Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "April 2008." Includes bibliographical references (p. 235-244). Also available via the World Wide Web.

Thesis (Ph.D.)--Michigan State University. Dept. of Mechanical Engineering, 2008. / Title from PDF t.p. (viewed on July 7, 2009) Includes bibliographical references (p. 114-117). Also issued in print.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvii, 221 p.; also includes graphics (some col.). Includes bibliographical references (p. 210-221). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Makola M. Abdullah, FAMU-FSU College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed Sept. 15, 2005). Document formatted into pages; contains xl, 414 pages. Includes bibliographical references.

Thesis (Ph.D. in Mechanical Engineering) -- University of Dayton. / Title from PDF t.p. (viewed 10/06/09). Advisor: Reza Kashani. Includes bibliographical references (p. 98-102).

An analysis is presented on the use of a proof-mass actuator as a regenerative force actuator for the mitigation of earthquake disturbances in civil structures. A proof-mass actuator is a machine which accelerates a mass along a linear path. Such actuators can facilitate two-way power flow. In regenerative force actuation, a bi- directional power-electronic drive is used to facilitate power flow both to and from the proof-mass actuator power supply. With proper control system design, this makes it possible to suppress a disturbance on a structure using mostly energy extracted from the disturbance itself, rather than from an external power source. In this study, three main objectives are accomplished. First, a new performance measure, called the "required energy capacity," is proposed as an assessment of the minimum size of the electric power supply necessary to facilitate the power flow required of the closed-loop system for a given disturbance. The relationship between the required energy capacity and the linear control system design, which is based on positive position feedback concepts, is developed. The dependency of the required energy capacity on hybrid realizations of the control law are discussed, and hybrid designs are found which minimize this quantity for specific disturbance characteristics. As the second objective, system identification and robust estimation methods are used to develop a stochastic approach to the performance assessment of structural control systems, which evaluates the average worst-case performance for all earthquakes "similar" to an actual data record. This technique is used to evaluate the required energy capacity for a control system design. In the third objective, a way is found to design a battery capacity which takes into account the velocity rating of the proof-mass actuator. Upon sizing this battery, two nonlinear controllers are proposed which automatically regulate the power flow in the closed-loop system to accommodate a power supply with a finite energy capacity, regardless of the disturbance size. Both controllers are based on a linear control system design. One includes a nonlinearity which limits power flow out of the battery supply. The other includes a nonlinearity which limits the magnitude of the proof-mass velocity. The latter of these is shown to yield superior performance. / Master of Science

We extend the application of the substructure synthesis method to more complex structures, and establish a design methodology for base isolation and active control in a distributed model of a building under seismic excitation. Our objective is to show that passive and active control complement each other in such an advantageous manner for the case at hand, that simple devices for both types of control are sufficient to achieve excellent response characteristics with very low control forces. The Rayleigh-Ritz based substructure synthesis method proved to be highly successful in analyzing a structure more complex than the ones previously analyzed with it. Comparing the responses of the hybridly controlled building and the conventional fixed building under El Centro excitation, we conclude that the stresses are reduced by 99.6 %, the base displacement is reduced by 91.7 % and the required control force to achieve this is 1.1 % of the building weight. / Ph. D.

The active control of structures is a diverse field of study, with new applications being developed continually. One structural system, which is often not considered a dynamic system, is the floor of a building. In many cases the dynamics of a floor system are neglected in the design phase of a building structure. Occasionally, this omission results in a floor which has dynamic characteristics found to be unacceptable for the intended use of the building. Floor motion of very small amplitudes, often caused by pedestrian movement, is sometimes found objectionable by occupants of the building space. Improving an unacceptable floor system's dynamic characteristics after construction can be disruptive, difficult and costly. In search of alternative repair measures, analytical and experimental research implementing active control techniques was conducted to improve the vibration characteristics of problem floors. Specifically, a control scheme was developed utilizing the measured movement of the floor to compute the input signal to an electromagnetic actuator which, by the movement of the actuator reaction mass, supplies a force that reduces the transient and resonant vibration levels. Included in the analytical component of this research is the development of a mathematical model for a full scale experimental test floor. This model is studied, using a matrix computation software, to evaluate the effectiveness of the control scheme. The experimental component of the research serves two purposes. The first is the verification of the system behavior assumed in the analytical component of the research. The second is the verification of control system effectiveness for various excitations, control gains, and actuator locations on the experimental test floor and six additional floors. / Ph. D.

This thesis presents an initial investigation into Active Damage Control (AD C) using Artificial Intelligence (AI). AI can alleviate the sometimes complicated task of modelling the system and also provides an adaptable solution process. The two research areas of ADC, damage identification and damage control, are studied in separate investigations. An AI technique called "rule induction" is used for the damage identification study. Velocity data from three plates (one without damage, one with damage at the center, and one with damage at the edge) are acquired using a laser data acquisition system. A set of rules is then induced from these data which accurately identifies which plates have damage and where the damage is located. With regard to the damage control, a real-time, machine-learning technique called "BOXES" is used to locally control the vibration of various systems by identifying their vibrational patterns. Using this technique, it is shown that the computer successfully learns an effective control law for various simulations using its trials and failures as the only learning information. It is also seen that the learning algorithm is somewhat less effective when experimentally applying this method to a pin-pin, aluminum beam. A discussion of possible improvements are presented in the future work section. / Master of Science

With the increased deterioration of infrastructure in this country, it has become important to find ways to maintain the strength and integrity of a structure over its design life. Being able to control the amount a structure displaces or vibrates during a seismic event, as well as being able to model this nonlinear behavior, provides a new challenge for structural engineers. This research proposes a wavelet-based adaptive neuro- fuzzy inference system for use in system identification and structural control of civil engineering structures. This algorithm combines aspects of fuzzy logic theory, neural networks, and wavelet transforms to create a new system that effectively reduces the number of sensors needed in a structure to capture its seismic response and the amount of computation time needed to model its nonlinear behavior. The algorithm has been tested for structural control using a three-story building equipped with a magnetorheological damper for system identification, an eight-story building, and a benchmark highway bridge. Each of these examples has been tested using a variety of earthquakes, including the El-Centro, Kobe, Hachinohe, Northridge, and other seismic events.