JP5901348B2 - Seismic isolation structure - Google Patents

Description

  The present invention relates to a seismic isolation structure that can selectively reduce higher-order mode vibrations of the seismic isolation structure.

  Generally, in a base isolation structure with base isolation layers formed on the base and intermediate floors, steel dampers, lead dampers, viscoelastic dampers, oil dampers and other damping dampers are interposed in the base isolation layers. Damping the vibration of the superstructure.

By the way, in setting the damping force of the damping damper, there is a contradictory relationship between the relative displacement between the upper and lower structures in the seismic isolation layer and the vibration transmissibility to the upper structure.
That is, if the damping force is set low, the vibration transmission rate to the superstructure can be lowered and the acceleration response of the superstructure can be reduced. However, since the relative displacement in the seismic isolation layer is large, It becomes necessary to set a large clearance with the building.

  On the other hand, if the damping force is set high, the relative displacement in the seismic isolation layer can be reduced, but the transmission rate of high frequency components higher than the secondary mode to the superstructure is increased, resulting in an acceleration response. Increase.

Therefore, if it is difficult to ensure sufficient clearance due to the fact that the site is small, the damping force has to be set high, and as a result, the acceleration reduction effect on the superstructure is reduced. There was a problem.
Therefore, as means for solving the above problems, there are various systems and methods for installing a damping device with variable damping force in the seismic isolation device of the seismic isolation structure and controlling the damping force according to the magnitude of vibration. Proposed.

  For example, in the following Patent Document 1, the present applicant uses a damping device having a variable damping force in the seismic isolation layer to set a reference amplitude value between the upper and lower structures in advance, and between the upper and lower structures by a sensor or the like. Relative amplitude value and velocity are measured, a predicted amplitude value after a certain period of vibration is calculated from these amplitude values and velocity, and the damping force is calculated when the predicted amplitude value is larger than the reference amplitude value. A seismic isolation control method was proposed in which the damping force is decreased when the predicted amplitude value is smaller than the reference amplitude value.

  However, in the above seismic isolation control method, the relative amplitude value and speed between the upper and lower structures are measured momentarily by a sensor or the like, and the predicted amplitude value after a certain time of the vibration is constantly calculated from these. Development of a seismic isolation system that replaces the semi-active seismic isolation system that is even easier and more maintenance-reliable. Was desired.

  Therefore, in the following Patent Document 2, the present applicant is provided with a variable damping damper capable of switching the damping coefficient to two or three stages in the base isolation layer, and based on the detection signal from the response detection means of the superstructure, When an earthquake occurs, the damping coefficient of the above variable damping damper is minimized, and when the response amount of the superstructure exceeding the set value is detected, the damping force of the variable damping damper is increased to increase the damping force. A seismic isolation system was proposed to prevent excessive relative displacement between the upper and lower structures.

  According to the seismic isolation system having the above-described configuration, it is possible to exhibit a high vibration insulation effect during an earthquake with simple equipment without requiring an arithmetic device or a complicated control device, and the upper and lower parts during a large earthquake. An effect of preventing an excessive relative displacement between the structures can be obtained.

  However, in the above seismic isolation system, after the damping coefficient of the variable damping damper is largely switched, the acceleration reduction effect remains small until it is restored. For this reason, there has been a drawback that it is necessary to set the damping coefficient of the variable damping damper to the minimum value again after a large earthquake. In addition, since priority is given to suppressing excessive relative displacement during a large earthquake, the acceleration response of the superstructure can be reduced during small and medium-sized earthquakes. There was also a problem that it could not be obtained.

  On the other hand, in Patent Document 3 below, as a seismic isolation structure that selectively reduces higher-order mode vibrations, a rotation that exhibits a response reduction effect on higher-order mode vibrations of the upper structure is provided in the seismic isolation layer. An inertial mass damper installed in parallel with a seismic isolation device has been proposed.

  However, in the above-mentioned seismic isolation structure, the rotary inertia mass damper is installed in parallel with the seismic isolation device, and the weight is rotated by the relative displacement generated between the upper and lower structures to exert the response reduction effect. In addition to the complexity of the structure, there is a drawback in that it is necessary to protect and maintain the ball screw part of the rotary inertia mass damper even in normal times so that the mechanical rotational movement of the weight is surely generated in the event of an earthquake. In addition, in general, the rotary inertia mass damper tends to amplify the vibration input from the ground with respect to the vibration of the higher order mode, and may conversely amplify the acceleration response of the structure. .

Japanese Patent No. 4556384 JP 2009-19383 A JP 2009-263925 A

  The present invention has been made in view of the above circumstances, and with a simple facility, it is possible to obtain an effect of reducing acceleration response to vibrations of higher-order modes of the structure, and also a seismic isolation structure that is easy to maintain and manage. It is a problem to provide.

In order to solve the above-mentioned problem, the invention according to claim 1 is a seismic isolation structure in which a seismic isolation layer is formed between an upper structure and a lower structure, and a lower surface of the upper structure in the seismic isolation layer, A tuned mass damper tuned to the natural frequency of the n-order mode (n is an integer equal to or greater than 1) of the superstructure is installed, and the tuned mass damper includes a weight, the weight, and a column of the superstructure. And the weight is movably provided between the four pillars of the upper structure, and the spring and the oil damper are respectively in the center of the weight. It is arranged at a position that is point-symmetric with respect to the point.

  The invention described in claim 2 is the invention described in claim 1, wherein the n is an integer of 2 or more.

  Further, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the lower structure is a foundation constructed on the ground, and the tuning mass damper installed on the lower surface of the upper structure. The weight is supported on the foundation so as to be movable in the horizontal direction.

  On the other hand, the invention according to claim 4 is the tuning mass damper according to claim 1 or 2, wherein the seismic isolation layer is provided on an intermediate floor and installed on the lower surface of the upper structure. The weight is supported on the upper surface of the lower floor wall, which is the lower structure, so as to be movable in the horizontal direction.

As shown in FIG. 7 , when the structure is shaken due to a disturbance such as an earthquake or strong wind, the vibrations are a combination of the modes. At this time, the primary mode, the secondary mode, and the tertiary mode vibrate at the primary natural frequency, the secondary natural frequency, and the tertiary natural frequency, respectively. In the seismic isolation structure shown in the figure, although the proportion of vibration due to the primary mode in which the seismic isolation layer greatly deforms is large, the natural frequency of the seismic isolation structure itself, seismic motion, etc. Depending on conditions, vibrations caused by higher-order modes higher than the second-order mode may not be ignored.

  And according to invention of any one of Claims 1-4, the tuned mass damper tuned to the natural frequency of the 1st or more mode of the said upper structure on the lower surface of the upper structure of a seismic isolation structure Because it is installed, not only during a large earthquake, but also during small and medium earthquakes and strong winds, it is possible to demonstrate a high vibration isolation effect during an earthquake with a simple facility without the need for arithmetic devices or complex control devices. At the same time, it is possible to prevent excessive relative displacement between the upper and lower structures during a large earthquake.

  Furthermore, according to the invention described in claim 2, since the tuned mass damper tuned to the natural frequency of the secondary mode or higher is installed, the transmission rate to the superstructure is higher than that of the secondary mode. By absorbing the frequency component, the acceleration response of the superstructure can be reliably reduced.

  In addition, unlike the variable damping damper that switches the damping coefficient, the switching operation is not required, and further, the mechanical rotation movement of the weight like the rotary inertia mass damper is not required. Excellent operation reliability and ease of maintenance.

In addition, the tuned mass damper installed on the lower surface of the upper structure is mechanically disconnected from the lower structure in the horizontal direction, so that the ground (lower structure) can be used like a variable damping damper or a rotary inertia mass damper. The vibration is not transmitted to the superstructure, and the acceleration response in the superstructure can be reliably reduced.
In addition, since the tuned mass damper is disposed in the seismic isolation layer that originally becomes a dead space, it contributes to the effective use of the space as the entire structure.

  Further, according to the invention described in claim 3 or claim 4, since the vertical load of the weight of the tuned mass damper is supported by the foundation or the lower floor wall as the lower structure, the weight is lifted. There is no need to do this, and the workability is excellent.

  In addition, in the invention according to any one of claims 1 to 4, if the tuned mass damper is installed so as to operate in the short side direction of a structure in which shaking tends to be large, the superstructure can be more effectively provided. This is preferable because the acceleration response can be reduced.

It is a schematic block diagram which shows 1st Embodiment of the seismic isolation structure which concerns on this invention. FIG. 2 is an enlarged view of part A of FIG. 1, (a) is a longitudinal sectional view, and (b) is a plan view. It is a top view which shows the 1st modification of the said 1st Embodiment. It is a top view which shows the 2nd modification similarly. It is a longitudinal cross-sectional view of the principal part which shows other embodiment of this invention . It is a graph of the acceleration response function which shows the analysis result performed in order to verify the effect of this invention . It is the schematic which shows the form of the vibration in each mode when a disturbance acts on a structure .

(First embodiment)
1 and 2 show an embodiment of a seismic isolation structure according to the present invention, and FIGS. 3 to 6 show modifications thereof.
In FIG. 1 and FIG. 2, this seismic isolation structure is a foundation (lower structure) in which a pillar 2a of a structure (upper structure) 1 is constructed on the ground via a seismic isolation device 4 and a damping damper 5 made of laminated rubber. By being supported on 3, the seismic isolation layer 6 is formed between the structure 1 and the foundation 3.

  A tuned mass damper 7 is installed on the lower surface of the floor beam 2 b in the seismic isolation layer 6. The tuned mass damper 7 is roughly constituted by a weight 8, and a spring 9 and an oil damper 10 interposed between the weight 8 and the column 2a. Here, the weight 8 is provided on the foundation 3 so as to be movable in two horizontal directions without transmitting force between the foundation 3 and the floor beam 2b via the sliding means 11 such as a roller or a guide rail. It has been.

  Further, the weights 8 are integrated with support members 8a extending in four orthogonal directions toward the pillars 2a located in each of the four directions, and the front ends of the support members 8a and the front ends are interposed. A spring 9 is interposed between one pillar 2a sandwiched between them, and an oil damper 10 is interposed between the other pillar 2a. Incidentally, the spring 9 and the oil damper 10 are disposed at positions that are point-symmetric with respect to the center of the weight 8 in the plan view shown in FIG.

  The tuning mass damper 7 is set so that the specifications of the weight 8, the spring 9, and the oil damper 10 are synchronized with the natural frequency of the secondary mode of the structure 1. At this time, generally, since the vibration characteristics in the X direction and the Y direction in the structure 1 are different, the spring 9 and the oil damper 10 acting in the X direction and the spring 9 and the oil damper 10 acting in the Y direction are used. Are set according to the vibration characteristics in the X direction and Y direction, respectively.

In the seismic isolation structure having the above configuration, the tuned mass damper 7 tuned to the natural frequency of the secondary mode of the structure 1 is installed on the lower surface of the floor beam 2b of the structure 1. Therefore, not only during large earthquakes, but also during small and medium earthquakes and strong winds, as shown in the analysis results of FIG. 1 acceleration response can be reliably reduced.

  In addition, unlike the conventional variable damping damper that switches the damping coefficient, the tuned mass damper 7 does not require a switching operation and further does not require a mechanical rotational movement of a weight like a rotary inertia mass damper. The structure is simple and the operation is reliable and easy to maintain.

  Further, since the tuned mass damper 7 installed on the lower surface of the floor beam 2b of the structure 1 is mechanically disconnected from the foundation 3 in the horizontal direction, the foundation 3 swings like a rotary inertia mass damper. Is not transmitted to the structure 1, and the acceleration response in the structure 1 can be reliably reduced. In addition, since the tuned mass damper 7 is arranged in the seismic isolation layer 6 that originally becomes a dead space, it contributes to the effective use of the space as the entire structure.

Furthermore, since the vertical load of the weight 8 of the tuned mass damper 7 is supported by the foundation 3, it is not necessary to lift the weight 8 to the structure 1, and the workability is excellent.
Furthermore, since the tuned mass damper 7 is installed in the seismic isolation layer 6, the seismic isolation structure according to the present invention can take various forms.

  For example, FIG. 3 shows a first modification of the first embodiment. This seismic isolation structure is similar to the first embodiment in that the weight 8 is placed between the four columns 2a in two horizontal directions. In addition to being provided movably, a spring 9 and an oil damper 10 are interposed between the weight 8 and the diagonal column 2a sandwiching the weight 8 therebetween, whereby the inertial force of the weight 8 is reduced to X. Acting in both the direction and the Y direction.

  Further, in the second modification shown in FIG. 4, the weight 8 of the tuned mass damper 7 is movable only in the X direction on a rail (not shown) laid in the X direction (left and right direction in the figure). The spring 9 and the oil damper 10 are interposed between the both ends and the pillar 2a facing the moving direction.

  Incidentally, in this modified example, the weight 8 of the tuned mass damper 7 is installed so as to be movable in the short side direction of the structure 1 that is likely to be greatly shaken, and the weight 8, the spring 9 and the oil damper 10 are variously arranged. The element is preferably set so as to be tuned to the natural frequency of the secondary mode in the short side direction of the structure 1.

(Second Embodiment)
In the first embodiment, the present invention is applied to a base-isolated base isolation structure in which the base isolation layer 6 is formed between the structure 1 and the foundation 3 constructed on the ground. However, the present invention is not limited to this, and the same applies to the case where a seismic isolation layer is formed on the intermediate floor of the structure as in the second embodiment shown in FIG. Can do.

  That is, in this seismic isolation structure, the seismic isolation device 4 is interposed between the column 21a of the lower structure 21 and the beam 22 of the upper floor (upper structure) on the intermediate floor of the structure 20. Thus, a seismic isolation layer 24 is formed between the wall 23 constructed between the columns 21 a and the beam 22.

A tuned mass damper 25 is installed on the lower surface of the beam 22 on the upper floor.
Reference numeral 26 in the drawing indicates a weight of the tuned mass damper 25. The weight 26 is provided on a rail 27 laid on the upper surface of the wall 23 so as to be able to run in the left-right direction in the drawing. In addition, mounting plates 28a and 28b are erected on the upper surface of the weight 26 at intervals, and the lower surface of the beam 22 is opposed to the mounting plates 28a and 28b at intervals. Support plates 29a and 29b are suspended. A spring 30 is interposed between the mounting plate 28a and the support plate 29a, and an oil damper 31 is interposed between the mounting plate 28b and the support plate 29b. Is configured.

Also in the tuned mass damper 25, the specifications such as the weight 26, the spring 30 and the oil damper 31 are set so as to tune to the natural frequency of the secondary mode of the upper structure of the seismic isolation layer 24.
Therefore, even with the seismic isolation structure having the above-described configuration, the same effects as those shown in FIGS. 1 and 2 can be obtained for the upper structure of the seismic isolation layer 24.

  In the first and second embodiments, only the case where the tuned mass dampers 7 and 25 are set so as to be tuned to the natural frequency of the secondary mode of the structure (upper structure) 1 will be described. However, the present invention is not limited to this, and when the proportion of vibration by the primary mode is large due to characteristics such as the structure of the structure, the tuning mass damper vibrates in the primary mode. You may set so that it may synchronize with.

1 Structure (superstructure)
3 Foundation (under structure)
6, 24 Base isolation layer 7, 25 Tuned mass damper 8, 26 Weight 9, 30 Spring 10, 31 Oil damper

Claims (4)

In a base-isolated structure in which a base isolation layer is formed between the superstructure and the substructure,
A tuned mass damper tuned to the natural frequency of the n-order mode (n is an integer of 1 or more) of the superstructure is installed on the bottom surface of the superstructure in the seismic isolation layer,
The tuned mass damper includes a weight, and a spring and an oil damper interposed between the weight and the column of the superstructure ,
The weight is provided movably between the four pillars of the superstructure, and the spring and the oil damper are respectively arranged at positions that are point-symmetric with respect to the center of the weight. Seismic isolation structure.   2. The seismic isolation structure according to claim 1, wherein n is an integer of 2 or more.   The lower structure is a foundation constructed on the ground, and the weight of the tuning mass damper installed on the lower surface of the upper structure is supported on the foundation so as to be movable in the horizontal direction. The seismic isolation structure according to 1 or 2.   The seismic isolation layer is provided on an intermediate floor, and supports the weight of the tuned mass damper installed on the lower surface of the upper structure so as to be movable in the horizontal direction on the upper surface of the lower floor wall serving as the lower structure. The seismic isolation structure according to claim 1 or 2.

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