Inelastic Response Spectra Using Conventional and Pulse R -Factors

Inelastic response spectra may be estimated by dividing elastic response spectra by \iR-factors derived from the response to a simple pulse. The pulse \iR-factor depends on the pulse shape, ductility (μ), and load-deformation model and the period of the system (\iT) relative to the characteristic period of the pulse (\IT\dp\N). Inelastic spectra estimated using pulse \iR-factors are compared with those obtained using other contemporary \iR–\iμ–\iT relationships for elastoplastic, bilinear, and stiffness-degrading single-degree-of-freedom systems. Strong motion records used in this study consist of short- and long-duration records as well as near-fault records having forward directivity features. The accuracy of the estimates is influenced by the characteristic period of the ground motion and the presence of soft soil deposits that lead to nearly harmonic surface waveforms. Pulse \iR-factors are found to be slightly better than the \iR–\iμ–\iT relations determined by other investigators. Because the pulse \iR-factors are defined implicitly by the specification of the pulse shape, they may be useful for a variety of load-deformation models and hysteretic relationships.