Cracking behaviour of frc flexural beams without stirrups

The experimental research presented herein is focused on the study of the flexural behaviour of Fibre Reinforced Concrete (FRC) beams. Ten full scale specimens were prepared and tested under a four point bending scheme. The beams were built without transverse steel reinforcement along the region that was tested with a constant flexural moment and shear null. Experimental variables were the concrete mix, the type of short fibres used as dispersed reinforcement (steel and polymeric fibres) and volume fraction of fibres used in the concrete matrix. Two repetition specimens were tested for each concrete mix. Experimental results show strain monitoring in the longitudinal steel at increasing loads, strain monitoring in compressed concrete, flexural deflection along the beams. The results highlight the great importance of the beneficial role exercised by the short fibres dispersed in the cement matrix in reducing cracking of reinforced concrete (RC) beams. In particular results obtained herein in absence of the web reinforcement provide new original data since it was avoided to have the onset of the cracks along the stirrups. In correspondence of different five load levels the distance, the height and the maximum width of the cracks were also measured over the whole length of the beams, with particular attention to the constant moment region. The steel fibres demonstrated to be more effective than respect to polyester fibres as crack arrestors. The experimental data were also compared to the design values obtained by applying the analytical models of the new FIB Model Code 2010.