FE-Analysis of the Behaviour of Concrete Elements with Coupled Elasto-Plastic-Damage Models with Non-Local Softening

The analysis of concrete elements is complex due to their stiffness degradation during cyclic loading caused by strain localization in the form of cracks and shear zones. The determination of the width and spacing of strain localization is crucial to evaluate the material strength at peak and in the post-peak regime. The aim of the present paper is to show the capability of two different coupled elasto-plasticdamage continuum models to describe strain localization and stiffness degradation in concrete elements subject cyclic loading during bending, uniaxial compression and extension. First, a coupled elasto-plastic-damage model based on the idea by Pamin and de Borst [1] was used [2]. Second, a coupled elasto-plastic-damage model using the formulation proposed by Carol et al. [3] and Hansen and Willam [4] was taken into account. To describe properly strain localization, to preserve the well-posedness of the boundary value problem, to obtain FE-results free from spurious discretization sensitivity and to capture a deterministic size effect, a integral-type non-local theory was used as a regularization technique in a softening regime [5]. It was achieved by weighted spatial averaging over a neighborhood of each material point of a suitable state variable. Thus, the stress at a certain material point depended not only on the state variable at that point but also on the distribution of the state variable in a finite neighborhood of the point considered.