Advances in meso-mechanical analysis of concrete specimens using zero-thickness interface elements

Mesomechanical analysis is emerging as a powerful tool for the modeling of material behavior. The group of mechanics of materials at ETSECCPB has been developing such tools for concrete, with the distinctive feature of the way of representing a key ingredient of concrete behavior, cracking. All lines in the FE mesh are considered as potential crack lines and, for them, traction-separation constitutive models based on principles of non-linear fracture mechanics have been developed and implemented. This approach has been implemented in the context of the FEM, originally in 2D and more recently in 3D, via systematic use of zero-thickness interface elements. The geometry of the particles (larger aggregates) is generated numerically using Delaunai/Noronoi theory, shrunk to allow space for mortar, and finally the overall specimen is "cut" to its final shape. Results of mechanical analysis turn out very realistic, both mesoscopically (distributed microcrack, coalescence, localization) and macroscopically (average stress-strain curves for specimen). Ongoing work aims at more complex geometries and loading cases, more efficient computational methods and to extension to diffusion-dominated and coupled phenomena such as environmental deterioration or high temperatures.