Displacement spectra and displacement modification factors, based on records from Greece

Elastic and inelastic displacement spectra (for periods up to 4.0 s) are derived, using a representative sample of acceleration records from Greece, carefully selected based on magnitude, distance and peak ground acceleration criteria, and grouped into three ground type categories according to the Eurocode 8 (EC8) provisions. The modification factor for the elastic design spectrum adopted in EC8 for accounting for damping is verified herein and is found to be satisfactory in the short to medium period range and less so in the long period range. The equivalent viscous damping ratio concept is also evaluated and is found to lead to underestimation of inelastic displacement spectra. Finally, based on the previously derived elastic and inelastic spectra, equations suitable for design and/or assessment purposes, are proposed for the corresponding displacement modification factors. ► Elastic and inelastic displacement spectra are derived. ► A representative sample of acceleration records from Greece is used. ► Accuracy of EC8 elastic design spectrum modification factor for damping is verified. ► Accuracy of the equivalent viscous damping ratio concept is evaluated. ► Equations are proposed for design/assessment of displacement modification factors.