Full normalization of the cyclic creep curve of steel-fiber reinforced concrete

The cyclic creep curve represents the evolution of the maximum strain, ε, versus the number of cycles to failure, N, and it can be used to predict fatigue failure and its scatter. In this kind of curves, two random phenomena are observed. The first one is related to the evolution of ε as the number of cycles increases. It represents the damage progress identified as fatigue creep. Meanwhile, the second phenomenon is referred to the scatter of N, commonly used in fatigue life assessment. From this curve and the phenomena involved, this work proposes a new probabilistic failure criterion for strain-based fatigue in plain and steel-fiber reinforced concrete. It is based on a double normalization, from which these curves fit accurately to a Weibull distribution function of minima. The first normalization is referred to N, meanwhile the second one is related to ε. The proposed methodology allows the entire cyclic creep curve and the definition of the ultimate limit state to be predicted. It is validated with a series of low-cycle fatigue tests of concrete mixes with different amounts of fiber sharing the same concrete matrix.