Dynamic analysis of a half-through concrete-filled steel tubular arch bridge

This paper presents the analytical and experimental dynamic analysis of a concrete-filled steel tubular (CFST) half-through arch bridge, with a span of 90 m, located at the center of Xining City, Qinghai Province, China. A three-dimensional finite element (FE) model is developed and an analytical modal analysis is carried out to obtain natural frequencies and mode shapes. Dynamic field testing under ambient excitations was conducted before the opening of the bridge to traffic. Three independent but complementary output-only modal identification techniques are used for system identification. They are a modified single-degree-of-freedom identification (SDOFI) method and a peak picking (PP) method in the frequency domain and the stochastic subspace identification (SSI) method in the time domain. There is a good correlation among the modal parameters identified from the three independent identification techniques. The initial FE model is then corrected with the help of measured natural frequencies and mode shapes by varying some influential parameters of the bridge making use of engineering intuition. The model thus obtained can be treated as the baseline FE model and is suitable for long term monitoring and safety evaluation of the bridge in different severe circumstances such as earthquakes and wind loading.