Thermal analysis of concrete subjected to fire

[mauinostroza]

Hi, I'm studying a concrete reinforced slab in 2D subjected to fire, with ISO 834 transmitting heat to the element by convection and radiation in the inferior face. My problem is that the temperatures in the unheated face of the element are too high, like 500 °C in a 100 mm slab, meanwhile the temperatures in the steel reinforcement are what is expected. I think the problem is in the conduction of the heat by the concrete, which transmits heat with time dependent propierties, the steel too. If someone can give me some advice about this problem would be great.