engleski

Modelling of concrete at high temperature

In the present paper a fully coupled transient three-dimensional thermohygro- mechanical model for concrete is presented. The model is formulated in the framework of continuum mechanics based on the principles of irreversible thermodynamics. Distribution of moisture, pore pressure, temperature, stresses and strains are calculated by employing a three-dimensional transient finite element analysis of implicit type. The mechanical strain, which is due to loading, temperature induced stresses and pore pressure, is calculated by employing temperature dependent microplane model for concrete. To investigate the failure mechanism of explosive spalling of high strength concrete, an extensive 3D finite element parametric study of a wall exposed to high temperature is carried out. Concrete mechanical properties, permeability, porosity and humidity are varied in the analysis. The results indicate that relatively high pore pressure together with local instabilities (geometrical non-linearity) due to compressive stresses that are generated in direction parallel to the heated concrete surface, are main reasons for explosive spalling. It turns out that permeability is the most sensitive concrete property with respect to the risk of explosive spalling.

modelling; concrete; high temperature

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