engleski

Numerical analysis of spalling of concrete cover at high temperature

In the present paper a thermo-hygro-mechanical model for concrete and its application in the numerical analysis of explosive spalling of concrete at high temperature are discussed. For given boundary conditions the distribution of moisture, pore pressure, temperature, stresses and strains are calculated by employing a three-dimensional transient finite element analysis. The used thermo-hygro-mechanical model accounts for the interaction between hygral and thermal properties of concrete. Moreover, these properties are coupled with the mechanical properties of concrete, i.e. it is assumed that the mechanical properties (damage) have an effect on the distribution of moisture (pore pressure) and temperature. The mechanical strain, which is due to loading, temperature induced stresses and pore pressure, is calculated by employing temperature dependent microplane model. To study explosive spalling of concrete cover, a 3D finite element analysis of a concrete slab, which was locally exposed to high temperature, is performed. In the analysis are varied thermo-hygral and mechanical properties of concrete. The results indicate that relatively high pore pressure in concrete can cause spalling of concrete cover and that the governing parameter that controls spalling is the permeability of concrete. The used model is still under development and, therefore, the presented results are only preliminary.

concrete; high temperature; explosive spalling; modelling; FE method

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