Behavioral response of reinforced concrete beams with ultra-ductile fiber-reinforced cementitious composite layers - Experiments, models and reinforcement limits

Ultra-ductile fiber-reinforced cementitious composite-reinforced concrete beams (RC-UDFRC) lack well-established bar-reinforcement limits and accurate behavioral modeling. Based on the experimental results obtained in this study, analytical formulae have been presented for calculating bar reinforcement limits for RC-UDFRC beams. A comprehensive numerical method has also been proposed that combines the use of equilibrium conditions, constitutive material models, and finite layers for predicting the entire flexural behavior of RC-UDFRC beams. Results of the study showed that introducing UDFRC into RC beam construction significantly impacted the minimum bar reinforcement requirements. Further, the simplified analytical approach for the ultimate moment capacity of RC-UDFRC beams exhibited reasonable predictability. The proposed model produced relatively accurate curvatures at cracking and ultimate loading with mean error values of 15 and 7%, respectively. Additionally, the proposed numerical method had rational cracking, yielding, and ultimate loading calculations with the mean of the tested-predicted values of 1.08, 1.11, and 0.98, respectively.