Strengthening of RC columns by longitudinal CFRP sheets: Effect of strengthening technique

Abstract

In the present study, the effect of utilizing longitudinal carbon fiber reinforced polymer (CFRP), as external compression reinforcement, on the behavior of strengthened RC columns is investigated. To do so, 10 RC columns including 5 circular columns with diameter of 150mm and 5 square columns with dimension of 133mm were cast. Four different methods including conventional externally bonded reinforcement (EBR) and near surface mounted (NSM) techniques, as well as the recently introduced grooving method (GM) in the forms of externally bonded reinforcement on grooves (EBROG, to be pronounced as /ebrΛg/) and externally bonded reinforcement in grooves (EBRIG, to be pronounced as /ebrIg/) techniques were used to strengthen the specimens in compression with CFRP. The specimens were tested under monotonic uniaxial compression, and different effects of the strengthening techniques were comprehensively discussed. Furthermore, an image-based deformation measurement technique, i.e. particle image velocimetry (PIV) was used to further investigate the stress transfer between longitudinal CFRP sheet and concrete substrate. Experimental results demonstrated that utilizing grooving method (GM) for bonding CFRP to concrete surface postpones the CFRP buckling, and subsequently, a significant increase in load carrying capacity of strengthened RC columns by compression CFRP sheets was observed.