Modal Indicators for Operational Modal Identification

Modal validation is of paramount importance for all two-stage time domain modal identification algorithms. However, due to a higher noise/signal ratio in operationaUambient modal analysis, being able to determine the right model order and to distinguish between structural modes and computational modes become more signiilcant than in traditional modal analysis. The two major modal indicators, i.e. Modal Confidence Factor (MCF) and Modal Amplitude Coherence (MAmC) are extended to two-stage time domain modal idemi.tication algorithms, together with a newly developed indicator, named as Modal Participation Indicator (MPI). The application of the three indicators is illustrated on different cases of operationahambient modal identification. Three major time domain modal identification algorithms are used the Polyreference