Validation of a modal identification procedure for linear frames under unmeasured seismic input

Modal Analysis of a Frame Model Under Unmeasured Seismic Input

“…As shown by comparison between modal parameters in Table 5 and Table 6, the outputonly procedure, introduced in [1] and modified in [3] with an improved minimization algorithm, provides, for the sample case described here, a good agreement with the classical inputoutput procedure, as also shown by the comparison of modal shapes in Figure 6. Table 6: Modal parameters identified by the output-only procedure for the case m0t5 of Table 3.…”

“…The modal parameters are identified by means of a minimisation algorithm, improved from the computational point of view as described in [3]. The error function to be minimised compares, in the least square sense, the analytical relationships of the dynamic response and their experimental counterparts.…”

“…It is based on the independence by the input measure of the ratio between the Fourier transforms (FT) of the responses measured at different dofs of the structure. The procedure has been numerically validated in [1] and checked by the writers in a preliminary experimental campaign [3].…”

“…On the other hand, the modification of the unknown parameters from complex to real values is not in contrast with their actual nature; the modal parameters are in fact real values from a physical point of view, but become complex for their inclusion in complex-valued functions. Details of the procedure can be found in [3].…”

“…The present study is part of a research, still in progress, aimed at providing a comprehensive experimental validation of the above procedure, following a previous pilot work [3] where the original procedure was improved through a more refined minimization algorithm in the complex field.…”