Experimental and analytical studies on dynamic characteristics of a large span cable-stayed bridge

An analytical and experimental modal analysis has been carried out on the Qingzhou cable-stayed bridge in Fuzhou, China. Its main span of 605 m is currently the longest span among the completed composite-deck cable-stayed bridges in the world. An analytical modal analysis is performed on the developed three-dimensional finite element model starting from the deformed configuration to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the bridge deck and all stay cables were conducted just prior to the opening of the bridge. The output-only modal parameter identification is then carried out by using the peak picking of the average normalized power spectral densities in the frequency-domain and stochastic subspace identification in the time-domain. A good correlation is achieved between the finite element and ambient vibration test results. It is demonstrated that the analytical and experimental modal analysis provide a comprehensive study on the dynamic properties of the bridge. The ambient vibration tests are sufficient to identify the most significant modes below 1.0 Hz of this kind of large span cable-stayed bridge. The validated finite element model with respect to ambient vibration test results can serve as the baseline for a more precise dynamic response prediction and long-term health monitoring of the bridge.