JPS6229589B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a seismic isolation support device for supporting structures with rollable objects in order to prevent structures from being destroyed or overturned or overflowing of liquid in a tank during an earthquake.

Conventional seismic isolation support devices of this type often use rolling elements with spherical rolling surfaces, but since the restoring force applied to the supported object increases with displacement, the ability to absorb vibration energy due to earthquakes is reduced. It has the disadvantage of increasing its size. Furthermore, if the maximum acceleration that the supported object receives during an earthquake is reduced, even a small external force causes a large displacement, and the amplitude of the supported object tends to increase.

This invention solves these problems and makes it possible for the restoring force exerted by the rolling elements on the supported object to remain almost constant regardless of displacement and not increase, thereby making it difficult for the supported object to sway and further acting on the supported object. The present invention provides a seismic isolation support device that can maintain the acceleration value at approximately a predetermined value.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, 1
Reference numeral 0 denotes a rolling element which can roll and is arranged between a supporting surface 11 which is a horizontal plane and a supported surface 13 which is a horizontal plane of the supported object 12. As shown in the cross-sectional diagram of FIG. 2, the rolling element 10 has a surface shape that is vertically symmetrical with respect to the center O, that is, the origin of polar coordinates to be described later. It is constituted by a flat part 16.
The curved surface portion 15 is formed by a rotating surface obtained by rotating a radius vector of θ=π/2 using a curve obtained by drawing the following function on a polar coordinate plane as a generating line, and the extended portion is indicated by a dotted line. The function is as follows, where r is a variable expressed as a radius vector, θ is an angle variable expressed in radians, and r ₀ , θ ₀ , and α are positive constants.

r=r ₀ e〓 ⁽ 〓 ^0- 〓 ⁾ ...(1) The function expressed by equation (1) generally becomes an exponential vortex line as shown in Figure 3. In general, θ ₀ can be any value, but if we set it so that θ ₀ =tan ^-1 1/α...(2), then the polar coordinates of point A, where the tangent to the curve representing this function is horizontal, are constants r ₀ and θ It is equal to ₀ . Further, it is desirable that α is generally a value smaller than 1, such as 0.2 or 0.3. When rotating around a direction in which θ is π/2 using a curve created by such a function as a generating line, if θ becomes larger than the position of point A, the surface becomes concave and has no practical meaning, so this range is connected by the flat part 16. be.

Next, as shown in FIG. 4, if the supported object 12 is displaced horizontally with respect to the supporting surface 11 as indicated by the arrow u, there will be sufficient space between the rolling elements 10, the supporting surface 11, and the supported surface 13. When the frictional force is applied and no sliding occurs, the rolling elements 10 roll and are inclined as shown. In this case, a force W based on the weight of the supported object 12 acts on the rolling element 10 from above, and a force W due to a reaction force equal to the gravity acts upward from the supporting surface 11. Further, a force F based on the frictional force exerted from the rolling elements 10 acts on the supporting surface 11 and the supported surface 13 of the supported object 12 in opposite directions as shown in the figure. The rolling elements 10 are each subjected to forces F of the same magnitude but in opposite directions at the upper and lower contact points C and D, and the moments due to the force W and the force F received by the rolling elements 10 are balanced. Therefore, if the lengths representing the vertical and horizontal distances between contact points C and D are H and L, respectively, the relationship WL=FH (3) holds true. Here, the lengths H and L are equal to twice the distance of the tangent and normal to the origin O at the contact point C in equation (1), respectively, so from this, the value of the force F can be calculated as follows. It will be done.

Expression (1) in Cartesian coordinates (x, y) centered on the origin O
Expressed as √ ² + ² = e ^(C1- 〓 ^tan-1 〓 ⁾ ...(4), where e ^C1 = r ₀ e〓〓 ⁰ . Differentiating equation (4) yields the following equation.

y'=dy/dx=dy-x/dx-y...
…(5) Also, From equations (3), (6), and (7), F=L/HW=αW...(8) is obtained. This force F acts on the supported object 12 as a restoring force, and its magnitude is unrelated to the displacement of the supported object 12 and has a constant value. The function expressed by equation (1) is not a coincidence, but is obtained as a result of finding a curve in which L/H is a constant α.
That is, the solution of the differential equation α(y-y'x)=yy'+x...(9) obtained by referring to equations (6) and (7) is obtained. Next, N with the same value of α
The total restoring force F acting on the supported object 12 supported by the individual rolling elements 10 is expressed by W representing the total weight of the supported object 12, M representing the total mass, and g representing the acceleration of gravity. If the restoring force received is Fi, and the weight supported by each rolling element 10 is Wi, then becomes. That is, the total restoring force F is a constant value αgM regardless of the position of the contact point of the rolling element 10. Further, the acceleration a that the supported object 12 receives is a constant value of a=αg. When the supported object 12 returns to the initial position due to the restoring force F, since the speed has increased, it is displaced to the opposite side due to inertia, and the rolling elements 10 roll in the opposite direction. In this case, restoring force F and acceleration a
changes its direction, but its absolute value remains the same. Therefore, the restoring force F and acceleration a with respect to the horizontal displacement X of the supported object 12 are as shown in FIGS. 5 and 6. The potential energy E _P that the supported object 12 has when it is displaced X in the horizontal direction is E _P =αXW=FX. This value is expressed by the shaded area in FIG. 5 when X is _X1 .

In the conventional seismic isolation support device, the restoring force F and acceleration a relative to the displacement X of the supported object change, for example, as shown by the chain lines in FIGS. 5 and 6, respectively. In such a conventional case, the potential energy E _P for the displacement of the supported object is approximately 1/2 that of the present invention for the same displacement. Generally, the vibrational energy of an object becomes the potential energy E _P at its maximum amplitude. Therefore, when the vibration energy of the supported object is the same, it is necessary for the conventional seismic isolation support device to have at least one or both of the maximum restoring force and displacement larger than that of the present invention. It is easy to break or fall over. In this invention, all vibrational energy can be converted into potential energy E _P with the least amount of displacement while minimizing the maximum restoring force and the maximum acceleration. In other words, there are practical differences between the conventional seismic isolation support device and the seismic isolation support device of the present invention in terms of how they can be used against medium-sized earthquakes and large earthquakes, or whether they can be used in places where the ground is bad or where the ground is good. Even if the supported object breaks or falls over due to unexpected vibrations in conventional devices, this invention can prevent this from happening.

The seismic isolation support device of the present invention may be configured such that a building is supported as the supported object 12 by a large number of rolling elements 10 each having the same value of α, as shown in FIG. 7, or as shown in FIG. Supported object 12
As shown in FIG. 9, an oil tank which is an outdoor installation is supported by a similar number of rolling elements 10, and an indoor installation such as a computer is supported by a similar number of rolling elements 10 as a supported object 12, as shown in FIG. This can be done in certain cases. Generally, in such a case, it is desirable that three or more rolling elements 10 having the same α are used. Further, in addition to the rolling elements 10, a vibration damping device such as a known oil damper or a friction damper may be used in combination to construct a seismic isolation device with the highest performance. Also, if the value of α is determined so that the restoring force when supporting a supported object 12 that is exposed to wind force by an outdoor installation such as a building or an oil tank is a value slightly larger than the maximum wind load, It is possible to make it not move at all against the wind force. Also, in the case of an indoor installation such as a computer, if the restoring force is set to be slightly larger than the maximum load that is applied on a daily basis, the movement of the supported object 12 can be prevented by providing a seismic isolation support device. It is possible.

In this invention, for example, the upper surface of the rolling element 10 may be configured to have a spherical surface connected to the vicinity of the upper end of the curved surface portion 15 without providing the flat portion 16.
The curved surface portion 15 of the rolling element 10 is formed with irregularities, and at least half of the surface that may come into contact with the supporting surface 11 and the supported surface 13 during rolling of the rolling element 10 is substantially the above-mentioned curved surface portion. It is sufficient if it is formed along the line 15.

Since this invention is configured as described above,
The restoring force and acceleration acting on the supported object 12 during an earthquake can be made almost constant regardless of displacement, the amplitude can be kept to a minimum, and the supported object 12 can be prevented from receiving wind force or other forces that may normally be received. It has the effect of being able to prevent it from moving even when it is in use. Therefore, in a small earthquake, the supported object 12 does not shake significantly, and even in a large earthquake, the acceleration is kept below the allowable amplitude, and the amplitude does not increase, preventing destruction, overturning, and overflow of liquids such as oil, so that it can be used with peace of mind. It is.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a cross-sectional diagram of a rolling element, Fig. 3 is a diagram showing a function for forming the surface of the rolling element, and Fig. 4 is a displacement diagram. Front view showing the seismic isolation support device in a state where
Figure 6 is a diagram showing restoring force, Figure 6 is a diagram showing acceleration, Figure 7 is a front view showing the state in which the building is supported, Figure 8 is a front view showing the state in which the oil tank is supported, and Figure 6 is the diagram showing the acceleration. FIG. 9 is a front view showing the state in which the computer is supported. 10 is a rolling element, 11 is a supporting surface, 12 is a supported object, 13 is a supported surface, 15 is a curved surface portion, and 16 is a flat portion.

Claims (1)

[Claims] 1. In a device that has rolling elements arranged between a supporting surface and a supported surface that are substantially horizontal, when the rolling elements roll due to the movement of the supporting surface and supported surface, there is a possibility that they will come into contact with the supporting surface and the supported surface. At least half of a certain surface has a variable where r is expressed as a radius,
Let θ be an angle variable expressed in radians, and r ₀ , θ
₀ , α is a positive constant, the curve drawn by the function r=r ₀ e〓 ⁽ 〓 ^0- 〓 ⁾ on the polar coordinate plane is the generating line, and θ
A seismic isolation support device characterized in that a rotating curved surface formed when rotating around a direction of =π/2 approximately follows a surface formed when vertically symmetrically arranged around the origin of polar coordinates.