Earthquake-induced structural response output-only identification by two different Operational Modal Analysis techniques

Output-only system identification is developed here towards assessing current modal dynamic properties of buildings under seismic excitation. Earthquake-induced structural response signals are adopted as input channels for two different Operational Modal Analysis (OMA) techniques, namely, a refined Frequency Domain Decomposition (rFDD) algorithm and an improved Data-Driven Stochastic Subspace Identification (SSI-DATA) procedure. Despite that short-duration, non-stationary, earthquake-induced structural response signals shall not fulfil traditional OMA assumptions, these implementations are specifically formulated to operate with seismic responses and simultaneous heavy damping (in terms of identification challenge), for a consistent estimation of natural frequencies, mode shapes, and modal damping ratios. A linear ten-storey frame structure under a set of ten selected earthquake base-excitation instances is numerically simulated, by comparing the results from the two identification methods. According to this study, best up-to-date, reinterpreted OMA techniques may effectively be used to characterize the current dynamic behaviour of buildings, thus allowing for potential Structural Health Monitoring approaches in the Earthquake Engineering range.