Monotonic and cyclic behaviour of deficient reinforced concrete slabs retrofitted with externally bonded carbon fibre reinforced polymer

Abstract

Fibre reinforced polymer (FRP) retrofitting of reinforced concrete (RC) slabs has been widely investigated; however, the flexural behaviour of deficient RC slabs retrofitted with FRP under cyclic loading are limitedly explored. Towards this aim, this study experimentally and theoretically investigated the behaviour of RC slabs retrofitted with carbon fibre reinforced polymer (CFRP) under monotonic/cyclic loadings. Seven full-scale RC slabs, including one control slab and six slabs retrofitted by 1/2 and one CFRP layer, namely retrofitting types I and II, were tested under monotonic and cyclic loadings until failure. The results indicated that FRP retrofitted slabs failed by CFRP debonding while the control slab failed by steel yielding. CFRP retrofitted slabs exhibited tri-linear behaviour. CFRP retrofitting types I and II improved the yield load-carrying capacity by 43.5% and 83.5%, and the maximum load-carrying capacity by 81.9% and 217.4% compared with the capacity of the control slab, respectively. The stiffness of the retrofitted slabs increased significantly, leading to a substantial reduction in the deflection capacity. Although the ductility decreased, the safety factors based on load-carrying capacity of CFRP retrofitted slabs were much higher than the safety factor of the control slab. Cyclic loading caused a marginal strength degradation while it slightly reduced the ultimate deflections. Finally, a model to compute the moment capacity of CFRP retrofitted slabs was proposed, which can be useful for engineers in practice due to its simplicity and reasonable accuracy.