Sensitivity Analysis of a Simplified Fire Dynamic Model

This paper discusses a method for performing a sensitivity analysis of parameters used in a simplified fire model for
temperature estimates in the upper smoke layer during a fire. The results from the sensitivity analysis can be used when individual
parameters affecting fire safety are assessed. If the variation of a single parameter is found to have a major impact on fire safety, it
may be necessary to conservatively select this parameter in order to incorporate additional safety. We compare fire scenarios in rooms
surrounded by lightweight as well as heavy walls in order to investigate which parameters are the most significant in each case. We
apply the Sobol method, which is a quantitative method that gives the percentage of the total output variance that each parameter
accounts for. The most important parameter is found to be the energy release rate that explains 92% of the uncertainty in the calculated
results for the period before thermal penetration (tp) has occurred. The analysis is also done for all combinations of two parameters in
order to find the combination with the largest effect. The Sobol total for pairs had the highest value for the combination of energy
release rate and area of opening, which explains 96% of the uncertainty. After thermal penetration, the energy release rate is still the
most important parameter, but now only explains 49% of the variation. The second parameter is the thickness of the surface material,
which explains 43%.