Static structures (e.g. – buildings) – Controlled by condition responsive means
Patent
1996-07-22
1998-06-16
Friedman, Carl D.
Static structures (e.g., buildings)
Controlled by condition responsive means
521672, 18832219, 188304, E04H 900
Patent
active
057653135
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates generally to a method and apparatus for controlling the displacement (or vibration) of a structure when subjected to the application of external energy due to external forces such as an earthquake or wind, the apparatus employing novel damping/coupling devices and mounts therefor; and more particularly to a method and apparatus to adjust the dynamic parameters (mass, damping, stiffness coefficients) of a structure by using new devices mounted in novel manners in accordance with novel processes developed from newly proposed control laws.
BACKGROUND OF THE INVENTION
It is well known that structures can fail when subjected to external forces of sufficient magnitude, as for example high winds or a moderate to strong earthquake. Many proposals have been made for improving the ability of a structure to withstand such forces without damage or failure of the structure. The approaches range from making the structure rigid, making it flexible, to mounting the structure upon the surface of the ground so that it can move relative to the ground, by coupling or uncoupling the structure to a mass to change its resonant frequencies, etc. One such example is shown in U.S. Pat. No. 5,036,633 invented by Kobori wherein an apparatus is disclosed for controlling the response of a structure to external forces such as seismic vibration and/or wind impacting against the structure, the control apparatus including variable stiffness means secured to and bracing the structure, variable damping means interposed between the structure and the variable stiffness means, and a computer which is programmed to monitor external forces impacting against the structure and to control the variable damping means by selecting a coefficient of damping suitable to render the structure non-resonant relative to the monitored external forces. The foregoing patent of Kobori, as well as other patents of Kobori, and patents of others, are based on feedback control principles which include changing stiffness to avoid resonance according to ground motion forecasting, changing damping coefficient according to preset damping standards, and varying the stiffness of a local member by locking or unlocking a device disposed between the ends of a member. The approach of the prior art emphasizes identifying individual structural vibration-reduction-devices, but does not perform an analysis of the whole structural system's behavior. Furthermore, the prior art analysis tends to focus on a single plane of the structure and the analysis is not three dimensional.
SUMMARY AND OBJECTS OF THE INVENTION
The major concept of the present invention is to provide a method and apparatus for controlling a structure to minimize time-varying motion of the structure by a real-time modification of structure parameters to achieve a cost-effective control of structural deformation, internal force, buckling, destructive energy and related damages caused by multi-directional loading such as earthquake, winds, traffic, and/or other type of ambient loading. The control is based upon the use of control devices in accordance with control principles which are non-linear, time dependent, and adaptive; the control devices making the system more robust, and hence more stable. Since this approach actually controls the physical parameters of the structure through adaptive control devices, it is called functional adaptive control, and a structure which is capable of modifying its dynamic performance is called an adaptive structure.
The present invention contemplates changing within an adaptive structure the coefficients of the displacement, velocity and acceleration, namely the stiffness, damping, and mass. In addition, the present invention may also change certain coefficients of the input driving forces. For example, it may change the friction coefficients of base-isolation devices for structures to minimize the input force/energy for ground motion. Since the new approach actually controls the physical parameters of the structures, it therefore
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Lee George C.
Liang Zhong
Tong Mai
Friedman Carl D.
Research Foundation of State University of New York
Smith Creighton
Thompson John C.
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