Optimum isolation damping for minimum acceleration response of base-is
olated structures subjected to stationary random excitation is investi
gated. Three linear models are considered to account for the energy di
ssipation mechanism of the isolation system: a Kelvin element, a linea
r hysteretic element and a standard solid linear element, commonly use
d viscoelastic models for isolation systems comprising natural rubber
bearings and viscous dampers. The criterion selected for optimality is
the minimization of the mean-square floor acceleration response. The
effects of the frequency content of the excitation and superstructure
properties on the optimum damping and on the mean-square acceleration
response are addressed. The study basically shows that the attainable
reduction in the floor acceleration largely depends on the energy diss
ipation mechanism assumed for the isolation system as well as on the f
requency content of the ground acceleration process. Special care shou
ld be taken in accurately modelling the mechanical behaviour of the en
ergy dissipation devices.