MANISH SHRIKHANDE
Department of Earthquake
Engineering, University of Roorkee, Roorkee-247667, India
VINAY K. GUPTA
Department of
Civil Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India
A new approach has been presented to characterise phase spectra for simulating realistic nonstationary characteristics in synthetic accelerograms. The phase characteristics of the recorded earthquake accelerograms have been studied for this purpose and it has been found that the phase curve/unwrapped phases exhibit a monotonic downward trend which allows the problem of phase characterisation to be cast as a constrained nonlinear programming problem. The phase spectrum is first characterised by matching mean and variance of the generated distribution of relative phases with those obtained from recorded motions. As a practical application, it is shown how phase spectra can be characterised for an ensemble of synthetic accelerograms so as to maximise the severity of sample realisations.
Keywords: Strong motion, synthetic accelerogram, phase unwrapping, phase
spectrum, Fourier synthesis, nonlinear programming.