EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2006; 35:39–55 Published online 30 September 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/eqe.530 Adapting earthquake actions in Eurocode 8 for performance-based seismic design Julian J. Bommer 1;∗; † and Rui Pinho 2 1 Department of Civil and Environmental Engineering; Imperial College London; SW7 2AZ; U.K. 2 ROSE School; c/o EUCENTRE; Via Ferrata 1; 27100 Pavia; Italy SUMMARY 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 mo- tion, 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 eective control on damage at dierent limit states. The adequacy of current earthquake actions in EC8 are reviewed from this perspective and areas requiring additional development are identied. The implications of these representations of the seismic loads, in terms of mapping and zonation, are discussed. The current practice of dening 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. Copyright ? 2005 John Wiley & Sons, Ltd. KEY WORDS: performance-based seismic design; earthquake actions; return periods; design levels; loss modelling; Eurocode 8 1. INTRODUCTION Performance-based seismic design (PBSD) is essentially the formalization of the often cited objectives of designing structures to withstand minor or frequent earthquake shaking with- out damage, moderate levels of shaking with only non-structural damage and severe shak- ing without collapse and a threat to life safety [1]. In the Vision 2000 document [2] this is elegantly stated as the ‘coupling of expected performance level with expected levels of seismic ground motions’. Motivation for formalizing performance-based design criteria and objectives has been triggered to a large degree by the fact that in highly developed regions ∗ Correspondence to: J. J. Bommer, Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, U.K. † E-mail: j.bommer@imperial.ac.uk Received 1 November 2004 Revised 3 May 2005 Copyright ? 2005 John Wiley & Sons, Ltd. Accepted 10 May 2005