Base-isolated structure

Abstract

To provide a base-isolated structure capable of improving earthquake resistance of an upper structure at the time of excessive earthquake input.SOLUTION: A base isolation structure 100 including a base isolation layer 20, and an upper layer structure 22 placed above the base isolation layer 20 includes: a laminated rubber 24 which is provided on the base isolation layer 20, and has such hardening property as to reduce displacement of the base isolation layer 20; an elasto-plastic damper 26 and an oil damper 28 provided on the base isolation layer 20; and an oil damper 30 which is provided on the undermost layer of the upper structure 22, and suppresses vibration of the upper structure 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seismic isolation structure equipped with a seismic isolation layer. [Background technology]

[0002] Seismic isolation structures equipped with a seismic isolation layer have been known for some time. Typical seismic isolation structures are highly earthquake-resistant, as they can reduce the response acceleration and inter-story deformation of the upper structure above the seismic isolation layer within the range of assumed input earthquake motion. This prevents damage to structural components during an earthquake, and prevents damage and overturning of equipment and fixtures. In the design of typical seismically isolated buildings, the design earthquake motions used are the level 2 earthquakes announced, observed waves, site waves, etc., which are extremely rare earthquake motions.

[0003] Figure 5(1) shows the horizontal load-deformation relationship of laminated rubber commonly used in seismic isolation structures (Source: Non-Patent Document 1). In seismic isolation structures using laminated rubber, the horizontal response deformation of the seismic isolation layer in response to the design input earthquake motion is designed to be kept below the deformation region where the horizontal load of the laminated rubber rises rapidly (the region of horizontal deformation δ1 or greater in Figure 5(1); hereafter referred to as the hardening region). In this case, an energy absorption device called a damper is installed in the seismic isolation layer alongside the laminated rubber, minimizing the transmission of force to the superstructure while suppressing the response displacement of the seismic isolation layer. Generally, a force greater than the maximum response shear force generated in the seismic isolation layer is used as the design shear force for the lowest layer of the superstructure, and the superstructure is designed rationally according to each structure.

[0004] In recent major earthquakes, seismic motions exceeding the aforementioned Notification Wave Level 2 have been observed. In addition, there are concerns about earthquakes occurring along the Nankai Trough and the Sagami Trough, and the possibility of earthquake motions greater than the design input earthquake motions to date cannot be denied. As an example of verifying safety in the event of earthquake motions greater than the design earthquake motions, there are cases where verification is required in which the earthquake motion is 1.5 times the aforementioned Notification Wave Level 2 input.

[0005] In a typical seismically isolated building that uses laminated rubber, if an input earthquake motion greater than the design earthquake motion occurs, the deformation of the laminated rubber will reach the hardening region, the shear force of the seismic isolation layer will increase, reducing the seismic isolation effect and transmitting the shear force of the earthquake motion to the superstructure. In this case, the superstructure will experience a shear force greater than that considered for the design earthquake motion, depending on the rigidity of the hardening region of the seismic isolation layer. In order to prevent damage to the superstructure even when an input of 1.5 times the designated earthquake wave level 2 occurs, it will be necessary to increase the rigidity and strength of the building compared to cases where only the design earthquake motion was considered.

[0006] A known conventional structure for dealing with the characteristics of the superstructure when the base isolation layer is subjected to excessive deformation is, for example, that described in Patent Document 1. The structure described in Patent Document 1 is a building in which friction stoppers are incorporated into the base isolation layer to suppress excessive deformation of the base isolation layer, and in which a damping device is provided on the lowest floor of the superstructure, which is the floor directly above the base isolation layer. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] "Development of Seismic Isolation Technology for Next-Generation Light Water Reactors (Part 14) Hardening Test of Full-Scale Seismic Isolation Device (Part 1)", Hirotani et al., Structure II, Abstracts of Academic Lectures at the Architectural Institute of Japan Annual Meeting (Tokai), pp.1251-1252, September 2012 [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-237962 Summary of the Invention [Problem to be solved by the invention]

[0009] The above-mentioned Patent Document 1 shows the response evaluation at the time of excessive earthquake input exceeding the notification wave level 2 based on the results of earthquake response analysis of a five-mass model assuming a reinforced concrete structure as the superstructure. This analysis model is shown in Figure 5 (2), and the analysis results are shown in Figures 5 (3) to (5). However, it is assumed that the seismic isolation devices installed in the seismic isolation layer are laminated rubber, steel dampers, and friction stoppers, and the ratio of secondary stiffness to initial stiffness Kr1 (Kr2 / Kr1) is set to 2 to 4 (hardening twice to four times) as the restoring force characteristics of the laminated rubber, and the damping force C of the oil damper (damping device) installed in the lowest layer of the superstructure is set to 0, 100, 200, 300, or 400 tf / (cm / s).

[0010] Figures 5 (3) to (5) show the value of the damping coefficient set for the lowest story of the superstructure, that is, the inter-story deformation angle of each story when an excessive earthquake input occurs due to differences in the capacity of the oil damper (damping device). As can be seen from these figures, the inter-story deformation is reduced on the lowest floor, where the oil damper is installed, but the effect of the oil damper is not seen on the other floors. If the superstructure criterion is an inter-story deformation angle of 0.02 (1 / 50) or less, the safety of the lowest story will be improved by installing an oil damper, but under these conditions, it is not considered necessary to install an oil damper on the lowest story. This is thought to be influenced by the rigidity ratio shown in Figure 5 (2).

[0011] Furthermore, if a reinforced concrete structure is deformed to a story drift angle of 0.02, it is highly likely that it will not collapse, but it will suffer significant damage, and large-scale repairs will be necessary for continued use, and it is thought that a long period of time will be required for reuse or full recovery of functionality. For this reason, there was a need for technology to improve the seismic resistance of the superstructure in the event of an excessive earthquake input.

[0012] The present invention has been made in view of the above, and aims to provide a seismic isolation structure that can improve the earthquake resistance of the upper structure when an excessive earthquake input occurs. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems and achieve the object, the seismic isolation structure of the present invention is a seismic isolation structure comprising a seismic isolation layer and a superstructure arranged above the seismic isolation layer, characterized in that it comprises laminated rubber provided in the seismic isolation layer and having hardening properties that enable the displacement of the seismic isolation layer to be reduced, an elastic-plastic damper and an oil damper provided in the seismic isolation layer, and an oil damper provided in the lowest layer of the superstructure that suppresses vibration of the superstructure.

[0014] Another seismic isolation structure according to the present invention is a seismic isolation structure comprising, in the above-mentioned invention, a seismic isolation layer and a superstructure arranged above the seismic isolation layer, and further comprising laminated rubber having hardening properties that enable the seismic isolation layer to be reduced in displacement, and an elastic-plastic damper and an oil damper provided in the seismic isolation layer, wherein the superstructure is constructed of a wall frame structure in which each layer from the lowest layer to the top layer is made up of a seismic wall.

[0015] Furthermore, another seismic isolation structure according to the present invention is characterized in that, in the above-mentioned invention, the laminated rubber has a ratio of secondary stiffness to initial stiffness set to 2 to 3.5 so as to regulate the horizontal displacement of the seismic isolation layer. [Effects of the Invention]

[0016] The seismic isolation structure of the present invention is a seismic isolation structure comprising a seismic isolation layer and a superstructure arranged above the seismic isolation layer, and is equipped with laminated rubber provided in the seismic isolation layer and having hardening properties that enable the displacement of the seismic isolation layer to be reduced, an elastic-plastic damper and an oil damper provided in the seismic isolation layer, and an oil damper provided in the lowest layer of the superstructure that suppresses vibration of the superstructure, thereby achieving the effect of improving the seismic resistance of the superstructure in the event of an excessive earthquake input.

[0017] Furthermore, another seismic isolation structure according to the present invention is a seismic isolation structure comprising a seismic isolation layer and an upper structure arranged above the seismic isolation layer, and comprising laminated rubber having hardening properties that enable the displacement of the seismic isolation layer to be reduced, and an elastic-plastic damper and an oil damper that are provided in the seismic isolation layer, and the upper structure is constructed of a wall frame structure in which each layer from the lowest to the top is made up of a seismic wall, thereby achieving the effect of improving the seismic resistance of the upper structure in the event of an excessive earthquake input.

[0018] In addition, according to another seismic isolation structure of the present invention, the ratio of secondary stiffness to initial stiffness of the laminated rubber is set to 2 to 3.5 so as to regulate the horizontal displacement of the seismic isolation layer, thereby achieving the effect of appropriately reducing the horizontal displacement of the seismic isolation layer. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1(1) is a schematic diagram (analysis model diagram) showing an embodiment of a seismic isolation structure according to the present invention, and (2) to (4) are diagrams showing restoring force characteristics. [Figure 2] Figure 2 shows the time history waveform of an extremely rare earthquake motion (level 2). [Figure 3] 3(1) to (3) are diagrams showing the analysis results of the embodiment, and (4) to (6) are diagrams showing the analysis results of a normal design using only earthquake motion (level 2) that occurs extremely rarely. [Figure 4] FIG. 4(1) to (3) are diagrams showing the analysis results of the modified examples, and (4) is a diagram showing the ratio of the story deformation angle when excessive earthquake motion is input (Example / Comparative Example). [Figure 5] FIG. 5(1) shows the horizontal load-deformation relationship of a typical laminated rubber, (2) shows a conventional analysis model, and (3) to (5) show the results of conventional analysis. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a seismic isolation structure according to the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the preferred embodiment.

[0021] As shown in Figure 1 (1), a seismic isolation structure 100 according to an embodiment of the present invention comprises a seismic isolation layer 20 on the ground G, and a superstructure 22 disposed above the seismic isolation layer 20. In this embodiment, the seismic isolation structure 100 is assumed to be a 14-story high-rise reinforced concrete building with the seismic isolation layer 20 at the bottom, but the present invention is not limited to this. Furthermore, the seismic isolation structure 100 may be constructed by reinforcing or renovating an existing seismic isolation structure, or may be newly constructed.

[0022] The input earthquake motion for the design target is the extremely rare earthquake motion (Level 2) used in conventional base-isolated structures and excessive earthquake motion (for example, 1.5 times the notified wave Level 2). Regarding the story stiffness and strength of the superstructure 22, the horizontal stiffness and strength of the main structure of the lowest story shall be set to reasonable stiffness and strength for the extremely rare earthquake motion (Level 2). The stiffness and strength of the superstructures other than the lowest story of the superstructure 22 shall be set to satisfy the design criteria for excessive earthquake motion. For example, if earthquake-resistant walls or braces are installed in the superstructures other than the lowest story of the superstructure 22, it is possible to realize a structure that satisfies the design criteria.

[0023] The base isolation layer 20 is provided with laminated rubber 24 having hardening properties that can reduce displacement of the base isolation layer 20, an elasto-plastic damper 26, and an oil damper 28. In addition, the lowest layer of the superstructure 22 is provided with an oil damper 30 that suppresses vibration of the superstructure 22. Note that a friction stopper that restricts horizontal displacement of the base isolation layer 20 may also be provided.

[0024] The ratio of secondary stiffness to initial stiffness of the laminated rubber 24 is set to 2 to 3.5 so as to restrict the horizontal displacement of the seismic isolation layer 20. Specifically, the horizontal restoring force characteristics of the laminated rubber exhibit linear behavior, but when the horizontal deformation exceeds a certain deformation, the secant stiffness increases to 2 to 3.5 times the initial stiffness, and the laminated rubber exhibits hardening behavior.

[0025] The elasto-plastic damper 26 has a bilinear restoring force characteristic. Specifically, when the yield displacement is reached, its rigidity drops sharply, suppressing the increase in shear force due to the progression of horizontal displacement. The elasto-plastic damper 26 can be made of, for example, a steel damper or a lead damper.

[0026] The oil dampers 28 and 30 have bilinear damping force characteristics. The capacity of the oil damper 30 is set to satisfy the design criteria of the superstructure 22 even in the event of excessive seismic motion.

[0027] The seismic isolation structure 100 configured as described above can improve the seismic safety of the superstructure 22 against excessive earthquake motions that are greater than the extremely rare earthquake motions (level 2) that have previously been considered the target of design.

[0028] (Example) Next, an embodiment of the present invention will be described. The effectiveness of the seismic isolation structure 100 was examined. As mentioned above, the input earthquake motion was not only the extremely rare earthquake motion (Level 2), but also 1.5 times the level 2 earthquake motion, which is an excessive earthquake motion. For comparison, a standard study was also conducted using only the extremely rare earthquake motion (Level 2). The seismic isolation layer 20 was equipped with laminated rubber 24 (without built-in damper), oil damper 28, and elasto-plastic damper 26 (steel damper and lead damper).

[0029] The design criteria were as follows: first, the maximum story drift angle of the superstructure 22 must be 1 / 150 (=0.00667) or less for stories made of rigid frame construction, and 1 / 200 (=0.005) or less for stories made of wall-frame construction with shear walls. This not only protects the lives of those inside the building even in the event of an excessive earthquake, but also limits structural damage to a level that allows continued use with minor repairs. Furthermore, the linear limit deformation of the laminated rubber 24 is considered to be 0.5 m, and the limit deformation is 0.8 m. The maximum deformation criteria for the seismic isolation layer 20 are set to 0.5 m or less in the event of an extremely rare earthquake (Level 2), and 0.7 m or less in the event of an excessive earthquake. Furthermore, the maximum response acceleration during an extremely rare earthquake (Level 2) is 2.0 m / s. 2 The following measures were taken to prevent equipment and fixtures inside the building from falling over and to improve livability.

[0030] Next, an earthquake response analysis was carried out using a 15-mass equivalent shear model in which each floor of the superstructure 22 (14th floor) of this example was replaced with one mass (mass 1 to 15) as shown in Figure 1 (1). The upper mass mass mi was set to 1000 ton uniformly for each mass. Figure 1 (2) shows the horizontal restoring force characteristics of the laminated rubber 24 installed in the seismic isolation layer 20. The laminated rubber 24 was assumed to exhibit two-fold nonlinear elastic behavior, and the linear limit deformation was set to 0.5 m. When the horizontal deformation becomes larger than the linear limit deformation, it exhibits hardening behavior in which the shear force rises sharply, and the second stiffness K R 2 is the initial stiffness K R The initial stiffness K is set to 2 to 3.5 times that of 1. R 1 is set so that the period is 4 seconds for the total mass M of the superstructure 22. Two types of elasto-plastic dampers 26 are used (steel dampers and lead dampers). A schematic diagram of the restoring force characteristics of the elasto-plastic dampers 26 is shown in Figure 1 (3). This restoring force characteristic is a normal bilinear model, and the yield displacement d y When the load reaches the yield point Q, the stiffness drops sharply, and the increase in shear force due to the progression of horizontal displacement is suppressed. DAy is 0.04 times the total weight of the superstructure W, and the yield displacement d DAy is 0.03m, stiffness ratio K DA 2 / K DA1 is 0.02. Yield load Q of damper B (assuming a lead damper) DBy is 0.03 times the total weight of the superstructure W, and the yield displacement d DBy is 0.0067m, stiffness ratio K DB 2 / K DB 1 is 0.0001. The oil damper 28 installed in the seismic isolation layer 20 is a bilinear type, with the first viscous damping coefficient C1 being 4712.4 (kNs / m), which corresponds to a damping constant of 10% for a seismic isolation period of 4 seconds, the second damping coefficient ratio C2 / C1 being 0.0678, and the relief speed being 0.32 m / s.

[0031] The superstructure 22 was modeled with the trilinear restoring force characteristics shown in Figure 1(4) for the horizontal deformation-shear force relationship of each story. The bottom story was modeled as a rigid frame structure using the Takeda model, and stories other than the bottom story were modeled as an origin-oriented model with earthquake-resistant walls installed. Table 1 shows the model specifications for the superstructure 22.

[0032] [Table 1]

[0033] The yield shear coefficient αy (= Cy / W) of the bottom story was set to 0.17, based on the response value of an extremely rare earthquake motion (Level 2). The yield shear coefficient αy of the superstructure 22 for stories other than the bottom story was set to 0.3, and was increased according to the number of stories, assuming that the shear force distribution in the height direction follows the Ai distribution. The yield displacement dy of the Takeda model was set to the displacement equivalent to 1 / 150 of the story drift angle, and the yield displacement dy of the origin-oriented model was set to the displacement equivalent to 1 / 200 of the story drift angle. The primary natural period of the superstructure 22 when fixed to its foundation was 0.644 seconds. The oil dampers 30 installed on the bottom story were bilinear, with a first viscous damping coefficient C1 of 4.694×105 (kNs / m), a second damping coefficient ratio C2 / C1 of 0.03, and a relief speed of 0.3 (m / s).

[0034] The input earthquake motion for the study was the notified level 2 JMA Kobe NS phase wave, which is an earthquake motion that occurs extremely rarely (Level 2), and 1.5 times the notified level 2 JMA Kobe NS phase wave, which is an excessive earthquake motion. The time history waveform of the notified level 2 JMA Kobe NS phase wave is shown in Figure 2. Damping is applied only to the superstructure 22, and is an initial stiffness proportional type with a damping constant of 3% for the first natural period of the fixed base.

[0035] As the maximum response values ​​in the earthquake response analysis, the maximum displacement of each mass point is shown in Figure 3(1), the maximum inter-story drift angle of the superstructure 22 is shown in Figure 3(2), and the maximum absolute acceleration is shown in Figure 3(3). Note that Figures 3(1) to 3(3) show the maximum inter-story drift angle of the superstructure 22 when the second stiffness K R 2 is the initial stiffness K R The results are for the case where the input is 3.5 times larger than the reference input. The maximum displacement of the seismic isolation layer 20 is 0.479m≦0.5m at level 2 input and 0.663m≦0.7m at excessive input, both of which satisfy the design criteria. From Figure 3 (1), the maximum story drift angle is below the design criteria shown by the broken line, and therefore satisfies the criteria. The maximum response acceleration at level 2 input is 2.0m / s 2 The following is true, and the design criteria are met. Therefore, the examined example satisfies all the criteria.

[0036] On the other hand, in a normal design that uses only earthquake motions (Level 2) that occur extremely rarely, the superstructure 22 can be designed as a rigid frame structure with the yield shear force coefficient Cy of the lowest story of the superstructure 22 set to 0.17 and the shear force distribution in the height direction assumed to be Ai distribution. The first natural period of the superstructure 22 when the foundation is fixed is 0.84 seconds. The results of earthquake response analysis in this case when a Level 2 input and an excessive earthquake motion are shown in Figures 3 (4) to (6). Note that Figures 3 (4) to (6) also show the case where the maximum story drift angle of the superstructure 22 becomes large, and the secondary stiffness K of the laminated rubber is also used. R 2 is the initial stiffness K R The results are for the case where the earthquake ground motion is 3.5 times larger than the earthquake ground motion 1. The maximum displacement of the seismic isolation layer 20 at the time of input of level 2 is 0.452 m ≦ 0.5 m, the maximum inter-story deformation angle is 0.00267 ≦ 0.0067 (= 1 / 150) at the largest story, and the maximum acceleration is 1.45 m / s2 ≦2.0 m / s 2 This satisfies the design criteria for Level 2 input. However, the maximum story drift angle during excessive earthquake motion (see Figure 3 (5)) is 0.014 (= 1 / 73) at the maximum story (bottom story), which means that the reinforced concrete rigid frame structure will be in a state of moderate to severe damage, and although the functionality of the building is thought to be preserved to a limited extent, some degree of renovation will be necessary for permanent use.

[0037] In the specifications of the example shown in Table 1 for the specifications of the superstructure 22, the shear stiffness and strength of the lowest story as a rigid frame structure are set to stiffness and strength taking into account only earthquake motion (Level 2) that occurs extremely rarely. It is also possible to design the superstructure 22 as a wall frame structure with earthquake-resistant walls on all stories, without installing oil dampers 30 on the lowest story. Table 2 shows the specifications (variant) of the superstructure 22 in this case.

[0038] [Table 2]

[0039] The yield shear coefficient αy of the lowest story is set to 0.3, and a shear wall is also installed in the lowest story. All specifications except for the lowest story are the same as those in Table 1. The design criteria are the same as those applied to the structure in Table 1, but since all stories are wall-frame structures, the criterion for the maximum story drift angle is 0.005 (= 1 / 200) or less for all stories. The analysis results for all stories with wall-frame structures are shown in Figures 4 (1) to (3). The maximum displacement of the seismic isolation story 20 is 0.481 m ≦ 0.5 m at Level 2 input and 0.673 m ≦ 0.7 m at excessive earthquake input, both of which satisfy the design criteria. The maximum story drift angle is 0.005 or less for all stories, also satisfying the design criteria. The maximum response acceleration at Level 2 input is 2.0 m / s 2 The following is true, and the design criteria are met. Therefore, the full-story wall frame structure (modified example) shown in Table 2 also meets all the criteria.

[0040] The maximum story drift angle of each story during excessive earthquake motion input was compared between the above-mentioned Example and the Modified Example. Figure 4 (4) shows the ratio of the story drift angle of each story during excessive earthquake motion input for the case with oil dampers installed in the lowest story (Example) shown in Table 1 to the case with all-story wall frames (Modified Example) shown in Table 2. Due to differences in design criteria, the maximum story drift angle of the lowest story in the Example is 1.45 times that of the case with all-story wall frames. However, in the superstructure 22 above the bottom story, the maximum story drift angle in the Example is reduced by up to approximately 10% compared to the Modified Example. Therefore, in the Example, the maximum story drift angle is reduced in all stories except the bottom story of the superstructure 22 compared to the Modified Example. This is thought to further reduce damage to structural members in all stories except the bottom story, contributing to improved seismic resistance.

[0041] As described above, the seismic isolation structure of the present invention is a seismic isolation structure comprising a seismic isolation layer and a superstructure arranged above the seismic isolation layer, and is equipped with laminated rubber having hardening properties that are provided in the seismic isolation layer and enable the displacement of the seismic isolation layer to be reduced, an elasto-plastic damper and an oil damper provided in the seismic isolation layer, and an oil damper provided in the lowest layer of the superstructure that suppresses vibration of the superstructure, thereby improving the seismic resistance of the superstructure during excessive earthquake input.

[0042] Furthermore, another seismic isolation structure according to the present invention is a seismic isolation structure comprising a seismic isolation layer and a superstructure arranged above the seismic isolation layer, and comprising laminated rubber having hardening properties provided in the seismic isolation layer and capable of reducing displacement of the seismic isolation layer, and an elastic-plastic damper and an oil damper provided in the seismic isolation layer, and the superstructure is constructed of a wall frame structure in which each layer from the lowest to the top layer is made up of a seismic wall, thereby improving the seismic resistance of the superstructure in the event of an excessive earthquake input.

[0043] In addition, according to another seismic isolation structure of the present invention, the ratio of secondary stiffness to initial stiffness of the laminated rubber is set to 2 to 3.5 so as to regulate the horizontal displacement of the seismic isolation layer, thereby enabling the horizontal displacement of the seismic isolation layer to be appropriately reduced.

[0044] The Sustainable Development Goals (SDGs) are 17 international goals that were adopted at the United Nations Summit in September 2015. The seismic isolation structure according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation." [Industrial Applicability]

[0045] As described above, the seismic isolation structure according to the present invention is useful for seismic isolation structures having a seismic isolation layer, and is particularly suitable for improving the seismic resistance of the superstructure in the event of an excessive earthquake input. [Explanation of symbols]

[0046] 20 Seismic isolation layer 22 Superstructure 24 Multilayer Rubber 26 Elastoplastic damper 28 Oil damper 30 Oil damper 100 Seismic isolation structures

Claims

1. A seismic isolation structure comprising a seismic isolation layer and a superstructure disposed above the seismic isolation layer, A seismic isolation structure characterized by comprising laminated rubber provided in the seismic isolation layer and having hardening properties that enable the displacement of the seismic isolation layer to be reduced, an elastic-plastic damper and an oil damper provided in the seismic isolation layer, and an oil damper provided in the lowest layer of the superstructure that suppresses vibration of the superstructure.

2. A seismic isolation structure comprising a seismic isolation layer and a superstructure disposed above the seismic isolation layer, A seismic isolation structure comprising laminated rubber provided in the seismic isolation layer and having hardening properties that enable the displacement of the seismic isolation layer to be reduced, and elastic-plastic dampers and oil dampers provided in the seismic isolation layer, wherein the upper structure is constructed of a wall frame structure in which each layer from the lowest to the top layer is made up of an earthquake-resistant wall.

3. A seismic isolation structure as described in claim 1 or 2, characterized in that the ratio of secondary stiffness to initial stiffness of the laminated rubber is set to 2 to 3.5 so as to regulate the horizontal displacement of the seismic isolation layer.

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