A damage-plastic model for simulation of reinforced concrete failure

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

Barcelona, España

Conferencia; X International Conference on Computational Plasticity. COMPLAS X; 2009

The concrete displays very different mechanical responses either if it is under tensile or compressive loads. This is particularly true in relation with the failure modes. Under tensile stresses, the concrete displays a much lower strength than in compressive states. Also, it shows a higher brittleness in tensile stress conditions. In fact, formation of cracks are expected only if tensile states are observed while in compressive states, the concrete behaves like a plastic material, sometimes displaying a crushing failure mechanism. Additionally, in reinforced concrete structures, due to the reinforcement, the concrete is generally subjected to high confinement stress regimes, which plays a very important role in the 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 the phenomenology observed under both tensile and compressive stress conditions. This motivates the concrete model presented in this contribution. The constitutive model we propose for the concrete is described by a damage-elastoplastic law which reproduces the distributed, as also localized, fracture pattern observed in reinforced concrete structures. Its main features are the following: i) the fracture phenomenon, typical of tensile stress states, are described by an isotropic damage evolution law, adopted from Oliver [1], being regularized by the Continuum-strong Discontinuity Approach (CSDA), see Oliver et al. [2]. The damage evolution is possible when the mean stress, Sm, is positive (Sm > 0). In this case, the material softening induces instability and strain localization, being the precursor mechanism for the crack formation;the fracture phenomenon, typical of tensile stress states, are described by an isotropic damage evolution law, adopted from Oliver [1], being regularized by the Continuum-strong Discontinuity Approach (CSDA), see Oliver et al. [2]. The damage evolution is possible when the mean stress, Sm, is positive (Sm > 0). In this case, the material softening induces instability and strain localization, being the precursor mechanism for the crack formation;, is positive (Sm > 0). In this case, the material softening induces instability and strain localization, being the precursor mechanism for the crack formation; ii) in compressive stress regimes, (Sm < 0), the concrete behaves like a plastic material following the Willam’s elastoplastic model, see Willam et al. [3]. There is not damage evolution and furthermore, the plastic model has an enough large hardening modulus in order to induce a stable response. In order to simulate reinforced concrete structures, this constitutitve relation is inserted into a homogenized, via mixing theory (Linero [4]), composite material model. Applications of this approach are shown.in compressive stress regimes, (Sm < 0), the concrete behaves like a plastic material following the Willam’s elastoplastic model, see Willam et al. [3]. There is not damage evolution and furthermore, the plastic model has an enough large hardening modulus in order to induce a stable response. In order to simulate reinforced concrete structures, this constitutitve relation is inserted into a homogenized, via mixing theory (Linero [4]), composite material model. Applications of this approach are shown.