08-10-2014, 04:17 PM
Strength reduction factors (SRFs) continue to play a key role in obtaining inelastic spectra from elastic design spectra (through response reductions factors) for ductility-based earthquake-resistant design. Despite several years of sustained research efforts, it remains interesting to explore how best to estimate these factors for a given design situation. This study proposes a new model to estimate the strength reduction factor (SRF) spectrum, in terms of a pseudo spectral acceleration (PSA) spectrum (normalized with respect to peak ground acceleration, PGA) and ductility demand ratio, with the help of two coefficients. The proposed model is illustrated for an elasto-plastic oscillator, in case of ten recorded accelerograms and three ductility ratios. The proposed model is more convenient to use in real-life applications and is able to predict SRF spectra reasonably well, particularly at periods up to 1.0 sec. Its parameters may be determined either by matching with the SRF spectrum for a single accelerogram or from the SRF spectra for a suite of accelerograms that are