Static structures (e.g. – buildings) – Means compensating earth-transmitted force – Dynamic force generator
Patent
1993-11-18
1995-08-22
Friedman, Carl D.
Static structures (e.g., buildings)
Means compensating earth-transmitted force
Dynamic force generator
52 1, 521671, 521678, E04H 902
Patent
active
054428831
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
1. Field of Invention The field of invention relates to vibration control devices of the active type for reducing the response of a structure to earthquake and wind vibrations or the like, by applying a control force on the structure. These devices are suitable for vibration control of large scale structures having comparatively long natural periods, such as multi-storied buildings and high rises.
2. Description of Related Art
As used in this specification, symbols and terms are defined as follows: control force such as hydraulic, electromagnetic, electrical, electro-mechanical means, or any combination thereof. seismic (or wind) vibration.
Dynamic dampers (designated hereinafter as DD) of the passive type are disclosed in Japanese Pat. Laid-open No. 63-76932 and Japanese Pat. Publication No. 3-38386.
Prior art FIG. 6 of this application shows a vibration model of a DD to be applied to a structure, wherein m.sub.1 is a mass of a main body of a structure constituting a main vibration system, and m.sub.d is a mass of an additional mass body constituting a damping system. Also, k.sub.1 is a spring constant of the main body of the structure. The main body of the structure having a mass m.sub.1 and the additional mass body are mutually connected through a spring having a spring constant k.sub.d and a damper having a damping coefficient c.sub.d. Further, x.sub.1 represents a displacement of the structure, and x.sub.d represents a displacement of the additional mass body m.sub.d.
A natural angular frequency of the main vibration system is given by:
In the DD, a mass m.sub.d of the damping system is designed so that the ratio of the mass m.sub.d to the mass.sub.1 of the main vibration system may be set to be or equal to:
At this time, the natural angular frequency of the damping system is given by:
A damping coefficient c.sub.d and a damping factor h.sub.d are respectively represented by:
Active type control devices, or Active Mass Drivers (designated hereinafter as AMD) are disclosed in U.S. Pat. No. 5,022,201.
Prior art FIG. 7 of this application shows a vibration model of an AMD which applies a control force u(t) by an actuator such as a hydraulic or electromagnetic device, between a main body of the structure having a mass m.sub.1 and an additional mass body having a mass m.sub.d to actively control the vibration of the structure.
In the AMD, assuming that a spring between the main body of the structure and the additional mass body constituting a vibration control device is set under a soft condition, i.e., circuit (AGC) or the like against the response speed of the structure and attains the correspondences of large inputs through small inputs. The second term in the above equation gives a damping property to the side of the additional mass body as well to attain stability thereof by adding the product of a gain G.sub.2 (negative sign) to a vibration speed on the side of the additional mass body to the control force.
In response to the above defined AMD, some studies have been made which add a spring having a spring constant k.sub.d in parallel with the control force due to the actuator as shown in the vibration model of FIG. 8 and to obtain a vibration control effect to the same degree with that of the AMD by means of less control force in comparison with that of the AMD (designated hereinafter as ATMD, the abbreviation for Active Tuned Damper.)
In an ATMD, a spring constant k.sub.d is set so that the vibration of an additional mass body may synchronize with that of a structure, that is, following equation: -x.sub.d) inertial force applying on the additional mass body at a vibration time due to the third term in the above equation so that the additional mass body may be vibrated by less control force.
Japanese Pat. Publication No. 3-70075 discloses means for controlling the structural vibration due to earthquake or the like by an extremely small control force by connecting a second additional mass body having a mass less than that of the additional mass body of a DD to the additional
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Nishimura Isao
Sakamoto Mitsuo
Sasaki Katsuyasu
Friedman Carl D.
Kajima Corporation
Tilberry James H.
Wilkens Kevin D.
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