Generation of Elastic as well as Inelastic Design Spectra Compatible Accelerogram Using Time- Frequency Analysis

A new methodology is proposed to simulate accelerogram which is compatible to both linear and nonlinear design spectra. For this purpose, a wavelet-based parametric characterization of earthquake accelerogram is adopted and the parameters are optimized to tune its non-stationary features. A modified form of L-P basis is considered for wavelet transform which has the unique feature to decompose the signal in non-overlapping bands. The parameters in each frequency bands are then optimized in such a way that the simulated accelerogram is compatible with linear and non-linear design spectra. In this context, the non-linear design spectrum is obtained by varying the initial period of an elasto-perfectly-plastic oscillator for a given ductility demand. As the duration of a motion influences its energy based damage causing capacity, the proposed model allows the designer to obtain different time histories with different strong motion durations for a given pair of linear and non-linear design spectra.