Response Control of Structural Systems Using Semi-Actively Controlled Interactions

Citation

Hayen, Jeffrey Clyde (1996) Response Control of Structural Systems Using Semi-Actively Controlled Interactions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2c70-e383. https://resolver.caltech.edu/CaltechTHESIS:01032013-113224489

Abstract

The objective of the research described herein is to demonstrate conditions under which controlled interactions between two structures or structural components can be made effective in reducing the response of structures that are subjected to seismic excitation. It is shown that the effectiveness depends upon such factors as the control strategy implementation, the interaction element mechanical properties, and the parameters which characterize the dynamic behavior of the structural systems.

A study is conducted to examine the performance of a structural response control approach referred to as Active Interface Damping (AID). This control approach utilizes controlled interactions between two distinct structural systems or different components of a single structural system to reduce the resonance buildup that develops during an external excitation. Control devices or elements may be employed to physically produce the interactions between the systems. The proposed control approach differs from some other control approaches in that the sensors, processors, and switching components all operate actively, whereas the interaction elements function passively. The major advantage of this semi-active control technology is that relatively large control forces can be generated with minimal power requirements, which is of prime importance for the control of relatively massive systems, such as structures.

In the most simple form, the strategy of the control approach is to remove energy associated with vibration from only one system (the primary system). This process is accomplished through the transfer of energy to another system (the auxiliary system) by means of interaction elements, the dissipation of energy directly in the interaction elements, or a combination of both these methods. In a more complex form, the control strategy may be to minimize some composite response measure of the combined primary-auxiliary system. Only the most simple form of the control strategy is considered in the present study.

Several physical interpretations of the control approach are possible: one is that the systems represent two adjacent multi-story buildings; another is that the primary system represents a single multi-story building, while the auxiliary system could represent either an externally- situated resilient frame or a relatively small, unrestrained mass - or even be completely absent (in this latter scenario, the interaction elements are internally-mounted control devices). The interactions consist of reaction forces that are developed within and transmitted through the elements which are located between the two systems (or different points of a single system). The mechanical properties of these elements can be altered in real time by control signals, so the reaction forces applied to the systems may be changed, and the response control objective is achieved by actively changing the interactions at the interface of the two systems (or different points of a single system).

Initially, a preliminary study of the proposed control approach is conducted within the specialized setting of linear single-degree-of-freedom (SDOF) primary and auxiliary systems. Numerical simulations are performed for a series of control cases using horizontal ground accelerations from an ensemble of earthquake time histories as excitation input. Subsequently, a follow-on study of the proposed control approach is conducted for linear multiple-degree-of-freedom (MDOF) primary and auxiliary systems intended to represent actual structural systems. Based upon the investigation and insight obtained from the preliminary study, a limited number of control cases are considered which include those deemed most effective and implementable. Numerical simulations are again performed using the same excitation input as for the SDOF systems. The control approach is targeted at reducing the response contribution from the fundamental or dominant mode of vibration associated with the primary system. Uniformly-discretized models of a 6-story primary structural system capable of only lateral deformations are considered in most cases. A few cases involving models of a 3-story primary structural system are also examined.

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