Identification of structural damping in time domain

A structural damping identification procedure is proposed based on the sensitivity of acceleration response of the analytical model with model updating technique making use of the measured acceleration response. The viscous damping model obtained from the inverse modal transformation is adopted. The time-varying sensitivity matrix is computed by the Newmark method. Numerical study with a three-dimensional five-bay frame structure subjected to support excitation and a one-storey plane frame structure is performed to demonstrate the efficiency and validity of the proposed method. The effect of different sampling rates is studied. The damping ratios can be identified accurately from two “measured” acceleration responses with a high level of measurement white noise as well as model errors in the analytical model. The same procedure is later shown to be able to monitor the damping ratios of a time-varying system using moving windows of data in the identification with satisfactory results.