ABSTRACT
Size-effect of quasi-brittle materials such as concrete defines the relation between nominal strength and structural size when material fractures. One main type of size-effect, which is the focus of this manuscript, is the so-called energetic size-effect and is due to the release of stored energy of the structure into the fracture front. In contrast to brittle materials, the fracture process zone size has a non-negligible size in concrete, which makes the size-effect law non-linear. In order to simulate size-effect, a numerical model must be able to describe accurately the development and propagation of the fracture process zone. Over the years, a number of models have been proposed to describe the fracturing process in concrete. Nevertheless, it appears challenging to obtain a correct description of fracture and size-effect when the structural dimension and shape are varying. In this study, the Lattice Discrete Particle Model (LDPM) was proposed to overcome this lack of accurate models. The use of mesoscale discrete models such as LDPM, which describes concrete at the aggregate level, is especially adequate in simulating complex cracking mechanisms. In order to investigate the effect of structural dimension and geometry on the fracturing process and the nominal strength, one of the most comprehensive experimental data set available in the literature was considered, which includes three-point bending tests of notched and unnotched beams. First, the relevant material parameters in LDPM were calibrated on a single size notched beam on the corresponding entire load-Crack Mouth Opening Displacement (CMOD) curve. The model was then used to predict the load-CMOD curves of different beam sizes with the same notch length. Predictions on one unnotched beam were also made to test the model’s capability to simulate crack initiation from a smooth surface. Preliminary results show very a good agreement with the experimental data, which suggests that LDPM is an efficient model in predicting concrete size-effect.
