Engineering reliability-based condition assessment for stay cables using non-destructive interferometric radar

Structural health monitoring (SHM) of cable-stayed bridges requires periodic assessment for the deteriorating stay cables to ensure a long-term service life of the bridge. However, conducting the non-destructive SHM for operating cable-stayed bridges and analyzing the safety statuses of all the working cables are still challenging, due to the lack of in situ cable data for previously constructed bridges. This study developed an innovative framework of health condition assessment for stay cables based on cable vibration frequencies from an interferometric radar (IBIS-FS) using engineering reliability analysis (ERA). Taking a cable-stayed bridge in Victoria, Australia as a target structure for the case study, it shows that the presented framework can remotely monitor the accurate real-time load bearing conditions of stay cables by calculating tension forces, and effectively assess their health conditions. The results show that the natural frequency (up to the fifth mode) of a healthy cable remains constant under different external loadings but varies for damaged cables. The measured reliability index of all the stay cables is higher than the safety threshold factor at ultimate limit states, while one carries tension force higher than the maximum design load (lower than the minimum breaking load) and other three cables need to be monitored regularly due to their low reliability indices. This is attributed to an integrated effect of applied tension force, cable diameters, and minimum breaking loads.