Dynamic characterization and seismic performance evaluation of multi-span flyover bridge using ambient vibration testing and finite element modeling

Abstract

This study aims to evaluate the dynamic and seismic performance of an eight-span flyover bridge with a total length of 331 m using a combination of ambient vibration testing, finite element modeling, and non-linear seismic time-history analysis. The velocity data recorded during normal operation were evaluated using the Fast Fourier Transform to calculate the bridge's predominant natural frequency and validate a three-dimensional CSiBridge model. The natural frequencies obtained from the field measurement and numerical model were 3.670 Hz and 3.727 Hz, respectively, with a difference of 1.53%, which indicates reasonable agreement in the dominant frequency. The validated model was then analyzed by using artificial ground motions scaled to the required response spectrum with 5% damping. The seismic responses of the bridge piers were studied in terms of displacement, shear force, bending moment and axial force in the X and Y directions. The data suggest that the strongest seismic demands were focused at the middle piers, particularly at Pier 4. Furthermore, the comparison of the present bridge condition and the bridge with lead rubber bearings showed that the bearings reduced the displacement, shear force, and bending moment responses considerably. The results demonstrate that the model validation based on the vibration data provides a preliminary basis for subsequent seismic response analysis, and the lead rubber bearing can improve the seismic performance of multi-span flyover bridges efficiently.