ABSTRACT
Scour is one of the main hidden diseases of bridge substructure, which will lead to the significant loss of foundation stiffness and bearing capacity. A scour diagnostic method of pile foundation based on time-varying frequency was proposed and verified by several field bridge tests. Firstly, the traffic-induced vibration of the pier were collected, and the instantaneous frequency of the pier was extracted based on Wavelet Synchrosqueezed Transform. Secondly, the probability distribution of instantaneous frequency was fitted and the scour indicator was defined based on the confidence interval. Field test results showed that the vibration response of the middle part of the pier contains more high-order modal information than that of the top part. The scour indicator changed significantly for two tested piers with a height of 7.23m and 8.98m, which indirectly verified its sensitivity to the change of free length of piers. For short and medium-span bridges, effective vibration signals can be collected by a short test under open traffic conditions. The proposed method can be used for real-time monitoring or rapid detection of bridge scour.
