Shear behaviour of lightweight concrete beams strengthened with CFRP composite

This paper presents the experimental results obtained from lightweight concrete (LWC) and normal-weight concrete (NWC) beams with closed and U-shaped configurations of epoxy-bonded carbon fibre-reinforced polymer (CFRP) reinforcement in order to compare the shear-resisting mechanisms between LWC and NWC beams. The experimental results show that the CFRP can successfully be applied in the strengthening of LWC beams, and that the shear strength gained due to CFRP reinforcement for lightweight samples is less than the NWC samples while the modes of failures are the same. In contrast, diagonal shear cracks propagate through the lightweight aggregate compared to cracks around normal aggregate in the concrete matrix. Furthermore, the numerical study shows that the design guidelines to estimate the CFRP contribution, which do not differentiate between concrete types, overestimate the effect of U-shaped CFRP reinforcement on LWC beams where the effective bond length of CFRP could not be achieved due to lower tensile strength of LWC.