Dynamic Identification of A Cable-Stayed Bridge Induced by Random Traffic Flow

The paper presents an experimental study of the dynamic response of a cable-stayed road bridge with a steel-UHPC (Ultra High Performance Concrete) composite deck slab, excited by daily random traffic flow along a three-lane highway with high traffic intensity. For this purpose, temporary in-situ measurements of vertical vibration accelerations of the box girder were performed along the entire length of the bridge. The measured data were then analyzed using three estimation techniques, i.e., the Peak Picking, Frequency Domain Decomposition, and Random Decrement technique. Their impact on the obtained results was determined. The results obtained using these approaches were compared. The first five modal frequencies and mode shapes of the bridge-vehicle system, as well as the corresponding damping ratios, were analyzed. It was found that the obtained vibration frequency values were variable in the range of 0.1-3.1%. In the case of the damping ratio, the variability in the range of 19-44% was observed, which may indicate a high sensitivity of this parameter to dynamic effects induced by traffic flow. Moreover, it was shown that the extracted modal shapes, corresponding to the natural frequencies of the bridge in the range up to 2.1 Hz, are related to the bending, torsion, and bending-torsion forms. The frequency components of bridge vibrations related to vehicle movement were in the range of 8-16 Hz. The obtained results provided essential data that can be helpful in monitoring the dynamic behavior and technical state of other bridges with a similar structural system.