Experimental evaluation of seismic performance of corroded precast RC bridge columns and the retrofit measure using CFRP jackets

Precast reinforced concrete (RC) bridge columns are critical substructure components for Accelerated Bridge Construction (ABC), which attracts significant attention all over the world in recent decades. However, seismic behavior of precast RC bridge columns in corrosive environment and related retrofit methods are rarely studied. To fill out this knowledge gap, in this study, four, 1/4-scaled precast RC bridge columns of various corrosion levels were designed, constructed and tested in a pseudo-static manner to gain in-depth understanding of corrosion on the seismic behavior of this type of columns. Two of these columns with higher corrosion levels were retrofitted with carbon fiber reinforced polymer (CFRP) fabrics in the plastic hinge zone to assess the effectiveness of this retrofit measure. Corrosion levels of the specimens were obtained through an electrochemical method to accelerate the corrosion process at the plastic region. It was found that corrosion in the reinforcement was uneven across the section and was much severer at the joint of precast bridge columns. It was also found that even the low corrosion level of longitudinal reinforcement (i.e. 7.2%) can result in a significant decrease (i.e. >15%) in the lateral load capacity, energy dissipation, ductility and ultimate displacement. Hence, the retrofit of corroded precast RC bridge columns should be performed at low-level of corrosion. The test results also indicate that corrosion has more adverse effect on the ultimate displacement and ductility than the strength. In addition, retrofitting bridge columns of higher corrosion levels (i.e., >10%) using CFRP jackets could effectively protect the columns from damage in the plastic hinge zones. However, the damage pattern was shifted to fracture of the longitudinal rebars at the column-footing interface, resulting in substantial reduction in the ultimate displacement capacity. Therefore, it is not recommended to retrofit precast RC bridge columns of high corrosion level using CFRP jackets alone.

Automated summary

The seismic behavior of precast reinforced concrete bridge columns is significantly affected by corrosion levels, with even low levels causing substantial decreases in lateral load capacity, energy dissipation, ductility, and ultimate displacement. Retrofitting should be done at low corrosion levels, as using CFRP jackets on columns with higher corrosion levels may shift damage patterns and reduce ultimate displacement capacity. Corrosion has a more adverse effect on ultimate displacement and ductility than on strength, highlighting the importance of proper retrofit measures in corrosive environments.