A MESOSCALE INVESTIGATION ON THE SIZE EFFECT OF THE FRACTURE CHARACTERISTICS IN CONCRETE

Abstract

The size effect or scaling phenomenon is a fundamental problem when dealing with
fracture of geomaterials. Concrete is considered as one of world’s most widely used construction materials.
The design in civil engineering of structural concrete should take into account the size effect when
extrapolating the experimental tests at laboratory scale to structures with large dimensions. The size effect is
generally investigated on the nominal strength which is an important parameter for design in civil
engineering. However, the fracture characteristics are also considered in structural concrete codes. The
limitation of cracking (crack width, crack length , etc. ) are important aspects to consider in order to
guarantee a safe conception. This paper deals with a numerical analysis of size effect on the nominal strength
and on the cracking characteristics in concrete beams. Numerical simulations of geometrically similar
notched beams of various sizes are performed using a mesoscopic approach with an isotropic damage model.
In order to properly describe the cracking process, a post processing method based on the fracture energy
regularization is adopted. The size effect on crack-opening and crack length evolution is investigated by
comparing the numerical results with experimental data obtained by digital image correlation technique. The
numerical results prove the ability of the mesoscopic approach to describe the size effect on the global
behavior and the local behavior of concrete. The numerical investigation reveals the existing of a size effect
on the cracking process evolution.