ABSTRACT
The dynamic identification method for bridge scour has attracted a lot of attentions in recent years due to its simplicity, efficiency, and low cost. The key for a successful application of the method is to properly analyze the measuring vibration data under the complex field environment around bridges. Aiming at such the technical bottleneck, the present study developed a bridge scour identification method based on the time-frequency analysis combined with the trend-change detection. The idea behind this method is to scientifically consider the interference-induced random variation in the modal analysis when capturing the scour-induced change trend of dynamic features. A cable-stayed bridge was selected to illustrate the application using the numerical simulation. The white-noise earthquake wave was input as the environmental vibration excitation on the bridge. The pile-soil interaction was continuously adjusted to simulate scour development. Then, using the time-frequency analysis fully captured the whole variation process of the natural frequencies based on the vibration data. The change trend of the continuously-varied natural frequencies was obtained and its correlation with the scour development was investigated. The scour-induced frequency change was further separated from the interference-induced random variation by anomaly detection method based on control chart. This application shows that the proposed method for identifying bridge scour based on time-frequency analysis of superstructures is effective and convenient. It is feasible to quickly assess scour conditions for a large number of bridges without underwater devices and operations.
