Spectral Matching of Real Ground Motions: Applications to Horizontally Irregular Systems in Elastic Range

In the context of performance-based seismic design (PBSD), ground motions are often scaled to certain convenient target spectra derived from probabilistic seismic hazard analysis (PSHA). While Uniform Hazard Spectrum (UHS) is more widely used, Conditional Mean Spectrum (CMS) is recently proposed to be more desirable for scaling of real accelerograms. In this backdrop, a set of near-field and far-field ground motions are spectrally scaled, using wavelets, to both UHS and CMS. Seismic demand of horizontally irregular structures under bi-directional ground motion is assessed under both scaled and seed records in the elastic range. Spectral matching, within limits, of both the horizontal components of real records to a single hazard spectrum is observed to adequately predict the amplification in response due to asymmetry (at least for the records and target spectra relevant to soil class D). Further, such scaling effectively reduces the variability in predicted magnification from one ground motion to other. Dynamic amplification factors recommended in international codes to apply in equivalent static design of asymmetric systems are shown to be deficient.