3D Thermo-hygro-mechanical model for concrete

In the present paper a transient three-dimensional thermo-hygro-mechanical model for concrete is presented. For a given boundary conditions the distribution of moisture, pore pressure, temperature, stresses and strains is calculated by employing a three-dimensional transient finite element analysis. The model accounts for the interaction between hygro and thermal properties of the material. 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 for concrete. To better understand spalling of concrete cover, a preliminary 3D finite element analysis of a concrete slab exposed to high temperature is carried out. It is shown that relatively high pore pressure together with local instabilities (geometrical non-linearity) can cause spalling of concrete cover.