Macro vs mesoscale modelling of fracture in concrete beams: size effect and crack openings

The size effect in concrete structures is a well-known phenomenon. In the present paper both macro and meso scale approaches were used to numerically investigate the size effect on notched beams under three point bending. The scale effect is investigated on the nominal strength and on the crack openings. For the macroscopic approach, concrete is considered as a monophasic material described by a softening damage law whereas for the mesoscopic approach, concrete is considered as a biphasic material made of two components (the aggregates and the matrix phase). A damage based model is used to describe the behavior of both the aggregates particles and the matrix phase. The main objective of this work is to investigate the size effect on crack openings. A numerical post processing method developed by Matallah et al [2] is used in order to study the crack openings process. The numerical results of the simulations of the both approaches are compared to those obtained experimentally by Y. Alam [3].