Vibration controlling apparatus for buildings

Abstract: A vibration controlling apparatus (100) for buildings, wherein an additional mass (5) is attached to a building (2) through an elastic support means (4) utilizing a lateral elasticity of a laminated elastic body obtained by alternately laminating an elastomer layer and a reinforcing plate one upon the other, and an excitation force of a given waveform corresponding to vibration of said building is applied to said additional mass (5), and wherein an auxiliary vibration system comprised of said elastic support means (4) and said additional mass (5) is used as a passive dynamic vibration reducer without applying said excitation force to said additional mass.

Description: This invention relates to a vibration controlling apparatus for buildings which reduces the swaying in a building of a flexible structure system such as high-rise building, tower or the like due to an earthquake, wind or the like. In high buildings such as high-rise buildings, various towers and the like, there is adopted a flexible structure system for absorbing vibration energy to increase the earthquake proof strength. In this flexible structure system, however, the swaying is not only caused by a strong wind or earthquake but also becomes large even at normal wind, so that the living comfortability may be adversely affected. As a means for reducing the vibration amplitude at normal wind to improve the living comfortability and at the same time reducing the deformation of the building as a whole even in a strong wind or earthquake, therefore, it has been proposed to arrange a dynamic vibration reducer (i.e. dynamic damper) for the generation of vibration counteracting the swaying of the building, which comprises a combination of a main spring system consisting of the building itself and an auxiliary spring system connected to the building through a spring means and provided with an additional mass and is set so that the natural frequency (vibration period) is approximately equal between the main spring system and the auxiliary spring system to realize the vibration absorbing effect. Fig. 13 shows a structure of this type of conventional dynamic vibration reducer. As shown in Fig. 13, a lower mass 33 movable along a pair of rails 32 horizontally placed on a building 31 (e.g. on top of a tower or the like) in a given direction (Y-direction) and an upper mass 35 movable along a pair of rails 34 horizontally placed on the lower mass 33 in a given direction (X-direction) are supported by spring members (not shown) extending in the Y-direction and X-direction, respectively. Further, each of these masses 33, 35 is slidably supported by a roll having a small friction coefficient, respectively. Thus, the conventional dynamic vibration reducer for the building is a two-dimensional apparatus, wherein the dynamic vibration reducing effect to the vibration (swaying) of the building 31 in the Y-direction is obtained by the auxiliary spring system consisting of springs of the Y-direction and the upper mass 35 and lower mass 33, and the dynamic vibration reducing effect to the vibration (swaying) in the X-direction is obtained by the auxiliary spring system consisting of springs of the X-direction and the upper mass 35. In the conventional vibration controlling apparatus for buildings, however, the main spring system and auxiliary spring system having substantially the same vibration period are merely connected to each other (passive damper), so that if it is intended to make the vibration controlling effect large, the mass ratio of the building 31 to additional masses 33, 35 becomes large (in a direction approaching to 1.0) and consequently it is required to increase the strength of the building 31, which is difficult to practically realize. Since the conventional vibration controlling apparatus is a passive damper as mentioned above, the vibration response ratio is determined by the masses 33, 35, spring constant and vibration damping coefficient of the dynamic vibration reducer (auxiliary spring system). As a result, this apparatus has a large effect for a particular vibration frequency component, but can not provide the vibration reducing effect against vibrations of wide frequency band such as random vibration. Further, each of the masses 33, 35 is supported by a roll bearing or the like, so that the static friction coefficient is large in the vibration reducing operation and consequently only the reducing effect against large external force is obtained and the effect against minute vibration cannot be obtained. Attention is also drawn to the disclosures of JP-A-60-211143 and US-A-4499694. The document JP-A-60-211143 discloses a vertical quake damping mechanism comprising a cylindrical body 10, a columnar body 9 disposed in the cylindrical body at a given space, and a laminated body arranged in the space for connecting the cylindrical body to the columnar body and comprised of rubber plates 11 and a metal plate 12, in which either one of the columnar body and the cylindrical body is fixed on a frame 1 and the other is fixed to a lower face of a frame 6 supporting machine or structural body to be damped as shown in Figs. 2(b) and 3(a) + (b). In JP-A-60-211143, however, an elastic body (or ball 3) is arranged between the frame 1 and a base 2, so that the influence of friction force cannot be eliminated. In particular, the mechanism of JP-A-60-211143 can not sufficiently develop the effect of reducing vibrations of small input such as normal wind or a slight earthquake. The document US-A-4499694 is concerned with a cyclic shear energy absorber in which an energy absorbing core 2 and a flexible restraining means 3 surrounding the core are disposed in a cylindrical void formed in the center of a resilient support 4 consisting of alternate layers of resilient material 5 and stiffener plates 6. In the absorber of the document US-A-4499694, energy is absorbed by the plastic deformation of the core 2 while uniform shear deformation is given to the core 2 through the means 3. The present invention aims to overcome the aforementioned problems of the conventional techniques and to provide a vibration controlling apparatus for buildings which can largely reduce the vibrations (swaying) of the building over the whole of a wide frequency band and can respond immediately to small vibrations because the friction sliding portion is not existent even in the vibration reducing operation. The present invention provides a vibration controlling apparatus for buildings, comprising an additional mass attached to a building, wherein the additional mass is attached to the building through an elastic support means utilizing a lateral elasticity of a laminated elastic body obtained by alternately laminating an elastomer layer and a reinforcing plate one upon the other, characterized in that the elastic support means is comprised of multi-stage elastic units obtained by piling a plurality of the laminated elastic bodies one upon the other through stabilizing plates each connecting the lower end of one body to the upper end of another body. The invention will be further described, by way of example only with reference to the accompanying drawings, wherein: Fig. 1 is a schematic elevational view of a building provided with a vibration controlling apparatus according to the invention; Fig. 2 is a front view of a dynamic vibration reducer shown in Fig. 1; Fig. 3 is a sectional view taken along a line III-III of Fig. 2; Fig. 4 is a longitudinally sectional view of a laminated elastic body shown in Fig. 2; Fig. 5 is a sectional view taken along a line V-V of Fig. 4; Fig. 6 is a front view of another embodiment of the dynamic vibration reducer; Fig. 7 is a transversely sectional view taken along a line VII-VII of Fig. 6; Fig. 8 is a diagrammatical view showing a vibration mode of the dynamic vibration reducer having no mode correcting rod; Fig. 9 is a diagrammatical view showing a vibration mode of the dynamic vibration reducer having a mode correcting rod; Fig. 10 is a block diagram showing the construction of the vibration controlling apparatus according to the invention; Fig. 11 is a longitudinally sectional view of another embodiment of the laminated elastic body of Fig. 2; Fig. 12 is a sectional view taken along a line XII-XII of Fig. 11; and Fig. 13 is a perspective view of the conventional dynamic vibration reducer for a building. The invention will be described in detail with reference to Figs. 1 to 12 below. Fig. 1 schematically shows a building provided with the vibration controlling apparatus according to the invention. In Fig. 1, a tower-like building 2 is built on a ground 1, and the vibration controlling apparatus 100 according to the invention is placed on a top floor of the building 2. As a typical example of the building 2, mention may be made of a steel structure building having a section of square, rectangle, lozenge or the like with a side of, for example, 10-25 m and a height of 60-150 m and swaying, for example, at a vibration period of about 2 seconds and an amplitude of few meters through wind pressure, and the like. In the vibration controlling apparatus 100, an additional mass 5 is attached to the building 2 through a horizontal spring means 4 to construct a dynamic vibration reducer 3, while the vibration (swaying) of the building 2 is detected by a vibration sensor 6 and then a vibration waveform counteracting the vibration of the building 2 is produced by a control unit 7 based on the detected signal and vibration is applied to the additional mass 5 by an actuator 8 actuating based on the vibration waveform to thereby reduce the swaying of the building 2. The horizontal spring means or elastic support means 4 acts to elastically support the additional mass 5 to the building 2 at a horizontally displaceable state and has a structure utilizing the lateral elasticity of a laminated elastic body (rubber laminate) obtained by alternately laminating an elastomer layer and a reinforcing plate one upon the other as mentioned later. That is, the vibration controlling apparatus 100 comprises the dynamic vibration reducer 3 consisting of a main vibration system of the building 2 and an auxiliary spring system connecting thereto and composed of the horizontal spring means 4 and the additional mass 5 having substantially the same vibration period and can effectively reduce the swaying of the building 2 by producing a vibration waveform counteracting the vibration state of the building 2 and then vibrating the additional mass 5 through the actuator 8 actuating based on the vibration waveform even when the building 2 is subjected to various excitation forces of a wide frequency band. Fig. 2 shows a front view of the auxiliary spring system constituting the dynamic vibration reducer, and Fig. 3 shows a transversely sectional view taken along a line III-III of Fig. 2. In Figs. 2 and 3, the dynamic vibration reducer 3 is constructed by the spring means 4 utilizing the lateral elasticity of the laminated elastic body 11 and the additional mass 5 attached onto the spring means. In the illustrated embodiment, the spring means 4 is comprised of multi-stage elastic units by piling plural laminated elastic bodies (4 bodies) one upon the other (4 stages) through stabilizing plates 12 each connecting the lower end of the body 11 to the upper end of the other body 11. Each of these stabilizing plates 12 is a rigid plate and serves to increase an elastical and horizontal displacement ability without causing buckling when the plate is subjected to lateral loading by earthquake or wind. In the illustrated embodiment, a damping device 13 for damping vibrations in the horizontal direction is incorporated between the adjoining stabilizing plates 12, 12 in a given arrangement. If necessary, the spring means (elastic support means) 4 may be comprised of a single laminated elastic body 11. Fig. 4 shows a longitudinally sectional view of the laminated elastic body 11, and Fig. 5 shows a section taken along a line V-V of Fig. 4. In Figs. 4 and 5, the laminated elastic body 11 has a structure of alternately laminating a layer 14 of rubber or other elastomer and a reinforcing plate 15 such as metal plate or rigid plastic plate one upon the other, and flange plates 17, 17 each having plural fitting holes 16 are usually bonded to the upper and lower ends of the body 11 by baking, adhesion or the like. Such a laminated elastic body 11 has a high spring constant in the longitudinal direction and a relatively low spring constant in the horizontal direction. Fig. 6 shows a longitudinally sectional view of the dynamic vibration reducer 3 having a mode correcting rod, and Fig. 7 shows a section taken along a line VII-VII of Fig. 6. In Figs. 6 and 7, plural through-holes 51 are formed at given positions (5 positions in the illustrated embodiment) in each of the stabilizing plates 12, and a mode correcting rod 52 is inserted into each of these through-holes 51. The lower end of the mode correcting rod 52 is pivoted to the building 2 through a pivot point 53, while the upper end thereof is engaged to the additional mass 5. Moreover, the through-hole 51 in the stabilizing plate 12 has such a diameter that the mode correcting rod 52 is freely inserted into the through-hole at a certain gap. The mode correcting rod 52 is to correct the distortion of vibration mode in horizontal direction of the multi-stage laminated elastic body unit and prevent the degradation of the vibration damping effect. Fig. 8 schematically shows a vibration mode of the dynamic vibration reducer 3 having no mode correcting rod 52, while Fig. 9 schematically shows a vibration mode of the dynamic vibration reducer 3 having the mode correcting rod 52. As seen from Figs. 8 and 9, the distortion of the vibration mode as shown in Fig. 8 is avoided by extending the mode correcting rod 52 from the building 2 through each of the stabilizing plates 12 to the additional mass 5, whereby the dynamic vibration reducer for the building capable of holding the linearity and preventing the degradation of the damping effect is obtained. Fig. 10 shows a block diagram illustrating the construction of the vibration controlling apparatus 100 shown in Fig. 1. The vibration controlling apparatus 100 according to the invention is constructed to reduce the vibration or swaying of the building 2 by attaching the additional mass 5 to the building 2 through the spring means (elastic support means) 4 explained in Fig. 2, and detecting vibrations generated in the building 2, and applying an excitation force of a given waveform adjusted in accordance with the vibration of the building 2 to the additional mass 5. In Fig. 10, the control circuit 7 is so constructed that a vibration waveform of a component counteracting the vibration of the building 2 is produced based on a detected signal from vibration sensor 6 detecting the vibration (swaying) of the building 2 to thereby actuate the actuator 8 and then the waveform counteracting the vibration of the building 2 is applied to the additional mass 5. As shown in Fig. 10, the control circuit 7 is comprised by connecting a charge amplifier 21, a low-pass filter 22, an analog-digital convertor 23, a digital filter 24, a digital-analog convertor 25, a low-pass filter 26 and a power amplifier (signal amplifier) 27 in order, and functions to output a vibration waveform counteracting the vibration of the building 2 from the power amplifier 27 based on the detected signal for the vibration of the building 2 input from the vibration sensor 6 into the charge amplifier 21. The output from the power amplifier 27 is input to the actuator 8, so that the actuator 8 excites the additional mass 5 at a state of counteracting the vibration of the building 2 and as a result the dynamic vibration reducer 3 acts as an active dynamic damper. The digital filter 24 has a most important function of forming the waveform signal in the control circuit 7. If the control signal output from the control circuit 7 exceeds the capacity of the actuator 8, the additional mass 5 is separated from the actuator 8 to shut off the transmission of excitation force, whereby the dynamic vibration reducer 3 consisting of the additional mass 5 and the elastic support means (spring means) 4 can be used as an active dynamic damper. That is, the illustrated dynamic vibration reducer 3 is comprised of the auxiliary spring system having substantially the same natural frequency as in the building (main spring system) 2, so that it possesses a function that a large vibration in the vicinity of resonant frequency of the building 2 is effectively damped together with the passive damper. According to the above mentioned embodiment, the vibration state of the building 2 is detected by the vibration sensor 6 arranged on the building 2, and then a signal calculated from the detected signal by the control circuit 7 so as to reduce the vibration of the building is input to the actuator 8 to thereby actuate the active dynamic vibration reducer (dynamic damper), so that the reducer has a structure of small size and light weight. Therefore, a vibration controlling apparatus capable of effectively reducing vibrations over a whole frequency band is obtained even when the building 2 is excited by the external force of the wide frequency band. Further, the spring of the dynamic vibration reducer 3 is constructed by utilizing the lateral elasticity of the laminated elastic body 11, so that the static friction force can be eliminated, and consequently a vibration controlling apparatus capable of surely responding to small external force is obtained. Also, a laminated elastic body 11 having uniform spring properties in all of the two-dimensional directions is used, so that the structure of the dynamic vibration reducer 3 can be made simple and cheap. Moreover, when the multi-stage elastomer unit is formed by laminating plural laminated elastic bodies 11 through the stabilizing plates 12 (for example, about 10 stages), even after the unit is assembled on the building 2, the dynamic vibration damping characteristics can easily be adjusted by increasing or decreasing the number of the stages, and consequently a vibration controlling apparatus having an excellent handling property is obtained. Fig. 11 shows another embodiment of the laminated elastic body 11, and Fig. 12 shows a sectional view taken along a line XII-XII of Fig. 11. In Figs. 11 and 12, a hollow portion 41 of a closed state is formed in a central portion of the laminated elastic body 11 obtained by alternately laminating the elastomer layer 14 and the reinforcing plate 15 one upon the other, and a vibration damping means having an increased internal loss is arranged in the hollow portion 41. In the illustrated embodiment, each of protrusions 42, 42 projecting toward the hollow portion 41 is formed on the inner face of each of the flange plates 17, 17 constituting both end faces of the laminated elastic body, while a liquid or viscous fluidizing substance (water, oil, green rubber, plastic, asphalt, clay or the like) is filled in the hollow portion 41. In the laminated elastic body 11 shown in Figs. 11 and 12, the vibration damping performances may further be improved by utilizing the vibration damping means arranged in the hollow portion as compared with the case of Figs. 4 and 5. As mentioned above, in the vibration controlling apparatus for buildings according to the invention, the additional mass is attached through the elastic spring means utilizing the lateral elasticity of the laminated elastic body obtained by alternately laminating the elastomer layer and the reinforcing plate one upon the other, and the excitation force of a given waveform in accordance with the vibration of the building is applied to the additional mass, so that the apparatus is small in size and light in weight, and also the vibrations can effectively be reduced over the whole of the wide frequency range. Furthermore, a vibration controlling apparatus capable of surely responding to small external force to reduce the swaying is obtained.

Claims: A vibration controlling apparatus (100) for buildings, comprising an additional mass (5) attached to a building (2), wherein the additional mass is attached to the building through an elastic support means (4) utilizing a lateral elasticity of a laminated elastic body (11) obtained by alternately laminating an elastomer layer and a reinforcing plate one upon the other, characterized in that the elastic support means (4) is comprised of multi-stage elastic units obtained by piling a plurality of the laminated elastic bodies (11) one upon the other through stabilizing plates (12) each connecting the lower end of one body (11) to the upper end of another body (11).

Inventors: FUJITA TAKAFUMI, KURABAYASHI HIROSHI, MASAKI NOBUO, SUIZU YOJI, FUJITA, TAKAFUMI, KURABAYASHI, HIROSHI, MASAKI, NOBUO, SUIZU, YOJI
Applicants: BRIDGESTONE CORP, FUJITA TAKAFUMI, BRIDGESTONE CORPORATION, FUJITA, TAKAFUMI
Application year: 1988
Main classification: E04B1
IPC codes: E04B1