Seismic Performance of Corroded Post-Tensioned Precast Concrete Columns Reinforced with GFRP Spirals

This study investigated the impact of corrosion on the seismic performance of bridges constructed using accelerated bridge construction with a focus on post-tensioned (PT) concrete column-to-footing connections. The precast concrete columns were reinforced with longitudinal mild steel bars and either steel spirals (all-steel specimens) or glass fiber–reinforced polymer (GFRP) spirals (hybrid specimens). High-strength steel unbonded PT bars were used to connect the precast concrete columns to the footings. A carbon fiber–reinforced polymer jacket was applied to accommodate the increased axial force due to post-tensioning. Four column-to-footing joint specimens were constructed, two with a steel spiral and two with a GFRP spiral. Each column type had one control and one corroded specimen. Quasi-static cyclic load tests were performed to investigate the influence of corrosion on seismic performance. The control specimens with either steel or GFRP spirals reached a 10.0% drift ratio without any bar fracture. However, for the corroded specimens, bar fracture occurred at 5.0% and 7.0% drift ratios for the specimens with steel and GFRP spirals, respectively. The superior performance of the corroded hybrid specimen is attributed to the GFRP spiral in the column, which does not corrode, and thus, it effectively confines the column concrete core. All columns exceeded the 4.0% drift ratio, satisfying the drift limit set in seismic design codes. At a 4.0% drift ratio, the residual drift of the steel spiral–reinforced corroded specimen was 1.4%, whereas the GFRP spiral–reinforced specimen exhibited lower residual displacements under corroded conditions, with a residual drift of 0.7%. At a 4.0% drift ratio, the residual drift of the steel spiral–reinforced control specimen was 0.8% and that of the GFRP spiral–reinforced specimen was 0.5%. Thus, at a 4.0% drift ratio, the two control specimens and the GFRP spiral–reinforced specimen exposed to corrosion exhibit a residual drift below 1.0%, which is acceptable.