Foundation scour poses a serious threat to bridge safety in the whole life cycle and leads to many bridge failure incidents. Recently, as an important subfield of bridge structural health monitoring, vibration-based scour diagnosis methods have garnered widespread attention, particularly due to their rapid and low-cost features, which overcomes the difficulties of complex equipment installation associated with the traditional approaches. Recent advances of this method within the last decade are reviewed in this paper. Firstly, the principle of scour diagnosis and vibration excitation methods are introduced. Then, existing qualitative and quantitative studies on scour diagnosis are reviewed, respectively. The former refers to identifying the scour location based on the bridge dynamic characteristics or dynamic response changes, and the latter refers to identifying scour depth based on model updating or machine learning methods. Based on the above review, some important but neglected issues are summarized and discussed in depth, and some challenges and future trends are proposed, including innovative excitation methods, mitigation of environmental conditions interference, soil–structure interaction prediction and application of machine learning techniques.

Several innovative scour diagnostic indexes are proposed based on the cross-correlation analysis for bridge dynamic response excited by vehicle braking. Firstly, a vehicle-bridge coupled vibration model considering vehicle braking is established and its accuracy is verified by a field loading test. Secondly, the fixed shape characteristic of cross-correlation function amplitude vector of the braking-induced dynamic response is theoretically deduced and verified numerically with a continuous girder bridge example considering various test parameters, which is the basic for scour diagnosis. Further, two scour diagnostic indexes are proposed, one is the cross-correlation function amplitude change rate vector, which is used to identify the scour location with a threshold of 2%, and the other is the transversal cross-correlation function amplitude change rate vector, which is used to identify the scour uniformity. The good applicability and accuracy of proposed indexes for different scour states is verified by numerical simulation for above bridge example. The proposed diagnostic indexes are very sensitive to foundation scour and have strong error tolerance for test parameters. The dynamic response required for scour diagnosis can be obtained with regular bridge loading test.

A highly efficient and accurate mapping relationship model of subgrade disease and track geometry is significant for determining criterion of subgrade deformation and evaluating operation safety of High-speed Railway. In this paper, an innovative spatial mapping relationship model (SMRM) is proposed for describing track spatial geometry under subgrade disease of differential settlement and frost heave. Starting from analysing the theoretical interaction mechanism between subgrade and ballastless track, and presenting the flowchart of SMRM and its implementation process are described in detail. The good accuracy and applicability of SMRM method is verified based on the finite element model (FEM) and scale model experiment. The results indicate that it can better simulate the spatial characteristic of above mapping relationship than traditional theoretical model and avoid complicated and time-consuming FEM analysis process. It has high accuracy and reliability for the most application scenarios. The proposed method also can analyse the influences of others’ diseases on track geometry as long as the disease description function is available.