Simulation of fatigue fracture propagation in concrete using a lattice model

The fracture propagation in concrete under fatigue loading is analysed using a two-dimensional lattice model. A regular triangular lattice model (formed by pin-joined truss elements) accounting for the actual multiphase structure (at the meso-scale level) of the material is developed (an automatic image processing procedure for phase detection is adopted). The properties of each truss in the lattice are assigned according to the phase (coarse aggregate, mortar matrix, air bubble, mortar-aggregate interface) the truss lies over. Under monotonic loading, the trusses are assumed to have a linear elastic behavior in compression, whereas in tension a linear elastic behavior up to a certain peak load is followed by a linear softening branch. Fatigue damage is accounted for by considering a suitable elastic stiffness degradation. Some numerical results related to high-performance concrete specimens under high-cycle bending loading are presented.