Effectiveness of Passive CFRP and Active Fe-SMA Confinement in Enhancing Drift Capacity and Seismic Performance of RC Columns Under Extreme Drift Levels

Abstract

This study presents an experimental investigation into the seismic performance of seismically deficient reinforced concrete (RC) bridge columns retrofitted with passive and active confinement systems. Four single-cantilever RC columns, representing 1/3-scale bridge piers, were constructed with poor transverse reinforcement detailing to simulate seismic deficiency. One column was left un-strengthened for baseline comparison, while the remaining three were retrofitted using: (1) a CFRP jacket, (2) welded Fe-SMA plates, and (3) bolted Fe-SMA plates. All columns were subjected to quasi-static lateral cyclic push-only loading reaching extreme drift levels exceeding 16% and high loading rates up to 6 mm/s. The study specifically explores the confinement effectiveness of CFRP and thermally activated Fe-SMA plates, comparing their contributions to lateral strength, ductility, energy dissipation, failure mode, and damage suppression. The results show that while the as-built column failed at 3.65% drift due to brittle flexural-shear failure, all retrofitted columns demonstrated significantly enhanced ductility, drift capacity, and post-peak behaviour. The CFRP and Fe-SMA jackets effectively delayed damage initiation, minimized core degradation, and improved energy dissipation. The bolted Fe-SMA system exhibited the highest and full restoration of lateral strength, while the welded system achieved the greatest increase in cumulative energy dissipation of around 40%. This research highlights the practical advantages and seismic effectiveness of Fe-SMA and CFRP confinement systems under extreme drift levels. However, future work should explore full-scale column applications, refine anchorage techniques for improved composite interaction, and investigate long-term durability under cyclic environmental conditions.