Cable-stayed bridges, diagnostic survey of stays

Abstract The safety and service life of cable-stayed bridges directly depend on the structural condition of individual stay cable. The diagnostics of the cables and their anchorage systems is an integral part of the complete bridge assessment. The paper summarizes the results of an extensive diagnostic survey carried out on three major bridge structures in the Czech Republic: the single-span bridge in Hrachovec, the single-span bridge in Židlochovice, and the three-span highway bridge over the Elbe River near Poděbrady. The basic diagnostic phase included visual inspection of the outer sheath, acoustic tracing, and moisture measurement of the prestressed reinforcement. The advanced phase employed dynamic testing of natural frequencies and strain gauge monitoring to verify tensile forces and prepare data for force rectification. Calibration of the dynamic methods using hydraulic post-tensioning confirmed the high accuracy of these non-invasive techniques. The results demonstrate that the combination of standard and advanced diagnostic methods provides an effective tool for predictive maintenance and enhanced reliability of cable-stayed bridge structures. Moreover, dynamic analysis offers new possibilities for long-term monitoring and targeted extension of the structural service life.