'Smart' isolation for seismic control

Consideration of near-source, high velocity, long-period seismic pulses, as were recorded during the Northridge and Kobe earthquakes, has taught engineers and researchers that ground motions due to such earthquakes can be difficult to accommodate. This paper discusses a base isolation system using 'smart' dampers, such as magnetorheological fluid dampers, that can adapt to, and protect against, seismic excitation of different characteristics. A linear, two degree-of-freedom, lumped-mass model of a base-isolated building is used as the testbed for this study. Linear viscous dampers are shown to have an optimal damping level for several design earthquakes to achieve minimum peak accelerations. A study of a family of controllers for the smart damper is used to find an 'optimal' isolation system over the suite of ground motions considered. This 'optimal' system further decreases the base drift compared to the 'optimal' linear viscous damper without increasing the accelerations imparted into the superstructure. The 'smart' damper is shown to be a most effective alternative for a broad class of earthquakes including near-source events.