Abstract:This study investigated the seismic performance of unequal-span continuous beam bridges in high-intensity regions. A finite-element model for dynamic analysis was established based on a typical unequal-span continuous girder bridge with a main span of (40+60+35) m on a highway, and the modal characteristics were obtained. Both the response spectrum analysis and time-history analysis methods were adopted to calculate the seismic response of the unequal-span bridge under E1 and E2 probability earthquakes. Finally, the seismic performance of the bridge was evaluated according to the bending moment-curvature curve of the pier section. The analysis results showed that the results from the dynamic time-history analysis were basically consistent with that from the response spectrum analysis. Because we assumed linear elasticity in the latter analysis but elastoplastic properties of the material in the former, the individual response values of the two methods were different under the E2 probability level. The response spectrum method is the combination of the maximum responses at the respective modes, but the dynamic time-history analysis is the combination of the structural responses induced by seismic waves at a given time; therefore, there were some errors between the calculation results in the time domain and the frequency domain, and the the calculation results in the frequency domain were conservative. The bridge was found to still work within the elastic range under the E1 and E2 probability earthquakes, which can meet the elastic design requirements.
