The objective of this paper is to present an investigation on the impact factors of a CFST arch bridge which has double parabolic arches in one arch rib under vehicle loads. A bridge called Yuanshi Bridge, with a span of 84m, located in Ningbo, China, is selected for the investigation. Vibration field testing was conducted to obtain the dynamic characteristics. The FFT (Fast Fourier Transformation) and ERA (Eigensystem Realization Algorithm) methods were used to identify the modal parameters, including natural frequencies, damping ratio and mode shapes. A 3D finite element model was developed and corrected with the help of measured modal parameters by varying material properties. The impact factors are discussed based on vehicle-bridge coupled vibration analysis. The results show that, in this specially-shaped arch bridge, the impact factors vary remarkably with vehicle speed. Large variation in impact factors is observed among different components, even if in the same component, the impact factors vary obviously with sections.
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