Fir Simulation And Safety Research Of Large Shopping Mall Based On Fire Load

In recent years,the number of large-scale shopping malls in China has increased rapidly,but the fire safety level is low.There have been many large-scale shopping mall fire accidents,and caused huge loss of life and property.It is a difficult to study the large-space building fires.The research on fires in public buildings such as large-scale shopping malls at home and abroad is mainly based on the laws of smoke movement and evacuation,and there are few studies on fire spread.This paper studies the fire spread of large shopping malls based on fire load and analyses the changes of temperature,radiant heat,visibility and oxygen during the fire.At the same time,it discusses the influence of automatic sprinkler system on the development of shopping mall fires and puts forward the rational design of automatic sprinkler system in shopping malls to improve the fire safety level of shopping malls.The fire load survey was conducted on shopping malls to determine the fire load of different types of clothing shops and compare with the existing fire load data at home and abroad.The characteristics of fire load density of different shops were analyzed.The average fire load density of the stores was 543 MJ/m²,and the85%,90%and 95%quantile values are 820MJ/m²,871MJ/m² and 975MJ/m²,respectively.The fire load density of the clothing layer in the mall is approximately obeyed.According to a large number of full-scale combustion tests conducted at home and abroad,the numerical model of combustibles such as clothing,sofas,shoes,bedding and decorative wood boards is established by the equivalent method.Ensuring the heat release rate and combustion tendency is basically consistent with the results of the physical test under the condition that the calorific value of combustibles is equal.On the basis of study,select the reasonable fire load density and simulate the real scene according to the layout of the mall,then establish a full-scale shopping mall building model.The FDS software was used to simulate the fire spread of a fire in a large shopping mall.When the temperature of the smoke layer reached 700°C,the flashover occurred.After the consumption of a large amount of oxygen,the heat release rate of the fire was kept at around 600 MW.At 400 s,the visibility of the three floors of the mall was reduced to 2m,the upper floor is the focus of evacuation.To study the influence of automatic sprinkler system with different water spray intensity and RTI value on the development of fire,select 4L/（min·m²）,6 L/（min·m²）and 8 L/（min·m²）respectively.The fast response nozzle have a better result of fire extinguishing and the heat release rate is below 2MW in different tests.The standard response nozzle has a slow start-up time,as the water spray intensity is4L/（min·m²）and the response time index is 250（m·s）^0.5,Fire extinguishing failure.For better fire-extinguishing effect and avoiding the loss of goods caused by the occlusion of fire and other nozzles response,it is more reasonable to choose 8L/（min·m²）fast response nozzle for fast fire in the mall.In this paper,the development of fires in shopping malls under large fire load density was analysed by simulating the fire of the shopping mall.This paper studies the initial development of fire in shopping malls under the action of different automatic sprinkler systems and discusses the designing essentials of the automatic sprinkler systems in shopping malls.Based on the numerical simulation,the development of fire and fire risk characteristics of shopping malls are analyzed,and feasible suggestions are put forward to improve the overall fire safety level of shopping malls.