An analytical approach for estimating uncertainty in measured temperatures of concrete slab during fire

• An analytical model for computing uncertainty in temperatures of slab was developed.
• Uncertainty in temperature from analytical model and Monte Carlo method agrees well.
• Uncertainties in gas temperature affect strongly uncertainties in slab temperatures.

To evaluate the fire resistance of concrete slabs used in composite floor systems, the temporal and spatial variation of measured temperatures must be accurately determined. Temperature profiles in a concrete section are a function of concrete thermophysical properties and boundary conditions. However, there can be considerable uncertainty in the estimates typically used for thermophysical properties and boundary conditions in fire. In this study, an analytical approach was developed to compute uncertainties in concrete slab temperatures during exposure to a fire and the results obtained with this approach were verified against those obtained with the Monte Carlo method. A simple 1-D heat flow model was constructed to demonstrate the usefulness of this approach. It is shown that uncertainty in gas temperatures has a substantial effect on the overall uncertainty in computed member temperatures. Also, uncertainties associated with computed concrete temperatures increase with increase in fire exposure time.