ABSTRACT
A preliminary seismic design method is postulated for simple base isolated bridges based on conservation of displacement and energy for the long and short period ranges of structural response, respectively. The approach focuses on estimation of overall displacements of the deck level of the bridge. Simple, physically based equations are presented which allow displacements and design forces in the supporting columns to be determined. Application is demonstrated for friction sliding systems. A special non-dimensionalized form of the equations of motion for simple bridge structures is introduced to help assess the adequacy of this design approach and to identify, through a parametric investigation, the variation of response indices with changes in ground motion, isolator and structure characteristics.
