Inelastic-strength spectra in probabilistic seismic-hazard analysis

A comparison between two methods to compute uniform-hazard inelastic-strength spectra for single-degree-of-freedom systems subjected to earthquake ground motions is presented. In the first method the inelastic spectra are obtained by reducing uniform-hazard elastic pseudoacceleration (SA) spectra with deterministic strength-reduction factors, while in the second method inelastic-strength spectra are computed with a probabilistic seismic-hazard analysis that accounts for the variability in the strength-reduction factor. It is demonstrated that the first method yields similar results to the probabilistic analysis if the product of the slope of the hazard curve of SA and the standard deviation of the logarithm of the strength-reduction factor is small.