A damage-plastic model for simulation of reinforced concrete failure

P. J. SANCHEZ; G. DIAZ; A.E HUESPE; OLIVER J

Barcelona

Congreso; COMPLAS X: Computational Plasticity. Fundamentals and Applications; 2009

CIMNE

The concrete displays very different mechanical responses either if it is undertensile or compressive loads. This is particularly true in relation with the failure modes. Undertensile stresses, the concrete displays a much lower strength than in compressive states. Also, itshows a higher brittleness in tensile stress conditions. In fact, formation of cracks are expectedonly if tensile states are observed while in compressive states, the concrete behaves like a plasticmaterial, sometimes displaying a crushing failure mechanism.Additionally, in reinforced concrete structures, due to the reinforcement, the concrete isgenerally subjected to high confinement stress regimes, which plays a very important role inthe structural strength, suggesting that this effect must be considered in the concrete model.Therefore, it is advisable to use a concrete constitutive relation having the ability to capture thephenomenology observed under both tensile and compressive stress conditions. This motivatesthe concrete model presented in this contribution.The constitutive model we propose for the concrete is described by a damage-elastoplasticlaw which reproduces the distributed, as also localized, fracture pattern observed in reinforcedconcrete structures. Its main features are the following:i) the fracture phenomenon, typical of tensile stress states, are described by an isotropicdamage evolution law, adopted from Oliver [1], being regularized by the Continuum-strongDiscontinuity Approach (CSDA), see Oliver et al. [2]. The damage evolution is possiblewhen the mean stress, m, is positive (m > 0). In this case, the material softening inducesinstability and strain localization, being the precursor mechanism for the crack formation;ii) in compressive stress regimes, (m < 0), the concrete behaves like a plastic materialfollowing the Willam’s elastoplastic model, see Willam et al. [3]. There is not damageevolution and furthermore, the plastic model has an enough large hardening modulus inorder to induce a stable response.In order to simulate reinforced concrete structures, this constitutitve relation is inserted intoa homogenized, via mixing theory (Linero [4]), composite material model. Applications of thisapproach are shown.