Uncertainty Quantification and Fragility Development of Deteriorating RC Bridge Piers

Abstract

Corrosion can reduce structural capacity and increase the risk of bridge damage/failure under extreme events. The impact of corrosion on seismic fragility of bridges has been well studied. However, the methodology used in most existing studies requires detailed information on the structural design and condition of a bridge, which is a major hindrance in conducting seismic risk assessment for a large population of bridges. Furthermore, existing studies do not adequately address the time-dependency of uncertainties associated with fragility curve development. This study presents a methodology to generate time-dependent seismic fragility curves for deteriorating highway bridges based only on the limited information available from National Bridge Inventory (NBI) and the HAZUS technical manual. As a result, the methodology can be implemented for a large number of bridges and potentially be integrated in existing bridge management practice. Despite the limited information required, a full probabilistic analysis was conducted in this study to develop these fragility curves, accounting for various uncertainties in material properties, geometric imperfection, corrosion development, and model error of seismic capacity/demand models. The methodology was implemented as an example for highway bridge class 5, as defined by the HAZUS technical manual. Results showed that during the 100-year service life, corrosion can potentially cause 30% decrease in median seismic capacity and 20% increase in capacity-side uncertainty. However, the effect of corrosion hinges on the corrosion models and model parameters.