JP2004353257A - Floating body damping apparatus, and floating body type base isolated structure equipped with floating body damping apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floating body damping apparatus and a floating body type base isolated structure using the floating body damping apparatus capable of suppressing the horizontal behavior of a floating body even to horizontal external force in a periodic band close to a natural period applied to the floating body. <P>SOLUTION: The floating body damping apparatus 8 is installed at the bottom face of a floating body structure body 2 of the floating body type base isolated structure 1 constituted such that load (W<SB>1</SB>-ΔW<SB>1</SB>) excluding a part (ΔW<SB>1</SB>) of fixed load W<SB>1</SB>of the floating body structure body 2 is offset by buoyancy B and that fluctuating load W<SB>2</SB>and the part (ΔW<SB>1</SB>) of the fixed load W1 are supported by a low shearing rigidity structure 9. The floating body damping apparatus 8 is composed of a member with water permeating performance and formed as a solid structure with prescribed thickness and area. The floating body damping apparatus 8 acquires damping performance utilizing energy dispersion caused by the viscosity of liquid according to the relative velocity of the floating body damping apparatus 8 and liquid particles infiltrating inside. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a floating body damping device for stably maintaining the behavior of a floating body floating in a liquid, and a floating type seismic isolation structure provided with the floating body damping device.
[0002]
[Prior art]
Conventionally, as shown in FIG. 5, a floating type seismic isolation structure 11 of a complete floating structure, which has a long natural period by floating a structure body 12 in a liquid 13, has a high resistance to horizontal earthquake motion. It is widely known as a structure capable of obtaining a seismic isolation effect (see Non-Patent Document 1). Although the floating type seismic isolation structure 11 having such a completely floating structure has high seismic isolation performance, the structure main body 12 easily tilts due to the fluctuating load generated on the structure main body 12, or follows the fluctuation of the liquid level. Thus, there has been a problem in terms of comfort and usability, for example, the structure body 12 fluctuates in the vertical direction.
[0003]
Therefore, in order to cope with these problems, as shown in FIG. 6, a part of the fixed load of the structure main body 12 itself is removed by a seismic isolation device or the like without completely floating the structure main body 12 in the liquid 13. A floating type seismic isolation structure 11 having a partially floating structure that is supported via a low shear structure 15 has been devised (see Patent Document 1). The floating type seismic isolation structure 11 having the partial floating structure can suppress the vertical behavior while securing the same seismic isolation performance as the floating type seismic isolation structure 11 having the completely floating structure described above, and can be used as a fixed structure. It is possible to secure the same livability and usability.
[0004]
[Non-patent document 1]
Taku Oyama et al., "Study on Floating Type Seismic Isolation Method-Horizontal Seismic Isolation Performance and Stability to Wind Force-", Proc. Of the Architectural Institute of Japan Conference, p765-766, September 1999 [Patent Document 1]
Japanese Patent Application No. 2002-188430 [0005]
[Problems to be solved by the invention]
Such a floating type seismic isolation structure 11 realizes a structure that is substantially not shaken by an earthquake by shifting the natural period of the structure body 12 from the predominant period band of the seismic motion to the long period side. is there. However, when building a floating seismic isolation structure 11 on soft ground, the seismic motion is prolonged in the process of propagating through soft ground, so the external force input to the structure body 12 has a long-period component. The seismic isolation performance is likely to deteriorate. In addition to the seismic motion, not only the seismic motion but also the wind external force including many long-period components acts on the structure main body 12. Therefore, simply shifting the natural period to the long-period side increases the sway of the structure during strong winds, and secures the livability. It will be difficult.
[0006]
In view of the above circumstances, the present invention is directed to a floating body damping device capable of suppressing horizontal behavior of a floating body, even for a horizontal external force in a cycle band close to a natural period acting on the floating body, and a floating body type using the floating body damping device. It aims to provide seismic isolation structures.
[0007]
[Means for Solving the Problems]
The floating body damping device according to the first aspect is provided on the bottom surface of the floating body floating in the liquid, is formed into a three-dimensional structure, and has water permeability.
[0008]
A floating type seismic isolation structure provided with the floating body damping device according to claim 2, a floating body damping device according to claim 1, a seismic isolation pit constructed by excavating the ground, and a filling in the seismic isolation pit. Liquid, a floating structure main body inserted into the liquid to a depth that does not generate a buoyancy greater than at least a fixed load, and a vertical downward fluctuating load, which is disposed on the ground and generated in the floating structure main body, and buoyancy It has a vertical rigidity that can support a fixed load that does not cancel out, and has a low shear rigid structure that insulates the floating structure main body and the ground, and the floating body damping device is installed on the bottom surface of the floating structure main body. It is characterized by that.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a floating body damping device according to the present invention and a floating type seismic isolation structure provided with the floating body damping device will be described in detail with reference to FIGS. The floating body damping device of the present invention is formed by a three-dimensional structure having water permeability, and utilizes energy dissipation caused by the viscosity of the liquid generated when the liquid moves inside the floating body damping device. By providing the floating body damping device in a partially floating floating type seismic isolation structure, high seismic isolation performance can be achieved even for horizontal external forces such as strong ground motions and strong winds including long-period components. [0010]
As shown in FIG. 1, the floating seismic isolation structure 1 includes a floating structure main body 2, a seismic isolation pit 3, a liquid 7, a low shear rigid structure 9, and a floating body damping device 8. The floating structure main body 2 has a living room function such as a living space or an office space, and the seismic isolation pit 3 is formed by excavating the ground 6 to a desired depth, and is subjected to earth pressure around the outside. The underground outer wall 5 is provided. The seismic isolation pit 3 has a predetermined width of clearance between the outer wall surface and the underground outer wall 5 of the seismic isolation pit 3 when the floating structure main body 2 is disposed inside the seismic isolation pit 3. It is constructed in a planar shape of a size that does not contact the underground outer wall 5 even when the floating structure main body 2 moves in the horizontal direction due to an earthquake.
[0011]
Such a seismic isolation pit 3 is a space provided for the purpose of disposing the liquid 7 therein. That is, the floating type seismic isolation structure 1 is configured such that the liquid 7 is disposed in the seismic isolation pit 3 and the floating structure main body 2 is disposed so as to float on the liquid 7. Floating load W of such floating structure body 2 includes a fixed load W ₁ of floating structure body 2, positive acting vertically downward, including a live load caused by the movement or the like of the live load and user by interior like is that the sum of the fluctuating load _{W 2} value _{(W = W 1 + W 2} ). In the present embodiment, the load (W ₁ −) excluding a part (ΔW ₁ ) of the fixed load W ₁ of the floating structure main body 2 without offsetting the entire floating load W of the floating structure main body 2 by buoyancy. ΔW ₁ ) is inserted into the liquid 7 to a depth that cancels out the buoyancy B. Therefore, the floating structure main body 2 generates a part (ΔW ₁ ) of the fluctuating load W ₂ and the fixed load W _{1 in} a vertically downward direction, and the load W ₂ + ΔW ₁ causes the low shear rigid structure 9 to move. Supported by the ground 6.
[0012]
By the way, it is generally known that in order to secure a high seismic isolation performance for a structure, a high seismic isolation effect can be obtained by increasing the natural period of the structure. Therefore, in the present embodiment, the upper structure 2a of the floating structure main body 2 is formed to have a shape in plan view that is large enough to protrude from the seismic isolation pit 3, and the ground near the outer peripheral edge of the seismic isolation pit 3 is formed. 6, a plurality of low shear rigid structures 9 such as rubber having a small shear modulus are arranged at a predetermined distance, and the upper structure 2a of the floating structure main body 2 is softened to the low shear rigid structures 9. It is configured to land.
In addition, when using the low shear rigid structure 9 which can be used in water, the low shear rigid structure 9 may be installed between the bottom surface of the floating structure main body 2 and the excavation bottom surface 4 of the seismic isolation pit 3.
[0013]
As described above, in the present embodiment, the floating structure main body 2 receives the load (W ₁ −ΔW ₁ ) from the liquid 7 excluding a part (ΔW ₁ ) of the fixed load W ₁ by the buoyancy B. Since the structure is designed to cancel, the low shear rigid structure 9 used here has a function of supporting a part (ΔW ₁ ) of the variable load W ₂ and the fixed load W ₁ generated in the floating structure body 2, It functions as an isolator having the function of insulating the horizontal behavior between the floating structure main body 2 and the seismic isolation pit 3 and extending the period.
[0014]
In the present embodiment, laminated rubber is used for the low-shear rigid structure 9. However, the present invention is not limited to this, and supports a part (ΔW ₁ ) of the above-mentioned variable load W ₂ and fixed load W _1. Any low-shear stiffness structure as long as it has a function of insulating the horizontal movement between the floating structure main body 2 and the seismic isolation pit 3 and extending the natural frequency of the floating structure main body 2 A body may be used. However, it is assumed that the liquid 7 in the seismic isolation pit 3 drops due to any phenomenon, and in such a case, the buoyancy B decreases and _one of the fixed loads W1 of the floating structure main body 2 is reduced. The part (ΔW ₁ ) increases. Even when the low shear rigid structure 9 supports a part (ΔW ₁ ) of the fixed load W ₁ when the liquid 7 reaches the lowermost liquid level, the floating structure can be used without impairing the function described above. The strength which can support the main body 2 is secured.
[0015]
Further, the load (W ₁ −ΔW ₁ ) excluding a part (ΔW ₁ ) of the fixed load W ₁ of the floating structure main body 2 is offset by the buoyancy B, and the low shear rigid structure 9 has the variable load W ₂ and The configuration for supporting a part (ΔW ₁ ) of the fixed load W ₁ is provided in case that the liquid 7 arranged in the seismic isolation pit 3 causes a liquid level displacement due to any cause. In other words, when the liquid level of the liquid 7 arranged in the seismic isolation pit 3 rises due to some phenomenon, the increased buoyancy B is offset by a part (ΔW ₁ ) of the fixed load W ₁ , and thus the floating structure is provided. This prevents the main body 2 from rising.
[0016]
Therefore, even when the insertion depth of the floating structure main body 2 into the liquid 7 at all times is such that the liquid level of the liquid 7 arranged in the seismic isolation pit 3 rises and reaches the uppermost liquid level, the fixed load is maintained. It is necessary to adjust the maximum value of the liquid depth or the uppermost level of the liquid surface so that a part (ΔW ₁ ) of W ₁ becomes an insertion depth of not less than 0, whereby the liquid 7 becomes the highest. Even when the liquid body reaches the liquid level, the state in which the floating structure main body 2 is supported by the low-shear rigid structure 9 can be maintained without completely floating.
[0017]
Incidentally, the seismic isolation pit 3 liquid 7 disposed is, when no liquid level displacement, the insertion depth of the floating structure in a liquid 7 of the body 2, buoyancy B all of the fixed load W ₁ in advance adjusted to cancel, the low shear rigid structure 9 may be configured to support only the variable load W _2.
[0018]
In the floating seismic isolation structure 1 having the above-described configuration, a floating body damping device 8 is installed on the bottom surface of the floating structure main body 2. The floating body damping device 8 is formed of a member having water permeability, and is formed in a three-dimensional structure having a predetermined thickness and area. In the present embodiment, a three-dimensional nonwoven fabric is used as the material of the floating body damping device 8, but it is not necessarily limited to this, and is composed of a debris material such as asphalt and a cement-based material such as mortar and concrete. Any material having a high porosity and a high water permeability such as a mat having water permeability or a slit-shaped storage device storing pumice or the like may be used.
[0019]
In the present embodiment, the floating body damping device 8 is installed on the entire bottom surface of the floating structure main body 2; however, the present invention is not limited to this, and the floating body damping device 8 may be singly or plurally divided at any position on the bottom surface. It may be installed. Therefore, the main body 2 of the floating structure is not necessarily formed by forming the upper structure so that the shape of the upper structure 2a in a plan view is larger than the seismic isolation pit 3 and on the ground 6 near the outer peripheral edge of the seismic isolation pit 3. It is not necessary to support the low-shear rigidity structure 9 disposed at the bottom, and the bottom surface of the floating structure main body 2 where the floating body damping device 8 is not installed is disposed on the excavation bottom surface 4 of the seismic isolation pit 3. It is good also as a structure which makes the structure 9 soft-bottom.
[0020]
The above-described structure in which the floating body damping device 8 is installed on the bottom surface of the floating structure main body 2 has a structure in which the viscosity of the liquid is adjusted in accordance with the relative speed between the liquid particles entering the inside of the floating body damping device 8 and the floating body damping device 8. It uses energy dissipation, that is, the damping force that is caused by kinetic energy, and the kinetic energy dissipation becomes remarkable when the shape is made into a three-dimensional structure, so that greater damping performance can be obtained. . The damping performance by adding the floating body damping device 8 can be adjusted by the porosity and the water permeability of the material used for the floating body damping device 8, and by changing the volume of the floating body damping device 8. Also, the desired damping performance can be ensured.
[0021]
Therefore, when it is desired to improve the damping performance of the floating body damping device 8 of the same material, the damping performance can be improved by increasing the volume of the floating body damping device 8. However, the floating body damping device 8 is installed on the bottom surface of the floating structure main body 2, and it is necessary to consider the clearance between the seismic isolation pit 3 and the excavated bottom surface 4. When adjusting the performance, the damping performance may be adjusted by keeping the member thickness constant and expanding and reducing the area.
[0022]
In order to grasp the effect of the damping function of the above-mentioned floating-type seismic isolation structure 1, the bottom surface of the above-mentioned floating-structure main body 2 is made smooth without any installation, as shown in FIG. A first case, a second case for installing a plurality of protrusions 10 as shown in FIG. 2B, and a third case for installing the floating body damping device 8 as shown in FIG. 2C. , And three conditions were compared. The conditions of the floating seismic isolation structure 1 are shown below.
[0023]
First, as shown in FIG. 2A, the floating structure main body 2 uses an acrylic model having a width of 1 m and a length of 2 m, and supports 2/3 of the fixed load by buoyancy, and 1/3 of the fixed load. It is configured to be supported on the ground 6 via the low shear rigid structure 9.
Further, the protrusions 10 used in the second case are made of a square material of 1 cm square, and as shown in FIG. 2B, 1000 protrusions are fixed to the bottom surface of the floating structure main body 2 with a predetermined spacing. . The configuration in which the plurality of protrusions 10 are installed on the bottom surface of the floating structure main body 2 generates a vortex in the liquid 7 when the protrusions 10 move in the horizontal direction in conjunction with the floating structure main body 2. This has been conventionally devised as a method of dissipating kinetic energy to obtain a damping force.
Further, the floating body damping device 8 used in the third case is composed of a water permeable mat made of a nonwoven fabric having a porosity of 96%, a water permeability of 13.7 cm / s, and a thickness of 2.5 cm, as shown in FIG. In addition, it is fixed to the entire bottom surface of the floating structure main body 2.
[0024]
FIG. 3 shows an acceleration transfer function with respect to horizontal vibration of each case when sine wave excitation is performed at various frequencies for the above-mentioned three cases of the floating type seismic isolation structure 1. In the first case where the bottom surface of the floating structure main body 2 is a smooth surface, the maximum value of the acceleration response magnification reaches 22.6, and the equivalent damping coefficient is only 2.2%. In the second case in which the projection 10 is fixed to the bottom surface, the maximum response magnification is reduced to 19.2, and the equivalent damping coefficient is increased to 2.6%. .
On the other hand, in the third case in which the floating body damping device 8 is attached to the bottom surface, the maximum response magnification is reduced to 3.3, and the equivalent damping coefficient is greatly increased to 15.2%, exhibiting a high damping effect. You can see the situation.
[0025]
As described above, for the third case using the floating body damping device 8 having a high damping effect and the first case having a smooth bottom surface, tuft waves (EW direction in 1952) and Hachinohe waves (1968) obtained from strong motion records. NS direction), and four types of seismic waves, site waves 1 (NS direction) and site waves 2 (EW direction), which are simulated ground waves that reproduce the Kanto seismic waves on the engineering base at the site of soft ground (40 m thick). FIGS. 4A and 4B show the acceleration response magnification and the maximum relative displacement at the time of application.
The acceleration response magnification is the ratio of the maximum response acceleration of the structure to the maximum acceleration of the earthquake, and the maximum relative displacement is the ratio of the maximum value of the difference between the structure displacement and the ground displacement to the maximum displacement of the ground.
[0026]
As shown in FIG. 4A, in the first case in which the bottom surface is smooth, the response acceleration magnification is larger than that of the site wave on the soft ground, and reaches 0.56 for the site wave 2. . On the other hand, in the third case using the floating body damping device 8 on the bottom surface, the numerical value of the site wave 2 having the largest response acceleration magnification is less than 0.4. It can be seen that the addition of the floating structure improves the seismic isolation performance of the floating seismic isolation structure 1 even in the case of seismic waves on soft ground.
[0027]
As described above, the manner in which the seismic isolation performance is improved even on soft ground also appears in the maximum relative displacement shown in FIG. 4 (b), and particularly, the damping effect on the tuft wave appears remarkably. This is because the tuft wave contains more components near the natural frequency than the Hachinohe wave.
From the results described above, the floating type seismic isolation structure 1 in which the floating body damping device 8 is installed on the bottom surface of the floating structure main body 2 can reduce the variation in seismic isolation performance due to the nature of the seismic wave, and any seismic wave It can be seen that stable seismic isolation performance can be obtained.
[0028]
According to the above-described configuration, the floating body damping device 8 has a water-permeability, and uses the energy dissipation caused by the viscosity of the liquid generated when the liquid moves inside the floating body damping device 8 to increase the damping performance. Since it is possible to suppress the resonance phenomenon of the floating body by being installed on the bottom surface of the floating body such as the floating structure main body 2, it is possible to provide the floating body with an effective damping function.
[0029]
Further, as described above, the floating body damping device 8 has a water-permeating property, and utilizes the energy dissipation caused by the viscosity of the liquid generated when the liquid moves inside the floating body damping device 8 to provide a damping force. Therefore, compared to the dampers used for general seismic isolation structures such as oil dampers commonly used as damping devices and high damping laminated rubber, it is possible to reduce the cost and eliminate the need for maintenance. Become.
Further, the damping performance of the floating body damping device 8 can be adjusted by the porosity and water permeability of the material used for the floating body damping device 8 and can be controlled by the volume of the floating body damping device 8 as compared with a conventional damper. Handling can be performed easily.
[0030]
In the floating type seismic isolation structure 1 including the floating body damping device 8, the floating body damping device 8 includes a large number of long-period components because the floating body damping device 8 is installed on the bottom surface of the floating structure main body 2. Since it is effective as a passive damping mechanism for reducing the sway of the floating structure body 2 against soft ground motion and external wind force, high seismic isolation performance is maintained even during strong ground motion or strong wind including long-period components. This makes it possible to ensure comfortable living and usability.
[0031]
【The invention's effect】
According to the floating body damping device of the first aspect, the floating body is provided on the bottom surface of the floating body that floats in the liquid, and is formed into a three-dimensional shape and has water permeability, so that the liquid moves inside the floating body damping device. In addition to obtaining the damping performance by utilizing the energy dissipation caused by the viscosity of the liquid generated at the time of performing, the resonance phenomenon of the floating body can be suppressed, and it is possible to provide an effective damping function to the floating body Become.
If these are provided on the bottom surface of a marine structure such as a megafloat, they can effectively act to reduce the sway caused by waves.
[0032]
In addition, since the floating body damping device obtains damping performance by having water permeability as described above, it is used for a general seismic isolation structure such as an oil damper or a high damping laminated rubber which is generally used as a damping device. As compared with a damper that is used, it is possible to reduce the cost and eliminate the need for maintenance.
[0033]
Furthermore, the damping performance of the floating body damping device can be adjusted by the porosity and water permeability of the material used for the floating body damping device, and can be controlled by the volume of the floating body damping device, which makes handling easier than conventional dampers. It is possible to do it.
[0034]
According to the floating type seismic isolation structure provided with the floating body damping device according to claim 2, the floating body damping device according to claim 1, a seismic isolation pit constructed by excavating the ground, and A filled liquid, a floating structure body inserted into the liquid to a depth that does not generate a buoyancy greater than at least a fixed load, and a vertically downward fluctuating load generated in the floating structure body, and fixing not offset by buoyancy It has a vertical rigidity capable of supporting a load and has a low-shear rigid structure that insulates the floating structure main body from the ground. The floating body damping device is installed on the bottom surface of the floating structure main body.
[0035]
Thereby, in the floating type seismic isolation structure, the floating body damping device provided on the bottom surface of the floating body main body reduces the vibration of the floating body main body due to seismic motion and wind external force on soft ground containing many long-period components. Is effective as a passive damping mechanism, which can suppress the shaking of the floating structure body even during an earthquake or strong wind that includes long-period components, ensuring comfortable living and usability. Become.
[Brief description of the drawings]
It is a figure showing an example.
FIG. 1 is a view showing a floating seismic isolation structure according to the present invention.
FIG. 2 is a view showing another floating seismic isolation structure used for performance comparison of the floating seismic isolation structure according to the present invention.
FIG. 3 is a graph showing an acceleration transfer function with respect to horizontal vibration of a floating seismic isolation structure.
FIG. 4 is a graph showing the acceleration response magnification and the maximum relative displacement of a floating seismic isolation structure with respect to four types of typical seismic waves.
FIG. 5 is a diagram showing a conventional floating type seismic isolation structure having a complete floating structure.
FIG. 6 is a view showing a conventional floating type seismic isolation structure having a partial floating structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Floating type seismic isolation structure 2 Floating structure main body 2a Superstructure 3 Seismic isolation pit 4 Excavation bottom 5 Underground outer wall 6 Ground 7 Liquid 8 Floating body damping device 9 Low shear rigid structure 10 Projection 11 Floating type seismic isolation structure 12 Structure body 13 Liquid 14 Seismic isolation pit 15 Low shear structure

Claims (2)

It is provided on the bottom of the floating body that floats in the liquid,
A floating body damping device formed into a three-dimensional structure and having water permeability. A floating body damping device according to claim 1,
Seismic isolation pits that are built by excavating the ground,
A liquid filled in the seismic isolation pit,
A floating structure main body inserted into the liquid to a depth that does not generate buoyancy greater than at least a fixed load;
A low-shear rigid structure that is arranged on the ground and has a vertical rigidity capable of supporting a vertical variable load generated in the floating structure main body and a fixed load that does not cancel out due to buoyancy, and insulates the floating structural body from the ground. With a body,
A floating seismic isolation structure having a floating body damping device, wherein the floating body damping device is installed on a bottom surface of the floating structure main body.

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