A comparative study in the semi-active control of isolated structures

A comparative analytical and experimental study of several algorithms for the control of seismically excited floor- and base-isolated structures is pursued in the current study. A hybrid isolation system that is comprised of a bidirectional roller–pendulum system (RPS) and augmented by controllable magnetorheological (MR) dampers is proposed to reduce the potential for damage to structures and sensitive equipment. Bidirectional motions are intelligently ameliorated in real time by the modulation of MR damper resistance. A Bouc–Wen model is adopted in numerical and experimental trials to predict behavior of the MR dampers. Three contrasting control techniques are examined. They include neural network control, LQR/clipped optimal control with variable gains and fuzzy logic control. Each control scheme is a candidate for mitigating the response of a superstructure to near- and far-field seismic loadings. Minimization of displacement and acceleration responses of the structure are considered in the formulation of each approach to control. Results of the numerical and large-scale experimental efforts reveal that the response of the isolated structure is effectively alleviated by all of the considered control methods, although they do not perform equally well. The LQR/clipped optimal controller with variable gains is superior to the other controllers in 50% of the investigated cases, while the fuzzy logic controller performs well for earthquakes with large accelerations. Neural network control is found to be effective in minimizing the acceleration of the superstructure that is subject to moderate excitation.