Scour effect on dynamic performance of bridges under excitations of vehicles with various driving conditions

Abstract:

To investigate the scour effect on the changes in the vehicle-induced dynamic behaviors of bridges, and to promote the research on the scour diagnosis based on vibrations, a vehicle-bridge coupled vibration analysis model was established which can simulate the excitations of vehicles with various driving conditions (i.e., uniform speed, different speeds, and braking). The influence law of the vehicle-induced dynamic behaviors of a prestressed concrete continuous bridge in time domain and frequency domain was analyzed through numerical simulation. Results show that the local vibration mode frequency of the scoured piers decreased significantly with the increase in the scour depth, and the mode frequency of the non-scouring piers showed no evident change. As the scour depth increased from 1 m to 4 m, the longitudinal displacement and acceleration response peaks of the pier tops increased obviously under the excitations of vehicles in various driving states, and the response peak was the largest at braking under the same scouring condition. Compared with the non-scouring condition, the longitudinal displacement and acceleration response peak grew linearly with an increase of 72.72% and 56.26% respectively. Moreover, the spectral amplitude of the scouring sensitive response increased significantly, and the center frequency shifted to low frequency. The results can provide theoretical basis and index reference for the foundation scour diagnosis of bridges based on vehicle-induced dynamic responses.