Local damage control in asymmetric single-pylon cable-stayed bridges with different pylon-girder restraint systems under seismic action

Asymmetric single-pylon cable-stayed bridges typically employ a pylon-girder rigid connection to balance the significant asymmetry in mass and stiffness. However, under strong seismic action, this conventional design leads to severe bending moment concentration in the joint zone, posing a high risk of local damage. To address this critical issue, this study proposes a vertical hinged connection system. This study focuses on an asymmetric single-pylon cable-stayed bridge with a total length of 320 m and a main span of 190 m. Utilizing dynamic time-history analysis, the global seismic responses and the detailed strain behavior in the joint zone under seismic excitation were systematically compared between the two systems, validating the effectiveness of the proposed vertical hinged connection in local damage control. The findings of the study indicate that in scenarios involving combined vertical and longitudinal seismic actions, the conventional rigid connection method gives rise to a significant concentration of bending moment in the joint zone. This is attributable to the effects of pylon offset and girder vertical bending, which collectively result in elevated strain levels and considerable local damage risk. Conversely, the vertical hinged connection effectively releases the girder's rotational degree of freedom about the transverse direction, thereby eliminating bending moment in the joint zone induced by pylon offset and girder vertical bending during earthquakes. This approach has been shown to significantly reduce principal strains in both the girder and the lower pylon segment within the joint area, thereby mitigating the risk of cracking at the girder-pylon joint. The findings provide a valuable reference for the seismic design of pylon-girder restraint systems in asymmetric single-pylon cable-stayed bridges aimed at local damage control.