Extracting modal parameters of high-speed railway bridge using the TDD technique

In case the excitation frequency induced by a high-speed train passage coincides with the natural frequency of a railway bridge, a resonance of the bridge occurs. In addition, if the train is passing through the bridge very quickly, measurable time samples can be of limited numbers and thus modal parameters of the bridge can hardly be obtained. To get over this, effective technique for the extraction of modal parameters is proposed in the present study. With the cross correlations among free vibration responses immediately after the train passes, mode shapes are obtained by TDD (time domain decomposition) technique while temporal modal parameters are extracted by the proposed sensitivity-updating system identification technique. A two-span steel composite girder bridge, which is of typical Korean high-speed railway bridge system, is employed to verify the proposed approach. Comparative studies reveal that the predictions of the proposed approach agree well with those by the well-known existing methods. It is thus postulated that the present approach is promising in terms of both accuracy and applicability.