JP5382367B2 - Floating-type seismic isolation structure with pressurized liquid - Google Patents

Description

The present invention relates to a floating type seismic isolation structure using pressurized liquid.

Conventionally, as shown in FIG. 8 , the floating body structure 12 is floated in a seismic isolation pit 13 and insulated from the ground to obtain a high seismic isolation effect against horizontal ground motion. The seismic structure 11 is generally known widely (see Non-Patent Document 1).
However, in such a completely floating seismic isolation structure, the structure easily tilts due to a fluctuating load generated in the floating structure main body 12, or the floating structure main body 12 fluctuates in the vertical direction following the change in the liquid level. There were problems in terms of comfort and usability.
Therefore, as shown in FIG. 9 , a partial floating type seismic isolation structure is proposed in which part of the variable load and fixed load of the floating structure body is supported by the ground 16 via a low shear rigid structure 17 such as a seismic isolation device. (See Patent Document 1).

In the case of this partially floating type seismic isolation structure, as shown in FIG. 9 , the load W of the floating structure main body 12 includes a fixed load W1 of the floating structure main body 12 and a positive variable load W2 acting vertically downward. It is the sum (W = W1 + W2). The floating body main body 12 is inserted into the seismic isolation pit 13 so that the load ΔW1 obtained by removing the variable load W2 and the buoyancy B from the load W becomes a positive value. Buoyancy B is represented by W1- △ W1. The load supported by the ground 16 through the low shear rigidity structure 17 is W2 + ΔW1 .

In addition, if the floating body bottom surface of the floating structure body 12 is horizontal and its area is A, and the height from the bottom surface to the water line is d, the amount of drainage is A · d, and the buoyancy B is ρ · A · d · g (ρ Is the density of the liquid and g is the acceleration of gravity.

Although the above floating body type seismic isolation structure has seismic isolation characteristics for horizontal ground motion, it did not have seismic isolation characteristics for vertical (up and down) ground motions. There is a proposal to obtain the seismic isolation for vertical ground motion that cannot be obtained by the air cushion effect.
In addition, a floating-type seismic isolation structure having an air chamber is proposed in which static stability is maintained and restoring force is obtained by equally dividing the air chamber into at least four in one direction of the bottom of the floating body ( Patent Document 2).
On the other hand, closes the opening that will be formed between the side wall and the inner wall of the seismic isolation pit of the lower structure constituting the floating base isolation structures, it has also been proposed floating seismic isolation by liquid pressure. (See Patent Document 3).

Oyama Taku et al., “Research on Floating-type Seismic Isolation Method: Horizontal Seismic Isolation Performance and Stability to Wind Force”, Architectural Institute of Japan Conference Annual Meeting p765-766, September 1999 JP 2004-27732 A JP 2000-110402 A JP-A-2005-83018

The conventional seismic isolation pit in the floating type base isolation structure includes a side wall and a floor bottom that are formed by digging the ground to a desired depth and have strength to withstand earth pressure. In addition, a clearance having a predetermined width must be provided over the entire circumference between the side wall of the floating structure body and the side wall of the seismic isolation pit.
The introduction of a conventional floating-type seismic isolation structure to a small-scale building or a general house requires a large seismic isolation pit in proportion to the scale, and lacks rationality and economy.

The present invention was made in view of the circumstances as described above, the provision of the seismic isolation layer to confine Alternative pressurized liquid seismic isolation pit between the floating structure body and a flat earth plate It is an object of the present invention to provide a floating type seismic isolation structure with pressurized liquid that is more functional and economical.

In the present invention, characterized in that as a means of confining the liquid, provided with a seismic isolation layer surrounded by the sealing material having both of Alternative example elastic function of MenShinpi Tsu bets between the floating structure body and flat ground And
Floating-type seismic isolation structure is first a partial floating body, with a seismic isolation layer, a pressurized liquid injected into the seismic isolation layer, and a liquid pressurization mechanism for pressurizing and adjusting the pressurized liquid. A seismic isolation device that supports part of the fixed load and insulates the horizontal behavior of the floating structure body and the ground is provided.
The liquid pressurizing mechanism uses, for example, the pressure due to the height from the upper surface of the seismic isolation layer in contact with the bottom of the floating structure body to the liquid level of the liquid storage tank installed in the floating structure body. Pressurized liquid pressure-adjusted by the pressure mechanism is injected into the seismic isolation layer and acts as a buoyancy B that pushes the upper surface of the seismic isolation layer vertically upward.
For example, during normal or small-scale earthquakes, the floating body seismic isolation structure should function as a partially floating body isolation structure by partially floating the floating structure body with pressurized liquid that has been pressurized and adjusted by the liquid pressure mechanism. Is possible.

In the present invention, a fluid chamber composed of an air layer and a liquid layer is provided in a recess formed at the bottom of the floating structure main body and the upper part of the seismic isolation layer, and a compressed air mechanism for sending compressed air into the fluid chamber is provided. Features.
For example, when a large-scale earthquake occurs, the compressed air mechanism operates and compressed air is injected into the fluid chamber, so that the floating body seismic isolation structure instantly moves the floating structure body from a partial floating body to a fully floating body. It can function as a seismic isolation structure.

In the present invention, the fluid chamber includes a partition wall, a resistance plate, an extension piece, and a resistance body of a water-permeable attenuation material . With these resistors, the floating type base isolation structure can exhibit a damping effect and improve the base isolation performance.

In the present invention, each side of the fluid chamber is divided into two or more by a partition, and the fluid chamber is divided into four or more small chambers. By dividing the fluid chamber, the floating base-isolated structure can maintain the static stability of the fully floating base-isolated structure and obtain a restoring force.

The present invention is characterized in that a plurality of air chambers having different volumes are provided in the basement or the like outside the floating structure main body to communicate with each air layer. As a result, a sufficient volume of air layer can be secured while keeping the center of gravity of the floating structure main body low, and the floating-type seismic isolation structure can improve vertical isolation performance and prevent resonance.

According to the present invention, a seismic isolation layer surrounded by a sealing material instead of the seismic isolation pit between the floating structure main body and the flat ground and a liquid pressurizing mechanism for pressurizing the liquid are provided. Pressurized liquid is injected into the seismic isolation layer, and the sealing material on the side of the seismic isolation layer is combined with an elastic function such as rubber, or a member with an elastic function is placed inside or outside the sealing material, and it fluctuates. By providing a seismic isolation device that supports a part of the load and fixed load and insulates the horizontal behavior of the floating structure body and the ground, the floating structure body can be freely adjusted from the partial floating body to the complete floating body. . In the partial floating type seismic isolation structure, the horizontal seismic isolation effect can be exhibited.

According to the present invention, by providing a fluid chamber composed of an air layer and a liquid layer surrounded by a partition wall in a recess formed at the bottom of the floating structure body and the upper part of the seismic isolation layer, and by providing a compressed air mechanism, For example, compressed air can be injected into the fluid chamber during a large earthquake, and the floating structure main body can be instantaneously transferred from the partial floating body to the complete floating body.
In the fully floating seismic isolation structure, the horizontal seismic isolation effect can be further enhanced, and the vertical seismic isolation effect can be exhibited by the air cushion effect of the air layer of the fluid chamber.

According to the present invention, the damping effect can be exhibited by providing the water-permeable damping material in the liquid layer of the fluid chamber.

According to the present invention, a partition wall that divides the fluid chamber, a resistance plate arranged in parallel to the partition wall, an extension piece perpendicular to the partition wall end and the resistance plate end, and the like are provided. When moving in the liquid in the liquid layer, the liquid's resistance proportional to the square of the velocity is received, and a damping effect can be exhibited.

According to the present invention, the partition wall, the resistance plate, the extension piece and the like are provided in the same manner as in the previous section, so that when these move in the liquid of the base isolation layer and the liquid layer, the resistance force of the liquid proportional to the acceleration is also received, and the mass As a result, an additional mass effect is obtained that behaves as if increased. That is, the weight of the floating structure main body is apparently increased, and the seismic isolation cycle can be prolonged and the seismic isolation performance can be improved.

According to the present invention, an air layer having a different height is provided in each of the small chambers, each side of which is divided into two or more by a partition wall and the fluid chamber is divided into four or more, so that the static chamber during the complete floating body is provided. It is possible to maintain the mechanical stability and obtain the restoring force, and to prevent the resonance with the dominant frequency of the earthquake motion.

According to the present invention, a plurality of air chambers having different volumes are provided in the basement or the like outside the floating structure main body so as to communicate with each air layer, so that an air layer having a sufficient volume amount while keeping the center of gravity of the floating structure main body low. Can be secured, and the effect of preventing the resonance by improving the seismic isolation performance in the vertical direction can be provided.

A floating-type seismic isolation structure using pressurized liquid that does not require the seismic isolation pit according to the first embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a diagram showing an outline of a partially floating seismic isolation structure and a liquid pressurizing mechanism related to a floating body seismic isolation structure using a pressurized liquid that does not require a seismic isolation pit according to the first embodiment of the present invention.

As shown in FIG. 1, the floating-type seismic isolation structure 1 using pressurized liquid that does not require the seismic isolation pit of the first embodiment includes a floating structure main body 2 and a flat ground 6 as a means for confining the liquid 4 . the seismic isolation layer 3 surrounded provided by the sealing member 5 to substitute for seismic isolation pit between, for example, allowed Awasemota the elastic function such as rubber sealant fifth aspect of the isolation layer 3, the seismic isolation layer 3 A pressurized liquid 4 injected into the liquid, a liquid pressurizing mechanism 8 for adjusting the pressure of the liquid 4, and a seismic isolation device 7 that insulates the horizontal behavior of the floating structure body 2 and the ground 6 during partial floating. It is prepared for.
Here, the side sealing material 5 is provided with an elastic function such as rubber, but a member having a similar elastic function may be arranged inside or outside the side sealing material 5.
In FIG. 1, an elastic sliding bearing is used as the seismic isolation device 7, and the vertical fluctuation load generated in the floating body 2 and the remaining fixed load offset by the buoyancy caused by the pressurized liquid 4 It is supported by the ground 6 through a sliding bearing.

The liquid pressurizing mechanism 8 in FIG. 1 shows an outline of using pressure depending on height. The liquid 4 injected into the seismic isolation layer 3 is pressurized by the liquid pressurizing mechanism 8.
In the present invention, an active mechanical liquid pressurizing mechanism may be used because the liquid 4 only needs to be pressurized.
As shown in FIG. 1, for example, the liquid pressurizing mechanism 8 includes a liquid storage tank 8a for storing the liquid 4, a liquid distribution pipe 8b for injecting, discharging or supplying the liquid 4, and a liquid distribution attached to the liquid distribution pipe 8b. It consists of a pipe valve 8c and a water level adjustment slider 8d for adjusting the horizontal position of the liquid level in the liquid storage tank 8a. In the initial state where the seismic isolation layer 3 is filled with air, the liquid 4 is injected into the seismic isolation layer 3 while the leak and relief valve 10d is opened and evacuated.

In the liquid pressurizing mechanism 8 in FIG. 1, the pressure in the base isolation layer 3 is adjusted by controlling the height d from the upper surface of the base isolation layer 3 to the liquid level in the liquid storage tank 8a.
When the effective pressure receiving area of the isolation layer 3 upper surface in contact with the mass floating structure body 2 bottom of floating structure body 2, A,: floating construction load W = M · g ·· · ( 1) of the main body 2 M The upper surface of the seismic isolation layer 3 receives buoyancy B caused by pressurized liquid.
Buoyancy B is as follows.
B = ρ · A · d · g ·········· · (2) ρ: density of the liquid 4 (g / cm ³⁾ Here, M and 20 × ¹⁰ 3 kg, the [rho 1 g / When cm ³ and A are 20 × 10 ⁴ cm ² , (1) and (2) are as follows. In addition, since the force of the rubber | gum etc. of the side seal material 5 is small compared with W, it does not consider.
M · g = 20 × 10 ³ × 10 ³ (g) × g (cm / sec ² )
B = 1 (g / cm ³ ) × 20 × 10 ⁴ (cm ² ) × d (cm) × g (cm / sec ² )
When the elastic sliding bearing of the seismic isolation device 7 is lifted from the ground 6, (1) = (2) .
Therefore, d = 100 cm is obtained.
That is, when the liquid level adjustment slider 8d is set so that the liquid level in the liquid storage tank 8a is 100 cm above the upper surface of the seismic isolation layer 3, and the liquid 4 is injected to that level, the liquid level in the liquid storage tank 8a Becomes a draft and the floating structure main body 2 becomes a complete floating body.
In that case, the pressure (= gauge pressure) of the upper surface of the seismic isolation layer 3 that receives buoyancy is 0.1 at (engineering pressure, kgf / cm ² ), and the absolute pressure is 1.1 at.
In addition, the floating structure main body 2 is a partial floating body in the range of 0 cm <d <100 cm. By controlling the height of the liquid level in the liquid storage tank 8a from 0 cm to 100 cm from the upper surface of the seismic isolation layer 3, the absolute pressure on the upper surface of the seismic isolation layer 3 is proportionally increased from 1.0 at to 1.1 at. It becomes possible to adjust.
That is, by operating the liquid level in the liquid storage tank 8a with the water level adjustment slider 8d, the floating structure body 2 can be freely adjusted from the partial floating body to the complete floating body.

FIG. 4 is a diagram showing an outline of a cross section when an elastic body such as rubber is used for the side seal material 5 of the seismic isolation layer 3. When liquid 4 is poured into the seismic isolation layer 3 and the liquid level reaches the upper surface of the seismic isolation layer 3 (d = 0), the water level is the height h of the seismic isolation layer 3 and the pressure at the bottom is H It is said. Further, when the liquid 4 continues to be injected and the liquid level in the liquid storage tank 8a of the liquid pressurizing mechanism 8 reaches d from the upper surface of the base isolation layer 3, the pressure on the upper surface of the base isolation layer 3 that receives buoyancy. Is D.
When the liquid level is 0 from the upper surface of the seismic isolation layer 3, the side seal material 5 is shaped so that the liquid pressure is applied as it falls downward as shown in FIG. It is assumed that when the height reaches the height, the shape is close to an arc as shown in FIG.
That is, the length of the elastic body such as rubber in the cross section of the side sealing material 5 extending from FIG. 4A to FIG. 4B is the length of the liquid 4 injected from the liquid level height 0 to d. Due to pressure D. In addition, the volume of the liquid 4 injected at that time is approximately the arc area Sarc increased from FIG. 4A to FIG. 4B multiplied by the length of the entire side surface of the seismic isolation layer 3. .

When an elastic body such as rubber is used for the side seal material 5 of the seismic isolation layer 3, the side seal material 5 also functions as a horizontal spring material for controlling the horizontal deformation amount.
Therefore, as shown in FIG. 1, the seismic isolation layer 3 has a function of supporting the floating structure main body 2 by generating the buoyancy B with the pressurized liquid 4, and the entire side surface of the seismic isolation layer 3 becomes a horizontal spring material and is horizontal. Since it has deformation capability and restoration performance, the entire seismic isolation layer 3 functions as a huge seismic isolation device.

The seismic isolation device 7 is, for example, an elastic sliding support, and a plurality of seismic isolation devices 7 are arranged on the ground 6 with a predetermined distance, and the floating structure main body 2 is disposed on the upper part. The elastic sliding bearing is a sliding bearing in which laminated rubbers are connected in series.
In the present invention, the seismic isolation device 7 is not limited to the elastic sliding bearing.
The seismic isolation device 7 thus arranged has a function of supporting a load excluding the buoyancy B received from the upper surface of the seismic isolation layer 3 from the load of the floating structure main body 2 during partial floating, and the floating structure main body 2. It has a function of insulating the horizontal behavior from the ground 6.
In FIG. 1 and FIG. 2, the seismic isolation device 7 is disposed outside the seismic isolation layer 3, but may be disposed inside the seismic isolation layer 3.

The first embodiment of the present invention is here for the purpose of dealing with, for example, small and medium-sized earthquakes, and has a standby mode for instantaneously shifting to the second embodiment for large-scale earthquakes.
In the first embodiment, when an elastic body such as rubber is used for the side sealing material 5 of the seismic isolation layer 3 and an elastic sliding bearing is used for the seismic isolation device 7, for example, the sliding bearing does not slip during a small-scale earthquake. Then, since the horizontal spring of the side surface sealing material 5 and the laminated rubber of the elastic sliding bearing are configured in parallel, the sum of their horizontal rigidity becomes all the rigidity in the seismic isolation layer portion.
Further, for example, if the elastic sliding bearing slides during an earthquake of medium scale or larger, the laminated rubber is insulated from the ground 6 and the rigidity of the seismic isolation layer is only the horizontal spring of the side sealing material 5.

A floating-type seismic isolation structure using pressurized liquid that does not require the seismic isolation pit according to the second embodiment of the present invention will be described below with reference to FIG.
FIG. 2 is a diagram showing an outline of a fully floating seismic isolation structure, a fluid chamber, and a compressed air mechanism related to a floating seismic isolation structure using a pressurized liquid that does not require a seismic isolation pit according to the second embodiment of the present invention.
As shown in FIG. 2, the second embodiment includes a fluid chamber 9 and a fluid chamber in addition to the floating-type seismic isolation structure 1 using pressurized liquid that does not require the seismic isolation pit of the first embodiment of FIG. 1. 9 is provided with a compressed air mechanism 10 for sending compressed air.

As shown in FIG. 2, the fluid chamber 9 is installed by being surrounded by a partition wall in a recess formed in the bottom of the floating structure body 2 and the upper part of the seismic isolation layer 3. Further, each fluid chamber 9 is divided into two or more by a partition on each side, and the fluid chamber 9 is divided into four or more small chambers.
The fluid chamber 9 includes an upper air layer 9a in which compressed air is injected and the compressed air is accumulated, and a liquid layer 9b in which the liquid 4 is accumulated in the lower part.
The fluid chamber 9 includes a partition wall 9c that surrounds and divides the fluid chamber 9, a resistance plate 9d that is disposed in parallel to the partition wall 9c, a water-permeable damping material 9e that is disposed in the liquid layer 9b, an end of the partition wall 9c, and It consists of the extension piece 9f arrange | positioned orthogonally to the resistance board 9d end.
The fluid chamber 9 has a strong damping function as a damper due to its shape. The number of resistor plates 9d is effectively arranged according to the size of the fluid chamber 9.
Note that the surface receiving the buoyancy is considered to be the boundary surface between each air layer 9a and the liquid layer 9b of the fluid chamber 9 and the upper surface of the seismic isolation layer 3 excluding the fluid chamber 9, and the fluid chamber is provided. The effective pressure receiving area does not change. The average horizontal plane of the upper surface of the seismic isolation layer 3 excluding the boundary surfaces of the fluid chamber 9 and the fluid chamber 9 portion is the height of the surface receiving buoyancy.
Therefore, in the liquid pressurizing mechanism 8, the height from the average horizontal plane to the liquid level in the liquid storage tank 8a is the height at which the liquid 4 is pressurized.

As shown in FIG. 2, for example, the compressed air mechanism 10 includes an air tank 10 e that stores compressed air, an air pipe 10 a that connects the air tank 10 e and the fluid chamber 9, and the like to prevent backflow that flows compressed air in only one direction. Supplying compressed air to the check valve 10b, an air valve 10c with an earthquake detector attached to the air pipe 10a, a leak and relief valve 10d including a compressed air vent valve such as a fluid chamber 9 and a safety valve in parallel, and an air tank 10e Air compressor 10f and the like.

Normally, the floating structure body 2 is provided as a partial floating body. For example, when a large-scale earthquake motion is detected, the air valve 10c with the earthquake detector is opened, and the air tank 10e is passed through the air pipe 10a to the air layer 9a. Compressed air is injected, and the floating structure main body 2 becomes a complete floating body instantaneously by the pressure.
Each valve can be opened and closed manually.

As a simulation model of the floating seismic isolation structure 1 in FIG. 2, the specification values are determined as shown in FIG. 7, and the natural period and the like are analyzed below.

従って、液体４の付加質量効果、抵抗による減衰効果を考慮しなければ、完全浮体時の水平方向の運動方程式は次のとおり。ただしＭは浮体構造物本体２の質量とする。

Ｋ_Ｇは免震層３の側面シール材５のゴムの剛性の総和であり、次のとおり。
Ｋ_Ｇ ＝Ｇ・Ｅ／ｈ ・・・・・・・・・・・・・・・・・（４）
Ｇ ：ゴムせん断弾性率
Ｅ ：ゴム断面積
浮体式免震構造物１の諸元値を図７より参照し、ゴム断面積Ｅ＝３６０ｃｍ^２を得る。
Ｇ＝２、３、４ｋｇｆ／ｃｍ^２の３種とすると、（４）からＫ_Ｇ＝２４、３６、４８ｋｇｆ／ｃｍを得る。初速値は総エネルギー入力の速度換算値Ｖｅとして、１２０、１５０、２００ｃｍ／ｓｅｃの３種とする。
（３）式に上記数値を設定し、０．００２秒刻みで数値計算して得られた解を、Ｇ別Ｖｅ別にグラフ化し図示したものが図５（ａ）、（ｂ）におけるＯＲＧ線である。結論として、せん断弾性率、初速値が小さい程、免震周期が長期化する。
（３）式における免震周期Ｔ_Ｏは、Ｇ＝４ｋｇｆ／ｃｍ^２、Ｖｅ ＝２００ｃｍ／ｓｅｃの場合、免震性能の指標となる４秒免震を超える次の数値が得られる。
Ｔ_Ｏ ＝ ４．７ｓｅｃ ・・・・・・・・・・・・・・・・・・（５） As shown in FIG. 2, in the completely floating body into which the compressed air is injected, the elastic sliding bearing of the seismic isolation device 7 is in a state of being levitated away from the ground 6.
When a rubber elastic body is used for the side sealing material 5 of the seismic isolation layer 3, the side sealing material 5 becomes a horizontal spring material for controlling the horizontal deformation amount.
FIG. 4 (c) shows that when rubber is used for the side sealing material 5, the rubber surface is not a curved surface but is a plane instead of a curved surface for convenience, the height of the seismic isolation layer 3 is h, and it is horizontal by xcm from the initial value. The horizontal rigidity when the floating structure main body 2 is relatively displaced is illustrated. In the following, when the floating structure body 2 is completely floated, an equation of motion in the x-axis direction by the side sealing material 5 of the seismic isolation layer 3 is established and the seismic isolation period which is its natural period is considered.
Elongation △ hx rubber elongation △ h and its horizontal direction when the horizontal displacement was x, as follows.

Therefore, if the additional mass effect of liquid 4 and the damping effect due to resistance are not considered, the equation of motion in the horizontal direction when completely floating is as follows. However, M is the mass of the floating structure body 2.

K _G is the sum of the stiffness of the rubber of the side seal member 5 of the base isolation layer 3, as follows.
_{K G = G · E / h} ················ · (4)
G: Rubber shear modulus E: Rubber cross sectional area Floating body type seismic isolation structure 1 is referred to from FIG. 7, and rubber cross sectional area E = 360 cm ² is obtained.
Assuming three types of G = ² , 3, 4 kgf / cm ² , K _G = 24, 36, 48 kgf / cm is obtained from (4) . There are three initial speed values of 120, 150, and 200 cm / sec as the speed converted value Ve of the total energy input.
The values obtained by setting the above numerical values in equation (3) and calculating the numerical values in increments of 0.002 seconds are graphed and illustrated by Ve for each G. The ORG lines in FIGS. 5 (a) and 5 (b) are shown. is there. In conclusion, the smaller the shear modulus and initial velocity value, the longer the seismic isolation cycle.
As for the seismic isolation period T _{O in the} equation (3) , when G = 4 kgf / cm ² and Ve = 200 cm / sec, the following numerical value exceeding the 4-second seismic isolation serving as an index of the seismic isolation performance is obtained.
_{T O = 4.7sec ················· · (5} )

ρ ：液体の密度
Ｃｄ：抵抗係数
Ｖ^２：速度の二乗
Ｓ ：運動方向からの投射断面積（造波抵抗等のときＳ→▽^２／３ ▽：排水容量）なお、緩やかな運動における速度に比例する粘性抵抗は小さいので考慮しない。
従って、（３）の運動方程式に上記抗力Ｒを付加すると次の式のとおり。

ただし、ｓｉｇｎ（ｘ′）はｘ′の正負符号を表す。
ここで、抗力のうち形状抵抗のみを考慮し、ρ＝１ｇ／ｃｍ^３、Ｃｄ＝１．２とする。
また水平運動における隔壁９ｃおよび抵抗板９ｄの運動方向からの投射断面積について、Ｓ＝１０、１３、１６×１０^４ｃｍ^２とする。
透水減衰材９ｅおよび延出片９ｆは、ここでは水平運動の形状抵抗体として考慮しない。（６）式を前項と同様に数値計算して、Ｓ＝１６ｍ^２でＧ別Ｖｅ別にグラフ化し図示したものが図５（ａ）、（ｂ）におけるＳ線であり、投射断面積Ｓ別に図示したものが図５（ｃ）である。結論として、せん断弾性率、初速値が小さい程、また投射断面積が大きい程、免震周期が長期化する。In the preceding paragraph, when the partition wall 9c, the resistance plate 9d, the extension piece 9f, etc. move in the liquid 4 of the seismic isolation layer 3 and the liquid layer 9b, shape resistance (pressure or inertial resistance), wave resistance, vortex Receive resistance. The drag R is as follows:

ρ: Density of liquid Cd: Resistance coefficient V ² : Square of velocity S: Projected cross section from the direction of motion (when wave resistance etc. S → ▽ ^2/3 ▽: Drainage capacity) The proportional viscous resistance is small and is not considered.
Therefore, when the drag R is added to the equation of motion of (3), the following equation is obtained.

However, sign (x ′) represents the sign of x ′.
Here, ρ = 1 g / cm ³ and Cd = 1.2 are considered in consideration of only the shape resistance of the drag.
Moreover, it is set as S = 10, 13, 16 * 10 < ⁴ > cm < ² > about the projection sectional area from the moving direction of the partition 9c and the resistance board 9d in horizontal movement.
Here, the water-permeable damping material 9e and the extension piece 9f are not considered as shape resistors for horizontal movement. The equation (6) is numerically calculated in the same manner as in the previous section, and S = 16 m ² and graphed for each Ve by G. The S lines in FIGS. FIG. 5C shows the result. In conclusion, the smaller the shear modulus and initial velocity value and the larger the projected cross section, the longer the seismic isolation period.

As in the previous section, when the partition wall 9c, the resistance plate 9d and the extension piece 9f move in the liquid 4 of the base isolation layer 3 and the liquid layer 9b, a resistance proportional to the acceleration is also received.
At that time, if the resistance coefficient is Mr, −Mr · x ″ is added as a drag to the right side of the equation of motion of (6) . If this is moved to the left side and arranged, it becomes (M + Mr) · x ″. It can be seen that an additional mass effect on the inertial force occurs.
In other words, the additional mass effect increases the apparent mass, thereby prolonging the base isolation cycle and improving the base isolation performance.

Ｎｙ面のゴムの力ｆｙ ＝Ｋｙ・Ｌｘ／２・θ＝ ２．６７×１０^３θ（ｋｇｆ）

Ｎｘ面のゴムの力ｆｘ ＝Ｋｘ・ｘ・θ＝０．０２６７θ・ｘ^２（ｋｇｆ）

重心Ｇの慣性モーメントＩ_Ｇ、ＧからＬｚ／２だけ鉛直下方にあるＢの慣性モーメントＩ_Ｂは次のとおり。

Ｂを原点とし、ｚ’軸がθだけ傾いたときの運動方程式は次のとおり。

右辺＝−Ｃ・θとする。
（７）、（８）、（１０）よりＣは次のとおり。ただし、１ ｋｇｆ＝９８０ｋｇ・ｃｍ／ｓｅｃ^２とする。
Ｃ＝ ４．５６×１０^９ ・・・・・・・・・・・・・・・・（１１）
従って、（１０）の運動方程式の周期Ｔｒは、（９）（１１）より次のとおり。

図７の諸元表の条件等で免震層３部分は４．８秒程度の固有ローリング周期をもつ。
（５）および（６）式の水平免震周期に近いことから、共振によるロッキング運動への注意が必要である。Rolling of the seismic isolation layer 3 portion when the liquid 4 is injected and the fluid chamber 9 is filled with only the liquid 4 in a situation where air is extracted from the fluid chamber 9 by the leak and relief valve 10d, and the floating structure body 2 is completely floated. Analyze movement.
Since the air layer 9a does not exist in the fluid chamber 9, the floating structure main body 2 does not move up and down, and only the rolling motion occurs, and the resistance and additional moment of inertia due to the seismic isolation layer 3 are not considered. For the specification values, refer to FIG. 7 and the shear modulus G of rubber is 4 kgf / cm ² .
The outline of the rolling motion of the seismic isolation layer 3 is as shown in FIGS. 6 (a) and 6 (b).
A case is assumed in which rolling is performed about the axis of the y ′ axis with the origin B as the center of the buoyancy of the upper surface of the seismic isolation layer 3 and the z ′ axis is inclined by θ.
Since θ is small, it is linearly approximated as sin θ = θ. Moreover, even if it inclines only (theta), the elastic sliding bearing of the seismic isolation apparatus 7 will be in the state which has floated away from the ground 6. FIG.
The moment by the rubber in the rolling motion is as follows.

Ny-plane rubber force fy = Ky · Lx / 2 · θ = 2.67 × 10 ³ θ (kgf)

Nx face rubber force fx = Kx · x · θ = 0.0267θ · x ² (kgf)

Moment of inertia _I G of the center of gravity G, the moment of inertia _{I B} of B with only Lz / 2 vertically downward from G as follows.

The equation of motion when B is the origin and the z ′ axis is tilted by θ is as follows.

Right side = −C · θ.
From (7), (8) and (10) , C is as follows. However, 1 kgf = 980 kg · cm / sec ² .
^{C = 4.56 × 10 9 ··············· ·} (11)
Therefore, the period Tr of the equation of motion of (10) is as follows from (9) and (11) .

The seismic isolation layer 3 has a natural rolling period of about 4.8 seconds due to the conditions in the specification table of FIG.
Since it is close to the horizontal seismic isolation cycle of equations (5) and (6) , attention to rocking motion due to resonance is necessary.

Assuming that the effective pressure receiving areas of the fluid chamber 9 and the seismic isolation layer 3 are substantially equal during the complete floating body in which the compressed air is injected, the floating structure body 2 floats due to the fluid chamber 9 receiving a buoyant force substantially equal to the load W. The load applied to the liquid chamber 9 is supported by the seismic isolation layer 3 via the air layer 9a of the fluid chamber 9 in series.
That is, it can be expected that a seismic isolation effect in the vertical direction is obtained by the air cushion effect due to the rigidity of the air in the air layer 9a.

γ ：ポリトロピック数で動１．４
Ｐａ：絶対圧力（Ｐ＋１）
Ｖａ：空気層９ａの容積
Ｖｔ：エアータンク１０ｅの容積
ここではエアータンク１０ｅの容積Ｖｔおよび免震層３側面シール材５の剛性は考慮しないものとする。
空気層９ａの気柱の高さをＨａ（Ｈａ＝Ｖａ／Ａａ）とすると（１２）式は次のとおり、

空気層９ａの固有周期Ｔａ、固有振動数ｆａは一般に次のとおり。

ただし、空気層にかかる浮体構造物本体２の荷重をＷａ（Ｗａ＝（Ｐａ−１）・Ａａ）と し、Ｗａ／Ａａ＝Ｗ／Ａとする。また、図７の諸元表の条件でＰａ＝１．１ａｔとする。 固有振動数ｆａが１Ｈｚ以下であれば十分な免震効果が得られることが知られている。
ここでは空気層９ａの高さＨａが約３８０ｃｍ以上であれば、ｆａは１Ｈｚ以下となる。 Here the effective pressure receiving area of the air layer 9a and Aa, consider the air cushion effect by the air layer 9a when the A ≒ Aa.
The air spring constant Ka of the air layer 9a is approximately as follows.

γ: Movement by polytropic number 1.4
Pa: Absolute pressure (P + 1)
Va: volume of the air layer 9a Vt: volume of the air tank 10e Here, the volume Vt of the air tank 10e and the rigidity of the seismic isolation layer 3 side surface sealing material 5 are not considered.
If the height of the air column of the air layer 9a is Ha (Ha = Va / Aa) , the formula (12) is as follows:

The natural period Ta and the natural frequency fa of the air layer 9a are generally as follows.

However, the load of the floating structure main body 2 applied to the air layer is Wa (Wa = (Pa−1) · Aa), and Wa / Aa = W / A. In addition, Pa = 1.1 at in the conditions of the specification table of FIG. It is known that a sufficient seismic isolation effect can be obtained if the natural frequency fa is 1 Hz or less.
Here, if the height Ha of the air layer 9a is about 380 cm or more, fa is 1 Hz or less.

Although it is not necessary to consider the resonance of the seismic isolation layer 3 and the air layer 9a under the conditions in the specification table of FIG. 7, the resonance with the ground motion is prevented by the fact that the natural frequency fa is about the same as the dominant frequency of the ground motion. Consideration is necessary.
In order to prevent resonance with seismic motion, for example, the compressed air injection method is devised to change the height Ha of each air layer 9a in the small chamber of the fluid chamber 9.
In order to obtain a sufficient seismic isolation effect by the air spring under the conditions shown in the specification table of FIG. 7, the height Ha of the air column of the air layer 9a needs to be about 380 cm or more as described above. In order to fill the volume Va of the air layer 9a with the compressed air, a large volume of compressed air is injected, and it takes time for the injection, and the floating structure body 2 may not be completely floated instantaneously.
Therefore, the compressed air is injected into the air layer 9a of the fluid chamber 9 in advance to the required height in order to cope with the injection amount .

Even in the present invention characterized by providing a seismic isolation layer, when compressed air is injected into the fluid chamber 9, the static stability of the floating body 2 is maintained and a restoring force is obtained in the same manner as in Patent Document 2. Therefore, it is necessary to divide each side of the fluid chamber 9 into two or more by the partition wall 9c and divide the fluid chamber into four or more small chambers. When dividing, it is desirable that they are equally spaced and symmetric at the buoyancy center point .

A floating-type seismic isolation structure using pressurized liquid that does not require the seismic isolation pit according to the third embodiment of the present invention will be described below with reference to FIG.
FIG. 3 is a diagram showing an outline of a fully floating seismic isolation structure and an air chamber related to a floating seismic isolation structure using a pressurized liquid that does not require a seismic isolation pit according to the third embodiment of the present invention.
As shown in FIG. 3, the third embodiment is configured by providing an air chamber 9g in addition to the floating-type seismic isolation structure 1 using pressurized liquid that does not require the seismic isolation pit of the second embodiment of FIG. Is done.

In the air layer 9a in the second embodiment, in order to obtain an effective seismic isolation effect by the air spring , it is necessary to secure a sufficient volume , that is , a sufficient height of the air column.
However, since the light air layer is positioned at the bottom of the floating structure main body 2 as it is, the position of the center of gravity of the floating structure main body 2 becomes high, resulting in a poorly balanced structure.
Therefore, as shown in FIG. 3, for example, by installing a plurality of independent air chambers 9g having different volumes in the basement below the floating structure body 2 and communicating with the air layers 9a, a sufficiently large air column can be obtained. An air layer with a height of can be secured.
Each air chamber 9g may be installed anywhere outside the floating structure main body 2 as long as it is airtight and can be pressurized and communicated with each air layer 9a by a flexible air pipe or the like.
The air chamber 9g can secure a sufficient volume of the air layer 9a while keeping the center of gravity of the floating structure main body 2 low, improve the vertical seismic isolation performance and prevent resonance with the dominant frequency of seismic motion, etc. It becomes possible.

The figure which shows the outline | summary of the partial floating-type seismic isolation structure and liquid pressurization mechanism regarding the floating-type seismic isolation structure by the pressurized liquid which does not require the seismic isolation pit of 1st embodiment in this invention The figure which shows the outline | summary of the completely floating body type seismic isolation structure regarding the floating body type base isolation structure by the pressurized liquid which does not require the base isolation pit of 2nd embodiment in this invention, a fluid chamber, and a compressed air mechanism The figure which shows the outline | summary of the complete floating body type seismic isolation structure and air chamber regarding the floating type base isolation structure by the pressurized liquid which does not require the base isolation pit of 3rd embodiment in this invention The figure which shows the cross-sectional outline | summary of the seismic isolation layer in this invention The figure which shows the seismic isolation period analysis of the horizontal motion of the seismic isolation layer part in this invention The figure which shows the outline | summary of the rolling motion of the seismic isolation layer part in this invention Specification table for floating seismic isolation structure in simulation model The figure which shows the outline of the conventional full floating type seismic isolation structure The figure which shows the outline of the conventional partial floating type seismic isolation structure

DESCRIPTION OF SYMBOLS 1 Floating type seismic isolation structure 2 Floating structure main body 3 Seismic isolation layer 4 Liquid 5 Sealing material 6 Ground 7 Seismic isolation device 8 Liquid pressurization mechanism 8a Liquid storage tank 8b Liquid distribution pipe 8c Liquid distribution pipe valve 8d Water level adjustment slider 9 Fluid chamber 9a Air layer 9b Liquid layer 9c Partition wall 9d Resistance plate 9e Permeable damping material 9f Extension piece 9g Air chamber 10 Compressed air mechanism 10a Air pipe 10b Check valve 10c Air valve 10d with seismic detector Leak & relief valve 10e Air tank 10f Air compressor 11 Floating type seismic isolation structure 12 Floating structure main body 13 Seismic isolation pit 14 Liquid 15 Drilling bottom surface 16 Ground 17 Seismic isolation device (low shear rigidity structure)

Claims (7)

A seismic isolation layer surrounded by a sealing material instead of the seismic isolation pit is provided between the floating structure main body and the flat ground, and the sealing material has an elastic function or a member having an elastic function. Basically, it is placed inside or outside the sealing material, and by injecting pressurized liquid into the seismic isolation layer, the floating body itself is partially or completely floated to obtain horizontal seismic isolation performance. In the partially floating type seismic isolation structure, it has a vertical rigidity that supports a fixed load that does not cancel the floating body with pressurized liquid in the seismic isolation layer, and insulates the horizontal behavior of the floating structure body and the ground inside or outside the base isolation layer A floating-type seismic isolation structure comprising a liquid pressurization mechanism for pressurizing and adjusting a liquid to be injected into the seismic isolation layer in a part or a complete floating-type seismic isolation structure. 2. The floating body-type isolation system according to claim 1, wherein a fluid chamber composed of an air layer and a liquid layer is provided in a recess formed in the bottom of the floating structure body and the top of the isolation layer. Seismic structure. 3. The floating type seismic isolation structure according to claim 2, further comprising a compressed air mechanism for sending compressed air into the fluid chamber. 4. The floating type seismic isolation structure according to claim 3, wherein a permeable damping material, a partition wall, a resistance plate, and an extension piece are arranged in the fluid chamber as a resistance body. . 5. The fully floating seismic isolation structure according to claim 4, wherein each side of the fluid chamber is divided into two or more by a partition and the fluid chamber is divided into four or more small chambers, thereby maintaining the static stability of the floating structure main body. A floating seismic isolation system characterized by having a restoring force. 6. The fully floating body-isolated structure according to claim 5, wherein resonance with the dominant frequency of seismic motion is prevented by changing the compressed air capacity of each air layer in the fluid chamber. 6. The fully floating seismic isolation structure according to claim 5, wherein a floating structure is provided in order to maintain a low center of gravity of the floating structure main body and secure a sufficient volume of air layer to improve vertical isolation performance and prevent resonance. A floating-type seismic isolation structure characterized by providing a plurality of air chambers with different volumes in the basement outside the body.

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