On the Evolutionary Characteristics of the Acceleration Records Generated From Linear Time-Variant Systems

Abstract

Abstract. This paper discusses the time-varying characteristics of the output signals resulted from Linear Time Variant (LTV) systems using level-crossing properties. These systems, used for generating synthetic records based on a target record, contain two identi cation processes: 1) amplitude modulating function; and 2) time-varying Impulse Response Function (IRF) parameters. To track the IRF parameters e ciently, the zerocrossing and positive minima/negative maxima cumulative curves are usually utilized as the measures of the instantaneous spectral power. Using spectral moments, analytic relations for zero-crossing and positive minima/negative maxima cumulative count are developed with respect to the IRF's evolutionary power spectrum. In order to investigate the low-frequency components of the output records e ciently, the zero-crossing rate of the velocity and the displacement records are tracked and rigorous analytic equations for their descriptions are developed. Some of the issues concerning application of the developed equations are explored using two LVT models, and the limitations of the proposed procedures are explained. Through introduction of new compatibility measures, the necessity of implementing Monte Carlo simulations would no longer be needed, and it would be possible to generate synthetic acceleration records with desirable evolutionary characteristics with much shorter computation time.

A Semi-Analytic Method to Estimate the Response Spectrum of the Synthetic Acceleration Records with Evolutionary Spectrum

“…The double frequency model (DFM), is a site-based filtered white noise stochastic method proposed by Waezi and Rofoeei [16,18,32], which is capable of generating both amplitude and frequency non-stationary records, with 13 model parameters. It was shown that the 13 model parameters can be regressed against source-path-site characteristics which enables the model to generate an ensemble of records conditioned on a specific scenario.…”

“…Waezi and Rofooei [16,17] introduced a new site-based method for the stochastic generation of nonstationary acceleration records. The proposed model is capable of considering two large and one small dominant frequency for efficient capturing of recorded strong motion's power spectrum.…”