Adapting earthquake actions in Eurocode 8 for performance-based seismic design

Performance-based seismic design (PBSD) can be considered as the coupling of expected levels of ground motion with desired levels of structural performance, with the objective of achieving greater control over earthquake-induced losses. Eurocode 8 (EC8) already envisages two design levels of motion, for no collapse and damage limitation performance targets, anchored to recommended return periods of 475 and 95 years, respectively. For PBSD the earthquake actions need to be presented in ways that are appropriate to the estimation of inelastic displacements, since these provide an eective control on damage at dierent limit states. The adequacy of current earthquake actions in EC8 are reviewed from this perspective and areas requiring additional development are identied. The implications of these representations of the seismic loads, in terms of mapping and zonation, are discussed. The current practice of dening the loading levels on the basis of the pre-selected return periods is challenged, and ideas are discussed for calibrating the loading-performance levels for design on the basis of quantitative earthquake loss estimation.