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EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS, vol.36, no.10, pp.1275-1301, 2007 (SCI-Expanded)
Empirical equations are presented for the prediction of displacement response ordinates for damping ratios of 2, 5, 10, 20 and 30% of critical and for response periods up to 4 s, using 532 accelerograms from the strong-motion databank from Europe and the Middle East. The records were all re-processed and only employed for regressions at periods within the usable range, defined as a fraction of the filter cut-off and depending on the instrument type (digital or analogue), earthquake magnitude and site class. The equations can be applied to predict the geometric mean displacement and pseudo-acceleration spectra for earthquakes with moment magnitudes (M) between 5 and 7.6, and for distances up to 100km. The equations also include style-of-faulting and site class as explanatory variables. The predictions obtained from these new equations suggest that earlier European equations for spectral displacements underestimate the ordinates at longer periods as a result of severe filtering and the use of the spectral ordinates at periods too close to the filter cut-off. The results also confirm that the period defining the start of the constant displacement plateau in the Eurocode 8 (EC8) spectrum is excessively short at 2 s. The results not only show that the scaling factor defined in EC8 for estimating the spectral ordinates at damping ratios different from 5% of critical are a good general approximation, but also that this scaling varies with magnitude and distance (reflecting the influence of duration) and also displays a mild dependence on response period. Copyright (c) 2007 John Wiley & Sons, Ltd.