Identification of the thermal properties of concrete for the temperature calculation of concrete slabs and columns subjected to a standard fire-Methodology and proposal for simplified formulations

- The thermal analysis of concrete members according to EN 1992-1-2 shows errors.
- Improvements of the involved physical parameters are indicated.
- A sensitivity analysis is performed to identify the governing parameters.
- A nonlinear optimization method is applied to improve the thermal conductivity.
- The proposal is partly validated by the recalculation of laboratory tests.

The fire resistance of concrete members is controlled by the temperature distribution of the considered cross section. The thermal analysis can be performed with the advanced temperature dependent physical properties provided by EN 1992-1-2. But the recalculation of laboratory tests on columns from TU Braunschweig shows, that there are deviations between the calculated and measured temperatures. Therefore it can be assumed, that the mathematical formulation of these thermal properties could be improved. A sensitivity analysis is performed to identify the governing parameters of the temperature calculation and a nonlinear optimization method is used to enhance the formulation of the thermal properties. The proposed simplified properties are partly validated by the recalculation of measured temperatures of concrete columns. These first results show, that the scatter of the differences from the calculated to the measured temperatures can be reduced by the proposed simple model for the thermal analysis of concrete.