Analytical study of base-isolated buildings with smart devices: STFT Controller

Elastomeric base isolation systems, consisting of laminated rubber bearings, are very effective in reducing seismic response due to lateral flexibility, which results in longer fundamental period and reduced forces in the superstructure. Such a strategy is aimed at far fault earthquakes that are predominant in the short period range. Longer period near fault earthquakes tend to produce larger base displacements in elastomeric base isolated structures. Introduction of semi-active variable stiffness and damping is expected to reduce the base displacement and interstory drifts. The objective of this thesis is to analytically study the effectiveness of both variable damping devices, such as Magneto-Rheological dampers, and variable stiffness devices such as Semi-Active Variable Stiffness system (SAIVS) in reducing the seismic response. Various control algorithms for MR dampers are evaluated and reductions in response are evident. A new control algorithm is developed based on Time-Frequency principles and Short Term Fourier Transform (STFT) for the SAIVS device and the simulated results demonstrate significant potential for seismic response reduction.