Seismic isolation structure

Abstract

To provide a seismic structure without the need for increasing a thickness of a skeleton while restricting a breakage of a seismic device.SOLUTION: A seismic structure 20 has: a lower structure 12; a pedestal 12B which is provided in the lower structure 12 and to which a seismic device 14 is fixed; an upper structure 16 which is supported by the seismic device 14; a stopper 30 which is fixed to a beam material (a beam 16B) of the upper structure 16 and projects downward; and a load receiving part 40 which is provided in the lower structure 12, is fixed to the pedestal 12B, and faces the stopper 30.SELECTED DRAWING: Figure 1A

Description

【Technical Field】 【0006】 , 【0001】 The present invention relates to a seismic isolation structure. 【Background Art】 【0002】 The following Patent Document 1 discloses a seismic isolation structure with a fail-safe mechanism. In this seismic isolation structure, a displacement regulation main body part (stopper) is joined to the lower structure of a seismic isolation building. When the upper structure is displaced relative to the lower structure, the contact part (load receiving part) of the upper structure is made to collide with the stopper to mitigate the impact and prevent the rupture or buckling of the seismic isolation device. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2015 - 183495 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the seismic isolation structure with a fail-safe mechanism of Patent Document 1 above, when the upper structure collides with the stopper of the lower structure, an external force acts on the stopper. And a bending moment acts on the portion of the lower structure where the stopper is joined. The body of the lower structure where the stopper is joined needs to resist this bending moment, for example, by increasing its thickness. 【0005】 However, it is not reasonable to increase the thickness of the body in order to resist the bending moment that acts temporarily during an earthquake. For example, in Patent Document 1 above, the stopper is joined to the slab, but increasing the thickness of the slab increases the amount of concrete used and also requires a longer construction time. 【0006】 Taking the above facts into consideration, the present invention aims to provide a seismic isolation structure that suppresses the fracture of seismic isolation devices while eliminating the need to increase the thickness of the building structure. [Means for solving the problem] 【0007】 The seismic isolation structure of claim 1 comprises a lower structure, a base provided on the lower structure to which a seismic isolation device is fixed, and an upper structure supported by the seismic isolation device. Across the entire width in the vertical direction The aforementioned base Fixed to the side A load-receiving portion and a portion fixed to the beam of the upper structure and protruding downward, with the lower end being in an elevation view The load-receiving portion and It has opposing stoppers. 【0008】 In the seismic isolation structure of claim 1, when the superstructure is displaced relative to the substructure during an earthquake, a stopper fixed to the superstructure comes into contact with the load-bearing portion. Since the load-bearing portion is fixed to the base, the load-bearing portion and the base exert a resistive force. This suppresses the fracture of the seismic isolation device. Furthermore, the volume of the load-bearing portion can be reduced compared to the case where the load-bearing portion is provided independently without being fixed to the base. 【0009】 Furthermore, a reaction force acts on the stopper fixed to the beam of the superstructure from the load-bearing part. A bending moment then acts on the part of the beam where the stopper is joined. The beam can exert resistance against this bending moment. Generally, beams have higher resistance to bending moments compared to slabs of typical thickness. Therefore, they are more resistant to bending moments compared to when the stopper is fixed to the slab. As a result, it is not necessary to increase the thickness of the structure to resist the bending moment that acts for a short period during an earthquake. 【0010】 The seismic isolation structure of claim 2 is the seismic isolation structure of claim 1, wherein the stopper and the load-receiving portion face each other in the direction of the material axis of the beam member, but do not face each other in a direction perpendicular to the material axis of the beam member. 【0011】 In the seismic isolation structure of claim 2, the load-receiving portion and the stopper face each other in the direction of the beam's material axis. Therefore, the axial load-bearing capacity and bending load-bearing capacity of the beam can be exerted. Furthermore, the load-receiving portion and the stopper do not face each other in a direction perpendicular to the beam's material axis. Therefore, the acting of forces in the weak axis direction on the beam can be suppressed. 【0012】 The seismic isolation structure of claim 3 is the seismic isolation structure of claim 1 or 2, wherein a cushioning material is attached to the outer circumferential surface of the stopper. 【0013】 In the seismic isolation structure of claim 3, a cushioning material is attached to the outer surface of the stopper. This reduces the impact force when the stopper and the load-bearing part collide. The seismic isolation structure of claim 4 is, It comprises a lower structure, a base provided on the lower structure to which a seismic isolation device is fixed, an upper structure supported by the seismic isolation device, a stopper fixed to a beam of the upper structure and projecting downward, with its lower end facing the base in an elevation view, and a load-receiving portion provided on the lower structure and fixed to the base and facing the lower end, The lower end portion is octagonal in plan view, and the load-receiving portion faces three sides of the lower end portion. The seismic isolation structure of claim 5 is the seismic isolation structure of claim 4, wherein in the load-receiving portion, the thickness of the opposing portion facing the lower end in a direction intersecting the axial direction of the beam member is greater than the thickness of the opposing portion facing the lower end along the axial direction of the beam member. The seismic isolation structure of claim 6 is the seismic isolation structure of claim 1, further comprising a load-receiving portion fixed to the foundation beam and not fixed to another base, on the opposite side of the base with the stopper in between. [Effects of the Invention] 【0014】 According to the present invention, it is not necessary to increase the thickness of the building structure while suppressing the fracture of the seismic isolation device. [Brief explanation of the drawing] 【0015】 [Figure 1A] This is a vertical cross-sectional view showing a seismic isolation structure according to an embodiment of the present invention. [Figure 1B] Figure 1A is a cross-sectional view along line BB. [Figure 2] This is a plan view showing the seismic isolation structure according to the embodiment. [Figure 3]It is a plan sectional view showing a modification of the arrangement of the buffer material in the seismic isolation structure according to the embodiment. [Figure 4A] It is a vertical sectional view showing a modification of the configuration of the column base part in the seismic isolation structure according to the embodiment. [Figure 4B] It is a vertical sectional view showing another modification of the configuration of the column base part in the seismic isolation structure according to the embodiment. [Figure 5] It is a plan view showing a modification of the plan layout of the seismic isolation structure according to the embodiment. [Figure 6] It is a plan view showing another modification of the plan layout of the seismic isolation structure according to the embodiment. [Figure 7] It is a plan view showing a modification of the seismic isolation structure according to the embodiment. 【MODE FOR CARRYING OUT THE INVENTION】 【0016】 Hereinafter, the seismic isolation structure according to the embodiment of the present invention will be described with reference to the drawings. Components shown with the same reference numerals in each drawing mean the same components. However, unless otherwise specified in the specification, each component is not limited to one, and there may be a plurality of them. 【0017】 【0018】 In each figure, the directions indicated by the arrows X and Y are directions along the horizontal plane and are perpendicular to each other. Also, the direction indicated by the arrow Z is a direction along the vertical direction (up and down direction). In each figure, the directions indicated by the arrows X, Y, and Z are assumed to coincide with each other. 【0019】 <Seismic isolation structure> Figures 1A and 1B show a seismic isolation structure 20 according to an embodiment of the present invention. The seismic isolation structure 20 is a structure applied to a building 10 comprising a substructure 12, a seismic isolation device 14 fixed to the substructure 12, and an upper structure 16 supported by the seismic isolation device 14. Furthermore, the seismic isolation structure 20 suppresses the fracture of the seismic isolation device 14 by a collision buffer mechanism 22, which will be described later. 【0020】 (building) The substructure 12 in building 10 is the foundation of building 10, and a base plate 12B is provided at the intersection of the foundation beams 12A. The base plate 12B is a structure for fixing the seismic isolation device 14. 【0021】 The seismic isolation device 14 is a seismic isolation bearing that seismically supports the superstructure 16 relative to the lower structure 12, and is composed of laminated rubber 14B placed between the upper and lower flanges 14A. The lower flange 14A of the seismic isolation device 14 is bolted to the base 12B. The upper flange 14A is bolted to the base plate 16C provided on the column 16A of the superstructure 16. 【0022】 The superstructure 16 is a steel-framed column-beam structure, composed of columns 16A and beams 16B joined together. The lower end of column 16A protrudes below the lower end surface of beam 16B, which is located at the very bottom. Therefore, the base plate 16C is positioned below the lower end surface of beam 16B. The superstructure 16 may also be made of reinforced concrete. 【0023】 <Collision buffer mechanism> The seismic isolation structure 20 is equipped with a collision buffer mechanism 22 to suppress the fracture of the seismic isolation device 14. The collision buffer mechanism 22 is composed of a stopper 30, load receiving parts 40, 42, and a buffer material 50. 【0024】 (stopper) The stopper 30 is a steel protruding member fixed to the beam 16B of the superstructure 16 and projecting downward. As shown in Figure 1B, the lower end of the stopper 30 is approximately octagonal in plan view, and plates 30A, 30B, and 30C are joined along the sides of the octagon. 【0025】 Plate 30A is a plate positioned facing the axial direction of beam 16B (in other words, a plate positioned along a direction perpendicular to the axial direction of beam 16B). Plate 30A is provided on both the base 12B side and the opposite side of base 12B of the substructure 12. 【0026】 Plate 30B is a plate positioned along the axial direction of beam 16B (in other words, a plate positioned facing a direction perpendicular to the axial direction of beam 16B). Plate 30B is provided on both the one side and the other side of beam 16B. 【0027】 Plate 30C is a plate positioned facing a direction intersecting the axial direction of beam 16B. In a plan view, plate 30C is positioned across the end of plate 30A and the end of plate 30B. 【0028】 In other words, in the stopper 30 which is formed in an octagonal shape in plan view, plates 30A are arranged on two opposing sides in the axial direction of the beam 16B, plates 30B are arranged on two opposing sides in a direction perpendicular to the axial direction of the beam 16B, and plates 30C are arranged on the remaining four sides. 【0029】 Of these, the widths (horizontal dimensions) of plates 30A and 30C are formed to be approximately equal, while the width of plate 30B is formed to be smaller than the widths of plates 30A and 30C. 【0030】 (Load-bearing section) The lower structure has load-receiving parts 40 and 42 that face the stopper 30. Load-receiving part 40 is a concrete member fixed to the base 12B, and load-receiving part 42 is a concrete member fixed to the foundation beam 12A. 【0031】 The load-bearing portion 40 is fixed to the base 12B on the side of the stopper 30. In a plan view, the load-bearing portion 40 is positioned to partially surround the stopper 30. Specifically, the load-bearing portion 40 has an opposing portion 40A that faces the plate 30A of the stopper 30, and an opposing portion 40C that faces the plate 30C of the stopper 30. 【0032】 Comparing the thickness T1 of the opposing portion 40A with the thickness T2 of the opposing portion 40C, the thickness T2 is larger. Here, "thickness" refers to the dimension in the direction along the opposing direction of plates 30A and 30C. 【0033】 Furthermore, if the distance between the opposing part 40A and the plate 30A is denoted as distance L1, and the distance between the opposing part 40C and the plate 30C is denoted as distance L2, then distances L1 and L2 are formed to be equal. Note that these distances L1 and L2 are set to be less than or equal to the deformation dimension at which the laminated rubber 14B of the seismic isolation device 14 begins to undergo plastic deformation when it undergoes shear deformation during an earthquake. 【0034】 In other words, when the superstructure 16 undergoes relative displacement with respect to the substructure 12 during an earthquake, even if the plate 30A or 30C of the stopper 30 collides with the opposing part 40A or 40C of the load-receiving part 40, the laminated rubber 14B does not break because it is deformed within its elastic range. 【0035】 The ends of the reinforcing bars (for example, reinforcing bars B1, B2, and B3 (reinforcing bar B3 is shown in Figure 1A)) arranged in the load-receiving section 40 are inserted into the base 12B in order to transmit the external force acting from the stopper 30 to the base 12B. 【0036】 As shown in Figure 1A, the load-bearing portion 42 is fixed to the foundation beam 12A on the side opposite the base 12B, with the stopper 30 in between. As shown in Figure 1A, the load-bearing portion 42 is positioned to partially surround the stopper 30 in a plan view. 【0037】 Specifically, the load-receiving portion 42 has an opposing portion 42A that faces the plate 30A of the stopper 30, and an opposing portion 42C that faces the plate 30C of the stopper 30. 【0038】 In this example, of the two plates 30C positioned on the load-receiving portion 42 side, an opposing portion 42C is provided on the side facing one of the plates 30C (the upper one in Figure 1B), while an opposing portion 42C is not provided on the side facing the other plate 30C (the lower one in Figure 1B). 【0039】 This makes it easier to secure working space for reinforcing the load-receiving sections 40 and 42, pouring concrete, and installing the buffer material 50 described later, thereby improving constructability. As shown by the dashed line in Figure 1B, an opposing section 42C may also be provided on the side facing the other plate 30C. 【0040】 The thickness of the opposing portion 42C is equal to the thickness of the opposing portion 40C, and is set to a thickness T2. It is preferable that the thickness T3 of the opposing portion 42A be approximately the same as the thickness T2 of the opposing portion 42C, but in this example, the thickness T3 is larger. 【0041】 Furthermore, the distance between the opposing part 42A and the plate 30A is equal to the distance L1 described above. In addition, the distance between the opposing part 42C and the plate 30C is equal to the distance L2 described above. 【0042】 As shown in Figure 1A, the ends of the reinforcing bars (e.g., reinforcing bar B4) arranged in the load-receiving section 42 are inserted into the foundation beam 12A in order to transmit the external force acting from the stopper 30 to the foundation beam 12A. 【0043】 (buffer material) The cushioning material 50 is formed using an elastic material such as rubber and is fixed to the surfaces of plates 30A and 30C. The cushioning material 50 reduces the impact when the stopper 30 collides with the load-receiving portion 40 or 42. The cushioning material 50 may also be designed to absorb collision energy by undergoing plastic deformation. 【0044】 Furthermore, the cushioning material 50 does not need to be provided on plates that do not face the load-receiving portion 42, such as the other plate 30C mentioned above. 【0045】 <Planar arrangement of collision damping mechanism> Figure 2 shows an example of the planar arrangement of the collision absorbing mechanism 22 in building 10. Of these, the collision absorbing mechanism 22 equipped with a stopper 30 fixed to a beam 16B along the X direction is referred to as collision absorbing mechanism 22X. Similarly, the collision absorbing mechanism 22 equipped with a stopper 30 fixed to a beam 16B along the Y direction is referred to as collision absorbing mechanism 22Y. 【0046】 As indicated by arrow X1, in the collision buffer mechanism 22X, the stopper 30 and the load receiving parts 40 and 42 face each other in the X direction, which is the axis direction of the beam 16B, but do not face each other in the Y direction, which is perpendicular to the axis direction of the beam 16B. 【0047】 Furthermore, the stopper 30 is positioned opposite the load-receiving portion on both sides in the X direction. That is, one side of the stopper 30 faces the load-receiving portion 40, and the other side faces the load-receiving portion 42. 【0048】 Similarly, as indicated by arrow Y1, in the collision buffer mechanism 22Y, the stopper 30 and the load receiving parts 40 and 42 face each other in the Y direction, which is the axis direction of the beam 16B, but do not face each other in the X direction, which is perpendicular to the axis direction of the beam 16B. 【0049】 Furthermore, the stopper 30 is positioned opposite the load-receiving portion on both sides in the Y direction. That is, one side of the stopper 30 faces the load-receiving portion 40, and the other side faces the load-receiving portion 42. 【0050】 Here, in the substructure 12, bases 12B are formed at each intersection of the foundation beam 12A along the X direction (see Figure 1A) and the foundation beam 12A along the Y direction. However, the collision buffer mechanism 22 does not need to be provided on all bases 12B. As shown in Figure 2, the collision buffer mechanism 22 only needs to be formed on some of the bases 12B. 【0051】 Although only a portion of the building 10 is shown in Figure 2, it is preferable that the number of collision absorbing mechanisms 22X and 22Y be equal when the building 10 is viewed from above. 【0052】 <Mechanism and Effects> In the seismic isolation structure 20 according to an embodiment of the present invention, when the superstructure 16 shown in Figure 1A is displaced relative to the lower structure 12 during an earthquake, the stopper 30 fixed to the superstructure 16 (more precisely, the cushioning material 50 fixed to the stopper 30) comes into contact with the load-receiving portion 40 or 42. Since the load-receiving portion 40 is fixed to the base 12B, the load-receiving portion 40 and the base 12B exert a resistive force. 【0053】 This makes it possible to suppress the rupture of the laminated rubber 14B in the seismic isolation device 14. In addition, the volume of the load-bearing part can be reduced compared to the case where the load-bearing part is provided independently without being fixed to the base 12B. 【0054】 In this embodiment, for example, the thickness T1 of the opposing portion 40A in the load-receiving portion 40 is smaller than the thickness T3 of the opposing portion 42A in the load-receiving portion 42. Therefore, the volume of the opposing portion 40A is smaller than the volume of the opposing portion 42A in the load-receiving portion 42. Here, "volume" refers to the volume per unit area of ​​the surface facing the stopper 30 in the opposing portions 40A and 42A. If the volume is small, as in the case of the opposing portion 40A, the amount of concrete used to form the load-receiving portion 40 will be reduced, and the construction time can also be shortened. 【0055】 Furthermore, the stopper 30 fixed to the beam 16B of the superstructure 16 is subjected to reaction forces from the load-receiving parts 40 and 42. Then, as shown in Figure 1A, a bending moment M1 acts on the part of the beam 16B where the stopper 30 is joined. The beam 16B can exert resistance against this bending moment M1. 【0056】 Beam 16B is designed to have higher resistance to bending moments compared to a typical reinforced concrete slab (not shown) of a common thickness (e.g., about 200 mm) that spans beam 16B. Therefore, it is easier to resist the bending moment M1 compared to cases where the stopper 30 is fixed to the slab. As a result, there is no need to increase the thickness of the structure (slab) to resist the bending moment M1 that acts in the short term during an earthquake. 【0057】 Furthermore, even when an external force is applied from the stopper 32 to the load-receiving portion 42, a bending moment M2 acts on the portion of the lower structure 12 to which the load-receiving portion 42 is joined. The foundation beam 12A can exert resistance against this bending moment M2. 【0058】 Furthermore, in the seismic isolation structure 20, as shown in Figure 2, the load-receiving parts 40, 42 and the stopper 30 face each other in the direction of the beam 16B's material axis. Therefore, the axial load-bearing capacity and bending load-bearing capacity of the beam 16B can be fully utilized. Also, the load-receiving parts 40, 42 and the stopper 30 do not face each other in a direction perpendicular to the beam 16B's material axis. Therefore, the acting of forces in the weak axis direction on the beam 16B can be suppressed. 【0059】 Furthermore, in the seismic isolation structure 20, as shown in Figure 1B, a cushioning material 50 is attached to the outer surface of the stopper 30. This reduces the impact force when the stopper 30 collides with the load-receiving parts 40 and 42. In addition, the impact energy can be absorbed by plastically deforming the cushioning material 50. 【0060】 The cushioning material 50 may also be attached to the opposing parts 40A and 40C of the load-receiving part 40, and the opposing parts 42A and 42C of the load-receiving part 42, as shown in Figure 3. 【0061】 <Other Embodiments> In the above embodiment, as shown in Figure 1B, the lower end of the column 16A of the superstructure 16 is formed to protrude below the beam 16B, but the embodiments of the present invention are not limited to this. For example, as shown in Figure 4A, the lower end surface of the base plate 16C placed at the lower end of the column 16A and the lower end surface of the beam 16B may be at the same height. 【0062】 Furthermore, in the examples shown in Figures 1B and 4A, a base plate 16C is provided on the lower end surface of the column 16A and fixed to the flange 14A of the seismic isolation device 14, but the embodiments of the present invention are not limited to this. 【0063】 For example, as shown in Figure 4B, the base plate on the lower end surface of the column 16A may be made to be about the size of an outer diaphragm, and the end of the beam 16B may be fixed or rested on the flange 14A. 【0064】 Furthermore, in the above embodiment, as shown in Figure 1B, plates 30B and 30C are arranged on the stopper 30 facing a direction intersecting the axial direction of beam 16B, but the embodiments of the present invention are not limited to this. 【0065】 For example, as shown in Figure 7, the plate to be provided on the stopper 30 is a plate 30A facing the axial direction of the beam 16B on which the stopper 30 is installed, and plates 30B and 30C may be omitted. 【0066】 If plate 30C is omitted, the opposing portion 40C in the load-receiving portion 40 and the opposing portion 42C in the load-receiving portion 42 may also be omitted. 【0067】 Furthermore, in the above embodiment, as shown in Figure 2, a load-receiving portion 42 is provided on the side opposite to the base 12B with the stopper 30 in between to form a collision cushioning mechanism 22, but the embodiments of the present invention are not limited to this. For example, as shown in the collision cushioning mechanism 24 in Figure 5, the load-receiving portion 42 may be omitted. 【0068】 Among the collision absorbing mechanisms 24, those equipped with a stopper 30 fixed to a beam 16B along the X direction are referred to as collision absorbing mechanisms 24XA and 24XB. Collision absorbing mechanism 24XA is equipped with a load-receiving portion 40 on one side of the stopper 30 (right side in Figure 5). On the other hand, collision absorbing mechanism 24XB is equipped with a load-receiving portion 40 on the other side of the stopper 30 (left side in Figure 5). 【0069】 Similarly, among the collision absorbing mechanisms 24, those equipped with a stopper 30 fixed to a beam 16B along the Y direction are referred to as collision absorbing mechanisms 24YA and 24YB. The collision absorbing mechanism 24YA is equipped with a load-receiving portion 40 on one side of the stopper 30 (the lower side in Figure 5). On the other hand, the collision absorbing mechanism 24YB is equipped with a load-receiving portion 40 on the other side of the stopper 30 (the upper side in Figure 5). 【0070】 In this way, by combining multiple collision buffer mechanisms 24 and configuring each stopper 30 and load-receiving portion 40 to face each other in both directions along the X-direction and both directions along the Y-direction, the stopper 30 and load-receiving portion 40 can be brought into contact with each other regardless of the direction in which the upper structure 16 is displaced relative to the lower structure 12, thereby suppressing the fracture of the seismic isolation device. 【0071】 Furthermore, in the embodiments shown in Figures 2 and 5, multiple collision absorbing mechanisms are combined to accommodate displacement in all directions, but the embodiments of the present invention are not limited to these. For example, as shown in collision absorbing mechanism 26 in Figure 6, it is also possible to accommodate displacement in all directions with only one collision absorbing mechanism. 【0072】 In the collision buffer mechanism 26, load-receiving sections 40 are formed in four directions on a single base 12B. In addition, stoppers 30 are fixed to the beam 16B in both directions of the base 12B in the X direction. Similarly, stoppers 30 are fixed to the beam 16B in both directions of the base 12B in the Y direction. 【0073】 With this configuration, no matter what direction the upper structure 16 is displaced relative to the lower structure 12, the stopper 30 and the load-receiving part 40 will come into contact, thereby suppressing the fracture of the seismic isolation device. 【0074】 In addition, in the collision cushioning mechanism 26, the load-receiving portion 42 may or may not be provided on the side opposite to the base 12B with the stopper 30 in between. 【0075】 When the load-receiving section 42 is provided, when the upper structure 16 is displaced relative to the lower structure 12, one of the stoppers 30 will come into contact with the load-receiving section 40, and another stopper 30 will come into contact with the load-receiving section 42. On the other hand, when the load-receiving section 42 is not provided, one of the stoppers 30 will come into contact with the load-receiving section 40. In either case, the stopper 30 can be brought into contact with the load-receiving section 40 or 42 to suppress the fracture of the seismic isolation device. [Explanation of symbols] 【0076】 10 Buildings 12 Substructure 12B Pedestal 14. Seismic isolation device 16B Beam (beam material) 16 Superstructure 20. Seismic isolation structure 30 Stoppers 40 Load-bearing section 42 Load-bearing section 50 Cushioning material

Claims

[Claim 1] Substructure and A base provided on the aforementioned lower structure, to which the seismic isolation device is fixed, The superstructure supported by the aforementioned seismic isolation device, A load-receiving portion fixed to the side surface of the base over its entire width in the vertical direction, A stopper is fixed to the beam member of the superstructure and protrudes downward, with its lower end facing the load-receiving portion in an upright view, A seismic isolation structure. [Claim 2] The seismic isolation structure according to claim 1, wherein the stopper and the load-receiving portion face each other in the direction of the beam axis, but do not face each other in a direction perpendicular to the beam axis. [Claim 3] The seismic isolation structure according to claim 1 or 2, wherein a cushioning material is attached to the outer circumferential surface of the stopper. [Claim 4] A substructure and A base provided on the aforementioned lower structure, to which the seismic isolation device is fixed, The superstructure supported by the aforementioned seismic isolation device, A stopper is fixed to the beam of the upper structure and protrudes downward, with its lower end facing the base in an elevation view, A load-receiving portion is provided on the lower structure, fixed to the base, and facing the lower end; It has, The aforementioned lower end is octagonal in plan view. The load-receiving portion is opposite to the three sides of the lower end, Seismic isolation structure. [Claim 5] In the aforementioned load-receiving portion, The thickness of the opposing portion facing the lower end in a direction intersecting the axial direction of the beam member is: The thickness of the opposing portion facing the lower end along the axial direction of the beam member is greater than the thickness of the opposing portion facing the lower end. The seismic isolation structure according to claim 4. [Claim 6] The seismic isolation structure according to claim 1, further comprising a load-receiving portion fixed to a foundation beam and not fixed to another base, on the opposite side of the base with the stopper in between.

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