Stochastic Modeling of Single–Fiber Pull-Out Creep Under Sustained Loading

The time-dependent pull-out behavior of fibers in concrete exhibits wide scattering, even for nominally identical specimens in a controlled environment. This variation limits the capabilities and insights provided by deterministic modeling approaches. Nevertheless, little work has been done toward understanding the stochastic nature of single-fiber pull-out under sustained loading. Such understanding is necessary for modeling the performance of load-carrying members made of fiber-reinforced concrete. For this research study, pull-out creep under sustained loading is modeled using a discontinuous Markov process. Along with damage development, the creep process affects progressive debonding along the fiber–matrix interface. Therefore, for physical consistency, the transition probability to the debonded state is quantified through an energy balance approach within the framework of fracture mechanics. Considering interaction between the energy release rate and the corresponding fracture resistance, models are useful to assess debonding propagation over time until complete pull-out. Results demonstrate that the probabilities of the pull-out time deviate from a normal distribution.