Investigations on behaviour of flexural deficient and CFRP strengthened reinforced concrete beams under static and fatigue loading

In this study, experimental investigations are carried out on control (without flexural deficiency) and flexural deficient reinforced concrete (RC) beams with two levels (FD1-20% and FD2-30% deficient) of deficiency, under monotonic as well as fatigue loading. After confirming the load carrying capacities under monotonic loading, studies are carried out on flexural deficient RC beams under fatigue loading by considering four load ranges (20-55%, 20-65%, 20-75% and 20-85% of load carrying capacity of control beam, P-uc). It is found that load carrying capacities of FD1 and FD2 RC beams are around 8% and 20% respectively less than that of control beam. But, the fatigue lives of flexural deficient RC beams FD1 and FD2 are drastically less than that of control beam. Fatigue lives of FD1 and FD2 beams under fatigue with load range of 20-75% of P-uc are respectively only 4840 and 292 cycles compared with 1.07387 cycles for control beam. Flexural deficient RC beams are strengthened with CFRP fabric to attain the required moment carrying capacity and are tested under monotonic and fatigue loading. The fatigue lives of flexural deficient RC beams strengthened with one layer of CFRP fabric (SFD1 and SFD2) are increased beyond that of control beam. Further, numerical models are also developed to evaluate the performance of control, deficient and CFRP strengthened flexural deficient RC beams. The fatigue life evaluated by numerical simulations, based on the maximum fracturing strain comprising of contributions from the static loading, stress cycling and cyclic crack opening, corroborated well with that evaluated from experimental investigations. Numerical approach presented in this study would provide inexpensive means for assessing the fatigue life of deficient as well as CFRP strengthened flexural deficient RC beams and would help to devise an appropriate strengthening strategy to attain the required fatigue life. (C) 2019 Elsevier Ltd. All rights reserved.