| Abstract: | The work deals with the identification of modal parameters of a structure from earthquake records when the input ground motion is unknown. This may occur, for example, owing to instrumental malfunctions. The procedure is based on the assumption that at least two responses are available and consists of two main steps. In the first one, modal frequencies are estimated by searching relative minima of a function that involves the ratio of the Fourier amplitudes of the two records, while the second phase is devoted to the identification of other modal quantities (i.e. effective participation factors and modal dampings). Once the identification process has been completed, an estimate of the unknown base input may be performed by means of the IFFT algorithm. The proposed approach has been checked against both finite element simulations of simple structures and field measurements on real buildings. |
