Mitigation of structural damage in MDOF systems using active/semiactive hybrid control with optimized control parameter suites

Seismic response mitigation of multi-story, MDOF structures is investigated using an optimal control strategy that employs the use of a hybrid control system. After comparing the efficacy of several different strategies, an instantaneous optimal control (IOC) strategy is selected for implementation, using a linear quadratic regulator (LQR) approach. The IOC control system is used to formulate an optimized, non-linear, semi-active control stage, utilizing variable viscosity dampers, together with a passive, base isolation stage tuned to provide optimal performance for the semi-active stage.; Extended studies of seismic response under a number of different seismic excitation records suggests that proper choice of objective function weighting matrices Q and R provide the potential for significant improvement in control efficiency. Using a multivariate downhill simplex algorithm, optimal weighting matrices are established for several different seismic excitation records, and for two different composite spectra. It is shown that certain terms in the Q and R matrices have limited significance, while others may be scaled to improve control performance significantly. Performance of benchmark structures under linear active control, continuously variable damping, and stepwise variable damping are compared for systems with no base isolation, and with passive base isolation designed to provide specific low pass filter behavior to the structure.; Semi-active/passive hybrid control is shown to be a viable alternative to active control with the advantage of demanding little external energy during a critical event. A global approach synthesized from this information that provides enhanced performance of hybrid control in mitigation of seismic effects on multistory structures.