The present paper deals with the combination of plasticity and damage applied to modeling of concrete failure. First, the local uniqueness conditions of two types of combinations of stress-based plasticity and strain-driven scalar damage are studied. Then a triaxial damage-plastic model for the failure of concrete is presented. The plasticity part is based on the effective stress and the damage model is driven by the plastic strain. The implementation of the model in the form of a fully implicit integration scheme is discussed and the corresponding algorithmic stiffness matrix is derived. The constitutive response is compared to a wide range of experimental results. Finally, the model is applied to the structural analysis of reinforced concrete columns. A regularized version of this model with weighted spatial averaging of the damage-driving variable is published in a separate paper.

a b s t r a c tA meso-scale analysis is performed to determine the fracture process zone of concrete subjected to uniaxial tension. The meso-structure of concrete is idealised as stiff aggregates embedded in a soft matrix and separated by weak interfaces. The mechanical response of the matrix, the inclusions and the interface between the matrix and the inclusions is modelled by a discrete lattice approach. The inelastic response of the lattice elements is described by a damage approach, which corresponds to a continuous reduction of the stiffness of the springs. The fracture process in uniaxial tension is approximated by an analysis of a two-dimensional cell with periodic boundary conditions. The spatial distribution of dissipated energy density at the meso-scale of concrete is determined. The size and shape of the deterministic FPZ is obtained as the average of random meso-scale analyses. Additionally, periodicity of the discretisation is prescribed to avoid influences of the boundaries of the periodic cell on fracture patterns. The results of these analyses are then used to calibrate an integral-type nonlocal model.

A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse the failure of concrete structures. The aim is to obtain a model, which describes the important characteristics of the failure process of concrete subjected to multiaxial loading. This is achieved by combining an effective stress based plasticity model with a damage model based on plastic and elastic strain measures. The model response in tension, uni-, bi- and triaxial compression is compared to experimental results. The model describes well the increase in strength and displacement capacity for increasing confinement levels. Furthermore, the model is applied to the structural analyses of tensile and compressive failure.Comment: arXiv admin note: text overlap with arXiv:1103.128

The size effect on the fracture process zone in notched and unnotched three point bending tests of concrete beams is analysed by a meso-scale approach. Concrete is modelled at the meso-scale as stiff aggregates embedded in a soft matrix separated by weak interfaces.The mechanical response of the three phases is modelled by a discrete lattice approach.The model parameters were chosen so that the global model response in the form of loadcrack mouth opening displacement curves were in agreement with experimental results reported in the literature. The fracture process zone of concrete is determined numerically by evaluating the average of spatial distribution of dissipated energy densities of random 1 arXiv:1107.2311v2 [cond-mat.mtrl-sci] meso-scale analyses. The influence of size and boundary conditions on the fracture process zone in concrete is investigated by comparing the results for beams of different sizes and boundary conditions.

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