Behaviour of CFRP wrapped square RC columns under eccentric loading

Fibre Reinforced Polymer (FRP) is an excellent material to strengthen existing structures. However, the confinement efficiency of FRP - confined square columns is relatively low compared to circular columns due to stress concentration at the sharp corners. This paper presents a new techniqu e aimed to maximise the efficiency of FRP confinement for square concrete columns : circularisation using segmental circular concrete covers . Sixteen square reinforced concrete columns were cast. Four were used as a reference group; four were rounded 20 mm at each corner and wrapped with three layers of CFRP simulating the conventional methods; the rest eight columns were bonded with four pieces of segmental circular concrete covers simulating the proposed technique , after which four of them were wrapped with three layers of CFRP and the other four were confined with steel straps. From each group, one column was tested under concentric loading, one at 15 mm eccentricity, one at 25 mm eccentricity and the last specimen was tested under flexural loading . Results of the experimental program showed that circularisation significantly increase s the efficiency of the FRP confinement compared to convention al methods which round the sharp corners. Meanwhile, steel straps had been demonstrated to be an excellent alternative f or confining concrete .