Effect of uncertainties in cable corrosion and material strength on seismic fragility of long-span cable-stayed bridges in marine environments

Abstract

This paper presents an investigation into the seismic fragility of cable-stayed bridges and considers the complex uncertainties in cable corrosion and material strength. Under certain assumptions and using the limited measured data available for steel corrosion, a cable corrosion model is established. The probability distribution of several parameters, including the corrosion rate, corrosion initiation time, chloride concentration, and cable replacement in the corrosion model, is considered. In addition, the influence of the stress level of cables is also considered in the model by the amplification coefficient of the corrosion rate. To consider the effect of the uncertainties in cable corrosion and material strength on the seismic fragility of this bridge, the uniform design (UD) method is used to generate reasonable bridge samples and to build probabilistic seismic demand models. The results indicate that cable corrosion has a significant impact on the seismic fragility of cable-stayed bridges. The seismic fragility of girders and piers are the smallest and the highest among all bridge components, respectively. The material strength uncertainties have a significant influence on the seismic fragility of bridge components. The coupling between the uncertainties in cable corrosion and material strength does not increase the seismic fragility of the bridge components in most cases because of the cancellation effect of the two uncertainties to some extent. In addition, cable replacement has a significant influence on the seismic fragility of bridge components. In order to correctly evaluate the performance of cable-stayed bridges in service, it is necessary to consider the uncertainties in cable corrosion and material strength in a seismic fragility analysis of long-span cable-stayed bridges with different service periods.