Design method for floating body-type base isolation system, and floating body-type base isolation system

Abstract

This design method for a floating body-type base isolation system 100 including a floating body-type structure 120, a storage space 116 in which a liquid 118 for floating the floating body-type structure 120 is stored, a gas storage space 132 which is provided at a location in contact with the liquid 118 at a lower part or below the floating body-type structure 120, and stores a gas 134, and accessory equipment 140 installed on the floating body-type structure 120, the design method including: a first step for determining a lower limit value of a ratio of a horizontal projection area of the gas storage space 132 to a horizontal projection area of the floating body-type structure 120 on the basis of allowable acceleration of the accessory equipment 140 with respect to a seismic wave; and a second step for designing the gas storage space 132 on the basis of the lower limit value.

Description

Design method for floating seismic isolation systems, and floating seismic isolation systems

[0001] This disclosure relates to a design method for a floating seismic isolation system and to a floating seismic isolation system. This application claims priority under Japanese Patent Application No. 2025-005590, filed on 15 January 2025, the contents of which are incorporated herein by reference.

[0002] Conventionally, floating seismic isolation systems have been developed that levitate floating structures using liquid stored in a reservoir. As an example of a floating seismic isolation system, Patent Document 1 discloses a technology in which an air chamber is provided at the bottom of a floating structure, and vertical vibrations of the floating structure are reduced by the spring effect due to the compressibility of the air in the air chamber.

[0003] Japanese Patent Publication No. 2002-242990

[0004] Conventional floating structures, such as the one described in Patent Document 1 above, are equipped with air chambers. However, simply providing air chambers in a floating structure may not attenuate the energy of some frequency bands of seismic waves, which may be transmitted to the floating structure.

[0005] In view of these challenges, this disclosure aims to provide a design method for a floating seismic isolation system capable of suitably attenuating the energy of seismic waves, and a floating seismic isolation system.

[0006] To solve the above problems, a design method for a floating seismic isolation system according to one aspect of the present disclosure is a design method for a floating seismic isolation system comprising a floating structure, a storage space in which a liquid for levitating the floating structure is stored, a gas storage space provided at a location in contact with the liquid below or below the floating structure and for storing gas, and ancillary equipment installed on the floating structure, comprising: a first step of determining a lower limit value for the ratio of the horizontal projection area of ​​the gas storage space to the horizontal projection area of ​​the floating structure based on the allowable acceleration of the ancillary equipment against seismic waves; and a second step of designing the gas storage space based on the lower limit value.

[0007] The floating structure has a wall that forms a gas storage space at the lower part of the floating structure. The design method of the floating seismic isolation system further includes a third step of determining an upper limit value of the ratio based on the strength of the wall. In the second step, in addition to the lower limit value, the gas storage space may be designed based on the upper limit value.

[0008] The gas storage space is provided at the lower part of the floating structure and includes a heat exchanger that exchanges heat between the liquid stored in the storage space and the heat medium. In the third step, in addition to the strength of the wall, the upper limit value may be determined based on the heat exchange efficiency between the heat medium of the heat exchanger and the liquid stored in the storage space.

[0009] To solve the above problems, a floating seismic isolation system according to an aspect of the present disclosure includes a floating structure, a storage space in which a liquid for floating the floating structure is stored, a gas storage space provided at a location where the floating structure contacts the liquid at the lower part or below the floating structure, and auxiliary equipment installed on the floating structure. The ratio of the horizontal projected area of the gas storage space to the horizontal projected area of the floating structure is set so that the acceleration of the seismic wave acting on the auxiliary equipment through the floating structure is not more than the allowable acceleration of the auxiliary equipment.

[0010] According to the present disclosure, it is possible to suitably attenuate the energy of seismic waves.

[0011] FIG. 1 is a schematic diagram showing the configuration of a floating seismic isolation system according to an embodiment of the present disclosure. FIG. 2 is a flowchart showing the processing flow of the design method of the floating seismic isolation system according to the same embodiment. FIG. 3 is a plan view of the floating seismic isolation system according to the same embodiment as viewed from above. FIG. 4 is a cross-sectional view of the floating seismic isolation system according to the same embodiment. FIG. 5 is a graph showing an example of a response spectrum when C / A is a first value. FIG. 6 is a graph showing an example of a response spectrum when C / A is a second value. FIG. 7 is a graph showing an example of the relationship between the ratio of the horizontal projected area of the gas storage space to the horizontal projected area of the floating structure, the response acceleration, and the rigidity of the wall. FIG. 8 is a schematic diagram showing the configuration of a floating seismic isolation system according to a modified example.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail while referring to the attached drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for ease of understanding, and do not limit the present disclosure unless otherwise specified. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals, and redundant descriptions are omitted. Also, elements not directly related to the present disclosure are not shown in the drawings.

[0013] [1. Outline of the floating seismic isolation system] First, referring to FIG. 1, the outline of the floating seismic isolation system 100 according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic diagram showing the configuration of the floating seismic isolation system 100 according to the present embodiment. As shown in FIG. 1, the floating seismic isolation system 100 according to the present embodiment includes a liquid storage section 110, a floating structure 120, a gas storage chamber 130, auxiliary equipment 140, and a heat exchanger 150.

[0014] The liquid storage section 110 has a bottom wall 112 and side walls 114. The bottom wall 112 is a wall extending in the horizontal direction or a substantially horizontal direction. The side walls 114 are walls extending in the vertical direction or a substantially vertical direction from the bottom wall 112. A storage space 116 is defined by the bottom wall 112 and the side walls 114. That is, it can be said that the bottom wall 112 and the side walls 114 are wall surfaces that define the storage space 116. A liquid 118 is stored in the storage space 116 of the liquid storage section 110. Note that the liquid storage section 110 may be, for example, a depression or a hole formed by digging the ground.

[0015] The liquid 118 is, for example, water. However, it is not limited thereto, and the liquid 118 may be any other liquid other than water, or may be another liquid having water as a main component (for example, seawater).

[0016] The floating structure 120 is positioned floating in the liquid 118 stored in the storage space 116 of the liquid storage section 110. The floating structure 120 is positioned at a distance from the bottom wall 112 and side walls 114 of the liquid storage section 110. The floating structure 120 is, for example, a floating nuclear power plant. However, it is not limited to this, and the floating structure 120 may be a structure of other plants such as a wind power plant, a wave power plant, or a solar power plant, or it may be a structure on which any other equipment is mounted. In this embodiment, the floating structure 120 is, for example, a floating plant floating on an artificial lake, but it may also be an offshore plant floating on the sea.

[0017] The gas containment chamber 130 forms a gas containment space 132. The gas containment space 132 contains the gas 134. In this embodiment, the gas containment space 132 is provided at a location in the lower part of the floating structure 120 that comes into contact with the liquid 118. The gas containment space 132 is formed, for example, by the lower wall 122 of the floating structure 120. In this embodiment, the gas containment chamber 130 is formed by a depression in the center of the bottom surface of the floating structure 120, and the gas containment space 132 is formed within the gas containment chamber 130. The gas containment space 132 is sealed by the floating structure 120 and the liquid 118. In the example shown in Figure 1, the gas containment space 132 is a sealed space surrounded by the five walls of the gas containment chamber 130 and the liquid surface of the liquid 118.

[0018] The ancillary equipment 140 is installed on the floating structure 120. The ancillary equipment 140 is equipment (devices) attached to the various plants described above. Examples of ancillary equipment 140 include measuring instruments, computers, pumps, turbines, generators, pressure vessels, and piping.

[0019] As will be explained in more detail later, in this embodiment, the ratio (C / A) of the horizontal projection area C (see Figure 3) of the gas containment space 132 to the horizontal projection area A (see Figure 3) of the floating structure 120 is set such that the acceleration of seismic waves acting on the ancillary equipment 140 through the floating structure 120 is less than or equal to the allowable acceleration of the ancillary equipment 140.

[0020] The heat exchanger 150 exchanges heat between the liquid 118 stored in the storage space 116 and the heat transfer medium. The heat exchanger 150 is installed, for example, at the bottom of the floating structure 120. The heat exchanger 150 cools the heat transfer medium with the liquid 118 stored in the storage space 116. The heat exchanger 150 supplies the heat transfer medium after heat exchange to cooling equipment. The cooling equipment is, for example, a condenser or a fuel containment vessel.

[0021] [2. Design Method for Floating Seismic Isolation System] Next, the design method for the floating seismic isolation system 100 according to this embodiment will be described with reference to Figures 2 to 4. Figure 2 is a flowchart showing the processing flow of the design method for the floating seismic isolation system 100 according to this embodiment.

[0022] When an earthquake occurs, longitudinal waves (also called compressional waves) of the seismic waves propagate through the fluid containing liquid 118 and gas 134 and are transmitted to the floating structure 120 and ancillary equipment 140. Therefore, in the design method of the floating seismic isolation system 100 according to this embodiment, the transmission of seismic wave energy to the floating structure 120 and ancillary equipment 140 is attenuated by suitably designing the gas containment space 132.

[0023] [2.1. Determination of the Volume of the Gas Containment Space 132] In the design method of the floating seismic isolation system 100 according to this embodiment, first, in step S110, the volume of the gas containment space 132 is determined. In step S110 of this embodiment, the volume of the gas containment space 132 is determined based on the natural frequency of the system that responds to seismic waves propagating through a fluid containing liquid 118 and gas 134. The system that responds to seismic waves propagating through a fluid containing liquid 118 and gas 134 is a single system consisting of the floating structure 120, ancillary equipment 140, liquid 118 contained in the storage space 116, and gas 134 contained in the gas containment space 132.

[0024] Figure 3 is a plan view of the floating seismic isolation system 100 according to this embodiment, viewed from above. Figure 4 is a cross-sectional view of the floating seismic isolation system 100 according to this embodiment. Note that in Figures 3 and 4, the ancillary equipment 140 and the heat exchanger 150 are omitted for ease of understanding.

[0025] In FIG. 3, "A" represents the horizontal projected area [m ,

[0029] ,

[0028] , ,

[0027] , １ , , ２ , , １ , and the horizontal projected area A can also be said to be the area of the bottom surface of the floating structure 120 (including the gas storage chamber 130). In FIG. 3, "B" represents the horizontal projected area [m ２ of the liquid 118. The horizontal projected area B is a value obtained by subtracting the horizontal projected area A from the horizontal projected area of the storage space 116. In other words, the horizontal projected area B is a value obtained by subtracting the horizontal projected area A from the horizontal projected area of the region defined by the bottom wall 112 and the side wall 114 of the liquid storage section 110. In FIG. 3, "C" represents the horizontal projected area [m<000,003> of the gas storage space 132. Note that the horizontal projected area A includes the horizontal projected area C.

[0026] In FIG. 4, "m" represents the mass [kg] of the floating structure 120. "g" represents the gravitational acceleration [m / s ２ . "h " ０ " represents the depth (distance) [m] from the bottom surface 120a of the floating structure 120 to the liquid surface 118a of the liquid 118. "P" represents the depth [m] that is considered to move in conjunction with the movement of the floating structure 120. "d " ０ " represents the depth (distance) [m] from the depth P to the bottom surface 120a of the floating structure 120. "hc " ０ " represents the depth (distance) [m] from the bottom surface 120a of the floating structure 120 to the liquid surface 118b in the gas storage space 132. "X "<OOOOOO8>" represents the displacement of the vertical vibration of the liquid storage section 110. "X " １ " represents the displacement of the vertical vibration of the floating structure 120. "X " ２ " represents the displacement of the vertical vibration of the liquid surface 118a of the liquid 118.

[0027] Here, the vertical vibration that is considered to be excited by the seismic wave on the floating structure 120 can be represented by the following equation of motion (1).

[0028]

[0029] In the above equation (1), "x " １ " is the above "X " １"Similarly, this represents the displacement of the vertical vibration of the floating structure 120. ２ " is the above "X ２ Similarly, it represents the displacement of the vertical vibration of the liquid surface 118a of the liquid 118. Also, in equation (1), "k １１ "k １２ "k ２１ ", and "k ２２ " represents the stiffness matrix, and "m １１ "m １２ "m ２１ ", and "m ２２ " represents the mass matrix. １１ " is expressed by the following equation (2), and "k １２ " is expressed by the following equation (3), and "k ２１ " is expressed by the following equation (4), and "k ２２ " is expressed by the following equation (5). Also, in equation (1), "m １１ " is expressed by the following equation (6), and "m １２ " is expressed by the following equation (7), and "m ２１ " is expressed by the following equation (8), and "m ２２ This is expressed by the following equation (9). In the above equation (1), "F" represents the external force acting on the floating structure 120 and the liquid 118 in the storage space 116 due to vertical seismic motion.

[0030]

[0031]

[0032] In equations (2) to (9) above, "A" is the horizontal projection area [m²] of the floating structure 120. ２ ] represents the horizontal projected area of ​​liquid 118 [m²]. "B" represents the horizontal projected area of ​​liquid 118 [m²]. ２ ] represents the horizontal projection area [m²] of the gas containment space 132. ２ ] represents "V ０ " is the volume [m³] of the gas containment space 132 ３ ] represents "K ｖ " is the bulk modulus [N / m²] of the gas containment space 132. ２ ] represents "K ｖ" is expressed by the following equation (10). K ｖ = γ * (P ０ +P ａｔｍ ) ...Equation (10) In Equation (10), "γ" represents the specific heat ratio of the gas 134 contained in the gas containment space 132, and "P ０ " is the pressure generated in the gas containment space 132 due to the mass of the floating structure 120 (= ρg(h) ０ -hc ０ )) represents "P ａｔｍ " represents atmospheric pressure.

[0033] In equations (2) to (9) above, "ρ" is the density of liquid 118 [kg / m³]. ３ This represents the acceleration due to gravity [m / s²]. "g" represents the acceleration due to gravity [m / s²]. ２ ] represents. "m" represents the mass [kg] of the floating structure 120. "hc ０ " represents the depth (distance) [m] from the bottom surface 120a of the floating structure 120 to the liquid surface 118b in the gas containment space 132. ０ " represents the depth (distance) [m] from depth P to the bottom surface 120a of the floating structure 120. ０ This can also be considered as the depth [m] of the liquid 118 to be taken into account as added mass.

[0034] By substituting equations (2) to (9) above into equation (1) and solving equation (1), the natural frequencies f1 and f2 of the two vibration modes can be determined. Natural frequencies f1 and f2 represent the natural frequencies when the floating structure 120, ancillary equipment 140, liquid 118, and gas 134 act as a single system (hereinafter simply referred to as the system). Natural frequency f1 is the natural frequency of the system's first mode (hereinafter referred to as mode 1), and natural frequency f2 is the natural frequency of the system's second mode (hereinafter referred to as mode 2). Here, mode 1 is the mode in which the floating structure 120 and ancillary equipment 140 and the liquid 118 and gas 134 vibrate in opposite directions. Mode 2 is the mode in which the floating structure 120 and ancillary equipment 140 and the liquid 118 and gas 134 vibrate in the same direction.

[0035] The relationship between natural frequencies f1, f2, and f3 is disclosed in Japanese Patent Publication No. 2021-188403, so a detailed explanation will be omitted, but the natural frequency f1 of mode 1 is at depth d ０ Even if changes, it remains at an approximately constant value. On the other hand, the natural frequency f2 of mode 2 is at depth d ０ As the value increases, it becomes smaller, and can be set to a value smaller than the natural frequency f3. Note that the natural frequency f3 is the natural frequency of the ancillary equipment 140.

[0036] Furthermore, the natural frequency f1 of mode 1 is equal to the volume V of the gas containment space 132. ０ Even if it changes, it remains at an approximately constant value. On the other hand, the natural frequency f2 of mode 2 is the volume V of the gas containment space 132. ０ The larger the value, the smaller the value becomes, and it can be made smaller than the natural frequency f3. Also, the volume V of the gas containment space 132 ０ The larger the value, the more the seismic response of the floating structure 120 and its ancillary facilities 140 can be reduced.

[0037] The natural frequency f3 of the ancillary equipment 140 is several Hz (e.g., 5 Hz) to several tens of Hz (e.g., 30 Hz). Volume V of the gas containment space 132 ０ When = 0, the natural frequency f2 of mode 2 of the system approximates the natural frequency f3. Therefore, the volume V of the gas containment space 132 ０ When the value is 0, the longitudinal waves of the seismic wave excite the ancillary equipment 140. In other words, the ancillary equipment 140 vibrates significantly.

[0038] Here, the natural vibration characteristics of a wave propagating through a fluid depend on the bulk modulus of the fluid. In this embodiment, the volume V of the gas containment space 132 ０ By appropriately setting this, the equivalent bulk modulus determined by the liquid 118 and gas 134 is adjusted, separating the natural frequency f2 of mode 2 of the system from the natural frequencies of the floating structure 120 and ancillary equipment 140. This suppresses the excitation of the system's seismic response. The equivalent bulk modulus of the fluid is the bulk modulus of the entire fluid, which is the sum of the liquid 118 and gas 134. The equivalent bulk modulus is the volume V of the gas containment space 132. ０and correlates with the volume of liquid 118. Here, the volume V of the gas containment space 132 ０ As the value increases, the equivalent bulk modulus decreases.

[0039] Thus, in step S110, the volume V of the gas containment space 132 is determined based on the natural frequency of the system that responds to seismic waves propagating through the fluid containing the liquid 118 and the gas 134. ０ The volume V of the gas containment space 132 is determined such that the natural frequency of the system responding to seismic waves is smaller than the natural frequency of the floating structure 120 and the ancillary equipment 140. ０ This will be decided.

[0040] The natural frequency of the system that responds to seismic waves is the natural frequency f2 of mode 2 described above. Volume V of the gas containment space 132 ０ As the value increases, the equivalent bulk modulus decreases, and the natural frequency of the system responding to seismic waves decreases. This reduces the excitation of the floating structure 120 and its ancillary equipment 140 in response to earthquakes.

[0041] Furthermore, the volume V of the gas containment space 132 is set such that the natural frequency of the system responding to seismic waves is less than 1 Hz. ０ It is preferable that this is determined. The natural frequency (dominant frequency) of a typical earthquake is, for example, 1 Hz to 10 Hz. By setting the natural frequency of the system to less than 1 Hz, the natural frequency of the system can be separated from the natural frequency of the earthquake. As a result, the excitation of the floating structure 120 and ancillary equipment 140 in response to earthquakes can be reduced.

[0042] [2.2. Determination of the lower limit of C / A] Next, in step S120 (first step), for example, the lower limit of the ratio (C / A) of the horizontal projection area C of the gas containment space 132 to the horizontal projection area A of the floating structure 120 is determined using equation (1) above.

[0043] Figure 5 is a graph showing an example of the response spectrum when C / A is a first value. Figure 6 is a graph showing an example of the response spectrum when C / A is a second value. In Figures 5 and 6, the vertical axis represents the response acceleration [gal]. In Figures 5 and 6, the horizontal axis represents the frequency [Hz]. The second value is a value greater than the first value. The first value is, for example, 25 [%]. The second value is, for example, 42 [%]. The response spectra shown in Figures 5 and 6 are created using the above equation (1).

[0044] As shown in Figures 5 and 6, around a frequency of 0.5 Hz, the response acceleration [gal] is greater than the input acceleration (seismic wave) in all cases of damping ratio h = 0.01, h = 0.02, h = 0.05, h = 0.10, and h = 0.20. This indicates that around a frequency of 0.5 Hz is the natural frequency f2 of the floating structure 120.

[0045] As shown in Figure 5, when C / A is the first value, the response acceleration [gal] with a damping ratio h = 0.01 at a frequency of around 8.3 [Hz] becomes close to the input acceleration. On the other hand, as shown in Figure 6, when C / A is the second value, the response accelerations [gal] with damping ratios h = 0.01, h = 0.02, h = 0.05, h = 0.10, and h = 0.20 at a frequency of around 8.3 [Hz] are significantly smaller than when C / A is the first value. From this result, it can be seen that the larger C / A, the smaller the response acceleration [gal].

[0046] Therefore, in step S120 of this embodiment, the lower limit of C / A is determined based on the allowable acceleration of the ancillary equipment 140 in response to seismic waves. For example, the lower limit of C / A is determined so that it is less than or equal to the allowable acceleration of the ancillary equipment 140 in response to seismic waves.

[0047] The permissible acceleration of the ancillary equipment 140 is the seismic wave acceleration [gal] that the ancillary equipment 140 can tolerate. For example, if the acceleration of the seismic wave acting on the ancillary equipment 140 is less than or equal to the permissible acceleration, the ancillary equipment 140 will operate normally and be able to properly perform its function. On the other hand, if the acceleration of the seismic wave acting on the ancillary equipment 140 is greater than the permissible acceleration, the ancillary equipment 140 may not be able to operate normally and may not be able to properly perform its function, or it may become difficult to properly perform the function. The permissible acceleration of the ancillary equipment 140 may vary depending on, for example, the type of seismic wave, the importance of the ancillary equipment 140, or the safety factor of the ancillary equipment 140. The permissible acceleration of the ancillary equipment 140 may be predetermined based on, for example, the type of seismic wave, the type of ancillary equipment 140, the importance of the ancillary equipment 140, or the safety factor of the ancillary equipment 140.

[0048] [2.3. Determination of the upper limit of C / A] Next, in step S130 (third step), the upper limit of the ratio (C / A) is determined based on the strength of the wall 122 that forms the gas containment space 132 at the lower part of the floating structure 120.

[0049] Figure 7 is a graph illustrating an example of the relationship between the ratio (C / A) of the horizontal projection area C of the gas containment space 132 to the horizontal projection area A of the floating structure 120, the response acceleration, and the stiffness of the wall 122. In Figure 7, the left vertical axis represents the response acceleration (normalized value). In Figure 7, the right vertical axis represents the stiffness (normalized value). In Figure 7, the horizontal axis represents C / A [%]. The solid line in Figure 7 shows the relationship between C / A and the response acceleration. The dashed line in Figure 7 shows the relationship between C / A and the stiffness of the wall 122. In the example shown in Figure 7, the response acceleration is shown at a frequency of approximately 8 [Hz].

[0050] As shown in Figure 7, the larger the C / A ratio, the smaller the response acceleration. On the other hand, the larger the C / A ratio, the lower the rigidity of the wall 122. Therefore, in step S130 of this embodiment, it is preferable to determine the upper limit of C / A such that it is greater than or equal to the required strength of the wall 122.

[0051] For example, in the example shown in Figure 7, suppose the required rigidity of the wall 122 is 0.3. In this case, the upper limit of C / A would be, for example, 33%. Also, for example, in the example shown in Figure 7, suppose the allowable acceleration of the ancillary equipment 140 is 0.8. In this case, the lower limit of C / A would be, for example, 13%.

[0052] Furthermore, in step S130, the upper limit of C / A may be determined based on the heat exchange efficiency between the heat transfer medium of the heat exchanger 150 and the liquid 118 stored in the storage space 116, in addition to the strength of the wall 122. The larger the C / A, the smaller the heat exchange area of ​​the heat exchanger 150 that exchanges heat with the liquid 118. In other words, the larger the C / A, the lower the heat exchange efficiency between the heat transfer medium of the heat exchanger 150 and the liquid 118. Therefore, in step S130 of this embodiment, it is preferable to determine the upper limit of C / A so as to be greater than or equal to the heat exchange area of ​​the heat exchanger 150 that exchanges heat with the liquid 118, which satisfies the heat exchange efficiency required for the heat exchanger 150.

[0053] [2.4. Design of the gas containment space] Next, in step S140 (second step), the volume V of the gas containment space 132 determined in step S110 above ０ Based on the lower limit of C / A determined in step S120 and the upper limit of C / A determined in step S130, the gas containment space 132 is designed. In step S140 of this embodiment, for example, the volume V of the gas containment space 132 determined in step S110 ０ The volume and horizontal projection area (opening area) of the gas containment space 132 are designed such that the C / A ratio is greater than or equal to the lower limit determined in step S120 and less than or equal to the upper limit determined in step S130.

[0054] [3. Summary] The design method for the floating seismic isolation system 100 according to this embodiment and the floating seismic isolation system 100 have been described above.

[0055] The design method for the floating seismic isolation system 100 according to this embodiment includes a floating structure 120, a storage space 116 in which a liquid 118 for levitating the floating structure 120 is stored, a gas storage space 132 for containing a gas 134 provided at a location in contact with the liquid 118 below or below the floating structure 120, and an ancillary equipment 140 installed on the floating structure 120, and includes a first step of determining a lower limit of the ratio (C / A) of the horizontal projection area C of the gas storage space 132 to the horizontal projection area A of the floating structure 120 based on the allowable acceleration of the ancillary equipment 140 with respect to seismic waves, and a second step of designing the gas storage space 132 based on the lower limit.

[0056] As described above, the larger the ratio (C / A) of the horizontal projection area C of the gas containment space 132 to the horizontal projection area A of the floating structure 120, the smaller the response acceleration of the floating structure 120 and the ancillary equipment 140. Therefore, the design method for the floating seismic isolation system 100 according to this embodiment determines a lower limit of the ratio (C / A) based on the allowable acceleration of the ancillary equipment 140 to seismic waves, and designs the gas containment space 132 based on this lower limit. As a result, the design method for the floating seismic isolation system 100 according to this embodiment makes it possible to design a gas containment space 132 that can attenuate the response acceleration of the ancillary equipment 140 to less than or equal to the allowable acceleration of the ancillary equipment 140 to seismic waves. Consequently, the design method for the floating seismic isolation system 100 according to this embodiment makes it possible to suitably attenuate the energy of seismic waves. For example, the design method for the floating seismic isolation system 100 according to this embodiment makes it possible to design a gas containment space 132 that can attenuate the energy of waves in a part of the frequency band of the entire frequency band of seismic waves. In particular, the design method for the floating seismic isolation system 100 according to this embodiment makes it possible to design a gas containment space 132 that can attenuate the energy of waves in the frequency band higher than the natural frequencies of the floating structure 120 and ancillary equipment 140, out of the total frequency band of seismic waves.

[0057] The floating structure 120 has a wall 122 that forms a gas containment space 132 at the lower part of the floating structure 120, and the design method for the floating seismic isolation system 100 further includes a third step of determining an upper limit of the ratio (C / A) based on the strength of the wall 122, and in the second step, the gas containment space 132 may be designed based on the upper limit in addition to the lower limit.

[0058] As described above, the larger the ratio (C / A) of the horizontal projection area C of the gas containment space 132 to the horizontal projection area A of the floating structure 120, the lower the rigidity of the wall 122 of the floating structure 120. Therefore, in the design method of the floating seismic isolation system 100 according to this embodiment, it is preferable to determine the upper limit of the ratio (C / A) based on the strength of the wall 122, and to design the gas containment space 132 based on the upper limit of the ratio (C / A) in addition to the lower limit of the ratio (C / A). As a result, the design method of the floating seismic isolation system 100 according to this embodiment makes it possible to design a gas containment space 132 that can suitably attenuate the energy of seismic waves while ensuring the necessary strength of the wall 122 of the floating structure 120.

[0059] The gas containment space 132 is located at the bottom of the floating structure 120 and includes a heat exchanger 150 that exchanges heat between the liquid 118 stored in the storage space 116 and a heat transfer medium. In the third step, the upper limit may be determined based on the strength of the wall 122 as well as the heat exchange efficiency between the heat transfer medium of the heat exchanger 150 and the liquid 118 stored in the storage space 116.

[0060] As described above, the larger the ratio (C / A) of the horizontal projection area C of the gas containment space 132 to the horizontal projection area A of the floating structure 120, the lower the heat exchange efficiency between the heat transfer medium flowing through the heat exchanger 150 and the liquid 118. Therefore, in the design method of the floating seismic isolation system 100 according to this embodiment, it is preferable to determine the upper limit of the ratio (C / A) based on the heat exchange efficiency between the heat transfer medium flowing through the heat exchanger 150 and the liquid 118, in addition to the strength of the wall 122. This makes it possible to design a gas containment space 132 that can suitably attenuate the energy of seismic waves while ensuring the heat exchange efficiency required for the heat exchanger 150.

[0061] The floating seismic isolation system 100 according to this embodiment comprises a floating structure 120, a storage space 116 in which a liquid 118 for levitating the floating structure 120 is stored, a gas storage space 132 for containing a gas 134, provided at a location in contact with the liquid 118 below or below the floating structure 120, and ancillary equipment 140 installed on the floating structure 120. The ratio of the horizontal projection area C of the gas storage space 132 to the horizontal projection area A of the floating structure 120 is set so that the acceleration of seismic waves acting on the ancillary equipment 140 through the floating structure 120 is less than or equal to the allowable acceleration of the ancillary equipment 140.

[0062] As a result, the floating seismic isolation system 100 according to this embodiment can attenuate the response acceleration of the ancillary equipment 140 to less than or equal to the allowable acceleration of the ancillary equipment 140 in response to seismic waves. Therefore, the floating seismic isolation system 100 according to this embodiment can suitably attenuate the energy of seismic waves. For example, the floating seismic isolation system 100 according to this embodiment can attenuate the energy of waves in a portion of the total frequency band of seismic waves. In particular, the floating seismic isolation system 100 according to this embodiment can attenuate the energy of waves in a frequency band higher than the natural frequencies of the floating structure 120 and the ancillary equipment 140 within the total frequency band of seismic waves.

[0063] While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0064] For example, in the above embodiment, the gas containment space 132 is provided at the lower part of the floating structure 120. However, the gas containment space 132 only needs to be provided at a location that comes into contact with the liquid 118 and be sealed, and does not need to be formed in the floating structure 120. For example, the gas containment space 132 may be provided below the floating structure 120 and in the liquid 118.

[0065] Figure 8 is a schematic diagram showing the configuration of a modified floating seismic isolation system 200. Components that are substantially the same as those in the floating seismic isolation system 100 of the above embodiment are denoted by the same reference numerals and their descriptions are omitted. The modified floating seismic isolation system 200 differs from the floating seismic isolation system 100 in that it includes a gas containment chamber 230 instead of the gas containment chamber 130 of the floating seismic isolation system 100. All other components are the same as those of the floating seismic isolation system 100.

[0066] The gas containment chamber 230 is equipped with an elastic membrane 240. Inside the elastic membrane 240, a gas containment space 232 is formed. The elastic membrane 240 is made of, for example, rubber material and is elastic. The gas 134 is contained within the gas containment space 232. The gas containment space 232 is provided at a location that comes into contact with the liquid 118 and is formed in a sealed state within the liquid 118. In a modified example, the gas containment space 232 is located between the bottom surface 116a of the storage space 116 (the upper surface of the bottom wall 112) and the bottom surface 120a of the floating structure 120.

[0067] In the modified example, similar to the design method for the floating seismic isolation system 100 described above, it is preferable to determine the lower limit of the ratio (C / A) of the horizontal projection area C of the gas containment space 232 to the horizontal projection area A of the floating structure 120 based on the allowable acceleration of the ancillary equipment 140 in response to seismic waves. This makes it possible to obtain the same functions and effects as in the above embodiment.

[0068] Furthermore, in the above embodiment, the floating seismic isolation system 100 was given as an example in which it has one gas containment space 132. However, the floating seismic isolation system 100 may have multiple gas containment spaces 132. In this case, the horizontal projected area C of the gas containment space 132 is the sum of the horizontal projected areas of the multiple gas containment spaces 132.

[0069] Furthermore, in the above embodiment, an example was given in which the upper limit of the ratio (C / A) is determined based on the strength of the wall 122. However, the design method for the floating seismic isolation system 100 may determine the upper limit of the ratio (C / A) based on other factors. For example, the design method for the floating seismic isolation system 100 may determine the upper limit of the ratio (C / A) based solely on the heat exchange efficiency between the heat transfer medium of the heat exchanger 150 and the liquid 118 stored in the storage space 116. Alternatively, the design method for the floating seismic isolation system 100 may use a preset value as the upper limit.

[0070] Furthermore, in the above embodiment, an example was given in which the gas containment space 132 is designed based on the upper limit of the ratio (C / A). However, in the design method for the floating seismic isolation system 100, it is sufficient if the gas containment space 132 can be designed based on at least the lower limit of the ratio (C / A).

[0071] Furthermore, in the above embodiment, the design method for the floating seismic isolation system 100 is such that the natural frequency of the system that responds to seismic waves is smaller than the natural frequency of the floating structure 120 and the ancillary equipment 140, and the volume V of the gas containment space 132 is set accordingly. ０ An example was given of a case where the volume V is determined. However, in the design method for the floating seismic isolation system 100, it is sufficient to be able to design the gas containment space 132 based on at least the lower limit of the ratio (C / A). For example, in the design method for the floating seismic isolation system 100, the volume V of the gas containment space 132 is determined based on the heat exchange efficiency between the heat transfer medium of the heat exchanger 150 and the liquid 118 stored in the storage space 116. ０ It may be said that this is determined.

[0072] Furthermore, the design method for the floating seismic isolation system described above may be performed by a computer. For example, a computer has one or more processors and one or more memories connected to the processors. The processor includes, for example, a CPU (Central Processing Unit). The memory includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM is a memory element that stores programs and calculation parameters used by the CPU. The RAM is a memory element that temporarily stores data such as variables and parameters used in processing performed by the CPU. The processor executes the programs contained in the memory to perform, for example, at least the processing of step S120 (first step) and step S140 (second step) described above. It is preferable that the processor executes the processes of step S120 (first step), step S130 (third step), and step S140 (second step) by executing a program contained in memory. It is even more preferable that the processor executes the processes of steps S110 to S140 by executing a program contained in memory.

[0073] A: Horizontal projection area of ​​floating structure C: Horizontal projection area of ​​gas containment space 100: Floating seismic isolation system 116: Storage space 120: Floating structure 122: Wall 132: Gas containment space 140: Ancillary equipment 150: Heat exchanger 200: Floating seismic isolation system 232: Gas containment space

Claims

1. A method for designing a floating seismic isolation system comprising a floating structure, a storage space for storing a liquid that buoys the floating structure, a gas storage space provided at a location in contact with the liquid below or below the floating structure for storing a gas, and ancillary equipment installed on the floating structure, the method comprising: a first step of determining a lower limit value for the ratio of the horizontal projection area of ​​the gas storage space to the horizontal projection area of ​​the floating structure based on the allowable acceleration of the ancillary equipment with respect to seismic waves; and a second step of designing the gas storage space based on the lower limit value.

2. The floating structure has a wall at the lower part of the floating structure that forms the gas containment space, and the design method for the floating seismic isolation system further includes a third step of determining an upper limit of the ratio based on the strength of the wall, and in the second step, the gas containment space is designed based on the upper limit in addition to the lower limit, the design method for the floating seismic isolation system according to claim 1.

3. The gas containment space is provided at the lower part of the floating structure and includes a heat exchanger for exchanging heat between the liquid stored in the storage space and a heat transfer medium, wherein in the third step, the upper limit is determined based on the strength of the wall and the heat exchange efficiency between the heat transfer medium of the heat exchanger and the liquid stored in the storage space, the method for designing a floating seismic isolation system according to claim 2.

4. A floating seismic isolation system comprising: a floating structure; a storage space containing a liquid that buoys the floating structure; a gas storage space provided at a location in contact with the liquid below or below the floating structure for containing gas; and ancillary equipment installed on the floating structure, wherein the ratio of the horizontal projection area of ​​the gas storage space to the horizontal projection area of ​​the floating structure is set such that the acceleration of seismic waves acting on the ancillary equipment through the floating structure is less than or equal to the allowable acceleration of the ancillary equipment.

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