Cracking localization in tensile conventionally reinforced fibrous concrete bars

This paper presents an experimental verification and quantification of the cracking localization phenomenon in reinforced concrete (RC) tensile prismatic bars with steel fibers. The phenomenon is characterized by significant widening of single or few cracks out of the total number of cracks that develop under tension (as opposed to nearly uniform widening in plain RC members). The experimental program included specimens with two contents of hooked-end fibers (30 and 60 kg/m3 that correspond to 0.38 and 0.76% in volume), as well as control specimens without fibers. For each type of mixture, the conventional reinforcement consisted of centrally located deformed rebars at reinforcement ratios of 0.79-4.91%. Results of the tests further support the existence of the cracking localization phenomenon and the trend of its decrease with increasing reinforcement ratio. A quantitative measure of this phenomenon is represented by a ratio between the number of the significantly wide cracks and the total number of cracks in the specimen. Furthermore, the results show that for a given conventional reinforcement ratio, cracking localization is more pronounced for larger amounts of fiber content (and vice versa). A previously developed and presently enhanced theoretical model has been calibrated and it shows good agreement with the experimental results.