DISPLACEMENT SPECTRA FOR SEISMIC DESIGN

Abstract

Displacement-based seismic design and assessment of structures require the reliable definition of displacement spectra for a wide range of periods and damping levels. The displacement spectra derived from acceleration spectra in existing seismic codes do not provide a suitable answer and there are no existing frequency-dependent attenuation relationships derived specifically for this purpose. Using a carefully processed dataset of European strong motion records, attenuation relationships have been derived for horizontal displacement response spectral ordinates. The results have been simplified into a parametric form that allows the straightforward construction of displacement design spectra for rock, stiff soil and soft soil sites at distances of up to 50 km from earthquakes with magnitudes between 5.5 and 7.5, for six damping levels and up to response periods of 3.0 seconds. Results from recent studies linking levels of ductility to equivalent damping, using a complex hysteretic model and the same strong motion databank, are also reported.