3D meso-mechanical analysis of concrete specimens under biaxial loading

In recent years, the mechanics of materials group at ETSECCPB-UPC has developed an approach for meso-mechanical analysis of concrete using zero-thickness interface elements in 2D and more recently in 3D. In this methodology, the meso-structure is generated with in-house developed computer programs based on Voronoi/Delaunay theory. In the analysis, continuum elements are assumed linear elastic. Non-linearity and fracture phenomena are made possible by the systematic use of zero-thickness interface elements inserted on a priori determined potential fracture planes. In this paper, the results obtained for a 3D specimen under biaxial loading are presented. The results turn out to be very satisfactory and, in particular, it is observed that even the specimens which contain a reduced number of aggregates (14 in the present calculations) lead to a realistic failure envelope under biaxial loading, and they also capture the tendencies of cracking and fracture orientations observed in experiments for different rates of biaxial loading. The special limit case of biaxial loading under restrained out-of-plane deformations is also analysed, leading to practically elastic behaviour as shown by available experimental evidence.