This study intends to present a fragility analysis method suitable for concrete cable-stayed bridges by performing an analysis reflecting design criteria and material characteristics in the results of inelastic time-history analysis. Also, the seismic fragility curve according to the boundary conditions is created for the target bridge, and the effect of these conditions on the seismic fragility of the target bridge is evaluated. An analysis model for the target bridge is constructed using Midas Civil, and a nonlinear time history analysis is performed by applying the fiber element, concrete and rebar material models. To obtain the fragility curve of the cable-stayed bridge, the limit state of the main components of the bridge are determined, and the damage state is classified by comparing them with the response value based on inelastic time history analysis.
As a result of seismic fragility analysis of the pylon, the rigid model showed the highest damage probability in all PGA, and the LRB bearing model showed the lowest damage probability. Numerically, the probability of the slight damage state(SD) under 0.5g earthquake is 87% for the rigid condition, 68% for the floating condition, 60% for the pot bearing condition, and 46% for the LRB bearing condition. Also, it is evaluated that the target bridge has a seismic performance required by the design criteria because the probability of the complete damage state for an earthquake with a return period of 2400 years is less than 1% regardless of boundary conditions. As a result of the seismic fragility analysis for the connection part, it is confirmed that the damage probability of the LRB bearing model is significantly lower in all damage states than other models. From this, it is judged that the application of the LRB bearing can reduce the load and the displacement transmitted from the superstructure and improve the seismic performance of the bridge. In the seismic fragility curve of the cable, the difference in the probability of damage states for each boundary condition is not large compared to other members. In addition, it is found that the probability of the complete damage state in which cable breakage may occur was within 10% in all boundary condition models at 1.0 g. It is analyzed that the seismic fragility of the cable is the least affected by the boundary conditions compared to other members.