Experimental investigation on the resilience-based seismic retrofitting of non-uniformly corroded bridge columns using FRP wraps and bars

The seismic retrofitting of corroded bridge columns presents the challenge of enhancing the self-centering capability while maintaining a satisfactory energy dissipation capacity. Existing retrofitting methods place less emphasis on the self-centering capability, which is a critical indicator of seismic resilience. This study aims to bridge this gap by proposing and validating a new retrofitting strategy. In the authors’ previous research^[1], the seismic resilience of hybrid reinforced concrete (HRC) columns containing both fibre-reinforced polymer (FRP) and steel longitudinal bars was demonstrated. In this paper, a resilience-based seismic retrofitting method referred to as the “FRP-confined HRC (FHRC)” strategy is further studied. First, five large-scale bridge column specimens were prepared, including one control and four corroded reinforced concrete (RC) columns. In particular, non-uniform corrosion along the column height was introduced when preparing the corroded specimens. Second, the retrofitting design method and construction procedure were developed. Two of the four corroded columns were retrofitted with internal carbon FRP (CFRP) bars and external CFRP wraps. Third, quasi-static tests were conducted. Test results indicated that, in comparison with two corroded but un-retrofitted specimens and one un-corroded specimen, the two retrofitted specimens not only exhibited significantly reduced residual drift ratios but also achieved higher energy dissipation capabilities. Such retrofitting effects are critical to upgrading seismic resilience, yet have been rarely reported in the literature. These results were further interpreted by an energy-based analysis. Furthermore, the effectiveness of the retrofitting method on non-uniformly corroded bridge columns was evaluated as well.