Bridge Scour Identification and Field Application Based on Ambient Vibration Measurements of Superstructures

Abstract

A scour identification method was developed based on the ambient vibration measurements of superstructures. The Hangzhou Bay Bridge, a cable-stayed bridge with high scour potential, was selected to illustrate the application of this method. Firstly, two ambient vibration measurements were conducted in 2013 and 2016 by installing the acceleration sensors on the girders and pylon. By modal analysis, the natural frequencies of the superstructures were calculated with respect to different mode shapes. Then, by tracing the change of dynamic features between two measurements in 2013 and 2016, the discrepancies of the support boundary conditions, i.e., at the foundation of the Hangzhou Bay Bridge, were detected, which, in turn, qualitatively identified the existence of bridge foundation scour. Secondly, an FE model of the bridge considering soil-pile interaction was established to further quantify the scour depth in two steps. (1) The stiffness of the soil springs representing the support boundary of the bridge was initially identified by the model updating method. In this step, the principle for a successful identification is to make the simulation results best fit the measured natural frequencies of those modes insensitive to the scour. (2) Then, using the updated FE model, the scour depth was identified by updating the depth of supporting soils. In this step, the principle of model updating is to make the simulation results best fit the measured natural frequency changes of those modes sensitive to the scour. Finally, a comparison to the underwater terrain map of the Hangzhou Bay Bridge was carried out to verify the accuracy of the predicted scour depth. Based on the study in this paper, it shows that the proposed method for identifying bridge scour based on the ambient vibration measurements 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.

Coastal Geohazard and Offshore Geotechnics

“…Xiong et al [12] developed a scour identification method, based on the ambient vibration measurements of superstructures. The Hangzhou Bay Bridge was selected to illustrate the application of the proposed model.…”

“…(2) evaluation of stability of marine infrastructures, including pipelines [6][7][8], piled foundation and bridge piers [9][10][11][12], submarine tunnel [13], and other supported foundations [14]; and (3) coastal geohazard, including submarine landslide and slope stability [15,16] and other geohazard issue [17,18]. More details of each contribution are summarized in the following subsections.…”

Experimental Demonstration of a Mode Shape-Based Scour-Monitoring Method for Multispan Bridges with Shallow Foundations

“…Flexibility-based deflection is recommended as the most practical way to detect scour. In a separate study, Xiong et al (2019) present a scour identification approach based on measuring the ambient vibration of the superstructure of a cable-stayed bridge. By analysing the change in the mode shapes at two different times, qualitative scour identification is possible.…”

Anomaly detection for large span bridges during operational phase using structural health monitoring data

“…Large span bridges are usually in the critical locations within the modern traffic networks, which play a key role in regional economic development [1][2][3]. Meanwhile, these bridges are facing diverse threats resulting from their own structural failures and aggressive operational environments [4][5][6]. Owing to the scale of large span bridge structures as well as the concealment of threats, anomaly detection is a crucial task for large-scale civil structures.…”