Fracture in random quasibrittle media: I. Discrete mesoscale simulations of load capacity and fracture process zone

Abstract

Numerical simulations of concrete fracture performed with a probabilistic mesoscale discrete model are presented. The model represents a substantial part of material randomness by assigning random locations to the largest aggregates. The remaining part of randomness is introduced by causing material parameters to fluctuate randomly via a homogeneous random field. An extensive numerical study performed with the model considers beams loaded in uniaxial tension with both fixed and rotating platens, and also beams with and without a notch loaded in three point bending. The results show the nontrivial effect of (i) autocorrelation length and (ii) variance of the random field on the fracture behavior of the model. Statistics of the peak load are presented as well as the size and shape of an active zone at the time when the maximum load is attained. The active zone is a region that is dissipating energy at a certain loading stage, it is understood as an instantaneous contribution to the fracture process zone. Local averaging within the active zone and weakest-link are identified as underlying mechanisms explaining the reported results.The companion paper, Part II [79], introduces an analytical model capable of predicting the distribution of the peak load obtained with the probabilistic discrete model via the simple estimation of extremes of a random field obtained as moving average of local strength.