Control of smart base isolated buildings with new semiactive devices and novel H2/LQG, H-infinity and time-frequency controllers
Doctor of Philosophy thesis
The large base displacement demands imposed by near field earthquakes on base isolated buildings and the development and implementation of novel semiactive control devices and new algorithms to overcome this problem, is a key challenge in the design of smart isolation systems, which is the main goal of this study. In this dissertation a comprehensive class of smart base isolated buildings, new control algorithms based on H 2/LQG, Hinfinity and time-frequency methods are developed. The frequency content of the earthquakes is incorporated into the H2/LQG and H infinity controllers using newly developed weighting filters. The time-frequency content of the earthquakes is also estimated by new control algorithm developed based on time-frequency methods, for variable stiffness isolation systems. Novel semiactive variable friction, variable damping and variable stiffness control devices are developed and their behavior studied analytically and experimentally. The new control algorithms and semiactive devices developed in this study are inherently smooth and do not cause sharp increases in floor accelerations or interstory drifts, while achieving reductions in base displacements. The newly developed semiactive devices and control algorithms are implemented in linear and nonlinear multi degree of freedom two and three dimensional smart base isolated buildings, subjected to a suite of near field earthquakes, and shown to be effective in reducing the response. A new smart base isolated benchmark building is developed to demonstrate the feasibility of implementation of the newly developed semiactive devices and controllers in full scale three dimensional structures subjected to strong near field earthquakes.
Applied Mechanics; Engineering, Civil