engleski

Modeling of concrete exposed to severe loading conditions - impact and fire

The first part of the present paper focuses on 3D finite-elements studies of concrete structures of different kind exposed to impact loading. In the numerical studies the rate sensitivity microplane model is used as a constitutive law. The strain-rate influence is captured by the activation energy theorem. Inertia forces are implicitly accounted for through dynamic finite element analysis. The results of the study show that the failure mode and structural resistance strongly depend on the loading rate. In the second part of the paper a three-dimensional model, which is based on the thermo-hydro-mechanical coupling between thermo (temperature), hydro (moisture and pore pressure) and mechanical properties of concrete is discussed. The model is formulated in the framework of continuum mechanics under the assumption of validity of irreversible thermodynamics. The response of the model is controlled by the following state variables: temperature, pore pressure, stress and strains. Temperature, moisture and pore pressure are coupled with stress and strains i.e. thermo-hydro part of the model depends on damage of concrete. Moreover, the relevant mechanical properties of concrete (tensile strength, compressive strength and fracture energy) are temperature dependent. In the mechanical part of the model the temperature dependent microplane model is used. The application of the model is illustrated on several numerical examples.

concrete; fire; fracture; impact loading; microplane model; pore pressure

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