Life-cycle seismic performance assessment of aging RC bridges considering multi-failure modes of bridge columns

•Seismic fragility analysis is conducted for aging RC bridges in a life-cycle context;•The columns will fail in flexure-shear modes at severer corrosion levels;•Seismic fragility of the bridge significantly increases in case of flexure-shear failure of the columns;•Results highlight the importance of considering the potential shear failure of the bridge columns. Corrosion of steel reinforcements is a major factor causing seismic performance deterioration of reinforced concrete (RC) bridges. More critically, corrosion could induce failure mode shift of the bridge columns as evidenced by some recent experimental studies. This phenomenon has not been well considered in existing studies regarding seismic performance assessment of aging RC bridges. This paper presents seismic fragility analysis of aging RC bridges in a life-cycle context considering failure mode shift of the bridge columns. A numerical model that can capture shear capacity deterioration and flexure-shear coupling behaviors of the corroded columns are developed and validated with experimental tests results. A two-span RC bridge is selected to conduct seismic fragility analysis at variant corrosion time. Time-variant structural capacity of the bridge columns are investigated with the developed numerical model. Seismic fragility curves of the bridge component as well as the bridge system are developed via dynamic analysis using near fault ground motions. Results indicate that the bridge columns will experience failure mode shift due to corrosion effects. The columns will fail in flexure-shear mode at severer corrosion levels although they were initially ductile-designed. Seismic fragility of the bridge significantly increases in case of flexure-shear failure of the columns. The results highlight the importance of considering the potential shear failure of the bridge columns in life-cycle seismic performance assessment of aging RC bridges.