JP6132157B2 - Vibration isolation structure for liquid storage tank - Google Patents

Description

  The present invention relates to a vibration isolation structure for a liquid storage tank that stores liquid, such as an oil tank, and more particularly to a vibration isolation structure that can suppress sloshing of stored liquid.

  Conventionally, for example, an oil tank is configured to include a bottomed cylindrical tank (tank body, tank structure) for storing oil therein and a floating roof provided inside the tank so as to float on the stored oil. ing.

  In this type of oil tank, there is a risk that the oil in the tank resonates and sloshing occurs during an earthquake, particularly due to a long-period component of ground motion. In some cases, the floating roof was actually damaged or sinked by a large oscillating displacement, and the oil was exposed to the atmosphere and ignited, resulting in a large-scale fire.

  Currently, there are more than 2000 oil tanks that can store more than 10,000 kiloliters of oil in the country, and there are more than 10,000 oil tanks of more than 500 kiloliters. Recently, attention has been focused on, and many anti-sloshing measures are not considered.

  On the other hand, by providing a seismic isolation device (vibration isolation device) between the tank body that stores the liquid and the foundation and the ground, that is, between the tank and the support surface on which the tank is installed, A method has been proposed in which the damage of the liquid is prevented by the seismic isolation effect and the sloshing of the liquid stored in the tank body is suppressed (see, for example, Patent Document 1 and Patent Document 2).

JP 2012-229026 A JP 2007-253968 A

  Here, the primary natural period for the sloshing of the liquid stored in the tank (tank body) can be expressed by the following formula (1) by the Hausner formula. From this equation (1), for example, gravity acceleration is g, oil is stored in an oil tank having a diameter D = 70 m, a height H = 30 m, and an oil storage amount of 110,000 kiloliters at a storage depth h = 20 to 30 m. When stored, the sloshing primary natural period is 9.2 to 9.9 sec.

  And the primary natural period of 9.2 to 9.9 sec of such an oil tank is significantly longer than that of a high-rise building. In addition, the attenuation of oil tanks against sloshing is very small, and the attenuation is only about 0.5% (by the way, high-rise buildings are designed with an attenuation constant of about 2%). For this reason, when long-period ground motions act on the oil tank, the sloshing vibration increases with time, which may lead to the above-mentioned accident.

  On the other hand, for example, as shown in FIGS. 11 to 13, a seismic isolation device (vibration isolation mechanism) 4 such as laminated rubber is provided on the seismic isolation layer 3 between the oil tank 1 and the foundation and the ground (support surface 2). It has been proposed to improve the seismic resistance of the oil tank 1 by installing a damping device (vibration control mechanism) 5 such as an oil damper. However, the natural period of such a seismic isolation structure (isolation structure) A is generally about 3 to 4 seconds, and even if the tank 1 having a long period is 2 to 3 times longer than this, the response at the time of earthquake is reduced. The effect is small.

  Specifically, for example, a description will be given of a case where the oil tank 1 is filled with the oil tank 1 having a diameter D = 70 m, a height H = 30 m, and a storage amount of the oil (liquid) 6 of 110,000 kiloliters.

Assuming that the liquid weight in the tank 1 is 100,000 ton, the tank body 1a has its own weight 10000 ton, the equivalent stiffness k ₂ = 46.6 kN / mm of the liquid part from T ₁ = 9.2 sec, and the natural period of the seismic isolation layer 3 is 3.5 sec. The rigidity of the seismic isolation layer 3 is k ₁ = 355 kN / mm (= 7.60 k ₂ ). The displacement response times of the liquid (m ₂ ) with respect to the ground surface are as shown in FIG. Ten times more.
Note that ω ₀ is an angular frequency corresponding to T ₁ = 9.2 sec, ω ₀ = 0.68 rad / sec, and the sloshing attenuation is small, so it was ignored in calculating the optimum value.

  As described above, since the response reduction effect is small even when the conventional seismic isolation structure A is applied, a method capable of improving the earthquake resistance and effectively suppressing the sloshing of the liquid 6 has been strongly desired.

The vibration isolation structure for a liquid storage tank according to the present invention is a vibration isolation structure for a tank for storing a liquid, wherein a vibration isolation mechanism and an inertia are provided between a lower portion of the tank and a support surface on which the tank is installed. It comprises a mass damper and a viscous damper, and is configured to be provided with a tuning type vibration damping mechanism that synchronizes with the sloshing of the liquid in the tank .

  In the vibration isolation structure for a liquid storage tank according to the present invention, the tank is preferably an oil tank.

In the vibration isolating structure for the liquid storage tank of the present invention, an anti-vibration mechanism comprising an anti-vibration device such as laminated rubber is interposed between the lower part of the tank and the support surface on which the tank is installed, and is rotated. It is equipped with an inertial mass damper such as an inertial mass damper and a viscous damper such as an oil damper, and is equipped with a synchronized vibration control mechanism that synchronizes with the sloshing of the liquid in the tank. In addition, the sloshing of the liquid stored in the tank can be effectively suppressed.

Further, by there use the inertial mass damper can constitute a tunable vibration control mechanism can be suppressed sloshing of the liquid in the tank more effectively displacement or damper reaction force of the seismic Fuso (isolation layer) Can be accommodated in a design range without difficulty.

It is a figure showing a liquid storage tank (tank) and a vibration isolating structure concerning one embodiment of the present invention. It is the X1-X1 arrow view figure of FIG. FIG. 2 is an X2-X2 arrow view of FIG. 1. It is a figure which shows the analysis model of the tank (tank) for liquid storage which concerns on one Embodiment of this invention, and a vibration isolation structure. It is a figure which shows the simulation result (the displacement response magnification of a liquid and a tank) of the liquid storage tank (tank) which concerns on one Embodiment of this invention. It is a figure which shows the simulation result (displacement response magnification) of the liquid storage tank (tank) which concerns on one Embodiment of this invention, and is a figure compared with the case where the conventional vibration isolation structure is provided. It is a figure which shows the waveform of the input ground motion used in the simulation of the tank (tank) for liquid storage which concerns on one Embodiment of this invention. It is a figure which shows the simulation result (displacement amount of the liquid in a tank) of the liquid storage tank (tank) which concerns on one Embodiment of this invention. It is a figure which shows the simulation result (acceleration of the liquid in a tank) of the liquid storage tank (tank) which concerns on one Embodiment of this invention. It is a figure which shows the simulation result (displacement of a seismic isolation layer) of the liquid storage tank (tank) which concerns on one Embodiment of this invention. It is a figure which shows the conventional tank (tank) for liquid storage, and a vibration isolation structure. It is a X1-X1 line arrow directional view of FIG. It is a figure which shows the analysis model of the conventional liquid storage tank (tank) and a vibration isolation structure. It is a figure which shows the simulation result (the displacement response magnification of a liquid and a tank) of the conventional liquid storage tank (tank).

  Hereinafter, with reference to FIG. 1 to FIG. 10, a vibration isolation structure (hereinafter referred to as a vibration isolation structure) for a liquid storage tank according to an embodiment of the present invention will be described.

  The tank 1 of the present embodiment is a floating roof type tank for oil storage, and stores oil (liquid) 6 in a bottomed cylindrical tank body 1a as shown in FIGS. The tank body 1a is provided with a floating roof 1b provided so as to float on the oil 6 and arranged to be movable up and down according to the amount of oil 6 stored.

  On the other hand, as shown in FIGS. 1 to 3, the vibration isolation structure B of the present embodiment is provided at the bottom of the tank body (tank structure) 1a, that is, the bottom plate of the tank body 1a and the ground surface (foundation, ground, support surface). ) A seismic isolation layer 3 is provided between the two, and the seismic isolation layer 3 is made of laminated rubber and the like, and has a plurality of vibration isolators having lateral slip resistance and lateral and vertical elasticity (vibration isolation bearings). 4 is interposed. A plurality of the seismic isolation devices 4 are provided so as to support the tank main body 1a by connecting the upper end thereof to the tank main body 1a side and the lower end thereof to the ground surface 2 side, thereby constituting the vibration isolation mechanism 7.

  Further, the vibration isolation structure B of the present embodiment is provided with a vibration isolation mechanism 7 including the vibration isolation device 4 in the vibration isolation layer 3 and a vibration suppression mechanism 10 including the inertia mass damper 8 and the oil damper 9. It is configured. The inertia mass damper 8 and the oil damper 9 are arranged in a balanced manner in the circumferential direction and the radial direction around the axis of the tank 1 (symmetrically arranged around the axis of the tank 1), and the same vibration isolation in any horizontal direction. It is configured to demonstrate its performance.

  That is, the vibration isolation structure B of the present embodiment is provided with the vibration isolation device 4 and the inertia mass damper 8 (and the oil damper 9) in the seismic isolation layer 3, and with respect to the conventional vibration isolation structure A, By adding damping to the seismic isolation layer 3, the tank body 1 a is configured to greatly suppress shaking.

  Furthermore, in the vibration isolating structure B of the present embodiment, the vibration damping mechanism 10 interposed between the lower portion of the tank body 1a and the ground surface (support surface) 2 is used for sloshing the oil (liquid) 6 in the tank 1. It is configured as a tuned type vibration control mechanism that synchronizes with respect to.

Here, in this vibration isolation structure B, if the angle between the damper axis direction and the direction of action of the seismic force is θ, the damper performance is cos ² θ. The direction (vibration action direction) equivalent damper performance is n / 2 per unit.

  Based on this, for example, as shown in FIGS. 1, 2, and 4, as shown in FIGS. 1, 2, and 4, oil 6 is filled into an oil tank 1 having a diameter D = 70 m, a height H = 30 m, and a storage capacity of 110,000 kiloliters of oil 6. The examination in the state of having been made is explained. Here, only the point which added the inertia mass damper 8 differs with respect to the examination with respect to the conventional vibration isolation structure A shown in FIGS. In addition, the floating roof 1b is not an essential condition, and even if there is no floating roof 1b, the response reduction effect does not change.

Assuming that the liquid weight in the tank is 100,000 ton and the own weight of the tank body (tank structure) 1a is 10000 ton, the equivalent stiffness of the liquid part k ₂ = 46.6 kN / mm from the T ₁ = 9.2 sec, and the natural period of the seismic isolation layer 3 is 3 .5 sec. Thereby, the rigidity of the seismic isolation layer 3 is k ₁ = 355 kN / mm (= 7.60 k ₂ ).

The specifications of the damper to be installed are set as follows.
In this embodiment, regarding the installation of the specifications of this damper, etc., see “Kazuhiko Hamada, Tetsuya Hanzawa, Kazuo Tamura: Basic research on low-rise concentrated control incorporating inertia mass dampers: Architectural Institute of Japan, Proceedings of the structural system The optimal value of the inertial mass Ψ (overall) installed in the seismic isolation layer 3 is based on the method described in “Japan Architectural Institute of Japan, No. 666, pp. 713-722, April 2013”. Set by equation (2).

On the other hand, the optimum value of the attenuation c ₁ (overall) installed in the seismic isolation layer 3 is set by the following equation (3).

In the trial calculation example for the oil tank 1 having a diameter D = 70 m and a height H = 30 m, Ψ = 757000 ton, c ₁ = 230,000 kN · sec / m = 2300 kN / kine = 235 tonf / kine.

  In general, the inertia mass damper 8 having a maximum proof stress of about 10,000 tons per unit is manufactured, so 75 or more units are required in the earthquake direction. On the other hand, in the vibration isolation structure B of the present embodiment, as described above, since the number of dampers installed n is the seismic direction conversion damper performance of the entire seismic isolation layer, n / 2 per unit, 150 inertia mass dampers 8 is arranged in a well-balanced seismic isolation layer 3 between the tank body 1a and the ground surface 2.

  In addition, if an oil damper with a damping coefficient C = 6 tonf / kine is used for additional damping, 40 units or more are required in the earthquake direction, and the number of dampers installed is n per seismic direction conversion damper performance for the entire seismic isolation layer. Therefore, it is only necessary to arrange 80 oil dampers 9 in the seismic isolation layer 3 between the tank body 1a and the ground surface 2 in a well-balanced manner.

In the vibration isolation structure B of the present embodiment configured as described above, the inertia mass damper 8 is added as shown in the analysis results of FIGS. 5 and 6 in which the displacement response magnification is shown in the form of a frequency transfer function. As a result, it was confirmed that the maximum response magnification was reduced by 72% and the resonance characteristics were significantly improved as compared with the conventional case of only viscous damping. In addition, with respect to attenuation, it was confirmed that c ₁ = 580 ton / kine in the present embodiment, whereas c ₁ = 235 ton / kine in the present embodiment, which is c ₁ = 580 ton / kine, which is reduced to 40%.

  Next, the examination result of the response reduction effect of the vibration isolation structure B of this embodiment by time history response analysis will be described.

  Here, Case 1 (without vibration isolation and vibration control) in which the tank 1 is directly installed on the ground surface, Case 2 of the conventional vibration isolation structure A (only viscous damping: giving an optimum damping coefficient), and the vibration isolation structure B of the present embodiment Case 3 (inertial mass and viscous damping: giving an optimal inertial mass and damping coefficient) was examined, and the superiority of Case 3 of the vibration isolation structure B of this embodiment was confirmed.

The input ground motion was the building center wave (level 2) shown in FIG. In the earthquake waveform shown in FIG. 7, the horizontal axis represents time (sec), the vertical axis represents acceleration (m / sec ² ), and max: maximum acceleration. This seismic motion has a maximum acceleration of 356 gal and a duration of 120 seconds, but the analysis time was set to 160 seconds in order to consider backswing.

  FIG. 8 is an analysis showing the relationship between the displacement amount (vertical axis: m) and time (horizontal axis: sec) of the liquid 6 in the tank 1 in each case of Case 1, Case 2, and Case 3, and max: the maximum displacement amount. It is a result.

  From this result, first, in Case 1 with no anti-vibration or vibration control measures, as shown in FIG. 8 (a), a sloshing fluctuation with a period of about 10 sec grows as time passes and decays easily even after time passes. It was confirmed that the scale was not doubled (the scale of the vertical axis was doubled in other cases).

  In Case 2 with vibration isolation and attenuation, as shown in FIG. 8 (b), it was confirmed that the vibration increased during the main movement, but thereafter attenuated relatively quickly.

  On the other hand, in Case 3 with vibration isolation, inertial mass, and damping of this embodiment, as shown in FIG. 8C, the shaking does not increase during the main movement, and the shaking ends most rapidly after the earthquake. It was confirmed. This can be said to be a result of the effects (features) of the periodically tuned vibration damping mechanism 10 appearing.

  Moreover, the displacement amount of the liquid in the tank 1 is 3.94 m in Case 1, 1.93 m in Case 2, and 1.17 m in Case 3, and the sloshing can be significantly suppressed by adopting the vibration isolation structure B of this embodiment. Was confirmed.

  Furthermore, Case 2 is the one in which specifications are optimized so that the response can be reduced most by using the conventional vibration isolation structure A. The vibration isolation structure B of the present embodiment of Case 3 not only can reduce the maximum response displacement by 40% than Case 3, but also has a large response duration (number of times) and effective value (a relatively large response value (Case 2 that appears several times). Is 1.8 m, and Case 3 is about 0.9 m)).

Next, FIG. 9 shows the relationship between the acceleration (vertical axis: m / sec ² ) and time (horizontal axis: sec) of the liquid 6 in the tank 1 in each case of Case 1, Case 2, and Case 3, and max: maximum acceleration. Analysis results.

  From this result, in Case 1 without measures for vibration isolation and vibration control, as shown in FIG. 9 (a), a sloshing fluctuation with a period of about 10 sec grows as time passes, and does not readily attenuate even after time passes ( It was confirmed that the scale of the vertical axis was double that of the other cases).

  In Case 2 with vibration isolation and attenuation, as shown in FIG. 9 (b), it was confirmed that the vibration increased during the main movement, but thereafter attenuated relatively quickly.

  In Case 3 with vibration isolation, inertial mass, and damping of this embodiment, as shown in FIG. 9 (c), the maximum response value is generated by the first large shaking of the earthquake, but the shaking increases during the main motion. After the earthquake, it was confirmed that the shaking ended most quickly (the scale on the vertical axis was 0.6 times that of Case 2).

  Further, the acceleration of the liquid 6 in the tank 1 is 184 gal in Case 1, 90 gal in Case 2, and 55 gal in Case 3, and it was confirmed that the acceleration can be significantly suppressed by adopting the vibration isolation structure B of this embodiment.

  Next, FIG. 10 is an analysis result showing the relationship between displacement (vertical axis: m) and time (horizontal axis: sec) of the seismic isolation layer 3 in each case of Case 2 and Case 3, and max: maximum displacement. Case 1 is excluded from the analysis because there is no seismic isolation layer 3.

  From this result, it was confirmed that in Case 2 with vibration isolation and attenuation, as shown in FIG. 10 (a), the shaking continued at about 15 to 20 cm during the main movement.

  On the other hand, in Case 3 with vibration isolation, inertial mass, and damping of the present embodiment, as shown in FIG. 10 (b), a vibration of about 25 cm is initially generated. It was confirmed that the shaking stopped immediately after the earthquake.

  Moreover, the displacement amount of the seismic isolation layer 3 was 17 cm in Case 2 and 26 cm in Case 3, and it was confirmed that both cases could be accommodated with a displacement equal to or less than that of a general isolation building.

  Furthermore, with regard to the damper reaction force, the total reaction force of the oil damper 9 in Case 2 is 84000 kN, and by installing 80 units (total number of 160 units) in terms of the earthquake direction, a normal oil damper 9 of about 1000 kN can be handled.

  In Case 3, the total reaction force of the inertial mass damper 8 is 106000kN. By installing 75 units (total of 150 units) in terms of the earthquake direction, the inertial mass damper 8 of about 1400kN can be used, and the oil damper 9 has a total reaction force of 39000kN. Thus, by installing 40 units (total of 80 units) in terms of earthquake direction, it is possible to cope with a normal oil damper 9 of about 1000 kN. From the above, it was confirmed that the current product can sufficiently cope with the damper reaction force.

Therefore, in the vibration isolating structure B of the liquid storage tank according to the present embodiment, the vibration isolating mechanism including the vibration isolating device 4 such as laminated rubber is provided between the lower portion of the tank 1 and the support surface 2 on which the tank 1 is installed. 7, an inertial mass damper such as a rotary inertial mass damper 8, and a viscous damper such as an oil damper 9, and a tuned vibration damping mechanism 10 that synchronizes with the sloshing of the liquid 6 in the tank 1. By interposing, the vibration isolation effect of the tank 1 can be obtained, and the sloshing of the liquid 6 stored in the tank 1 can be effectively suppressed.

Further, by there use the inertial mass damper 8, it is possible to configure the tuning type vibration control mechanism can be suppressed sloshing of the liquid 6 in the tank 1 more effectively, immune Fuso (isolation layer) 3 of the displacement And the damper reaction force can be kept within the design range without difficulty.

  Furthermore, by providing a large inertial mass in the first layer of the two-layer model, the natural period is increased by about 10%, so that the effect of reducing the earthquake input energy by about 10% can be obtained. ("Kazuhiko Hamada, Tetsuya Hanzawa, Kazuo Tamura: Study on seismic input energy to structures incorporating inertial mass dampers: Architectural Institute of Japan, Architectural Institute of Japan, Architectural Institute of Japan, No.650, pp.751- 759, April 2010 ")

  As mentioned above, although one embodiment of the vibration isolating structure of the liquid storage tank according to the present invention has been described, the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist thereof. .

  For example, in the present embodiment, the liquid storage tank according to the present invention has been described as being the oil tank 1, but the liquid storage tank vibration isolation structure according to the present invention is not provided in the tank that stores the liquid. It imparts vibration performance and suppresses liquid sloshing, and can be applied to any tank that requires this effect. That is, it is possible to obtain the same effect as that of the present embodiment without particularly limiting the type of tank.

1 Oil tank (tank)
1a Tank body 1b Floating roof 2 Ground surface (foundation, ground, support surface)
3 Seismic isolation layer (isolation layer)
4 Isolation device (Seismic isolation device, vibration isolation mechanism)
5 Damping mechanism 6 Petroleum (liquid)
7 Isolation mechanism 8 Inertial mass damper 9 Oil damper 10 Damping mechanism A Conventional isolation structure for liquid storage tank B Isolation structure for liquid storage tank

Claims (2)

A vibration isolation structure for a tank that stores liquid,
An anti- vibration mechanism, an inertial mass damper, and a viscous damper are provided between a lower part of the tank and a support surface on which the tank is installed, and are tuned to control the sloshing of the liquid in the tank. A vibration isolating structure for a liquid storage tank, characterized in that the structure is provided with a vibration mechanism . The vibration isolation structure for a liquid storage tank according to claim 1,
An isolation structure for a liquid storage tank, wherein the tank is an oil tank.

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