intermediate layer effects in performance of frp-confined rc columns

the use of polymer composite (frp) as a reinforcement material for the repair and strengthening of important components of reinforced concrete structures, particularly columns, has found wide spread. in this study, the effect of intermediate layer on improving the confinement behavior of reinforced concrete columns has been investigated. to achieve the objectives of the study, 14 cylindrical reinforced concrete specimens with 150 mm diameter and 500 mm height were tested under pure axial load. the columns have been classified into four groups and were reinforced by one or two layers of carbon fibers and then to investigate the research topic, confinement with intermittent cfrp strips was performed in both traditional (without intermediate layer) and modern method examined in the present study and the results were compared together and with the results of loading columns with internal reinforcement and without external reinforcement (the control sample). the new method involves using a thin layer of galvanized sheet (thickness 0.13 mm) which is mounted under the frp sheet to prevent the transmission of stress concentration induced cracking concrete to frp sheets.the middle layer reduces the transfer of biaxial stress to frp sheettoo. the results suggest that specimens reinforced with frp and galvanized sheets have higher strength and ductility than specimens reinforced with frp and without galvanized.