Post-strengthening rapid repair of damaged RC columns using CFRP sheets for confinement and NSM-CFRP ropes for flexural strengthening

RC columns have been upgraded and strengthened with FRP confinement all around the globe. Future cases of repair will likely encounter RC columns that were strengthened previously with FRP confinement. However, studies on repairing damaged columns that were enhanced by confinement before damage are not currently available. Moreover, there is a vital need for an emergency repair technique that can be used to rapidly repair damaged columns of essential structures after a seismic event. In this study, the time required to complete the repair was a key factor to propose a rapid CFRP-based repair technique. A total of four specimens, each one consisted of two columns, were fabricated and tested. All parameters were kept the same except the difference in using CFRP between the control specimen and the strengthened and repaired specimens. The technique was applied to half-scale square RC columns subjected to combined axial and cyclic lateral loads. NSM-CFRP ropes were used for flexural strengthening and EB-CFRP sheets were used for lateral confinement. It was found that the repair technique was completed in three days. Test results showed that the proposed repair technique was effective not only by restoring the original strength, but also by improving the strength significantly. A strength improvement of at least 65% and a ductility ratio of at least 6.12 were observed. The measured and idealized load-displacement response showed that the ductility of the repaired column was reasonably acceptable. The proposed technique appears promising and may be considered as a permanent repair technique.