh concrete is also filled inside the formwork that forms the periphery of the tie beam 12 and allowed to solidify, forming the tie beam 12 integrated with the solidification member 9. The formwork is then removed, and a seismic isolation device 13 is installed on the top surface of the pile head.

In this way, by configuring the upper surface of the solidification member 9 to protrude above the upper end of the steel pipe 3, the pile head and the tie beam 12 can be molded integrally without any seams in the concrete 9a, so that the pile head and the tie beam 12 can be joined more firmly and the unity of the two can be further improved. In addition, the upper part of the pile head is not limited to a cylindrical shape, and can be made into any desired shape and size, such as a rectangular prism shape (polygonal shape), making it possible to apply it to seismic isolation devices 13 of various shapes.

In each of the above-described embodiments, the case where ready-mixed concrete is poured in the construction process to form the solidification member 9 is exemplified, but it is also possible to construct the pile-head seismic isolation structure 1 using a columnar concrete member that has been solidified in advance (hereinafter referred to as a precast solidification member 9A) as the solidification member 9, as in the embodiments illustrated in Figures 8 and 9 and the embodiments illustrated in Figures 10 and 11.

In the embodiment illustrated in Figures 8 and 9, a precast solidification member 9A is used, in which multiple fixing devices 8 are embedded at intervals around the pile and multiple vertical reinforcement bars 6 are embedded and solidified. This precast solidification member 9A is manufactured in advance at a factory or the like and transported to the construction site. In the construction process, after the prefabricated pile 2 is driven into the ground G, the precast solidification member 9A is fitted into the hollow portion 2a of the pile head, and the vertical reinforcement bars 6 are connected to the upper ends of each reinforcing anchor bolt 5, filling the hollow portion 2a with the precast solidification member 9A. The procedures for the subsequent work of installing the seismic isolation device 13 and the work of forming the tie beam 12 are the same as those of the embodiment illustrated in Figures 1 to 4.

More specifically, in this embodiment, the connection portion 5a provided at the upper end of the reinforcing anchor bolt 5 is provided with a fitting hole extending in the longitudinal direction of the pile into which the lower end of the vertical reinforcement bar 6 fits. In addition, the lower end of each vertical reinforcement bar 6 protrudes downward from the lower end surface of the large diameter portion of the precast solidification member 9A that abuts against the upper end surface of the outer shell concrete 4. Then, by fitting the precast solidification member 9A into the inner hollow portion 2a with the lower end of each vertical reinforcement bar 6 aligned with the fitting hole of the connection portion 5a, the lower end of each vertical reinforcement bar 6 fits into the fitting hole of the connection portion 5a. The vertical reinforcement bar 6 is then horizontally restrained relative to the reinforcing anchor bolt 5.

In this embodiment, a convex guide portion 3c extending in the longitudinal direction of the pile is provided on the inner peripheral surface of the upper end of the steel pipe 3, which protrudes above the outer shell concrete 4. A concave guide groove 9c extending in the longitudinal direction of the pile is provided on the outer peripheral surface of the large diameter portion of the precast solidification member 9A. The guide groove 9c of the precast solidification member 9A is fitted into the guide portion 3c of the steel pipe 3, so that the lower end of the vertical reinforcement bar 6 is aligned with the fitting hole of the connection portion 5a. The guide portion 3c and guide groove 9c can be provided as needed.

In the embodiment illustrated in Fig. 10 and Fig. 11, a precast solidification member 9A is used, which has a plurality of fixing devices 8 embedded at intervals in the circumferential direction of the pile and a plurality of insertion holes 9b through which a plurality of vertical reinforcement bars 6 can be inserted. This precast solidification member 9A is manufactured in advance in a factory or the like and transported to the construction site. In the construction process, after the prefabricated pile 2 is driven into the ground G, the precast solidification member 9A is fitted into the inner hollow portion 2a of the pile head. Then, the vertical reinforcement bars 6 inserted into the respective insertion holes 9b are connected to the upper ends of the respective reinforcing anchor bolts 5, and the inner hollow portion 2a is filled with the precast solidification member 9A. The procedures for the subsequent work of installing the seismic isolation device 13 and the work of forming the tie beams 12 are the same as those of the embodiment illustrated in Figs. 1 to 4.

More specifically, in this embodiment, the upper end of the reinforcing anchor bolt 5 protrudes above the upper end surface of the outer shell concrete 4. The upper end of the reinforcing anchor bolt 5 is fitted into the insertion hole 9b so that the insertion hole 9b and the upper end of the reinforcing anchor bolt 5 are aligned. For example, the steel pipe 3 and the precast solidified member 9A in this embodiment may be configured to have a guide portion 3c and a guide groove 9c.

In this embodiment, the vertical reinforcement 6 is inserted through the insertion hole 9b from above the precast solidification member 9A fitted into the hollow portion 2a, and the lower end of the vertical reinforcement 6 is screwed into the connection portion 5a of the reinforcing anchor bolt 5, thereby connecting the vertical reinforcement 6 to the reinforcing anchor bolt 5. The precast solidification member 9A and the vertical reinforcement 6 are integrated by filling the gap between the insertion hole 9b and the vertical reinforcement 6 with a filler such as mortar and solidifying it.

In addition, the work procedure is not limited to the above. For example, after connecting the vertical reinforcement 6 to the upper end of the reinforcing anchor bolt 5, the vertical reinforcement 6 can be inserted from above the vertical reinforcement 6 into the insertion hole 9b of the precast solidification member 9A, and the precast solidification member 9A can be fitted into the inner hollow portion 2a.

In this way, even when a pre-solidified precast solidification member 9A is used as the solidification member 9, the precast solidification member 9A fits into the hollow portion 2a of the pile head of the prefabricated pile 2, and the multiple vertical reinforcement bars 6 embedded in the precast solidification member 9A and the multiple reinforcing anchor bolts 5 embedded in the shell concrete 4 of the prefabricated pile 2 are connected. Therefore, the prefabricated pile 2 and the precast solidification member 9A are firmly integrated. When using the precast solidification member 9A, it is more advantageous to increase the integration between the prefabricated pile 2 and the precast solidification member 9A by fitting the precast solidification member 9A into the hollow portion 2a with an adhesive such as mortar applied to the outer surface of the precast solidification member 9A and the inner surface of the prefabricated pile 2.

In a construction method using precast solidification members 9A, no curing period is required during the construction process to solidify the fresh concrete that forms the solidification members 9. Therefore, the construction period can be significantly shortened compared to when fresh concrete is poured to form the solidification members 9 during the construction process.

Comparing the construction method illustrated in Figures 8 and 9 with the construction method illustrated in Figures 10 and 11, the construction method illustrated in Figures 8 and 9 does not require the work of filling and solidifying the filler between the insertion hole 9b of the precast solidification member 9A and the vertical reinforcement 6, so the pile head seismic isolation structure 1 can be constructed with fewer work hours. On the other hand, in the construction method illustrated in Figures 10 and 11, when connecting the vertical reinforcement 6 to the upper end of the reinforcing anchor bolt 5, each vertical reinforcement 6 can be moved individually. Therefore, it is possible to connect the vertical reinforcement 6 to the connection part 5a at the upper end of the reinforcing anchor bolt 5 by screwing it, and the connection strength between the vertical reinforcement 6 and the reinforcing anchor bolt 5 in the pile longitudinal direction can be increased.

In each of the embodiments exemplified above, the seismic isolation device 13 is placed directly on the top surface of the pile head, but for example, an intervening member (such as a pedestal or waterproof sheet) can be provided between the top surface of the pile head and the seismic isolation device 13 (lower flange 16). In that case, a through hole is formed in the intervening member through which the fixing bolt 17 is inserted.

1 Pile head seismic isolation structure 2 Prefabricated pile 2a Inner hollow portion 3 Steel pipe 3a Convex portion 3b Through hole 3c Guide portion 4 Outer shell concrete 5 Reinforcement anchor bolt 5a Connection portion 6 Vertical reinforcement 6a (Vertical reinforcement) upper end portion 7 Horizontal reinforcement 8 Fixing device 8a Connection portion 9 Solidification member 9A Precast solidification member 9a Concrete 9b Insertion hole 9c Guide groove 10 Filling material 11 Stud bolt 12 Tie beam 12a Steel bar 13 Seismic isolation device 14 Laminated rubber 15 Upper flange 16 Lower flange 17 Fixing bolt 18 Upper structure 19 Enlarged head pile G Ground

Claims (10)

In a manufacturing process of a prefabricated pile, fresh concrete placed inside a steel pipe is solidified into a cylindrical shape to manufacture a prefabricated pile having a cylindrical outer shell concrete with the steel pipe integrated on its outer periphery and an upper end of the steel pipe protruding in the longitudinal direction of the pile beyond the upper end surface of the outer shell concrete, and in a construction process at a construction site, after the prefabricated pile is driven into the ground, the hollow part of the pile head is filled with a solidifying member to flatten the upper surface of the pile head, and a plurality of fixing devices are embedded in the solidifying member at intervals in the circumferential direction of the pile, and then a seismic isolation device is placed on the upper surface and the seismic isolation device is fixed to the prefabricated pile via the plurality of fixing devices,
In the manufacturing process, a plurality of reinforcing anchor bolts are embedded in the ready-mixed concrete arranged inside the steel pipe, and the ready-mixed concrete is solidified into a cylindrical shape to manufacture the prefabricated pile in which a plurality of the reinforcing anchor bolts are embedded at intervals in the circumferential direction of the pile at an upper end of the outer shell concrete,
The construction process involves driving the prefabricated piles into the ground, connecting the upper ends of each of the reinforcing anchor bolts to a vertical reinforcing bar extending in the longitudinal direction of the pile separate from the fixing device , and filling the hollow portion with the solidification material, thereby resulting in a state in which multiple vertical reinforcing bars are embedded in the solidification material.This is a method for constructing a pile head seismic isolation structure, characterized in that The method for constructing a pile-top seismic isolation structure according to claim 1, in which the vertical reinforcement bars are connected to each other by horizontal reinforcement bars extending in the circumferential direction of the pile, and the horizontal reinforcement bars are embedded in the solidification member. The method for constructing a pile head seismic isolation structure according to claim 1 or 2, in which, in the construction process, after the prefabricated piles are driven into the ground, the vertical reinforcing bars are connected to the upper ends of the reinforcing anchor bolts, and the hollow space is filled with ready-mixed concrete while the vertical reinforcing bars and the fixing devices are placed in the hollow space, and the ready-mixed concrete is solidified while the vertical reinforcing bars and the fixing devices are embedded in the hollow space, forming the solidified member, and filling the hollow space with the solidified member. The method for constructing a pile-head seismic isolation structure according to claim 1 or 2, in which a columnar concrete member in which a plurality of the fixing devices are embedded at intervals in the pile circumferential direction and a plurality of the vertical reinforcement bars are embedded and solidified is used as the solidification member, and this concrete member is fitted into the hollow portion, and the vertical reinforcement bars are connected to the upper ends of each of the reinforcing anchor bolts, filling the hollow portion with the concrete member. The method for constructing a pile-head seismic isolation structure according to claim 1 or 2, in which a plurality of the fixing devices are embedded at intervals in the pile circumferential direction and a pre-solidified columnar concrete member having a plurality of insertion holes through which the plurality of vertical reinforcing bars can be inserted is used as the solidification member, and this concrete member is fitted into the hollow portion, and the vertical reinforcing bars inserted into the respective insertion holes are connected to the upper ends of the respective reinforcing anchor bolts, filling the hollow portion with the concrete member. A method for constructing a pile-head seismic isolation structure according to any one of claims 1 to 5, in which a plurality of the fixing devices are arranged at intervals in the circumferential direction of the pile above the upper end surface of the outer shell concrete. A method for constructing a pile-head seismic isolation structure according to any one of claims 1 to 6, in which the vertical reinforcement is embedded in the solidification member by extending it above the lower end of the fixing device. A method for constructing a pile-top seismic isolation structure according to any one of claims 1 to 7, in which the upper surface of the solidification member and the upper end of the steel pipe are set at the same level. A method for constructing a pile-head seismic isolation structure according to any one of claims 1 to 7, in which the upper surface of the solidification member is made to protrude above the upper end of the steel pipe. In a pile-head seismic isolation structure in which a prefabricated pile has a cylindrical outer shell concrete with a steel pipe integrated on its outer periphery, with the upper end of the steel pipe protruding in the longitudinal direction of the pile beyond the upper end surface of the outer shell concrete, the inner hollow portion of the pile head is filled with a solidification member to make the upper surface of the pile head flat, and a plurality of fixing devices are embedded in the solidification member at positions above the upper end surface of the outer shell concrete at intervals in the circumferential direction of the pile, and a seismic isolation device is fixed to the prefabricated pile via the plurality of fixing devices,
A pile head seismic isolation structure characterized in that the prefabricated piles used have multiple reinforcing anchor bolts embedded in the upper end of the outer shell concrete at intervals around the pile, and the solidification member has vertical reinforcing bars extending in the longitudinal direction of the pile connected to the upper ends of each of the reinforcing anchor bolts embedded separately from the fixing devices .

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