Experimental Modal Analysis of a Concrete-filled Tube Arch Bridge

This paper presents the experimental and analytical modal analysis of a concrete-filled (CFT) tube half-through arch bridge, with the span length of 90m, located at the center of Xining City, Qinghai province, China. Dynamic field test was carried out just prior to the official opening of bridge in order to inspect the dynamic characteristics of the bridge and make a baseline record for the future health monitoring. Vibration testing was carried out under ambient excitations. Three independent but complementary output-only modal identification techniques were used for modal identification. They were modified single degree of freedom identification (SDOFI) method, peak picking (PP) method in the frequency domain and the stochastic subspace identification (SSI) method in the time domain. The 3-D finite element model was developed and performed analytical modal analysis to achieve natural frequencies and mode shapes. Some key parameters of initial finite element model were calibrated with respect to experimental results, which lead some conclusions about this type of arch bridge.