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

Abstract

SUMMARYPerformance-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 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 identiÿed. The implications of these representations of the seismic loads, in terms of mapping and zonation, are discussed. The current practice of deÿning 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.

Long‐period earthquake ground displacements recorded on Guadeloupe (French Antilles)

“…This will widen the plateau in order to encompass the localized peak. Bommer & Pinho [7] recently suggested that the control periods in Eurocode 8 may need to be lengthened to correctly specify…”

“…The importance of examining the shape of the displacement spectra proposed in design codes has recently been highlighted by Bommer & Pinho [7]. In a seismological context, a possible generation mechanism (fluids within the source) for these large-amplitude long-period motions is suggested based on previous observations of similar motions.…”

Hazard-consistent response spectra in the Region of Murcia (Southeast Spain): comparison to earthquake-resistant provisions

“…Only the Eurocode 8 (type 2) response spectrum, anchored with the PGA475 values obtained in this study, reproduces the shape of the hazard-consistent response spectra reasonably well. This result gives an example of the known limitations of using a code spectral shape scaled with a single PGA value and the convenience of considering a spectral shape anchored at representative short-and longperiod spectral accelerations derived from PSHA estimates (e.g., Bommer and Pinho 2006), such as the 2003-NEHRP Provisions. More interestingly, this result shows that EC8 type 2 spectrum (intended for relatively stable regions) is more consistent with the UHS at the 475-year return period derived for the Region of Murcia than EC8 type 1 spectrum (intended for active regions).…”

“…Hence, an over-or under-estimation of the first (as in Cartagena, see Figs. 6 and 7) and/or an unconstrained definition of the second may lead to unrealistic hazard-consistent response spectra (Pousse et al 2005;Bommer and Pinho 2006;Gaspar-Escribano and Benito 2007). This limitation is stronger in the NCSE-02 code, since the implementation of two spectral shapes in Eurocode 8 allows better constraint of the final spectrum.…”

“…However, this is achieved at the cost of knowing the magnitude of earthquakes that contribute most to the seismic hazard defined for the purpose of probabilistic seismic hazard assessment (CEN 2004), information that is not always accessible for end-users. Provided that the UHS can be approximated by the envelope of two single SRS corresponding to magnitude-distance-epsilon bins with the highest contributions to short-and long-period target motions, respectively, it seems more appropriate to define the code design spectrum by anchoring a spectral shape at two spectral accelerations (for short and long periods, respectively) than by a single acceleration at the lowermost bound of the period domain (e. g., Bommer and Pinho 2006;Karakostas et al 2007). This possibility is explored following the approach detailed in the 2003-NEHRP Provisions (BSSC 2003), which is implemented, for instance, in the International Building Code (ICC, 2006).…”