Study on dynamic characteristics and seismic response of the extradosed cable-stayed bridge with single pylon and single cable plane

Taking Sifang Bridge in Suijiang County, Yunnan Province as a research object, this paper established a three-dimensional finite-element model of the entire bridge. In the semi-floating structure system, the dynamic characteristics were calculated according to the pile–soil interaction, and the influence of pile–soil interaction on the dynamic characteristics of the structure was analyzed. Based on this, the seismic dynamic time history analysis method was used by considering the cable sag, nonlinearity of the support, rigidity of the structure, boundary condition setting, and the pile–soil interaction. Then, we analyzed the seismic performance of the structure and its responses by providing the seismic wave at different levels. The results showed that the structure can be softened by the pile–soil interaction. The dynamic characteristics of the structure in each direction could be accurately reflected by considering the pile–soil interaction. Due to the weak lateral stiffness of the main pylon, the other structural measures should be added in the design. The support between the pylon and girder was the most unfavorable part in the along bridge segment, while the bottom of the pylon was the most unfavorable part in the across bridge segment. Under the earthquake magnitude E1, the bridge sustained the damage and the structure was in the elastic working range. Under the earthquake magnitude E2, some local repairable damage has been detected in some segment of the bridge. The results of this study can be used as a potential reference for practical engineering problems as well as can provide the parameter basis for the subsequent seismic design of the bridge. At the same time, this study has also provided a theoretical reference and an effective method for the seismic analysis of cable-stayed bridge with single pylon and single cable plane of the same kind.