JPH0259261B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a method for determining the natural vibration period of a structure from the vibration period of seismic motion between a structure such as a building as an upper structure and a foundation as a lower structure. The present invention relates to a seismic isolation device capable of reducing earthquake energy transmitted to a structure by shifting the structure, and furthermore, once vibration occurs, the vibration can be quickly damped by a damping means and the vibration amplitude at that time can be reduced.

(b) Prior art In addition to increasing the strength of the structure, seismic design methods for buildings include methods that dynamically view the building as a vibration system and extend its vibration period to protect the building from external inputs such as earthquakes. There is a method called seismic isolation or seismic damping construction that reduces the response acceleration of the earthquake. An isolation member (isolator) 1 as shown in FIGS. 1 and 2 is an example of achieving this through local treatment at the foundation of a building. This is formed by vertically stacking metal plates 2, 2, etc., such as steel plates, and thin elastic plates 3, 3, etc., such as natural rubber or neoprene rubber, and fixing them with adhesive.
As shown in FIG. 3, the upper structure 4 is interposed between the upper structure 4 and the lower structure 5 so as to support the upper structure 4. Since the thin elastic plate 3 is sandwiched between the metal plates 2, the isolation member 1 has a large vertical rigidity and a small horizontal rigidity due to shear deformation of the rubber. Therefore, since the period of the entire structure system is increased, the input acceleration of the earthquake transmitted to the superstructure when an earthquake occurs can be reduced.

However, if the upper structure 4 is supported only by the isolation member 1, the following problem arises because the isolation member 1 has low rigidity in the horizontal direction.

The first problem is that once the superstructure 4 begins to vibrate due to earthquake motion, it takes time for the shaking to subside, and the vibration amplitude is
It will be larger than without it, and even if physical safety is guaranteed, residents will remain in a psychologically unstable state for a long time, making it unsuitable as a seismic isolation device for buildings. It is.

The second problem is that when a wind load is applied to a building in one direction during a typhoon, the superstructure 4 may shift in that direction, and stability is not guaranteed.

C. Purpose of the Invention The present invention provides a method for quickly damping vibrations in the case where the upper structure vibrates by arranging a vibration damping member with a simple structure in parallel with the above isolation member between the upper structure and the lower structure. The purpose of the present invention is to attenuate the structure while keeping the amplitude within a predetermined limit, and to ensure a sufficient fixing effect against unidirectional loads on the superstructure due to typhoons and the like.

D. Structure of the Invention The present invention provides a plurality of isolating members, each of which has a cushioning effect by stacking a plurality of metal plates and one or more elastic plates alternately in a vertical seam, between a plurality of isolation members between an upper structure and a lower structure. A tapered rod whose thickness gradually decreases from the root to the tip is made of an elastoplastic material such as steel, and the root is fixed to either the upper structure or the lower structure, and the rod is made of an elastoplastic material such as steel. It has a configuration in which the tip is slidably inserted into a hole provided in the other of the upper structure and the lower structure in the insertion/extraction direction.

E. Embodiment An embodiment of the present invention is shown in FIG. The upper structure 4, which is the main body part of a building, is supported on the lower structure 5, which is the foundation part thereof, via a plurality of isolation members 1, 1, . . .
A rod 6 is disposed between the rods 6, which deforms elastically and plastically in response to relative horizontal movement thereof to achieve the present invention and the above-mentioned objects. The isolation members 1, 1, . . . are those described in FIGS. 1 and 2. Further, as shown in FIG. 5, the rod 6 has a tapered shape whose thickness gradually decreases from the root portion made of an elastoplastic material such as steel. The rod 6 has its root 6a fixed to the upper structure 4, and its tip 6b fitted into a hole 7 provided in the lower structure 5 so as to be slidable in the insertion/extraction direction. The root portion 6a is fixed using a portion of the beam 4a projecting from the bottom of the upper structure and a flange 6a' provided at the root portion. Further, the hole 7 for receiving the tip 6b of the rod 6 is formed at the upper end opening 5 of the rectangular frame 5a which is formed to protrude from a part of the lower structure 5.
It is bored in the center of the metal plate 8 fixed to a'. This hole 7 is formed on the rod 7 side so that when the rod 6 slides in the insertion/extraction direction while deforming elastically and plastically as shown in FIG. 6, it can easily follow the tip 6b of the rod 6. The inner surface is tapered.

In the embodiment described above, the rod 6 is fixed to the upper structure 4 and a hole into which it is inserted is provided in the lower structure, but this attachment method may be reversed.

In the above configuration, seismic motion occurs and the superstructure 4
When the lower structure 5 makes a relative movement in the horizontal direction, the rod 6 reads in response to this relative movement as shown in FIG. Here, the root portion 6a of the rod 6 is fixed to the upper structure 4, and the tip portion 6b is fitted into the hole 7 of the lower structure 5 so as to be slidable in the insertion/extraction direction, so that the bending causes the root portion 6a to The bending stress that occurs at the center of rotation and is applied to each part of the rod 6 increases as it approaches the root 6a from the tip 6b, as shown in the bending moment diagram of FIG. 7, for example. The rod 6 is made of an elastoplastic material, and exhibits hysteresis characteristics as shown in FIG. 8 in terms of stress F and strain amount δ in response to vibrations within a certain range, and one vibration period. It absorbs vibration energy in proportion to the shaded area and damps vibrations.

Note that the absorbed energy at this time is dispersed and absorbed in each part of the rod 6, but as mentioned above, the thickness of the rod 6 gradually decreases from the root toward the tip. There is a proportional relationship between the thickness of each part and the bending stress that acts on it. Therefore, the way the absorbed energy is distributed per unit volume is approximately equal in each part, and there is no shearing due to local concentration of energy, and energy absorption can be performed efficiently throughout the rod 6. Can be done.

Next, the effect of damping vibration energy when using the damping rod 6 as shown in FIG. 4 will be explained using actually measured data. Figures 9 and 10 show how the vibration energy attenuates over time after the upper structure 4 begins to shake due to free vibration due to forced displacement. Deflection δ of the upper structure 4 relative to the lower structure 5
Fig. 10 shows the temporal change in the input acceleration (gal) to the upper structure 4.

In FIGS. 9 and 10, the data in A is for the case where the isolation member 1 is used in combination with the damping rod 6, and the data in B is for the case where only the isolation member 1 is used.

As can be seen from these figures, the damping rod 6
If there are displacement (δ) and acceleration (gal)
Both decay quickly. Comparing this to the case (B) without the rod 6, it can be seen that there is a significant difference.
As can be understood from the comparison results of the above data, according to the seismic isolation device of the present invention, once the building starts vibrating, the time it takes for it to stop, in other words, the time it takes for the occupants in the building to The time it takes for the vibrations to no longer be felt after an earthquake occurs is extremely shortened.

The dimensions and shape of the rod 6 of the present invention are such that it deforms elastically and plastically only when a horizontal stress of a magnitude necessary for seismic isolation is applied, and hardly deforms under a small lateral load such as the wind load of a typhoon. determined by the value.
This results in a fixing effect of the upper structure on the lower structure.

F. Effects of the Invention Since the present invention provides a tapered rod made of an elastoplastic material as a vibration damping member disposed in parallel with the isolation member, when the upper structure vibrates, the vibration energy is absorbed and the vibration is quickly absorbed. can be attenuated to Therefore, the discomfort felt by building occupants during an earthquake can be minimized. In addition, since the rod regulates the positional relationship between the upper structure and the lower structure, even if a small lateral load is applied to the upper structure due to a typhoon, etc., the upper structure can be maintained in a constant positional relationship with respect to the lower structure. can. In particular, the rod pair of the present invention is processed into a tapered shape so that the stress applied to each part matches the strength thereof, so that the rod pair deforms elastically and plastically as a whole and does not suffer local damage. Therefore, the damping effect is effective and the durability is high. Further, since the rod of the present invention has its tip fitted into a hole provided in the lower structure (upper structure) so as to be slidable in the insertion/extraction direction, the upper structure and the lower structure are separated at a certain distance (separation member The damping effect can be performed while maintaining the height of the isolation member, and the operation of the isolation member is not restricted. Further, the dimensions of the rod according to the present invention can be determined simply by moment calculations using the base of the rod as a fulcrum, making the design easy.

[Brief explanation of the drawing]

Figures 1 and 2 are a front view and a plan view of the isolation member, Figure 3 is a front view showing a conventional seismic isolation structure, and Figure 4 is a front view of the isolation member.
The figure is a front view of the seismic isolation structure according to the present invention, FIG. 5 is a sectional view showing an example of the rod mounting structure according to the present invention, and FIG.
FIG. 7 is a cross-sectional view showing the operating state of the rod, FIG. 7 is a view showing stress applied to the rod, and FIG. 8 is an explanatory view of vibration energy absorbed by the rod. Figure 9 and 1
Figure 0 shows the state in which the vibrations of the upper structure are attenuated over time, and in the case of the seismic isolation structure shown in Figure 3,
The case of the seismic isolation structure shown in the figure is compared with A, and FIG. 9 shows the change in displacement, and FIG. 10 shows the change in acceleration. DESCRIPTION OF SYMBOLS 1... Isolation member, 2... Metal plate, 3... Elastic plate, 4... Upper structure, 5... Lower structure, 6... Rod, 6a... Root, 6b... Tip, 7... Hole.

Claims (1)

[Claims] 1. A plurality of isolating members, each of which has a cushioning effect by vertically stacking multiple metal plates and one or more elastic plates, are interposed between the upper structure and the lower structure.
A tapered rod made of an elastoplastic material and whose thickness gradually decreases from the root to the tip is fixed with the root to either the upper structure or the lower structure, and the tip is attached to the upper structure or the lower structure. A seismic isolation device characterized in that it is slidably inserted into a hole provided on the other side in a sliding direction.