Seismic isolation building

Abstract

This invention provides a rational and economical configuration and construction method for the seismic isolation layer and the seismic isolation layer foundation structure in a seismically isolated building. [Solution] In the seismic isolation layer, sliding bearings with a rotation mechanism that can absorb the inclination angle of the support points during an earthquake are used at all load support points that support the weight of the superstructure, and seismic isolation devices (restoring materials) for horizontal restoring force are placed in positions that do not support the weight of the building. The beams that restrain the rotational bending deformation associated with the horizontal deformation of the restoration material are positioned in an inverted beam shape above the seismic isolation layer slab, and their ends are not connected to the foundation structure directly below the sliding bearings. Only the seismic isolation layer slab is placed on the lower floor surface of the seismic isolation layer, and no underground beams are placed to connect the foundation structure directly below the sliding bearings that support the weight of the building.

Description

[Technical Field]

[0001] The present invention relates to a method for constructing a seismic isolation building. [Background Art]

[0002] As a structural method for improving the safety of buildings against earthquakes, there is a seismic isolation structure. A seismically isolated building (hereinafter referred to as "base-isolated building") is composed of three parts: a lower structure such as a foundation, an upper structure which is the target building, and a seismic isolation layer provided between the lower structure and the upper structure.

[0003] It is generally understood that the seismic isolation layer is composed of an isolator (seismic isolation bearing) that horizontally deforms while supporting the weight of the upper structure, and a damper that does not support weight but is intended to absorb vibration energy (seismic input energy) during an earthquake. There are also seismic isolation bearings that have both functions. Various types of laminated rubber bearings, sliding bearings, rolling bearings, and the like are known as isolators.

[0004] As specific examples of seismic isolation devices, for laminated rubber bearings, natural rubber-based laminated rubber bearings are the basic type , and high-damping laminated rubber bearings that combine this restoring function with a damper function, plug-inserted laminated rubber bearings such as those with lead plugs and tin plugs, have been developed. There also exist restoring rubber devices that use non-laminated rubber bodies which do not support weight and are only intended for providing horizontal restoring force. . As sliding bearings, there are "elastic sliding bearings" (Patent Document 1) that use relatively thin laminated rubber bodies,[1] and "rigid sliding bearings" (Patent Document 2) that do not use laminated rubber bodies.

[0005] On the other hand, when focusing on the "mounting conditions and installation conditions" of seismic isolation devices, the following perspectives are premised. Generally, seismic isolation devices control their horizontal resistance to the relative horizontal displacement between the foundation on the ground side and the superstructure. Any seismic isolation device assumes horizontal shear deformation between the upper and lower structures, and if the support point on the foundation side below the device is tilted, the horizontal performance of the device will be affected.

[0006] For seismic isolation devices to exhibit stable horizontal performance, it is generally necessary for laminated rubber bearings to have their support point inclination angle suppressed to 1 / 100 (rad) or less, and for elastic sliding bearings with thin rubber layers in the laminated rubber body, it is necessary to limit the inclination angle during an earthquake to 1 / 200 (rad) or less. In a sliding bearing, during sliding motion, the contact surface between the sliding material and the sliding plate is in full contact condition. Maintaining this is a necessary and important condition. To provide stable sliding performance without being affected by the inclination angle of the ground-side support point during an earthquake, a "sliding bearing with a rotation mechanism" (Patent Document 3) and its advanced version, a "two-stage sliding bearing with a rotation mechanism" (Patent Document 4), have been realized. These sliding bearings incorporate a pin support point that can absorb the inclination angle of the support point in all directions (360°) with respect to the vertical axis of the seismic isolation device. In Japan, the initial approach to constructing base-isolated buildings using these various seismic isolation devices involved placing various types of laminated rubber bearings under each column, and then combining these with laminated rubber bearings that also function as dampers, or with separate dampers that do not support the weight of the building.

[0007] Subsequently, with the practical application of seismic isolation devices such as sliding bearings, the construction method for seismically isolated buildings has become: The number of cases employing "a construction method that combines laminated rubber bearings and sliding bearings" (Patent Documents 5 and 6) has increased.

[0008] Furthermore, even if the support point lifts up during an earthquake, a method has been proposed (Patent Document 7) to maintain the resistance of the laminated rubber at that location by using a seismic isolation device in which a sliding bearing is connected in series to the upper side of the laminated rubber, and by connecting the upper flanges of adjacent laminated rubbers. This allows the laminated rubber below to experience the same horizontal displacement as the adjacent laminated rubber, even if the sliding bearing above lifts up, thereby enabling the seismic isolation device at the lifting point to also exert horizontal resistance.

[0009] Furthermore, if uplift occurs in a base-isolated building, rocking vibrations occur throughout the entire building, causing tilting deformation. A proposal for a base-isolated building (Patent Document 8) has also been made to restrain and suppress the tilting deformation of the building that occurs due to this rocking. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2005-54447 (Elastic sliding bearing) [Patent Document 2] Japanese Patent Publication No. 2003-301625 (Rigid sliding bearing) [Patent Document 3] Japanese Patent Publication No. 2023-103898 (BSL) [Patent Document 4] Patent Application No. 2024-126058 (BSL-WS) [Patent Document 5] Japanese Patent Publication No. 2018-84100 (Laminated rubber + 2 types of sliding bearings) [Patent Document 6] Japanese Patent Publication No. 2022-014608 (Laminated rubber + elastic sliding bearing) [Patent Document 7] Japanese Patent Application No. 2012-129337 (Series connection of laminated rubber and sliding bearing) [Patent Document 8] Japanese Patent Application No. 10-311162 (Rocking Prevention Seismic Isolation) [Overview of the project] [Problems that the invention aims to solve]

[0011] As described above, various proposals have been made regarding the construction method of base-isolated buildings, utilizing various base isolation devices that have been realized to date. However, in any case, for base isolation devices to perform normally, regardless of the type of base isolation device, they need to undergo horizontal shear deformation. Therefore, it is usually necessary to have beams of the superstructure above the base isolation layer where the base isolation devices are placed, and to have underground beams on the base of the base isolation layer floor below the base isolation layer that connect the foundations supporting the base isolation devices. Therefore, floor slabs and beams are present above and below the seismic isolation device, and constructing a seismic isolation layer adds one extra layer to the structural frame of a seismically isolated building. This increase in structural frame by one layer due to the construction of the seismic isolation layer is a major factor in the increased cost of seismically isolated buildings and a major reason hindering their widespread adoption.

[0012] To address this challenge, a sliding bearing with a rotation mechanism, known as BSL (hereinafter referred to as BSL seismic isolation device or simply BSL), has been developed, which incorporates a pin support that can absorb the tilt angle of support points such as pile heads during an earthquake. A "BSL pile head seismic isolation method" has also been developed, which involves placing this device in the seismic isolation layer.

[0013] However, since the BSL seismic isolation device is a sliding bearing and does not possess horizontal restoring force, it is necessary to combine it with a restoring material such as laminated rubber in order to construct a seismically isolated building. This has been realized as a hybrid seismic isolation method combining "restoring material (laminated rubber) + BSL". In this case, since the pivot point of the BSL, which has a rotation mechanism, can tolerate the seismic tilt angle of the pile head, underground beams are not required at the locations connecting the BSL pivot points. On the other hand, at support points where laminated rubber bearings are placed to provide restorative force, it is necessary to suppress the seismic tilt angle of the pile head to about 1 / 100 (rad) or less, making the placement of underground beams essential.

[0014] As seen in the example of large-scale logistics warehouses that have been attracting attention in recent years, for a seismically isolated building with an extremely large planar shape where the length of one side exceeds 100 meters, the number of fulcrums where the seismic isolation device BSL is arranged increases, and there are more positions where underground beams connecting BSLs can be omitted. Therefore, this BSL pile head seismic isolation method can exert a very large economically beneficial effect.

[0015] On the other hand, when the scale of a seismically isolated building is small, the effect of omitting underground beams provided by this pile head seismic isolation method cannot be sufficiently exerted. For example, in the case of a square-plan building with only four columns (four-column structure), the arrangement of laminated rubber must be prioritized at the fulcrums, so sliding bearings BSL cannot be arranged, resulting in no BSL being provided. Next, in the case of a H-shaped planar building (six-column structure), laminated rubber is provided at the four corner positions, and BSLs are arranged at only two positions. There is only one underground beam with BSLs at both ends, and the reduction effect among the total seven underground beams is only 1 / 7.

[0016] Next, in the case of a #-shaped planar building with eight columns, laminated rubber is provided at the four corners, and four BSLs are provided at other positions. Therefore, there are four underground beams connecting BSLs to each other, and the reduction effect among the total ten underground beams is 4 / 10 = 2 / 5 Next, in the case of a grid-shaped planar building (nine-column structure), laminated rubber is provided at the four corners, and five BSLs are provided at other positions. Therefore, there are four underground beams connecting BSLs to each other, and the reduction effect among the total twelve underground beams is 4 / 12 = 1 / 3

[0017] As described above, in the BSL pile head seismic isolation construction method adopting the sliding bearing BSL with a rotation mechanism, for a building with a large planar shape, the economic effect of omitting pile head underground beams on the seismic isolation layer floor can be greatly expected. However, for common buildings such as the numerous small-scale condominiums existing in society, the economic effect obtained by omitting underground beams cannot be sufficiently exerted. The current situation is that the pile head seismic isolation construction method has not become a breakthrough for the popularization of seismic isolation structures in general small to medium-sized seismically isolated buildings. [[Means for Solving the Problem]]

[0018] This invention was made to solve the above problems, and the following configuration is a means to solve the above problems and achieve the objective. <Configuration 1> (BSL + seismic isolation layer slab at all support points, no underground beams) A base-isolated building having multiple base isolation devices between the substructure and the superstructure, and having the following characteristics. (a) The seismic isolation device comprises two types of bearings: a sliding bearing that supports the vertical load of the superstructure and is capable of horizontal movement, and a horizontal restoring force device that exerts a horizontal restoring force to return the superstructure to its original position in response to the relative horizontal displacement of the superstructure with respect to the substructure. (b) The sliding support consists of two parts: a sliding plate and a slider, the sliding plate being a flat plate and fixed to the superstructure. (c) The slider positioned below the sliding plate has a sliding material on its upper surface or its upper surface is treated to be a sliding surface. The slider body located below it is for absorbing the tilt angle of the lower structure during an earthquake, and is separated into two or three members vertically, with each contact surface being a combination of a concave sphere and a convex sphere with different radii of curvature. (d) The sliding bearings are placed at all of the vertical load support points on which the weight of the superstructure acts. (e) The horizontal restoring force device is positioned at a location other than the vertical load support point, and at a location where the sum of the rotational moments around the vertical axis of the center of gravity due to the horizontal restoring force is approximately zero with respect to the center of gravity of the superstructure. (f) The substructure has a foundation frame that supports the sliding bearing directly below the sliding bearing and a seismic isolation layer slab covering the entire underside of the seismic isolation layer, but does not have underground beams connecting the foundation frame.

[0019] <Configuration 2> (BSL for sliding bearings + rubber bearings for restoring material) In the seismically isolated building described in Configuration 1, A base-isolated building characterized in that the sliding bearing and the horizontal restoring force device are as follows. (a) The sliding bearing is a sliding bearing with a rotation mechanism for absorbing the tilt angle of the lower structure during an earthquake, wherein the slider constituting the sliding bearing is composed of two members, in the order from top to bottom, a convex member having a convex spherical surface on its contact surface and a concave member having a concave spherical surface on its contact surface, or three members, a concave member, a convex member, and a concave member, and the radius of curvature r of the convex spherical surface and the radius of curvature R of the concave spherical surface are in the relationship r≪R. (b) The horizontal restoring force device is a rubber bearing that includes either a laminated rubber bearing or a non-laminated rubber body, or both. (c) The laminated rubber bearing is one or a combination of a natural rubber laminated rubber bearing, a high-damping rubber laminated rubber bearing, or a plug-insertion type laminated rubber bearing containing lead, tin, or other plugs. (d) The rubber bearing is fixed to an upper mounting body which is integrated with the main beam, secondary beam or slab of the superstructure on the upper surface of the device, and to a lower mounting body which is integrated with an inverted beam type mounting beam which is configured in an inverted beam shape on the upper side of the seismic isolation layer slab or the seismic isolation layer slab. (e) The inverted beam type mounting beam is integrated with the seismic isolation layer slab, but is not connected to the foundation structure.

[0020] <Configuration 3> (Heterogeneous foundation structure method and its combination) In a seismically isolated building as described in Configuration 1 or 2, A base-isolated building characterized in that the foundation work, pile work, etc. (hereinafter referred to as "foundation structure method") that supports the foundation frame directly below the sliding bearing, which is integrated with the base isolation layer slab, is one of the following. (a) A foundation structure method using a direct foundation in which the foundation frame is in direct contact with the supporting ground. (b) A foundation structure system using short piles, in which the foundation frame is supported by one or more short piles. (c) A foundation structure system using long piles, in which the aforementioned foundation frame is supported by one or more long piles. (d) A foundation structure that employs one of the following pile types as described in (b) and (c) above: cast-in-place concrete piles, various types of precast concrete piles, various types of steel pipe piles, steel pipe concrete piles, or connected piles of steel pipe piles and precast concrete piles. (e) A foundation structure that employs different pile types as described in (d) above in different foundation structures. (f) A mixed foundation structure that uses different foundation structure methods described in (a) to (e) above.

[0021] <Configuration 4> (without seismic isolation layer slab) In a seismically isolated building as described in configuration 1, 2, or 3, A base-isolated building characterized in that a portion of the base isolation layer slab in the substructure is removed, or the entire base isolation layer slab is removed. [Effects of the Invention]

[0022] (Effects of Configurations 1 and 2) First, let's explain the effect of Configuration 1, in which all support points are sliding bearings with a rotation mechanism. (Effect 1: No need for underground beams in small buildings → Cost reduction and shorter construction period) In a hybrid seismic isolation method using a combination of a sliding bearing with a rotating mechanism, such as the BSL seismic isolation device, and laminated rubber, as described in paragraphs 0014 to 0016, the economic benefit of being able to omit the underground beams in the seismic isolation layer pit due to the effect of the sliding bearing with a rotating mechanism (BSL seismic isolation device) has not been realized to a great extent in conventional small-scale seismic isolation buildings. However, in this invention, regardless of the size of the seismic isolation building, it is possible to omit all underground beams connecting the support points of all seismic isolation devices. In short, the effect of this invention is that "all underground beams on the seismic isolation layer floor surface are unnecessary, regardless of the size of the seismically isolated building."

[0023] In a seismic isolation layer pit, if sliding bearings with a rotation mechanism are installed at both ends of the underground beam, the underground beam is unnecessary. However, if there are laminated rubber bearings for restoration at both ends or one end, the underground beam needs to be installed to suppress the tilt angle of the pile heads during an earthquake at the support points where the laminated rubber bearings are located. Even small-scale seismically isolated buildings require at least four laminated rubber bearings for restorative purposes, meaning that laminated rubber bearings will be placed at least at the four corners of the building. This has been the conventional wisdom, and from the perspective of seismic isolation device costs, the method of placing laminated rubber bearings at the four corners of the building and sliding bearings with rotational mechanisms at the remaining points has been considered economically rational, and this arrangement policy and plan has been fully adopted in the design of actual seismically isolated buildings.

[0024] However, in this invention, instead of focusing solely on the cost of seismic isolation devices, we take a comprehensive approach that includes the seismic isolation devices, seismic isolation layer pits, and foundation structure as a whole. By arranging sliding bearings with a rotation mechanism at all support points, while the cost of the devices alone increases, we have achieved a far greater advantage in many respects, not just economically, by "eliminating the need for underground beams throughout the entire building."

[0025] Generally, the columns at the four corners of a building have a load-bearing area that is only about one-quarter that of the central columns, so their long-term support weight is relatively small. However, as laminated rubber bearings for restoration, it is necessary to ensure the horizontal deformation performance during the largest possible earthquake, so even if the support load is small, small laminated rubber bearings cannot be used. In contrast, with a rotating sliding bearing BSL, the device size can be selected according to the magnitude of the support load. Since a smaller size device can be selected for the BSLs at the four corners of a building where the long-term support load is small, the additional cost for the BSLs at the four corners will be relatively small. On the other hand, the cost reduction effect of eliminating underground beams for the entire building is very significant, and because there are no underground beams, the bottom of the seismic isolation pit foundation becomes flat, which reduces the amount of excavated soil for the foundation and greatly increases excavation efficiency, resulting in a considerable reduction in construction time.

[0026] (Effect 2: Restoration equipment can be streamlined → Cost reduction and shortened construction period) By using sliding bearings with a rotation mechanism at all support points, the position of the laminated rubber, which acts as a restorative material, away from the points supporting the building's weight, produces another significant effect. In other words, the horizontal deformation performance of laminated rubber is mainly governed by two factors: 1) the amount of horizontal shear deformation of the rubber layer and 2) the buckling phenomenon associated with horizontal deformation. However, eliminating the need for load support performance in the laminated rubber of the restoring device frees the laminated rubber from the constraints of the buckling phenomenon mentioned in 2). As a result, the deformation performance of the laminated rubber is improved, and at the same time, the degree of freedom in its shape and specifications is greatly increased, making it possible to make economically advantageous choices. In other words, since laminated rubber is no longer susceptible to buckling, it becomes possible to select smaller diameter laminated rubber or laminated rubber with a large layer thickness and fewer layers when the building weight is small, and in the extreme case, it becomes possible to select a single layer of rubber as a restorative material, which has a significant economic effect.

[0027] (Effect 3: Rationalization of the fixing method for the restoration device, inverted beam method → ​​cost reduction and shortened construction period) The placement of the non-load-bearing restoring devices will be at any location other than the building's support points. Since only a slab exists beneath the seismic isolation pit, the restorative material (laminated rubber for restoration) is installed by placing the lower attachment body of the restorative material on the slab of the seismic isolation pit, and its bending deformation is restrained by placing an inverted beam-type attachment beam on the upper surface of the slab. Reinforcement work can be done on the upper surface of the pit slab, and formwork construction is also done by installing beam-type side formwork on the slab surface, and concrete pouring is also done on the slab, making the work extremely easy and efficient. Moreover, the ends of the inverted beam are not connected to the foundation structure of the support points of the device (they should not be connected in order to not bend and restrain the foundation structure of support points such as pile heads), so bending and anchoring of the beam reinforcement ends is unnecessary, the reinforcement shape is extremely simple, and the reinforcement work is easy.

[0028] (Effect 4: Increased freedom in the placement of the restorative material, improved eccentricity and torsional control) Furthermore, the degree of freedom in the placement of the restorative materials on the building's plan is greatly improved. Two important points regarding the placement of the restorative materials are that their resistance force is not eccentric with respect to the building's center of gravity, i.e., the eccentricity ratio is as close to zero as possible, and at the same time, the torsional resistance force provided by the restorative materials is as large as possible. Since the placement of the restoration material is not restricted by the building's column positions, any position can be freely selected. Therefore, a position where the resistance force of the restoration material is symmetrical with respect to the building's center of gravity, and as far away from the building's center of gravity as possible, is advantageous.

[0029] (Effects of Configuration 3) (Effect 5: It became possible to use and mix different types of foundations.) In the design of building foundations, the conventional principle from the perspective of seismic design was that the use of different types of foundations within a single building should be avoided. In other words, a design in the same building where direct foundations, short pile foundations, and long pile foundations are mixed depending on the position of the columns is not acceptable according to conventional structural design standards. This is because it is not easy to determine the seismic load at each foundation location, and there are many uncertainties in terms of seismic design, which may be dangerous.

[0030] However, in this invention, which employs sliding bearings with a rotation mechanism at all column support points and does not restrict the rotational performance of the foundation structure during earthquakes, even if different rotation angles (tilt angles) occur at each column support point, the sliding bearings with a rotation mechanism at each support point absorb their respective tilt angles during earthquakes, thus avoiding any impact on the sliding performance at each location. Therefore, the occurrence of different tilt angles during earthquakes at each support point does not pose an obstacle to seismic design.

[0031] In real-world building design, ground conditions at construction sites vary considerably. Depending on the column location, there may be cases where the supporting layer is shallow and direct foundations are appropriate, or conversely, cases where the supporting ground is deep and long piles are required. In such cases, it has been extremely difficult to design with a unified foundation method for all column locations, as it has been required to avoid mixing different types of foundations. As a result, in some locations, it becomes necessary to use unsuitable foundation methods that are not appropriate for the ground conditions.

[0032] In contrast, the present invention does not require uniform control of the support point inclination angle during an earthquake at each column location. Therefore, it is possible to freely select and adopt a foundation structure method that suits the ground conditions at each column location, and the design of the foundation structure can be carried out very rationally in accordance with the ground conditions. In the design of foundation structures, the ability to freely mix different types of foundations is a groundbreaking development compared to conventional design methods that prohibited the use of different types of foundations.

[0033] (Effect of Configuration 4) (Effect 6: Eliminated the need for a rigid foundation assumption → Allowed for input of different seismic motions) In conventional seismic design for buildings, the principle is that the seismic motion input to the building is the same at all column locations and foundation input locations. While there is no guarantee that the actual seismic motion input to buildings satisfies this condition, conventional seismic design techniques for real buildings can only cope with the simplified condition that the same seismic motion is input at the foundation position of each column support point. To this end, at the foundation level of the building, a rigid RC foundation slab is poured across the entire building, and seismic design is carried out assuming that a rigid floor condition (horizontal displacement at each column position moves in the same way) is met throughout the entire building. In the building design, the seismic design system is constructed on the premise that the rigid floor condition is met on each floor of the superstructure, and in the design of the foundation structure, the seismic design system for the foundation structure is constructed on the premise that this rigid floor condition is met at the foundation level and at the input points of seismic motion.

[0034] However, in recent years, examples of designs for extremely large buildings with side lengths well over 100 meters have emerged, raising serious doubts about whether the conditions for a rigid floor at the foundation level and the premise that the same seismic motion is applied to each column position are met. For example, because the side length is very large, the depth of the supporting layer in the ground may vary greatly depending on the location. In terms of seismic motion input, the problem of a time difference in input seismic motion depending on the direction in which the seismic motion is transmitted, known as the phase difference input problem, becomes a practical challenge.

[0035] To address these complex challenges in seismic design, recent advancements have made it possible to construct 3D FEM analysis models of the ground over a fairly wide area centered on the building's location, perform 3D nonlinear propagation analysis of seismic motion, and determine the input seismic motion based on the planar location within the building. Furthermore, in the seismic response analysis of buildings, it is also possible to perform time-history seismic response analysis using "simultaneous multi-point input," where different seismic motions are input depending on the planar location of the foundation. These specialized seismic design methods are currently extremely advanced technologies and are not yet commonplace as design methods. However, the applicant has gained new insights into this problem through their previous experience in design and analysis.

[0036] To summarize briefly, in simultaneous multi-point input analysis of a building, when different seismic motions are input depending on the location, the effects of the input seismic motions cancel each other out due to the differences in seismic motions at each location. It has been found that the most stringent condition for inputting seismic motions to a building is almost always when the same seismic motion with the same phase is input to the entire building. Furthermore, numerous analysis results have been obtained showing that even in phase difference input problems involving time lags in large buildings, relatively severe torsional vibrations are not induced.

[0037] Based on these analysis results, the conventional rigid floor assumption that "the movement of each column in the horizontal plane is controlled uniformly" at the building's foundation is a conservative assumption in evaluating the seismic performance of a building, but it can be concluded that "it is not necessarily an indispensable absolute condition for seismic design." In other words, configuration 4 of the present invention incorporates the cutting-edge finding that "rigid floor conditions at the foundation input position can be made unnecessary for seismic design," thereby increasing the degree of freedom in foundation design and opening the way to rational and economical design. However, since this knowledge is considered to be specialized knowledge possessed by only a very small number of engineers, including the applicant, at present, we believe that we should avoid carelessly extending its application to people who do not fully understand this issue. [Brief explanation of the drawing]

[0038] [Figure 1] This is a conventional seismically isolated building that uses a combination of restoration devices and sliding bearings. (1) is a floor plan (downward view) of the lowest floor (1st floor) of the superstructure, and (2) is a diagram (downward view) of the arrangement of seismic isolation devices in the seismic isolation layer. [Figure 2] The present invention is a seismically isolated building that uses a combination of a restoration device and a sliding bearing, (1) is a plan view (downward view) of the lowest floor (1st floor) of the superstructure, and (2) is a diagram (downward view) of the arrangement of seismic isolation devices in the seismic isolation layer. [Figure 3] These are cross-sectional diagrams of the seismic isolation layer: (1) is a cross-sectional diagram of a conventional seismic isolation building; (2) is a cross-sectional diagram of the seismic isolation building of the present invention, showing the column alignment; and (3) is a cross-sectional diagram of the seismic isolation building of the present invention, showing the alignment of the restoration materials. [Figure 4] Diagrams illustrating the slider configuration of a sliding bearing with a rotation mechanism: (A) is a 3-member configuration, (1) is a plan view of the upper recessed member, (2) is a cross-sectional view, and (3) is a plan view of the lower recessed member. (B) is a 2-member configuration, (1) is a plan view of the upper convex member, (2) is a cross-sectional view, and (3) is a plan view of the lower recessed member. (B') is the same as (B) for the 2-member configuration, but rotated by 45°. (1) is a plan view of the upper convex member, (2) is a cross-sectional view in the diagonal direction, and (3) is a plan view of the lower recessed member. [Figure 5] Full-scale demonstration test results confirming that the inclination angle of the support point (pile head) does not affect the sliding performance of the sliding bearing with a rotation mechanism. [Figure 6] Arrangement of seismic isolation devices and foundation structure plan for a large-scale base-isolated building (1) Arrangement plan of seismic isolation devices (plan view) (2) Cross-sectional diagram of the seismic isolation layer and foundation [Modes for carrying out the invention]

[0039] Embodiments of the present invention will be described in detail below with reference to the drawings. (Figure 1: Conventional seismic isolation device layout plan) Figure 1 shows the arrangement of devices in a conventional seismic isolation building and the configuration of the structures above and below it, for comparison with Figure 2 which explains the features of the present invention. Figure 1(1) is a top-down view showing the floor plan of the lowest level (1st floor) of the superstructure, and Figure 1(2) is a top-down view showing the arrangement of seismic isolation devices in the seismic isolation layer. When a seismic isolation device is "composed of a combination of sliding bearings and horizontal restoring force devices (abbreviated as restoring members)", as illustrated in Figure 1(2), in relatively small seismically isolated buildings, the restoring members are placed at the four corners of the building, and sliding bearings are placed at the other column positions.

[0040] In this case, as shown in Figure 1(1), a main beam connecting all the columns is placed on the floor surface of the superstructure. In the seismic isolation layer pit floor surface shown in Figure 1(2), underground beams are required at the positions indicated by dashed lines in order to suppress the seismic tilt angle of the support points (pile heads) of the restoration materials (represented by laminated rubber bearings) placed at the four corners. If "sliding bearings with a rotation mechanism" are used for the sliding bearings, underground beams can be omitted if both ends are sliding bearings with a rotation mechanism. However, looking at the entire seismic isolation layer, as long as the reinforcing material is present, it is not possible to omit all of the underground beams. In this example, of the 12 underground beams in total, only the four beams in the central cross shape can be omitted.

[0041] (Figure 2: Arrangement of the seismic isolation device of the present invention and plan of the superstructure and substructure) Figure 2 shows the arrangement method of the seismic isolation device of the present invention and the configuration plan of the superstructure and substructure in the same building plan as Figure 1. The distinguishing feature of this invention is the placement of "sliding bearings with a rotating mechanism" at all nine column positions (support points) that support the weight of the superstructure. That is, in Figure 2(2), sliding bearings with a rotating mechanism 21 are placed below all column positions. As a result, no underground beams are placed in the floor slab of the seismic isolation layer pit, and only the floor slab 41 exists in the floor of the seismic isolation layer pit.

[0042] On the other hand, the horizontal restoring force device (restoring member) 30 is positioned at a location other than the column's support point, and this restoring member (laminated rubber) does not bear the vertical load. Therefore, if this restoring member is a laminated rubber bearing or a rubber bearing consisting only of rubber, buckling due to horizontal deformation will not occur, and horizontal shear deformation due to the stretching deformation of the rubber material will be exerted.

[0043] (Figure 3: Explanatory diagram of the cross-sectional structure of the seismic isolation layer, (1) in the case of conventional seismic isolation, (2)(3) in the case of the present invention) The installation methods for the seismic isolation devices 20 and 30 are shown in the plan view in Figure 2(2) and the cross-sectional view in Figure 3(3). Specifically, the upper surface of the restoration material 30 is fixed to an upper mounting body 31 which is integrated with the superstructure 1, and the lower surface of the device 30 is fixed to a lower mounting body 32 which is integrated with the floor slab 41 of the seismic isolation layer pit. The upper mounting body 31 is integrated with the floor slab 11 and the superstructure 1 by the joist 14 of the superstructure. The lower attachment body 32 is restrained from bending deformation (rotation) by an inverted beam-type attachment beam 43 configured in an inverted beam shape on the upper side of the seismic isolation layer slab 41, and this inverted beam-type attachment beam 43 is not connected to the foundation structure 44 and piles 45 of the sliding bearings located at the load support points. Therefore, the inverted beam-type attachment beam 43 that restrains the bending deformation of the restoration member 30 during an earthquake does not receive rotational deformation of the pile heads during an earthquake, and no seismic stress is generated from the pile heads. This inverted beam-type attachment beam 43 is positioned to restrain the rotational deformation of the restoration member 30 during an earthquake, and the end connected to the restoration member 30 bears bending stress, but the opposite end of this beam 43 is stopped at the slab position, and the bending stress at that end during an earthquake is zero, and it only transmits shear force to the slab 41.

[0044] With the above configuration, the seismic isolation layer structure of the present invention requires only a floor slab 41, and achieves a configuration in which there are no underground beams whatsoever in the seismic isolation layer. In other words, in the cross-sectional view of a conventional seismic isolation system, Figure 3(1), there is an underground beam 42 beneath the seismic isolation layer slab 41, and because it is integrated with the foundation frame 44 and piles 45 of the lower structure below the seismic isolation device, large seismic stresses are generated during earthquakes due to rotational deformation of the pile heads. In contrast, in the present invention, as shown in the cross-sectional views of Figures 3(2) and (3), there is no underground beam itself in the seismic isolation layer pit, resulting in a structural form in which pile head stresses are not generated due to the tilting of the pile heads during earthquakes.

[0045] Furthermore, as shown in the cross-sectional view of the present invention, Figures 3(2) and (3), the lower surface of the seismic isolation layer floor slab 41 has no beam-like structure and is a simple flat plate shape. This makes the excavation work for the foundation simple and easy, and along with the reduction in the amount of excavated soil, earth retaining and formwork construction for underground beam-like structures become unnecessary. As a result, the efficiency of the excavation work is greatly increased, and the earthwork and foundation work becomes extremely economical.

[0046] Furthermore, as shown in Figure 3(3), the inverted beam-type mounting beam 43 that restrains the rotational deformation of the restoration material 30 in the present invention is positioned above the seismic isolation layer pit floor slab 41. Therefore, the reinforcement work on the beam cross section and the formwork construction on the beam sides can be carried out on this floor slab 41, and the concrete pouring work is also extremely easy.

[0047] (Figure 4: Method for constructing the slider rotation mechanism to form a "sliding bearing with rotation mechanism") If the support points, such as the pile heads supporting the sliding bearing, tilt during an earthquake, the sliding performance of the sliding bearing, which is based on full-surface contact conditions, may be significantly affected. To avoid the effects of the tilt angle of the sliding bearing support points during an earthquake, a rotation mechanism capable of absorbing the tilt angle of the support points is required between the sliding material located on the upper surface of the sliding bearing slider or the sliding surface and the lower support point. Figure 4 shows a method for introducing a rotation absorption mechanism to the slider of a sliding bearing. In all cases, the slider needs to be divided into two or three members. Figure 4(A) shows the case with three members, Figure 4(B) shows the case with two members, and (B') is (B) rotated by 45°.

[0048] The left side (A) of Figure 4 shows a slider configuration consisting of three members, with an intermediate double-sided convex member placed between the upper concave member and the lower concave member. In all cases, the contact surface of the concave member is a concave spherical surface, and the contact surface of the convex member is a convex spherical surface, and the radius of curvature r of the convex spherical surface and the radius of curvature R of the concave member are in the relationship r≪R. The two rightmost columns (B) and (B') in Figure 4 show a case where the slider is constructed with two members, with the upper member being a convex member and the lower member being a concave member. The radii of curvature of the contact spherical surfaces of the two members similarly have the relationship r≪R.

[0049] The displacement-limiting bolt (guide pin) 244, fixed to the lower recessed member shown in the planar corner of Figure 4(B)(B') and inserted into the loose hole 246 with ample clearance in the upper convex member, is a safety guide measure that prevents excessive lateral displacement of the planar positions of both the upper and lower members while allowing relative inclination.

[0050] Figure 4(B')(2) shows a positioning suspension eyebolt 245 that fits almost perfectly into the inner diameter of the loose hole 246 above the guide pin 244 provided at the corner of the upper convex member. This eyebolt 245 facilitates suspension and handling during equipment assembly work in the factory, and also enables accurate positioning of the relative horizontal position of the lower recess member and the upper convex member during on-site installation work of the equipment. Furthermore, this eyebolt will be removed after the slider installation work is completed on-site.

[0051] (Figure 5: Effect of "sliding bearing with rotating mechanism": Demonstration data showing no effect on sliding performance due to support point inclination angle) Figure 5 shows the results of measuring the change in the sliding friction coefficient when a sliding performance test was conducted using an actual BSL sliding bearing with a rotation mechanism, while applying a variable inclination (where the inclination angle also changes in response to the horizontal sliding displacement) with the maximum inclination angle of the support point set to 0 (no inclination), 1 / 50, 1 / 33, and 1 / 20 (rad). As shown in this figure, when the maximum tilt angle of the support point is ±1 / 50 (rad), the sliding friction coefficient ratio is 1.006 (0.6% variation) compared to no tilt; when the maximum tilt angle of the support point is ±1 / 33 (rad), the sliding friction coefficient ratio is 0.997 (-0.3% variation); and when the maximum tilt angle of the support point is ±1 / 20 (rad), the sliding friction coefficient ratio is 0.995 (-0.5% variation). These test results confirm that with the BSL sliding bearing with a rotation mechanism, the sliding performance does not change by more than 1% even when an earthquake tilt angle of 1 / 20 (rad) occurs at the support point. Furthermore, the maximum tilt angle of the pile head during an earthquake is approximately 1 / 50 to 1 / 40 (rad), and BSL ensures an allowable tilt angle twice that of the above.

[0052] In this invention, sliding bearings with a rotation mechanism are employed at all column support points, and the rotational performance of the foundation structure at these support points during an earthquake is not constrained. Therefore, if the ground conditions differ, such as the depth of the supporting layer of the ground varying depending on the location of the support point, it is assumed that the inclination angle of the support point (pile head) during an earthquake will vary depending on the location of the support point. However, even if the inclination angle of the support point during an earthquake varies wildly depending on the location, the sliding bearing with a rotation mechanism can avoid the influence of the inclination angle of the support point, thus ensuring that stable sliding performance can always be achieved. To put it another way, "if you use sliding bearings with a rotating mechanism at all support points, you don't need to worry about the differences in the seismic tilt angles of each support point during a major earthquake."

[0053] (Figure 6: Design example of a seismically isolated building with a mixture of various types of foundations) In real-world building design, ground conditions at construction sites vary considerably. Depending on the location, some sites may have shallow supporting layers where direct foundations are appropriate, while others may have deep supporting layers requiring long piles. This is especially true for large buildings, where ground conditions can differ significantly even within a single building depending on the column placement. In response to these conditions, the present invention does not require uniform control of the support point inclination angle during an earthquake at each column location. Therefore, it is possible to freely adopt different foundation structure methods tailored to the ground conditions at each column location, and to select and design an appropriate foundation structure according to the ground conditions.

[0054] Figure 6 shows an example of a base-isolated building design where different foundation types are used to accommodate varying ground conditions at different locations, resulting in a large-scale base-isolated building design. Figure 6(1) is a plan view (downward view) of the seismic isolation layer pit, showing the arrangement of the seismic isolation devices, the layout of the seismic isolation layer pit floor, and the shape of the upper surface of the foundation structure by dashed lines. Figure 6(2) shows the cross-sectional configuration from the seismic isolation layer pit to the supporting layer of the ground below.

[0055] First, as a seismic isolation device, sliding bearings 21 with a rotation mechanism are placed at all column support points, and laminated rubber bearings 30 are placed as restorative materials at positions that do not support the weight of the building. The restoration members 30 are arranged in sets of four in a square shape near both ends of the building. This arrangement allows for efficient placement of secondary beams on the superstructure side and inverted beam-type fixed beams in the seismic isolation pits on the substructure side. This square arrangement allows for restraint of the bending (rotational) deformation of the restoration members with a minimum number of beams in both the X and Y directions.

[0056] Next, looking at the type of foundation structure that supports the seismic isolation devices (sliding bearings) 21 at the load-bearing points of the columns that support the weight of the building, a direct foundation type 51 is adopted in the two rows of columns at both ends of the building because the supporting ground is shallow. Next, in the third and fourth columns from the left of the building, the supporting ground is slightly too deep for a direct foundation, so cast-in-place concrete piles 52 are used. Furthermore, near the center of the building where the supporting layer is even deeper, pile foundations 53 using precast piles are employed. As described above, a major feature of the present invention is that the most appropriate and rational foundation types can be freely mixed and adopted in accordance with the ground conditions of the support points. This is because, by employing sliding bearings with a rotating mechanism at all support points, the degree of inclination angle at the support points (pile heads) during an earthquake and the effects of differences are completely eliminated.

[0057] Furthermore, a major feature of this invention is that there are no underground beams connecting each foundation structure, i.e., the foundation structures of the direct foundation footings and pile heads, and the only structural member constituting the seismic isolation layer pit floor surface is the floor slab 41. Furthermore, the beams for the restoration members 30, which are arranged in sets of four, are equipped with inverted beam-type restraining beams 43, but they are not connected to the foundation structure at the column support points, the direct foundation footing, or the foundation structure above the pile foundation.

[0058] Next, let's look at the floor slab 41 of the seismic isolation pit shown in Figure 6(1). In this design example, the floor slab 41 is generally placed across the entire plane of the floor surface of the seismic isolation layer pit, but there is a section 40 near the center of the plane where the floor slab 41 does not exist. Conventional foundation structural design assumed a rigid floor configuration across the entire building plan (that each support point experiences the same horizontal displacement during an earthquake). However, in buildings with large floor plans, the condition that all support points experience the same horizontal displacement during an earthquake is practically unrealistic. Furthermore, in cases where the depth of the supporting layer varies significantly depending on the location, as shown in Figure 6(2), the input ground motion will likely differ depending on the location.

[0059] In recent analytical studies conducted by the inventors, it has been confirmed that even when ground motion with the same phase is applied to the bedrock, the ground surface acceleration waveform differs significantly depending on the location. This was achieved by performing a nonlinear propagation analysis of seismic motion using a 3D FEM model of the ground in complex ground where the geological structure is not stratified and the depth of the supporting layer varies greatly depending on the location. Furthermore, when conducting simultaneous multi-point input seismic response analyses where different seismic motions are applied to numerous support points of seismic isolation devices depending on their location, it has been confirmed that the maximum seismic response of the superstructure is actually easier (reduced) than when the same phase seismic motion is applied to all supports. This can be understood as meaning that the different input seismic motions at different locations cancel each other out, resulting in favorable (safer) input conditions for the superstructure.

[0060] Based on these results, it is not necessary to deliberately align the phase of the seismic input to a long, horizontally-oriented building at all support points, and simultaneous input of different seismic motions can be tolerated. This invention is based on the latest analytical findings and knowledge regarding the effects of simultaneous multi-point input of different seismic motions on building response, as described above. It adopts and introduces a sophisticated engineering judgment (which deviates from the conventional wisdom of seismic design) into building design: "In buildings with long planar lengths, the rigid floor assumption as a seismic input condition is unnecessary." According to the present invention, in a long-scale seismic isolation building, by introducing sliding bearings with a rotation mechanism to all support points, it is possible to eliminate all underground beams in the seismic isolation layer that connect all support points in the long seismic isolation layer pit, and it is also possible to partially or completely eliminate the floor slab of the long seismic isolation layer pit itself. [Explanation of symbols]

[0061] 1: Superstructure of a seismically isolated building (general term) 11: Floor slab of the superstructure 12: Columns of the superstructure 13: Main beams of the superstructure 14: Secondary beams of the superstructure 2: Seismic isolation devices (general term) 20: Sliding bearing 21: Sliding bearing with rotating mechanism 22: Sliding plate of a sliding bearing 23: Foundation structure for fixing the sliding plate 24: Slider of sliding bearing 241: Sliding material (or sliding surface) 242: Convex part of the slider 243: Recessed material for slider 244: Bolts (guide pins) for limiting misalignment of uneven surfaces 245: Suspension eyebolt for positioning uneven surfaces 246: Loose Hole 3: Horizontal restoring force device (restoring material) 30: Laminated rubber bearing (or rubber body) as a restorative material 31: Upper mounting body for restoration material 32: Lower mounting body for restoration material 4: Substructure (general term) 40: Omitted seismic isolation pit floor slab (part without floor slab) 41: Floor slab of the substructure (seismic isolation pit floor slab) 42: Main beams of the substructure (seismic isolation pit beams, pile head underground beams) 43: Inverted beam type mounting beam for fixing the restoration material 44: Foundation frame of the substructure 45:Pile 46: Retaining wall surrounding the seismic isolation layer pit of the lower structure 5: Basics 51:Direct foundation 52: Cast-in-place concrete foundation 53: Pile foundation (precast piles) 6: Ground 61: Surface ground 62:Support layer

Claims

1. A base-isolated building having multiple base isolation devices between the substructure and the superstructure, and having the following characteristics. (a) The seismic isolation device comprises two types of bearings: a sliding bearing that supports the vertical load of the superstructure and is capable of horizontal movement, and a horizontal restoring force device that exerts a horizontal restoring force to return the superstructure to its original position in response to the relative horizontal displacement of the superstructure with respect to the substructure. (b) The sliding support consists of two parts: a sliding plate and a slider, the sliding plate being a flat plate and fixed to the superstructure. (c) The slider positioned below the sliding plate has a sliding material on its upper surface or its upper surface is treated to be a sliding surface. The slider body located below it is for absorbing the tilt angle of the lower structure during an earthquake, and is separated into two or three members vertically, with each contact surface being a combination of a concave spherical surface and a convex spherical surface with different radii of curvature. (d) The sliding bearings are placed at all of the vertical load support points on which the weight of the superstructure acts. (e) The horizontal restoring force device is positioned at a location other than the vertical load support point, and at a location where the sum of the rotational moments around the vertical axis of the center of gravity due to the horizontal restoring force is approximately zero with respect to the center of gravity of the superstructure. (f) The substructure has a foundation frame supporting the sliding bearing directly below the sliding bearing and a seismic isolation layer slab covering the entire underside of the seismic isolation layer, but does not have underground beams connecting the foundation frame.

2. In the seismically isolated building described in claim 1, A base-isolated building characterized in that the sliding bearing and the horizontal restoring force device are as follows. (a) The sliding bearing is a sliding bearing with a rotation mechanism for absorbing the tilt angle of the lower structure during an earthquake, wherein the slider constituting the sliding bearing is composed of two members, in the order from top to bottom, a convex member having a convex spherical surface on its contact surface and a concave member having a concave spherical surface on its contact surface, or three members, a concave member, a convex member, and a concave member, wherein the radius of curvature r of the convex spherical surface and the radius of curvature R of the concave spherical surface are in the relationship r ≪ R. (b) The horizontal restoring force device is a rubber bearing that includes either a laminated rubber bearing or a non-laminated rubber body, or both. (c) The laminated rubber bearing is one or a combination of a natural rubber laminated rubber bearing, a high-damping rubber laminated rubber bearing, or a plug-insertion type laminated rubber bearing containing lead, tin, or other plugs. (d) The rubber bearing is fixed to an upper mounting body which is integrated with the main beam, secondary beam or slab of the superstructure on the upper surface of the device, and to a lower mounting body which is integrated with an inverted beam type mounting beam which is configured in an inverted beam shape on the upper side of the seismic isolation layer slab or the seismic isolation layer slab. (e) The inverted beam type mounting beam is integrated with the seismic isolation layer slab, but is not connected to the foundation structure.

3. In the seismically isolated building according to claim 1 or 2, A base-isolated building characterized in that the foundation work, pile work, etc. (hereinafter referred to as "foundation structure method") that supports the foundation frame directly below the sliding bearing, which is integrated with the base isolation layer slab, is one of the following. (a) A foundation structure method using a direct foundation in which the foundation frame is in direct contact with the supporting ground. (b) A foundation structure method using short piles, in which the foundation frame is supported by one or more short piles. (c) A foundation structure method using long piles, in which the foundation frame is supported by one or more long piles. (d) A foundation structure that employs one of the following pile types as described in (b) and (c) above: cast-in-place concrete piles, various types of precast concrete piles, various types of steel pipe piles, steel pipe concrete piles, or connected piles of steel pipe piles and precast concrete piles. (e) A foundation structure method that employs different pile types as described in (d) above in different foundation structures. (f) A mixed foundation structure that uses different foundation structure methods described in (a) to (e) above.

4. In the seismically isolated building according to claim 1, 2, or 3, A base-isolated building characterized in that a portion of the base isolation layer slab in the substructure is removed, or the entire base isolation layer slab is removed.

Images