Study On Uncertainty Of Occupant Safety Evacuation Based On Reliability Theory

How to ensure the life safety of occupant is the primary objectives and more attention should be paid to when fire occurs.the occurrence and development of fire have both the rule of certainty and randomicity, occupant safety evacuation also has the double characteristic. Since various factors can affect occupant safety evacuation and exist lots of uncertainty. Therefore, how to deal with this uncertainty properly needs to further studied. The uncertainty of occupant safety evacuation is studied using probabilistic reliability theory in this article, this study is helpful to improve the occupant safety evacuation of fire environment.Influencing factors of occupant safety evacuation under building fires are firstly analyzed and identified based on occupant characteristics, building characteristics and fire characteristics. Decision-Making and Trial Evaluation Laboratory (DEMATEL) method and Interpretive Structural Modeling (ISM) method are effectively combined. Firstly, a structural model of influencing factors of occupant safety evacuation is established using the ISM method, and the reasons of surface, shallow and deep affecting the occupant safety evacuation are found and classified. Quantitative analysis and mathematical characterization of these influencing factors are then carried out using the DEMATEL approach. Finally,the influence relationship and influence degree of each factor are examined, and the key influencing factors affecting the occupant safety evacuation are identified. This study can provide scientific fundamentals for management and decision making of related departments.The basic theory and method expressing safety level of occupant evacuation is discussed firstly, escape safety time margin is used to express safety level of occupant evacuation by the comparison between the available safety evacuation time (ASET) and the required safety evacuation time (RSET), reliability index and probability of failure are then solved to evaluate the evacuation level. Two criterions of available safety evacuation time (ASET) are determined based on the temperature and the height of smoke layer, and two stochastic model of ASET are then established using orthogonal design and response surface method, respectively. Finally, two model of probabilistic reliability of occupant evacuation are determined, their series parallel connection are analyzed and studied, and the method for solving system failure probability are further put forward.The common methods for solving reliability index are introduced and analyzed, first order second moment method (FOSM), advanced first order second moment method (AFOSM), JC method and Monte Carlo method. The advantages, disadvantages and scope of these methods are analyzed, then the optimization method are put forward and developed based on these methods, and these methods are compared with each other by application examples. In addition,comparative analysis is employed between the model of probabilistic reliability established in this article and existing model. Finally, the relationship of three parameters (fire growth rate, building height and safety exit width) affecting reliability index and probability of failure are further studied.The fundamental theory and method of reliability sensitivity are introduced, the sensitivity of occupant safety evacuation are analyzed by application examples, the relationship of the distribution of four parameters (fire growth rate, occupant response time, occupant density and the specific flow capacity of a doorway) affecting occupant safety evacuation are further analyzed and studied based on the partial derivative of probability of failure to mean value and standard deviation.