SSI-COV method applied to ambient vibrations of a concrete block of a dam: Uncertainty of modal parameters

Resumo

Due to advances and automation in operational modal analysis (OMA) methods, it is possible to extract
modal parameters (natural frequencies, damping ratios and vibration modes) in a quick and easy way solely from
data collected during operation. However, one of the shortcomings of these methods lies in the assessment of the
accuracy of the information obtained. In this work, the uncertainty in the identified modal data is quantified by
calculating confidence intervals using the Bootstrap technique. The modal parameters of a concrete block of a dam
are identified through the application of the SSI-COV method to acceleration measurements from a triaxial sensor
installed in the block. Then, the bootstrap technique is applied and a comparison is made between three common
methods of resampling the time series based on nonrandom as well as random block lengths.