Mechanical behaviour of recycled concrete filled steel tube conlumns strengthened by CFRP

This paper presented an experimental research on the behavior of circular, concrete-filled solid and hollow steel stub columns with recycled aggregate concrete (RAC) and normal aggregate concrete (NAC) concentrically loaded in compression to failure. Ten specimens were tested to investigate the effects of deformability, stiffness, failure modes and the ultimate carrying capacities of the RAC and NAC columns reinforced by carbon fibre reinforced polymer (CFRP). The ratio of the external tube dimension to the wall thickness of the tube sections varied from 50 to 57 covering compact sections. The main experimental parameters included the reinforcement ratio of CFRP, the cross section of columns strengthened, the portion of the RAC used and the length of the steel tube columns. The results show that CFRP contribution the significant increase in ultimate strength and ductility of the columns strengthened. The test results also indicated that the strength of columns strengthened increased greatly by the more layers of CFRP, and the stiffness of the strengthened columns was improved more significantly than the columns strengthened by full wrapping arrangement of CFRP.