Mesoscale modeling of concrtee: microplane-based approach

In the paper mesoscale model for plain concrete, based on the microplane theory is presented. In the model concrete is treated as a bi-phase composite material, consisting of coarse aggregate and mortar matrix. The presence of interfacial transition zone (ITZ) between the two phases is neglected. The numerical study is based on the experimental tests performed by Wang and Wu [2] on small square concrete columns confined with CFRP and subjected to uniaxial compressive loads. The tests results, reported in terms of axial stress-strain relationships and failure modes, represent useful data base for the calibration of numerical models. In the first step of the study, only the unconfined concrete cylinder (R75) has been modeled at mesoscale. An important aspect of the proposed model is the generation of a random aggregate structure in concrete, which is based on a generation procedure implemented in Matlab R2013b. The mesoscale analysis of the unconfined cylinder is performed by using the finite element code MASA. The constitutive law for mortar is based on the microplane model, while aggregates have been considered linear elastic. It is demonstrated that the numerical model is capable to correctly reproduce the mechanical behavior of the unconfined cylinder, confirming the predictability of the used approach.