Research Of Smoke Parameters In High-rise Building Stairwell Based On Sensitivity Screening And Global-Factors-involved Analysis

Stairwell in high-rise building is a crucial structure in fire science considering it is the only pass for people to escape.Sensitivity analysis on this type of structures may derive the sensitivity sequence of involved factors,analyze its effects,screen the most important ones and simplify current model.One classification of sensitivity analysis is factor screening which would calculate the sensitivity index and the result can be used for filtering out factors with high sensitivity as a first step since its relatively low computational cost.Another one is global sensitivity analysis from which first-order index and total index can be derived.The first-order index is defined as the contribution of an individual factor to the uncertainty of system response and can reveal where to direct effort to control uncertainty.The total index indicates the sum of all effects involving the very factor and its relative difference with first-order index can be seen as indices of interaction among factors.On the other hand,utilizing numerical experiments would reduce the cost of research significantly.Be that as it may,the model of stairwell in high-rise building,however,requires a unaffordable computational cost,which limits the practicability of the mentioned analysis accordingly for the reason that the Monte-Carlo-based sensitivity analysis demands a relatively large number of duplicate experiments.In this paper,computational cost was reduced eventually up to 50%without sacrifice of accuracy using a variance based global sensitivity analysis method.A sensitivity screening platform and a global sensitivity analysis platform were established in this paper.Functions involved in the two platforms were performed in MATLAB programs and CFD module was implanted to generate sensitivity results.Factor with little influence was filtered out after 70 runs of stairwell fire simulation in the sensitivity screening platform and then the global analysis was implemented in the other platform with a variance based global method.Then the first-order and total indexes of building structure sizes,heat release rate and ambient parameters on the characteristics of smoke turbulence and transportation were calculated after 312 simulations.The sensitivity results shows that heat release rate bring forth greatest influence on the smoke behavior and have little interactions with other factors on turbulent mean temperature and mean horizontal velocity,etc.,but it has strong interaction with the width of vent for certain response such as intensity of temperature fluctuation and mean velocity.Analysis respectively is required because sensitivity distribution vary between each output response.Additionally,ambient parameters exert little impacts on all responses discussed in this paper.