Performance-based Fire Protection Design Of Large-space Structures Exposed To Localized Fire

The large-space steel structures mainly include public buildings and factory premises buildings. There are high crowded person and a great many fire loads in these buildings and thus the risk of personnel evacuation is high. The quantitative assessment of smoke harm, risk of structural collapse and personnel evacuation’s 萨safety degree are very important for performance-based fire safety design scientifically. The existing research results show that the fire temperature fields present typically non-uniform in these buildings which are different from conventional enclosure fire.Fully considering temperature fields’ spatial and temporal characteristic and adopting the method of combining theoretical analysis, experiment research and numerical simulation, this dissertation establishes a non-uniform temperature field’s model of whole fire course and puts forward a simplified calculation method of steel temperature development warming with considering flame thermal radiation. Coupling the non-uniform temperature fields to the stress fields of steel members, this dissertation quantitatively analyze the global stability of steel structures in whole fire course. At the same time, this dissertation studies the evacuation behavior in large space buildings and proposes the performance-based fire safety design in the whole fire course systematically. The research will enrich the theory of overall steel structures fire resistance and offer a fire risk assessment tool for these buildings. My analytic works are mainly as follows:1) The tests testify the feasibility of large-eddy simulation technology forecasting the fire temperature fields in large space buildings. By means of large-eddy simulation technology, I research on the fire temperature fields of nearly one hundred large space buildings with different building altitude, different covered area of structure and different fire power and put forward a non-uniform temperature field’s model. The model could give the fire temperature field’s development characteristics and non-uniform distribution rules accurately and roundly.2) This dissertation establishes a steel members heat balance equation and studies the rules of effects of flames thermal radiation, smoke thermal convection and smoke thermal radiation on steel members. Making references to ignition fire source model, this dissertation establishes a model of flame radiating steel members and proposes steel temperature development model and calculation methods where the flame heat radiation are taken into account. Meanwhile, the model and calculation methods are also testified by tests. After these, the effect of shape coefficient, building altitude, fire power, the distance between members and fire and some other main parameters on temperature curve of steel members exposed to fire are analyzed at last.3) An analytical method of overall stability of steel members which are under fire unequally in the whole fire course is put forward in the paper. Exerting non-uniform temperature fields to finite element analysis model, this dissertation couple the temperature fields to the stress fields of steel members. The method make up the insufficiency of using ISO standard curve, BS EN 1991-1-2:2002 temperature curve and some other uniformity temperature curve, and can reflect the structure additional internal forces and stress redistribution caused by temperature gradient difference of non-uniform temperature fields.4) This dissertation establishes a personnel density prediction model of large space based on the black box theory, and proposes evacuation action time calculation methods based on hydraulic model and numerical simulation. The accuracy of these two methods is experimental verified and discussed at the same time.5) Some general procedure and key issues of performance-based fire protection design in large-space steel structures are studied at the end of the article. The general security goals and the mathematical expression of the performance-based fire protection design of large-space building are determined, and predicting available evacuation time and required evacuation time accurately is a key parameter of judging personnel safety evacuation in the building. Meanwhile, this dissertation discusses and analyzes the hazard factors of the personnel evacuation process, and raise the quantitative prediction and analysis method of these hazard factors. Through the quantitative analysis of risk factors and the dynamic prediction of personnel evacuation, this dissertation realizes the quantitative evaluation of performance-based design scheme.