Seismic fragility curves development for double-column piers of highway bridges applying Cox hazard models of survival analyses

Fragility analyses have undoubtedly been critical steps in the seismic risk assessment of highway bridges, and even in transportation networks. In view of the shortcomings of the previous fragility analysis methods, this paper discusses the application of survival analysis based on the Cox hazard model in the establishment of bridge pier seismic fragility. In the IDA framework, the ground motion intensity and censored value (damage state) are taken as dependent variables, and the pier attributes are used as covariates to generate fragility curves. Next, the uniform design experiment is used to generate the attribute data set training model of the pier samples. It can be observed that compared with the traditional strip analysis method, the proposed procedure can provide accurate estimation of the fragility curves, and the fragility curves established by the traditional method are in fact the fragility curve corresponding to the pier average sample. In addition, the primary survival analysis of the pier samples with average value and the hazard ratio provided by the Cox model can be used to quickly analyze the impact of significant factors on the fragility curves and estimate the seismic loss. The pier height, reinforcement ratio and reinforcement strength may be the dominant factors affecting the pier seismic loss in highway bridges.