New Model for Estimating the Time-Variant Seismic Performance of Corroding RC Bridge Columns

Abstract

Corrosion of reinforcement is a predominant reason for reduced service lives of reinforced concrete (RC) structures exposed to aggressive environments. This deterioration process can lead to damage resulting in capacity loss or even structural failure, especially in coastal marine environments or where deicing or antiicing applications occur. Based on data from the National Bridge Inventory in 2010, the average bridge age in the country is 40 years old. Thirty percent of the bridges have exceeded 50 years, 7% have exceeded 75 years, and 25% are deemed deficient. For bridges exposed to chlorides (coastal areas or deicing or antiicing exposure), these older bridges often experience corrosion of the reinforcement. When reinforcement corrodes, the capacity of the structure is likely reduced, although little work has been reported on quantifying the reduction in performance and reliability. In seismic areas, this reduction in capacity may be magnified due to the loading demands during a seismic event. Therefore, understanding the time-variant risks associated with corroding structures will assist engineers and decision makers in making sound decisions with respect to optimization of design, inspection, repair, strengthening, and/or replacement of RC structures. This paper develops a new deterministic corrosion rate model and then uses the new model to assess the time-variant reliability of a corroding column subjected to a seismic event. The results indicate that corrosion can significantly reduce the reliability of an existing bridge column over relatively short durations.