R-FRF-based modal analysis: additional modal parameters for local diagnoses of perturbated systems

Transmissibility functions play a key role in the areas of identification, damage detection, and continu- ous monitoring of structures. The present research effort is dedicated to a specific class of transmissibility functions, here called Response-based Frequency-Response-Functions (R-FRFs), and it comprises a first investigation on the estimation process of R-FRFs followed by a derivation of the relevant modal model, suitable for being tackled through frequency-domain estimators from the field of experimental and opera- tional modal analysis, which let these additional modal parameters to be identified. It is demonstrated how modes retrieved from R-FRFs are related to the system under investigation, but, virtually, with a different set of boundary conditions. The particular properties give this additional modal parameters the advantage of being local, in turn confirming the significance of response-based frequency response functions in the field of damage detection. Such a concept is corroborated by real-world experimental case studies that offer a number of application scenarios for results discussion.