JPH11303289A - Base isolation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain base isolation effect by inserting a rubber-made ball between upper structure and lower structure, and fixing a circular column rubber through an attaching plate at the other part away from the rubber ball between the upper structure and the lower structure. SOLUTION: A rubber ball 1 supporting upper structure B is inserted between the upper structure B and lower structure A, and since the weight of the upper structure B is supported by the rubber ball 1, it is in a slightly collapsed state. At the time of an earthquake, horizontal acceleration acts from the lower structure A, the rubber ball 1 rolls, acceleration transmitted to the upper structure B is reduced to a third or below lower than that of the lower structure A, and earthquake force is hardly transmitted to the upper structure B. Next, as the rubber ball 1 rolls, the collapsed part of the rubber moves, a part receiving compression strain and tension strain changes, in addition, rolling of the rubber ball 1 is not permanently continued, and stops rolling in the range of ±30 cm from the initial position. Thus, economically highly safe base isolation structure can be easily formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be used for relatively light buildings (for example, buildings with 3 stories or less, detached houses, etc.) and floors of buildings, and can be used to reduce the rolling of buildings and floors when an earthquake occurs. It is related to seismic isolation structure to prevent or mitigate.

[0002]

2. Description of the Related Art Heretofore, as this type of seismic isolation device, there have been proposed some devices in which a hard ball (bearing) made of steel or the like for supporting an upper structure is inserted between an upper structure and a lower structure. Various types of inventions have been made for a damping device that limits the amount of rolling of a steel ball because the rolling is difficult to stop because the friction resistance is small with only a hard ball. As a specific example, as in JP-A-64-17945, a ball bearing that supports the weight of an upper structure and a stud made of a hard vibration-isolating rubber are used, but these examples are as follows. There is a technical problem.

[0003]

The above prior art is inferior to the present invention in the following points. Because a hard ball (bearing) does not deform itself,
The contact area between the upper structure and the lower structure and the sphere becomes very small, and the compressive stress at the contact portion tends to be excessive. If the compressive stress is high, local dents (dents) are likely to occur on the sphere and on the upper and lower bearings in contact with the sphere, and the rolling motion is not smooth. Therefore, it is necessary to take measures such as increasing the number of balls, increasing the diameter of the balls, and reinforcing the contact points with the steel balls of the upper and lower structures with a thick steel material, which is economically high. Since a hard sphere does not deform itself, if there is slight differential subsidence (partial subsidence) in the lower structure, the sphere and the upper structure may be separated. As a result, the load distribution of the ball and the lower structure is biased. During construction, accuracy errors in the vertical direction of the lower and upper structures occur. For this reason, problems such as an excessive compression force being generated on the hard sphere and a gap being generated between the sphere and the upper structure are likely to occur. ) Since a hard sphere does not deform itself, it is necessary to take measures to reduce the displacement caused by the earthquake. One is to insert a damping mechanism (damper) to absorb seismic energy and reduce the amount of shaking. The other method is to reduce the displacement of the sway by making the lower bearing that supports the hard sphere have a gentle concave shape and changing the seismic energy to the potential energy of the upper structure when shaking due to an earthquake. This 2
Both approaches are technically effective, but lead to higher costs.

[004]

According to the present invention, there is provided a seismic isolation structure in which a rubber ball is inserted between an upper structure and a lower structure. In the present invention,
A columnar rubber may be fixed between the upper structure and the lower structure at a position different from the rubber ball via a mounting plate. Further, the present invention is characterized by a seismic isolation structure in which a rubber ball is arranged on a lower floor of a building, and an upper floor is placed on the rubber ball.

According to the seismic isolation structure of the present invention, an ordinary (always)
Since the rubber ball supports the upper structure, the rubber ball is in a slightly crushed state. In the event of an earthquake, the lower structure sways horizontally, so that the rubber ball can be rolled freely in the horizontal direction with the rubber ball collapsed. By rolling, the part that receives the compressive force moves constantly, so the rubber ball itself (exhibits the damping effect)
Absorbs seismic energy and reduces horizontal displacement. The acceleration transmitted to the superstructure is reduced to about 1/3 or less of the acceleration of the lower structure, and the seismic force is hardly transmitted to the upper structure. With rubber balls alone, when horizontal displacement occurs during an earthquake, there is no force (restoring force) to return to the original position, so there is a high possibility that permanent (residual) displacement will occur after the earthquake. There are the following two solutions to this problem. (1) If permanent horizontal (residual) displacement occurs after the earthquake, return it to its original position with a jack or the like. (2) Avoid permanent horizontal (residual) displacement after an earthquake. Specifically, by fixing a cylindrical rubber having elastic spring characteristics between the upper and lower structures, a restoring force is secured, and after an earthquake, it is returned to its original position. Claim 2 of the present invention has the second solution as a gist.

[0000]

(Embodiment 1) In FIGS. 1 and 2, FIG.
A rubber ball 1 for supporting the upper structure is inserted between the upper structure B and the lower structure A. Usually, since the weight of the upper structure B is supported by the rubber ball, the upper structure B is in a slightly crushed state. At this time, the rubber spheres are arranged so that the weights borne by the rubber spheres are equal, and the crushing amounts of the rubber spheres are equalized, so that the lower portion of the upper structure B is not deformed. During construction,
Vertical accuracy errors occur in the lower structure and the upper structure. However, since the softness of the rubber ball absorbs this accuracy error, the workability is good. During an earthquake, a horizontal acceleration acts on the lower structure, causing the rubber balls to roll. For this reason, the acceleration transmitted to the upper structure B is about 1 of the acceleration of the lower structure A.
The seismic force is hardly transmitted to the superstructure (seismic isolation effect).

As the rubber ball rolls, the crushed portion of the rubber moves, and the location where the compressive or tensile strain is applied changes constantly. The seismic energy changes once to the kinetic energy of the upper building, but then the rubber ball deforms Is absorbed by Due to this effect, the rolling of the rubber ball does not continue indefinitely, and even in the case of a large earthquake, it can be stopped within a range of ± 30 cm or less from the original position. The contact point (supporting portion) between the rubber ball and the upper / lower structure is required not to be depressed by the pressure of the rubber ball. There is no problem as long as it is a normal building structural material such as wood, steel, concrete, and ALC.

FIG. 5 shows the restoring force characteristics of the rubber ball of FIG. With rubber balls alone, when horizontal displacement occurs during an earthquake,
Since there is no restoring force (restoring force), there is a high possibility that permanent horizontal (residual) displacement after the earthquake will occur. If a permanent (residual) displacement occurs after the earthquake, it can be easily returned to the original position by returning it with a jack or the like.

(Embodiment 2) In FIG. 3, a rubber ball 1 for supporting the upper structure B is inserted between the upper structure B and the lower structure A, and between the upper structure B and the lower structure A, A seismic isolation structure is shown in which a cylindrical rubber 2 is fixed at a different place from the rubber ball 1 with mounting plates 3B and 3A and stud bolts 4. (The same as in Example 1 below)

The rubber 2 has a function of causing a shear deformation during an earthquake and returning the rubber to its original position. FIG. 6 shows the restoring force characteristics of the rubber ball and the column rubber of FIG. Cylindrical rubber exhibits linear (elastic) behavior, and rubber spheres exhibit characteristics as shown in FIG.
With a rubber ball alone, when horizontal displacement occurs during an earthquake, there is no force to restore it (restoring force), so there is a high possibility of permanent horizontal (residual) displacement after the earthquake. By attaching the columnar rubber 2, the upper structure B can be returned to almost the original position even after the earthquake.

(Embodiment 3) FIG. 4 shows a lower floor C of a building.
1 shows a seismic isolation floor structure in which a rubber ball 1 is placed on a floor and an upper floor D is placed thereon. FIG. 2 is an invention for making the entire building seismically isolated, while FIG. 4 is an invention for making a part of the floor in the building seismically isolated. Other details are the same as in the first embodiment.

[0111]

According to the seismic isolation structure of the present invention, the following effects can be obtained. During an earthquake, a horizontal acceleration acts on the lower structure, causing the rubber balls to roll. Therefore, the acceleration transmitted to the upper structure is reduced to about 1/3 or less of the acceleration of the lower structure,
Almost no seismic force is transmitted to the superstructure (seismic isolation effect). Since rubber balls are inexpensive, an economical and highly safe seismic isolation structure can be easily realized by the seismic isolation effect. As the rubber ball rolls, the crushed portion of the rubber moves, and the portion subjected to compressive strain or tensile strain constantly changes. The seismic energy is first converted to kinetic energy of the upper building, but then absorbed by the thermal energy from the deformation energy of the rubber sphere. Due to this effect, the rolling of the rubber ball does not continue forever, ± 20-30cm from the original position
Rolling stops in the following range. Since the rubber ball itself supports the superstructure and absorbs seismic energy, it is a very simple mechanism and much more economical than conventional seismic isolation devices. The amount of rubber crushed may change with respect to the differential subsidence of the lower structure (partial subsidence).
It can cope with uneven settlement of the substructure. During construction, accuracy errors in the vertical direction of the lower and upper structures occur. In a conventional steel ball, this accuracy error is a problem, but the softness of the rubber ball absorbs this accuracy error, so that the workability is good.

[Brief description of the drawings]

FIG. 1 is a diagram of a house in which the present invention is implemented.

FIG. 2 is a longitudinal sectional view showing an embodiment of a bearing in the seismic isolation structure according to the present invention.

FIG. 3 is a longitudinal sectional view showing an embodiment of a bearing in the seismic isolation structure according to the present invention.

FIG. 4 shows a longitudinal section of an embodiment in which only the floor is seismically isolated.

FIG. 5 shows the restoring force characteristics of the seismic isolation structure of FIGS.

FIG. 6 shows a restoring force characteristic of the seismic isolation structure of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rubber ball 2 Cylindrical rubber 3A, 3B Mounting plate 4 Stud bolt

Claims (3)

[Claims] 1. A seismic isolation structure in which a rubber ball 1 is inserted between an upper structure B and a lower structure A. 2. Attachment plates 3A, 3B at a position different from the position where the rubber ball 1 is disposed between the upper structure B and the lower structure A.
The seismic isolation structure according to claim 1, wherein the columnar rubber (2) is fixed through the (2). 3. A seismic isolation structure in which a rubber ball 1 is placed on a lower floor C of a building and an upper floor D is placed on the rubber ball 1.