Use of non-linear localization for isolating structures from earthquake-induced motions

The dynamic response due to earthquake-induced excitations of multi-storey buildings simulated by a cantilever (with attached concentrated masses) sup ported on a flexible foundation, is reconsidered when stiffness non-lineari ties are included. To this end, a suitable non-linear spring-mass device is placed between the ground and the mass of the foundation, which under cert ain conditions can absorb a significant amount of seismic energy over a lar ge frequency range, thus drastically reducing the seismic response of the f oundation. This is achieved by the stiffness non-linearity that gives rise to a localization phenomenon, according to which motions generated by exter nal disturbances remain passively localized close to the point of seismic e xcitation instead of 'spreading' to the entire structure. The implications of these findings to the design of earthquake-resistant structures are disc usssed. Copyright (C) 1999 John Wiley & Sons, Ltd.